See Change: Cosmology Analysis Update for the Supernova Cosmology Project High-z Cluster Supernova Survey

NASA Astrophysics Data System (ADS)

Hayden, Brian; Aldering, Gregory; Amanullah, Rahman; Barbary, Kyle; Bohringer, Hans; Boone, Kyle Robert; Brodwin, Mark; Cunha, Carlos; Currie, Miles; Deustua, Susana; Dixon, Samantha; Eisenhardt, Peter; Fassbender, Rene; Fruchter, Andrew; Gladders, Michael; Gonzalez, Anthony; Goobar, Ariel; Hildebrandt, Hendrik; Hilton, Matt; Hoekstra, Henk; Hook, Isobel; Huang, Xiaosheng; Huterer, Dragan; Jee, Myungkook James; Kim, Alex; Kowalski, Marek; Lidman, Chris; Linder, Eric; Luther, Kyle; Meyers, Joshua; Muzzin, Adam; Nordin, Jakob; Pain, Reynald; Perlmutter, Saul; Richard, Johan; Rosati, Piero; Rozo, Eduardo; Rubin, David; Ruiz-Lapuente, Pilar; Rykoff, Eli; Santos, Joana; Myers Saunders, Clare; Sofiatti, Caroline; Spadafora, Anthony L.; Stanford, Spencer; Stern, Daniel; Suzuki, Nao; Webb, Tracy; Wechsler, Risa; Williams, Steven; Willis, Jon; Wilson, Gillian; Yen, Mike

2018-01-01

The Supernova Cosmology Project has finished executing a large (174 orbits, cycles 22-23) Hubble Space Telescope program, which has measured ~30 type Ia Supernovae above z~1 in the highest-redshift, most massive galaxy clusters known to date. We present the status of the ongoing blinded cosmology analysis, demonstrating substantial improvement to the uncertainty on the Dark Energy density above z~1. Our extensive HST and ground-based campaign has already produced unique results; we have confirmed several of the highest redshift cluster members known to date, confirmed the redshift of one of the most massive galaxy clusters expected across the entire sky, and characterized one of the most extreme starburst environments yet known in a z~1.7 cluster. We have also discovered a lensed SN Ia at z=2.22 magnified by a factor of ~2.8, which is the highest spectroscopic redshift SN Ia currently known.

Infrared surface photometry of 3C 65: Stellar evolution and the Tolman signal

NASA Astrophysics Data System (ADS)

Rigler, M. A.; Lilly, S. J.

1994-06-01

We present an analysis of the infrared surface brightness profile of the high-redshift radio galaxy 3C 65 (z = 1.176), which is well fitted by a de Vaucouleurs r1/4 law. A model surface fitting routine yields characteristic photometric parameters comparable to those of low-redshift radio galaxies and brightest cluster members (BCMs) in standard cosmologies. The small displacement of this galaxy from the locus of low-redshift systems on the mur - log(re) plane suggests that little or no luminosity evolution is required in a cosmological model with (Omega0, lambda0 = (1,0), while a modest degree of luminosity evolution, accountable by passive evolution of the stellar population, is implied in models with (0, 0) or (0.1, 0.9). A nonexpanding cosmology is unlikely because it would require 3C 65 to lie at the extreme end of the distribution of properties of local gE galaxies, and the effects of plausible stellar and/or dynamic evolution would make 3C 65 even more extreme by the present epoch.

The Physical Constraints on a New LoBAL QSO at z = 4.82

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Weimin; Bai, Jin-Ming; Green, Richard

Very few low-ionization broad absorption line (LoBAL) QSOs have been found at high redshifts, to date. One high-redshift LoBAL QSO, J0122+1216, was recently discovered by the Lijiang 2.4 m Telescope, with an initial redshift determination of 4.76. Aiming to investigate its physical properties, we carried out follow-up observations in the optical and near-IR spectroscopy. Near-IR spectra from UKIRT and P200 confirm that it is a LoBAL, with a new redshift determination of 4.82 ± 0.01 based on the Mg ii emission-line. The new Mg ii redshift determination reveals strong blueshifts and asymmetry of the high-ionization emission lines. We estimate amore » black hole mass of ∼2.3 × 10{sup 9} M {sub ⊙} and Eddington ratio of ∼1.0 according to the empirical Mg ii-based single-epoch relation and bolometric correction factor. It is possible that strong outflows are the result of an extreme quasar environment driven by the high Eddington ratio. A lower limit on the outflowing kinetic power (>0.9% L {sub Edd}) is derived from both emission and absorption lines, indicating that these outflows play a significant role in the feedback process that regulates the growth of its black hole, as well as host galaxy evolution.« less

Very deep IRAS survey - constraints on the evolution of starburst galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hacking, P.; Houck, J.R.; Condon, J.J.

1987-05-01

Counts of sources (primarily starburst galaxies) from a deep 60 microns IRAS survey published by Hacking and Houck (1987) are compared with four evolutionary models. The counts below 100 mJy are higher than expected if no evolution has taken place out to a redshift of approximately 0.2. Redshift measurements of the survey sources should be able to distinguish between luminosity-evolution and density-evolution models and detect as little as a 20 percent brightening or increase in density of infrared sources per billion years ago (H/0/ = 100 km/s per Mpc). Starburst galaxies cannot account for the reported 100 microns background withoutmore » extreme evolution at high redshifts. 21 references.« less

RECONSTRUCTING REDSHIFT DISTRIBUTIONS WITH CROSS-CORRELATIONS: TESTS AND AN OPTIMIZED RECIPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, Daniel J.; Newman, Jeffrey A., E-mail: djm70@pitt.ed, E-mail: janewman@pitt.ed

2010-09-20

Many of the cosmological tests to be performed by planned dark energy experiments will require extremely well-characterized photometric redshift measurements. Current estimates for cosmic shear are that the true mean redshift of the objects in each photo-z bin must be known to better than 0.002(1 + z), and the width of the bin must be known to {approx}0.003(1 + z) if errors in cosmological measurements are not to be degraded significantly. A conventional approach is to calibrate these photometric redshifts with large sets of spectroscopic redshifts. However, at the depths probed by Stage III surveys (such as DES), let alonemore » Stage IV (LSST, JDEM, and Euclid), existing large redshift samples have all been highly (25%-60%) incomplete, with a strong dependence of success rate on both redshift and galaxy properties. A powerful alternative approach is to exploit the clustering of galaxies to perform photometric redshift calibrations. Measuring the two-point angular cross-correlation between objects in some photometric redshift bin and objects with known spectroscopic redshift, as a function of the spectroscopic z, allows the true redshift distribution of a photometric sample to be reconstructed in detail, even if it includes objects too faint for spectroscopy or if spectroscopic samples are highly incomplete. We test this technique using mock DEEP2 Galaxy Redshift survey light cones constructed from the Millennium Simulation semi-analytic galaxy catalogs. From this realistic test, which incorporates the effects of galaxy bias evolution and cosmic variance, we find that the true redshift distribution of a photometric sample can, in fact, be determined accurately with cross-correlation techniques. We also compare the empirical error in the reconstruction of redshift distributions to previous analytic predictions, finding that additional components must be included in error budgets to match the simulation results. This extra error contribution is small for surveys that sample large areas of sky (>{approx}10{sup 0}-100{sup 0}), but dominant for {approx}1 deg{sup 2} fields. We conclude by presenting a step-by-step, optimized recipe for reconstructing redshift distributions from cross-correlation information using standard correlation measurements.« less

Extremely red objects in the fields of high redshift radio galaxies

NASA Technical Reports Server (NTRS)

Persson, S. E.; Mccarthy, P. J.; Dressler, Alan; Matthews, Keith

1993-01-01

We are engaged in a program of infrared imaging photometry of high redshift radio galaxies. The observations are being done using NICMOS2 and NICMOS3 arrays on the DuPont 100-inch telescope at Las Campanas Observatory. In addition, Persson and Matthews are measuring the spectral energy distributions of normal cluster galaxies in the redshift range 0 to 1. These measurements are being done with a 58 x 62 InSb array on the Palomar 5-m telescope. During the course of these observations we have imaged roughly 20 square arcminutes of sky to limiting magnitudes greater than 20 in the J, H, and K passbands (3 sigma in 3 square arcseconds). We have detected several relatively bright, extremely red, extended objects during the course of this work. Because the radio galaxy program requires Thuan-Gunn gri photometry, we are able to construct rough photometric energy distributions for many of the objects. A sample of the galaxy magnitudes within 4 arcseconds diameter is given. All the detections are real; either the objects show up at several wavelengths, or in subsets of the data. The reddest object in the table, 9ab'B' was found in a field of galaxies in a rich cluster at z = 0.4; 9ab'A' lies 8 arcseconds from it.

First direct comparison of high and low ionization line kinematics in active galactic nuclei

NASA Technical Reports Server (NTRS)

Sulentic, J. W.; Marziani, P.; Dultzin-Hacyan, D.; Calvani, M.; Moles, M.

1995-01-01

We present first results of a comparison of emission line shift properties for the high (HILs) and low (LILs) ionization lines in 43 low-reshift quasars. We identify a core sample of C IV lambda 1549 and hydrogen beta profiles with a wide distribution of red- and blueshifts (less than or equal to +/- 1000 km/sec). We also identify two tails in this distribution: one with large hydrogen beta redshifts (greater than or equal to 2000 km/sec) and another with large C IV blueshifts (greater than or equal to 1500 km/sec). The tails are mutually exclusive. All objects with extreme hydrogen beta redshift are radio loud, and all objects with extreme C IV blueshift are radio quiet. The core samples of smaller shifts can be most simply divided into: (1) hydrogen beta - a redshifted radio-loud population (related to the tail) and a radio-quiet population with mean shift near zero, and (2) C IV - a blueshifted radio-quiet population (related to the tail) and a radio-loud population with mean shift near zero. The results suggest fundamentally different kinematics for the HILs and LILs. They also suggest very different kinematics for radio-loud and radio-quiet active galactic nuclei. They also favor a predominance of radial motion in a large fraction of the sample.

Herschel Extreme Lensing Line Observations: [CII] Variations in Galaxies at Redshifts z=1-3*

NASA Technical Reports Server (NTRS)

Malhotra, Sangeeta; Rhoads, James E.; Finkelstein, K.; Yang, Huan; Carilli, Chris; Combes, Francoise; Dassas, Karine; Finkelstein, Steven; Frye, Brenda; Gerin, Maryvonne;

Herschel Extreme Lensing Line Observations: [CII] Variations in Galaxies at Redshifts z=1-3

NASA Astrophysics Data System (ADS)

Malhotra, Sangeeta; Rhoads, James E.; Finkelstein, K.; Yang, Huan; Carilli, Chris; Combes, Françoise; Dassas, Karine; Finkelstein, Steven; Frye, Brenda; Gerin, Maryvonne; Guillard, Pierre; Nesvadba, Nicole; Rigby, Jane; Shin, Min-Su; Spaans, Marco; Strauss, Michael A.; Papovich, Casey

2017-01-01

We observed the [C II] line in 15 lensed galaxies at redshifts 1 < z < 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3σ or better. High magnifications enable even modestly luminous galaxies to be detected in [C II] with Herschel. The [C II] luminosity in this sample ranges from 8 × 107 L⊙ to 3.7 × 109 L⊙ (after correcting for magnification), confirming that [C II] is a strong tracer of the ISM at high redshifts. The ratio of the [C II] line to the total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C II]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C II]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C II]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C II]/FIR correlates most strongly with dust temperature. The [C II] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

HERSCHEL EXTREME LENSING LINE OBSERVATIONS: [C ii] VARIATIONS IN GALAXIES AT REDSHIFTS z = 1–3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malhotra, Sangeeta; Rhoads, James E.; Yang, Huan

We observed the [C ii] line in 15 lensed galaxies at redshifts 1 < z < 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3 σ or better. High magnifications enable even modestly luminous galaxies to be detected in [C ii] with Herschel . The [C ii] luminosity in this sample ranges from 8 × 10{sup 7} L {sub ⊙} to 3.7 × 10{sup 9} L {sub ⊙} (after correcting for magnification), confirming that [C ii] is a strong tracer of the ISM at high redshifts. The ratio of the [C ii] line to themore » total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C ii]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C ii]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C ii]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C ii]/FIR correlates most strongly with dust temperature. The [C ii] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating.« less

Extremes of the jet–accretion power relation of blazars, as explored by NuSTAR

DOE PAGES

Sbarrato, T.; Ghisellini, G.; Tagliaferri, G.; ...

2016-07-18

Hard X-ray observations are crucial to study the non-thermal jet emission from high-redshift, powerful blazars. We observed two bright z > 2 flat spectrum radio quasars (FSRQs) in hard X-rays to explore the details of their relativistic jets and their possible variability. S5 0014+81 (at z = 3.366) and B0222+185 (at z=2.690) have been observed twice by the Nuclear Spectroscopic Telescope Array (NuSTAR) simultaneously with Swift/XRT, showing different variability behaviors. We found that NuSTAR is instrumental to explore the variability of powerful high-redshift blazars, even when no gamma-ray emission is detected. The two sources have proven to have respectively themore » most luminous accretion disk and the most powerful jet among known blazars. Furthermore, thanks to these properties, they are located at the extreme end of the jet-accretion disk relation previously found for gamma-ray detected blazars, to which they are consistent.« less

Extremes of the jet–accretion power relation of blazars, as explored by NuSTAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sbarrato, T.; Ghisellini, G.; Tagliaferri, G.

Hard X-ray observations are crucial to study the non-thermal jet emission from high-redshift, powerful blazars. We observed two bright z > 2 flat spectrum radio quasars (FSRQs) in hard X-rays to explore the details of their relativistic jets and their possible variability. S5 0014+81 (at z = 3.366) and B0222+185 (at z=2.690) have been observed twice by the Nuclear Spectroscopic Telescope Array (NuSTAR) simultaneously with Swift/XRT, showing different variability behaviors. We found that NuSTAR is instrumental to explore the variability of powerful high-redshift blazars, even when no gamma-ray emission is detected. The two sources have proven to have respectively themore » most luminous accretion disk and the most powerful jet among known blazars. Furthermore, thanks to these properties, they are located at the extreme end of the jet-accretion disk relation previously found for gamma-ray detected blazars, to which they are consistent.« less

Probing Black Holes With Gravitational Radiation

NASA Astrophysics Data System (ADS)

Cornish, Neil J.

2006-09-01

Gravitational radiation can provide unique insights into the dynamics and evolution of black holes. Gravitational waveforms encode detailed information about the spacetime geometry, much as the sounds made by a musical instrument reflect the geometry of the instrument. The LISA gravitational wave observatory will be able to record black holes colliding out to the edge of the visible Universe, with an expected event rate of tens to thousands per year. LISA has unmatched capabilities for studying the role of black holes in galactic evolution, in particular, by studying the mergers of seed black holes at very high redshift, z > 5. Merger events at lower redshift will be detected at extremely high signal-to-noise, allowing for precision tests of the black hole paradigm. Below z=1 LISA will be able to record stellar remnants falling into supermassive black holes. These extreme mass ratio inspiral events will yield insights into the dynamics of galactic cusps, and the brighter events will provide incredibly precise tests of strong field, dynamical gravity.

X-ray Counterparts of Infrared Faint Radio Sources

NASA Astrophysics Data System (ADS)

Schartel, Norbert

2011-10-01

Infrared Faint Radio Sources (IFRS) are radio sources with extremely faint or even absent infrared emission in deep Spitzer Surveys. Models of their spectral energy distributions, the ratios of radio to infrared flux densities and their steep radio spectra strongly suggest that IFRS are AGN at high redshifts (2

Disentangling Hadronic and Leptonic Cascade Scenarios from the Very-High-Energy Gamma-Ray Emission of Distant Hard-Spectrum Blazars

DOE PAGES

Takami, Hajime; Murase, Kohta; Dermer, Charles D.

2013-06-26

We show that recent data from the Fermi Large Area Telescope have revealed about a dozen distant hard-spectrum blazars that have very-high-energy (VHE; ≳ 100 eV) photons associated with them, but most of them have not yet been detected by imaging atmospheric Cherenkov Telescopes. Most of these high-energy gamma-ray spectra, like those of other extreme high-frequency peaked BL Lac objects, can be well explained either by gamma rays emitted at the source or by cascades induced by ultra-high-energy cosmic rays, as we show specifically for KUV 00311–1938. We consider the prospects for detection of the VHE sources by the plannedmore » Cherenkov Telescope Array (CTA) and show how it can distinguish the two scenarios by measuring the integrated flux above ~500 GeV (depending on source redshift) for several luminous sources with z ≲ 1 in the sample. Strong evidence for the origin of ultra-high-energy cosmic rays could be obtained from VHE observations with CTA. Depending on redshift, if the often quoted redshift of KUV 00311–1938 (z = 0.61) is believed, then preliminary H.E.S.S. data favor cascades induced by ultra-high-energy cosmic rays. Lastly, accurate redshift measurements of hard-spectrum blazars are essential for this study.« less

A search for moderate-redshift survivors from the population of luminous compact passive galaxies at high redshift

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stockton, Alan; Shih, Hsin-Yi; Larson, Kirsten

2014-01-10

From a search of a ∼2400 deg{sup 2} region covered by both the Sloan Digital Sky Survey and UKIRT Infrared Deep Sky Survey databases, we have attempted to identify galaxies at z ∼ 0.5 that are consistent with their being essentially unmodified examples of the luminous passive compact galaxies found at z ∼ 2.5. After isolating good candidates via deeper imaging, we further refine the sample with Keck moderate-resolution spectroscopy and laser guide star adaptive-optics imaging. For four of the five galaxies that so far remain after passing through this sieve, we analyze plausible star-formation histories based on our spectramore » in order to identify galaxies that may have survived with little modification from the population formed at high redshift. We find two galaxies that are consistent with having formed ≳ 95% of their mass at z > 5. We attempt to estimate masses both from our stellar population determinations and from velocity dispersions. Given the high frequency of small axial ratios, both in our small sample and among samples found at high redshifts, we tentatively suggest that some of the more extreme examples of passive compact galaxies may have prolate morphologies.« less

THE AzTEC/SMA INTERFEROMETRIC IMAGING SURVEY OF SUBMILLIMETER-SELECTED HIGH-REDSHIFT GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Younger, Joshua D.; Fazio, Giovanni G.; Huang Jiasheng

We present results from a continuing interferometric survey of high-redshift submillimeter galaxies (SMGs) with the Submillimeter Array, including high-resolution (beam size approx2 arcsec) imaging of eight additional AzTEC 1.1 mm selected sources in the COSMOS field, for which we obtain six reliable (peak signal-to-noise ratio (S/N) >5 or peak S/N >4 with multiwavelength counterparts within the beam) and two moderate significance (peak S/N >4) detections. When combined with previous detections, this yields an unbiased sample of millimeter-selected SMGs with complete interferometric follow up. With this sample in hand, we (1) empirically confirm the radio-submillimeter association, (2) examine the submillimeter morphology-includingmore » the nature of SMGs with multiple radio counterparts and constraints on the physical scale of the far infrared-of the sample, and (3) find additional evidence for a population of extremely luminous, radio-dim SMGs that peaks at higher redshift than previous, radio-selected samples. In particular, the presence of such a population of high-redshift sources has important consequences for models of galaxy formation-which struggle to account for such objects even under liberal assumptions-and dust production models given the limited time since the big bang.« less

Spectroscopic Needs for Imaging Dark Energy Experiments

DOE PAGES

Newman, Jeffrey A.; Slosar, Anze; Abate, Alexandra; ...

2015-03-15

Ongoing and near-future imaging-based dark energy experiments are critically dependent upon photometric redshifts (a.k.a. photo-z’s): i.e., estimates of the redshifts of objects based only on flux information obtained through broad filters. Higher-quality, lower-scatter photo-z’s will result in smaller random errors on cosmological parameters; while systematic errors in photometric redshift estimates, if not constrained, may dominate all other uncertainties from these experiments. The desired optimization and calibration is dependent upon spectroscopic measurements for secure redshift information; this is the key application of galaxy spectroscopy for imaging-based dark energy experiments. Hence, to achieve their full potential, imaging-based experiments will require large setsmore » of objects with spectroscopically-determined redshifts, for two purposes: Training: Objects with known redshift are needed to map out the relationship between object color and z (or, equivalently, to determine empirically-calibrated templates describing the rest-frame spectra of the full range of galaxies, which may be used to predict the color-z relation). The ultimate goal of training is to minimize each moment of the distribution of differences between photometric redshift estimates and the true redshifts of objects, making the relationship between them as tight as possible. The larger and more complete our “training set” of spectroscopic redshifts is, the smaller the RMS photo-z errors should be, increasing the constraining power of imaging experiments; Requirements: Spectroscopic redshift measurements for ~30,000 objects over >~15 widely-separated regions, each at least ~20 arcmin in diameter, and reaching the faintest objects used in a given experiment, will likely be necessary if photometric redshifts are to be trained and calibrated with conventional techniques. Larger, more complete samples (i.e., with longer exposure times) can improve photo-z algorithms and reduce scatter further, enhancing the science return from planned experiments greatly (increasing the Dark Energy Task Force figure of merit by up to ~50%); Options: This spectroscopy will most efficiently be done by covering as much of the optical and near-infrared spectrum as possible at modestly high spectral resolution (λ/Δλ > ~3000), while maximizing the telescope collecting area, field of view on the sky, and multiplexing of simultaneous spectra. The most efficient instrument for this would likely be either the proposed GMACS/MANIFEST spectrograph for the Giant Magellan Telescope or the OPTIMOS spectrograph for the European Extremely Large Telescope, depending on actual properties when built. The PFS spectrograph at Subaru would be next best and available considerably earlier, c. 2018; the proposed ngCFHT and SSST telescopes would have similar capabilities but start later. Other key options, in order of increasing total time required, are the WFOS spectrograph at TMT, MOONS at the VLT, and DESI at the Mayall 4 m telescope (or the similar 4MOST and WEAVE projects); of these, only DESI, MOONS, and PFS are expected to be available before 2020. Table 2-3 of this white paper summarizes the observation time required at each facility for strawman training samples. To attain secure redshift measurements for a high fraction of targeted objects and cover the full redshift span of future experiments, additional near-infrared spectroscopy will also be required; this is best done from space, particularly with WFIRST-2.4 and JWST; Calibration: The first several moments of redshift distributions (the mean, RMS redshift dispersion, etc.), must be known to high accuracy for cosmological constraints not to be systematics-dominated (equivalently, the moments of the distribution of differences between photometric and true redshifts could be determined instead). The ultimate goal of calibration is to characterize these moments for every subsample used in analyses - i.e., to minimize the uncertainty in their mean redshift, RMS dispersion, etc. – rather than to make the moments themselves small. Calibration may be done with the same spectroscopic dataset used for training if that dataset is extremely high in redshift completeness (i.e., no populations of galaxies to be used in analyses are systematically missed). Accurate photo-z calibration is necessary for all imaging experiments; Requirements: If extremely low levels of systematic incompleteness (<~0.1%) are attained in training samples, the same datasets described above should be sufficient for calibration. However, existing deep spectroscopic surveys have failed to yield secure redshifts for 30–60% of targets, so that would require very large improvements over past experience. This incompleteness would be a limiting factor for training, but catastrophic for calibration. If <~0.1% incompleteness is not attainable, the best known option for calibration of photometric redshifts is to utilize cross-correlation statistics in some form. The most direct method for this uses cross-correlations between positions on the sky of bright objects of known spectroscopic redshift with the sample of objects that we wish to calibrate the redshift distribution for, measured as a function of spectroscopic z. For such a calibration, redshifts of ~100,000 objects over at least several hundred square degrees, spanning the full redshift range of the samples used for dark energy, would be necessary; and Options: The proposed BAO experiment eBOSS would provide sufficient spectroscopy for basic calibrations, particularly for ongoing and near-future imaging experiments. The planned DESI experiment would provide excellent calibration with redundant cross-checks, but will start after the conclusion of some imaging projects. An extension of DESI to the Southern hemisphere would provide the best possible calibration from cross-correlation methods for DES and LSST. We thus anticipate that our two primary needs for spectroscopy – training and calibration of photometric redshifts – will require two separate solutions. For ongoing and future projects to reach their full potential, new spectroscopic samples of faint objects will be needed for training; those new samples may be suitable for calibration, but the latter possibility is uncertain. In contrast, wide-area samples of bright objects are poorly suited for training, but can provide high-precision calibrations via cross-correlation techniques. Additional training/calibration redshifts and/or host galaxy spectroscopy would enhance the use of supernovae and galaxy clusters for cosmology. We also summarize additional work on photometric redshift techniques that will be needed to prepare for data from ongoing and future dark energy experiments.« less

The binary Feige 24 - The mass, radius, and gravitational redshift of the DA white dwarf

NASA Technical Reports Server (NTRS)

Vennes, Stephane; Shipman, Harry L.; Thorstensen, John R.; Thejll, Peter

1991-01-01

Observations are reported which refine the binary ephemeris of the Feige 24 system, which contains a peculiar hot DA white dwarf and an M dwarf with an atmosphere illuminated by extreme ultraviolet radiation from the white dwarf. With the new ephemeris and a set of IUE high-dispersion spectra, showing phase-dependent redshifted C IV, N V, and Si IV resonance lines, the orbital velocity, and hence the mass (0.54 + or - 0.20 solar masses), and the gravitational redshift of the white dwarf (14.1 + or - 5.2 km/s) are determined independently. It is shown that the measured Einstein redshift is consistent with an estimated radius for the white dwarf obtained from a model atmosphere solid angle and a parallax measurement. This radius is twice the Hamada-Salpeter radius for the given mass and offers a prospect to investigate the presence of a massive hydrogen envelope in that white dwarf star.

Definitive test of the Rh = ct universe using redshift drift

NASA Astrophysics Data System (ADS)

Melia, Fulvio

2016-11-01

The redshift drift of objects moving in the Hubble flow has been proposed as a powerful model-independent probe of the underlying cosmology. A measurement of the first- and second-order redshift derivatives appears to be well within the reach of upcoming surveys using as the Extremely Large Telescope high resolution spectrometer (ELT-HIRES) and the Square Kilometer Phase 2 Array (SKA). Here we show that an unambiguous prediction of the Rh = ct cosmology is zero drift at all redshifts, contrasting sharply with all other models in which the expansion rate is variable. For example, multiyear monitoring of sources at redshift z = 5 with the ELT-HIRES is expected to show a velocity shift Δv = -15 cm s-1 yr-1 due to the redshift drift in Planck ΛCDM, while Δv = 0 cm s-1 yr-1 in Rh = ct. With an anticipated ELT-HIRES measurement error of ±5 cm s-1 yr-1 after 5 yr, these upcoming redshift drift measurements might therefore be able to differentiate between Rh = ct and Planck ΛCDM at ˜3σ, assuming that any possible source evolution is well understood. Such a result would provide the strongest evidence yet in favour of the Rh = ct cosmology. With a 20-yr baseline, these observations could favour one of these models over the other at better than 5σ.

The extreme ultraviolet spectra of low-redshift radio-loud quasars

NASA Astrophysics Data System (ADS)

Punsly, Brian; Reynolds, Cormac; Marziani, Paola; O'Dea, Christopher P.

2016-07-01

This paper reports on the extreme ultraviolet (EUV) spectrum of three low-redshift (z ˜ 0.6) radio-loud quasars, 3C 95, 3C 57 and PKS 0405-123. The spectra were obtained with the Cosmic Origins Spectrograph of the Hubble Space Telescope. The bolometric thermal emission, Lbol, associated with the accretion flow is a large fraction of the Eddington limit for all of these sources. We estimate the long-term time-averaged jet power, overline{Q}, for the three sources. overline{Q}/L_{bol}, is shown to lie along the correlation of overline{Q}/L_{bol}, and αEUV found in previous studies of the EUV continuum of intermediate and high-redshift quasars, where the EUV continuum flux density between 1100 and 700 Å is defined by F_{ν } ˜ ν ^{-α _{EUV}}. The high Eddington ratios of the three quasars extend the analysis into a wider parameter space. Selecting quasars with high Eddington ratios has accentuated the statistical significance of the partial correlation analysis of the data. Namely, the correlation of overline{Q}/L_{bol} and αEUV is fundamental, and the correlation of overline{Q} and αEUV is spurious at a very high statistical significance level (99.8 per cent). This supports the regulating role of ram pressure of the accretion flow in magnetically arrested accretion models of jet production. In the process of this study, we use multifrequency and multiresolution Very Large Array radio observations to determine that one of the bipolar jets in 3C 57 is likely frustrated by galactic gas that keeps the jet from propagating outside the host galaxy.

Tackling The Dragon: Investigating Lensed Galaxy Structure

NASA Astrophysics Data System (ADS)

Fortenberry, Alexander; Livermore, Rachael

2018-01-01

Galaxies have been seen to have a rapid decrease in star formation beginning at a redshift of around 1-2 up to the present day. To understand the processes underpinning this change, we need to observe the inner structure of galaxies and understand where and how the stellar mass builds up. However, at high redshifts our observable resolution is limited, which hinders the accuracy of the data. The lack of resolution at high redshift can be counteracted with the use of gravitational lensing. The magnification provided by the gravitational lens between us and the galaxies in question enables us to see extreme detail within the galaxies. To begin fine-tuning this process, we used Hubble data of Abell 370, a galaxy cluster, which lenses a galaxy know as “The Dragon” at z=0.725. With the increased detail proved by the gravitational lens we provide a detailed analysis of the galaxy’s spatially resolved star formation rate, stellar age, and masses.

New LMT High Resolution Imaging and CO Spectroscopic Studies of the Brightest AzTEC 1.1mm Sources

NASA Astrophysics Data System (ADS)

Yun, Min S.; Aretxaga, Itziar; Hughes, David; Montana, A.; Pope, A.; Bruzual, Gustavo; Ferrusca, D.; Rosa Gonzalez, D.; Sanchez-Arguelles, D.; Narayanan, G.; Wilson, Grant; Gim, Hansung; Ibarra, H.; Mo, H.; Lowenthal, James; Zavala, J.; Carrasco, L.; Chavez, M.; Valazquez, M.; Zeballos, M.; Vega, O.; Schloerb, P.; Cybulsky, J. R.; Casey, Caitlin M.; Tang, Y.

2015-08-01

A substantial population of quiescent galaxies with stellar masses exceeding 10 billion solar masses have been found to z~4, suggesting a rapid formation and quenching of massive galaxies at z~6 or earlier. The submillimeter bright galaxies (SMGs) with SFR > 100-1000 solar masses per year represent natural candidates for the progenitor systems undergoing an epoch of rapid formation and cessation of stellar mass build up. Many of the most luminous SMGs are also extremely red and faint in the optical, suggesting a high redshift and are beyond the reach of the current optical spectroscopic redshift surveys. There is also a growing concern that these most luminous SMGs may be blends of several unrelated sources as a result of a poor angular resolution of the existing surveys (18" & 28" for the AzTEC 1.1mm surveys on JCMT and ASTE, respectively). We have obtained new 8" resolution AzTEC images of 40 brightest AzTEC sources previously found in the GOODS and COSMOS fields using the Large Millimeter Telescope (LMT) to examine the multiplicity question and for the identification of multi-wavelength counterparts. We have also conducted a CO redshift survey using the Redshift Search Receiver on the LMT. We will report the results of these analysis and several new CO redshifts.

Using r-process enhanced galaxies to estimate the neutron star merger rate at high redshift

NASA Astrophysics Data System (ADS)

Roederer, Ian

2018-01-01

The rapid neutron-capture process, or r-process, is one of the fundamental ways that stars produce heavy elements. I describe a new approach that uses the existence of r-process enhanced galaxies, like the recently discovered ultra-faint dwarf galaxy Reticulum II, to derive a rate for neutron star mergers at high redshift. This method relies on three assertions. First, several lines of reasoning point to neutron star mergers as a rare yet prolific producer of r-process elements, and one merger event is capable of enriching most of the stars in a low-mass dwarf galaxy. Second, the Local Group is cosmologically representative of the halo mass function at the mass scales of low-luminosity dwarf galaxies, and the volume that their progenitors spanned at high redshifts can be estimated from simulations. Third, many of these dwarf galaxies are extremely old, and the metals found in their stars today date from the earliest times at high redshift. These galaxies occupy a quantifiable volume of the Universe, from which the frequency of r-process enhanced galaxies can be estimated. This frequency may be interpreted as lower limit to the neutron star merger rate at a redshift (z ~ 5-10) that is much higher than is accessible to gravitational wave observatories. I will present a proof of concept demonstration using medium-resolution multi-object spectroscopy from the Michigan/Magellan Fiber System (M2FS) to recover the known r-process galaxy Reticulum II, and I will discuss future plans to apply this method to other Local Group dwarf galaxies.

OT2_smalhotr_3: Herschel Extreme Lensing Line Observations (HELLO)

NASA Astrophysics Data System (ADS)

Malhotra, S.

2011-09-01

We request 59.8 hours of Herschel time to observe 20 normal star-forming galaxies in the [CII] 158 micron and [OI] 63 micron lines. These galaxies lie at high redshift (1

The SPT+Herschel+ALMA+Spitzer Legacy Survey: The stellar content of high redshift strongly lensed systems

NASA Astrophysics Data System (ADS)

Vieira, Joaquin; Ashby, Matt; Carlstrom, John; Chapman, Scott; DeBreuck, Carlos; Fassnacht, Chris; Gonzalez, Anthony; Phadke, Kedar; Marrone, Dan; Malkan, Matt; Reuter, Cassie; Rotermund, Kaja; Spilker, Justin; Weiss, Axel

2018-05-01

The South Pole Telescope (SPT) has systematically identified 90 high-redshift strongly gravitationally lensed submillimeter galaxies (SMGs) in a 2500 square-degree cosmological survey of the millimeter (mm) sky. These sources are selected by their extreme mm flux, which is largely independent of redshift and lensing configuration. We are undertaking a comprehensive and systematic followup campaign to use these "cosmic magnifying glasses" to study the infrared background in unprecedented detail, inform the condition of the interstellar medium in starburst galaxies at high redshift, and place limits on dark matter substructure. Here we ask for 115.4 hours of deep Spitzer/IRAC imaging to complete our survey of 90 systems to a uniform depth of 30min integrations at 3.6um and 60min at 4.5um. In our sample of 90 systems, 16 have already been fully observed, 30 have been partially observed, and 44 have not been observed at all. Our immediate goals are to: 1) constrain the specific star formation rates of the background high-redshift submillimeter galaxies by combining these Spitzer observations with our APEX, Herschel, and ALMA data, 2) robustly determine the stellar masses and mass-to-light ratios of all the foreground lensing galaxies in the sample by combining these observations with our VLT and Gemini data, the Dark Energy Survey, and ALMA; and 3) provide complete, deep, and uniform NIR coverage of our entire sample of lensed systems to characterize the environments of high redshift SMGs, maximize the discovery potential for additional spectacular and rare sources, and prepare for JWST. This program will provide the cornerstone data set for two PhD theses: Kedar Phadke at Illinois will lead the analysis of stellar masses for the background SMGs, and Kaja Rotermund at Dalhousie will lead the analysis of stellar masses for the foreground lenses.

Photometric Redshifts with the LSST: Evaluating Survey Observing Strategies

NASA Astrophysics Data System (ADS)

Graham, Melissa L.; Connolly, Andrew J.; Ivezić, Željko; Schmidt, Samuel J.; Jones, R. Lynne; Jurić, Mario; Daniel, Scott F.; Yoachim, Peter

2018-01-01

In this paper we present and characterize a nearest-neighbors color-matching photometric redshift estimator that features a direct relationship between the precision and accuracy of the input magnitudes and the output photometric redshifts. This aspect makes our estimator an ideal tool for evaluating the impact of changes to LSST survey parameters that affect the measurement errors of the photometry, which is the main motivation of our work (i.e., it is not intended to provide the “best” photometric redshifts for LSST data). We show how the photometric redshifts will improve with time over the 10 year LSST survey and confirm that the nominal distribution of visits per filter provides the most accurate photo-z results. The LSST survey strategy naturally produces observations over a range of airmass, which offers the opportunity of using an SED- and z-dependent atmospheric affect on the observed photometry as a color-independent redshift indicator. We show that measuring this airmass effect and including it as a prior has the potential to improve the photometric redshifts and can ameliorate extreme outliers, but that it will only be adequately measured for the brightest galaxies, which limits its overall impact on LSST photometric redshifts. We furthermore demonstrate how this airmass effect can induce a bias in the photo-z results, and caution against survey strategies that prioritize high-airmass observations for the purpose of improving this prior. Ultimately, we intend for this work to serve as a guide for the expectations and preparations of the LSST science community with regard to the minimum quality of photo-z as the survey progresses.

Gamma-Ray Bursts and Cosmology

NASA Technical Reports Server (NTRS)

Norris, Jay P.

2003-01-01

The unrivalled, extreme luminosities of gamma-ray bursts (GRBs) make them the favored beacons for sampling the high redshift Universe. To employ GRBs to study the cosmic terrain -- e.g., star and galaxy formation history -- GRB luminosities must be calibrated, and the luminosity function versus redshift must be measured or inferred. Several nascent relationships between gamma-ray temporal or spectral indicators and luminosity or total energy have been reported. These measures promise to further our understanding of GRBs once the connections between the luminosity indicators and GRB jets and emission mechanisms are better elucidated. The current distribution of 33 redshifts determined from host galaxies and afterglows peaks near z $\\sim$ 1, whereas for the full BATSE sample of long bursts, the lag-luminosity relation predicts a broad peak z $\\sim$ 1--4 with a tail to z $\\sim$ 20, in rough agreement with theoretical models based on star formation considerations. For some GRB subclasses and apparently related phenomena -- short bursts, long-lag bursts, and X-ray flashes -- the present information on their redshift distributions is sparse or entirely lacking, and progress is expected in Swift era when prompt alerts become numerous.

A unified model for galactic discs: star formation, turbulence driving, and mass transport

NASA Astrophysics Data System (ADS)

Krumholz, Mark R.; Burkhart, Blakesley; Forbes, John C.; Crocker, Roland M.

2018-06-01

We introduce a new model for the structure and evolution of the gas in galactic discs. In the model the gas is in vertical pressure and energy balance. Star formation feedback injects energy and momentum, and non-axisymmetric torques prevent the gas from becoming more than marginally gravitationally unstable. From these assumptions we derive the relationship between galaxies' bulk properties (gas surface density, stellar content, and rotation curve) and their star formation rates, gas velocity dispersions, and rates of radial inflow. We show that the turbulence in discs can be powered primarily by star formation feedback, radial transport, or a combination of the two. In contrast to models that omit either radial transport or star formation feedback, the predictions of this model yield excellent agreement with a wide range of observations, including the star formation law measured in both spatially resolved and unresolved data, the correlation between galaxies' star formation rates and velocity dispersions, and observed rates of radial inflow. The agreement holds across a wide range of galaxy mass and type, from local dwarfs to extreme starbursts to high-redshift discs. We apply the model to galaxies on the star-forming main sequence, and show that it predicts a transition from mostly gravity-driven turbulence at high redshift to star-formation-driven turbulence at low redshift. This transition and the changes in mass transport rates that it produces naturally explain why galaxy bulges tend to form at high redshift and discs at lower redshift, and why galaxies tend to quench inside-out.

Physical properties of distant red galaxies in the COSMOS/UltraVISTA field

NASA Astrophysics Data System (ADS)

Ma, Zhongyang; Fang, Guanwen; Kong, Xu; Fan, Lulu

2015-10-01

We present a study on physical properties for a large distant red galaxy (DRG) sample, using the K-selected multi-band photometry catalog of the COSMOS/UltraVISTA field and the CANDELS near-infrared data. Our sample includes 4485 DRGs with (J - K)AB > 1.16 and KAB < 23.4 mag, and 132 DRGs have HST/WFC3 morphological measurements. The results of nonparametric measurements of DRG morphology are consistent with our rest-frame UVJ color classification; quiescent DRGs are generally compact while star-forming DRGs tend to have extended structures. We find the star formation rate (SFR) and the stellar mass of star-forming DRGs present tight "main sequence" relations in all redshift bins. Moreover, the specific SFR (sSFR) of DRGs increases with redshift in all stellar mass bins and DRGs with higher stellar masses generally have lower sSFRs, which indicates that galaxies were much more active on average in the past, and star formation contributes more to the mass growth of low-mass galaxies than to high-mass galaxies. The infrared-derived SFR dominates the total SFR of DRGs which occupy the high-mass range, implying that the J - K color criterion effectively selects massive and dusty galaxies. DRGs with higher M* generally have redder (U - V)rest colors, and the (U - V)rest colors of DRGs become bluer at higher redshifts, suggesting high-mass galaxies have higher internal dust extinctions or older stellar ages and they evolve with time. Finally, we find that DRGs have different overlap among extremely red objects, BzK galaxies, IRAC-selected extremely red objects, and high-z ultraluminous infrared galaxies, indicating that DRGs are not a special population and they can also be selected by other color criteria.

A CONSTRAINT ON QUASAR CLUSTERING AT z = 5 FROM A BINARY QUASAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGreer, Ian D.; Fan, Xiaohui; Eftekharzadeh, Sarah

2016-03-15

We report the discovery of a quasar pair at z = 5 separated by 21″. Both objects were identified as quasar candidates using simple color selection techniques applied to photometric catalogs from the Canada–France–Hawaii Telescope (CFHT) Legacy Survey (CFHTLS). Spectra obtained with the MMT present no discernible offset in redshift between the two objects; on the other hand, there are clear differences in the emission line profiles and in the multiwavelength spectral energy distributions that strongly disfavor the hypothesis that they are gravitationally lensed images of a single quasar. Both quasars are surprisingly bright given their proximity (a projected separation of ∼135more » kpc), with i = 19.4 and i = 21.4. Previous measurements of the luminosity function demonstrate that luminous quasars are extremely rare at z = 5; the existence of this pair suggests that quasars have strong small-scale clustering at high redshift. Assuming a real-space correlation function of the form ξ(r) ∝ (r/r{sub 0}){sup −2}, this discovery implies a correlation length of r{sub 0} ≳ 20h{sup −1} Mpc, consistent with a rapid strengthening of quasar clustering at high redshift as seen in previous observations and predicted by theoretical models where feedback effects are inefficient at shutting down black hole growth at high redshift.« less

The most distant, luminous, dusty star-forming galaxies: redshifts from NOEMA and ALMA spectral scans

NASA Astrophysics Data System (ADS)

Fudamoto, Y.; Ivison, R. J.; Oteo, I.; Krips, M.; Zhang, Z.-Y.; Weiss, A.; Dannerbauer, H.; Omont, A.; Chapman, S. C.; Christensen, L.; Arumugam, V.; Bertoldi, F.; Bremer, M.; Clements, D. L.; Dunne, L.; Eales, S. A.; Greenslade, J.; Maddox, S.; Martinez-Navajas, P.; Michalowski, M.; Pérez-Fournon, I.; Riechers, D.; Simpson, J. M.; Stalder, B.; Valiante, E.; van der Werf, P.

2017-12-01

We present 1.3- and/or 3-mm continuum images and 3-mm spectral scans, obtained using Northern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter Array (ALMA), of 21 distant, dusty, star-forming galaxies. Our sample is a subset of the galaxies selected by Ivison et al. on the basis of their extremely red far-infrared (far-IR) colours and low Herschel flux densities; most are thus expected to be unlensed, extraordinarily luminous starbursts at z ≳ 4, modulo the considerable cross-section to gravitational lensing implied by their redshift. We observed 17 of these galaxies with NOEMA and four with ALMA, scanning through the 3-mm atmospheric window. We have obtained secure redshifts for seven galaxies via detection of multiple CO lines, one of them a lensed system at z = 6.027 (two others are also found to be lensed); a single emission line was detected in another four galaxies, one of which has been shown elsewhere to lie at z = 4.002. Where we find no spectroscopic redshifts, the galaxies are generally less luminous by 0.3-0.4 dex, which goes some way to explaining our failure to detect line emission. We show that this sample contains the most luminous known star-forming galaxies. Due to their extreme star-formation activity, these galaxies will consume their molecular gas in ≲ 100 Myr, despite their high molecular gas masses, and are therefore plausible progenitors of the massive, 'red-and-dead' elliptical galaxies at z ≈ 3.

Perspectives on Gamma-Ray Burst Physics and Cosmology with Next Generation Facilities

NASA Astrophysics Data System (ADS)

Yuan, Weimin; Amati, Lorenzo; Cannizzo, John K.; Cordier, Bertrand; Gehrels, Neil; Ghirlanda, Giancarlo; Götz, Diego; Produit, Nicolas; Qiu, Yulei; Sun, Jianchao; Tanvir, Nial R.; Wei, Jianyan; Zhang, Chen

2016-12-01

High-redshift Gamma-Ray Bursts (GRBs) beyond redshift {˜}6 are potentially powerful tools to probe the distant early Universe. Their detections in large numbers and at truly high redshifts call for the next generation of high-energy wide-field instruments with unprecedented sensitivity at least one order of magnitude higher than the ones currently in orbit. On the other hand, follow-up observations of the afterglows of high-redshift GRBs and identification of their host galaxies, which would be difficult for the currently operating telescopes, require new, extremely large facilities of at multi-wavelengths. This chapter describes future experiments that are expected to advance this exciting field, both being currently built and being proposed. The legacy of Swift will be continued by SVOM, which is equipped with a set of space-based multi-wavelength instruments as well as and a ground segment including a wide angle camera and two follow-up telescopes. The established Lobster-eye X-ray focusing optics provides a promising technology for the detection of faint GRBs at very large distances, based on which the THESEUS, Einstein Probe and other mission concepts have been proposed. Follow-up observations and exploration of the reionization era will be enabled by large facilities such as SKA in the radio, the 30 m class telescopes in the optical/near-IR, and the space-borne WFIRST and JWST in the optical/near-IR/mid-IR. In addition, the X-ray and γ-ray polarization experiment POLAR is also introduced.

Dark-ages reionization and galaxy formation simulation-XI. Clustering and halo masses of high redshift galaxies

NASA Astrophysics Data System (ADS)

Park, Jaehong; Kim, Han-Seek; Liu, Chuanwu; Trenti, Michele; Duffy, Alan R.; Geil, Paul M.; Mutch, Simon J.; Poole, Gregory B.; Mesinger, Andrei; Wyithe, J. Stuart B.

2017-12-01

We investigate the clustering properties of Lyman-break galaxies (LBGs) at z ∼ 6 - 8. Using the semi-analytical model MERAXES constructed as part of the dark-ages reionization and galaxy-formation observables from numerical simulation (DRAGONS) project, we predict the angular correlation function (ACF) of LBGs at z ∼ 6 - 8. Overall, we find that the predicted ACFs are in good agreement with recent measurements at z ∼ 6 and z ∼ 7.2 from observations consisting of the Hubble eXtreme Deep Field, the Hubble Ultra Deep Field and cosmic sssembly near-infrared deep extragalactic legacy survey field. We confirm the dependence of clustering on luminosity, with more massive dark matter haloes hosting brighter galaxies, remains valid at high redshift. The predicted galaxy bias at fixed luminosity is found to increase with redshift, in agreement with observations. We find that LBGs of magnitude MAB(1600) < -19.4 at 6 ≲ z ≲ 8 reside in dark matter haloes of mean mass ∼1011.0-1011.5 M⊙, and this dark matter halo mass does not evolve significantly during reionisation.

Deep Keck u-Band Imaging of the Hubble Ultra Deep Field: A Catalog of z ~ 3 Lyman Break Galaxies

NASA Astrophysics Data System (ADS)

Rafelski, Marc; Wolfe, Arthur M.; Cooke, Jeff; Chen, Hsiao-Wen; Armandroff, Taft E.; Wirth, Gregory D.

2009-10-01

We present a sample of 407 z ~ 3 Lyman break galaxies (LBGs) to a limiting isophotal u-band magnitude of 27.6 mag in the Hubble Ultra Deep Field. The LBGs are selected using a combination of photometric redshifts and the u-band drop-out technique enabled by the introduction of an extremely deep u-band image obtained with the Keck I telescope and the blue channel of the Low Resolution Imaging Spectrometer. The Keck u-band image, totaling 9 hr of integration time, has a 1σ depth of 30.7 mag arcsec-2, making it one of the most sensitive u-band images ever obtained. The u-band image also substantially improves the accuracy of photometric redshift measurements of ~50% of the z ~ 3 LBGs, significantly reducing the traditional degeneracy of colors between z ~ 3 and z ~ 0.2 galaxies. This sample provides the most sensitive, high-resolution multi-filter imaging of reliably identified z ~ 3 LBGs for morphological studies of galaxy formation and evolution and the star formation efficiency of gas at high redshift.

The Constant Average Relationship Between Dust-obscured Star Formation and Stellar Mass from z=0 to z=2.5

NASA Astrophysics Data System (ADS)

Whitaker, Katherine E.; Pope, Alexandra; Cybulski, Ryan; Casey, Caitlin M.; Popping, Gergo; Yun, Min; 3D-HST Collaboration

2018-01-01

The total star formation budget of galaxies consists of the sum of the unobscured star formation, as observed in the rest-frame ultraviolet (UV), together with the obscured component that is absorbed and re-radiated by dust grains in the infrared. We explore how the fraction of obscured star formation depends (SFR) and stellar mass for mass-complete samples of galaxies at 0 < z < 2.5. We combine GALEX and WISE photometry for SDSS-selected galaxies with the 3D-HST treasury program and Spitzer/MIPS 24μm photometry in the well-studied 5 extragalactic CANDELS fields. We find a strong dependence of the fraction of obscured star formation (f_obscured=SFR_IR/SFR_UV+IR) on stellar mass, with remarkably little evolution in this fraction with redshift out to z=2.5. 50% of star formation is obscured for galaxies with log(M/M⊙)=9.4 although unobscured star formation dominates the budget at lower masses, there exists a tail of low mass extremely obscured star-forming galaxies at z > 1. For log(M/M⊙)>10.5, >90% of star formation is obscured at all redshifts. We also show that at fixed total SFR, f_obscured is lower at higher redshift. At fixed mass, high-redshift galaxies are observed to have more compact sizes and much higher star formation rates, gas fractions and hence surface densities (implying higher dust obscuration), yet we observe no redshift evolution in f_obscured with stellar mass. This poses a challenge to theoretical models to reproduce, where the observed compact sizes at high redshift seem in tension with lower dust obscuration.

The Constant Average Relationship between Dust-obscured Star Formation and Stellar Mass from z = 0 to z = 2.5

NASA Astrophysics Data System (ADS)

Whitaker, Katherine E.; Pope, Alexandra; Cybulski, Ryan; Casey, Caitlin M.; Popping, Gergö; Yun, Min S.

2017-12-01

The total star formation budget of galaxies consists of the sum of the unobscured star formation, as observed in the rest-frame ultraviolet (UV), together with the obscured component that is absorbed and re-radiated by dust grains in the infrared. We explore how the fraction of obscured star formation depends on stellar mass for mass-complete samples of galaxies at 0< z< 2.5. We combine GALEX and WISE photometry for SDSS-selected galaxies with the 3D-HST treasury program and Spitzer/MIPS 24 μm photometry in the well-studied five extragalactic Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) fields. We find a strong dependence of the fraction of obscured star formation (f obscured = SFRIR/SFRUV+IR) on stellar mass, with remarkably little evolution in this fraction with redshift out to z = 2.5. 50% of star formation is obscured for galaxies with log(M/M ⊙) = 9.4 although unobscured star formation dominates the budget at lower masses, there exists a tail of low-mass, extremely obscured star-forming galaxies at z> 1. For log(M/M ⊙) > 10.5, >90% of star formation is obscured at all redshifts. We also show that at fixed total SFR, {f}{obscured} is lower at higher redshift. At fixed mass, high-redshift galaxies are observed to have more compact sizes and much higher star formation rates, gas fractions, and hence surface densities (implying higher dust obscuration), yet we observe no redshift evolution in {f}{obscured} with stellar mass. This poses a challenge to theoretical models, where the observed compact sizes at high redshift seem in tension with lower dust obscuration.

Redshift measurement of Fermi blazars for the Cherenkov telescope array

NASA Astrophysics Data System (ADS)

Pita, S.; Goldoni, P.; Boisson, C.; Cotter, G.; Lefaucheur, J.; Lenain, J.-P.; Lindfors, E.; Williams, D. A.

2017-01-01

Blazars are active galactic nuclei, and the most numerous High Energy (HE) and Very High Energy (VHE) γ-ray emitters. Their optical emission is often dominated by non-thermal, and, in the case of BL Lacs, featureless continuum radiation. This makes the determination of their redshift extremely difficult. Indeed, as of today only about 50% of γ-ray blazars have a measured spectroscopic redshift. The knowledge of redshift is fundamental because it allows the precise modeling of the VHE emission and also of its interaction with the extragalactic background light (EBL). The beginning of the Cherenkov Telescope Array (CTA) operations in the near future will allow the detection of several hundreds of new blazars. Using the Fermi catalogue of sources above 50 GeV (2FHL), we performed simulations which indicate that a significant fraction of the 2FHL blazars detectable by CTA will not have a measured redshift. As a matter of fact, the organization of observing campaigns to measure the redshift of these blazars has been recognized as a necessary support for the AGN Key Science Project of CTA. We are planning such an observing campaign. In order to optimize our chances of success, we will perform preliminary deep imaging observations aimed at detecting or setting upper limits to the host galaxy. We will then take spectra of the candidates with the brightest host galaxies. Taking advantage of the recent success of an X-shooter GTO observing campaign, these observations will be different with respect to previous ones due to the use of higher resolution spectrographs and of 8 meter class telescopes. We are starting to submit proposals for these observations. In this paper we briefly describe how candidates are selected and the corresponding observation program.

PROSPECTS FOR MEASURING THE MASS OF BLACK HOLES AT HIGH REDSHIFTS WITH RESOLVED KINEMATICS USING GRAVITATIONAL LENSING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hezaveh, Yashar D.

2014-08-20

Application of the most robust method of measuring black hole masses, spatially resolved kinematics of gas and stars, is presently limited to nearby galaxies. The Atacama Large Millimeter/sub-millimeter Array (ALMA) and 30m class telescopes (the Thirty Meter Telescope, the Giant Magellan Telescope, and the European Extremely Large Telescope) with milli-arcsecond resolution are expected to extend such measurements to larger distances. Here, we study the possibility of exploiting the angular magnification provided by strong gravitational lensing to measure black hole masses at high redshifts (z ∼ 1-6), using resolved gas kinematics with these instruments. We show that in ∼15% and ∼20%more » of strongly lensed galaxies, the inner 25 and 50 pc could be resolved, allowing the mass of ≳ 10{sup 8} M {sub ☉} black holes to be dynamically measured with ALMA, if moderately bright molecular gas is present at these small radii. Given the large number of strong lenses discovered in current millimeter surveys and future optical surveys, this fraction could constitute a statistically significant population for studying the evolution of the M-σ relation at high redshifts.« less

THINK OUTSIDE THE COLOR BOX: PROBABILISTIC TARGET SELECTION AND THE SDSS-XDQSOQUASAR TARGETING CATALOG

DOE Office of Scientific and Technical Information (OSTI.GOV)

BOVY, J.; Sheldon, E.; Hennawi, J.F.

2011-03-10

We present the SDSS-XDQSO quasar targeting catalog for efficient flux-based quasar target selection down to the faint limit of the Sloan Digital Sky Survey (SDSS) catalog, even at medium redshifts (2.5 {approx}< z {approx}< 3) where the stellar contamination is significant. We build models of the distributions of stars and quasars in flux space down to the flux limit by applying the extreme-deconvolution method to estimate the underlying density. We convolve this density with the flux uncertainties when evaluating the probability that an object is a quasar. This approach results in a targeting algorithm that is more principled, more efficient,more » and faster than other similar methods. We apply the algorithm to derive low-redshift (z < 2.2), medium-redshift (2.2 {le} z {le} 3.5), and high-redshift (z > 3.5) quasar probabilities for all 160,904,060 point sources with dereddened i-band magnitude between 17.75 and 22.45 mag in the 14,555 deg{sup 2} of imaging from SDSS Data Release 8. The catalog can be used to define a uniformly selected and efficient low- or medium-redshift quasar survey, such as that needed for the SDSS-III's Baryon Oscillation Spectroscopic Survey project. We show that the XDQSO technique performs as well as the current best photometric quasar-selection technique at low redshift, and outperforms all other flux-based methods for selecting the medium-redshift quasars of our primary interest. We make code to reproduce the XDQSO quasar target selection publicly available.« less

OT2_eegami_6: SPIRE Snapshot Survey II: Using SPT/CODEX Massive Clusters as Powerful Gravitational Lenses

NASA Astrophysics Data System (ADS)

Egami, E.

2011-09-01

On the extragalactic side, one of the most remarkable results coming out of Herschel is the discovery of extremely bright (>100 mJy in the SPIRE bands) gravitationally lensed galaxies. The great sensitivity and mapping speed of SPIRE have enabled us to find these rare extraordinary objects. What is truly exciting about these bright lensed galaxies is that they enable a variety of detailed multi-wavelength follow-up observations, shedding new light on the physical properties of these high-redshift sources. In this regard, our OT1 program, "SPIRE Snapshot Survey of Massive Galaxy Clusters" turned out to be a great success. After imaging ~50 galaxies out of 279 in the program, we have already found two spectacularly bright lensed galaxies, one of which is at a redshift of 4.69. This type of cluster-lensed sources are not only bright but also spatially stretched over a large scale, so ALMA (or NOEMA in the north) is likely to be able to study them at the level of individual GMCs. Such studies will open up a new frontier in the study of high-redshift galaxies. Here, we propose to extend this highly efficient and effective survey of gravitationally lensed galaxies to another 353 clusters carefully chosen from the SPT and CODEX cluster samples. These samples contain newly discovered high-redshift (z>0.3) massive (>3-4e14 Msun) clusters, which can be used as powerful gravitational lenses to magnify sources at high redshift. With the OT1 and OT2 surveys together, we expect to find ~20 highly magnified SPIRE sources with exceptional brightnesses (assuming a discovery rate of ~1/30). Such a unique sample of extraordinary objects will enable a variety of follow-up sciences, and will therefore remain as a great legacy of the Herschel mission for years to come.

An optical view of extragalactic gamma-ray emitters

NASA Astrophysics Data System (ADS)

Paiano, Simona; Falomo, Renato; Landoni, Marco; Treves, Aldo; Scarpa, Riccardo

2017-11-01

The Fermi Gamma-ray Observatory discovered about a thousand extragalactic sources emitting energy from 100 MeV to 100 GeV. The majority of these sources belong to the class of blazars characterized by a quasi-featureless optical spectrum (BL Lac Objects). This hampers the determination of their redshift and therefore hinders the characterization of this class of objects. To investigate the nature of these sources and to determine their redshift, we are carrying out an extensive campaign at the 10m Gran Telescopio Canarias to secure high signal-to-noise ratio optical spectra. These observations allow us to confirm the blazar nature of the targets, to find new redshifts or to set stringent limits on the redshift based on the minimum equivalent width of absorption features expected from their host galaxy, assuming it is a massive elliptical galaxy.These results are of importance for the multi-frequencies emission models of the blazars, to test their extreme physics, to shed light on their cosmic evolution and abundance in the far Universe.These gamma emitters are also of great importance for the characterization of the extragalactic background light through the absorption by the IR-optical background photons.

HST Imaging of the Eye of Horus, a Double Source Plane Gravitational Lens

NASA Astrophysics Data System (ADS)

Wong, Kenneth

2017-08-01

Double source plane (DSP) gravitational lenses are extremely rare alignments of a massive lens galaxy with two background sources at distinct redshifts. The presence of two source planes provides important constraints on cosmology and galaxy structure beyond that of typical lens systems by breaking degeneracies between parameters that vary with source redshift. While these systems are extremely valuable, only a handful are known. We have discovered the first DSP lens, the Eye of Horus, in the Hyper Suprime-Cam survey and have confirmed both source redshifts with follow-up spectroscopy, making this the only known DSP lens with both source redshifts measured. Furthermore, the brightest image of the most distant source (S2) is split into a pair of images by a mass component that is undetected in our ground-based data, suggesting the presence of a satellite or line-of-sight galaxy causing this splitting. In order to better understand this system and use it for cosmology and galaxy studies, we must construct an accurate lens model, accounting for the lensing effects of both the main lens galaxy and the intermediate source. Only with deep, high-resolution imaging from HST/ACS can we accurately model this system. Our proposed multiband imaging will clearly separate out the two sources by their distinct colors, allowing us to use their extended surface brightness distributions as constraints on our lens model. These data may also reveal the satellite galaxy responsible for the splitting of the brightest image of S2. With these observations, we will be able to take full advantage of the wealth of information provided by this system.

Transition Region and Chromospheric Signatures of Impulsive Heating Events. I. Observations

NASA Astrophysics Data System (ADS)

Warren, Harry P.; Reep, Jeffrey W.; Crump, Nicholas A.; Simões, Paulo J. A.

2016-09-01

We exploit the high spatial resolution and high cadence of the Interface Region Imaging Spectrograph (IRIS) to investigate the response of the transition region and chromosphere to energy deposition during a small flare. Simultaneous observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager provide constraints on the energetic electrons precipitating into the flare footpoints, while observations of the X-Ray Telescope, Atmospheric Imaging Assembly, and Extreme Ultraviolet Imaging Spectrometer (EIS) allow us to measure the temperatures and emission measures from the resulting flare loops. We find clear evidence for heating over an extended period on the spatial scale of a single IRIS pixel. During the impulsive phase of this event, the intensities in each pixel for the Si IV 1402.770 Å, C II 1334.535 Å, Mg II 2796.354 Å, and O I 1355.598 Å emission lines are characterized by numerous small-scale bursts typically lasting 60 s or less. Redshifts are observed in Si IV, C II, and Mg II during the impulsive phase. Mg II shows redshifts during the bursts and stationary emission at other times. The Si IV and C II profiles, in contrast, are observed to be redshifted at all times during the impulsive phase. These persistent redshifts are a challenge for one-dimensional hydrodynamic models, which predict only short-duration downflows in response to impulsive heating. We conjecture that energy is being released on many small-scale filaments with a power-law distribution of heating rates.

Simulating the detection and classification of high-redshift supernovae with HARMONI on the ELT

NASA Astrophysics Data System (ADS)

Bounissou, S.; Thatte, N.; Zieleniewski, S.; Houghton, R. C. W.; Tecza, M.; Hook, I.; Neichel, B.; Fusco, T.

2018-02-01

We present detailed simulations of integral field spectroscopic observations of a supernova in a host galaxy at z ˜ 3, as observed by the HARMONI spectrograph on the Extremely Large Telescope, asssisted by laser tomographic adaptive optics. The goal of the simulations, using the HSIM simulation tool, is to determine whether HARMONI can discern the supernova Type from spectral features in the supernova spectrum. We find that in a 3 hour observation, covering the near-infrared H and K bands, at a spectral resolving power of ˜3000, and using the 20×20 mas spaxel scale, we can classify supernova Type Ia and their redshift robustly up to 80 days past maximum light (20 days in the supernova rest frame). We show that HARMONI will provide spectra at z ˜ 3 that are of comparable (or better) quality to the best spectra we can currently obtain at z ˜ 1, thus allowing studies of cosmic expansion rates to be pushed to substantially higher redshifts.

The clustering evolution of distant red galaxies in the GOODS-MUSIC sample

NASA Astrophysics Data System (ADS)

Grazian, A.; Fontana, A.; Moscardini, L.; Salimbeni, S.; Menci, N.; Giallongo, E.; de Santis, C.; Gallozzi, S.; Nonino, M.; Cristiani, S.; Vanzella, E.

2006-07-01

Aims.We study the clustering properties of Distant Red Galaxies (DRGs) to test whether they are the progenitors of local massive galaxies. Methods.We use the GOODS-MUSIC sample, a catalog of ~3000 Ks-selected galaxies based on VLT and HST observation of the GOODS-South field with extended multi-wavelength coverage (from 0.3 to 8~μm) and accurate estimates of the photometric redshifts to select 179 DRGs with J-Ks≥ 1.3 in an area of 135 sq. arcmin.Results.We first show that the J-Ks≥ 1.3 criterion selects a rather heterogeneous sample of galaxies, going from the targeted high-redshift luminous evolved systems, to a significant fraction of lower redshift (1

Planck intermediate results: XXXIX. The Planck list of high-redshift source candidates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ade, P. A. R.; Aghanim, N.; Arnaud, M.

The Planck mission, thanks to its large frequency range and all-sky coverage, has a unique potential for systematically detecting the brightest, and rarest, submillimetre sources on the sky, including distant objects in the high-redshift Universe traced by their dust emission. In this paper, a novel method, based on a component-separation procedure using a combination of Planck and IRAS data, has been validated and characterized on numerous simulations, and applied to select the most luminous cold submillimetre sources with spectral energy distributions peaking between 353 and 857 GHz at 5' resolution. A total of 2151 Planck high-z source candidates (the PHZ)more » have been detected in the cleanest 26% of the sky, with flux density at 545 GHz above 500 mJy. Embedded in the cosmic infrared background close to the confusion limit, these high-z candidates exhibit colder colours than their surroundings, consistent with redshifts z > 2, assuming a dust temperature of T xgal = 35 K and a spectral index of β xgal = 1.5. Exhibiting extremely high luminosities, larger than 10 14L ⊙, the PHZ objects may be made of multiple galaxies or clumps at high redshift, as suggested by a first statistical analysis based on a comparison with number count models. Furthermore, first follow-up observations obtained from optical to submillimetre wavelengths, which can be found in companion papers, have confirmed that this list consists of two distinct populations. A small fraction (around 3%) of the sources have been identified as strongly gravitationally lensed star-forming galaxies at redshift 2 to 4, while the vast majority of the PHZ sources appear as overdensities of dusty star-forming galaxies, having colours consistent with being at z > 2, and may be considered as proto-cluster candidates. The PHZ provides an original sample, which is complementary to the Planck Sunyaev-Zeldovich Catalogue (PSZ2); by extending the population of virialized massive galaxy clusters detected below z < 1.5 through their SZ signal to a population of sources at z > 1.5, the PHZ may contain the progenitors of today’s clusters. Therefore the Planck list of high-redshift source candidates opens a new window on the study of the early stages of structure formation, particularly understanding the intensively star-forming phase at high-z.« less

Planck intermediate results: XXXIX. The Planck list of high-redshift source candidates

DOE PAGES

Ade, P. A. R.; Aghanim, N.; Arnaud, M.; ...

2016-12-12

The Planck mission, thanks to its large frequency range and all-sky coverage, has a unique potential for systematically detecting the brightest, and rarest, submillimetre sources on the sky, including distant objects in the high-redshift Universe traced by their dust emission. In this paper, a novel method, based on a component-separation procedure using a combination of Planck and IRAS data, has been validated and characterized on numerous simulations, and applied to select the most luminous cold submillimetre sources with spectral energy distributions peaking between 353 and 857 GHz at 5' resolution. A total of 2151 Planck high-z source candidates (the PHZ)more » have been detected in the cleanest 26% of the sky, with flux density at 545 GHz above 500 mJy. Embedded in the cosmic infrared background close to the confusion limit, these high-z candidates exhibit colder colours than their surroundings, consistent with redshifts z > 2, assuming a dust temperature of T xgal = 35 K and a spectral index of β xgal = 1.5. Exhibiting extremely high luminosities, larger than 10 14L ⊙, the PHZ objects may be made of multiple galaxies or clumps at high redshift, as suggested by a first statistical analysis based on a comparison with number count models. Furthermore, first follow-up observations obtained from optical to submillimetre wavelengths, which can be found in companion papers, have confirmed that this list consists of two distinct populations. A small fraction (around 3%) of the sources have been identified as strongly gravitationally lensed star-forming galaxies at redshift 2 to 4, while the vast majority of the PHZ sources appear as overdensities of dusty star-forming galaxies, having colours consistent with being at z > 2, and may be considered as proto-cluster candidates. The PHZ provides an original sample, which is complementary to the Planck Sunyaev-Zeldovich Catalogue (PSZ2); by extending the population of virialized massive galaxy clusters detected below z < 1.5 through their SZ signal to a population of sources at z > 1.5, the PHZ may contain the progenitors of today’s clusters. Therefore the Planck list of high-redshift source candidates opens a new window on the study of the early stages of structure formation, particularly understanding the intensively star-forming phase at high-z.« less

C III] Emission in Star-forming Galaxies Near and Far

NASA Astrophysics Data System (ADS)

Rigby, J. R.; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Wuyts, E.; Dahle, H.; Johnson, T.; Peña-Guerrero, M.

2015-11-01

We measure [C iii] 1907, C iii] 1909 Å emission lines in 11 gravitationally lensed star-forming galaxies at z ˜ 1.6-3, finding much lower equivalent widths than previously reported for fainter lensed galaxies. While it is not yet clear what causes some galaxies to be strong C iii] emitters, C iii] emission is not a universal property of distant star-forming galaxies. We also examine C iii] emission in 46 star-forming galaxies in the local universe, using archival spectra from GHRS, FOS, and STIS on HST and IUE. Twenty percent of these local galaxies show strong C iii] emission, with equivalent widths < -5 Å. Three nearby galaxies show C iii] emission equivalent widths as large as the most extreme emitters yet observed in the distant universe; all three are Wolf-Rayet galaxies. At all redshifts, strong C iii] emission may pick out low-metallicity galaxies experiencing intense bursts of star formation. Such local C iii] emitters may shed light on the conditions of star formation in certain extreme high-redshift galaxies.

C III] Emission in Star-Forming Galaxies Near and Far

NASA Technical Reports Server (NTRS)

Rigby, J, R.; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Wuyts, E.; Dahle, H.; Johnson, T.; Pena-Guerrero, M.

2015-01-01

We measure C III Lambda Lambda 1907, 1909 Angstrom emission lines in eleven gravitationally-lensed star-forming galaxies at zeta at approximately 1.6-3, finding much lower equivalent widths than previously reported for fainter lensed galaxies (Stark et al. 2014). While it is not yet clear what causes some galaxies to be strong C III] emitters, C III] emission is not a universal property of distant star-forming galaxies. We also examine C III] emission in 46 star-forming galaxies in the local universe, using archival spectra from GHRS, FOS, and STIS on HST, and IUE. Twenty percent of these local galaxies show strong C III] emission, with equivalent widths less than -5 Angstrom. Three nearby galaxies show C III] emission equivalent widths as large as the most extreme emitters yet observed in the distant universe; all three are Wolf-Rayet galaxies. At all redshifts, strong C III] emission may pick out low-metallicity galaxies experiencing intense bursts of star formation. Such local C III] emitters may shed light on the conditions of star formation in certain extreme high-redshift galaxies.

Constraints on cold dark matter theories from observations of massive x-ray-luminous clusters of galaxies at high redshift

NASA Technical Reports Server (NTRS)

Luppino, G. A.; Gioia, I. M.

1995-01-01

During the course of a gravitational lensing survey of distant, X-ray selected Einstein Observatory Extended Medium Sensitivity Survey (EMSS) clusters of galaxies, we have studied six X-ray-luminous (L(sub x) greater than 5 x 10(exp 44)(h(sub 50)(exp -2))ergs/sec) clusters at redshifts exceeding z = 0.5. All of these clusters are apparently massive. In addition to their high X-ray luminosity, two of the clusters at z approximately 0.6 exhibit gravitationally lensed arcs. Furthermore, the highest redshift cluster in our sample, MS 1054-0321 at z = 0.826, is both extremely X-ray luminous (L(sub 0.3-3.5keV)=9.3 x 10(exp 44)(h(sub 50)(exp -2))ergs/sec) and exceedingly rich with an optical richness comparable to an Abell Richness Class 4 cluster. In this Letter, we discuss the cosmological implications of the very existence of these clusters for hierarchical structure formation theories such as standard Omega = 1 CDM (cold dark matter), hybrid Omega = 1 C + HDM (hot dark matter), and flat, low-density Lambda + CDM models.

Young Galaxy Candidates in the Hubble Frontier Fields. IV. MACS J1149.5+2223

NASA Astrophysics Data System (ADS)

Zheng, Wei; Zitrin, Adi; Infante, Leopoldo; Laporte, Nicolas; Huang, Xingxing; Moustakas, John; Ford, Holland C.; Shu, Xinwen; Wang, Junxian; Diego, Jose M.; Bauer, Franz E.; Troncoso Iribarren, Paulina; Broadhurst, Tom; Molino, Alberto

2017-02-01

We search for high-redshift dropout galaxies behind the Hubble Frontier Fields (HFF) galaxy cluster MACS J1149.5+2223, a powerful cosmic lens that has revealed a number of unique objects in its field. Using the deep images from the Hubble and Spitzer space telescopes, we find 11 galaxies at z > 7 in the MACS J1149.5+2223 cluster field, and 11 in its parallel field. The high-redshift nature of the bright z ≃ 9.6 galaxy MACS1149-JD, previously reported by Zheng et al., is further supported by non-detection in the extremely deep optical images from the HFF campaign. With the new photometry, the best photometric redshift solution for MACS1149-JD reduces slightly to z = 9.44 ± 0.12. The young galaxy has an estimated stellar mass of (7+/- 2)× {10}8 {M}⊙ , and was formed at z={13.2}-1.6+1.9 when the universe was ≈300 Myr old. Data available for the first four HFF clusters have already enabled us to find faint galaxies to an intrinsic magnitude of {M}{UV}≃ -15.5, approximately a factor of 10 deeper than the parallel fields.

Probing galaxy growth through metallicity scaling relations over the past 12 Gyr of cosmic history

NASA Astrophysics Data System (ADS)

Sanders, Ryan; MOSDEF team

2018-01-01

A primary goal of galaxy evolution studies is to understand the processes governing the growth of the baryonic content of galaxies over cosmic history. Observations of galaxy metallicity scaling relations and their evolution with redshift, in combination with chemical evolution models, provide unique insight into the interplay between star formation, gas accretion, and feedback/outflows. I present measurements of the stellar mass-gas phase metallicity relation and its evolution over the past 12 Gyr from z~0 to z~3.5, utilizing data from the Mosfire Deep Evolution Field survey that uniquely provides rest-frame optical spectra of >1000 uniformly-selected galaxies at z=1.3-3.8. We find evolution towards lower metallicity at fixed stellar mass with increasing redshift that is consistent with current cosmological simulations including chemical evolution, with a large evolution of ~0.3 dex from z~0 to z~2.5 and minor evolution of <0.1 dex from z~2.5 to z~3.5. We unambiguously confirm the existence of star-formation rate dependence of the mass-metallicity relation at high redshift for the first time. A clear view of cosmic chemical evolution requires accounting for systematic biases in galaxy metallicity measurements at both low and high redshifts. We use a set of empirically-based models to correct for diffuse ionized gas contamination that biases metallicity estimates from z~0 global galaxy spectra. Evolving properties of ionized gas such as electron density, ionization parameter, hardness of the ionizing spectrum, and chemical abundance patterns may render locally-calibrated metallicity estimators unreliable at high redshifts. Using strong-line ratios alone, it is extremely difficult to break degenerate solutions between pure metallicity evolution and additional evolution of the ionization parameter and/or shape of the ionizing spectrum. Temperature-sensitive auroral-line measurements provide a way to directly and independently measure metallicities, breaking these degeneracies. We present measurements of auroral [OIII]4363 and direct-method metallicities at z>2, and discuss the potential of current and next-generation observational facilities to obtain statistical auroral-line samples at high redshifts.

TEMPLATES: Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star formation

NASA Astrophysics Data System (ADS)

Spilker, Justin; Rigby, Jane R.; Vieira, Joaquin D.; TEMPLATES Team

2018-06-01

TEMPLATES is a JWST Early Release Science program designed to produce high signal-to-noise imaging and IFU spectroscopic data cubes for four gravitationally lensed galaxies at high redshift. The program will spatially resolve the star formation in galaxies across the peak of cosmic star formation in an extinction-robust manner. Lensing magnification pushes JWST to the highest spatial resolutions possible at these redshifts, to map the key spectral diagnostics of star formation and dust extinction: H-alpha, Pa-alpha, and 3.3um PAH emission within individual distant galaxies. Our targets are among the brightest, best-characterized lensed systems known, and include both UV-bright 'normal' galaxies and heavily dust-obscured submillimeter galaxies, at a range of stellar masses and luminosities. I will describe the scientific motivation for this program, detail the targeted galaxies, and describe the planned data products to be delivered to the community in advance of JWST Cycle 2.

Extreme emission-line galaxies out to z ~ 1 in zCOSMOS. I. Sample and characterization of global properties

NASA Astrophysics Data System (ADS)

Amorín, R.; Pérez-Montero, E.; Contini, T.; Vílchez, J. M.; Bolzonella, M.; Tasca, L. A. M.; Lamareille, F.; Zamorani, G.; Maier, C.; Carollo, C. M.; Kneib, J.-P.; Le Fèvre, O.; Lilly, S.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Bardelli, S.; Bongiorno, A.; Caputi, K.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Iovino, A.; Kampczyk, P.; Knobel, C.; Kovač, K.; Le Borgne, J.-F.; Le Brun, V.; Mignoli, M.; Pellò, R.; Peng, Y.; Presotto, V.; Ricciardelli, E.; Silverman, J. D.; Tanaka, M.; Tresse, L.; Vergani, D.; Zucca, E.

2015-06-01

Context. The study of large and representative samples of low-metallicity star-forming galaxies at different cosmic epochs is of great interest to the detailed understanding of the assembly history and evolution of low-mass galaxies. Aims: We present a thorough characterization of a large sample of 183 extreme emission-line galaxies (EELGs) at redshift 0.11 ≤ z ≤ 0.93 selected from the 20k zCOSMOS bright survey because of their unusually large emission line equivalent widths. Methods: We use multiwavelength COSMOS photometry, HST-ACS I-band imaging, and optical zCOSMOS spectroscopy to derive the main global properties of star-forming EELGs, such as sizes, stellar masses, star formation rates (SFR), and reliable oxygen abundances using both "direct" and "strong-line" methods. Results: The EELGs are extremely compact (r50 ~ 1.3 kpc), low-mass (M∗ ~ 107-1010 M⊙) galaxies forming stars at unusually high specific star formation rates (sSFR ≡ SFR/M⋆ up to 10-7 yr-1) compared to main sequence star-forming galaxies of the same stellar mass and redshift. At rest-frame UV wavelengths, the EELGs are luminous and show high surface brightness and include strong Lyα emitters, as revealed by GALEX spectroscopy. We show that zCOSMOS EELGs are high-ionization, low-metallicity systems, with median 12+log (O/H) = 8.16 ± 0.21 (0.2 Z⊙) including a handful of extremely metal-deficient (<0.1 Z⊙) EELGs. While ~80% of the EELGs show non-axisymmetric morphologies, including clumpy and cometary or tadpole galaxies, we find that ~29% of them show additional low-surface-brightness features, which strongly suggests recent or ongoing interactions. As star-forming dwarfs in the local Universe, EELGs are most often found in relative isolation. While only very few EELGs belong to compact groups, almost one third of them are found in spectroscopically confirmed loose pairs or triplets. Conclusions: The zCOSMOS EELGs are galaxies caught in a transient and probably early period of their evolution, where they are efficiently building up a significant fraction of their present-day stellar mass in an ongoing, galaxy-wide starburst. Therefore, the EELGs constitute an ideal benchmark for comparison studies between low- and high-redshift low-mass star-forming galaxies. Full Tables 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A105

Vigorous star formation in a bulge-dominated extremely red object at z= 1.34

NASA Astrophysics Data System (ADS)

Cotter, Garret; Simpson, Chris; Bolton, Rosemary C.

2005-06-01

We present near-infrared (near-IR) spectroscopy of three extremely red objects (EROs) using the OHS/CISCO spectrograph at the Subaru Telescope. One target exhibits a strong emission line, which we identify as Hα at z= 1.34. Using new and existing ground-based optical and near-IR imaging, and archival Hubble Space Telescope imaging, we argue that this target is essentially an elliptical galaxy, with an old stellar population of around 4 × 1011Msolar, but having a dust-enshrouded star-forming component with a star formation rate (SFR) of some 50-100Msolar yr-1. There is no evidence that the galaxy contains an active galactic nucleus. Analysis of a further two targets, which do not exhibit any features in our near-IR spectra, suggests that one is a quiescent galaxy in the redshift range 1.2 < z < 1.6, but that the other cannot be conclusively categorized as either star-forming or quiescent. Even though our first target has many of the properties of an old elliptical, the ongoing star formation means that it cannot have formed all of its stellar population at high redshift. While we cannot infer any robust values for the SFR in ellipticals at z > 1 from this one object, we argue that the presence of an object with such a high SFR in such a small sample suggests that a non-negligible fraction of the elliptical galaxy population may have formed a component of their stellar population at redshifts z~ 1-2. We suggest that this is evidence for ongoing star formation in the history of elliptical galaxies.

The nature of ultra-massive lens galaxies

NASA Astrophysics Data System (ADS)

Canameras, Raoul

2017-08-01

During the past decade, strong gravitational lensing analyses have contributed tremendously to the characterization of the inner properties of massive early-type galaxies, beyond the local Universe. Here we intend to extend studies of this kind to the most massive lens galaxies known to date, well outside the mass limits investigated by previous lensing surveys. This will allow us to probe the physics of the likely descendants of the most violent episodes of star formation and of the compact massive galaxies at high redshift. We propose WFC3 imaging (F438W and F160W) of four extremely massive early-type lens galaxies at z 0.5, in order to put them into context with the evolutionary trends of ellipticals as a function of mass and redshift. These systems were discovered in the SDSS and show one single main lens galaxy with a stellar mass above 1.5x10^12 Msun and large Einstein radii. Our high-resolution spectroscopic follow-up with VLT/X-shooter provides secure lens and source redshifts, between 0.3 and 0.7 and between 1.5 and 2.5, respectively, and confirm extreme stellar velocity dispersions > 400 km/s for the lenses. The excellent angular resolution of the proposed WFC3 imaging - not achievable from the ground - is the remaining indispensable piece of information to :(1) Resolve the lens structural parameters and obtain robust measurements of their stellar mass distributions,(2) Model the amount and distribution of the lens total masses and measure their M/L ratios and stellar IMF with joint strong lensing and stellar dynamics analyses,(3) Enhance our on-going lens models through the most accurate positions and morphologies of the blue multiply-imaged sources.

Quasar probabilities and redshifts from WISE mid-IR through GALEX UV photometry

NASA Astrophysics Data System (ADS)

DiPompeo, M. A.; Bovy, J.; Myers, A. D.; Lang, D.

2015-09-01

Extreme deconvolution (XD) of broad-band photometric data can both separate stars from quasars and generate probability density functions for quasar redshifts, while incorporating flux uncertainties and missing data. Mid-infrared photometric colours are now widely used to identify hot dust intrinsic to quasars, and the release of all-sky WISE data has led to a dramatic increase in the number of IR-selected quasars. Using forced photometry on public WISE data at the locations of Sloan Digital Sky Survey (SDSS) point sources, we incorporate this all-sky data into the training of the XDQSOz models originally developed to select quasars from optical photometry. The combination of WISE and SDSS information is far more powerful than SDSS alone, particularly at z > 2. The use of SDSS+WISE photometry is comparable to the use of SDSS+ultraviolet+near-IR data. We release a new public catalogue of 5537 436 (total; 3874 639 weighted by probability) potential quasars with probability PQSO > 0.2. The catalogue includes redshift probabilities for all objects. We also release an updated version of the publicly available set of codes to calculate quasar and redshift probabilities for various combinations of data. Finally, we demonstrate that this method of selecting quasars using WISE data is both more complete and efficient than simple WISE colour-cuts, especially at high redshift. Our fits verify that above z ˜ 3 WISE colours become bluer than the standard cuts applied to select quasars. Currently, the analysis is limited to quasars with optical counterparts, and thus cannot be used to find highly obscured quasars that WISE colour-cuts identify in significant numbers.

Following the Cosmic Evolution of Pristine Gas. II. The Search for Pop III–bright Galaxies

NASA Astrophysics Data System (ADS)

Sarmento, Richard; Scannapieco, Evan; Cohen, Seth

2018-02-01

Direct observational searches for Population III (Pop III) stars at high redshift are faced with the question of how to select the most promising targets for spectroscopic follow-up. To help answer this, we use a large-scale cosmological simulation, augmented with a new subgrid model that tracks the fraction of pristine gas, to follow the evolution of high-redshift galaxies and the Pop III stars they contain. We generate rest-frame ultraviolet (UV) luminosity functions for our galaxies and find that they are consistent with current z≥slant 7 observations. Throughout the redshift range 7≤slant z≤slant 15, we identify “Pop III–bright” galaxies as those with at least 75% of their flux coming from Pop III stars. While less than 1% of galaxies brighter than {m}UV,{AB}}=31.4 mag are Pop III–bright in the range 7≤slant z≤slant 8, roughly 17% of such galaxies are Pop III–bright at z = 9, immediately before reionization occurs in our simulation. Moving to z = 10, {m}UV,{AB}}=31.4 mag corresponds to larger, more luminous galaxies, and the Pop III–bright fraction falls off to 5%. Finally, at the highest redshifts, a large fraction (29% at z = 14 and 41% at z = 15) of all galaxies are Pop III–bright regardless of magnitude. While {m}UV,{AB}}=31.4 mag galaxies are extremely rare during this epoch, we find that 13% of galaxies at z = 14 are Pop III–bright with {m}UV,{AB}}≤slant 33 mag, a intrinsic magnitude within reach of the James Webb Space Telescope using lensing. Thus, we predict that the best redshift to search for luminous Pop III–bright galaxies is just before reionization, while lensing surveys for fainter galaxies should push to the highest redshifts possible.

Lyman Break Galaxies in the Hubble Ultra Deep Field through Deep U-Band Imaging

NASA Astrophysics Data System (ADS)

Rafelski, Marc; Wolfe, A. M.; Cooke, J.; Chen, H. W.; Armandroff, T. E.; Wirth, G. D.

2009-12-01

We introduce an extremely deep U-band image taken of the Hubble Ultra Deep Field (HUDF), with a one sigma depth of 30.7 mag arcsec-2 and a detection limiting magnitude of 28 mag arcsec-2. The observations were carried out on the Keck I telescope using the LRIS-B detector. The U-band image substantially improves the accuracy of photometric redshift measurements of faint galaxies in the HUDF at z=[2.5,3.5]. The U-band for these galaxies is attenuated by lyman limit absorption, allowing for more reliable selections of candidate Lyman Break Galaxies (LBGs) than from photometric redshifts without U-band. We present a reliable sample of 300 LBGs at z=[2.5,3.5] in the HUDF. Accurate redshifts of faint galaxies at z=[2.5,3.5] are needed to obtain empirical constraints on the star formation efficiency of neutral gas at high redshift. Wolfe & Chen (2006) showed that the star formation rate (SFR) density in damped Ly-alpha absorption systems (DLAs) at z=[2.5,3.5] is significantly lower than predicted by the Kennicutt-Schmidt law for nearby galaxies. One caveat to this result that we wish to test is whether LBGs are embedded in DLAs. If in-situ star formation is occurring in DLAs, we would see it as extended low surface brightness emission around LBGs. We shall use the more accurate photometric redshifts to create a sample of LBGs around which we will look for extended emission in the more sensitive and higher resolution HUDF images. The absence of extended emission would put limits on the SFR density of DLAs associated with LBGs at high redshift. On the other hand, detection of faint emission on scales large compared to the bright LBG cores would indicate the presence of in situ star formation in those DLAs. Such gas would presumably fuel the higher star formation rates present in the LBG cores.

