Science.gov

Sample records for high redshifts characterizing

  1. 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.

  2. High redshift GRBs

    NASA Astrophysics Data System (ADS)

    Gehrels, Neil; Cannizzo, John K.

    2012-09-01

    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.

  3. 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.

  4. Searches for High Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Stevens, R.

    In recent years, the technique of Lyman break imaging has proven very effective at identifying large numbers of galaxies at high redshifts through deep multicolour imaging (Steidel et al 1996b; Steidel et al 1999). The combination of an intrinsic break in the spectra of star-forming galaxies below the rest-frame wavelength of Lyman-alpha and attenuation by intervening HI systems on the line of sight to high redshifts makes for a pronounced drop in the flux of high redshift galaxies between 912 Å and 1216 Å in the rest-frame. At redshifts z> 3, the break is shifted sufficiently far into the optical window accessible to ground-based telescopes for galaxies at such redshift to be distinguished from the foreground galaxy population through photometry alone. Through modelling of the expected colours of a wide range of galaxy types, ages and redshifts, taking into account the effects of reddening (Calzetti, Kinney and Storchi-Bergmann 1994) and intergalactic attenuation (Madau 1995), we assess the likely colours of high redshift galaxies and determine the redshift ranges most effectively probed by the imaging filters. We obtain multicolour imaging of the fields of four high redshift radio galaxies, covering around 40 arcmin2 in each, allowing us to attempt to find ordinary galaxies at similar redshifts to the central radio galaxies through photometric colour selection techniques. Some idea as to the effectiveness comes through additional colour and morphological information obtained from high-resolution Hubble Space Telescope images and from data taken in the near infra-red. While we do not have spectroscopic evidence for the redshifts of our candidates, given the available evidence we conclude that the number densities of Lyman break galaxies in the radio galaxy fields are in broad agreement with the data of Steidel et al (1999). Finally, we assess the prospects for future studies of the high redshift Universe, in particular the potential of the Oxford Deep Wide Field

  5. Very high redshift radio galaxies

    SciTech Connect

    van Breugel, W.J.M., LLNL

    1997-12-01

    High redshift radio galaxies (HzRGs) provide unique targets for the study of the formation and evolution of massive galaxies and galaxy clusters at very high redshifts. We discuss how efficient HzRG samples ae selected, the evidence for strong morphological evolution at near-infracd wavelengths, and for jet-induced star formation in the z = 3 800 HzRG 4C41 17

  6. Metals at high redshifts

    NASA Astrophysics Data System (ADS)

    Petitjean, Patrick

    The amount of metals present in the Universe and its cosmological evolution is a key issue for our understanding of how star formation proceeds from the collapse of the first objects to the formation of present day galaxies. We discuss here recent results at the two extremes of the density scale. 1. Part of the tenuous intergalactic medium (IGM) revealed by neutral hydrogen absorptions in the spectra of remote quasars (the so-called Lyman-α forest) contains metals. This is not surprising as there is a close interplay between the formation of galaxies and the evolution of the IGM. The IGM acts as the baryonic reservoir from which galaxies form, while star formation in the forming galaxies strongly influences the IGM by enrichment with metals and the emission of ionizing radiation. The spatial distribution of metals in the IGM is largely unknown however. The possibility remains that metals are associated with the filaments and sheets of the dark matter spatial distribution where stars are expected to form, whereas the space delineated by these features remains unpolluted. 2. Damped Lyman-α (DLA) systems observed in the spectra of high-redshift quasars are considered as the progenitors of present-day galaxies. Indeed, the large neutral hydrogen column densities observed and the presence of metals imply that the gas is somehow closely associated with regions of star formation. The nature of the absorbing objects is unclear however. It is probable that very different objects contribute to this population of absorption systems. Here we concentrate on summarizing the properties of the gas: presence of dust in small amount; nucleosynthesis signature and lack of H_2 molecules. The presence of H_2 molecules has been investigated in the course of a mini-survey with UVES at the VLT. The upper limits on the molecular fraction, f = 2N(H_2)/(2N(H_2)+N(HI)), derived in eight systems are in the range 1.2 ×10^-7 - 1.6 × 10^-5. There is no evidence in this sample for any

  7. 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. PMID:16641986

  8. Dusty Quasars at High Redshifts

    NASA Astrophysics Data System (ADS)

    Weedman, Daniel; Sargsyan, Lusine

    2016-09-01

    A population of quasars at z ˜ 2 is determined based on dust luminosities νL ν (7.8 μm) that includes unobscured, partially obscured, and obscured quasars. Quasars are classified by the ratio νL ν (0.25 μm)/νL ν (7.8 μm) = UV/IR, assumed to measure obscuration of UV luminosity by the dust that produces IR luminosity. Quasar counts at rest-frame 7.8 μm are determined for quasars in the Boötes field of the NOAO Deep Wide Field Survey using 24 μm sources with optical redshifts from the AGN and Galaxy Evolution Survey (AGES) or infrared redshifts from the Spitzer Infrared Spectrograph. Spectral energy distributions are extended to far-infrared wavelengths using observations from the Herschel Space Observatory Spectral and Photometric Imaging Receiver (SPIRE), and new SPIRE photometry is presented for 77 high-redshift quasars from the Sloan Digital Sky Survey. It is found that unobscured and obscured quasars have similar space densities at rest-frame 7.8 μm, but the ratio L ν (100 μm)/L ν (7.8 μm) is about three times higher for obscured quasars than for unobscured, so that far-infrared or submillimeter quasar detections are dominated by obscured quasars. We find that only ˜5% of high-redshift submillimeter sources are quasars and that existing 850 μm surveys or 2 mm surveys should already have detected sources at z ˜ 10 if quasar and starburst luminosity functions remain the same from z = 2 until z = 10.

  9. IONIZED NITROGEN AT HIGH REDSHIFT

    SciTech Connect

    Decarli, R.; Walter, F.; Neri, R.; Cox, P.; Bertoldi, F.; Carilli, C.; Kneib, J. P.; Lestrade, J. F.; Maiolino, R.; Omont, A.; Richard, J.; Riechers, D.; Thanjavur, K.; Weiss, A.

    2012-06-10

    We present secure [N II]{sub 205{mu}m} detections in two millimeter-bright, strongly lensed objects at high redshift, APM 08279+5255 (z = 3.911) and MM 18423+5938 (z = 3.930), using the IRAM Plateau de Bure Interferometer. Due to its ionization energy [N II]{sub 205{mu}m} is a good tracer of the ionized gas phase in the interstellar medium. The measured fluxes are S([N II]{sub 205{mu}m}) = (4.8 {+-} 0.8) Jy km s{sup -1} and (7.4 {+-} 0.5) Jy km s{sup -1}, respectively, yielding line luminosities of L([N II]{sub 205{mu}m}) = (1.8 {+-} 0.3) Multiplication-Sign 10{sup 9} {mu}{sup -1} L{sub Sun} for APM 08279+5255 and L([N II]{sub 205{mu}m}) = (2.8 {+-} 0.2) Multiplication-Sign 10{sup 9} {mu}{sup -1} L{sub Sun} for MM 18423+5938. Our high-resolution map of the [N II]{sub 205{mu}m} and 1 mm continuum emission in MM 18423+5938 clearly resolves an Einstein ring in this source and reveals a velocity gradient in the dynamics of the ionized gas. A comparison of these maps with high-resolution EVLA CO observations enables us to perform the first spatially resolved study of the dust continuum-to-molecular gas surface brightness ({Sigma}{sub FIR}{proportional_to}{Sigma}{sup N}{sub CO}, which can be interpreted as the star formation law) in a high-redshift object. We find a steep relation (N = 1.4 {+-} 0.2), consistent with a starbursting environment. We measure a [N II]{sub 205{mu}m}/FIR luminosity ratio in APM 08279+5255 and MM 18423+5938 of 9.0 Multiplication-Sign 10{sup -6} and 5.8 Multiplication-Sign 10{sup -6}, respectively. This is in agreement with the decrease of the [N II]{sub 205{mu}m}/FIR ratio at high FIR luminosities observed in local galaxies.

  10. Simulation of High-Redshift Galactic Images

    NASA Astrophysics Data System (ADS)

    Morgan, Robert J.; Scannapieco, E.; Windhorst, R. A.; Thacker, R.

    2009-12-01

    We construct an observational model of galaxies at high redshifts (z 3 - 13) from numerical N-body and SPH simulations of galaxy formation using the computing cluster "Saguaro” at Arizona State University. The model uses a concordance Lambda-CDM model including baryonic components with gas heating and cooling and star formation using Gadget-2 simulations. Snapshots at various redshifts yield star "particles” (populations) with a modeled metallicity and age of formation. The Bruzual-Charlot '03 stellar population models are used to compute a red-shifted flux for various filters for each simulated star population. The flux and spatial coordinates are then used to create a pixel image in a fits file format. The different redshift "slices” are shifted randomly in the simulation periodic box, and resized according to the comoving distance to correct for the angular pixel mapping. The various redshift corrected fits images are then combined into a single image for each filter to produce simulated observational images. This is to enable the use of observational imaging tools to detect galaxies and to aid observational proposals at high redshifts including the new WFC3 camera to be installed on the HST. This method also permits estimates of the luminosity function at z >6 directly from the simulated stellar populations rather than just the size of the Dark Matter haloes. With runs of higher resolution, this will permit exploration of the faint end of the luminosity function. The computing time was supplied by the ASU Fulton HPC center.

  11. Astronomical redshifts of highly ionized regions

    NASA Astrophysics Data System (ADS)

    Hansen, Peter M.

    2014-07-01

    Astronomical or cosmological redshifts are an observable property of extragalactic objects and have historically been wholly attributed to the recessional velocity of that object. The question of other, or intrinsic, components of the redshift has been highly controversial since it was first proposed. This paper investigates one theoretical source of intrinsic redshift that has been identified. The highly ionized regions of Active Galactic Nuclei (AGN) and Quasi-Stellar Objects (QSO) are, by definition, plasmas. All plasmas have electromagnetic scattering characteristics that could contribute to the observed redshift. To investigate this possibility, one region of a generalized AGN was selected, the so called Broad Line Region (BLR). Even though unresolvable with current instrumentation, physical estimates of this region have been published for years in the astronomical literature. These data, selected and then averaged, are used to construct an overall model that is consistent with the published data to within an order of magnitude. The model is then subjected to a theoretical scattering investigation. The results suggest that intrinsic redshifts, derivable from the characteristics of the ambient plasma, may indeed contribute to the overall observed redshift of these objects.

  12. High redshift quasars and high metallicities

    NASA Technical Reports Server (NTRS)

    Ferland, Gary J.

    1997-01-01

    A large-scale code called Cloudy was designed to simulate non-equilibrium plasmas and predict their spectra. The goal was to apply it to studies of galactic and extragalactic emission line objects in order to reliably deduce abundances and luminosities. Quasars are of particular interest because they are the most luminous objects in the universe and the highest redshift objects that can be observed spectroscopically, and their emission lines can reveal the composition of the interstellar medium (ISM) of the universe when it was well under a billion years old. The lines are produced by warm (approximately 10(sup 4)K) gas with moderate to low density (n less than or equal to 10(sup 12) cm(sup -3)). Cloudy has been extended to include approximately 10(sup 4) resonance lines from the 495 possible stages of ionization of the lightest 30 elements, an extension that required several steps. The charge transfer database was expanded to complete the needed reactions between hydrogen and the first four ions and fit all reactions with a common approximation. Radiative recombination rate coefficients were derived for recombination from all closed shells, where this process should dominate. Analytical fits to Opacity Project (OP) and other recent photoionization cross sections were produced. Finally, rescaled OP oscillator strengths were used to compile a complete set of data for 5971 resonance lines. The major discovery has been that high redshift quasars have very high metallicities and there is strong evidence that the quasar phenomenon is associated with the birth of massive elliptical galaxies.

  13. GLAST observation of high-redshift GRBs

    SciTech Connect

    Bissaldi, Elisabetta; Longo, Francesco; Barbiellini, Guido; Calura, Francesco; Matteucci, Francesca; Omodei, Nicola

    2007-07-12

    We compare predicted Type Ib/c supernova (SNIb/c) rates with the observed long-duration Gamma-Ray-Burst (GRB) rates both locally and as a function of redshift, by assuming different star formation histories in galaxies of different morphological types. Due to the high star formation in spheroids at high redshift, we predict a large number of GRBs beyond z > 7. Moreover, based on our studies and on the current LAT performance, an estimate of the detection possibility of this burst population is presented.

  14. SCUBA Observations of High Redshift Radio Galaxies

    SciTech Connect

    Reuland, M; Rottgering, H; van Breugel, W

    2003-03-11

    High redshift radio galaxies (HzRGs) are key targets for studies of the formation and evolution of massive galaxies.The role of dust in these processes is uncertain. We have therefore observed the dust continuum emission from a sample of z > 3 radio galaxies with the SCUBA bolometer array. We confirm and strengthen the result found by Archibald et al. (1), that HzRGs are massive starforming systems and that submillimeter detection rate appears to be primarily a strong function of redshift. We also observed HzRG-candidates that have so far eluded spectroscopic redshift determination. Four of these have been detected, and provide evidence that they may be extremely obscured radio galaxies, possibly in an early stage of their evolution.

  15. 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.

  16. High Energy Continuum of High Redshift Quasars

    NASA Technical Reports Server (NTRS)

    Elvis, Martin

    2000-01-01

    Discussion with the RXTE team at GSFC showed that a sufficiently accurate background subtraction procedure had now, been derived for sources at the flux level of PKS 2126-158. However this solution does not apply to observations carried out before April 1997, including our observation. The prospect of an improved solution becoming available soon is slim. As a result the RXTE team agreed to re-observe PKS2126-158. The new observation was carried out in April 1999. Quasi-simultaneous optical observations were obtained, as Service observing., at the 4-meter Anglo-Australian Telescope, and ftp-ed from the AAT on 22April. The RXTE data was processed in late June, arriving at SAO in early July. Coincidentally, our collaborative Beppo-SAX observation of PKS2126-158 was made later in 1999, and a GTO Chandra observation (with which we are involved) was made on November 16. Since this gives us a unique monitoring data for a high redshift quasar over a broad pass-band we are now combining all three observations into a single comprehensive study Final publication of the RXTE data will thus take place under another grant.

  17. Finding high-redshift voids using Lyman α forest tomography

    NASA Astrophysics Data System (ADS)

    Stark, Casey W.; Font-Ribera, Andreu; White, Martin; Lee, Khee-Gan

    2015-11-01

    We present a new method of finding cosmic voids using tomographic maps of Lyα forest flux. We identify cosmological voids with radii of 2-12 h-1 Mpc in a large N-body simulation at z = 2.5, and characterize the signal of the high-redshift voids in density and Lyα forest flux. The void properties are similar to what has been found at lower redshifts, but they are smaller and have steeper radial density profiles. Similarly to what has been found for low-redshift voids, the radial velocity profiles have little scatter and agree very well with the linear theory prediction. We run the same void finder on an ideal Lyα flux field and tomographic reconstructions at various spatial samplings. We compare the tomographic map void catalogues to the density void catalogue and find good agreement even with modest-sized voids (r > 6 h-1 Mpc). Using our simple void-finding method, the configuration of the ongoing COSMOS Lyman Alpha Mapping And Tomography Observations (CLAMATO) survey covering 1 deg2 would provide a sample of about 100 high-redshift voids. We also provide void-finding forecasts for larger area surveys, and discuss how these void samples can be used to test modified gravity models, study high-redshift void galaxies, and to make an Alcock-Paczynski measurement. To aid future work in this area, we provide public access to our simulation products, catalogues, and sample tomographic flux maps.

  18. High-redshift QSOs in GOODS

    NASA Astrophysics Data System (ADS)

    Fontanot, Fabio; Monaco, Pierluigi; Cristiani, Stefano; Nonino, Mario; Vanzella, Eros

    2004-12-01

    Multiwavelenght surveys are a key instrument in detecting AGNs. AGNs are recognizable from their color properties and/or their infrared/X-ray emission. We discuss the recent developments of the GOODS survey and our selection of candidates based on optical color criteria and on the matching of the optical ACS database with infrared and X-rays counterparts. We pay particular attention to the high-z QSOs search in those fields. From these observation we obtain a sample of QSOs at redshifts from 3.5 to 5.2 and we put new constraints on the faint end of the Luminosity Function at those redshift, which is particularly important to understand the interplay between the formation of galaxies and super-massive black holes inside Dark Matter Halos and to measure the QSOs contribution to the UV ionizing background.

  19. Morphologies at High Redshift from Galaxy Zoo

    NASA Astrophysics Data System (ADS)

    Masters, Karen; Melvin, Tom; Simmons, Brooke; Willett, Kyle; Lintott, Chris

    2015-08-01

    I will present results from Galaxy Zoo classification of galaxies observed in public observed frame optical HST surveys (e.g. COSMOS, GOODS) as well as in observed frame NIR with (ie. CANDELS). Early science results from these classifications have investigated the changing bar fraction in disc galaxies as a function of redshift (to z~1 in Melvin et al. 2014; and at z>1 in Simmons et al. 2015), as well as how the morphologies of galaxies on the red sequence have been changing since z~1 (Melvin et al. in prep.). These unique dataset of quantitative visual classifications for high redshift galaxies will be made public in forthcoming publications (planned as Willett et al. for Galaxy Zoo Hubble, and Simmons et al. for Galaxy Zoo CANDELS).

  20. Dust Emission from High-Redshift QSOs.

    PubMed

    Carilli; Bertoldi; Menten; Rupen; Kreysa; Fan; Strauss; Schneider; Bertarini; Yun; Zylka

    2000-04-10

    We present detections of emission at 250 GHz (1.2 mm) from two high-redshift QSOs from the Sloan Digital Sky Survey sample using the bolometer array at the IRAM 30 m telescope. The sources are SDSSp 015048.83+004126.2 at z=3.7 and SDSSp J033829.31+002156.3 at z=5.0; the latter is the third highest redshift QSO known and the highest redshift millimeter-emitting source yet identified. We also present deep radio continuum imaging of these two sources at 1.4 GHz using the Very Large Array. The combination of centimeter and millimeter observations indicate that the 250 GHz emission is most likely thermal dust emission, with implied dust masses approximately 108 M middle dot in circle. We consider possible dust heating mechanisms, including UV emission from the active galactic nucleus (AGN) and a massive starburst concurrent with the AGN, with implied star formation rates greater than 103 M middle dot in circle yr-1. PMID:10727380

  1. Jets in AGN at extremely high redshifts

    NASA Astrophysics Data System (ADS)

    Gurvits, Leonid I.; Frey, Sándor; Paragi, Zsolt

    2015-03-01

    The jet phenomenon is a trademark of active galactic nuclei (AGN). In most general terms, the current understanding of this phenomenon explains the jet appearance by effects of relativistic plasma physics. The fundamental source of energy that feeds the plasma flow is believed to be the gravitational field of a central supermassive black hole. While the mechanism of energy transfer and a multitude of effects controlling the plasma flow are yet to be understood, major properties of jets are strikingly similar in a broad range of scales from stellar to galactic. They are supposed to be controlled by a limited number of physical parameters, such as the mass of a central black hole and its spin, magnetic field induction and accretion rate. In a very simplified sense, these parameters define the formation of a typical core-jet structure observed at radio wavelengths in the region of the innermost central tens of parsecs in AGN. These core-jet structures are studied in the radio domain by Very Long Baseline Interferometry (VLBI) with milli- and sub-milliarcsecond angular resolution. Such structures are detectable at a broad range of redshifts. If observed at a fixed wavelength, a typical core-jet AGN morphology would appear as having a steep-spectrum jet fading away with the increasing redshift while a flat-spectrum core becoming more dominant. If core-jet AGN constitute the same population of objects throughout the redshift space, the apparent ``prominence'' of jets at higher redshifts must decrease (Gurvits 1999): well pronounced jets at high z must appear less frequent than at low z.

  2. Spectra of High-Redshift Type Ia Supernovae and a Comparison withtheir Low-Redshift Counterparts

    SciTech Connect

    Hook, I.M.; Howell, D.A.; Aldering, G.; Amanullah, R.; Burns,M.S.; Conley, A.; Deustua, S.E.; Ellis, R.; Fabbro, S.; Fadeyev, V.; Folatelli, G.; Garavini, G.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D.E.; Kim, A.G.; Knop, R.A.; Kowalski, M.; Lidman, C.; Nobili, S.; Nugent, P.E.; Pain, R.; Pennypacker, C.R.; Perlmutter, S.; Ruiz-Lapuente,P.; Sainton, G.; Schaefer, B.E.; Smith, E.; Spadafora, A.L.; Stanishev,V.; Thomas, R.C.; Walton, N.A.; Wang, L.; Wood-Vasey, W.M.

    2005-07-20

    We present spectra for 14 high-redshift (0.17 < z < 0.83) supernovae, which were discovered by the Supernova Cosmology Project as part of a campaign to measure cosmological parameters. The spectra are used to determine the redshift and classify the supernova type, essential information if the supernovae are to be used for cosmological studies. Redshifts were derived either from the spectrum of the host galaxy or from the spectrum of the supernova itself. We present evidence that these supernovae are of Type Ia by matching to spectra of nearby supernovae. We find that the dates of the spectra relative to maximum light determined from this fitting process are consistent with the dates determined from the photometric light curves, and moreover the spectral time-sequence for SNe Type Ia at low and high redshift is indistinguishable. We also show that the expansion velocities measured from blueshifted Ca H&K are consistent with those measured for low-redshift Type Ia supernovae. From these first-level quantitative comparisons we find no evidence for evolution in SNIa properties between these low- and high-redshift samples. Thus even though our samples may not be complete, we conclude that there is a population of SNe Ia at high redshift whose spectral properties match those at low redshift.

  3. Studying the high redshift Universe with Athena

    NASA Astrophysics Data System (ADS)

    O'Brien, P. T.

    2016-04-01

    Athena is the second large mission selected in the ESA Cosmic Vision plan. With its large collecting area, high spectral-energy resolution (X-IFU instrument) and impressive grasp (WFI instrument), Athena will truly revolutionise X-ray astronomy. The most prodigious sources of high-energy photons are often transitory in nature. Athena will provide the sensitivity and spectral resolution coupled with rapid response to enable the study of the dynamic sky. Potential sources include: distant Gamma-Ray Bursts to probe the reionisation epoch and find ‘missing’ baryons in the cosmic web; tidal disruption events to reveal dormant supermassive and intermediate-mass black holes; and supernova explosions to understand progenitors and their environments.Using detailed simulations, we illustrate Athena’s extraordinary capabilities for transients out to the highest redshifts and show how it will be able to constrain the nature of explosive transients including gas metallicity and dynamics, constraining environments and progenitors.

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

    SciTech Connect

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

    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) We 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.

  5. High-redshift Insights from Low-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Hayes, Matthew; Östlin, Göran; Schaerer, Daniel; Mas-Hesse, J. Miguel; Melinder, Jens; Verhamme, Anne; Orlitova, Ivana; Cannon, John M.; Herenz, E. Christian; Adamo, Angela

    2015-08-01

    I will summarize results from an extensive multi-wavelength observational campaign to dissect local star-forming galaxies. The Lyman alpha Reference Sample, LARS, comprises ~55 local systems, selected in various ways (FUV luminosity, IR luminosity, H-alpha EW) to provide the closest analogues systems for galaxies that are routinely discovered in high-z surveys and dominate cosmic star formation at various epochs beyond z of 1. The data-set is complete with 8 band HST imaging (5 broadband, plus H-alpha, H-beta, and Ly-alpha narrowbands), HST/COS ultraviolet spectroscopy, direct HI measurements from 21 cm interferometry (GMRT and J-VLA), optical integral field spectroscopy (CAHA/PMAS or VLT/MUSE), far IR emission lines (Herschel or SOFIA), and more.For this talk I will focus on kinematic measurements in warm-ionized, warm-neutral, and cold-neutral interstellar media. I will discuss feedback from massive stars, and how local gas kinematics and ionization states is connected to the properties of the massive stellar population. I will also discuss the extended halos of Ly-alpha that arise when large HI envelopes scatter the radiation produced by recombinations in the HII. I will quantify the extents of Ly-alpha scattering halos, and contrast these with direct observations of HI, HII, and metal lines to show how the halos arise under certain conditions in the ionized and neutral media. With results from low-z galaxies in place I will discuss the validity of using Ly-alpha and UV absorption lines for measuring the properties of gas in the circumgalactic medium of high-z galaxies.

  6. Evolution of star formation conditions from high-redshift to low-redshift

    NASA Astrophysics Data System (ADS)

    Shirazi, Maryam

    2015-08-01

    There are some hints indicating extreme interstellar medium (ISM) conditions at high redshift e.g., harder ionsing radiation fields and higher electron densities. By analysing the ionisation state of galaxies using their [OIII]5007/[OII]3727 line ratios we recently showed that star-forming galaxies at z~ 1. 5 -- 3. 5 have higher ionisation parameters and higher gas densities relative to that of local galaxies with similar global properties (Shirazi et al. 2014). This means the intrinsic properties e.g., the density of star forming regions at high redshift is different from what we observe in the local Universe. Based on the distribution of galaxies in the BPT diagram, it is proposed that the transition to nearby like conditions happen at 0. 8 < z < 1. 5 (Kewley et al 2013). However, we do not know how star-forming regions of the intermediate redshift galaxies are compared to that of high redshift galaxies that have higher gas fractions and are close to the peak of star formation activity in the Universe. We use the unique capability of the MUSE to indirectly trace the ISM conditions at those redshifts. We measure the spatially-resolved ionisation parameter using [OIII ]5007/ [O II]3727 ratio and we measure the spatially resolved gas density using the [OII] 3727,3729 doublet. We probe the spatial distributions of the ionisation parameter and gas density and search for systematic differences between high, intermediate and low redshift galaxies in terms of their global galaxy properties.

  7. Broadband Observations of High Redshift Blazars

    NASA Astrophysics Data System (ADS)

    Paliya, Vaidehi S.; Parker, M. L.; Fabian, A. C.; Stalin, C. S.

    2016-07-01

    We present a multi-wavelength study of four high redshift blazars, S5 0014+81 (z = 3.37), CGRaBS J0225+1846 (z = 2.69), BZQ J1430+4205 (z = 4.72), and 3FGL J1656.2‑3303 (z = 2.40) using quasi-simultaneous data from the Swift, Nuclear Spectroscopic Telescope Array (NuSTAR) and the Fermi-Large Area Telescope (LAT) and also archival XMM-Newton observations. Other than 3FGL J1656.2‑3303, none of the sources were known as γ-ray emitters, and our analysis of ∼7.5 yr of LAT data reveals the first time detection of statistically significant γ-ray emission from CGRaBS J0225+1846. We generate the broadband spectral energy distributions (SED) of all the objects, centering at the epoch of NuSTAR observations and reproduce them using a one-zone leptonic emission model. The optical‑UV emission in all the objects can be explained by radiation from the accretion disk, whereas the X-ray to γ-ray windows of the SEDs are found to be dominated by inverse Compton scattering off the broad line region photons. All of them host black holes that are billions of solar masses. Comparing the accretion disk luminosity and the jet power of these sources with a large sample of blazars, we find them to occupy a high disk luminosity–jet power regime. We also investigate the X-ray spectral properties of the sources in detail with a major focus on studying the causes of soft X-ray deficit, a feature generally seen in high redshift radio-loud quasars. We summarize that this feature could be explained based on the intrinsic curvature in the jet emission rather than being due to the external effects predicted in earlier studies, such as host galaxy and/or warm absorption.

  8. The impact of foregrounds on redshift space distortion measurements with the highly redshifted 21-cm line

    NASA Astrophysics Data System (ADS)

    Pober, Jonathan C.

    2015-02-01

    The highly redshifted 21-cm line of neutral hydrogen has become recognized as a unique probe of cosmology from relatively low redshifts (z ˜ 1) up through the Epoch of Reionization (EoR) (z ˜ 8) and even beyond. To date, most work has focused on recovering the spherically averaged power spectrum of the 21-cm signal, since this approach maximizes the signal to noise in the initial measurement. However, like galaxy surveys, the 21-cm signal is affected by redshift space distortions, and is inherently anisotropic between the line of sight and transverse directions. A measurement of this anisotropy can yield unique cosmological information, potentially even isolating the matter power spectrum from astrophysical effects. However, in interferometric measurements, foregrounds also have an anisotropic footprint between the line of sight and transverse directions: the so-called foreground `wedge'. Although foreground subtraction techniques are actively being developed, a `foreground avoidance' approach of simply ignoring contaminated modes has arguably proven most successful to date. In this work, we analyse the effect of this foreground anisotropy in recovering the redshift space distortion signature in 21-cm measurements at both high and intermediate redshifts. We find the foreground wedge corrupts nearly all of the redshift space signal for even the largest proposed EoR experiments (Hydrogen Epoch of Reionization Array and the Square Kilometre Array), making cosmological information unrecoverable without foreground subtraction. The situation is somewhat improved at lower redshifts, where the redshift-dependent mapping from observed coordinates to cosmological coordinates significantly reduces the size of the wedge. Using only foreground avoidance, we find that a large experiment like Canadian Hydrogen Intensity Mapping Experiment can place non-trivial constraints on cosmological parameters.

  9. Stellar Population Maps of High-Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Fetherolf, Tara; Reddy, Naveen; MOSDEF

    2016-06-01

    A comprehensive study of resolved galaxy structure can shed light on the formation and evolution of galactic properties, such as the distribution of stars and interstellar dust that obscures starlight. This requires high-resolution, multi-waveband photometry and spectroscopy to completely characterize the galaxies. Previous studies lacked key spectroscopic information, were comprised of small samples, or focused on the local universe. We use HST ACS/WFC3 high-resolution, multi-waveband imaging from the CANDELS project in parallel with moderate-resolution Keck I MOSFIRE spectra from the MOSFIRE Deep Evolution Field (MOSDEF) survey to produce resolved stellar population and dust maps of ~500 galaxies at redshifts 1.4 < z < 2.6—covering the key epoch when galaxies accreted most of their mass. For data preparation and analysis we develop an automated Python program to process our large, comprehensive dataset. From the multi-waveband imaging and spectroscopic redshifts, we model the spectral energy distribution for every resolution element within each galaxy and compare these results to the spectroscopically measured global properties. From our stellar population and dust maps we identify resolved structures within these galaxies. We also investigate if spectroscopically measured galaxy properties are biased when compared with that of localized sub-galactic structures.

  10. Photometric Properties of the Most Massive High-Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Robertson, Brant; Li, Yuexing; Cox, Thomas J.; Hernquist, Lars; Hopkins, Philip F.

    2007-09-01

    We calculate the observable properties of the most massive high-redshift galaxies in the hierarchical formation scenario where stellar spheroid and supermassive black hole growth are fueled by gas-rich mergers. Combining high-resolution hydrodynamical simulations of the hierarchical formation of a z~6 quasar, stellar population synthesis models, template active galactic nucleus (AGN) spectra, prescriptions for interstellar and intergalactic absorption, and the response of modern telescopes, the photometric evolution of galaxies destined to host z~6 quasars is modeled at redshifts z~4-14. These massive galaxies, with enormous stellar masses of M*~1011.5-1012 Msolar and star formation rates of SFR~103-104 Msolar yr-1 at z>~7, satisfy a variety of photometric selection criteria based on Lyman break techniques, including V-band dropouts at z>~5, i-band dropouts at z>~6, and z-band dropouts at z>~7. The observability of the most massive high-redshift galaxies is assessed and compared with a wide range of existing and proposed photometric surveys, including the Sloan Digital Sky Survey (SDSS), Great Observatories Origins Deep Survey (GOODS)/Hubble Ultra Deep Field (HUDF), National Optical Astronomy Observatory Deep Wide-Field Survey (NDWFS), UKIRT Infared Deep Sky Survey (UKIDSS), Infrared Array Camera (IRAC) Shallow Survey, Ultradeep Visible and Infrared Survey Telescope for Astronomy (VISTA), Dark Universe Explorer (DUNE), Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), Large Synoptic Survey Telescope (LSST), and Supernova/Acceleration Probe (SNAP). Massive stellar spheroids descended from z~6 quasars will likely be detected at z~4 by existing surveys, but owing to their low number densities the discovery of quasar progenitor galaxies at z>7 will likely require future surveys of large portions of the sky (>~0.5%) at wavelengths λ>~1 μm. The detection of rare, starbursting, massive galaxies at redshifts z>~6 would provide support for the

  11. Spatial Distribution of Star Formation in High Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Cunnyngham, Ian; Takamiya, M.; Willmer, C.; Chun, M.; Young, M.

    2011-01-01

    Integral field unit spectroscopy taken of galaxies with redshifts between 0.6 and 0.8 utilizing Gemini Observatory’s GMOS instrument were used to investigate the spatial distribution of star-forming regions by measuring the Hβ and [OII]λ3727 emission line fluxes. These galaxies were selected based on the strength of Hβ and [OII]λ3727 as measured from slit LRIS/Keck spectra. The process of calibrating and reducing data into cubes -- possessing two spatial dimensions, and one for wavelength -- was automated via a custom batch script using the Gemini IRAF routines. Among these galaxies only the bluest sources clearly show [OII] in the IFU regardless of total galaxy luminosity. The brightest galaxies lack [OII] emission and it is posited that two different modes of star formation exist among this seemingly homogeneous group of z=0.7 star-forming galaxies. In order to increase the galaxy sample to include redshifts from 0.3 to 0.9, public Gemini IFU data are being sought. Python scripts were written to mine the Gemini Science Archive for candidate observations, cross-reference the target of these observations with information from the NASA Extragalactic Database, and then present the resultant database in sortable, searchable, cross-linked web-interface using Django to facilitate navigation. By increasing the sample, we expect to characterize these two different modes of star formation which could be high-redshift counterparts of the U/LIRGs and dwarf starburst galaxies like NGC 1569/NGC 4449. The authors acknowledge funds provided by the National Science Foundation (AST 0909240).

  12. Intensity correlation of ionizing background at high redshifts

    NASA Technical Reports Server (NTRS)

    Zuo, Lin

    1993-01-01

    Intensity correlation of ionizing background at high redshifts is discussed. The intensity correlation function xi(sub j) and the absorption line equivalent width correlation xi(sub 1/W) are discussed.

  13. First Detection of the [O(sub III)] 88 Micrometers Line at High Redshifts: Characterizing the Starburst and Narrow-Line Regions in Extreme Luminosity Systems

    NASA Technical Reports Server (NTRS)

    Ferkinhoff, C.; Hailey-Dunsheath, S.; Nikola, T.; Parshley, S. C.; Stacey, G. J.; Benford, D. J.; Staguhn, J. G.

    2010-01-01

    We have made the first detections of the 88 micrometers [O(sub III)] line from galaxies in the early universe, detecting the line from the lensed active galactic nucleus (AGN)/starburst composite systems APM 08279+5255 at z 3.911 and SMM J02399-0136 at z = 2.8076. The line is exceptionally bright from both systems, with apparent (lensed) luminosities approx.10(exp 11) Solar Luminosity, For APM 08279, the [O(sub III)] line flux can be modeled in a star formation paradigm, with the stellar radiation field dominated by stars with effective temperatures, T(sub eff) > 36,000 K, similar to the starburst found in M82. The model implies approx.35% of the total far-IR luminosity of the system is generated by the starburst, with the remainder arising from dust heated by the AGN. The 881,tm line can also be generated in the narrow-line region of the AGN if gas densities are around a few 1000 cu cm. For SMM J02399, the [O(sub III)] line likely arises from HII regions formed by hot (T(sub eff) > 40,000 K) young stars in a massive starburst that dominates the far-IR luminosity of the system. The present work demonstrates the utility of the [O(sub III)] line for characterizing starbursts and AGN within galaxies in the early universe. These are the first detections of this astrophysically important line from galaxies beyond a redshift of 0.05.s

  14. The growth of massive galaxies and clusters at high redshift

    NASA Astrophysics Data System (ADS)

    Lindner, Robert Raymond

    Massive galaxies and galaxy clusters gain much of their mass by merging with their neighbors; this hierarchical structure formation is the foundation of our understanding of galaxy evolution. Nevertheless, the detailed evolutionary processes needed to form the structures we see in the local Universe remain poorly understood. This thesis comprises four projects examining the growth of galaxies and clusters at high redshift by using radio, sub/millimeter, and X-ray observations to provide empirical constraints on their cosmic evolution. Chapter 2 presents deep 1.2mm imaging of the inner 20' x 20' of the Lockman Hole North (LHN) field to search for submillimeter galaxies (SMGs), rapidly star-forming, high-redshift galaxy mergers. We detect 41 SMGs with S/N>4.0 and use Monte Carlo simulations to estimate their number counts and angular clustering properties. Chapter 3 investigates the nuclear accretion properties of the LHN SMGs. In the sample's average rest-frame X-ray spectrum, we detect strong Fe K alpha emission (equivalent width EW >=1 keV) from highly-ionized Fe species -- evidence that beneath the galaxies' heavy obscuration, supermassive black holes may be growing rapidly. Chapter 4 describes a new 345 GHz and 2.1 GHz imaging campaign to study the intracluster media (ICM) of eleven massive Sunyaev Zel'dovich Effect (SZE)-detected clusters from the Atacama Cosmology Telescope (ACT) southern survey. In six of eleven, 345 GHz SZE increments are detected and used to characterize the spatial distribution and energy content of the ICM at high (19.2") resolution. This work helps us understand how SZE-mass scaling relations are affected by contamination from other sources along the line of sight and by dynamical properties of the ICM. Chapter 5 studies the non-thermal radio emission in one exceptional z=0.870 binary cluster merger (ACTJ0102-4915, ``El Gordo'') with the help of newly-acquired radio observations. El Gordo is the highest-redshift cluster known to host

  15. 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.

  16. The dust emission of high-redshift quasars

    NASA Astrophysics Data System (ADS)

    Leipski, C.; Meisenheimer, K.