The star-forming complex LMC-N79 as a future rival to 30 Doradus

NASA Astrophysics Data System (ADS)

Ochsendorf, Bram B.; Zinnecker, Hans; Nayak, Omnarayani; Bally, John; Meixner, Margaret; Jones, Olivia C.; Indebetouw, Remy; Rahman, Mubdi

2017-11-01

Within the early Universe, `extreme' star formation may have been the norm rather than the exception1,2. Super star clusters (with masses greater than 105 solar masses) are thought to be the modern-day analogues of globular clusters, relics of a cosmic time (redshift z ≳ 2) when the Universe was filled with vigorously star-forming systems3. The giant H ii region 30 Doradus in the Large Magellanic Cloud is often regarded as a benchmark for studies of extreme star formation4. Here, we report the discovery of a massive embedded star-forming complex spanning about 500 pc in the unexplored southwest region of the Large Magellanic Cloud, which manifests itself as a younger, embedded twin of 30 Doradus. Previously known as N79, this region has a star-formation efficiency greater than that of 30 Doradus, by a factor of about 2, as measured over the past 0.5 Myr. Moreover, at the heart of N79 lies the most luminous infrared compact source discovered with large-scale infrared surveys of the Large Magellanic Cloud and Milky Way, possibly a precursor to the central super star cluster of 30 Doradus, R136. The discovery of a nearby candidate super star cluster may provide invaluable information to understand how extreme star formation proceeds in the current and high-redshift Universe.

EVOLUTION OF GALAXIES AND THEIR ENVIRONMENTS AT z = 0.1-3 IN COSMOS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scoville, N.; Benson, A.; Fu, Hai

2013-05-01

Large-scale structures (LSSs) out to z < 3.0 are measured in the Cosmic Evolution Survey (COSMOS) using extremely accurate photometric redshifts (photoz). The K{sub s} -band-selected sample (from Ultra-Vista) is comprised of 155,954 galaxies. Two techniques-adaptive smoothing and Voronoi tessellation-are used to estimate the environmental densities within 127 redshift slices. Approximately 250 statistically significant overdense structures are identified out to z = 3.0 with shapes varying from elongated filamentary structures to more circularly symmetric concentrations. We also compare the densities derived for COSMOS with those based on semi-analytic predictions for a {Lambda}CDM simulation and find excellent overall agreement between themore » mean densities as a function of redshift and the range of densities. The galaxy properties (stellar mass, spectral energy distributions (SEDs), and star formation rates (SFRs)) are strongly correlated with environmental density and redshift, particularly at z < 1.0-1.2. Classifying the spectral type of each galaxy using the rest-frame b - i color (from the photoz SED fitting), we find a strong correlation of early-type galaxies (E-Sa) with high-density environments, while the degree of environmental segregation varies systematically with redshift out to z {approx} 1.3. In the highest density regions, 80% of the galaxies are early types at z = 0.2 compared to only 20% at z = 1.5. The SFRs and the star formation timescales exhibit clear environmental correlations. At z > 0.8, the SFR density is uniformly distributed over all environmental density percentiles, while at lower redshifts the dominant contribution is shifted to galaxies in lower density environments.« less

Planck intermediate results. XXXIX. The Planck list of high-redshift source candidates

NASA Astrophysics Data System (ADS)

Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Butler, R. C.; Calabrese, E.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombo, L. P. L.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Flores-Cacho, I.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Harrison, D. L.; Helou, G.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Nati, F.; Natoli, P.; Nesvadba, N. P. H.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Türler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, F.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Welikala, N.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-12-01

The Planck mission, thanks to its large frequency range and all-sky coverage, has a unique potential for systematically detecting the brightest, and rarest, submillimetre sources on the sky, including distant objects in the high-redshift Universe traced by their dust emission. A novel method, based on a component-separation procedure using a combination of Planck and IRAS data, has been validated and characterized on numerous simulations, and applied to select the most luminous cold submillimetre sources with spectral energy distributions peaking between 353 and 857 GHz at 5' resolution. A total of 2151 Planck high-z source candidates (the PHZ) have been detected in the cleanest 26% of the sky, with flux density at 545 GHz above 500 mJy. Embedded in the cosmic infrared background close to the confusion limit, these high-z candidates exhibit colder colours than their surroundings, consistent with redshifts z > 2, assuming a dust temperature of Txgal = 35 K and a spectral index of βxgal = 1.5. Exhibiting extremely high luminosities, larger than 1014L⊙, the PHZ objects may be made of multiple galaxies or clumps at high redshift, as suggested by a first statistical analysis based on a comparison with number count models. Furthermore, first follow-up observations obtained from optical to submillimetre wavelengths, which can be found in companion papers, have confirmed that this list consists of two distinct populations. A small fraction (around 3%) of the sources have been identified as strongly gravitationally lensed star-forming galaxies at redshift 2 to 4, while the vast majority of the PHZ sources appear as overdensities of dusty star-forming galaxies, having colours consistent with being at z > 2, and may be considered as proto-cluster candidates. The PHZ provides an original sample, which is complementary to the Planck Sunyaev-Zeldovich Catalogue (PSZ2); by extending the population of virialized massive galaxy clusters detected below z < 1.5 through their SZ signal to a population of sources at z > 1.5, the PHZ may contain the progenitors of today's clusters. Hence the Planck list of high-redshift source candidates opens a new window on the study of the early stages of structure formation, particularly understanding the intensively star-forming phase at high-z. The catalogue is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A100

A massive, quiescent galaxy at a redshift of 3.717.

PubMed

Glazebrook, Karl; Schreiber, Corentin; Labbé, Ivo; Nanayakkara, Themiya; Kacprzak, Glenn G; Oesch, Pascal A; Papovich, Casey; Spitler, Lee R; Straatman, Caroline M S; Tran, Kim-Vy H; Yuan, Tiantian

2017-04-05

Finding massive galaxies that stopped forming stars in the early Universe presents an observational challenge because their rest-frame ultraviolet emission is negligible and they can only be reliably identified by extremely deep near-infrared surveys. These surveys have revealed the presence of massive, quiescent early-type galaxies appearing as early as redshift z ≈ 2, an epoch three billion years after the Big Bang. Their age and formation processes have now been explained by an improved generation of galaxy-formation models, in which they form rapidly at z ≈ 3-4, consistent with the typical masses and ages derived from their observations. Deeper surveys have reported evidence for populations of massive, quiescent galaxies at even higher redshifts and earlier times, using coarsely sampled photometry. However, these early, massive, quiescent galaxies are not predicted by the latest generation of theoretical models. Here we report the spectroscopic confirmation of one such galaxy at redshift z = 3.717, with a stellar mass of 1.7 × 10 11 solar masses. We derive its age to be nearly half the age of the Universe at this redshift and the absorption line spectrum shows no current star formation. These observations demonstrate that the galaxy must have formed the majority of its stars quickly, within the first billion years of cosmic history in a short, extreme starburst. This ancestral starburst appears similar to those being found by submillimetre-wavelength surveys. The early formation of such massive systems implies that our picture of early galaxy assembly requires substantial revision.

A massive, quiescent galaxy at a redshift of 3.717

NASA Astrophysics Data System (ADS)

Glazebrook, Karl; Schreiber, Corentin; Labbé, Ivo; Nanayakkara, Themiya; Kacprzak, Glenn G.; Oesch, Pascal A.; Papovich, Casey; Spitler, Lee R.; Straatman, Caroline M. S.; Tran, Kim-Vy H.; Yuan, Tiantian

2017-04-01

Finding massive galaxies that stopped forming stars in the early Universe presents an observational challenge because their rest-frame ultraviolet emission is negligible and they can only be reliably identified by extremely deep near-infrared surveys. These surveys have revealed the presence of massive, quiescent early-type galaxies appearing as early as redshift z ≈ 2, an epoch three billion years after the Big Bang. Their age and formation processes have now been explained by an improved generation of galaxy-formation models, in which they form rapidly at z ≈ 3-4, consistent with the typical masses and ages derived from their observations. Deeper surveys have reported evidence for populations of massive, quiescent galaxies at even higher redshifts and earlier times, using coarsely sampled photometry. However, these early, massive, quiescent galaxies are not predicted by the latest generation of theoretical models. Here we report the spectroscopic confirmation of one such galaxy at redshift z = 3.717, with a stellar mass of 1.7 × 1011 solar masses. We derive its age to be nearly half the age of the Universe at this redshift and the absorption line spectrum shows no current star formation. These observations demonstrate that the galaxy must have formed the majority of its stars quickly, within the first billion years of cosmic history in a short, extreme starburst. This ancestral starburst appears similar to those being found by submillimetre-wavelength surveys. The early formation of such massive systems implies that our picture of early galaxy assembly requires substantial revision.

Highlights And Shadows Of High Redshift Starbursts: A Herschel­Fmos Joint Effort

NASA Astrophysics Data System (ADS)

Puglisi, Annagrazia

2017-06-01

Starburst galaxies represent a critical stage in galaxy evolution as they are the likely progenitors of passively evolving ellipticals. The properties of high-redshift starbursts are however still debated as it is not clear to which extent their vigorous star formation rate is caused by an enhanced gas fraction or an enhanced star formation efficiency, and what physical processes trigger such violent activity. Our study of the rest-frame optical spectra from the FMOS-COSMOS survey of twelve z 1.6 Herschel starbursts combined with a rich ancillary data-set from UV to ALMA, is shedding light on some of these questions. By measuring the nebular extinction from different indicators, we find that 90% of their extreme SFR arises from an heavily obscured component which is thick in the optical. We also measure their gas-phase metallicity, showing that starbursts are metal-rich outliers from the metallicity-SFR anticorrelation observed at fixed stellar mass for the main sequence population. Our findings are consistent with a major merger origin for the starburst event. I will present this study discussing its implications on our interpretation of the high-redshift starbursts physics. I will also briefly discuss possible extensions of this work with the future PFS survey and how we can take advantage of the IFU capabilities of JWST/NIRspec to unveil the complex structure of these elusive systems.

The ALMA Frontier Fields Survey. II. Multiwavelength Photometric analysis of 1.1 mm continuum sources in Abell 2744, MACSJ0416.1-2403 and MACSJ1149.5+2223

NASA Astrophysics Data System (ADS)

Laporte, N.; Bauer, F. E.; Troncoso-Iribarren, P.; Huang, X.; González-López, J.; Kim, S.; Anguita, T.; Aravena, M.; Barrientos, L. F.; Bouwens, R.; Bradley, L.; Brammer, G.; Carrasco, M.; Carvajal, R.; Coe, D.; Demarco, R.; Ellis, R. S.; Ford, H.; Francke, H.; Ibar, E.; Infante, L.; Kneissl, R.; Koekemoer, A. M.; Messias, H.; Muñoz Arancibia, A.; Nagar, N.; Padilla, N.; Pelló, R.; Postman, M.; Quénard, D.; Romero-Cañizales, C.; Treister, E.; Villard, E.; Zheng, W.; Zitrin, A.

2017-08-01

Context. The Hubble and Spitzer Space Telescope surveys of the Frontier Fields provide extremely deep images around six massive, strong-lensing clusters of galaxies. The ALMA Frontier Fields survey aims to cover the same fields at 1.1 mm, with maps reaching (unlensed) sensitivities of <70 μJy, in order to explore the properties of background dusty star-forming galaxies. Aims: We report on the multi-wavelength photometric analysis of all 12 significantly detected (>5σ) sources in the first three Frontier Fields clusters observed by ALMA, based on data from Hubble and Spitzer, the Very Large Telescope and the Herschel Space Observatory. Methods: We measure the total photometry in all available bands and determine the photometric redshifts and the physical properties of the counterparts via SED-fitting. In particular, we carefully estimate the far-infrared (FIR) photometry using 1.1 mm priors to limit the misidentification of blended FIR counterparts, which strongly affect some flux estimates in previous FIR catalogs. Due to the extremely red nature of these objects, we used a large range of parameters (e.g. 0.0

The Space Density of Luminous Dusty Star-forming Galaxies at z > 4: SCUBA-2 and LABOCA Imaging of Ultrared Galaxies from Herschel-ATLAS

NASA Astrophysics Data System (ADS)

Ivison, R. J.; Lewis, A. J. R.; Weiss, A.; Arumugam, V.; Simpson, J. M.; Holland, W. S.; Maddox, S.; Dunne, L.; Valiante, E.; van der Werf, P.; Omont, A.; Dannerbauer, H.; Smail, Ian; Bertoldi, F.; Bremer, M.; Bussmann, R. S.; Cai, Z.-Y.; Clements, D. L.; Cooray, A.; De Zotti, G.; Eales, S. A.; Fuller, C.; Gonzalez-Nuevo, J.; Ibar, E.; Negrello, M.; Oteo, I.; Pérez-Fournon, I.; Riechers, D.; Stevens, J. A.; Swinbank, A. M.; Wardlow, J.

2016-11-01

Until recently, only a handful of dusty, star-forming galaxies (DSFGs) were known at z > 4, most of them significantly amplified by gravitational lensing. Here, we have increased the number of such DSFGs substantially, selecting galaxies from the uniquely wide 250, 350, and 500 μm Herschel-ATLAS imaging survey on the basis of their extremely red far-infrared colors and faint 350 and 500 μm flux densities, based on which, they are expected to be largely unlensed, luminous, rare, and very distant. The addition of ground-based continuum photometry at longer wavelengths from the James Clerk Maxwell Telescope and the Atacama Pathfinder Experiment allows us to identify the dust peak in their spectral energy distributions (SEDs), with which we can better constrain their redshifts. We select the SED templates that are best able to determine photometric redshifts using a sample of 69 high-redshift, lensed DSFGs, then perform checks to assess the impact of the CMB on our technique, and to quantify the systematic uncertainty associated with our photometric redshifts, σ = 0.14 (1 + z), using a sample of 25 galaxies with spectroscopic redshifts, each consistent with our color selection. For Herschel-selected ultrared galaxies with typical colors of S 500/S 250 ˜ 2.2 and S 500/S 350 ˜ 1.3 and flux densities, S 500 ˜ 50 mJy, we determine a median redshift, {\\hat{z}}{phot}=3.66, an interquartile redshift range, 3.30-4.27, with a median rest-frame 8-1000 μm luminosity, {\\hat{L}}{IR}, of 1.3 × 1013 L ⊙. A third of the galaxies lie at z > 4, suggesting a space density, ρ z > 4, of ≈6 × 10-7 Mpc-3. Our sample contains the most luminous known star-forming galaxies, and the most overdense cluster of starbursting proto-ellipticals found to date.

Mean and extreme radio properties of quasars and the origin of radio emission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kratzer, Rachael M.; Richards, Gordon T.

2015-02-01

We investigate the evolution of both the radio-loud fraction (RLF) and (using stacking analysis) the mean radio loudness of quasars. We consider how these properties evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission-line region. We match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric), primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high redshift, we find that both the RLF and the mean radio luminosity increasemore » for increasing BH mass and decreasing accretion rate. Similarly, both the RLF and mean radio loudness increase for quasars that are argued to have weaker radiation line driven wind components of the broad emission-line region. In agreement with past work, we find that the RLF increases with increasing optical/UV luminosity and decreasing redshift, while the mean radio loudness evolves in the exact opposite manner. This difference in behavior between the mean radio loudness and the RLF in L−z may indicate selection effects that bias our understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, we argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences, but where only RQ quasars at one extreme of the distribution are likely to become RL, possibly through slight differences in spin and/or merger history.« less

See Change: the Supernova Sample from the Supernova Cosmology Project High Redshift Cluster Supernova Survey

NASA Astrophysics Data System (ADS)

Hayden, Brian; Perlmutter, Saul; Boone, Kyle; Nordin, Jakob; Rubin, David; Lidman, Chris; Deustua, Susana E.; Fruchter, Andrew S.; Aldering, Greg Scott; Brodwin, Mark; Cunha, Carlos E.; Eisenhardt, Peter R.; Gonzalez, Anthony H.; Jee, James; Hildebrandt, Hendrik; Hoekstra, Henk; Santos, Joana; Stanford, S. Adam; Stern, Daniel; Fassbender, Rene; Richard, Johan; Rosati, Piero; Wechsler, Risa H.; Muzzin, Adam; Willis, Jon; Boehringer, Hans; Gladders, Michael; Goobar, Ariel; Amanullah, Rahman; Hook, Isobel; Huterer, Dragan; Huang, Xiaosheng; Kim, Alex G.; Kowalski, Marek; Linder, Eric; Pain, Reynald; Saunders, Clare; Suzuki, Nao; Barbary, Kyle H.; Rykoff, Eli S.; Meyers, Joshua; Spadafora, Anthony L.; Sofiatti, Caroline; Wilson, Gillian; Rozo, Eduardo; Hilton, Matt; Ruiz-Lapuente, Pilar; Luther, Kyle; Yen, Mike; Fagrelius, Parker; Dixon, Samantha; Williams, Steven

2017-01-01

The Supernova Cosmology Project has finished executing a large (174 orbits, cycles 22-23) Hubble Space Telescope program, which has measured ~30 type Ia Supernovae above z~1 in the highest-redshift, most massive galaxy clusters known to date. Our SN Ia sample closely matches our pre-survey predictions; this sample will improve the constraint by a factor of 3 on the Dark Energy equation of state above z~1, allowing an unprecedented probe of Dark Energy time variation. When combined with the improved cluster mass calibration from gravitational lensing provided by the deep WFC3-IR observations of the clusters, See Change will triple the Dark Energy Task Force Figure of Merit. With the primary observing campaign completed, we present the preliminary supernova sample and our path forward to the supernova cosmology results. We also compare the number of SNe Ia discovered in each cluster with our pre-survey expectations based on cluster mass and SFR estimates. Our extensive HST and ground-based campaign has already produced unique results; we have confirmed several of the highest redshift cluster members known to date, confirmed the redshift of one of the most massive galaxy clusters at z~1.2 expected across the entire sky, and characterized one of the most extreme starburst environments yet known in a z~1.7 cluster. We have also discovered a lensed SN Ia at z=2.22 magnified by a factor of ~2.7, which is the highest spectroscopic redshift SN Ia currently known.

Infrared Color Selection of Massive Galaxies at z > 3

NASA Astrophysics Data System (ADS)

Wang, T.; Elbaz, D.; Schreiber, C.; Pannella, M.; Shu, X.; Willner, S. P.; Ashby, M. L. N.; Huang, J.-S.; Fontana, A.; Dekel, A.; Daddi, E.; Ferguson, H. C.; Dunlop, J.; Ciesla, L.; Koekemoer, A. M.; Giavalisco, M.; Boutsia, K.; Finkelstein, S.; Juneau, S.; Barro, G.; Koo, D. C.; Michałowski, M. J.; Orellana, G.; Lu, Y.; Castellano, M.; Bourne, N.; Buitrago, F.; Santini, P.; Faber, S. M.; Hathi, N.; Lucas, R. A.; Pérez-González, P. G.

2016-01-01

We introduce a new color selection technique to identify high-redshift, massive galaxies that are systematically missed by Lyman-break selection. The new selection is based on the H160 (H) and Infrared Array Camera (IRAC) 4.5 μm bands, specifically H-[4.5]\\gt 2.25 mag. These galaxies, called “HIEROs,” include two major populations that can be separated with an additional J - H color. The populations are massive and dusty star-forming galaxies at z\\gt 3 ({JH}-{blue}) and extremely dusty galaxies at z≲ 3 ({JH}-{red}). The 350 arcmin2 of the GOODS-North and GOODS-South fields with the deepest Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) near-infrared and IRAC data contain as many as 285 HIEROs down to [4.5]\\lt 24 mag. Inclusion of the most extreme HIEROs, not even detected in the H band, makes this selection particularly complete for the identification of massive high-redshift galaxies. We focus here primarily on {JH}-{blue} (z\\gt 3) HIEROs, which have a median photometric redshift < z> ˜ 4.4 and stellar mass {M}*˜ {10}10.6 {M}⊙ and are much fainter in the rest-frame UV than similarly massive Lyman-break galaxies (LBGs). Their star formation rates (SFRs), derived from their stacked infrared spectral energy distributions (SEDs), reach ˜240 {M}⊙ yr-1, leading to a specific SFR, {{sSFR}}\\equiv {{SFR}}/{M}*˜ 4.2 Gyr-1, suggesting that the sSFRs for massive galaxies continue to grow at z\\gt 2 but at a lower growth rate than from z = 0 to z = 2. With a median half-light radius of 2 kpc, including ˜ 20% as compact as quiescent (QS) galaxies at similar redshifts, {JH}-{blue} HIEROs represent perfect star-forming progenitors of the most massive ({M}*≳ {10}11.2 {M}⊙ ) compact QS galaxies at z˜ 3 and have the right number density. HIEROs make up ˜ 60% of all galaxies with {M}*\\gt {10}10.5 {M}⊙ identified at z\\gt 3 from their photometric redshifts. This is five times more than LBGs with nearly no overlap between the two populations. While HIEROs make up 15%-25% of the total SFR density at z˜ 4-5, they completely dominate the SFR density taking place in {M}*\\gt {10}10.5 {M}⊙ galaxies, and HIEROs are therefore crucial to understanding the very early phase of massive galaxy formation.

Molecular Gas Content of an Extremely Star-forming Herschel Observed Lensed Dusty Galaxy at z=2.685

NASA Astrophysics Data System (ADS)

Nayyeri, Hooshang; Cooray, Asantha R.; H-ATLAS

2017-01-01

We present the results of combined deep near-infrared, far infrared and millimeter observations of an extremely star forming lensed dusty star-forming galaxy (DSFG) identified from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). The high redshift DSFG is gravitationally lensed by a massive WISE identified cluster at z~1 (spectroscopically confirmed with Keck/DEIMOS and Gemini/GMOS) producing multiply lensed images and arcs observed in the optical. The DSFG is spectroscopically confirmed at z=2.685 from CO(1-0) observations by GBT and separately from CO(3-2) observations by CARMA. We use the combined spectroscopic and imaging observations to construct a detailed lens model of the background DSFG which allowed us to study the sources plane properties of the target. Multi-band data from Keck/NIRC2, HST/WFC3 and Herschel yields star formation rate and stellar mass well above the main sequence. Observations of the dust continuum by the Sub-millimeter Array yields an observed total ISM mass of 6.5E+11 M* which is responsible for the intense observed star formation rates. Comparing the measured SFR with molecular gas measurements from CO(1-0) observations reveals that this system has relatively short gas depletion time scale which is consistent with the starburst phase observed in high redshift sub-millimeter galaxies.

Zooming in on star formation in the brightest galaxies of the early Universe discovered with the Planck and Herschel satellites

NASA Astrophysics Data System (ADS)

Canameras, Raoul

2016-09-01

Strongly gravitationally lensed galaxies offer an outstanding opportunity to characterize the most intensely star-forming galaxies in the high-redshift universe. In the most extreme cases, one can probe the mechanisms that underlie the intense star formation on the scales of individual star-forming regions. This requires very fortuitous gravitational lensing configurations offering magnification factors >>10, which are particularly rare toward the high-redshift dusty star-forming galaxies. The Planck's Dusty GEMS (Gravitationally Enhanced subMillimeter Sources) sample contains eleven of the brightest high-redshift galaxies discovered with the Planck submillimeter all-sky survey, with flux densities between 300 and 1000 mJy at 350 microns, factors of a few brighter than the majority of lensed sources previously discovered with other surveys. Six of them are above the 90% completeness limit of the Planck Catalog of Compact Sources (PCCS), suggesting that they are among the brightest high-redshift sources on the sky selected by their active star formation. This thesis comes within the framework of the extensive multi-wavelength follow-up programme designed to determine the overall properties of the high-redshift sources and to probe the lensing configurations. Firstly, to characterize the intervening lensing structures and calculate lensing models, I use optical and near/mid-infrared imaging and spectroscopy. I deduce that our eleven GEMS are aligned with intervening matter overdensities at intermediate redshift, either massive isolated galaxies or galaxy groups and clusters. The foreground sources exhibit evolved stellar populations of a few giga years, characteristic of early-type galaxies. Moreover, the first detailed models of the light deflection toward the GEMS suggest magnification factors systematically >10, and >20 for some lines-of-sight. Secondly, we observe the GEMS in the far-infrared and sub-millimeter domains in order to characterize the background sources. The sub-arcsec resolution IRAM and SMA interferometry shows distorded morphologies which definitively confirm that the eleven sources are strongly lensed. I obtain dust temperatures between 33 and 50 K, and outstanding far-infrared luminosities of up to 2x1014 solar luminosities before correcting for the gravitational magnification. The relationship between dust temperatures and far-infrared luminosities also confirms that the GEMS are brighter than field galaxies at a given dust temperature. I conclude that dust heating seems to be strongly dominated by the star formation activity with an AGN contamination systematically below 30%. We find secure spectroscopic redshifts between 2.2 and 3.6 for the eleven targets thanks to the detection of at least two CO emission lines per source. Finally, I focus on the three gravitationally lensed sources showing the most remarkable properties including the brightest GEMS, a maximal starburst with star formation surface densities near the Eddington limit.

The Spectroscopic Ages of Passive Galaxies in a z=1.62 Protocluster

NASA Astrophysics Data System (ADS)

Lee-Brown, Donald

2017-07-01

IRC 0218 is a protocluster at z = 1.62 with a wealth of observations that make it an ideal target for resolving the interplay between galaxy properties and environment at high redshift. We have used extremely deep HST spectroscopic data to derive unambiguous membership and stellar ages via the 4000 angstrom break for 14 members with stellar masses log(M) > 10.2. We find that at high stellar masses, log(M) > 10.85, the fraction of quiescent galaxies in the cluster is 2× higher than the field value. At lower stellar masses, the protocluster and field have consistent quiescent fractions. Despite this mass trend, we see no comparable relation between galaxy stellar age and mass for the quiescent members. Taken together, these results may reflect the impact of dry mergers on the protocluster galaxies. Alternately, the results may imply that the mass trend we observe in the IRC 0218 quiescent fraction was imprinted over a short timescale. This talk will place our results in the context of studies of other high redshift clusters and likely descendent environments at z = 1.

High-z X-ray Obscured Quasars in Galaxies with Extreme Mid-IR/Optical Colors

NASA Astrophysics Data System (ADS)

Piconcelli, E.; Lanzuisi, G.; Fiore, F.; Feruglio, C.; Vignali, C.; Salvato, M.; Grappioni, C.

2009-05-01

Extreme Optical/Mid-IR color cuts have been used to uncover a population of dust-enshrouded, mid-IR luminous galaxies at high redshifts. Several lines of evidence point towards the presence of an heavily absorbed, possibly Compton-thick quasar at the heart of these systems. Nonetheless, the X-ray spectral properties of these intriguing sources still remain largely unexplored. Here we present an X-ray spectroscopic study of a large sample of 44 extreme dust-obscured galaxies (EDOGs) with F24 μm/FR>2000 and F24 μm>1.3 mJy selected from a 6 deg2 region in the SWIRE fields. The application of our selection criteria to a wide area survey has been capable of unveiling a population of X-ray luminous, absorbed z>1 quasars which is mostly missed in the traditional optical/X-ray surveys performed so far. Advances in the understanding of the X-ray properties of these recently-discovered sources by Simbol-X observations will be also discussed.

First detection of very-high-energy gamma-ray emission from the extreme blazar PGC 2402248 with the MAGIC telescopes

NASA Astrophysics Data System (ADS)

Mirzoyan, Razmik

2018-04-01

The MAGIC collaboration reports the first detection of very-high-energy (VHE; E > 100 GeV) gamma-ray emission from PGC 2402248, also known as 2WHSP J073326.7+515354 (Chang et al. 2016, A & A, 598, A17) with coordinates R.A.: 07:33:26.7 h, Dec: +51:53:54.99 deg. The source is classified as an extreme high-energy peaked BL Lacertae object of unknown redshift, included in the 2WHSP catalog with a synchrotron peak located at 10^17.9 Hz. PGC 2402248 was observed with the MAGIC telescopes from 2018/01/23 to 2018/04/18 (MJD 58141-58226) for about 23 h. The preliminary analysis of these data resulted in the detection of PGC 2402248 with a statistical significance of more than 6 standard deviations.

ON THE OXYGEN AND NITROGEN CHEMICAL ABUNDANCES AND THE EVOLUTION OF THE 'GREEN PEA' GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amorin, Ricardo O.; Perez-Montero, Enrique; Vilchez, J. M., E-mail: amorin@iaa.e, E-mail: epm@iaa.e, E-mail: jvm@iaa.e

2010-06-01

We have investigated the oxygen and nitrogen chemical abundances in extremely compact star-forming galaxies (SFGs) with redshifts between {approx}0.11 and 0.35, popularly referred to as 'green peas'. Direct and strong-line methods sensitive to the N/O ratio applied to their Sloan Digital Sky Survey (SDSS) spectra reveal that these systems are genuine metal-poor galaxies, with mean oxygen abundances {approx}20% solar. At a given metallicity these galaxies display systematically large N/O ratios compared to normal galaxies, which can explain the strong difference between our metallicities measurements and previous ones. While their N/O ratios follow the relation with stellar mass of local SFGsmore » in the SDSS, we find that the mass-metallicity relation of the 'green peas' is offset {approx_gt}0.3 dex to lower metallicities. We argue that recent interaction-induced inflow of gas, possibly coupled with a selective metal-rich gas loss, driven by supernova winds, may explain our findings and the known galaxy properties, namely high specific star formation rates, extreme compactness, and disturbed optical morphologies. The 'green pea' galaxy properties seem to be uncommon in the nearby universe, suggesting a short and extreme stage of their evolution. Therefore, these galaxies may allow us to study in great detail many processes, such as starburst activity and chemical enrichment, under physical conditions approaching those in galaxies at higher redshifts.« less

A massive core for a cluster of galaxies at a redshift of 4.3

NASA Astrophysics Data System (ADS)

Miller, T. B.; Chapman, S. C.; Aravena, M.; Ashby, M. L. N.; Hayward, C. C.; Vieira, J. D.; Weiß, A.; Babul, A.; Béthermin, M.; Bradford, C. M.; Brodwin, M.; Carlstrom, J. E.; Chen, Chian-Chou; Cunningham, D. J. M.; De Breuck, C.; Gonzalez, A. H.; Greve, T. R.; Harnett, J.; Hezaveh, Y.; Lacaille, K.; Litke, K. C.; Ma, J.; Malkan, M.; Marrone, D. P.; Morningstar, W.; Murphy, E. J.; Narayanan, D.; Pass, E.; Perry, R.; Phadke, K. A.; Rennehan, D.; Rotermund, K. M.; Simpson, J.; Spilker, J. S.; Sreevani, J.; Stark, A. A.; Strandet, M. L.; Strom, A. L.

2018-04-01

Massive galaxy clusters have been found that date to times as early as three billion years after the Big Bang, containing stars that formed at even earlier epochs1-3. The high-redshift progenitors of these galaxy clusters—termed `protoclusters'—can be identified in cosmological simulations that have the highest overdensities (greater-than-average densities) of dark matter4-6. Protoclusters are expected to contain extremely massive galaxies that can be observed as luminous starbursts7. However, recent detections of possible protoclusters hosting such starbursts8-11 do not support the kind of rapid cluster-core formation expected from simulations12: the structures observed contain only a handful of starbursting galaxies spread throughout a broad region, with poor evidence for eventual collapse into a protocluster. Here we report observations of carbon monoxide and ionized carbon emission from the source SPT2349-56. We find that this source consists of at least 14 gas-rich galaxies, all lying at redshifts of 4.31. We demonstrate that each of these galaxies is forming stars between 50 and 1,000 times more quickly than our own Milky Way, and that all are located within a projected region that is only around 130 kiloparsecs in diameter. This galaxy surface density is more than ten times the average blank-field value (integrated over all redshifts), and more than 1,000 times the average field volume density. The velocity dispersion (approximately 410 kilometres per second) of these galaxies and the enormous gas and star-formation densities suggest that this system represents the core of a cluster of galaxies that was already at an advanced stage of formation when the Universe was only 1.4 billion years old. A comparison with other known protoclusters at high redshifts shows that SPT2349-56 could be building one of the most massive structures in the Universe today.

A massive core for a cluster of galaxies at a redshift of 4.3.

PubMed

Miller, T B; Chapman, S C; Aravena, M; Ashby, M L N; Hayward, C C; Vieira, J D; Weiß, A; Babul, A; Béthermin, M; Bradford, C M; Brodwin, M; Carlstrom, J E; Chen, Chian-Chou; Cunningham, D J M; De Breuck, C; Gonzalez, A H; Greve, T R; Harnett, J; Hezaveh, Y; Lacaille, K; Litke, K C; Ma, J; Malkan, M; Marrone, D P; Morningstar, W; Murphy, E J; Narayanan, D; Pass, E; Perry, R; Phadke, K A; Rennehan, D; Rotermund, K M; Simpson, J; Spilker, J S; Sreevani, J; Stark, A A; Strandet, M L; Strom, A L

2018-04-01

Massive galaxy clusters have been found that date to times as early as three billion years after the Big Bang, containing stars that formed at even earlier epochs 1-3 . The high-redshift progenitors of these galaxy clusters-termed 'protoclusters'-can be identified in cosmological simulations that have the highest overdensities (greater-than-average densities) of dark matter 4-6 . Protoclusters are expected to contain extremely massive galaxies that can be observed as luminous starbursts 7 . However, recent detections of possible protoclusters hosting such starbursts 8-11 do not support the kind of rapid cluster-core formation expected from simulations 12 : the structures observed contain only a handful of starbursting galaxies spread throughout a broad region, with poor evidence for eventual collapse into a protocluster. Here we report observations of carbon monoxide and ionized carbon emission from the source SPT2349-56. We find that this source consists of at least 14 gas-rich galaxies, all lying at redshifts of 4.31. We demonstrate that each of these galaxies is forming stars between 50 and 1,000 times more quickly than our own Milky Way, and that all are located within a projected region that is only around 130 kiloparsecs in diameter. This galaxy surface density is more than ten times the average blank-field value (integrated over all redshifts), and more than 1,000 times the average field volume density. The velocity dispersion (approximately 410 kilometres per second) of these galaxies and the enormous gas and star-formation densities suggest that this system represents the core of a cluster of galaxies that was already at an advanced stage of formation when the Universe was only 1.4 billion years old. A comparison with other known protoclusters at high redshifts shows that SPT2349-56 could be building one of the most massive structures in the Universe today.

The Wide Field X-ray Telescope Mission

NASA Astrophysics Data System (ADS)

Murray, Stephen S.; WFXT Team

2010-01-01

To explore the high-redshift Universe to the era of galaxy formation requires an X-ray survey that is both sensitive and extensive, which complements deep wide-field surveys at other wavelengths. The Wide-Field X-ray Telescope (WFXT) is designed to be two orders of magnitude more effective than previous and planned X-ray missions for surveys. WFXT consists of three co-aligned wide-field X-ray telescopes with a 1 sq. deg. field of view and <10 arc sec (goal of 5 arc sec) angular resolution over the full field. With nearly ten times Chandra's collecting area and more than ten times Chandra's field of view, WFXT will perform sensitive deep surveys that will discover and characterize extremely large populations of high redshift AGN and galaxy clusters. In five years, WFXT will perform three extragalactic surveys: 1) 20,000 sq. deg. of extragalactic sky at 100-1000 times the sensitivity, and twenty times better angular resolution than the ROSAT All Sky Survey; 2) 3000 sq.deg. to deep Chandra sensitivity; and 3) 100 sq.deg. to the deepest Chandra sensitivity. WFXT will generate a legacy dataset of >500,000 galaxy clusters to redshifts about 2, measuring redshift, gas abundance and temperature for a significant fraction of them, and a sample of more than 10 million AGN to redshifts > 6, many with X-ray spectra sufficient to distinguish obscured from unobscured quasars. These surveys will address fundamental questions of how supermassive black holes grow and influence the evolution of the host galaxy and how clusters form and evolve, as well as providing large samples of massive clusters that can be used in cosmological studies. WFXT surveys will map systems spanning many square degrees including Galactic star forming regions, the Magellanic Clouds and the Virgo Cluster. WFXT data will become public through annual Data Releases that will constitute a vast scientific legacy.

Overdensities of SMGs around WISE-selected, ultraluminous, high-redshift AGNs

NASA Astrophysics Data System (ADS)

Jones, Suzy F.; Blain, Andrew W.; Assef, Roberto J.; Eisenhardt, Peter; Lonsdale, Carol; Condon, James; Farrah, Duncan; Tsai, Chao-Wei; Bridge, Carrie; Wu, Jingwen; Wright, Edward L.; Jarrett, Tom

2017-08-01

We investigate extremely luminous dusty galaxies in the environments around Wide-field Infrared Survey Explorer (WISE)-selected hot dust-obscured galaxies (Hot DOGs) and WISE/radio-selected active galactic nuclei (AGNs) at average redshifts of z = 2.7 and 1.7, respectively. Previous observations have detected overdensities of companion submillimetre-selected sources around 10 Hot DOGs and 30 WISE/radio AGNs, with overdensities of ˜2-3 and ˜5-6, respectively. We find that the space densities in both samples to be overdense compared to normal star-forming galaxies and submillimetre galaxies (SMGs) in the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) Cosmology Legacy Survey (S2CLS). Both samples of companion sources have consistent mid-infrared (mid-IR) colours and mid-IR to submm ratios as SMGs. The brighter population around WISE/radio AGNs could be responsible for the higher overdensity reported. We also find that the star formation rate densities are higher than the field, but consistent with clusters of dusty galaxies. WISE-selected AGNs appear to be good signposts for protoclusters at high redshift on arcmin scales. The results reported here provide an upper limit to the strength of angular clustering using the two-point correlation function. Monte Carlo simulations show no angular correlation, which could indicate protoclusters on scales larger than the SCUBA-2 1.5-arcmin scale maps.

Probabilistic Selection of High-redshift Quasars with Subaru/Hyper Suprime-Cam Survey

NASA Astrophysics Data System (ADS)

Onoue, Masafusa

High-redshift quasars are an important probe of the distant Universe. They enable observational studies of the early growth of supermassive blackholes, cosmic reionization, chemical enrichment of host galaxies, and so on. Through pioneering optical and near-infrared wide-area surveys such as the SDSS and the VIKING Survey, about one hundred quasars have been found at z > 6 (e.g., Fan et al. (2006b), Venemans et al. (2013)). However, its current small sample size and the fact that most of them are the most luminous (M 1450 <~ -24) population in this epoch prevents one from constraining statistics on high-redshift quasars, namely quasar luminosity function (QLF), and redshift evolution of IGM neutral fraction. Thus, discovery of large number of z > 6 quasars, especially low-luminous or z > 7 quasars, is highly desired for further understanding of the early universe. We are now starting a new ground-breaking survey of high-redshift (z > 6) quasars using the exquisite imaging data provided by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) Survey. Thanks to its extremely wide coverage and its high sensitivity thorough five optical bands (1,400 deg2 to the depth of r ~ 26 in HSC-Wide layer), it is one of the most powerful contemporary surveys that makes it possible for us to increase the number of z > 6 quasars by almost an order of magnitude, i.e., 300 at z ~ 6 and 50 at z ~ 7, based on the current estimate of the QLF at z > 6 by Willott et al. (2010b). One of the biggest challenges in z > 6 quasar candidate selection is contamination of Galactic brown dwarfs, which have the same point-like appearance as and similarly red colors to the quasars. To overcome this issue and maximize the selection efficiency, we apply a double-layered approach to the HSC survey products, namely combination of two probabilistic selections: SED-fitting and Bayesian selection. In particular, we have developed a template SED fitting method optimized to high-redshift quasars selection. Its application with 27 photometric bands to the COSMOS quasars at 3 < z < 5 have shown that almost all of the known quasars are correctly classified with small dispersion σ|Δz|/(1+z)=0.01 and as low as η=2.5% outlier rate. At present, the HSC survey have successfully covered ~100 deg2 of HSC-Wide area in full colors. From the first-year data products, we have already started z > 6 quasar selection, and it is expected that the first HSC quasar discovery will be in the near future.

OPTIMAL TIME-SERIES SELECTION OF QUASARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butler, Nathaniel R.; Bloom, Joshua S.

2011-03-15

We present a novel method for the optimal selection of quasars using time-series observations in a single photometric bandpass. Utilizing the damped random walk model of Kelly et al., we parameterize the ensemble quasar structure function in Sloan Stripe 82 as a function of observed brightness. The ensemble model fit can then be evaluated rigorously for and calibrated with individual light curves with no parameter fitting. This yields a classification in two statistics-one describing the fit confidence and the other describing the probability of a false alarm-which can be tuned, a priori, to achieve high quasar detection fractions (99% completenessmore » with default cuts), given an acceptable rate of false alarms. We establish the typical rate of false alarms due to known variable stars as {approx}<3% (high purity). Applying the classification, we increase the sample of potential quasars relative to those known in Stripe 82 by as much as 29%, and by nearly a factor of two in the redshift range 2.5 < z < 3, where selection by color is extremely inefficient. This represents 1875 new quasars in a 290 deg{sup 2} field. The observed rates of both quasars and stars agree well with the model predictions, with >99% of quasars exhibiting the expected variability profile. We discuss the utility of the method at high redshift and in the regime of noisy and sparse data. Our time-series selection complements well-independent selection based on quasar colors and has strong potential for identifying high-redshift quasars for Baryon Acoustic Oscillations and other cosmology studies in the LSST era.« less

The essential signature of a massive starburst in a distant quasar.

PubMed

Solomon, P; Vanden Bout, P; Carilli, C; Guelin, M

2003-12-11

Observations of carbon monoxide emission in high-redshift (zeta > 2) galaxies indicate the presence of large amounts of molecular gas. Many of these galaxies contain an active galactic nucleus powered by accretion of gas onto a supermassive black hole, and a key question is whether their extremely high infrared luminosities result from the active galactic nucleus, from bursts of massive star formation (associated with the molecular gas), or both. In the Milky Way, high-mass stars form in the dense cores of interstellar molecular clouds, where gas densities are n(H2) > 10(5) cm(-3) (refs 1, 2). Recent surveys show that virtually all galactic sites of high-mass star formation have similarly high densities. The bulk of the cloud material traced by CO observations, however, is at a much lower density. For galaxies in the local Universe, the HCN molecule is an effective tracer of high-density molecular gas. Here we report observations of HCN emission from the infrared-luminous 'Cloverleaf' quasar (at a redshift zeta = 2.5579). The HCN line luminosity indicates the presence of 10 billion solar masses of very dense gas, an essential feature of an immense starburst, which contributes, together with the active galactic nucleus it harbours, to its high infrared luminosity.

Herschel Far Infrared Spectra of Dusty Star-Forming Galaxies

NASA Astrophysics Data System (ADS)

Wilson, Derek; Cooray, Asantha R.; Nayyeri, Hooshang

2017-01-01

We stack archival spectra from the Herschel Space Observatory's SPIRE Spectrometer in three redshift bins from low redshifts (z < 0.2), through intermediate redshifts (0.2 < z < 1), and up to high redshifts (z > 1) in order to determine the average properties of the gas and dust in dusty, star-forming galaxies and (U)LIRGs. In the lower-redshift stack, we detect a host of water and carbon monoxide rotational transition lines, as well as some fine structure lines such as [NII]. At intermediate redshifts, only a [CII] line appears. The high-redshift stack displays strong [CII] emission, as well as faint emission from [OI] and [OIII]. The observed emission lines are used to model the average number density and radiation field strength in the photodissociation regions of our high-redshift sample, and the spectral line energy distributions of CO rotational transitions from the low-redshift stack are presented.

DCMDN: Deep Convolutional Mixture Density Network

NASA Astrophysics Data System (ADS)

D'Isanto, Antonio; Polsterer, Kai Lars

2017-09-01

Deep Convolutional Mixture Density Network (DCMDN) estimates probabilistic photometric redshift directly from multi-band imaging data by combining a version of a deep convolutional network with a mixture density network. The estimates are expressed as Gaussian mixture models representing the probability density functions (PDFs) in the redshift space. In addition to the traditional scores, the continuous ranked probability score (CRPS) and the probability integral transform (PIT) are applied as performance criteria. DCMDN is able to predict redshift PDFs independently from the type of source, e.g. galaxies, quasars or stars and renders pre-classification of objects and feature extraction unnecessary; the method is extremely general and allows the solving of any kind of probabilistic regression problems based on imaging data, such as estimating metallicity or star formation rate in galaxies.

The Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey III. Optical Identifications and New Redshifts

NASA Technical Reports Server (NTRS)

Pursimo, Tapio; Ojha, Roopesh; Jauncey, David L.; Rickett, Barney J.; Dutka, Michael S.; Koay, Jun Yi; Lovell, James E. J.; Bignall, Hayley E.; Kedziora-Chudczer, Lucyna; Macquart, Jean-Pierre

2013-01-01

Intraday variability (IDV) of the radio emission from active galactic nuclei is now known to be predominantly due to interstellar scintillation (ISS). The MASIV (The Microarcsecond Scintillation Induced Variability) survey of 443 at spectrum sources revealed that the IDV is related to the radio flux density and redshift. A study of the physical properties of these sources has been severely handicapped by the absence of reliable redshift measurements for many of these objects. This paper presents 79 new redshifts and a critical evaluation of 233 redshifts obtained from the literature. We classify spectroscopic identifications based on emission line properties, finding that 78% of the sources have broad emission lines and are mainly FSRQs. About 16% are weak lined objects, chiefly BL Lacs, and the remaining 6% are narrow line objects. The gross properties (redshift, spectroscopic class) of the MASIV sample are similar to those of other blazar surveys. However, the extreme compactness implied by ISS favors FSRQs and BL Lacs in the MASIV sample as these are the most compact object classes. We confirm that the level of IDV depends on the 5 GHz flux density for all optical spectral types. We find that BL Lac objects tend to be more variable than broad line quasars. The level of ISS decreases substantially above a redshift of about two. The decrease is found to be generally consistent with ISS expected for beamed emission from a jet that is limited to a fixed maximum brightness temperature in the source rest frame.

The link between quasar broad-line region and galaxy-scale outflows and accurate CIV-based black hole masses

NASA Astrophysics Data System (ADS)

Coatman, Liam; Hewett, Paul C.; Banerji, Manda; Richards, Gordon T.; Hennawi, Joseph F.; Prochaska, Jason X.

2017-01-01

Accurate black-hole (BH) mass estimates for high-redshift (z>2) quasars are essential for better understanding the relationship between super-massive BH accretion and star formation. Progress is currently limited by the large systematic errors in virial BH-masses derived from the CIV broad emission line, which is often significantly blueshifted relative to systemic, most likely due to outflowing gas in the quasar broad-line region. We have assembled Balmer-line based BH masses for a large sample of 230 high-luminosity (1045.5-1048 ergs-1), redshift 1.5 3000 kms-1), blueshifted [OIII] emission. We find a strong correlation between the CIV and [OIII] blueshifts. This correlation holds even for quasars at fixed luminosity and suggests that broad line region outflows in quasars are connected to galaxy-scale winds.

Water Emission from Early Universe

NASA Astrophysics Data System (ADS)

Jarugula, Sreevani; Vieira, Joaquin

2017-06-01

The study of dusty star forming galaxies (DSFGs) is important to understand galaxy assembly in early universe. A bulk of star formation at z ˜ 2-3 takes place in DSFGs but are obscured by dust in optical/UV. However, they are extremely bright in far infrared (FIR) and submillimeter with infrared luminosities of 10^{11} - 10^{13} L_{⊙}. ALMA, with its high spatial and spectral resolution, has opened up a new window to study molecular lines, which are vital to our understanding of the excitation and physical processes in the galaxy. Carbon monoxide (CO) being the second most abundant and bright molecule after hydrogen (H_{2}), is an important tracer of star forming potential. Besides CO, water (H_{2}O) is also abundant and it's line strength is comparable to high-J CO lines in high redshift Ultra Luminous Infrared Galaxies (ULIRGs). Studies have shown H_{2}O to directly trace the FIR field and hence the star forming regions. Moreover, L_{H_{2}O}/L_{IR} ratio is nearly constant for five of the most important water lines and does not depend on the presence of AGN implying that H_{2}O is one of the best tracers of star forming regions (SFRs). This incredible correlation holds for nearly five orders of magnitude in luminosity and observed in both local and high redshift luminous infrared galaxies. In this talk, I will discuss the importance of H_{2}O in tracing FIR field and show the preliminary results of resolved water emission from three high-redshift gravitationally lensed South Pole Telescope (SPT) sources obtained from ALMA cycle 3 and cycle 4. These sources are among the first H_{2}O observations with resolved spatial scales ˜ 1 kpc and will prove to be important for ALMA and galaxy evolution studies.

Planetary Habitability over Cosmic-Time Based on Cosmic-Ray Levels

NASA Astrophysics Data System (ADS)

Mason, Paul A.; Biermann, Peter L.

2016-01-01

Extreme cosmic-ray (CR) fluxes have a negative effect on life when flux densities are high enough to cause excessive biological, especially DNA, damage. The CR history of a planet plays an important role in its potential surface habitation. Both global and local CR conditions determine the ability of life to survive for astrobiologically relevant time periods. We highlight two CR life-limiting factors: 1) General galactic activity, starburst and AGN, was up by about a factor of 30 at redshift 1 - 2, per comoving frame, averaged over all galaxies. And 2) AGN activity is highly intermittent, so extreme brief but powerful bursts (Her A for example) can be detrimental at great distances. This means that during such brief bursts of AGN activity the extragalactic CRs might even overpower the local galactic CRs. But as shown by the starburst galaxy M82, the local CRs in a starburst can also be quite high. Moreover, in our cosmic neighborhood we have several super-massive black holes. These are in M31, M32, M81, NGC5128 (Cen A), and in our own Galaxy, all within about 4 Mpc today. Within about 20 Mpc today there are many more super-massive black holes. Cen A is of course the most famous one now, since it may be a major source of the ultra-high-energy CRs (UHECRs). Folding in what redshift means in terms of cosmic time, this implies that there may have been little chance for life to survive much earlier than Earth's starting epoch. We speculate, on whether the very slow start oflife on Earth is connected to the decay of disturbing CR activity.

Compton Thick AGN in the COSMOS field

NASA Astrophysics Data System (ADS)

Lanzuisi, Giorgio; Cosmos Collaboration

2015-09-01

I will present the results we published in a couple of recent papers (Lanzuisi et al. 2015, A&A 573A 137, Lanzuisi et al. 2015, arXiv 1505.01153) on the properties of X-ray selected Compton Thick (CT, NH>10^24 cm^-2) AGN, in the COSMOS survey. We exploited the rich multi-wavelength dataset available in this field, to show that CT AGN tend to harbor smaller, rapidly growing SMBH with respect to unobscured AGN, and have a higher chance of being hosted by star-forming, merging and post-merger systems.We also demonstrated the detectability of even more heavily obscured AGN (NH>10^25 cm^-2), thanks to a truly multi-wavelength approach in the same field. The extreme source detected in this way shows strong evidences of ongoing powerful AGN feedback, detected as blue-shifted wings of high ionization optical emission lines such as [NeV] and [FeVII], as well as of the [OIII] emission line.The results obtained from these works point toward a scenario in which highly obscured AGN occupy a peculiar place in the galaxy-AGN co-evolution process, in which both the host and the SMBH rapidly evolve toward the local relations.We will also present estimates on the detectability of such extreme sources up to redshift ~6-7 with Athena. Combining the most up to date models for the Luminosity Function of CT AGN at high z, aggressive data analysis techniques on faint sources, and the current Athena survey design, we demonstrate that we will detect, and recognize as such, a small (few to ten) but incredibly valuable sample of CT AGN at such high redshift.

A Distant, X-Ray Luminous Cluster of Galaxies at Redshift 0.83

NASA Technical Reports Server (NTRS)

Donahue, Megan

1999-01-01

We have observed the most distant (= 0.829) cluster of galaxies in the Einstein Extended Medium Sensitivity Survey (EMSS), with the ASCA and ROSAT satellites. We find an X-ray temperature of 12.3(sup 3.1, sub 2.2) keV for this cluster, and the ROSAT map reveals significant substructure. The high temperature of MS1054-0321 is consistent with both its approximate velocity dispersion, based on the redshifts of 12 cluster members we have obtained at the Keck and the Canada-France-Hawaii telescopes, and with its weak lensing signature. The X-ray temperature of this cluster implies a virial mass approximately 7.4 x 10(exp 14) /h solar mass, if the mean matter density in the universe equals the critical value (OMEGA(sub 0) = 1), or larger if OMEGA(sub 0) < 1. Finding such a hot, massive cluster in the EMSS is extremely improbable if clusters grew from Gaussian perturbations in an OMEGA(sub 0) = 1 universe. Combining the assumptions that OMEGA(sub 0) = 1 and that the initial perturbations were Gaussian with the observed X-ray temperature function at low redshift, we show that this probability of this cluster occurring in the volume sampled by the EMSS is less than a few times 10(exp -5). Nor is MS1054-0321 the only hot cluster at high redshift; the only two other z > 0.5 EMSS clusters already observed with ASCA also have temperatures exceeding 8 keV. Assuming again that the initial perturbations were Gaussian and OMEGA(sub 0) = 1, we find that each one is improbable at the < 10(exp -2) level. These observations, along with the fact that these luminosities and temperatures of the high-z clusters all agree with the low-z L(sub x) - T(sub x) relation, argue strongly that OMEGA(sub 0) < 1. Otherwise, the initial perturbations must be non-Gaussian, if these clusters' temperatures do indeed reflect their gravitational potentials.

Dark energy coupling with electromagnetism as seen from future low-medium redshift probes

NASA Astrophysics Data System (ADS)

Calabrese, E.; Martinelli, M.; Pandolfi, S.; Cardone, V. F.; Martins, C. J. A. P.; Spiro, S.; Vielzeuf, P. E.

2014-04-01

Beyond the standard cosmological model the late-time accelerated expansion of the Universe can be reproduced by the introduction of an additional dynamical scalar field. In this case, the field is expected to be naturally coupled to the rest of the theory's fields, unless a (still unknown) symmetry suppresses this coupling. Therefore, this would possibly lead to some observational consequences, such as space-time variations of nature's fundamental constants. In this paper we investigate the coupling between a dynamical dark energy model and the electromagnetic field, and the corresponding evolution of the fine structure constant (α) with respect to the standard local value α0. In particular, we derive joint constraints on two dynamical dark energy model parametrizations (the Chevallier-Polarski-Linder and early dark energy model) and on the coupling with electromagnetism ζ, forecasting future low-medium redshift observations. We combine supernovae and weak lensing measurements from the Euclid experiment with high-resolution spectroscopy measurements of fundamental couplings and the redshift drift from the European Extremely Large Telescope, highlighting the contribution of each probe. Moreover, we also consider the case where the field driving the α evolution is not the one responsible for cosmic acceleration and investigate how future observations can constrain this scenario.

Planck intermediate results: XXVII. High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel -SPIRE

DOE PAGES

Aghanim, N.; Altieri, B.; Arnaud, M.; ...

2015-09-30

We have used the Planck all-sky submillimetre and millimetre maps to search for rare sources distinguished by extreme brightness, a few hundred millijanskies, and their potential for being situated at high redshift. These “cold” Planck sources, selected using the High Frequency Instrument (HFI) directly from the maps and from the Planck Catalogue of Compact Sources (PCCS), all satisfy the criterion of having their rest-frame far-infrared peak redshifted to the frequency range 353–857 GHz. This colour-selection favours galaxies in the redshift range z = 2–4, which we consider as cold peaks in the cosmic infrared background. With a 4'.5 beam atmore » the four highest frequencies, our sample is expected to include overdensities of galaxies in groups or clusters, lensed galaxies, and chance line-of-sight projections. In this paper, we perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500μm sources, in comparison to reference SPIRE fields. About 94% of the SPIRE sources in the Planck fields are consistent with being overdensities of galaxies peaking at 350μm, with 3% peaking at 500μm, and none peaking at 250μm. About 3% are candidate lensed systems, all 12 of which have secure spectroscopic confirmations, placing them at redshifts z> 2.2. Only four targets are Galactic cirrus, yielding a success rate in our search strategy for identifying extragalactic sources within the Planck beam of better than 98%. The galaxy overdensities are detected with high significance, half of the sample showing statistical significance above 10σ. The SPIRE photometric redshifts of galaxies in overdensities suggest a peak at z ≃ 2, assuming a single common dust temperature for the sources of T d = 35 K. Under this assumption, we derive an infrared (IR) luminosity for each SPIRE source of about 4 × 10 12L ⊙, yielding star formation rates of typically 700 M ⊙ yr -1. If the observed overdensities are actual gravitationally-bound structures, the total IR luminosity of all their SPIRE-detected sources peaks at 4 × 10 13L ⊙, leading to total star formation rates of perhaps 7 × 10 3M ⊙ yr -1 per overdensity. Taken together, these sources show the signatures of high-z (z> 2) protoclusters of intensively star-forming galaxies. Finally, all these observations confirm the uniqueness of our sample compared to reference samples and demonstrate the ability of the all-skyPlanck-HFI cold sources to select populations of cosmological and astrophysical interest for structure formation studies.« less

Planck intermediate results: XXVII. High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel -SPIRE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aghanim, N.; Altieri, B.; Arnaud, M.

We have used the Planck all-sky submillimetre and millimetre maps to search for rare sources distinguished by extreme brightness, a few hundred millijanskies, and their potential for being situated at high redshift. These “cold” Planck sources, selected using the High Frequency Instrument (HFI) directly from the maps and from the Planck Catalogue of Compact Sources (PCCS), all satisfy the criterion of having their rest-frame far-infrared peak redshifted to the frequency range 353–857 GHz. This colour-selection favours galaxies in the redshift range z = 2–4, which we consider as cold peaks in the cosmic infrared background. With a 4'.5 beam atmore » the four highest frequencies, our sample is expected to include overdensities of galaxies in groups or clusters, lensed galaxies, and chance line-of-sight projections. In this paper, we perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500μm sources, in comparison to reference SPIRE fields. About 94% of the SPIRE sources in the Planck fields are consistent with being overdensities of galaxies peaking at 350μm, with 3% peaking at 500μm, and none peaking at 250μm. About 3% are candidate lensed systems, all 12 of which have secure spectroscopic confirmations, placing them at redshifts z> 2.2. Only four targets are Galactic cirrus, yielding a success rate in our search strategy for identifying extragalactic sources within the Planck beam of better than 98%. The galaxy overdensities are detected with high significance, half of the sample showing statistical significance above 10σ. The SPIRE photometric redshifts of galaxies in overdensities suggest a peak at z ≃ 2, assuming a single common dust temperature for the sources of T d = 35 K. Under this assumption, we derive an infrared (IR) luminosity for each SPIRE source of about 4 × 10 12L ⊙, yielding star formation rates of typically 700 M ⊙ yr -1. If the observed overdensities are actual gravitationally-bound structures, the total IR luminosity of all their SPIRE-detected sources peaks at 4 × 10 13L ⊙, leading to total star formation rates of perhaps 7 × 10 3M ⊙ yr -1 per overdensity. Taken together, these sources show the signatures of high-z (z> 2) protoclusters of intensively star-forming galaxies. Finally, all these observations confirm the uniqueness of our sample compared to reference samples and demonstrate the ability of the all-skyPlanck-HFI cold sources to select populations of cosmological and astrophysical interest for structure formation studies.« less

Planck intermediate results. XXVII. High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel-SPIRE

NASA Astrophysics Data System (ADS)

Planck Collaboration; Aghanim, N.; Altieri, B.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Beelen, A.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bethermin, M.; Bielewicz, P.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Calabrese, E.; Canameras, R.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chary, R.-R.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Couchot, F.; Crill, B. P.; Curto, A.; Danese, L.; Dassas, K.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Falgarone, E.; Flores-Cacho, I.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Frye, B.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Guéry, D.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Helou, G.; Hernández-Monteagudo, C.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Le Floc'h, E.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; MacKenzie, T.; Maffei, B.; Mandolesi, N.; Maris, M.; Martin, P. G.; Martinache, C.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Natoli, P.; Negrello, M.; Nesvadba, N. P. H.; Novikov, D.; Novikov, I.; Omont, A.; Pagano, L.; Pajot, F.; Pasian, F.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ristorcelli, I.; Rocha, G.; Roudier, G.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Sunyaev, R.; Sutton, D.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Valtchanov, I.; Van Tent, B.; Vieira, J. D.; Vielva, P.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Welikala, N.; Zacchei, A.; Zonca, A.

2015-10-01

We have used the Planck all-sky submillimetre and millimetre maps to search for rare sources distinguished by extreme brightness, a few hundred millijanskies, and their potential for being situated at high redshift. These "cold" Planck sources, selected using the High Frequency Instrument (HFI) directly from the maps and from the Planck Catalogue of Compact Sources (PCCS), all satisfy the criterion of having their rest-frame far-infrared peak redshifted to the frequency range 353-857 GHz. This colour-selection favours galaxies in the redshift range z = 2-4, which we consider as cold peaks in the cosmic infrared background. With a 4.´5 beam at the four highest frequencies, our sample is expected to include overdensities of galaxies in groups or clusters, lensed galaxies, and chance line-of-sight projections. We perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500μm sources, in comparison to reference SPIRE fields. About 94% of the SPIRE sources in the Planck fields are consistent with being overdensities of galaxies peaking at 350μm, with 3% peaking at 500μm, and none peaking at 250μm. About 3% are candidate lensed systems, all 12 of which have secure spectroscopic confirmations, placing them at redshifts z> 2.2. Only four targets are Galactic cirrus, yielding a success rate in our search strategy for identifying extragalactic sources within the Planck beam of better than 98%. The galaxy overdensities are detected with high significance, half of the sample showing statistical significance above 10σ. The SPIRE photometric redshifts of galaxies in overdensities suggest a peak at z ≃ 2, assuming a single common dust temperature for the sources of Td = 35 K. Under this assumption, we derive an infrared (IR) luminosity for each SPIRE source of about 4 × 1012L⊙, yielding star formation rates of typically 700 M⊙ yr-1. If the observed overdensities are actual gravitationally-bound structures, the total IR luminosity of all their SPIRE-detected sources peaks at 4 × 1013L⊙, leading to total star formation rates of perhaps 7 × 103M⊙ yr-1 per overdensity. Taken together, these sources show the signatures of high-z (z> 2) protoclusters of intensively star-forming galaxies. All these observations confirm the uniqueness of our sample compared to reference samples and demonstrate the ability of the all-skyPlanck-HFI cold sources to select populations of cosmological and astrophysical interest for structure formation studies. Appendices are available in electronic form at http://www.aanda.org

Infrared-faint radio sources remain undetected at far-infrared wavelengths. Deep photometric observations using the Herschel Space Observatory

NASA Astrophysics Data System (ADS)

Herzog, A.; Norris, R. P.; Middelberg, E.; Spitler, L. R.; Leipski, C.; Parker, Q. A.

2015-08-01

Context. Showing 1.4 GHz flux densities in the range of a few to a few tens of mJy, infrared-faint radio sources (IFRS) are a type of galaxy characterised by faint or absent near-infrared counterparts and consequently extreme radio-to-infrared flux density ratios up to several thousand. Recent studies showed that IFRS are radio-loud active galactic nuclei (AGNs) at redshifts ≳2, potentially linked to high-redshift radio galaxies (HzRGs). Aims: This work explores the far-infrared emission of IFRS, providing crucial information on the star forming and AGN activity of IFRS. Furthermore, the data enable examining the putative relationship between IFRS and HzRGs and testing whether IFRS are more distant or fainter siblings of these massive galaxies. Methods: A sample of six IFRS was observed with the Herschel Space Observatory between 100 μm and 500 μm. Using these results, we constrained the nature of IFRS by modelling their broad-band spectral energy distribution (SED). Furthermore, we set an upper limit on their infrared SED and decomposed their emission into contributions from an AGN and from star forming activity. Results: All six observed IFRS were undetected in all five Herschel far-infrared channels (stacking limits: σ = 0.74 mJy at 100 μm, σ = 3.45 mJy at 500 μm). Based on our SED modelling, we ruled out the following objects to explain the photometric characteristics of IFRS: (a) known radio-loud quasars and compact steep-spectrum sources at any redshift; (b) starburst galaxies with and without an AGN and Seyfert galaxies at any redshift, even if the templates were modified; and (c) known HzRGs at z ≲ 10.5. We find that the IFRS analysed in this work can only be explained by objects that fulfil the selection criteria of HzRGs. More precisely, IFRS could be (a) known HzRGs at very high redshifts (z ≳ 10.5); (b) low-luminosity siblings of HzRGs with additional dust obscuration at lower redshifts; (c) scaled or unscaled versions of Cygnus A at any redshift; and (d) scaled and dust-obscured radio-loud quasars or compact steep spectrum sources. We estimated upper limits on the infrared luminosity, the black hole accretion rate, and the star formation rate of IFRS, which all agreed with corresponding numbers of HzRGs. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

The X-ray structure of a galaxy cluster at z = 0.54 - Implications for cluster evolution and cosmology

NASA Technical Reports Server (NTRS)

White, S. D. M.; Silk, J.; Henry, J. P.

1981-01-01

High-resolution X-ray observations of the rich cluster 0016+16 at a redshift of 0.541 are presented. The emitting gas in this cluster is hot and extremely luminous, and its structure resembles that seen in the brightest nearby cluster sources. In most of its properties, 0016+16 resembles a richer version of the Coma cluster, and it offers little support to the hypothesis that clusters at z greater than 0.5 differ fundamentally from nearer objects.

A study of ten quasars with redshifts greater than four

NASA Technical Reports Server (NTRS)

Schneider, Donald P.; Schmidt, Maarten; Gunn, James E.

1989-01-01

Four quasars with redshifts greater than four were detected in a low-resolution CCD grism survey. CCD photometry and high S/N, moderate resolution spectra are presented for these quasars and the six other known quasars with redshifts above 4. The M sub B values of nine of the objects are between -27.5 and -25, with the tenth quasar having an M sub B value of -29. The emission lines and shapes of the continua of these ten quasars are similar to those of lower-redshift quasars. The results suggest that the C IV emission lines in high-redshift quasars may be weaker than those in lower-redshift quasars. The continua of all of the high-redshift quasars display strong depressions blueward of the Ly-alpha emission line.

Herschel Extreme Lensing Line Observations: Dynamics of Two Strongly Lensed Star-Forming Galaxies near Redshift z=2*

NASA Technical Reports Server (NTRS)

Rhoads, James E.; Rigby, Jane Rebecca; Malhotra, Sangeeta; Allam, Sahar; Carilli, Chris; Combes, Francoise; Finkelstein, Keely; Finkelstein, Steven; Frye, Brenda; Gerin, Maryvonne;

The mass function of black holes 1

NASA Astrophysics Data System (ADS)

Natarajan, Priyamvada; Volonteri, Marta

2012-05-01

In this paper, we compare the observationally derived black hole mass function (BHMF) of luminous (>1045-1046 erg s-1) broad-line quasars (BLQSOs) at 1 < z < 4.5 drawn from the Sloan Digital Sky Survey (SDSS) presented by Kelly et al., with models of merger-driven black hole (BH) growth in the context of standard hierarchical structure formation models. In these models, we explore two distinct black hole seeding prescriptions at the highest redshifts: 'light seeds'- remnants of Population III stars and 'massive seeds' that form from the direct collapse of pre-galactic discs. The subsequent merger triggered mass build-up of the black hole population is tracked over cosmic time under the assumption of a fixed accretion rate as well as rates drawn from the distribution derived by Merloni & Heinz. Four model snapshots at z= 1.25, 2, 3.25 and 4.25 are compared with the SDSS-derived BHMFs of BLQSOs. We find that the light seed models fall short of reproducing the observationally derived mass function of BLQSOs at MBH > 109 M⊙ throughout the redshift range; the massive seed models with a fixed accretion rate of 0.3 Edd, or with accretion rates drawn from the Merloni & Heinz distribution provide the best fit to the current observational data at z > 2, although they overestimate the high-mass end of the mass function at lower redshifts. At low redshifts, a drastic drop in the accretion rate is observed and this is explained as arising due to the diminished gas supply available due to consumption by star formation or changes in the geometry of the inner feeding regions. Therefore, the overestimate at the high-mass end of the black hole mass function for the massive seed models can be easily modified, as the accretion rate is likely significantly lower at these epochs than what we assume. For the Merloni & Heinz model, examining the Eddington ratio distributions fEdd, we find that they are almost uniformly sampled from fEdd= 10-2 to 1 at z≃ 1, while at high redshift, current observations suggest accretion rates close to Eddington, if not mildly super-Eddington, at least for these extremely luminous quasars. Our key findings are that the duty cycle of super-massive black holes powering BLQSOs increases with increasing redshift for all models and models with Population III remnants as black hole seeds are unable to fit the observationally derived BHMFs for BLQSOs, lending strong support for the massive seeding model.

Extreme Transients in the High Energy Universe

NASA Technical Reports Server (NTRS)

Kouveliotou, Chryssa

2013-01-01

The High Energy Universe is rich in diverse populations of objects spanning the entire cosmological (time)scale, from our own present-day Milky Way to the re-ionization epoch. Several of these are associated with extreme conditions irreproducible in laboratories on Earth. Their study thus sheds light on the behavior of matter under extreme conditions, such as super-strong magnetic fields (in excess of 10^14 G), high gravitational potentials (e.g., Super Massive Black Holes), very energetic collimated explosions resulting in relativistic jet flows (e.g., Gamma Ray Bursts, exceeding 10^53 ergs). In the last thirty years, my work has been mostly focused on two apparently different but potentially linked populations of such transients: magnetars (highly magnetized neutron stars) and Gamma Ray Bursts (strongly beamed emission from relativistic jets), two populations that constitute unique astrophysical laboratories, while also giving us the tools to probe matter conditions in the Universe to redshifts beyond z=10, when the first stars and galaxies were assembled. I did not make this journey alone I have either led or participated in several international collaborations studying these phenomena in multi-wavelength observations; solitary perfection is not sufficient anymore in the world of High Energy Astrophysics. I will describe this journey, present crucial observational breakthroughs, discuss key results and muse on the future of this field.

Interferometric imaging of the high-redshift radio galaxy, 4C60.07: an SMA, Spitzer and VLA study reveals a binary AGN/starburst

NASA Astrophysics Data System (ADS)

Ivison, R. J.; Morrison, G. E.; Biggs, A. D.; Smail, Ian; Willner, S. P.; Gurwell, M. A.; Greve, T. R.; Stevens, J. A.; Ashby, M. L. N.

2008-11-01

High-resolution submillimetre (submm) imaging of the high-redshift radio galaxy (HzRG), 4C60.07, at z = 3.8, has revealed two dusty components of roughly equal integrated flux. Spitzer imaging shows that one of these components (`B') is coincident with an extremely red active galactic nucleus (AGN), offset by ~4arcsec (~30kpc) from the HzRG core. The other submm component (`A') - resolved by our synthesized beam and devoid of emission at 3.6-8.0μm - lies between `B' and the HzRG core. Since the radio galaxy was discovered via its extremely young, steep-spectrum radio lobes and the creation of these lobes was likely triggered by the interaction, we argue that we are witnessing an early-stage merger, prior to its eventual equilibrium state. The interaction is between the host galaxy of an actively fuelled black hole (BH) and a gas-rich starburst/AGN (`B') marked by the compact submm component and coincident with broad CO(4-3) emission. The second submm component (`A') is a plume of cold, dusty gas, associated with a narrow (~150kms-1) CO feature, and may represent a short-lived tidal structure. It has been claimed that HzRGs and submillimetre-selected galaxies (SMGs) differ only in the activity of their AGNs, but such complex submm morphologies are seen only rarely amongst SMGs, which are usually older, more relaxed systems. Our study has important implications: where a galaxy's gas reservoir is not aligned with its central BH, CO may be an unreliable probe of dynamical mass, affecting work on the co-assembly of BHs and host spheroids. Our data support the picture wherein close binary AGN are induced by mergers. They also raise the possibility that some supposedly jet-induced starbursts may have formed co-evally (yet independently of) the radio jets, both triggered by the same interaction. Finally, we note that the HzRG host would have gone unnoticed without its jets and its companion, so there may be many other unseen BHs at high redshift, lost in the sea of ~5 × 108 similarly bright Infrared Array Camera (IRAC) sources - sufficiently massive to drive a >1027-W radio source, yet practically invisible unless actively fuelled.

Optical Spectroscopy of Distant Red Galaxies

NASA Astrophysics Data System (ADS)

Wuyts, Stijn; van Dokkum, Pieter G.; Franx, Marijn; Förster Schreiber, Natascha M.; Illingworth, Garth D.; Labbé, Ivo; Rudnick, Gregory

2009-11-01

We present optical spectroscopic follow-up of a sample of distant red galaxies (DRGs) with K tot s,Vega < 22.5, selected by (J - K)Vega>2.3, in the Hubble Deep Field South (HDFS), the MS 1054-03 field, and the Chandra Deep Field South (CDFS). Spectroscopic redshifts were obtained for 15 DRGs. Only two out of 15 DRGs are located at z < 2, suggesting a high efficiency to select high-redshift sources. From other spectroscopic surveys in the CDFS targeting intermediate to high-redshift populations selected with different criteria, we find spectroscopic redshifts for a further 30 DRGs. We use the sample of spectroscopically confirmed DRGs to establish the high quality (scatter in Δz/(1 + z) of ~0.05) of their photometric redshifts in the considered deep fields, as derived with EAZY. Combining the spectroscopic and photometric redshifts, we find that 74% of DRGs with K tot s,Vega < 22.5 lie at z>2. The combined spectroscopic and photometric sample is used to analyze the distinct intrinsic and observed properties of DRGs at z < 2 and z>2. In our photometric sample to K tot s,Vega < 22.5, low-redshift DRGs are brighter in Ks than high-redshift DRGs by 0.7 mag, and more extincted by 1.2 mag in AV . Our analysis shows that the DRG criterion selects galaxies with different properties at different redshifts. Such biases can be largely avoided by selecting galaxies based on their rest-frame properties, which requires very good multi-band photometry and high quality photometric redshifts.

THE MICRO-ARCSECOND SCINTILLATION-INDUCED VARIABILITY (MASIV) SURVEY. III. OPTICAL IDENTIFICATIONS AND NEW REDSHIFTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pursimo, Tapio; Ojha, Roopesh; Jauncey, David L.

2013-04-10

Intraday variability (IDV) of the radio emission from active galactic nuclei is now known to be predominantly due to interstellar scintillation (ISS). The MASIV (The Micro-Arcsecond Scintillation-Induced Variability) survey of 443 flat spectrum sources revealed that the IDV is related to the radio flux density and redshift. A study of the physical properties of these sources has been severely handicapped by the absence of reliable redshift measurements for many of these objects. This paper presents 79 new redshifts and a critical evaluation of 233 redshifts obtained from the literature. We classify spectroscopic identifications based on emission line properties, finding thatmore » 78% of the sources have broad emission lines and are mainly FSRQs. About 16% are weak lined objects, chiefly BL Lacs, and the remaining 6% are narrow line objects. The gross properties (redshift, spectroscopic class) of the MASIV sample are similar to those of other blazar surveys. However, the extreme compactness implied by ISS favors FSRQs and BL Lacs in the MASIV sample as these are the most compact object classes. We confirm that the level of IDV depends on the 5 GHz flux density for all optical spectral types. We find that BL Lac objects tend to be more variable than broad line quasars. The level of ISS decreases substantially above a redshift of about two. The decrease is found to be generally consistent with ISS expected for beamed emission from a jet that is limited to a fixed maximum brightness temperature in the source rest frame.« less

Photometric redshift estimation via deep learning. Generalized and pre-classification-less, image based, fully probabilistic redshifts

NASA Astrophysics Data System (ADS)

D'Isanto, A.; Polsterer, K. L.

2018-01-01

Context. The need to analyze the available large synoptic multi-band surveys drives the development of new data-analysis methods. Photometric redshift estimation is one field of application where such new methods improved the results, substantially. Up to now, the vast majority of applied redshift estimation methods have utilized photometric features. Aims: We aim to develop a method to derive probabilistic photometric redshift directly from multi-band imaging data, rendering pre-classification of objects and feature extraction obsolete. Methods: A modified version of a deep convolutional network was combined with a mixture density network. The estimates are expressed as Gaussian mixture models representing the probability density functions (PDFs) in the redshift space. In addition to the traditional scores, the continuous ranked probability score (CRPS) and the probability integral transform (PIT) were applied as performance criteria. We have adopted a feature based random forest and a plain mixture density network to compare performances on experiments with data from SDSS (DR9). Results: We show that the proposed method is able to predict redshift PDFs independently from the type of source, for example galaxies, quasars or stars. Thereby the prediction performance is better than both presented reference methods and is comparable to results from the literature. Conclusions: The presented method is extremely general and allows us to solve of any kind of probabilistic regression problems based on imaging data, for example estimating metallicity or star formation rate of galaxies. This kind of methodology is tremendously important for the next generation of surveys.

Tomographic local 2D analyses of the WISExSuperCOSMOS all-sky galaxy catalogue

NASA Astrophysics Data System (ADS)

Novaes, C. P.; Bernui, A.; Xavier, H. S.; Marques, G. A.

2018-05-01

The recent progress in obtaining larger and deeper galaxy catalogues is of fundamental importance for cosmological studies, especially to robustly measure the large scale density fluctuations in the Universe. The present work uses the Minkowski Functionals (MF) to probe the galaxy density field from the WISExSuperCOSMOS (WSC) all-sky catalogue by performing tomographic local analyses in five redshift shells (of thickness δz = 0.05) in the total range of 0.10 < z < 0.35. Here, for the first time, the MF are applied to 2D projections of the galaxy number count (GNC) fields with the purpose of looking for regions in the WSC catalogue with unexpected features compared to ΛCDM mock realisations. Our methodology reveals 1 - 3 regions of the GNC maps in each redshift shell with an uncommon behaviour (extreme regions), i.e., p-value < 1.4%. Indeed, the resulting MF curves show signatures that suggest the uncommon behaviour to be associated with the presence of over- or under-densities there, but contamination due to residual foregrounds is not discarded. Additionally, even though our analyses indicate a good agreement among data and simulations, we identify 1 highly extreme region, seemingly associated to a large clustered distribution of galaxies. Our results confirm the usefulness of the MF to analyse GNC maps from photometric galaxy datasets.

The EVE Doppler Sensitivity and Flare Observations

NASA Technical Reports Server (NTRS)

Hudson, H. S.; Woods, T. N.; Chamberlin, P. C.; Didkovsky, L.; Del Zanna, G.

2011-01-01

The Extreme-ultraviolet Variability Experiment (EVE) obtains continuous EUV spectra of the Sun viewed as a star. Its primary objective is the characterization of solar spectral irradiance, but its sensitivity and stability make it extremely interesting for observations of variability on time scales down to the limit imposed by its basic 10 s sample interval. In this paper we characterize the Doppler sensitivity of the EVE data. We find that the 30.4 nm line of He II has a random Doppler error below 0.001 nm (1 pm, better than 10 km/s as a redshift), with ample stability to detect the orbital motion of its satellite, the Solar Dynamics Observatory (SDO). Solar flares also displace the spectrum, both because of Doppler shifts and because of EVE's optical layout, which (as with a slitless spectrograph) confuses position and wavelength. As a flare develops, the centroid of the line displays variations that reflect Doppler shifts and therefore flare dynamics. For the impulsive phase of the flare SOL2010-06-12, we find the line centroid to have a redshift of 16.8 +/- 5.9 km/s relative to that of the flare gradual phase (statistical errors only). We find also that high-temperature lines, such as Fe XXIV 19.2 nm, have well-determined Doppler components for major flares, with decreasing apparent blueshifts as expected from chromospheric evaporation flows.

Witnessing the reionization history using Cosmic Microwave Background observation from Planck

NASA Astrophysics Data System (ADS)

Hazra, Dhiraj Kumar; Smoot, George F.

2017-11-01

We constrain the history of reionization using the data from Planck 2015 Cosmic Microwave Background (CMB) temperature and polarization anisotropy observations. We also use prior constraints on the reionization history at redshifts ~7-8 obtained from Lyman-α emission observations. Using the free electron fractions at different redshifts as free parameters, we construct the complete reionization history using polynomials. Our construction provides an extremely flexible framework to search for the history of reionization as a function of redshifts. We present a conservative and an optimistic constraint on reionization that are categorized by the flexibilities of the models and datasets used to constrain them, and we report that CMB data marginally favors extended reionization histories. In both the cases, we find the mean values of optical depth to be larger (≈0.09 and 0.1) than what we find in standard steplike reionization histories (0.079 ± 0.017). At the same time we also find that the maximum free electron fraction allowed by the data for redshifts more than 15 is ~0.25 at 95.4% confidence limit in the case of optimistic constraint.

Deep CO(1-0) Observations of z = 1.62 Cluster Galaxies with Substantial Molecular Gas Reservoirs and Normal Star Formation Efficiencies

NASA Astrophysics Data System (ADS)

Rudnick, Gregory; Hodge, Jacqueline; Walter, Fabian; Momcheva, Ivelina; Tran, Kim-Vy; Papovich, Casey; da Cunha, Elisabete; Decarli, Roberto; Saintonge, Amelie; Willmer, Christopher; Lotz, Jennifer; Lentati, Lindley

2017-11-01

We present an extremely deep CO(1-0) observation of a confirmed z = 1.62 galaxy cluster. We detect two spectroscopically confirmed cluster members in CO(1-0) with signal-to-noise ratio > 5. Both galaxies have log({{ M }}\\star /{{ M }}⊙ ) > 11 and are gas rich, with {{ M }}{mol}/({{ M }}\\star +{{ M }}{mol}) ˜ 0.17-0.45. One of these galaxies lies on the star formation rate (SFR)-{{ M }}\\star sequence, while the other lies an order of magnitude below. We compare the cluster galaxies to other SFR-selected galaxies with CO measurements and find that they have CO luminosities consistent with expectations given their infrared luminosities. We also find that they have gas fractions and star formation efficiencies (SFE) comparable to what is expected from published field galaxy scaling relations. The galaxies are compact in their stellar light distribution, at the extreme end for all high-redshift star-forming galaxies. However, their SFE is consistent with other field galaxies at comparable compactness. This is similar to two other sources selected in a blind CO survey of the HDF-N. Despite living in a highly quenched protocluster core, the molecular gas properties of these two galaxies, one of which may be in the process of quenching, appear entirely consistent with field scaling relations between the molecular gas content, stellar mass, star formation rate, and redshift. We speculate that these cluster galaxies cannot have any further substantive gas accretion if they are to become members of the dominant passive population in z< 1 clusters.

PHL 1092: A narrow-line quasar emerging from the darkness

NASA Astrophysics Data System (ADS)

Gallo, Luigi

2013-10-01

The radio quiet, narrow line quasar, PHL1092 exhibits the extreme behaviour associated with 1H0707 and IRAS13224, but at a high redshift (z=0.396) and with high luminosity (~10^45 erg/s). From a short, bright state observation of PHL1092 we discovered a super soft excess, possible relativistically broadened FeL and K emission, high radiative efficiency, and possible high velocity outflow. Follow up observations between 2008-10 caught the quasar in a deep minimum that could be attributed to disruption of the corona. We will monitor PHL1092 with Swift to catch the quasar emerging from its current low-flux state so that we can study the bright state of the AGN with a triggered 130ks XMM observation.

A Very Hot, High Redshift Cluster of Galaxies: More Trouble for Omega(0) = 1

NASA Technical Reports Server (NTRS)

Donahue, Megan; Voit, G. Mark; Gioia, Isabella; Luppino, Gerry; Hughes, John P.; Stocke, John T.

1998-01-01

We have observed the most distant (= 0.829) cluster of galaxies in the Einstein Extended Medium Sensitivity Survey (EMSS), with the ASCA and ROSAT satellites. We find an X-ray temperature of 12.3 (sup +3.1) (sub -2.2)keV for this cluster, and the ROSAT map reveals significant substructure. The high temperature of MS1054-0321 is consistent with both its approximate velocity dispersion, based on the redshifts of 12 cluster members we have obtained at the Keck and the Canada-France-Hawaii telescopes, and with its weak lensing signature. The X-ray temperature of this cluster implies a virial mass approx. 7.4 x 10 (sup 14) h (sup -1) M (circle dot), if the mean matter density in the universe equals the critical value (OMEGA (sub 0) = 1), or larger if OMEGA (sub 0) is less than 1. Finding such a hot, massive cluster in the EMSS is extremely improbable if clusters grew from Gaussian perturbations in an OMEGA (sub 0) = 1 universe. Combining the assumptions that OMEGA (sub 0) = 1 and that the initial perturbations were Gaussian with the observed X-ray temperature function at low redshift, we show that this probability of this cluster occurring in the volume sampled by the EMSS is less than a few times 10 (sup -5). Nor is MS1054-0321 the only hot cluster at high redshift; the only two other z greater than 0.5 EMSS clusters already observed with ASCA also have temperatures exceeding 8 keV. Assuming again that the initial perturbations were Gaussian and OMEGA (sub 0) = 1, we find that each one is improbable at the less than 10 (sup -2) level. These observations, along with the fact that these luminosities and temperatures of the high-z clusters all agree with the low-z L (sub X) - T (sub X) relation, argue strongly that OMEGA (sub 0) less than 1. Otherwise, the initial perturbations must be non-Gaussian, if these clusters' temperatures do indeed reflect their gravitational potentials.

The bright optical afterglow of the nearby gamma-ray burst of 29 March 2003.

PubMed

Price, P A; Fox, D W; Kulkarni, S R; Peterson, B A; Schmidt, B P; Soderberg, A M; Yost, S A; Berger, E; Djorgovski, S G; Frail, D A; Harrison, F A; Sari, R; Blain, A W; Chapman, S C

2003-06-19

Past studies of cosmological gamma-ray bursts (GRBs) have been hampered by their extreme distances, resulting in faint afterglows. A nearby GRB could potentially shed much light on the origin of these events, but GRBs with a redshift z

Star Formation in low mass galaxies

NASA Astrophysics Data System (ADS)

Mehta, Vihang

2018-01-01

Our current hierarchical view of the universe asserts that the large galaxies we see today grew via mergers of numerous smaller galaxies. As evidenced by recent literature, the collective impact of these low mass galaxies on the universe is more substantial than previously thought. Studying the growth and evolution of these low mass galaxies is critical to our understanding of the universe as a whole. Star formation is one of the most important ongoing processes in galaxies. Forming stars is fundamental to the growth of a galaxy. One of the main goals of my thesis is to analyze the star formation in these low mass galaxies at different redshifts.Using the Hubble UltraViolet Ultra Deep Field (UVUDF), I investigate the star formation in galaxies at the peak of the cosmic star formation history using the ultraviolet (UV) light as a star formation indicator. Particularly, I measure the UV luminosity function (LF) to probe the volume-averaged star formation properties of galaxies at these redshifts. The depth of the UVUDF is ideal for a direct measurement of the faint end slope of the UV LF. This redshift range also provides a unique opportunity to directly compare UV to the "gold standard" of star formation indicators, namely the Hα nebular emission line. A joint analysis of the UV and Hα LFs suggests that, on average, the star formation histories in low mass galaxies (~109 M⊙) are more bursty compared to their higher mass counterparts at these redshifts.Complementary to the analysis of the average star formation properties of the bulk galaxy population, I investigate the details of star formation in some very bursty galaxies at lower redshifts selected from Spitzer Large Area Survey with Hyper-Suprime Cam (SPLASH). Using a broadband color-excess selection technique, I identify a sample of low redshift galaxies with bright nebular emission lines in the Subaru-XMM Deep Field (SXDF) from the SPLASH-SXDF catalog. These galaxies are highly star forming and have extremely low masses (105-107 M⊙). They are much fainter equivalents of the "green pea" galaxies found in SDSS. These objects are followed up with HectoSpec on the MMT to confirm their redshift as well as study their star formation properties in detail.

Radio polarization properties of quasars and active galaxies at high redshifts

NASA Astrophysics Data System (ADS)

Vernstrom, T.; Gaensler, B. M.; Vacca, V.; Farnes, J. S.; Haverkorn, M.; O'Sullivan, S. P.

2018-04-01

We present the largest ever sample of radio polarization properties for z > 4 sources, with 14 sources having significant polarization detections. Using wide-band data from the Karl G. Jansky Very Large Array, we obtained the rest-frame total intensity and polarization properties of 37 radio sources, nine of which have spectroscopic redshifts in the range 1 ≤ z ≤ 1.4, with the other 28 having spectroscopic redshifts in the range 3.5 ≤ z ≤ 6.21. Fits are performed for the Stokes I and fractional polarization spectra, and Faraday rotation measures are derived using rotation measure synthesis and QU fitting. Using archival data of 476 polarized sources, we compare high-redshift (z > 3) source properties to a 15 GHz rest-frame luminosity matched sample of low-redshift (z < 3) sources to investigate if the polarization properties of radio sources at high redshifts are intrinsically different than those at low redshift. We find a mean of the rotation measure absolute values, corrected for Galactic rotation, of 50 ± 22 rad m-2 for z > 3 sources and 57 ± 4 rad m-2 for z < 3. Although there is some indication of lower intrinsic rotation measures at high-z possibly due to higher depolarization from the high-density environments, using several statistical tests we detect no significant difference between low- and high-redshift sources. Larger samples are necessary to determine any true physical difference.

Infrared/optical energy distributions of high redshifted quasars

NASA Technical Reports Server (NTRS)

Soifer, B. T.; Neugebauer, G.; Oke, J. B.; Matthews, K.; Lacy, J. H.

1982-01-01

Measurements at 1.2, 1.6 and 2.2 microns were combined with visual spectrophotometry of 21 quasars having redshifts z or = 2.66. The primary result is that the rest frame visual/ultraviolet continua of the high redshift quasars are well described by a sum of a power law continuum with slope of approximately -0.4 and a 3000 A bump. The rest frame visual/ultraviolet continua of these quasars are quite similar to that of 3C273, the archetype of low redshift quasars. There does not appear to be any visual/ultraviolet properties distinguishing high redshift quasars selected via visual or radio techniques.

MAPPING THE CLUMPY STRUCTURES WITHIN SUBMILLIMETER GALAXIES USING LASER-GUIDE STAR ADAPTIVE OPTICS SPECTROSCOPY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menendez-Delmestre, Karin; Goncalves, Thiago S.; Blain, Andrew W.

2013-04-20

We present the first integral-field spectroscopic observations of high-redshift submillimeter-selected galaxies (SMGs) using Laser-Guide Star Adaptive Optics. We target H{alpha} emission of three SMGs at redshifts z {approx} 1.4-2.4 with the OH-Suppressing Infrared Imaging Spectrograph on Keck. The spatially resolved spectroscopy of these galaxies reveals unresolved broad-H{alpha} line regions (FWHM >1000 km s{sup -1}) likely associated with an active galactic nucleus (AGN) and regions of diffuse star formation traced by narrow-line H{alpha} emission (FWHM {approx}< 500 km s{sup -1}) dominated by multiple H{alpha}-bright stellar clumps, each contributing 1%-30% of the total clump-integrated H{alpha} emission. We find that these SMGs hostmore » high star formation rate surface densities, similar to local extreme sources, such as circumnuclear starbursts and luminous infrared galaxies. However, in contrast to these local environments, SMGs appear to be undergoing such intense activity on significantly larger spatial scales as revealed by extended H{alpha} emission over 4-16 kpc. H{alpha} kinematics show no evidence of ordered global motion as would be found in a disk, but rather large velocity offsets ({approx}few Multiplication-Sign 100 km s{sup -1}) between the distinct stellar clumps. Together with the asymmetric distribution of the stellar clumps around the AGN in these objects, it is unlikely that we are unveiling a clumpy disk structure as has been suggested in other high-redshift populations of star-forming galaxies. The SMG clumps in this sample may correspond to remnants of originally independent gas-rich systems that are in the process of merging, hence triggering the ultraluminous SMG phase.« less

Galaxy luminosity function: evolution at high redshift

NASA Astrophysics Data System (ADS)

Martinet, N.; Durret, F.; Guennou, L.; Adami, C.

2014-12-01

There are some disagreements about the abundance of faint galaxies in high redshift clusters. DAFT/FADA (Dark energy American French Team) is a medium redshift (0.4

The formation of ultra compact dwarf galaxies and massive globular clusters. Quasar-like objects to test for a variable stellar initial mass function

NASA Astrophysics Data System (ADS)

Jeřábková, T.; Kroupa, P.; Dabringhausen, J.; Hilker, M.; Bekki, K.

2017-12-01

The stellar initial mass function (IMF) has been described as being invariant, bottom-heavy, or top-heavy in extremely dense star-burst conditions. To provide usable observable diagnostics, we calculate redshift dependent spectral energy distributions of stellar populations in extreme star-burst clusters, which are likely to have been the precursors of present day massive globular clusters (GCs) and of ultra compact dwarf galaxies (UCDs). The retention fraction of stellar remnants is taken into account to assess the mass to light ratios of the ageing star-burst. Their redshift dependent photometric properties are calculated as predictions for James Webb Space Telescope (JWST) observations. While the present day GCs and UCDs are largely degenerate concerning bottom-heavy or top-heavy IMFs, a metallicity- and density-dependent top-heavy IMF implies the most massive UCDs, at ages < 100 Myr, to appear as objects with quasar-like luminosities with a 0.1-10% variability on a monthly timescale due to core collapse supernovae.

High Redshift Supernova Search

Science.gov Websites

;on schedule." Before-and-after pictures (and Hubble Space Telescope picture) of a high-redshift High Redshift Supernova Search Home Page of the Supernova Cosmology Project This is the Lawrence Foretell Fate of the Universe." Pictures from the ground and from the Hubble Space Telescope: [PDF

Distant Galaxy Clusters Hosting Extreme Central Galaxies

NASA Astrophysics Data System (ADS)

McDonald, Michael

2014-09-01

The recently-discovered Phoenix cluster harbors the most star-forming central cluster galaxy of any cluster in the known Universe, by nearly a factor of 10. This extreme system appears to be fulfilling early cooling flow predictions, although the lack of similar systems makes any interpretation difficult. In an attempt to find other "Phoenix-like" clusters, we have cross-correlated archival all-sky surveys (in which Phoenix was detected) and isolated 4 similarly-extreme systems which are also coincident in position and redshift with an overdensity of red galaxies. We propose here to obtain Chandra observations of these extreme, Phoenix-like systems, in order to confirm them as relaxed, rapidly-cooling galaxy clusters.

Detecting First Supernovae with JWST

NASA Astrophysics Data System (ADS)

Regos, Eniko; FLARE

2018-01-01

We have applied for a JWST ERS First Transients Survey, FLARE to answer empirically how the Universe made its first stars. To quest the epoch of reionization we target what happened to these first stars by observing the most luminous events, supernovae. These transients provide direct constraints on star formation rates and the initial mass function.These very rare events can be reached by JWST at 27 mag AB in 2 micron and 4.4 micron over a field of 0.1 square degree visited multiple times each year.The survey may detect massive Pop III SNe at redshifts up to 10, pinpointing the redshift of first stars, a key scientific goal of JWST.We explore all models of star formation history (derived from UV luminosity densities and IR data), DTD, top heavy IMF of early, low metallicity stars, and normalizations to data of SN Ia, II rates (SNLS, CLASH, CANDELS, SDSS, SVISS), as well as SLSN (ROTSE, SNLS) to estimate the expected SN rates as function of redshift.Population synthesis of double degenerate and single degenerate scenarios of SN Ia shows that the shape of the DTD is rather insensitive to the assumptions (common envelope prescription and metallicities, or retention efficiency of accreted H to white dwarf core and mass transfer rate).Indeed GOODS High z SN Ia rates imply substantial delay in their progenitor model, and Hubble Higher z SN search constrains delay time distribution models as well.SLSN (I, II /H/ and extreme rare pulsational pair instability) are magnetars (ULGRB) in high local star formation rate, faint, low metallicity galaxies.

IGR J12319-0749: Evidence for Another Extreme Blazar Found with INTEGRAL

NASA Technical Reports Server (NTRS)

Bassani, L.; Landi, R.; Marshall, F. E.; Malizia, A.; Bazzano, A.; Bird, A. J.; Gehrels, N.; Ubertini, P.; Masetti, N.

2012-01-01

We report on the identification of a new soft gamma-ray source, IGR J12319-0749, detected with the IBIS imager on board the INTEGRAL satellite. The source, which has an observed 20-100 keV flux of approx 8.3 × 10(exp -12) erg/sq. cm/ s, is spatially coincident with an active galactic nucleus (AGN) at redshift z = 3.12. The broad-band continuum, obtained by combining XRT and IBIS data, is flat (Gamma = 1.3) with evidence for a spectral break around 25 keV (100 keV in the source restframe). X-ray observations indicate flux variability, which is also supported by a comparison with a previous ROSAT measurement. IGR J12319-0749 is also a radio-emitting object likely characterised by a flat spectrum and high radio loudness; optically it is a broad-line emitting object with a massive black hole (2.8 × 10(exp 9) solar masses) at its centre. The source spectral energy distribution is similar to another high-redshift blazar, 225155+2217 at z = 3.668: both objects are bright, with a high accretion disk luminosity and a Compton peak located in the hard X-ray/soft gamma-ray band. IGR J12319-0749 is likely the second-most distant blazar detected so far by INTEGRAL.

AGN radiative feedback in dusty quasar populations

NASA Astrophysics Data System (ADS)

Ishibashi, W.; Banerji, M.; Fabian, A. C.

2017-08-01

New populations of hyper-luminous, dust-obscured quasars have been recently discovered around the peak epoch of galaxy formation (z ˜ 2-3), in addition to similar sources found at lower redshifts. Such dusty quasars are often interpreted as sources 'in transition', from dust-enshrouded starbursts to unobscured luminous quasars, along the evolutionary sequence. Here we consider the role of the active galactic nucleus (AGN) radiative feedback, driven by radiation pressure on dust, in high-luminosity, dust-obscured sources. We analyse how the radiation pressure-driven dusty shell models, with different shell mass configurations, may be applied to the different populations of dusty quasars reported in recent observations. We find that expanding shells, sweeping up matter from the surrounding environment, may account for prolonged obscuration in dusty quasars, e.g. for a central luminosity of L ˜ 1047 erg s-1, a typical obscured phase (with extinction in the range AV ˜ 1-10 mag) may last a few ˜106 yr. On the other hand, fixed-mass shells, coupled with high dust-to-gas ratios, may explain the extreme outflows recently discovered in red quasars at high redshifts. We discuss how the interaction between AGN radiative feedback and the ambient medium at different temporal stages in the evolutionary sequence may contribute to shape the observational appearance of dusty quasar populations.

The WiggleZ Dark Energy Survey: final data release and the metallicity of UV-luminous galaxies

NASA Astrophysics Data System (ADS)

Drinkwater, Michael J.; Byrne, Zachary J.; Blake, Chris; Glazebrook, Karl; Brough, Sarah; Colless, Matthew; Couch, Warrick; Croton, Darren J.; Croom, Scott M.; Davis, Tamara M.; Forster, Karl; Gilbank, David; Hinton, Samuel R.; Jelliffe, Ben; Jurek, Russell J.; Li, I.-hui; Martin, D. Christopher; Pimbblet, Kevin; Poole, Gregory B.; Pracy, Michael; Sharp, Rob; Smillie, Jon; Spolaor, Max; Wisnioski, Emily; Woods, David; Wyder, Ted K.; Yee, Howard K. C.

2018-03-01

The WiggleZ Dark Energy Survey measured the redshifts of over 200 000 ultraviolet (UV)-selected (NUV < 22.8 mag) galaxies on the Anglo-Australian Telescope. The survey detected the baryon acoustic oscillation signal in the large-scale distribution of galaxies over the redshift range 0.2 < z < 1.0, confirming the acceleration of the expansion of the Universe and measuring the rate of structure growth within it. Here, we present the final data release of the survey: a catalogue of 225 415 galaxies and individual files of the galaxy spectra. We analyse the emission-line properties of these UV-luminous Lyman-break galaxies by stacking the spectra in bins of luminosity, redshift, and stellar mass. The most luminous (-25 mag

Reddened, Redshifted, or Intrinsically Red? Understanding Near-ultraviolet Colors of Type Ia Supernovae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Peter J.; Landez, Nancy J.; Milne, Peter A.

The intrinsic colors of Type Ia supernovae (SNe Ia) are important to understanding their use as cosmological standard candles. Understanding the effects of reddening and redshift on the observed colors are complicated and dependent on the intrinsic spectrum, the filter curves, and the wavelength dependence of reddening. We present ultraviolet and optical data of a growing sample of SNe Ia observed with the Ultraviolet/Optical Telescope on the Swift spacecraft and use this sample to re-examine the near-UV (NUV) colors of SNe Ia. We find that a small amount of reddening ( E ( B − V ) = 0.2 mag)more » could account for the difference between groups designated as NUV-blue and NUV-red, and a moderate amount of reddening ( E ( B − V ) = 0.5 mag) could account for the whole NUV-optical differences. The reddening scenario, however, is inconsistent with the mid-UV colors and color evolution. The effect of redshift alone only accounts for part of the variation. Using a spectral template of SN2011fe, we can forward model the effects of redshift and reddening and directly compare those with the observed colors. We find that some SNe are consistent with reddened versions of SN2011fe, but most SNe Ia are much redder in the uvw 1 − v color than SN2011fe reddened to the same b − v color. The absolute magnitudes show that two out of five NUV-blue SNe Ia are blue because their near-UV luminosity is high, and the other three are optically fainter. We also show that SN 2011fe is not a “normal” SN Ia in the UV, but has colors placing it at the blue extreme of our sample.« less

Extremely red quasars from SDSS, BOSS and WISE: classification of optical spectra

NASA Astrophysics Data System (ADS)

Ross, Nicholas P.; Hamann, Fred; Zakamska, Nadia L.; Richards, Gordon T.; Villforth, Carolin; Strauss, Michael A.; Greene, Jenny E.; Alexandroff, Rachael; Brandt, W. Niel; Liu, Guilin; Myers, Adam D.; Pâris, Isabelle; Schneider, Donald P.

2015-11-01

Quasars with extremely red infrared-to-optical colours are an interesting population that can test ideas about quasar evolution as well as orientation, obscuration and geometric effects in the so-called AGN unified model. To identify such a population, we match the quasar catalogues of the Sloan Digital Sky Survey (SDSS), the Baryon Oscillation Spectroscopic Survey (BOSS) to the Wide-Field Infrared Survey Explorer (WISE) to identify quasars with extremely high infrared-to-optical ratios. We identify 65 objects with rAB - W4Vega > 14 mag (i.e. Fν(22 μm)/Fν(r) ≳ 1000). This sample spans a redshift range of 0.28 < z < 4.36 and has a bimodal distribution, with peaks at z ˜ 0.8 and z ˜ 2.5. It includes three z > 2.6 objects that are detected in the W4 band but not W1 or W2 (i.e. `W1W2 dropouts'). The SDSS/BOSS spectra show that the majority of the objects are reddened type 1 quasars, type 2 quasars (both at low and high redshift) or objects with deep low-ionization broad absorption lines (BALs) that suppress the observed r-band flux. In addition, we identify a class of type 1 permitted broad emission-line objects at z ≃ 2-3 which are characterized by emission line rest-frame equivalent widths (REWs) of ≳150 Å, much larger than those of typical quasars. In particular, 55 per cent (45 per cent) of the non-BAL type 1s with measurable C IV in our sample have REW(C IV) > 100 (150) Å, compared to only 5.8 per cent (1.3 per cent) for non-BAL quasars in BOSS. These objects often also have unusual line ratios, such as very high N V/Ly α ratios. These large REWs might be caused by suppressed continuum emission analogous to type 2 quasars; however, there is no obvious mechanism in standard unified models to suppress the continuum without also obscuring the broad emission lines.

New solution to the problem of the tension between the high-redshift and low-redshift measurements of the Hubble constant

NASA Astrophysics Data System (ADS)

Bolejko, Krzysztof

2018-01-01

During my talk I will present results suggesting that the phenomenon of emerging spatial curvature could resolve the conflict between Planck's (high-redshift) and Riess et al. (low-redshift) measurements of the Hubble constant. The phenomenon of emerging spatial curvature is absent in the Standard Cosmological Model, which has a flat and fixed spatial curvature (small perturbations are considered in the Standard Cosmological Model but their global average vanishes, leading to spatial flatness at all times).In my talk I will show that with the nonlinear growth of cosmic structures the global average deviates from zero. As a result, the spatial curvature evolves from spatial flatness of the early universe to a negatively curved universe at the present day, with Omega_K ~ 0.1. Consequently, the present day expansion rate, as measured by the Hubble constant, is a few percent higher compared to the high-redshift constraints. This provides an explanation why there is a tension between high-redshift (Planck) and low-redshift (Riess et al.) measurements of the Hubble constant. In the presence of emerging spatial curvature these two measurements should in fact be different: high redshift measurements should be slightly lower than the Hubble constant inferred from the low-redshift data.The presentation will be based on the results described in arXiv:1707.01800 and arXiv:1708.09143 (which discuss the phenomenon of emerging spatial curvature) and on a paper that is still work in progress but is expected to be posted on arxiv by the AAS meeting (this paper uses mock low-redshift data to show that starting from the Planck's cosmological models (in the early universe) but with the emerging spatial curvature taken into account, the low-redshift Hubble constant should be 72.4 km/s/Mpc.

High redshift galaxies in the ALHAMBRA survey . I. Selection method and number counts based on redshift PDFs

NASA Astrophysics Data System (ADS)

Viironen, K.; Marín-Franch, A.; López-Sanjuan, C.; Varela, J.; Chaves-Montero, J.; Cristóbal-Hornillos, D.; Molino, A.; Fernández-Soto, A.; Vilella-Rojo, G.; Ascaso, B.; Cenarro, A. J.; Cerviño, M.; Cepa, J.; Ederoclite, A.; Márquez, I.; Masegosa, J.; Moles, M.; Oteo, I.; Pović, M.; Aguerri, J. A. L.; Alfaro, E.; Aparicio-Villegas, T.; Benítez, N.; Broadhurst, T.; Cabrera-Caño, J.; Castander, J. F.; Del Olmo, A.; González Delgado, R. M.; Husillos, C.; Infante, L.; Martínez, V. J.; Perea, J.; Prada, F.; Quintana, J. M.

2015-04-01

Context. Most observational results on the high redshift restframe UV-bright galaxies are based on samples pinpointed using the so-called dropout technique or Ly-α selection. However, the availability of multifilter data now allows the dropout selections to be replaced by direct methods based on photometric redshifts. In this paper we present the methodology to select and study the population of high redshift galaxies in the ALHAMBRA survey data. Aims: Our aim is to develop a less biased methodology than the traditional dropout technique to study the high redshift galaxies in ALHAMBRA and other multifilter data. Thanks to the wide area ALHAMBRA covers, we especially aim at contributing to the study of the brightest, least frequent, high redshift galaxies. Methods: The methodology is based on redshift probability distribution functions (zPDFs). It is shown how a clean galaxy sample can be obtained by selecting the galaxies with high integrated probability of being within a given redshift interval. However, reaching both a complete and clean sample with this method is challenging. Hence, a method to derive statistical properties by summing the zPDFs of all the galaxies in the redshift bin of interest is introduced. Results: Using this methodology we derive the galaxy rest frame UV number counts in five redshift bins centred at z = 2.5,3.0,3.5,4.0, and 4.5, being complete up to the limiting magnitude at mUV(AB) = 24, where mUV refers to the first ALHAMBRA filter redwards of the Ly-α line. With the wide field ALHAMBRA data we especially contribute to the study of the brightest ends of these counts, accurately sampling the surface densities down to mUV(AB) = 21-22. Conclusions: We show that using the zPDFs it is easy to select a very clean sample of high redshift galaxies. We also show that it is better to do statistical analysis of the properties of galaxies using a probabilistic approach, which takes into account both the incompleteness and contamination issues in a natural way. Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, jointly operated by the Max-Planck-Institut für Astronomie (MPIA) at Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC).

High Redshift Quasars

NASA Technical Reports Server (NTRS)

Elvis, Martin S.

1996-01-01

The report for this period includes three papers: 'Associated Absorption at Low and High Redshift'; 'Strong X-ray Absorption in a Broad Absorption Line Quasar: PHL5200'; and 'ASCA and ROSAT X-ray Spectra of High-Redshift Radio-Loud Quasars'. The first gives examples from both low and high redshift for combining information on absorbing material in active galactic nuclei from both x-ray and the UV. The second presents ASCA observations of the z = 1.98 prototype broad absorption line quasar (BALQSO): PHL 5200, detected with both the solid-state imaging spectrometers and the gas imaging spectometers. The third paper presents results on the x-ray properties of 9 high-redshift radio-loud quasars observed by ASCA and ROSAT, including ASCA observations of S5 0014+81 (z = 3.38) and S5 0836+71 (z = 2.17) and ROSAT observations of PKS 2126-158.

Simulating observations with HARMONI: the integral field spectrograph for the European Extremely Large Telescope

NASA Astrophysics Data System (ADS)

Zieleniewski, Simon; Thatte, Niranjan; Kendrew, Sarah; Houghton, Ryan; Tecza, Matthias; Clarke, Fraser; Fusco, Thierry; Swinbank, Mark

2014-07-01

With the next generation of extremely large telescopes commencing construction, there is an urgent need for detailed quantitative predictions of the scientific observations that these new telescopes will enable. Most of these new telescopes will have adaptive optics fully integrated with the telescope itself, allowing unprecedented spatial resolution combined with enormous sensitivity. However, the adaptive optics point spread function will be strongly wavelength dependent, requiring detailed simulations that accurately model these variations. We have developed a simulation pipeline for the HARMONI integral field spectrograph, a first light instrument for the European Extremely Large Telescope. The simulator takes high-resolution input data-cubes of astrophysical objects and processes them with accurate atmospheric, telescope and instrumental effects, to produce mock observed cubes for chosen observing parameters. The output cubes represent the result of a perfect data reduc- tion process, enabling a detailed analysis and comparison between input and output, showcasing HARMONI's capabilities. The simulations utilise a detailed knowledge of the telescope's wavelength dependent adaptive op- tics point spread function. We discuss the simulation pipeline and present an early example of the pipeline functionality for simulating observations of high redshift galaxies.

Fluctuations in radiation backgrounds at high redshift and the first stars

NASA Astrophysics Data System (ADS)

Holzbauer, Lauren Nicole

The first stars to light up our universe are as yet unseen, but there have been many attempts to elucidate their properties. The characteristics of these stars (`Population/Pop III' stars) that we do know lie mostly within theory; they formed out of metal-free hydrogen and helium gas contained in dark matter minihalos at redshifts z 20-30. The extent to which Pop III star formation reached into later times is unknown. Current and near future instruments are incapable of resolving individual Pop III stars. Consequently, astronomers must devise creative means with which to indirectly predict and measure and their properties. In this thesis, we will investigate a few of those means. We use a new method to model fluctuations of the Lyman-Werner (LW) and Lyman-alpha radiation backgrounds at high redshift. At these early epochs the backgrounds are symptoms of a universe newly lit with its first stars. LW photons (11.5-13.6 eV) are of particular interest because they dissociate molecular hydrogen, the primary coolant in the first minihalos that is necessary for star formation. By using a variation of the `halo model', which describes the spatial distribution and clustering of halos, we can efficiently generate power spectra for these backgrounds. Spatial fluctuations in the LW and (indirectly) the Lyman-alpha BG can tell us about the transition from primordial star formation to a more metal-enriched mode that marks the beginning of the second generation of stars in our Universe. The Near Infrared Background (NIRB) has for some time been considered a potential tool with which to indirectly observe the first stars. Ultraviolet (UV) emission from these stars is redshifted into the NIR band, making the NIRB amenable for hunting Pop III stellar signatures. There have been several measurements of the NIRB and subsequent theoretical studies attempting to explain them in recent years. Though controversial, residual levels of the mean NIRB intensity and anisotropies have been detected after subtracting all known foreground stars and galaxies. Pop III stars have been the leading candidates thought responsible for this observed NIRB excess. We model the Pop III stellar contribution to the NIRB mean intensity and fluctuations and generate observationally motivated values of the star formation (SF) efficiency using high redshift measurements of the UV luminosity density with UDF09, UDF12, and WMAP-9 data. This allows us to characterize the properties of a Pop III stellar population that are required to produce the measured excess. Finally, we propose a new method for detecting primordial metal-free and very metal-poor stellar populations by cross-correlating fluctuations in the intensity of Lyman-alpha and He II &λ;1640A emission sourced from high redshifts. Pop III stars are expected to be more massive and more compact than later generations of stars. This results in a much harder ionizing spectrum. A large portion of the ionizing photons have energies with hnu > 54.4 eV that carve out substantial patches of doubly ionized helium, He III. These photoionized regions then begin to shine brightly in He II recombination emission. Due to the lack of heavy elements in these regions, Pop III stars must rely on hydrogen and helium for cooling, enhancing both the Lyman-alpha and He II emission lines. In this regard, Pop III stars can be characterized as `dual emitters,' i.e. producers of both Lyman-alpha and He II emission signatures. Though Lyman-alpha emission is characteristic of both metal-free and metal-enriched stars, He II emission appears to be unique to extremely metal poor stars and metal-free stars, making it a very strong signature of the first stars. Detecting Lyman-alpha + He II dual emission in individual galaxies at high redshift is difficult and so far rare. The astrophysical engines powering the few Lyman-alpha + He II dual emitters that have been discovered have still not been clearly identified. Alternatively, we may be able to map fluctuations in the total intensity of the Lyman-alpha and He II lambda1640 lines, which will allow us to indirectly assess sources that are below typical luminosity thresholds of deep surveys. Cross-correlating these lines can provide us with a useful new tool for inferring properties of the first stars, since the two lines together allow us to better isolate the redshift of source emission and the presence of He II lambda1640 emission is extremely sensitive to stellar metallicity.

Machine-z: Rapid Machine-Learned Redshift Indicator for Swift Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Ukwatta, T. N.; Wozniak, P. R.; Gehrels, N.

2016-01-01

Studies of high-redshift gamma-ray bursts (GRBs) provide important information about the early Universe such as the rates of stellar collapsars and mergers, the metallicity content, constraints on the re-ionization period, and probes of the Hubble expansion. Rapid selection of high-z candidates from GRB samples reported in real time by dedicated space missions such as Swift is the key to identifying the most distant bursts before the optical afterglow becomes too dim to warrant a good spectrum. Here, we introduce 'machine-z', a redshift prediction algorithm and a 'high-z' classifier for Swift GRBs based on machine learning. Our method relies exclusively on canonical data commonly available within the first few hours after the GRB trigger. Using a sample of 284 bursts with measured redshifts, we trained a randomized ensemble of decision trees (random forest) to perform both regression and classification. Cross-validated performance studies show that the correlation coefficient between machine-z predictions and the true redshift is nearly 0.6. At the same time, our high-z classifier can achieve 80 per cent recall of true high-redshift bursts, while incurring a false positive rate of 20 per cent. With 40 per cent false positive rate the classifier can achieve approximately 100 per cent recall. The most reliable selection of high-redshift GRBs is obtained by combining predictions from both the high-z classifier and the machine-z regressor.

Moderate resolution spectrophotometry of high redshift quasars

NASA Technical Reports Server (NTRS)

Schneider, Donald P.; Schmidt, Maarten; Gunn, James E.

1991-01-01

A uniform set of photometry and high signal-to-noise moderate resolution spectroscopy of 33 quasars with redshifts larger than 3.1 is presented. The sample consists of 17 newly discovered quasars (two with redshifts in excess of 4.4) and 16 sources drawn from the literature. The objects in this sample have r magnitudes between 17.4 and 21.4; their luminosities range from -28.8 to -24.9. Three of the 33 objects are broad absorption line quasars. A number of possible high redshift damped Ly-alpha systems were found.

Reconciling the Stellar and Nebular Spectra of High-redshift Galaxies

NASA Astrophysics Data System (ADS)

Steidel, Charles C.; Strom, Allison L.; Pettini, Max; Rudie, Gwen C.; Reddy, Naveen A.; Trainor, Ryan F.

2016-08-01

We present a combined analysis of rest-frame far-UV (FUV; 1000-2000 Å) and rest-frame optical (3600-7000 Å) composite spectra formed from very deep Keck/LRIS and Keck/MOSFIRE observations of a sample of 30 star-forming galaxies with z=2.40+/- 0.11, selected to be broadly representative of the full KBSS-MOSFIRE spectroscopic survey. Since the same massive stars are responsible for the observed FUV continuum and for the excitation of the observed nebular emission, a self-consistent stellar population synthesis model should simultaneously match the details of the FUV stellar+nebular continuum and—when inserted as the excitation source in photoionization models—predict all observed nebular emission line ratios. We find that only models including massive star binaries, having low stellar metallicity ({Z}* /{Z}⊙ ≃ 0.1) but relatively high nebular (ionized gas-phase) abundances ({Z}{{neb}}/{Z}⊙ ≃ 0.5), can successfully match all of the observational constraints. We show that this apparent discrepancy is naturally explained by highly super-solar O/Fe (≃ 4{--}5 {({{O}}/{Fe})}⊙ ), expected for a gas whose enrichment is dominated by the products of core-collapse supernovae. While O dominates the physics of the ionized gas (and thus the nebular emission lines), Fe dominates the extreme-UV (EUV) and FUV opacity and controls the mass-loss rate from massive stars, resulting in particularly dramatic effects for massive stars in binary systems. This high nebular excitation—caused by the hard EUV spectra of Fe-poor massive stars—is much more common at high redshift (z≳ 2) than low redshift due to systematic differences in the star formation history of typical galaxies. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

An Extremely Rich Group Of Starbursts And Agns At A Z=3.1 Proto-Cluster Core

NASA Astrophysics Data System (ADS)

Umehata, Hideki

2017-06-01

The environment where galaxies inhabit is expected to play a critical role in shaping their evolution. Galaxies and nuclei in the dense environment at high redshift (i.e., proto-clusters) provide a good laboratory to investigate the accelerated, most extreme evolution of galaxies at a given epoch. Using ALMA band 3 and band 6, we mapped a 2'x3' region within the node at the junction of the 50 Mpc-scale filamentary three-dimensional structure traced by Lyman-alpha emitters (LAEs) in this field. We obtained 18 robustly detected 1.1mm sources (here after submillimeter galaxies, SMGs) with a signal-to-noise ratio (SNR) >5. We also detected CO(3-2) line from 8 SMGs, which in general shows relatively extended structure. Totally 12 ALMA SMGs have spectroscopic redshifts of z=3.09 and six of them host a X-ray luminous active galactic nuclei (AGN). We also find that multiple z=3.09 ALMA SMGs contribute to two AzTEC sources, supporting that interaction may be responsible for a significant fraction of multiplicity in single-dish sources. Our results suggest that the vigorous star formation activity and the growth of super massive black holes (SMBHs) occurred simultaneously in the densest regions at z 3, which is likely to correspond to the most active historical phase of the massive galaxy population found in the core of the clusters in the present universe.

Super-Eddington accreting massive black holes explore high-z cosmology: Monte-Carlo simulations

NASA Astrophysics Data System (ADS)

Cai, Rong-Gen; Guo, Zong-Kuan; Huang, Qing-Guo; Yang, Tao

2018-06-01

In this paper, we simulate Super-Eddington accreting massive black holes (SEAMBHs) as the candles to probe cosmology for the first time. SEAMBHs have been demonstrated to be able to provide a new tool for estimating cosmological distance. Thus, we create a series of mock data sets of SEAMBHs, especially in the high redshift region, to check their abilities to probe the cosmology. To fulfill the potential of the SEAMBHs on the cosmology, we apply the simulated data to three projects. The first is the exploration of their abilities to constrain the cosmological parameters, in which we combine different data sets of current observations such as the cosmic microwave background from Planck and type Ia supernovae from Joint Light-curve Analysis (JLA). We find that the high redshift SEAMBHs can help to break the degeneracies of the background cosmological parameters constrained by Planck and JLA, thus giving much tighter constraints of the cosmological parameters. The second uses the high redshift SEAMBHs as the complements of the low redshift JLA to constrain the early expansion rate and the dark energy density evolution in the cold dark matter frame. Our results show that these high redshift SEAMBHs are very powerful on constraining the early Hubble rate and the evolution of the dark energy density; thus they can give us more information about the expansion history of our Universe, which is also crucial for testing the Λ CDM model in the high redshift region. Finally, we check the SEAMBH candles' abilities to reconstruct the equation of state for dark energy at high redshift. In summary, our results show that the SEAMBHs, as the rare candles in the high redshift region, can provide us a new and independent observation to probe cosmology in the future.

ALMA observations of atomic carbon in z ˜ 4 dusty star-forming galaxies

NASA Astrophysics Data System (ADS)

Bothwell, M. S.; Aguirre, J. E.; Aravena, M.; Bethermin, M.; Bisbas, T. G.; Chapman, S. C.; De Breuck, C.; Gonzalez, A. H.; Greve, T. R.; Hezaveh, Y.; Ma, J.; Malkan, M.; Marrone, D. P.; Murphy, E. J.; Spilker, J. S.; Strandet, M.; Vieira, J. D.; Weiß, A.

2017-04-01

We present Atacama Large Millimeter Array [C I](1 - 0) (rest frequency 492 GHz) observations for a sample of 13 strongly lensed dusty star-forming galaxies (DSFGs) originally discovered at 1.4 mm in a blank-field survey by the South Pole Telescope (SPT). We compare these new data with available [C I] observations from the literature, allowing a study of the interstellar medium (ISM) properties of ˜30 extreme DSFGs spanning a redshift range 2 < z < 5. Using the [C I] line as a tracer of the molecular ISM, we find a mean molecular gas mass for SPT-DSFGs of 6.6 × 1010 M⊙. This is in tension with gas masses derived via low-J 12CO and dust masses; bringing the estimates into accordance requires either (a) an elevated CO-to-H2 conversion factor for our sample of αCO ˜ 2.5 and a gas-to-dust ratio ˜200, or (b) an high carbon abundance X_{C I} ˜ 7× 10^{-5}. Using observations of a range of additional atomic and molecular lines (including [C I], [C II]and multiple transitions of CO), we use a modern photodissociation region code (3D-PDR) to assess the physical conditions (including the density, UV radiation field strength and gas temperature) within the ISM of the DSFGs in our sample. We find that the ISM within our DSFGs is characterized by dense gas permeated by strong UV fields. We note that previous efforts to characterize photodissociation region regions in DSFGs may have significantly under-estimated the density of the ISM. Combined, our analysis suggests that the ISM of extreme dusty starbursts at high redshift consists of dense, carbon-rich gas not directly comparable to the ISM of starbursts in the local Universe.

Silver Nanoparticle Oligonucleotide Conjugates Based on DNA with Triple Cyclic Disulfide Moieties

PubMed Central

Lee, Jae-Seung; Lytton-Jean, Abigail K. R.; Hurst, Sarah J.; Mirkin, Chad A.

2011-01-01

We report a new strategy for preparing silver nanoparticle oligonucleotide conjugates that are based upon DNA with cyclic disulfide-anchoring groups. These particles are extremely stable and can withstand NaCl concentrations up to 1.0 M. When silver nanoparticles functionalized with complementary sequences are combined, they assemble to form DNA-linked nanoparticle networks. This assembly process is reversible with heating and is associated with a red-shifting of the particle surface plasmon resonance and a concomitant color change from yellow to pale red. Analogous to the oligonucleotide-functionalized gold nanoparticles, these particles also exhibit highly cooperative binding properties with extremely sharp melting transitions. This work is an important step towards being able to use silver nanoparticle oligonucleotide conjugates for a variety of purposes, including molecular diagnostic labels, synthons in programmable materials synthesis approaches, and functional components for nanoelectronic and plasmonic devices. PMID:17571909

A complex multi-notch astronomical filter to suppress the bright infrared sky.

PubMed

Bland-Hawthorn, J; Ellis, S C; Leon-Saval, S G; Haynes, R; Roth, M M; Löhmannsröben, H-G; Horton, A J; Cuby, J-G; Birks, T A; Lawrence, J S; Gillingham, P; Ryder, S D; Trinh, C

2011-12-06

A long-standing and profound problem in astronomy is the difficulty in obtaining deep near-infrared observations due to the extreme brightness and variability of the night sky at these wavelengths. A solution to this problem is crucial if we are to obtain the deepest possible observations of the early Universe, as redshifted starlight from distant galaxies appears at these wavelengths. The atmospheric emission between 1,000 and 1,800 nm arises almost entirely from a forest of extremely bright, very narrow hydroxyl emission lines that varies on timescales of minutes. The astronomical community has long envisaged the prospect of selectively removing these lines, while retaining high throughput between them. Here we demonstrate such a filter for the first time, presenting results from the first on-sky tests. Its use on current 8 m telescopes and future 30 m telescopes will open up many new research avenues in the years to come.

Canibalismo Extremo y Lente Gravitacional Intensa en el Cúmulo de Galaxias Abell 3827

NASA Astrophysics Data System (ADS)

Díaz, R. J.; West, M.; Bergmann, M.; Carrasco, E. R.; Gomez, P.; Lee, H.; Miller, B.; Turner, J.

Abell 3827 is one of the most massive known clusters and at its center we observe an extreme example of galactic canibalism: a super giant elliptical galaxy in its formation process, devoring five massive galaxies at the same time. Using high spatial resolution Gemini+GMOS imagery and multi-object spectroscopy, we derived the redshift (z=0.099) and the radial velocity dispersion of the 55 brightest galaxies in the cluster central region (1134 +- 125 km/s). The estimated virial mass is ~ 1E14 M(sun) inside a radius of 300 kpc of the cluster center. We have also found features corresponding to a strong gravitational lense, four anular features arranged in an Einstein Ring from a galaxy (z=0.2) at double redshift than the cluster, and a fifth arclet feature corresponding to the lensed light of a farther galaxy (z=0.4). The possible Einstein Ring is of small angular size and the gravitational lense morphology would confirm that the cluster is indeed very massive and dense. FULL TEXT IN SPANISH.

Accurate Emission Line Diagnostics at High Redshift

NASA Astrophysics Data System (ADS)

Jones, Tucker

2017-08-01

How do the physical conditions of high redshift galaxies differ from those seen locally? Spectroscopic surveys have invested hundreds of nights of 8- and 10-meter telescope time as well as hundreds of Hubble orbits to study evolution in the galaxy population at redshifts z 0.5-4 using rest-frame optical strong emission line diagnostics. These surveys reveal evolution in the gas excitation with redshift but the physical cause is not yet understood. Consequently there are large systematic errors in derived quantities such as metallicity.We have used direct measurements of gas density, temperature, and metallicity in a unique sample at z=0.8 to determine reliable diagnostics for high redshift galaxies. Our measurements suggest that offsets in emission line ratios at high redshift are primarily caused by high N/O abundance ratios. However, our ground-based data cannot rule out other interpretations. Spatially resolved Hubble grism spectra are needed to distinguish between the remaining plausible causes such as active nuclei, shocks, diffuse ionized gas emission, and HII regions with escaping ionizing flux. Identifying the physical origin of evolving excitation will allow us to build the necessary foundation for accurate measurements of metallicity and other properties of high redshift galaxies. Only then can we expoit the wealth of data from current surveys and near-future JWST spectroscopy to understand how galaxies evolve over time.

Distributions of Gas and Galaxies from Galaxy Clusters to Larger Scales

NASA Astrophysics Data System (ADS)

Patej, Anna

2017-01-01

We address the distributions of gas and galaxies on three scales: the outskirts of galaxy clusters, the clustering of galaxies on large scales, and the extremes of the galaxy distribution. In the outskirts of galaxy clusters, long-standing analytical models of structure formation and recent simulations predict the existence of density jumps in the gas and dark matter profiles. We use these features to derive models for the gas density profile, obtaining a simple fiducial model that is in agreement with both observations of cluster interiors and simulations of the outskirts. We next consider the galaxy density profiles of clusters; under the assumption that the galaxies in cluster outskirts follow similar collisionless dynamics as the dark matter, their distribution should show a steep jump as well. We examine the profiles of a low-redshift sample of clusters and groups, finding evidence for the jump in some of these clusters. Moving to larger scales where massive galaxies of different types are expected to trace the same large-scale structure, we present a test of this prediction by measuring the clustering of red and blue galaxies at z 0.6, finding low stochasticity between the two populations. These results address a key source of systematic uncertainty - understanding how target populations of galaxies trace large-scale structure - in galaxy redshift surveys. Such surveys use baryon acoustic oscillations (BAO) as a cosmological probe, but are limited by the expense of obtaining sufficiently dense spectroscopy. With the intention of leveraging upcoming deep imaging data, we develop a new method of detecting the BAO in sparse spectroscopic samples via cross-correlation with a dense photometric catalog. This method will permit the extension of BAO measurements to higher redshifts than possible with the existing spectroscopy alone. Lastly, we connect galaxies near and far: the Local Group dwarfs and the high redshift galaxies observed by Hubble and Spitzer. We examine how the local dwarfs may have appeared in the past and compare their properties to the detection limits of the upcoming James Webb Space Telescope (JWST), finding that JWST should be able to detect galaxies similar to the progenitors of a few of the brightest of the local galaxies, revealing a hitherto unobserved population of galaxies at high redshifts.

Evaluating and improving the redshifts of z > 2.2 quasars

NASA Astrophysics Data System (ADS)

Mason, Michelle; Brotherton, Michael S.; Myers, Adam

2017-08-01

Quasar redshifts require the best possible precision and accuracy for a number of applications, such as setting the velocity scale for outflows as well as measuring small-scale quasar-quasar clustering. The most reliable redshift standard in luminous quasars is arguably the narrow [O III] λλ4959, 5007 emission line doublet in the rest-frame optical. We use previously published [O III] redshifts obtained using near-infrared spectra in a sample of 45 high-redshift (z > 2.2) quasars to evaluate redshift measurement techniques based on rest-frame ultraviolet spectra. At redshifts above z = 2.2, the Mg II λ2798 emission line is not available in observed-frame optical spectra and the most prominent unblended and unabsorbed spectral feature available is usually C IV λ1549. Peak and centroid measurements of the C IV profile are often blueshifted relative to the rest-frame of the quasar, which can significantly bias redshift determinations. We show that redshift determinations for these high-redshift quasars are significantly correlated with the emission-line properties of C IV (I.e. the equivalent width, or EW, and the full width at half-maximum, or FWHM) as well as the luminosity, which we take from the Sloan Digital Sky Survey Data Release 7. We demonstrate that empirical corrections based on multiple regression analyses yield significant improvements in both the precision and accuracy of the redshifts of the most distant quasars and are required to establish consistency with redshifts determined in more local quasars.

A new method to search for high-redshift clusters using photometric redshifts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castignani, G.; Celotti, A.; Chiaberge, M.

2014-09-10

We describe a new method (Poisson probability method, PPM) to search for high-redshift galaxy clusters and groups by using photometric redshift information and galaxy number counts. The method relies on Poisson statistics and is primarily introduced to search for megaparsec-scale environments around a specific beacon. The PPM is tailored to both the properties of the FR I radio galaxies in the Chiaberge et al. sample, which are selected within the COSMOS survey, and to the specific data set used. We test the efficiency of our method of searching for cluster candidates against simulations. Two different approaches are adopted. (1) Wemore » use two z ∼ 1 X-ray detected cluster candidates found in the COSMOS survey and we shift them to higher redshift up to z = 2. We find that the PPM detects the cluster candidates up to z = 1.5, and it correctly estimates both the redshift and size of the two clusters. (2) We simulate spherically symmetric clusters of different size and richness, and we locate them at different redshifts (i.e., z = 1.0, 1.5, and 2.0) in the COSMOS field. We find that the PPM detects the simulated clusters within the considered redshift range with a statistical 1σ redshift accuracy of ∼0.05. The PPM is an efficient alternative method for high-redshift cluster searches that may also be applied to both present and future wide field surveys such as SDSS Stripe 82, LSST, and Euclid. Accurate photometric redshifts and a survey depth similar or better than that of COSMOS (e.g., I < 25) are required.« less

Machine- z: Rapid machine-learned redshift indicator for Swift gamma-ray bursts

DOE PAGES

Ukwatta, T. N.; Wozniak, P. R.; Gehrels, N.

2016-03-08

Studies of high-redshift gamma-ray bursts (GRBs) provide important information about the early Universe such as the rates of stellar collapsars and mergers, the metallicity content, constraints on the re-ionization period, and probes of the Hubble expansion. Rapid selection of high-z candidates from GRB samples reported in real time by dedicated space missions such as Swift is the key to identifying the most distant bursts before the optical afterglow becomes too dim to warrant a good spectrum. Here, we introduce ‘machine-z’, a redshift prediction algorithm and a ‘high-z’ classifier for Swift GRBs based on machine learning. Our method relies exclusively onmore » canonical data commonly available within the first few hours after the GRB trigger. Using a sample of 284 bursts with measured redshifts, we trained a randomized ensemble of decision trees (random forest) to perform both regression and classification. Cross-validated performance studies show that the correlation coefficient between machine-z predictions and the true redshift is nearly 0.6. At the same time, our high-z classifier can achieve 80 per cent recall of true high-redshift bursts, while incurring a false positive rate of 20 per cent. With 40 per cent false positive rate the classifier can achieve ~100 per cent recall. As a result, the most reliable selection of high-redshift GRBs is obtained by combining predictions from both the high-z classifier and the machine-z regressor.« less

Radio spectra of bright compact sources at z > 4.5

NASA Astrophysics Data System (ADS)

Coppejans, Rocco; van Velzen, Sjoert; Intema, Huib T.; Müller, Cornelia; Frey, Sándor; Coppejans, Deanne L.; Cseh, Dávid; Williams, Wendy L.; Falcke, Heino; Körding, Elmar G.; Orrú, Emanuela; Paragi, Zsolt; Gabányi, Krisztina É.

2017-05-01

High-redshift quasars are important to study galaxy and active galactic nuclei evolution, test cosmological models and study supermassive black hole growth. Optical searches for high-redshift sources have been very successful, but radio searches are not hampered by dust obscuration and should be more effective at finding sources at even higher redshifts. Identifying high-redshift sources based on radio data is, however, not trivial. Here we report on new multifrequency Giant Metrewave Radio Telescope observations of eight z > 4.5 sources previously studied at high angular resolution with very long baseline interferometry (VLBI). Combining these observations with those from the literature, we construct broad-band radio spectra of all 30 z > 4.5 sources that have been observed with VLBI. In the sample we found flat, steep and peaked spectra in approximately equal proportions. Despite several selection effects, we conclude that the z > 4.5 VLBI (and likely also non-VLBI) sources have diverse spectra and that only about a quarter of the sources in the sample have flat spectra. Previously, the majority of high-redshift radio sources were identified based on their ultrasteep spectra. Recently, a new method has been proposed to identify these objects based on their megahertz-peaked spectra. No method would have identified more than 18 per cent of the high-redshift sources in this sample. More effective methods are necessary to reliably identify complete samples of high-redshift sources based on radio data.

Tracing Large-Scale Structure with Radio Sources

NASA Astrophysics Data System (ADS)

Lindsay, S. N.

2015-02-01

In this thesis, I investigate the spatial distribution of radio sources, and quantify their clustering strength over a range of redshifts, up to z _ 2:2, using various forms of the correlation function measured with data from several multi-wavelength surveys. I present the optical spectra of 30 radio AGN (S1:4 > 100 mJy) in the GAMA/H-ATLAS fields, for which emission line redshifts could be deduced, from observations of 79 target sources with the EFOSC2 spectrograph on the NTT. The mean redshift of these sources is z = 1:2; 12 were identified as quasars (40 per cent), and 6 redshifts (out of 24 targets) were found for AGN hosts to multiple radio components. While obtaining spectra for hosts of these multi-component sources is possible, their lower success rate highlights the difficulty in acheiving a redshift-complete radio sample. Taking an existing spectroscopic redshift survey (GAMA) and radio sources from the FIRST survey (S1:4 > 1 mJy), I then present a cross-matched radio sample with 1,635 spectroscopic redshifts with a median value of z = 0:34. The spatial correlation function of this sample is used to find the redshiftspace (s0) and real-space correlation lengths (r0 _ 8:2 h Mpc), and a mass bias of _1.9. Insight into the redshift-dependence of these quantities is gained by using the angular correlation function and Limber inversion to measure the same spatial clustering parameters. Photometric redshifts! from SDSS/UKIDSS are incorporated to produce a larger matched radio sample at z ' 0:48 (and low- and high-redshift subsamples at z ' 0:30 and z ' 0:65), while their redshift distribution is subtracted from that taken from the SKADS radio simulations to estimate the redshift distribution of the remaining unmatched sources (z ' 1:55). The observed bias evolution over this redshift range is compared with model predictions based on the SKADS simulations, with good agreement at low redshift. The bias found at high redshift significantly exceeds these predictions, however, suggesting a more massive population of galaxies than expected, either due to the relative proportions of different radio sources, or a greater typical halo mass for the high-redshift sources. Finally, the reliance on a model redshift distribution to reach to higher redshifts is removed, as the angular cross-correlation function is used with deep VLA data (S1:4 > 90 _Jy) and optical/IR data from VIDEO/CFHTLS (Ks < 23:5) over 1 square degree. With high-quality photometric redshifts up to z _ 4, and a high signal-to-noise clustering measurement (due to the _100,000 Ks-selected galaxies), I am able to find the bias of a matched sample of only 766 radio sources (as well as of v vi the VIDEO sources), divided into 4 redshift bins reaching a median bias at z ' 2:15. Again, at high redshift, the measured bias appears to exceed the prediction made from the SKADS simulations. Applying luminosity cuts to the radio sample at L > 1023 WHz and higher (removing any non-AGN sources), I find a bias of 8-10 at z _ 1:5, considerably higher than for the full sample, and consistent with the more numerous FRI AGN having similar mass to the FRIIs (M _ 10^14 M_), contrary to the assumptions made in the SKADS simulations. Applying this adjustment to the model bias produces a better fit to the observations for the FIRST radio sources cross-matched with GAMA/SDSS/UKIDSS, as well as for the high-redshift radio sources in VIDEO. Therefore, I have shown that we require a more robust model of the evolution of AGN, and their relation to the underlying dark matter distribution. In particular, understanding these quantities for the abundant FRI population is crucial if we are to use such sources to probe the cosmological model as has been suggested by a number of authors (e.g. Raccanelli et al., 2012; Camera et al., 2012; Ferramacho et al., 2014).

Determination of astrophysical parameters of quasars within the Gaia mission

NASA Astrophysics Data System (ADS)

Delchambre, L.

2018-01-01

We describe methods designed to determine the astrophysical parameters of quasars based on spectra coming from the red and blue spectrophotometers of the Gaia satellite. These methods principally rely on two already published algorithms that are the weighted principal component analysis and the weighted phase correlation. The presented approach benefits from a fast implementation, an intuitive interpretation as well as strong diagnostic tools on the potential errors that may arise during predictions. The production of a semi-empirical library of spectra as they will be observed by Gaia is also covered and subsequently used for validation purpose. We detail the pre-processing that is necessary in order for these spectra to be fully exploitable by our algorithms along with the procedures that are used to predict the redshifts of the quasars, their continuum slopes, the total equivalent width of their emission lines and whether these are broad absorption line (BAL) quasars or not. Performances of these procedures were assessed in comparison with the extremely randomized trees learning method and were proven to provide better results on the redshift predictions and on the ratio of correctly classified observations though the probability of detection of BAL quasars remains restricted by the low resolution of these spectra as well as by their limited signal-to-noise ratio. Finally, the triggering of some warning flags allows us to obtain an extremely pure subset of redshift predictions where approximately 99 per cent of the observations come along with absolute errors that are below 0.1.

Evidence for a Major Merger Origin of High-Redshift Submillimeter Galaxies

NASA Astrophysics Data System (ADS)

Conselice, Christopher J.; Chapman, Scott C.; Windhorst, Rogier A.

2003-10-01

Submillimeter-detected galaxies located at redshifts z>1 host a major fraction of the bolometric luminosity at high redshifts due to thermal emission from heated dust grains, yet the nature of these objects remains a mystery. The major problem in understanding their origin is whether the dust-heating mechanism is predominantly caused by star formation or active galactic nuclei and what triggered this activity. We address this issue by examining the structures of 11 submillimeter galaxies imaged with STIS on the Hubble Space Telescope. We argue that ~61%+/-21% of these submillimeter sources are undergoing an active major merger using the CAS (concentration, asymmetry, clumpiness) quantitative morphological system. We rule out at ~5 σ confidence that these submillimeter galaxies are normal Hubble types at high redshift. This merger fraction appears to be higher than for Lyman break galaxies undergoing mergers at similar redshifts. Using reasonable constraints on the stellar masses of Lyman break galaxies and these submillimeter sources, we further argue that at redshifts z~2-3, systems with high stellar masses are more likely than lower mass galaxies to be involved in major mergers.

Prediction of emission line fluxes of gravitationally lensed very high-z galaxies

NASA Astrophysics Data System (ADS)

Inoue, Akio; Shimizu, Ikkoh; Okamoto, Takashi; Yoshida, Naoki; Matsuo, Hiroshi; Tamura, Yoichi

2015-08-01

Spectroscopic confirmation of very high-z galaxy candidates is extremely valuable because this is a direct proof of the existence of galaxies in the early Universe and put a strong constraint on the structure formation theory to produce such galaxies during the limited age of the Universe. Before the completion of the cosmic reionization, hydrogen Ly-alpha emission line is hard to be observed and we need other emission lines to confirm the redshift of galaxies. By using a state-of-the-art cosmological hydrodynamics simulation of galaxy formation and evolution with an emission line model based on Cloudy, we predict the line fluxes of some gravitationally-lensed very high-z galaxy candidates. We also discuss their detectability with the current and future telescopes.

Supernova Cosmology Inference with Probabilistic Photometric Redshifts (SCIPPR)

NASA Astrophysics Data System (ADS)

Peters, Christina; Malz, Alex; Hlozek, Renée

2018-01-01

The Bayesian Estimation Applied to Multiple Species (BEAMS) framework employs probabilistic supernova type classifications to do photometric SN cosmology. This work extends BEAMS to replace high-confidence spectroscopic redshifts with photometric redshift probability density functions, a capability that will be essential in the era the Large Synoptic Survey Telescope and other next-generation photometric surveys where it will not be possible to perform spectroscopic follow up on every SN. We present the Supernova Cosmology Inference with Probabilistic Photometric Redshifts (SCIPPR) Bayesian hierarchical model for constraining the cosmological parameters from photometric lightcurves and host galaxy photometry, which includes selection effects and is extensible to uncertainty in the redshift-dependent supernova type proportions. We create a pair of realistic mock catalogs of joint posteriors over supernova type, redshift, and distance modulus informed by photometric supernova lightcurves and over redshift from simulated host galaxy photometry. We perform inference under our model to obtain a joint posterior probability distribution over the cosmological parameters and compare our results with other methods, namely: a spectroscopic subset, a subset of high probability photometrically classified supernovae, and reducing the photometric redshift probability to a single measurement and error bar.

Correcting C IV-based virial black hole masses

NASA Astrophysics Data System (ADS)

Coatman, Liam; Hewett, Paul C.; Banerji, Manda; Richards, Gordon T.; Hennawi, Joseph F.; Prochaska, J. Xavier

2017-02-01

The C IVλλ1498,1501 broad emission line is visible in optical spectra to redshifts exceeding z ˜ 5. C IV has long been known to exhibit significant displacements to the blue and these `blueshifts' almost certainly signal the presence of strong outflows. As a consequence, single-epoch virial black hole (BH) mass estimates derived from C IV velocity widths are known to be systematically biased compared to masses from the hydrogen Balmer lines. Using a large sample of 230 high-luminosity (LBol = 1045.5-1048 erg s-1), redshift 1.5 < z < 4.0 quasars with both C IV and Balmer line spectra, we have quantified the bias in C IV BH masses as a function of the C IV blueshift. C IV BH masses are shown to be a factor of 5 larger than the corresponding Balmer-line masses at C IV blueshifts of 3000 km s-1and are overestimated by almost an order of magnitude at the most extreme blueshifts, ≳5000 km s-1. Using the monotonically increasing relationship between the C IV blueshift and the mass ratio BH(C IV)/BH(Hα), we derive an empirical correction to all C IV BH masses. The scatter between the corrected C IV masses and the Balmer masses is 0.24 dex at low C IV blueshifts (˜0 km s-1) and just 0.10 dex at high blueshifts (˜3000 km s-1), compared to 0.40 dex before the correction. The correction depends only on the C IV line properties - i.e. full width at half-maximum and blueshift - and can therefore be applied to all quasars where C IV emission line properties have been measured, enabling the derivation of unbiased virial BH-mass estimates for the majority of high-luminosity, high-redshift, spectroscopically confirmed quasars in the literature.

Steep radio spectra in high-redshift radio galaxies

NASA Technical Reports Server (NTRS)

Krolik, Julian H.; Chen, Wan

1991-01-01

The generic spectrum of an optically thin synchrotron source steepens by 0.5 in spectral index from low frequencies to high whenever the source lifetime is greater than the energy-loss timescale for at least some of the radiating electrons. Three effects tend to decrease the frequency nu(b) of this spectral bend as the source redshift increases: (1) for fixed bend frequency nu* in the rest frame, nu(b) = nu*/(1 + z); (2) losses due to inverse Compton scattering the microwave background rise with redshift as (1 + z) exp 4, so that, for fixed residence time in the radiating region, the energy of the lowest energy electron that can cool falls rapidly with increasing redshift; and (3) if the magnetic field is proportional to the equipartition field and the emitting volume is fixed or slowly varying, flux-limited samples induce a selection effect favoring low nu* at high z because higher redshift sources require higher emissivity to be included in the sample, and hence have stronger implied fields and more rapid synchrotron losses. A combination of these effects may explain the trend observed in the 3CR sample for higher redshift radio galaxies to have steeper spectra, and the successful use of ultrasteep spectrum surveys to locate high-redshift galaxies.

Optical Variability and Classification of High Redshift (3.5 < z < 5.5) Quasars on SDSS Stripe 82

NASA Astrophysics Data System (ADS)

AlSayyad, Yusra; McGreer, Ian D.; Fan, Xiaohui; Connolly, Andrew J.; Ivezic, Zeljko; Becker, Andrew C.

2015-01-01

Recent studies have shown promise in combining optical colors with variability to efficiently select and estimate the redshifts of low- to mid-redshift quasars in upcoming ground-based time-domain surveys. We extend these studies to fainter and less abundant high-redshift quasars using light curves from 235 sq. deg. and 10 years of Stripe 82 imaging reprocessed with the prototype LSST data management stack. Sources are detected on the i-band co-adds (5σ: i ~ 24) but measured on the single-epoch (ugriz) images, generating complete and unbiased lightcurves for sources fainter than the single-epoch detection threshold. Using these forced photometry lightcurves, we explore optical variability characteristics of high redshift quasars and validate classification methods with particular attention to the low signal limit. In this low SNR limit, we quantify the degradation of the uncertainties and biases on variability parameters using simulated light curves. Completeness/efficiency and redshift accuracy are verified with new spectroscopic observations on the MMT and APO 3.5m. These preliminary results are part of a survey to measure the z~4 luminosity function for quasars (i < 23) on Stripe 82 and to validate purely photometric classification techniques for high redshift quasars in LSST.

Photometric classification of type Ia supernovae in the SuperNova Legacy Survey with supervised learning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Möller, A.; Ruhlmann-Kleider, V.; Leloup, C.

In the era of large astronomical surveys, photometric classification of supernovae (SNe) has become an important research field due to limited spectroscopic resources for candidate follow-up and classification. In this work, we present a method to photometrically classify type Ia supernovae based on machine learning with redshifts that are derived from the SN light-curves. This method is implemented on real data from the SNLS deferred pipeline, a purely photometric pipeline that identifies SNe Ia at high-redshifts (0.2 < z < 1.1). Our method consists of two stages: feature extraction (obtaining the SN redshift from photometry and estimating light-curve shape parameters)more » and machine learning classification. We study the performance of different algorithms such as Random Forest and Boosted Decision Trees. We evaluate the performance using SN simulations and real data from the first 3 years of the Supernova Legacy Survey (SNLS), which contains large spectroscopically and photometrically classified type Ia samples. Using the Area Under the Curve (AUC) metric, where perfect classification is given by 1, we find that our best-performing classifier (Extreme Gradient Boosting Decision Tree) has an AUC of 0.98.We show that it is possible to obtain a large photometrically selected type Ia SN sample with an estimated contamination of less than 5%. When applied to data from the first three years of SNLS, we obtain 529 events. We investigate the differences between classifying simulated SNe, and real SN survey data. In particular, we find that applying a thorough set of selection cuts to the SN sample is essential for good classification. This work demonstrates for the first time the feasibility of machine learning classification in a high- z SN survey with application to real SN data.« less

The Lyman Continuum Escape Fraction of Emission Line-selected z ∼ 2.5 Galaxies Is Less Than 15%

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rutkowski, Michael J.; Hayes, Matthew; Scarlata, Claudia

Recent work suggests that strong emission line, star-forming galaxies (SFGs) may be significant Lyman continuum leakers. We combine archival Hubble Space Telescope broadband ultraviolet and optical imaging (F275W and F606W, respectively) with emission line catalogs derived from WFC3 IR G141 grism spectroscopy to search for escaping Lyman continuum (LyC) emission from homogeneously selected z ∼ 2.5 SFGs. We detect no escaping Lyman continuum from SFGs selected on [O ii] nebular emission ( N = 208) and, within a narrow redshift range, on [O iii]/[O ii]. We measure 1 σ upper limits to the LyC escape fraction relative to the non-ionizingmore » UV continuum from [O ii] emitters, f {sub esc} ≲ 5.6%, and strong [O iii]/[O ii] > 5 ELGs, f {sub esc} ≲ 14.0%. Our observations are not deep enough to detect f {sub esc} ∼ 10% typical of low-redshift Lyman continuum emitters. However, we find that this population represents a small fraction of the star-forming galaxy population at z ∼ 2. Thus, unless the number of extreme emission line galaxies grows substantially to z ≳ 6, such galaxies may be insufficient for reionization. Deeper survey data in the rest-frame ionizing UV will be necessary to determine whether strong line ratios could be useful for pre-selecting LyC leakers at high redshift.« less

Submillimeter Galaxies as Progenitors of Compact Quiescent Galaxies

NASA Technical Reports Server (NTRS)

Toft, S.; Smolcic, V.; Magnelli, B.; Karim, A.; Zirm, A.; Michalowski, M.; Capak, P.; Sheth, K.; Schawinski, K.; Krogager, J.-K.;

Submillimeter Galaxies as Progenitors of Compact Quiescent Galaxies

NASA Astrophysics Data System (ADS)

Toft, S.; Smolčić, V.; Magnelli, B.; Karim, A.; Zirm, A.; Michalowski, M.; Capak, P.; Sheth, K.; Schawinski, K.; Krogager, J.-K.; Wuyts, S.; Sanders, D.; Man, A. W. S.; Lutz, D.; Staguhn, J.; Berta, S.; Mccracken, H.; Krpan, J.; Riechers, D.

2014-02-01

Three billion years after the big bang (at redshift z = 2), half of the most massive galaxies were already old, quiescent systems with little to no residual star formation and extremely compact with stellar mass densities at least an order of magnitude larger than in low-redshift ellipticals, their descendants. Little is known about how they formed, but their evolved, dense stellar populations suggest formation within intense, compact starbursts 1-2 Gyr earlier (at 3 < z < 6). Simulations show that gas-rich major mergers can give rise to such starbursts, which produce dense remnants. Submillimeter-selected galaxies (SMGs) are prime examples of intense, gas-rich starbursts. With a new, representative spectroscopic sample of compact, quiescent galaxies at z = 2 and a statistically well-understood sample of SMGs, we show that z = 3-6 SMGs are consistent with being the progenitors of z = 2 quiescent galaxies, matching their formation redshifts and their distributions of sizes, stellar masses, and internal velocities. Assuming an evolutionary connection, their space densities also match if the mean duty cycle of SMG starbursts is 42^{+40}_{-29} Myr (consistent with independent estimates), which indicates that the bulk of stars in these massive galaxies were formed in a major, early surge of star formation. These results suggest a coherent picture of the formation history of the most massive galaxies in the universe, from their initial burst of violent star formation through their appearance as high stellar-density galaxy cores and to their ultimate fate as giant ellipticals.

Dwarf Galaxies in the Chandra COSMOS Legacy Survey

NASA Astrophysics Data System (ADS)

Civano, Francesca Maria; Mezcua, Mar; Fabbiano, Giuseppina; Marchesi, Stefano; Suh, Hyewon; Volonteri, Marta; cyrille

2018-01-01

The existence of intermediate mass black holes (100 < MBH < 106 Msun) has been invoked to explain the finding of extremely massive black holes at z>7. While detecting these seed black holes in the young Universe is observationally challenging, the nuclei of local dwarf galaxies are among the best places where to look for them as these galaxies resemble in mass and metallicity the first galaxies and they have not significantly grown through merger and accretion processes. We present a sample of 40 AGN in dwarf galaxies (107 <= M* <= 3x109 Msun) at z <=2.4, selected from the Chandra COSMOS-Legacy survey. Once the star formation contribution to the X-ray emission is subtracted, the AGN luminosities of the 40 dwarf galaxies are in the range L(0.5-10 keV)~1039 - 1044 erg/s. With 12 sources at z > 0.5, our sample constitutes the highest-redshift discovery of AGN in dwarf galaxies. One of the dwarf galaxies is the least massive galaxy (M* = 6.6x107 Msun) found so far to host an active BH. We also present for the first time the evolution of the AGN fraction with stellar mass, X-ray luminosity, and redshift in dwarf galaxies out to z = 0.7, finding that it decreases with X-ray luminosity and stellar mass. Unlike massive galaxies, the AGN fraction is found to decrease with redshift, suggesting that AGN in dwarf galaxies evolve differently than those in high-mass galaxies.

Fourier transform spectrometer observations of solar carbon monoxide. III - Time-resolved spectroscopy of the Delta V = 1 bands

NASA Astrophysics Data System (ADS)

Ayres, Thomas R.; Brault, James W.

1990-11-01

Time series of the 2100/cm Delta v = 1 absorption bands of CO at the center of the solar disk and at the extreme limb have been recorded by Fourier transform spectrometer. The photospheric 5-min oscillation appears prominently at sun center. The peak-to-peak brightness temperature amplitude is roughly 300 K, and the peak-to-peak Doppler shift is roughly 1100 m/s. The 70 deg phase lag of maximum core intensity with respect to maximum redshift for the strongest Delta v = 1 absorptions is less than the 90 deg expected in the adiabatic limit. No dominant four-minute signal in the line intensity like that reported by Deming et al. (1984, 1986, and 1987) is found, nor is evidence for extreme fluctuations on short time scales like those proposed by Kalkofen et al. (1984). The strong Delta v = 1 lines exhibit systematic Doppler shifts of less than about 1 km/s, contrary to the predictions of transonic redshifts if the CO 'clouds' are associated with a dynamic cooling phase of the Ca II 'cell flashes.'

THE REDSHIFT DISTRIBUTION OF DUSTY STAR-FORMING GALAXIES FROM THE SPT SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strandet, M. L.; Weiss, A.; Vieira, J. D.

2016-05-10

We use the Atacama Large Millimeter/submillimeter Array (ALMA) in Cycle 1 to determine spectroscopic redshifts of high-redshift dusty star-forming galaxies (DSFGs) selected by their 1.4 mm continuum emission in the South Pole Telescope (SPT) survey. We present ALMA 3 mm spectral scans between 84 and 114 GHz for 15 galaxies and targeted ALMA 1 mm observations for an additional eight sources. Our observations yield 30 new line detections from CO, [C i], [N ii], H{sub 2}O and NH{sub 3}. We further present Atacama Pathfinder Experiment [C ii] and CO mid- J observations for seven sources for which only a singlemore » line was detected in spectral-scan data from ALMA Cycle 0 or Cycle 1. We combine the new observations with previously published and new millimeter/submillimeter line and photometric data of the SPT-selected DSFGs to study their redshift distribution. The combined data yield 39 spectroscopic redshifts from molecular lines, a success rate of >85%. Our sample represents the largest data set of its kind today and has the highest spectroscopic completeness among all redshift surveys of high- z DSFGs. The median of the redshift distribution is z = 3.9 ± 0.4, and the highest-redshift source in our sample is at z = 5.8. We discuss how the selection of our sources affects the redshift distribution, focusing on source brightness, selection wavelength, and strong gravitational lensing. We correct for the effect of gravitational lensing and find the redshift distribution for 1.4 mm selected sources with a median redshift of z = 3.1 ± 0.3. Comparing to redshift distributions selected at shorter wavelengths from the literature, we show that selection wavelength affects the shape of the redshift distribution.« less

The Redshift Distribution of Dusty Star-forming Galaxies from the SPT Survey

NASA Astrophysics Data System (ADS)

Strandet, M. L.; Weiss, A.; Vieira, J. D.; de Breuck, C.; Aguirre, J. E.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bradford, C. M.; Carlstrom, J. E.; Chapman, S. C.; Crawford, T. M.; Everett, W.; Fassnacht, C. D.; Furstenau, R. M.; Gonzalez, A. H.; Greve, T. R.; Gullberg, B.; Hezaveh, Y.; Kamenetzky, J. R.; Litke, K.; Ma, J.; Malkan, M.; Marrone, D. P.; Menten, K. M.; Murphy, E. J.; Nadolski, A.; Rotermund, K. M.; Spilker, J. S.; Stark, A. A.; Welikala, N.

2016-05-01

We use the Atacama Large Millimeter/submillimeter Array (ALMA) in Cycle 1 to determine spectroscopic redshifts of high-redshift dusty star-forming galaxies (DSFGs) selected by their 1.4 mm continuum emission in the South Pole Telescope (SPT) survey. We present ALMA 3 mm spectral scans between 84 and 114 GHz for 15 galaxies and targeted ALMA 1 mm observations for an additional eight sources. Our observations yield 30 new line detections from CO, [C I], [N II], H2O and NH3. We further present Atacama Pathfinder Experiment [C II] and CO mid-J observations for seven sources for which only a single line was detected in spectral-scan data from ALMA Cycle 0 or Cycle 1. We combine the new observations with previously published and new millimeter/submillimeter line and photometric data of the SPT-selected DSFGs to study their redshift distribution. The combined data yield 39 spectroscopic redshifts from molecular lines, a success rate of >85%. Our sample represents the largest data set of its kind today and has the highest spectroscopic completeness among all redshift surveys of high-z DSFGs. The median of the redshift distribution is z = 3.9 ± 0.4, and the highest-redshift source in our sample is at z = 5.8. We discuss how the selection of our sources affects the redshift distribution, focusing on source brightness, selection wavelength, and strong gravitational lensing. We correct for the effect of gravitational lensing and find the redshift distribution for 1.4 mm selected sources with a median redshift of z = 3.1 ± 0.3. Comparing to redshift distributions selected at shorter wavelengths from the literature, we show that selection wavelength affects the shape of the redshift distribution.

The inevitable youthfulness of known high-redshift radio galaxies

NASA Astrophysics Data System (ADS)

Blundell, Katherine M.; Rawlings, Steve

1999-05-01

Some galaxies are very luminous in the radio part of the spectrum. These `radio galaxies' have extensive (hundreds of kiloparsecs) lobes of emission powered by plasma jets originating at a central black hole. Some radio galaxies can be seen at very high redshifts, where in principle they can serve as probes of the early evolution of the Universe. Here we show that, for any model of radio-galaxy evolution in which the luminosity decreases with time after an initial rapid increase (that is, essentially all reasonable models), all observable high-redshift radio galaxies must be seen when the lobes are less than 107 years old. This means that high-redshift radio galaxies can be used as a high-time-resolution probe of evolution in the early Universe. Moreover, this result explains many observed trends of radio-galaxy properties with redshift, without needing to invoke explanations based on cosmology or strong evolution of the surrounding intergalactic medium with cosmic time, thereby avoiding conflict with current theories of structure formation.

Detection of z~2 Type IIn Supernovae

NASA Astrophysics Data System (ADS)

Cooke, Jeff; Sullivan, Mark; Barton, Elizabeth J.

2009-05-01

Type IIn supernovae (SNe IIn) result from the deaths of massive stars. The broad magnitude distribution of SNe IIn make these some of the most luminous SN events ever recorded. In addition, they are the most luminous SN type in the rest-frame UV which make them ideal targets for wide-field optical high redshift searches. We briefly describe our method to detect z~2 SNe IIn events that involves monitoring color-selected galaxies in deep stacked images and our program that applies this method to the CFHTLS survey. Initial results have detected four compelling photometric candidates from their subtracted images and light curves. SNe IIn spectra exhibit extremely bright narrow emission lines as a result of the interaction between the SN ejecta and the circumstellar material released in pre-explosion outbursts. These emission lines remain bright for years after outburst and are above the thresholds of current 8 m-class telescope sensitivities to z~3. The deep spectroscopy required to confirm z~2 host galaxies has the potential to detect the SN emission lines and measure their energies. Finally, planned deep, wide-field surveys have the capability to detect and confirm SNe IIn to z~6. The emission lines of such high-redshift events are expected to be above the sensitivity of future 30 m-class telescopes and the James Webb Space Telescope.

IGR J12319-0749: Evidence for Another Extreme Blazar Found with INTEGRAL

NASA Technical Reports Server (NTRS)

Bassani, L.; Landi, R.; Marshall, F. E.; Malizia, A.; Bazzano, A.; Bird, A. J.; Gehrels, N.; Ubertini, P.; Masetti, N.

2012-01-01

We report on the identification of a new soft gamma-ray source, IGR J12319 C0749, detected with the IBIS imager on board the INTEGRAL satellite. The source, which has an observed 20 C100 keV flux of 8.3 10.12 erg cm.2 s.1, is spatially coincident with an AGN at redshift z = 3.12. The broad-band continuum, obtained by combining XRT and IBIS data, is flat ( =1.3) with evidence for a spectral break around 25 keV (100 keV in the source rest frame). X-ray observations indicate flux variability which is further supported by a comparison with a previous ROSAT measurement. IGR J12319 C0749 is also a radio emitting object likely characterized by a flat spectrum and high radio loudness; optically it is a broad-line emitting object with a massive black hole (2.8 109 solar masses) at its center. The source Spectral Energy Distribution is similar to another high redshift blazar, 225155+2217 at z = 3.668: both objects are bright, with a large accretion disk luminosity and a Compton peak located in the hard X-ray/soft gamma-ray band. IGR J12319 C0749 is likely the second most distant blazar detected so far by INTEGRAL.

Magnification-temperature correlation: The dark side of integrated Sachs-Wolfe measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

LoVerde, Marilena; Hui, Lam; Gaztanaga, Enrique

2007-02-15

Integrated Sachs-Wolfe (ISW) measurements, which involve cross-correlating the microwave background anisotropies with the foreground large-scale structure (e.g. traced by galaxies/quasars), have proven to be an interesting probe of dark energy. We show that magnification bias, which is the inevitable modulation of the foreground number counts by gravitational lensing, alters both the scale dependence and amplitude of the observed ISW signal. This is true especially at high redshifts because (1) the intrinsic galaxy-temperature signal diminishes greatly back in the matter-dominated era, (2) the lensing efficiency increases with redshift and (3) the number count slope generally steepens with redshift in a magnitudemore » limited sample. At z > or approx. 2, the magnification-temperature correlation dominates over the intrinsic galaxy-temperature correlation and causes the observed ISW signal to increase with redshift, despite dark energy subdominance--a result of the fact that magnification probes structures all the way from the observer to the sources. Ignoring magnification bias therefore can lead to (significantly) erroneous conclusions about dark energy. While the lensing modulation opens up an interesting high z window for ISW measurements, high redshift measurements are not expected to add much new information to low redshift ones if dark energy is indeed the cosmological constant. This is because lensing introduces significant covariance across redshifts. The most compelling reasons for pursuing high redshift ISW measurements are to look for potential surprises such as early dark energy domination or signatures of modified gravity. We conclude with a discussion of existing measurements, the highest redshift of which is at the margin of being sensitive to the magnification effect. We also develop a formalism which might be of more general interest: to predict biases in estimating parameters when certain physical effects are ignored in interpreting observations.« less

SPECTROSCOPY OF HIGH-REDSHIFT SUPERNOVAE FROM THE ESSENCE PROJECT: THE FIRST FOUR YEARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foley, R. J.; Chornock, R.; Silverman, J. M.

We present the results of spectroscopic observations from the ESSENCE high-redshift supernova (SN) survey during its first four years of operation. This sample includes spectra of all SNe Ia whose light curves were presented by Miknaitis et al. and used in the cosmological analyses of Davis et al. and Wood-Vasey et al. The sample represents 273 hr of spectroscopic observations with 6.5-10 m class telescopes of objects detected and selected for spectroscopy by the ESSENCE team. We present 184 spectra of 156 objects. Combining this sample with that of Matheson et al., we have a total sample of 329 spectramore » of 274 objects. From this, we are able to spectroscopically classify 118 Type Ia SNe. As the survey has matured, the efficiency of classifying SNe Ia has remained constant while we have observed both higher-redshift SNe Ia and SNe Ia farther from maximum brightness. Examining the subsample of SNe Ia with host-galaxy redshifts shows that redshifts derived from only the SN Ia spectra are consistent with redshifts found from host-galaxy spectra. Moreover, the phases derived from only the SN Ia spectra are consistent with those derived from light-curve fits. By comparing our spectra to local templates, we find that the rate of objects similar to the overluminous SN 1991T and the underluminous SN 1991bg in our sample are consistent with that of the local sample. We do note, however, that we detect no object spectroscopically or photometrically similar to SN 1991bg. Although systematic effects could reduce the high-redshift rate we expect based on the low-redshift surveys, it is possible that SN 1991bg-like SNe Ia are less prevalent at high redshift.« less

DETECTING RELATIVISTIC X-RAY JETS IN HIGH-REDSHIFT QUASARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKeough, Kathryn; Siemiginowska, Aneta; Kashyap, Vinay L.

We analyze Chandra X-ray images of a sample of 11 quasars that are known to contain kiloparsec scale radio jets. The sample consists of five high-redshift ( z  ≥ 3.6) flat-spectrum radio quasars, and six intermediate redshift (2.1 <  z  < 2.9) quasars. The data set includes four sources with integrated steep radio spectra and seven with flat radio spectra. A total of 25 radio jet features are present in this sample. We apply a Bayesian multi-scale image reconstruction method to detect and measure the X-ray emission from the jets. We compute deviations from a baseline model that does not include the jet,more » and compare observed X-ray images with those computed with simulated images where no jet features exist. This allows us to compute p -value upper bounds on the significance that an X-ray jet is detected in a pre-determined region of interest. We detected 12 of the features unambiguously, and an additional six marginally. We also find residual emission in the cores of three quasars and in the background of one quasar that suggest the existence of unresolved X-ray jets. The dependence of the X-ray to radio luminosity ratio on redshift is a potential diagnostic of the emission mechanism, since the inverse Compton scattering of cosmic microwave background photons (IC/CMB) is thought to be redshift dependent, whereas in synchrotron models no clear redshift dependence is expected. We find that the high-redshift jets have X-ray to radio flux ratios that are marginally inconsistent with those from lower redshifts, suggesting that either the X-ray emissions are due to the IC/CMB rather than the synchrotron process, or that high-redshift jets are qualitatively different.« less

Probing the extent and content of low ionization gas in galaxies: QSO absorption and HI emission

NASA Technical Reports Server (NTRS)

Womble, Donna S.

1993-01-01

The small projected separations of some QSO's and low-redshift galaxies provide unique opportunities to study the extent and content of gas in galaxies through observation of absorption in the QSO spectra. Observations of these systems provide valuable information on the connection between the absorbing gas and the galaxy, as well as detailed information on the morphology and environment of the galaxy itself. While there is direct evidence that galaxies can produce the intervening-type QSO absorption lines, over the past decade, the study of such 'QSO-galaxy pairs' (at low redshift) has been considered unsuccessful because new detections of absorption were seldom made. A fundamental problem concerning the relation between these low-redshift systems and those seen at moderate to high redshift remains unresolved. Direct and indirect measures of galaxy absorption cross sections at moderate to high redshifts (z is approximately greater than 20.5) are much larger than the optical and HI sizes of local galaxies. However, direct comparison of the low and moderate to high redshift systems is difficult since different ions are observed in different redshift regimes. Observations are presented for a new sample of QSO-galaxy pairs. Nine new QSO's which shine through nearby galaxies (on the sky-plane) were observed to search for CaII absorption in the QSO spectra at the foreground galaxy redshifts.

OUTFLOW AND METALLICITY IN THE BROAD-LINE REGION OF LOW-REDSHIFT ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Jaejin; Woo, Jong-Hak; Nagao, Tohru

2017-01-20

Outflows in active galactic nuclei (AGNs) are crucial to understand in investigating the co-evolution of supermassive black holes (SMBHs) and their host galaxies since outflows may play an important role as an AGN feedback mechanism. Based on archival UV spectra obtained with the Hubble Space Telescope and IUE , we investigate outflows in the broad-line region (BLR) in low-redshift AGNs ( z < 0.4) through detailed analysis of the velocity profile of the C iv emission line. We find a dependence of the outflow strength on the Eddington ratio and the BLR metallicity in our low-redshift AGN sample, which ismore » consistent with earlier results obtained for high-redshift quasars. These results suggest that BLR outflows, gas accretion onto SMBHs, and past star formation activity in host galaxies are physically related in low-redshift AGNs as in powerful high-redshift quasars.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ukwatta, T. N.; Wozniak, P. R.; Gehrels, N.

Studies of high-redshift gamma-ray bursts (GRBs) provide important information about the early Universe such as the rates of stellar collapsars and mergers, the metallicity content, constraints on the re-ionization period, and probes of the Hubble expansion. Rapid selection of high-z candidates from GRB samples reported in real time by dedicated space missions such as Swift is the key to identifying the most distant bursts before the optical afterglow becomes too dim to warrant a good spectrum. Here, we introduce ‘machine-z’, a redshift prediction algorithm and a ‘high-z’ classifier for Swift GRBs based on machine learning. Our method relies exclusively onmore » canonical data commonly available within the first few hours after the GRB trigger. Using a sample of 284 bursts with measured redshifts, we trained a randomized ensemble of decision trees (random forest) to perform both regression and classification. Cross-validated performance studies show that the correlation coefficient between machine-z predictions and the true redshift is nearly 0.6. At the same time, our high-z classifier can achieve 80 per cent recall of true high-redshift bursts, while incurring a false positive rate of 20 per cent. With 40 per cent false positive rate the classifier can achieve ~100 per cent recall. As a result, the most reliable selection of high-redshift GRBs is obtained by combining predictions from both the high-z classifier and the machine-z regressor.« less

The spectral energy distribution of galaxies at z > 2.5: Implication from the Herschel/SPIRE color-color diagram

NASA Astrophysics Data System (ADS)

Yuan, Fangting; Buat, Veronique; Burgarella, Denis; Ciesla, Laure; Heinis, Sebastien; Shen, Shiyin; Shao, Zhengyi; Hou, Jinliang

2015-08-01

We use the Herschel SPIRE color-color diagram to study the spectral energy distribution (SED) and the redshift estimation of high-z galaxies. We collect a sample of 57 galaxies with spectroscopically confirmed redshifts and reliable flux measurements at redshift z=2.5-6.4, and compare their average SPIRE colors with SED templates from local and high-z libraries. We find that local SEDs are inconsistent with high-z observations. For the libraries of Chary & Elbaz (2001) and Dale & Helou (2002), the local calibrations of the parameters LIR and alpha need to be adjusted to around 1011Lsun and 1.5 to describe the average colors given by the observations. For high-z libraries, the templates of Magdis et al. (2012) can well describe the average colors of the observations at high redshift, justifying their assumption of an evolution of SED from z=0 to 3. Using the templates of Magdis et al. (2012), we defined color cuts to divide the SPIRE color-color diagram into different regions with different mean redshifts. We tested this method and two other color cut methods 500 micron risers and the method of Amblard et al. (2010) using a large sample of 786 Herschel-selected galaxies, and find that these color cut methods can separate the sample into populations with different mean redshifts, although the dispersion of redshifts in each population is quite large.

ELTs adaptive optics for multi-objects 3D spectroscopy: key parameters and design rules

NASA Astrophysics Data System (ADS)

Neichel, B.; Conan, J.-M.; Fusco, T.; Gendron, E.; Puech, M.; Rousset, G.; Hammer, F.

2006-06-01

In the last few years, new Adaptive Optics [AO] techniques have emerged to answer new astronomical challenges: Ground-Layer AO [GLAO] and Multi-Conjugate AO [MCAO] to access a wider Field of View [FoV], Multi-Object AO [MOAO] for the simultaneous observation of several faint galaxies, eXtreme AO [XAO] for the detection of faint companions. In this paper, we focus our study to one of these applications : high red-shift galaxy observations using MOAO techniques in the framework of Extremely Large Telescopes [ELTs]. We present the high-level specifications of a dedicated instrument. We choose to describe the scientific requirements with the following criteria : 40% of Ensquared Energy [EE] in H band (1.65μm) and in an aperture size from 25 to 150 mas. Considering these specifications we investigate different AO solutions thanks to Fourier based simulations. Sky Coverage [SC] is computed for Natural and Laser Guide Stars [NGS, LGS] systems. We show that specifications are met for NGS-based systems at the cost of an extremely low SC. For the LGS approach, the option of low order correction with a faint NGS is discussed. We demonstrate that, this last solution allows the scientific requirements to be met together with a quasi full SC.

A distortion of very-high-redshift galaxy number counts by gravitational lensing.

PubMed

Wyithe, J Stuart B; Yan, Haojing; Windhorst, Rogier A; Mao, Shude

2011-01-13

The observed number counts of high-redshift galaxy candidates have been used to build up a statistical description of star-forming activity at redshift z ≳ 7, when galaxies reionized the Universe. Standard models predict that a high incidence of gravitational lensing will probably distort measurements of flux and number of these earliest galaxies. The raw probability of this happening has been estimated to be ∼0.5 per cent (refs 11, 12), but can be larger owing to observational biases. Here we report that gravitational lensing is likely to dominate the observed properties of galaxies with redshifts of z ≳ 12, when the instrumental limiting magnitude is expected to be brighter than the characteristic magnitude of the galaxy sample. The number counts could be modified by an order of magnitude, with most galaxies being part of multiply imaged systems, located less than 1 arcsec from brighter foreground galaxies at z ≈ 2. This lens-induced association of high-redshift and foreground galaxies has perhaps already been observed among a sample of galaxy candidates identified at z ≈ 10.6. Future surveys will need to be designed to account for a significant gravitational lensing bias in high-redshift galaxy samples.

Individual QSOs, Groups, & Clusters of High Redshift QSOs Associated with Low Redshift Spiral Galaxies

NASA Astrophysics Data System (ADS)

Burbidge, Geoffrey; Napier, W.

2009-01-01

Starting more than forty years ago it was found by Arp and others that many high redshift QSOs lie very close to comparatively nearby spiral galaxies. As time has gone on the implication of these results have been ignored. Implicitly they have been assumed to be accidental configurations. By now there are so many data, sometimes involving clusters of high z QSOs, that the data requires re-examination. We have done this using conservative statistical methods. We have concluded that the physical associations are real and thus it appears that QSOs are being ejected from spiral galaxies which often show other aspects of activity. Some examples of these phenomena will be described. Thus despite the fact that most investigators continue to use QSOs for cosmological investigations, the results are doomed to failure. Even more important the nature of the high redshifts of QSOs (but not the redshifts of normal galaxies) remains a puzzle yet to be solved.