    2012-07-01

    The detection of powerful near-infrared emission in high redshift (z > 5) quasars demonstrates that very hot dust is present close to the active nucleus also in the very early universe. A number of high-redshift objects even show significant excess emission in the rest frame NIR over more local AGN spectral energy distribution (SED) templates. In order to test if this is a result of the very high luminosities or redshifts, we construct mean SEDs from the latest SDSS quasar catalogue in combination with MIR data from the WISE preliminary data release for several redshift and luminosity bins. Comparing these mean SEDs with a large sample of z > 5 quasars we could not identify any significant trends of the NIR spectral slope with luminosity or redshift in the regime 2.5 < z lesssim 6 and 1045 < νLν (1350Å) lesssim 1047 erg/s. In addition to the NIR regime, our combined Herschel and Spitzer photometry provides full infrared SED coverage of the same sample of z > 5 quasars. These observations reveal strong FIR emission (LFIR gtrsim 1013 Lodot) in seven objects, possibly indicating star-formation rates of several thousand solar masses per year. The FIR excess emission has unusally high temperatures (T~65K) which is in contrast to the temperature typically expected from studies at lower redshift (T~45K). These objects are currently being investigated in more detail.

  17. 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.

  18. Early Star Formation and High-Redshift Quasars

    NASA Astrophysics Data System (ADS)

    Dietrich, Matthias; Peterson, B. M.

    2007-12-01

    We are investigating for a sample of about 30 high-redshift quasars, with redshifts up to z=6, the gas chemical metallicity based on emission line ratios and employing the FeII UV/MgII line ratio, we probe the differential metal enrichment timescale between iron and alpha-elements at these early epochs. The quasars show enhanced solar metallicities ( 5 times solar) in their broad emission-line region and no indication of a metallicity evolution up to redshifts z=6. The measured FeII UV/MgII ratios range from 3 to 5, typical for high redshift quasars, with a weighted mean of about 4. However, there is a weak tendency for a lower mean ratio at z>4.7. For the first time, we will compare the gas metallicity and the FeII UV/MgII ratio for high redshift quasars. In concert, the gas metallicity, the FeII UV/MgII ratio, and model-based estimated time scales for enriching the gas and building up the super-massive black holes suggest that a violent episode of star formation and the main growth of the black hole occur roughly contemporaneously beginning at redshifts z = 8 to 13. Support for this work was provided by NASA through grant HST-GO-10792 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  19. Lyman Break Analogs: Constraints on the Formation of Extreme Starbursts at Low and High Redshift

    NASA Technical Reports Server (NTRS)

    Goncalves, Thiago S.; Overzier, Roderik; Basu-Zych, Antara; Martin, D. Christopher

    2011-01-01

    Lyman Break Analogs (LBAs), characterized by high far-UV luminosities and surface brightnesses as detected by GALEX, are intensely star-forming galaxies in the low-redshift universe (z approximately equal to 0.2), with star formation rates reaching up to 50 times that of the Milky Way. These objects present metallicities, morphologies and other physical properties similar to higher redshift Lyman Break Galaxies (LBGs), motivating the detailed study of LBAs as local laboratories of this high-redshift galaxy population. We present results from our recent integral-field spectroscopy survey of LBAs with Keck/OSIRIS, which shows that these galaxies have the same nebular gas kinematic properties as high-redshift LBGs. We argue that such kinematic studies alone are not an appropriate diagnostic to rule out merger events as the trigger for the observed starburst. Comparison between the kinematic analysis and morphological indices from HST imaging illustrates the difficulties of properly identifying (minor or major) merger events, with no clear correlation between the results using either of the two methods. Artificial redshifting of our data indicates that this problem becomes even worse at high redshift due to surface brightness dimming and resolution loss. Whether mergers could generate the observed kinematic properties is strongly dependent on gas fractions in these galaxies. We present preliminary results of a CARMA survey for LBAs and discuss the implications of the inferred molecular gas masses for formation models.

  20. 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.

  1. Leveraging Spitzer's Legacy: Quasars and Feedback at High Redshift

    NASA Astrophysics Data System (ADS)

    Richards, Gordon; Anderson, Scott; Bauer, Franz; Deo, Rajesh; Fan, Xiaohui; Gallagher, Sarah; Myers, Adam; Strauss, Michael; Zakamska, Nadia

    2009-04-01

    Recent research efforts to understand the evolution of galaxies and quasars are beginning to form a consistent picture. Galaxies and their supermassive black holes grow through mergers, but with decreasing characteristic mass scales over time. Much less, however, is known about the evolution of galaxies at high redshifts and the role played by energy injection from the onset of active black hole growth. Understanding these events requires investigating a statistically significant number of high-redshift quasars and crossing the L* boundary in luminosity. To construct an appropriate data set requires both relatively wide-areas (to find these rare objects) and moderate-depth imaging (to probe below L* in luminosity). Unfortunately, existing optical and MIR surveys fail to meet both of these requirements. Furthermore, both optical and MIR quasar selection are blindest at the most crucial redshifts. Here we propose to address these gaps with targeted IRAC observations of a few hundred high-redshift quasars from the Sloan Digital Sky Survey. Such a sample will enable the construction of a proper training set for the discovery of 2.5high-redshift quasars in other fields over a large range in luminosity. With this knowledge, we will crack open the high-z quasar discovery space within existing IRAC legacy surveys (SWIRE, XFLS, Bootes, COSMOS). With a large sample of high-redshift quasars spanning a large range in luminosity, we can turn the quasar luminosity function and quasar clustering analysis into tools for distinguishing between different evolutionary models and feedback prescriptions. In all, we will observe 330 SDSS quasars using 307 pointings/AORs, totaling 48.5 hours of IRAC time.

  2. X-ray spectral evolution of high redshift quasars

    NASA Technical Reports Server (NTRS)

    Bechtold, Jill; Elvis, Martin; Fiore, Fabrizio; Kuhn, Olga; Cutri, Roc M.; Mcdowell, Jonathan C.; Rieke, Marcia; Siemiginowska, Aneta; Wilkes, Belinda J.

    1994-01-01

    At z approx. equals 3, the x-ray spectra of radio-loud and radio-quiet quasars are different. High-redshift radio-quiet quasars either have large absorbing columns, N(sub H), and steeper power law spectral indices, alpha(sub epsilon), than low redshift quasars, or no absorption and similar alpha(sub epsilon)'s. In contrast, the radio-loud quasars at high redshift have substantial absorption and similar alpha(sub epsilon)'s to low redshift quasars. Implications for the interpretation of the evolution of the luminosity function of quasars are discussed. If the absorption arises outside the central engine for both radio-loud and radio-quiet quasars, then radio-quiet quasars differ from the radio-loud quasars in that their emitted power law spectrum has evolved with redshift. We argue that this favors models where quasars are numerous and short-lived, rather than rare and long-lived.

  3. Using Morphology to Identify Galaxy Mergers at High Redshift

    NASA Astrophysics Data System (ADS)

    Blancato, Kirsten; Kartaltepe, J. S.; CANDELS Collaboration

    2014-01-01

    We analyzed a set of 22,003 galaxies in three of the five CANDELS fields: COSMOS, UDS, and GOODS-S, in order to determine how well automated image statistics did with classifying galaxy morphology and mergers at high redshifts (z > 1). For each galaxy in our set, we have multi-wavelength data, photometric redshifts from SED fitting, visual classifications from the CANDELS structure and morphology group, and automated image statistics. The redshifts of our sample range from z = .01 to 4 with = 1.33. We constructed a conservative set of 1,914 galaxies that we believe to be mergers and interactions. Of this set of merging galaxies, 1,343 were at a redshift greater than z = 1. We also identified a conservative set of 535 spheroids and a set of 2,902 disks. Several different quantitative methods were then used to attempt an automated classification of these visually classified samples. Of the different image statistics, we found M20 and Gini to be the most successful at picking out high redshift mergers and morphological characteristics. Blancato was supported by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).

  4. Pushing the Limits: High Redshift Fermi-LAT Blazars

    NASA Astrophysics Data System (ADS)

    Ojha, Roopesh; Gasparrini, Dario; Lott, Benoit; Cutini, Sara; Fermi-LAT Collaboration

    2016-01-01

    High-redshift blazars detected by the Fermi Large Area Telescope (LAT) are of great astrophysical import as they are extreme objects whose energetics remain a mystery. Such blazars are intrinsically interesting since they inform us about the evolution of gamma-ray blazars and are, by definition, some of the more luminous blazars in the LAT sample. They are also an excellent tool to study the EBL and thus the gamma-ray horizon. We present the latest high redshift blazar detections in the LAT and discuss some of their implications.

  5. Detectability of Gravitational Waves from High-Redshift Binaries

    NASA Astrophysics Data System (ADS)

    Rosado, Pablo A.; Lasky, Paul D.; Thrane, Eric; Zhu, Xingjiang; Mandel, Ilya; Sesana, Alberto

    2016-03-01

    Recent nondetection of gravitational-wave backgrounds from pulsar timing arrays casts further uncertainty on the evolution of supermassive black hole binaries. We study the capabilities of current gravitational-wave observatories to detect individual binaries and demonstrate that, contrary to conventional wisdom, some are, in principle, detectable throughout the Universe. In particular, a binary with rest-frame mass ≳1010M⊙ can be detected by current timing arrays at arbitrarily high redshifts. The same claim will apply for less massive binaries with more sensitive future arrays. As a consequence, future searches for nanohertz gravitational waves could be expanded to target evolving high-redshift binaries. We calculate the maximum distance at which binaries can be observed with pulsar timing arrays and other detectors, properly accounting for redshift and using realistic binary waveforms.

  6. Detectability of Gravitational Waves from High-Redshift Binaries.

    PubMed

    Rosado, Pablo A; Lasky, Paul D; Thrane, Eric; Zhu, Xingjiang; Mandel, Ilya; Sesana, Alberto

    2016-03-11

    Recent nondetection of gravitational-wave backgrounds from pulsar timing arrays casts further uncertainty on the evolution of supermassive black hole binaries. We study the capabilities of current gravitational-wave observatories to detect individual binaries and demonstrate that, contrary to conventional wisdom, some are, in principle, detectable throughout the Universe. In particular, a binary with rest-frame mass ≳10^{10}M_{⊙} can be detected by current timing arrays at arbitrarily high redshifts. The same claim will apply for less massive binaries with more sensitive future arrays. As a consequence, future searches for nanohertz gravitational waves could be expanded to target evolving high-redshift binaries. We calculate the maximum distance at which binaries can be observed with pulsar timing arrays and other detectors, properly accounting for redshift and using realistic binary waveforms. PMID:27015470

  7. Spectroscopy of Moderately High Redshift RCS-1 Clusters

    NASA Astrophysics Data System (ADS)

    Gilbank, David G.; Yee, H. K. C.; Ellingson, E.; Gladders, M. D.; Barrientos, L. F.; Blindert, K.

    2007-07-01

    We present spectroscopic observations of 11 moderately high-redshift (z~0.7-1.0) clusters from the first Red-Sequence Cluster Survey (RCS-1). We confirm that at least 10 of the 11 systems represent genuine overdensities in redshift space and show that for the remaining system, the spectroscopy was not deep enough to confirm a cluster. This is in good agreement with the estimated false positive rate of <5% at these redshifts from simulations. We find excellent agreement between the red-sequence-estimated redshift and the spectroscopic redshift, with a scatter of 10% at z>0.7. At the high-redshift end (z>~0.9) of the sample, we find that two of the systems selected are projections of pairs of comparably rich systems, with red sequences too close to discriminate in (R-z') color. In one of these systems, the two components are close enough to be physically associated. For a subsample of clusters with sufficient spectroscopic members, we examine the correlation between BgcR (optical richness) and the dynamical mass inferred from the velocity dispersion. We find these measurements to be compatible, within the relatively large uncertainties, with the correlation established at lower redshift for the X-ray-selected Canadian Network for Observational Cosmology clusters and also for a lower redshift sample of RCS-1 clusters. Confirmation of this and calibration of the scatter in the relation will require larger samples of clusters at these and higher redshifts. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. This work is based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT

  8. A Catalog of Candidate High-redshift Blazars for GLAST

    SciTech Connect

    Arias, Tersi M.; /SLAC /San Francisco State U.

    2006-09-27

    High-redshift blazars are promising candidates for detection by the Gamma-ray Large Area Space Telescope (GLAST). GLAST, expected to be launched in the Fall of 2007, is a high-energy gamma-ray observatory designed for making observations of celestial gamma-ray sources in the energy band extending from 10 MeV to more than 200 GeV. It is estimated that GLAST will find several thousand blazars. The motivations for measuring the gamma-ray emission from distant blazars include the study of the high-energy emission processes occurring in these sources and an indirect measurement of the extragalactic background light. In anticipation of the launch of GLAST we have compiled a catalog of candidate high-redshift blazars. The criteria for sources chosen for the catalog were: high radio emission, high redshift, and a flat radio spectrum. A preliminary list of 307 radio sources brighter than 70mJy with a redshift z {ge} 2.5 was acquired using data from the NASA Extragalactic Database. Flux measurements of each source were obtained at two or more radio frequencies from surveys and catalogs to calculate their radio spectral indices {alpha}. The sources with a flat-radio spectrum ({alpha} {le} 0.5) were selected for the catalog, and the final catalog includes about 200 sources.

  9. Radio-loud high-redshift protogalaxy canidates in Bootes

    SciTech Connect

    Croft, S; van Breugel, W; Brown, M J; de Vries, W; Dey, A; Eisenhardt, P; Jannuzi, B; Rottgering, H; Stanford, S A; Stern, D; Willner, S P

    2007-07-20

    We used the Near Infrared Camera (NIRC) on Keck I to obtain K{sub s}-band images of four candidate high-redshift radio galaxies selected using optical and radio data in the NOAO Deep Wide-Field Survey in Bootes. Our targets have 1.4 GHz radio flux densities greater than 1 mJy, but are undetected in the optical. Spectral energy distribution fitting suggests that three of these objects are at z > 3, with radio luminosities near the FR-I/FR-II break. The other has photometric redshift z{sub phot} = 1.2, but may in fact be at higher redshift. Two of the four objects exhibit diffuse morphologies in K{sub s}-band, suggesting that they are still in the process of forming.

  10. Large scale magnetic fields in galaxies at high redshifts

    NASA Astrophysics Data System (ADS)

    Bernet, M. L.; Miniati, F.; Lilly, S. J.; Kronberg, P. P.; Dessauges-Zavadsky, M.

    2012-09-01

    In a recent study we have used a large sample of extragalactic radio sources to investigate the redshift evolution of the Rotation Measure (RM) of polarized quasars up to z ≈ 3.0. We found that the dispersion in the RM distribution of quasars increases at higher redshifts and hypothesized that MgII intervening systems were responsible for the observed trend. To test this hypothesis, we have recently obtained high-resolution UVES/VLT spectra for 76 quasars in our sample and in the redshift range 0.6 < z < 2.0. We found a clear correlation between the presence of strong MgII systems and large RMs. This implies that normal galaxies at z ≈ 1 already had large-scale magnetic fields comparable to those seen today.

  11. High-redshift Gamma-Ray Burst Studies with GLAST

    SciTech Connect

    Bissaldi, Elisabetta; Longo, Francesco; Barbiellini, Guido; Calura, Francesco; Matteucci, Francesca

    2007-05-01

    We compare predicted Type Ib/c supernova (SN) rates with the observed long-duration gamma-ray burst (GRB) rates both locally and as a function of redshift. To do that, we assume different star formation histories in galaxies of different morphological type: ellipticals, spirals and irregulars. In particular, the predicted Type Ib/c SN rate (SNRIb/c) is always higher than the GRB rate, as expected, suggesting that only a small fraction (0.1-1%) of them become GRBs. We predict a ratio between the cosmic GRB rate and the cosmic SNRIb/c in the range 10-2 - 10-3, in agreement with previous estimates. Finally, due to the high star formation in spheroids at high redshift, we predict more GRBs at high redshift than previous estimates, a prediction which awaits to be proven by future observations by GLAST. Based on our studies and on the current LAT performance, an estimate of the detection possibility of this high-redshift burst population is finally presented.

  12. 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.

  13. Identifying high-redshift gamma-ray bursts with RATIR

    SciTech Connect

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

    2014-07-01

    We present a template-fitting algorithm for determining photometric redshifts, z {sub 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 {sub 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 {sub phot} in the ranges of 4 < z {sub phot} ≲ 8 and 9 < z {sub phot} < 10 and can robustly determine when z {sub 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 {sub phot} < 4 when z {sub sim} > 4, thereby minimizing false negatives and allowing us to rapidly identify all potential high-redshift events.

  14. Bimodal star formation - Constraints from galaxy colors at high redshift

    NASA Technical Reports Server (NTRS)

    Wyse, Rosemary F. G.; Silk, Joseph

    1987-01-01

    The possibility that at early epochs the light from elliptical galaxies is dominated by stars with an initial mass function (IMF) which is deficient in low-mass stars, relative to the solar neighborhood is investigated. V-R colors for the optical counterparts of 3CR radio sources offer the most severe constraints on the models. Reasonable fits are obtained to both the blue, high-redshift colors and the redder, low-redshift colors with a model galaxy which forms with initially equal star formation rates in each of two IMF modes: one lacking low-mass stars, and one with stars of all masses. The net effect is that the time-integrated IMF has twice as many high-mass stars as the solar neighborhood IMF, relative to low mass stars. A conventional solar neighborhood IMF does not simultaneously account for both the range in colors at high redshift and the redness of nearby ellipticals, with any single star formation epoch. Models with a standard IMF require half the stellar population to be formed in a burst at low redshift z of about 1.

  15. CMB quenching of high-redshift radio-loud AGNs

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Haardt, F.; Ciardi, B.; Sbarrato, T.; Gallo, E.; Tavecchio, F.; Celotti, A.

    2015-10-01

    The very existence of more than a dozen of high-redshift (z ≳ 4) blazars indicates that a much larger population of misaligned powerful jetted active galactic nucleus (AGN) was already in place when the Universe was ≲1.5 Gyr old. Such parent population proved to be very elusive, and escaped direct detection in radio surveys so far. High-redshift blazars themselves seem to be failing in producing extended radio lobes, raising questions about the connection between such class and the vaster population of radio galaxies. We show that the interaction of the jet electrons with the intense cosmic microwave background (CMB) radiation explains the lack of extended radio emission in high-redshift blazars and in their parent population, helping to explain the apparently missing misaligned counterparts of high-redshift blazars. On the other hand, the emission from the more compact and more magnetized hotspots are less affected by the enhanced CMB energy density. By modelling the spectral energy distribution of blazar lobes and hotspots, we find that most of them should be detectable by low-frequency deep radio observations, e.g. by LOw-Frequency ARray for radio astronomy and by relatively deep X-ray observations with good angular resolution, e.g. by the Chandra satellite. At high redshifts, the emission of a misaligned relativistic jet, being debeamed, is missed by current large sky area surveys. The isotropic flux produced in the hotspots can be below ˜1 mJy and the isotropic lobe radio emission is quenched by the CMB cooling. Consequently, even sources with very powerful jets can go undetected in current radio surveys, and misclassified as radio-quiet AGNs.

  16. 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}ȯ . 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.

  17. Local Analogs for High-redshift Galaxies: Resembling the Physical Conditions of the Interstellar Medium in High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    We present a sample of local analogs for high-redshift galaxies selected in the Sloan Digital Sky Survey (SDSS). The physical conditions of the interstellar medium (ISM) in these local analogs resemble those in high-redshift galaxies. These galaxies are selected based on their positions in the [O iii]/Hβ versus [N ii]/Hα nebular emission-line diagnostic diagram. We show that these local analogs share similar physical properties with high-redshift galaxies, including high specific star formation rates (sSFRs), flat UV continuums, and compact galaxy sizes. In particular, the ionization parameters and electron densities in these analogs are comparable to those in z ≃ 2–3 galaxies, but higher than those in normal SDSS galaxies by ≃0.6 dex and ≃0.9 dex, respectively. The mass–metallicity relation (MZR) in these local analogs shows ‑0.2 dex offset from that in SDSS star-forming galaxies at the low-mass end, which is consistent with the MZR of the z˜ 2{--}3 galaxies. We compare the local analogs in this study with those in other studies, including Lyman break analogs (LBA) and green pea (GP) galaxies. The analogs in this study share a similar star formation surface density with LBAs, but the ionization parameters and electron density in our analogs are higher than those in LBAs by factors of 1.5 and 3, respectively. The analogs in this study have comparable ionization parameters and electron densities to the GP galaxies, but our method can select galaxies in a wider redshift range. We find the high sSFR and SFR surface density can increase the electron density and ionization parameters, but still cannot fully explain the difference in ISM condition between nearby galaxies and the local analogs/high-redshift galaxies.

  18. Local Analogs for High-redshift Galaxies: Resembling the Physical Conditions of the Interstellar Medium in High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    We present a sample of local analogs for high-redshift galaxies selected in the Sloan Digital Sky Survey (SDSS). The physical conditions of the interstellar medium (ISM) in these local analogs resemble those in high-redshift galaxies. These galaxies are selected based on their positions in the [O iii]/Hβ versus [N ii]/Hα nebular emission-line diagnostic diagram. We show that these local analogs share similar physical properties with high-redshift galaxies, including high specific star formation rates (sSFRs), flat UV continuums, and compact galaxy sizes. In particular, the ionization parameters and electron densities in these analogs are comparable to those in z ≃ 2–3 galaxies, but higher than those in normal SDSS galaxies by ≃0.6 dex and ≃0.9 dex, respectively. The mass–metallicity relation (MZR) in these local analogs shows ‑0.2 dex offset from that in SDSS star-forming galaxies at the low-mass end, which is consistent with the MZR of the z∼ 2{--}3 galaxies. We compare the local analogs in this study with those in other studies, including Lyman break analogs (LBA) and green pea (GP) galaxies. The analogs in this study share a similar star formation surface density with LBAs, but the ionization parameters and electron density in our analogs are higher than those in LBAs by factors of 1.5 and 3, respectively. The analogs in this study have comparable ionization parameters and electron densities to the GP galaxies, but our method can select galaxies in a wider redshift range. We find the high sSFR and SFR surface density can increase the electron density and ionization parameters, but still cannot fully explain the difference in ISM condition between nearby galaxies and the local analogs/high-redshift galaxies.

  19. Evolution of high-redshift Lyman-limit absorption systems

    SciTech Connect

    Lanzetta, K.M. )

    1991-07-01

    Results are presented of a new spectroscopic survey of high-redshift Lyman-limit absorption systems. Based on this data set, the rate of incidence of the Lyman-limit systems with z greater than about 2.5 is found to evolve strongly with redshift in the sense that the product of the number density per unit comoving volume and the absorption cross section increases with increasing redshift. If the observed evolution indicates intrinsic evolution of the absorbers, this result suggests that the evolution detected previously for the C IV-selected absorbers over a similar redshift range is not naturally interpreted as evolution of the ionization level of the absorbers rather than as a chemical enrichment effect. The data are also used to investigate the H I column density distribution and to examine the multiple-component structure of the absorbing complexes. The H I column density distribution is found to be well fitted by a power-law form. 35 refs.

  20. Close companions to two high-redshift quasars

    SciTech Connect

    McGreer, Ian D.; Fan, Xiaohui; Bian, Fuyan; Strauss, Michael A.; Haiman, Zoltàn; Richards, Gordon T.; Jiang, Linhua; Schneider, Donald P.

    2014-10-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyα emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i {sub AB} = 23.6) located 2'' (12 kpc projected) from the quasar with strong Lyα emission (EW{sub 0} ≈ 100 Å) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z = 6.25), is included in our recent HST SNAP survey of z ∼ 6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ∼4.5 mag fainter than the quasar (Y {sub AB} = 25) at a separation of 0.''9. The red i {sub 775} – Y {sub 105} color of the galaxy and its proximity to the quasar (5 kpc projected if at the quasar redshift) strongly favor an association with the quasar. Although it is much fainter than the quasar, it is remarkably bright when compared to field galaxies at this redshift, while showing no evidence for lensing. Both systems may represent late-stage mergers of two massive galaxies, with the observed light for one dominated by powerful ongoing star formation and for the other by rapid black hole growth. Observations of close companions are rare; if major mergers are primarily responsible for high-redshift quasar fueling then the phase when progenitor galaxies can be observed as bright companions is relatively short.

  1. Magnetic fields in galaxies at high redshifts

    NASA Astrophysics Data System (ADS)

    Bernet, Martin Leo; Gaensler, Bryan; Lilly, Simon; O'Sullivan, Shane; Miniati, Francesco

    2013-04-01

    We have recently demonstrated an association between high Faraday Rotation of radio quasars and the presence of intervening strong MgII absorption and determined that the magnetized plasma in the associated galaxies extends up to 60 kpc. These findings are based on Rotation Measure (RM) observations typically performed at 5 GHz, but they can not be reproduced using RMs obtained at lower frequencies, e.g. using the Taylor et al. (2009) RM catalogue at 1.4 GHz. This apparent discrepancy can be explained by a model which takes into account the depolarization of the sources due to inhomogeneous Faraday Rotation screens and their partial coverage of the sources. We propose here to observe 27 sources of our sample which are accessible by the ATCA to test this hypothesis. Our goal is to observe the selected sources over the broad frequency range 1.1 -10.8 GHz to obtain depolarization curves and to perform Faraday Rotation Measure Synthesis. With this sample we will be able to determine the homogeneity of the Faraday screens in the intervening galaxies and to further strengthen the original result. Finally the outcome of this experiment has important implications for the design of future RM surveys.

  2. Formation of elongated galaxies with low masses at high redshift

    NASA Astrophysics Data System (ADS)

    Ceverino, Daniel; Primack, Joel; Dekel, Avishai

    2015-10-01

    We report the identification of elongated (triaxial or prolate) galaxies in cosmological simulations at z ≃ 2. These are preferentially low-mass galaxies (M* ≤ 109.5 M⊙), residing in dark matter (DM) haloes with strongly elongated inner parts, a common feature of high-redshift DM haloes in the Λ cold dark matter cosmology. Feedback slows formation of stars at the centres of these haloes, so that a dominant and prolate DM distribution gives rise to galaxies elongated along the DM major axis. As galaxies grow in stellar mass, stars dominate the total mass within the galaxy half-mass radius, making stars and DM rounder and more oblate. A large population of elongated galaxies produces a very asymmetric distribution of projected axis ratios, as observed in high-z galaxy surveys. This indicates that the majority of the galaxies at high redshifts are not discs or spheroids but rather galaxies with elongated morphologies.

  3. X-RAY ABSORPTION OF HIGH-REDSHIFT QUASARS

    SciTech Connect

    Eitan, Assaf; Behar, Ehud E-mail: behar@physics.technion.ac.il

    2013-09-01

    The soft X-ray photoelectric absorption of high-z quasars has been known for two decades, but has no unambiguous astrophysical context. We construct the largest sample to date of 58 high-redshift quasars (z > 0.45) selected from the XMM-Newton archive based on a high photon count criterion (>1800). We measure the optical depth {tau} at 0.5 keV and find that 43% of the quasars show significant absorption. We aim to find which physical parameters of the quasars, e.g., redshift, radio luminosity, radio loudness, or X-ray luminosity, drive their observed absorption. We compare the absorption behavior with redshift with the pattern expected if the diffuse intergalactic medium (IGM) is responsible for the observed absorption. We also compare the absorption with a comparison sample of gamma-ray burst (GRB) X-ray afterglows. Although the z > 2 quasar opacity is consistent with diffuse IGM absorption, many intermediate-z (0.45 < z < 2) quasars are not sufficiently absorbed for this scenario, and are appreciably less absorbed than GRBs. Only 10/37 quasars at z < 2 are absorbed, and only 5/30 radio-quiet quasars are absorbed. We find a weak correlation between {tau} and z, and an even weaker correlation between {tau} and radio luminosity. These findings lead to the conclusion that although a diffuse IGM origin for the quasar absorption is unlikely, the optical depth does seem to increase with redshift, roughly as (1 + z){sup 2.2{+-}0.6}, tending to {tau} Almost-Equal-To 0.4 at high redshifts, similar to the high-z GRBs. This result can be explained by an ionized and clumpy IGM at z < 2, and a cold, diffuse IGM at higher redshift. If, conversely, the absorption occurs at the quasar, and owing to the steep L{sub x} {proportional_to}(1 + z){sup 7.1{+-}0.5} correlation in the present sample, the host column density scales as N{sub H}{proportional_to}L{sub x}{sup 0.7{+-}0.1}.

  4. Radio continuum polarimetric imaging of high redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Carilli, C. L.; Owen, F. N.; Harris, D. E.

    1994-01-01

    Multifrequency images of total and polarized radio continuum emission from the two high redshift radio galaxies 0902+343 (z = 3.40) and 0647+415 (4C 41.17, z = 3.80) are presented. These images represent the most sensitive polarimetric study of high redshift ratio galaxies to date. The emission from both galaxies is substantially polarized, up to 30% in some regions, and both sources sit behind deep 'Faraday screens,' producing large rotation measures, over 10(exp 3) rad/sq. m in magnitude, and large rotation measure gradients across the sources. Such large rotation measures provide further evidence that high redshift radio galaxies are situated in very dense environments. Drawing the analogy to a class of low redshift powerful radio galaxies with similarly large rotation measures, we suggest that 0902+343 and 0647+415 are situated at the centers of dense, x-ray 'colling flow' clusters, and that the cluster gas is substantially magnetized. The remarkable similarity between the optical and radio morphologies of 0647+415 on scales as small as 0.1 sec is presented. We consider, and reject, both synchrotron and inverse Compton radiation as possible sources of the optical emission. We also consider both scattering of light out of a 'cone' of radiation from an obscured nucleus, and jet-induced star formation, and find that both models encounter difficulties in explaining this remarkably close radio-optical alignment. High resolution spectral index images reveal compact, flat spectrum components in both sources. We suggest that these components are the active nuclei of the galaxies. Lastly, high resolution images of 0902+343 show that the southernmost component forms a 'ring' of 0.2 sec radius. We discuss the possibility that this ring is the result of gravitational lensing, along the lines proposed by Kochanek & Lawrence (1990).

  5. Testing the CMB Quenching for High-Redshift Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Wu, Jianfeng; Gallo, Elena

    2016-04-01

    The identification of a dozen of high-redshift (z > 4) blazars implies that a much larger population of powerful, but mis-aligned jetted AGNs already exists in the early Universe. However, this parent population remains elusive, although they are expected to be within the sensitivity threshold of modern wide-field radio surveys. One appealing mechanism is that the CMB photons upscatter the diffuse synchrotron radio emission in the lobes to the X-ray band. In this scenario, the lobes will turn into luminous X-ray sources. We analyzed the extended X-ray emission around several radio galaxies at z~4 and constructed their broad-band spectral energy distributions (SEDs). Modeling their SEDs will test this CMB quenching scenario for high-redshift radio galaxies.

  6. 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.

  7. Theoretical considerations for star formation at low and high redshifts

    NASA Astrophysics Data System (ADS)

    Elmegreen, Bruce G.

    2015-08-01

    Star formation processes in strongly self-gravitating cloud cores should be similar at all redshifts, forming single or multiple stars with a range of masses determined by local magneto-hydrodynamics. The formation processes for these cores, however, as well as their structures, temperatures, Mach numbers, etc., and the boundedness and mass distribution functions of the resulting stars, should depend on environment, as should the characteristic mass, density, and column density at which cloud self-gravity dominates other forces. Because the environments for high and low redshift star formation differ significantly, we expect the resulting gas to stellar conversion details to differ also. At high redshift, the universe is denser and more gas-rich, so the active parts of galaxies are denser and more gas rich too, leading to shorter gas consumption timescales, higher cloud pressures, and denser, more massive, bound stellar clusters at the high mass end. With shorter consumption times corresponding to higher relative cosmic accretion rates, and with the resulting higher star formation rates and their higher feedback powers, the ISM has greater turbulent speeds relative to the rotation speeds, thicker gas disks, and larger cloud and star complex sizes at the characteristic Jeans length. The result is a more chaotic appearance at high redshift, bridging the morphology gap between today’s quiescent spirals and today’s major-mergers, with neither spiral nor major-merger processes actually in play at that time. The result is also a thick disk at early times, and after in-plane accretion from relatively large clump torques, a classical bulge. Today’s disks are much thinner and torque-driven accretion is much slower outside of the inner barred regions. This talk will review the basic theoretical processes involved with star formation in order to illustrate its evolution over time and environment.

  8. Implications of multiple high-redshift galaxy clusters

    SciTech Connect

    Hoyle, Ben; Jimenez, Raul; Verde, Licia

    2011-05-15

    To date, 14 high-redshift (z>1.0) galaxy clusters with mass measurements have been observed, spectroscopically confirmed, and are reported in the literature. These objects should be exceedingly rare in the standard {Lambda} cold dark matter ({Lambda}CDM) model. We conservatively approximate the selection functions of these clusters' parent surveys and quantify the tension between the abundances of massive clusters as predicted by the standard {Lambda}CDM model and the observed ones. We alleviate the tension, considering non-Gaussian primordial perturbations of the local type, characterized by the parameter f{sub NL}, and derive constraints on f{sub NL} arising from the mere existence of these clusters. At the 95% confidence level, f{sub NL}>467, with cosmological parameters fixed to their most likely WMAP5 values, or f{sub NL} > or approx. 123 (at 95% confidence) if we marginalize over prior WMAP5 parameters. In combination with f{sub NL} constraints from cosmic microwave background and halo bias, this determination implies a scale dependence of f{sub NL} at {approx_equal}3{sigma}. Given the assumptions made in the analysis, we expect any future improvements to the modeling of the non-Gaussian mass function, survey volumes, or selection functions to increase the significance of f{sub NL}>0 found here. In order to reconcile these massive, high-z clusters with f{sub NL}=0, their masses would need to be systematically lowered by 1.5{sigma}, or the {sigma}{sub 8} parameter should be {approx}3{sigma} higher than cosmic microwave background (and large-scale structure) constraints. The existence of these objects is a puzzle: it either represents a challenge to the {Lambda}CDM paradigm or it is an indication that the mass estimates of clusters are dramatically more uncertain than we think.

  9. A Global Probe of Cosmic Magnetic Fields to High Redshifts

    NASA Astrophysics Data System (ADS)

    Kronberg, P. P.; Bernet, M. L.; Miniati, F.; Lilly, S. J.; Short, M. B.; Higdon, D. M.

    2008-03-01

    Faraday rotation (rotation measure [RM]) probes of magnetic fields in the universe are sensitive to cosmological and evolutionary effects as z increases beyond ~1 because of the scalings of electron density and magnetic fields, and the growth in the number of expected intersections with galaxy-scale intervenors, dN/dz. In this new global analysis of an unprecedented large sample of RMs of high-latitude quasars extending out to z ~ 3.7, we find that the distribution of RM broadens with redshift in the 20-80 rad m-2 range, despite the (1 + z)-2 wavelength dilution expected in the observed Faraday rotation. Our results indicate that the universe becomes increasingly "Faraday-opaque" to sources beyond z ~ 2; that is, as z increases, progressively fewer sources are found with a "small" RM in the observer's frame. This is in contrast to sources at zlesssim 1. They suggest that the environments of galaxies were significantly magnetized at high redshifts, with magnetic field strengths that were at least as strong within a few Gyr of the big bang as at the current epoch. We separately investigate a simple unevolving toy model in which the RM is produced by Mg II absorber systems, and find that it can approximately reproduce the observed trend with redshift. An additional possibility is that the intrinsic RM associated with the radio sources was much higher in the past, and we show that this is not a trivial consequence of the higher radio luminosities of the high-redshift sources.

  10. 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.

  11. The growth efficiency of high-redshift black holes

    NASA Astrophysics Data System (ADS)

    Pacucci, Fabio; Volonteri, Marta; Ferrara, Andrea

    2015-09-01

    The observational evidence that Super-Massive Black Holes (M• ˜ 109-10 M⊙) are already in place less than 1 Gyr after the big bang poses stringent time constraints on the growth efficiency of their seeds. Among proposed possibilities, the formation of massive (˜103-6 M⊙) seeds and/or the occurrence of super-Eddington (dot{M}>dot{M}_{Edd}) accretion episodes may contribute to the solution of this problem. In this work, using a set of astrophysically motivated initial conditions, we analytically and numerically investigate the accretion flow on to high-redshift (z ˜ 10) black holes to understand the physical requirements favouring rapid and efficient growth. Our model identifies a `feeding-dominated' accretion regime and a `feedback-limited' one, the latter being characterized by intermittent (duty cycles D ≲ 0.5) and inefficient growth, with recurring outflow episodes. We find that low-mass seeds (≲103-4 M⊙) evolve in the feedback-limited regime, while more massive seeds (≳105-6 M⊙) grow very rapidly as they are found in the feeding-dominated regime. In addition to the standard accretion model with a fixed matter-energy conversion factor (ɛ = 0.1), we have also explored slim disc models, appropriate for super-Eddington accretion, where radiation is trapped in the disc and the radiative efficiency is reduced (ɛ ≲ 0.04), which may ensure a continuous growth with dot{M} ≫ dot{M}_{Edd} (up to {˜ } 300 dot{M}_{Edd} in our simulations). Under these conditions, outflows play a negligible role and a black hole can accrete 80-100 per cent of the gas mass of the host halo (˜107 M⊙) in ˜10 Myr, while in feedback-limited systems we predict that black holes can accrete only up to ˜15 per cent of the available mass.

  12. 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

  13. Accessing the population of high-redshift Gamma Ray Bursts

    NASA Astrophysics Data System (ADS)

    Ghirlanda, G.; Salvaterra, R.; Ghisellini, G.; Mereghetti, S.; Tagliaferri, G.; Campana, S.; Osborne, J. P.; O'Brien, P.; Tanvir, N.; Willingale, D.; Amati, L.; Basa, S.; Bernardini, M. G.; Burlon, D.; Covino, S.; D'Avanzo, P.; Frontera, F.; Götz, D.; Melandri, A.; Nava, L.; Piro, L.; Vergani, S. D.