Accounting for Cosmic Variance in Studies of Gravitationally Lensed High-redshift Galaxies in the Hubble Frontier Field Clusters

NASA Astrophysics Data System (ADS)

Robertson, Brant E.; Ellis, Richard S.; Dunlop, James S.; McLure, Ross J.; Stark, Dan P.; McLeod, Derek

2014-12-01

Strong gravitational lensing provides a powerful means for studying faint galaxies in the distant universe. By magnifying the apparent brightness of background sources, massive clusters enable the detection of galaxies fainter than the usual sensitivity limit for blank fields. However, this gain in effective sensitivity comes at the cost of a reduced survey volume and, in this Letter, we demonstrate that there is an associated increase in the cosmic variance uncertainty. As an example, we show that the cosmic variance uncertainty of the high-redshift population viewed through the Hubble Space Telescope Frontier Field cluster Abell 2744 increases from ~35% at redshift z ~ 7 to >~ 65% at z ~ 10. Previous studies of high-redshift galaxies identified in the Frontier Fields have underestimated the cosmic variance uncertainty that will affect the ultimate constraints on both the faint-end slope of the high-redshift luminosity function and the cosmic star formation rate density, key goals of the Frontier Field program.

The Universe Going Green: Extraordinarily Strong [OIII]5007 in Typical Dwarf Galaxies at z~3

NASA Astrophysics Data System (ADS)

Malkan, Matthew Arnold; Cohen, Daniel

2017-01-01

We constructed the average SEDs of U-dropout galaxies in the Subaru Deep Field. This sample contains more than 5000 Lyman-break galaxies at z~3. Their average near- and mid-IR colors were obtained by stacking JHK and IRAC imaging, in bins of stellar mass. At the lowest mass bins an increasingly strong excess flux is seen in the K filter. This excess can reach 1 magnitude in the broadband filter, and we attribute it to strong \\OIII $\\lambda{5007}$ line emission. The equivalent width is extraordinarily high, reaching almost 1000\\Ang\\ for the average z=3 galaxy at an i magnitude of 27. Such extreme [OIII] emission is very rare in the current epoch, only seen in a handful of metal-deficient dwarf starbursts sometimes referred to as ''Green Peas". In contrast, extreme [OIII]--strong enough to dominate the entire broad-band SED--was evidently the norm for faint galaxies at high redshift. We present evidence that these small but numerous galaxies were primarily responsible for the reionization of the Universe.

Environment of Submillimeter Galaxies

NASA Astrophysics Data System (ADS)

Hou, K.-c.; Chen, L.-w.

2013-10-01

To study the environment of high-redshift star-forming galaxies — submillimeter galaxies (SMGs) — and their role during large-scale structure formation, we have estimated the galaxy number density fluctuations around SMGs, and analyzed their cross correlation functions with Lyman alpha emitters (LAEs), and optical-selected galaxies with photometric redshift in the COSMOS and ECDFS fields. Only a marginal cross-correlation between SMGs and optical-selected galaxies at most redshifts intervals is found in our results, except a relatively strong correlation detected in the cases of AzTEC-detected SMGs with galaxies at z ˜2.6 and 3.6. The density fluctuations around SMGs with redshift estimated show most SMGs located in a high-density region. There is no correlation signal between LAEs and SMGs, and the galaxy density fluctuations indicate a slightly anti-correlation on a scale smaller than 2 Mpc. Furthermore, we also investigate the density fluctuations of passive and starforming galaxies selected by optical and near infrared colors at similar redshift around SMGs. Finally the implication from our results to the interconnection between high-redshift galaxy populations is discussed.

Optical Identifications of High-Redshift Galaxy Clusters from the Planck Sunyaev-Zeldovich Survey

NASA Astrophysics Data System (ADS)

Burenin, R. A.; Bikmaev, I. F.; Khamitov, I. M.; Zaznobin, I. A.; Khorunzhev, G. A.; Eselevich, M. V.; Afanasiev, V. L.; Dodonov, S. N.; Rubiño-Martín, J.-A.; Aghanim, N.; Sunyaev, R. A.

2018-05-01

We present the results of optical identifications and spectroscopic redshift measurements for galaxy clusters from the second Planck catalogue of Sunyaev-Zeldovich sources (PSZ2) located at high redshifts, z ≈ 0.7-0.9. We used the data of optical observations with the Russian-Turkish 1.5-mtelescope (RTT-150), the Sayan Observatory 1.6-m telescope, the Calar Alto 3.5-m telescope, and the 6-m SAO RAS telescope (BTA). The spectroscopic redshift measurements were obtained for seven galaxy clusters, including one cluster, PSZ2 G126.57+51.61, from the cosmological sample of the PSZ2 catalogue. In the central regions of two clusters, PSZ2 G069.39+68.05 and PSZ2 G087.39-34.58, we detected arcs of strong gravitational lensing of background galaxies, one of which is at redshift z = 4.262. The data presented below roughly double the number of known galaxy clusters in the second Planck catalogue of Sunyaev-Zeldovich sources at high redshifts, z ≈ 0.8.

Studying the Evolution of the Contamination of the Sunyaev-Zel'dovich effect due to High-redshift (sub-)mm Galaxies

NASA Astrophysics Data System (ADS)

Montana, Alfredo; Aretxaga, I.; Austermann, J.; Bock, J.; Chapin, E.; Gaztanaga, E.; Hughes, D.; Lowenthal, J.; Mauskopf, P.; Perera, T.; Scott, K.; Wilson, G.; Yun, M.

2007-05-01

We present simulations of the submillimetre/millimetre (sub-mm) sky to study the environment of luminous starburst galaxies, radio galaxies and AGN towards biased-regions (large-scale over-densities) in the high-redshift universe. Guided by recent results from AzTEC extragalactic surveys at 1.1mm, we describe the impact of this population of galaxies, that dominate the sub-mm extragalactic background, on the detectability of the Sunyaev-Zel'dovich effect (SZE) as a function of redshift. These results will be presented in the context of the next generation of wide-area surveys to identify high-redshift clusters via the SZE.

HIGH-REDSHIFT DUST OBSCURED GALAXIES: A MORPHOLOGY-SPECTRAL ENERGY DISTRIBUTION CONNECTION REVEALED BY KECK ADAPTIVE OPTICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melbourne, J.; Matthews, K.; Soifer, B. T.

A simple optical to mid-IR color selection, R - [24]>14, i.e., f {sub {nu}}(24 {mu}m)/f {sub {nu}}(R) {approx}> 1000, identifies highly dust obscured galaxies (DOGs) with typical redshifts of z {approx} 2 {+-} 0.5. Extreme mid-IR luminosities (L {sub IR} > 10{sup 12-14}) suggest that DOGs are powered by a combination of active galactic nuclei (AGNs) and star formation, possibly driven by mergers. In an effort to compare their photometric properties with their rest-frame optical morphologies, we obtained high-spatial resolution (0.''05-0.''1) Keck Adaptive Optics K'-band images of 15 DOGs. The images reveal a wide range of morphologies, including small exponentialmore » disks (eight of 15), small ellipticals (four of 15), and unresolved sources (two of 15). One particularly diffuse source could not be classified because of low signal-to-noise ratio. We find a statistically significant correlation between galaxy concentration and mid-IR luminosity, with the most luminous DOGs exhibiting higher concentration and smaller physical size. DOGs with high concentration also tend to have spectral energy distributions (SEDs) suggestive of AGN activity. Thus, central AGN light may be biasing the morphologies of the more luminous DOGs to higher concentration. Conversely, more diffuse DOGs tend to show an SED shape suggestive of star formation. Two of 15 in the sample show multiple resolved components with separations of {approx}1 kpc, circumstantial evidence for ongoing mergers.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, Peiyuan; Urry, C. Megan

We investigate a sample of 622 blazars with measured fluxes at 12 wavebands across the radio-to-gamma-ray spectrum but without spectroscopic or photometric redshifts. This sample includes hundreds of sources with newly analyzed X-ray spectra reported here. From the synchrotron peak frequencies, estimated by fitting the broadband spectral energy distributions (SEDs), we find that the fraction of high-synchrotron-peaked blazars in these 622 sources is roughly the same as in larger samples of blazars that do have redshifts. We characterize the no-redshift blazars using their infrared colors, which lie in the distinct locus called the WISE blazar strip, then estimate their redshiftsmore » using a KNN regression based on the redshifts of the closest blazars in the WISE color–color plot. Finally, using randomly drawn values from plausible redshift distributions, we simulate the SEDs of these blazars and compare them to known blazar SEDs. Based on all these considerations, we conclude that blazars without redshift estimates are unlikely to be high-luminosity, high-synchrotron-peaked objects, which had been suggested in order to explain the “blazar sequence”—an observed trend of SED shape with luminosity—as a selection effect. Instead, the observed properties of no-redshift blazars are compatible with a causal connection between jet power and electron cooling, i.e., a true blazar sequence.« less

The MUSE Hubble Ultra Deep Field Survey. II. Spectroscopic redshifts and comparisons to color selections of high-redshift galaxies

NASA Astrophysics Data System (ADS)

Inami, H.; Bacon, R.; Brinchmann, J.; Richard, J.; Contini, T.; Conseil, S.; Hamer, S.; Akhlaghi, M.; Bouché, N.; Clément, B.; Desprez, G.; Drake, A. B.; Hashimoto, T.; Leclercq, F.; Maseda, M.; Michel-Dansac, L.; Paalvast, M.; Tresse, L.; Ventou, E.; Kollatschny, W.; Boogaard, L. A.; Finley, H.; Marino, R. A.; Schaye, J.; Wisotzki, L.

2017-11-01

We have conducted a two-layered spectroscopic survey (1' × 1' ultra deep and 3' × 3' deep regions) in the Hubble Ultra Deep Field (HUDF) with the Multi Unit Spectroscopic Explorer (MUSE). The combination of a large field of view, high sensitivity, and wide wavelength coverage provides an order of magnitude improvement in spectroscopically confirmed redshifts in the HUDF; i.e., 1206 secure spectroscopic redshifts for Hubble Space Telescope (HST) continuum selected objects, which corresponds to 15% of the total (7904). The redshift distribution extends well beyond z> 3 and to HST/F775W magnitudes as faint as ≈ 30 mag (AB, 1σ). In addition, 132 secure redshifts were obtained for sources with no HST counterparts that were discovered in the MUSE data cubes by a blind search for emission-line features. In total, we present 1338 high quality redshifts, which is a factor of eight increase compared with the previously known spectroscopic redshifts in the same field. We assessed redshifts mainly with the spectral features [O II] at z< 1.5 (473 objects) and Lyα at 2.9

A universal minimal mass scale for present-day central black holes

NASA Astrophysics Data System (ADS)

Alexander, Tal; Bar-Or, Ben

2017-08-01

The early stages of massive black hole growth are poorly understood1. High-luminosity active galactic nuclei at very high redshift2 z further imply rapid growth soon after the Big Bang. Suggested formation mechanisms typically rely on the extreme conditions found in the early Universe (very low metallicity, very high gas or star density). It is therefore plausible that these black hole seeds were formed in dense environments, at least a Hubble time ago (z > 1.8 for a look-back time of tH = 10 Gyr)3. Intermediate-mass black holes (IMBHs) of mass M• ≈ 102-105 solar masses, M⊙, are the long-sought missing link4 between stellar black holes, born of supernovae5, and massive black holes6, tied to galaxy evolution by empirical scaling relations7,8. The relation between black hole mass, M•, and stellar velocity dispersion, σ★, that is observed in the local Universe over more than about three decades in massive black hole mass, correlates M• and σ★ on scales that are well outside the massive black hole's radius of dynamical influence6, rh≈GM•/σ★2. We show that low-mass black hole seeds that accrete stars from locally dense environments in galaxies following a universal M•/σ★ relation9,10 grow over the age of the Universe to be above M0≈3×105M⊙ (5% lower limit), independent of the unknown seed masses and formation processes. The mass M0 depends weakly on the uncertain formation redshift, and sets a universal minimal mass scale for present-day black holes. This can explain why no IMBHs have yet been found6, and it implies that present-day galaxies with σ★ < S0 ≈ 40 km s-1 lack a central black hole, or formed it only recently. A dearth of IMBHs at low redshifts has observable implications for tidal disruptions11 and gravitational wave mergers12.

Precise weak lensing constraints from deep high-resolution Ks images: VLT/HAWK-I analysis of the super-massive galaxy cluster RCS2 J 232727.7-020437 at z = 0.70

NASA Astrophysics Data System (ADS)

Schrabback, Tim; Schirmer, Mischa; van der Burg, Remco F. J.; Hoekstra, Henk; Buddendiek, Axel; Applegate, Douglas; Bradač, Maruša; Eifler, Tim; Erben, Thomas; Gladders, Michael D.; Hernández-Martín, Beatriz; Hildebrandt, Hendrik; Hoag, Austin; Klaes, Dominik; von der Linden, Anja; Marchesini, Danilo; Muzzin, Adam; Sharon, Keren; Stefanon, Mauro

2018-03-01

We demonstrate that deep good-seeing VLT/HAWK-I Ks images complemented with g + z-band photometry can yield a sensitivity for weak lensing studies of massive galaxy clusters at redshifts 0.7 ≲ z ≲ 1.1, which is almost identical to the sensitivity of HST/ACS mosaics of single-orbit depth. Key reasons for this good performance are the excellent image quality frequently achievable for Ks imaging from the ground, a highly effective photometric selection of background galaxies, and a galaxy ellipticity dispersion that is noticeably lower than for optically observed high-redshift galaxy samples. Incorporating results from the 3D-HST and UltraVISTA surveys we also obtained a more accurate calibration of the source redshift distribution than previously achieved for similar optical weak lensing data sets. Here we studied the extremely massive galaxy cluster RCS2 J232727.7-020437 (z = 0.699), combining deep VLT/HAWK-I Ks images (point spread function with a 0.''35 full width at half maximum) with LBT/LBC photometry. The resulting weak lensing mass reconstruction suggests that the cluster consists of a single overdensity, which is detected with a peak significance of 10.1σ. We constrained the cluster mass to M200c/(1015 M⊙) = 2.06-0.26+0.28(stat.) ± 0.12(sys.) assuming a spherical Navarro, Frenk & White model and simulation-based priors on the concentration, making it one of the most massive galaxy clusters known in the z ≳ 0.7 Universe. We also cross-checked the HAWK-I measurements through an analysis of overlapping HST/ACS images, yielding fully consistent estimates of the lensing signal. Based on observations conducted with the ESO Very Large Telescope, the Large Binocular Telescope, and the NASA/ESA Hubble Space Telescope, as detailed in the acknowledgements.

Morphology and Structure of High-redshift Massive Galaxies in the CANDELS Fields

NASA Astrophysics Data System (ADS)

Guan-wen, Fang; Ze-sen, Lin; Xu, Kong

2018-01-01

Using the multi-band photometric data of all five CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) fields and the near-infrared (F125W and F160W) high-resolution images of HST WFC3 (Hubble Space Telescope Wide Field Camera 3), a quantitative study of morphology and structure of mass-selected galaxies is presented. The sample includes 8002 galaxies with a redshift 1 < z < 3 and stellar mass M*> 1010M⊙. Based on the Convolutional Neural Network (ConvNet) criteria, we classify the sample galaxies into SPHeroids (SPH), Early-Type Disks (ETD), Late-Type Disks (LTD), and IRRegulars (IRR) in different redshift bins. The findings indicate that the galaxy morphology and structure evolve with redshift up to z ∼ 3, from irregular galaxies in the high-redshift universe to the formation of the Hubble sequence dominated by disks and spheroids. For the same redshift interval, the median values of effective radii (re) of different morphological types are in a descending order: IRR, LTD, ETD, and SPH. But for the Sérsic index (n), the order is reversed (SPH, ETD, LTD, and IRR). In the meantime, the evolution of galaxy size (re) with the redshift is explored for the galaxies of different morphological types, and it is confirmed that their size will enlarge with time. However, such a phenomenon is not found in the relations between the redshift (1 < z < 3) and the mean axis ratio (b/a), as well as the Sérsic index (n).

The Infrared Properties of Sources Matched in the Wise All-Sky and Herschel ATLAS Surveys

NASA Technical Reports Server (NTRS)

Bond, Nicholas A.; Benford, Dominic J.; Gardner, Jonathan P.; Amblard, Alexandre; Fleuren, Simone; Blain, Andrew W.; Dunne, Loretta; Smith, Daniel J. B.; Maddox, Steve J.; Hoyos, Carlos;

The Infrared Properties of Sources Matched in the WISE All-Sky and Herschel Atlas Surveys

NASA Technical Reports Server (NTRS)

Bond, Nicholas A.; Benford, Dominic J.; Gardner, Jonathan P.; Eisenhardt, Peter; Amblard, Alexandre; Temi, Pasquale; Fleuren, Simone; Blain, Andrew W.; Dunne, Loretta; Smith, Daniel J.;

THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: BIASES IN z  > 1.46 REDSHIFTS DUE TO QUASAR DIVERSITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denney, K. D.; Peterson, B. M.; Horne, Keith

We use the coadded spectra of 32 epochs of Sloan Digital Sky Survey (SDSS) Reverberation Mapping Project observations of 482 quasars with z  > 1.46 to highlight systematic biases in the SDSS- and Baryon Oscillation Spectroscopic Survey (BOSS)-pipeline redshifts due to the natural diversity of quasar properties. We investigate the characteristics of this bias by comparing the BOSS-pipeline redshifts to an estimate from the centroid of He ii λ 1640. He ii has a low equivalent width but is often well-defined in high-S/N spectra, does not suffer from self-absorption, and has a narrow component which, when present (the case for aboutmore » half of our sources), produces a redshift estimate that, on average, is consistent with that determined from [O ii] to within the He ii and [O ii] centroid measurement uncertainties. The large redshift differences of ∼1000 km s{sup −1}, on average, between the BOSS-pipeline and He ii-centroid redshifts, suggest there are significant biases in a portion of BOSS quasar redshift measurements. Adopting the He ii-based redshifts shows that C iv does not exhibit a ubiquitous blueshift for all quasars, given the precision probed by our measurements. Instead, we find a distribution of C iv-centroid blueshifts across our sample, with a dynamic range that (i) is wider than that previously reported for this line, and (ii) spans C iv centroids from those consistent with the systemic redshift to those with significant blueshifts of thousands of kilometers per second. These results have significant implications for measurement and use of high-redshift quasar properties and redshifts, and studies based thereon.« less

ON THE USE OF THE INDEX N2 TO DERIVE THE METALLICITY IN METAL-POOR GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morales-Luis, A. B.; Almeida, J. Sánchez; Muñoz-Tuñón, C.

2014-12-20

The N2 index ([N II] λ6584/Hα) is used to determine emission line galaxy metallicities at all redshifts, including high redshift, where galaxies tend to be metal-poor. The initial aim of this work was to improve the calibrations used to infer oxygen abundance from N2 by employing updated low-metallicity galaxy databases. We compare N2 and the metallicity determined using the direct method for the set of extremely metal-poor galaxies compiled by Morales-Luis et al. To our surprise, the oxygen abundance presents a tendency to be constant with N2, with a very large scatter. Consequently, we find that the existing N2 calibrators overestimatemore » the oxygen abundance for most low-metallicity galaxies, and can therefore only be used to set upper limits to the true metallicity in low-metallicity galaxies. An explicit expression for this limit is given. In addition, we try to explain the observed scatter using photoionization models. It is mostly due to the different evolutionary state of the H II regions producing the emission lines, but it also arises due to differences in N/O among the galaxies.« less

A massive protocluster of galaxies at a redshift of z ≈ 5.3.

PubMed

Capak, Peter L; Riechers, Dominik; Scoville, Nick Z; Carilli, Chris; Cox, Pierre; Neri, Roberto; Robertson, Brant; Salvato, Mara; Schinnerer, Eva; Yan, Lin; Wilson, Grant W; Yun, Min; Civano, Francesca; Elvis, Martin; Karim, Alexander; Mobasher, Bahram; Staguhn, Johannes G

2011-02-10

Massive clusters of galaxies have been found that date from as early as 3.9 billion years (3.9 Gyr; z = 1.62) after the Big Bang, containing stars that formed at even earlier epochs. Cosmological simulations using the current cold dark matter model predict that these systems should descend from 'protoclusters'-early overdensities of massive galaxies that merge hierarchically to form a cluster. These protocluster regions themselves are built up hierarchically and so are expected to contain extremely massive galaxies that can be observed as luminous quasars and starbursts. Observational evidence for this picture, however, is sparse because high-redshift protoclusters are rare and difficult to observe. Here we report a protocluster region that dates from 1 Gyr (z = 5.3) after the Big Bang. This cluster of massive galaxies extends over more than 13 megaparsecs and contains a luminous quasar as well as a system rich in molecular gas. These massive galaxies place a lower limit of more than 4 × 10(11) solar masses of dark and luminous matter in this region, consistent with that expected from cosmological simulations for the earliest galaxy clusters.

A Tale of Two Faint Bursts: GRB 050223 and GRB 050911

NASA Astrophysics Data System (ADS)

Page, K. L.; Barthelmy, S. D.; Beardmore, A. P.; Burrows, D. N.; Campana, S.; Chincharini, G.; Cummings, J. R.; Cusumano, G.; Gehrels, N.; Giommi, P.; Goad, M. R.; Godet, O.; Graham, J.; Kaneko, Y.; Kennea, J. A.; Mangano, V.; Markwardt, C. B.; O'Brien, P. T.; Osborne, J. P.; Reichart, D. E.; Rol, E.; Sakamoto, T.; Tagliaferri, G.; Tanvir, N. R.; Wells, A. A.; Zhang, B.

2006-05-01

GRBs 050223 and 050911 were discovered by the Swift Burst Alert Telescope (BAT) on 23rd February and 11th September 2005 respectively. The observation of GRB 050223 showed a faint, fading X-ray source, which was identified as the afterglow; GRB 050911, however, was not detected, making any X-ray afterglow extremely faint. The faintness of the afterglow of GRB 050223 could be explained by a large opening or viewing angle, or by the burst being at high redshift. The non-detection of GRB 050911 may indicate the burst occurred in a low-density environment, or, alternatively, was due to a compact object merger, in spite of the apparent long duration of the burst.

A faint field-galaxy redshift survey in quasar fields

NASA Technical Reports Server (NTRS)

Yee, Howard K. C.; Ellingson, Erica

1993-01-01

Quasars serve as excellent markers for the identification of high-redshift galaxies and galaxy clusters. In past surveys, nearly 20 clusters of Abell richness class 1 or richer associated with quasars in the redshift range 0.2 less than z less than 0.8 were identified. In order to study these galaxy clusters in detail, a major redshift survey of faint galaxies in these fields using the CFHT LAMA/MARLIN multi-object spectroscopy system was carried out. An equally important product in such a survey is the redshifts of the field galaxies not associated with the quasars. Some preliminary results on field galaxies from an interim set of data from our redshift survey in quasar fields are presented.

Probabilistic Selection of High-redshfit Quasars with Subaru / Hyper Suprime-Cam Survey

NASA Astrophysics Data System (ADS)

Onoue, Masafusa

2015-08-01

High-redshift quasrs are an important probe of the distant Universe. They enable observational studies of the early growth of supermassive blackholes, cosmic reionization, chemical enrichment of host galaxies, and so on. We are now starting a new ground-breaking survey of high-redsfhit quasars (z>6) using the exquisite imaging data provided by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) Survey. With the extremely wide-area coverage and high sensitivity thorugh five optical bands (1,400 deg2 to the depth of r~26 in Wide layer), it is one of the most powerful contemporary surveys that makes it possible for the HSC-AGN collaboration to increase the number of z>6 quasars by almost an order of magnitude, i.e., 300 at z~6 and 50 at z~7 based on the current estimate of the QLF at z>6 (Willott et al. 2010).One of the biggest challenges in the candidate selection is the significant contamination of Galactic brown dwarfs, which have the same point-like appearance as and similarly red colors to z>6 quasars. To overcome this issue, we have developed template SED fitting method optimized to high-redshift quasars selection for constructing the largest z>6 quasar sample with the HSC survey. Since 500 deg2 of the footprints of the HSC survey overlaps with the VISTA/VIKING survey, it is expected that z>6 quasars, with characteristic large Lyman break and flat red-continuum in its SED, can be separated out from contaminating sources by applying SED fitting with multi-wavelength photometric data. In practice, its application with 27 photometric bands to the COSMOS quasars at 36 quasar search with the first-year data products of the HSC survey, which results in extracting several promising candidates including one possible highest-redshift quasar at zphoto=7.3.

High-Redshift Blazars Through NuSTAR Eyes

NASA Astrophysics Data System (ADS)

Marcotulli, Lea

MeV blazars are the most powerful sources among the blazar class. With bolometric luminosities exceeding 1048 erg s-1 and powerful relativistic jets, they are usually detected at high-redshifts (z > 2) and they generally harbor extremely massive black holes (MBH 109Msun). Being able to derive their physical properties such as jet power, accretion disk luminosity, bulk Lorentz factor of the jet (Gamma) and black hole mass, enables us to put constraints in the understanding of this not well sampled class of objects and use them for example to probe the formation of massive black holes in the early universe. In this thesis we have analyzed the broadband emission of three high redshift blazars, focusing on the high energy part of their spectral energy distribution. In fact, being able to obtain hard X-ray data from the recently launched NuSTAR and having gamma-ray detections from the Fermi-LAT, we were able to constrain more accurately the high energy peak of their distribution and therefore more precisely infer their jet power, underlying electron distribution, Gamma and viewing angle (theta v). Gathering optical and UV data allowed us to determine the black hole mass of such powerful objects as well as their accretion disk luminosity. This work has recently been published in ApJ (Marcotulli et al., 2017). In Section 1, the broad family of active galactic nuclei (ANGs) and their main physical characteristics are introduced, with a focus on the subclass of blazars and specifically MeV blazars. In Section 2, the main instruments used in our research to gather and analyze data are described, with a particular interest on imaging in the hard X-ray regime. Section 3 contains the data analysis description, the results obtained combining the observations with a one-zone leptonic emission model and the discussion on our findings. In Section 4 we report our conclusions and present an outlook on future MeV blazars studies possibilities. Appendix A, B and C contain an overlook of relativistic beaming, radiative processes and model used for these sources.

Deep 1.1 mm-wavelength imaging of the GOODS-S field by AzTEC/ASTE - II. Redshift distribution and nature of the submillimetre galaxy population

NASA Astrophysics Data System (ADS)

Yun, Min S.; Scott, K. S.; Guo, Yicheng; Aretxaga, I.; Giavalisco, M.; Austermann, J. E.; Capak, P.; Chen, Yuxi; Ezawa, H.; Hatsukade, B.; Hughes, D. H.; Iono, D.; Johnson, S.; Kawabe, R.; Kohno, K.; Lowenthal, J.; Miller, N.; Morrison, G.; Oshima, T.; Perera, T. A.; Salvato, M.; Silverman, J.; Tamura, Y.; Williams, C. C.; Wilson, G. W.

2012-02-01

We report the results of the counterpart identification and a detailed analysis of the physical properties of the 48 sources discovered in our deep 1.1-mm wavelength imaging survey of the Great Observatories Origins Deep Survey-South (GOODS-S) field using the AzTEC instrument on the Atacama Submillimeter Telescope Experiment. One or more robust or tentative counterpart candidate is found for 27 and 14 AzTEC sources, respectively, by employing deep radio continuum, Spitzer/Multiband Imaging Photometer for Spitzer and Infrared Array Camera, and Large APEX Bolometer Camera 870 μm data. Five of the sources (10 per cent) have two robust counterparts each, supporting the idea that these galaxies are strongly clustered and/or heavily confused. Photometric redshifts and star formation rates (SFRs) are derived by analysing ultraviolet(UV)-to-optical and infrared(IR)-to-radio spectral energy distributions (SEDs). The median redshift of zmed˜ 2.6 is similar to other earlier estimates, but we show that 80 per cent of the AzTEC-GOODS sources are at z≥ 2, with a significant high-redshift tail (20 per cent at z≥ 3.3). Rest-frame UV and optical properties of AzTEC sources are extremely diverse, spanning 10 mag in the i- and K-band photometry (a factor of 104 in flux density) with median values of i= 25.3 and K= 22.6 and a broad range of red colour (i-K= 0-6) with an average value of i-K≈ 3. These AzTEC sources are some of the most luminous galaxies in the rest-frame optical bands at z≥ 2, with inferred stellar masses M*= (1-30) × 1010 M⊙ and UV-derived SFRs of SFRUV≳ 101-3 M⊙ yr-1. The IR-derived SFR, 200-2000 M⊙ yr-1, is independent of z or M*. The resulting specific star formation rates, SSFR ≈ 1-100 Gyr-1, are 10-100 times higher than similar mass galaxies at z= 0, and they extend the previously observed rapid rise in the SSFR with redshift to z= 2-5. These galaxies have a SFR high enough to have built up their entire stellar mass within their Hubble time. We find only marginal evidence for an active galactic nucleus (AGN) contribution to the near-IR and mid-IR SEDs, even among the X-ray detected sources, and the derived M* and SFR show little dependence on the presence of an X-ray bright AGN.

Very Long Baseline Array Imaging of Type-2 Seyferts with Double-peaked Narrow Emission Lines: Searches for Sub-kpc Dual AGNs and Jet-powered Outflows

NASA Astrophysics Data System (ADS)

Liu, Xin; Lazio, T. Joseph W.; Shen, Yue; Strauss, Michael A.

2018-02-01

This paper presents Very Long Baseline Array (VLBA) observations of 13 double-peaked [O III] emission-line type-2 active galactic nuclei (AGNs) at redshifts 0.06 < z < 0.41 (with a median redshift of z ∼ 0.15) identified in the Sloan Digital Sky Survey. Such double-peaked emission-line objects may result from jets or outflows from the central engine or from a dual AGN. The VLBA provides an angular resolution of ≲10 pc at the distance of many of these galaxies, sufficient to resolve the radio emission from extremely close dual AGNs and to contribute to understanding the origin of double-peaked [O III] emission lines. Of the 13 galaxies observed at 3.6 cm (8.4 GHz), we detect six at a 1σ sensitivity level of ∼0.15 mJy beam‑1, two of which show clear jet structures on scales ranging from a few milliarcseconds to tens of milliarcseconds (corresponding to a few pc to tens of pc at a median redshift of 0.15). We suggest that radio-loud, double-peaked emission-line type-2 AGNs may be indicative of jet produced structures, but a larger sample of double-peaked [O III] AGNs with high angular resolution radio observations will be required to confirm this suggestion. Based, in part, on observations made with the Very Long Baseline Array, obtained at the Long Baseline Observatory. The Long Baseline Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Estimating sizes of faint, distant galaxies in the submillimetre regime

NASA Astrophysics Data System (ADS)

Lindroos, L.; Knudsen, K. K.; Fan, L.; Conway, J.; Coppin, K.; Decarli, R.; Drouart, G.; Hodge, J. A.; Karim, A.; Simpson, J. M.; Wardlow, J.

2016-10-01

We measure the sizes of redshift ˜2 star-forming galaxies by stacking data from the Atacama Large Millimeter/submillimeter Array (ALMA). We use a uv-stacking algorithm in combination with model fitting in the uv-domain and show that this allows for robust measures of the sizes of marginally resolved sources. The analysis is primarily based on the 344 GHz ALMA continuum observations centred on 88 submillimetre galaxies in the LABOCA ECDFS Submillimeter Survey (ALESS). We study several samples of galaxies at z ≈ 2 with M* ≈ 5 × 1010 M⊙, selected using near-infrared photometry (distant red galaxies, extremely red objects, sBzK-galaxies, and galaxies selected on photometric redshift). We find that the typical sizes of these galaxies are ˜0.6 arcsec which corresponds to ˜5 kpc at z = 2, this agrees well with the median sizes measured in the near-infrared z band (˜0.6 arcsec). We find errors on our size estimates of ˜0.1-0.2 arcsec, which agree well with the expected errors for model fitting at the given signal-to-noise ratio. With the uv-coverage of our observations (18-160 m), the size and flux density measurements are sensitive to scales out to 2 arcsec. We compare this to a simulated ALMA Cycle 3 data set with intermediate length baseline coverage, and we find that, using only these baselines, the measured stacked flux density would be an order of magnitude fainter. This highlights the importance of short baselines to recover the full flux density of high-redshift galaxies.

Dark matter annihilation in the circumgalactic medium at high redshifts

NASA Astrophysics Data System (ADS)

Schön, S.; Mack, K. J.; Wyithe, J. S. B.

2018-03-01

Annihilating dark matter (DM) models offer promising avenues for future DM detection, in particular via modification of astrophysical signals. However, when modelling such potential signals at high redshift, the emergence of both DM and baryonic structure, as well as the complexities of the energy transfer process, needs to be taken into account. In the following paper, we present a detailed energy deposition code and use this to examine the energy transfer efficiency of annihilating DM at high redshift, including the effects on baryonic structure. We employ the PYTHIA code to model neutralino-like DM candidates and their subsequent annihilation products for a range of masses and annihilation channels. We also compare different density profiles and mass-concentration relations for 105-107 M⊙ haloes at redshifts 20 and 40. For these DM halo and particle models, we show radially dependent ionization and heating curves and compare the deposited energy to the haloes' gravitational binding energy. We use the `filtered' annihilation spectra escaping the halo to calculate the heating of the circumgalactic medium and show that the mass of the minimal star-forming object is increased by a factor of 2-3 at redshift 20 and 4-5 at redshift 40 for some DM models.

ACCOUNTING FOR COSMIC VARIANCE IN STUDIES OF GRAVITATIONALLY LENSED HIGH-REDSHIFT GALAXIES IN THE HUBBLE FRONTIER FIELD CLUSTERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robertson, Brant E.; Stark, Dan P.; Ellis, Richard S.

Strong gravitational lensing provides a powerful means for studying faint galaxies in the distant universe. By magnifying the apparent brightness of background sources, massive clusters enable the detection of galaxies fainter than the usual sensitivity limit for blank fields. However, this gain in effective sensitivity comes at the cost of a reduced survey volume and, in this Letter, we demonstrate that there is an associated increase in the cosmic variance uncertainty. As an example, we show that the cosmic variance uncertainty of the high-redshift population viewed through the Hubble Space Telescope Frontier Field cluster Abell 2744 increases from ∼35% atmore » redshift z ∼ 7 to ≳ 65% at z ∼ 10. Previous studies of high-redshift galaxies identified in the Frontier Fields have underestimated the cosmic variance uncertainty that will affect the ultimate constraints on both the faint-end slope of the high-redshift luminosity function and the cosmic star formation rate density, key goals of the Frontier Field program.« less

The Complete Calibration of the Color–Redshift Relation (C3R2) Survey: Survey Overview and Data Release 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masters, Daniel C.; Stern, Daniel K.; Rhodes, Jason D.

A key goal of the Stage IV dark energy experiments Euclid , LSST, and WFIRST is to measure the growth of structure with cosmic time from weak lensing analysis over large regions of the sky. Weak lensing cosmology will be challenging: in addition to highly accurate galaxy shape measurements, statistically robust and accurate photometric redshift (photo- z ) estimates for billions of faint galaxies will be needed in order to reconstruct the three-dimensional matter distribution. Here we present an overview of and initial results from the Complete Calibration of the Color–Redshift Relation (C3R2) survey, which is designed specifically to calibratemore » the empirical galaxy color–redshift relation to the Euclid depth. These redshifts will also be important for the calibrations of LSST and WFIRST . The C3R2 survey is obtaining multiplexed observations with Keck (DEIMOS, LRIS, and MOSFIRE), the Gran Telescopio Canarias (GTC; OSIRIS), and the Very Large Telescope (VLT; FORS2 and KMOS) of a targeted sample of galaxies that are most important for the redshift calibration. We focus spectroscopic efforts on undersampled regions of galaxy color space identified in previous work in order to minimize the number of spectroscopic redshifts needed to map the color–redshift relation to the required accuracy. We present the C3R2 survey strategy and initial results, including the 1283 high-confidence redshifts obtained in the 2016A semester and released as Data Release 1.« less

The SDSS-XDQSO quasar targeting catalog

NASA Astrophysics Data System (ADS)

Bovy, Jo; Hennawi, J. F.; Hogg, D. W.; Myers, A. D.; Ross, N. P.

2011-01-01

We present the SDSS-XDQSO quasar targeting catalog for efficient flux-based quasar target selection down to the faint limit of the SDSS catalog, even at medium redshifts (2.5 < z < 3). We build models of the distributions of stars and quasars in flux space down to the flux limit by applying the extreme-deconvolution method (XD) to estimate the underlying density. We properly convolve this density with the flux uncertainties when evaluating the probability that an object is a quasar. This results in a targeting algorithm that is more principled, more efficient, and faster than other similar methods. We apply the algorithm to derive low- (z < 2.2), medium- (2.2 <= z 3.5) quasar probabilities for all 160,904,060 point-sources with dereddened i-and magnitude between 17.75 and 22.45 mag in SDSS Data Release 8. The catalog can be used to define a uniformly selected and efficient low- or medium-redshift quasar survey, such as that needed for the SDSS-III Baryon Oscillation Spectroscopic Survey project. We show that the XDQSO technique performs as well as the current best photometric quasar selection technique at low redshift, and out-performs all other flux-based methods for selecting the medium-redshift quasars of our primary interest. Research supported by NASA (grant NNX08AJ48G) and the NSF (grant AST-0908357).

SPECTROSCOPY OF LUMINOUS COMPACT BLUE GALAXIES IN DISTANT CLUSTERS. II. PHYSICAL PROPERTIES OF dE PROGENITOR CANDIDATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crawford, S. M.; Wirth, Gregory D.; Bershady, M. A.

2016-02-01

Luminous Compact Blue Galaxies (LCBGs) are an extreme star-bursting population of galaxies that were far more common at earlier epochs than today. Based on spectroscopic and photometric measurements of LCBGs in massive (M > 10{sup 15} M{sub ⊙}), intermediate redshift (0.5 < z < 0.9) galaxy clusters, we present their rest-frame properties including star formation rate, dynamical mass, size, luminosity, and metallicity. The appearance of these small, compact galaxies in clusters at intermediate redshift helps explain the observed redshift evolution in the size–luminosity relationship among cluster galaxies. In addition, we find the rest-frame properties of LCBGs appearing in galaxy clusters are indistinguishable from field LCBGs atmore » the same redshift. Up to 35% of the LCBGs show significant discrepancies between optical and infrared indicators of star formation, suggesting that star formation occurs in obscured regions. Nonetheless, the star formation for LCBGs shows a decrease toward the center of the galaxy clusters. Based on their position and velocity, we estimate that up to 10% of cluster LCBGs are likely to merge with another cluster galaxy. Finally, the observed properties and distributions of the LCBGs in these clusters lead us to conclude that we are witnessing the quenching of the progenitors of dwarf elliptical galaxies that dominate the number density of present-epoch galaxy clusters.« less

THE EXTREMELY RED HOST GALAXY OF GRB 080207

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunt, Leslie; Cresci, Giovanni; Palazzi, Eliana

2011-08-01

We present optical, near-infrared, and Spitzer IRAC and MIPS observations of the host galaxy of the dark Swift gamma-ray burst GRB 080207. The host is faint, with extremely red optical-infrared colors (R - K = 6.3, 24 {mu}m/R-band flux {approx}1000) making it an extremely red object (ERO) and a dust-obscured galaxy (DOG). The spectral energy distribution (SED) shows the clear signature of the 1.6 {mu}m photometric 'bump', typical of evolved stellar populations. We use this bump to establish the photometric redshift z{sub phot} as 2.2{sup +0.2}{sub -0.3}, using a vast library of SED templates, including M 82. The star formationmore » rate (SFR) inferred from the SED fitting is {approx}119 M{sub sun} yr{sup -1}, the stellar mass 3 x 10{sup 11} M{sub sun}, and A{sub V} extinction from 1 to 2 mag. The ERO and DOG nature of the host galaxy of the dark GRB 080207 may be emblematic of a distinct class of dark GRB hosts, with high SFRs, evolved and metal-rich stellar populations, and significant dust extinction within the host galaxy.« less

A high deuterium abundance at redshift z = 0.7.

PubMed

Webb, J K; Carswell, R F; Lanzetta, K M; Ferlet, R; Lemoine, M; Vidal-Madjar, A; Bowen, D V

1997-07-17

Of the light elements, the primordial abundance of deuterium relative to hydrogen, (D/H)p, provides the most sensitive diagnostic for the cosmological mass density parameter, omegaB. Recent high-redshift D/H measurements are highly discrepant, although this may reflect observational uncertainties. The larger primordial D/H values imply a low omegaB (requiring the Universe to be dominated by non-baryonic matter), and cause problems for galactic chemical evolution models, which have difficulty in reproducing the steep decline in D/H to the present-day values. Conversely, the lower D/H values measured at high redshift imply an omegaB greater than that derived from 7Li and 4He abundance measurements, and may require a deuterium-abundance evolution that is too low to easily explain. Here we report the first measurement of D/H at intermediate redshift (z = 0.7010), in a gas cloud selected to minimize observational uncertainties. Our analysis yields a value of D/H ((2.0 +/- 0.5) x 10[-4]) which is at the upper end of the range of values measured at high redshifts. This finding, together with other independent observations, suggests that there may be inhomogeneity in (D/H)p of at least a factor of ten.

The Clustering of High-Redshift (2.9 < z < 5.4) Quasars in SDSS Stripe 82

NASA Astrophysics Data System (ADS)

Timlin, John; Ross, Nicolas; Richards, Gordon; Myers, Adam; Bauer, Franz Erik; Lacy, Mark; Schneider, Donald; Wollack, Edward; Zakamska, Nadia

2018-01-01

We present the data from the Spitzer IRAC Equatorial Survey (SpIES) along with our first high-redshift (2.9

The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts

NASA Technical Reports Server (NTRS)

Newman, Jeffrey A.; Cooper, Michael C.; Davis, Marc; Faber, S. M.; Coil, Alison L; Guhathakurta, Puraga; Koo, David C.; Phillips, Andrew C.; Conroy, Charlie; Dutton, Aaron A.;

LATE POP III STAR FORMATION DURING THE EPOCH OF REIONIZATION: RESULTS FROM THE RENAISSANCE SIMULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Hao; Norman, Michael L.; O’Shea, Brian W.

2016-06-01

We present results on the formation of Population III (Pop III) stars at redshift 7.6 from the Renaissance Simulations, a suite of extremely high-resolution and physics-rich radiation transport hydrodynamics cosmological adaptive-mesh refinement simulations of high-redshift galaxy formation performed on the Blue Waters supercomputer. In a survey volume of about 220 comoving Mpc{sup 3}, we found 14 Pop III galaxies with recent star formation. The surprisingly late formation of Pop III stars is possible due to two factors: (i) the metal enrichment process is local and slow, leaving plenty of pristine gas to exist in the vast volume; and (ii) strongmore » Lyman–Werner radiation from vigorous metal-enriched star formation in early galaxies suppresses Pop III formation in (“not so”) small primordial halos with mass less than ∼3 × 10{sup 7} M {sub ⊙}. We quantify the properties of these Pop III galaxies and their Pop III star formation environments. We look for analogs to the recently discovered luminous Ly α emitter CR7, which has been interpreted as a Pop III star cluster within or near a metal-enriched star-forming galaxy. We find and discuss a system similar to this in some respects, however, the Pop III star cluster is far less massive and luminous than CR7 is inferred to be.« less

Luminous Infrared Galaxies Observed from the Ground and Space in the 2020s

NASA Astrophysics Data System (ADS)

Inami, Hanae; Armus, L.; Packham, C.; Dickinson, M.

2014-07-01

The dust-penetrating power of infrared observations will allow us to reveal the physical and chemical properties in and around the dust enshrouded nuclei of galaxies. While current near-infrared spectroscopic observations with 8-10m class telescopes can access to z=1-3 regime, they are still very challenging and limited to luminous targets. For z=0 objects, these telescopes can resolve HII regions, but we still do not fully understand the properties of more extreme star formation environments (e.g., rich in gas), which are more prevalent at higher redshifts. Near- and mid-infrared TMT instruments (e.g., two of the first light instruments IRIS and IRMS, and a planned mid-infrared instrument MICHI) will exploit TMT's unprecedented high spatial resolution to constrain the physical processes in individual dusty, intense star-forming regions of local galaxies as well as obtain resolved spectra for z=2-3 star-forming galaxies. During the era of 2020, JWST and SPICA are also expected to be commissioned. The high sensitivity of these space-based infrared observatories will facilitate investigations of the properties of dusty galaxies at even higher redshifts (z > 3). Only with the combination of ground- and space-observatories, we will be able to obtain a complete picture of star formation and AGN activity to explore the evolution of LIRGs which dominate the peak of the galaxy growth in the universe.

A high stellar velocity dispersion for a compact massive galaxy at redshift z = 2.186.

PubMed

van Dokkum, Pieter G; Kriek, Mariska; Franx, Marijn

2009-08-06

Recent studies have found that the oldest and most luminous galaxies in the early Universe are surprisingly compact, having stellar masses similar to present-day elliptical galaxies but much smaller sizes. This finding has attracted considerable attention, as it suggests that massive galaxies have grown in size by a factor of about five over the past ten billion years (10 Gyr). A key test of these results is a determination of the stellar kinematics of one of the compact galaxies: if the sizes of these objects are as extreme as has been claimed, their stars are expected to have much higher velocities than those in present-day galaxies of the same mass. Here we report a measurement of the stellar velocity dispersion of a massive compact galaxy at redshift z = 2.186, corresponding to a look-back time of 10.7 Gyr. The velocity dispersion is very high at km s(-1), consistent with the mass and compactness of the galaxy inferred from photometric data. This would indicate significant recent structural and dynamical evolution of massive galaxies over the past 10 Gyr. The uncertainty in the dispersion was determined from simulations that include the effects of noise and template mismatch. However, we cannot exclude the possibility that some subtle systematic effect may have influenced the analysis, given the low signal-to-noise ratio of our spectrum.

The Bright and Dark Sides of High-redshift Starburst Galaxies from Herschel and Subaru Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Puglisi, A.; Rodighiero, G.; Rodríguez-Muñoz, L.

2017-04-01

We present rest-frame optical spectra from the FMOS-COSMOS survey of 12 z ∼ 1.6 Herschel starburst galaxies, with star formation rate (SFR) elevated by ×8, on average, above the star-forming main sequence (MS). Comparing the H α to IR luminosity ratio and the Balmer decrement, we find that the optically thin regions of the sources contain on average only ∼10% of the total SFR, whereas ∼90% come from an extremely obscured component that is revealed only by far-IR observations and is optically thick even in H α . We measure the [N ii]{sub 6583}/H α ratio, suggesting that the lessmore » obscured regions have a metal content similar to that of the MS population at the same stellar masses and redshifts. However, our objects appear to be metal-rich outliers from the metallicity–SFR anticorrelation observed at fixed stellar mass for the MS population. The [S ii]{sub 6732}/[S ii]{sub 6717} ratio from the average spectrum indicates an electron density n {sub e} ∼ 1100 cm{sup −3} , larger than what was estimated for MS galaxies but only at the 1.5 σ level. Our results provide supporting evidence that high- z MS outliers are analogous of local ULIRGs and are consistent with a major-merger origin for the starburst event.« less

Weak Emission-line Quasars in the Context of a Modified Baldwin Effect

NASA Astrophysics Data System (ADS)

Shemmer, Ohad

2016-01-01

Based on spectroscopic data for a sample of high-redshift quasars, I will show that the anti-correlation between the rest-frame equivalent width (EW) of the C IV λ1549 broad-emission line and the Hβ-based Eddington ratio extends across the widest possible ranges of redshift (0 < z < 3.5) and bolometric luminosity(~1044 < L < ~1048 erg s-1). Given this anti-correlation, hereby referred to as a modified Baldwin effect (MBE), weak emission line quasars (WLQs), typically showing EW(C IV) < ~10 Å, are expected to have extremely high Eddington ratios (L/LEdd > ~4). I will present new near-infrared spectroscopy of the broad Hβ line, as well as complementary EW(C IV) information, for all WLQs for which such information is currently available, nine sources in total. I will show that while four of these WLQs can be accommodated by the MBE, the otherfive deviate significantly from this relation, at the > ~3σ level, by exhibiting C IV lines much weaker than predicted from their Hβ-based Eddington ratios. Assuming the supermassive black hole masses in all quasars can be determined reliably using the single-epoch Hβ-method, these results indicate that EW(C IV)cannot depend solely on the Eddington ratio. I will briefly discuss a strategy for further investigation into the roles that basic physical properties play in controlling the relative strengths of broad-emission lines in quasars.

Interstellar medium conditions in z 0.2 Lyman-break analogs

NASA Astrophysics Data System (ADS)

Contursi, A.; Baker, A. J.; Berta, S.; Magnelli, B.; Lutz, D.; Fischer, J.; Verma, A.; Nielbock, M.; Grácia Carpio, J.; Veilleux, S.; Sturm, E.; Davies, R.; Genzel, R.; Hailey-Dunsheath, S.; Herrera-Camus, R.; Janssen, A.; Poglitsch, A.; Sternberg, A.; Tacconi, L. J.

2017-10-01

We present an analysis of far-infrared (FIR) [CII] and [OI] fine structure line and continuum observations obtained with Herschel/PACS, and 12CO(1-0) observations obtained with the IRAM Plateau de Bure Interferometer, of Lyman-break analogs (LBAs) at z 0.2. The principal aim of this work is to determine the typical interstellar medium (ISM) properties of z 1-2 main sequence (MS) galaxies, with stellar masses between 109.5 and 1011M⊙, which are currently not easily detectable in all these lines even with ALMA and NOEMA. We perform PDR modeling and apply different infared diagnostics to derive the main physical parameters of the far-infrared (FIR)-emitting gas and dust and we compare the derived ISM properties to those of galaxies on and above the MS at different redshifts. We find that the ISM properties of LBAs are quite extreme (low gas temperature and high density and thermal pressure) with respect to those found in local normal spirals and more active local galaxies. LBAs have no [CII] deficit despite having the high specific star formation rates (sSFRs) typical of starbursts. Although LBAs lie above the local MS, we show that their ISM properties are more similar to those of high-redshift MS galaxies than of local galaxies above the main sequence. This data set represents an important reference for planning future ALMA [CII] observations of relatively low-mass MS galaxies at the epoch of the peak of the cosmic star formation.

Jekyll & Hyde: quiescence and extreme obscuration in a pair of massive galaxies 1.5 Gyr after the Big Bang

NASA Astrophysics Data System (ADS)

Schreiber, C.; Labbé, I.; Glazebrook, K.; Bekiaris, G.; Papovich, C.; Costa, T.; Elbaz, D.; Kacprzak, G. G.; Nanayakkara, T.; Oesch, P.; Pannella, M.; Spitler, L.; Straatman, C.; Tran, K.-V.; Wang, T.

2018-03-01

We obtained ALMA spectroscopy and deep imaging to investigate the origin of the unexpected sub-millimeter emission toward the most distant quiescent galaxy known to date, ZF-COSMOS-20115 at z = 3.717. We show here that this sub-millimeter emission is produced by another massive (M* 1011 M⊙), compact (r1/2 = 0.67 ± 0.14 kpc) and extremely obscured galaxy (AV 3.5), located only 0.43'' (3.1 kpc) away from the quiescent galaxy. We dub the quiescent and dusty galaxies Jekyll and Hyde, respectively. No dust emission is detected at the location of the quiescent galaxy, implying SFR < 13 M⊙ yr-1 which is the most stringent upper limit ever obtained for a quiescent galaxy at these redshifts. The two sources are spectroscopically confirmed to lie at the same redshift thanks to the detection of [C II]158 in Hyde (z = 3.709), which provides one the few robust redshifts for a highly-obscured "H-dropout" galaxy (H - [4.5] = 5.1 ± 0.8). The [C II] line shows a clear rotating-disk velocity profile which is blueshifted compared to the Balmer lines of Jekyll by 549 ± 60 km s-1, demonstrating that it is produced by another galaxy. Careful de-blending of the Spitzer imaging confirms the existence of this new massive galaxy, and its non-detection in the Hubble images requires extremely red colors and strong attenuation by dust. Full modeling of the UV-to-far-IR emission of both galaxies shows that Jekyll has fully quenched at least 200Myr prior to observation and still presents a challenge for models, while Hyde only harbors moderate star-formation with SFR ≲ 120 M⊙ yr-1, and is located at least a factor 1.4 below the z 4 main sequence. Hyde could also have stopped forming stars less than 200 Myr before being observed; this interpretation is also suggested by its compactness comparable to that of z 4 quiescent galaxies and its low [C II]/FIR ratio, but significant on-going star-formation cannot be ruled out. Lastly, we find that despite its moderate SFR, Hyde hosts a dense reservoir of gas comparable to that of the most extreme starbursts. This suggests that whatever mechanism has stopped or reduced its star-formation must have done so without expelling the gas outside of the galaxy. Because of their surprisingly similar mass, compactness, environment and star-formation history, we argue that Jekyll and Hyde can be seen as two stages of the same quenching process, and provide a unique laboratory to study this poorly understood phenomenon. The reduced ALMA image, spectrum, and data cube are available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A22

XMM-Newton X-ray and HST weak gravitational lensing study of the extremely X-ray luminous galaxy cluster Cl J120958.9+495352 (z = 0.902)

NASA Astrophysics Data System (ADS)

Thölken, Sophia; Schrabback, Tim; Reiprich, Thomas H.; Lovisari, Lorenzo; Allen, Steven W.; Hoekstra, Henk; Applegate, Douglas; Buddendiek, Axel; Hicks, Amalia

2018-03-01

Context. Observations of relaxed, massive, and distant clusters can provide important tests of standard cosmological models, for example by using the gas mass fraction. To perform this test, the dynamical state of the cluster and its gas properties have to be investigated. X-ray analyses provide one of the best opportunities to access this information and to determine important properties such as temperature profiles, gas mass, and the total X-ray hydrostatic mass. For the last of these, weak gravitational lensing analyses are complementary independent probes that are essential in order to test whether X-ray masses could be biased. Aims: We study the very luminous, high redshift (z = 0.902) galaxy cluster Cl J120958.9+495352 using XMM-Newton data. We measure global cluster properties and study the temperature profile and the cooling time to investigate the dynamical status with respect to the presence of a cool core. We use Hubble Space Telescope (HST) weak lensing data to estimate its total mass and determine the gas mass fraction. Methods: We perform a spectral analysis using an XMM-Newton observation of 15 ks cleaned exposure time. As the treatment of the background is crucial, we use two different approaches to account for the background emission to verify our results. We account for point spread function effects and deproject our results to estimate the gas mass fraction of the cluster. We measure weak lensing galaxy shapes from mosaic HST imaging and select background galaxies photometrically in combination with imaging data from the William Herschel Telescope. Results: The X-ray luminosity of Cl J120958.9+495352 in the 0.1-2.4 keV band estimated from our XMM-Newton data is LX = (13.4+1.2-1.0) × 1044 erg/s and thus it is one of the most X-ray luminous clusters known at similarly high redshift. We find clear indications for the presence of a cool core from the temperature profile and the central cooling time, which is very rare at such high redshifts. Based on the weak lensing analysis, we estimate a cluster mass of M500/1014 M⊙ = 4.4+2.2-2.0 (stat.) + 0.6 (sys.) and a gas mass fraction of fgas,2500 = 0.11-0.03+0.06 in good agreement with previous findings for high redshift and local clusters.

Mach's Principle to Hubble's Law and Light Relativity

NASA Astrophysics Data System (ADS)

Zhang, Tianxi

2018-01-01

Discovery of the redshift-distance relation to be linear (i.e. Hubble's law) for galaxies in the end of 1920s instigated us to widely accept expansion of the universe, originated from a big bang around 14 billion years ago. Finding of the redshift-distance relation to be weaker than linear for distant type Ia supernovae nearly two decades ago further precipitated us to largely agree with recent acceleration of the universe, driven by the mysterious dark energy. The time dilation measured for supernovae has been claimed as a direct evidence for the expansion of the universe, but scientists could not explain why quasars and gamma-ray bursts had not similar time dilations. Recently, an anomaly was found in the standard template for the width of supernova light curves to be proportional to the wavelength, which exactly removed the time dilation of supernovae and hence was strongly inconsistent with the conventional redshift mechanism. In this study, we have derived a new redshift-distance relation from Mach's principle with light relativity that describes the effect of light on spacetime as well as the influence of disturbed spacetime on the light inertia or frequency. A moving object or photon, because of its continuously keeping on displacement, disturbs the rest of the entire universe or distorts/curves the spacetime. The distorted or curved spacetime then generates an effective gravitational force to act back on the moving object or photon, so that reduces the object inertia or photon frequency. Considering the disturbance of spacetime by a photon is extremely weak, we have modelled the effective gravitational force to be Newtonian and derived the new redshift-distance relation that can not only perfectly explain the redshift-distance measurement of distant type Ia supernovae but also inherently obtain Hubble's law as an approximate at small redshift. Therefore, the result obtained from this study does neither support the acceleration of the universe nor the expansion of the universe but prefers to Einstein's simplest cosmology of the static universe or Zhang's static or dynamic cosmology of the black hole universe. This work was partially supported by NSF/REU (Grant #: PHY-1559870) at Alabama A & M University

Galaxy And Mass Assembly (GAMA): spectroscopic analysis

NASA Astrophysics Data System (ADS)

Hopkins, A. M.; Driver, S. P.; Brough, S.; Owers, M. S.; Bauer, A. E.; Gunawardhana, M. L. P.; Cluver, M. E.; Colless, M.; Foster, C.; Lara-López, M. A.; Roseboom, I.; Sharp, R.; Steele, O.; Thomas, D.; Baldry, I. K.; Brown, M. J. I.; Liske, J.; Norberg, P.; Robotham, A. S. G.; Bamford, S.; Bland-Hawthorn, J.; Drinkwater, M. J.; Loveday, J.; Meyer, M.; Peacock, J. A.; Tuffs, R.; Agius, N.; Alpaslan, M.; Andrae, E.; Cameron, E.; Cole, S.; Ching, J. H. Y.; Christodoulou, L.; Conselice, C.; Croom, S.; Cross, N. J. G.; De Propris, R.; Delhaize, J.; Dunne, L.; Eales, S.; Ellis, S.; Frenk, C. S.; Graham, Alister W.; Grootes, M. W.; Häußler, B.; Heymans, C.; Hill, D.; Hoyle, B.; Hudson, M.; Jarvis, M.; Johansson, J.; Jones, D. H.; van Kampen, E.; Kelvin, L.; Kuijken, K.; López-Sánchez, Á.; Maddox, S.; Madore, B.; Maraston, C.; McNaught-Roberts, T.; Nichol, R. C.; Oliver, S.; Parkinson, H.; Penny, S.; Phillipps, S.; Pimbblet, K. A.; Ponman, T.; Popescu, C. C.; Prescott, M.; Proctor, R.; Sadler, E. M.; Sansom, A. E.; Seibert, M.; Staveley-Smith, L.; Sutherland, W.; Taylor, E.; Van Waerbeke, L.; Vázquez-Mata, J. A.; Warren, S.; Wijesinghe, D. B.; Wild, V.; Wilkins, S.

2013-04-01

The Galaxy And Mass Assembly (GAMA) survey is a multiwavelength photometric and spectroscopic survey, using the AAOmega spectrograph on the Anglo-Australian Telescope to obtain spectra for up to ˜300 000 galaxies over 280 deg2, to a limiting magnitude of rpet < 19.8 mag. The target galaxies are distributed over 0 < z ≲ 0.5 with a median redshift of z ≈ 0.2, although the redshift distribution includes a small number of systems, primarily quasars, at higher redshifts, up to and beyond z = 1. The redshift accuracy ranges from σv ≈ 50 km s-1 to σv ≈ 100 km s-1 depending on the signal-to-noise ratio of the spectrum. Here we describe the GAMA spectroscopic reduction and analysis pipeline. We present the steps involved in taking the raw two-dimensional spectroscopic images through to flux-calibrated one-dimensional spectra. The resulting GAMA spectra cover an observed wavelength range of 3750 ≲ λ ≲ 8850 Å at a resolution of R ≈ 1300. The final flux calibration is typically accurate to 10-20 per cent, although the reliability is worse at the extreme wavelength ends, and poorer in the blue than the red. We present details of the measurement of emission and absorption features in the GAMA spectra. These measurements are characterized through a variety of quality control analyses detailing the robustness and reliability of the measurements. We illustrate the quality of the measurements with a brief exploration of elementary emission line properties of the galaxies in the GAMA sample. We demonstrate the luminosity dependence of the Balmer decrement, consistent with previously published results, and explore further how Balmer decrement varies with galaxy mass and redshift. We also investigate the mass and redshift dependencies of the [N II]/Hα versus [O III]/Hβ spectral diagnostic diagram, commonly used to discriminate between star forming and nuclear activity in galaxies.

Extreme [O III] Emitters at z ∼ 0.5

NASA Astrophysics Data System (ADS)

Li, Zhihui; Malkan, Matthew A.

2018-06-01

We have found a sample of extreme emission-line galaxies (EELGs) with strong [O III]λ5007 emission at z ∼ 0.5. Using broadband photometric selection and requiring small uncertainties in photometry, we searched the 14th Data Release of the Sloan Digital Sky Survey (SDSS) and found 2658 candidates with strong i-band excess (i – z ≤ r – i – 0.7). We further obtained 649 SDSS spectra of these objects, and visually identified 22 [O III] emitters lying at 0.40 < z < 0.63. Having constructed their ultraviolet–infrared spectral energy distributions, we found that they have fairly blue r – W2 and red W1 – W4 colors, indicative of strong, warm dust emission. Their rest-frame [O III]λ5007 equivalent widths are mostly 200–600 Å, and their high [O III]λ5007/Hβ ratios put them at the boundary of star-forming galaxies and active galactic nuclei on line ratio classification diagrams. The typical E(B–V) and electron temperature of [O III] emitters are ∼0.1–0.3 mag and ∼104 K, respectively. The lowest metallicity of our [O III] emitters with S/N[O III]λ4363 > 3 is 12 + log(O/H) = {7.98}-0.02+0.12, with a median value of {8.24}-0.04+0.05. Our [O III] emitters exhibit remarkably high line luminosity—18/22 have L [O III]λ5007 > 5 × 1042 erg s‑1 and 5/22 have L [O III]λ5007 > 1043 erg s‑1. Their estimated volume number density at z ∼ 0.5 is ∼2 × 10‑8 Mpc‑3, with L [O III]λ5007 down to ∼3 × 1042 erg s‑1. The cumulative number distribution of EELGs across different redshifts is indicative of a strong redshift evolution at the bright end of the [O III] luminosity function.

AN EVOLVING STELLAR INITIAL MASS FUNCTION AND THE GAMMA-RAY BURST REDSHIFT DISTRIBUTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, F. Y.; Dai, Z. G.

2011-02-01

Recent studies suggest that Swift gamma-ray bursts (GRBs) may not trace an ordinary star formation history (SFH). Here, we show that the GRB rate turns out to be consistent with the SFH with an evolving stellar initial mass function (IMF). We first show that the latest Swift sample of GRBs reveals an increasing evolution in the GRB rate relative to the ordinary star formation rate at high redshifts. We then assume only massive stars with masses greater than the critical value to produce GRBs and use an evolving stellar IMF suggested by Dave to fit the latest GRB redshift distribution.more » This evolving IMF would increase the relative number of massive stars, which could lead to more GRB explosions at high redshifts. We find that the evolving IMF can well reproduce the observed redshift distribution of Swift GRBs.« less

Optical study of the DAFT/FADA galaxy cluster survey

NASA Astrophysics Data System (ADS)

Martinet, N.; Durret, F.; Clowe, D.; Adami, C.

2013-11-01

DAFT/FADA (Dark energy American French Team) is a large survey of ˜90 high redshift (0.42×10^{14} M_{⊙}) clusters with HST weak lensing oriented data, plus BVRIZJ 4m ground based follow up to compute photometric redshifts. The main goals of this survey are to constrain dark energy parameters using weak lensing tomography and to study a large homogeneous sample of high redshift massive clusters. We will briefly review the latest results of this optical survey, focusing on two ongoing works: the calculation of galaxy luminosity functions from photometric redshift catalogs and the weak lensing analysis of ground based data.

Lyman Continuum Escape Fraction of Star-forming Dwarf Galaxies at z ˜ 1

NASA Astrophysics Data System (ADS)

Rutkowski, Michael J.; Scarlata, Claudia; Haardt, Francesco; Siana, Brian; Henry, Alaina; Rafelski, Marc; Hayes, Matthew; Salvato, Mara; Pahl, Anthony J.; Mehta, Vihang; Beck, Melanie; Malkan, Matthew; Teplitz, Harry I.

2016-03-01

To date, no direct detection of Lyman continuum emission has been measured for intermediate-redshift (z˜ 1) star-forming galaxies. We combine Hubble Space Telescope grism spectroscopy with GALEX UV and ground-based optical imaging to extend the search for escaping Lyman continuum to a large (˜600) sample of z˜ 1 low-mass ({log}(\\bar{M}) ≃ 9.3{M}⊙ ), moderately star-forming (\\bar{{{\\Psi }}} ≲ 10{M}⊙ yr-1) galaxies selected initially on Hα emission. The characteristic escape fraction of LyC from star-forming galaxies (SFGs) that populate this parameter space remains weakly constrained by previous surveys, but these faint (sub-L⋆) SFGs are assumed to play a significant role in the reionization of neutral hydrogen in the intergalactic medium (IGM) at high redshift z\\gt 6. We do not make an unambiguous detection of escaping LyC radiation from this z˜ 1 sample, individual non-detections to constrain the absolute Lyman continuum escape fraction, {f}{esc} \\lt 2.1% (3σ). We measure an upper limit of {f}{esc} \\lt 9.6% from a sample of SFGs selected on high Hα equivalent width (EW \\gt 200 {{\\mathringA }}), which are thought to be close analogs of high redshift sources of reionization. For reference, we also present an emissivity-weighted escape fraction that is useful for measuring the general contribution SFGs to the ionizing UV background. In the discussion, we consider the implications of these intermediate redshift constraints for the reionization of hydrogen in the IGM at high (z\\gt 6) redshift. If we assume our z˜ 1 SFGs, for which we measure this emissivity-weighted {f}{esc}, are analogs to the high redshift sources of reionization, we find it is difficult to reconcile reionization by faint ({M}{UV}≲ -13) SFGs with a low escape fraction ({f}{esc} \\lt 3%), with constraints from independent high redshift observations. If {f}{esc} evolves with redshift, reionization by SFGs may be consistent with observations from Planck.

The Number Density Evolution of Extreme Emission Line Galaxies in 3D-HST: Results from a Novel Automated Line Search Technique for Slitless Spectroscopy

NASA Astrophysics Data System (ADS)

Maseda, Michael V.; van der Wel, Arjen; Rix, Hans-Walter; Momcheva, Ivelina; Brammer, Gabriel B.; Franx, Marijn; Lundgren, Britt F.; Skelton, Rosalind E.; Whitaker, Katherine E.

2018-02-01

The multiplexing capability of slitless spectroscopy is a powerful asset in creating large spectroscopic data sets, but issues such as spectral confusion make the interpretation of the data challenging. Here we present a new method to search for emission lines in the slitless spectroscopic data from the 3D-HST survey utilizing the Wide-Field Camera 3 on board the Hubble Space Telescope. Using a novel statistical technique, we can detect compact (extended) emission lines at 90% completeness down to fluxes of 1.5(3.0)× {10}-17 {erg} {{{s}}}-1 {{cm}}-2, close to the noise level of the grism exposures, for objects detected in the deep ancillary photometric data. Unlike previous methods, the Bayesian nature allows for probabilistic line identifications, namely redshift estimates, based on secondary emission line detections and/or photometric redshift priors. As a first application, we measure the comoving number density of Extreme Emission Line Galaxies (restframe [O III] λ5007 equivalent widths in excess of 500 Å). We find that these galaxies are nearly 10× more common above z ∼ 1.5 than at z ≲ 0.5. With upcoming large grism surveys such as Euclid and WFIRST, as well as grisms featured prominently on the NIRISS and NIRCam instruments on the James Webb Space Telescope, methods like the one presented here will be crucial for constructing emission line redshift catalogs in an automated and well-understood manner. This work is based on observations taken by the 3D-HST Treasury Program and the CANDELS Multi-Cycle Treasury Program with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

New probe of magnetic fields in the prereionization epoch. I. Formalism

NASA Astrophysics Data System (ADS)

Venumadhav, Tejaswi; Oklopčić, Antonija; Gluscevic, Vera; Mishra, Abhilash; Hirata, Christopher M.

2017-04-01

We propose a method of measuring extremely weak magnetic fields in the intergalactic medium prior to and during the epoch of cosmic reionization. The method utilizes the Larmor precession of spin-polarized neutral hydrogen in the triplet state of the hyperfine transition. This precession leads to a systematic change in the brightness temperature fluctuations of the 21-cm line from the high-redshift universe, and thus the statistics of these fluctuations encode information about the magnetic field the atoms are immersed in. The method is most suited to probing fields that are coherent on large scales; in this paper, we consider a homogenous magnetic field over the scale of the 21-cm fluctuations. Due to the long lifetime of the triplet state of the 21-cm transition, this technique is naturally sensitive to extremely weak field strengths, of order 10-19 G at a reference redshift of ˜20 (or 10-21 G if scaled to the present day). Therefore, this might open up the possibility of probing primordial magnetic fields just prior to reionization. If the magnetic fields are much stronger, it is still possible to use this method to infer their direction, and place a lower limit on their strength. In this paper (Paper I in a series on this effect), we perform detailed calculations of the microphysics behind this effect, and take into account all the processes that affect the hyperfine transition, including radiative decays, collisions, and optical pumping by Lyman-α photons. We conclude with an analytic formula for the brightness temperature of linear-regime fluctuations in the presence of a magnetic field, and discuss its limiting behavior for weak and strong fields.

SAFARI new and improved: extending the capabilities of SPICA's imaging spectrometer

NASA Astrophysics Data System (ADS)

Roelfsema, Peter; Giard, Martin; Najarro, Francisco; Wafelbakker, Kees; Jellema, Willem; Jackson, Brian; Sibthorpe, Bruce; Audard, Marc; Doi, Yasuo; di Giorgio, Anna; Griffin, Matthew; Helmich, Frank; Kamp, Inga; Kerschbaum, Franz; Meyer, Michael; Naylor, David; Onaka, Takashi; Poglitch, Albrecht; Spinoglio, Luigi; van der Tak, Floris; Vandenbussche, Bart

2014-08-01

The Japanese SPace Infrared telescope for Cosmology and Astrophysics, SPICA, aims to provide astronomers with a truly new window on the universe. With a large -3 meter class- cold -6K- telescope, the mission provides a unique low background environment optimally suited for highly sensitive instruments limited only by the cosmic background itself. SAFARI, the SpicA FAR infrared Instrument SAFARI, is a Fourier Transform imaging spectrometer designed to fully exploit this extremely low far infrared background environment. The SAFARI consortium, comprised of European and Canadian institutes, has established an instrument reference design based on a Mach-Zehnder interferometer stage with outputs directed to three extremely sensitive Transition Edge Sensor arrays covering the 35 to 210 μm domain. The baseline instrument provides R > 1000 spectroscopic imaging capabilities over a 2' by 2' field of view. A number of modifications to the instrument to extend its capabilities are under investigation. With the reference design SAFARI's sensitivity for many objects is limited not only by the detector NEP but also by the level of broad band background radiation - the zodiacal light for the shorter wavelengths and satellite baffle structures for the longer wavelengths. Options to reduce this background are dedicated masks or dispersive elements which can be inserted in the optics as required. The resulting increase in sensitivity can directly enhance the prime science goals of SAFARI; with the expected enhanced sensitivity astronomers would be in a better position to study thousands of galaxies out to redshift 3 and even many hundreds out to redshifts of 5 or 6. Possibilities to increase the wavelength resolution, at least for the shorter wavelength bands, are investigated as this would significantly enhance SAFARI's capabilities to study star and planet formation in our own galaxy.

A millimetre-wave redshift search for the unlensed HyLIRG, HS1700.850.1

NASA Astrophysics Data System (ADS)

Chapman, S. C.; Bertoldi, F.; Smail, Ian; Steidel, C. C.; Blain, A. W.; Geach, J. E.; Gurwell, M.; Ivison, R. J.; Petitpas, G. R.; Reddy, N.

2015-10-01

We report the redshift of an unlensed, highly obscured submillimetre galaxy (SMG), HS1700.850.1, the brightest SMG (S850 μm = 19.1 mJy) detected in the James Clerk Maxwell Telescope/Submillimetre Common-user Bolometer Array-2 (JCMT/SCUBA-2) Baryonic Structure Survey, based on the detection of its 12CO line emission. Using the Institute Radio Astronomie Millimetrique Plateau de Bure Interferometer with 3.6 GHz band width, we serendipitously detect an emission line at 150.6 GHz. From a search over 14.5 GHz in the 3- and 2-mm atmospheric windows, we confirm the identification of this line as 12CO(5-4) at z = 2.816, meaning that it does not reside in the z ˜ 2.30 proto-cluster in this field. Measurement of the 870 μm source size (<0.85 arcsec) from the Sub-Millimetre Array (SMA) confirms a compact emission in a S870 μm = 14.5 mJy, LIR ˜ 1013 L⊙ component, suggesting an Eddington-limited starburst. We use the double-peaked 12CO line profile measurements along with the SMA size constraints to study the gas dynamics of a HyLIRG, estimating the gas and dynamical masses of HS1700.850.1. While HS1700.850.1 is one of the most extreme galaxies known in the Universe, we find that it occupies a relative void in the Lyman-Break Galaxy distribution in this field. Comparison with other extreme objects at similar epochs (HyLIRG Quasars), and cosmological simulations, suggests such an anti-bias of bright SMGs could be relatively common, with the brightest SMGs rarely occupying the most overdense regions at z = 2-4.

PdBI cold dust imaging of two extremely red H – [4.5] > 4 galaxies discovered with SEDS and CANDELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caputi, K. I.; Popping, G.; Spaans, M.

2014-06-20

We report Plateau de Bure Interferometer (PdBI) 1.1 mm continuum imaging toward two extremely red H – [4.5] > 4 (AB) galaxies at z > 3, which we have previously discovered making use of Spitzer SEDS and Hubble Space Telescope CANDELS ultra-deep images of the Ultra Deep Survey field. One of our objects is detected on the PdBI map with a 4.3σ significance, corresponding to S{sub ν}(1.1 mm)=0.78±0.18 mJy. By combining this detection with the Spitzer 8 and 24 μm photometry for this source, and SCUBA2 flux density upper limits, we infer that this galaxy is a composite active galacticmore » nucleus/star-forming system. The infrared (IR)-derived star formation rate is SFR ≈ 200 ± 100 M {sub ☉} yr{sup –1}, which implies that this galaxy is a higher-redshift analogue of the ordinary ultra-luminous infrared galaxies more commonly found at z ∼ 2-3. In the field of the other target, we find a tentative 3.1σ detection on the PdBI 1.1 mm map, but 3.7 arcsec away of our target position, so it likely corresponds to a different object. In spite of the lower significance, the PdBI detection is supported by a close SCUBA2 3.3σ detection. No counterpart is found on either the deep SEDS or CANDELS maps, so, if real, the PdBI source could be similar in nature to the submillimeter source GN10. We conclude that the analysis of ultra-deep near- and mid-IR images offers an efficient, alternative route to discover new sites of powerful star formation activity at high redshifts.« less

The Complete Calibration of the Color-Redshift Relation (C3R2) survey for Euclid

NASA Astrophysics Data System (ADS)

Cohen, Judith; Masters, Daniel; C3R2 Team

2018-06-01

The complete calibration of the color-redshift relation (C3R2) survey is a multi-institution, mutli-instrument survey with the Keck telescopes that aims to map out the empirical galaxy color-redshift relation in preparation for the Stage IV dark energy missions Euclid and WFIRST. A key challenge for weak lensing cosmology with these missions will be measuring highly accurate redshift distributions for billions of faint galaxies using only broad-band photometric observations. Well-calibrated photometric redshifts will thus be critical to their success. C3R2 uses an innovative technique that maps the color distribution of galaxies in the high-dimensional color space (u-g, ..., J-H) expected for Euclid and WFIRST, allowng us to focus spectroscopic effort on those regions of galaxy color space which are currently unexplored. C3R2 is a joint effort involving all of the Keck partners, with 44.5 nights allocated thus far. DR1 is published (Masters, Stern, Cohen et al, ApJ, 841, 111), and DR2, with > 3000 new redshifts, will be submitted in mid 2018.

VLA observations of unidentified Leiden-Berkeley Deep-Survey sources - Luminosity and redshift dependence of spectral properties

NASA Technical Reports Server (NTRS)

Kapahi, Vijay K.; Kulkarni, Vasant K.

1990-01-01

VLA observations of a complete subset of the Leiden-Berkeley Deep Survey sources that have S(1.4 GHz) greater than 10 mJy and are not optically identified down to F=22 mag are reported. By comparing the spectral and structural properties of the sources with samples from the literature, an attempt was made to disentangle the luminosity and redshift dependence of the spectral indices of extended emission in radio galaxies and of the incidence of compact steep-spectrum sources. It is found that the fraction of compact sources among those with a steep spectrum is related primarily to redshift, being much larger at high redshifts for sources of similar radio luminosity. Only a weak and marginally significant dependence of spectral indices of the extended sources on luminosity and redshift is found in samples selected at 1.4 and 2.7 GHz. It is pointed out that the much stronger correlation of spectral indices with luminosity may be arising partly from spectral curvature, and partly due to the preferential inclusion of very steep-spectrum sources from high redshift in low-frequency surveys.

Leveraging 3D-HST Grism Redshifts to Quantify Photometric Redshift Performance

NASA Astrophysics Data System (ADS)

Bezanson, Rachel; Wake, David A.; Brammer, Gabriel B.; van Dokkum, Pieter G.; Franx, Marijn; Labbé, Ivo; Leja, Joel; Momcheva, Ivelina G.; Nelson, Erica J.; Quadri, Ryan F.; Skelton, Rosalind E.; Weiner, Benjamin J.; Whitaker, Katherine E.

2016-05-01

We present a study of photometric redshift accuracy in the 3D-HST photometric catalogs, using 3D-HST grism redshifts to quantify and dissect trends in redshift accuracy for galaxies brighter than JH IR > 24 with an unprecedented and representative high-redshift galaxy sample. We find an average scatter of 0.0197 ± 0.0003(1 + z) in the Skelton et al. photometric redshifts. Photometric redshift accuracy decreases with magnitude and redshift, but does not vary monotonically with color or stellar mass. The 1σ scatter lies between 0.01 and 0.03 (1 + z) for galaxies of all masses and colors below z < 2.5 (for JH IR < 24), with the exception of a population of very red (U - V > 2), dusty star-forming galaxies for which the scatter increases to ˜0.1 (1 + z). We find that photometric redshifts depend significantly on galaxy size; the largest galaxies at fixed magnitude have photo-zs with up to ˜30% more scatter and ˜5 times the outlier rate. Although the overall photometric redshift accuracy for quiescent galaxies is better than that for star-forming galaxies, scatter depends more strongly on magnitude and redshift than on galaxy type. We verify these trends using the redshift distributions of close pairs and extend the analysis to fainter objects, where photometric redshift errors further increase to ˜0.046 (1 + z) at {H}F160W=26. We demonstrate that photometric redshift accuracy is strongly filter dependent and quantify the contribution of multiple filter combinations. We evaluate the widths of redshift probability distribution functions and find that error estimates are underestimated by a factor of ˜1.1-1.6, but that uniformly broadening the distribution does not adequately account for fitting outliers. Finally, we suggest possible applications of these data in planning for current and future surveys and simulate photometric redshift performance in the Large Synoptic Survey Telescope, Dark Energy Survey (DES), and combined DES and Vista Hemisphere surveys.

A model for the origin of bursty star formation in galaxies

NASA Astrophysics Data System (ADS)

Faucher-Giguère, Claude-André

2018-01-01

We propose a simple analytic model to understand when star formation is time steady versus bursty in galaxies. Recent models explain the observed Kennicutt-Schmidt relation between star formation rate and gas surface densities in galaxies as resulting from a balance between stellar feedback and gravity. We argue that bursty star formation occurs when such an equilibrium cannot be stably sustained, and identify two regimes in which galaxy-scale star formation should be bursty: (i) at high redshift (z ≳ 1) for galaxies of all masses, and (ii) at low masses (depending on gas fraction) for galaxies at any redshift. At high redshift, characteristic galactic dynamical time-scales become too short for supernova feedback to effectively respond to gravitational collapse in galactic discs (an effect recently identified for galactic nuclei), whereas in dwarf galaxies star formation occurs in too few bright star-forming regions to effectively average out. Burstiness is also enhanced at high redshift owing to elevated gas fractions in the early Universe. Our model can thus explain the bursty star formation rates predicted in these regimes by recent high-resolution galaxy formation simulations, as well as the bursty star formation histories observationally inferred in both local dwarf and high-redshift galaxies. In our model, bursty star formation is associated with particularly strong spatiotemporal clustering of supernovae. Such clustering can promote the formation of galactic winds and our model may thus also explain the much higher wind mass loading factors inferred in high-redshift massive galaxies relative to their z ∼ 0 counterparts.

Discovery of Compact Quiescent Galaxies at Intermediate Redshifts in DEEP2

NASA Astrophysics Data System (ADS)

Blancato, Kirsten; Chilingarian, Igor; Damjanov, Ivana; Moran, Sean; Katkov, Ivan

2015-01-01

Compact quiescent galaxies in the redshift range 0.6 < z < 1.1 are the missing link needed to complete the evolutionary histories of these objects from the high redshift z ≥ 2 Universe to the local z ~ 0 Universe. We identify the first intermediate redshift compact quiescent galaxies by searching a sample of 1,089 objects in the DEEP2 Redshift Survey that have multi-band photometry, spectral fitting, and readily available structural parameters. We find 27 compact quiescent candidates between z = 0.6 and z = 1.1 where each candidate galaxy has archival Hubble Space Telescope (HST) imaging and is visually confirmed to be early-type. The candidates have half-light radii ranging from 0.83 < Re,c < 7.14 kpc (median Re,c = 1.77 kpc) and virial masses ranging from 2.2E10 < Mdyn < 5.6E11 Msun (median Mdyn = 7.7E10 Msun). Of our 27 compact quiescent candidates, 13 are truly compact with sizes at most half of the size of their z ~ 0 counterparts of the same mass. In addition to their structural properties bridging the gap between their high and low redshift counterparts, our sample of intermediate redshift quiescent galaxies span a large range of ages but is drawn from two distinct epochs of galaxy formation: formation at z > 2 which suggests these objects may be the relics of the observed high redshift compact galaxies and formation at z ≤ 2 which suggests there is an additional population of more recently formed massive compact galaxies. This work is supported in part by the NSF REU and DOD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

AEGIS: The Diversity of Bright Near-IR-selected Distant Red Galaxies

NASA Astrophysics Data System (ADS)

Conselice, C. J.; Newman, J. A.; Georgakakis, A.; Almaini, O.; Coil, A. L.; Cooper, M. C.; Eisenhardt, P.; Foucaud, S.; Koekemoer, A.; Lotz, J.; Noeske, K.; Weiner, B.; Willmer, C. N. A.

2007-05-01

We use deep and wide near-infrared (NIR) imaging from the Palomar telescope combined with DEEP2 spectroscopy and HST and Chandra imaging to investigate the nature of galaxies that are red in NIR colors. We locate these ``distant red galaxies'' (DRGs) through the color cut (J-K)Vega>2.3 over 0.7 deg2, where we find 1010 DRG candidates down to Ks=20.5. We combine 95 high-quality spectroscopic redshifts with photometric redshifts from BRIJK photometry to determine the redshift and stellar mass distributions for these systems, and the morphological/structural and X-ray properties for 107 DRGs in the Extended Groth Strip. We find that many bright (J-K)Vega>2.3 galaxies with Ks<20.5 are at redshifts z<2, with 64% in the range 12 systems being massive with M*>1011 Msolar. HST imaging shows that the structural properties and morphologies of DRGs are also diverse, with the majority elliptical/compact (57%) and the remainder edge-on spiral (7%) and peculiar (29%). The DRGs at z<1.4 with high-quality spectroscopic redshifts are generally compact, with small half-light radii, and span a range in rest-frame optical properties. The spectral energy distribution for the DRGs at z<1.4 differs from higher redshift DRGs: they are bluer by 1 mag in observed (I-J) color. A pure IR color selection of high-redshift populations is not sufficient to identify unique populations, and other colors or spectroscopic redshifts are needed to produce homogeneous samples.

ULTRA STEEP SPECTRUM RADIO SOURCES IN THE LOCKMAN HOLE: SERVS IDENTIFICATIONS AND REDSHIFT DISTRIBUTION AT THE FAINTEST RADIO FLUXES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afonso, J.; Bizzocchi, L.; Grossi, M.

2011-12-20

Ultra steep spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (z {approx}> 2). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to sub-mJy levels, thanks to the recent appearance of sensitive low-frequency radio facilities. Here a first detailed analysis of the nature of the faintest USS sources is presented. By using Giant Metrewave Radio Telescope and Very Large Array radio observations of the Lockman Hole at 610 MHz and 1.4 GHz, a sample of 58 USS sources, with 610more » MHz integrated fluxes above 100 {mu}Jy, is assembled. Deep infrared data at 3.6 and 4.5 {mu}m from the Spitzer Extragalactic Representative Volume Survey (SERVS) are used to reliably identify counterparts for 48 (83%) of these sources, showing an average total magnitude of [3.6]{sub AB} = 19.8 mag. Spectroscopic redshifts for 14 USS sources, together with photometric redshift estimates, improved by the use of the deep SERVS data, for a further 19 objects, show redshifts ranging from z = 0.1 to z = 2.8, peaking at z {approx} 0.6 and tailing off at high redshifts. The remaining 25 USS sources, with no redshift estimate, include the faintest [3.6] magnitudes, with 10 sources undetected at 3.6 and 4.5 {mu}m (typically [3.6] {approx}> 22-23 mag from local measurements), which suggests the likely existence of higher redshifts among the sub-mJy USS population. The comparison with the Square Kilometre Array Design Studies Simulated Skies models indicates that Fanaroff-Riley type I radio sources and radio-quiet active galactic nuclei may constitute the bulk of the faintest USS population, and raises the possibility that the high efficiency of the USS technique for the selection of high-redshift sources remains even at the sub-mJy level.« less

Discovery of extreme [O III] λ5007 Å outflows in high-redshift red quasars

NASA Astrophysics Data System (ADS)

Zakamska, Nadia L.; Hamann, Fred; Pâris, Isabelle; Brandt, W. N.; Greene, Jenny E.; Strauss, Michael A.; Villforth, Carolin; Wylezalek, Dominika; Alexandroff, Rachael M.; Ross, Nicholas P.

2016-07-01

Black hole feedback is now a standard component of galaxy formation models. These models predict that the impact of black hole activity on its host galaxy likely peaked at z = 2-3, the epoch of strongest star formation activity and black hole accretion activity in the Universe. We used XSHOOTER on the Very Large Telescope to measure rest-frame optical spectra of four z ˜ 2.5 extremely red quasars with infrared luminosities ˜1047 erg s-1. We present the discovery of very broad (full width at half max = 2600-5000 km s-1), strongly blueshifted (by up to 1500 km s-1) [O III] λ5007 Å emission lines in these objects. In a large sample of type 2 and red quasars, [O III] kinematics are positively correlated with infrared luminosity, and the four objects in our sample are on the extreme end in both [O III] kinematics and infrared luminosity. We estimate that at least 3 per cent of the bolometric luminosity in these objects is being converted into the kinetic power of the observed wind. Photo-ionization estimates suggest that the [O III] emission might be extended on a few kpc scales, which would suggest that the extreme outflow is affecting the entire host galaxy of the quasar. These sources may be the signposts of the most extreme form of quasar feedback at the peak epoch of galaxy formation, and may represent an active `blow-out' phase of quasar evolution.

Identifying High-redshift Gamma-Ray Bursts with RATIR

NASA Astrophysics Data System (ADS)

Littlejohns, O. M.; Butler, N. R.; Cucchiara, A.; Watson, A. M.; Kutyrev, A. S.; Lee, W. H.; Richer, M. G.; Klein, C. R.; Fox, O. D.; Prochaska, J. X.; Bloom, J. S.; Troja, E.; Ramirez-Ruiz, E.; de Diego, J. A.; Georgiev, L.; González, J.; Román-Zúñiga, C. G.; Gehrels, N.; Moseley, H.

2014-07-01

We present a template-fitting algorithm for determining photometric redshifts, z phot, of candidate high-redshift gamma-ray bursts (GRBs). Using afterglow photometry, obtained by the Reionization and Transients InfraRed (RATIR) camera, this algorithm accounts for the intrinsic GRB afterglow spectral energy distribution, host dust extinction, and the effect of neutral hydrogen (local and cosmological) along the line of sight. We present the results obtained by this algorithm and the RATIR photometry of GRB 130606A, finding a range of best-fit solutions, 5.6 < z phot < 6.0, for models of several host dust extinction laws (none, the Milky Way, Large Magellanic Clouds, and Small Magellanic Clouds), consistent with spectroscopic measurements of the redshift of this GRB. Using simulated RATIR photometry, we find that our algorithm provides precise measures of z phot in the ranges of 4 < z phot <~ 8 and 9 < z phot < 10 and can robustly determine when z phot > 4. Further testing highlights the required caution in cases of highly dust-extincted host galaxies. These tests also show that our algorithm does not erroneously find z phot < 4 when z sim > 4, thereby minimizing false negatives and allowing us to rapidly identify all potential high-redshift events.

High-Redshift SNe with Subaru and HST

NASA Astrophysics Data System (ADS)

Rubin, David; Suzuki, Nao; Regnault, Nicolas; Aldering, Gregory; Amanullah, Rahman; Antilogus, Pierre; Astier, Pierre; Barbary, Kyle; Betoule, Marc; Boone, Kyle Robert; Currie, Miles; Deustua, Susana; Doi, Mamoru; Fruchter, Andrew; Goobar, Ariel; Hayden, Brian; Hazenberg, Francois; Hook, Isobel; Huang, Xiaosheng; Jiang, Jian; Kato, Takahiro; Kim, Alex; Kowalski, Marek; Lidman, Chris; Linder, Eric; Maeda, Keiichi; Morokuma, Tomoki; Nordin, Jakob; Pain, Reynald; Perlmutter, Saul; Ruiz-Lapuente, Pilar; Sako, Masao; Myers Saunders, Clare; Spadafora, Anthony L.; Tanaka, Masaomi; Tominaga, Nozomu; Yasuda, Naoki; Yoshida, Naoki

2018-01-01

High-redshift type Ia supernovae are crucial for constraining any time variation in dark energy. Here, we present the first discoveries and light curves from the SUbaru Supernovae with Hubble Infrared (SUSHI) program, which combines high-redshift SN discoveries from the Subaru Strategic Program (SSP, as well as other Subaru time) with HST WFC3 IR followup. This program efficiently uses the wide field and high collecting area of Subaru Hyper Suprime-Cam for optical light curves, but still obtains a precision NIR color. We are on track to double the number of well-measured SNe Ia at z > 1.1, triggering on 23 SNe Ia in our first season.

Confusion-limited galaxy fields. I - Simulated optical and near-infrared images

NASA Technical Reports Server (NTRS)

Chokshi, Arati; Wright, Edward L.

1988-01-01

Techniques for simulating images of galaxy fields are presented that extend to high redshifts and a surface density of galaxies high enough to produce overlapping images. The observed properties of galaxies and galaxy-ensembles in the 'local' universe are extrapolated to high redshifts using reasonable scenarios for the evolution of galaxies and their spatial distribution. This theoretical framework is then employed with Monte Carlo techniques to create fairly realistic two-dimensional distributions of galaxies plus optical and near-infrared sky images in a variety of model universes, using the appropriate density, luminosity, and angular size versus redshift relations.

Type II supernovae as a significant source of interstellar dust.

PubMed

Dunne, Loretta; Eales, Stephen; Ivison, Rob; Morgan, Haley; Edmunds, Mike

2003-07-17

Large amounts of dust (>10(8)M(o)) have recently been discovered in high-redshift quasars and galaxies corresponding to a time when the Universe was less than one-tenth of its present age. The stellar winds produced by stars in the late stages of their evolution (on the asymptotic giant branch of the Hertzsprung-Russell diagram) are thought to be the main source of dust in galaxies, but they cannot produce that dust on a short enough timescale (&<1 Gyr) to explain the results in the high-redshift galaxies. Supernova explosions of massive stars (type II) are also a potential source, with models predicting 0.2-4M(o) of dust. As massive stars evolve rapidly, on timescales of a few Myr, these supernovae could be responsible for the high-redshift dust. Observations of supernova remnants in the Milky Way, however, have hitherto revealed only 10(-7)-10(-3)M(o) each, which is insufficient to explain the high-redshift data. Here we report the detection of approximately 2-4M(o) of cold dust in the youngest known Galactic supernova remnant, Cassiopeia A. This observation implies that supernovae are at least as important as stellar winds in producing dust in our Galaxy and would have been the dominant source of dust at high redshifts.

Extreme magnification of an individual star at redshift 1.5 by a galaxy-cluster lens

NASA Astrophysics Data System (ADS)

Kelly, Patrick L.; Diego, Jose M.; Rodney, Steven; Kaiser, Nick; Broadhurst, Tom; Zitrin, Adi; Treu, Tommaso; Pérez-González, Pablo G.; Morishita, Takahiro; Jauzac, Mathilde; Selsing, Jonatan; Oguri, Masamune; Pueyo, Laurent; Ross, Timothy W.; Filippenko, Alexei V.; Smith, Nathan; Hjorth, Jens; Cenko, S. Bradley; Wang, Xin; Howell, D. Andrew; Richard, Johan; Frye, Brenda L.; Jha, Saurabh W.; Foley, Ryan J.; Norman, Colin; Bradac, Marusa; Zheng, Weikang; Brammer, Gabriel; Benito, Alberto Molino; Cava, Antonio; Christensen, Lise; de Mink, Selma E.; Graur, Or; Grillo, Claudio; Kawamata, Ryota; Kneib, Jean-Paul; Matheson, Thomas; McCully, Curtis; Nonino, Mario; Pérez-Fournon, Ismael; Riess, Adam G.; Rosati, Piero; Schmidt, Kasper Borello; Sharon, Keren; Weiner, Benjamin J.

2018-04-01

Galaxy-cluster gravitational lenses can magnify background galaxies by a total factor of up to 50. Here we report an image of an individual star at redshift z = 1.49 (dubbed MACS J1149 Lensed Star 1) magnified by more than ×2,000. A separate image, detected briefly 0.26″ from Lensed Star 1, is probably a counterimage of the first star demagnified for multiple years by an object of ≳3 solar masses in the cluster. For reasonable assumptions about the lensing system, microlensing fluctuations in the stars' light curves can yield evidence about the mass function of intracluster stars and compact objects, including binary fractions and specific stellar evolution and supernova models. Dark-matter subhaloes or massive compact objects may help to account for the two images' long-term brightness ratio.

Astrophysics of Red Supergiants

NASA Astrophysics Data System (ADS)

Levesque, Emily M.

2017-12-01

'Astrophysics of Red Supergiants' is the first book of its kind devoted to our current knowledge of red supergiant stars, a key evolutionary phase that is critical to our larger understanding of massive stars. It provides a comprehensive overview of the fundamental physical properties of red supergiants, their evolution, and their extragalactic and cosmological applications. It serves as a reference for researchers from a broad range of fields (including stellar astrophysics, supernovae, and high-redshift galaxies) who are interested in red supergiants as extreme stages of stellar evolution, dust producers, supernova progenitors, extragalactic metallicity indicators, members of massive binaries and mergers, or simply as compelling objects in their own right. The book is accessible to a range of experience levels, from graduate students up to senior researchers.

Galaxy And Mass Assembly (GAMA): AUTOZ spectral redshift measurements, confidence and errors

NASA Astrophysics Data System (ADS)

Baldry, I. K.; Alpaslan, M.; Bauer, A. E.; Bland-Hawthorn, J.; Brough, S.; Cluver, M. E.; Croom, S. M.; Davies, L. J. M.; Driver, S. P.; Gunawardhana, M. L. P.; Holwerda, B. W.; Hopkins, A. M.; Kelvin, L. S.; Liske, J.; López-Sánchez, Á. R.; Loveday, J.; Norberg, P.; Peacock, J.; Robotham, A. S. G.; Taylor, E. N.

2014-07-01

The Galaxy And Mass Assembly (GAMA) survey has obtained spectra of over 230 000 targets using the Anglo-Australian Telescope. To homogenize the redshift measurements and improve the reliability, a fully automatic redshift code was developed (AUTOZ). The measurements were made using a cross-correlation method for both the absorption- and the emission-line spectra. Large deviations in the high-pass-filtered spectra are partially clipped in order to be robust against uncorrected artefacts and to reduce the weight given to single-line matches. A single figure of merit (FOM) was developed that puts all template matches on to a similar confidence scale. The redshift confidence as a function of the FOM was fitted with a tanh function using a maximum likelihood method applied to repeat observations of targets. The method could be adapted to provide robust automatic redshifts for other large galaxy redshift surveys. For the GAMA survey, there was a substantial improvement in the reliability of assigned redshifts and in the lowering of redshift uncertainties with a median velocity uncertainty of 33 km s-1.

A HIGHLY ELONGATED PROMINENT LENS AT z = 0.87: FIRST STRONG-LENSING ANALYSIS OF EL GORDO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zitrin, Adi; Menanteau, Felipe; Hughes, John P.

We present the first strong-lensing (SL) analysis of the galaxy cluster ACT-CL J0102-4915 (El Gordo), in recent HST/ACS images, revealing a prominent strong lens at a redshift of z = 0.87. This finding adds to the already-established unique properties of El Gordo: it is the most massive, hot, X-ray luminous, and bright Sunyaev-Zeldovich effect cluster at z {approx}> 0.6, and the only {sup b}ullet{sup -}like merging cluster known at these redshifts. The lens consists of two merging massive clumps, where, for a source redshift of z{sub s} {approx} 2, each clump exhibits only a small, separate critical area, with amore » total area of 0.69 {+-} 0.11{open_square}' over the two clumps. For a higher source redshift, z{sub s} {approx} 4, the critical curves of the two clumps merge together into one bigger and very elongated lens (axis ratio {approx_equal} 5.5), enclosing an effective area of 1.44 {+-} 0.22{open_square}'. The critical curves continue expanding with increasing redshift so that for high-redshift sources (z{sub s} {approx}> 9) they enclose an area of {approx}1.91 {+-} 0.30{open_square}' (effective {theta}{sub e} {approx_equal} 46.''8 {+-} 3.''7) and a mass of 6.09 {+-} 1.04 Multiplication-Sign 10{sup 14} M{sub Sun }. According to our model, the area of high magnification ({mu} > 10) for such high-redshift sources is {approx_equal}1.2{open_square}', and the area with {mu} > 5 is {approx_equal}2.3{open_square}', making El Gordo a compelling target for studying the high-redshift universe. We obtain a strong lower limit on the total mass of El Gordo, {approx}> 1.7 Multiplication-Sign 10{sup 15} M{sub Sun} from the SL regime alone, suggesting a total mass of roughly M{sub 200} {approx} 2.3 Multiplication-Sign 10{sup 15} M{sub Sun }. Our results should be revisited when additional spectroscopic and HST imaging data are available.« less

A cross-correlation-based estimate of the galaxy luminosity function

NASA Astrophysics Data System (ADS)

van Daalen, Marcel P.; White, Martin

2018-06-01

We extend existing methods for using cross-correlations to derive redshift distributions for photometric galaxies, without using photometric redshifts. The model presented in this paper simultaneously yields highly accurate and unbiased redshift distributions and, for the first time, redshift-dependent luminosity functions, using only clustering information and the apparent magnitudes of the galaxies as input. In contrast to many existing techniques for recovering unbiased redshift distributions, the output of our method is not degenerate with the galaxy bias b(z), which is achieved by modelling the shape of the luminosity bias. We successfully apply our method to a mock galaxy survey and discuss improvements to be made before applying our model to real data.

The Swift Gamma-Ray Burst Host Galaxy Legacy Survey. I. Sample Selection and Redshift Distribution

NASA Technical Reports Server (NTRS)

Perley, D. A.; Kruhler, T.; Schulze, S.; Postigo, A. De Ugarte; Hjorth, J.; Berger, E.; Cenko, S. B.; Chary, R.; Cucchiara, A.; Ellis, R.;

High-redshift post-reionization cosmology with 21cm intensity mapping

NASA Astrophysics Data System (ADS)

Obuljen, Andrej; Castorina, Emanuele; Villaescusa-Navarro, Francisco; Viel, Matteo

2018-05-01

We investigate the possibility of performing cosmological studies in the redshift range 2.5

Sub-mm galaxies as progenitors of compact quiescent galaxies

NASA Astrophysics Data System (ADS)

Toft, Sune

2015-08-01

Three billion years after the big bang (at redshift z=2), half of the most massive galaxies were already old, quiescent systems with little to no residual star formation and extremely compact with stellar mass densities at least an order of magnitude larger than in low redshift ellipticals, their descendants. Little is known about how they formed, but their evolved, dense stellar populations suggest formation within intense, compact starbursts 1-2 Gyr earlier (at 3 < z < 6). Simulations show that gas-rich major mergers can give rise to such starbursts which produce dense remnants. Sub-millimetre selected galaxies (SMGs) are prime examples of intense, gas-rich, starbursts. With a new, mass-complete spectroscopic sample of compact quiescent galaxies at z=2 and a statistically well-understood sample of SMGs, we show that z = 3 -6 SMGs are consistent with being the progenitors of z = 2 quiescent galaxies, matching their formation redshifts and their distributions of sizes, stellar masses and internal velocities. Assuming an evolutionary connection, their space densities also match if the mean duty cycle of SMG starbursts is 42 (+40/-29) Myr (consistent with independent estimates), indicating that the bulk of stars in these massive galaxies were formed in a major, early surge of star-formation. These results suggests a coherent picture of the formation history of the most massive galaxies in the universe, from their initial burst of violent star-formation through their appearance as high stellardensity galaxy cores and to their ultimate fate as giant ellipticals.If time permits i will show novel, spatially resolved spectroscopic observations of the inner regions (r2, allowing for strong new constraints on their formation and evolutionary path

Revealing the z ~ 2.5 Cosmic Web with 3D Lyα Forest Tomography: a Deformation Tensor Approach

NASA Astrophysics Data System (ADS)

Lee, Khee-Gan; White, Martin

2016-11-01

Studies of cosmological objects should take into account their positions within the cosmic web of large-scale structure. Unfortunately, the cosmic web has only been extensively mapped at low redshifts (z\\lt 1), using galaxy redshifts as tracers of the underlying density field. At z\\gt 1, the required galaxy densities are inaccessible for the foreseeable future, but 3D reconstructions of Lyα forest absorption in closely separated background QSOs and star-forming galaxies already offer a detailed window into z˜ 2-3 large-scale structure. We quantify the utility of such maps for studying the cosmic web by using realistic z = 2.5 Lyα forest simulations matched to observational properties of upcoming surveys. A deformation tensor-based analysis is used to classify voids, sheets, filaments, and nodes in the flux, which are compared to those determined from the underlying dark matter (DM) field. We find an extremely good correspondence, with 70% of the volume in the flux maps correctly classified relative to the DM web, and 99% classified to within one eigenvalue. This compares favorably to the performance of galaxy-based classifiers with even the highest galaxy densities from low-redshift surveys. We find that narrow survey geometries can degrade the recovery of the cosmic web unless the survey is ≳ 60 {h}-1 {Mpc} or ≳ 1 deg on the sky. We also examine halo abundances as a function of the cosmic web, and find a clear dependence as a function of flux overdensity, but little explicit dependence on the cosmic web. These methods will provide a new window on cosmological environments of galaxies at this very special time in galaxy formation, “high noon,” and on overall properties of cosmological structures at this epoch.

Spectroscopy of 10 γ -Ray BL Lac Objects at High Redshift

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paiano, Simona; Falomo, Renato; Landoni, Marco

2017-08-01

We present optical spectra with high signal-to-noise ratio of 10 BL Lac objects detected at GeV energies by the Fermi satellite (3FGL catalog), which previous observations suggested are at relatively high redshift. The new observations, obtained at the 10 m Gran Telescopio Canarias, allowed us to find the redshift for J0814.5+2943 ( z = 0.703), and we can set a spectroscopic lower limit for J0008.0+4713 ( z > 1.659) and J1107.7+0222 ( z > 1.0735) on the basis of Mg ii intervening absorption features. In addition we confirm the redshifts for J0505.5+0416 ( z = 0.423) and J1450+5200 ( zmore » > 2.470). Finally we contradict the previous z estimates for five objects (J0049.7+0237, J0243.5+7119, J0802.0+1005, J1109.4+2411, and J2116.1+3339).« less

A Lyman Break Galaxy in the Epoch of Reionization from Hubble Space Telescope (HST) Grism Spectroscopy

NASA Technical Reports Server (NTRS)

Rhoads, James E.; Malhotra, Sangeeta; Stern, Daniel K.; Gardner, Jonathan P.; Dickinson, Mark; Pirzkal, Norbert; Spinrad, Hyron; Reddy, Naveen; Dey, Arjun; Hathi, Nimish;

Modelling the flaring activity of the high-z, hard X-ray-selected blazar IGR J22517+2217: Flaring activity of IGR J22517+2217

DOE PAGES

Lanzuisi, G.; De Rosa, A.; Ghisellini, G.; ...

2012-03-21

We present new Suzaku and Fermi data and re-analysed archival hard X-ray data from the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) and Swift–Burst Alert Telescope (BAT) surveys to investigate the physical properties of the luminous, high-redshift, hard X-ray-selected blazar IGR J22517+2217, through the modelling of its broad-band spectral energy distribution (SED) in two different activity states. Through analysis of new Suzaku data and flux-selected data from archival hard X-ray observations, we build the source SED in two different states, one for the newly discovered flare that occurred in 2005 and one for the following quiescent period. Both SEDs are strongly dominatedmore » by the high-energy hump peaked at 10 20–10 22 Hz, which is at least two orders of magnitude higher than the low-energy (synchrotron) one at 10 11–10 14 Hz and varies by a factor of 10 between the two states. In both states the high-energy hump is modelled as inverse Compton emission between relativistic electrons and seed photons produced externally to the jet, while the synchrotron self-Compton component is found to be negligible. In our model the observed variability can be accounted for by a variation of the total number of emitting electrons and by a dissipation region radius changing from inside to outside the broad-line region as the luminosity increases. In its flaring activity, IGR J22517+2217 is revealed as one of the most powerful jets among the population of extreme, hard X-ray-selected, high-redshift blazars observed so far.« less

The origin of compact galaxies with anomalously high black hole masses

NASA Astrophysics Data System (ADS)

Barber, Christopher; Schaye, Joop; Bower, Richard G.; Crain, Robert A.; Schaller, Matthieu; Theuns, Tom

2016-07-01

Observations of local galaxies harbouring supermassive black holes (BH) of anomalously high mass, MBH, relative to their stellar mass, M*, appear to be at odds with simple models of the co-evolution between galaxies and their central BHs. We study the origin of such outliers in a Λ cold dark matter context using the EAGLE cosmological, hydrodynamical simulation. We find 15 `MBH(M*)-outlier' galaxies, defined as having MBH more than 1.5 dex above the median MBH(M*) relation in the simulation, MBH, med(M*). All MBH(M*)-outliers are satellite galaxies, typically with M* ˜ 1010 M⊙ and MBH ˜ 108 M⊙. They have all become outliers due to a combination of tidal stripping of their outer stellar component acting over several Gyr and early formation times leading to rapid BH growth at high redshift, with the former mechanism being most important for 67 per cent of these outliers. The same mechanisms also cause the MBH(M*)-outlier satellites to be amongst the most compact galaxies in the simulation, making them ideal candidates for ultracompact dwarf galaxy progenitors. The 10 most extreme central galaxies found at z = 0 (with log10(MBH/MBH, med(M*)) ∈ [1.2, 1.5]) grow rapidly in MBH to lie well above the present-day MBH - M* relation at early times (z ≳ 2), and either continue to evolve parallel to the z = 0 relation or remain unchanged until the present day, making them `relics' of the high-redshift universe. This high-z formation mechanism may help to explain the origin of observed MBH(M*)-outliers with extended dark matter haloes and undisturbed morphologies.

Anisotropies of gravitational-wave standard sirens as a new cosmological probe without redshift information

NASA Astrophysics Data System (ADS)

Nishizawa, Atsushi; Namikawa, Toshiya; Taruya, Atsushi

2016-03-01

Gravitational waves (GWs) from compact binary stars at cosmological distances are promising and powerful cosmological probes, referred to as the GW standard sirens. With future GW detectors, we will be able to precisely measure source luminosity distances out to a redshift z 5. To extract cosmological information, previous studies using the GW standard sirens rely on source redshift information obtained through an extensive electromagnetic follow-up campaign. However, the redshift identification is typically time-consuming and rather challenging. Here we propose a novel method for cosmology with the GW standard sirens free from the redshift measurements. Utilizing the anisotropies of the number density and luminosity distances of compact binaries originated from the large-scale structure, we show that (i) this anisotropies can be measured even at very high-redshifts (z = 2), (ii) the expected constraints on the primordial non-Gaussianity with Einstein Telescope would be comparable to or even better than the other large-scale structure probes at the same epoch, (iii) the cross-correlation with other cosmological observations is found to have high-statistical significance. A.N. was supported by JSPS Postdoctoral Fellowships for Research Abroad No. 25-180.

Detecting the Attenuation of Blazar Gamma-ray Emission by Extragalactic Background Light with GLAST

NASA Technical Reports Server (NTRS)

Chen, Andrew; Ritz, Steven

1999-01-01

Gamma rays with energy above 10 GeV interact with optical-UV photons resulting in pair production. Therefore, a large sample of high redshift sources of these gamma rays can be used to probe the extragalactic background starlight (EBL) by examining the redshift dependence of the attenuation of the flux above 10 GeV. GLAST, the next generation high-energy gamma-ray telescope, will for the first time have the unique capability to detect thousands of gamma-ray blazars up to redshifts of at least z = 4, with enough angular resolution to allow identification of a large fraction of their optical counterparts. By combining recent determinations of the gamma-ray blazar luminosity function, recent calculations of the high energy gamma-ray opacity due to EBL absorption, and the expected GLAST instrument performance to produce simulated samples of blazars that GLAST would detect, including their redshifts and fluxes, we demonstrate that these blazars have the potential to be a highly effective probe of the EBL.

How Well Do Submillimeter Galaxies Trace Protoclusters?

NASA Astrophysics Data System (ADS)

Hayward, Christopher C.

2017-07-01

It has been suggested that associations of (or even individual) high-redshift submillimeter galaxies (SMGs) may serve as beacons of protoclusters because SMGs are high-mass galaxies undergoing rapid assembly. Moreover, it has been claimed that the protocluster environment may lead to 'synchronized' starbursts and thus multiple SMGs within the protocluster region. We investigate this possibility using the Bolshoi cosmological N-body simulation and a model for populating the simulation with SMGs. We find that although SMG associations correspond to some of the highest overdensities at z > 2.5, they are highly incomplete tracers because of stochastic sampling effects. At lower redshift, because of 'downsizing' (i.e. the most massive galaxies have already ceased forming stars and are thus not SMGs), the highest dark matter overdensities are not well traced by SMG associations. I will close by discussing the implications of this work for observational studies of protoclusters and how the highest-redshift SMGs can be used to maximize the potential of JWST for studying very high redshift galaxies.

Digging for the Truth: Photon Archeology with GLAST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stecker, F. W.

2007-07-12

Stecker, Malkan and Scully, have shown how ongoing deep surveys of galaxy luminosity functions, spectral energy distributions and backwards evolution models of star formation rates can be used to calculate the past history of intergalactic photon densities for energies from 0.03 eV to the Lyman limit at 13.6 eV and for redshifts out to 6 (called here the intergalactic background light or IBL). From these calculations of the IBL at various redshifts, they predict the present and past optical depth of the universe to high energy {gamma}-rays owing to interactions with photons of the IBL and the 2.7 K CMB.more » We discuss here how this proceedure can be reversed by looking for sharp cutoffs in the spectra of extragalactic {gamma}-ray sources such as blazars at high redshifts in the multi-GeV energy range with GLAST (Gamma-Ray Large Are Space Telescope). By determining the cutoff energies of sources with known redshifts, we can refine our determination of the IBL photon densities in the past, i.e., the archeo-IBL, and therefore get a better measure of the past history of the total star formation rate. Conversely, observations of sharp high energy cutoffs in the {gamma}-ray spectra of sources at unknown redshifts can be used instead of spectral lines to give a measure of their redshifts.« less

DETECTION OF AN ULTRA-BRIGHT SUBMILLIMETER GALAXY BEHIND THE SMALL MAGELLANIC CLOUD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takekoshi, Tatsuya; Minamidani, Tetsuhiro; Sorai, Kazuo

2013-09-10

We report the discovery of a new ultra-bright submillimeter galaxy (SMG) behind the Small Magellanic Cloud (SMC). This SMG is detected as a 43.3 {+-} 8.4 mJy point source (MM J01071-7302, hereafter MMJ0107) in the 1.1 mm continuum survey of the SMC by AzTEC on the ASTE telescope. MMJ0107 is also detected in the radio (843 MHz), Herschel/SPIRE, Spitzer MIPS 24 {mu}m, all IRAC bands, Wide-field Infrared Survey Explorer, and near-infrared (J, H, K{sub S} ). We find an optical (U, B, V) source, which might be the lensing object, at a distance of 1.''4 from near-infrared and IRAC sources.more » Photometric redshift estimates for the SMG using representative spectral energy distribution templates show the redshifts of 1.4-3.9. We estimate total far-infrared luminosity of (0.3-2.2) Multiplication-Sign 10{sup 14} {mu}{sup -1} L{sub Sun} and a star formation rate of 5600-39, 000 {mu}{sup -1} M{sub Sun} yr{sup -1}, where {mu} is the gravitational magnification factor. This apparent extreme star formation activity is likely explained by a highly magnified gravitational lens system.« less

A Candidate for an Intrinsic Dusty Absorber with a Metal-rich Damped Lyα Absorption Line System in the Quasar J170542.91+354340.2

NASA Astrophysics Data System (ADS)

Pan, Xiang; Zhou, Hongyan; Ge, Jian; Jiang, Peng; Yang, Bin; Lu, Honglin; Ji, Tuo; Zhang, Shaohua; Shi, Xiheng

2017-02-01

We present a detailed analysis of the unusual damped Lyα absorption line system (DLA) toward the quasar SDSS J170542.91+354340.2 at a redshift of 2, previously reported by Noterdaeme et al. as one of the very few CO absorbers known to date at high z. This DLA is exceptional in that: (1) its extinction curve is similar to peculiar Milky Way sightlines penetrating star formation regions; (2) its absorption components are redshifted at a speed of several hundred km s-1 compared to broad Balmer emission lines; (3) its gas-phase metallicity is super-solar as evaluated from more than 30 absorption lines; (4) detection of residual flux in the DLA trough and variability of {{C}} {{IV}} absorption is possible. Based on these facts, we argue that this dusty DLA is a good candidate for an intrinsic quasar 2175 Å absorber, and can originate from star formation regions of the quasar’s host galaxy. We discuss in detail the gas and dust properties, and the dust depletion. Follow-up observations, such as spectropolarimetry and optical/infrared spectroscopy, will help to confirm the system’s intrinsic nature and to explore how dust grains behave in the extreme environments proximate to quasars.

Observations of Electron-driven Evaporation in a Flare Precursor

NASA Astrophysics Data System (ADS)

Li, Dong; Li, Ying; Su, Wei; Huang, Yu; Ning, Zongjun

2018-02-01

We investigate the relationship between the blueshifts of a hot emission line and the nonthermal emissions in microwave and hard X-ray (HXR) wavelengths in the precursor of a solar flare on 2014 October 27. The flare precursor is identified as a small but well-developed peak in the soft X-ray and extreme-ultraviolet passbands before the GOES flare onset, which is accompanied by a pronounced burst in microwave 17 and 34 GHz and in HXR 25–50 keV. The slit of the Interface Region Imaging Spectrograph (IRIS) stays on one ribbon-like transient during the flare precursor phase, which shows visible nonthermal emissions in Nobeyama Radioheliograph and RHESSI images. The IRIS spectroscopic observations show that the hot line of Fe XXI 1354.09 Å (log T ∼ 7.05) displays blueshifts, while the cool line of Si IV 1402.77 Å (log T ∼ 4.8) exhibits redshifts. The blueshifts and redshifts are well correlated with each other, indicative of an explosive chromospheric evaporation during the flare precursor phase combining a high nonthermal energy flux with a short characteristic timescale. In addition, the blueshifts of Fe XXI 1354.09 Å are well correlated with the microwave and HXR emissions, implying that the explosive chromospheric evaporation during the flare precursor phase is driven by nonthermal electrons.

Cosmic structure and dynamics of the local Universe

NASA Astrophysics Data System (ADS)

Kitaura, Francisco-Shu; Erdoǧdu, Pirin; Nuza, Sebastián. E.; Khalatyan, Arman; Angulo, Raul E.; Hoffman, Yehuda; Gottlöber, Stefan

2012-11-01

We present a cosmography analysis of the local Universe based on the recently released Two-Micron All-Sky Redshift Survey catalogue. Our method is based on a Bayesian Networks Machine Learning algorithm (the KIGEN-code) which self-consistently samples the initial density fluctuations compatible with the observed galaxy distribution and a structure formation model given by second-order Lagrangian perturbation theory (2LPT). From the initial conditions we obtain an ensemble of reconstructed density and peculiar velocity fields which characterize the local cosmic structure with high accuracy unveiling non-linear structures like filaments and voids in detail. Coherent redshift-space distortions are consistently corrected within 2LPT. From the ensemble of cross-correlations between the reconstructions and the galaxy field and the variance of the recovered density fields, we find that our method is extremely accurate up to k˜ 1 h Mpc-1 and still yields reliable results down to scales of about 3-4 h-1 Mpc. The motion of the Local Group we obtain within ˜80 h-1 Mpc (vLG = 522 ± 86 km s-1, lLG = 291° ± 16°, bLG = 34° ± 8°) is in good agreement with measurements derived from the cosmic microwave background and from direct observations of peculiar motions and is consistent with the predictions of ΛCDM.

Probing high-redshift clusters with HST/ACS gravitational weak-lensing and Chandra x-ray observations

NASA Astrophysics Data System (ADS)

Jee, Myungkook James

2006-06-01

Clusters of galaxies, the largest gravitationally bound objects in the Universe, are useful tracers of cosmic evolution, and particularly detailed studies of still-forming clusters at high-redshifts can considerably enhance our understanding of the structure formation. We use two powerful methods that have become recently available for the study of these distant clusters: spaced- based gravitational weak-lensing and high-resolution X-ray observations. Detailed analyses of five high-redshift (0.8 < z < 1.3) clusters are presented based on the deep Advanced Camera for Surveys (ACS) and Chandra X-ray images. We show that, when the instrumental characteristics are properly understood, the newly installed ACS on the Hubble Space Telescope (HST) can detect subtle shape distortions of background galaxies down to the limiting magnitudes of the observations, which enables the mapping of the cluster dark matter in unprecedented high-resolution. The cluster masses derived from this HST /ACS weak-lensing study have been compared with those from the re-analyses of the archival Chandra X-ray data. We find that there are interesting offsets between the cluster galaxy, intracluster medium (ICM), and dark matter centroids, and possible scenarios are discussed. If the offset is confirmed to be uniquitous in other clusters, the explanation may necessitate major refinements in our current understanding of the nature of dark matter, as well as the cluster galaxy dynamics. CL0848+4452, the highest-redshift ( z = 1.27) cluster yet detected in weak-lensing, has a significant discrepancy between the weak- lensing and X-ray masses. If this trend is found to be severe and common also for other X-ray weak clusters at redshifts beyond the unity, the conventional X-ray determination of cluster mass functions, often inferred from their immediate X-ray properties such as the X-ray luminosity and temperature via the so-called mass-luminosity (M-L) and mass-temperature (M-T) relations, will become highly unstable in this redshift regime. Therefore, the relatively unbiased weak-lensing measurements of the cluster mass properties can be used to adequately calibrate the scaling relations in future high-redshift cluster investigations.

Rational approximations of f(R) cosmography through Pad'e polynomials

NASA Astrophysics Data System (ADS)

Capozziello, Salvatore; D'Agostino, Rocco; Luongo, Orlando

2018-05-01

We consider high-redshift f(R) cosmography adopting the technique of polynomial reconstruction. In lieu of considering Taylor treatments, which turn out to be non-predictive as soon as z>1, we take into account the Pad&apose rational approximations which consist in performing expansions converging at high redshift domains. Particularly, our strategy is to reconstruct f(z) functions first, assuming the Ricci scalar to be invertible with respect to the redshift z. Having the so-obtained f(z) functions, we invert them and we easily obtain the corresponding f(R) terms. We minimize error propagation, assuming no errors upon redshift data. The treatment we follow naturally leads to evaluating curvature pressure, density and equation of state, characterizing the universe evolution at redshift much higher than standard cosmographic approaches. We therefore match these outcomes with small redshift constraints got by framing the f(R) cosmology through Taylor series around 0zsimeq . This gives rise to a calibration procedure with small redshift that enables the definitions of polynomial approximations up to zsimeq 10. Last but not least, we show discrepancies with the standard cosmological model which go towards an extension of the ΛCDM paradigm, indicating an effective dark energy term evolving in time. We finally describe the evolution of our effective dark energy term by means of basic techniques of data mining.

A Chandra Survey of high-redshift (0.7 < z < 0.8) clusters selected in the 100 deg^2 SPT-Pol Deep Field

NASA Astrophysics Data System (ADS)

Garmire, Gordon

2016-09-01

We propose to observe a complete sample of 10 galaxy clusters at 1e14 < M500 < 5e14 and 0.7 < z < 0.8. These systems were selected from the 100 deg^2 deep field of the SPT-Pol SZ survey. This survey are has significant complementary data, including uniform depth ATCA, Herschel, Spitzer, and DES imaging, enabling a wide variety of astrophysical and cosmological studies. This sample complements the successful SPT-XVP survey, which has a broad redshift range and a narrow mass range, by including clusters over a narrow redshift range and broad mass range. These systems are such low mass and high redshift that they will not be detected in the eRosita all-sky survey.

The variance of dispersion measure of high-redshift transient objects as a probe of ionized bubble size during reionization

NASA Astrophysics Data System (ADS)

Yoshiura, Shintaro; Takahashi, Keitaro

2018-01-01

The dispersion measure (DM) of high-redshift (z ≳ 6) transient objects such as fast radio bursts can be a powerful tool to probe the intergalactic medium during the Epoch of Reionization. In this paper, we study the variance of the DMs of objects with the same redshift as a potential probe of the size distribution of ionized bubbles. We calculate the DM variance with a simple model with randomly distributed spherical bubbles. It is found that the DM variance reflects the characteristics of the probability distribution of the bubble size. We find that the variance can be measured precisely enough to obtain the information on the typical size with a few hundred sources at a single redshift.

High Redshift Radio Galaxies at Low Redshift, and Some Other Issues

NASA Astrophysics Data System (ADS)

Antonucci, Robert

Cygnus A is the only high redshift radio galaxy at low redshift, that is it's the only nearby object with radio power in the range of the high redshift 3C objects. It is clear now that this is somewhat misleading in that Cyg A is an overachiever in the radio, and that its actual bolometric luminosity is much more modest than this would indicate. (This point has been explored and generalized in Barthel and Arnaud 1996; also see Carilli and Barthel 1996 for a detailed review of Cyg A). But the energy content of the lobes is famously large. There is a whole history of attempts to show that Cygnus A fits the Unified Model, and our particular contribution was detecting an apparent broad MgII line with the HST (Antonucci, Kinney and Hurt 1994, which includes references to previous work). The spectral signal-to-noise ratio (SNR) was less than amazing; furthermore an unflagged dead diode took out ~12 Å from the line profile; and there was an uncertain ``noise" contribution from confusing narrow lines (gory details in Antonucci 1994). One of the referees of our paper - the favorable one - stated that ``only a mother could love that line." Thus we reobserved it with somewhat better SNR and with the bad diode flagged, and the old and new data are presented to the same scale in Figure 1. Most of the bins are within the combined 1 σ statistical errors, and the many statistically significant wiggles are almost all present in NGC1068 as well (Antonucci, Hurt and Miller 1994). The point is that the errors are believable, and that the continuum should be set low. I believe the MgII line is there and is broader than we thought originally. (A detailed discussion of the spectrum is in prep.) In the 1994 paper we also stated that the polarization in the UV (F320W FOC filter) is ~6 %, and perpendicular to the radio axis, indicating that there is a fairly large contribution from scattered light from a quasar in this region. This is consistent with the scenario of Jackson and Tadhunter (1993), amongst others. Using the mighty Keck it has finally become possible to show the broad H alpha line in polarized flux, and it is extremely broad (~26,000 km/sec - Ogle et al 1997). Ogle et al compared the total broad H alpha and MgII fluxes in the SE component, corrected for Galactic reddening, and concluded that dust scattering must be important. (Specifically it would have to produce most of the broad MgII.) This was also our picture in the 1994 paper (and that of other workers). Caveats include aperture effects and velocity ranges for integration of the line fluxes, but the conclusion is likely to stand.

Spectroscopy of High-Redshift Supernovae from the ESSENCE Project: The First 2 Years

NASA Astrophysics Data System (ADS)

Matheson, Thomas; Blondin, Stéphane; Foley, Ryan J.; Chornock, Ryan; Filippenko, Alexei V.; Leibundgut, Bruno; Smith, R. Chris; Sollerman, Jesper; Spyromilio, Jason; Kirshner, Robert P.; Clocchiatti, Alejandro; Aguilera, Claudio; Barris, Brian; Becker, Andrew C.; Challis, Peter; Covarrubias, Ricardo; Garnavich, Peter; Hicken, Malcolm; Jha, Saurabh; Krisciunas, Kevin; Li, Weidong; Miceli, Anthony; Miknaitis, Gajus; Prieto, Jose Luis; Rest, Armin; Riess, Adam G.; Salvo, Maria Elena; Schmidt, Brian P.; Stubbs, Christopher W.; Suntzeff, Nicholas B.; Tonry, John L.

2005-05-01

We present the results of spectroscopic observations of targets discovered during the first 2 years of the ESSENCE project. The goal of ESSENCE is to use a sample of ~200 Type Ia supernovae (SNe Ia) at moderate redshifts (0.2<~z<~0.8) to place constraints on the equation of state of the universe. Spectroscopy not only provides the redshifts of the objects but also confirms that some of the discoveries are indeed SNe Ia. This confirmation is critical to the project, as techniques developed to determine luminosity distances to SNe Ia depend on the knowledge that the objects at high redshift have the same properties as the ones at low redshift. We describe the methods of target selection and prioritization, the telescopes and detectors, and the software used to identify objects. The redshifts deduced from spectral matching of high-redshift SNe Ia with low-redshift SNe Ia are consistent with those determined from host-galaxy spectra. We show that the high-redshift SNe Ia match well with low-redshift templates. We include all spectra obtained by the ESSENCE project, including 52 SNe Ia, five core-collapse SNe, 12 active galactic nuclei, 19 galaxies, four possibly variable stars, and 16 objects with uncertain identifications. Based in part on observations obtained at the Cerro Tololo Inter-American Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under a cooperative agreement with the National Science Foundation (NSF); the European Southern Observatory, Chile (ESO Programme 170.A-0519) the Gemini Observatory, which is operated by AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership (the NSF [United States], the Particle Physics and Astronomy Research Council [United Kingdom], the National Research Council [Canada], CONICYT [Chile], the Australian Research Council [Australia], CNPq [Brazil], and CONICET [Argentina] [programs GN-2002B-Q-14, GN-2003B-Q-14, and GS-2003B-Q-11]) the Magellan Telescopes at Las Campanas Observatory; the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona; and the F. L. Whipple Observatory, which is operated by the Smithsonian Astrophysical Observatory. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration; the Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

A supernova origin for dust in a high-redshift quasar.

PubMed

Maiolino, R; Schneider, R; Oliva, E; Bianchi, S; Ferrara, A; Mannucci, F; Pedani, M; Sogorb, M Roca

2004-09-30

Interstellar dust plays a crucial role in the evolution of the Universe by assisting the formation of molecules, by triggering the formation of the first low-mass stars, and by absorbing stellar ultraviolet-optical light and subsequently re-emitting it at infrared/millimetre wavelengths. Dust is thought to be produced predominantly in the envelopes of evolved (age >1 Gyr), low-mass stars. This picture has, however, recently been brought into question by the discovery of large masses of dust in the host galaxies of quasars at redshift z > 6, when the age of the Universe was less than 1 Gyr. Theoretical studies, corroborated by observations of nearby supernova remnants, have suggested that supernovae provide a fast and efficient dust formation environment in the early Universe. Here we report infrared observations of a quasar at redshift 6.2, which are used to obtain directly its dust extinction curve. We then show that such a curve is in excellent agreement with supernova dust models. This result demonstrates a supernova origin for dust in this high-redshift quasar, from which we infer that most of the dust at high redshifts probably has the same origin.

Remeasurement of the H I Gunn-Peterson Effect toward QSO PKS 1937-101 with Keck Observations

NASA Astrophysics Data System (ADS)

Fang, Yihu; Fan, Xiaoming; Tytler, David; Crotts, Arlin P. S.

1998-04-01

We present the first measurement of the H I Gunn-Peterson effect using the Keck 10 m telescope, observing the high-redshift QSO PKS 1937-101 (z = 3.787). The high-resolution echelle (HIRES) spectra, with FWHM ~15 km s-1 and a signal-to-noise ratio (S/N) ~50 per spectral resolution element, allows us to resolve many weak lines down to NH I = 1012 cm-2, thus reducing the line-blanketing problem compared with previous data. Based on intensity-distribution analysis, we find that a maximum likelihood best fit yields a Gunn-Peterson type of opacity τGP = 0.113 +/- 0.020 in addition to a power-law Lyα absorption-line population with β of 1.7 down to NH I = 1012 cm-2. There remains systematic uncertainty in this result because of problems extrapolating the spectral continuum from the red side of the Lyα emission line. This is consistent with the previous study of the same QSO in low S/N data using weighted intensity function analysis (Fang & Crotts 1995). It indicates that this previous method succeeds in measuring the Lyα forest continuum level at low S/N, which is essential in extending the technique to possible fainter QSOs with minimum emission-line contamination for reliable continuum extrapolation. We further discuss problems of severe line blanketing, even in Keck spectra for QSOs at z >= 4.5, and show the effectiveness of the weighted intensity function method in measuring continuum levels in extremely crowded Lyα absorption spectra for redshifts as high as z > 5.

Supernova Cosmology Project

Science.gov Websites

Space Telescope Cluster Supernova Survey: II. The Type Ia Supernova Rate in High-Redshift Galaxy /abs/0809.1648 Constraining Dust and Color Variations of High-z SNe Using NICMOS on the Hubble Space /0804.4142 A New Determination of the High-Redshift Type Ia Supernova Rates with the Hubble Space Telescope

Remarkable optical red shift and extremely high optical absorption coefficient of V-Ga co-doped TiO2

NASA Astrophysics Data System (ADS)

Deng, Quanrong; Han, Xiaoping; Gao, Yun; Shao, Guosheng

2012-07-01

A first attempt has been made to study the effect of codoping of transition metal and sp metal on the electronic structure and associated optical properties of TiO2, through V-Ga codoped thin films. V-Ga codoped rutile TiO2 films were fabricated on fused quartz substrates using pulsed laser ablation, followed by heat treatment at high temperatures. Gigantic redshift in the optical absorption edge was observed in V-Ga co-doped TiO2 materials, from UV to infrared region with high absorption coefficient. Through combined structural characterization and theoretical modeling, this is attributed to the p-d hybridization between the two metals. This leads to additional energy bands to overlap with the minimum of the conduction band, leading to remarkably narrowed band gap free of mid-gap states. The direct-gap of the co-doped phase is key to the remarkably high optical absorption coefficient of the coped titania.

The spectral energy distribution of the redshift 7.1 quasar ULAS J1120+0641

NASA Astrophysics Data System (ADS)

Barnett, R.; Warren, S. J.; Banerji, M.; McMahon, R. G.; Hewett, P. C.; Mortlock, D. J.; Simpson, C.; Venemans, B. P.; Ota, K.; Shibuya, T.

2015-03-01

We present new observations of the highest-redshift quasar known, ULAS J1120+0641, redshift z = 7.084, obtained in the optical, at near-, mid-, and far-infrared wavelengths, and in the sub-mm. We combine these results with published X-ray and radio observations to create the multiwavelength spectral energy distribution (SED), with the goals of measuring the bolometric luminosity Lbol, and quantifying the respective contributions from the AGN and star formation. We find three components are needed to fit the data over the wavelength range 0.12-1000 μm: the unobscured quasar accretion disk and broad-line region, a dusty clumpy AGN torus, and a cool 47K modified black body to characterise star formation. Despite the low signal-to-noise ratio of the new long-wavelength data, the normalisation of any dusty torus model is constrained within ±40%. We measure a bolometric luminosity Lbol = 2.6 ± 0.6 × 1047 erg s-1 = 6.7 ± 1.6 × 1013 L⊙, to which the three components contribute 31%,32%,3%, respectively, with the remainder provided by the extreme UV < 0.12 μm. We tabulate the best-fit model SED. We use local scaling relations to estimate a star formation rate (SFR) in the range 60-270 M⊙/yr from the [C ii] line luminosity and the 158 μm continuum luminosity. An analysis of the equivalent widths of the [C ii] line in a sample of z> 5.7 quasars suggests that these indicators are promising tools for estimating the SFR in high-redshift quasars in general. At the time observed the black hole was growing in mass more than 100 times faster than the stellar bulge, relative to the mass ratio measured in the local universe, i.e. compared to MBH/Mbulge ≃ 1.4 × 10-3, for ULAS J1120+0641 we measure ṀBH/Ṁbulge ≃ 0.2. Full Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A31

Giving cosmic redshift drift a whirl

NASA Astrophysics Data System (ADS)

Kim, Alex G.; Linder, Eric V.; Edelstein, Jerry; Erskine, David

2015-03-01

Redshift drift provides a direct kinematic measurement of cosmic acceleration but it occurs with a characteristic time scale of a Hubble time. Thus redshift observations with a challenging precision of 10-9 require a 10 year time span to obtain a signal-to-noise of 1. We discuss theoretical and experimental approaches to address this challenge, potentially requiring less observer time and having greater immunity to common systematics. On the theoretical side we explore allowing the universe, rather than the observer, to provide long time spans; speculative methods include radial baryon acoustic oscillations, cosmic pulsars, and strongly lensed quasars. On the experimental side, we explore beating down the redshift precision using differential interferometric techniques, including externally dispersed interferometers and spatial heterodyne spectroscopy. Low-redshift emission line galaxies are identified as having high cosmology leverage and systematics control, with an 8 h exposure on a 10-m telescope (1000 h of exposure on a 40-m telescope) potentially capable of measuring the redshift of a galaxy to a precision of 10-8 (few ×10-10). Low-redshift redshift drift also has very strong complementarity with cosmic microwave background measurements, with the combination achieving a dark energy figure of merit of nearly 300 (1400) for 5% (1%) precision on drift.

Cosmology without cosmic variance

DOE PAGES

Bernstein, Gary M.; Cai, Yan -Chuan

2011-10-01

The growth of structures in the Universe is described by a function G that is predicted by the combination of the expansion history of the Universe and the laws of gravity within it. We examine the improvements in constraints on G that are available from the combination of a large-scale galaxy redshift survey with a weak gravitational lensing survey of background sources. We describe a new combination of such observations that in principle this yields a measure of the growth rate that is free of sample variance, i.e. the uncertainty in G can be reduced without bound by increasing themore » number of redshifts obtained within a finite survey volume. The addition of background weak lensing data to a redshift survey increases information on G by an amount equivalent to a 10-fold increase in the volume of a standard redshift-space distortion measurement - if the lensing signal can be measured to sub-per cent accuracy. This argues that a combined lensing and redshift survey over a common low-redshift volume of the Universe is a more powerful test of general relativity than an isolated redshift survey over larger volume at high redshift, especially as surveys begin to cover most of the available sky.« less

How does ionizing radiation escape from galaxies?

NASA Astrophysics Data System (ADS)

Orlitova, Ivana

2016-10-01

Search for sources that reionized the Universe from z 15 to z 6 is one of the main drivers of present-day astronomy. Low-mass star-forming galaxies are the most favoured sources of ionizing photons, but the searches of escaping Lyman continuum (LyC) have not been extremely successful. Our team has recently detected prominent LyC escape from five Green Pea galaxies at redshift 0.3, using the HST/COS spectrograph, which represents a significant breakthrough. We propose here to study the LyC escape of the strongest among these leakers, J1152, with spatial resolution. From the comparison of the ionizing and non-ionizing radiation maps, and surface brightness profiles, we will infer the major mode in which LyC is escaping: from the strongest starburst, from the galaxy edge, through a hole along our line-of-sight, through clumpy medium, or directly from all the production sites due to highly ionized medium in the entire galaxy. In parallel, we will test the predictive power of two highly debated indirect indicators of LyC leakage: the [OIII]5007/[OII]3727 ratio, and Lyman-alpha. We predict that their spatial distribution should closely follow that of the ionizing continuum if column densities of the neutral gas are low. This combined study, which relies on the HST unique capabilities, will bring crucial information on the structure of the leaking galaxies, provide constraints for hydrodynamic simulations, and will lead to efficient future searches for LyC leakers across a large range of redshifts.

High redshift QSOs and the x ray background

NASA Technical Reports Server (NTRS)

Impey, Chris

1993-01-01

ROSAT pointed observations were made of 9 QSO's from the Large Bright Quasar Survey (LBQS). The LBQS is based on machine measurement of objective prism plates taken with the UK Schmidt Telescope. Software has been used to select QSO's by both color and by the presence of spectral features and continuum breaks. The probability of detection can be calculated as a function of magnitude, redshift and spectral features, and the completeness of the survey can be accurately estimated. Nine out of 1040 QSO's in the LBQS have z greater than 3. The observations will provide an important data point in the X-ray luminosity function of QSO's at high redshift. The QSO's with z greater than 3 span less than a magnitude in M(sub B), so can be combined as a homogeneous sample. This analysis is only possible with a sample drawn from a large and complete catalog such as the LBQS. Four of the 9 QSO's that were observed with the ROSAT PSPC for this proposal were detected, including one of the most luminous X-ray sources ever observed. The April 1992 version of the PROS DETECT package was used to reduce the data. The results have been used to search for evolution of the X-ray properties of QSO's in redshift. The 9 QSO's lie in the range -28.7 less than M(sub B) less than -27.8. When combined with data for 16 QSO's in a similar luminosity range at lower redshift correlations with luminosity and redshift can be separated out. The LBQS sample also yields a new constraint on the contribution of high redshift QSO's to the X-ray background. An initial requirement is knowledge of the X-ray properties (alpha(sub OX)) as a function of redshift. Integration over the evolving luminosity function of the LBQS then gives the QSO contribution to the source counts.

VizieR Online Data Catalog: VANDELS High-Redshift Galaxy Evolution (McLure+, 2017)

NASA Astrophysics Data System (ADS)

McLure, R.; Pentericci, L.; Vandels Team

2017-11-01

This is the first data release (DR1) of the VANDELS survey, an ESO public spectroscopy survey targeting the high-redshift Universe. The VANDELS survey uses the VIMOS spectrograph on ESO's VLT to obtain ultra-deep, medium resolution, optical spectra of galaxies within the UKIDSS Ultra Deep Survey (UDS) and Chandra Deep Field South (CDFS) survey fields (0.2 sq. degree total area). Using robust photometric redshift pre-selection, VANDELS is targeting ~2100 galaxies in the redshift interval 1.0=3. In addition, VANDELS is targeting a substantial number of passive galaxies in the redshift interval 1.0

Unseen Progenitors of Luminous High-z Quasars in the R h = ct Universe

NASA Astrophysics Data System (ADS)

Fatuzzo, Marco; Melia, Fulvio

2017-09-01

Quasars at high redshift provide direct information on the mass growth of supermassive black holes (SMBHs) and, in turn, yield important clues about how the universe evolved since the first (Pop III) stars started forming. Yet even basic questions regarding the seeds of these objects and their growth mechanism remain unanswered. The anticipated launch of eROSITA and ATHENA is expected to facilitate observations of high-redshift quasars needed to resolve these issues. In this paper, we compare accretion-based SMBH growth in the concordance ΛCDM model with that in the alternative Friedmann-Robertson-Walker cosmology known as the R h = ct universe. Previous work has shown that the timeline predicted by the latter can account for the origin and growth of the ≳109 M ⊙ highest redshift quasars better than that of the standard model. Here, we significantly advance this comparison by determining the soft X-ray flux that would be observed for Eddington-limited accretion growth as a function of redshift in both cosmologies. Our results indicate that a clear difference emerges between the two in terms of the number of detectable quasars at redshift z ≳ 7, raising the expectation that the next decade will provide the observational data needed to discriminate between these two models based on the number of detected high-redshift quasar progenitors. For example, while the upcoming ATHENA mission is expected to detect ˜0.16 (I.e., essentially zero) quasars at z ˜ 7 in R h = ct, it should detect ˜160 in ΛCDM—a quantitatively compelling difference.

Sky Mining - Application to Photomorphic Redshift Estimation

NASA Astrophysics Data System (ADS)

Nayak, Pragyansmita

The field of astronomy has evolved from the ancient craft of observing the sky. In it's present form, astronomers explore the cosmos not just by observing through the tiny visible window used by our eyes, but also by exploiting the electromagnetic spectrum from radio waves to gamma rays. The domain is undoubtedly at the forefront of data-driven science. The data growth rate is expected to be around 50%--100% per year. This data explosion is attributed largely to the large-scale wide and deep surveys of the different regions of the sky at multiple wavelengths (both ground and space-based surveys). This dissertation describes the application of machine learning methods to the estimation of galaxy redshifts leveraging such a survey data. Galaxy is a large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space. Our view of the universe is closely tied to our understanding of galaxy formation. Thus, a better understanding of the relative location of the multitudes of galaxies is crucial. The position of each galaxy can be characterized using three coordinates. Right Ascension (ra) and Declination (dec) are the two coordinates that locate the galaxy in two dimensions on the plane of the sky. It is relatively straightforward to measure them. In contrast, fixing the third coordinate that is the galaxy's distance from the observer along the line of sight (redshift 'z') is considerably more challenging. "Spectroscopic redshift" method gives us accurate and precise measurements of z. However, it is extremely time-intensive and unusable for faint objects. Additionally, the rate at which objects are being identified via photometric surveys far exceeds the rate at which the spectroscopic redshift measurements can keep pace in determining their distance. As the surveys go deeper into the sky, the proportion of faint objects being identified also continues to increase. In order to tackle both these drawbacks increasing in severity every day, alternative method "Photometric redshift" has been studied in the past. It uses the brightness of the object viewed through various standard filters, each of which lets through a relatively broad spectrum of colors. However, these methods are bound by the degeneracy problem (objects with different color profiles have the same redshift) which leads to low predictive accuracy. As part of our study, we are looking beyond color attributes to identify other measured attributes as degeneracy resolvers as well as generate estimators that are highly accurate; termed as "Photomorphic redshift" estimators. The present study investigates the photometric information of the objects such as color and magnitude (= observed flux) and morphology attributes such as shape, size, orientation and concentration in the different wavelengths. The specific type of magnitude used in this study are the PSF, Fiber and Petrosian magnitude. The morphology attributes are the ratio of Fiber to Petrosian magnitude, concentration index and Petrosian radius. All these attributes are in the five bands ugriz of the Sloan Digital Sky Survey (SDSS). Machine learning techniques based on Naive Bayes (NB), Bayesian Network (BN) and Generalized Linear Model (GLM) are researched to better understand their applicability, advantages and resulting predictive performance in terms of efficiency and accuracy. Note: The SDSS Data Release (DR) 10 data was used in the executed experiments (total of 700,777 galaxies with forty-five attributes associated with each galaxy). The significant findings of the present work are as follows: 1. Magnitude and morphology attributes have been found to be successful degeneracy resolvers. 2. Magnitude and morphology attributes have been found to be better redshift estimators than color attributes alone. 3. Naive Bayes, Bayesian Network and GLM have been found to be viable redshift estimation methods. Attribute selection is an important factor in computational performance. 4. In addition to the redshift estimate, the likelihood distribution of the estimate is even more useful, and my Bayesian Network models provide that information. This is particularly useful in ensemble methods as well as the kernel for mass distribution in the universe. 5. The generated Bayesian Network models can be applied to any of the variables, not just limited to redshift. Example applications include quality analysis and missing value imputation. Different types of Bayesian Network learning algorithms---constraint-based, score-based and hybrid---were investigated in detail.

Studying Lyman-alpha escape and reionization in Green Pea galaxies

NASA Astrophysics Data System (ADS)

Yang, Huan; Malhotra, Sangeeta; Rhoads, James E.; Gronke, Max; Leitherer, Claus; Wofford, Aida; Dijkstra, Mark

2017-01-01

Green Pea galaxies are low-redshift galaxies with extreme [OIII]5007 emission line. We built the first statistical sample of Green Peas observed by HST/COS and used them as analogs of high-z Lyman-alpha emitters to study Ly-alpha escape and Ly-alpha sizes. Using the HST/COS 2D spectra, we found that Ly-alpha sizes of Green Peas are larger than the UV continuum sizes. We found many correlations between Ly-alpha escape fraction and galactic properties -- dust extinction, Ly-alpha kinematic features, [OIII]/[OII] ratio, and gas outflow velocities. We fit an empirical relation to predict Ly-alpha escape fraction from dust extinction and Ly-alpha red-peak velocity. In the JWST era, we can use this relation to derive the IGM HI column density along the line of sight of each high-z Ly-alpha emitter and probe the reionization process.

Charting the Parameter Space of the 21-cm Power Spectrum

NASA Astrophysics Data System (ADS)

Cohen, Aviad; Fialkov, Anastasia; Barkana, Rennan

2018-05-01

The high-redshift 21-cm signal of neutral hydrogen is expected to be observed within the next decade and will reveal epochs of cosmic evolution that have been previously inaccessible. Due to the lack of observations, many of the astrophysical processes that took place at early times are poorly constrained. In recent work we explored the astrophysical parameter space and the resulting large variety of possible global (sky-averaged) 21-cm signals. Here we extend our analysis to the fluctuations in the 21-cm signal, accounting for those introduced by density and velocity, Lyα radiation, X-ray heating, and ionization. While the radiation sources are usually highlighted, we find that in many cases the density fluctuations play a significant role at intermediate redshifts. Using both the power spectrum and its slope, we show that properties of high-redshift sources can be extracted from the observable features of the fluctuation pattern. For instance, the peak amplitude of ionization fluctuations can be used to estimate whether heating occurred early or late and, in the early case, to also deduce the cosmic mean ionized fraction at that time. The slope of the power spectrum has a more universal redshift evolution than the power spectrum itself and can thus be used more easily as a tracer of high-redshift astrophysics. Its peaks can be used, for example, to estimate the redshift of the Lyα coupling transition and the redshift of the heating transition (and the mean gas temperature at that time). We also show that a tight correlation is predicted between features of the power spectrum and of the global signal, potentially yielding important consistency checks.

GALAXY CLUSTERS DISCOVERED VIA THE SUNYAEV-ZEL'DOVICH EFFECT IN THE 2500-SQUARE-DEGREE SPT-SZ SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bleem, L. E.; Stalder, B.; de Haan, T.

2015-01-29

We present a catalog of galaxy clusters selected via their Sunyaev-Zel'dovich (SZ) effect signature from 2500 deg(2) of South Pole Telescope (SPT) data. This work represents the complete sample of clusters detected at high significance in the 2500 deg(2) SPT-SZ survey, which was completed in 2011. A total of 677 (409) cluster candidates are identified above a signal-to-noise threshold of ξ = 4.5 (5.0). Ground- and space-based optical and near-infrared (NIR) imaging confirms overdensities of similarly colored galaxies in the direction of 516 (or 76%) of the ξ > 4.5 candidates and 387 (or 95%) of the ξ > 5 candidates, the measured purity is consistent with expectations from simulations. Of these confirmed clusters, 415 were first identified in SPT data, including 251 new discoveries reported in this work. We estimate photometric redshifts for all candidates with identified optical and/or NIR counterparts, we additionally report redshifts derived from spectroscopic observations for 141 of these systems. The mass threshold of the catalog is roughly independent of redshift above z ~ 0.25 leading to a sample of massive clusters that extends to high redshift. The median mass of the sample is M (500c)(ρ(crit))more » $$\\sim 3.5\\times 10^{14}\\,M_\\odot \\,h_{70}^{-1}$$, the median redshift is z (med) = 0.55, and the highest-redshift systems are at z > 1.4. The combination of large redshift extent, clean selection, and high typical mass makes this cluster sample of particular interest for cosmological analyses and studies of cluster formation and evolution.« less

GALAXY CLUSTERS DISCOVERED VIA THE SUNYAEV-ZEL'DOVICH EFFECT IN THE 2500-SQUARE-DEGREE SPT-SZ SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bleem, L. E.; Stalder, B.; de Haan, T.

2015-01-29

We present a catalog of galaxy clusters selected via their Sunyaev-Zel'dovich (SZ) effect signature from 2500 deg(2) of South Pole Telescope (SPT) data. This work represents the complete sample of clusters detected at high significance in the 2500 deg(2) SPT-SZ survey, which was completed in 2011. A total of 677 (409) cluster candidates are identified above a signal-to-noise threshold of xi = 4.5 (5.0). Ground-and space-based optical and near-infrared (NIR) imaging confirms overdensities of similarly colored galaxies in the direction of 516 (or 76%) of the xi > 4.5 candidates and 387 (or 95%) of the xi > 5 candidates;more » the measured purity is consistent with expectations from simulations. Of these confirmed clusters, 415 were first identified in SPT data, including 251 new discoveries reported in this work. We estimate photometric redshifts for all candidates with identified optical and/or NIR counterparts; we additionally report redshifts derived from spectroscopic observations for 141 of these systems. The mass threshold of the catalog is roughly independent of redshift above z similar to 0.25 leading to a sample of massive clusters that extends to high redshift. The median mass of the sample is M-500c(rho(crit)) similar to 3.5 x 10(14) M-circle dot h(70)(-1) 70, the median redshift is z(med) = 0.55, and the highest-redshift systems are at z > 1.4. The combination of large redshift extent, clean selection, and high typical mass makes this cluster sample of particular interest for cosmological analyses and studies of cluster formation and evolution.« less

GALAXY CLUSTERS DISCOVERED VIA THE SUNYAEV-ZEL'DOVICH EFFECT IN THE 2500-SQUARE-DEGREE SPT-SZ SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.

2015-02-01

We present a catalog of galaxy clusters selected via their Sunyaev-Zel'dovich (SZ) effect signature from 2500 deg{sup 2} of South Pole Telescope (SPT) data. This work represents the complete sample of clusters detected at high significance in the 2500 deg{sup 2} SPT-SZ survey, which was completed in 2011. A total of 677 (409) cluster candidates are identified above a signal-to-noise threshold of ξ = 4.5 (5.0). Ground- and space-based optical and near-infrared (NIR) imaging confirms overdensities of similarly colored galaxies in the direction of 516 (or 76%) of the ξ > 4.5 candidates and 387 (or 95%) of the ξ > 5more » candidates; the measured purity is consistent with expectations from simulations. Of these confirmed clusters, 415 were first identified in SPT data, including 251 new discoveries reported in this work. We estimate photometric redshifts for all candidates with identified optical and/or NIR counterparts; we additionally report redshifts derived from spectroscopic observations for 141 of these systems. The mass threshold of the catalog is roughly independent of redshift above z ∼ 0.25 leading to a sample of massive clusters that extends to high redshift. The median mass of the sample is M {sub 500c}(ρ{sub crit}) ∼3.5×10{sup 14} M{sub ⊙} h{sub 70}{sup −1}, the median redshift is z {sub med} = 0.55, and the highest-redshift systems are at z > 1.4. The combination of large redshift extent, clean selection, and high typical mass makes this cluster sample of particular interest for cosmological analyses and studies of cluster formation and evolution.« less

Jellyfish: the origin and distribution of extreme ram-pressure stripping events in massive galaxy clusters

NASA Astrophysics Data System (ADS)

McPartland, Conor; Ebeling, Harald; Roediger, Elke; Blumenthal, Kelly

2016-01-01

We investigate the observational signatures and physical origin of ram-pressure stripping (RPS) in 63 massive galaxy clusters at z = 0.3-0.7, based on images obtained with the Hubble Space Telescope. Using a training set of a dozen `jellyfish' galaxies identified earlier in the same imaging data, we define morphological criteria to select 211 additional, less obvious cases of RPS. Spectroscopic follow-up observations of 124 candidates so far confirmed 53 as cluster members. For the brightest and most favourably aligned systems, we visually derive estimates of the projected direction of motion based on the orientation of apparent compression shocks and debris trails. Our findings suggest that the onset of these events occurs primarily at large distances from the cluster core (>400 kpc), and that the trajectories of the affected galaxies feature high-impact parameters. Simple models show that such trajectories are highly improbable for galaxy infall along filaments but common for infall at high velocities, even after observational biases are accounted for, provided the duration of the resulting RPS events is ≲500 Myr. We thus tentatively conclude that extreme RPS events are preferentially triggered by cluster mergers, an interpretation that is supported by the disturbed dynamical state of many of the host clusters. This hypothesis implies that extreme RPS might occur also near the cores of merging poor clusters or even merging groups of galaxies. Finally, we present nine additional `jellyfish" galaxies at z > 0.3 discovered by us, thereby doubling the number of such systems known at intermediate redshift.

The Arecibo Galaxy Environment Survey - VII. A dense filament with extremely long H I streams

NASA Astrophysics Data System (ADS)

Taylor, R.; Minchin, R. F.; Herbst, H.; Davies, J. I.; Rodriguez, R.; Vazquez, C.

2014-09-01

We present completed observations of the NGC 7448 galaxy group and background volume as part of the blind neutral hydrogen Arecibo Galaxy Environment Survey. Our observations cover a region spanning 5°× 4°, over a redshift range of approximately -2000

Cross-correlation redshift calibration without spectroscopic calibration samples in DES Science Verification Data

NASA Astrophysics Data System (ADS)

Davis, C.; Rozo, E.; Roodman, A.; Alarcon, A.; Cawthon, R.; Gatti, M.; Lin, H.; Miquel, R.; Rykoff, E. S.; Troxel, M. A.; Vielzeuf, P.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Doel, P.; Drlica-Wagner, A.; Fausti Neto, A.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Giannantonio, T.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Jain, B.; James, D. J.; Jeltema, T.; Krause, E.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; March, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Ogando, R. L. C.; Plazas, A. A.; Romer, A. K.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Vikram, V.; Walker, A. R.; Wechsler, R. H.

2018-06-01

Galaxy cross-correlations with high-fidelity redshift samples hold the potential to precisely calibrate systematic photometric redshift uncertainties arising from the unavailability of complete and representative training and validation samples of galaxies. However, application of this technique in the Dark Energy Survey (DES) is hampered by the relatively low number density, small area, and modest redshift overlap between photometric and spectroscopic samples. We propose instead using photometric catalogues with reliable photometric redshifts for photo-z calibration via cross-correlations. We verify the viability of our proposal using redMaPPer clusters from the Sloan Digital Sky Survey (SDSS) to successfully recover the redshift distribution of SDSS spectroscopic galaxies. We demonstrate how to combine photo-z with cross-correlation data to calibrate photometric redshift biases while marginalizing over possible clustering bias evolution in either the calibration or unknown photometric samples. We apply our method to DES Science Verification (DES SV) data in order to constrain the photometric redshift distribution of a galaxy sample selected for weak lensing studies, constraining the mean of the tomographic redshift distributions to a statistical uncertainty of Δz ˜ ±0.01. We forecast that our proposal can, in principle, control photometric redshift uncertainties in DES weak lensing experiments at a level near the intrinsic statistical noise of the experiment over the range of redshifts where redMaPPer clusters are available. Our results provide strong motivation to launch a programme to fully characterize the systematic errors from bias evolution and photo-z shapes in our calibration procedure.

Cross-correlation redshift calibration without spectroscopic calibration samples in DES Science Verification Data

DOE PAGES

Davis, C.; Rozo, E.; Roodman, A.; ...

2018-03-26

Galaxy cross-correlations with high-fidelity redshift samples hold the potential to precisely calibrate systematic photometric redshift uncertainties arising from the unavailability of complete and representative training and validation samples of galaxies. However, application of this technique in the Dark Energy Survey (DES) is hampered by the relatively low number density, small area, and modest redshift overlap between photometric and spectroscopic samples. We propose instead using photometric catalogs with reliable photometric redshifts for photo-z calibration via cross-correlations. We verify the viability of our proposal using redMaPPer clusters from the Sloan Digital Sky Survey (SDSS) to successfully recover the redshift distribution of SDSS spectroscopic galaxies. We demonstrate how to combine photo-z with cross-correlation data to calibrate photometric redshift biases while marginalizing over possible clustering bias evolution in either the calibration or unknown photometric samples. We apply our method to DES Science Verification (DES SV) data in order to constrain the photometric redshift distribution of a galaxy sample selected for weak lensing studies, constraining the mean of the tomographic redshift distributions to a statistical uncertainty ofmore » $$\\Delta z \\sim \\pm 0.01$$. We forecast that our proposal can in principle control photometric redshift uncertainties in DES weak lensing experiments at a level near the intrinsic statistical noise of the experiment over the range of redshifts where redMaPPer clusters are available. Here, our results provide strong motivation to launch a program to fully characterize the systematic errors from bias evolution and photo-z shapes in our calibration procedure.« less

Cross-correlation redshift calibration without spectroscopic calibration samples in DES Science Verification Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, C.; Rozo, E.; Roodman, A.

Galaxy cross-correlations with high-fidelity redshift samples hold the potential to precisely calibrate systematic photometric redshift uncertainties arising from the unavailability of complete and representative training and validation samples of galaxies. However, application of this technique in the Dark Energy Survey (DES) is hampered by the relatively low number density, small area, and modest redshift overlap between photometric and spectroscopic samples. We propose instead using photometric catalogs with reliable photometric redshifts for photo-z calibration via cross-correlations. We verify the viability of our proposal using redMaPPer clusters from the Sloan Digital Sky Survey (SDSS) to successfully recover the redshift distribution of SDSS spectroscopic galaxies. We demonstrate how to combine photo-z with cross-correlation data to calibrate photometric redshift biases while marginalizing over possible clustering bias evolution in either the calibration or unknown photometric samples. We apply our method to DES Science Verification (DES SV) data in order to constrain the photometric redshift distribution of a galaxy sample selected for weak lensing studies, constraining the mean of the tomographic redshift distributions to a statistical uncertainty ofmore » $$\\Delta z \\sim \\pm 0.01$$. We forecast that our proposal can in principle control photometric redshift uncertainties in DES weak lensing experiments at a level near the intrinsic statistical noise of the experiment over the range of redshifts where redMaPPer clusters are available. Here, our results provide strong motivation to launch a program to fully characterize the systematic errors from bias evolution and photo-z shapes in our calibration procedure.« less

The Las Campanas Infrared Survey - II. Photometric redshifts, comparison with models and clustering evolution

NASA Astrophysics Data System (ADS)

Firth, A. E.; Somerville, R. S.; McMahon, R. G.; Lahav, O.; Ellis, R. S.; Sabbey, C. N.; McCarthy, P. J.; Chen, H.-W.; Marzke, R. O.; Wilson, J.; Abraham, R. G.; Beckett, M. G.; Carlberg, R. G.; Lewis, J. R.; Mackay, C. D.; Murphy, D. C.; Oemler, A. E.; Persson, S. E.

2002-05-01

The Las Campanas Infrared (LCIR) Survey, using the Cambridge Infra-Red Survey Instrument (CIRSI), reaches H ~21 over nearly 1deg2 . In this paper we present results from 744arcmin2 centred on the Hubble Deep Field South for which UBVRI optical data are publicly available. Making conservative magnitude cuts to ensure spatial uniformity, we detect 3177 galaxies to H =20.0 in 744arcmin2 and a further 842 to H =20.5 in a deeper subregion of 407arcmin2 . We compare the observed optical-infrared (IR) colour distributions with the predictions of semi-analytic hierarchical models and find reasonable agreement. We also determine photometric redshifts, finding a median redshift of ~0.55. We compare the redshift distributions N (z ) of E, Sbc, Scd and Im spectral types with models, showing that the observations are inconsistent with simple passive-evolution models while semi-analytic models provide a reasonable fit to the total N (z ) but underestimate the number of z ~1 red spectral types relative to bluer spectral types. We also present N (z ) for samples of extremely red objects (EROs) defined by optical-IR colours. We find that EROs with R -H >4 and H <20.5 have a median redshift z m ~1 while redder colour cuts have slightly higher z m . In the magnitude range 194 comprise ~18 per cent of the observed galaxy population, while in semi-analytic models they contribute only ~4 per cent. We also determine the angular correlation function w (θ ) for magnitude, colour, spectral type and photometric redshift-selected subsamples of the data and use the photometric redshift distributions to derive the spatial clustering statistic ξ (r ) as a function of spectral type and redshift out to z ~1.2. Parametrizing ξ (r ) by ξ (r c ,z )=[r c /r *(z )]-1.8 , where r c is in comoving coordinates, we find that r *(z ) increases by a factor of 1.5-2 from z =0 to z ~1.2. We interpret this as a selection effect - the galaxies selected at z ~1.2 are intrinsically very luminous, about 1-1.5mag brighter than L *. When galaxies are selected by absolute magnitude, we find no evidence for evolution in r * over this redshift range. Extrapolated to z =0, we find r *(z =0)~6.5h -1 Mpc for red galaxies and r *(z =0)~2-4h -1 Mpc for blue galaxies. We also find that, while the angular clustering amplitude of EROs with R -H >4 or I -H >3 is up to four times that of the whole galaxy population, the spatial clustering length r *(z =1) is ~7.5-10.5h -1 Mpc, which is only a factor of ~1.7 times r *(z =1) for R -H <4 and I -H <3 galaxies lying in a similar redshift and luminosity range. This difference is similar to that observed between red and blue galaxies at low redshifts.

Quasars at the High Redshift Frontier

NASA Astrophysics Data System (ADS)

Bosman, Sarah E. I.

2017-11-01

In recent years the formation of primordial galaxies, cosmic metal enrichment, and hydrogen reionisation have been studied using both refined observations and powerful numerical simulations. High-redshift quasars have become a ubiquitous tool in the study of this era with more than 115 quasars now spectroscopically confirmed at z>6.0. In this thesis, I use spectra of high-redshift quasars to provide improved observational constraints through a mixture of existing and new techniques. I first investigate the claim of neutral gas around the most distant known quasar, ULASJ1120+0641(J1120), with a cosmological redshift of z=7.1. Its spectrum shows a relatively weak Lyman-α emission line, which has been interpreted as evidence of absorption by neutral gas. Attributing this to a Gunn-Peterson damping wing has led to claims that the intergalactic medium is at least 10% neutral at that redshift. However, these claims rely on a reconstruction of the unabsorbed quasar emission. Initial attempts using composite spectra of lower-redshift quasars mismatched the CIV emission line of J1120, a feature known to correlate with Lyman-α and which is strongly blueshifted in J1120. I attempt to establish whether this mismatch could explain the apparently weak Lyman-α emission line. I find that among a C IV-matched sample the Lyman-α line of J1120 is not anomalous. This raises doubts as to the interpretation of absorbed Lyman-α emission lines in the context of reionisation. I then use a high quality X-Shooter spectrum of the same z=7 quasar to measure the abundances of diffuse metals within one billion years of the Big Bang. I measure the occurrence rates of CIV, CII, SiII, FeII and MgII, producing the first measurement at z>6 for many of these ions. I find that the incidence of CIV systems is consistent with a continuing decline in the total mass density of highly ionized metals, a trend seen at lower redshifts. The ratio CII/CIV, however, seems to remain constant or increase with redshift, in line with predictions from models which include a decline of the ionising ultraviolet background. The evolution in MgII appears somewhat more complex; while the number density of strong systems continues to decline at high redshift,the number density of weak systems remains high and may even increase. This could signal an increase with redshift in the cross-section of low-ionisation metals. Large numbers of weak MgII systems are also seen at z˜2, suggesting they were already in place when reionisation was ending. I use this X-Shooter spectrum to study metal absorbers associated with the z=7 quasar itself. I find that one such absorber shows signs of only partially covering the line-of-sight, and investigate the possible implications for the quasar's environment. Finally, I investigate the evolution of the intergalactic medium's Lyman-α opacity using spectra of quasars at 5.7

High Redshift GRBs

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Cannizzo, John K.

2012-01-01

The Swift mission has opened a new, high redshift window on the universe. In this review we provide an overview of gamma-ray burst (GRB) science, describe the Swift mission, discuss high-z GRBs and tools for high-z studies, and look forward at future capabilities. A new mission concept - Lobster - is described that would monitor the X-ray sky at order of magnitude higher sensitivity than current missions.

Formation of a Malin 1 analogue in IllustrisTNG by stimulated accretion

NASA Astrophysics Data System (ADS)

Zhu, Qirong; Xu, Dandan; Gaspari, Massimo; Rodriguez-Gomez, Vicente; Nelson, Dylan; Vogelsberger, Mark; Torrey, Paul; Pillepich, Annalisa; Zjupa, Jolanta; Weinberger, Rainer; Marinacci, Federico; Pakmor, Rüdiger; Genel, Shy; Li, Yuexing; Springel, Volker; Hernquist, Lars

2018-06-01

The galaxy Malin 1 contains the largest stellar disk known but the formation mechanism of this structure has been elusive. In this paper, we report a Malin 1 analogue in the 100 Mpc IllustrisTNG simulation and describe its formation history. At redshift zero, this massive galaxy, having a maximum circular velocity Vmax of 430 km s-1, contains a 100 kpc gas/stellar disk with morphology similar to Malin 1. The simulated galaxy reproduces well many observed features of Malin 1's vast disk, including its stellar ages, metallicities, and gas rotation curve. We trace the extended disk back in time and find that a large fraction of the cold gas at redshift zero originated from the cooling of hot halo gas, triggered by the merger of a pair of intruding galaxies. Our finding provides a novel way to form large galaxy disks as extreme as Malin 1 within the current galaxy formation framework.

“Direct” Gas-phase Metallicity in Local Analogs of High-redshift Galaxies: Empirical Metallicity Calibrations for High-redshift Star-forming Galaxies

NASA Astrophysics Data System (ADS)

Bian, Fuyan; Kewley, Lisa J.; Dopita, Michael A.

2018-06-01

We study the direct gas-phase oxygen abundance using the well-detected auroral line [O III]λ4363 in the stacked spectra of a sample of local analogs of high-redshift galaxies. These local analogs share the same location as z ∼ 2 star-forming galaxies on the [O III]λ5007/Hβ versus [N II]λ6584/Hα Baldwin–Phillips–Terlevich diagram. This type of analog has the same ionized interstellar medium (ISM) properties as high-redshift galaxies. We establish empirical metallicity calibrations between the direct gas-phase oxygen abundances (7.8< 12+{log}({{O}}/{{H}})< 8.4) and the N2 (log([N II]λ6584/Hα))/O3N2 (log(([O III]λ5007/Hβ)/([N II]λ6584/Hα))) indices in our local analogs. We find significant systematic offsets between the metallicity calibrations for our local analogs of high-redshift galaxies and those derived from the local H II regions and a sample of local reference galaxies selected from the Sloan Digital Sky Survey (SDSS). The N2 and O3N2 metallicities will be underestimated by 0.05–0.1 dex relative to our calibration, if one simply applies the local metallicity calibration in previous studies to high-redshift galaxies. Local metallicity calibrations also cause discrepancies of metallicity measurements in high-redshift galaxies using the N2 and O3N2 indicators. In contrast, our new calibrations produce consistent metallicities between these two indicators. We also derive metallicity calibrations for R23 (log(([O III]λλ4959,5007+[O II]λλ3726,3729)/Hβ)), O32(log([O III]λλ4959,5007/[O II]λλ3726,3729)), {log}([O III]λ5007/Hβ), and log([Ne III]λ3869/[O II]λ3727) indices in our local analogs, which show significant offset compared to those in the SDSS reference galaxies. By comparing with MAPPINGS photoionization models, the different empirical metallicity calibration relations in the local analogs and the SDSS reference galaxies can be shown to be primarily due to the change of ionized ISM conditions. Assuming that temperature structure variations are minimal and ISM conditions do not change dramatically from z ∼ 2 to z ∼ 5, these empirical calibrations can be used to measure relative metallicities in galaxies with redshifts up to z ∼ 5.0 in ground-based observations.

Finding high-order analytic post-Newtonian parameters from a high-precision numerical self-force calculation

NASA Astrophysics Data System (ADS)

Shah, Abhay G.; Friedman, John L.; Whiting, Bernard F.

2014-03-01

We present a novel analytic extraction of high-order post-Newtonian (pN) parameters that govern quasicircular binary systems. Coefficients in the pN expansion of the energy of a binary system can be found from corresponding coefficients in an extreme-mass-ratio inspiral computation of the change ΔU in the redshift factor of a circular orbit at fixed angular velocity. Remarkably, by computing this essentially gauge-invariant quantity to accuracy greater than one part in 10225, and by assuming that a subset of pN coefficients are rational numbers or products of π and a rational, we obtain the exact analytic coefficients. We find the previously unexpected result that the post-Newtonian expansion of ΔU (and of the change ΔΩ in the angular velocity at fixed redshift factor) have conservative terms at half-integral pN order beginning with a 5.5 pN term. This implies the existence of a corresponding 5.5 pN term in the expansion of the energy of a binary system. Coefficients in the pN series that do not belong to the subset just described are obtained to accuracy better than 1 part in 10265-23n at nth pN order. We work in a radiation gauge, finding the radiative part of the metric perturbation from the gauge-invariant Weyl scalar ψ0 via a Hertz potential. We use mode-sum renormalization, and find high-order renormalization coefficients by matching a series in L=ℓ+1/2 to the large-L behavior of the expression for ΔU. The nonradiative parts of the perturbed metric associated with changes in mass and angular momentum are calculated in the Schwarzschild gauge.

Untitled Document

Science.gov Websites

(Linear Redshift scale), with magnitude residuals from best fit cosmology. Postscript Figure 9: Age of the an equation of state w = p/rho. Postscript Figure 2: Hubble Diagram with 42 High- Redshift Supernovae

STELLAR POPULATIONS AND EVOLUTION OF EARLY-TYPE CLUSTER GALAXIES: CONSTRAINTS FROM OPTICAL IMAGING AND SPECTROSCOPY OF z = 0.5-0.9 GALAXY CLUSTERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jorgensen, Inger; Chiboucas, Kristin, E-mail: ijorgensen@gemini.edu, E-mail: kchiboucas@gemini.edu

2013-03-15

We present an analysis of stellar populations and evolutionary history of galaxies in three similarly rich galaxy clusters MS0451.6-0305 (z = 0.54), RXJ0152.7-1357 (z = 0.83), and RXJ1226.9+3332 (z = 0.89). Our analysis is based on high signal-to-noise ground-based optical spectroscopy and Hubble Space Telescope imaging for a total of 17-34 members in each cluster. Using the dynamical masses together with the effective radii and the velocity dispersions, we find no indication of evolution of sizes or velocity dispersions with redshift at a given galaxy mass. We establish the Fundamental Plane (FP) and scaling relations between absorption line indices andmore » velocity dispersions. We confirm that the FP is steeper at z Almost-Equal-To 0.86 compared to the low-redshift FP, indicating that under the assumption of passive evolution the formation redshift, z{sub form}, depends on the galaxy velocity dispersion (or alternatively mass). At a velocity dispersion of {sigma} = 125 km s{sup -1} (Mass = 10{sup 10.55} M{sub Sun }) we find z{sub form} = 1.24 {+-} 0.05, while at {sigma} = 225 km s{sup -1} (Mass = 10{sup 11.36} M{sub Sun }) the formation redshift is z{sub form} = 1.95{sup +0.3}{sub -0.2}, for a Salpeter initial mass function. The three clusters follow similar scaling relations between absorption line indices and velocity dispersions as those found for low-redshift galaxies. The zero point offsets for the Balmer lines depend on cluster redshifts. However, the offsets indicate a slower evolution, and therefore higher formation redshift, than the zero point differences found from the FP, if interpreting the data using a passive evolution model. Specifically, the strength of the higher order Balmer lines H{delta} and H{gamma} implies z{sub form} > 2.8. The scaling relations for the metal indices in general show small and in some cases insignificant zero point offsets, favoring high formation redshifts for a passive evolution model. Based on the absorption line indices and recent stellar population models from Thomas et al., we find that MS0451.6-0305 has a mean metallicity [M/H] approximately 0.2 dex below that of the other clusters and our low-redshift sample. We confirm our previous result that RXJ0152.7-1357 has a mean abundance ratio [{alpha}/Fe] approximately 0.3 dex higher than that of the other clusters. The differences in [M/H] and [{alpha}/Fe] between the high-redshift clusters and the low-redshift sample are inconsistent with a passive evolution scenario for early-type cluster galaxies over the redshift interval studied. Low-level star formation may be able to bring the metallicity of MS0451.6-0305 in agreement with the low-redshift sample, while we speculate whether galaxy mergers can lead to sufficiently large changes in the abundance ratios for the RXJ0152.7-1357 galaxies to allow them to reach the low-redshift sample values in the time available.« less

Galaxies and large scale structure at high redshifts

PubMed Central

Steidel, Charles C.

1998-01-01

It is now straightforward to assemble large samples of very high redshift (z ∼ 3) field galaxies selected by their pronounced spectral discontinuity at the rest frame Lyman limit of hydrogen (at 912 Å). This makes possible both statistical analyses of the properties of the galaxies and the first direct glimpse of the progression of the growth of their large-scale distribution at such an early epoch. Here I present a summary of the progress made in these areas to date and some preliminary results of and future plans for a targeted redshift survey at z = 2.7–3.4. Also discussed is how the same discovery method may be used to obtain a “census” of star formation in the high redshift Universe, and the current implications for the history of galaxy formation as a function of cosmic epoch. PMID:9419319

High-resolution observations of radio-source hot spots at 329 MHz

NASA Technical Reports Server (NTRS)

Linfield, R.; Simon, R. S.