    2015-04-01

    Gamma Ray Bursts (GRBs) are a powerful probe of the high-redshift Universe. We present a tool to estimate the detection rate of high-z GRBs by a generic detector with defined energy band and sensitivity. We base this on a population model that reproduces the observed properties of GRBs detected by Swift, Fermi and CGRO in the hard X-ray and γ-ray bands. We provide the expected cumulative distributions of the flux and fluence of simulated GRBs in different energy bands. We show that scintillator detectors, operating at relatively high energies (e.g. tens of keV to the MeV), can detect only the most luminous GRBs at high redshifts due to the link between the peak spectral energy and the luminosity (Epeak-Liso) of GRBs. We show that the best strategy for catching the largest number of high-z bursts is to go softer (e.g. in the soft X-ray band) but with a very high sensitivity. For instance, an imaging soft X-ray detector operating in the 0.2-5 keV energy band reaching a sensitivity, corresponding to a fluence, of ˜10-8 erg cm-2 is expected to detect ≈40 GRBs yr-1 sr-1 at z ≥ 5 (≈3 GRBs yr-1 sr-1 at z ≥ 10). Once high-z GRBs are detected the principal issue is to secure their redshift. To this aim we estimate their NIR afterglow flux at relatively early times and evaluate the effectiveness of following them up and construct usable samples of events with any forthcoming GRB mission dedicated to explore the high-z Universe.

  14. Metal-rich absorbers at high redshifts: abundance patterns

    NASA Astrophysics Data System (ADS)

    Levshakov, S. A.; Agafonova, I. I.; Molaro, P.; Reimers, D.; Hou, J. L.

    2009-11-01

    Aims: To study chemical composition of metal-rich absorbers at high redshifts in order to understand their nature and to determine sources of their metal enrichment. Methods: From six spectra of high-z QSOs, we select eleven metal-rich, Z ⪆ Z_⊙, and optically-thin to the ionizing radiation, N(H i) < 1017 cm-2, absorption systems ranging between z = 1.5 and z = 2.9 and revealing lines of different ions in subsequent ionization stages. Computations are performed using the Monte Carlo inversion (MCI) procedure complemented with the adjustment of the spectral shape of the ionizing radiation. This procedure along with selection criteria for the absorption systems guarantee the accuracy of the ionization corrections and of the derived element abundances (C, N, O, Mg, Al, Si, Fe). Results: The majority of the systems (10 from 11) show abundance patterns which relate them to outflows from low and intermediate mass stars. One absorber is enriched prevalently by SNe II, however, a low percentage of such systems in our sample is conditioned by the selection criteria. All systems have sub-kpc linear sizes along the line-of-sight with many less than 20 pc. In several systems, silicon is deficient, presumably due to the depletion onto dust grains in the envelopes of dust-forming stars and the subsequent gas-dust separation. At any value of [C/H], nitrogen can be either deficient, [N/C] < 0, or enhanced, [N/C] > 0, which supposes that the nitrogen enrichment occurs irregularly. In some cases, the lines of Mg ii λλ2796, 2803 appear to be shifted, probably as a result of an enhanced content of heavy isotopes 25Mg and 26Mg in the absorbing gas relative to the solar isotopic composition. Seven absorbers are characterized by low mean ionization parameter U, logU < - 2.3, among them only one system has a redshift z > 2 (z_abs = 2.5745) whereas all others are found at z 1.8. This statistics is not affected by any selection criteria and reflects the real rise in number of such

  15. High-redshift galaxy populations and their descendants

    NASA Astrophysics Data System (ADS)

    Guo, Qi; White, Simon D. M.

    2009-06-01

    We study predictions in the concordance Λ cold dark matter cosmology for the abundance and clustering of high-redshift galaxies and for the properties of their descendants. We focus on three high-redshift populations: Lyman break galaxies (LBGs) at z ~ 3, optically selected star-forming galaxies at z ~ 2 (BXs) and distant red galaxies (DRGs) at z ~ 2. We select galaxies from mock catalogues based on the Millennium Simulation using the observational colour and apparent magnitude criteria. With plausible dust assumptions, our galaxy formation model can simultaneously reproduce the abundances, redshift distributions and clustering of all three observed populations. The star formation rates (SFRs) of model LBGs and BXs are lower than those quoted for the real samples, reflecting differing initial mass functions and scatter in model dust properties. About 85 per cent of model galaxies selected as DRGs are star forming, with SFRs in the range 1 to ~100Msolaryr-1. Model LBGs, BXs and DRGs together account for less than half of all star formation over the range 1.5 < z < 3.2; many massive, star-forming galaxies are predicted to be too heavily obscured to appear in these populations. Model BXs have metallicities which agree roughly with observation, but model LBGs are only slightly more metal poor, in disagreement with recent observational results. The model galaxies are predominantly disc dominated. Stellar masses for LBGs and BXs are ~109.9Msolar, and for DRGs are ~1010.7Msolar. Only about 30 per cent of model galaxies with M* > 1011Msolar are classified as LBGs or BXs at the relevant redshifts, while 65 per cent are classified as DRGs. Almost all model LBGs and BXs are the central galaxies of their dark haloes, but fewer than half of the haloes of any given mass have an LBG or BX central galaxy. Half of all LBG descendants at z = 2 would be identified as BXs, but very few as DRGs. Clustering increases with decreasing redshift for descendants of all three populations

  16. The rest-frame submillimeter spectrum of high-redshift, dusty, star-forming galaxies

    SciTech Connect

    Spilker, J. S.; Marrone, D. P.; Aguirre, J. E.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bothwell, M. S.; Brodwin, M.; Carlstrom, J. E.; Crawford, T. M.; Chapman, S. C.; De Breuck, C.; Gullberg, B.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Hezaveh, Y.; Holzapfel, W. L.; and others

    2014-04-20

    We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250 to 770 GHz. This spectrum was constructed by stacking Atacama Large Millimeter/submillimeter Array (ALMA) 3 mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z = 2.0-5.7. In addition to multiple bright spectral features of {sup 12}CO, [C I], and H{sub 2}O, we also detect several faint transitions of {sup 13}CO, HCN, HNC, HCO{sup +}, and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the {sup 13}CO brightness in these objects is comparable to that of the only other z > 2 star-forming galaxy in which {sup 13}CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO{sup +}, and CN is consistent with a warm, dense medium with T {sub kin} ∼ 55 K and n{sub H{sub 2}}≳10{sup 5.5} cm{sup –3}. High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlikely to be significant for the bulk of these systems. We quantify the average emission from several species with no individually detected transitions, and find emission from the hydride CH and the linear molecule CCH for the first time at high redshift, indicating that these molecules may be powerful probes of interstellar chemistry in high-redshift systems. These observations represent the first constraints on many molecular species with rest-frame transitions from 0.4 to 1.2 mm in star-forming systems at high redshift, and will be invaluable in making effective use of ALMA in full science operations.

  17. 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

  18. Cosmic Lighthouses : Unveiling the nature of high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Dayal, Pratika

    2011-01-01

    We are in the golden age for the search for high-redshift galaxies, made possible by a combination of new instruments and innovative search techniques. One of the major aims of such searches is to constrain the epoch of reionization (EoR), which marks the second major change in the ionization state of the Universe. Understanding the EoR is difficult since whilst it is galaxy evolution which drives reionization, reionization itself influences galaxy evolution through feedback effects. Unraveling the interplay of reionization and galaxy evolution is further complicated by of a lack of understanding of the metal enrichment and dust distribution in high redshift galaxies. To this end, a class of galaxies called Lyman Alpha Emitters (LAEs) have been gaining enormous popularity as probes of all these three processes. In this thesis, we couple state of the art cosmological SPH simulations (GADGET-2) with a physically motivated, self-consistent model for LAEs, so as to be able to understand the importance of the intergalactic medium (IGM) ionization state, dust and peculiar velocities in shaping their observed properties. By doing so, the aim is to gain insight on the nature of LAEs, put precious constraints on their elusive physical properties and make predictions for future instruments such as the Atacama Large Millimeter Array (ALMA). Using our LAE model in conjunction with a code that builds the MW merger tree (GAMETE), we build a bridge between the high-redshift and the local Universe. We also use SPH simulations (GADGET-2) to study the nature of the earliest galaxies that have been detected as of yet, place constraints on their contribution to reionization, and predict their detectability using the next generation of instruments, such as the James Web Space Telescope (JWST).

  19. POPULATION III STARS AND REMNANTS IN HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Xu Hao; Norman, Michael L.; Wise, John H. E-mail: mlnorman@ucsd.edu

    2013-08-20

    Recent simulations of Population III star formation have suggested that some fraction form in binary systems, in addition to having a characteristic mass of tens of solar masses. The deaths of metal-free stars result in the initial chemical enrichment of the universe and the production of the first stellar-mass black holes. Here we present a cosmological adaptive mesh refinement simulation of an overdense region that forms a few 10{sup 9} M{sub Sun} dark matter halos and over 13,000 Population III stars by redshift 15. We find that most halos do not form Population III stars until they reach M{sub vir} {approx} 10{sup 7} M{sub Sun} because this biased region is quickly enriched from both Population III and galaxies, which also produce high levels of ultraviolet radiation that suppress H{sub 2} formation. Nevertheless, Population III stars continue to form, albeit in more massive halos, at a rate of {approx}10{sup -4} M{sub Sun} yr{sup -1} Mpc{sup -3} at redshift 15. The most massive starless halo has a mass of 7 Multiplication-Sign 10{sup 7} M{sub Sun }, which could host massive black hole formation through the direct gaseous collapse scenario. We show that the multiplicity of the Population III remnants grows with halo mass above 10{sup 8} M{sub Sun }, culminating in 50 remnants located in 10{sup 9} M{sub Sun} halos on average. This has implications that high-mass X-ray binaries and intermediate-mass black holes that originate from metal-free stars may be abundant in high-redshift galaxies.

  20. The High Redshift Universe Seen Through the Eyes of ALMA

    NASA Astrophysics Data System (ADS)

    Wiklind, Tommy

    2012-07-01

    The Atacama Large Millimeter/submm Array (ALMA) is an interferometric telescope currently under construction on the Chajnantor Plateau in northern Chile. It is situated at an altitude of 5000m, in one of the driest places in the world. The combination of the meteorological conditions, increased total collecting area and the use of state-of-the-art receivers means that the fully operational ALMA is a factor 10-1000 more sensitive than existing facilities, depending on the wavelength. When completed in 2013, ALMA will consists of 66 antennas, with maximum baselines of up to 15 km and it will be able to observe at wavelengths from 10 millimeter to ~350micron. ALMA will be able to provide an angular resolution of ~0.05 arcseconds. ALMA is still under construction, but has started producing science in an 'Early Science' phase. The goal with ALMA has from the beginning been to provide very high sensitivity as well as an angular resolution matching that of space based optical observatories such as the HST. One of three main drivers when designing ALMA has been the ability to study the high redshift universe. The main reason behind this is that almost half of the integrated background radiation comes from the far-infrared wavelength regime. This emission is interpreted as originating from dust re-radiated stellar emission in high redshift galaxies. Interstellar dust is almost invariably associated with molecular gas, that can be studied using molecular rotational transitions. The shape of the dust spectral energy distribution ensures that the observed flux at a fixed wavelength long-ward of the far-infrared peak (about 100micron) remains more or less constant over a redshift range z=1-10. This aspect makes dust continuum emission extraordinarily important for studying galaxies and Active Galactic Nuclei at high redshift. Through observations of line emission from molecular transitions it is possible to study the associated molecular gas distribution and its kinematics. The

  1. Candidate High Redshift Clusters of Dusty Galaxies from Herschel & Planck

    NASA Astrophysics Data System (ADS)

    Clements, David L.

    2015-08-01

    The cross identification of Planck compact sources with objects in karger area Herschel surveys, such as HerMES and H-ATLAS, has led to the discovery of candidate high redshift (out to z~3) clusters of far-IR luminous star forming galaxies. These objects are not easily reproduced in the current generations of galaxy and large scale formation simulations and are thus a potentially powerful new tool for comnstraining galaxy and cluster formation models. We will review the current results on these sources and examine future prospects for progress in this novel and potentially important new field.

  2. THE FIRST HIGH-REDSHIFT QUASAR FROM Pan-STARRS

    SciTech Connect

    Morganson, Eric; De Rosa, Gisella; Decarli, Roberto; Walter, Fabian; Rix, Hans-Walter; Chambers, Ken; Burgett, William; Flewelling, Heather; Hodapp, Klaus; Kaiser, Nick; Magnier, Eugene; Sweeney, Bill; Waters, Christopher; McGreer, Ian; Fan, Xiaohui; Greiner, Jochen; Price, Paul

    2012-06-15

    We present the discovery of the first high-redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an i{sub P1} dropout in PS1, confirmed photometrically with the SAO Wide-field InfraRed Camera at Arizona's Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared Detector at the MPG 2.2 m telescope in La Silla. The quasar was verified spectroscopically with the MMT Spectrograph, Red Channel and the Cassegrain Twin Spectrograph at the Calar Alto 3.5 m telescope. Its near-infrared spectrum was taken at the Large Binocular Telescope Observatory (LBT) with the LBT Near-Infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research. It has a redshift of 5.73, an AB z{sub P1} magnitude of 19.4, a luminosity of 3.8 Multiplication-Sign 10{sup 47} erg s{sup -1}, and a black hole mass of 6.9 Multiplication-Sign 10{sup 9} M{sub Sun }. It is a broad absorption line quasar with a prominent Ly{beta} peak and a very blue continuum spectrum. This quasar is the first result from the PS1 high-redshift quasar search that is projected to discover more than 100 i{sub P1} dropout quasars and could potentially find more than 10 z{sub P1} dropout (z > 6.8) quasars.

  3. Photometric Selection of High-Redshift Type Ia Supernova Candidates

    NASA Astrophysics Data System (ADS)

    Sullivan, M.; Howell, D. A.; Perrett, K.; Nugent, P. E.; Astier, P.; Aubourg, E.; Balam, D.; Basa, S.; Carlberg, R. G.; Conley, A.; Fabbro, S.; Fouchez, D.; Guy, J.; Hook, I.; Lafoux, H.; Neill, J. D.; Pain, R.; Palanque-Delabrouille, N.; Pritchet, C. J.; Regnault, N.; Rich, J.; Taillet, R.; Aldering, G.; Baumont, S.; Bronder, J.; Filiol, M.; Knop, R. A.; Perlmutter, S.; Tao, C.

    2006-02-01

    We present a method for selecting high-redshift Type Ia supernovae (SNe Ia) located via rolling SN searches. The technique, using both color and magnitude information of events from only two to three epochs of multiband real-time photometry, is able to discriminate between SNe Ia and core-collapse SNe. Furthermore, for SNe Ia the method accurately predicts the redshift, phase, and light-curve parameterization of these events based only on pre-maximum-light data. We demonstrate the effectiveness of the technique on a simulated survey of SNe Ia and core-collapse SNe, where the selection method effectively rejects most core-collapse SNe while retaining SNe Ia. We also apply the selection code to real-time data acquired as part of the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). During the period 2004 May to 2005 January in the SNLS, 440 SN candidates were discovered, of which 70 were confirmed spectroscopically as SNe Ia and 15 as core-collapse events. For this test data set, the selection technique correctly identifies 100% of the identified SNe II as non-SNe Ia with only a 1%-2% false rejection rate. The predicted parameterization of the SNe Ia has a precision of Δz/(1+zspec)<0.09 in redshift and +/-2-3 rest-frame days in phase, providing invaluable information for planning spectroscopic follow-up observations. We also investigate any bias introduced by this selection method on the ability of surveys such as SNLS to measure cosmological parameters (e.g., w and ΩM) and find any effect to be negligible.

  4. Probing Gravity in the High-Redshift Universe with HETDEX

    NASA Astrophysics Data System (ADS)

    Malz, A. I.; Shandera, S.

    2014-01-01

    The addition of dark matter and dark energy to general relativity is degenerate with a modification of the dependence of curvature on the stress-energy tensor in the absence of exotic sources of matter and energy; it is thus valuable to explore the latter as a potential improvement over the former. Though it is inherently difficult to distinguish existing evidence for the general relativity paradigm from that of its more promising alternatives, such theories are associated with different histories for the largely unexplored growth of structure. Zhang, et al. (2007) have enabled discrimination of these possibilities via a new observable parameter EG and have predicted the efficacy of several future astronomical surveys to determine its value. In this work, we examine the ability of the Hobby Eberly Telescope Dark Energy Experiment (HETDEX) to contribute to calculations of this indicator of gravity at the highest redshifts (1.9 < z < 3.5). We show that a prerequisite of such a measurement is a deeper understanding of the nature of Lyman-α emitting galaxies (LAEs). If HETDEX can constrain the statistical properties of the typical LAE velocity dispersion, then it will not be necessary to wait for the (as yet unplanned) next generation of high-resolution spectrographs to obtain a test of general relativity in the high-redshift universe.

  5. First broadband characterization and redshift determination of the VHE blazar MAGIC J2001+439

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Carreto Fidalgo, D.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Caneva, G.; de Lotto, B.; Delgado Mendez, C.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Farina, E.; Ferenc, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadasch, D.; Hayashida, M.; Herrera, J.; Herrero, A.; Hildebrand, D.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Kodani, K.; Konno, Y.; Krause, J.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Niedzwiecki, A.; Nilsson, K.; Nishijima, K.; Noda, K.; Nowak, N.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Partini, S.; Persic, M.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Preziuso, S.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Rügamer, S.; Saggion, A.; Saito, T.; Saito, K.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Stamatescu, V.; Stamerra, A.; Steinbring, T.; Storz, J.; Strzys, M.; Sun, S.; Surić, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Zandanel, F.; Zanin, R.; MAGIC Collaboration

    2014-12-01

    Aims: We aim to characterize the broadband emission from 2FGL J2001.1+4352, which has been associated with the unknown-redshift blazar MG4 J200112+4352. Based on its gamma-ray spectral properties, it was identified as a potential very high energy (VHE; E> 100 GeV) gamma-ray emitter. We investigate whether this object is aVHE emitter, characterize its gamma-ray spectrum, and study the broadband emission within the one-zone synchrotron self-Compton (SSC) scenario, which is commonly used to describe the emission in blazars. Moreover, we also intend to determine the redshift of this object, which is a crucial parameter for its scientific interpretation. Methods: The source was observed with MAGIC first in 2009 and later in 2010 within a multi-instrument observation campaign. The MAGIC observations yielded 14.8 h of good quality stereoscopic data. Besides MAGIC, the campaign involved, observations with Fermi-LAT, Swift-XRT/UVOT, the optical telescopes KVA, Goddard Robotic Telescope, Galaxy View observatory, Crimean Astrophysical observatory, St. Petersburg observatory, and the Owens Valley Radio Observatory. The object was monitored at radio, optical and gamma-ray energies during the years 2010 and 2011. We characterize the radio to VHE spectral energy distribution and quantify the multiband variability and correlations over short (few days) and long (many months) timescales. We also organized deep imaging optical observations with the Nordic Optical Telescope in 2013 to determine the source redshift. Results: The source, named MAGIC J2001+439, is detected for the first time at VHE with MAGIC at a statistical significance of 6.3σ (E > 70 GeV) during a 1.3 h long observation on 2010 July 16. The multi-instrument observations show variability in all energy bands with the highest amplitude of variability in the X-ray and VHE bands. Besides the variability on few-day timescales, the long-term monitoring of MAGIC J2001+439 shows that, the gamma-ray, optical, and radio

  6. Star formation and mass assembly in high redshift galaxies

    NASA Astrophysics Data System (ADS)

    Santini, P.; Fontana, A.; Grazian, A.; Salimbeni, S.; Fiore, F.; Fontanot, F.; Boutsia, K.; Castellano, M.; Cristiani, S.; de Santis, C.; Gallozzi, S.; Giallongo, E.; Menci, N.; Nonino, M.; Paris, D.; Pentericci, L.; Vanzella, E.

    2009-09-01

    Aims: The goal of this work is to infer the star formation properties and the mass assembly process of high redshift (0.3 ≤ z < 2.5) galaxies from their IR emission using the 24 μm band of MIPS-Spitzer. Methods: We used an updated version of the GOODS-MUSIC catalog, which has multiwavelength coverage from 0.3 to 24 μm and either spectroscopic or accurate photometric redshifts. We describe how the catalog has been extended by the addition of mid-IR fluxes derived from the MIPS 24 μm image. We compared two different estimators of the star formation rate (SFR hereafter). One is the total infrared emission derived from 24 μm, estimated using both synthetic and empirical IR templates. The other one is a multiwavelength fit to the full galaxy SED, which automatically accounts for dust reddening and age-star formation activity degeneracies. For both estimates, we computed the SFR density and the specific SFR. Results: We show that the two SFR indicators are roughly consistent, once the uncertainties involved are taken into account. However, they show a systematic trend, IR-based estimates exceeding the fit-based ones as the star formation rate increases. With this new catalog, we show that: a) at z>0.3, the star formation rate is correlated well with stellar mass, and this relationship seems to steepen with redshift if one relies on IR-based estimates of the SFR; b) the contribution to the global SFRD by massive galaxies increases with redshift up to ≃ 2.5, more rapidly than for galaxies of lower mass, but appears to flatten at higher z; c) despite this increase, the most important contributors to the SFRD at any z are galaxies of about, or immediately lower than, the characteristic stellar mass; d) at z≃ 2, massive galaxies are actively star-forming, with a median {SFR} ≃ 300 M_⊙ yr-1. During this epoch, our targeted galaxies assemble a substantial part of their final stellar mass; e) the specific SFR (SSFR) shows a clear bimodal distribution. Conclusions

  7. OPTIMAL MASS CONFIGURATIONS FOR LENSING HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Wong, Kenneth C.; Zabludoff, Ann I.; Ammons, S. Mark; Keeton, Charles R.

    2012-06-20

    We investigate the gravitational lensing properties of lines of sight containing multiple cluster-scale halos, motivated by their ability to lens very high redshift (z {approx} 10) sources into detectability. We control for the total mass along the line of sight, isolating the effects of distributing the mass among multiple halos and of varying the physical properties of the halos. Our results show that multiple-halo lines of sight can increase the magnified source-plane region compared to the single cluster lenses typically targeted for lensing studies and thus are generally better fields for detecting very high redshift sources. The configurations that result in optimal lensing cross sections benefit from interactions between the lens potentials of the halos when they overlap somewhat on the sky, creating regions of high magnification in the source plane not present when the halos are considered individually. The effect of these interactions on the lensing cross section can even be comparable to changing the total mass of the lens from 10{sup 15} M{sub Sun} to 3 Multiplication-Sign 10{sup 15} M{sub Sun }. The gain in lensing cross section increases as the mass is split into more halos, provided that the lens potentials are projected close enough to interact with each other. A nonzero projected halo angular separation, equal halo mass ratio, and high projected halo concentration are the best mass configurations, whereas projected halo ellipticity, halo triaxiality, and the relative orientations of the halos are less important. Such high-mass, multiple-halo lines of sight exist in the Sloan Digital Sky Survey.

  8. THE DARK SIDE OF QSO FORMATION AT HIGH REDSHIFTS

    SciTech Connect

    Romano-Diaz, Emilio; Shlosman, Isaac; Trenti, Michele; Hoffman, Yehuda

    2011-07-20

    Observed high-redshift QSOs, at z {approx} 6, may reside in massive dark matter (DM) halos of more than 10{sup 12} M{sub sun} and are thus expected to be surrounded by overdense regions. In a series of 10 constrained simulations, we have tested the environment of such QSOs. The usage of constrained realizations has enabled us to address the issue of cosmic variance and to study the statistical properties of the QSO host halos. Comparing the computed overdensities with respect to the unconstrained simulations of regions empty of QSOs, assuming there is no bias between the DM and baryon distributions, and invoking an observationally constrained duty cycle for Lyman break galaxies, we have obtained the galaxy count number for the QSO environment. We find that a clear discrepancy exists between the computed and observed galaxy counts in the Kim et al. samples. Our simulations predict that on average eight z {approx} 6 galaxies per QSO field should have been observed, while Kim et al. detect on average four galaxies per QSO field compared to an average of three galaxies in a control sample (GOODS fields). While we cannot rule out a small number of statistics for the observed fields to high confidence, the discrepancy suggests that galaxy formation in the QSO neighborhood proceeds differently than in the field. We also find that QSO halos are the most massive of the simulated volume at z {approx} 6 but this is no longer true at z {approx} 3. This implies that QSO halos, even in a case where they are the most massive ones at high redshifts, do not evolve into the most massive galaxy clusters at z = 0.

  9. Non-steller light from high-redshift radiogalaxies

    NASA Technical Reports Server (NTRS)

    Rawlings, Steve; Eales, Stephen A.

    1990-01-01

    With the aid of a new IRCAM image of 3C356, researchers question the common assumption that radiosource-stimulated starbursts are responsible for the extended optical emission aligned with radio structures in high-redshift radiogalaxies. They propose an alternative model in which the radiation from a hidden luminous quasar is beamed along the radio axis and illuminates dense clumps of cool gas to produce both extended narrow emission line regions and, by Thomson scattering, extended optical continua. Simple observational tests of this model are possible and necessary if we are to continue to accept that the color, magnitude and shape evolution of radiogalaxies are controlled by the active evolution of stellar populations.

  10. The KMOS AGN Survey at High Redshift (KASHz)

    NASA Astrophysics Data System (ADS)

    Harrison, C.; Alexander, D.; Mullaney, J.; Stott, J.; Swinbank, M.; Arumugam, V.; Bauer, F.; Bower, R.; Bunker, A.; Sharples, R.

    2016-03-01

    The KMOS AGN Survey at High Redshift (KASHz) is an extensive observational programme to obtain spatially resolved spectroscopy of distant galaxies that host rapidly growing supermassive black holes (i.e., active galactic nuclei [AGN]). By exploiting the unique capabilities of KMOS we will spatially resolve the ionised gas kinematics in around 200 such galaxies. A fundamental prediction of galaxy formation models is that AGN inject considerable energy into their host galaxies and ultimately destroy or remove star-forming material via outflows. However, until now, observational constraints of this prediction have been limited to only a small number of distant galaxies. KASHz will provide the strongest constraints to date on the prevalence, properties and impact of ionised outflows in the host galaxies of distant AGN. The survey is described and our first results presented.

  11. Relativistic jet feedback in high-redshift galaxies I: Dynamics

    NASA Astrophysics Data System (ADS)

    Mukherjee, Dipanjan; Bicknell, Geoffrey V.; Sutherland, Ralph; Wagner, Alex

    2016-06-01

    We present the results of three dimensional relativistic hydrodynamic simulations of interaction of AGN jets with a dense turbulent two-phase interstellar medium, which would be typical of high redshift galaxies. We describe the effect of the jet on the evolution of the density of the turbulent ISM. The jet driven energy bubble affects the gas to distances up to several kiloparsecs from the injection region. The shocks resulting from such interactions create a multi-phase ISM and radial outflows. One of the striking result of this work is that low power jets (Pjet ≲ 1043ergs-1) although less efficient in accelerating clouds, are trapped in the ISM for a longer time and hence affect the ISM over a larger volume. Jets of higher power drill through with relative ease. Although the relativistic jets launch strong outflows, there is little net mass ejection to very large distances, supporting a galactic fountain scenario for local feedback.

  12. Relativistic jet feedback in high-redshift galaxies - I. Dynamics

    NASA Astrophysics Data System (ADS)

    Mukherjee, Dipanjan; Bicknell, Geoffrey V.; Sutherland, Ralph; Wagner, Alex

    2016-09-01

    We present the results of 3D relativistic hydrodynamic simulations of interaction of active galactic nucleus jets with a dense turbulent two-phase interstellar medium, which would be typical of high-redshift galaxies. We describe the effect of the jet on the evolution of the density of the turbulent interstellar medium (ISM). The jet-driven energy bubble affects the gas to distances up to several kiloparsecs from the injection region. The shocks resulting from such interactions create a multiphase ISM and radial outflows. One of the striking result of this work is that low-power jets (Pjet ≲ 1043 ergs-1), although less efficient in accelerating clouds, are trapped in the ISM for a longer time and hence affect the ISM over a larger volume. Jets of higher power drill through with relative ease. Although the relativistic jets launch strong outflows, there is little net mass ejection to very large distances, supporting a galactic fountain scenario for local feedback.

  13. Superwind Model of Extended Lyalpha Emitters at High Redshift.

    PubMed

    Taniguchi; Shioya

    2000-03-20

    We propose a new model for the extended Lyalpha blobs found recently at high redshift (z approximately 3). The observational properties of these blobs are as follows: (1) the observed Lyalpha luminosities are approximately 1043 h-2 ergs s-1, (2) they appear elongated morphologically, (3) their sizes amount to approximately 100 kpc, (4) the observed line widths amount to approximately 1000 km s-1, and (5) they are not associated with strong radio continuum sources. All these observational properties seem to be explained in terms of galactic winds driven by successive supernova explosions shortly after the initial burst of massive star formation in the galactic centers. The observed number density of Lyalpha blobs ( approximately 3.4x10-5 h3 Mpc-3) may be explained if their present-day counterparts are elliptical galaxies with a luminosity above approximately 1L*. PMID:10702121

  14. Can quasars photoionize the intergalactic medium at high redshift?

    NASA Technical Reports Server (NTRS)

    Meiksin, Avery; Madau, Piero

    1993-01-01

    The reionization of the intergalactic medium (IGM) by quasar sources at high redshift are discussed. The integrated UV background from observed QSO's, taking into account the hydrogen opacity associated with intervening Ly-alpha clouds and Lyman limit systems are computed. It is noted that the published data appear to indicate a significant underdensity of absorption systems in the Ly-alpha forest with column densities N(sub HI) greater than 10(exp 15) cm(sup -2). This deficit results in a reduction of the opacity of the universe by a factor of 1.5-3 at z = 3-5 relative to previous estimates. The QSO contribution to the metagalactic flux at the Lyman edge may be as large as J(sub 912)(z) is approximately 6((1 + z)/4.5)(sup 0.5) x 10(exp -22) erg cm(sup -2) s(sup -1) Hz(sup -1) sr(sup -1) for q(sup o) = O, and slightly lower for q(sub o) = 1/2. For a density of the diffuse component of the IGM of omega(sub D)(h(sub 50)(sup 2)) less than 0.025, QSO's could photoionize a smooth IGM sufficiently to satisfy the constraints imposed by the Gunn-Peterson effect. The epoch of reionization could be as recent as z is approximately greater than 5. As a result, neutral patches of IGM would be detectable in the spectra of high redshift quasars. The patches would appear as absorption line systems with typical column densities of 10(exp 19) - 10(exp 20) cm(sup -2), and velocity widths of 100 - 1000 km s(sup -1).

  15. An empirical SFR estimator for high redshift galaxies:

    NASA Astrophysics Data System (ADS)

    Arnouts, Stephane

    2015-08-01

    At high redshift, most of the SFR indicators are limited to the most massive galaxies (Far-IR, radio) and out of reach of optical spectroscopy (Halpha). The UV continuum is the only one available at all redshifts and for galaxies within a large range of mass. The main question is then to properly account for dust absorption. The SED fitting are always limited in the choice of popular attenuation laws (if not only one, starburst) which relies on the slope of the UV continuum. The alternative is to measure the net budget between the absorbed vs un-absorbed UV light i.e. the infrared excess (IRX= Lir/Luv).By using the deep 24 micron in the COSMOS field, we have observed a remarkable behaviour of IRX stripes within the (NUV-r)o vs (r-K)o color diagram which can be used to derive robust SFR estimates just with the Luv, Lr and Lk luminosities (Arnouts et al, 2013). We have shown that we can explain the correlation if we consider a two component models for the birth clouds and the ISM and also a complete model for galaxy inclination to explain the extrem IRX values. We are now extended the method with Herschel data at higher redshift (z~2) and lower masses (M~10^8Mo) by using stacking techniques and find that the IRX-NUVrK correlation persists (Le Floc’h , in prep). This method allows us to derive an accurate SFR for each individual galaxy based on its location in the NUVrK diagram and with no assumption on dust attenuation law, a main caveat for SED fitting technique.We investigated the behavior of the scatter of the SFR-Mass in GOODS and COSMOS fields and find that both SFR (Lir+Luv) or SFR(NUVrK) estimatesare consistent (Ilbert et al., 2015). Finally will investigate the dust-free UV luminosity functions in between 0

  16. FRONTIER FIELDS: HIGH-REDSHIFT PREDICTIONS AND EARLY RESULTS

    SciTech Connect

    Coe, Dan; Bradley, Larry; Zitrin, Adi

    2015-02-20

    The Frontier Fields program is obtaining deep Hubble and Spitzer Space Telescope images of new ''blank'' fields and nearby fields gravitationally lensed by massive galaxy clusters. The Hubble images of the lensed fields are revealing nJy sources (AB mag > 31), the faintest galaxies yet observed. The full program will transform our understanding of galaxy evolution in the first 600 million years (z > 9). Previous programs have yielded a dozen or so z > 9 candidates, including perhaps fewer than expected in the Ultra Deep Field and more than expected in shallower Hubble images. In this paper, we present high-redshift (z > 6) number count predictions for the Frontier Fields and candidates in three of the first Hubble images. We show the full Frontier Fields program may yield up to ∼70 z > 9 candidates (∼6 per field). We base this estimate on an extrapolation of luminosity functions observed between 4 < z < 8 and gravitational lensing models submitted by the community. However, in the first two deep infrared Hubble images obtained to date, we find z ∼ 8 candidates but no strong candidates at z > 9. We defer quantitative analysis of the z > 9 deficit (including detection completeness estimates) to future work including additional data. At these redshifts, cosmic variance (field-to-field variation) is expected to be significant (greater than ±50%) and include clustering of early galaxies formed in overdensities. The full Frontier Fields program will significantly mitigate this uncertainty by observing six independent sightlines each with a lensing cluster and nearby blank field.

  17. Obscured Starburst Activity in High Redshift Clusters and Groups

    NASA Astrophysics Data System (ADS)

    Kocevski, Dale; Lemaux, B.; Lubin, L.; Gal, R.

    2011-01-01

    Using Spitzer MIPS 24um imaging and extensive Keck spectroscopy we have found evidence for environmentally triggered starburst activity within six clusters and groups at z 0.9. I will show that the density of 24um-detected galaxies in the cluster environment is nearly twice that of the surrounding field at this redshift and that this overdensity scales with the cluster's dynamical state. The 24um-bright members often appear optically unremarkable and exhibit only moderate [OII] line emission due to severe obscuration. Although their spatial distribution suggests they are an infalling population, a close examination of their spectral properties, morphologies and optical colors indicate they are not simply analogs of the field population that have yet to be quenched. Using stacked DEIMOS spectra, we find the 24um-detected cluster and group galaxies exhibit elevated levels of Balmer absorption compared to galaxies undergoing normal, continuous star formation. A similar excess is not observed in field galaxies with equivalent infrared luminosities, indicating a greater fraction of the detected cluster and group members have experienced a burst of star formation in the recent past compared to their counterparts in the field. Our results suggest that gas-rich galaxies at high redshift experience a temporary increase in their star formation activity as they assemble into denser environments. Using HST ACS imaging we find that disturbed morphologies are common among the obscured starburst population and become more prevalent in regions of higher galaxy density. We conclude that mergers are the dominant triggering mechanism responsible for the enhanced star formation found in the group galaxies, while a mix of harassment and mergers are likely driving the activity of the cluster galaxies.

  18. Obscured Starburst Activity in High-redshift Clusters and Groups

    NASA Astrophysics Data System (ADS)

    Kocevski, Dale D.; Lemaux, Brian C.; Lubin, Lori M.; Gal, Roy; McGrath, Elizabeth J.; Fassnacht, Christopher D.; Squires, Gordon K.; Surace, Jason A.; Lacy, Mark

    2011-07-01

    Using Spitzer-Multiband Imaging Photometer 24 μm imaging and extensive Keck spectroscopy, we examine the nature of the obscured star-forming population in three clusters and three groups at z ~ 0.9. These six systems are the primary components of the Cl1604 supercluster, the largest structure imaged by Spitzer at redshifts approaching unity. We find that the average density of 24 μm detected galaxies within the Cl1604 clusters is nearly twice that of the surrounding field and that this overdensity scales with the cluster's dynamical state. The 24 μm bright members often appear optically unremarkable and exhibit only moderate [O II] line emission due to severe obscuration. Their spatial distribution suggests that they are an infalling population, but an examination of their spectral properties, morphologies, and optical colors indicates that they are not simply analogs of the field population that have yet to be quenched. Using stacked composite spectra, we find that the 24 μm detected cluster and group galaxies exhibit elevated levels of Balmer absorption compared with galaxies undergoing normal, continuous star formation. A similar excess is not observed in field galaxies with equivalent infrared luminosities, indicating a greater fraction of the detected cluster and group members have experienced a burst of star formation in the recent past compared to their counterparts in the field. Our results suggest that gas-rich galaxies at high redshift experience a temporary increase in their star formation activity as they assemble into denser environments. Using Hubble Space Telescope Advanced Camera for Surveys imaging, we find that disturbed morphologies are common among the 24 μm detected cluster and group members and become more prevalent in regions of higher galaxy density. We conclude that mergers are the dominant triggering mechanism responsible for the enhanced star formation found in the Cl1604 groups, while a mix of harassment and mergers are likely

  19. Probing the Intergalactic Medium with high-redshift quasars

    NASA Astrophysics Data System (ADS)

    Calverley, Alexander Peter

    2011-11-01

    Clues about the timing of reionization and the nature of the ionizing sources responsible are imprinted in the ionization and thermal state of the IGM. In this thesis, I use high-resolution quasar spectra in conjunction with state-of-the-art hydrodynamical simulations to probe the IGM at high redshift, focusing on the ionization and thermal state of the gas. After reionization, the ionization state of the IGM is set by the intensity of the ultraviolet background (UVB), quantified by the hydrogen photoionization rate, Γ_bkg. At high redshifts this has been estimated by measuring the mean flux in the Lyα forest, and scaling Γ_bkg in simulations such that the simulated mean flux matches the observed value. In Chapter 3 I investigate whether the precision of these estimates can be improved by using the entire flux probability distribution function (PDF) instead of only the mean flux. Although I find it cannot improve the precision directly, the flux PDF can potentially be used to constrain other sources of error in observational estimates of Γ_bkg, and so may increase the precision indirectly. The ionizing output of a quasar will locally dominate over the UVB, and this leads to enhanced transmission bluewards of the quasar Lyα line, known as the proximity effect. In Chapter 4 I present the first measurements of Γ_bkg at z > 5 from the proximity effect. The UVB intensity declines smoothly with redshift over 4.6 < z < 6.4, implying a smooth evolution in the mean free path of ionizing photons. This suggests that reionization ends at z > 6.4. There is a drop in Γ_bkg by roughly a factor of five, which corresponds to a drop in the ionizing emissivity by about a factor of two. Such a redshift evolution in the emissivity cannot continue to much higher redshift without reionization failing to complete, which suggests that reionization cannot have ended much higher than z = 6.4. Estimates of Γ_bkg from the proximity effect and the mean flux are generally discrepant

  20. X-Ray Absorption of High- Redshift Quasars

    NASA Astrophysics Data System (ADS)

    Behar, Ehud; Eitan, Assaf

    2012-09-01

    Soft X-ray absorption of high-z quasars has been known for more than a decade, but its astrophysical context remains a mystery. In order to better understand this absorption, we have constructed the largest to date high-S/N sample of high-z quasars (z > 0.5) from the XMM-Newton archive. We find that generally, z<2 and radio quiet objects provide only upper limits for the 0.5 keV optical depth (tau). Thus, we use censored statistics methods to seek correlations between tau and other quasar parameters. We find a dramatic increase of tau with z [(1+z)^{2.5}], although the correlation is rather weak. The correlation of tau with radio luminosity (or loudness) is even weaker. We also compare the absorption behavior with redshift with a large sample of GRBs, and with the pattern expected if the diffuse intergalactic medium (IGM) is responsible for the observed absorption. We find that although the z > 2 quasar opacity is consistent with a diffuse IGM effect and with the high-z GRB opacities, absorption of intermediate z (0.5 < z < 2) quasars is too low for this scenario, which leads to the conclusion that a simple IGM origin for this absorption is unlikely.