1984-01-01

The hot spots of several luminous double radio sources have been observed at 329 MHz with VLBI at fringe spacings ranging from 0.05 to 0.70 arcsec. Two out of two high-redshift (z = about 0.5) sources, but only one of six low-redshift (z = about 0.05) sources, were detected. For the low-redshift source (3C 234) which was detected, either the hot spot is larger at 329 MHz than at 15 GHz, or else the brightness contrast between it and the surrounding lobe is lower at the lower frequency.

Detecting Patchy Reionization in the Cosmic Microwave Background.

PubMed

Smith, Kendrick M; Ferraro, Simone

2017-07-14

Upcoming cosmic microwave background (CMB) experiments will measure temperature fluctuations on small angular scales with unprecedented precision. Small-scale CMB fluctuations are a mixture of late-time effects: gravitational lensing, Doppler shifting of CMB photons by moving electrons [the kinematic Sunyaev-Zel'dovich (KSZ) effect], and residual foregrounds. We propose a new statistic which separates the KSZ signal from the others, and also allows the KSZ signal to be decomposed in redshift bins. The decomposition extends to high redshift and does not require external data sets such as galaxy surveys. In particular, the high-redshift signal from patchy reionization can be cleanly isolated, enabling future CMB experiments to make high-significance and qualitatively new measurements of the reionization era.

Keck Spectroscopy of Redshift z ~ 3 Galaxies in the Hubble Deep Field

NASA Astrophysics Data System (ADS)

Lowenthal, James D.; Koo, David C.; Guzmán, Rafael; Gallego, Jesús; Phillips, Andrew C.; Faber, S. M.; Vogt, Nicole P.; Illingworth, Garth D.; Gronwall, Caryl

1997-05-01

We have obtained spectra with the 10 m Keck telescope of a sample of 24 galaxies having colors consistent with star-forming galaxies at redshifts 2 <~ z <~ 4.5 in the Hubble deep field (HDF). Eleven of these galaxies are confirmed to be at high redshift (zmed = 3.0), one is at z = 0.5, and the other 12 have uncertain redshifts but have spectra consistent with their being at z > 2. The spectra of the confirmed high-redshift galaxies show a diversity of features, including weak Lyα emission, strong Lyα breaks or damped Lyα absorption profiles, and the stellar and interstellar rest-UV absorption lines common to local starburst galaxies and high-redshift star-forming galaxies reported recently by others. The narrow profiles and low equivalent widths of C IV, Si IV, and N V absorption lines may imply low stellar metallicities. Combined with the five high-redshift galaxies in the HDF previously confirmed with Keck spectra by Steidel et al. (1996a), the 16 confirmed sources yield a comoving volume density of n >= 2.4 × 10-4 h350 Mpc-3 for q0 = 0.05, or n >= 1.1 × 10-3 h350 Mpc-3 for q0 = 0.5. These densities are 3-4 times higher than the recent estimates of Steidel et al. (1996b) based on ground-based photometry with slightly brighter limits and are comparable to estimates of the local volume density of galaxies brighter than L*. The high-redshift density measurement is only a lower limit and could be almost 3 times higher still if all 29 of the unconfirmed candidates in our original sample, including those not observed, are indeed also at high redshift. The galaxies are small but luminous, with half-light radii 1.8 < r1/2 < 6.5 h-150 kpc and absolute magnitudes -21.5 > MB > -23. The HST images show a wide range of morphologies, including several with very close, small knots of emission embedded in wispy extended structures. Using rest-frame UV continuum fluxes with no dust correction, we calculate star formation rates in the range 7-24 or 3-9 h-250 Msolar yr-1 for q0 = 0.05 and q0 = 0.5, respectively. These rates overlap those for local spiral and H II galaxies today, although they could be more than twice as high if dust extinction in the UV is significant. If the objects at z = 3 were simply to fade by 5 mag (assuming a 107 yr burst and passive evolution) without mergers in the 14 Gyr between then and now (for q0 = 0.05, h50 = 1.0), they would resemble average dwarf elliptical/spheroidal galaxies in both luminosity and size. However, the variety of morphologies and the high number density of z = 3 galaxies in the HDF suggest that they represent a range of physical processes and stages of galaxy formation and evolution, rather than any one class of object, such as massive ellipticals. A key issue remains the measurement of masses. These high-redshift objects are likely to be the low-mass, starbursting building blocks of more massive galaxies seen today. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology, and with the NASA/ESA Hubble Space Telescope, which is operated by AURA, Inc., under contract with NASA.

Cluster mass calibration at high redshift: HST weak lensing analysis of 13 distant galaxy clusters from the South Pole Telescope Sunyaev-Zel'dovich Survey

NASA Astrophysics Data System (ADS)

Schrabback, T.; Applegate, D.; Dietrich, J. P.; Hoekstra, H.; Bocquet, S.; Gonzalez, A. H.; von der Linden, A.; McDonald, M.; Morrison, C. B.; Raihan, S. F.; Allen, S. W.; Bayliss, M.; Benson, B. A.; Bleem, L. E.; Chiu, I.; Desai, S.; Foley, R. J.; de Haan, T.; High, F. W.; Hilbert, S.; Mantz, A. B.; Massey, R.; Mohr, J.; Reichardt, C. L.; Saro, A.; Simon, P.; Stern, C.; Stubbs, C. W.; Zenteno, A.

2018-02-01

We present an HST/Advanced Camera for Surveys (ACS) weak gravitational lensing analysis of 13 massive high-redshift (zmedian = 0.88) galaxy clusters discovered in the South Pole Telescope (SPT) Sunyaev-Zel'dovich Survey. This study is part of a larger campaign that aims to robustly calibrate mass-observable scaling relations over a wide range in redshift to enable improved cosmological constraints from the SPT cluster sample. We introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scaling relations significantly. First, we efficiently remove cluster members from the source sample by selecting very blue galaxies in V - I colour. Our estimate of the source redshift distribution is based on Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) data, where we carefully mimic the source selection criteria of the cluster fields. We apply a statistical correction for systematic photometric redshift errors as derived from Hubble Ultra Deep Field data and verified through spatial cross-correlations. We account for the impact of lensing magnification on the source redshift distribution, finding that this is particularly relevant for shallower surveys. Finally, we account for biases in the mass modelling caused by miscentring and uncertainties in the concentration-mass relation using simulations. In combination with temperature estimates from Chandra we constrain the normalization of the mass-temperature scaling relation ln (E(z)M500c/1014 M⊙) = A + 1.5ln (kT/7.2 keV) to A=1.81^{+0.24}_{-0.14}(stat.) {± } 0.09(sys.), consistent with self-similar redshift evolution when compared to lower redshift samples. Additionally, the lensing data constrain the average concentration of the clusters to c_200c=5.6^{+3.7}_{-1.8}.

Cluster Mass Calibration at High Redshift: HST Weak Lensing Analysis of 13 Distant Galaxy Clusters from the South Pole Telescope Sunyaev-Zel'dovich Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schrabback, T.; et al.

We present an HST/ACS weak gravitational lensing analysis of 13 massive high-redshift (z_median=0.88) galaxy clusters discovered in the South Pole Telescope (SPT) Sunyaev-Zel'dovich Survey. This study is part of a larger campaign that aims to robustly calibrate mass-observable scaling relations over a wide range in redshift to enable improved cosmological constraints from the SPT cluster sample. We introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scaling relations significantly. First, we efficiently remove cluster members from the source sample by selecting very blue galaxies in V-I colour. Our estimate of the sourcemore » redshift distribution is based on CANDELS data, where we carefully mimic the source selection criteria of the cluster fields. We apply a statistical correction for systematic photometric redshift errors as derived from Hubble Ultra Deep Field data and verified through spatial cross-correlations. We account for the impact of lensing magnification on the source redshift distribution, finding that this is particularly relevant for shallower surveys. Finally, we account for biases in the mass modelling caused by miscentring and uncertainties in the mass-concentration relation using simulations. In combination with temperature estimates from Chandra we constrain the normalisation of the mass-temperature scaling relation ln(E(z) M_500c/10^14 M_sun)=A+1.5 ln(kT/7.2keV) to A=1.81^{+0.24}_{-0.14}(stat.) +/- 0.09(sys.), consistent with self-similar redshift evolution when compared to lower redshift samples. Additionally, the lensing data constrain the average concentration of the clusters to c_200c=5.6^{+3.7}_{-1.8}.« less

Extreme Mergers from the Massive Cluster Survey

NASA Astrophysics Data System (ADS)

Morris, Roger

2010-09-01

We propose to observe two extraordinary, high-redshift galaxy clusters from the Massive Cluster Survey. Both targets are very rare, triple merger systems (one a nearly co-linear merger), and likely lie at the deepest nodes of the cosmic web. Both targets show multiple strong gravitational lensing arcs in the cluster cores. These targets only possess very short (10ks) Chandra observations, and are unobserved by XMM-Newton. The X-ray data will be used to probe the mass distribution of hot, baryonic gas, and to reveal the details of the merger physics and the process of cluster assembly. We will also search for hints of X-ray emission from filaments between the merging clumps. Subaru and Hubble Space Telescope imaging data are in hand; we request additional HST coverage for one object.

Black-hole Merger Simulations for LISA Science

NASA Technical Reports Server (NTRS)

Kelly, Bernard J.; Baker, John G.; vanMeter, James R.; Boggs, William D.; Centrella, Joan M.; McWilliams, Sean T.

2009-01-01

The strongest expected sources of gravitational waves in the LISA band are the mergers of massive black holes. LISA may observe these systems to high redshift, z>10, to uncover details of the origin of massive black holes, and of the relationship between black holes and their host structures, and structure formation itself. These signals arise from the final stage in the development of a massive black-hole binary emitting strong gravitational radiation that accelerates the system's inspiral toward merger. The strongest part of the signal, at the point of merger, carries much information about the system and provides a probe of extreme gravitational physics. Theoretical predictions for these merger signals rely on supercomputer simulations to solve Einstein's equations. We discuss recent numerical results and their impact on LISA science expectations.

Extreme Wolf-Rayet Galaxies with HST/COS: Understanding CIII] Emission in the Reionization Era

NASA Astrophysics Data System (ADS)

Stark, Daniel

2017-08-01

The first deep spectra of reionization-era galaxies have revealed strong UV nebular emission in high-ionization lines. This is in striking contrast to massive galaxies at lower redshifts, where emission from CIII], OIII], HeII, and CIV is rarely seen. These lines will likely be the only probe available for the most distant galaxies JWST will detect; but we are still unprepared to interpret them. Modeling predicts that intense UV nebular emission can only be produced below a tenth solar metallicity. However, recent HST/COS observations of local galaxies suggest that extreme populations of Wolf-Rayet (WR) stars, the hot exposed cores of massive O stars, may be capable of powering CIII] at metallicities as high as a half-solar. If these moderately metal-poor extreme WR galaxies are indeed a viable source of strong CIII] emission, our interpretation of CIII] detections in the reionization era will be dramatically altered; but we presently have sufficient UV coverage for only three examples. Here, we propose HST/COS G160M and G185M observations of an additional seven extreme WR galaxies spanning 0.5 dex in metallicity around half-solar. These observations will constrain the maximum CIII] equivalent width these galaxies can power as a function of metallicity. The moderate resolution gratings will robustly characterize the massive O and WR star populations, allowing us to link the nebular emission directly to the massive stars responsible. These data will provide a stringent test for the population synthesis codes which will be applied to JWST observations. Without this empirical baseline, our understanding of the most distant galaxies JWST finds will be severely limited.

Discovering Massive z > 1 Galaxy Clusters with Spitzer and SPTpol

NASA Astrophysics Data System (ADS)

Bleem, Lindsey; Brodwin, Mark; Ashby, Matthew; Stalder, Brian; Klein, Matthias; Gladders, Michael; Stanford, Spencer; Canning, Rebecca

2018-05-01

We propose to obtain Spitzer/IRAC imaging of 50 high-redshift galaxy cluster candidates derived from two new completed SZ cluster surveys by the South Pole Telescope. Clusters from the deep SPTpol 500-square-deg main survey will extend high-redshift SZ cluster science to lower masses (median M500 2x10^14Msun) while systems drawn from the wider 2500-sq-deg SPTpol Extended Cluster Survey are some of the rarest most massive high-z clusters in the observable universe. The proposed small 10 h program will enable (1) confirmation of these candidates as high-redshift clusters, (2) measurements of the cluster redshifts (sigma_z/(1+z) 0.03), and (3) estimates of the stellar masses of the brightest cluster members. These observations will yield exciting and timely targets for the James Webb Space Telescope--and, combined with lower-z systems--will both extend cluster tests of dark energy to z>1 as well as enable studies of galaxy evolution in the richest environments for a mass-limited cluster sample from 0

Herschel-ATLAS: The Angular Correlation Function of Submillimetre Galaxies at High and Low Redshift

NASA Technical Reports Server (NTRS)

Maddox, S. J.; Dunne, L.; Rigby, E.; Eales, S.; Cooray, A.; Scott, D.; Peacock, J. A.; Negrello, M.; Smith, D. J. B.; Benford, D.;

Optical signatures of high-redshift galaxy clusters

NASA Technical Reports Server (NTRS)

Evrard, August E.; Charlot, Stephane

1994-01-01

We combine an N-body and gasdynamic simulation of structure formation with an updated population synthesis code to explore the expected optical characteristics of a high-redshift cluster of galaxies. We examine a poor (2 keV) cluster formed in a biased, cold dark matter cosmology and employ simple, but plausible, threshold criteria to convert gas into stars. At z = 2, the forming cluster appears as a linear chain of very blue (g-r approximately equals 0) galaxies, with 15 objects brighter than r = 25 within a 1 square arcmin field of view. After 2 Gyr of evolution, the cluster viewed at z = 1 displays both freshly infalling blue galaxies and red galaxies robbed of recent accretion by interaction with the hot intracluster medium. The range in G-R colors is approximately 3 mag at z = 1, with the reddest objects lying at sites of highest galaxy density. We suggest that red, high-redshift galaxies lie in the cores of forming clusters and that their existence indicates the presence of a hot intracluster medium at redshifts z approximately equals 2. The simulated cluster viewed at z = 2 has several characteristics similar to the collection of faint, blue objects identified by Dressler et al. in a deep Hubble Space Telescope observation. The similarities provide some support for the interpretation of this collection as a high-redshift cluster of galaxies.

Dark-ages Reionization and Galaxy Formation Simulation - XIV. Gas accretion, cooling, and star formation in dwarf galaxies at high redshift

NASA Astrophysics Data System (ADS)

Qin, Yuxiang; Duffy, Alan R.; Mutch, Simon J.; Poole, Gregory B.; Geil, Paul M.; Mesinger, Andrei; Wyithe, J. Stuart B.

2018-06-01

We study dwarf galaxy formation at high redshift (z ≥ 5) using a suite of high-resolution, cosmological hydrodynamic simulations and a semi-analytic model (SAM). We focus on gas accretion, cooling, and star formation in this work by isolating the relevant process from reionization and supernova feedback, which will be further discussed in a companion paper. We apply the SAM to halo merger trees constructed from a collisionless N-body simulation sharing identical initial conditions to the hydrodynamic suite, and calibrate the free parameters against the stellar mass function predicted by the hydrodynamic simulations at z = 5. By making comparisons of the star formation history and gas components calculated by the two modelling techniques, we find that semi-analytic prescriptions that are commonly adopted in the literature of low-redshift galaxy formation do not accurately represent dwarf galaxy properties in the hydrodynamic simulation at earlier times. We propose three modifications to SAMs that will provide more accurate high-redshift simulations. These include (1) the halo mass and baryon fraction which are overestimated by collisionless N-body simulations; (2) the star formation efficiency which follows a different cosmic evolutionary path from the hydrodynamic simulation; and (3) the cooling rate which is not well defined for dwarf galaxies at high redshift. Accurate semi-analytic modelling of dwarf galaxy formation informed by detailed hydrodynamical modelling will facilitate reliable semi-analytic predictions over the large volumes needed for the study of reionization.

On modeling and measuring the temperature of the z ∼ 5 intergalactic medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lidz, Adam; Malloy, Matthew, E-mail: alidz@sas.upenn.edu

2014-06-20

The temperature of the low-density intergalactic medium (IGM) at high redshift is sensitive to the timing and nature of hydrogen and He II reionization, and can be measured from Lyman-alpha (Lyα) forest absorption spectra. Since the memory of intergalactic gas to heating during reionization gradually fades, measurements as close as possible to reionization are desirable. In addition, measuring the IGM temperature at sufficiently high redshifts should help to isolate the effects of hydrogen reionization since He II reionization starts later, at lower redshift. Motivated by this, we model the IGM temperature at z ≳ 5 using semi-numeric models of patchymore » reionization. We construct mock Lyα forest spectra from these models and consider their observable implications. We find that the small-scale structure in the Lyα forest is sensitive to the temperature of the IGM even at redshifts where the average absorption in the forest is as high as 90%. We forecast the accuracy at which the z ≳ 5 IGM temperature can be measured using existing samples of high resolution quasar spectra, and find that interesting constraints are possible. For example, an early reionization model in which reionization ends at z ∼ 10 should be distinguishable—at high statistical significance—from a lower redshift model where reionization completes at z ∼ 6. We discuss improvements to our modeling that may be required to robustly interpret future measurements.« less

Bulge Growth Through Disc Instabilities in High-Redshift Galaxies

NASA Astrophysics Data System (ADS)

Bournaud, Frédéric

The role of disc instabilities, such as bars and spiral arms, and the associated resonances, in growing bulges in the inner regions of disc galaxies have long been studied in the low-redshift nearby Universe. There it has long been probed observationally, in particular through peanut-shaped bulges (Chap. 14 10.1007/978-3-319-19378-6_14"). This secular growth of bulges in modern disc galaxies is driven by weak, non-axisymmetric instabilities: it mostly produces pseudobulges at slow rates and with long star-formation timescales. Disc instabilities at high redshift (z > 1) in moderate-mass to massive galaxies (1010 to a few 1011 M⊙ of stars) are very different from those found in modern spiral galaxies. High-redshift discs are globally unstable and fragment into giant clumps containing 108-9 M⊙ of gas and stars each, which results in highly irregular galaxy morphologies. The clumps and other features associated to the violent instability drive disc evolution and bulge growth through various mechanisms on short timescales. The giant clumps can migrate inward and coalesce into the bulge in a few 108 years. The instability in the very turbulent media drives intense gas inflows toward the bulge and nuclear region. Thick discs and supermassive black holes can grow concurrently as a result of the violent instability. This chapter reviews the properties of high-redshift disc instabilities, the evolution of giant clumps and other features associated to the instability, and the resulting growth of bulges and associated sub-galactic components.

RELICS: Strong-lensing Analysis of the Massive Clusters MACS J0308.9+2645 and PLCK G171.9‑40.7

NASA Astrophysics Data System (ADS)

Acebron, Ana; Cibirka, Nathália; Zitrin, Adi; Coe, Dan; Agulli, Irene; Sharon, Keren; Bradač, Maruša; Frye, Brenda; Livermore, Rachael C.; Mahler, Guillaume; Salmon, Brett; Umetsu, Keiichi; Bradley, Larry; Andrade-Santos, Felipe; Avila, Roberto; Carrasco, Daniela; Cerny, Catherine; Czakon, Nicole G.; Dawson, William A.; Hoag, Austin T.; Huang, Kuang-Han; Johnson, Traci L.; Jones, Christine; Kikuchihara, Shotaro; Lam, Daniel; Lovisari, Lorenzo; Mainali, Ramesh; Oesch, Pascal A.; Ogaz, Sara; Ouchi, Masami; Past, Matthew; Paterno-Mahler, Rachel; Peterson, Avery; Ryan, Russell E.; Sendra-Server, Irene; Stark, Daniel P.; Strait, Victoria; Toft, Sune; Trenti, Michele; Vulcani, Benedetta

2018-05-01

Strong gravitational lensing by galaxy clusters has become a powerful tool for probing the high-redshift universe, magnifying distant and faint background galaxies. Reliable strong-lensing (SL) models are crucial for determining the intrinsic properties of distant, magnified sources and for constructing their luminosity function. We present here the first SL analysis of MACS J0308.9+2645 and PLCK G171.9‑40.7, two massive galaxy clusters imaged with the Hubble Space Telescope, in the framework of the Reionization Lensing Cluster Survey (RELICS). We use the light-traces-mass modeling technique to uncover sets of multiply imaged galaxies and constrain the mass distribution of the clusters. Our SL analysis reveals that both clusters have particularly large Einstein radii (θ E > 30″ for a source redshift of z s = 2), providing fairly large areas with high magnifications, useful for high-redshift galaxy searches (∼2 arcmin2 with μ > 5 to ∼1 arcmin2 with μ > 10, similar to a typical Hubble Frontier Fields cluster). We also find that MACS J0308.9+2645 hosts a promising, apparently bright (J ∼ 23.2–24.6 AB), multiply imaged high-redshift candidate at z ∼ 6.4. These images are among the brightest high-redshift candidates found in RELICS. Our mass models, including magnification maps, are made publicly available for the community through the Mikulski Archive for Space Telescopes.

The Evolution of the Cluster X-ray Scaling Relations in the Wide Angle ROSAT Pointed Survey Sample at 0.6 < z < 1.0

NASA Technical Reports Server (NTRS)

Maughan, B. J.; Jones, L. R.; Ebeling, H.; Scharf, C.

2006-01-01

The X-ray properties of a sample of 11 high-redshift (0.6 < z < 1 .O) clusters observed with Chardm and/or XMM-Newton are used to investigate the evolution of the cluster scaling relations. The observed evolution in the normalization of the L-T, M-T, M(sub 2)-T and M-L relations is consistent with simple self-similar predictions, in which the properties of clusters reflect the properties of the Universe at their redshift of observation. Under the assumption that the model of self-similar evolution is correct and that the local systems formed via a single spherical collapse, the high-redshift L-T relation is consistent with the high-z clusters having virialized at a significantly higher redshift than the local systems. The data are also consistent with the more realistic scenario of clusters forming via the continuous accretion of material. The slope of the L-T relation at high redshift (B = 3.32 +/- 0.37) is consistent with the local relation, and significantly steeper than the self-similar prediction of B = 2. This suggests that the same non-gravitational processes are responsible for steepening the local and high-z relations, possibly occurring universally at z is approximately greater than 1 or in the early stages of the cluster formation, prior to their observation. The properties of the intracluster medium at high redshift are found to be similar to those in the local Universe. The mean surface-brightness profile slope for the sample is Beta = 0.66 +/- 0.05, the mean gas mass fractions within R(sub 2500(z)) and R(200(z)) are 0.069 +/- 0.012 and 0.11 +/- 0.02, respectively, and the mean metallicity of the sample is 0.28 +/- 0.11 Z(sub solar).

Unseen Progenitors of Luminous High- z Quasars in the R {sub h} = ct Universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fatuzzo, Marco; Melia, Fulvio, E-mail: fatuzzo@xavier.edu, E-mail: fmelia@email.arizona.edu

Quasars at high redshift provide direct information on the mass growth of supermassive black holes (SMBHs) and, in turn, yield important clues about how the universe evolved since the first (Pop III) stars started forming. Yet even basic questions regarding the seeds of these objects and their growth mechanism remain unanswered. The anticipated launch of eROSITA and ATHENA is expected to facilitate observations of high-redshift quasars needed to resolve these issues. In this paper, we compare accretion-based SMBH growth in the concordance ΛCDM model with that in the alternative Friedmann–Robertson–Walker cosmology known as the R {sub h} = ct universe.more » Previous work has shown that the timeline predicted by the latter can account for the origin and growth of the ≳10{sup 9} M {sub ⊙} highest redshift quasars better than that of the standard model. Here, we significantly advance this comparison by determining the soft X-ray flux that would be observed for Eddington-limited accretion growth as a function of redshift in both cosmologies. Our results indicate that a clear difference emerges between the two in terms of the number of detectable quasars at redshift z ≳ 7, raising the expectation that the next decade will provide the observational data needed to discriminate between these two models based on the number of detected high-redshift quasar progenitors. For example, while the upcoming ATHENA mission is expected to detect ∼0.16 (i.e., essentially zero) quasars at z ∼ 7 in R {sub h} = ct , it should detect ∼160 in ΛCDM—a quantitatively compelling difference.« less

The MOSDEF Survey: A Stellar Mass–SFR–Metallicity Relation Exists at z ∼ 2.3

NASA Astrophysics Data System (ADS)

Sanders, Ryan L.; Shapley, Alice E.; Kriek, Mariska; Freeman, William R.; Reddy, Naveen A.; Siana, Brian; Coil, Alison L.; Mobasher, Bahram; Davé, Romeel; Shivaei, Irene; Azadi, Mojegan; Price, Sedona H.; Leung, Gene; Fetherholf, Tara; de Groot, Laura; Zick, Tom; Fornasini, Francesca M.; Barro, Guillermo

2018-05-01

We investigate the nature of the relation among stellar mass, star formation rate, and gas-phase metallicity (the {M}* –SFR–Z relation) at high redshifts using a sample of 260 star-forming galaxies at z ∼ 2.3 from the MOSDEF survey. We present an analysis of the high-redshift {M}* –SFR–Z relation based on several emission-line ratios for the first time. We show that a {M}* –SFR–Z relation clearly exists at z ∼ 2.3. The strength of this relation is similar to predictions from cosmological hydrodynamical simulations. By performing a direct comparison of stacks of z ∼ 0 and z ∼ 2.3 galaxies, we find that z ∼ 2.3 galaxies have ∼0.1 dex lower metallicity at fixed {M}* and SFR. In the context of chemical evolution models, this evolution of the {M}* –SFR–Z relation suggests an increase with redshift of the mass-loading factor at fixed {M}* , as well as a decrease in the metallicity of infalling gas that is likely due to a lower importance of gas recycling relative to accretion from the intergalactic medium at high redshifts. Performing this analysis simultaneously with multiple metallicity-sensitive line ratios allows us to rule out the evolution in physical conditions (e.g., N/O ratio, ionization parameter, and hardness of the ionizing spectrum) at fixed metallicity as the source of the observed trends with redshift and with SFR at fixed {M}* at z ∼ 2.3. While this study highlights the promise of performing high-order tests of chemical evolution models at high redshifts, detailed quantitative comparisons ultimately await a full understanding of the evolution of metallicity calibrations with redshift. Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

The Star Formation History of SHADES Sources

NASA Astrophysics Data System (ADS)

Aretxaga, Itziar; SHADES Consortium; AzTEC Team

2006-12-01

We present the redshift distribution of the SHADES 850um selected galaxy population based on the rest-frame radio-mm-FIR colours of 120 robustly detected sources in the Lockman Hole East (LH) and Subaru XMM-Newton Deep Field (SXDF). The redshift of sources constrained with at least two photometric bands peaks at z 2.4 and has a near-Gaussian distribution. The inclusion of sources detected only at 850um, for which only very weak redshift constraints are available, leads to the possibility of a high-redshit tail. We find a small difference between the redshift distributions in the two fields; the SXDF peaking at a slightly lower redshift than the LH, which we mainly attribute to the noise properties of the photometry used. We discuss the impact of the AzTEC data on the further precission of these results. Finally we present a brief comparison with sub-mm galaxy formation models and their predicted and assumed redshift distributions and derive the contribution of these sources to the star formation rate density at different epochs.

Quasar Absorption in the UV: Probing the Intergalactic Medium

NASA Technical Reports Server (NTRS)

Weinberg, David; Katz, Neal

1998-01-01

The purpose of this project is to model the low-redshift Lyman-alpha forest and exploration of the relation between Lyman-alpha absorbers and galaxies. This paper shows that the simulation models that are so successful at explaining properties of the high-redshift forest also account for the most important results of observational studies of the low-redshift forest, from HST (especially the Quasar Absorption Line Key Project) and ground-based follow-up.

THE REDSHIFT DISTRIBUTION OF GIANT ARCS IN THE SLOAN GIANT ARCS SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bayliss, Matthew B.; Gladders, Michael D.; Koester, Benjamin P.

2011-01-20

We measure the redshift distribution of a sample of 28 giant arcs discovered as a part of the Sloan Giant Arcs Survey. Gemini/GMOS-North spectroscopy provides precise redshifts for 24 arcs, and 'redshift desert' constrains for the remaining 4 arcs. This is a direct measurement of the redshift distribution of a uniformly selected sample of bright giant arcs, which is an observable that can be used to inform efforts to predict giant arc statistics. Our primary giant arc sample has a median redshift z = 1.821 and nearly two-thirds of the arcs, 64%, are sources at z {approx}> 1.4, indicating thatmore » the population of background sources that are strongly lensed into bright giant arcs resides primarily at high redshift. We also analyze the distribution of redshifts for 19 secondary strongly lensed background sources that are not visually apparent in Sloan Digital Sky Survey imaging, but were identified in deeper follow-up imaging of the lensing cluster fields. Our redshift sample for the secondary sources is not spectroscopically complete, but combining it with our primary giant arc sample suggests that a large fraction of all background galaxies that are strongly lensed by foreground clusters reside at z {approx}> 1.4. Kolmogorov-Smirnov tests indicate that our well-selected, spectroscopically complete primary giant arc redshift sample can be reproduced with a model distribution that is constructed from a combination of results from studies of strong-lensing clusters in numerical simulations and observational constraints on the galaxy luminosity function.« less

Investigations of gain redshift in high peak power Ti:sapphire laser systems

NASA Astrophysics Data System (ADS)

Wu, Fenxiang; Yu, Linpeng; Zhang, Zongxin; Li, Wenkai; Yang, Xiaojun; Wu, Yuanfeng; Li, Shuai; Wang, Cheng; Liu, Yanqi; Lu, Xiaoming; Xu, Yi; Leng, Yuxin

2018-07-01

Gain redshift in high peak power Ti:sapphire laser systems can result in narrowband spectral output and hence lengthen the compressed pulse duration. In order to realize broadband spectral output in 10 PW-class Ti:sapphire lasers, the influence on gain redshift induced by spectral pre-shaping, gain distribution of cascaded amplifiers and Extraction During Pumping (EDP) technique have been investigated. The theoretical and experimental results show that the redshift of output spectrum is sensitive to the spectral pre-shaping and the gain distribution of cascaded amplifiers, while insensitive to the pumping scheme with or without EDP. Moreover, the output spectrum from our future 10 PW Ti:sapphire laser is theoretically analyzed based on the investigations above, which indicates that a Fourier-transform limited (FTL) pulse duration of 21 fs can be achieved just by optimizing the spectral pre-shaping and gain distribution in 10 PW-class Ti:sapphire lasers.

X-ray morphological study of galaxy cluster catalogues

NASA Astrophysics Data System (ADS)

Democles, Jessica; Pierre, Marguerite; Arnaud, Monique

2016-07-01

Context : The intra-cluster medium distribution as probed by X-ray morphology based analysis gives good indication of the system dynamical state. In the race for the determination of precise scaling relations and understanding their scatter, the dynamical state offers valuable information. Method : We develop the analysis of the centroid-shift so that it can be applied to characterize galaxy cluster surveys such as the XXL survey or high redshift cluster samples. We use it together with the surface brightness concentration parameter and the offset between X-ray peak and brightest cluster galaxy in the context of the XXL bright cluster sample (Pacaud et al 2015) and a set of high redshift massive clusters detected by Planck and SPT and observed by both XMM-Newton and Chandra observatories. Results : Using the wide redshift coverage of the XXL sample, we see no trend between the dynamical state of the systems with the redshift.

Detecting Massive, High-Redshift Galaxy Clusters Using the Thermal Sunyaev-Zel'dovich Effect

NASA Astrophysics Data System (ADS)

Adams, Carson; Steinhardt, Charles L.; Loeb, Abraham; Karim, Alexander; Staguhn, Johannes; Erler, Jens; Capak, Peter L.

2017-01-01

We develop the thermal Sunyaev-Zel'dovich (SZ) effect as a direct astrophysical measure of the mass distribution of dark matter halos. The SZ effect increases with cosmological distance, a unique astronomical property, and is highly sensitive to halo mass. We find that this presents a powerful methodology for distinguishing between competing models of the halo mass function distribution, particularly in the high-redshift domain just a few hundred million years after the Big Bang. Recent surveys designed to probe this epoch of initial galaxy formation such as CANDELS and SPLASH report an over-abundance of highly massive halos as inferred from stellar ultraviolet (UV) luminosities and the stellar mass to halo mass ratio estimated from nearby galaxies. If these UV luminosity to halo mass relations hold to high-redshift, observations estimate several orders of magnitude more highly massive halos than predicted by hierarchical merging and the standard cosmological paradigm. Strong constraints on the masses of these galaxy clusters are essential to resolving the current tension between observation and theory. We conclude that detections of thermal SZ sources are plausible at high-redshift only for the halo masses inferred from observation. Therefore, future SZ surveys will provide a robust determination between theoretical and observational predictions.

An extremely young massive clump forming by gravitational collapse in a primordial galaxy.

PubMed

Zanella, A; Daddi, E; Le Floc'h, E; Bournaud, F; Gobat, R; Valentino, F; Strazzullo, V; Cibinel, A; Onodera, M; Perret, V; Renaud, F; Vignali, C

2015-05-07

When cosmic star formation history reaches a peak (at about redshift z ≈ 2), galaxies vigorously fed by cosmic reservoirs are dominated by gas and contain massive star-forming clumps, which are thought to form by violent gravitational instabilities in highly turbulent gas-rich disks. However, a clump formation event has not yet been observed, and it is debated whether clumps can survive energetic feedback from young stars, and afterwards migrate inwards to form galaxy bulges. Here we report the spatially resolved spectroscopy of a bright off-nuclear emission line region in a galaxy at z = 1.987. Although this region dominates star formation in the galaxy disk, its stellar continuum remains undetected in deep imaging, revealing an extremely young (less than ten million years old) massive clump, forming through the gravitational collapse of more than one billion solar masses of gas. Gas consumption in this young clump is more than tenfold faster than in the host galaxy, displaying high star-formation efficiency during this phase, in agreement with our hydrodynamic simulations. The frequency of older clumps with similar masses, coupled with our initial estimate of their formation rate (about 2.5 per billion years), supports long lifetimes (about 500 million years), favouring models in which clumps survive feedback and grow the bulges of present-day galaxies.

The evolution of the cluster optical galaxy luminosity function between z = 0.4 and 0.9 in the DAFT/FADA survey

NASA Astrophysics Data System (ADS)

Martinet, Nicolas; Durret, Florence; Guennou, Loïc; Adami, Christophe; Biviano, Andrea; Ulmer, Melville P.; Clowe, Douglas; Halliday, Claire; Ilbert, Olivier; Márquez, Isabel; Schirmer, Mischa

2015-03-01

Context. There is some disagreement about the abundance of faint galaxies in high-redshift clusters, with contradictory results in the literature arising from studies of the optical galaxy luminosity function (GLF) for small cluster samples. Aims: We compute GLFs for one of the largest medium-to-high-redshift (0.4 ≤ z < 0.9) cluster samples to date in order to probe the abundance of faint galaxies in clusters. We also study how the GLF depends on cluster redshift, mass, and substructure and compare the GLFs of clusters with those of the field. We separately investigate the GLFs of blue and red-sequence (RS) galaxies to understand the evolution of different cluster populations. Methods: We calculated the GLFs for 31 clusters taken from the DAFT/FADA survey in the B,V,R, and I rest-frame bands. We used photometric redshifts computed from BVRIZJ images to constrain galaxy cluster membership. We carried out a detailed estimate of the completeness of our data. We distinguished the red-sequence and blue galaxies using a V - I versus I colour-magnitude diagram. We studied the evolution of these two populations with redshift. We fitted Schechter functions to our stacked GLFs to determine average cluster characteristics. Results: We find that the shapes of our GLFs are similar for the B,V,R, and I bands with a drop at the red GLF faint ends that is more pronounced at high redshift: αred ~ -0.5 at 0.40 ≤ z < 0.65 and αred > 0.1 at 0.65 ≤ z < 0.90. The blue GLFs have a steeper faint end (αblue ~ -1.6) than the red GLFs, which appears to be independent of redshift. For the full cluster sample, blue and red GLFs meet at MV = -20, MR = -20.5, and MI = -20.3. A study of how galaxy types evolve with redshift shows that late-type galaxies appear to become early types between z ~ 0.9 and today. Finally, the faint ends of the red GLFs of more massive clusters appear to be richer than less massive clusters, which is more typical of the lower redshift behaviour. Conclusions: Our results indicate that these clusters form at redshifts higher than z = 0.9 from galaxy structures that already have an established red sequence. Late-type galaxies then appear to evolve into early types, enriching the red sequence between this redshift and today. This effect is consistent with the evolution of the faint-end slope of the red sequence and the galaxy type evolution that we find. Finally, faint galaxies accreted from the field environment at all redshifts might have replaced the blue late-type galaxies that converted into early types, explaining the lack of evolution in the faint-end slopes of the blue GLFs. Appendix is available in electronic form at http://www.aanda.org

Absorption in X-ray spectra of high-redshift quasars

NASA Technical Reports Server (NTRS)

Elvis, Martin; Fiore, Fabrizio; Wilkes, Belinda; Mcdowell, Jonathan; Bechtold, Jill

1994-01-01

We present evidence that X-ray absorption is common in high-redshift quasars. We have studied six high-redshift (z approximately 3) quasars with the ROSAT Position Sensitive Proportional Counter (PSPC) of which four are in directions of low Galactic N(sub H). Three out of these four show excess absorption, while only three in approximately 50 z approximately less than 0.4 quasars do, indicating that such absorption must be common, but not ubiquitous, at high redshifts, and that the absorbers must lie at z greater than 0.4. The six quasars were: S5 0014+81, Q0420-388, PKS 0438-436, S4 0636+680. PKS 2000-330, PKS 2126-158, which have redshifts between 2.85 and 3.78. PKS 0438-436 and PKS 2126-158 show evidence for absorption above the local Galactic value at better than 99.999% confidence level. If the absorber is at the redshift of the quasar, then values of N(sub H) = (0.86(+0.49, -0.28)) x 10(exp 22) atoms/sq cm for PKS 0438-436, and N(sub H) = (1.45(+1.20, -0.64)) x 10(exp 22) atoms/ sq cm for PKS 2126-158, are implied, assuming solar abundances. The spectrum of S4 0636+680 also suggests the presence of a similarly large absorption column density at the 98% confidence level. This absorption reverses the trend for the most luminous active galactic nuclei (AGN) to have the least X-ray absorption, so a new mechanism is likely to be responsible. Intervening absorption due to damped Lyman(alpha) systems is a plausible cause. We also suggest, as an intrinsic model, that intracluster material, e.g., a cooling flow, around the quasar could account for both the X-ray spectrum and other properties of these quasars. All the quasars are radio-loud and three are gigahertz peaked (two of the three showing absorption). No excess absorption above the Galactic value is seen toward Q0420-388. This quasar has two damped Lyman(alpha) systems at z = 3.08. The limit on the X-ray column density implies a low ionization fraction, N(H I)/N(H) approximately greater than 4 x 10(exp -3) (3 (sigma)), for solar abundances, for these systems, and can set a weak limit on the size of the absorber. In the emitted frame these PSPC spectra cover the band approximately 0.5-10 keV, which has been well observed for low-redshift quasars and AGN. Comparison of high and low-redshift spectra in this emitted band shows no change of mean spectral index greater than Delta alpha(sub E) greater than 0.3 (99% confidence) with either redshift or luminosity, for radio-loud quasars.

QUANTITATIVE EVALUATION OF THE HYPOTHESIS THAT BL LACERTAE OBJECTS ARE QSO REMNANTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borra, E. F.

2014-11-20

We evaluate with numerical simulations the hypothesis that BL Lacertae objects (BLLs) are the remnants of quasi-stellar objects. This hypothesis is based on their highly peculiar redshift evolution. They have a comoving space density that increases with decreasing redshift, contrary to all other active galactic nuclei. We assume that relativistic jets are below detection in young radio-quiet quasars and increase in strength with cosmic time so that they eventually are detected as BLLs. Our numerical simulations fit very well the observed redshift distributions of BLLs. There are strong indications that only the high-synchrotron-peaked BLLs could be QSO remnants.

Redshifts of groups and clusters in the rich superclusters 1451+22 and 1615+43

NASA Technical Reports Server (NTRS)

Ciardullo, R.; Ford, H.; Bartko, F.; Harms, R.

1983-01-01

Redshift measurements and finding charts are presented for galaxy clusters in the field of two rich, distant superclusters. Both systems are shown to have morphological and dynamical properties similar to the nearby superclusters, including small internal velocity dispersions and high density contrasts in redshift space. This data is consistent with two interpretations: either both superclusters are highly flattened systems with major axes close to the plane of the sky, or the observed velocity dispersions do not arise from unperturbed Hubble flow. If the latter explanation is correct, these radial velocity data are a powerful probe of the large scale matter density in the universe.

High-redshift galaxy populations.

PubMed

Hu, Esther M; Cowie, Lennox L

2006-04-27

We now see many galaxies as they were only 800 million years after the Big Bang, and that limit may soon be exceeded when wide-field infrared detectors are widely available. Multi-wavelength studies show that there was relatively little star formation at very early times and that star formation was at its maximum at about half the age of the Universe. A small number of high-redshift objects have been found by targeting X-ray and radio sources and most recently, gamma-ray bursts. The gamma-ray burst sources may provide a way to reach even higher-redshift galaxies in the future, and to probe the first generation of stars.

Stars and gas in high redshift galaxies

NASA Astrophysics Data System (ADS)

Pettini, Max

Recent advances in instrumentation and observing techniques have made it possible to begin to study in detail the stellar populations and the interstellar media of galaxies at redshift z=3, when the universe was still in its "teen years". In keeping with the theme of this conference, I show how our knowledge of local star-forming regions can be applied directly to these distant galaxies to deduce their ages, metallicities, initial mass function, and masses. I also discuss areas where current limitations in stellar astrophysics have a direct bearing on the interpretation of the data being gathered, at an ever increasing rate, on the high redshift universe.

Extreme gaseous outflows in radio-loud narrow-line Seyfert 1 galaxies

NASA Astrophysics Data System (ADS)

Komossa, S.; Xu, D. W.; Wagner, A. Y.

2018-07-01

We present four radio-loud narrow-line Seyfert 1 (NLS1) galaxies with extreme emission-line shifts, indicating radial outflow velocities of the ionized gas of up to 2450 km s-1, above the escape velocity of the host galaxies. The forbidden lines show strong broadening, up to 2270 km s-1. An ionization stratification (higher line shift at higher ionization potential) implies that we see a large-scale outflow rather than single, localized jet-cloud interactions. Similarly, the paucity of zero-velocity [O III] λ5007 emitting gas implies the absence of a second narrow-line region (NLR) component at rest, and therefore a large part of the high-ionization NLR is affected by the outflow. Given the radio loudness of these NLS1 galaxies, the observations are consistent with a pole on view onto their central engines, so that the effects of polar outflows are maximized. In addition, a very efficient driving mechanism is required to reach the high observed velocities. We explore implications from recent hydrodynamic simulations of the interaction between fast winds or jets with the large-scale NLR. Overall, the best agreement with observations (and especially the high outflow speeds of the [Ne V] emitting gas) can be reached if the NLS1 galaxies are relatively young sources with lifetimes not much exceeding 1 Myr. These systems represent sites of strong feedback at NLR scales at work, well below redshift one.

Extreme Gaseous Outflows in Radio-Loud Narrow-Line Seyfert 1 Galaxies

NASA Astrophysics Data System (ADS)

Komossa, S.; Xu, D. W.; Wagner, A. Y.

2018-04-01

We present four radio-loud NLS1 galaxies with extreme emission-line shifts, indicating radial outflow velocities of the ionized gas of up to 2450 km/s, above the escape velocity of the host galaxies. The forbidden lines show strong broadening, up to 2270 km/s. An ionization stratification (higher line shift at higher ionization potential) implies that we see a large-scale outflow rather than single, localized jet-cloud interactions. Similarly, the paucity of zero-velocity [OIII]λ5007 emitting gas implies the absence of a second narrow-line region (NLR) component at rest, and therefore a large part of the high-ionization NLR is affected by the outflow. Given the radio loudness of these NLS1 galaxies, the observations are consistent with a pole on view onto their central engines, so that the effects of polar outflows are maximized. In addition, a very efficient driving mechanism is required, to reach the high observed velocities. We explore implications from recent hydrodynamic simulations of the interaction between fast winds or jets with the large-scale NLR. Overall, the best agreement with observations (and especially the high outflow speeds of the [NeV] emitting gas) can be reached if the NLS1 galaxies are relatively young sources with lifetimes not much exceeding 1 Myr. These systems represent sites of strong feedback at NLR scales at work, well below redshift one.

Multiple Streaming and the Probability Distribution of Density in Redshift Space

NASA Astrophysics Data System (ADS)

Hui, Lam; Kofman, Lev; Shandarin, Sergei F.

2000-07-01

We examine several aspects of redshift distortions by expressing the redshift-space density in terms of the eigenvalues and orientation of the local Lagrangian deformation tensor. We explore the importance of multiple streaming using the Zeldovich approximation (ZA), and compute the average number of streams in both real and redshift space. We find that multiple streaming can be significant in redshift space but negligible in real space, even at moderate values of the linear fluctuation amplitude (σl<~1). Moreover, unlike their real-space counterparts, redshift-space multiple streams can flow past each other with minimal interactions. Such nonlinear redshift-space effects, which are physically distinct from the fingers-of-God due to small-scale virialized motions, might in part explain the well-known departure of redshift distortions from the classic linear prediction by Kaiser, even at relatively large scales where the corresponding density field in real space is well described by linear perturbation theory. We also compute, using the ZA, the probability distribution function (PDF) of the density, as well as S3, in real and redshift space, and compare it with the PDF measured from N-body simulations. The role of caustics in defining the character of the high-density tail is examined. We find that (non-Lagrangian) smoothing, due to both finite resolution or discreteness and small-scale velocity dispersions, is very effective in erasing caustic structures, unless the initial power spectrum is sufficiently truncated.

The impact of Spitzer infrared data on stellar mass estimates - and a revised galaxy stellar mass function at 0 < z < 5

NASA Astrophysics Data System (ADS)

Elsner, F.; Feulner, G.; Hopp, U.

2008-01-01

Aims:We estimate stellar masses of galaxies in the high redshift universe with the intention of determining the influence of newly available Spitzer/IRAC infrared data on the analysis. Based on the results, we probe the mass assembly history of the universe. Methods: We use the GOODS-MUSIC catalog, which provides multiband photometry from the U-filter to the 8 μm Spitzer band for almost 15 000 galaxies with either spectroscopic (for ≈7% of the sample) or photometric redshifts, and apply a standard model fitting technique to estimate stellar masses. We than repeat our calculations with fixed photometric redshifts excluding Spitzer photometry and directly compare the outcomes to look for systematic deviations. Finally we use our results to compute stellar mass functions and mass densities up to redshift z = 5. Results: We find that stellar masses tend to be overestimated on average if further constraining Spitzer data are not included into the analysis. Whilst this trend is small up to intermediate redshifts z ⪉ 2.5 and falls within the typical error in mass, the deviation increases strongly for higher redshifts and reaches a maximum of a factor of three at redshift z ≈ 3.5. Thus, up to intermediate redshifts, results for stellar mass density are in good agreement with values taken from literature calculated without additional Spitzer photometry. At higher redshifts, however, we find a systematic trend towards lower mass densities if Spitzer/IRAC data are included.

Modelling the line-of-sight contribution in substructure lensing

NASA Astrophysics Data System (ADS)

Despali, Giulia; Vegetti, Simona; White, Simon D. M.; Giocoli, Carlo; van den Bosch, Frank C.

2018-04-01

We investigate how Einstein rings and magnified arcs are affected by small-mass dark-matter haloes placed along the line of sight to gravitational lens systems. By comparing the gravitational signature of line-of-sight haloes with that of substructures within the lensing galaxy, we derive a mass-redshift relation that allows us to rescale the detection threshold (i.e. lowest detectable mass) for substructures to a detection threshold for line-of-sight haloes at any redshift. We then quantify the line-of-sight contribution to the total number density of low-mass objects that can be detected through strong gravitational lensing. Finally, we assess the degeneracy between substructures and line-of-sight haloes of different mass and redshift to provide a statistical interpretation of current and future detections, with the aim of distinguishing between cold dark matter and warm dark matter. We find that line-of-sight haloes statistically dominate with respect to substructures, by an amount that strongly depends on the source and lens redshifts, and on the chosen dark-matter model. Substructures represent about 30 percent of the total number of perturbers for low lens and source redshifts (as for the SLACS lenses), but less than 10 per cent for high-redshift systems. We also find that for data with high enough signal-to-noise ratio and angular resolution, the non-linear effects arising from a double-lens-plane configuration are such that one is able to observationally recover the line-of-sight halo redshift with an absolute error precision of 0.15 at the 68 per cent confidence level.

Cosmic ray heating of intergalactic medium: patchy or uniform?

NASA Astrophysics Data System (ADS)

Jana, Ranita; Nath, Biman B.

2018-06-01

We study the heating of the intergalactic medium (IGM) surrounding high redshift star forming galaxies due to cosmic rays (CR). We take into account the diffusion of low energy cosmic rays and study the patchiness of the resulting heating. We discuss the case of IGM heating around a high redshift minihalo (z ˜ 10-20, M˜105-107 M⊙),and put an upper limit on the diffusion coefficient D ≤ 1 × 1026 cm2 s-1 for the heating to be inhomogeneous at z ˜ 10 and D ≤ 5-6 × 1026 cm2 s-1 at z ˜ 20. For typical values of D, our results suggest uniform heating by CR at high redshift, although there are uncertainties in magnetic field and other CR parameters. We also discuss two cases with continuous star formation, one in which the star formation rate (SFR) of a galaxy is high enough to make the IGM in the vicinity photoionized, and another in which the SFR is low enough to keep it neutral but high enough to cause significant heating by cosmic ray protons. In the neutral case (low SFR), we find that the resulting heating can make the gas hotter than the cosmic microwave background (CMB) radiation for D < 1030 cm2 s-1, within a few kpc of the galaxy, and unlikely to be probed by near future radio observations. In the case of photoionized IGM (high SFR), the resulting heating of the gas in the vicinity of high redshift (z ˜ 4) galaxies of mass ≥1012 M⊙ can suppress gas infall into the galaxy. At lower redshifts (z ˜ 0), an SFR of ˜1 M⊙ yr-1 can suppress the infall into galaxies of mass ≤1010 M⊙.

THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE 'GREEN PEA' GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaskot, A. E.; Oey, M. S.

2013-04-01

Although Lyman-continuum (LyC) radiation from star-forming galaxies likely drove the reionization of the universe, observations of star-forming galaxies at low redshift generally indicate low LyC escape fractions. However, the extreme [O III]/[O II] ratios of the z = 0.1-0.3 Green Pea galaxies may be due to high escape fractions of ionizing radiation. To analyze the LyC optical depths and ionizing sources of these rare, compact starbursts, we compare nebular photoionization and stellar population models with observed emission lines in the Peas' Sloan Digital Sky Survey (SDSS) spectra. We focus on the six most extreme Green Peas, the galaxies with themore » highest [O III]/[O II] ratios and the best candidates for escaping ionizing radiation. The Balmer line equivalent widths and He I {lambda}3819 emission in the extreme Peas support young ages of 3-5 Myr, and He II {lambda}4686 emission in five extreme Peas signals the presence of hard ionizing sources. Ionization by active galactic nuclei or high-mass X-ray binaries is inconsistent with the Peas' line ratios and ages. Although stacked spectra reveal no Wolf-Rayet (WR) features, we tentatively detect WR features in the SDSS spectra of three extreme Peas. Based on the Peas' ages and line ratios, we find that WR stars, chemically homogeneous O stars, or shocks could produce the observed He II emission. If hot stars are responsible, then the Peas' optical depths are ambiguous. However, accounting for emission from shocks lowers the inferred optical depth and suggests that the Peas may be optically thin. The Peas' ages likely optimize the escape of LyC radiation; they are old enough for supernovae and stellar winds to reshape the interstellar medium, but young enough to possess large numbers of UV-luminous O or WR stars.« less

The SDSS-IV extended baryon oscillation spectroscopic survey: Luminous red galaxy target selection

DOE PAGES

Prakash, Abhishek; Licquia, Timothy C.; Newman, Jeffrey A.; ...

2016-06-08

Here, we describe the algorithm used to select the luminous red galaxy (LRG) sample for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV) using photometric data from both the SDSS and the Wide-field Infrared Survey Explorer. LRG targets are required to meet a set of color selection criteria and have z-band and i-band MODEL magnitudes z < 19.95 and 19.9 < i < 21.8, respectively. Our algorithm selects roughly 50 LRG targets per square degree, the great majority of which lie in the redshift range 0.6 < z < 1.0 (median redshift 0.71).more » We also demonstrate that our methods are highly effective at eliminating stellar contamination and lower-redshift galaxies. We perform a number of tests using spectroscopic data from SDSS-III/BOSS ancillary programs to determine the redshift reliability of our target selection and its ability to meet the science requirements of eBOSS. The SDSS spectra are of high enough signal-to-noise ratio that at least ~89% of the target sample yields secure redshift measurements. Finally, we present tests of the uniformity and homogeneity of the sample, demonstrating that it should be clean enough for studies of the large-scale structure of the universe at higher redshifts than SDSS-III/BOSS LRGs reached.« less

THE SDSS-IV EXTENDED BARYON OSCILLATION SPECTROSCOPIC SURVEY: LUMINOUS RED GALAXY TARGET SELECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prakash, Abhishek; Licquia, Timothy C.; Newman, Jeffrey A.

2016-06-01

We describe the algorithm used to select the luminous red galaxy (LRG) sample for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV) using photometric data from both the SDSS and the Wide-field Infrared Survey Explorer . LRG targets are required to meet a set of color selection criteria and have z -band and i -band MODEL magnitudes z < 19.95 and 19.9 < i < 21.8, respectively. Our algorithm selects roughly 50 LRG targets per square degree, the great majority of which lie in the redshift range 0.6 < z < 1.0 (medianmore » redshift 0.71). We demonstrate that our methods are highly effective at eliminating stellar contamination and lower-redshift galaxies. We perform a number of tests using spectroscopic data from SDSS-III/BOSS ancillary programs to determine the redshift reliability of our target selection and its ability to meet the science requirements of eBOSS. The SDSS spectra are of high enough signal-to-noise ratio that at least ∼89% of the target sample yields secure redshift measurements. We also present tests of the uniformity and homogeneity of the sample, demonstrating that it should be clean enough for studies of the large-scale structure of the universe at higher redshifts than SDSS-III/BOSS LRGs reached.« less

Complete Calibration of the Color-Redshift Relation (C3R2): A Critical Foundation for Weak Lensing Cosmology with Euclid and WFIRST

NASA Astrophysics Data System (ADS)

Masters, Daniel C.; Stern, Daniel; Cohen, Judy; Capak, Peter

2018-01-01

A primary objective of both WFIRST and Euclid is to provide a 3D map of the distribution of matter across a significant fraction of the universe from the weak lensing shear field. Doing so will require accurate redshifts to the billions of galaxies that comprise the weak lensing samples of these surveys; achieving the required accuracy is a “tall pole” challenge for both missions. Here we present the ongoing Complete Calibration of the Color-Redshift Relation (C3R2) survey, designed specifically to calibrate the empirical galaxy color-redshift relation to Euclid depth. C3R2 is an ambitious Keck spectroscopy program, with a survey design based on a machine learning technique that allows us to optimally select the most important galaxies to sample the full range of galaxy colors. C3R2 is a multi-center program with time from all the primary Keck partners (Caltech, UC, Hawaii, and NASA), with a total of 34.5 Keck nights allocated to this project. Data Release 1, including 1283 high-confidence spectroscopic redshifts, is published as Masters, Stern, Cohen, Capak, et al. (2017), and we are currently completing Data Release 2, which will include >2000 additional high-confidence spectroscopic redshifts (Masters et al., in prep.). We will discuss current results and prospects for the survey going forward.

On the Evolution of High-redshift Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Mao, Jirong; Kim, Minsun

2016-09-01

We build a simple physical model to study the high-redshift active galactic nucleus (AGN) evolution within the co-evolution framework of central black holes (BHs) and their host galaxies. The correlation between the circular velocity of a dark halo V c and the velocity dispersion of a galaxy σ is used to link the dark matter halo mass and BH mass. The dark matter halo mass function is converted to the BH mass function for any given redshift. The high-redshift optical AGN luminosity functions (LFs) are constructed. At z˜ 4, the flattening feature is not shown at the faint end of the optical AGN LF. This is consistent with observational results. If the optical AGN LF at z˜ 6 can be reproduced in the case in which central BHs have the Eddington-limited accretion, it is possible for the AGN lifetime to have a small value of 2× {10}5 {{years}}. The X-ray AGN LFs and X-ray AGN number counts are also calculated at 2.0\\lt z\\lt 5.0 and z\\gt 3, respectively, using the same parameters adopted in the calculation for the optical AGN LF at z˜ 4. It is estimated that about 30 AGNs per {{{\\deg }}}2 at z\\gt 6 can be detected with a flux limit of 3× {10}-17 {erg} {{cm}}-2 {{{s}}}-1 in the 0.5-2 keV band. Additionally, the cosmic reionization is also investigated. The ultraviolet photons emitted from the high-redshift AGNs mainly contribute to the cosmic reionization, and the central BHs of the high-redshift AGNs have a mass range of {10}6{--}{10}8{M}⊙ . We also discuss some uncertainties in both the AGN LFs and AGN number counts originating from the {M}{{BH}}{--}σ relation, Eddington ratio, AGN lifetime, and X-ray attenuation in our model.

Pulsar Timing Array Based Search for Supermassive Black Hole Binaries in the Square Kilometer Array Era

NASA Astrophysics Data System (ADS)

Wang, Yan; Mohanty, Soumya D.

2017-04-01

The advent of next generation radio telescope facilities, such as the Square Kilometer Array (SKA), will usher in an era where a pulsar timing array (PTA) based search for gravitational waves (GWs) will be able to use hundreds of well timed millisecond pulsars rather than the few dozens in existing PTAs. A realistic assessment of the performance of such an extremely large PTA must take into account the data analysis challenge posed by an exponential increase in the parameter space volume due to the large number of so-called pulsar phase parameters. We address this problem and present such an assessment for isolated supermassive black hole binary (SMBHB) searches using a SKA era PTA containing 1 03 pulsars. We find that an all-sky search will be able to confidently detect nonevolving sources with a redshifted chirp mass of 1 010 M⊙ out to a redshift of about 28 (corresponding to a rest-frame chirp mass of 3.4 ×1 08 M⊙). We discuss the important implications that the large distance reach of a SKA era PTA has on GW observations from optically identified SMBHB candidates. If no SMBHB detections occur, a highly unlikely scenario in the light of our results, the sky-averaged upper limit on strain amplitude will be improved by about 3 orders of magnitude over existing limits.

Gamma-Ray Bursts, their Hosts, and their Supernovae

NASA Astrophysics Data System (ADS)

Bersier, David; Rhoads, James; Rest, Armin; Merrill, Michael; Levan, Andrew; Fruchter, Andrew; Gorosabel Urkia, Javier; Kouveliotou, Chryssa; Hjorth, Jens; Castro Cerón, J. M.; Patel, Sandeep; Strolger, Lou; Tanvir, Nial

2005-08-01

We request rapid optical and near-IR followup observations of gamma ray bursts (GRBs), which will exploit unique NOAO capabilities to obtain (a) rapid afterglow identifications and (b) detailed physical information on selected events. We will use the Mosaic cameras on the 4m telescopes for rapid identification of GRB afterglows. These instruments provide unsurpassed sensitivity over a wide field. This cycle, they will (a) help identify low-redshift bursts found by HETE-2, which may constitute a large fraction of low-z bursts even in the Swift era; and (b) search for Swift bursts found by the hard X-ray BAT instrument in case the Swift narrow- field instruments do not find a bright counterpart. Afterglow IDs from this program will provide targets for our imaging and spectroscopy programs with Spitzer and Gemini. Large area near-IR imaging with ISPI and FLAMINGOS, and simultaneous multicolor imaging with SQIID, will help address several open questions about GRBs and their afterglows: (1) Are ``dark'' GRBs (without detected optical afterglows) a consequence of dust absorption in the GRB environment? (2) Are observed breaks in GRB light curves truly wavelength-independent, as predicted under models of beamed burst afterglows? (3) Can IR observations find bursts at extreme redshifts? (4) How well do afterglow models stand up to detailed comparison with high precision spectral slope and light curve measurements?

Gas kinematics of Lyman Alpha Blobs at z=2-3

NASA Astrophysics Data System (ADS)

Yang, Yujin

2015-08-01

High-redshift Lyman alpha nebulae (Ly-alpha "blobs", LABs) are the site of massive galaxy formation and their early interaction with the intergalactic medium. Research in the past decade has struggled to make progress on the question of what powers these huge Ly-alpha halos and whether the Ly-alpha-emitting gas is outflowing or infalling. First, I will present our optical and NIR spectroscopic observations for the Ly-alpha and the redshifted nebular emission lines such as [OII], [OIII] and Halpha. Using three independent measures --- the velocity offset between the Ly-alpha line and the nonresonant [O III] or Halpha line, the offset of stacked interstellar metal absorption lines, and the spectrally resolved [O III] line profile --- we study the kinematics of gas along the line of sight to galaxies within each blob center. All these kinematic measures show that there are only weak outflows, therefore excluding gas inflows and extreme hyper/superwinds as a source of the extended Ly-alpha emission. I will also present the first detection of molecular gas from a Ly-alpha blob and our on-going effort to characterize the physical conditions of its ISM. The large velocity gradient (LVG) modeling using PdBI observations of CO(3-2), CO(5-4), CO(7-6), CI(2-1) lines suggests that two-phase medium is required to explain the blob's CO SEDs and dust continuum.

Pulsar Timing Array Based Search for Supermassive Black Hole Binaries in the Square Kilometer Array Era.

PubMed

Wang, Yan; Mohanty, Soumya D

2017-04-14

The advent of next generation radio telescope facilities, such as the Square Kilometer Array (SKA), will usher in an era where a pulsar timing array (PTA) based search for gravitational waves (GWs) will be able to use hundreds of well timed millisecond pulsars rather than the few dozens in existing PTAs. A realistic assessment of the performance of such an extremely large PTA must take into account the data analysis challenge posed by an exponential increase in the parameter space volume due to the large number of so-called pulsar phase parameters. We address this problem and present such an assessment for isolated supermassive black hole binary (SMBHB) searches using a SKA era PTA containing 10^{3} pulsars. We find that an all-sky search will be able to confidently detect nonevolving sources with a redshifted chirp mass of 10^{10}  M_{⊙} out to a redshift of about 28 (corresponding to a rest-frame chirp mass of 3.4×10^{8}  M_{⊙}). We discuss the important implications that the large distance reach of a SKA era PTA has on GW observations from optically identified SMBHB candidates. If no SMBHB detections occur, a highly unlikely scenario in the light of our results, the sky-averaged upper limit on strain amplitude will be improved by about 3 orders of magnitude over existing limits.

Charting the parameter space of the global 21-cm signal

NASA Astrophysics Data System (ADS)

Cohen, Aviad; Fialkov, Anastasia; Barkana, Rennan; Lotem, Matan

2017-12-01

The early star-forming Universe is still poorly constrained, with the properties of high-redshift stars, the first heating sources and reionization highly uncertain. This leaves observers planning 21-cm experiments with little theoretical guidance. In this work, we explore the possible range of high-redshift parameters including the star formation efficiency and the minimal mass of star-forming haloes; the efficiency, spectral energy distribution and redshift evolution of the first X-ray sources; and the history of reionization. These parameters are only weakly constrained by available observations, mainly the optical depth to the cosmic microwave background. We use realistic semi-numerical simulations to produce the global 21-cm signal over the redshift range z = 6-40 for each of 193 different combinations of the astrophysical parameters spanning the allowed range. We show that the expected signal fills a large parameter space, but with a fixed general shape for the global 21-cm curve. Even with our wide selection of models, we still find clear correlations between the key features of the global 21-cm signal and underlying astrophysical properties of the high-redshift Universe, namely the Ly α intensity, the X-ray heating rate and the production rate of ionizing photons. These correlations can be used to directly link future measurements of the global 21-cm signal to astrophysical quantities in a mostly model-independent way. We identify additional correlations that can be used as consistency checks.

Dust Formation, Evolution, and Obscuration Effects in the Very High-Redshift Universe

NASA Technical Reports Server (NTRS)

Dwek, Eli; Staguhn, Johannes; Arendt, Richard G.; Kovacs, Attila; Su, Ting; Benford, Dominic J.

2014-01-01

The evolution of dust at redshifts z > or approx. 9, and consequently the dust properties, differs greatly from that in the local universe. In contrast to the local universe, core collapse supernovae (CCSNe) are the only source of thermally-condensed dust. Because of the low initial dust-to-gas mass ratio, grain destruction rates are low, so that CCSNe are net producers of interstellar dust. Galaxies with large initial gas mass or high mass infall rate will therefore have a more rapid net rate of dust production comported to galaxies with lower gas mass, even at the same star formation rate. The dust composition is dominated by silicates, which exhibit a strong rise in the UV opacity near the Lyman break. This "silicate-UV break" may be confused with the Lyman break, resulting in a misidentification of a galaxies' photometric redshift. In this paper we demonstrate these effects by analyzing the spectral energy distribution (SED) of MACS1149-JD, a lensed galaxy at z = 9.6. A potential 2mm counterpart of MACS1149-JD has been identified with GISMO. While additional observations are required to corroborate this identification, we use this possible association to illustrate the physical processes and the observational effects of dust in the very high redshift universe. Subject headings: galaxies: high-redshift - galaxies: evolution - galaxies: individual (MACS1149- JD) - Interstellar medium (ISM), nebulae: dust, extinction - physical data and processes: nuclear reactions, nucleosynthesis, abundances.

Submillimeter Follow-up of WISE-selected Hyperluminous Galaxies

NASA Astrophysics Data System (ADS)

Wu, Jingwen; Tsai, Chao-Wei; Sayers, Jack; Benford, Dominic; Bridge, Carrie; Blain, Andrew; Eisenhardt, Peter R. M.; Stern, Daniel; Petty, Sara; Assef, Roberto; Bussmann, Shane; Comerford, Julia M.; Cutri, Roc; Evans, Neal J., II; Griffith, Roger; Jarrett, Thomas; Lake, Sean; Lonsdale, Carol; Rho, Jeonghee; Stanford, S. Adam; Weiner, Benjamin; Wright, Edward L.; Yan, Lin

2012-09-01

We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (~1000 all-sky) population of galaxies at high redshift (peaks at z = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 μm, yet are clearly detected at 12 and 22 μm. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (z > 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 μm, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 μm, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature. We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 1013 L ⊙. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe. We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

Radio Jet Feedback and Star Formation in Heavily Obscured, Hyperluminous Quasars at Redshifts ˜ 0.5-3. I. ALMA Observations

NASA Astrophysics Data System (ADS)

Lonsdale, Carol J.; Lacy, M.; Kimball, A. E.; Blain, A.; Whittle, M.; Wilkes, B.; Stern, D.; Condon, J.; Kim, M.; Assef, R. J.; Tsai, C.-W.; Efstathiou, A.; Jones, S.; Eisenhardt, P.; Bridge, C.; Wu, J.; Lonsdale, Colin J.; Jones, K.; Jarrett, T.; Smith, R.

2015-11-01

We present Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm (345 GHz) data for 49 high-redshift (0.47 < z < 2.85), luminous (11.7\\lt {log}({L}{{bol}}/{L}⊙ )\\lt 14.2) radio-powerful active galactic nuclei (AGNs), obtained to constrain cool dust emission from starbursts concurrent with highly obscured radiative-mode black hole (BH) accretion in massive galaxies that possess a small radio jet. The sample was selected from the Wide-field Infrared Survey Explorer with extremely steep (red) mid-infrared colors and with compact radio emission from NVSS/FIRST. Twenty-six sources are detected at 870 μm, and we find that the sample has large mid- to far-infrared luminosity ratios, consistent with a dominant and highly obscured quasar. The rest-frame 3 GHz radio powers are 24.7\\lt {log}({P}\\text{3.0 GHz}/{{{W}} {Hz}}-1)\\lt 27.3, and all sources are radio-intermediate or radio-loud. BH mass estimates are 7.7 < log(MBH/M⊙) < 10.2. The rest-frame 1-5 μm spectral energy distributions are very similar to the “Hot DOGs” (hot dust-obscured galaxies), and steeper (redder) than almost any other known extragalactic sources. ISM masses estimated for the ALMA-detected sources are 9.9 < log (MISM/M⊙) < 11.75 assuming a dust temperature of 30 K. The cool dust emission is consistent with star formation rates reaching several thousand M⊙ yr-1, depending on the assumed dust temperature, but we cannot rule out the alternative that the AGN powers all the emission in some cases. Our best constrained source has radiative transfer solutions with approximately equal contributions from an obscured AGN and a young (10-15 Myr) compact starburst.

A Study of PG Quasar-Driven Outflows with COS

NASA Astrophysics Data System (ADS)

Hamann, Frederick

2013-10-01

Quasar outflows are an important part of the quasar phenomenon, but many questions remain about their energetics, physical properties and the role they might play in providing feedback to host galaxy evolution. We searched our own COS far-UV observations from the QUEST survey and other large COS programs to find a sample of 6 bright PG quasars with broad {FWHM > 400 km/s} high velocity {v > 1000 km/s} absorption lines that clearly form in quasar-driven winds. These quasars can fill an important gap in our understanding between local Seyferts with low-speed winds and high-redshift quasars with extreme BAL outflows. They are also well-studied at other wavelengths, with some evidence for the quasars driving galaxy-scale blowouts and shutting down star formation. But almost nothing is known about the quasar outflows themselves. We propose a detailed study of these 6 outflow quasars using new COS FUV observations to 1} expand the existing wavelength coverage across critical lines that are diagnostic of the outflow physical conditions, kinetic energies, and metallicities, and 2} check for line variability as an indicator of the outflow structure and locations. This quasar sample includes unusual cases with many low-abundance {PV 1118,1128 and SIV 1063} and excited-state lines {SIV 1073*, CIII* 1175, CII* 1335} that will provide unprecedented constraints on the outflow properties, plus the first known OVI-only mini-BAL outflow {no lower ions detected} for which we will cover NeVIII 770,780 to probe the highest ionization gas. The high FUV sensitivity of COS is uniquely able to measure this wide range of outflow lines in low-redshift quasars with no Lya forest contamination.

Submillimeter Follow-Up of WISE-Selected Hyperluminous Galaxies

NASA Technical Reports Server (NTRS)

Wu, Jingwen; Tsai, Chao-Wei; Sayers, Jack; Benford, Dominic; Bridge, Carrie; Blain, Andrew; Eisenhardt, Peter R.; Stern, Daniel; Petty, Sara; Assef, Roberto;

Submillimeter Follow-up of Wise-Selected Hyperluminous Galaxies

NASA Technical Reports Server (NTRS)

Wu, Jingwen; Tsai, Chao-Wei; Sayers, Jack; Benford, Dominic; Bridge, Carrie; Blain, Andrew; Eisenhardt, Peter R. M.; Stern, Daniel; Petty, Sara; Assef, Roberto;

INVISIBLE ACTIVE GALACTIC NUCLEI. II. RADIO MORPHOLOGIES AND FIVE NEW H i 21 cm ABSORPTION LINE DETECTORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Ting; Stocke, John T.; Darling, Jeremy

2016-03-15

This is the second paper directed toward finding new highly redshifted atomic and molecular absorption lines at radio frequencies. To this end, we selected a sample of 80 candidates for obscured radio-loud active galactic nuclei (AGNs) and presented their basic optical/near-infrared (NIR) properties in Paper I. In this paper, we present both high-resolution radio continuum images for all of these sources and H i 21 cm absorption spectroscopy for a few selected sources in this sample. A-configuration 4.9 and 8.5 GHz Very Large Array continuum observations find that 52 sources are compact or have substantial compact components with size <0.″5more » and flux densities >0.1 Jy at 4.9 GHz. The 36 most compact sources were then observed with the Very Long Baseline Array at 1.4 GHz. One definite and 10 candidate Compact Symmetric Objects (CSOs) are newly identified, which is a detection rate of CSOs ∼three times higher than the detection rate previously found in purely flux-limited samples. Based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption-line searches. Twenty-seven sources were observed for H i 21 cm absorption at their photometric or spectroscopic redshifts with only six detections (five definite and one tentative). However, five of these were from a small subset of six CSOs with pure galaxy optical/NIR spectra (i.e., any AGN emission is obscured) and for which accurate spectroscopic redshifts place the redshifted 21 cm line in a radio frequency intereference (RFI)-free spectral “window” (i.e., the percentage of H i 21 cm absorption-line detections could be as high as ∼90% in this sample). It is likely that the presence of ubiquitous RFI and the absence of accurate spectroscopic redshifts preclude H i detections in similar sources (only 1 detection out of the remaining 22 sources observed, 13 of which have only photometric redshifts); that is, H i absorption may well be present but is masked by the RFI. Future searches for highly redshifted H i and molecular absorption can easily find more distant CSOs among bright, “blank field” radio sources, but will be severely hampered by an inability to determine accurate spectroscopic redshifts due to their lack of rest-frame UV continuum.« less

A Model-independent Photometric Redshift Estimator for Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Wang, Yun

2007-01-01

The use of Type Ia supernovae (SNe Ia) as cosmological standard candles is fundamental in modern observational cosmology. In this Letter, we derive a simple empirical photometric redshift estimator for SNe Ia using a training set of SNe Ia with multiband (griz) light curves and spectroscopic redshifts obtained by the Supernova Legacy Survey (SNLS). This estimator is analytical and model-independent it does not use spectral templates. We use all the available SNe Ia from SNLS with near-maximum photometry in griz (a total of 40 SNe Ia) to train and test our photometric redshift estimator. The difference between the estimated redshifts zphot and the spectroscopic redshifts zspec, (zphot-zspec)/(1+zspec), has rms dispersions of 0.031 for 20 SNe Ia used in the training set, and 0.050 for 20 SNe Ia not used in the training set. The dispersion is of the same order of magnitude as the flux uncertainties at peak brightness for the SNe Ia. There are no outliers. This photometric redshift estimator should significantly enhance the ability of observers to accurately target high-redshift SNe Ia for spectroscopy in ongoing surveys. It will also dramatically boost the cosmological impact of very large future supernova surveys, such as those planned for the Advanced Liquid-mirror Probe for Astrophysics, Cosmology, and Asteroids (ALPACA) and the Large Synoptic Survey Telescope (LSST).

Seeing Red and Shooting Blanks: A Study of Red Quasars and Blank Field X-Ray Sources

NASA Technical Reports Server (NTRS)

Elvis, Martin; Oliversen, Ronald J. (Technical Monitor)

2002-01-01

We have identified a population of 'blank field sources' (or 'blanks') among the ROSAT (Roentgen Satellite) bright unidentified X-ray sources with faint optical counterparts. The extreme X-ray over optical flux ratio of blank field sources is not compatible with the main classes of X-ray emitters except for extreme BL Lacertae objects at fx/fv is equal to or less than 35. From the analysis of ROSAT archival data we found evidence for only three sources, out of 16, needing absorption in excess of the Galactic value and no indication of variability. We also found evidence for an extended nature for only one of the five blanks with a serendipitous HRI (High Resolution Imager) detection; this source (1WGA J1226.9+3332) was confirmed as a z=0.89 cluster of galaxies. Palomar images reveal the presence of a red (O - E is equal to or greater than 2) counterpart in the X-ray error circle for six blanks. The identification process brought to the discovery of another high z cluster of galaxies, one (possibly extreme) BL Lac and two apparently normal type 1 AGNs (Active Galactic Nuclei). These AGNs, together with four more AGN-like objects seem to form a well defined group: they present type 1 X-ray spectra but red Palomar counterparts. We discuss the possible explanations for the discrepancy between the X-ray and optical data, among which: a suppressed big blue bump emission, an extreme dust to gas (approximately 40 - 60 the Galactic ratio) ratio value and a high redshift (z is greater than or equal to 3.5) QSO (Quasi-Stellar Object) nature. These AGN-like blanks seem to be the bright (and easier to study) analogs of the sources which are being found in deep Chandra observations. Five more blanks have a still an unknown nature.

Lens models and magnification maps of the six Hubble Frontier Fields clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Traci L.; Sharon, Keren; Bayliss, Matthew B.

2014-12-10

We present strong-lensing models as well as mass and magnification maps for the cores of the six Hubble Space Telescope (HST) Frontier Fields galaxy clusters. Our parametric lens models are constrained by the locations and redshifts of multiple image systems of lensed background galaxies. We use a combination of photometric redshifts and spectroscopic redshifts of the lensed background sources obtained by us (for A2744 and AS1063), collected from the literature, or kindly provided by the lensing community. Using our results, we (1) compare the derived mass distribution of each cluster to its light distribution, (2) quantify the cumulative magnification powermore » of the HST Frontier Fields clusters, (3) describe how our models can be used to estimate the magnification and image multiplicity of lensed background sources at all redshifts and at any position within the cluster cores, and (4) discuss systematic effects and caveats resulting from our modeling methods. We specifically investigate the effect of the use of spectroscopic and photometric redshift constraints on the uncertainties of the resulting models. We find that the photometric redshift estimates of lensed galaxies are generally in excellent agreement with spectroscopic redshifts, where available. However, the flexibility associated with relaxed redshift priors may cause the complexity of large-scale structure that is needed to account for the lensing signal to be underestimated. Our findings thus underline the importance of spectroscopic arc redshifts, or tight photometric redshift constraints, for high precision lens models. All products from our best-fit lens models (magnification, convergence, shear, deflection field) and model simulations for estimating errors are made available via the Mikulski Archive for Space Telescopes.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gair, Jonathan R.; Tang, Christopher; Volonteri, Marta

One of the sources of gravitational waves for the proposed space-based gravitational wave detector, the Laser Interferometer Space Antenna (LISA), are the inspirals of compact objects into supermassive black holes in the centers of galaxies--extreme-mass-ratio inspirals (EMRIs). Using LISA observations, we will be able to measure the parameters of each EMRI system detected to very high precision. However, the statistics of the set of EMRI events observed by LISA will be more important in constraining astrophysical models than extremely precise measurements for individual systems. The black holes to which LISA is most sensitive are in a mass range that ismore » difficult to probe using other techniques, so LISA provides an almost unique window onto these objects. In this paper we explore, using Bayesian techniques, the constraints that LISA EMRI observations can place on the mass function of black holes at low redshift. We describe a general framework for approaching inference of this type--using multiple observations in combination to constrain a parametrized source population. Assuming that the scaling of the EMRI rate with the black-hole mass is known and taking a black-hole distribution given by a simple power law, dn/dlnM=A{sub 0}(M/M{sub *}){sup {alpha}}{sub 0}, we find that LISA could measure the parameters to a precision of {Delta}(lnA{sub 0}){approx}0.08, and {Delta}({alpha}{sub 0}){approx}0.03 for a reference model that predicts {approx}1000 events. Even with as few as 10 events, LISA should constrain the slope to a precision {approx}0.3, which is the current level of observational uncertainty in the low-mass slope of the black-hole mass function. We also consider a model in which A{sub 0} and {alpha}{sub 0} evolve with redshift, but find that EMRI observations alone do not have much power to probe such an evolution.« less

Far-Infrared Line Emission from High Redshift Quasars

NASA Technical Reports Server (NTRS)

Benford, D. J.; Cox, P.; Hunter, T. R.; Malhotra, S.; Phillips, T. G.; Yun, M. S.

2002-01-01

Recent millimeter and submillimeter detections of line emission in high redshift objects have yielded new information and constraints on star formation at early epochs. Only CO transitions and atomic carbon transitions have been detected from these objects, yet bright far-infrared lines such as C+ at 158 microns and N+ at 205 microns should be fairly readily detectable when redshifted into a submillimeter atmospheric window. We have obtained upper limits for C+ emission &om two high redshift quasars, BR1202-0725 at z=4.69 and BRI1335-0415 at z=4.41. These limits show that the ratio of the C+ line luminosity to the total far-infrared luminosity is less than 0.0l%, ten times smaller than has been observed locally. Additionally, we have searched for emission in the N+ 205 micron line from the Cloverleaf quasar, H1413+117, and detected emission in CO J=7-6. The N+ emission is found to be below the amount predicted based on comparison to the only previous detection of this line, in the starburst galaxy M82.

A Study of Nine High-Redshift Clusters of Galaxies. II. Photometry, Spectra, and Ages of Clusters 0023+0423 and 1604+4304

NASA Astrophysics Data System (ADS)

Postman, Marc; Lubin, Lori M.; Oke, J. B.

1998-08-01

We present an extensive photometric and spectroscopic study of two high-redshift clusters of galaxies based on data obtained from the Keck 10 m telescopes and the Hubble Space Telescope. The clusters Cl 0023+0423 (z = 0.84) and Cl 1604+4304 (z = 0.90) are part of a multiwavelength program of Oke, Postman & Lubin to study nine candidate clusters at z >~ 0.6. Based on these observations, we study in detail both the field and cluster populations. From the confirmed cluster members, we find that Cl 0023+0423 actually consists of two components separated by ~2900 km s^-1. A kinematic analysis indicates that the two components are a poor cluster with ~3 x 10^14 M_⊙ and a less massive group with ~10^13 M_⊙. Cl 1604+4304 is a centrally concentrated, rich cluster at z = 0.8967 with a velocity dispersion of 1226 km s^-1 and a mass of ~3 x 10^15 M_⊙. A large percentage of the cluster members show high levels of star formation activity. Approximately 57% and 50% of the galaxies are active in Cl 0023+0423 and Cl 1604+4304, respectively. These numbers are significantly larger than those found in intermediate-redshift clusters. We also observe many old, red galaxies. Found mainly in Cl 1604+4304, they have spectra consistent with passive stellar evolution, typical of the populations of early-type galaxies in low- and intermediate-redshift clusters. We have calculated their ages by comparing their spectral energy distributions to standard Bruzual & Charlot evolutionary models. We find that their colors are consistent with models having an exponentially decreasing star formation rate with a time constant of 0.6 Gyr. We also observe a significant luminosity brightening in our brightest cluster galaxies. Compared with brightest cluster galaxies at z ~ 0.1, we find a luminosity increase of ~1 mag in the rest M_B and ~0.8 mag in the rest M_V. In the field, we find that ~76% of the galaxies with z > 0.4 show emission-line activity. These numbers are consistent with previous studies. We find that an exponentially decaying star formation rate is required to produce the observed amount of star formation for the majority of the galaxies in our sample. A time constant of tau = 0.6 Gyr appears to be optimal. We also detect several interesting galaxies at z > 1. Two of these galaxies are extremely luminous, with strong Mg ii lambda2800 absorption and Fe ii resonance-line absorption. These lines are so strong that we conclude that they must be generated within the atmospheres of a large population of young, hot stars.

The ionisation parameter of star-forming galaxies evolves with the specific star formation rate

NASA Astrophysics Data System (ADS)

Kaasinen, Melanie; Kewley, Lisa; Bian, Fuyan; Groves, Brent; Kashino, Daichi; Silverman, John; Kartaltepe, Jeyhan

2018-04-01

We investigate the evolution of the ionisation parameter of star-forming galaxies using a high-redshift (z ˜ 1.5) sample from the FMOS-COSMOS survey and matched low-redshift samples from the Sloan Digital Sky Survey. By constructing samples of low-redshift galaxies for which the stellar mass (M*), star formation rate (SFR) and specific star formation rate (sSFR) are matched to the high-redshift sample we remove the effects of an evolution in these properties. We also account for the effect of metallicity by jointly constraining the metallicity and ionisation parameter of each sample. We find an evolution in the ionisation parameter for main-sequence, star-forming galaxies and show that this evolution is driven by the evolution of sSFR. By analysing the matched samples as well as a larger sample of z < 0.3, star-forming galaxies we show that high ionisation parameters are directly linked to high sSFRs and are not simply the byproduct of an evolution in metallicity. Our results are physically consistent with the definition of the ionisation parameter, a measure of the hydrogen ionising photon flux relative to the number density of hydrogen atoms.

Tidal Disruption Events Across Cosmic Time

NASA Astrophysics Data System (ADS)

Fialkov, Anastasia; Loeb, Abraham

2017-01-01

Tidal disruption events (TDEs) of stars by single or binary super-massive black holes illuminate the environment around quiescent black holes in galactic nuclei allowing to probe dorment black holes. We predict the TDE rates expected to be detected by next-generation X-ray surveys. We include events sourced by both single and binary super-massive black holes assuming that 10% of TDEs lead to the formation of relativistic jets and are therefore observable to higher redshifts. Assigning the Eddington luminosity to each event, we show that if the occupation fraction of intermediate black holes is high, more than 90% of the brightest TDE might be associated with merging black holes which are potential sources for eLISA. Next generation telescopes with improved sensitivities should probe dim local TDE events as well as bright events at high redshifts. We show that an instrument which is 50 times more sensitive than the Swift Burst Alert Telescope (BAT) is expected to trigger ~10 times more events than BAT. Majority of these events originate at low redshifts (z<0.5) if the occupation fraction of IMBHs is high and at high-redshift (z>2) if it is low.

Synchrotron pair halo and echo emission from blazars in the cosmic web: application to extreme TeV blazars

NASA Astrophysics Data System (ADS)

Oikonomou, Foteini; Murase, Kohta; Kotera, Kumiko

2014-08-01

High frequency peaked, high redshift blazars, are extreme in the sense that their spectrum is particularly hard and peaks at TeV energies. Standard leptonic scenarios require peculiar source parameters and/or a special setup in order to account for these observations. Electromagnetic cascades seeded by ultra-high energy cosmic rays (UHECR) in the intergalactic medium have also been invoked, assuming a very low intergalactic magnetic field (IGMF). Here we study the synchrotron emission of UHECR secondaries produced in blazars located in magnetised environments, and show that it can provide an alternative explanation to these challenged channels, for sources embedded in structured regions with magnetic field strengths of the order of 10-7 G. To demonstrate this, we focus on three extreme blazars: 1ES 0229+200, RGB J0710+591, and 1ES 1218+304. We model the expected gamma-ray signal from these sources through a combination of numerical Monte Carlo simulations and solving the kinetic equations of the particles in our simulations, and explore the UHECR source and intergalactic medium parameter space to test the robustness of the emission. We show that the generated synchrotron-pair halo and echo flux at the peak energy is not sensitive to variations in the overall IGMF strength. This signal is unavoidable in contrast to the inverse Compton-pair halo and echo intensity, which is appealing in view of the large uncertainties on the IGMF in voids of large scale structure. It is also shown that the variability of blazar gamma-ray emission can be accommodated by the synchrotron emission of secondary products of UHE neutral beams if these are emitted by UHECR accelerators inside magnetised regions.

Galaxy Evolution in the Reddest Possible Filter

NASA Astrophysics Data System (ADS)

Richards, E. A.