  1. Sources and Evolution of Dust in the High Redshift Universe

    NASA Astrophysics Data System (ADS)

    Dwek, Eli

    2015-08-01

    Understanding the sources and evolution of dust in the very high redshift universe (z > 8-9) poses unique challenges to observers and theorists alike.The peak of the infrared emission from the dust falls in the ~ 80-120 micron region in the rest frame of the galaxy, or about 850 micron to 2 mm in the observers' frame. Sensitivity and background confusion are the main obstacles for the detection of these high-z galaxies and their association with optical and near-IR counterparts. Observations with instruments such as the SCUBA-2, AzTEC, Mambo, Laboca, and GISMO2 offer the best hope for detecting such sources.On the theoretical side, the sources of dust in these galaxies are confined to massive stars with main sequence lifetimes that are shorter than the age of the universe. This leaves core collapse supernovae (CCSNe) as the main source of thermally-condensed dust in these objects. Dust is not only produced by CCSNe, but also destroyed by them in the remnant phase of their evolution. Accounting for the mass of dust inferred from the far-IR/millimeter observations requires therefore an understanding of the various physical processes affecting the evolution of dust in the very high-z universe, and a carefull evaluation of the balance between their different dust formation and destruction mechanisms.

  2. Stellar Populations. A User Guide from Low to High Redshift

    NASA Astrophysics Data System (ADS)

    Greggio, Laura; Renzini, Alvio

    2011-09-01

    This textbook is meant to illustrate the specific role played by stellar population diagnostics in our attempt to understand galaxy formation and evolution. The book starts with a rather unconventional summary of the results of stellar evolution theory (Chapter 1), as they provide the basis for the construction of synthetic stellar populations. Current limitations of stellar models are highlighted, which arise from the necessity to parametrize all those physical processes that involve bulk mass motions, such as convection, mixing, mass loss, etc. Chapter 2 deals with the foundations of the theory of synthetic stellar populations, and illustrates their energetics and metabolic functions, providing basic tools that will be used in subsequent chapters. Chapters 3 and 4 deal with resolved stellar populations, first addressing some general problems encountered in photometric studies of stellar fields. Then some highlights are presented illustrating our current capacity of measuring stellar ages in Galactic globular clusters, in the Galactic bulge and in nearby galaxies. Chapter 5 is dedicated to the exemplification of synthetic spectra of simple as well as composite stellar populations, drawing attention to those spectral features that may depend on less secure results of stellar evolution models. Chapter 6 illustrates how synthetic stellar populations are used to derive basic galaxy properties, such as star formation rates, stellar masses, ages and metallicities, and does so for galaxies at low as well as at high redshifts. Chapter 7 is dedicated to supernovae, distinguishing them in core collapse and thermonuclear cases, describing the evolution of their rates for various star formation histories, and estimating the supernova productivity of stellar populations and their chemical yields. In Chapter 8 the stellar initial mass function (IMF) is discussed, first showing how even apparently small IMF variations may have large effects on the demo! graphy of stellar

  3. Properties of Lyman-alpha Absorbers at High-Redshift

    NASA Astrophysics Data System (ADS)

    Peroux, C.

    2001-09-01

    In recent years, an extremely successful method to observationally study early stages of galaxy formation has been provided by the study of quasar absorbers. Quasar absorption lines are systems intercepting our line-of-sight to a given quasar and thus produce a feature in the quasar spectrum. Damped Lyman-α systems (hereafter DLAs) have N (H I) > 2 × 1020 atoms cm-2, and were originally thought to be the precursors of present day disk galaxies but there is evidence that they may be dominated by gas-rich proto-dwarf galaxies representing the basic building blocks of hierarchical growth of structure. Since their detection is independent of their size, shape, and covering factor, they provide a unbiased method with which to study early galaxies. DLAs are a subset of Lyman-limit Systems (hereafter LLS) which have hydrogen column densities N (H I) > 1.6 × 1017 atoms cm-2. At z < 1, they are probably associated with galactic halos. Finally, the Lyman-α forest is composed of many small column density systems ranging from N (H I) =1012 to 1.6 × 1017 atoms cm-2. This thesis presents a sample of 66 bright z ⪆ 4 quasars observed with the 4 m Cerro Tololo Inter-American Observatory telescope and the 4.2 m William Hershel telescope. The first part of the study concentrates on the quasars themselves via the fitting of quasar continua and the measurement of continuum depression parameters characterising the mean absorption across the Lyman-α forest. The quasar spectra are then analysed to investigate the absorption systems they contain. This led to the discovery of 26 new DLAs, 34 LLS and many associated metal lines which enables the analysis of the evolution of the column density distribution, f(N,z), and the total mass in high-column density neutral hydrogen quasar absorbers. The observed number of LLS per unit redshift is used to constrain f(N,z) below the DLA limit in the range N(HI) = 1.6 × 1017 to 2× 1020 atoms cm-2. The joint analysis shows unambiguously that f

  4. Clumpy Galaxies at High Redshifts: Insights from the FIRE Simulations

    NASA Astrophysics Data System (ADS)

    Oklopcic, Antonija; Hopkins, Philip F.; Keres, Dusan; Faucher-Giguere, Claude-Andre; Quataert, Eliot

    2015-01-01

    It has been observationally established that star-forming galaxies at high redshifts have more irregular morphologies compared to the ones in the local Universe. The morphologies of these galaxies are often dominated by large clumps which are believed to form via gravitational instabilities in gas-rich disks. Typically, these clumps have masses on the order of 107-109 solar masses, and extend over kiloparsec scales. It has been proposed in a number of studies that giant clumps, provided that they live long enough, could have an important impact on the morphology and evolution of their host galaxy. For example, as clumps migrate inwards through dynamical friction, they can sink to the center of the galaxy and form a bulge. However, this picture holds only if clumps can survive sufficiently long to reach the center without being destroyed by feedback from intense star formation that takes place within them. Therefore, determining typical lifetime of a giant clump, while taking into account different modes of feedback from star formation, is crucial for understanding the role they play in the evolution of their host galaxy. In this study we use the results of the FIRE (Feedback in Realistic Environments) simulations of galaxy evolution - a suite of high-resolution cosmological simulations with explicit physical models of stellar feedback and the multi-phase interstellar medium (Hopkins et al. 2014) - to investigate how feedback affects the formation and evolution of giant clumps in massive, gas-rich galaxies around z~2.

  5. Selection and Physical Properties of High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Fang, G. W.

    2014-09-01

    that the fraction of OGs and DGs in our sample (COSMOS) is similar, about 52% of them are DGs, and the other 48% are OGs. For 24 EROs in the UDF, 16 fall into DGs, while 8 are OGs. To reduce the redundancy of these three different classification methods, we perform a principal component analysis on the measurements of EROs, and find that the nonparametric measures and SEDs are efficient in segregating DGs and OGs. We investigate the dependence of the fraction of EROs on their observational properties, and the results suggest that DGs become increasingly important toward fainter magnitudes, redder colors, and higher redshifts. Moreover, we find that the clustering of EROs is much stronger than that of full K-limited samples of galaxies; and the clustering amplitude of OGs is a factor of ˜2 larger than DGs. In Chapter 3, we pick out 1609 star-forming galaxies (sgzKs: gzK=(z-K)_{AB}-1.4(g-z)_{AB}≥ 0.2) and 422 passively evolving galaxies (pgzKs: gzK<0.2 and (z-K)_{AB}>2.7) at z˜2 in the AEGIS field (K_{AB} < 22.0). The number counts of pgzKs in our sample turn over at K_{AB} ˜ 21.0, and both the number of faint and bright objects (including sgzKs and pgzKs) exceed the predictions of a recent semi-analytic model of galaxy formation. A more successful model is needed to explain this diversity. It is also found that the star formation rate (SFR) and specific SFR (sSFR) of sgzKs increase with redshift at all masses, implying that star-forming galaxies were much more active on average in the past. Moreover, the sSFR of massive galaxies is lower at all redshifts, suggesting that the mass growth of low-mass galaxies is more attributed to the star formation while comparing with high-mass galaxies. From the HST WFC3/F160W imaging data, we find that gzKs not only have diffuse structures, but also have single-object morphologies, implying that there are morphological variety and different formation processes for these galaxies at z˜2. In addition, we also find ˜ 10% of 828 gz

  6. High-redshift gamma-ray bursts: observational signatures of superconducting cosmic strings?

    PubMed

    Cheng, K S; Yu, Yun-Wei; Harko, T

    2010-06-18

    The high-redshift gamma-ray bursts (GRBs), GRBs 080913 and 090423, challenge the conventional GRB progenitor models by their short durations, typical for short GRBs, and their high energy releases, typical for long GRBs. Meanwhile, the GRB rate inferred from high-redshift GRBs also remarkably exceeds the prediction of the collapsar model, with an ordinary star formation history. We show that all these contradictions could be eliminated naturally, if we ascribe some high-redshift GRBs to electromagnetic bursts of superconducting cosmic strings. High-redshift GRBs could become a reasonable way to test the superconducting cosmic string model because the event rate of cosmic string bursts increases rapidly with increasing redshifts, whereas the collapsar rate decreases. PMID:20867291

  7. The fate of high-redshift massive compact galaxies

    NASA Astrophysics Data System (ADS)

    de la Rosa, Ignacio G.; La Barbera, Francesco; Ferreras, Ignacio; Sánchez Almeida, Jorge; Dalla Vecchia, Claudio; Martínez-Valpuesta, Inma; Stringer, Martin

    2016-04-01

    Massive high-redshift quiescent compact galaxies (nicknamed red nuggets) have been traditionally connected to present-day elliptical galaxies, often overlooking the relationships that they may have with other galaxy types. We use large bulge-disc decomposition catalogues based on the Sloan Digital Sky Survey to check the hypothesis that red nuggets have survived as compact cores embedded inside the haloes or discs of present-day massive galaxies. In this study, we designate a compact core as the bulge component that satisfies a prescribed compactness criterion. Photometric and dynamic mass-size and mass-density relations are used to show that, in the inner regions of galaxies at z ˜ 0.1, there are abundant compact cores matching the peculiar properties of the red nuggets, an abundance comparable to that of red nuggets at z ˜ 1.5. Furthermore, the morphology distribution of the present-day galaxies hosting compact cores is used to demonstrate that, in addition to the standard channel connecting red nuggets with elliptical galaxies, a comparable fraction of red nuggets might have ended up embedded in discs. This result generalizes the inside-out formation scenario; present-day massive galaxies can begin as dense spheroidal cores (red nuggets), around which either a spheroidal halo or a disc is formed later.

  8. MAGNETICALLY REGULATED GAS ACCRETION IN HIGH-REDSHIFT GALACTIC DISKS

    SciTech Connect

    Birnboim, Yuval

    2009-09-10

    Disk galaxies are in hydrostatic equilibrium along their vertical axis. The pressure allowing for this configuration consists of thermal, turbulent, magnetic, and cosmic-ray components. For the Milky Way the thermal pressure contributes {approx}10% of the total pressure near the plane, with this fraction dropping toward higher altitudes. Out of the rest, magnetic fields contribute {approx}1/3 of the pressure to distances of {approx}3 kpc above the disk plane. In this Letter, we attempt to extrapolate these local values to high-redshift, rapidly accreting, rapidly star-forming disk galaxies and study the effect of the extra pressure sources on the accretion of gas onto the galaxies. In particular, magnetic field tension may convert a smooth cold-flow accretion to clumpy, irregular star formation regions and rates. The infalling gas accumulates on the edge of the magnetic fields, supported by magnetic tension. When the mass of the infalling gas exceeds some threshold mass, its gravitational force cannot be balanced by magnetic tension anymore, and it falls toward the disk's plane, rapidly making stars. Simplified estimations of this threshold mass are consistent with clumpy star formation observed in SINS, UDF, GOODS, and GEMS surveys. We discuss the shortcomings of pure hydrodynamic codes in simulating the accretion of cold flows into galaxies, and emphasize the need for magnetohydrodynamic simulations.

  9. The High-Redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey

    NASA Astrophysics Data System (ADS)

    Paterno-Mahler, Rachel; Blanton, Elizabeth L.; Wing, Joshua; Ashby, M. L. N.; Brodwin, Mark; Golden-Marx, Emmet

    2015-08-01

    The number of confirmed, high-redshift galaxy clusters is very low compared to the number of well-studied clusters nearby. Bent, double-lobed radio sources are frequently found in galaxy clusters, and thus can be used as tracers for efficiently locating high-redshift clusters. Using our Spitzer Snapshot Survey, we have identified approximately 300 potential new clusters with redshifts 0.7high-redshift portion of the Cluster Occupied by Bent Radio AGN (COBRA) survey. We have created color-magnitude diagrams using infrared and optical data. Using the colors of the radio source host and the red sequence we can estimate redshifts for our clusters, as well as examine the evolution of the cluster galaxies over a large range of cosmic time.

  10. High-Redshift Supernovae in the Hubble Deep Field

    SciTech Connect

    Gilliland, R.L.; Nugent, P.E.; Phillips, M.M.

    1999-08-01

    Two supernovae detected in the Hubble Deep Field (HDF) using the original 1995 December epoch and data from a shorter (63,000 s in F814W) 1997 December visit with {ital HST} are discussed. The supernovae (SNe) are both associated with distinct galaxies at redshifts of 0.95 (spectroscopic) from Cohen et al. and 1.32 (photometric) from the work of Fern{acute a}ndez-Soto, Lanzetta, & Yahil. These redshifts are near, in the case of 0.95, and well beyond, for 1.32, the greatest distance reported previously for SNe. We show that our observations are sensitive to supernovae to z{approx_lt}1.8 in either epoch for an event near peak brightness. Detailed simulations are discussed that quantify the level at which false events from our search phase would start to arise and the completeness of our search as a function of both SN brightness and host galaxy redshift. The number of Type Ia and Type II SNe expected as a function of redshift in the two HDF epochs are discussed in relation to several published predictions and our own detailed calculations. A mean detection frequency of one SN per epoch for the small HDF area is consistent with expectations from current theory. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}

  11. High-Redshift Supernovae in the Hubble Deep Field

    NASA Astrophysics Data System (ADS)

    Gilliland, Ronald L.; Nugent, Peter E.; Phillips, M. M.

    1999-08-01

    Two supernovae detected in the Hubble Deep Field (HDF) using the original 1995 December epoch and data from a shorter (63,000 s in F814W) 1997 December visit with HST are discussed. The supernovae (SNe) are both associated with distinct galaxies at redshifts of 0.95 (spectroscopic) from Cohen et al. and 1.32 (photometric) from the work of Fernández-Soto, Lanzetta, & Yahil. These redshifts are near, in the case of 0.95, and well beyond, for 1.32, the greatest distance reported previously for SNe. We show that our observations are sensitive to supernovae to z<~1.8 in either epoch for an event near peak brightness. Detailed simulations are discussed that quantify the level at which false events from our search phase would start to arise and the completeness of our search as a function of both SN brightness and host galaxy redshift. The number of Type Ia and Type II SNe expected as a function of redshift in the two HDF epochs are discussed in relation to several published predictions and our own detailed calculations. A mean detection frequency of one SN per epoch for the small HDF area is consistent with expectations from current theory. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  12. Intergalactic Helium Absorption toward High-Redshift Quasars

    NASA Technical Reports Server (NTRS)

    Giroux, Mark L.; Fardal, Mark A.; Shull, J. Michael

    1995-01-01

    The recent Hubble Space Telescope (HST) observations of the z(q) = 3.286 quasar Q0302-003 (Jakobsen et at. 1994) and the z(q) = 3.185 quasar Q1935-67 by Tytler (1995) show absorption edges at the redshifted wavelength of He II 304 A. A key goal is to distinguish between contributions from discrete Ly-alpha forest clouds and a smoothly distributed intergalactic medium (IGM). We model the contributions from each of these sources of He II absorption, including the distribution of line Doppler widths and column densities, the 'He II proximity effect' from the quasar, and a self-consistent derivation of the He II opacity of the universe as a function of the spectrum of ionizing sources, with the assumption that both the clouds and the IGM are photoionized. The He II edge can be fully accounted for by He II line blanketing for reasonable distributions of line widths and column densities in the Ly-alpha forest, provided that the ionizing sources have spectral index alpha(s) greater than 1.5, and any He II proximity effect is neglected. Even with some contribution from a diffuse IGM, it is difficult to account for the edge observed by Jakobsen et al. (1994) with a 'hard' source spectrum (alpha(s) less than 1.3). The proximity effect modifies the relative contributions of the clouds and IGM to tau(He II) near the quasar (z approx. less than z(q)) and markedly increases the amount of He II absorption required. This implies, for example, that to account for the He II edge with line blanketing alone, the minimum spectral index alpha(s) must be increased from 1.5 to 1.9. We demonstrate the need for higher resolution observations that characterize the change in transmission as z approaches z(q) and resolve line-free gaps in the continuum. We set limits on the density of the diffuse IGM and suggest that the IGM and Ly-alpha clouds are likely to be a significant repository for dark baryons.

  13. A Search for Moderate-redshift Survivors from the Population of Luminous Compact Passive Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Stockton, Alan; Shih, Hsin-Yi; Larson, Kirsten; Mann, Andrew W.

    2014-01-01

    From a search of a ~2400 deg2 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 spectra 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. 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.

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

    SciTech Connect

    Stockton, Alan; Shih, Hsin-Yi; Larson, Kirsten; Mann, Andrew W. E-mail: hsshih@ifa.hawaii.edu E-mail: amann@ifa.hawaii.edu

    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 spectra 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.

  15. High Redshift Simulations Using the GALEX Ultraviolet Images of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Yeom, Bum-Suk; Kim, Young Kwang; Rey, Soo-Chang; Joe, Young Hoon; Gil de Paz, Armando

    2009-03-01

    We present simulated optical images of galaxies at high redshift using diverse and high-quality ultraviolet (UV) images of nearby galaxies obtained through the GALEX (Galaxy Evolution Explorer). Galaxy morphology plays an important role in the study of the evolution of galaxies. In this respect, the appearance of galaxies at high redshift requires images of nearby galaxies with various morphologies in the UV bandpass. Our simulation will be important in providing the basic information needed to study the evolution of galaxies.

  16. GALAXY CLUSTERS AT HIGH REDSHIFT AND EVOLUTION OF BRIGHTEST CLUSTER GALAXIES

    SciTech Connect

    Wen, Z. L.; Han, J. L.

    2011-06-10

    Identification of high-redshift clusters is important for studies of cosmology and cluster evolution. Using photometric redshifts of galaxies, we identify 631 clusters from the Canada-France-Hawaii Telescope (CFHT) wide field, 202 clusters from the CFHT deep field, 187 clusters from the Cosmic Evolution Survey (COSMOS) field, and 737 clusters from the Spitzer Wide-area InfraRed Extragalactic Survey (SWIRE) field. The redshifts of these clusters are in the range 0.1 {approx}< z {approx}< 1.6. Merging these cluster samples gives 1644 clusters in the four survey fields, of which 1088 are newly identified and more than half are from the large SWIRE field. Among 228 clusters of z {>=} 1, 191 clusters are newly identified, and most of them from the SWIRE field. With this large sample of high-redshift clusters, we study the color evolution of the brightest cluster galaxies (BCGs). The r' - z' and r{sup +} - m{sub 3.6{mu}m} colors of the BCGs are consistent with a stellar population synthesis model in which the BCGs are formed at redshift z{sub f} {>=} 2 and evolved passively. The g' - z' and B - m{sub 3.6{mu}m} colors of the BCGs at redshifts z > 0.8 are systematically bluer than the passive evolution model for galaxies formed at z{sub f} {approx} 2, indicating star formation in high-redshift BCGs.

  17. WISH: Wide-field Imaging Durvayor for High-redshift

    NASA Astrophysics Data System (ADS)

    Yamada, Toru

    2015-08-01

    We introduce the concept and current status of WISH project and discuss the science cases. WISH is a proposed space science mission for JAXA, which is dedicated for the deep and wide-field near-infrared imaging surveys. The mission contains the 1.5m cooled telescope as well as the imager with the FoV of ~850 square arcmin. The main goal of WISH is to detect and study galaxies at z=8-15 in the earliest history of structure formation in the universe. The key feature is to conduct WISH Ultra Deep Survey, which images in total of 100 square degrees in 6 broad-band filters at 0.9-4.5 micron down to 28AB magnitude. While more than 10^5 galaxies at z=8-9, 10^4 galaxies at z=11-12 will be detected, WISH-UDS is designed to constrain UV luminosity function at z=15. Depending on the models of the earliest evolution history, 1-1000 galaxies at z~15 (~100 galaxies for the moderate cases) will be detected. The UV spectral properties as well as the clustering properties of galaxies at z=8-15 can be studied as well; UV slope can be measured up to z=15, and the stellar and dark-matter-halo masses can be obtained up to z=9. WISH UDS can provide excellent opportunities for studying SNe at high redshift. Up to ~7000 type Ia SNe at z>1 can be detected and the distance modulus can be constrained with the precision of 0.9-1.5% at z>1.5. More than 100 Super Luminous SNe at z>6, and 10 SLSN at z>10 can also be detected, which allow us to study the earliest history of massive star formation in the universe. WISH imaging surveys as well as WISHSpec, which is an optional parallel-operation simple IFU spectrograph, also provide unique opportunities in various astronomical fields. WISH mission proposal was submitted to JAXA in February 2015 for the first down selection of JAXA Large Strategic Science Mission targeting the launch date in 2020-22. International collaborations including SAO (G.Fazio et al.), LAM (D. Burgarella et al.) and Canada (M.Sawicki et al.) are also actively coordinated.

  18. Quantitative comparison between type Ia supernova spectra at low and high redshifts: a case study

    NASA Astrophysics Data System (ADS)

    Garavini, G.; Folatelli, G.; Nobili, S.; Aldering, G.; Amanullah, R.; Antilogus, P.; Astier, P.; Blanc, G.; Bronder, T.; Burns, M. S.; Conley, A.; Deustua, S. E.; Doi, M.; Fabbro, S.; Fadeyev, V.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D. E.; Hook, I.; Howell, D. A.; Kashikawa, N.; Kim, A. G.; Kowalski, M.; Kuznetsova, N.; Lee, B. C.; Lidman, C.; Mendez, J.; Morokuma, T.; Motohara, K.; Nugent, P. E.; Pain, R.; Perlmutter, S.; Quimby, R.; Raux, J.; Regnault, N.; Ruiz-Lapuente, P.; Sainton, G.; Schahmaneche, K.; Smith, E.; Spadafora, A. L.; Stanishev, V.; Thomas, R. C.; Walton, N. A.; Wang, L.; Wood-Vasey, W. M.; Yasuda, N.

    2007-08-01

    We develop a method to measure the strength of the absorption features in type Ia supernova (SN Ia) spectra and use it to make a quantitative comparisons between the spectra of type Ia supernovae at low and high redshifts. In this case study, we apply the method to 12 high-redshift (0.212 ≤ z ≤ 0.912) SNe Ia observed by the Supernova Cosmology Project. Through measurements of the strengths of these features and of the blueshift of the absorption minimum in Ca ii H&K, we show that the spectra of the high-redshift SNe Ia are quantitatively similar to spectra of nearby SNe Ia (z < 0.15). One supernova in our high redshift sample, SN 2002fd at z = 0.279, is found to have spectral characteristics that are associated with peculiar SN 1991T/SN 1999aa-like supernovae.

  19. Quantitative comparison between Type Ia supernova spectra at low and high redshifts: A case study

    SciTech Connect

    Supernova Cosmology Project; Nugent, Peter E; Garavini, G.; Folatelli, G.; Nobili, S.; Aldering, G.; Amanullah, R.; Antilogus, P.; Astier, P.; Blanc, G.; Bronder, J.; Burns, M.S.; Conley, A.; Deustua, S. E.; Doi, M.; Fabbro, S.; Fadeyev, V.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D. E.; Hook, I.; Howell, D. A.; Kashikawa, N.; Kim, A. G.; Kowalski, M.; Kuznetsova, N.; Lee, B. C.; Lidman, C.; Mendez, J.; Morokuma, T.; Motohara, K.; Nugent, P. E.; Pain, R.; Perlmutter, S.; Quimby, R.; Raux, J.; Regnault, N.; Ruiz-Lapuente, P.; Sainton, G.; Schahmaneche, K.; Smith, E.; Spadafora, A. L.; Stanishev, V.; Thomas, R. C.; Walton, N. A.; Wang, L.; Wood-Vasey, W. M.; Yasuda, N.

    2008-03-24

    We develop a method to measure the strength of the absorption features in type Ia supernova (SN Ia) spectra and use it to make a quantitative comparisons between the spectra of type Ia supernovae at low and high redshifts. In this case study, we apply the method to 12 high-redshift (0.212 = z = 0.912) SNe Ia observed by the Supernova Cosmology Project. Through measurements of the strengths of these features and of the blueshift of theabsorption minimum in Ca ii H&K, we show that the spectra of the high-redshift SNe Ia are quantitatively similar to spectra of nearby SNe Ia (z< 0.15). One supernova in our high redshift sample, SN 2002fd at z = 0.279, is found to have spectral characteristics that are associated with peculiar SN 1991T/SN 1999aa-like supernovae.

  20. ON THE SHAPES AND STRUCTURES OF HIGH-REDSHIFT COMPACT GALAXIES

    SciTech Connect

    Chevance, Melanie; Damjanov, Ivana; Abraham, Roberto G.; Weijmans, Anne-Marie; Simard, Luc; Van den Bergh, Sidney; Caris, Evelyn; Glazebrook, Karl

    2012-08-01

    Recent deep Hubble Space Telescope WFC3 imaging suggests that a majority of compact quiescent massive galaxies at z {approx} 2 may contain disks. To investigate this claim, we have compared the ellipticity distribution of 31 carefully selected high-redshift massive quiescent compact galaxies to a set of mass-selected ellipticity and Sersic index distributions obtained from two-dimensional structural fits to {approx}40, 000 nearby galaxies from the Sloan Digital Sky Survey. A Kolmogorov-Smirnov test shows that the distribution of ellipticities for the high-redshift galaxies is consistent with the ellipticity distribution of a similarly chosen sample of massive early-type galaxies. However, the distribution of Sersic indices for the high-redshift sample is inconsistent with that of local early-type galaxies, and instead resembles that of local disk-dominated populations. The mismatch between the properties of high-redshift compact galaxies and those of both local early-type and disk-dominated systems leads us to conclude that the basic structures of high-redshift compact galaxies probably do not closely resemble those of any single local galaxy population. Any galaxy population analog to the high-redshift compact galaxies that exists at the current epoch is either a mix of different types of galaxies, or possibly a unique class of objects on their own.

  1. BINARY QUASARS AT HIGH REDSHIFT. I. 24 NEW QUASAR PAIRS AT z {approx} 3-4

    SciTech Connect

    Hennawi, Joseph F.; Myers, Adam D.; Shen, Yue; Strauss, Michael A.; Djorgovski, S. G.; Glikman, Eilat; Mahabal, Ashish; Fan Xiaohui; Martin, Crystal L.; Richards, Gordon T.; Schneider, Donald P.; Shankar, Francesco

    2010-08-20

    The clustering of quasars on small scales yields fundamental constraints on models of quasar evolution and the buildup of supermassive black holes. This paper describes the first systematic survey to discover high-redshift binary quasars. Using color-selection and photometric redshift techniques, we searched 8142 deg{sup 2} of Sloan Digital Sky Survey imaging data for binary quasar candidates, and confirmed them with follow-up spectroscopy. Our sample of 27 high-redshift binaries (24 of them new discoveries) at redshifts 2.9 < z < 4.3 with proper transverse separations 10 kpc < R{sub perpendicular} < 650 kpc increases the number of such objects known by an order of magnitude. Eight members of this sample are very close pairs with R{sub perpendicular} < 100 kpc, and of these close systems four are at z>3.5. The completeness and efficiency of our well-defined selection algorithm are quantified using simulated photometry and we find that our sample is {approx}50% complete. Our companion paper uses this knowledge to make the first measurement of the small-scale clustering (R < 1 h {sup -1} Mpc comoving) of high-redshift quasars. High-redshift binaries constitute exponentially rare coincidences of two extreme (M {approx}> 10{sup 9} M {sub sun}) supermassive black holes. At z {approx} 4, there is about one close binary per 10 Gpc{sup 3}, thus these could be the highest sigma peaks, the analogs of superclusters, in the early universe.

  2. UV Spectroscopy of Type Ia Supernovae at Low- andHigh-Redshift

    SciTech Connect

    Nugent, Peter

    2005-04-20

    In the past three years two separate programs were initiated to study the restframe UV properties of Type Ia Supernovae. The low-redshift study was carried out using several ground-based facilities coupled with HST/STIS observations. The high-redshift program is an offshoot of the CFHT Legacy Survey and uses Keck/LRIS to obtain spectra. Here we present the preliminary results from each program and their implications for current cosmology measurements.

  3. A Systematic Meta-Survey of High Redshift Quasars Probing their Environments and Evolution

    NASA Astrophysics Data System (ADS)

    Gobeille, Doug B. P.

    We have constructed a meta-survey of 298 quasars in the window from 7 to 17.5 hours in right ascension and 0 to 65 degrees in declination. These quasars span three decades of total power and redshifts from 0.158 to 5.284. All sources had a flux density of greater than 70 mJy at 1.4 GHz. At redshifts z > 2.5 our sample is complete. It is also complete for z < 1 and P Tot1:4 > 1027.55 W/Hz. Our quasar sample is built from archival Very Large Array (VLA) observations, as well as three observations in 2007 and 2008. This sample represents one of the most complete meta-surveys to date of the high redshift universe. In the 1980's, two competing groups (Ne, Gower and Hutchings, and Barthel, Miley, and Lonsdale) investigated the high redshift universe, seeking to investigate the dependence of largest linear size (LLS) and bending angles on redshift, core power, and extended power. Using our sample we test the differing results of these groups and build our own model of source evolution with redshift and power. We also seek a relationship between bending angles and core dominance, modeling this dependence on the thoughts of Orr & Browne showing that projected bending angles grow as the angle to the line of sight approaches the intrinsic bending angle of the quasar. We will also present an additional component of our high redshift quasar observations seeking arcsecond scale jets to be observed with the space based Chandra x-ray telescope. These observations will be used to investigate the nature of x-ray emission from the knots of kiloparsec jets in the high redshift universe.

  4. Was Star Formation Suppressed in High-Redshift Minihalos?

    NASA Astrophysics Data System (ADS)

    Haiman, Zoltán; Bryan, Greg L.

    2006-10-01

    The primordial gas in the earliest dark matter halos, collapsing at redshifts z~20, with masses Mhalo~106 Msolar and virial temperatures Tvir<104 K, relied on the presence of molecules for cooling. Several theoretical studies have suggested that gas contraction and star formation in these minihalos was suppressed by radiative, chemical, thermal, and dynamical feedback processes. The recent measurement by the Wilkinson Microwave Anisotropy Probe (WMAP) of the optical depth to electron scattering, τ~0.09+/-0.03, provides the first empirical evidence for this suppression. The new WMAP result is consistent with vanilla models of reionization, in which ionizing sources populate cold dark matter halos down to a virial temperature of Tvir=104 K. On the other hand, we show that in order to avoid overproducing the optical depth, the efficiency for the production of ionizing photons in minihalos must have been about an order of magnitude lower than expected from massive metal-free stars and lower than the efficiency in large halos that can cool via atomic hydrogen (Tvir>104 K). This conclusion is insensitive to assumptions about the efficiency of ionizing photon production in the large halos, as long as reionization ends by z=6, as required by the spectra of bright quasars at z<~6. Our conclusion is strengthened if the clumping of the ionized gas evolves with redshift, as suggested by semianalytical predictions and three-dimensional numerical simulations.

  5. DISTRIBUTION OF SATELLITE GALAXIES IN HIGH-REDSHIFT GROUPS

    SciTech Connect

    Wang Yougang; Chen Xuelei; Park, Changbom; Hwang, Ho Seong

    2010-08-01

    We use galaxy groups at redshifts between 0.4 and 1.0 selected from the Great Observatories Origins Deep Survey to study the color-morphological properties of satellite galaxies and investigate possible alignment between the distribution of the satellites and the orientation of their central galaxy. We confirm the bimodal color and morphological-type distribution for satellite galaxies at this redshift range: the red and blue classes correspond to the early and late morphological types, respectively, and the early-type satellites are on average brighter than the late-type ones. Furthermore, there is a morphological conformity between the central and satellite galaxies: the fraction of early-type satellites in groups with an early-type central is higher than those with a late-type central galaxy. This effect is stronger at smaller separations from the central galaxy. We find a marginally significant signal of alignment between the major axis of the early-type central galaxy and its satellite system, while for the late-type centrals no significant alignment signal is found. We discuss the alignment signal in the context of shape evolution of groups.

  6. Spectral Evolution in High Redshift Quasars from the Final BOSS Sample

    NASA Astrophysics Data System (ADS)

    Jensen, Trey; Bautista, Julian; Dawson, Kyle; Harris, David; Kamble, Vikrant; Mariappan, Vivek; Suzuki, Nao

    2016-01-01

    We report on a study of the spectral variations in a sample of 102,150 quasars from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III). After mitigating selection effects and Malmquist bias over the redshift range 2.1 ≤ z ≤ 3.5, we create high signal-to-noise composite spectra binned by luminosity, spectral index, and redshift. We use these composite spectra to inspect the variations in quasar properties as a function of each of these three parameters. We confirm the traditional Baldwin effect (i.e. the anti-correlation of CIV equivalent width and luminosity) and identify physical trends associated with spectral index and redshift. In this poster, we will present these results with a particular focus on the clear spectroscopic signature that we find in redshift evolution.

  7. A systematic search for lensed high-redshift galaxies in HST images of MACS clusters

    NASA Astrophysics Data System (ADS)

    Repp, A.; Ebeling, H.; Richard, J.

    2016-04-01

    We present the results of a 135-arcmin2 search for high-redshift galaxies lensed by 29 clusters from the MAssive Cluster and extended MAssive Cluster Surveys. We use relatively shallow images obtained with the Hubble Space Telescope in four passbands, namely, F606W, F814W, F110W, and F140W. We identify 130 F814W dropouts as candidates for galaxies at z ≳ 6. In order to fit the available broad-band photometry to galaxy spectral energy distribution (SED) templates, we develop a prior for the level of dust extinction at various redshifts. We also investigate the systematic biases incurred by the use of SED-fit software. The fits we obtain yield an estimate of 20 Lyman-break galaxies with photometric redshifts from z ˜ 7 to 9. In addition, our survey has identified over 100 candidates with a significant probability of being lower redshift (z ˜ 2) interlopers. We conclude that even as few as four broad-band filters - when combined with fitting the SEDs - are capable of isolating promising objects. Such surveys thus allow one both to probe the bright end (M1500 ≲ -19) of the high-redshift ultraviolet luminosity function and to identify candidate massive evolved galaxies at lower redshifts.

  8. Narrow-band surveys for very high redshift Lyman-α emitters

    NASA Astrophysics Data System (ADS)

    Nilsson, K. K.; Orsi, A.; Lacey, C. G.; Baugh, C. M.; Thommes, E.