We describe an observational programme aimed at understanding the radio emission from distant, rapidly evolving galaxy populations. These observations were carried out at 1.4 and 8.5 GHz with the VLA, centred on the Hubble Deep Field, obtaining limiting flux densities of 40 and 8 μJy respectively. The differential count of the radio sources is marginally sub-Euclidean to the completeness limits (γ = - 2.4 +/- 0.1) and fluctuation analysis suggests nearly 60 sources per arcmin^2 at the 1 μJy level. Using high-resolution 1.4 GHz observations obtained with MERLIN, we resolve all radio sources detected in the VLA complete sample and measure a median angular size for the microjansky radio population of 1-2``. This clue, coupled with the steep spectral index of the 1.4 GHz selected sample, suggests diffuse synchrotron radiation in z ~ 1 galactic discs. The wide-field HST and ground-based optical exposures show that the radio sources are identified primarily with disc systems composed of irregulars, peculiars, interacting/merging galaxies and a few isolated field spirals. Only 20% of the radio sources can be attributed to AGN - the majority are probably associated with starburst activity. The available redshifts range from 0.1 to 3, with a mean of about 0.8. We are plrobably witnessing a major episode of starburst activity in these luminous (L > L_*) systems, occasionally accompanied by an embedded AGN. About 20% of the radio sources remain unidentified to I = 26-28 in the HDF and flanking fields. Several of these objects have extremely red counterparts. We suggest that these are high-redshift dusty protogalaxies.

Science from a glimpse: Hubble SNAPshot observations of massive galaxy clusters

NASA Astrophysics Data System (ADS)

Repp, A.; Ebeling, H.

2018-06-01

Hubble Space Telescope SNAPshot surveys of 86 X-ray selected galaxy clusters at 0.3 < z < 0.5 from the MACS sample have proven invaluable for the exploration of a wide range of astronomical research topics. We here present an overview of the four MACS SNAPshot surveys conducted from Cycle 14 to Cycle 20 as part of a long-term effort aimed at identifying exceptional cluster targets for in-depth follow up by the extragalactic community. We also release redshifts and X-ray luminosities of all clusters observed as part of this initiative. To illustrate the power of SNAPshot observations of MACS clusters, we explore several aspects of galaxy evolution illuminated by the images obtained for these programmes. We confirm the high lensing efficiency of X-ray selected clusters at z > 0.3. Examining the evolution of the slope of the cluster red sequence, we observe at best a slight decrease with redshift, indicating minimal age contribution since z ˜ 1. Congruent to previous studies' findings, we note that the two BCGs which are significantly bluer (≥5σ) than their clusters' red sequences reside in relaxed clusters and exhibit pronounced internal structure. Thanks to our targets' high X-ray luminosity, the subset of our sample observed with Chandra adds valuable leverage to the X-ray luminosity-optical richness relation, which, albeit with substantial scatter, is now clearly established from groups to extremely massive clusters of galaxies. We conclude that SNAPshot observations of MACS clusters stand to continue to play a vital pathfinder role for astrophysical investigations across the entire electromagnetic spectrum.

Four hot DOGs in the microwave

NASA Astrophysics Data System (ADS)

Frey, Sándor; Paragi, Zsolt; Gabányi, Krisztina Éva; An, Tao

2016-01-01

Hot dust-obscured galaxies (hot DOGs) are a rare class of hyperluminous infrared galaxies identified with the Wide-field Infrared Survey Explorer (WISE) satellite. The majority of them are at high redshifts (z ˜ 2-3), at the peak epoch of star formation in the Universe. Infrared, optical, radio, and X-ray data suggest that hot DOGs contain heavily obscured, extremely luminous active galactic nuclei (AGN). This class may represent a short phase in the life of the galaxies, signifying the transition from starburst- to AGN-dominated phases. Hot DOGs are typically radio-quiet, but some of them show mJy-level emission in the radio (microwave) band. We observed four hot DOGs using the technique of very long baseline interferometry (VLBI). The 1.7 GHz observations with the European VLBI Network (EVN) revealed weak radio features in all sources. The radio is free from dust obscuration and, at such high redshifts, VLBI is sensitive only to compact structures that are characteristic of AGN activity. In two cases (WISE J0757+5113, WISE J1603+2745), the flux density of the VLBI-detected components is much smaller than the total flux density, suggesting that ˜70-90 per cent of the radio emission, while still dominated by AGN, originates from angular scales larger than that probed by the EVN. The source WISE J1146+4129 appears a candidate compact symmetric object, and WISE J1814+3412 shows a 5.1 kpc double structure, reminiscent of hotspots in a medium-sized symmetric object. Our observations support that AGN residing in hot DOGs may be genuine young radio sources where starburst and AGN activities coexist.

Gamma-ray blazars within the first 2 billion years

DOE PAGES

Ackermann, M.; Ajello, M.; Baldini, L.; ...

2017-02-27

Here, the detection of high-redshift (more » $$z\\,\\gt 3$$) blazars enables the study of the evolution of the most luminous relativistic jets over cosmic time. More importantly, high-redshift blazars tend to host massive black holes and can be used to constrain the space density of heavy black holes in the early universe. Here, we report the first detection with the Fermi-Large Area Telescope of five γ-ray-emitting blazars beyond z = 3.1, more distant than any blazars previously detected in γ-rays. Among these five objects, NVSS J151002+570243 is now the most distant known γ-ray-emitting blazar at z = 4.31. These objects have steeply falling γ-ray spectral energy distributions (SEDs), and those that have been observed in X-rays have a very hard X-ray spectrum, both typical of powerful blazars. Their Compton dominance (ratio of the inverse Compton to synchrotron peak luminosities) is also very large ($$\\gt 20$$). All of these properties place these objects among the most extreme members of the blazar population. Their optical spectra and the modeling of their optical-UV SEDs confirm that these objects harbor massive black holes ($${M}_{\\mathrm{BH}}\\sim {10}^{8-10}\\,{M}_{\\odot }$$). We find that, at $$z\\approx 4$$, the space density of $$\\gt {10}^{9}\\,{M}_{\\odot }$$ black holes hosted in radio-loud and radio-quiet active galactic nuclei are similar, implying that radio-loudness may play a key role in rapid black hole growth in the early universe.« less

Conversion of gas into stars in the Galactic center

NASA Astrophysics Data System (ADS)

Longmore, S. N.

2014-05-01

The star formation rate in the central 500 pc of the Milky Way is lower by a factor of > 10 than expected for the substantial amount of dense gas it contains, which challenges current star formation theories. I discuss which physical mechanisms could be causing this observation and put forward a self-consistent cycle of star formation in the Galactic center, in which the plausible star formation inhibitors are combined. Their ubiquity suggests that the perception of a lowered central SFR should be a common phenomenon in other galaxies with direct implications for galactic star formation and also potentially supermassive black hole growth. I then describe a scenario to explain the presence of super star clusters in the Galactic center environment, in which their formation is triggered by gas streams passing close to the minimum of the global Galactic gravitational potential at the location of the central supermassive black hole, Sgr A*. If this triggering mechanism can be verified, we can use the known time interval since closest approach to Sgr A* to study the physics of stellar mass assembly in an extreme environment as a function of absolute time. I outline the first results from detailed numerical simulations testing this scenario. Finally, I describe a study showing that in terms of the baryonic composition, kinematics, and densities, the gas in the Galactic center is indistinguishable from high-redshift clouds and galaxies. As such, the Galactic center clouds may be used as a template to understand the evolution (and possibly the life cycle) of high-redshift clouds and galaxies.

The Diverse Environments of Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Perley, Daniel Alan

I present results from several years of concerted observations of the afterglows and host galaxies of gamma-ray bursts (GRBs), the most energetic explosions in the Universe. Short gamma-ray bursts originate from a wide variety of environments, including disk galaxies, elliptical galaxies, galaxy haloes, and intracluster and intergalactic space. Long gamma ray bursts associate almost exclusively with star-forming hosts, but the properties of these galaxies also vary widely. Some are hosted in extremely small galaxies, difficult to identify directly in emission or infer from the absorption of afterglow light, but the host luminosity distribution extends up to very luminous (> L*) systems as well. A significant fraction of long GRBs are observed along highly dust-obscured sightlines through their host medium. Some of these events are hosted within conspicuously dusty galaxies, although the hosts of other dust-obscured events show no outward signs of significant internal dust content. By measuring the wavelength dependence of dust absorption profiles using a few well-observed GRB afterglows, I provide evidence for ordinary dust with properties similar to those of dust in the Milky Way in a system at z ˜ 3, but a very different absorption profile from the dust in a galaxy at z ˜ 5, providing tentative evidence to support a transition in dust composition early in the history of the Universe. I present an observationally-determined redshift distribution for Swift GRBs, showing few to originate from high redshifts (z ≳ 5). I also provide the first photometric and spectroscopic catalogs from one of the largest GRB host-galaxy surveys ever conducted, including observations of almost 150 distinct GRB fields.

ON THE ORIGIN OF THE HIGHEST REDSHIFT GAMMA-RAY BURSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belczynski, Krzysztof; Holz, Daniel E.; Fryer, Chris L.

2010-01-01

GRB 080913 and GRB 090423 are the most distant gamma-ray bursts (GRBs) known to date, with spectroscopically determined redshifts of z = 6.7 and z = 8.1, respectively. The detection of bursts at this early epoch of the universe significantly constrains the nature of GRBs and their progenitors. We perform population synthesis studies of the formation and evolution of early stars, and calculate the resulting formation rates of short- and long-duration GRBs at high redshift. The peak of the GRB rate from Population II stars occurs at z approx 7 for a model with efficient/fast mixing of metals, while itmore » is found at z approx 3 for an inefficient/slow metallicity evolution model. We show that in the redshift range 6 approx< z approx< 10, essentially all GRBs originate from Population II stars, regardless of the metallicity evolution model. These stars (having small, but non-zero metallicity) are the most likely progenitors for both long GRBs (collapsars) and short GRBs (neutron star-neutron star or blackhole-neutron star mergers) at this epoch. Although the predicted intrinsic rates of long and short GRBs are similar at these high redshifts, observational selection effects lead to higher (a factor of approx10) observed rates for long GRBs. We conclude that the two recently observed high-z GRB events are most likely long GRBs originating from Population II collapsars.« less

Calibration of GRB Luminosity Relations with Cosmography

NASA Astrophysics Data System (ADS)

Gao, He; Liang, Nan; Zhu, Zong-Hong

For the use of gamma-ray bursts (GRBs) to probe cosmology in a cosmology-independent way, a new method has been proposed to obtain luminosity distances of GRBs by interpolating directly from the Hubble diagram of SNe Ia, and then calibrating GRB relations at high redshift. In this paper, following the basic assumption in the interpolation method that objects at the same redshift should have the same luminosity distance, we propose another approach to calibrate GRB luminosity relations with cosmographic fitting directly from SN Ia data. In cosmography, there is a well-known fitting formula which can reflect the Hubble relation between luminosity distance and redshift with cosmographic parameters which can be fitted from observation data. Using the Cosmographic fitting results from the Union set of SNe Ia, we calibrate five GRB relations using GRB sample at z ≤ 1.4 and deduce distance moduli of GRBs at 1.4 < z ≤ 6.6 by generalizing above calibrated relations at high redshift. Finally, we constrain the dark energy parameterization models of the Chevallier-Polarski-Linder (CPL) model, the Jassal-Bagla-Padmanabhan (JBP) model and the Alam model with GRB data at high redshift, as well as with the cosmic microwave background radiation (CMB) and the baryonic acoustic oscillation (BAO) observations, and we find the ΛCDM model is consistent with the current data in 1-σ confidence region.

Indications of a spatial variation of the fine structure constant.

PubMed

Webb, J K; King, J A; Murphy, M T; Flambaum, V V; Carswell, R F; Bainbridge, M B

2011-11-04

We previously reported Keck telescope observations suggesting a smaller value of the fine structure constant α at high redshift. New Very Large Telescope (VLT) data, probing a different direction in the Universe, shows an inverse evolution; α increases at high redshift. Although the pattern could be due to as yet undetected systematic effects, with the systematics as presently understood the combined data set fits a spatial dipole, significant at the 4.2 σ level, in the direction right ascension 17.5 ± 0.9 h, declination -58 ± 9 deg. The independent VLT and Keck samples give consistent dipole directions and amplitudes, as do high and low redshift samples. A search for systematics, using observations duplicated at both telescopes, reveals none so far which emulate this result.

SIX MORE QUASARS AT REDSHIFT 6 DISCOVERED BY THE CANADA-FRANCE HIGH-z QUASAR SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willott, Chris J.; Crampton, David; Hutchings, John B.

2009-03-15

We present imaging and spectroscopic observations for six quasars at z {>=} 5.9 discovered by the Canada-France High-z Quasar Survey (CFHQS). The CFHQS contains subsurveys with a range of flux and area combinations to sample a wide range of quasar luminosities at z {approx} 6. The new quasars have luminosities 10-75 times lower than the most luminous Sloan Digital Sky Survey quasars at this redshift. The least luminous quasar, CFHQS J0216-0455 at z = 6.01, has absolute magnitude M {sub 1450} = -22.21, well below the likely break in the luminosity function. This quasar is not detected in a deepmore » XMM-Newton survey showing that optical selection is still a very efficient tool for finding high-redshift quasars.« less

Steep Hard-X-ray Spectra Indicate Extremely High Accretion Rates in Weak Emission-Line Quasars

NASA Astrophysics Data System (ADS)

Marlar, Andrea; Shemmer, Ohad; Anderson, Scott F.; Brandt, W. Niel; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Luo, Bin; Plotkin, Richard; Richards, Gordon T.; Schneider, Donald P.; Wu, Jianfeng

2018-06-01

We present XMM-Newton imaging spectroscopy of ten weak emission-line quasars (WLQs) at 0.928 ≤ z ≤ 3.767, six of which are radio quiet and four which are radio intermediate. The new X-ray data enabled us to measure the hard-X-ray power-law photon index (Γ) in each source with relatively high accuracy. These measurements allowed us to confirm previous reports that WLQs have steeper X-ray spectra, therefore indicating higher accretion rates with respect to "typical" quasars. A comparison between the Γ values of our radio-quiet WLQs and those of a carefully-selected, uniform sample of 84 quasars shows that the first are significantly higher, at the ≥ 3σ level. Collectively, the four radio-intermediate WLQs have lower Γ values with respect to the six radio-quiet WLQs, as may be expected if the spectra of the first group are contaminated by X-ray emission from a jet. These results suggest that, in the absence of significant jet emission along our line of sight, WLQs constitute the extreme high end of the accretion rate distribution in quasars. We detect soft excess emission in our lowest-redshift radio-quiet WLQ, in agreement with previous findings suggesting that the prominence of this feature is associated with a high accretion rate. We have not detected signatures of Compton reflection, Fe Kα lines, or strong variability between two X-ray epochs in any of our WLQs.

Early Science with the Large Millimeter Telescope: CO and [C II] Emission in the z = 4.3 AzTEC J095942.9+022938 (COSMOS AzTEC-1)

NASA Astrophysics Data System (ADS)

Yun, Min S.; Aretxaga, I.; Gurwell, M. A.; Hughes, D. H.; Montaña, A.; Narayanan, G.; Rosa-González, D.; Sánchez-Argüelles, D.; Schloerb, F. P.; Snell, R. L.; Vega, O.; Wilson, G. W.; Zeballos, M.; Chavez, M.; Cybulski, R.; Díaz-Santos, T.; De La Luz, V.; Erickson, N.; Ferrusca, D.; Gim, H. B.; Heyer, M. H.; Iono, D.; Pope, A.; Rogstad, S. M.; Scott, K. S.; Souccar, K.; Terlevich, E.; Terlevich, R.; Wilner, D.; Zavala, J. A.

2015-12-01

Measuring redshifted CO line emission is an unambiguous method for obtaining an accurate redshift and total cold gas content of optically faint, dusty starburst systems. Here, we report the first successful spectroscopic redshift determination of AzTEC J095942.9+022938 (`COSMOS AzTEC-1'), the brightest 1.1 mm continuum source found in the AzTEC/James Clerk Maxwell Telescope survey (Scott et al.), through a clear detection of the redshifted CO (4-3) and CO (5-4) lines using the Redshift Search Receiver on the Large Millimeter Telescope. The CO redshift of z = 4.3420 ± 0.0004 is confirmed by the detection of the redshifted 158 μm [C II] line using the Submillimeter Array. The new redshift and Herschel photometry yield LFIR = (1.1 ± 0.1) × 1013 L⊙ and SFR ≈ 1300 M⊙ yr-1. Its molecular gas mass derived using the ultraluminous infrared galaxy conversion factor is 1.4 ± 0.2 × 1011M⊙ while the total interstellar medium mass derived from the 1.1 mm dust continuum is 3.7 ± 0.7 × 1011M⊙ assuming Td = 35 K. Our dynamical mass analysis suggests that the compact gas disc (r ≈ 1.1 kpc, inferred from dust continuum and spectral energy distribution analysis) has to be nearly face-on, providing a natural explanation for the uncommonly bright, compact stellar light seen by the HST. The [C II] line luminosity L_[C II]= 7.8± 1.1 × 10^9 L_{⊙} is remarkably high, but it is only 0.04 per cent of the total IR luminosity. AzTEC COSMOS-1 and other high redshift sources with a spatially resolved size extend the tight trend seen between [C II]/FIR ratio and ΣFIR among IR-bright galaxies reported by Díaz-Santos et al. by more than an order of magnitude, supporting the explanation that the higher intensity of the IR radiation field is responsible for the `[C II] deficiency' seen among luminous starburst galaxies.

THE EVOLUTION OF EARLY- AND LATE-TYPE GALAXIES IN THE COSMIC EVOLUTION SURVEY UP TO z {approx} 1.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pannella, Maurilio; Gabasch, Armin; Drory, Niv

2009-08-10

The Cosmic Evolution Survey (COSMOS) allows for the first time a highly significant census of environments and structures up to redshift 1, as well as a full morphological description of the galaxy population. In this paper we present a study aimed to constrain the evolution, in the redshift range 0.2 < z < 1.2, of the mass content of different morphological types and its dependence on the environmental density. We use a deep multicolor catalog, covering an area of {approx}0.7 deg{sup 2} inside the COSMOS field, with accurate photometric redshifts (i {approx}< 26.5 and {delta}z/(z {sub spec} + 1) {approx}more » 0.035). We estimate galaxy stellar masses by fitting the multicolor photometry to a grid of composite stellar population models. We quantitatively describe the galaxy morphology by fitting point-spread function convolved Sersic profiles to the galaxy surface brightness distributions down to F814 = 24 mag for a sample of 41,300 objects. We confirm an evolution of the morphological mix with redshift: the higher the redshift the more disk-dominated galaxies become important. We find that the morphological mix is a function of the local comoving density: the morphology density relation extends up to the highest redshift explored. The stellar mass function of disk-dominated galaxies is consistent with being constant with redshift. Conversely, the stellar mass function of bulge-dominated systems shows a decline in normalization with redshift. Such different behaviors of late-types and early-types stellar mass functions naturally set the redshift evolution of the transition mass. We find a population of relatively massive, early-type galaxies, having high specific star formation rate (SSFR) and blue colors which live preferentially in low-density environments. The bulk of massive (>7 x 10{sup 10} M {sub sun}) early-type galaxies have similar characteristic ages, colors, and SSFRs independently of the environment they belong to, with those hosting the oldest stars in the universe preferentially belonging to the highest density regions. The whole catalog including morphological information and stellar mass estimates analyzed in this work is made publicly available.« less

Cluster Mass Calibration at High Redshift: HST Weak Lensing Analysis of 13 Distant Galaxy Clusters from the South Pole Telescope Sunyaev-Zel’dovich Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schrabback, T.; Applegate, D.; Dietrich, J. P.

Here we present an HST/Advanced Camera for Surveys (ACS) weak gravitational lensing analysis of 13 massive high-redshift (z median = 0.88) galaxy clusters discovered in the South Pole Telescope (SPT) Sunyaev–Zel'dovich Survey. This study is part of a larger campaign that aims to robustly calibrate mass–observable scaling relations over a wide range in redshift to enable improved cosmological constraints from the SPT cluster sample. We introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scaling relations significantly. First, we efficiently remove cluster members from the source sample by selecting very blue galaxies in V-I colour. Our estimate of the source redshift distribution is based on Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) data, where we carefully mimic the source selection criteria of the cluster fields. We apply a statistical correction for systematic photometric redshift errors as derived from Hubble Ultra Deep Field data and verified through spatial cross-correlations. We account for the impact of lensing magnification on the source redshift distribution, finding that this is particularly relevant for shallower surveys. Finally, we account for biases in the mass modelling caused by miscentring and uncertainties in the concentration–mass relation using simulations. In combination with temperature estimates from Chandra we constrain the normalization of the mass–temperature scaling relation ln (E(z)M 500c/10 14 M ⊙) = A + 1.5ln (kT/7.2 keV) to A=1.81more » $$+0.24\\atop{-0.14}$$(stat.)±0.09(sys.), consistent with self-similar redshift evolution when compared to lower redshift samples. Additionally, the lensing data constrain the average concentration of the clusters to c 200c=5.6$$+3.7\\atop{-1.8}$$.« less

Cluster Mass Calibration at High Redshift: HST Weak Lensing Analysis of 13 Distant Galaxy Clusters from the South Pole Telescope Sunyaev-Zel’dovich Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schrabback, T.; Applegate, D.; Dietrich, J. P.

We present an HST/Advanced Camera for Surveys (ACS) weak gravitational lensing analysis of 13 massive high-redshift (z(median) = 0.88) galaxy clusters discovered in the South Pole Telescope (SPT) Sunyaev-Zel'dovich Survey. This study is part of a larger campaign that aims to robustly calibrate mass-observable scaling relations over a wide range in redshift to enable improved cosmological constraints from the SPT cluster sample. We introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scaling relations significantly. First, we efficiently remove cluster members from the source sample by selecting very blue galaxies in Vmore » - I colour. Our estimate of the source redshift distribution is based on Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) data, where we carefully mimic the source selection criteria of the cluster fields. We apply a statistical correction for systematic photometric redshift errors as derived from Hubble Ultra Deep Field data and verified through spatial cross-correlations. We account for the impact of lensing magnification on the source redshift distribution, finding that this is particularly relevant for shallower surveys. Finally, we account for biases in the mass modelling caused by miscentring and uncertainties in the concentration-mass relation using simulations. In combination with temperature estimates from Chandra we constrain the normalization of the mass-temperature scaling relation ln (E(z) M-500c/10(14)M(circle dot)) = A + 1.5ln (kT/7.2 keV) to A = 1.81(-0.14)(+0.24)(stat.)+/- 0.09(sys.), consistent with self-similar redshift evolution when compared to lower redshift samples. Additionally, the lensing data constrain the average concentration of the clusters to c(200c) = 5.6(-1.8)(+3.7).« less

Cluster Mass Calibration at High Redshift: HST Weak Lensing Analysis of 13 Distant Galaxy Clusters from the South Pole Telescope Sunyaev-Zel’dovich Survey

DOE PAGES

Schrabback, T.; Applegate, D.; Dietrich, J. P.; ...

2017-10-14

Here we present an HST/Advanced Camera for Surveys (ACS) weak gravitational lensing analysis of 13 massive high-redshift (z median = 0.88) galaxy clusters discovered in the South Pole Telescope (SPT) Sunyaev–Zel'dovich Survey. This study is part of a larger campaign that aims to robustly calibrate mass–observable scaling relations over a wide range in redshift to enable improved cosmological constraints from the SPT cluster sample. We introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scaling relations significantly. First, we efficiently remove cluster members from the source sample by selecting very blue galaxies in V-I colour. Our estimate of the source redshift distribution is based on Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) data, where we carefully mimic the source selection criteria of the cluster fields. We apply a statistical correction for systematic photometric redshift errors as derived from Hubble Ultra Deep Field data and verified through spatial cross-correlations. We account for the impact of lensing magnification on the source redshift distribution, finding that this is particularly relevant for shallower surveys. Finally, we account for biases in the mass modelling caused by miscentring and uncertainties in the concentration–mass relation using simulations. In combination with temperature estimates from Chandra we constrain the normalization of the mass–temperature scaling relation ln (E(z)M 500c/10 14 M ⊙) = A + 1.5ln (kT/7.2 keV) to A=1.81more » $$+0.24\\atop{-0.14}$$(stat.)±0.09(sys.), consistent with self-similar redshift evolution when compared to lower redshift samples. Additionally, the lensing data constrain the average concentration of the clusters to c 200c=5.6$$+3.7\\atop{-1.8}$$.« less

The K-Band Quasar Luminosity Function from an SDSS and UKIDSS Matched Catalog

NASA Astrophysics Data System (ADS)

Peth, Michael; Ross, N. P.; Schneider, D. P.

2010-01-01

We match the 1,015,082 quasars from the Sloan Digital Sky Survey (SDSS) DR6 Photometric Quasar catalog to the UKIRT Infrared Digital Sky Survey (UKIDSS) Large Area Survey (LAS) DR3 to produce a catalog of 130,827 objects with optical (ugriz) and infrared (YJHK) measurements over an area of 1,200 sq. deg. A matching radius of 1'’ is used; the positional standard deviations of SDSS DR6 quasars and UKIDSS LAS is δRA = 0.137'’ and δDec = 0.131''. The catalog contains 74,351 K-band detections and 42,133 objects have coverage in all four NIR bands. In addition to the catalog, we present optical and NIR color-redshift and color-color plots. The photometric vs. spectroscopic redshift plots demonstrate how unreliable high reported photometric redshifts can be. This forces us to focus on z4.6 quasars are compared to our highest redshift objects. The giK color-color plot demonstrates that stellar contamination only affects a small sample of the objects. Distributions for Y,J,H,K and i-bands reveal insights into the flux limits in each magnitude. We investigate the distribution of redshifts from different data sets and investigate the legitimacy of certain measured photometric redshift regions. For in-depth analysis, we focus on the 300 sq. deg area equatorial SDSS region designated as Stripe 82. We measure the observed K-band quasar luminosity function (QLF) for a subset of 9,872, z<2.2 objects. We find the shape of the K-band QLF is very similar to that of the optical QLF, over the considered redshift ranges. Our calculated K-Band QLFs broadly match previous optical QLFs calculated from the SDSS and 2SLAQ QSO surveys and should provide important constraints linking unobscured optical quasars to Mid-Infrared detected, dusty and obscured AGNs at high-redshift.

Multiple Streaming and the Probability Distribution of Density in Redshift Space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hui, Lam; Kofman, Lev; Shandarin, Sergei F.

2000-07-01

We examine several aspects of redshift distortions by expressing the redshift-space density in terms of the eigenvalues and orientation of the local Lagrangian deformation tensor. We explore the importance of multiple streaming using the Zeldovich approximation (ZA), and compute the average number of streams in both real and redshift space. We find that multiple streaming can be significant in redshift space but negligible in real space, even at moderate values of the linear fluctuation amplitude ({sigma}{sub l}(less-or-similar sign)1). Moreover, unlike their real-space counterparts, redshift-space multiple streams can flow past each other with minimal interactions. Such nonlinear redshift-space effects, which aremore » physically distinct from the fingers-of-God due to small-scale virialized motions, might in part explain the well-known departure of redshift distortions from the classic linear prediction by Kaiser, even at relatively large scales where the corresponding density field in real space is well described by linear perturbation theory. We also compute, using the ZA, the probability distribution function (PDF) of the density, as well as S{sub 3}, in real and redshift space, and compare it with the PDF measured from N-body simulations. The role of caustics in defining the character of the high-density tail is examined. We find that (non-Lagrangian) smoothing, due to both finite resolution or discreteness and small-scale velocity dispersions, is very effective in erasing caustic structures, unless the initial power spectrum is sufficiently truncated. (c) 2000 The American Astronomical Society.« less

The kinematic component of the cosmological redshift

NASA Astrophysics Data System (ADS)

Chodorowski, Michał J.

2011-05-01

It is widely believed that the cosmological redshift is not a Doppler shift. However, Bunn & Hogg have recently pointed out that to solve this problem properly, one has to transport parallelly the velocity four-vector of a distant galaxy to the observer's position. Performing such a transport along the null geodesic of photons arriving from the galaxy, they found that the cosmological redshift is purely kinematic. Here we argue that one should rather transport the velocity four-vector along the geodesic connecting the points of intersection of the world-lines of the galaxy and the observer with the hypersurface of constant cosmic time. We find that the resulting relation between the transported velocity and the redshift of arriving photons is not given by a relativistic Doppler formula. Instead, for small redshifts it coincides with the well-known non-relativistic decomposition of the redshift into a Doppler (kinematic) component and a gravitational one. We perform such a decomposition for arbitrary large redshifts and derive a formula for the kinematic component of the cosmological redshift, valid for any Friedman-Lemaître-Robertson-Walker (FLRW) cosmology. In particular, in a universe with Ωm= 0.24 and ΩΛ= 0.76, a quasar at a redshift 6, at the time of emission of photons reaching us today had the recession velocity v= 0.997c. This can be contrasted with v= 0.96c, had the redshift been entirely kinematic. Thus, for recession velocities of such high-redshift sources, the effect of deceleration of the early Universe clearly prevails over the effect of its relatively recent acceleration. Last but not the least, we show that the so-called proper recession velocities of galaxies, commonly used in cosmology, are in fact radial components of the galaxies' four-velocity vectors. As such, they can indeed attain superluminal values, but should not be regarded as real velocities.

Do Massive Galaxies at z~6 Present a Challenge for Hierarchical Merging?

NASA Astrophysics Data System (ADS)

Steinhardt, Charles L.; Capak, Peter L.; Masters, Daniel; Speagle, Josh S.; Splash

2015-01-01

The Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH) recently released an initial view of the massive star-forming galaxy population at 4 < z < 6 over 1.8 square degrees. SPLASH found approximately 100 galaxy candidates with best-fit stellar masses over 10^11 solar. If even 10% of these are truly this massive and at such a high redshift, the corresponding number density would be inconsistent with the halo mass functions produced at these redshifts by numerical simulations. We will discuss these candidates, prospects for followup observations, and the potential implications for our understanding of the initial formation and early evolution of galaxies in the high-redshift universe.

RELICS: Reionization Lensing Cluster Survey - Discovering Brightly Lensed Distant Galaxies for JWST

NASA Astrophysics Data System (ADS)

Coe, Dan; Bradley, Larry; Salmon, Brett; Avila, Roberto J.; Ogaz, Sara; Bradac, Marusa; Huang, Kuang-Han; Strait, Victoria; Hoag, Austin; Sharon, Keren q.; Cerny, Catherine; Paterno-Mahler, Rachel; Johnson, Traci Lin; Mahler, Guillaume; Zitrin, Adi; Sendra Server, Irene; Acebron, Ana; Cibirka, Nathália; Rodney, Steven; Strolger, Louis; Riess, Adam; Dawson, William; Jones, Christine; Andrade-Santos, Felipe; Lovisari, Lorenzo; Czakon, Nicole; Umetsu, Keiichi; Trenti, Michele; Vulcani, Benedetta; Carrasco, Daniela; Livermore, Rachael; Stark, Daniel P.; Mainali, Ramesh; Frye, Brenda; Oesch, Pascal; Lam, Daniel; Toft, Sune; Ryan, Russell; Peterson, Avery; Past, Matthew; Kikuchihara, Shotaro; Ouchi, Masami; Oguri, Masamune

2018-01-01

The Reionization Lensing Cluster Survey (RELICS) Hubble Treasury Program has completed observations of 41 massive galaxy clusters with 188 orbits of HST ACS and WFC3/IR imaging and 390 hours of Spitzer IRAC imaging. This poster presents an overview of the program and data releases. Reduced images, catalogs, and lens models for all clusters are now available on MAST. RELICS is studying the clusters, supernovae, and lensed high-redshift galaxies. A companion poster presents our high-redshift results: over 300 lensed z ~ 6 - 10 candidates, including some of the brightest known at these redshifts (Salmon et al. 2018). These will be excellent targets for detailed follow-up study in JWST Cycle 1 GO proposals.

Sumo Puff: Tidal debris or disturbed ultra-diffuse galaxy?

NASA Astrophysics Data System (ADS)

Greco, Johnny P.; Greene, Jenny E.; Price-Whelan, Adrian M.; Leauthaud, Alexie; Huang, Song; Goulding, Andy D.; Strauss, Michael A.; Komiyama, Yutaka; Lupton, Robert H.; Miyazaki, Satoshi; Takada, Masahiro; Tanaka, Masayuki; Usuda, Tomonori

2018-01-01

We report the discovery of a diffuse stellar cloud with an angular extent ≳30″, which we term "Sumo Puff", in data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). While we do not have a redshift for this object, it is in close angular proximity to a post-merger galaxy at redshift z = 0.0431 and is projected within a few virial radii (assuming similar redshifts) of two other ˜L⋆ galaxies, which we use to bracket a potential redshift range of 0.0055 < z < 0.0431. The object's light distribution is flat, as characterized by a low Sérsic index (n ˜ 0.3). It has a low central g-band surface brightness of ˜26.4 mag arcsec-2, large effective radius of ˜13″ (˜11 kpc at z = 0.0431 and ˜1.5 kpc at z = 0.0055), and an elongated morphology (b/a ˜ 0.4). Its red color (g - i ˜ 1) is consistent with a passively evolving stellar population and similar to the nearby post-merger galaxy, and we may see tidal material connecting Sumo Puff with this galaxy. We offer two possible interpretations for the nature of this object: (1) it is an extreme, galaxy-sized tidal feature associated with a recent merger event, or (2) it is a foreground dwarf galaxy with properties consistent with a quenched, disturbed, ultra-diffuse galaxy. We present a qualitative comparison with simulations that demonstrates the feasibility of forming a structure similar to this object in a merger event. Follow-up spectroscopy and/or deeper imaging to confirm the presence of the bridge of tidal material will be necessary to reveal the true nature of this object.

Observing the high redshift Universe with Euclid

NASA Astrophysics Data System (ADS)

Laureijs, René; Euclid Collaboration

2018-05-01

Euclid enables the exploration of large sky areas with diffraction limited resolution in the optical and near-infrared, and is sensitive enough to detect targets at cosmological distances. This combination of capabilities gives Euclid a clear advantage over telescope facilities with larger apertures, both on ground and in space. The decision to mount in the NISP instrument one extra grism for the wavelength range 0.92-1.3 μm with a spectral resolution of R ~260 makes possible a rest-frame UV survey of the early Universe in the redshift range 6.5 < z < 9.7. Euclid's standard imaging with VIS in the 0.55-0.9 μm band and with NISP in the Y, J, H bands provide complementary photometry for further target identification and characterization. Euclid is a suitable facility to discover and map the spatial distribution of rare high-redshift targets and to collect statistically relevant samples, in particular of high redshift Lyα emitters and QSOs, which can be used as signposts of the cosmic structures. The Euclid surveys are also a starting point for deeper follow up observations of the individual high-z objects. We present the Euclid mission and discuss the detectability of high-z objects to probe the epoch of ionization.

First Results from the AKARI FU-HYU Mission Program

NASA Astrophysics Data System (ADS)

Pearson, C.; Serjeant, S.; Takagi, T.; Jeong, W.-S.; Negrello, M.; Matsuhara, H.; Wada, T.; Oyabu, S.; Lee, H. M.; Im, M.

2009-12-01

The AKARI FU-HYU mission program has carried out mid-infrared imaging of several well studied Spitzer fields. This imaging fills in the wavelength coverage lacking from the Spitzer surveys and gives an extremely high scientific return for minimal input for AKARI. We select fields already rich in multi-wavelength data from radio to X-ray wavelengths and present the results from our initial analysis in the GOODS-N field. We utilize the comprehansive multiwavelength coverage in the GOODS-N field to produce a multiwavelength catalogue from infrared to ultraviolet wavelengths including photometric redshifts. Using the FU-HYU catalogue we present colour-colour diagrams that map the passage of PAH features through our observation bands. These colour-colours diagrams are used as tools to extract anomalous colour populations, in particular a population of Silicate Break galaxies from the GOODS-N field.

Extreme Mergers from the Massive Cluster Survey

NASA Astrophysics Data System (ADS)

Morris, R.

2010-09-01

We will observe an extraordinary, high-redshift galaxy cluster from the Massive Cluster Survey. The target is a very rare, triple merger system, and likely lies at the one of deepest nodes of the cosmic web. The target shows multiple strong gravitational lensing arcs in the cluster core. This target only possesses a very short {10ks} Chandra observations, and is unobserved by XMM-Newton. The X-ray data from this joint Chandra/HST proposal will be used to probe the mass distribution of hot, baryonic gas, and to reveal the details of the merger physics and the process of cluster assembly. We will also search for hints of X-ray emission from filaments between the merging clumps. Subaru and some Hubble Space Telescope imaging data are in hand; we will gather additional HST coverage for a lensing analysis.

GRB 130427A: A Nearby Ordinary Monster

NASA Technical Reports Server (NTRS)

Maselli, A.; Melandri, A.; Nava, L.; Mundell, C. G.; Kawai, N.; Campana, S.; Covino, S.; Cummings, J. R.; Cusumano, G.; Evans, P. A.;

GRB 130427A: a nearby ordinary monster.

PubMed

Maselli, A; Melandri, A; Nava, L; Mundell, C G; Kawai, N; Campana, S; Covino, S; Cummings, J R; Cusumano, G; Evans, P A; Ghirlanda, G; Ghisellini, G; Guidorzi, C; Kobayashi, S; Kuin, P; La Parola, V; Mangano, V; Oates, S; Sakamoto, T; Serino, M; Virgili, F; Zhang, B-B; Barthelmy, S; Beardmore, A; Bernardini, M G; Bersier, D; Burrows, D; Calderone, G; Capalbi, M; Chiang, J; D'Avanzo, P; D'Elia, V; De Pasquale, M; Fugazza, D; Gehrels, N; Gomboc, A; Harrison, R; Hanayama, H; Japelj, J; Kennea, J; Kopac, D; Kouveliotou, C; Kuroda, D; Levan, A; Malesani, D; Marshall, F; Nousek, J; O'Brien, P; Osborne, J P; Pagani, C; Page, K L; Page, M; Perri, M; Pritchard, T; Romano, P; Saito, Y; Sbarufatti, B; Salvaterra, R; Steele, I; Tanvir, N; Vianello, G; Wiegand, B; Weigand, B; Wiersema, K; Yatsu, Y; Yoshii, T; Tagliaferri, G

2014-01-03

Long-duration gamma-ray bursts (GRBs) are an extremely rare outcome of the collapse of massive stars and are typically found in the distant universe. Because of its intrinsic luminosity (L ~ 3 × 10(53) ergs per second) and its relative proximity (z = 0.34), GRB 130427A reached the highest fluence observed in the γ-ray band. Here, we present a comprehensive multiwavelength view of GRB 130427A with Swift, the 2-meter Liverpool and Faulkes telescopes, and by other ground-based facilities, highlighting the evolution of the burst emission from the prompt to the afterglow phase. The properties of GRB 130427A are similar to those of the most luminous, high-redshift GRBs, suggesting that a common central engine is responsible for producing GRBs in both the contemporary and the early universe and over the full range of GRB isotropic energies.

The Chandra Deep Field-North Survey and the cosmic X-ray background.

PubMed

Brandt, W Nielsen; Alexander, David M; Bauer, Franz E; Hornschemeier, Ann E

2002-09-15

Chandra has performed a 1.4 Ms survey centred on the Hubble Deep Field-North (HDF-N), probing the X-ray Universe 55-550 times deeper than was possible with pre-Chandra missions. We describe the detected point and extended X-ray sources and discuss their overall multi-wavelength (optical, infrared, submillimetre and radio) properties. Special attention is paid to the HDF-N X-ray sources, luminous infrared starburst galaxies, optically faint X-ray sources and high-to-extreme redshift active galactic nuclei. We also describe how stacking analyses have been used to probe the average X-ray-emission properties of normal and starburst galaxies at cosmologically interesting distances. Finally, we discuss plans to extend the survey and argue that a 5-10 Ms Chandra survey would lay key groundwork for future missions such as XEUS and Generation-X.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juneau, Stéphanie; Bournaud, Frédéric; Daddi, Emanuele

Emission line diagnostic diagrams probing the ionization sources in galaxies, such as the Baldwin-Phillips-Terlevich (BPT) diagram, have been used extensively to distinguish active galactic nuclei (AGN) from purely star-forming galaxies. However, they remain poorly understood at higher redshifts. We shed light on this issue with an empirical approach based on a z ∼ 0 reference sample built from ∼300,000 Sloan Digital Sky Survey galaxies, from which we mimic selection effects due to typical emission line detection limits at higher redshift. We combine this low-redshift reference sample with a simple prescription for luminosity evolution of the global galaxy population to predictmore » the loci of high-redshift galaxies on the BPT and Mass-Excitation (MEx) diagnostic diagrams. The predicted bivariate distributions agree remarkably well with direct observations of galaxies out to z ∼ 1.5, including the observed stellar mass-metallicity (MZ) relation evolution. As a result, we infer that high-redshift star-forming galaxies are consistent with having normal interstellar medium (ISM) properties out to z ∼ 1.5, after accounting for selection effects and line luminosity evolution. Namely, their optical line ratios and gas-phase metallicities are comparable to that of low-redshift galaxies with equivalent emission-line luminosities. In contrast, AGN narrow-line regions may show a shift toward lower metallicities at higher redshift. While a physical evolution of the ISM conditions is not ruled out for purely star-forming galaxies and may be more important starting at z ≳ 2, we find that reliably quantifying this evolution is hindered by selections effects. The recipes provided here may serve as a basis for future studies toward this goal. Code to predict the loci of galaxies on the BPT and MEx diagnostic diagrams and the MZ relation as a function of emission line luminosity limits is made publicly available.« less

QUEST FOR COSMOS SUBMILLIMETER GALAXY COUNTERPARTS USING CARMA AND VLA: IDENTIFYING THREE HIGH-REDSHIFT STARBURST GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smolcic, V.; Navarrete, F.; Bertoldi, F.

2012-05-01

We report on interferometric observations at 1.3 mm at 2''-3'' resolution using the Combined Array for Research in Millimeter-wave Astronomy. We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F{sub 1m} > 5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, {approx}10''-30'', resolution. All three sources-AzTEC/C1, Cosbo-3, and Cosbo-8-are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but with that farther away from it. This illustrates the need for intermediate-resolution ({approx}2'') mm-observations to identify themore » correct counterparts of single-dish-detected SMGs. All of our three sources become prominent only at NIR wavelengths, and their mm-to-radio flux based redshifts suggest that they lie at redshifts z {approx}> 2. As a proof of concept, we show that photometric redshifts can be well determined for SMGs, and we find photometric redshifts of 5.6 {+-} 1.2, 1.9{sup +0.9}{sub -0.5}, and {approx}4 for AzTEC/C1, Cosbo-3, and Cosbo-8, respectively. Using these we infer that these galaxies have radio-based star formation rates of {approx}> 1000 M{sub Sun} yr{sup -1}and IR luminosities of {approx}10{sup 13} L{sub Sun} consistent with properties of high-redshift SMGs. In summary, our sources reflect a variety of SMG properties in terms of redshift and clustering, consistent with the framework that SMGs are progenitors of z {approx} 2 and today's passive galaxies.« less

ULTRAVIOLET SPECTROSCOPY OF RAPIDLY ROTATING SOLAR-MASS STARS: EMISSION-LINE REDSHIFTS AS A TEST OF THE SOLAR-STELLAR CONNECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linsky, Jeffrey L.; Bushinsky, Rachel; Ayres, Tom

2012-07-20

We compare high-resolution ultraviolet spectra of the Sun and thirteen solar-mass main-sequence stars with different rotational periods that serve as proxies for their different ages and magnetic field structures. In this, the second paper in the series, we study the dependence of ultraviolet emission-line centroid velocities on stellar rotation period, as rotation rates decrease from that of the Pleiades star HII314 (P{sub rot} = 1.47 days) to {alpha} Cen A (P{sub rot} = 28 days). Our stellar sample of F9 V to G5 V stars consists of six stars observed with the Cosmic Origins Spectrograph on the Hubble Space Telescopemore » (HST) and eight stars observed with the Space Telescope Imaging Spectrograph on HST. We find a systematic trend of increasing redshift with more rapid rotation (decreasing rotation period) that is similar to the increase in line redshift between quiet and plage regions on the Sun. The fastest-rotating solar-mass star in our study, HII314, shows significantly enhanced redshifts at all temperatures above log T = 4.6, including the corona, which is very different from the redshift pattern observed in the more slowly rotating stars. This difference in the redshift pattern suggests that a qualitative change in the magnetic-heating process occurs near P{sub rot} = 2 days. We propose that HII314 is an example of a solar-mass star with a magnetic heating rate too large for the physical processes responsible for the redshift pattern to operate in the same way as for the more slowly rotating stars. HII314 may therefore lie above the high activity end of the set of solar-like phenomena that is often called the 'solar-stellar connection'.« less

On the Redshift of TeV BL Lac Objects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paiano, Simona; Falomo, Renato; Landoni, Marco

2017-03-10

We report results of a spectroscopic campaign carried out at the 10 m Gran Telescopio Canarias for a sample of 22 BL Lac objects detected (or candidates) at TeV energies, aiming to determine or constrain their redshift. This is of fundamental importance for the interpretation of their emission models and for population studies and is also mandatory for studying the interaction of high-energy photons with the extragalactic background light using TeV sources. Optical spectra with high signal-to-noise ratios in the range 4250–10000 Å were obtained to search for faint emission or absorption lines from both the host galaxy and themore » nucleus. We determine a new redshift for PKS 1424+240 ( z = 0.604) and a tentative one for 1ES 0033+595 ( z = 0.467). We are able to set new spectroscopic redshift lower limits for three other sources on the basis of Mg ii and Ca ii intervening absorption features: BZB J1243+3627 ( z > 0.483), BZB J1540+8155 ( z > 0.672), and BZB 0J2323+4210 ( z > 0.267). We confirm previous redshift estimates for four blazars: S3 0218+357 ( z = 0.944), 1ES 1215+303 ( z = 0.129), W Comae ( z = 0.102), and MS 1221.8+2452 ( z = 0.218). For the remaining targets, in seven cases (S2 0109+22, 3C 66A, VER J0521+211, S4 0954+65, BZB J1120+4214, S3 1227+25, BZB J2323+4210), we do not validate the proposed redshift. Finally, for all sources of still-unknown redshift, we set a lower limit based on the minimum equivalent width of absorption features expected from the host galaxy.« less

The Foundation Supernova Survey: motivation, design, implementation, and first data release

NASA Astrophysics Data System (ADS)

Foley, Ryan J.; Scolnic, Daniel; Rest, Armin; Jha, S. W.; Pan, Y.-C.; Riess, A. G.; Challis, P.; Chambers, K. C.; Coulter, D. A.; Dettman, K. G.; Foley, M. M.; Fox, O. D.; Huber, M. E.; Jones, D. O.; Kilpatrick, C. D.; Kirshner, R. P.; Schultz, A. S. B.; Siebert, M. R.; Flewelling, H. A.; Gibson, B.; Magnier, E. A.; Miller, J. A.; Primak, N.; Smartt, S. J.; Smith, K. W.; Wainscoat, R. J.; Waters, C.; Willman, M.

2018-03-01

The Foundation Supernova Survey aims to provide a large, high-fidelity, homogeneous, and precisely calibrated low-redshift Type Ia supernova (SN Ia) sample for cosmology. The calibration of the current low-redshift SN sample is the largest component of systematic uncertainties for SN cosmology, and new data are necessary to make progress. We present the motivation, survey design, observation strategy, implementation, and first results for the Foundation Supernova Survey. We are using the Pan-STARRS telescope to obtain photometry for up to 800 SNe Ia at z ≲ 0.1. This strategy has several unique advantages: (1) the Pan-STARRS system is a superbly calibrated telescopic system, (2) Pan-STARRS has observed 3/4 of the sky in grizyP1 making future template observations unnecessary, (3) we have a well-tested data-reduction pipeline, and (4) we have observed ˜3000 high-redshift SNe Ia on this system. Here, we present our initial sample of 225 SN Ia grizP1 light curves, of which 180 pass all criteria for inclusion in a cosmological sample. The Foundation Supernova Survey already contains more cosmologically useful SNe Ia than all other published low-redshift SN Ia samples combined. We expect that the systematic uncertainties for the Foundation Supernova Sample will be two to three times smaller than other low-redshift samples. We find that our cosmologically useful sample has an intrinsic scatter of 0.111 mag, smaller than other low-redshift samples. We perform detailed simulations showing that simply replacing the current low-redshift SN Ia sample with an equally sized Foundation sample will improve the precision on the dark energy equation-of-state parameter by 35 per cent, and the dark energy figure of merit by 72 per cent.

Reionization of Hydrogen and Helium by Early Stars and Quasars

NASA Astrophysics Data System (ADS)

Wyithe, J. Stuart B.; Loeb, Abraham

2003-04-01

We compute the reionization histories of hydrogen and helium caused by the ionizing radiation fields produced by stars and quasars. For the quasars we use a model based on halo-merger rates that reproduces all known properties of the quasar luminosity function at high redshifts. The less constrained properties of the ionizing radiation produced by stars are modeled with two free parameters: (i) a transition redshift, ztran, above which the stellar population is dominated by massive, zero-metallicity stars and below which it is dominated by a Scalo mass function; and (ii) the product of the escape fraction of stellar ionizing photons from their host galaxies and the star formation efficiency, fescf*. We constrain the allowed range of these free parameters at high redshifts on the basis of the lack of the H I Gunn-Peterson trough at z<~6 and the upper limit on the total intergalactic optical depth for electron scattering, τes<0.18, from recent cosmic microwave background (CMB) experiments. We find that quasars ionize helium by a redshift z~4, but cannot reionize hydrogen by themselves before z~6. A major fraction of the allowed combinations of fescf* and ztran leads to an early peak in the ionized fraction because of the presence of metal-free stars at high redshifts. This sometimes results in two reionization epochs, namely, an early H II or He III overlap phase followed by recombination and a second overlap phase. Even if early overlap is not achieved, the peak in the visibility function for scattering of the CMB often coincides with the early ionization phase rather than with the actual reionization epoch. Consequently, τes does not correspond directly to the reionization redshift. We generically find values of τes>~7%, which should be detectable by the MAP satellite.

Emerging spatial curvature can resolve the tension between high-redshift CMB and low-redshift distance ladder measurements of the Hubble constant

NASA Astrophysics Data System (ADS)

Bolejko, Krzysztof

2018-05-01

The measurements of the Hubble constant reveal a tension between high-redshift (CMB) and low-redshift (distance ladder) constraints. So far neither observational systematics nor new physics has been successfully implemented to explain away this tension. This paper presents a new solution to the Hubble constant problem. The solution is based on the Simsilun simulation (relativistic simulation of the large scale structure of the Universe) with the ray-tracing algorithm implemented. The initial conditions for the Simsilun simulation were set up as perturbations around the Λ CDM model. However, unlike in the standard cosmological model (i.e., Λ CDM model +perturbations ), within the Simsilun simulation relativistic and nonlinear evolution of cosmic structures lead to the phenomenon of emerging spatial curvature, where the mean spatial curvature evolves from the spatial flatness of the early Universe towards the slightly curved present-day Universe. Consequently, the present-day expansion rate is slightly faster compared to the spatially flat Λ CDM model. The results of the ray-tracing analysis show that the Universe which starts with initial conditions consistent with the Planck constraints should have the Hubble constant H0=72.5 ±2.1 km s-1 Mpc-1 . When the Simsilun simulation was rerun with no inhomogeneities imposed, the Hubble constant inferred within such a homogeneous simulation was H0=68.1 ±2.0 km s-1 Mpc-1 . Thus, the inclusion of nonlinear relativistic evolution that leads to the emergence of the spatial curvature can explain why the low-redshift measurements favor higher values compared to the high-redshift constraints and alleviate the tension between the CMB and distance ladder measurements of the Hubble constant.

(Sub)millimetre-Selected Galaxies and the Cosmic Star-Formation History

NASA Astrophysics Data System (ADS)

Koprowski, Maciej

2015-03-01

Understanding the time evolution of the star formation in the Universe is one of the main aims of observational astronomy. Since a significant portion of the UV starlight is being absorbed by dust and re-emitted in the IR, we need to understand both of those regimes to properly describe the cosmic star formation history. In UV, the depth and the resolution of the data permits calculations of the star formation rate densities out to very high redshifts (z˜8-9). In IR however, the large beam sizes and the relatively shallow data limits these calculations to z˜2. In this thesis, I explore the SMA and PdBI high-resolution follow-up of 30 bright sources originally selected by AzTEC and LABOCA instruments at 1.1 mm and 870 μm respectively in conjunction with the SCUBA-2 Cosmology Legacy Survey (S2CLS) deep COSMOS and wide UDS maps, where 106 and 283 sources were detected, with the signal-to-noise ratio of > 5 and > 3.5 at 850 μm respectively. I find that the (sub)mm-selected galaxies reside and the mean redshifts of z ≈ 2.5±0.05 with the exception of the brightest sources which z seem to lie at higher redshifts (z ≈ 3.5±0.2), most likely due to the apparent z correlation of the (sub)mm flux with redshift, where brighter sources tend to lie at higher redshifts. Stellar masses, M\\dot, and star formation rates, SFRs, were found (M\\dot ≥ 10^10 M⊙ and SFR ≥ 100 M⊙ yr-1 ) and used to calculate the specific SFRs. I determine that the (sub)mm-selected sources mostly lie on the high-mass end of the star formation 'main-sequence' which makes them a high-mass extension of normal star forming galaxies. I also find that the specific SFR slightly evolves at redshifts 2 - 4, suggesting that the efficiency of the star formation seems to be increasing at these redshifts. Using the S2CLS data, the bolometric IR luminosity functions (IR LFs) were found for a range of redshifts z = 1.2 - 4.2 and the contribution of the SMGs tothe total star formation rate density (SFRD) was calculated. The IR LFs were found to evolve out to redshift ∼ 2.5. The star formation activity in the Universe was found to peak at z ≈ 2 followed by a slight decline. Assuming the IR to total SFRD correction found in the literature the SFRD found in this work closely follows the best-fitting function of Madau & Dickinson (2014).

The X-ray properties of high redshift, optically selected QSOs. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Anderson, S. F.

1985-01-01

In order to study the X-ray properties of high redshift QSOs, grism/grens plates covering 17 deg. of sky previously imaged to very sensitive X-ray flux levels with the Einstein Observatory were taken. Following optical selection of the QSO, the archived X-ray image is examined to extract an X-ray flux detection or a sensitive upper limit.

A quasar discovered at redshift 6.6 from Pan-STARRS1

NASA Astrophysics Data System (ADS)

Tang, Ji-Jia; Goto, Tomotsugu; Ohyama, Youichi; Chen, Wen-Ping; Walter, Fabian; Venemans, Bram; Chambers, Kenneth C.; Bañados, Eduardo; Decarli, Roberto; Fan, Xiaohui; Farina, Emanuele; Mazzucchelli, Chiara; Kaiser, Nick; Magnier, Eugene A.

2017-04-01

Luminous high-redshift quasars can be used to probe of the intergalactic medium in the early universe because their UV light is absorbed by the neutral hydrogen along the line of sight. They help us to measure the neutral hydrogen fraction of the high-z universe, shedding light on the end of reionization epoch. In this paper, we present a discovery of a new quasar (PSO J006.1240+39.2219) at redshift z = 6.61 ± 0.02 from Panoramic Survey Telescope & Rapid Response System 1. Including this quasar, there are nine quasars above z > 6.5 up to date. The estimated continuum brightness is M1450 = -25.96 ± 0.08. PSO J006.1240+39.2219 has a strong Ly α emission compared with typical low-redshift quasars, but the measured near-zone region size is RNZ = 3.2 ± 1.1 proper megaparsecs, which is consistent with other quasars at z ˜ 6.

Ecology of dark matter haloes - II. Effects of interactions on the alignment of halo pairs

NASA Astrophysics Data System (ADS)

L'Huillier, Benjamin; Park, Changbom; Kim, Juhan

2017-04-01

We use the Horizon Run 4 cosmological N-body simulation to study the effects of distant and close interactions on the alignments of the shapes, spins and orbits of targets haloes with their neighbours, and their dependence on the local density environment and neighbour separation. Interacting targets have a significantly lower spin and higher sphericity and oblateness than all targets. Interacting pairs initially have antiparallel spins, but the spins develop parallel alignment as time goes on. Neighbours tend to evolve in the plane of rotation of the target, and in the direction of the major axis of prolate haloes. Moreover, interactions are preferentially radial, while pairs with non-radial orbits are preferentially prograde. The alignment signals are stronger at high mass and for close separations, and independent of the large-scale density. Positive alignment signals are found at redshifts up to 4, and increase with decreasing redshifts. Moreover, the orbits tend to become prograde at low redshift, while no alignment is found at high redshift (z = 4).

Redshift and blueshift of GaNAs/GaAs multiple quantum wells induced by rapid thermal annealing

NASA Astrophysics Data System (ADS)

Sun, Yijun; Cheng, Zhiyuan; Zhou, Qiang; Sun, Ying; Sun, Jiabao; Liu, Yanhua; Wang, Meifang; Cao, Zhen; Ye, Zhi; Xu, Mingsheng; Ding, Yong; Chen, Peng; Heuken, Michael; Egawa, Takashi

2018-02-01

The effects of rapid thermal annealing (RTA) on the optical properties of GaNAs/GaAs multiple quantum wells (MQWs) grown by chemical beam epitaxy (CBE) are studied by photoluminescence (PL) at 77 K. The results show that the optical quality of the MQWs improves significantly after RTA. With increasing RTA temperature, PL peak energy of the MQWs redshifts below 1023 K, while it blueshifts above 1023 K. Two competitive processes which occur simultaneously during RTA result in redshift at low temperature and blueshift at high temperature. It is also found that PL peak energy shift can be explained neither by nitrogen diffusion out of quantum wells nor by nitrogen reorganization inside quantum wells. PL peak energy shift can be quantitatively explained by a modified recombination coupling model in which redshift nonradiative recombination and blueshift nonradiative recombination coexist. The results obtained have significant implication on the growth and RTA of GaNAs material for high performance optoelectronic device application.

The faint intergalactic-medium red-shifted emission balloon: future UV observations with EMCCDs

NASA Astrophysics Data System (ADS)

Kyne, Gillian; Hamden, Erika T.; Lingner, Nicole; Morrissey, Patrick; Nikzad, Shouleh; Martin, D. Christopher

2016-08-01

We present the latest developments in our joint NASA/CNES suborbital project. This project is a balloon-borne UV multi-object spectrograph, which has been designed to detect faint emission from the circumgalactic medium (CGM) around low redshift galaxies. One major change from FIREBall-1 has been the use of a delta-doped Electron Multiplying CCD (EMCCD). EMCCDs can be used in photon-counting (PC) mode to achieve extremely low readout noise (¡ 1e-). Our testing initially focused on reducing clock-induced-charge (CIC) through wave shaping and well depth optimisation with the CCD Controller for Counting Photons (CCCP) from Nüvü. This optimisation also includes methods for reducing dark current, via cooling and substrate voltage adjustment. We present result of laboratory noise measurements including dark current. Furthermore, we will briefly present some initial results from our first set of on-sky observations using a delta-doped EMCCD on the 200 inch telescope at Palomar using the Palomar Cosmic Web Imager (PCWI).

Gamma Ray Bursts-Afterglows and Counterparts

NASA Technical Reports Server (NTRS)

Fishman, Gerald J

1998-01-01

Several breakthrough discoveries were made last year of x-ray, optical and radio afterglows and counterparts to gamma-ray bursts, and a redshift has been associated with at least one of these. These discoveries were made possible by the fast, accurate gamma-ray burst locations of the BeppoSAX satellite. It is now generally believed that the burst sources are at cosmological distances and that they represent the most powerful explosions in the Universe. These observations also open new possibilities for the study of early star formation, the physics of extreme conditions and perhaps even cosmology. This session will concentrate on recent x-ray, optical and radio afterglow observations of gamma-ray bursts, associated redshift measurements, and counterpart observations. Several review and theory talks will also be presented, along with a summary of the astrophysical implications of the observations. There will be additional poster contributions on observations of gamma-ray burst source locations at wavelengths other than gamma rays. Posters are also solicited that describe new observational capabilities for rapid follow-up observations of gamma-ray bursts.

Galactic conformity and central/satellite quenching, from the satellite profiles of M* galaxies at 0.4 < z < 1.9 in the UKIDSS UDS

NASA Astrophysics Data System (ADS)

Hartley, W. G.; Conselice, C. J.; Mortlock, A.; Foucaud, S.; Simpson, C.

2015-08-01

We explore the redshift evolution of a curious correlation between the star formation properties of central galaxies and their satellites (`galactic conformity') at intermediate to high redshift (0.4 < z < 1.9). Using an extremely deep near-infrared survey, we study the distribution and properties of satellite galaxies with stellar masses, log(M*/M⊙) > 9.7, around central galaxies at the characteristic Schechter function mass, M ˜ M*. We fit the radial profiles of satellite number densities with simple power laws, finding slopes in the range -1.1 to -1.4 for mass-selected satellites, and -1.3 to -1.6 for passive satellites. We confirm the tendency for passive satellites to be preferentially located around passive central galaxies at 3σ significance and show that it exists to at least z ˜ 2. Meanwhile, the quenched fraction of satellites around star-forming galaxies is consistent with field galaxies of equal stellar masses. We find no convincing evidence for a redshift-dependent evolution of these trends. One simple interpretation of these results is that only passive central galaxies occupy an environment that is capable of independently shutting off star formation in satellite galaxies. By examining the satellites of higher stellar mass star-forming galaxies (log(M*/M⊙) > 11), we conclude that the origin of galactic conformity is unlikely to be exclusively due to the host dark matter halo mass. A halo-mass-independent correlation could be established by either formation bias or a more physical connection between central and satellite star formation histories. For the latter, we argue that a star formation (or active galactic nucleus) related outburst event from the central galaxy could establish a hot halo environment which is then capable of quenching both central and satellite galaxies.

Hubble Space Telescope Observations of the Luminous IRAS Source FSC 10214+4724: A Gravitationally Lensed Infrared Quasar

NASA Technical Reports Server (NTRS)

Eisenhardt, Peter R.; Armus, Lee; Hogg, David W.; Soifer, B. T.; Neugebauer, G.; Werner, Michael W.

1996-01-01

With a redshift of 2.3, the IRAS source FSC 10214+4724 is apparently one of the most luminous objects known in the universe. We present an image of FSC 10214+4724 at 0.8 pm obtained with the Hubble Space Telescope (HST) WFPC2 Planetary Camera. The source appears as an unresolved (less then 0.06) arc 0.7 long, with significant substructure along its length. The center of curvature of the arc is located near an elliptical galaxy 1.18 to the north. An unresolved component 100 times fainter than the arc is clearly detected on the opposite side of this galaxy. The most straightforward interpretation is that FSC 10214+4724 is gravitationally lensed by the foreground elliptical galaxy, with the faint component a counter-image of the IRAS source. The brightness of the arc in the HST image is then magnified by approx. 100, and the intrinsic source diameter is approx. 0.0l (80 pc) at 0.25 microns rest wavelength. The bolometric luminosity is probably amplified by a smaller factor (approx. 30) as a result of the larger extent expected for the source in the far-infrared. A detailed lensing model is presented that reproduces the observed morphology and relative flux of the arc and counterimage and correctly predicts the position angle of the lensing galaxy. The model also predicts reasonable values for the velocity dispersion, mass, and mass-to-light ratio of the lensing galaxy for a wide range of galaxy redshifts. A redshift for the lensing galaxy of -0.9 is consistent with the measured surface brightness profile from the image, as well as with the galaxy's spectral energy distribution. The background lensed source has an intrinsic luminosity approx. 2 x 10(exp 13) L(solar mass) and remains a highly luminous quasar with an extremely large ratio of infrared to optical/ultraviolet luminosity.

Low Masses and High Redshifts: The Evolution of the Mass-Metallicity Relation

NASA Technical Reports Server (NTRS)

Henry, Alaina; Scarlata, Claudia; Dominguez, Alberto; Malkan, Matthew; Martin, Crystal L.; Siana, Brian; Atek, Hakim; Bedregal, Alejandro G.; Colbert, James W.; Rafelski, Marc;

Evolution of the real-space correlation function from next generation cluster surveys. Recovering the real-space correlation function from photometric redshifts

NASA Astrophysics Data System (ADS)

Sridhar, Srivatsan; Maurogordato, Sophie; Benoist, Christophe; Cappi, Alberto; Marulli, Federico

2017-04-01

Context. The next generation of galaxy surveys will provide cluster catalogues probing an unprecedented range of scales, redshifts, and masses with large statistics. Their analysis should therefore enable us to probe the spatial distribution of clusters with high accuracy and derive tighter constraints on the cosmological parameters and the dark energy equation of state. However, for the majority of these surveys, redshifts of individual galaxies will be mostly estimated by multiband photometry which implies non-negligible errors in redshift resulting in potential difficulties in recovering the real-space clustering. Aims: We investigate to which accuracy it is possible to recover the real-space two-point correlation function of galaxy clusters from cluster catalogues based on photometric redshifts, and test our ability to detect and measure the redshift and mass evolution of the correlation length r0 and of the bias parameter b(M,z) as a function of the uncertainty on the cluster redshift estimate. Methods: We calculate the correlation function for cluster sub-samples covering various mass and redshift bins selected from a 500 deg2 light-cone limited to H < 24. In order to simulate the distribution of clusters in photometric redshift space, we assign to each cluster a redshift randomly extracted from a Gaussian distribution having a mean equal to the cluster cosmological redshift and a dispersion equal to σz. The dispersion is varied in the range σ(z=0)=\\frac{σz{1+z_c} = 0.005,0.010,0.030} and 0.050, in order to cover the typical values expected in forthcoming surveys. The correlation function in real-space is then computed through estimation and deprojection of wp(rp). Four mass ranges (from Mhalo > 2 × 1013h-1M⊙ to Mhalo > 2 × 1014h-1M⊙) and six redshift slices covering the redshift range [0, 2] are investigated, first using cosmological redshifts and then for the four photometric redshift configurations. Results: From the analysis of the light-cone in cosmological redshifts we find a clear increase of the correlation amplitude as a function of redshift and mass. The evolution of the derived bias parameter b(M,z) is in fair agreement with theoretical expectations. We calculate the r0-d relation up to our highest mass, highest redshift sample tested (z = 2,Mhalo > 2 × 1014h-1M⊙). From our pilot sample limited to Mhalo > 5 × 1013h-1M⊙(0.4 < z < 0.7), we find that the real-space correlation function can be recovered by deprojection of wp(rp) within an accuracy of 5% for σz = 0.001 × (1 + zc) and within 10% for σz = 0.03 × (1 + zc). For higher dispersions (besides σz > 0.05 × (1 + zc)), the recovery becomes noisy and difficult. The evolution of the correlation in redshift and mass is clearly detected for all σz tested, but requires a large binning in redshift to be detected significantly between individual redshift slices when increasing σz. The best-fit parameters (r0 and γ) as well as the bias obtained from the deprojection method for all σz are within the 1σ uncertainty of the zc sample.

Order statistics applied to the most massive and most distant galaxy clusters

NASA Astrophysics Data System (ADS)

Waizmann, J.-C.; Ettori, S.; Bartelmann, M.

2013-06-01

In this work, we present an analytic framework for calculating the individual and joint distributions of the nth most massive or nth highest redshift galaxy cluster for a given survey characteristic allowing us to formulate Λ cold dark matter (ΛCDM) exclusion criteria. We show that the cumulative distribution functions steepen with increasing order, giving them a higher constraining power with respect to the extreme value statistics. Additionally, we find that the order statistics in mass (being dominated by clusters at lower redshifts) is sensitive to the matter density and the normalization of the matter fluctuations, whereas the order statistics in redshift is particularly sensitive to the geometric evolution of the Universe. For a fixed cosmology, both order statistics are efficient probes of the functional shape of the mass function at the high-mass end. To allow a quick assessment of both order statistics, we provide fits as a function of the survey area that allow percentile estimation with an accuracy better than 2 per cent. Furthermore, we discuss the joint distributions in the two-dimensional case and find that for the combination of the largest and the second largest observation, it is most likely to find them to be realized with similar values with a broadly peaked distribution. When combining the largest observation with higher orders, it is more likely to find a larger gap between the observations and when combining higher orders in general, the joint probability density function peaks more strongly. Having introduced the theory, we apply the order statistical analysis to the Southpole Telescope (SPT) massive cluster sample and metacatalogue of X-ray detected clusters of galaxies catalogue and find that the 10 most massive clusters in the sample are consistent with ΛCDM and the Tinker mass function. For the order statistics in redshift, we find a discrepancy between the data and the theoretical distributions, which could in principle indicate a deviation from the standard cosmology. However, we attribute this deviation to the uncertainty in the modelling of the SPT survey selection function. In turn, by assuming the ΛCDM reference cosmology, order statistics can also be utilized for consistency checks of the completeness of the observed sample and of the modelling of the survey selection function.

The Role of the CMB in Redshift Related Departures from the Gao–Solomon Relation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tunnard, R.; Greve, T. R., E-mail: richard.tunnard.13@ucl.ac.uk

A strong correlation between the far-IR and HCN(1−0) line luminosities, known as the Gao–Solomon relation, has been observed to hold over more than 10 orders of magnitude in the local universe. Departures from this relation at redshifts ≳1.5 have been interpreted as evidence for increased dense gas star formation efficiency in luminous galaxies during the period of peak of star formation in the history of the universe. We examine whether the offsets from the relation can be explained by the hotter Cosmic Microwave Background (CMB) at high redshift, which, due to a loss of contrast against the hotter background, reducesmore » the observable molecular-line flux far more significantly than the far-IR continuum bands. Simple line-of-sight modeling argues for highly significant departures from the Gao–Solomon relation at high redshift for kinetic temperatures ∼15 K, while more complex toy-galaxy models based on NGC 1068 suggest a much weaker effect with the galaxy integrated HCN line flux falling by only 10% at z = 3, within the intrinsic scatter of the relation. We conclude that, while the CMB is unlikely to explain the deviations reported in the literature, it may introduce a second-order effect on the relation by raising the low-luminosity end of the Gao–Solomon relation in cooler galaxies. A similar examination of the CO-IR relation finds tantalizing signs of the CMB having a measurable effect on the integrated CO emission in high-redshift galaxies, but these signs cannot be confirmed with the current data.« less

A faint galaxy redshift survey behind massive clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frye, Brenda Louise

1999-05-01

This thesis is concerned with the gravitational lensing effect by massive galaxy clusters. We have explored a new technique for measuring galaxy masses and for detecting high-z galaxies by their optical colors. A redshift survey has been obtained at the Keck for a magnitude limited sample of objects (I<23) behind three clusters, A1689, A2390, and A2218 within a radius of 0.5M pc. For each cluster we see both a clear trend of increasing flux and redshift towards the center. This behavior is the result of image magnifications, such that at fixed redshift one sees further down the luminosity function. Themore » gradient of this magnification is, unlike measurements of image distortion, sensitive to the mass profile, and found to depart strongly from a pure isothermal halo. We have found that V RI color selection can be used effectively as a discriminant for finding high-z galaxies behind clusters and present five 4.1 < z < 5.1 spectra which are of very high quality due to their high mean magnification of ~20, showing strong, visibly-saturated interstellar metal lines in some cases. We have also investigated the radio ring lens PKS 1830-211, locating the source and multiple images and detected molecular absorption at mm wavelengths. Broad molecular absorption of width 1/40kms is found toward the southwest component only, where surprisingly it does not reach the base of the continuum, which implies incomplete coverage of the SW component by molecular gas, despite the small projected size of the source, less than 1/8h pc at the absorption redshift.« less

The Role of the CMB in Redshift Related Departures from the Gao-Solomon Relation

NASA Astrophysics Data System (ADS)

Tunnard, R.; Greve, T. R.

2017-11-01

A strong correlation between the far-IR and HCN(1-0) line luminosities, known as the Gao-Solomon relation, has been observed to hold over more than 10 orders of magnitude in the local universe. Departures from this relation at redshifts ≳1.5 have been interpreted as evidence for increased dense gas star formation efficiency in luminous galaxies during the period of peak of star formation in the history of the universe. We examine whether the offsets from the relation can be explained by the hotter Cosmic Microwave Background (CMB) at high redshift, which, due to a loss of contrast against the hotter background, reduces the observable molecular-line flux far more significantly than the far-IR continuum bands. Simple line-of-sight modeling argues for highly significant departures from the Gao-Solomon relation at high redshift for kinetic temperatures ˜15 K, while more complex toy-galaxy models based on NGC 1068 suggest a much weaker effect with the galaxy integrated HCN line flux falling by only 10% at z = 3, within the intrinsic scatter of the relation. We conclude that, while the CMB is unlikely to explain the deviations reported in the literature, it may introduce a second-order effect on the relation by raising the low-luminosity end of the Gao-Solomon relation in cooler galaxies. A similar examination of the CO-IR relation finds tantalizing signs of the CMB having a measurable effect on the integrated CO emission in high-redshift galaxies, but these signs cannot be confirmed with the current data.

ON INFERRING EXTINCTION LAWS IN z {approx} 6 QUASARS AS SIGNATURES OF SUPERNOVA DUST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hjorth, Jens; Vreeswijk, Paul M.; Gall, Christa

Unusual extinction curves of high-redshift QSOs have been taken as evidence that dust is primarily produced by supernovae at high redshift. In particular, the 3000 A Todini-Ferrara-Maiolino kink in the extinction curve of the z = 6.20 SDSS J1048+4637 has been attributed to supernova dust. Here we discuss the challenges in inferring robust extinction curves of high-redshift QSOs and critically assess previous claims of detection of supernova dust. In particular, we address the sensitivity to the choice of intrinsic QSO spectrum, the need for a long wavelength baseline, and the drawbacks in fitting theoretical extinction curves. In a sample ofmore » 21 QSOs at z {approx} 6 we detect significant ultraviolet extinction using existing broadband optical, near-infrared, and Spitzer photometry. The median extinction curve is consistent with a Small Magellanic Cloud curve with A{sub 1450} {approx} 0.7 mag and does not exhibit any conspicuous (rest frame) 2175 A or 3000 A features. For two QSOs, SDSS J1044-0125 at z = 5.78 and SDSS J1030+0524 at z = 6.31, we further present X-shooter spectra covering the wavelength range 0.9-2.5 {mu}m. The resulting non-parametric extinction curves do not exhibit the 3000 A kink. Finally, in a re-analysis of literature spectra of SDSS J1048+4637, we do not find evidence for a conspicuous kink. We conclude that the existing evidence for a 3000 A feature is weak and that the overall dust properties at high and low redshifts show no significant differences. This, however, does not preclude supernovae from dominating the dust budget at high redshift.« less

On Inferring Extinction Laws in Z -approximately 6 Quasars as Signatures of Supernova Dust

NASA Technical Reports Server (NTRS)

Hjorth, Jens; Vreeswijk, Paul M.; Gall, Christa; Watson, Darach

2013-01-01

Unusual extinction curves of high-redshift QSOs have been taken as evidence that dust is primarily produced by supernovae at high redshift. In particular, the 3000 °A Todini-Ferrara-Maiolino kink in the extinction curve of the z = 6.20 SDSS J1048+4637 has been attributed to supernova dust. Here we discuss the challenges in inferring robust extinction curves of high-redshift QSOs and critically assess previous claims of detection of supernova dust. In particular, we address the sensitivity to the choice of intrinsic QSO spectrum, the need for a long wavelength baseline, and the drawbacks in fitting theoretical extinction curves. In a sample of 21 QSOs at z 6 we detect significant ultraviolet extinction using existing broad-band optical, near-infrared, and Spitzer photometry. The median extinction curve is consistent with a Small Magellanic Cloud curve with A1450 0.7 mag and does not exhibit any conspicuous (restframe) 2175 °A or 3000 °A features. For two QSOs, SDSS J1044-0125 at z = 5.78 and SDSS J1030+0524 at z = 6.31, we further present X-shooter spectra covering the wavelength range 0.9-2.5 µm. The resulting non-parametric extinction curves do not exhibit the 3000 °A kink. Finally, in a re-analysis of literature spectra of SDSS J1048+4637, we do not find evidence for a conspicuous kink. We conclude that the existing evidence for a 3000 °A feature is weak and that the overall dust properties at high and low redshift show no significant differences. This, however, does not preclude supernovae from dominating the dust budget at high redshift.

The Strong Gravitationally Lensed Herschel Galaxy HLock01: Optical Spectroscopy Reveals a Close Galaxy Merger with Evidence of Inflowing Gas

NASA Astrophysics Data System (ADS)

Marques-Chaves, Rui; Pérez-Fournon, Ismael; Gavazzi, Raphael; Martínez-Navajas, Paloma I.; Riechers, Dominik; Rigopoulou, Dimitra; Cabrera-Lavers, Antonio; Clements, David L.; Cooray, Asantha; Farrah, Duncan; Ivison, Rob J.; Jiménez-Ángel, Camilo E.; Nayyeri, Hooshang; Oliver, Seb; Omont, Alain; Scott, Douglas; Shu, Yiping; Wardlow, Julie

2018-02-01

The submillimeter galaxy (SMG) HERMES J105751.1+573027 (hereafter HLock01) at z = 2.9574 ± 0.0001 is one of the brightest gravitationally lensed sources discovered in the Herschel Multi-tiered Extragalactic Survey. Apart from the high flux densities in the far-infrared, it is also extremely bright in the rest-frame ultraviolet (UV), with a total apparent magnitude m UV ≃ 19.7 mag. We report here deep spectroscopic observations with the Gran Telescopio Canarias of the optically bright lensed images of HLock01. Our results suggest that HLock01 is a merger system composed of the Herschel-selected SMG and an optically bright Lyman break-like galaxy (LBG), separated by only 3.3 kpc in projection. While the SMG appears very massive (M * ≃ 5 × 1011 M ⊙), with a highly extinguished stellar component (A V ≃ 4.3 ), the LBG is a young, lower-mass (M * ≃ 1 × 1010 M ⊙), but still luminous (10× {L}UV}* ) satellite galaxy. Detailed analysis of the high signal-to-noise ratio (S/N) rest-frame UV spectrum of the LBG shows complex kinematics of the gas, exhibiting both blueshifted and redshifted absorption components. While the blueshifted component is associated with strong galactic outflows from the massive stars in the LBG, as is common in most star-forming galaxies, the redshifted component may be associated with gas inflow seen along a favorable sightline to the LBG. We also find evidence of an extended gas reservoir around HLock01 at an impact parameter of 110 kpc, through the detection of C II λλ1334 absorption in the red wing of a bright Lyα emitter at z ≃ 3.327. The data presented here highlight the power of gravitational lensing in high S/N studies to probe deeply into the physics of high-z star-forming galaxies.

LMT imaging of the Extended Groth Strip: a search for the high-redshift tail of the sub-mm galaxy population

NASA Astrophysics Data System (ADS)

Aretxaga, Itziar

2015-08-01

The combination of short and long-wavelength deep (sub-)mm surveys can effectively be used to identify high-redshift sub-millimeter galaxies (z>4). Having star formation rates in excess of 500 Msun/yr, these bright (sub-)mm sources have been identified with the progenitors of massive elliptical galaxies undergoing rapid growth. With this purpose in mind, we are surveying a 20 sq. arcmin field within the Extended Groth Strip with the 1.1mm AzTEC camera mounted at the Large Millimeter Telescope that overlaps with the deep 450/850um SCUBA-2 Cosmology Legacy Survey and the CANDELS deep NIR imaging. The improved beamsize of the LMT (8”) over previous surveys aids the identification of the most prominent optical/IR counterparts. We discuss the high-redshift candidates found.

Mean Occupation Function of High-redshift Quasars from the Planck Cluster Catalog

NASA Astrophysics Data System (ADS)

Chakraborty, Priyanka; Chatterjee, Suchetana; Dutta, Alankar; Myers, Adam D.

2018-06-01

We characterize the distribution of quasars within dark matter halos using a direct measurement technique for the first time at redshifts as high as z ∼ 1. Using the Planck Sunyaev-Zeldovich (SZ) catalog for galaxy groups and the Sloan Digital Sky Survey (SDSS) DR12 quasar data set, we assign host clusters/groups to the quasars and make a measurement of the mean number of quasars within dark matter halos as a function of halo mass. We find that a simple power-law fit of {log}< N> =(2.11+/- 0.01) {log}(M)-(32.77+/- 0.11) can be used to model the quasar fraction in dark matter halos. This suggests that the quasar fraction increases monotonically as a function of halo mass even to redshifts as high as z ∼ 1.

Redshift remapping and cosmic acceleration in dark-matter-dominated cosmological models

NASA Astrophysics Data System (ADS)

Wojtak, Radosław; Prada, Francisco

2017-10-01

The standard relation between the cosmological redshift and cosmic scalefactor underlies cosmological inference from virtually all kinds of cosmological observations, leading to the emergence of the Λ cold-dark-matter (ΛCDM) cosmological model. This relation is not a fundamental theory and thus observational determination of this function (redshift remapping) should be regarded as an insightful alternative to holding its standard form in analyses of cosmological data. Here we present non-parametric reconstructions of redshift remapping in dark-matter-dominated models and constraints on cosmological parameters from a joint analysis of all primary cosmological probes including the local measurement of the Hubble constant, Type Ia supernovae, baryon acoustic oscillations (BAO), Planck observations of the cosmic microwave background (CMB) radiation (temperature power spectrum) and cosmic chronometers. The reconstructed redshift remapping points to an additional boost of redshift operating in late epoch of cosmic evolution, but affecting both low-redshift observations and the CMB. The model predicts a significant difference between the actual Hubble constant, h = 0.48 ± 0.02, and its local determination, hobs = 0.73 ± 0.02. The ratio of these two values coincides closely with the maximum expansion rate inside voids formed in the corresponding open cosmological model with Ωm = 0.87 ± 0.03, whereas the actual value of the Hubble constant implies the age of the Universe that is compatible with the Planck ΛCDM cosmology. The model with redshift remapping provides excellent fits to all data and eliminates recently reported tensions between the PlanckΛCDM cosmology, the local determination of the Hubble constant and the BAO measurements from the Ly α forest of high-redshift quasars.

Redshift remapping and cosmic acceleration in dark-matter-dominated cosmological models

DOE PAGES

Wojtak, Radosław; Prada, Francisco

2017-06-21

The standard relation between the cosmological redshift and cosmic scale factor underlies cosmological inference from virtually all kinds of cosmological observations, leading to the emergence of the LambdaCDM cosmological model. This relation is not a fundamental theory and thus observational determination of this function (redshift remapping) should be regarded as an insightful alternative to holding its standard form in analyses of cosmological data. We present non-parametric reconstructions of redshift remapping in dark-matter-dominated models and constraints on cosmological parameters from a joint analysis of all primary cosmological probes including the local measurement of the Hubble constant, Type Ia supernovae, baryonic acousticmore » oscillations (BAO), Planck observations of the cosmic microwave background (CMB) radiation (temperature power spectrum) and cosmic chronometers. The reconstructed redshift remapping points to an additional boost of redshift operating in late epoch of cosmic evolution, but affecting both low-redshift observations and the CMB. The model then predicts a significant difference between the actual Hubble constant, h=0.48±0.02, and its local determination, h obs=0.73±0.02. The ratio of these two values coincides closely with the maximum expansion rate inside voids formed in the corresponding open cosmological model with Ω m=0.87±0.03, whereas the actual value of the Hubble constant implies the age of the Universe that is compatible with the Planck LambdaCDM cosmology. The new dark-matter-dominated model with redshift remapping provides excellent fits to all data and eliminates recently reported tensions between the Planck LambdaCDM cosmology, the local determination of the Hubble constant and the BAO measurements from the Ly α forest of high-redshift quasars.« less

The VIMOS Public Extragalactic Redshift Survey (VIPERS). Star formation history of passive red galaxies

NASA Astrophysics Data System (ADS)

Siudek, M.; Małek, K.; Scodeggio, M.; Garilli, B.; Pollo, A.; Haines, C. P.; Fritz, A.; Bolzonella, M.; de la Torre, S.; Granett, B. R.; Guzzo, L.; Abbas, U.; Adami, C.; Bottini, D.; Cappi, A.; Cucciati, O.; De Lucia, G.; Davidzon, I.; Franzetti, P.; Iovino, A.; Krywult, J.; Le Brun, V.; Le Fèvre, O.; Maccagni, D.; Marchetti, A.; Marulli, F.; Polletta, M.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zanichelli, A.; Arnouts, S.; Bel, J.; Branchini, E.; Ilbert, O.; Gargiulo, A.; Moscardini, L.; Takeuchi, T. T.; Zamorani, G.

2017-01-01

Aims: We trace the evolution and the star formation history of passive red galaxies, using a subset of the VIMOS Public Extragalactic Redshift Survey (VIPERS). The detailed spectral analysis of stellar populations of intermediate-redshift passive red galaxies allows the build up of their stellar content to be followed over the last 8 billion years. Methods: We extracted a sample of passive red galaxies in the redshift range 0.4

Measuring the Clustering Around Normal and Dust-Obscured Quasars at 2 in the Spitzer Extragalactic Representative Volume Survey (SERVS)

NASA Astrophysics Data System (ADS)

Jones, Kristen M.; Lacy, M.; Spitzer Extragalactic Representative Volume Survey Team

2014-01-01

Little is known about the environments of high redshift quasars, particularly those obscured by dust. Previous work suggests that dust-shrouded (type 2) quasars are at least as common as un-obscured optical (type 1) quasars; therefore, in order to fully understand the role quasars play in the evolutionary history of the universe, we must understand both types of objects. This project seeks to explore the environments in which obscured quasars form. In this poster, we present mid-infrared clustering measurements for a sample of 45 quasars with 1.3 < z < 2.5, a redshift range that is unexplored in the literature. The objects were selected using IRAC multi-color criteria to remove low-redshift starburst and quiescent galaxies, and subsequently had spectroscopy carried out to both obtain redshifts, and to distinguish between type 1 and type 2 quasars; the high-redshift sample presented in this paper is roughly evenly distributed between the two types. We use the SERVS galaxy catalogs to estimate the cross-correlation between each quasar and its surrounding galaxies. The amplitude of this function gives us the richness of the environments in which these quasars are found, and we compare our results with a matched sample with z < 1.3.

Quenching of Star-formation Activity of High-redshift Galaxies in Clusters and Field

NASA Astrophysics Data System (ADS)

Lee, Seong-Kook; Im, Myungshin; Kim, Jae-Woo; Lotz, Jennifer; McPartland, Conor; Peth, Michael; Koekemoer, Anton

At local, galaxy properties are well known to be clearly different in different environments. However, it is still an open question how this environment-dependent trend has been shaped. We present the results of our investigation about the evolution of star-formation properties of galaxies over a wide redshift range, from z ~ 2 to z ~ 0.5, focusing its dependence on their stellar mass and environment (Lee et al. 2015). In the UKIDSS/UDS region, covering ~2800 square arcmin, we estimated photometric redshifts and stellar population properties, such as stellar masses and star-formation rates, using the deep optical and near-infrared data available in this field. Then, we identified galaxy cluster candidates within the given redshift range. Through the analysis and comparison of star-formation (SF) properties of galaxies in clusters and in field, we found interesting results regarding the evolution of SF properties of galaxies: (1) regardless of redshifts, stellar mass is a key parameter controlling quenching of star formation in galaxies; (2) At z < 1, environmental effects become important at quenching star formation regardless of stellar mass of galaxies; and (3) However, the result of the environmental quenching is prominent only for low mass galaxies (M* < 1010 M⊙) since the star formation in most of high mass galaxies are already quenched at z > 1.