    2007-11-01

    Context: Many current and future surveys aim to detect the highest redshift (z ⪆ 7) sources through their Lyman-α (Lyα) emission, using the narrow-band imaging method. However, to date the surveys have only yielded non-detections and upper limits as no survey has reached the necessary combination of depth and area to detect these very young star forming galaxies. Aims: We aim to calculate model luminosity functions and mock surveys of Lyα emitters at z ⪆ 7 based on a variety of approaches calibrated and tested on observational data at lower redshifts. Methods: We calculate model luminosity functions at different redshifts based on three different approaches: a semi-analytical model based on CDM, a simple phenomenological model, and an extrapolation of observed Schechter functions at lower redshifts. The results of the first two models are compared with observations made at redshifts z ˜ 5.7 and z ˜ 6.5, and they are then extrapolated to higher redshift. Results: We present model luminosity functions for redshifts between z = 7{-}12.5 and give specific number predictions for future planned or possible narrow-band surveys for Lyα emitters. We also investigate what constraints future observations will be able to place on the Lyα luminosity function at very high redshift. Conclusions: It should be possible to observe z = 7{-}10 Lyα emitters with present or near-future instruments if enough observing time is allocated. In particular, large area surveys such as ELVIS (Emission Line galaxies with VISTA Survey) will be useful in collecting a large sample. However, to get a large enough sample to constrain well the z ≥ 10 Lyα luminosity function, instruments further in the future, such as an ELT, will be necessary.

  9. PROBING PRE-GALACTIC METAL ENRICHMENT WITH HIGH-REDSHIFT GAMMA-RAY BURSTS

    SciTech Connect

    Wang, F. Y.; Dai, Z. G.; Bromm, Volker; Greif, Thomas H.; Stacy, Athena; Loeb, Abraham; Cheng, K. S.

    2012-11-20

    We explore high-redshift gamma-ray bursts (GRBs) as promising tools to probe pre-galactic metal enrichment. We utilize the bright afterglow of a Population III (Pop III) GRB exploding in a primordial dwarf galaxy as a luminous background source, and calculate the strength of metal absorption lines that are imprinted by the first heavy elements in the intergalactic medium (IGM). To derive the GRB absorption line diagnostics, we use an existing highly resolved simulation of the formation of a first galaxy which is characterized by the onset of atomic hydrogen cooling in a halo with virial temperature {approx}> 10{sup 4} K. We explore the unusual circumburst environment inside the systems that hosted Pop III stars, modeling the density evolution with the self-similar solution for a champagne flow. For minihalos close to the cooling threshold, the circumburst density is roughly proportional to (1 + z) with values of about a few cm{sup -3}. In more massive halos, corresponding to the first galaxies, the density may be larger, n {approx}> 100 cm{sup -3}. The resulting afterglow fluxes are weakly dependent on redshift at a fixed observed time, and may be detectable with the James Webb Space Telescope and Very Large Array in the near-IR and radio wavebands, respectively, out to redshift z {approx}> 20. We predict that the maximum of the afterglow emission shifts from near-IR to millimeter bands with peak fluxes from mJy to Jy at different observed times. The metal absorption line signature is expected to be detectable in the near future. GRBs are ideal tools for probing the metal enrichment in the early IGM, due to their high luminosities and featureless power-law spectra. The metals in the first galaxies produced by the first supernova (SN) explosions are likely to reside in low-ionization stages (C II, O I, Si II and Fe II). We show that, if the afterglow can be observed sufficiently early, analysis of the metal lines may distinguish whether the first heavy elements were

  10. Probing Pre-Galactic Metal Enrichment with High-Redshift Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Wang, F. Y.; Bromm, Volker; Greif, Thomas H.; Stacy, Athena; Dai, Z. G.; Loeb, Abraham; Cheng, K. S.

    2012-01-01

    We explore high-redshift gamma-ray bursts (GRBs) as promising tools to probe pre-galactic metal enrichment. We utilize the bright afterglow of a Population III (Pop III) GRB exploding in a primordial dwarf galaxy as a luminous background source, and calculate the strength of metal absorption lines that are imprinted by the first heavy elements in the intergalactic medium (IGM). To derive the GRB absorption line diagnostics, we use an existing highly resolved simulation of the formation of a first galaxy which is characterized by the onset of atomic hydrogen cooling in a halo with virial temperature approximately greater than10(exp 4) K.We explore the unusual circumburst environment inside the systems that hosted Pop III stars, modeling the density evolution with the self-similar solution for a champagne flow. For minihalos close to the cooling threshold, the circumburst density is roughly proportional to (1 + z) with values of about a few cm(exp -3). In more massive halos, corresponding to the first galaxies, the density may be larger, n approximately greater than100 cm(exp -3). The resulting afterglow fluxes are weakly dependent on redshift at a fixed observed time, and may be detectable with the James Webb Space Telescope and Very Large Array in the near-IR and radio wavebands, respectively, out to redshift z approximately greater than 20. We predict that the maximum of the afterglow emission shifts from near-IR to millimeter bands with peak fluxes from mJy to Jy at different observed times. The metal absorption line signature is expected to be detectable in the near future. GRBs are ideal tools for probing the metal enrichment in the early IGM, due to their high luminosities and featureless power-law spectra. The metals in the first galaxies produced by the first supernova (SN) explosions are likely to reside in low-ionization stages (C II, O I, Si II and Fe II). We show that, if the afterglow can be observed sufficiently early, analysis of the metal lines may

  11. Probing Pre-galactic Metal Enrichment with High-redshift Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Wang, F. Y.; Bromm, Volker; Greif, Thomas H.; Stacy, Athena; Dai, Z. G.; Loeb, Abraham; Cheng, K. S.

    2012-11-01

    We explore high-redshift gamma-ray bursts (GRBs) as promising tools to probe pre-galactic metal enrichment. We utilize the bright afterglow of a Population III (Pop III) GRB exploding in a primordial dwarf galaxy as a luminous background source, and calculate the strength of metal absorption lines that are imprinted by the first heavy elements in the intergalactic medium (IGM). To derive the GRB absorption line diagnostics, we use an existing highly resolved simulation of the formation of a first galaxy which is characterized by the onset of atomic hydrogen cooling in a halo with virial temperature >~ 104 K. We explore the unusual circumburst environment inside the systems that hosted Pop III stars, modeling the density evolution with the self-similar solution for a champagne flow. For minihalos close to the cooling threshold, the circumburst density is roughly proportional to (1 + z) with values of about a few cm-3. In more massive halos, corresponding to the first galaxies, the density may be larger, n >~ 100 cm-3. The resulting afterglow fluxes are weakly dependent on redshift at a fixed observed time, and may be detectable with the James Webb Space Telescope and Very Large Array in the near-IR and radio wavebands, respectively, out to redshift z >~ 20. We predict that the maximum of the afterglow emission shifts from near-IR to millimeter bands with peak fluxes from mJy to Jy at different observed times. The metal absorption line signature is expected to be detectable in the near future. GRBs are ideal tools for probing the metal enrichment in the early IGM, due to their high luminosities and featureless power-law spectra. The metals in the first galaxies produced by the first supernova (SN) explosions are likely to reside in low-ionization stages (C II, O I, Si II and Fe II). We show that, if the afterglow can be observed sufficiently early, analysis of the metal lines may distinguish whether the first heavy elements were produced in a pair

  12. Lyman alpha emitting galaxies at high redshift: Direct detection of young galaxies in a young universe

    NASA Astrophysics Data System (ADS)

    Dawson, Steven Arthur

    An early result of galaxy formation theory was the prediction that the copious ionizing radiation produced in nascent galaxies undergoing their first starbursts should in turn produce a strong Lya emission line. We report on our efforts to detect and characterize primeval galaxies by searching for this expected Lya signature with two observational techniques: serendipitous slit spectroscopy, and narrowband imaging selection. In Part I, we describe our serendipitous slit spectroscopy survey of the Hubble Deep Field and its environs, which resulted in a catalog of 74 spectroscopic redshifts spanning 0.10 < z < 5.77, including a galaxy cluster at z = 0.85 and five galaxies at z > 5. Follow-up observations at higher resolution resulted in the additional serendipitous detection of a strong Lya-emitting galaxy at z = 5.190 (ES1). At the time of its discovery, ES1 was one of only nine known galaxies at z > 5, and was the sixth most distant known galaxy. The unprecedented spectral purity of the observation offers evidence for a galaxy-scale outflow with a. velocity of v > 300 km s -1 , consistent with wind speeds observed in powerful local starbursts (typically 10 2 to 10 3 km s -1 ), and with simulations of the late- stage evolution of Lya emission in star-forming systems. Our final serendipitous detection is the remarkable source CXOHDFN J123635.6+621424, which is both the highest redshift known spiral galaxy, and a rare example of a high redshift, hard X-ray-emitting Type II AGN. Significantly, all of these results were acquired with no direct allocation of telescope time. In Part II, we report on our implementation of narrowband imaging selection, with which we traded redshift coverage for survey volume, focusing on the systematic study of galaxies at a particular epoch in favor of chasing that rare, most-distant object. This effort resulted in a catalog of 76 z [approximate] 4.5 Lya-emitting galaxies spectroscopically-confirmed in campaigns of Keck/LRIS and Keck

  13. RUNAWAY STARS AND THE ESCAPE OF IONIZING RADIATION FROM HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Conroy, Charlie; Kratter, Kaitlin M.

    2012-08-20

    Approximately 30% of all massive stars in the Galaxy are runaways with velocities exceeding 30 km s{sup -1}. Their high speeds allow them to travel {approx}0.1-1 kpc away from their birthplace before they explode at the end of their several Myr lifetimes. At high redshift, when galaxies were much smaller than in the local universe, runaways could venture far from the dense inner regions of their host galaxies. From these large radii, and therefore low column densities, much of their ionizing radiation is able to escape into the intergalactic medium. Runaways may therefore significantly enhance the overall escape fraction of ionizing radiation, f{sub esc}, from small galaxies at high redshift. We present simple models of the high-redshift runaway population and its impact on f{sub esc} as a function of halo mass, size, and redshift. We find that the inclusion of runaways enhances f{sub esc} by factors of Almost-Equal-To 1.1-8, depending on halo mass, galaxy geometry, and the mechanism of runaway production, implying that runaways may contribute 50%-90% of the total ionizing radiation escaping from high-redshift galaxies. Runaways may therefore play an important role in reionizing the universe.

  14. Relic HII regions and radiative feedback at high redshifts

    NASA Astrophysics Data System (ADS)

    Mesinger, Andrei; Bryan, Greg L.; Haiman, Zoltán

    2009-11-01

    Ultraviolet (UV) radiation from early astrophysical sources could have a large impact on subsequent star formation in nearby protogalaxies, and in general on the progress of cosmological reionization. Theoretical arguments based on the absence of metals in the early Universe suggest that the first stars were likely massive, bright, yet short-lived, with lifetimes of a few million years. Here we study the radiative feedback arising from such stars using hydrodynamical simulations with transient UV backgrounds (UVBs) and persistent Lyman-Werner backgrounds (LWBs) of varying intensity. We extend our prior work in Mesinger et al., by studying a more typical region whose protogalaxies form at lower redshifts, z ~ 13-20, in the epoch likely preceding the bulk of reionization. We confirm our previous results that feedback in the relic HII regions resulting from such transient radiation is itself transient. Feedback effects dwindle away after ~30 per cent of the Hubble time, and the same critical specific intensity of JUV ~ 0.1 × 10-21ergs-1cm-2Hz-1sr-1 separates positive and negative feedback regimes. This suggests that overall feedback is fairly insensitive to the large-scale environment, overdensity and redshift-dependent halo parameters, and can accurately be modelled in this regime with just the intensity of the impinging UVB. Additionally, we discover a second episode of eventual positive feedback in haloes which have not yet collapsed when their progenitor regions were exposed to the transient UVB. When exposed to the transient UVB, this gas suffers relatively little density depletion but a significant enhancement of the molecular hydrogen abundance, thus resulting in net positive feedback. This eventual positive feedback appears in all runs, regardless of the strength of the UVB. However, this feedback regime is very sensitive to the presence of Lyman-Werner radiation, and notable effects disappear under fairly modest background intensities of JLW >~ 10-3 × 10

  15. Intensity Mapping of Molecular Gas at High Redshift

    NASA Astrophysics Data System (ADS)

    Bower, Geoffrey; Keating, Garrett; Marrone, Dan; DeBoer, David; Chang, Tzu-Ching; Chen, Ming-Tang; Jiang, Homin; Koch, Patrick; Kubo, Derek; Li, Chao-Te; Lin, K. Y.; Srinivasan, Ranjani; Darling, Jeremy

    2015-08-01

    The origin and evolution of structure in the Universe is one of the major challenges of observational astronomy. How and when did the first stars and galaxies form? How does baryonic structure trace the underlying dark matter? A multi-wavelength, multi-tool approach is necessary to provide the complete story or the evolution of structure in the Universe. Intensity mapping, which relies on the ability to detect many objects at once through their integrated emission rather than direct detection of individual objects, is a critical part of this mosaic. Intensity mapping provides a window on lower luminosity objects that cannot be detected individually but that collectively drive important processes. In particular, our understanding of the molecular gas component of massive galaxies is being revolutionized by ALMA and EVLA but the population of smaller, star-forming galaxies, which provide the bulk of star formation cannot be individually probed by these instruments.In this talk, I will summarize two intensity mapping experiments to detect molecular gas through the carbon monoxide (CO) rotational transition. We are currently completing sensitive observations with the Sunyaev-Zel'dovic Array (SZA) telescope at a wavelength of 1 cm that are sensitive to emission at redshifts 2.3 to 3.3. The SZA experiments sets strong limits on models for the CO emission and demonstrates the ability to reject foregrounds and telescope systematics in very deep integrations. I also describe the development of an intensity mapping capability for the Y.T. Lee Array, a 13-element interferometer located on Mauna Loa. In its first phase, this project focuses on detection of CO at redshifts 2.3 - 3.3 with detection via power spectrum and cross-correlation with other surveys. The project includes a major technical upgrade, a new digital correlator and IF electronics component to be deployed in 2015/2016. The Y.T. Lee Array observations will be more sensitive and extend to larger angular scales

  16. Infrared-faint radio sources are at high redshifts. Spectroscopic redshift determination of infrared-faint radio sources using the Very Large Telescope

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    Context. Infrared-faint radio sources (IFRS) are characterised by relatively high radio flux densities and associated faint or even absent infrared and optical counterparts. The resulting extremely high radio-to-infrared flux density ratios up to several thousands were previously known only for high-redshift radio galaxies (HzRGs), suggesting a link between the two classes of object. However, the optical and infrared faintness of IFRS makes their study difficult. Prior to this work, no redshift was known for any IFRS in the Australia Telescope Large Area Survey (ATLAS) fields which would help to put IFRS in the context of other classes of object, especially of HzRGs. Aims: This work aims at measuring the first redshifts of IFRS in the ATLAS fields. Furthermore, we test the hypothesis that IFRS are similar to HzRGs, that they are higher-redshift or dust-obscured versions of these massive galaxies. Methods: A sample of IFRS was spectroscopically observed using the Focal Reducer and Low Dispersion Spectrograph 2 (FORS2) at the Very Large Telescope (VLT). The data were calibrated based on the Image Reduction and Analysis Facility (IRAF) and redshifts extracted from the final spectra, where possible. This information was then used to calculate rest-frame luminosities, and to perform the first spectral energy distribution modelling of IFRS based on redshifts. Results: We found redshifts of 1.84, 2.13, and 2.76, for three IFRS, confirming the suggested high-redshift character of this class of object. These redshifts and the resulting luminosities show IFRS to be similar to HzRGs, supporting our hypothesis. We found further evidence that fainter IFRS are at even higher redshifts. Conclusions: Considering the similarities between IFRS and HzRGs substantiated in this work, the detection of IFRS, which have a significantly higher sky density than HzRGs, increases the number of active galactic nuclei in the early universe and adds to the problems of explaining the formation of

  17. Fluctuations in radiation backgrounds at high redshift and the first stars

    NASA Astrophysics Data System (ADS)

    Holzbauer, Lauren Nicole

    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

  18. ZEN and the Search for High-Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Willis, J. P.

    2006-01-01

    We present the ZEN (z equals nine) survey: a deep, narrow J-band search for proto-galactic Lya emission at redshifts z=9. In the first phase of the survey, dubbed ZEN1, we combine an exceptionally deep image of the Hubble Deep Field South, obtained using a narrow band filter centred on the wavelength 1.187 microns, with existing deep, broad band images covering optical to near infrared wavelengths. Candidate z=9 Lya-emitting galaxies display a significant narrow band excess relative to the Js-band that are undetected at optical wavelengths. We detect no sources consistent with this criterion to the 90% point source flux limit of the NB image, F_NB = 3.28e-18 ergs/s/cm2. The survey selection function indicates that we have sampled a volume of approximately 340 h^{-3} Mpc3 to a Lya emission luminosity of 10e43 h^{-2} ergs/s. When compared to the predicted properties of z=9 galaxies based upon no evolution of observed z=6 Lya-emitting galaxies, the `volume shortfall' of the current survey, i.e. the volume required to detect this putative population, is a factor of at least 8 to 10. We also discuss continuing narrow J-band imaging surveys that will reduce the volume shortfall factor to the point where the no-evolution prediction from z=6 is probed in a meaningful manner.

  19. Morphology of High Redshifted Galaxies using GALEX Ultraviolet Observations of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Yeom, Bum-Suk; Kim, Y.; Rey, S.; Kim, S.; Joe, Y.; Gil de Paz, A.

    2009-01-01

    Galaxy morphology provides clues about the processes in the understanding of the formation and evolution of galaxies. In this respect, the prediction of optical-band morphologies at high redshifts requires ultraviolet (UV) images of local galaxies with various morphologies. We simulated optical images at high redshifts using more diverse and high-quality nearby galaxies obtained through the Galaxy Evolution Explorer (GALEX) UV observations. We present a quantitative analysis of the morphology of galaxies at near-ultraviolet (NUV) and simulated optical images. We also present a correlation between the isophotal-shape parameter and UV colors for nearby early-type galaxies.

  20. Soft X-Ray Absorption by High-Redshift Intergalactic Helium.

    PubMed

    Miralda-Escudé

    2000-01-01

    The Lyalpha absorption from intergalactic, once-ionized helium (He ii) has been measured with the Hubble Space Telescope in four quasars over the last few years in the redshift range 2.4redshifts is, however, model-dependent and difficult to determine from these observations, since the intergalactic medium (IGM) can be completely optically thick to Lyalpha photons when only a small fraction of the helium remains as He ii. In addition, finding quasars in which the He ii Lyalpha absorption can be observed becomes increasingly difficult at higher redshift owing to the large abundance of hydrogen Lyman limit systems. It is pointed out here that He ii in the IGM should also cause detectable continuum absorption in the soft X-rays. The spectrum of a high-redshift source seen behind the IGM when most of the helium was He ii should recover from the He ii Lyman continuum absorption at an observed energy of approximately 0.1 keV. Galactic absorption will generally be stronger, but not by a large factor; the intergalactic He ii absorption can be detected as an excess over the expected Galactic absorption from the 21 cm H i column density. In principle, this method allows a direct determination of the fraction of helium that was singly ionized as a function of redshift if the measurement is done on a large sample of high-redshift sources over a range of redshifts. PMID:10587481

  1. Neutral hydrogen at the present epoch: A constraint on the evolution of high redshift systems

    NASA Technical Reports Server (NTRS)

    Rao, Sandhya; Briggs, Frank H.

    1993-01-01

    Damped Lyman-alpha and metal absorption lines in the spectra of quasars indicate the presence of intervening gas-rich systems at high redshift (z greater than 2). These systems have characteristic size scales, velocity dispersions, and neutral hydrogen column densities (N(H1)) similar to present day spirals and are thus thought to be their progenitors. Constraints on galaxy evolution can be derived by comparing the H1 properties of high redshift systems to the present galaxy population. Good observational statistics on high redshift absorbers specify the number of these systems along the line of sight as a function of N(H1), the column density of neutral hydrogen per absorber. Similar statistics for nearby (z = 0) galaxies of which spirals are the only gas-rich systems that provide a significant cross-section for the interception of light from quasars is derived.

  2. Pressure-driven fragmentation of multiphase clouds at high redshift

    NASA Astrophysics Data System (ADS)

    Dhanoa, H.; Mackey, J.; Yates, J.

    2014-11-01

    The discovery of a hyper metal-poor star with total metallicity of ≤10-5 Z⊙ has motivated new investigations of how such objects can form from primordial gas polluted by a single supernova. In this paper, we present a shock-cloud model which simulates a supernova remnant interacting with a cloud in a metal-free environment at redshift z = 10. Pre-supernova conditions are considered, which include a multiphase neutral medium and H II region. A small dense clump (n = 100 cm-3), located 40 pc from a 40 M⊙ metal-free star, embedded in an n = 10 cm-3 ambient cloud. The evolution of the supernova remnant and its subsequent interaction with the dense clump is examined. We include a comprehensive treatment of the non-equilibrium hydrogen and helium chemistry and associated radiative cooling that is occurring at all stages of the shock-cloud model, covering the temperature range 10-109 K. Deuterium chemistry and its associated cooling are not included because the UV radiation field produced by the relic H II region and supernova remnant is expected to suppress deuterium chemistry and cooling. We find a 103 times density enhancement of the clump (maximum density ≈78 000 cm-3) within this metal-free model. This is consistent with Galactic shock-cloud models considering solar metallicity gas with equilibrium cooling functions. Despite this strong compression, the cloud does not become gravitationally unstable. We find that the small cloud modelled here is destroyed for shock velocities ≳50 km s-1, and not significantly affected by shocks with velocity ≲30 km s-1. Rather specific conditions are required to make such a cloud collapse, and substantial further compression would be required to reduce the local Jeans mass to sub-solar values.

  3. A study of massive and evolved galaxies at high redshift

    SciTech Connect

    Nayyeri, H.; Mobasher, B.; Hemmati, S.; De Barros, S.; Ferguson, H. C.; Wiklind, T.; Dahlen, T.; Kassin, S.; Koekemoer, A.; Dickinson, M.; Giavalisco, M.; Fontana, A.; Paris, D.; Ashby, M.; Willner, S.; Barro, G.; Guo, Y.; Hathi, N. P.; Dunlop, J. S.; Targett, T. A.

    2014-10-10

    We use data taken as part of Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) observations of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) to identify massive and evolved galaxies at 3 < z < 4.5. This is performed using the strength of the Balmer break feature at rest-frame 3648 Å, which is a diagnostic of the age of the stellar population in galaxies. Using the WFC3 H-band-selected catalog for the CANDELS GOODS-S field and deep multi-waveband photometry from optical (HST) to mid-infrared (Spitzer) wavelengths, we identify a population of old and evolved post-starburst galaxies based on the strength of their Balmer breaks (Balmer break galaxies, BBGs). The galaxies are also selected to be bright in rest-frame near-IR wavelengths and hence massive. We identify a total of 16 BBGs. Fitting the spectral energy distribution of the BBGs shows that the candidate galaxies have average estimated ages of ∼800 Myr and average stellar masses of ∼5 × 10{sup 10} M {sub ☉}, consistent with being old and massive systems. Two of our BBG candidates are also identified by the criteria that are sensitive to star-forming galaxies (Lyman break galaxy selection). We find a number density of ∼3.2 × 10{sup –5} Mpc{sup –3} for the BBGs, corresponding to a mass density of ∼2.0 × 10{sup 6} M {sub ☉} Mpc{sup –3} in the redshift range covering the survey. Given the old age and the passive evolution, it is argued that some of these objects formed the bulk of their mass only a few hundred million years after the big bang.

  4. ZEN and the search for high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Willis, Jon; Courbin, Frédéric; Kneib, Jean-Paul; Minniti, Dante

    2006-03-01

    We present the ZEN ( z equals nine) survey: a deep, narrow J-band search for proto-galactic Ly α emission at redshifts z ˜ 9. In the first phase of the survey, dubbed ZEN1, we combine an exceptionally deep image of the Hubble Deep Field South, obtained using a narrow-band filter centred on the wavelength 1.187 μm, with existing deep, broad band images covering optical to near infrared wavelengths. Candidate z ˜ 9 Ly α-emitting galaxies display a significant narrow-band excess relative to the Js-band that are undetected at optical wavelengths. We detect no sources consistent with this criterion to the 90% point source flux limit of the NB image, FNB = 3.28 × 10 -18 ergs s -1 cm -2. The survey selection function indicates that we have sampled a volume of approximately 340 h -3 Mpc 3 to a Ly α emission luminosity of 10 43 h -2 ergs s -1. When compared to the predicted properties of z ˜ 9 galaxies based upon no evolution of observed z ˜ 6 Ly α-emitting galaxies, the 'volume shortfall' of the current survey, i.e., the volume required to detect this putative population, is a factor of at least 8-10. We also discuss continuing narrow J-band imaging surveys that will reduce the volume shortfall factor to the point where the no-evolution prediction from z ˜ 6 is probed in a meaningful manner.

  5. Probing the dark ages: Observations of the high-redshift universe

    NASA Astrophysics Data System (ADS)

    Stevens, Daniel Keith

    This thesis attempts to describe some of the earliest phases in the collapse of galaxies from an observational standpoint. The work is composed of an assortment of projects which sample objects at very high redshift, probing the Universe 1-3 Gyr after the Big Bang. The first section of the thesis concerns high-redshift galaxies. Search techniques for identifying distant galaxies are extensively reviewed. Radio selection was once the primary vehicle to targeting the early Universe. Keck spectroscopy of high-redshift radio galaxies from the MIT-Greenbank radio catalog (S5GHz >~ 50 mJy) are discussed. We synthesize a composite radio galaxy spectrum, which we compare with other composite active galaxy spectra. Our data suggests a correlation between radio power and ionization state in high-redshift radio galaxies. The following three chapters detail individual galaxies confirmed at z > 5. These galaxies are among the half-dozen most distant sources known at the close of the 20th Century. Two of the galaxies were photometrically-selected from the Hubble Deep Field (HDF 4-473.0 at z = 5.60 and HDF 3-951.0 at z = 5.34 +/- 0.01). The third is TN J0924-2201, a radio galaxy at z = 5.19 selected on the basis of steep radio spectral index and faint K-band brightness. This source contains the most distant active galactic nucleus currently known, requiring early formation of supermassive blackholes within a Gyr after the Big Bang. The second section of the thesis concerns searches for high-redshift Lyα emission, identified either from deep, narrow-band imaging surveys or deep slit spectra. We discuss in detail one faint, high equivalent width line-emitter. Conventional wisdom would suggest identifying the 9185 Å line with Lyα at z = 6.55. We argue [O II] λ3727 at z = 1.46 is the more likely identification and discuss observational tests to distinguish Lyα-emitters at high redshift from foreground (active) sources. The final section of the thesis concerns high-redshift

  6. Five New High-Redshift Quasar Lenses from the Sloan Digital Sky Survey

    SciTech Connect

    Inada, Naohisa; Oguri, Masamune; Shin, Min-Su; Kayo, Issha; Strauss, Michael A.; Morokuma, Tomoki; Schneider, Donald P.; Becker, Robert H.; Bahcall, Neta A.; York, Donald G.

    2008-09-08

    We report the discovery of five gravitationally lensed quasars from the Sloan Digital Sky Survey (SDSS). All five systems are selected as two-image lensed quasar candidates from a sample of high-redshift (z > 2.2) SDSS quasars. We confirmed their lensing nature with additional imaging and spectroscopic observations. The new systems are SDSS J0819+5356 (source redshift z{sub s} = 2.237, lens redshift z{sub l} = 0.294, and image separation {theta} = 4.04 inch), SDSS J1254+2235 (z{sub s} = 3.626, {theta} = 1.56 inch), SDSS J1258+1657 (z{sub s} = 2.702, {theta} = 1.28 inch), SDSS J1339+1310 (z{sub s} = 2.243, {theta} = 1.69 cin), and SDSS J1400+3134 (z{sub s} = 3.317, {theta} = 1.74 inch). We estimate the lens redshifts of the latter four systems to be z{sub l} = 0.4-0.6 from the colors and magnitudes of the lensing galaxies. We find that the image configurations of all systems are well reproduced by standard mass models. Although these lenses will not be included in our statistical sample of z{sub s} < 2.2 lenses, they expand the number of lensed quasars which can be used for high-redshift galaxy and quasar studies.

  7. 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

  8. High-Redshift Candidates and the Nature of Small Galaxies in the Hubble Deep Field

    NASA Astrophysics Data System (ADS)

    Storrie-Lombardi, Lisa J.; Weymann, Ray J.; Thompson, Rodger I.

    2003-07-01

    We present results on two related topics: (1) a discussion of high-redshift candidates (z>4.5) and (2) a study of very small galaxies at intermediate redshifts, both sets being detected in the region of the northern Hubble Deep Field (HDF) covered by the deep NICMOS observations at 1.6 and 1.1 μm. The high-redshift candidates are just those with redshift z>4.5 as given in the recent catalog of Thompson, Weymann, and Storrie-Lombardi, while the ``small galaxy'' sample is defined to be those objects with isophotal area <=0.2 arcsec2 and with photometric redshift 1<=z<=4.5. Of the 19 possible high-redshift candidates listed in the Thompson et al. catalog, 11 have (nominal) photometric redshifts less than 5.0. Of these, however, only four are ``robust'' in the sense of yielding high redshifts when the fluxes are randomly perturbed with errors comparable to the estimated measuring error in each wave band. For the eight other objects with nominal photometric redshifts greater than 5.0, one (WFPC2 4-473) has a published spectroscopic redshift. Of the remaining seven, four are robust in the sense indicated above. Two of these form a close pair (NIC 586 and NIC 107). The redshift of the object having formally the highest redshift, at 6.56 (NIC 118=WFPC2 4-601), is problematic, since F606W and F814W flux are clearly present, and the nature of this object poses a dilemma. Previous work by Colley et al. has suggested that compact sources in the WFPC2 HDF images are subgalactic components at redshifts z>0.5 since they are correlated on scales less than 1", corresponding to physical scales of less than 8 kpc (H0=65 km s-1 Mpc-1, q0=0.125). We confirm these correlations in the WFPC2 data. However, we do not detect the correlation of close pairs of galaxies on small scales in the ~0.65 arcmin2 region of the HDF that we surveyed with NICMOS. The smaller area surveyed and lower resolution will make any real correlation more difficult to measure in these data. We have examined

  9. The Lyman-continuum photon production efficiency in the high-redshift Universe

    NASA Astrophysics Data System (ADS)

    Wilkins, Stephen M.; Feng, Yu; Di-Matteo, Tiziana; Croft, Rupert; Stanway, Elizabeth R.; Bouwens, Rychard J.; Thomas, Peter

    2016-05-01

    The Lyman-continuum photon production efficiency (ξion) is a critical ingredient for inferring the number of photons available to reionize the intergalactic medium. To estimate the theoretical production efficiency in the high-redshift Universe we couple the BlueTides cosmological hydrodynamical simulation with a range of stellar population synthesis models. We find Lyman-continuum photon production efficiencies of log10(ξion/erg-1 Hz) ≈ 25.1-25.5 depending on the choice of stellar population synthesis model. These results are broadly consistent with recent observational constraints at high-redshift though favour a model incorporating the effects of binary evolution.

  10. Local Counterparts to High-Redshift Turbulent Galaxies: What are the Stellar Kinematics?

    NASA Astrophysics Data System (ADS)

    Bassett, Robert; Glazebrook, Karl; Fisher, David; Abraham, Roberto; Damjanov, Ivana

    2014-02-01

    We aim to measure the stellar kinematics of 4 low redshift turbulent, clumpy disks with the GMOS IFU. Recent observations of high redshift galaxies show that gaseous disks in high redshift (z 2) galaxies are turbulent. The source of this turbulence remains an open question. A possible scenario is that turbulent disks are fed by streams of cold gas, flowing along cosmic filaments, which drive the large H-alpha velocity dispersions and clumpy star formation observed (for example by the SINS survey). However, the recent discovery of low redshift disk galaxies with clumpy-high velocity dispersion disks shows that galaxies with similar properties to high-z clumpy disks can exists in absence of cold flows, therefore an alternate driver for turbulence seems likely to explain, at least these nearby galaxies. A contrasting scenario is that the turbulence is driven by feedback from extreme star formation originating from a thin stellar disk. These nearby star forming disks are very rare, yet they provide an oppurtunity to study clumpy disks with techniques which are impossible at high redshift (due to both resolution and surface brightness dimming). Here we propose one such study, to measure the stellar kinematics from Balmer absorption lines. If the stars and gas have similar velocity dispersion, this would favor externally driven turbulence by gas accretion (a rare thing in the low redshift Universe); conversely if the gas and stars have different dynamics then this would suggest that internally driven turbelence from feedback is a plausible scenario. We currently have GMOS IFU observations of two disk systems, and we propose here to extend our sample. To identify galaxies as disks we use lower resolution IFU emission line kinematics from AAO, surface photometry from UKIDSS and SDSS, and Halpha maps from Hubble Space Telescope.

  11. Non-linear violent disc instability with high Toomre's Q in high-redshift clumpy disc galaxies

    NASA Astrophysics Data System (ADS)

    Inoue, Shigeki; Dekel, Avishai; Mandelker, Nir; Ceverino, Daniel; Bournaud, Frédéric; Primack, Joel

    2016-02-01

    We utilize zoom-in cosmological simulations to study the nature of violent disc instability in clumpy galaxies at high redshift, z = 1-5. Our simulated galaxies are not in the ideal state assumed in Toomre instability, of linear fluctuations in an isolated, uniform, rotating disc. There, instability is characterized by a Q parameter below unity, and lower when the disc is thick. Instead, the high-redshift discs are highly perturbed. Over long periods they consist of non-linear perturbations, compact massive clumps and extended structures, with new clumps forming in interclump regions. This is while the galaxy is subject to frequent external perturbances. We compute the local, two-component Q parameter for gas and stars, smoothed on a ˜1 kpc scale to capture clumps of 108-9 M⊙. The Q < 1 regions are confined to collapsed clumps due to the high surface density there, while the interclump regions show Q significantly higher than unity. Tracing the clumps back to their relatively smooth Lagrangian patches, we find that Q prior to clump formation typically ranges from unity to a few. This is unlike the expectations from standard Toomre instability. We discuss possible mechanisms for high-Q clump formation, e.g. rapid turbulence decay leading to small clumps that grow by mergers, non-axisymmetric instability, or clump formation induced by non-linear perturbations in the disc. Alternatively, the high-Q non-linear VDI may be stimulated by the external perturbations such as mergers and counter-rotating streams. The high Q may represent excessive compressive modes of turbulence, possibly induced by tidal interactions.

  12. The fate of high redshift massive compact galaxies in dense environments

    SciTech Connect

    Kaufmann, Tobias; Mayer, Lucio; Carollo, Marcella; Feldmann, Robert; /Fermilab /Chicago U., KICP

    2012-01-01

    Massive compact galaxies seem to be more common at high redshift than in the local universe, especially in denser environments. To investigate the fate of such massive galaxies identified at z {approx} 2 we analyse the evolution of their properties in three cosmological hydrodynamical simulations that form virialized galaxy groups of mass {approx} 10{sup 13} M{sub {circle_dot}} hosting a central massive elliptical/S0 galaxy by redshift zero. We find that at redshift {approx} 2 the population of galaxies with M{sub *} > 2 x 10{sup 10} M{sub {circle_dot}} is diverse in terms of mass, velocity dispersion, star formation and effective radius, containing both very compact and relatively extended objects. In each simulation all the compact satellite galaxies have merged into the central galaxy by redshift 0 (with the exception of one simulation where one of such satellite galaxy survives). Satellites of similar mass at z = 0 are all less compact than their high redshift counterparts. They form later than the galaxies in the z = 2 sample and enter the group potential at z < 1, when dynamical friction times are longer than the Hubble time. Also, by z = 0 the central galaxies have increased substantially their characteristic radius via a combination of in situ star formation and mergers. Hence in a group environment descendants of compact galaxies either evolve towards larger sizes or they disappear before the present time as a result of the environment in which they evolve. Since the group-sized halos that we consider are representative of dense environments in the {Lambda}CDM cosmology, we conclude that the majority of high redshift compact massive galaxies do not survive until today as a result of the environment.

  13. Galaxy formation in the Planck cosmology - III. The high-redshift universe

    NASA Astrophysics Data System (ADS)

    Clay, Scott J.; Thomas, Peter A.; Wilkins, Stephen M.; Henriques, Bruno M. B.

    2015-08-01

    We present high-redshift predictions of the star formation rate distribution function (SFRDF), UV luminosity function (UVLF), galactic stellar mass function (GSMF), and specific star formation rates (sSFRs) of galaxies from the latest version of the Munich semi-analytic model L-GALAXIES. We find a good fit to both the shape and normalization of the SFRDF at z = 4-7, apart from a slight underprediction at the low-SFR end at z = 4. Likewise, we find a good fit to the faint number counts for the observed UVLF at brighter magnitudes our predictions lie below the observations, increasingly so at higher redshifts. At all redshifts and magnitudes, the raw (unattenuated) number counts for the UVLF lie above the observations. Because of the good agreement with the SFR we interpret our underprediction as an overestimate of the amount of dust in the model for the brightest galaxies, especially at high redshift. While the shape of our GSMF matches that of the observations, we lie between (conflicting) observations at z = 4-5, and underpredict at z = 6-7. The sSFRs of our model galaxies show the observed trend of increasing normalization with redshift, but do not reproduce the observed mass dependence. Overall, we conclude that the latest version of L-GALAXIES, which is tuned to match observations at z ≤ 3, does a fair job of reproducing the observed properties of galaxies at z ≥ 4. More work needs to be done on understanding observational bias at high redshift, and upon the dust model, before strong conclusions can be drawn on how to interpret remaining discrepancies between the model and observations.

  14. Chemical abundances in high-redshift galaxies: a powerful new emission line diagnostic

    NASA Astrophysics Data System (ADS)

    Dopita, Michael A.; Kewley, Lisa J.; Sutherland, Ralph S.; Nicholls, David C.

    2016-02-01

    This Letter presents a new, remarkably simple diagnostic specifically designed to derive chemical abundances for high redshift galaxies. It uses only the Hα, [N ii] and [S ii] emission lines, which can usually be observed in a single grating setting, and is almost linear up to an abundance of 12+log (O/H) = 9.05. It can be used over the full abundance range encountered in high redshift galaxies. By its use of emission lines located close together in wavelength, it is also independent of reddening. Our diagnostic depends critically on the calibration of the N/O ratio. However, by using realistic stellar atmospheres combined with the N/O vs. O/H abundance calibration derived locally from stars and H ii regions, and allowing for the fact that high-redshift H ii regions have both high ionisation parameters and high gas pressures, we find that the observations of high-redshift galaxies can be simply explained by the models without having to invoke arbitrary changes in N/O ratio, or the presence of unusual quantities of Wolf-Rayet stars in these galaxies.

  15. Weak Line Quasars at High Redshift: Extremely High Accretion Rates or Anemic Broad-line Regions?

    NASA Astrophysics Data System (ADS)

    Shemmer, Ohad; Trakhtenbrot, Benny; Anderson, Scott F.; Brandt, W. N.; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Lira, Paulina; Netzer, Hagai; Plotkin, Richard M.; Richards, Gordon T.; Schneider, Donald P.; Strauss, Michael A.

    2010-10-01

    We present Gemini-North K-band spectra of two representative members of the class of high-redshift quasars with exceptionally weak rest-frame ultraviolet emission lines (WLQs), SDSS J114153.34+021924.3 at z = 3.55 and SDSS J123743.08+630144.9 at z = 3.49. In both sources, we detect an unusually weak broad Hβ line and place tight upper limits on the strengths of their [O III] lines. Virial, Hβ-based black hole mass determinations indicate normalized accretion rates of L/L Edd=0.4 for these sources, which is well within the range observed for typical quasars with similar luminosities and redshifts. We also present high-quality XMM-Newton imaging spectroscopy of SDSS J114153.34+021924.3 and find a hard-X-ray photon index of Γ = 1.91+0.24 -0.22, which supports the virial L/L Edd determination in this source. Our results suggest that the weakness of the broad emission lines in WLQs is not a consequence of an extreme continuum-emission source but instead due to abnormal broad emission line region properties.

  16. WEAK LINE QUASARS AT HIGH REDSHIFT: EXTREMELY HIGH ACCRETION RATES OR ANEMIC BROAD-LINE REGIONS?

    SciTech Connect

    Shemmer, Ohad; Trakhtenbrot, Benny; Netzer, Hagai; Anderson, Scott F.; Brandt, W. N.; Schneider, Donald P.; Diamond-Stanic, Aleksandar M.; Fan Xiaohui; Lira, Paulina; Plotkin, Richard M.; Richards, Gordon T.; Strauss, Michael A.

    2010-10-20

    We present Gemini-North K-band spectra of two representative members of the class of high-redshift quasars with exceptionally weak rest-frame ultraviolet emission lines (WLQs), SDSS J114153.34+021924.3 at z = 3.55 and SDSS J123743.08+630144.9 at z = 3.49. In both sources, we detect an unusually weak broad H{beta} line and place tight upper limits on the strengths of their [O III] lines. Virial, H{beta}-based black hole mass determinations indicate normalized accretion rates of L/L {sub Edd}=0.4 for these sources, which is well within the range observed for typical quasars with similar luminosities and redshifts. We also present high-quality XMM-Newton imaging spectroscopy of SDSS J114153.34+021924.3 and find a hard-X-ray photon index of {Gamma} = 1.91{sup +0.24} {sub -0.22}, which supports the virial L/L {sub Edd} determination in this source. Our results suggest that the weakness of the broad emission lines in WLQs is not a consequence of an extreme continuum-emission source but instead due to abnormal broad emission line region properties.

  17. 21 Centimeter Tomography of the Intergalactic Medium at High Redshift

    NASA Astrophysics Data System (ADS)

    Madau, Piero; Meiksin, Avery; Rees, Martin J.

    1997-02-01

    We investigate the 21 cm signature that may arise from the intergalactic medium (IGM) prior to the epoch of full reionization (z > 5). In scenarios in which the IGM is reionized by discrete sources of photoionizing radiation, the neutral gas that has not yet been engulfed by an H II region may easily be preheated to temperatures well above that of the cosmic background radiation (CBR), rendering the IGM invisible in absorption against the CBR. We identify three possible preheating mechanisms: (1) photoelectric heating by soft X-rays from QSOs, (2) photoelectric heating by soft X-rays from early galactic halos, and (3) resonant scattering of the continuum UV radiation from an early generation of stars. We find that bright quasars with only a small fraction of the observed comoving density at z ~ 4 will suffice to preheat the entire universe at z >~ 6. We also show that, in a cold dark matter dominated cosmology, the thermal bremsstrahlung radiation associated with collapsing galactic mass halos (1010-1011 M⊙) may warm the IGM to ~100 K by z ~ 7. Alternatively, the equivalent of ~10% of the star formation rate density in the local universe, whether in isolated pregalactic stars, dwarf, or normal galaxies, would be capable of heating the entire IGM to a temperature above that of the CBR by Lyα scattering in a small fraction of the Hubble time at z ~ 6. In the presence of a sufficiently strong ambient flux of Lyα photons, the hyperfine transition in the warmed H I will be excited. A beam differencing experiment would detect a patchwork of emission, both in frequency and in angle across the sky. This patchwork could serve as a valuable tool for understanding the epoch, nature, and sources of the reionization of the universe, and their implications for cosmology. We demonstrate that isolated QSOs will produce detectable signals at meter wavelengths within their ``spheres of influence'' over which they warm the IGM. As a result of the redshifted 21 cm radiation

  18. In Pursuit of the Thermal State of the IGM at Redshift 20: Radio Foreground Characterization

    NASA Astrophysics Data System (ADS)

    Greenhill, Lincoln J.; LEDA Collaboration

    2014-01-01

    One of the great challenges of cosmology today is tracing the thermal history of the Universe from global reionization back to recombination. The Large Aperture Experiment to Detect the Dark Age (LEDA) will set direct constraints on sky-averaged spectral-line absorption of the Cosmic Microwave Background by neutral Hydrogen in the intergalactic medium at redshift ~ 20. Line intensity, breadth, and center frequency enable hypothesis testing for models of heating during the preceding Dark Age and the epoch at which sustained star formation began. LEDA has begun science observations at the Long Wavelength Array in Owens Valley. I will report initial characterizations of the foreground sky, effectiveness of subtraction, and assessment of how difficult or easy it may be to take the next step: measurement of the angular power spectrum of HI fluctuations just after the end of the Dark Age.

  19. Improving dark energy constraints with high-redshift Type Ia supernovae from CANDELS and CLASH

    NASA Astrophysics Data System (ADS)

    Salzano, Vincenzo; Rodney, Steven A.; Sendra, Irene; Lazkoz, Ruth; Riess, Adam G.; Postman, Marc; Broadhurst, Tom; Coe, Dan

    2013-09-01

    Aims: We investigated the degree of improvement in dark energy constraints that can be achieved by extending Type Ia supernova (SN Ia) samples to redshifts z > 1.5 with the Hubble Space Telescope (HST), particularly in the ongoing Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and the Cluster Lensing and Supernova survey with Hubble (CLASH) multi-cycle treasury programs. Methods: Using the popular Chevalier-Polarski-Linder (CPL) parametrization of the dark energy w = w0 + wa(1 - a) we generated mock SN Ia samples that can be projected out to higher redshifts. The synthetic datasets thus generated were fitted to the CPL model, and we evaluated the improvements that a high-z sample can add to improve the statistical and systematic uncertainties on cosmological parameters. Results: In an optimistic but still very achievable scenario, we find that extending the HST sample beyond CANDELS+CLASH to reach a total of 28 SN Ia at z > 1.0 could improve the uncertainty in the wa parameter σwaby up to 21%. The corresponding improvement in the figure of merit (FoM) would be as high as 28%. Finally, we consider the use of high-redshift SN Ia samples to detect non-cosmological evolution in SN Ia luminosities with redshift, finding that these tests could be undertaken by future space-based infrared surveys using the James Webb Space Telescope (JWST).

  20. 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.

  1. ON THE REDSHIFT OF THE VERY HIGH ENERGY BLAZAR 3C 66A

    SciTech Connect

    Furniss, A.; Williams, D. A.; Fumagalli, M.; Danforth, C.; Prochaska, J. X.

    2013-03-20

    As a bright gamma-ray source, 3C 66A is of great interest to the high-energy astrophysics community, having a potential for placing cosmological constraints on models for the extragalactic background light (EBL) and the processes which contribute to this photon field. No firm spectroscopic redshift measurement has been possible for this blazar due to a lack of intrinsic emission and absorption features in optical spectra. We present new far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph (HST/COS) of the BL Lac object 3C 66A covering the wavelength range 1132-1800 A. The data show a smooth continuum with intergalactic medium absorption features which can be used to place a firm lower limit on the blazar redshift of z {>=} 0.3347. An upper limit is set by statistically treating the non-detection of additional absorbers beyond z = 0.3347, indicating a redshift of less than 0.41 at 99% confidence and ruling out z {>=} 0.444 at 99.9% confidence. We conclude by showing how the redshift limits derived from the COS spectra remove the potential for this gamma-ray emitting blazar to place an upper limit on the flux of the EBL using high energy data from a flare in 2009 October.

  2. Understanding the Physical Conditions in Local Analogs of High-Redshift Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Spiewak, Renée; Erb, Dawn; Tremonti, Christina A.; Berg, Danielle

    2016-01-01

    Observations of strong nebular emission lines in high-redshift galaxies (z~2) can be illuminated through the use of analogous local galaxies (z<0.4), for which many more emission lines can be measured. The observed offset in the "BPT" ([N II]λ6584/Hα vs. [O III]λ5007/Hβ) nebular diagnostic diagram between the locus of high redshift galaxies and that of typical local galaxies indicates a change in the physical conditions of the galaxies with redshift; the cause of this offset is unknown, but it may be associated with the ionization parameter, the hardness of the ionizing spectrum, or the N/O abundance ratio. To study the offset, we have selected a sample of local galaxies from the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey Data Release 12 (SDSS-III/BOSS DR12), which occupies the same space in the [N II]λ6584/Hα vs. [O III]λ5007/Hβ diagnostic diagram as the z~2 sample. Using a suite of >50 different emission lines, most of which are unavailable in analyses of higher redshift galaxies, and a novel method of improving the spectrophotometric calibration of BOSS data, we investigate the metallicity, ionization state, and abundance ratios of this offset sample in order to shed light on the physical conditions in galaxies in the early universe.

  3. Strong magnetic fields in normal galaxies at high redshift

    NASA Astrophysics Data System (ADS)

    Bernet, Martin L.; Miniati, Francesco; Lilly, Simon J.; Kronberg, Philipp P.; Dessauges-Zavadsky, Miroslava

    2008-07-01

    The origin and growth of magnetic fields in galaxies is still something of an enigma. It is generally assumed that seed fields are amplified over time through the dynamo effect, but there are few constraints on the timescale. It was recently demonstrated that field strengths as traced by rotation measures of distant (and hence ancient) quasars are comparable to those seen today, but it was unclear whether the high fields were in the unusual environments of the quasars themselves or distributed along the lines of sight. Here we report high-resolution spectra that demonstrate that the quasars with strong MgII absorption lines are unambiguously associated with larger rotation measures. Because MgII absorption occurs in the haloes of normal galaxies along the sightlines to the quasars, this association requires that organized fields of surprisingly high strengths are associated with normal galaxies when the Universe was only about one-third of its present age.

  4. WERE PROGENITORS OF LOCAL L* GALAXIES Ly{alpha} EMITTERS AT HIGH REDSHIFT?

    SciTech Connect

    Yajima, Hidenobu; Li Yuexing; Zhu Qirong; Gronwall, Caryl; Ciardullo, Robin; Abel, Tom

    2012-08-01

    The Ly{alpha} emission has been observed from galaxies over a redshift span z {approx} 0-8.6. However, the evolution of high-redshift Ly{alpha} emitters (LAEs), and the link between these populations and local galaxies, remains poorly understood. Here, we investigate the Ly{alpha} properties of progenitors of a local L* galaxy by combining cosmological hydrodynamic simulations with three-dimensional radiative transfer calculations using the new ART{sup 2} code. We find that the main progenitor (the most massive one) of a Milky-Way-like galaxy has a number of Ly{alpha} properties close to those of observed LAEs at z {approx} 2-6, but most of the fainter ones appear to fall below the detection limits of current surveys. The Ly{alpha} photon escape fraction depends sensitively on a number of physical properties of the galaxy, such as mass, star formation rate, and metallicity, as well as galaxy morphology and orientation. Moreover, we find that high-redshift LAEs show blueshifted Ly{alpha} line profiles characteristic of gas inflow, and that the Ly{alpha} emission by excitation cooling increases with redshift, and becomes dominant at z {approx}> 6. Our results suggest that some observed LAEs at z {approx} 2-6 with luminosity of L{sub Ly{alpha}} {approx} 10{sup 42}-10{sup 43} erg s{sup -1} may be similar to the main progenitor of the Milky Way at high redshift, and that they may evolve into present-day L* galaxies.

  5. THE POPULATION OF HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI IN THE CHANDRA-COSMOS SURVEY

    SciTech Connect

    Civano, F.; Elvis, M.; Hao, H.; Brusa, M.; Comastri, A.; Zamorani, G.; Gilli, R.; Mignoli, M.; Salvato, M.; Capak, P.; Kakazu, Y.; Masters, D.; Fiore, F.; Ikeda, H.; Kartaltepe, J. S.; Miyaji, T.; Puccetti, S.; Shankar, F.; Silverman, J.; Vignali, C.

    2011-11-10

    We present the high-redshift (3 redshifts plus 20 sources with a formal z{sub phot} < 3 but with a broad photometric redshift probability distribution, such that z{sub phot} + 1{sigma} > 3. Eighty-one sources are selected in the 0.5-2 keV band, fourteen are selected in the 2-10 keV and six in the 0.5-10 keV bands. We sample the high-luminosity (log L{sub (2-10keV)} > 44.15 erg s{sup -1}) space density up to z {approx} 5 and a fainter luminosity range (43.5 erg s{sup -1} < log L{sub (2-10keV)} < 44.15 erg s{sup -1}) than previous studies, up to z = 3.5. We weighted the contribution to the number counts and the space density of the sources with photometric redshift by using their probability of being at z > 3. We find that the space density of high-luminosity AGNs declines exponentially at all the redshifts, confirming the trend observed for optically selected quasars. At lower luminosity, the measured space density is not conclusive, and a larger sample of faint sources is needed. Comparisons with optical luminosity functions and black hole formation models are presented together with prospects for future surveys.

  6. Candidate high-redshift and primeval galaxies in Hubble Deep Field South

    NASA Astrophysics Data System (ADS)

    Clements, D. L.; Eales, S. A.; Baker, A. C.

    1999-09-01

    We present the results of colour selection of candidate high-redshift galaxies in Hubble Deep Field South (HDF-S) using the Lyman dropout scheme. The HDF-S data we discuss were taken in a number of different filters extending from the near-UV (F300W) to the infrared (F222M) in two different fields. This allows us to select candidates with redshifts from z~3 to z~12. We find 15 candidate z~3 objects (F300W dropouts), one candidate z~4 object (F450W dropout) and 16 candidate z~5 objects (F606W dropouts) in the ~4.7-arcmin^2 WFPC-2 field, and four candidate z~6 objects (optical dropouts) and one candidate z~8 object (F110W dropout) in the 0.84-arcmin^2 NICMOS-3 field. No F160W dropouts are found (z~12). We compare our selection technique with existing data for Hubble Deep Field North (HDF-N) and discuss alternative interpretations of the objects. We conclude that there are a number of lower redshift interlopers in the selections, including one previously identified object, and reject those objects most likely to be foreground contaminants. Even after this we conclude that the F606W dropout list is likely to still contain substantial foreground contamination. The lack of candidate very-high-redshift UV-luminous galaxies supports earlier conclusions by Lanzetta et al. We discuss the morphologies and luminosity functions of the high-redshift objects, and their cosmological implications.

  7. High-Redshift Galaxies with the James Webb Space Telescope

    NASA Astrophysics Data System (ADS)

    Gardner, Jonathan P.

    2015-08-01

    The James Webb Space Telescope is the scientific successor to the Hubble and Spitzer Space Telescopes and will continue their rich legacy of high-z galaxy studies with a combination of deep, high-resolution infrared photometry and multi-object or integral field spectroscopy. As a large (6.6m) cold (50K) space telescope, JWST is well optimized for studying high-z galaxies and the science goals include the formation of the first stars and galaxies in the early universe and the chemical, morphological and dynamical buildup of galaxies. Webb has four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Near-Infrared Imager and Slitless Spectrograph will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. The observatory is confirmed for launch into orbit around the second Earth-Sun Lagrange point in 2018; the design is complete and it is in its construction and test phase. It is a partnership of NASA with the European and Canadian Space Agencies. Recent progress includes the completion of the mirrors and scientific instruments and the start of high-level assembly and cryogenic testing. Proposals for the first cycle of scientific observations will be due in February 2018; the community should begin planning their proposals now.

  8. "Observing and Analyzing" Images from a Simulated High-Redshift Universe

    NASA Astrophysics Data System (ADS)

    Morgan, Robert J.; Windhorst, Rogier A.; Scannapieco, Evan; Thacker, Robert J.

    2015-09-01

    We investigate the high-redshift evolution of the rest-frame UV-luminosity function (LF) of galaxies via hydrodynamical cosmological simulations, coupled with an emulated observational astronomy pipeline that provides a direct comparison with observations. We do this by creating mock images and synthetic galaxy catalogs of ≈100 arcmin-2 fields from the numerical model at redshifts ≈4.5 to 10.4. We include the effects of dust extinction and the point-spread function (PSF) for the Hubble WFC3 camera for comparison with space observations. We also include the expected zodiacal background to predict its effect on space observations, including future missions such as the James Webb Space Telescope (JWST). When our model catalogs are fitted to Schechter function parameters, we predict that the faint-end slope (α) of the LF evolves as α = -1.16-0.12z over the redshift range z ≈ 4.5-7.7, in excellent agreement with observations from, e.g., Hathi and coworkers. However, for redshifts z ≈ 6-10.4, α(z) appears to display a shallower evolution, α = -1.79-0.03z. Augmenting the simulations with more detailed physics—specifically stellar winds and supernovae (SN)—produces similar results. The model shows an overproduction of galaxies, especially at faint magnitudes, compared with the observations, although the discrepancy is reduced when dust extinction is taken into account.

  9. The high-redshift star formation history from carbon-monoxide intensity maps

    NASA Astrophysics Data System (ADS)

    Breysse, Patrick C.; Kovetz, Ely D.; Kamionkowski, Marc

    2016-03-01

    We demonstrate how cosmic star formation history can be measured with one-point statistics of carbon-monoxide intensity maps. Using a P(D) analysis, the luminosity function of CO-emitting sources can be inferred from the measured one-point intensity PDF. The star formation rate density (SFRD) can then be obtained, at several redshifts, from the CO luminosity density. We study the effects of instrumental noise, line foregrounds, and target redshift, and obtain constraints on the CO luminosity density of the order of 10 per cent. We show that the SFRD uncertainty is dominated by that of the model connecting CO luminosity and star formation. For pessimistic estimates of this model uncertainty, we obtain an error of the order of 50 per cent on SFRD for surveys targeting redshifts between two and seven with reasonable noise and foregrounds included. However, comparisons between intensity maps and galaxies could substantially reduce this model uncertainty. In this case, our constraints on SFRD at these redshifts improve to roughly 5 - 10 per cent, which is highly competitive with current measurements.

  10. Constraining the minimum luminosity of high redshift galaxies through gravitational lensing

    NASA Astrophysics Data System (ADS)

    Mashian, Natalie; Loeb, Abraham

    2013-12-01

    We simulate the effects of gravitational lensing on the source count of high redshift galaxies as projected to be observed by the Hubble Frontier Fields program and the James Webb Space Telescope (JWST) in the near future. Taking the mass density profile of the lensing object to be the singular isothermal sphere (SIS) or the Navarro-Frenk-White (NFW) profile, we model a lens residing at a redshift of zL = 0.5 and explore the radial dependence of the resulting magnification bias and its variability with the velocity dispersion of the lens, the photometric sensitivity of the instrument, the redshift of the background source population, and the intrinsic maximum absolute magnitude (Mmax) of the sources. We find that gravitational lensing enhances the number of galaxies with redshifts zgtrsim 13 detected in the angular region θE/2 <= θ <= 2θE (where θE is the Einstein angle) by a factor of ~ 3 and 1.5 in the HUDF (df/dν0 ~ 9 nJy) and medium-deep JWST surveys (df/dν0 ~ 6 nJy). Furthermore, we find that even in cases where a negative magnification bias reduces the observed number count of background sources, the lensing effect improves the sensitivity of the count to the intrinsic faint-magnitude cut-off of the Schechter luminosity function. In a field centered on a strong lensing cluster, observations of zgtrsim 6 and zgtrsim 13 galaxies with JWST can be used to infer this cut-off magnitude for values as faint as Mmax ~ -14.4 and -16.1 mag (Lmin ≈ 2.5 × 1026 and 1.2 × 1027 erg s-1 Hz-1) respectively, within the range bracketed by existing theoretical models. Gravitational lensing may therefore offer an effective way of constraining the low-luminosity cut-off of high-redshift galaxies.

  11. Galactic Synchrotron Emission and the Far-infrared–Radio Correlation at High Redshift

    NASA Astrophysics Data System (ADS)

    Schober, J.; Schleicher, D. R. G.; Klessen, R. S.

    2016-08-01

    Theoretical scenarios, including the turbulent small-scale dynamo, predict that strong magnetic fields already exist in young galaxies. Based on the assumption of energy equipartition between magnetic fields and turbulence, we determine the galactic synchrotron flux as a function of redshift z. Galaxies in the early universe are different from local galaxies, in particular, the former have more intense star formation. To cover a large range of conditions, we consider two different systems: one model galaxy comparable to the Milky Way and one typical high-z starburst galaxy. We include a model of the steady-state cosmic ray spectrum and find that synchrotron emission can be detected up to cosmological redshifts with current and future radio telescopes. The turbulent dynamo theory is in agreement with the origin of the observed correlation between the far-infrared (FIR) luminosity L FIR and the radio luminosity L radio. Our model reproduces this correlation well at z = 0. We extrapolate the FIR–radio correlation to higher redshifts and predict a time evolution with a significant deviation from its present-day appearance already at z≈ 2 for a gas density that increases strongly with z. In particular, we predict a decrease of the radio luminosity with redshift which is caused by the increase of cosmic ray energy losses at high z. The result is an increase of the ratio between L FIR and L radio. Simultaneously, we predict that the slope of the FIR–radio correlation becomes shallower with redshift. This behavior of the correlation could be observed in the near future with ultra-deep radio surveys.

  12. The Premature Formation of High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Melia, Fulvio

    2014-05-01

    Observations with WFC3/IR on the Hubble Space Telescope and the use of gravitational lensing techniques have facilitated the discovery of galaxies as far back as z ~ 10-12, a truly remarkable achievement. However, this rapid emergence of high-z galaxies, barely ~200 Myr after the transition from Population III star formation to Population II, appears to be in conflict with the standard view of how the early universe evolved. This problem has much in common with the better known (and probably related) premature appearance of supermassive black holes at z >~ 6. It is difficult to understand how ~109 M ⊙ black holes could have appeared so quickly after the big bang without invoking non-standard accretion physics and the formation of massive seeds, neither of which is seen in the local universe. In earlier work, we showed that the appearance of high-z quasars could instead be understood more reasonably in the context of the R h = ct universe, which does not suffer from the same time compression issues as ΛCDM does at early epochs. Here, we build on that work by demonstrating that the evolutionary growth of primordial galaxies was consistent with the current view of how the first stars formed, but only with the timeline afforded by the R h = ct cosmology. We also show that the growth of high-z quasars was mutually consistent with that of the earliest galaxies, though it is not yet clear whether the former grew from 5-20 M ⊙ seeds created in Population III or Population II supernova explosions.

  13. The premature formation of high-redshift galaxies

    SciTech Connect

    Melia, Fulvio

    2014-05-01

    Observations with WFC3/IR on the Hubble Space Telescope and the use of gravitational lensing techniques have facilitated the discovery of galaxies as far back as z ∼ 10-12, a truly remarkable achievement. However, this rapid emergence of high-z galaxies, barely ∼200 Myr after the transition from Population III star formation to Population II, appears to be in conflict with the standard view of how the early universe evolved. This problem has much in common with the better known (and probably related) premature appearance of supermassive black holes at z ≳ 6. It is difficult to understand how ∼10{sup 9} M {sub ☉} black holes could have appeared so quickly after the big bang without invoking non-standard accretion physics and the formation of massive seeds, neither of which is seen in the local universe. In earlier work, we showed that the appearance of high-z quasars could instead be understood more reasonably in the context of the R {sub h} = ct universe, which does not suffer from the same time compression issues as ΛCDM does at early epochs. Here, we build on that work by demonstrating that the evolutionary growth of primordial galaxies was consistent with the current view of how the first stars formed, but only with the timeline afforded by the R {sub h} = ct cosmology. We also show that the growth of high-z quasars was mutually consistent with that of the earliest galaxies, though it is not yet clear whether the former grew from 5-20 M {sub ☉} seeds created in Population III or Population II supernova explosions.

  14. On the [CII]-SFR Relation in High Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Vallini, L.; Gallerani, S.; Ferrara, A.; Pallottini, A.; Yue, B.

    2015-11-01

    After two Atacama Large Millimeter/submillimeter Array (ALMA) observing cycles, only a handful of [C ii] 158 μm emission line searches in z > 6 galaxies have reported a positive detection, questioning the applicability of the local [C ii]-star formation rate (SFR) relation to high-z systems. To investigate this issue we use the Vallini et al. (V13) model,based on high-resolution, radiative transfer cosmological simulations to predict the [C ii] emission from the interstellar medium of a z ≈ 7 (halo mass Mh = 1.17 × 1011 M⊙) galaxy. We improve the V13 model by including (a) a physically motivated metallicity (Z) distribution of the gas, (b) the contribution of photodissociation regions (PDRs), and (c) the effects of cosmic microwave background (CMB) on the [C ii] line luminosity. We study the relative contribution of diffuse neutral gas to the total [C ii] emission (Fdiff/Ftot) for different SFR and Z values. We find that the [C ii] emission arises predominantly from PDRs: regardless of the galaxy properties, Fdiff/Ftot ≤ 10%, since at these early epochs the CMB temperature approaches the spin temperature of the [C ii] transition in the cold neutral medium (TCMB ˜ {T}s{{CNM}} ˜ 20 K). Our model predicts a high-z [C ii]-SFR relation, consistent with observations of local dwarf galaxies (0.02 < Z/Z⊙ < 0.5). The [C ii] deficit suggested by actual data (LCii < 2.0 × 107 L⊙ in BDF3299 at z ≈ 7.1) if confirmed by deeper ALMA observations, can be ascribed to negative stellar feedback disrupting molecular clouds around star formation sites. The deviation from the local [C ii]-SFR would then imply a modified Kennicutt-Schmidt relation in z > 6 galaxies. Alternatively/in addition, the deficit might be explained by low gas metallicities (Z < 0.1 Z⊙).

  15. A high-redshift quasar absorber without C IV. A galactic outflow caught in the act?

    NASA Astrophysics Data System (ADS)

    Fox, Anne; Richter, Philipp

    2016-04-01

    We present a detailed analysis of a very unusual sub-damped Lyman α (sub-DLA) system at redshift z = 2.304 towards the quasar Q 0453-423, based on high signal-to-noise (S/N), high-resolution spectral data obtained with VLT/UVES. With a neutral hydrogen column density of log N(H i) = 19.23 and a metallicity of -1.61 as indicated by [O i/H i] the sub-DLA mimics the properties of many other optically thick absorbers at this redshift. A very unusual feature of this system is, however, the lack of any C iv absorption at the redshift of the neutral hydrogen absorption, although the relevant spectral region is free of line blends and has very high S/N. Instead, we find high-ion absorption from C iv and O vi in another metal absorber at a velocity more than 220 km s-1 redwards of the neutral gas component. We explore the physical conditions in the two different absorption systems using Cloudy photoionisation models. We find that the weakly ionised absorber is dense and metal-poor while the highly ionised system is thin and more metal-rich. The absorber pair towards Q 0453-423 mimics the expected features of a galactic outflow with highly ionised material that moves away with high radial velocities from a (proto)galactic gas disk in which star-formation takes place. We discuss our findings in the context of C iv absorption line statistics at high redshift and compare our results to recent galactic-wind and outflow models.

  16. PROBING THE PHYSICAL CONDITIONS OF ATOMIC GAS AT HIGH REDSHIFT

    SciTech Connect

    Neeleman, Marcel; Wolfe, Arthur M.; Prochaska, J. Xavier

    2015-02-10

    A new method is used to measure the physical conditions of the gas in damped Lyα systems (DLAs). Using high-resolution absorption spectra of a sample of 80 DLAs, we are able to measure the ratio of the upper and lower fine-structure levels of the ground state of C{sup +} and Si{sup +}. These ratios are determined solely by the physical conditions of the gas. We explore the allowed physical parameter space using a Monte Carlo Markov chain method to constrain simultaneously the temperature, neutral hydrogen density, and electron density of each DLA. The results indicate that at least 5% of all DLAs have the bulk of their gas in a dense, cold phase with typical densities of ∼100 cm{sup –3} and temperatures below 500 K. We further find that the typical pressure of DLAs in our sample is log (P/k{sub B} ) = 3.4 (K cm{sup –3}), which is comparable to the pressure of the local interstellar medium (ISM), and that the components containing the bulk of the neutral gas can be quite small with absorption sizes as small as a few parsecs. We show that the majority of the systems are consistent with having densities significantly higher than expected for a purely canonical warm neutral medium, indicating that significant quantities of dense gas (i.e., n {sub H} > 0.1 cm{sup –3}) are required to match observations. Finally, we identify eight systems with positive detections of Si II*. These systems have pressures (P/k{sub B} ) in excess of 20,000 K cm{sup –3}, which suggest that these systems tag a highly turbulent ISM in young, star-forming galaxies.

  17. Contemporaneous Broadband Observations of Three High-redshift BL LAC Objects

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; An, H.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bonino, R.; Bregeon, J.; Britto, R. J.; Bruel, P.; Buehler, R.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi, J.; Costanza, F.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Di Mauro, M.; Di Venere, L.; Domínguez, A.; Drell, P. S.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Finke, J.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.; Green, D.; Grenier, I. A.; Guiriec, S.; Horan, D.; Jóhannesson, G.; Katsuragawa, M.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill, J.; Maldera, S.; Manfreda, A.; Mayer, M.; Mazziotta, M. N.; Michelson, P. F.; Mirabal, N.; Mitthumsiri, W.; Mizuno, T.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Negro, M.; Nuss, E.; Ohsugi, T.; Okada, C.; Orlando, E.; Paneque, D.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, O.; Rau, A.; Romani, R. W.; Schady, P.; Sgrò, C.; Simone, D.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Stern, D.; Takahashi, H.; Thayer, J. B.; Torres, D. F.; Tosti, G.; Troja, E.; Vianello, G.; Wood, K. S.; Wood, M.

    2016-03-01

    We have collected broadband spectral energy distributions (SEDs) of three BL Lac objects 3FGL J0022.1-1855 (z = 0.689), 3FGL J0630.9-2406 (z\\quad ≳ 1.239), and 3FGL J0811.2-7529 (z = 0.774), detected by Fermi with relatively flat gigaelectronvolt spectra. By observing simultaneously in the near-infrared to hard X-ray band, we can well characterize the high end of the synchrotron component of the SED. Thus, fitting the SEDs to synchro-Compton models of the dominant emission from the relativistic jet, we can constrain the underlying particle properties and predict the shape of the gigaelectronvolt Compton component. Standard extragalactic background light (EBL) models explain the high-energy absorption well, with poorer fits for high-ultraviolet models. The fits show clear evidence for EBL absorption in the Fermi spectrum of our highest-redshift source 3FGL J0630.9-2406. While synchrotron self-Compton models adequately describe the SEDs, the situation may be complicated by possible external Compton components. For 3FGL J0811.2-7529, we also discover a nearby serendipitous source in the X-ray data, which is almost certainly another lower synchrotron peak frequency ({ν }{{pk}}{{sy}}) BL Lac, that may contribute flux in the Fermi band. Since our sources are unusual high-luminosity, moderate {ν }{{pk}}{{sy}} BL Lacs, we compare these quantities and the Compton dominance, the ratio of peak inverse Compton to peak synchrotron luminosities ({L}{{pk}}{{IC}}/{L}{{pk}}{{sy}}), with those of the full Fermi BL Lac population.

  18. Exploring the Web : Galaxy Evolution in High-Redshift Superclusters

    NASA Astrophysics Data System (ADS)

    Lubin, Lori; Fassnacht, Christopher; Gal, Roy; Kocevski, Dale; Lacy, Mark; Lemaux, Brian; Miller, Neal; Squires, Gordon; Surace, Jason

    2008-03-01

    We propose deep IRAC and MIPS mapping of the Cl 1324 supercluster at z = 0.7 which contains 7+ clusters and extends 22 Mpc x 100 Mpc. The supercluster is already the subject of a multi-faceted program including (1) deep r'i'z'JK imaging from the Palomar 5-m and UKIRT 3.8-m to measure optical/near-IR colors, (2) spectroscopy with DEIMOS on the Keck 10-m to measure stellar content and [OII] emission for over 400 supercluster members, and (3) high-angular-resolution Chandra and VLA observations to study the starburst and AGN populations. Based on comparisons with our well-studied (in the optical, mid-IR, radio, and X-ray) and similarly-sized Cl 1604 supercluster at z = 0.9, we find significant evolution over only ~1 Gyr, with substantially smaller contributions from [OII]-emitting and starburst galaxies in the Cl 1324 supercluster. Because dust will severely bias measurements made in the optical, we require 3.6-24 micron observations to measure accurately stellar mass, star formation rate, and nuclear/starburst activity in the member galaxies and determine the true extent of evolution over this timescale. With the combined observations of the Cl 1324 and Cl 1604 superclusters, we have the unique opportunity to constrain the effect of large scale environment on galaxy evolution, the physical mechanisms responsible for fueling starburst and nuclear activity, and the timescales of gas quenching and black-hole accretion.

  19. Jet and torus orientations in high redshift radio galaxies

    NASA Astrophysics Data System (ADS)

    Drouart, G.; De Breuck, C.; Vernet, J.; Laing, R. A.; Seymour, N.; Stern, D.; Haas, M.; Pier, E. A.; Rocca-Volmerange, B.

    2012-12-01

    We examine the relative orientation of radio jets and dusty tori surrounding the active galactic nucleus (AGN) in powerful radio galaxies at z > 1. The radio core dominance R = Pcore^20 GHz/P_extended^500 MHz serves as an orientation indicator, measuring the ratio between the anisotropic Doppler-beamed core emission and the isotropic lobe emission. Assuming a fixed cylindrical geometry for the hot, dusty torus, we derive its inclination i by fitting optically-thick radiative transfer models to spectral energy distributions obtained with the Spitzer Space Telescope. We find a highly significant anti-correlation (p < 0.0001) between R and i in our sample of 35 type 2 AGN combined with a sample of 18 z ~ 1 3CR sources containing both type 1 and 2 AGN. This analysis provides observational evidence both for the Unified scheme of AGN and for the common assumption that radio jets are in general perpendicular to the plane of the torus. The use of inclinations derived from mid-infrared photometry breaks several degeneracies which have been problematic in earlier analyses. We illustrate this by deriving the core Lorentz factor Γ from the R-i anti-correlation, finding Γ ≳ 1.3. Figures 11, 12, and Tables 1, 2, 6 are available in electronic form at http://www.aanda.org

  20. Scale-Free Processes in Galaxy Formation at High Redshift

    NASA Astrophysics Data System (ADS)

    Dekel, Avishai

    2015-08-01

    Key processes of galaxy formation in the Einstein-de Sitter cosmological phase are scale free. For example, 1. The specific accretion rate into dark-matter halos, and that of baryons into the central galaxies, is mass independent and scales as a generic power-law (1+z)^{5/2}. 2. The main-sequence of star-forming galaxies is evolving self-similarly accordingly. Its confinement is determined by generic evolution of galaxies through a sequence of compaction and quenching events. 3. The evolution of the overall gas and stellar content of galaxies can be addressed via a very simple and useful bathtub toy model, which converges to a self-similar quasi-steady-state solution. 4. The spin parameter of the halos, and of the baryons in the galaxy, as built up by streams from the cosmic web, is independent of mass and cosmic time. 5. Counter-rotating streams, self-similar on all scales, may play a major role in generating compaction events and stimulating disk instability. 6. The violent disk instability in the gas-rich high-z galaxies is manifested in a scale-free mass function of clumps. 7. This instability is nonlinear, stimulated by the intense gas inflow into the galaxies, and it may involve scale-free compressive modes of turbulence. These processes are studied using toy models and cosmological simulations.

  1. OUTFLOW AND HOT DUST EMISSION IN HIGH-REDSHIFT QUASARS

    SciTech Connect

    Wang, Huiyuan; Xing, Feijun; Wang, Tinggui; Zhou, Hongyan; Zhang, Kai; Zhang, Shaohua

    2013-10-10

    Correlations of hot dust emission with outflow properties are investigated, based on a large z ∼ 2 non-broad absorption line quasar sample built from the Wide-field Infrared Survey and the Sloan Digital Sky Survey data releases. We use the near-infrared slope and the infrared to UV luminosity ratio to indicate the hot dust emission relative to the emission from the accretion disk. In our luminous quasars, these hot dust emission indicators are almost independent of the fundamental parameters, such as luminosity, Eddington ratio and black hole mass, but moderately dependent on the blueshift and asymmetry index (BAI) and FWHM of C IV lines. Interestingly, the latter two correlations dramatically strengthen with increasing Eddington ratio. We suggest that, in high Eddington ratio quasars, C IV regions are dominated by outflows so the BAI and FWHM (C IV) can reliably reflect the general properties and velocity of outflows, respectively. In low Eddington ratio quasars, on the other hand, C IV lines are primarily emitted by virialized gas so the BAI and FWHM (C IV) become less sensitive to outflows. Therefore, the correlations for the highest Eddington ratio quasars are more likely to represent the true dependence of hot dust emission on outflows and the correlations for the entire sample are significantly diluted by the low Eddington ratio quasars. Our results show that an outflow with a large BAI or velocity can double the hot dust emission on average. We suggest that outflows either contain hot dust in themselves or interact with the dusty interstellar medium or torus.