AGN Populations in Large-volume X-Ray Surveys: Photometric Redshifts and Population Types Found in the Stripe 82X Survey

NASA Astrophysics Data System (ADS)

Ananna, Tonima Tasnin; Salvato, Mara; LaMassa, Stephanie; Urry, C. Megan; Cappelluti, Nico; Cardamone, Carolin; Civano, Francesca; Farrah, Duncan; Gilfanov, Marat; Glikman, Eilat; Hamilton, Mark; Kirkpatrick, Allison; Lanzuisi, Giorgio; Marchesi, Stefano; Merloni, Andrea; Nandra, Kirpal; Natarajan, Priyamvada; Richards, Gordon T.; Timlin, John

2017-11-01

Multiwavelength surveys covering large sky volumes are necessary to obtain an accurate census of rare objects such as high-luminosity and/or high-redshift active galactic nuclei (AGNs). Stripe 82X is a 31.3 X-ray survey with Chandra and XMM-Newton observations overlapping the legacy Sloan Digital Sky Survey Stripe 82 field, which has a rich investment of multiwavelength coverage from the ultraviolet to the radio. The wide-area nature of this survey presents new challenges for photometric redshifts for AGNs compared to previous work on narrow-deep fields because it probes different populations of objects that need to be identified and represented in the library of templates. Here we present an updated X-ray plus multiwavelength matched catalog, including Spitzer counterparts, and estimated photometric redshifts for 5961 (96% of a total of 6181) X-ray sources that have a normalized median absolute deviation, σnmad=0.06, and an outlier fraction, η = 13.7%. The populations found in this survey and the template libraries used for photometric redshifts provide important guiding principles for upcoming large-area surveys such as eROSITA and 3XMM (in X-ray) and the Large Synoptic Survey Telescope (optical).

Results from the REFLEX Cluster Survey

NASA Astrophysics Data System (ADS)

Bohringer, H.; Guzzo, L.; Collins, C. A.; Neumann, D. M.; Schindler, S.; Schuecker, P.; Cruddace, R.; Chincarini, G.; de Grandi, S.; Edge, A. C.; MacGillivray, H. T.; Shaver, P.; Vettolani, G.; Voges, W.

Based on the ROSAT All-Sky Survey we have conducted a large redshift survey as an ESO key programme to identify and secure redshifts for the X-ray brightest clusters found in the southern hemisphere. We present first results for a highly controlled sample for a flux limit of 3cdot 10^{-12} erg s^{-1} cm^{-2} (0.1 - 2.4 keV) comprising 475 clusters (87% with redshifts). The logN-logS function of the sample shows an almost perfect Euclidian slope and a preliminary X-ray luminosity function is presented.

Active Galactic Nuclei with James Webb Space Telescope (JWST)

NASA Technical Reports Server (NTRS)

Rigby, Jane R.

2011-01-01

I'll discuss several ways in which JWST will probe the cosmic history of accretion onto supermassive black holes, and the co-evolution of host galaxies. Key investigations include: 1) Measurements of redshift, luminosity, and AGN fraction for obscured AGN candidates identified by other missions. 2) Measurements of AGN hosts at all redshifts, including stellar masses, morphology, interactions, and star formation rates. 3) Measurements of stellar mass and black hole mass in AGN at high redshift, to chart the early history of black hole and galaxy growth.

The Kinematics of Multiple-peaked Lyα Emission in Star-forming Galaxies at z ~ 2-3

NASA Astrophysics Data System (ADS)

Kulas, Kristin R.; Shapley, Alice E.; Kollmeier, Juna A.; Zheng, Zheng; Steidel, Charles C.; Hainline, Kevin N.

2012-01-01

We present new results on the Lyα emission-line kinematics of 18 z ~ 2-3 star-forming galaxies with multiple-peaked Lyα profiles. With our large spectroscopic database of UV-selected star-forming galaxies at these redshifts, we have determined that ~30% of such objects with detectable Lyα emission display multiple-peaked emission profiles. These profiles provide additional constraints on the escape of Lyα photons due to the rich velocity structure in the emergent line. Despite recent advances in modeling the escape of Lyα from star-forming galaxies at high redshifts, comparisons between models and data are often missing crucial observational information. Using Keck II NIRSPEC spectra of Hα (z ~ 2) and [O III]λ5007 (z ~ 3), we have measured accurate systemic redshifts, rest-frame optical nebular velocity dispersions, and emission-line fluxes for the objects in the sample. In addition, rest-frame UV luminosities and colors provide estimates of star formation rates and the degree of dust extinction. In concert with the profile sub-structure, these measurements provide critical constraints on the geometry and kinematics of interstellar gas in high-redshift galaxies. Accurate systemic redshifts allow us to translate the multiple-peaked Lyα profiles into velocity space, revealing that the majority (11/18) display double-peaked emission straddling the velocity-field zero point with stronger red-side emission. Interstellar absorption-line kinematics suggest the presence of large-scale outflows for the majority of objects in our sample, with an average measured interstellar absorption velocity offset of langΔv absrang = -230 km s-1. A comparison of the interstellar absorption kinematics for objects with multiple- and single-peaked Lyα profiles indicate that the multiple-peaked objects are characterized by significantly narrower absorption line widths. We compare our data with the predictions of simple models for outflowing and infalling gas distributions around high-redshift galaxies. While popular "shell" models provide a qualitative match with many of the observations of Lyα emission, we find that in detail there are important discrepancies between the models and data, as well as problems with applying the framework of an expanding thin shell of gas to explain high-redshift galaxy spectra. Our data highlight these inconsistencies, as well as illuminating critical elements for success in future models of outflow and infall in high-redshift galaxies. Based, in part, on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

AGN-driven helium reionization and the incidence of extended He III regions at redshift z > 3

NASA Astrophysics Data System (ADS)

Compostella, Michele; Cantalupo, Sebastiano; Porciani, Cristiano

2014-12-01

We use hydrodynamic simulations post-processed with the radiative-transfer code RADAMESH to assess recent claims that the low He II opacity observed in z > 3 quasar spectra may be incompatible with models of He II reionization driven by the observed population of active galactic nuclei (AGNs). In particular, building upon our previous work, we consider an early population of sources and start the radiative-transfer calculation at redshifts z ≥ 5. Our model faithfully reproduces the emissivity of optically selected AGNs as inferred from measurements of their luminosity function. We find that He II reionization is very extended in redshift (Δz ≥ 2) and highly spatially inhomogeneous. In fact, mock spectra extracted from the simulations show a large variability in the evolution of the He II effective optical depth within chunks of size Δz = 0.04. Regions with low opacity (τ_ {He {II}}^eff < 3) can be found at high redshift, in agreement with the most recent observations of UV-transmitting quasars. At the highest redshift currently probed by observations (z ˜ 3.4), our updated model predicts a much lower He II effective optical depth than previous simulations in the literature relieving most of the tension with the current data, that, however, still persists at about the (Gaussian) 1σ to 2σ level. Given the very small number of observed lines of sight, our analysis indicates that current data cannot rule out a purely AGN-driven scenario with high statistical significance.

Resolved Star Formation in Galaxies Using Slitless Spectroscopy

NASA Astrophysics Data System (ADS)

Pirzkal, Norbert; Finkelstein, Steven L.; Larson, Rebecca L.; Malhotra, Sangeeta; Rhoads, James E.; Ryan, Russell E.; Tilvi, Vithal; FIGS Team

2018-06-01

The ability to spatially resolve individual star-formation regions in distant galaxies and simultaneously extract their physical properties via emission lines is a critical step forward in studying the evolution of galaxies. While efficient, deep slitless spectroscopic observations offer a blurry view of the summed properties of galaxies. We present our studies of resolved star formation over a wide range of redshifts, including high redshift Ly-a sources. The unique capabilities of the WFC3 IR Grism and our two-dimensional emission line method (EM2D) allows us to accurately identify the specific spatial origin of emission lines in galaxies, thus creating a spatial map of star-formation sites in any given galaxy. This method requires the use of multiple position angles on the sky to accurately derive both the location and the observed wavelengths of these emission lines. This has the added benefit of producing better defined redshifts for these sources. Building on our success in applying the EM2D method towards galaxies with [OII]. [OIII], and Ha emission lines, we have also applied EM2D to high redshift (z>6) Ly-a emitting galaxies. We are also able to produce accurate 2D emission line maps (MAP2D) of the Ly-a emission in WFC3 IR grism observations, looking for evidence that a significant amount of resonant scattering is taking place in high redshift galaxies such as in a newly identified z=7.5 Faint Infrared Galaxy Survey (FIGS) Ly-a galaxy.

The ionization parameter of star-forming galaxies evolves with the specific star formation rate

NASA Astrophysics Data System (ADS)

Kaasinen, Melanie; Kewley, Lisa; Bian, Fuyan; Groves, Brent; Kashino, Daichi; Silverman, John; Kartaltepe, Jeyhan

2018-07-01

We investigate the evolution of the ionization parameter of star-forming galaxies using a high-redshift (z˜ 1.5) sample from the FMOS-COSMOS (Fibre Multi-Object Spectrograph-COSMic evOlution Survey) and matched low-redshift samples from the Sloan Digital Sky Survey. By constructing samples of low-redshift galaxies for which the stellar mass (M*), star formation rate (SFR), and specific star formation rate (sSFR) are matched to the high-redshift sample, we remove the effects of an evolution in these properties. We also account for the effect of metallicity by jointly constraining the metallicity and ionization parameter of each sample. We find an evolution in the ionization parameter for main-sequence, star-forming galaxies and show that this evolution is driven by the evolution of sSFR. By analysing the matched samples as well as a larger sample of z< 0.3, star-forming galaxies we show that high ionization parameters are directly linked to high sSFRs and are not simply the by-product of an evolution in metallicity. Our results are physically consistent with the definition of the ionization parameter, a measure of the hydrogen ionizing photon flux relative to the number density of hydrogen atoms.

Stars and reionization: the cross-correlation of the 21 cm line and the near-infrared background

NASA Astrophysics Data System (ADS)

Fernandez, Elizabeth R.; Zaroubi, Saleem; Iliev, Ilian T.; Mellema, Garrelt; Jelić, Vibor

2014-05-01

With improving telescopes, it may now be possible to observe the Epoch of Reionization in multiple ways. We examine two of these observables - the excess light in the near-infrared background that may be due to high-redshift stars and ionized HII bubbles, and the 21 cm emission from neutral hydrogen. Because these two forms of emission should result from different, mutually exclusive regions, an anticorrelation should exist between them. We discuss the strengths of using cross-correlations between these observations to learn more about high-redshift star formation and reionization history. In particular, we create simulated maps of emission from both the near-infrared background and 21 cm emission. We find that these observations are anticorrelated, with the strongest anticorrelation originating from times when the universe is half ionized. This result is robust and does not depend on the properties of the stars themselves. Rather, it depends on the ionization history. Cross-correlations can provide redshift information, which the near-infrared background cannot provide alone. In addition, cross-correlations can help separate foreground emission from the true high-redshift component, making it possible to say with greater certainty that we are indeed witnessing the Epoch of Reionization.

Intra-cluster Globular Clusters in a Simulated Galaxy Cluster

NASA Astrophysics Data System (ADS)

Ramos-Almendares, Felipe; Abadi, Mario; Muriel, Hernán; Coenda, Valeria

2018-01-01

Using a cosmological dark matter simulation of a galaxy-cluster halo, we follow the temporal evolution of its globular cluster population. To mimic the red and blue globular cluster populations, we select at high redshift (z∼ 1) two sets of particles from individual galactic halos constrained by the fact that, at redshift z = 0, they have density profiles similar to observed ones. At redshift z = 0, approximately 60% of our selected globular clusters were removed from their original halos building up the intra-cluster globular cluster population, while the remaining 40% are still gravitationally bound to their original galactic halos. As the blue population is more extended than the red one, the intra-cluster globular cluster population is dominated by blue globular clusters, with a relative fraction that grows from 60% at redshift z = 0 up to 83% for redshift z∼ 2. In agreement with observational results for the Virgo galaxy cluster, the blue intra-cluster globular cluster population is more spatially extended than the red one, pointing to a tidally disrupted origin.

Long High Redshift GRB and Xrt/swift Lightcurves

NASA Astrophysics Data System (ADS)

Arkhangelskaja, Irene

At February of 2010 the volume of Swift GRB subset with known redshift consisted of more than 150 bursts. Long GRB redshift distribution analysis has shown that confidence level of single peak approximation of this distribution is only ˜60%. Moreover, more than 40% of GRB are in very heavy tails outside 3σ level for this fit. More detailed analysis of long GRB redshift distribution reveals that at 97% confidence level at least two subgroups could be separated with following parameters: = 0.9 ± 0.1 and = 2.7 ± 0.2. It allows to make conclusion that Swift long GRB sources subset is not uniform. In the presented article attention is paid on the measure of discrepancy of long GRB with z>3 and subset of other long GRB with known redshifts. XRT/Swift lightcurves for these groups of GRB were considered and it have shown that at least 90% XRT/Swift lightcurves for GRB with z>3 are more complicated and have got a number of maxima.

The Hubble Space Telescope quasar absorption line key project. 6: Properties of the metal-rich systems

NASA Technical Reports Server (NTRS)

Bergeron, Jacqueline; Petitjean, Patrick; Sargent, W. L. W.; Bahcall, John N.; Boksenberg, Alec; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Savage, Blair D.; Schneider, Donald P.

1994-01-01

We present an analysis of the properties of a sample of 18 metal-rich, low-redshift z(sub abs) much less than z(sub em) absorbers seen in low- and medium-resolution spectra obtained for the Quasar Absorption Line Key Project with the Hubble Space Telescope Faint Object Spectrograph (HST/FOS). For most of the C IV and Lyman-limit systems, observations in the optical wavelength range of the expected associated Mg II absorption are available. As at high redshift (z approximately 2), there are two subclasses of absorbers which are characterized by the presence or absence of MG II absorption. However, some low-redshift Mg II and Fe absorptions originate from regions optically thin to UV ionizing photons and thus, at low redshift, the low-ionization systems do not always trace high opacities, as is the case at high redshift. This implies that the mean ionization state of metal-rich, optically thin absorbing clouds falls with decreasing redshift, which is consistent with the hypothesis that the gas is photoionized by the metagalactic UV background radiation field. Two main constraints are derived from the analysis of the Lyman-limit sample, assuming photoionization models are valid. First, a low opacity to ionizing photons (tau(sub LL) approximately less than 1), as observed for several Mg II-Fe II systems at z approximately 0.5, sets limits on the ionization level of hydrogen, thus on the total hydrogen column density and the heavy element abundances, (Z/H) approximately -0.5 to -0.3. Second, the dimensions of individual Mg II clouds are smaller than at high redshift by a factor 3-10. At z approximately greater than 0.6, the O VI absorption doublet is detected in four of the five z(sub abs) much less than z(sub em) systems for which the O VI wavelength range has been observed, whereas the associated N V doublet is detected in only two cases. This suggests that the presence of a high-ionization O VI phase is a general property of z approximately 0.6-1 absorption systems, as is also probably the case at high redshift. These O VI absorbers can be ionized by the UV metagalactic field if their density is low, nH approximately less than 3 x 10(exp -4)/cc. The O VI phase would then be a homogeneous region of large extent, r approximately greater than 50 kpc. A detailed photoionization model of the z(sub abs) = 0.791 absorber toward PKS 2145+06 confirms the properties derived from the Mg II, C IV, O VI, and Lyman-limit samples. The galaxy causing this extensive metal-line absorption system has been identified, and its possible contribution to the UV ionizing flux does not substantially modify the value of the derived parameters. The heavy element abundances are about half the solar values. The O VI region has a density about 20 times lower than the Mg II clouds and a size of approximately 70 kpc. Alternatively, the high-ionization phase could be collisionally ionized and trace gas associated with a possible group of galaxies at the absorber redshift.

Multipole analysis of redshift-space distortions around cosmic voids

NASA Astrophysics Data System (ADS)

Hamaus, Nico; Cousinou, Marie-Claude; Pisani, Alice; Aubert, Marie; Escoffier, Stéphanie; Weller, Jochen

2017-07-01

We perform a comprehensive redshift-space distortion analysis based on cosmic voids in the large-scale distribution of galaxies observed with the Sloan Digital Sky Survey. To this end, we measure multipoles of the void-galaxy cross-correlation function and compare them with standard model predictions in cosmology. Merely considering linear-order theory allows us to accurately describe the data on the entire available range of scales and to probe void-centric distances down to about 2 h-1Mpc. Common systematics, such as the Fingers-of-God effect, scale-dependent galaxy bias, and nonlinear clustering do not seem to play a significant role in our analysis. We constrain the growth rate of structure via the redshift-space distortion parameter β at two median redshifts, β(bar z=0.32)=0.599+0.134-0.124 and β(bar z=0.54)=0.457+0.056-0.054, with a precision that is competitive with state-of-the-art galaxy-clustering results. While the high-redshift constraint perfectly agrees with model expectations, we observe a mild 2σ deviation at bar z=0.32, which increases to 3σ when the data is restricted to the lowest available redshift range of 0.15

VLA observations of unidentified Leiden-Berkeley Deep-Survey sources - Luminosity and redshift dependence of spectral properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kapahi, V.K.; Kulkarni, V.K.

1990-05-01

VLA observations of a complete subset of the Leiden-Berkeley Deep Survey sources that have S(1.4 GHz) greater than 10 mJy and are not optically identified down to F=22 mag are reported. By comparing the spectral and structural properties of the sources with samples from the literature, an attempt was made to disentangle the luminosity and redshift dependence of the spectral indices of extended emission in radio galaxies and of the incidence of compact steep-spectrum sources. It is found that the fraction of compact sources among those with a steep spectrum is related primarily to redshift, being much larger at highmore » redshifts for sources of similar radio luminosity. Only a weak and marginally significant dependence of spectral indices of the extended sources on luminosity and redshift is found in samples selected at 1.4 and 2.7 GHz. It is pointed out that the much stronger correlation of spectral indices with luminosity may be arising partly from spectral curvature, and partly due to the preferential inclusion of very steep-spectrum sources from high redshift in low-frequency surveys. 54 refs.« less

Predicting the High Redshift Galaxy Population for JWST

NASA Astrophysics Data System (ADS)

Flynn, Zoey; Benson, Andrew

2017-01-01

The James Webb Space Telescope will be launched in Oct 2018 with the goal of observing galaxies in the redshift range of z = 10 - 15. As redshift increases, the age of the Universe decreases, allowing us to study objects formed only a few hundred million years after the Big Bang. This will provide a valuable opportunity to test and improve current galaxy formation theory by comparing predictions for mass, luminosity, and number density to the observed data. We have made testable predictions with the semi-analytical galaxy formation model Galacticus. The code uses Markov Chain Monte Carlo methods to determine viable sets of model parameters that match current astronomical data. The resulting constrained model was then set to match the specifications of the JWST Ultra Deep Field Imaging Survey. Predictions utilizing up to 100 viable parameter sets were calculated, allowing us to assess the uncertainty in current theoretical expectations. We predict that the planned UDF will be able to observe a significant number of objects past redshift z > 9 but nothing at redshift z > 11. In order to detect these faint objects at redshifts z = 11-15 we need to increase exposure time by at least a factor of 1.66.

21-cm radiation: a new probe of variation in the fine-structure constant.

PubMed

Khatri, Rishi; Wandelt, Benjamin D

2007-03-16

We investigate the effect of variation in the value of the fine-structure constant (alpha) at high redshifts (recombination > z > 30) on the absorption of the cosmic microwave background (CMB) at 21 cm hyperfine transition of the neutral atomic hydrogen. We find that the 21 cm signal is very sensitive to the variations in alpha and it is so far the only probe of the fine-structure constant in this redshift range. A change in the value of alpha by 1% changes the mean brightness temperature decrement of the CMB due to 21 cm absorption by >5% over the redshift range z < 50. There is an effect of similar magnitude on the amplitude of the fluctuations in the brightness temperature. The redshift of maximum absorption also changes by approximately 5%.

Physical association and periodicity in quasar families with SDSS and 2MRS

NASA Astrophysics Data System (ADS)

Fulton, C. C.; Arp, H. C.; Hartnett, J. G.

2018-07-01

We have used the Sloan Digital Sky Survey (SDSS) data release 7 (DR7) and the 2MASS (Two Micron All Sky Survey) Redshift Survey (2MRS) Ks ≤11.75 mag data release to test for physical association of candidate companion quasars with putative parent galaxies by virtue of Karlsson periodicity in quasar redshifts. We conducted this analysis using the quasar family detection algorithm described in Fulton and Arp (Astrophys. J. 754:134, 2012) and used therein to analyze the 2dF Galaxy Redshift Survey (2dFGRS) and the 2dF Quasar Redshift Survey (2QZ). The SDSS and 2MRS data sets confirm the 2dF results and allow us to examine additional object behaviors also at high significance.

Cosmological constraints with clustering-based redshifts

NASA Astrophysics Data System (ADS)

Kovetz, Ely D.; Raccanelli, Alvise; Rahman, Mubdi

2017-07-01

We demonstrate that observations lacking reliable redshift information, such as photometric and radio continuum surveys, can produce robust measurements of cosmological parameters when empowered by clustering-based redshift estimation. This method infers the redshift distribution based on the spatial clustering of sources, using cross-correlation with a reference data set with known redshifts. Applying this method to the existing Sloan Digital Sky Survey (SDSS) photometric galaxies, and projecting to future radio continuum surveys, we show that sources can be efficiently divided into several redshift bins, increasing their ability to constrain cosmological parameters. We forecast constraints on the dark-energy equation of state and on local non-Gaussianity parameters. We explore several pertinent issues, including the trade-off between including more sources and minimizing the overlap between bins, the shot-noise limitations on binning and the predicted performance of the method at high redshifts, and most importantly pay special attention to possible degeneracies with the galaxy bias. Remarkably, we find that once this technique is implemented, constraints on dynamical dark energy from the SDSS imaging catalogue can be competitive with, or better than, those from the spectroscopic BOSS survey and even future planned experiments. Further, constraints on primordial non-Gaussianity from future large-sky radio-continuum surveys can outperform those from the Planck cosmic microwave background experiment and rival those from future spectroscopic galaxy surveys. The application of this method thus holds tremendous promise for cosmology.

Environmental Effects for Gravitational-wave Astrophysics

NASA Astrophysics Data System (ADS)

Barausse, Enrico; Cardoso, Vitor; Pani, Paolo

2015-05-01

The upcoming detection of gravitational waves by terrestrial interferometers will usher in the era of gravitational-wave astronomy. This will be particularly true when space-based detectors will come of age and measure the mass and spin of massive black holes with exquisite precision and up to very high redshifts, thus allowing for better understanding of the symbiotic evolution of black holes with galaxies, and for high-precision tests of General Relativity in strong-field, highly dynamical regimes. Such ambitious goals require that astrophysical environmental pollution of gravitational-wave signals be constrained to negligible levels, so that neither detection nor estimation of the source parameters are significantly affected. Here, we consider the main sources for space-based detectors - the inspiral, merger and ringdown of massive black-hole binaries and extreme mass-ratio inspirals - and account for various effects on their gravitational waveforms, including electromagnetic fields, cosmological evolution, accretion disks, dark matter, “firewalls” and possible deviations from General Relativity. We discover that the black-hole quasinormal modes are sharply different in the presence of matter, but the ringdown signal observed by interferometers is typically unaffected. The effect of accretion disks and dark matter depends critically on their geometry and density profile, but is negligible for most sources, except for few special extreme mass-ratio inspirals. Electromagnetic fields and cosmological effects are always negligible. We finally explore the implications of our findings for proposed tests of General Relativity with gravitational waves, and conclude that environmental effects will not prevent the development of precision gravitational-wave astronomy.

The red and blue galaxy populations in the GOODS field: evidence for an excess of red dwarfs

NASA Astrophysics Data System (ADS)

Salimbeni, S.; Giallongo, E.; Menci, N.; Castellano, M.; Fontana, A.; Grazian, A.; Pentericci, L.; Trevese, D.; Cristiani, S.; Nonino, M.; Vanzella, E.

2008-01-01

Aims: We study the evolution of the galaxy population up to z˜ 3 as a function of its colour properties. In particular, luminosity functions and luminosity densities were derived as a function of redshift for the blue/late and red/early populations. Methods: We use data from the GOODS-MUSIC catalogue, which have typical magnitude limits z850≤ 26 and K_s≤ 23.5 for most of the sample. About 8% of the galaxies have spectroscopic redshifts; the remaining have well calibrated photometric redshifts derived from the extremely wide multi-wavelength coverage in 14 bands (from the U band to the Spitzer 8~ μm band). We have derived a catalogue of galaxies complete in the rest-frame B-band, which has been divided into two subsamples according to their rest-frame U-V colour (or derived specific star formation rate) properties. Results: We confirm a bimodality in the U-V colour and specific star formation rate of the galaxy sample up to z˜ 3. This bimodality is used to compute the luminosity functions of the blue/late and red/early subsamples. The luminosity functions of the blue/late and total samples are well represented by steep Schechter functions evolving in luminosity with increasing redshifts. The volume density of the luminosity functions of the red/early populations decreases with increasing redshift. The shape of the red/early luminosity functions shows an excess of faint red dwarfs with respect to the extrapolation of a flat Schechter function and can be represented by the sum of two Schechter functions. Our model for galaxy formation in the hierarchical clustering scenario, which also includes external feedback due to a diffuse UV background, shows a general broad agreement with the luminosity functions of both populations, the larger discrepancies being present at the faint end for the red population. Hints on the nature of the red dwarf population are given on the basis of their stellar mass and spatial distributions.

Ultra-compact structure in intermediate-luminosity radio quasars: building a sample of standard cosmological rulers and improving the dark energy constraints up to z 3

NASA Astrophysics Data System (ADS)

Cao, Shuo; Zheng, Xiaogang; Biesiada, Marek; Qi, Jingzhao; Chen, Yun; Zhu, Zong-Hong

2017-09-01

Context. Ultra-compact structure in radio sources (especially in quasars that can be observed up to very high redshifts), with milliarcsecond angular sizes measured by very-long-baseline interferometry (VLBI), is becoming an important astrophysical tool for probing both cosmology and the physical properties of AGN. Aims: We present a newly compiled data set of 120 milliarcsec. compact radio sources representing intermediate-luminosity quasars covering the redshift range 0.46 < z < 2.76 and check the possibility of using these sources as independent cosmological probes. These quasars observed at 2.29 GHz show negligible dependence on redshifts and intrinsic luminosity, and thus represent a fixed comoving-length of standard ruler. Methods: For a cosmological ruler with intrinsic length lm, the angular size-redshift relation can be written as θ(z) = lm/DA(z, where θ(z) is the angular size at redshift z, and DA(z) is the corresponding angular diameter distance. We use a compilation of angular size and redshift data for ultra-compact radio sources from a well-known VLBI survey, and implement a new cosmology-independent technique to calibrate the linear size of this standard ruler, which is also used to test different cosmological models with and without the flat universe assumption. Results: We determine the linear size of this standard ruler as lm = 11.03 ± 0.25 pc, which is the typical radius at which AGN jets become opaque at the observed frequency ν 2 GHz. Our measurement of this linear size is also consistent with the previous and recent radio observations at other different frequencies. In the framework of flat ΛCDM model, we find a high value of the matter density parameter, Ωm = 0.322+0.244-0.141, and a low value of the Hubble constant, H0 = 67.6+7.8-7.4 km s-1 Mpc-1, which is in excellent agreement with the cosmic microwave background (CMB) anisotropy measurements by Planck. We obtain Ωm = 0.309+0.215-0.151, w = -0.970+0.500-1.730 at 68.3% CL for the constant w of a dynamical dark-energy model, which demonstrates no significant deviation from the concordance ΛCDM model. Consistent fitting results are also obtained for other cosmological models explaining the cosmic acceleration, like Ricci dark energy (RDE) or the Dvali-Gabadadze-Porrati (DGP) brane-world scenario. While no significant change in w with redshift is detected, there is still considerable room for evolution in w and the transition redshift at which w departing from -1 is located at z 2.0. Our results demonstrate that the method extensively investigated in our work on observational radio quasar data can be used to effectively derive cosmological information. Finally, we find the combination of high-redshift quasars and low-redshift clusters may provide an important source of angular diameter distances, considering the redshift coverage of these two astrophysical probes.

The faint end of the red sequence galaxy luminosity function: unveiling surface brightness selection effects with the CLASH clusters

NASA Astrophysics Data System (ADS)

Martinet, Nicolas; Durret, Florence; Adami, Christophe; Rudnick, Gregory

2017-08-01

Characterizing the evolution of the faint end of the cluster red sequence (RS) galaxy luminosity function (GLF) with redshift is a milestone in understanding galaxy evolution. However, the community is still divided in that respect, hesitating between an enrichment of the RS due to efficient quenching of blue galaxies from z 1 to present-day or a scenario in which the RS is built at a higher redshift and does not evolve afterwards. Recently, it has been proposed that surface brightness (SB) selection effects could possibly solve the literature disagreement, accounting for the diminishing RS faint population in ground-based observations. We investigate this hypothesis by comparing the RS GLFs of 16 CLASH clusters computed independently from ground-based Subaru/Suprime-Cam V and Ip or Ic images and space-based HST/ACS F606W and F814W images in the redshift range 0.187 ≤ z ≤ 0.686. We stack individual cluster GLFs in two redshift bins (0.187 ≤ z ≤ 0.399 and 0.400 ≤ z ≤ 0.686) and two mass (6 × 1014M⊙ ≤ M200< 1015M⊙ and 1015M⊙ ≤ M200) bins, and also measure the evolution with the enclosing radius from 0.5 Mpc up to the virial radius for the Subaru large field of view data. Finally, we simulate the low-redshift clusters at higher redshift to investigate SB dimming effects. We find similar RS GLFs for space- and ground-based data, with a difference of 0.2σ in the faint end parameter α when stacking all clusters together and a maximum difference of 0.9σ in the case of the high-redshift stack, demonstrating a weak dependence on the type of observation in the probed range of redshift and mass. When considering the full sample, we estimate α = - 0.76 ± 0.07 and α = - 0.78 ± 0.06 with HST and Subaru, respectively. We note a mild variation of the faint end between the high- and low-redshift subsamples at a 1.7σ and 2.6σ significance. We investigate the effect of SB dimming by simulating our low-redshift galaxies at high redshift. We measure an evolution in the faint end slope of less than 1σ in this case, implying that the observed signature is larger than one would expect from SB dimming alone, and indicating a true evolution in the faint end slope. Finally, we find no variation with mass or radius in the probed range of these two parameters. We therefore conclude that quenching is mildly affecting cluster galaxies at z ≲ 0.7 leading to a small enrichment of the RS until today, and that the different faint end slopes observed in the literature are probably due to specific cluster-to-cluster variation. Based on publicly available HST data acquired with ACS through the CLASH and COSMOS surveys. Also based on Subaru Suprime-Cam archive data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

The mid-infrared properties and gas content of active galaxies over large lookback times

NASA Astrophysics Data System (ADS)

Curran, S. J.; Duchesne, S. W.

2018-05-01

Upon an expansion of all of the searches for redshifted H I 21-cm absorption (0.002 1 ≤ z ≤ 5.19), we update recent results regarding the detection of 21-cm in the non-local Universe. Specifically, we confirm that photo-ionization of the gas is the mostly likely cause of the low detection rate at high redshift, in addition to finding that at z ≲ 0.1 there may also be a decrease in the detection rate, which we suggest is due to the dilution of the absorption strength by 21-cm emission. By assuming that associated and intervening absorbers have similar cosmological mass densities, we find evidence that the spin temperature of the gas evolves with redshift, consistent with heating by ultraviolet photons. From the near-infrared (λ = 3.4, 4.6 and 12 μm) colours, we see that radio galaxies become more quasar-like in their activity with increasing redshift. We also find that the non-detection of 21-cm absorption at high redshift is not likely to be due to the selection of gas-poor ellipticals, in addition to a strong correlation between the ionizing photon rate and the [3.4] - [4.6] colour, indicating that the UV photons arise from AGN activity. Like previous studies, we find a correlation between the detection of 21-cm absorption and the [4.6] - [12] colour, which is a tracer of star-forming activity. However, this only applies at the lowest redshifts (z ≲ 0.1), the range considered by the other studies.

Cosmology with XMM galaxy clusters: the X-CLASS/GROND catalogue and photometric redshifts

NASA Astrophysics Data System (ADS)

Ridl, J.; Clerc, N.; Sadibekova, T.; Faccioli, L.; Pacaud, F.; Greiner, J.; Krühler, T.; Rau, A.; Salvato, M.; Menzel, M.-L.; Steinle, H.; Wiseman, P.; Nandra, K.; Sanders, J.

2017-06-01

The XMM Cluster Archive Super Survey (X-CLASS) is a serendipitously detected X-ray-selected sample of 845 galaxy clusters based on 2774 XMM archival observations and covering an approximately 90 deg2 spread across the high-Galactic latitude (|b| > 20°) sky. The primary goal of this survey is to produce a well-selected sample of galaxy clusters on which cosmological analyses can be performed. This paper presents the photometric redshift follow-up of a high signal-to-noise ratio subset of 265 of these clusters with declination δ < +20° with Gamma-Ray Burst Optical and Near-Infrared Detector (GROND), a 7-channel (grizJHK) simultaneous imager on the MPG 2.2-m telescope at the ESO La Silla Observatory. We use a newly developed technique based on the red sequence colour-redshift relation, enhanced with information coming from the X-ray detection to provide photometric redshifts for this sample. We determine photometric redshifts for 232 clusters, finding a median redshift of z = 0.39 with an accuracy of Δz = 0.02(1 + z) when compared to a sample of 76 spectroscopically confirmed clusters. We also compute X-ray luminosities for the entire sample and find a median bolometric luminosity of 7.2 × 1043 erg s-1 and a median temperature of 2.9 keV. We compare our results to those of the XMM-XCS and XMM-XXL surveys, finding good agreement in both samples. The X-CLASS catalogue is available online at http://xmm-lss.in2p3.fr:8080/l4sdb/.

The redshift evolution of major merger triggering of luminous AGNs: a slight enhancement at z ˜ 2

NASA Astrophysics Data System (ADS)

Hewlett, Timothy; Villforth, Carolin; Wild, Vivienne; Mendez-Abreu, Jairo; Pawlik, Milena; Rowlands, Kate

2017-09-01

Active galactic nuclei (AGNs), particularly the most luminous AGNs, are commonly assumed to be triggered through major mergers; however, observational evidence for this scenario is mixed. To investigate any influence of galaxy mergers on AGN triggering and luminosities through cosmic time, we present a sample of 106 luminous X-ray-selected type 1 AGNs from the COSMOS survey. These AGNs occupy a large redshift range (0.5 < z < 2.2) and two orders of magnitude in X-ray luminosity (˜1043-1045 erg s-1). AGN hosts are carefully mass and redshift matched to 486 control galaxies. A novel technique for identifying and quantifying merger features in galaxies is developed, subtracting galfit galaxy models and quantifying the residuals. Comparison to visual classification confirms this measure reliably picks out disturbance features in galaxies. No enhancement of merger features with increasing AGN luminosity is found with this metric, or by visual inspection. We analyse the redshift evolution of AGNs associated with galaxy mergers and find no merger enhancement in lower redshift bins. Contrarily, in the highest redshift bin (z ˜ 2) AGNs are ˜4 times more likely to be in galaxies exhibiting evidence of morphological disturbance compared to control galaxies, at 99 per cent confidence level (˜2.4σ) from visual inspection. Since only ˜15 per cent of these AGNs are found to be in morphologically disturbed galaxies, it is implied that major mergers at high redshift make a noticeable but subdominant contribution to AGN fuelling. At low redshifts, other processes dominate and mergers become a less significant triggering mechanism.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruehler, Thomas; Malesani, Daniele; Milvang-Jensen, Bo

We present simultaneous optical and near-infrared (NIR) spectroscopy of 19 Swift {gamma}-ray burst (GRB) host galaxies observed with the VLT/X-shooter with the aim of measuring their redshifts. Galaxies were selected from The Optically Unbiased GRB Host (TOUGH) survey (15 of the 19 galaxies) or because they hosted GRBs without a bright optical afterglow. Here we provide emission-line redshifts for 13 of the observed galaxies with brightnesses between F606W > 27 mag and R = 22.9 mag (median R-tilde =24.6 mag). The median redshift is z-tilde =2.1 for all hosts and z-tilde =2.3 for the TOUGH hosts. Our new data significantlymore » improve the redshift completeness of the TOUGH survey, which now stands at 77% (53 out of 69 GRBs). They furthermore provide accurate redshifts for nine prototype dark GRBs (e.g., GRB 071021 at z = 2.452 and GRB 080207 at z = 2.086), which are exemplary of GRBs where redshifts are challenging to obtain via afterglow spectroscopy. This establishes X-shooter spectroscopy as an efficient tool for redshift determination of faint, star-forming, high-redshift galaxies such as GRB hosts. It is hence a further step toward removing the bias in GRB samples that is caused by optically dark events, and provides the basis for a better understanding of the conditions in which GRBs form. The distribution of column densities as measured from X-ray data (N{sub H,X}), for example, is closely related to the darkness of the afterglow and skewed toward low N{sub H,X} values in samples that are dominated by bursts with bright optical afterglows.« less

Identifications and Photometric Redshifts of the 2 Ms Chandra Deep Field-South Sources

NASA Astrophysics Data System (ADS)

Luo, B.; Brandt, W. N.; Xue, Y. Q.; Brusa, M.; Alexander, D. M.; Bauer, F. E.; Comastri, A.; Koekemoer, A.; Lehmer, B. D.; Mainieri, V.; Rafferty, D. A.; Schneider, D. P.; Silverman, J. D.; Vignali, C.

2010-04-01

We present reliable multiwavelength identifications and high-quality photometric redshifts for the 462 X-ray sources in the ≈2 Ms Chandra Deep Field-South (CDF-S) survey. Source identifications are carried out using deep optical-to-radio multiwavelength catalogs, and are then combined to create lists of primary and secondary counterparts for the X-ray sources. We identified reliable counterparts for 442 (95.7%) of the X-ray sources, with an expected false-match probability of ≈ 6.2%; we also selected four additional likely counterparts. The majority of the other 16 X-ray sources appear to be off-nuclear sources, sources associated with galaxy groups and clusters, high-redshift active galactic nuclei (AGNs), or spurious X-ray sources. A likelihood-ratio method is used for source matching, which effectively reduces the false-match probability at faint magnitudes compared to a simple error-circle matching method. We construct a master photometric catalog for the identified X-ray sources including up to 42 bands of UV-to-infrared data, and then calculate their photometric redshifts (photo-z's). High accuracy in the derived photo-z's is accomplished owing to (1) the up-to-date photometric data covering the full spectral energy distributions (SEDs) of the X-ray sources, (2) more accurate photometric data as a result of source deblending for ≈10% of the sources in the infrared bands and a few percent in the optical and near-infrared bands, (3) a set of 265 galaxy, AGN, and galaxy/AGN hybrid templates carefully constructed to best represent all possible SEDs, (4) the Zurich Extragalactic Bayesian Redshift Analyzer used to derive the photo-z's, which corrects the SED templates to best represent the SEDs of real sources at different redshifts and thus improves the photo-z quality. The reliability of the photo-z's is evaluated using the subsample of 220 sources with secure spectroscopic redshifts. We achieve an accuracy of |Δz|/(1 + z) ≈ 1% and an outlier [with |Δz|/(1 + z)>0.15] fraction of ≈1.4% for sources with spectroscopic redshifts. We performed blind tests to derive a more realistic estimate of the photo-z quality for sources without spectroscopic redshifts. We expect there are ≈9% outliers for the relatively brighter sources (R <~ 26), and the outlier fraction will increase to ≈15%-25% for the fainter sources (R >~ 26). The typical photo-z accuracy is ≈6%-7%. The outlier fraction and photo-z accuracy do not appear to have a redshift dependence (for z ≈ 0-4). These photo-z's appear to be the best obtained so far for faint X-ray sources, and they have been significantly (gsim50%) improved compared to previous estimates of the photo-z's for the X-ray sources in the ≈2 Ms Chandra Deep Field-North and ≈1 Ms CDF-S.

Concentrations of Simulated Dark Matter Halos

NASA Astrophysics Data System (ADS)

Child, Hillary

2017-01-01

We present the concentration-mass (c-M) relation of dark matter halos in two new high-volume high-resolution cosmological N-body simulations, Q Continuum and Outer Rim. Concentration describes the density of the central regions of halos; it is highest for low-mass halos at low redshift, decreasing at high mass and redshift. The shape of the c-M relation is an important probe of cosmology. We discuss the redshift dependence of the c-M relation, several different methods to determine concentrations of simulated halos, and potential sources of bias in concentration measurements. To connect to lensing observations, we stack halos, which also allows us to assess the suitability of the Navarro-Frenk-White profile and other profiles, such as Einasto, with an additional shape parameter. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144082.

Age of high redshift objects—a litmus test for the dark energy models

NASA Astrophysics Data System (ADS)

Jain, Deepak; Dev, Abha

2006-02-01

The discovery of the quasar, the APM 08279+5255 at z=3.91 whose age is 2 3 Gyr has once again led to “age crisis”. The noticeable fact about this object is that it cannot be accommodated in a universe with Ω=0.27, currently accepted value of matter density parameter and ω=const. In this work, we explore the concordance of various dark energy parameterizations (w(z) models) with the age estimates of the old high redshift objects. It is alarming to note that the quasar cannot be accommodated in any dark energy model even for Ω=0.23, which corresponds to 1σ deviation below the best fit value provided by WMAP. There is a need to look for alternative cosmologies or some other dark energy parameterizations which allow the existence of the high redshift objects.

Unveiling early black holes with JWST

NASA Astrophysics Data System (ADS)

Natarajan, Priyamvada

The formation of direct collapse black hole seeds with masses ~104 - 105 ~M⊙ could help explain the assembly of supermassive black holes powering high redshift quasars. Conditions conducive to the formation of these massive initial seeds exist at high redshift. Halos hosting these massive seeds merge promptly with a nearby galaxy. These early stage mergers at high redshift produce a new class of transient galaxies that contain an accreting black hole that is over-massive compared to the newly acquired stellar component - Obese Black hole Galaxies (OBGs). During this phase, the accretion luminosity of the direct collapse black hole seed exceeds that of the acquired stellar component. Here we calculate the multi-wavelength spectrum of this short-lived OBG stage, and show that there exist unique observational signatures in long wavelengths spanning near, mid to far-infrared that should be detectable by instruments aboard the upcoming James Webb Space Telescope (JWST).

Probing black hole accretion in quasar pairs at high redshift

NASA Astrophysics Data System (ADS)

Vignali, C.; Piconcelli, E.; Perna, M.; Hennawi, J.; Gilli, R.; Comastri, A.; Zamorani, G.; Dotti, M.; Mathur, S.

2018-06-01

Models and observations suggest that luminous quasar activity is triggered by mergers, so it should preferentially occur in the most massive primordial dark matter haloes, where the frequency of mergers is expected to be the highest. Since the importance of galaxy mergers increases with redshift, we identify the high-redshift Universe as the ideal laboratory for studying dual AGN. Here, we present the X-ray properties of two systems of dual quasars at z = 3.0-3.3 selected from the SDSS DR6 at separations of 6-8 arcsec (43-65 kpc) and observed by Chandra for ≈65 ks each. Both members of each pair are detected with good photon statistics to allow us to constrain the column density, spectral slope and intrinsic X-ray luminosity. We also include a recently discovered dual quasar at z = 5 (separation of 21 arcsec, 136 kpc) for which XMM-Newton archival data allow us to detect the two components separately. Using optical spectra we derived bolometric luminosities, BH masses and Eddington ratios that were compared to those of luminous SDSS quasars in the same redshift ranges. We find that the brighter component of both quasar pairs at z ≈ 3.0-3.3 has high luminosities compared to the distribution of SDSS quasars at similar redshift, with J1622A having an order magnitude higher luminosity than the median. This source lies at the luminous end of the z ≈ 3.3 quasar luminosity function. While we cannot conclusively state that the unusually high luminosities of our sources are related to their having a close companion, for J1622A there is only a 3 per cent probability that it is by chance.

Linking black hole growth with host galaxies: the accretion-stellar mass relation and its cosmic evolution

NASA Astrophysics Data System (ADS)

Yang, G.; Brandt, W. N.; Vito, F.; Chen, C.-T. J.; Trump, J. R.; Luo, B.; Sun, M. Y.; Xue, Y. Q.; Koekemoer, A. M.; Schneider, D. P.; Vignali, C.; Wang, J.-X.

2018-04-01

Previous studies suggest that the growth of supermassive black holes (SMBHs) may be fundamentally related to host-galaxy stellar mass (M⋆). To investigate this SMBH growth-M⋆ relation in detail, we calculate long-term SMBH accretion rate as a function of M⋆ and redshift [\\overlineBHAR(M_{\\star }, z)] over ranges of log (M⋆/M⊙) = 9.5-12 and z = 0.4-4. Our \\overlineBHAR(M_{\\star }, z) is constrained by high-quality survey data (GOODS-South, GOODS-North and COSMOS), and by the stellar mass function and the X-ray luminosity function. At a given M⋆, \\overlineBHAR is higher at high redshift. This redshift dependence is stronger in more massive systems [for log (M⋆/M⊙) ≈ 11.5, \\overlineBHAR is three decades higher at z = 4 than at z = 0.5], possibly due to AGN feedback. Our results indicate that the ratio between \\overlineBHAR and average star formation rate (\\overlineSFR) rises towards high M⋆ at a given redshift. This \\overlineBHAR/\\overlineSFR dependence on M⋆ does not support the scenario that SMBH and galaxy growth are in lockstep. We calculate SMBH mass history [MBH(z)] based on our \\overlineBHAR(M_{\\star }, z) and the M⋆(z) from the literature, and find that the MBH-M⋆ relation has weak redshift evolution since z ≈ 2. The MBH/M⋆ ratio is higher towards massive galaxies: it rises from ≈1/5000 at log M⋆ ≲ 10.5 to ≈1/500 at log M⋆ ≳ 11.2. Our predicted MBH/M⋆ ratio at high M⋆ is similar to that observed in local giant ellipticals, suggesting that SMBH growth from mergers is unlikely to dominate over growth from accretion.

Functional Green-Tuned Proteorhodopsin from Modern Stromatolites

PubMed Central

Albarracín, Virginia Helena; Kraiselburd, Ivana; Bamann, Christian; Wood, Phillip G.; Bamberg, Ernst; Farias, María Eugenia; Gärtner, Wolfgang

2016-01-01

The sequenced genome of the poly-extremophile Exiguobacterium sp. S17, isolated from modern stromatolites at Laguna Socompa (3,570 m), a High-Altitude Andean Lake (HAAL) in Argentinean Puna revealed a putative proteorhodopsin-encoding gene. The HAAL area is exposed to the highest UV irradiation on Earth, making the microbial community living in the stromatolites test cases for survival strategies under extreme conditions. The heterologous expressed protein E17R from Exiguobacterium (248 amino acids, 85% sequence identity to its ortholog ESR from E. sibiricum) was assembled with retinal displaying an absorbance maximum at 524 nm, which makes it a member of the green-absorbing PR-subfamily. Titration down to low pH values (eventually causing partial protein denaturation) indicated a pK value between two and three. Global fitting of data from laser flash-induced absorption changes gave evidence for an early red-shifted intermediate (its formation being below the experimental resolution) that decayed (τ1 = 3.5 μs) into another red-shifted intermediate. This species decayed in a two-step process (τ2 = 84 μs, τ3 = 11 ms), to which the initial state of E17-PR was reformed with a kinetics of 2 ms. Proton transport capability of the HAAL protein was determined by BLM measurements. Additional blue light irradiation reduced the proton current, clearly identifying a blue light absorbing, M-like intermediate. The apparent absence of this intermediate is explained by closely matching formation and decay kinetics. PMID:27187791

Functional Green-Tuned Proteorhodopsin from Modern Stromatolites.

PubMed

Albarracín, Virginia Helena; Kraiselburd, Ivana; Bamann, Christian; Wood, Phillip G; Bamberg, Ernst; Farias, María Eugenia; Gärtner, Wolfgang

2016-01-01

The sequenced genome of the poly-extremophile Exiguobacterium sp. S17, isolated from modern stromatolites at Laguna Socompa (3,570 m), a High-Altitude Andean Lake (HAAL) in Argentinean Puna revealed a putative proteorhodopsin-encoding gene. The HAAL area is exposed to the highest UV irradiation on Earth, making the microbial community living in the stromatolites test cases for survival strategies under extreme conditions. The heterologous expressed protein E17R from Exiguobacterium (248 amino acids, 85% sequence identity to its ortholog ESR from E. sibiricum) was assembled with retinal displaying an absorbance maximum at 524 nm, which makes it a member of the green-absorbing PR-subfamily. Titration down to low pH values (eventually causing partial protein denaturation) indicated a pK value between two and three. Global fitting of data from laser flash-induced absorption changes gave evidence for an early red-shifted intermediate (its formation being below the experimental resolution) that decayed (τ1 = 3.5 μs) into another red-shifted intermediate. This species decayed in a two-step process (τ2 = 84 μs, τ3 = 11 ms), to which the initial state of E17-PR was reformed with a kinetics of 2 ms. Proton transport capability of the HAAL protein was determined by BLM measurements. Additional blue light irradiation reduced the proton current, clearly identifying a blue light absorbing, M-like intermediate. The apparent absence of this intermediate is explained by closely matching formation and decay kinetics.

A dusty, normal galaxy in the epoch of reionization.

PubMed

Watson, Darach; Christensen, Lise; Knudsen, Kirsten Kraiberg; Richard, Johan; Gallazzi, Anna; Michałowski, Michał Jerzy

2015-03-19

Candidates for the modest galaxies that formed most of the stars in the early Universe, at redshifts z > 7, have been found in large numbers with extremely deep restframe-ultraviolet imaging. But it has proved difficult for existing spectrographs to characterize them using their ultraviolet light. The detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have become sufficiently enriched in dust and metals. So far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dust emission is only at z = 3.2 (ref. 5), and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z ≥ 7. Here we report thermal dust emission from an archetypal early Universe star-forming galaxy, A1689-zD1. We detect its stellar continuum in spectroscopy and determine its redshift to be z = 7.5 ± 0.2 from a spectroscopic detection of the Lyman-α break. A1689-zD1 is representative of the star-forming population during the epoch of reionization, with a total star-formation rate of about 12 solar masses per year. The galaxy is highly evolved: it has a large stellar mass and is heavily enriched in dust, with a dust-to-gas ratio close to that of the Milky Way. Dusty, evolved galaxies are thus present among the fainter star-forming population at z > 7.

The Red Radio Ring: a gravitationally lensed hyperluminous infrared radio galaxy at z = 2.553 discovered through the citizen science project SPACE WARPS

NASA Astrophysics Data System (ADS)

Geach, J. E.; More, A.; Verma, A.; Marshall, P. J.; Jackson, N.; Belles, P.-E.; Beswick, R.; Baeten, E.; Chavez, M.; Cornen, C.; Cox, B. E.; Erben, T.; Erickson, N. J.; Garrington, S.; Harrison, P. A.; Harrington, K.; Hughes, D. H.; Ivison, R. J.; Jordan, C.; Lin, Y.-T.; Leauthaud, A.; Lintott, C.; Lynn, S.; Kapadia, A.; Kneib, J.-P.; Macmillan, C.; Makler, M.; Miller, G.; Montaña, A.; Mujica, R.; Muxlow, T.; Narayanan, G.; O'Briain, D.; O'Brien, T.; Oguri, M.; Paget, E.; Parrish, M.; Ross, N. P.; Rozo, E.; Rusu, Cristian E.; Rykoff, E. S.; Sanchez-Argüelles, D.; Simpson, R.; Snyder, C.; Schloerb, F. P.; Tecza, M.; Wang, W.-H.; Van Waerbeke, L.; Wilcox, J.; Viero, M.; Wilson, G. W.; Yun, M. S.; Zeballos, M.

2015-09-01

We report the discovery of a gravitationally lensed hyperluminous infrared galaxy (intrinsic LIR ≈ 1013 L⊙) with strong radio emission (intrinsic L1.4 GHz ≈ 1025 W Hz-1) at z = 2.553. The source was identified in the citizen science project SPACE WARPS through the visual inspection of tens of thousands of iJKs colour composite images of luminous red galaxies (LRGs), groups and clusters of galaxies and quasars. Appearing as a partial Einstein ring (re ≈ 3 arcsec) around an LRG at z = 0.2, the galaxy is extremely bright in the sub-millimetre for a cosmological source, with the thermal dust emission approaching 1 Jy at peak. The redshift of the lensed galaxy is determined through the detection of the CO(3→2) molecular emission line with the Large Millimetre Telescope's Redshift Search Receiver and through [O III] and Hα line detections in the near-infrared from Subaru/Infrared Camera and Spectrograph. We have resolved the radio emission with high-resolution (300-400 mas) eMERLIN L-band and Very Large Array C-band imaging. These observations are used in combination with the near-infrared imaging to construct a lens model, which indicates a lensing magnification of μ ≈ 10. The source reconstruction appears to support a radio morphology comprised of a compact (<250 pc) core and more extended component, perhaps indicative of an active nucleus and jet or lobe.

A Submillimeter Survey of Dust Continuum Emission in Local Dust-Obscured Galaxies

NASA Astrophysics Data System (ADS)

Lee, Jong Chul; Hwang, Ho Seong; Lee, Gwang-Ho

2015-08-01

Dusty star-forming galaxies are responsible for the bulk of cosmic star formation at 1

High-Resolution Near-Infrared Spectroscopy of an Equivalent Width-Selected Sample of Starbursting Dwarf Galaxies

NASA Technical Reports Server (NTRS)

Maseda, Michael V.; VanDerWeL, Arjen; DaChuna, Elisabete; Rix, Hans-Walter; Pacafichi, Camilla; Momcheva, Ivelina; Brammer, Gabriel B.; Franx, Marijn; VanDokkum, Pieter; Bell, Eric F.;

On the Kennicutt-Schmidt Relation of Low-Metallicity High-Redshift Galaxies

NASA Astrophysics Data System (ADS)

Gnedin, Nickolay Y.; Kravtsov, Andrey V.

2010-05-01

We present results of self-consistent, high-resolution cosmological simulations of galaxy formation at z ~ 3. The simulations employ a recently developed recipe for star formation based on the local abundance of molecular hydrogen, which is tracked self-consistently during the course of simulation. The phenomenological H2 formation model accounts for the effects of dissociating UV radiation of stars in each galaxy, as well as self-shielding and shielding of H2 by dust, and therefore allows us to explore effects of lower metallicities and higher UV fluxes prevalent in high-redshift galaxies on their star formation. We compare stellar masses, metallicities, and star formation rates of the simulated galaxies to available observations of the Lyman break galaxies (LBGs) and find a reasonable agreement. We find that the Kennicutt-Schmidt (KS) relation exhibited by our simulated galaxies at z ≈ 3 is substantially steeper and has a lower amplitude than the z = 0 relation at ΣH <~ 100 M odot pc-2. The predicted relation, however, is consistent with existing observational constraints for the z ≈ 3 damped Lyα and LBGs. Our tests show that the main reason for the difference from the local KS relation is lower metallicity of the interstellar medium in high-redshift galaxies. We discuss several implications of the metallicity-dependence of the KS relation for galaxy evolution and interpretation of observations. In particular, we show that the observed size of high-redshift exponential disks depends sensitively on their KS relation. Our results also suggest that significantly reduced star formation efficiency at low gas surface densities can lead to strong suppression of star formation in low-mass high-redshift galaxies and long gas consumption time scales over most of the disks in large galaxies. The longer gas consumption time scales could make disks more resilient to major and minor mergers and could help explain the prevalence of the thin stellar disks in the local universe.

Evolution Of The Galaxy Major Merger Rate Since Z 6 In The Muse Hubble Ultra Deep Field Survey.

NASA Astrophysics Data System (ADS)

Ventou, E.; Contini, T.; MUSE-GTO Collaboration

2017-06-01

Over the past two decades, strong evidence that galaxies have undergone a significant evolution over cosmic time were found. Do galaxy mergers, one of the main driving mechanisms behind the growth of galaxies, played a key role in their evolution at significant look-back time? Due to the difficulty to identify these violent interactions between galaxies at high redshifts, the major merger rate, involving two galaxies of similar masses, was constrained so far up to redshift z 3, from previous studies of spectrocopic pair counts. Thanks to MUSE, which is perfectly suited to identify close pairs of galaxies with secure spectroscopic redshifts, we are now able to extend such studies up to z 6. I will present the results obtained from deep (10-30h) MUSE observations in the Hubble Ultra Deep Field. We provide the first constraints on the galaxy major merger evolution over 12 Gyrs (0.2 < z < 6) and over a broad range of stellar masses, showing that there is a flattening of the major merger rate evolution at very high redshift.

Selection of High-Redshift QSOs using Subaru and CFHT Photometry

NASA Astrophysics Data System (ADS)

Jones, Victoria; White, Cameron; Hasinger, Guenther; Hu, Esther

2018-01-01

We present 31 high redshift (5.0 ≤ z ≤ 6.0) quasar candidates using photometry from the Subaru and Canada France Hawaii telescopes. These candidates were observed as part of the Hawaii EROsita Ecliptic Pole Survey (HEROES) of the North Ecliptic Pole in 2016 and again in 2017. The ongoing HEROES survey is gathering ground-based imaging data in preparation for the eROSITA X-Ray mission. For this selection, we utilized optical-near IR imaging data of a 36 square degree field in one narrowband and five broadband filters on Subaru’s Hyper Suprime-Cam (HSC). We also utilized less complete coverage of the field in the U and J bands from CFHT’s MegaCam and WIRCam respectively. Photometric redshifts were calculated using SED fitting techniques in comparison with stellar, quasar, and galaxy models. Selections were then made through extendedness cuts, color-color comparisons, and color-redshift plots. Follow-up spectroscopic observations of these candidates with the DEIMOS spectrograph on Keck and X-Ray observations with eROSITA in the coming years will allow for reliable classifications of our selected candidates.

The Atacama Cosmology Telescope: Cross-Correlation of Cosmic Microwave Background Lensing and Quasars

NASA Technical Reports Server (NTRS)

Sherwin, Blake D; Das, Sudeep; Haijian, Amir; Addison, Graeme; Bond, Richard; Crichton, Devin; Devlin, Mark J.; Dunkley, Joanna; Gralla, Megan B.; Halpern, Mark;

A High Space Density of Luminous Lyman Alpha Emitters at z ∼ 6.5

NASA Astrophysics Data System (ADS)

Bagley, Micaela B.; Scarlata, Claudia; Henry, Alaina; Rafelski, Marc; Malkan, Matthew; Teplitz, Harry; Dai, Y. Sophia; Baronchelli, Ivano; Colbert, James; Rutkowski, Michael; Mehta, Vihang; Dressler, Alan; McCarthy, Patrick; Bunker, Andrew; Atek, Hakim; Garel, Thibault; Martin, Crystal L.; Hathi, Nimish; Siana, Brian

2017-03-01

We present the results of a systematic search for Lyα emitters (LAEs) at 6≲ z≲ 7.6 using the HST WFC3 Infrared Spectroscopic Parallel (WISP) Survey. Our total volume over this redshift range is ∼ 8× {10}5 Mpc3, comparable to many of the narrowband surveys despite their larger area coverage. We find two LAEs at z = 6.38 and 6.44 with line luminosities of {L}Lyα }∼ 4.7× {10}43 erg s‑1, putting them among the brightest LAEs discovered at these redshifts. Taking advantage of the broad spectral coverage of WISP, we are able to rule out almost all lower-redshift contaminants. The WISP LAEs have a high number density of 7.7× {10}-6 Mpc‑3. We argue that the LAEs reside in megaparsec-scale ionized bubbles that allow the Lyα photons to redshift out of resonance before encountering the neutral intergalactic medium. We discuss possible ionizing sources and conclude that the observed LAEs alone are not sufficient to ionize the bubbles.

Outflows in low-mass galaxies at z >1

NASA Astrophysics Data System (ADS)

Maseda, Michael V.; MUSE GTO Consortium

2017-03-01

Star formation histories of local dwarf galaxies, derived through resolved stellar populations, appear complex and varied. The general picture derived from hydrodynamical simulations is one of cold gas accretion and bursty star formation, followed by feedback from supernovae and winds that heat and eject the central gas reservoirs. This ejection halts star formation until the material cools and re-accretes, resulting in an episodic SFH, particularly at stellar masses below ~ 109 M⊙. Such feedback has often been cited as the driving force behind the observed slowly-rising rotation curves in local dwarfs, due to an under-density of dark matter compared to theoretical models, which is one of the primary challenges to LCDM cosmology. However, these events have not yet been directly observed at high-redshift. Recently, using HST imaging and grism spectroscopy, we have uncovered an abundant population of low-mass galaxies (M* < 109 M⊙) at z = 1 - 2 that are undergoing strong bursts of star formation, in agreement with the theoretical predictions. These Extreme Emission Line Galaxies, with high specific SFRs and shallow gravitational potential wells, are ideal places to test the theoretical prediction of strong feedback-driven outflows. Here we use deep MUSE spectroscopy to search these galaxies for signatures of outflowing material, namely kinematic offsets between absorption lines (in the restframe optical and UV), which trace cool gas, and the nebular emission lines, which define the systemic redshift of the galaxy. Although the EELGs are intrinsically very faint, stacked spectra reveal blueshifted velocity centroids for Fe II absorption, which is indicative of outflowing cold gas. This represents the first constraint on outflows in M* < 109 M⊙ galaxies at z = 1 - 2. These outflows should regulate the star formation histories of low-mass galaxies at early cosmic times and thus play a crucial role in galaxy growth and evolution.

Molecular jet of IRAS 04166+2706

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Liang-Yao; Shang, Hsien; Su, Yu-Nung

2014-01-01

The molecular outflow from IRAS 04166+2706 was mapped with the Submillimeter Array at a 350 GHz continuum and CO J = 3-2 at an angular resolution of ∼1''. The field of view covers the central arcminute, which contains the inner four pairs of knots of the molecular jet. On the channel map, conical structures are clearly present in the low-velocity range (|V – V {sub 0}| < 10 km s{sup –1}), and the highly collimated knots appear in the extremely high velocity range (50 >|V – V {sub 0}| > 30 km s{sup –1}). The higher angular resolution of ∼1''more » reveals the first blue-shifted knot (B1) that was missing in previous Plateau de Bure Interferometer observation of Santiago-García et al. at an offset of ∼6'' to the northeast of the central source. This identification completes the symmetric sequence of knots in both the blue- and red-shifted lobes of the outflow. The innermost knots R1 and B1 have the highest velocities within the sequence. Although the general features appear to be similar to previous CO J = 2-1 images in Santiago-García et al., the emission in CO J = 3-2 almost always peaks further away from the central source than that of CO J = 2-1 in the red-shifted lobe of the channel maps. This gives rise to a gradient in the line-ratio map of CO J = 3-2/J = 2-1 from head to tail within a knot. A large velocity gradient analysis suggests that the differences may reflect a higher gas kinetic temperature at the head. We also explore possible constraints imposed by the nondetection of SiO J = 8-7.« less

Extended Star-formation and Disk-like Kinematics in a z~3 Massive ``Main-Sequence'' Galaxy through [CII] Imaging and Multi-J CO Line Observations

NASA Astrophysics Data System (ADS)

Leung, Tsz Kuk Daisy; Riechers, Dominik A.; Clements, David; Cooray, Asantha; Ivison, Rob; Perez-Fournon, Ismael; Wardlow, Julie

2018-01-01

Dusty star-forming galaxies (SFG) at high redshifts are the main contributors to the comoving star formation rate (SFR) density, which peaks between the redshift of z=1-3 (``Cosmic Noon''). Yet, new insights into their gas dynamics, and thus, structural evolution are awaiting spatially resolved observations. I will present the latest results from our kpc-scale [CII] imaging and multi-J CO line observations obtained with ALMA, CARMA, PdBI, and the VLA in one of the most massive ``main-sequence'' disk galaxy known. XMM03 (z=2.9850) is an extremely IR-luminous galaxy with a SFR of ~3000 Msun/yr, but its molecular gas excitation is surprisingly similar to the Milky Way up to J=5, which is in stark contrast with most high-z galaxies studied to date. The monotonic velocity gradient seen in the [CII] line emission suggest that it is a rotating disk galaxy. Based on the molecular gas surface density and the far-UV radiation flux determined from photo-dissociation region (PDR) modeling, the star-forming environment of XMM03 is similar to nearby SFGs. These findings together with the ~1100 km/s wide CO(1-0) line across the entire disk of ~8 kpc in radius showcase the different interstellar medium (ISM) environment that we are probing at the most massive end of galaxies in the early Universe. With a stellar mass of M*~10^12, its specific SFR is consistent with an extrapolation of the ``star-forming main-sequence'' up to M*~10^12 Msun at z~3. Our findings therefore confirm the prevalence of disk-wide star formation responsible for assembling most of the stellar masses toward the ``Cosmic Noon''.

Understanding The Heating And Cooling Of Galaxies Over Cosmic Time With BLISS on SPICA

NASA Astrophysics Data System (ADS)

Armus, Lee; Helou, G.; Bradford, M.; Murphy, E.; Appleton, P.

2011-05-01

In order to gain a comprehensive picture of galaxy evolution, we need to accurately measure the growing population of stars and super-massive black holes in dark matter halos. The processes that regulate this evolution are invariably those that are the most difficult to simulate, namely gas heating and cooling, star formation, black hole fueling and feedback from supernovae and AGN. Measurements of the PAH features, atomic fine-structure and H2 lines in the mid-infrared with Spitzer have been used successfully to probe the dust properties, power sources and state of the ISM in normal, starburst and AGN host galaxies at 0 < z < 3. At high redshifts, these lines enter the far-infrared, which is also home to critical diagnostics of the neutral and ionized ISM, such as [OI], [OIII], [NII], and [CII]. Recent results from Herschel, CSO, IRAM and APEX suggest that there is an extremely large range in far-infrared line fluxes and physical conditions among the most luminous, high-z galaxies. However, to measure the rest-frame far-infrared cooling lines in galaxies that dominate the far-infrared background, along with the full suite of mid-infrared atomic and molecular gas and dust features in ULIRGs over a wide range in redshift, a broadband spectrometer capable of reaching the natural astrophysical background over the 30-400 micron range is required. The Background Limited Infrared Sub-millimeter Spectrometer (BLISS) on the Japanese-led SPICA mission, would deliver unmatched sensitivity to evolving, dusty galaxies over all epochs. Here we discuss the scientific rationale behind BLISS and the opportunities afforded by US participation in the SPICA mission.

Physical properties and H-ionizing-photon production rates of extreme nearby star-forming regions

NASA Astrophysics Data System (ADS)

Chevallard, Jacopo; Charlot, Stéphane; Senchyna, Peter; Stark, Daniel P.; Vidal-García, Alba; Feltre, Anna; Gutkin, Julia; Jones, Tucker; Mainali, Ramesh; Wofford, Aida

2018-06-01

Measurements of the galaxy UV luminosity function at z ≳ 6 suggest that young stars hosted in low-mass star-forming galaxies produced the bulk of hydrogen-ionizing photons necessary to reionize the intergalactic medium (IGM) by redshift z ˜ 6. Whether star-forming galaxies dominated cosmic reionization, however, also depends on their stellar populations and interstellar medium properties, which set, among other things, the production rate of H-ionizing photons, ξ _{ion}^\\star, and the fraction of these escaping into the IGM. Given the difficulty of constraining with existing observatories the physical properties of z ≳ 6 galaxies, in this work we focus on a sample of ten nearby objects showing UV spectral features comparable to those observed at z ≳ 6. We use the new-generation BEAGLE tool to model the UV-to-optical photometry and UV/optical emission lines of these Local `analogues' of high-redshift galaxies, finding that our relatively simple, yet fully self-consistent, physical model can successfully reproduce the different observables considered. Our galaxies span a broad range of metallicities and are characterised by high ionization parameters, low dust attenuation, and very young stellar populations. Through our analysis, we derive a novel diagnostic of the production rate of H-ionizing photons per unit UV luminosity, ξ _{ion}^\\star, based on the equivalent width of the bright [O III]49595007 line doublet, which does not require measurements of H-recombination lines. This new diagnostic can be used to estimate ξ _{ion}^\\star from future direct measurements of the [O III]49595007 line using JWST/NIRSpec (out to z ˜ 9.5), and by exploiting the contamination by Hβ +[O III]{4959}{5007}} of photometric observations of distant galaxies, for instance from existing Spitzer/IRAC data and from future ones with JWST/NIRCam.

Modellierung dreidimensionaler Strahlungsfelder im frühen Universum %t Modelling three dimensional radiation fields in the early universe

NASA Astrophysics Data System (ADS)

Meinköhn, Erik

2002-11-01

The present work aims at the modelling of three-dimensional radiation fields in gas clouds from the early universe, in particular as to the influence of varying distributions of density and velocity. In observations of high-redshift gas clouds, the Lyα transition from the first excited energy level to the ground state of the hydrogen atom is usually found to be the only prominent emission lines in the entire spectrum. It is a well-known assumption that high-redshifted hydrogen clouds are the precursors of present-day galaxies. Thus, the investigation of the Lyα line is of paramount importance of the theory of galaxy formation and evolution. The observed Lyα line - or rather, to be precise, its profile - reveals both the complexity of the spatial distribution and of the kinematics of the interstellar gas, and also the nature of the photon source. In this thesis we have developed a code which is capable of solving the three-dimensional frequency-dependent radiative transfer equation for arbitrarily nonrelativistically moving media. The numerical treatment of the associated partial integro-differential equation is an extremely challenging task, since radiation intensity depends on 6 variables, namely 3 space variables, 2 variables describing the direction of photon propagation, and the frequency. With the goal of a quantitative comparison with observational data in mind, the implementation of very efficient methods for a sufficiently accurate solution of the complex radiative transfer problems turned out to be a necessity. The size of the resulting linear system of equations makes the use of parallelization techniques and grid refinement strategies indispensable.

Improving Photometric Redshifts for Hyper Suprime-Cam

NASA Astrophysics Data System (ADS)

Speagle, Josh S.; Leauthaud, Alexie; Eisenstein, Daniel; Bundy, Kevin; Capak, Peter L.; Leistedt, Boris; Masters, Daniel C.; Mortlock, Daniel; Peiris, Hiranya; HSC Photo-z Team; HSC Weak Lensing Team

2017-01-01

Deriving accurate photometric redshift (photo-z) probability distribution functions (PDFs) are crucial science components for current and upcoming large-scale surveys. We outline how rigorous Bayesian inference and machine learning can be combined to quickly derive joint photo-z PDFs to individual galaxies and their parent populations. Using the first 170 deg^2 of data from the ongoing Hyper Suprime-Cam survey, we demonstrate our method is able to generate accurate predictions and reliable credible intervals over ~370k high-quality redshifts. We then use galaxy-galaxy lensing to empirically validate our predicted photo-z's over ~14M objects, finding a robust signal.

Generation of multi-millijoule red-shifted pulses for seeding stimulated Raman backscattering amplifiers.

PubMed

Landgraf, Björn; Hoffmann, Andreas; Kartashov, Daniil; Gärtner, Felix; Samsonova, Zhanna; Polynkin, Pavel; Jacoby, Joachim; Kühl, Thomas; Spielmann, Christian

2015-03-23

The efficient generation of redshifted pulses from chirped femtosecond joule level Bessel beam pulses in gases is studied. The redshift spans from a few 100 cm⁻¹ to several 1000 cm⁻¹ corresponding to a shift of 50-500 nm for Nd:glass laser systems. The generated pulses have an almost perfect Gaussian beam profile insensitive of the pump beam profile, and are much shorter than the pump pulses. The highest measured energy is as high as 30 mJ, which is significantly higher than possible with solid state nonlinear frequency shifters.

Reconstructing the dark sector interaction with LISA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Rong-Gen; Yang, Tao; Tamanini, Nicola, E-mail: cairg@itp.ac.cn, E-mail: nicola.tamanini@cea.fr, E-mail: yangtao@itp.ac.cn

We perform a forecast analysis of the ability of the LISA space-based interferometer to reconstruct the dark sector interaction using gravitational wave standard sirens at high redshift. We employ Gaussian process methods to reconstruct the distance-redshift relation in a model independent way. We adopt simulated catalogues of standard sirens given by merging massive black hole binaries visible by LISA, with an electromagnetic counterpart detectable by future telescopes. The catalogues are based on three different astrophysical scenarios for the evolution of massive black hole mergers based on the semi-analytic model of E. Barausse, Mon. Not. Roy. Astron. Soc. 423 (2012) 2533.more » We first use these standard siren datasets to assess the potential of LISA in reconstructing a possible interaction between vacuum dark energy and dark matter. Then we combine the LISA cosmological data with supernovae data simulated for the Dark Energy Survey. We consider two scenarios distinguished by the time duration of the LISA mission: 5 and 10 years. Using only LISA standard siren data, the dark sector interaction can be well reconstructed from redshift z ∼1 to z ∼3 (for a 5 years mission) and z ∼1 up to z ∼5 (for a 10 years mission), though the reconstruction is inefficient at lower redshift. When combined with the DES datasets, the interaction is well reconstructed in the whole redshift region from 0 z ∼ to z ∼3 (5 yr) and z ∼0 to z ∼5 (10 yr), respectively. Massive black hole binary standard sirens can thus be used to constrain the dark sector interaction at redshift ranges not reachable by usual supernovae datasets which probe only the z ∼< 1.5 range. Gravitational wave standard sirens will not only constitute a complementary and alternative way, with respect to familiar electromagnetic observations, to probe the cosmic expansion, but will also provide new tests to constrain possible deviations from the standard ΛCDM dynamics, especially at high redshift.« less

THE AGE SPREAD OF QUIESCENT GALAXIES WITH THE NEWFIRM MEDIUM-BAND SURVEY: IDENTIFICATION OF THE OLDEST GALAXIES OUT TO z {approx} 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whitaker, Katherine E.; Van Dokkum, Pieter G.; Brammer, Gabriel

2010-08-20

With a complete, mass-selected sample of quiescent galaxies from the NEWFIRM Medium-Band Survey, we study the stellar populations of the oldest and most massive galaxies (>10{sup 11} M{sub sun}) to high redshift. The sample includes 570 quiescent galaxies selected based on their extinction-corrected U - V colors out to z = 2.2, with accurate photometric redshifts, {sigma} {sub z}/(1 + z) {approx} 2%, and rest-frame colors, {sigma}{sub U-V} {approx} 0.06 mag. We measure an increase in the intrinsic scatter of the rest-frame U - V colors of quiescent galaxies with redshift. This scatter in color arises from the spread inmore » ages of the quiescent galaxies, where we see both relatively quiescent red, old galaxies and quiescent blue, younger galaxies toward higher redshift. The trends between color and age are consistent with the observed composite rest-frame spectral energy distributions (SEDs) of these galaxies. The composite SEDs of the reddest and bluest quiescent galaxies are fundamentally different, with remarkably well-defined 4000 A and Balmer breaks, respectively. Some of the quiescent galaxies may be up to four times older than the average age and up to the age of the universe, if the assumption of solar metallicity is correct. By matching the scatter predicted by models that include growth of the red sequence by the transformation of blue galaxies to the observed intrinsic scatter, the data indicate that most early-type galaxies formed their stars at high redshift with a burst of star formation prior to migrating to the red sequence. The observed U - V color evolution with redshift is weaker than passive evolution predicts; possible mechanisms to slow the color evolution include increasing amounts of dust in quiescent galaxies toward higher redshift, red mergers at z {approx}< 1, and a frosting of relatively young stars from star formation at later times.« less

Atomic and molecular far-infrared lines from high redshift galaxies

NASA Astrophysics Data System (ADS)

Vallini, L.

2015-03-01

The advent of Atacama Large Millimeter-submillimeter Array (ALMA), with its unprecedented sensitivity, makes it possible the detection of far-infrared (FIR) metal cooling and molecular lines from the first galaxies that formed after the Big Bang. These lines represent a powerful tool to shed light on the physical properties of the interstellar medium (ISM) in high-redshift sources. In what follows we show the potential of a physically motivated theoretical approach that we developed to predict the ISM properties of high redshift galaxies. The model allows to infer, as a function of the metallicity, the luminosities of various FIR lines observable with ALMA. It is based on high resolution cosmological simulations of star-forming galaxies at the end of the Epoch of Reionization (z˜eq6) , further implemented with sub-grid physics describing the cooling and the heating processes that take place in the neutral diffuse ISM. Finally we show how a different approach based on semi-analytical calculations can allow to predict the CO flux function at z>6.

Toward Gas Chemistry in Low Metallicity Starburst Galaxies

NASA Astrophysics Data System (ADS)

Meier, David S.; Anderson, Crystal N.; Turner, Jean; Ott, Juergen; Beck, Sara C.

2017-01-01

Dense gas, which is intimately connected with star formation, is key to understanding star formation. Though challenging to study, dense gas in low metallicity starbursts is important given these system's often extreme star formation and their potential implications for high redshift analogs. High spatial resolution (~50 pc) ALMA observations of several key probes of gas chemistry, including HCN(1-0), HCO+(1-0), CS(2-1), CCH(1-0;3/2-1/2) and SiO(2-1), towards the nearby super star-cluster (SSC) forming, sub-solar metallicity galaxy NGC 5253 are discussed. Dense gas is observed to be extended well beyond the current compact starburst, reaching into the apparently infalling molecular streamer. The faintness of HCN, the standard dense gas tracer, is extreme both in an absolute sense relative to high metallicity starbursts of a similar intensity and in a relative sense, with the HCO+/HCN ratio being one of the most elevated observed. UV-irradiated molecular gas, traced by CCH, is also extended over the mapped region, not being strongly correlated with the SSC. Despite the accretion of molecular gas from the halo and the intense burst of star formation, chemical signatures of shocked gas, traced by SiO (and HNCO), are not obvious. By placing NGC 5253 in context with other local starbursts, like 30 Doradus in the Large Magellanic Clouds and the high metallicity proto-typical starburst NGC 253, it is suggested that a combination of gas excitation and abundance changes associated with the sub solar metallicity may explain these anomalous dense gas properties.

High-precision Predictions for the Acoustic Scale in the Nonlinear Regime

NASA Astrophysics Data System (ADS)

Seo, Hee-Jong; Eckel, Jonathan; Eisenstein, Daniel J.; Mehta, Kushal; Metchnik, Marc; Padmanabhan, Nikhil; Pinto, Phillip; Takahashi, Ryuichi; White, Martin; Xu, Xiaoying

2010-09-01

We measure shifts of the acoustic scale due to nonlinear growth and redshift distortions to a high precision using a very large volume of high-force-resolution simulations. We compare results from various sets of simulations that differ in their force, volume, and mass resolution. We find a consistency within 1.5σ for shift values from different simulations and derive shift α(z) - 1 = (0.300 ± 0.015) %[D(z)/D(0)]2 using our fiducial set. We find a strong correlation with a non-unity slope between shifts in real space and in redshift space and a weak correlation between the initial redshift and low redshift. Density-field reconstruction not only removes the mean shifts and reduces errors on the mean, but also tightens the correlations. After reconstruction, we recover a slope of near unity for the correlation between the real and redshift space and restore a strong correlation between the initial and the low redshifts. We derive propagators and mode-coupling terms from our N-body simulations and compare with the Zel'dovich approximation and the shifts measured from the χ2 fitting, respectively. We interpret the propagator and the mode-coupling term of a nonlinear density field in the context of an average and a dispersion of its complex Fourier coefficients relative to those of the linear density field; from these two terms, we derive a signal-to-noise ratio of the acoustic peak measurement. We attempt to improve our reconstruction method by implementing 2LPT and iterative operations, but we obtain little improvement. The Fisher matrix estimates of uncertainty in the acoustic scale is tested using 5000 h -3 Gpc3 of cosmological Particle-Mesh simulations from Takahashi et al. At an expected sample variance level of 1%, the agreement between the Fisher matrix estimates based on Seo and Eisenstein and the N-body results is better than 10%.

Weak lensing magnification of SpARCS galaxy clusters

NASA Astrophysics Data System (ADS)

Tudorica, A.; Hildebrandt, H.; Tewes, M.; Hoekstra, H.; Morrison, C. B.; Muzzin, A.; Wilson, G.; Yee, H. K. C.; Lidman, C.; Hicks, A.; Nantais, J.; Erben, T.; van der Burg, R. F. J.; Demarco, R.

2017-12-01

Context. Measuring and calibrating relations between cluster observables is critical for resource-limited studies. The mass-richness relation of clusters offers an observationally inexpensive way of estimating masses. Its calibration is essential for cluster and cosmological studies, especially for high-redshift clusters. Weak gravitational lensing magnification is a promising and complementary method to shear studies, that can be applied at higher redshifts. Aims: We aim to employ the weak lensing magnification method to calibrate the mass-richness relation up to a redshift of 1.4. We used the Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS) galaxy cluster candidates (0.2 < z < 1.4) and optical data from the Canada France Hawaii Telescope (CFHT) to test whether magnification can be effectively used to constrain the mass of high-redshift clusters. Methods: Lyman-break galaxies (LBGs) selected using the u-band dropout technique and their colours were used as a background sample of sources. LBG positions were cross-correlated with the centres of the sample of SpARCS clusters to estimate the magnification signal, which was optimally-weighted using an externally-calibrated LBG luminosity function. The signal was measured for cluster sub-samples, binned in both redshift and richness. Results: We measured the cross-correlation between the positions of galaxy cluster candidates and LBGs and detected a weak lensing magnification signal for all bins at a detection significance of 2.6-5.5σ. In particular, the significance of the measurement for clusters with z> 1.0 is 4.1σ; for the entire cluster sample we obtained an average M200 of 1.28 -0.21+0.23 × 1014 M⊙. Conclusions: Our measurements demonstrated the feasibility of using weak lensing magnification as a viable tool for determining the average halo masses for samples of high redshift galaxy clusters. The results also established the success of using galaxy over-densities to select massive clusters at z > 1. Additional studies are necessary for further modelling of the various systematic effects we discussed.

Cluster redshifts in five suspected superclusters

NASA Technical Reports Server (NTRS)

Ciardullo, R.; Ford, H.; Harms, R.

1985-01-01

Redshift surveys for rich superclusters were carried out in five regions of the sky containing surface-density enhancements of Abell clusters. While several superclusters are identified, projection effects dominate each field, and no system contains more than five rich clusters. Two systems are found to be especially interesting. The first, field 0136 10, is shown to contain a superposition of at least four distinct superclusters, with the richest system possessing a small velocity dispersion. The second system, 2206 - 22, though a region of exceedingly high Abell cluster surface density, appears to be a remarkable superposition of 23 rich clusters almost uniformly distributed in redshift space between 0.08 and 0.24. The new redshifts significantly increase the three-dimensional information available for the distance class 5 and 6 Abell clusters and allow the spatial correlation function around rich superclusters to be estimated.

Detection of molecular gas in the quasar BR1202 - 0725 at redshift z = 4.69.

PubMed

Ohta, K; Yamada, T; Nakanishi, K; Kohno, K; Akiyama, M; Kawabe, R

1996-08-01

Although great efforts have been made to locate molecular gas--the material out of which stars form--in the early Universe, there have been only two firm detections at high redshift. Both are gravitationally lensed objects at redshift z approximately = 2.5 (refs 9-14). Here we report the detection of CO emission from the radio-quiet quasar BR1202 - 0725, which is at redshift z = 4.69. From the observed CO luminosity, we estimate that almost 10(11) solar masses of molecular hydrogen are associated with the quasar; this is comparable to the stellar mass of a present-day luminous galaxy. Our results suggest that BR1202 - 0725 is a massive galaxy, in which the gas is largely concentrated in the central region, and that is currently undergoing a large burst of star formation.

A dust-obscured massive maximum-starburst galaxy at a redshift of 6.34.

PubMed

Riechers, Dominik A; Bradford, C M; Clements, D L; Dowell, C D; Pérez-Fournon, I; Ivison, R J; Bridge, C; Conley, A; Fu, Hai; Vieira, J D; Wardlow, J; Calanog, J; Cooray, A; Hurley, P; Neri, R; Kamenetzky, J; Aguirre, J E; Altieri, B; Arumugam, V; Benford, D J; Béthermin, M; Bock, J; Burgarella, D; Cabrera-Lavers, A; Chapman, S C; Cox, P; Dunlop, J S; Earle, L; Farrah, D; Ferrero, P; Franceschini, A; Gavazzi, R; Glenn, J; Solares, E A Gonzalez; Gurwell, M A; Halpern, M; Hatziminaoglou, E; Hyde, A; Ibar, E; Kovács, A; Krips, M; Lupu, R E; Maloney, P R; Martinez-Navajas, P; Matsuhara, H; Murphy, E J; Naylor, B J; Nguyen, H T; Oliver, S J; Omont, A; Page, M J; Petitpas, G; Rangwala, N; Roseboom, I G; Scott, D; Smith, A J; Staguhn, J G; Streblyanska, A; Thomson, A P; Valtchanov, I; Viero, M; Wang, L; Zemcov, M; Zmuidzinas, J

2013-04-18

Massive present-day early-type (elliptical and lenticular) galaxies probably gained the bulk of their stellar mass and heavy elements through intense, dust-enshrouded starbursts--that is, increased rates of star formation--in the most massive dark-matter haloes at early epochs. However, it remains unknown how soon after the Big Bang massive starburst progenitors exist. The measured redshift (z) distribution of dusty, massive starbursts has long been suspected to be biased low in z owing to selection effects, as confirmed by recent findings of systems with redshifts as high as ~5 (refs 2-4). Here we report the identification of a massive starburst galaxy at z = 6.34 through a submillimetre colour-selection technique. We unambiguously determined the redshift from a suite of molecular and atomic fine-structure cooling lines. These measurements reveal a hundred billion solar masses of highly excited, chemically evolved interstellar medium in this galaxy, which constitutes at least 40 per cent of the baryonic mass. A 'maximum starburst' converts the gas into stars at a rate more than 2,000 times that of the Milky Way, a rate among the highest observed at any epoch. Despite the overall downturn in cosmic star formation towards the highest redshifts, it seems that environments mature enough to form the most massive, intense starbursts existed at least as early as 880 million years after the Big Bang.

LOFAR-Boötes: properties of high- and low-excitation radio galaxies at 0.5 < z < 2.0

NASA Astrophysics Data System (ADS)

Williams, W. L.; Calistro Rivera, G.; Best, P. N.; Hardcastle, M. J.; Röttgering, H. J. A.; Duncan, K. J.; de Gasperin, F.; Jarvis, M. J.; Miley, G. K.; Mahony, E. K.; Morabito, L. K.; Nisbet, D. M.; Prandoni, I.; Smith, D. J. B.; Tasse, C.; White, G. J.

2018-04-01

This paper presents a study of the redshift evolution of radio-loud active galactic nuclei (AGN) as a function of the properties of their galaxy hosts in the Boötes field. To achieve this we match low-frequency radio sources from deep 150-MHz LOFAR (LOw Frequency ARray) observations to an I-band-selected catalogue of galaxies, for which we have derived photometric redshifts, stellar masses, and rest-frame colours. We present spectral energy distribution (SED) fitting to determine the mid-infrared AGN contribution for the radio sources and use this information to classify them as high- versus low-excitation radio galaxies (HERGs and LERGs) or star-forming galaxies. Based on these classifications, we construct luminosity functions for the separate redshift ranges going out to z = 2. From the matched radio-optical catalogues, we select a sub-sample of 624 high power (P150 MHz > 1025 W Hz-1) radio sources between 0.5 ≤ z < 2. For this sample, we study the fraction of galaxies hosting HERGs and LERGs as a function of stellar mass and host galaxy colour. The fraction of HERGs increases with redshift, as does the fraction of sources in galaxies with lower stellar masses. We find that the fraction of galaxies that host LERGs is a strong function of stellar mass as it is in the local Universe. This, combined with the strong negative evolution of the LERG luminosity functions over this redshift range, is consistent with LERGs being fuelled by hot gas in quiescent galaxies.