  2. RED-SEQUENCE GALAXIES AT HIGH REDSHIFT BY THE COMBO-17+4 SURVEY

    SciTech Connect

    Nicol, Marie-Helene; Meisenheimer, Klaus; Wolf, Christian; Tapken, Christian E-mail: meise@mpia.de E-mail: ctapken@aip.de

    2011-01-20

    We investigate the evolution of the galaxy population since redshift 2 with a focus on the color bimodality and mass density of the red sequence. We obtain precise and reliable photometric redshifts up to z = 2 by supplementing the optical survey COMBO-17 with observations in four near-infrared bands on 0.2 deg{sup 2} of the COMBO-17 A901-field. Our results are based on an H-band-selected catalog of 10,692 galaxies complete to H = 21fm7. We measure the rest-frame color (U{sub 280}-V) of each galaxy, which across the redshift range of our interest requires no extrapolation and is robust against moderate redshift errors by staying clear of the 4000 A break. We measure the color-magnitude relation of the red sequence as a function of look-back time from the peak in a color-error-weighted histogram, and thus trace the galaxy bimodality out to z {approx_equal} 1.65. The (U{sub 280}-V) of the red sequence is found to evolve almost linearly with look-back time. At high redshift, we find massive galaxies in both the red and the blue population. Red-sequence galaxies with log M{sub *}/M{sub sun}>11 increase in mass density by a factor of {approx}4 from z {approx} 2 to 1 and remain nearly constant at z < 1. However, some galaxies as massive as log M{sub *}/M{sub sun} = 11.5 are already in place at z {approx} 2.

  3. An empirical model for the galaxy luminosity and star formation rate function at high redshift

    NASA Astrophysics Data System (ADS)

    Mashian, Natalie; Oesch, Pascal A.; Loeb, Abraham

    2016-01-01

    Using the most recent measurements of the ultraviolet (UV) luminosity functions (LFs) and dust estimates of early galaxies, we derive updated dust-corrected star formation rate functions (SFRFs) at z ˜ 4-8, which we model to predict the evolution to higher redshifts, z > 8. We employ abundance matching techniques to calibrate a relation between galaxy star formation rate (SFR) and host halo mass Mh by mapping the shape of the observed SFRFs at z ˜ 4-8 to that of the halo mass function. The resulting scaling law remains roughly constant over this redshift range. We apply the average SFR-Mh relation to reproduce the observed SFR functions at 4 ≲ z ≲ 8 and also derive the expected UV LFs at higher redshifts. At z ˜ 9 and z ˜ 10 these model LFs are in excellent agreement with current observed estimates. Our predicted number densities and UV LFs at z > 10 indicate that James Webb Space Telescope will be able to detect galaxies out to z ˜ 15 with an extensive treasury sized program. We also derive the redshift evolution of the star formation rate density (SFRD) and associated reionization history by galaxies. Models which integrate down to the current HUDF12/XDF detection limit (MUV ˜ -17.7 mag) result in a SFRD that declines as (1 + z)-10.4 ± 0.3 at high redshift and fail to reproduce the observed cosmic microwave background electron scattering optical depth, τ ≃ 0.066, to within 1σ. On the other hand, we find that the inclusion of galaxies with SFRs well below the current detection limit (MUV < -5.7 mag) leads to a fully reionized universe by z ˜ 6.5 and an optical depth of τ ≃ 0.054, consistent with the recently derived Planck value at the 1σ level.

  4. Astrophysical dynamos and the growth of magnetic fields in high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Rieder, Michael; Teyssier, Romain

    2015-08-01

    The origin and evolution of magnetic fields in the Universe is still an open question. Observations of galaxies at high-redshift give evidence for strong galactic magnetic fields even in the early Universe which are consistently measured at later times up to the present age. However, primordial magnetic fields and seed field generation by battery processes cannot explain such high field strengths, suggesting the presence of a rapid growth mechanism in those high-redshift galaxies and subsequent maintenance against decay. Astrophysical dynamo theory provides efficient means of field amplification where even weak initial fields can grow exponentially on sufficiently fast timescales, driving the conversion of kinetic energy into magnetic energy. We investigate the role which feedback mechanisms play in the creation of the turbulence necessary for dynamos to operate. Performing magnetohydrodynamic simulations of cooling halos of dwarf and Milky Way-like high-redshift progenitors, we compare the magnetic field evolution of weak seed fields with various topologies and stellar feedback mechanisms. We find that strong feedback can drive galactic gas turbulence which gives rise to velocity fields with fast exponential magnetic field growth. The simulations display a high gas fraction and a clumpy morphology with kinematics resembling Kolmogorov turbulence and magnetic energy spectra as predicted by Kazantsev dynamo theory. Magnetic fields reach equipartition with $\\mu$G field strength. In a final quiescent phase where feedback is turned off, gas turbulence is reduced and a quadrupole symmetry is observed in the magnetic field. These findings support the theory of rapid magnetic field amplification inside high-redshift galaxies, when the Universe was still young.

  5. The long lives of giant clumps and the birth of outflows in gas-rich galaxies at high redshift

    SciTech Connect

    Bournaud, Frédéric; Renaud, Florent; Daddi, Emanuele; Duc, Pierre-Alain; Elbaz, David; Gabor, Jared M.; Juneau, Stéphanie; Kraljic, Katarina; Le Floch', Emeric; Dekel, Avishai; Elmegreen, Bruce G.; Elmegreen, Debra M.; Teyssier, Romain

    2014-01-01

    Star-forming disk galaxies at high redshift are often subject to violent disk instability, characterized by giant clumps whose fate is yet to be understood. The main question is whether the clumps disrupt within their dynamical timescale (≤50 Myr), like the molecular clouds in today's galaxies, or whether they survive stellar feedback for more than a disk orbital time (≈300 Myr) in which case they can migrate inward and help building the central bulge. We present 3.5-7 pc resolution adaptive mesh refinement simulations of high-redshift disks including photoionization, radiation pressure, and supernovae feedback. Our modeling of radiation pressure determines the mass loading and initial velocity of winds from basic physical principles. We find that the giant clumps produce steady outflow rates comparable to and sometimes somewhat larger than their star formation rate, with velocities largely sufficient to escape the galaxy. The clumps also lose mass, especially old stars, by tidal stripping, and the stellar populations contained in the clumps hence remain relatively young (≤200 Myr), as observed. The clumps survive gaseous outflows and stellar loss, because they are wandering in gas-rich turbulent disks from which they can reaccrete gas at high rates compensating for outflows and tidal stripping, overall keeping realistic and self-regulated gaseous and stellar masses. The outflow and accretion rates have specific timescales of a few 10{sup 8} yr, as opposed to rapid and repeated dispersion and reformation of clumps. Our simulations produce gaseous outflows with velocities, densities, and mass loading consistent with observations, and at the same time suggest that the giant clumps survive for hundreds of Myr and complete their migration to the center of high-redshift galaxies. These long-lived clumps are gas-dominated and contain a moderate mass fraction of stars; they drive inside-out disk evolution, thickening, spheroid growth, and fueling of the central

  6. Hard X-Ray Detection of the High Redshift Quasar 4C 71.07

    NASA Technical Reports Server (NTRS)

    Malizia, A.; Bassani, L.; Dean, A. J.; McCollough, M. L.; Stephen, J. B.; Zhang, S. N.

    1999-01-01

    BATSE/OSSE observations of the high redshift quasar 4C 71.07 indicate that this is the brightest and furthest AGN so far detected 20 keV. BATSE Earth occultation data have been used to search for emission from 4C 71.07 from nearly 3 years of observation. The mean source flux over the- whole period in the BATSE energy range 20-100 keV is (13.2 +/- 1.06) x 10(exp -11) erg/square cm/s corresponding to a luminosity of 2 x 10(exp 48 erg/s. The BATSE light curve over the 3 years of observations shows several flare-like events, one of which (in January 1996) is associated with an optical flare (R=16.1) but with a delay of 55 days. The OSSE/BATSE spectral analysis indicates that the source is characterized by a flat power spectrum (Gamma is approximately 1.1- 1.3) when in a low state: this spectral form is consistent within errors with the ASCA and ROSAT spectra. This means that the power law observed from 0.1 to 10 keV extends up to at least 1 MeV but steepens soon after to meet EGRET high energy data. BATSE data taken around the January 1996 flare suggests that the spectrum could be steeper when the source is in a bright state. The upsilon-F-upsilon representation of the source is typical of a low frequency peaked/ gamma- ray dominated blazar, with the synchrotron peak in the mm-FIR band and the Compton peak in the MeV band. The BATSE and OSSE spectral data seem to favour a model in which the high energy - flux is due to the sum of the synchrotron self-Compton and the external Compton contributions: this is also supported by the- variability behaviour of the source.

  7. What are protoclusters? - Defining high-redshift galaxy clusters and protoclusters

    NASA Astrophysics Data System (ADS)

    Muldrew, Stuart I.; Hatch, Nina A.; Cooke, Elizabeth A.

    2015-09-01

    We explore the structures of protoclusters and their relationship with high-redshift clusters using the Millennium Simulation combined with a semi-analytic model. We find that protoclusters are very extended, with 90 per cent of their mass spread across ˜35 h-1 Mpc comoving at z = 2 ( ˜ 30 arcmin). The `main halo', which can manifest as a high-redshift cluster or group, is only a minor feature of the protocluster, containing less than 20 per cent of all protocluster galaxies at z = 2. Furthermore, many protoclusters do not contain a main halo that is massive enough to be identified as a high-redshift cluster. Protoclusters exist in a range of evolutionary states at high redshift, independent of the mass they will evolve to at z = 0. We show that the evolutionary state of a protocluster can be approximated by the mass ratio of the first and second most massive haloes within the protocluster, and the z = 0 mass of a protocluster can be estimated to within 0.2 dex accuracy if both the mass of the main halo and the evolutionary state are known. We also investigate the biases introduced by only observing star-forming protocluster members within small fields. The star formation rate required for line-emitting galaxies to be detected is typically high, which leads to the artificial loss of low-mass galaxies from the protocluster sample. This effect is stronger for observations of the centre of the protocluster, where the quenched galaxy fraction is higher. This loss of low-mass galaxies, relative to the field, distorts the size of the galaxy overdensity, which in turn can contribute to errors in predicting the z = 0 evolved mass.

  8. 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

  9. Clustering of High Redshift (z>2.9) Quasars from the Sloan Digital Sky Survey

    SciTech Connect

    Shen, Yue; Strauss, Michael A.; Oguri, Masamune; Hennawi, Joseph F.; Fan, Xiaohui; Richards, Gordon T.; Hall, Patrick B.; Schneider, Donald P.; Szalay, Alexander S.; Thakar, Anirudda R.; Berk, Daniel E.Vanden; Anderson, Scott F.; Bahcall, Neta A.; /KIPAC, Menlo Park

    2006-11-30

    We study the two-point correlation function of a uniformly selected sample of 4,428 optically selected luminous quasars with redshift 2.9 {le} z {le} 5.4 selected over 4041 deg{sup 2} from the Fifth Data Release of the Sloan Digital Sky Survey. We fit a power-law to the projected correlation function w{sub p}(r{sub p}) to marginalize over redshift space distortions and redshift errors. For a real-space correlation function of the form {zeta}(r) = (r/r{sub 0}){sup -{gamma}}, the fitted parameters in comoving coordinates are r{sub 0} = 15.2 {+-} 2.7 h{sup -1} Mpc and {gamma} = 2.0 {+-} 0.3, over a scale range 4 {le} r{sub p} {le} 150 h{sup -1} Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their z {approx} 1.5 counterparts, which have a comoving clustering length r{sub 0} {approx} 6.5 h{sup -1} Mpc. Dividing our sample into two redshift bins: 2.9 {le} z {le} 3.5 and z {ge} 3.5, and assuming a power-law index {gamma} = 2.0, we find a correlation length of r{sub 0} = 16.9 {+-} 1.7 h{sup -1} Mpc for the former, and r{sub 0} = 24.3 {+-} 2.4 h{sup -1} Mpc for the latter. Strong clustering at high redshift indicates that quasars are found in very massive, and therefore highly biased, halos. Following Martini & Weinberg, we relate the clustering strength and quasar number density to the quasar lifetimes and duty cycle. Using the Sheth & Tormen halo mass function, the quasar lifetime is estimated to lie in the range 4 {approx} 50 Myr for quasars with 2.9 {le} z {le} 3.5; and 30 {approx} 600 Myr for quasars with z {ge} 3.5. The corresponding duty cycles are 0.004 {approx} 0.05 for the lower redshift bin and 0.03 {approx} 0.6 for the higher redshift bin. The minimum mass of halos in which these quasars reside is 2-3 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with 2.9 {le} z {le} 3.5 and 4-6 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with z {ge} 3.5; the effective bias factor b{sub eff} increases with redshift, e.g., b

  10. Panel Discussion II. Reconciling Observations and Modeling of Star Formation at High Redshifts

    NASA Astrophysics Data System (ADS)

    Knapen, J. H.

    2008-06-01

    This is the written account of the second of two panel discussions, on Reconciling observations and modeling of star formation at high redshifts. The chair of the panel was Pavel Kroupa, and panel members were Marc Balcells, John Beckman, Christopher Conselice, and Joseph Silk. After a short introduction by each of the panelists, panel and audience entered into a lively discussion, centered around the following six themes: the mass function of pre-stellar gas clouds; a possible top-heavy initial mass function at high redshifts versus mini-quasars as the first sources of ionization; the integrated galactic initial mass function; possible differences in specific star formation rates in disks and in massive galaxies; whether merging rates yield a wrong prediction for massive galaxies, and what is the physics behind the onset of the red sequence of galaxies; and the case of dark matter-dominated dwarf galaxies versus tidal dwarf galaxies.

  11. Are globular clusters the natural outcome of regular high-redshift star formation?

    NASA Astrophysics Data System (ADS)

    Kruijssen, J. M. Diederik

    2016-02-01

    We summarise the recent progress in understanding the formation and evolution of globular clusters (GCs) in the context of galaxy formation and evolution. It is discussed that an end-to-end model for GC formation and evolution should capture four different phases: (1) star and cluster formation in the high-pressure interstellar medium of high-redshift galaxies, (2) cluster disruption by tidal shocks in the gas-rich host galaxy disc, (3) cluster migration into the galaxy halo, and (4) the final evaporation-dominated evolution of GCs until the present day. Previous models have mainly focussed on phase 4. We present and discuss a simple model that includes each of these four steps - its key difference with respect to previous work is the simultaneous addition of the high-redshift formation and early evolution of young GCs, as well as their migration into galaxy haloes. The new model provides an excellent match to the observed GC mass spectrum and specific frequency, as well as the relations of GCs to the host dark matter halo mass and supermassive black hole mass. These results show (1) that the properties of present-day GCs are reproduced by assuming that they are the natural outcome of regular high-redshift star formation (i.e. they form according to same physical processes that govern massive cluster formation in the local Universe), and (2) that models only including GC evaporation strongly underestimate their integrated mass loss over a Hubble time.

  12. Resolved properties of high-redshift lensed galaxies seen with MUSE

    NASA Astrophysics Data System (ADS)

    Patricio, Vera; Richard, Johan; Verhamme, Anne; Christensen, Lise; Lagattuta, David; Clément, Benjamin; Mahler, Guillaume

    2015-08-01

    Spatially resolved properties of high redshift galaxies provide important insights into galaxy formation processes. However, with the current instrumentation we have been limited to the analysis of the Lyman alpha line and UV continuum through long-slit observations of individual galaxies or stacking. Combining the power of the newly commissioned integral field spectrograph MUSE on VLT with strong gravitational lensing, it is now possible to spatially probe the rest-frame UV properties of individual high-z galaxies.I will present the study of a 109 M⊙ galaxy at z = 3.5 strongly lensed by the SMACS2031 cluster for which we were able to obtain 2D resolved spatial information of Lyman alpha, and, for the fist time, CIII] emission. The exceptional signal to noise of the data also allows the study of the UV continuum as well as emission and absorption lines rarely measured at these redshifts. We compare the spatial Lyman alpha information and continuum properties with radiative transfer models, resulting in a unique view of an individual high-z galaxy.Additionally, I will present the first results from a sample of 8 high redshift (z = 0.7 - 1.5) extended lensed arcs in the Frontier Fields, also observed with MUSE.With this sample, wederive gas kinematics from both emission and absorption lines, as well as properties of resolved stellar populations.

  13. High resolution frequency analysis techniques with application to the redshift experiment

    NASA Technical Reports Server (NTRS)

    Decher, R.; Teuber, D.

    1975-01-01

    High resolution frequency analysis methods, with application to the gravitational probe redshift experiment, are discussed. For this experiment a resolution of .00001 Hz is required to measure a slowly varying, low frequency signal of approximately 1 Hz. Major building blocks include fast Fourier transform, discrete Fourier transform, Lagrange interpolation, golden section search, and adaptive matched filter technique. Accuracy, resolution, and computer effort of these methods are investigated, including test runs on an IBM 360/65 computer.

  14. 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.

  15. GRB 050502B optical afterglow: a jet-break at high redshift

    NASA Astrophysics Data System (ADS)

    Afonso, P.; Greiner, J.; Pian, E.; Covino, S.; Malesani, D.; Küpcü Yoldaş, A.; Krühler, T.; Clemens, C.; McBreen, S.; Rau, A.; Giannios, D.; Hjorth, J.

    2011-02-01

    Aims: Swift GRB 050502B is well known for the very bright flare displayed in its X-ray light curve. Despite extensive studies, however, the optical light curve has never been discussed and its redshift is unconstrained. Possible correlations between optical and X-ray data are analysed. Methods: Photometric data from TNG in the R and I bands were used to compare the optical afterglow with the X-ray light curve. The HyperZ package and a late-time VLT host observation were used to derive redshift estimates. Results: The I-band afterglow decay followed a power law of index α = 2.1±0.6, after a late break at ~ 1.3×105 s. The R-I colour is remarkably red and the broadband spectral index βOX = 0.9±0.1 is consistent with the X-ray spectral slope βX. Although a photometric redshift of z > 4 is the most conservative result to consider, a photometric redshift of z = 5.2±0.3 is suggested with no extinction in the host, based on which an isotropic energy Eγ,iso = (3.8±0.7)×1052 erg and a jet opening angle θ ~ 3.7° are subsequently derived. Conclusions: The combined X-ray and optical data suggest an achromatic break, which we interpret as a jet-break. The post jet-break slope roughly obeys the closure relation for the jet's slow cooling model. Because of the afterglow's very red colour, in order for the redshift to be low (z < 1), extinction must be significantly high if present in the host. Since the optical-to-X-ray index is consistent with the X-ray spectrum, and there is no XRT evidence for excess NH, GRB 050502B was likely at high redshift. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (programme AOT11-59) and with ESO Telescopes at the La Silla Paranal Observatories under programme ID 177.A-0591.

  16. 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.; Amblard, A.; Auld, R.; Baes, M.; Bonfield, D.; Burgarella, D.; Buttiglione, S.; Cava, A.; Clements, D.; Dariush, A.; deZotti, G.; Dye, S.; Frayer, D.; Fritz, J.; Gonzalez-Nuevo, J.; Herranz, D.

    2010-01-01

    We present measurements of the angular correlation function of galaxies selected from the first field of the H-ATLAS survey. Careful removal of the background from galactic cirrus is essential, and currently dominates the uncertainty in our measurements. For our 250 micrometer-selected sample we detect no significant clustering, consistent with the expectation that the 250 pm-selected sources are mostly normal galaxies at z < or equal to 1. For our 350 micrometer and 500 micrometer-selected samples we detect relatively strong clustering with correlation amplitudes A of 0.2 and 1.2 at 1', but with relatively large uncertainties. For samples which preferentially select high redshift galaxies at z approx. 2-3 we detect significant strong clustering, leading to an estimate of r(0) approx. 7-11/h Mpc. The slope of our clustering measurements is very steep. delta approx. 2. The measurements are consistent with the idea that sub-mm sources consist of a low redshift population of normal galaxies and a high redshift population of highly clustered star-bursting galaxies.

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

    SciTech Connect

    Younger, Joshua D.; Fazio, Giovanni G.; Huang Jiasheng; Ashby, Matthew L. N.; Gurwell, Mark A.; Petitpas, Glen R.; Wilner, David J.; Yun, Min S.; Wilson, Grant W.; Scott, Kimberly S.; Austermann, Jason; Perera, Thushara; Peck, Alison B.; Hughes, David H.; Aretxaga, Itziar; Kim, Sungeun; Lowenthal, James D.

    2009-10-10

    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-including 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.

  18. The High Energy Telescope on EXIST: Hunting High Red-shift GRBs and Other Exotic Transients

    NASA Astrophysics Data System (ADS)

    Hong, JaeSub; Grindlay, J.; Allen, B.; Skinner, G. K.; Finger, M. H.; Jernigan, J. G.; EXIST Team

    2009-01-01

    The current baseline design of the High Energy Telescope (HET) on EXIST will localize high red-shift Gamma-Ray Bursts (GRBs) and other exotic transients fast (<10 sec) and accurately (<17") in order to allow the rapid (<1-2 min) follow-up onboard optical/IR imaging and spectroscopy. HET employs coded-aperture imaging with 5.5m2 CZT detector and a large hybrid tungsten mask (See also Skinner et al. in this meeting). The wide energy band coverage (5-600 keV) is optimal for capturing these transients and highly obscured AGNs. The continuous scan with the wide field of view ( 45 deg radius at 25% coding fraction) increases the chance of capturing rare elusive events such as soft Gamma-ray repeaters and tidal disruption events of stars by dormant supermassive black holes. Sweeping nearly the entire sky every two orbits (3 hour) will also establish a finely-sampled long-term history of the X-ray variability of many X-ray sources, opening up a new time domain of the variability study. In light of the new EXIST design concept, we review the observing strategy to maximize the science return and report the latest development of the CZT detectors for HET.

  19. High redshift signatures in the 21 cm forest due to cosmic string wakes

    NASA Astrophysics Data System (ADS)

    Tashiro, Hiroyuki; Sekiguchi, Toyokazu; Silk, Joseph

    2014-01-01

    Cosmic strings induce minihalo formation in the early universe. The resultant minihalos cluster in string wakes and create a ``21 cm forest'' against the cosmic microwave background (CMB) spectrum. Such a 21 cm forest can contribute to angular fluctuations of redshifted 21 cm signals integrated along the line of sight. We calculate the root-mean-square amplitude of the 21 cm fluctuations due to strings and show that these fluctuations can dominate signals from minihalos due to primordial density fluctuations at high redshift (zgtrsim10), even if the string tension is below the current upper bound, Gμ < 1.5 × 10-7. Our results also predict that the Square Kilometre Array (SKA) can potentially detect the 21 cm fluctuations due to strings with Gμ ≈ 7.5 × 10-8 for the single frequency band case and 4.0 × 10-8 for the multi-frequency band case.

  20. MAGNIFICATION AS A PROBE OF DARK MATTER HALOS AT HIGH REDSHIFTS

    SciTech Connect

    Van Waerbeke, L.; Ford, J.; Milkeraitis, M.; Hildebrandt, H.

    2010-11-01

    We propose a new approach for measuring the mass profile of dark matter halos by stacking the lensing magnification of distant background galaxies behind groups and clusters of galaxies. The main advantage of lensing magnification is that, unlike lensing shear, it relies on accurate photometric redshifts only and not on galaxy shapes, thus enabling the study of the dark matter distribution with unresolved source galaxies. We present a feasibility study, using a real population of z {>=} 2.5 Lyman break galaxies as source galaxies, and where, similar to galaxy-galaxy lensing, foreground lenses are stacked in order to increase the signal-to-noise ratio. We find that there is an interesting new observational window for gravitational lensing as a probe of dark matter halos at high redshift, which does not require a measurement of galaxy shapes.

  1. The Evolution of Metals and Dust in the High-Redshift Universe (z greater than 6)

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2007-01-01

    Dusty hyperluminous galaxies in the early universe provide unique environments for studying the role of massive stars in the formation and destruction of dust. At redshifts above approx. 6, when the universe was less than approx. 1 Gyr old, dust could have only condensed in the explosive ejecta of Type-II supernovae (SNe), since most of the progenitors of the AGB stars, the major alternative source of interstellar dust, did not have time to evolve off the main sequence. I will present analytical models for the evolution of the gas, dust, and metals in high redshift galaxies, with a special application to SDSS J1148+5251, a hyperluminous quasar at $z = 6.4$. I will also discuss possible star formation scenarios consistent with observational constraints on the dust and gas content of this object.

  2. Massive Elliptical Galaxies at High Redshift: NICMOS Imaging of z~1 Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Zirm, Andrew W.; Dickinson, Mark; Dey, Arjun

    2003-03-01

    We present deep, ~1.6 μm, continuum images of 11 high-redshift (0.811high-redshift radio galaxies to lower redshift counterparts. We find that their sizes are similar to those of local FRII radio source hosts and are in general larger than other local galaxies. The derived host galaxy luminosities are very high and lie at the bright end of luminosity functions constructed at similar redshifts. This indicates that the high-redshift radio galaxies are likely rare, massive sources. The galaxies in our sample are also brighter than the rest-frame size-surface-brightness locus defined by the low-redshift sources. Passive evolution roughly aligns the z~1 galaxies with the low-redshift samples with a slope equal to 4.7. This value is intermediate between the canonical Kormendy relation (~3.5) and a constant luminosity line (=5). The optical host is sometimes centered on a local minimum in the rest-frame UV

  3. 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

  4. High-Redshift Clusters form NVSS: The TexOx Cluster (TOC) Survey

    SciTech Connect

    Croft, S; Rawlings, S; Hill, G J

    2003-02-11

    The TexOx Cluster (TOC) Survey uses overdensities of radiosources in the NVSS to trace clusters of galaxies. The links between radiosources and rich environments make this a powerful way to find clusters which may potentially be overlooked by other selection techniques. By including constraints from optical surveys, TOC is an extremely efficient way to find clusters at high redshift. One such field, TOC J0233.3+3021, contains at least one galaxy cluster (at z {approx} 1.4) and has been detected using the Sunyaev-Zel'dovich (SZ) effect. Even in targeted deep optical observations, however, distinguishing the cluster galaxies from the background is difficult, especially given the tendency of TOC to select fields containing multiple structures at different redshifts.

  5. High redshift signatures in the 21 cm forest due to cosmic string wakes

    SciTech Connect

    Tashiro, Hiroyuki; Sekiguchi, Toyokazu; Silk, Joseph E-mail: toyokazu.sekiguchi@nagoya-u.jp

    2014-01-01

    Cosmic strings induce minihalo formation in the early universe. The resultant minihalos cluster in string wakes and create a ''21 cm forest'' against the cosmic microwave background (CMB) spectrum. Such a 21 cm forest can contribute to angular fluctuations of redshifted 21 cm signals integrated along the line of sight. We calculate the root-mean-square amplitude of the 21 cm fluctuations due to strings and show that these fluctuations can dominate signals from minihalos due to primordial density fluctuations at high redshift (z∼>10), even if the string tension is below the current upper bound, Gμ < 1.5 × 10{sup −7}. Our results also predict that the Square Kilometre Array (SKA) can potentially detect the 21 cm fluctuations due to strings with Gμ ≈ 7.5 × 10{sup −8} for the single frequency band case and 4.0 × 10{sup −8} for the multi-frequency band case.

  6. 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

  7. Using Bayesian Evidence to Deduce the Dust-Attenuation Law at High Redshift

    NASA Astrophysics Data System (ADS)

    Salmon, Brett W.; Papovich, Casey J.; Finkelstein, Steven L.; Closson Ferguson, Henry; Long, James; CANDELS

    2016-01-01

    Although the nature of dust attenuation affects nearly all aspects of galaxy evolution, very little is known about the form of the dust-attenuation law in the distant Universe. Dust enshrouds and obscures UV star formation, convoluting our understanding of galaxy evolution at high redshift. Recent literature has recognized how the inferred physical properties of distant galaxies can be influenced by the non-universality of their attenuation curve shape. In this talk, I will present a Bayesian method to quantitatively constrain the dust-attenuation curve in high-redshift star-forming galaxies. This method is tested on galaxies at z~2 where we have CANDELS UV-to-optical photometry and Spitzer/Herschel IR luminosities. We find that the dust law implied from using only UV/optical data to calculate the full posterior probability densities supports the observed IR luminosities as predicted by that dust law. This method shows promise to deduce the shape of the attenuation curve at higher redshifts (z>4), as supported by our experiments using mock data from a semi-analytic model with qualities like those of the CANDELS GOODS fields.

  8. Dust Formation, Evolution, and Obscuration Effects in the Very High-Redshift Universe

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Staguhn, Johannes; Arendt, Richard G.; Kovacks, 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-togas 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.

  9. A critical analysis of high-redshift, massive, galaxy clusters. Part I

    SciTech Connect

    Hoyle, Ben; Jimenez, Raul; Verde, Licia; Hotchkiss, Shaun E-mail: licia.verde@icc.ub.edu E-mail: shaun.hotchkiss@helsinki.fi

    2012-02-01

    We critically investigate current statistical tests applied to high redshift clusters of galaxies in order to test the standard cosmological model and describe their range of validity. We carefully compare a sample of high-redshift, massive, galaxy clusters with realistic Poisson sample simulations of the theoretical mass function, which include the effect of Eddington bias. We compare the observations and simulations using the following statistical tests: the distributions of ensemble and individual existence probabilities (in the > M, > z sense), the redshift distributions, and the 2d Kolmogorov-Smirnov test. Using seemingly rare clusters from Hoyle et al. (2011), and Jee et al. (2011) and assuming the same survey geometry as in Jee et al. (2011, which is less conservative than Hoyle et al. 2011), we find that the ( > M, > z) existence probabilities of all clusters are fully consistent with ΛCDM. However assuming the same survey geometry, we use the 2d K-S test probability to show that the observed clusters are not consistent with being the least probable clusters from simulations at > 95% confidence, and are also not consistent with being a random selection of clusters, which may be caused by the non-trivial selection function and survey geometry. Tension can be removed if we examine only a X-ray selected sub sample, with simulations performed assuming a modified survey geometry.

  10. DUST FORMATION, EVOLUTION, AND OBSCURATION EFFECTS IN THE VERY HIGH-REDSHIFT UNIVERSE

    SciTech Connect

    Dwek, Eli; Benford, Dominic J.; Staguhn, Johannes; Su, Ting; Arendt, Richard G.; Kovacks, Attila

    2014-06-20

    The evolution of dust at redshifts z ≳ 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 compared 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 galaxy's photometric redshift. In this Letter we demonstrate these effects by analyzing the spectral energy distribution of MACS1149-JD, a lensed galaxy at z = 9.6. A potential 2 mm 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.

  11. Distance Estimates for High Redshift Clusters SZ and X-Ray Measurements

    NASA Technical Reports Server (NTRS)

    Joy, Marshall K.

    1999-01-01

    I present interferometric images of the Sunyaev-Zel'dovich effect for the high redshift (z $ greater than $ 0.5) galaxy clusters in the \\emph(Einstein) Medium Sensitivity Survey: MS0451.5-0305 (z = 0.54), MS0015.9+1609 (z = 0.55), MS2053.7-0449 (z = 0.58), MS1 137.5+6625 (z = 0.78), and MS 1054.5-0321 (z = 0.83). Isothermal $\\beta$ models are applied to the data to determine the magnitude of the Sunyaev-Zel'dovich (S-Z) decrement in each cluster. Complementary ROSAT PSPC and HRI x-ray data are also analyzed, and are combined with the S-Z data to generate an independent estimate of the cluster distance. Since the Sunyaev-Zel'dovich Effect is invariant with redshift, sensitive S-Z imaging can provide an independent determination of the size, shape, density, and distance of high redshift galaxy clusters; we will discuss current systematic uncertainties with this approach, as well as future observations which will yield stronger constraints.

  12. GISMO, a 2 mm Bolometer Camera Optimized for the Study of High Redshift Galaxies

    NASA Technical Reports Server (NTRS)

    Staguhn, J.

    2007-01-01

    The 2mm spectral range provides a unique terrestrial window enabling ground based observations of the earliest active dusty galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. We present a progress report for our bolometer camera GISMO (the Goddard-IRAM Superconducting 2-Millimeter Observer), which will obtain large and sensitive sky maps at this wavelength. The instrument will be used at the IRAM 30 m telescope and we expect to install it at the telescope in 2007. The camera uses an 8 x 16 planar array of multiplexed TES bolometers, which incorporates our recently designed Backshort Under Grid (BUG) architecture. GISMO will be very efficient at detecting sources serendipitously in large sky surveys. With the background limited performance of the detectors, the camera provides significantly greater imaging sensitivity and mapping speed at this wavelength than has previously been possible. The major scientific driver for the instrument is to provide the IRAM 30 m telescope with the capability to rapidly observe galactic and extragalactic dust emission, in particular from high-zeta ULI RGs and quasar s, even in the summer season. The instrument will fill in the SEDs of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. Our source count models predict that GISMO will serendipitously detect one galaxy every four hours on the blank sky, and that one quarter of these galaxies will be at a redshift of zeta 6.5.

  13. An Increasing Stellar Baryon Fraction in Bright Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Finkelstein, Steven L.; Song, Mimi; Behroozi, Peter; Somerville, Rachel S.; Papovich, Casey; Milosavljević, Miloš; Dekel, Avishai; Narayanan, Desika; Ashby, Matthew L. N.; Cooray, Asantha; Fazio, Giovanni G.; Ferguson, Henry C.; Koekemoer, Anton M.; Salmon, Brett; Willner, S. P.

    2015-12-01

    Recent observations have shown that the characteristic luminosity of the rest-frame ultraviolet (UV) luminosity function does not significantly evolve at 4 < z < 7 and is approximately {M}{UV}*˜ -21. We investigate this apparent non-evolution by examining a sample of 173 bright, MUV < -21 galaxies at z = 4-7, analyzing their stellar populations and host halo masses. Including deep Spitzer/IRAC imaging to constrain the rest-frame optical light, we find that {M}{UV}* galaxies at z = 4-7 have similar stellar masses of log(M/M⊙) = 9.6-9.9 and are thus relatively massive for these high redshifts. However, bright galaxies at z = 4-7 are less massive and have younger inferred ages than similarly bright galaxies at z = 2-3, even though the two populations have similar star formation rates and levels of dust attenuation for a fixed dust-attenuation curve. Matching the abundances of these bright z = 4-7 galaxies to halo mass functions from the Bolshoi ΛCDM simulation implies that the typical halo masses in ˜ {M}{{UV}}* galaxies decrease from log(Mh/M⊙) = 11.9 at z = 4 to log(Mh/M⊙) = 11.4 at z = 7. Thus, although we are studying galaxies at a similar stellar mass across multiple redshifts, these galaxies live in lower mass halos at higher redshift. The stellar baryon fraction in ˜ {M}{{UV}}* galaxies in units of the cosmic mean Ωb/Ωm rises from 5.1% at z = 4 to 11.7% at z = 7; this evolution is significant at the ˜3σ level. This rise does not agree with simple expectations of how galaxies grow, and implies that some effect, perhaps a diminishing efficiency of feedback, is allowing a higher fraction of available baryons to be converted into stars at high redshifts.

  14. Harnessing High Redshift Beacons: IRS Spectra of Lensed Lyman Break Galaxies

    NASA Astrophysics Data System (ADS)

    Siana, Brian; Coppin, Kristen; Ebeling, Harald; Edge, Alastair; Ellis, Richard; Kneib, Jean-Paul; Pettini, Max; Richard, Johan; Smail, Ian; Swinbank, Mark; Teplitz, Harry

    2007-05-01

    Star-formation at high redshift occurs in two types of galaxies: dusty Ultra-Luminous Infrared Galaxies (ULIRGs) and UV-bright Lyman Break Galaxies (LBGs). In both populations dust absorbs most of the ultraviolet (UV) light from young stars and re-emits the energy in the infrared (IR). Therefore, detailed studies of the dust and the infrared SEDs of these galaxies are critical for understanding these important evolutionary stages in galaxy formation. ULIRGs at z ~ 2-3 are luminous enough for both submm detection and Spitzer IRS spectroscopy, so much has been learned recently about their interstellar medium and IR SEDs. LBGs are too faint to be detected with submm imaging or IRS spectroscopy so little can be discovered about their dust content and IR SEDs prior to JWST and ALMA. Fortunately, there exist a few rare examples of LBGs which are strongly lensed by a foreground cluster or galaxy, and are magnified by factors of 10-30. We can therefore study in detail the infrared properties of this otherwise inaccessible population. Our group will obtain (in an approved Cycle-3 program) IRS spectroscopy of the most famous LBG, cB58, but it is clearly dangerous to draw wide-ranging conclusions about the LBG population based on this single object. We therefore propose for a detailed Spitzer study of the only other known bright lensed LBGs: the 'Cosmic Eye' and the '8-O'clock Arc'. The requested program uses IRS spectroscopy, IRS Peak-Up 16 micron, MIPS 70 micron, and IRAC imaging to fully characterize the gas and dust in the ISM of these galaxies and determine the shape of the IR SEDs. Together, the three lensed sources span the full range of star-formation rates and dust attenuation levels observed in LBGs. Therefore, we can correlate these properties with the infrared SEDs and emission-line properties (PAHs) and apply the correlations when examining the entire LBG population.

  15. Dark bubbles around high-redshift radio-loud active galactic nucleus

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Sbarrato, T.

    2016-09-01

    At redshift larger than 3 there is a disagreement between the number of blazars (whose jet is pointing at us) and the number of expected parents (whose jet is pointing elsewhere). Now we strengthen this claim because (i) the number of blazars identified within the Sloan Digital Sky Survey (SDSS)+Faint Images of the Radio Sky at Twenty-cm (FIRST) survey footprint increased, demanding a more numerous parent population, and (ii) the detected blazars have a radio flux large enough to be above the FIRST flux limit even if the jet is slightly misaligned. The foreseen number of these slightly misaligned jets, in principle detectable, is much larger than the radio-detected sources in the FIRST+SDSS survey (at redshift larger than 4). This argument is independent of the presence of an isotropic radio component, such as the hotspot or the radio lobe, and does not depend on the bulk Lorentz factor Γ. We propose a scenario that ascribes the lack of slightly misaligned sources to an overobscuration of the nucleus by a `bubble' of dust, possibly typical of the first high-redshift quasars.

  16. CO Observations of the High Redshift Radio Galaxy 53W002

    NASA Astrophysics Data System (ADS)

    Yamada, Toru; Ohta, Kouji; Tomita, Akihiko; Takata, Tadafumi

    1995-10-01

    We observed a high redshift radio galaxy 53W002 at z =2.390 with the Nobeyama 45 m telescope aiming at a detection of a redshifted ^12^CO (J=1-0) emission line. The galaxy was discovered in the Leiden Berkeley Deep Survey and is known to have a blue SED and is a candidate for a genuinely young galaxy. We detected a weak (-5 mJy) emission-line feature at z = 2.392; the feature was significant in our November 1993 observations and marginally confirmed in the follow-up observations held in December 1993 and February 1994. If the detected emission-line feature is really a redshifted CO emission line associated with 53W002, its luminosity is 1.2 x 10^11^ h^-2^ K km s^-1^ pc^2^ (q_0_ = 0.5), or M(H_2_) ~ 5 x 10^11^ h^-2^ M_sun_, adopting the galactic CO-to-H_2_ conversion factor.

  17. The accelerated build-up of the red sequence in high-redshift galaxy clusters

    NASA Astrophysics Data System (ADS)

    Cerulo, P.; Couch, W. J.; Lidman, C.; Demarco, R.; Huertas-Company, M.; Mei, S.; Sánchez-Janssen, R.; Barrientos, L. F.; Muñoz, R. P.

    2016-04-01

    We analyse the evolution of the red sequence in a sample of galaxy clusters at redshifts 0.8 < z < 1.5 taken from the HAWK-I Cluster Survey (HCS). The comparison with the low-redshift (0.04 < z < 0.08) sample of the WIde-field Nearby Galaxy-cluster Survey (WINGS) and other literature results shows that the slope and intrinsic scatter of the cluster red sequence have undergone little evolution since z = 1.5. We find that the luminous-to-faint ratio and the slope of the faint end of the luminosity distribution of the HCS red sequence are consistent with those measured in WINGS, implying that there is no deficit of red galaxies at magnitudes fainter than M_V^{ast } at high redshifts. We find that the most massive HCS clusters host a population of bright red sequence galaxies at MV < -22.0 mag, which are not observed in low-mass clusters. Interestingly, we also note the presence of a population of very bright (MV < -23.0 mag) and massive (log (M*/M⊙) > 11.5) red sequence galaxies in the WINGS clusters, which do not include only the brightest cluster galaxies and which are not present in the HCS clusters, suggesting that they formed at epochs later than z = 0.8. The comparison with the luminosity distribution of a sample of passive red sequence galaxies drawn from the COSMOS/UltraVISTA field in the photometric redshift range 0.8 < zphot < 1.5 shows that the red sequence in clusters is more developed at the faint end, suggesting that halo mass plays an important role in setting the time-scales for the build-up of the red sequence.

  18. Evolution of neutral gas at high redshift: implications for the epoch of galaxy formation

    NASA Astrophysics Data System (ADS)

    Storrie-Lombardi, L. J.; McMahon, R. G.; Irwin, M. J.

    1996-12-01

    Although observationally rare, damped Lyalpha absorption systems dominate the mass density of neutral gas in the Universe. 11 high-redshift damped Lyalpha systems covering 2.8<=z<=4.4 were discovered in 26 QSOs from the APMz<~4 QSO survey, extending these absorption system surveys to the highest redshifts currently possible. Combining our new data set with previous surveys, we find that the cosmological mass density in neutral gas, Omega_g, does not rise as steeply prior to z~2 as indicated by previous studies. There is evidence in the observed Omega_g for a flattening at z~2 and a possible turnover at z~3. When combined with the decline at z<~3.5 in number density per unit redshift of damped systems with column densities log N_HI>=21 atom cm^-2, these results point to an epoch at z>~3 prior to which the highest column density damped systems are still forming. We find that, over the redshift range 2

  19. Can Life Survive Gamma-Ray Bursts in the High-redshift Universe?

    NASA Astrophysics Data System (ADS)

    Li, Ye; Zhang, Bing

    2015-09-01

    Nearby gamma-ray bursts (GRBs) have been proposed as a possible cause of mass extinctions on Earth. Due to the higher event rate of GRBs at higher redshifts, it has been speculated that life as we know it may not survive above a certain redshift (e.g., z\\gt 0.5). We examine the duty cycle of lethal (life-threatening) GRBs in the solar neighborhood, in the Sloan Digital Sky Survey (SDSS) galaxies, and GRB host galaxies, with the dependence of the long GRB rate on star formation and metallicity properly taken into account. We find that the number of lethal GRBs attacking Earth within the past 500 Myr (∼epoch of the Ordovician mass extinction) is 0.93. The number of lethal GRBs hitting a certain planet increases with redshift, as a result of the increasing star formation rate (SFR) and decreasing metallicity in high-z galaxies. Taking 1 per 500 Myr as a conservative duty cycle for life to survive, as evidenced by our existence, we find that there is still a good fraction of SDSS galaxies beyond z=0.5 where the GRB rate at half-mass radius is lower than this value. We derive the fraction of such benign galaxies as a function of redshift through Monte Carlo simulations, and we find that the fraction is ∼ 50% at z∼ 1.5 and ∼ 10% even at z∼ 3. The mass distribution of benign galaxies is dominated by Milky Way–like ones, due to their commonness, relatively large mass, and low SFR. GRB host galaxies are among the most dangerous ones.

  20. How absorption selected galaxies trace the general high-redshift galaxy population

    NASA Astrophysics Data System (ADS)

    Christensen, Lise

    2015-08-01

    Strong absorption lines seen in quasar spectra arise when the lines of sight to the quasars intersect intervening galaxies. The associated metal absorption lines from the strongest absorption lines, the damped Lyman alpha absorbers (DLAs), allow us to trace the metallicity of galaxies back to redshifts z>5. Typical metallicities range from 0.1-100% solar metallicities with a huge scatter at any given redshift. Understanding the nature of galaxies that host DLAs is one strategy to probe the early phase and origin of stars in the outskirts of present-day galaxy disks.The search for emission from the elusive high-redshift DLA galaxies has reached a mature state now that we have determined how to best identify the absorbing galaxies. From a growing number of emission-line detections from DLA galaxies at redshifts ranging between 0.1 and 3, we can analyse galaxies in both absorption and emission, and probe the gas-phase metallicities in the outskirts and halos of the galaxies.By combining information for galaxies seen in emission and absorption, I will show that there is a relation between DLA metallicities and the host galaxy luminosities similar to the well-known the mass-metallicity relation for luminosity selected galaxies. This implies that DLA galaxies are drawn from the general population of low- to intermediate mass galaxies. We can determine a metallicity gradient in the extended halo of the galaxies out to ~40 kpc, and this allows us to reproduce observed galaxy correlation functions derived from conventional samples of luminosity selected galaxies.

  1. LOW MASSES AND HIGH REDSHIFTS: THE EVOLUTION OF THE MASS-METALLICITY RELATION

    SciTech Connect

    Henry, Alaina; Straughn, Amber; Scarlata, Claudia; Bedregal, Alejandro G.; Domínguez, Alberto; Siana, Brian; Masters, Daniel; Malkan, Matthew; Ross, Nathaniel; Martin, Crystal L.; Atek, Hakim; Colbert, James W.; Rafelski, Marc; Teplitz, Harry; Bunker, Andrew J.; Dressler, Alan; Hathi, Nimish; McCarthy, Patrick

    2013-10-20

    We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 10{sup 8} ∼< M/M {sub ☉} ∼< 10{sup 10}, obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 ∼< z ∼< 2.3. For these redshifts, infrared grism spectroscopy with the Hubble Space Telescope Wide Field Camera 3 is sensitive to the R {sub 23} metallicity diagnostic: ([O II] λλ3726, 3729 + [O III] λλ4959, 5007)/Hβ. Using spectra stacked in four mass quartiles, we find a MZ relation that declines significantly with decreasing mass, extending from 12+log(O/H) = 8.8 at M = 10{sup 9.8} M {sub ☉}, to 12+log(O/H) = 8.2 at M = 10{sup 8.2} M {sub ☉}. After correcting for systematic offsets between metallicity indicators, we compare our MZ relation to measurements from the stacked spectra of galaxies with M ∼> 10{sup 9.5} M {sub ☉} and z ∼ 2.3. Within the statistical uncertainties, our MZ relation agrees with the z ∼ 2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift (z = 1.76) of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M {sub *} relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high star formation rates (SFRs). Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation.

  2. Imaging the host galaxies of high-redshift radio-quiet QSOs

    NASA Technical Reports Server (NTRS)

    Lowenthal, James D.; Heckman, Timothy M.; Lehnert, Matthew, D.; Elias, J. H.

    1995-01-01

    We present new deep K-band and optical images of four radio-quiet QSOs at z approximately = 1 and six radio-quiet QSOs at z approximately = 2.5, as well as optical images only of six more at z approximately = 2.5. We have examined the images carefully for evidence of extended 'fuzz' from any putative QSO host galaxy. None of the z approximately = 2.5 QSOs shows any extended emission, and only two of the z approximately = 1 QSOs show marginal evidence for extended emission. Our 3 sigma detection limits in the K images, m(sub K) approximately = 21 for an isolated source, would correspond approximately to an unevolved L(sup star) elliptical galaxy at z = 2.5 or 2-3 mag fainter than an L(sup star) elliptical at z = 1, although our limits on host galaxy light are weaker than this due to the difficulty of separating galaxy light from QSO light. We simulate simple models of disk and elliptical host galaxies, and find that the marginal emission around the two z approximately = 1 QSOs can be explained by disks or bulges that are approximately 1-2 mag brighter than an unevolved L(sup star) galaxy in one case and approximately 1.5-2.5 mag brighter than L(sub star) in the other. For two other z approximately = 1 QSOs, we have only upper limits (L approximately = L(sup star)). The hosts of the high-redshift sample must be no brighter than about 3 mag above an unevolved L(sup star) galaxy, and are at least 1 magnitude fainter than the hosts of radio-loud QSOs at the same redshift. If the easily detected K-band light surrounding a previous sample of otherwise similar but radio-loud QSOs is starlight, then it must evolve on timescales of greater than or approximately equal to 10(exp 8) yr (e.g., Chambers & Charlot 1990); therefore our non-detection of host galaxy fuzz around radio-quiet QSOs supports the view that high-redshift radio-quiet and radio-loud QSOs inhabit different host objects, rather than being single types of objects that turn their radio emission on and off over

  3. 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; Ross, Nathaniel; Teplitz, Harry; Bunker, Andrew J.; Dressler, Alan; Hathi, Nimish; Masters, Daniel; McCarthy, Patrick; Straughn, Amber

    2013-01-01

    We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 10(exp 8) < M/Stellar Mass < or approx. 10(exp 10), obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 < or approx. z < or approx. 2.3. For these redshifts, infrared grism spectroscopy with the Hubble Space Telescope Wide Field Camera 3 is sensitive to the R23 metallicity diagnostic: ([O II] (lambda)(lambda)3726, 3729 + [OIII] (lambda)(lambda)4959, 5007)/H(beta). Using spectra stacked in four mass quartiles, we find a MZ relation that declines significantly with decreasing mass, extending from 12+log(O/H) = 8.8 at M = 10(exp 9.8) Stellar Mass to 12+log(O/H)= 8.2 at M = 10(exp 8.2) Stellar Mass. After correcting for systematic offsets between metallicity indicators, we compare our MZ relation to measurements from the stacked spectra of galaxies with M > or approx. 10(exp 9.5) Stellar Mass and z approx. 2.3. Within the statistical uncertainties, our MZ relation agrees with the z approx. 2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift (z = 1.76) of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M* relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high star formation rates (SFRs). Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation.

  4. Constraining the minimum luminosity of high redshift galaxies through gravitational lensing

    SciTech Connect

    Mashian, Natalie; Loeb, Abraham E-mail: aloeb@cfa.harvard.edu

    2013-12-01

    We simulate the effects of gravitational lensing on the source count of high redshift galaxies as projected to be observed by the Hubble Frontier Fields program and the James Webb Space Telescope (JWST) in the near future. Taking the mass density profile of the lensing object to be the singular isothermal sphere (SIS) or the Navarro-Frenk-White (NFW) profile, we model a lens residing at a redshift of z{sub L} = 0.5 and explore the radial dependence of the resulting magnification bias and its variability with the velocity dispersion of the lens, the photometric sensitivity of the instrument, the redshift of the background source population, and the intrinsic maximum absolute magnitude (M{sub max}) of the sources. We find that gravitational lensing enhances the number of galaxies with redshifts z∼> 13 detected in the angular region θ{sub E}/2 ≤ θ ≤ 2θ{sub E} (where θ{sub E} is the Einstein angle) by a factor of ∼ 3 and 1.5 in the HUDF (df/dν{sub 0} ∼ 9 nJy) and medium-deep JWST surveys (df/dν{sub 0} ∼ 6 nJy). Furthermore, we find that even in cases where a negative magnification bias reduces the observed number count of background sources, the lensing effect improves the sensitivity of the count to the intrinsic faint-magnitude cut-off of the Schechter luminosity function. In a field centered on a strong lensing cluster, observations of z∼> 6 and z∼> 13 galaxies with JWST can be used to infer this cut-off magnitude for values as faint as M{sub max} ∼ -14.4 and -16.1 mag (L{sub min} ≈ 2.5 × 10{sup 26} and 1.2 × 10{sup 27} erg s{sup −1} Hz{sup −1}) respectively, within the range bracketed by existing theoretical models. Gravitational lensing may therefore offer an effective way of constraining the low-luminosity cut-off of high-redshift galaxies.

  5. Scheduled discoveries of 7+ high-Redshift supernovae: First cosmology results and bounds on q{sub 0}

    SciTech Connect

    Perlmutter, S., FNAL

    1998-09-01

    Our search for high-redshift Type Ia supernovae discovered, in its first years, a sample of seven supernovae. Using a ``batch`` search strategy, almost all were discovered before maximum light and were observed over the peak of their light curves. The spectra and light curves indicate that almost all were Type Ia supernovae at redshifts z = 0.35 - 0.5. These high-redshift supernovae can provide a distance indicator and ``standard clock`` to study the cosmological parameters q{sub 0} , {Lambda}, {Omega}{sub 0} , and H{sub 0}. This presentation and the following presentations of Kim et al. (1996), Goldhaber et al. (1996), and Pain et al. (1996) will discuss observation strategies and rates, analysis and calibration issues, the sources of measurement uncertainty, and the cosmological implications, including bounds on q{sub 0} , of these first high-redshift supernovae from our ongoing search.

  6. Modeling high-redshift galaxies: what can we learn from high and ultra-high resolution hydrodynamical simulations?

    NASA Astrophysics Data System (ADS)

    Devriendt, J.; Slyz, A.; Powell, L.; Pichon, C.; Teyssier, R.

    2010-04-01

    We present results from a high resolution cosmological galaxy formation simulation called Mare Nostrum and a ultra-high resimulation of the first 500 million years of a single, Milky Way (MW) sized galaxy. Using the cosmological run, we measure UV luminosity functions and assess their sensitivity to both cosmological parameters and dust extinction. We find remarkably good agreement with the existing data over the redshift range 4 < z < 7 provided we adopt the favoured cosmology (WMAP 5 year parameters) and a self-consistent treatment of the dust. Cranking up the resolution, we then study in detail a z = 9 protogalaxy sitting at the intersection of cold gas filaments. This high-z MW progenitor grows a dense, rapidly spinning, thin disk which undergoes gravitational fragmention. Star formation in the resulting gas clumps rapidly turns them into globular clusters. A far reaching galactic wind develops, co-powered by the protogalaxy and its cohort of smaller companions populating the filaments. Despite such an impressive blow out, the smooth filamentary material is hardly affected at these redshifts.

  7. A New Determination of the High Redshift Type Ia Supernova Rateswith the Hubble Space Telescope Advanced Camera for Surveys

    SciTech Connect

    Kuznetsova, N.; Barbary, K.; Connolly, B.; Kim, A.G.; Pain, R.; Roe, N.A.; Aldering, G.; Amanullah, R.; Dawson, K.; Doi, M.; Fadeyev, V.; Fruchter, A.S.; Gibbons, R.; Goldhaber, G.; Goober, A.; Gude, A.; Knop,R.A.; Kowalski, M.; Lidman, C.; Morokuma, T.; Meyers, J.; Perlmutter, S.; Rubin, D.; Schlegel, D.J.; Spadafora, A.L.; Stanishev, V.; Strovink, M.; Suzuki, N.; Wang, L.; Yasuda, N.

    2007-10-01

    We present a new measurement of the volumetric rate of Type Ia supernova up to a redshift of 1.7, using the Hubble Space Telescope (HST) GOODS data combined with an additional HST dataset covering the North GOODS field collected in 2004. We employ a novel technique that does not require spectroscopic data for identifying Type Ia supernovae (although spectroscopic measurements of redshifts are used for over half the sample); instead we employ a Bayesian approach using only photometric data to calculate the probability that an object is a Type Ia supernova. This Bayesian technique can easily be modified to incorporate improved priors on supernova properties, and it is well-suited for future high-statistics supernovae searches in which spectroscopic follow up of all candidates will be impractical. Here, the method is validated on both ground- and space-based supernova data having some spectroscopic follow up. We combine our volumetric rate measurements with low redshift supernova data, and fit to a number of possible models for the evolution of the Type Ia supernova rate as a function of redshift. The data do not distinguish between a flat rate at redshift > 0.5 and a previously proposed model, in which the Type Ia rate peaks at redshift {approx} 1 due to a significant delay from star-formation to the supernova explosion. Except for the highest redshifts, where the signal to noise ratio is generally too low to apply this technique, this approach yields smaller or comparable uncertainties than previous work.

  8. ON THE KENNICUTT-SCHMIDT RELATION OF LOW-METALLICITY HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Gnedin, Nickolay Y.; Kravtsov, Andrey V. E-mail: andrey@oddjob.uchicago.ed

    2010-05-01

    We present results of self-consistent, high-resolution cosmological simulations of galaxy formation at z {approx} 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 H{sub 2} formation model accounts for the effects of dissociating UV radiation of stars in each galaxy, as well as self-shielding and shielding of H{sub 2} 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 {approx} 3 is substantially steeper and has a lower amplitude than the z = 0 relation at {Sigma}{sub H} {approx_lt} 100 M{sub o-dot} pc{sup -2}. The predicted relation, however, is consistent with existing observational constraints for the z {approx} 3 damped Ly{alpha} 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

  9. What is the nature of high-redshift, dusty, star-forming galaxies?

    NASA Astrophysics Data System (ADS)

    Bethermin, Matthieu

    2015-08-01

    Herschel deep surveys (HerMES, PEP, H-GOODS) revealed that a large fraction of the star formation up to at least z=4 is hosted by massive, dusty, star-forming, galaxies (DSFGs). These galaxies are often missed by optical and near infrared surveys, because the majority of the light produced by their stars is absorbed by dust and re-emitted in the far-infrared and submillimeter domains. These galaxies are massive and gas-rich and some of them form several hundreds of solar masses of stars per year (e.g., Béthermin et al. 2015a). Using the fluctuations of the cosmic infrared background and the clustering of the brightest high-redshift galaxies detected by Herschel, we can also put constraints on their halo mass. They live in dark matter halos of a few 1012 Msun and should be the progenitors of today’s elliptical galaxies (e.g., Béthermin et al. 2013, 2014).I will discuss the best strategy to select samples of these high-redshift star-forming galaxies from (sub-)millimeter photometric surveys. This discussion will be based on a phenomenological model of galaxy evolution, which reproduces well the current observations (Béthermin et al. 2012c, 2015b). This model can predict how the wavelength and the depth the surveys impact the properties of the detected sources (redshift, sSFR, stellar mass). I will in particular focus on ALMA deep surveys. Surprisingly, going deeper and to longer wavelengths does not guarantee to build larger samples of high redshift galaxies.The strong galaxy-galaxy lensing also offers possibilities to study high-z DSFGs in depth. In particular, I will discuss the nature of the population discovered by the South Pole Telescope. Our model predicts that these objects are mainly massive, gas-rich galaxies rather than starbursts. The important magnification (~20) of these objects is a unique opportunity to detect a large set of (sub-)millimeter lines (CO, CII, CI, NII) and study the properties of the interstellar medium of galaxies up to z=6. I will

  10. Long-Term Multiwavelength Studies of High-Redshift Blazar 0836+710

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Akyuz, A.; Donato, D.; Perkins, J. S.; Larsson, S.; Sokolovsky, K.; Fuhrmann, L.; Kurtanidze, O.

    2012-01-01

    Following gamma-ray flaring activity of high-redshift (z=2.218) blazar 0836+710 in 2011, we have assembled a long-term multiwavelength study of this object. Although this source is monitored regularly by radio telescopes and the Fermi Large Area Telescope, its coverage at other wavelengths is limited. The optical flux appears generally correlated with the gamma-ray flux, while little variability has been seen at X-ray energies. The gamma-ray/radio correlation is complex compared to some other blazars. As for many blazars, the largest variability is seen at gamma-ray wavelengths.

  11. Updates to the High-Redshift Supernovae in the SCP Union Compilation

    NASA Astrophysics Data System (ADS)

    Rubin, David; Aldering, G. S.; Amanullah, R.; Barbary, K. H.; Bruce, A.; Dawson, K. S.; Doi, M.; Fakhouri, H.; Fruchter, A. S.; Goobar, A.; Huang, X.; Ihara, Y.; Kim, A. G.; Kowalski, M.; Krechmer, E.; Lidman, C.; Linder, E.; Meyers, J.; Morokuma, T.; Nordin, J.; Perlmutter, S.; Rykoff, E. S.; Saunders, C.; Spadafora, A. L.; Suzuki, N.; Takanashi, N.; Yasuda, N.; Cosmology Project, Supernova

    2013-01-01

    Building on the work presented in Amanullah et al. (ApJ, 2010) and Suzuki et al. (ApJ, 2012), adding new z > 1 supernovae discovered in ground-based work and a new analysis of existing HST SNe, we present an updated high-redshift dataset. We update the SCP Union compilation with this and other recent datasets and present updated cosmological fits. This work has been supported by the Office of Science, U.S. Department of Energy (through contract DE-AC02-05CH11231), and in part by NASA through grants associated with HST-GO-10496.

  12. PKS 0483-436 - A high-redshift quasar with strong X-ray absorption

    NASA Technical Reports Server (NTRS)

    Wilkes, Belinda J.; Elvis, Martin; Fiore, Fabrizio; Mcdowell, Jonathan C.; Tananbaum, Harvey; Lawrence, Andrew

    1992-01-01

    The first X-ray spectrum of a high-redshift (z = 2.85) quasar is reported. The Rosat PSPC spectrum of PKS 0438-436, covering 0.3-9 keV in the quasar's rest frame, reveals unexpected absorption of about 1 x 10 exp 22/sq cm, assuming it occurs at the source. Only one other high-luminosity quasar (of greater than about 50 observed by Einstein) shows significant absorption in its X-ray spectrum. Of the common line-of-sight absorbers, only highly ionized Ly-alpha forest clouds may be able to explain this amount of absorption. Candidates for an intrinsic absorber are discussed. Absorption at about 1 keV (rest frame) is due primarily to heavy elements. (O, Ne, Mg, Si, S) raising the possibility of measuring early universe abundances via X-ray absorption in this and like quasars. PKS 0438-436 may be a high-redshift member of a population of quasars which can contribute to the X-ray background above 2 keV, without being detectable by previous imaging missions.

  13. GRB hosts and the search for missing star formation at high redshift

    NASA Astrophysics Data System (ADS)

    Tanvir, Nial

    2014-10-01

    Measuring the star formation rate (SFR) at high redshift is crucial for understanding cosmic reionization and the formation of galaxies at early times. Two common, complementary approaches are Lyman-Break-Galaxy (LBG) surveys, providing large samples, and Gamma-Ray-Bursts (GRBs) which can sign-post star formation even in the smallest galaxies. Recent results of both methods have found evidence for a dominant population of very faint star-forming galaxies at z>5, representing a continuation of the steepening of the galaxy luminosity function with redshift. However, LBG surveys are affected by possible incompleteness and contamination, while the magnitude limit means very large correction factors must be applied to account for these unseen galaxies. On the other hand GRBs suffer small number statistics and have their own selection biases. We propose to construct a new sample of six 6redshifts of the targets means that this can be achieved relatively economically, since we can accept a lower level of significance and single filter. This method depends only on GRBs and SF tracing UV light (both likely at high-z), and in turn will constrain the completeness correction to be applied to LBG surveys in order to derive the ionizing photon budget.

  14. Reionisation and High-Redshift Galaxies: The View from Quasar Absorption Lines

    NASA Astrophysics Data System (ADS)

    Becker, George D.; Bolton, James S.; Lidz, Adam

    2015-12-01

    Determining when and how the first galaxies reionised the intergalactic medium promises to shed light on both the nature of the first objects and the cosmic history of baryons. Towards this goal, quasar absorption lines play a unique role by probing the properties of diffuse gas on galactic and intergalactic scales. In this review, we examine the multiple ways in which absorption lines trace the connection between galaxies and the intergalactic medium near the reionisation epoch. We first describe how the Ly α forest is used to determine the intensity of the ionising ultraviolet background and the global ionising emissivity budget. Critically, these measurements reflect the escaping ionising radiation from all galaxies, including those too faint to detect directly. We then discuss insights from metal absorption lines into reionisation-era galaxies and their surroundings. Current observations suggest a buildup of metals in the circumgalactic environments of galaxies over z ~ 6 to 5, although changes in ionisation will also affect the evolution of metal line properties. A substantial fraction of metal absorbers at these redshifts may trace relatively low-mass galaxies. Finally, we review constraints from the Ly α forest and quasar near zones on the timing of reionisation. Along with other probes of the high-redshift Universe, absorption line data are consistent with a relatively late end to reionisation (5.5 ≲ z ≲ 7); however, the constraints are still fairly week. Significant progress is expected to come through improved analysis techniques, increases in the number of known high-redshift quasars from optical and infrared sky surveys, large gains in sensitivity from next-generation observing facilities, and synergies with other probes of the reionisation era.

  15. THE GENTLE GROWTH OF GALAXIES AT HIGH REDSHIFTS IN OVERDENSE ENVIRONMENTS

    SciTech Connect

    Romano-Díaz, Emilio; Shlosman, Isaac; Choi, Jun-Hwan; Sadoun, Raphael

    2014-08-01

    We have explored prevailing modes of galaxy growth for redshifts z ∼ 6-14, comparing substantially overdense and normal regions of the universe, using high-resolution zoom-in cosmological simulations. Such rare overdense regions have been projected to host high-z quasars. We demonstrate that galaxies in such environments grow predominantly by a smooth accretion from cosmological filaments which dominates the mass input from major, intermediate, and minor mergers. We find that by z ∼ 6, the accumulated galaxy mass fraction from mergers falls short by a factor of 10 of the cumulative accretion mass for galaxies in the overdense regions, and by a factor of 5 in the normal environments. Moreover, the rate of the stellar mass input from mergers also lies below that of an in situ star formation (SF) rate. The fraction of stellar masses in galaxies contributed by mergers in overdense regions is ∼12%, and ∼33% in the normal regions, at these redshifts. Our median SF rates for ∼few × 10{sup 9} M {sub ☉} galaxies agrees well with the recently estimated rates for z ∼ 7 galaxies from Spitzer's SURF-UP survey. Finally, we find that the main difference between the normal and overdense regions lies in the amplified growth of massive galaxies in massive dark matter halos. This leads to the formation of ≳ 10{sup 10} M {sub ☉} galaxies due to the ∼100 fold increase in mass during the above time period. Such galaxies are basically absent in the normal regions at these redshifts.

  16. The Quest for Dusty Star-forming Galaxies at High Redshift z ≳ 4

    NASA Astrophysics Data System (ADS)

    Mancuso, C.; Lapi, A.; Shi, J.; Gonzalez-Nuevo, J.; Aversa, R.; Danese, L.

    2016-06-01

    We exploit the continuity equation approach and “main-sequence” star formation timescales to show that the observed high abundance of galaxies with stellar masses ≳ a few 1010 M ⊙ at redshift z ≳ 4 implies the existence of a galaxy population featuring large star formation rates (SFRs) ψ ≳ 102 M ⊙ yr‑1 in heavily dust-obscured conditions. These galaxies constitute the high-redshift counterparts of the dusty star-forming population already surveyed for z ≲ 3 in the far-IR band by the Herschel Space Observatory. We work out specific predictions for the evolution of the corresponding stellar mass and SFR functions out to z ∼ 10, determining that the number density at z ≲ 8 for SFRs ψ ≳ 30 M ⊙ yr‑1 cannot be estimated relying on the UV luminosity function alone, even when standard corrections for dust extinction based on the UV slope are applied. We compute the number counts and redshift distributions (including galaxy-scale gravitational lensing) of this galaxy population, and show that current data from the AzTEC-LABOCA, SCUBA-2, and ALMA-SPT surveys are already addressing it. We demonstrate how an observational strategy based on color preselection in the far-IR or (sub-)millimeter band with Herschel and SCUBA-2, supplemented by photometric data from on-source observations with ALMA, can allow us to reconstruct the bright end of the SFR functions out to z ≲ 8. In parallel, such a challenging task can be managed by exploiting current UV surveys in combination with (sub-)millimeter observations by ALMA and NIKA2 and/or radio observations by SKA and its precursors.

  17. Gravitational wave source counts at high redshift and in models with extra dimensions

    NASA Astrophysics Data System (ADS)

    García-Bellido, Juan; Nesseris, Savvas; Trashorras, Manuel

    2016-07-01

    Gravitational wave (GW) source counts have been recently shown to be able to test how gravitational radiation propagates with the distance from the source. Here, we extend this formalism to cosmological scales, i.e. the high redshift regime, and we discuss the complications of applying this methodology to high redshift sources. We also allow for models with compactified extra dimensions like in the Kaluza-Klein model. Furthermore, we also consider the case of intermediate redshifts, i.e. 0 < z lesssim 1, where we show it is possible to find an analytical approximation for the source counts dN/d(S/N). This can be done in terms of cosmological parameters, such as the matter density Ωm,0 of the cosmological constant model or the cosmographic parameters for a general dark energy model. Our analysis is as general as possible, but it depends on two important factors: a source model for the black hole binary mergers and the GW source to galaxy bias. This methodology also allows us to obtain the higher order corrections of the source counts in terms of the signal-to-noise S/N. We then forecast the sensitivity of future observations in constraining GW physics but also the underlying cosmology by simulating sources distributed over a finite range of signal-to-noise with a number of sources ranging from 10 to 500 sources as expected from future detectors. We find that with 500 events it will be possible to provide constraints on the matter density parameter at present Ωm,0 on the order of a few percent and with the precision growing fast with the number of events. In the case of extra dimensions we find that depending on the degeneracies of the model, with 500 events it may be possible to provide stringent limits on the existence of the extra dimensions if the aforementioned degeneracies can be broken.

  18. 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.

  19. AN OBSERVED LINK BETWEEN ACTIVE GALACTIC NUCLEI AND VIOLENT DISK INSTABILITIES IN HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Bournaud, Frederic; Juneau, Stephanie; Le Floc'h, Emeric; Mullaney, James; Daddi, Emanuele; Duc, Pierre-Alain; Elbaz, David; Salmi, Fadia; Dekel, Avishai; Dickinson, Mark

    2012-09-20

    We provide evidence for a correlation between the presence of giant clumps and the occurrence of active galactic nuclei (AGNs) in disk galaxies. Giant clumps of 10{sup 8}-10{sup 9} M{sub Sun} arise from violent gravitational instability in gas-rich galaxies, and it has been proposed that this instability could feed supermassive black holes (BHs). We use emission line diagnostics to compare a sample of 14 clumpy (unstable) disks and a sample of 13 smoother (stable) disks at redshift z {approx} 0.7. The majority of clumpy disks in our sample have a high probability of containing AGNs. Their [O III] {lambda}5007 emission line is strongly excited, inconsistent with low-metallicity star formation (SF) alone. [Ne III] {lambda}3869 excitation is also higher. Stable disks rarely have such properties. Stacking ultra sensitive Chandra observations (4 Ms) reveals an X-ray excess in clumpy galaxies, which confirms the presence of AGNs. The clumpy galaxies in our intermediate-redshift sample have properties typical of gas-rich disk galaxies rather than mergers, being in particular on the main sequence of SF. This suggests that our findings apply to the physically similar and numerous gas-rich unstable disks at z > 1. Using the observed [O III] and X-ray luminosities, we conservatively estimate that AGNs hosted by clumpy disks have typical bolometric luminosities of the order of a few 10{sup 43} erg s{sup -1}, BH growth rates m-dot{sub BH}{approx}10{sup -2} M{sub Sun} yr{sup -1}, and that these AGNs are substantially obscured in X-rays. This moderate-luminosity mode could provide a large fraction of today's BH mass with a high duty cycle (>10%), accretion bursts with higher luminosities being possible over shorter phases. Violent instabilities at high redshift (giant clumps) are a much more efficient driver of BH growth than the weak instabilities in nearby spirals (bars), and the evolution of disk instabilities with mass and redshift could explain the simultaneous downsizing of

  20. Awakening of The High-Redshift Blazar CGRaBS J0809+5341

    NASA Astrophysics Data System (ADS)

    Paliya, Vaidehi S.; Parker, M. L.; Stalin, C. S.; Fabian, A. C.; Ramya, S.; Covino, S.; Tagliaferri, G.; Sahayanathan, S.; Ravikumar, C. D.

    2015-04-01

    CGRaBS J0809+5341, a high-redshift blazar at z = 2.144, underwent a giant optical outburst on 2014 April 19 when it brightened by ˜5 mag and reached an unfiltered apparent magnitude of 15.7 mag. This implies an absolute magnitude of -30.5 mag, making it one of the brightest quasars in the universe. This optical flaring triggered us to carry out observations during the decaying part of the flare covering a wide energy range using the Nuclear Spectroscopic Telescope Array, Swift, and ground-based optical facilities. For the first time, the source is detected in γ-rays by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope. A high optical polarization of ˜10% is also observed. Using the Sloan Digital Sky Survey spectrum, the accretion disk luminosity and black hole mass are estimated as 1.5 × 1045 erg s-1 and 108.4 M⊙, respectively. Using a single zone leptonic emission model, we reproduce the spectral energy distribution of the source during the flaring activity. This analysis suggests that the emission region is probably located outside the broad-line region, and the jet becomes radiatively efficient. We also show that the overall properties of CGRaBS J0809+5341 seem to not be in agreement with the general properties observed in high-redshift blazars up to now.

  1. Nearby Clumpy, Gas Rich, Star-forming Galaxies: Local Analogs of High-redshift Clumpy Galaxies

    NASA Astrophysics Data System (ADS)

    Garland, C. A.; Pisano, D. J.; Mac Low, M.-M.; Kreckel, K.; Rabidoux, K.; Guzmán, R.

    2015-07-01

    Luminous compact blue galaxies (LCBGs) have enhanced star formation rates (SFRs) and compact morphologies. We combine Sloan Digital Sky Survey data with H i data of 29 LCBGs at redshift z ∼ 0 to understand their nature. We find that local LCBGs have high atomic gas fractions (∼50%) and SFRs per stellar mass consistent with some high-redshift star-forming galaxies (SFGs). Many local LCBGs also have clumpy morphologies, with clumps distributed across their disks. Although rare, these galaxies appear to be similar to the clumpy SFGs commonly observed at z ∼ 1–3. Local LCBGs separate into three groups: (1) interacting galaxies (∼20%) (2) clumpy spirals (∼40%) and (3) non-clumpy, non-spirals with regular shapes and smaller effective radii and stellar masses (∼40%). It seems that the method of building up a high gas fraction, which then triggers star formation, is not the same for all local LCBGs. This may lead to a dichotomy in galaxy characteristics. We consider possible gas delivery scenarios and suggest that clumpy spirals, preferentially located in clusters and with companions, are smoothly accreting gas from tidally disrupted companions and/or intracluster gas enriched by stripped satellites. Conversely, as non-clumpy galaxies are preferentially located in the field and tend to be isolated, we suggest clumpy, cold streams, which destroy galaxy disks and prevent clump formation, as a likely gas delivery mechanism for these systems. Other possibilities include smooth cold streams, a series of minor mergers, or major interactions.

  2. The environments of high-redshift radio galaxies and quasars: probes of protoclusters

    NASA Astrophysics Data System (ADS)

    Orsi, Álvaro A.; Fanidakis, Nikos; Lacey, Cedric G.; Baugh, Carlton M.

    2016-03-01

    We use the GALFORM semi-analytical model to study high-density regions traced by radio galaxies and quasars at high redshifts. We explore the impact that baryonic physics has upon the properties of galaxies in these environments. Star-forming emission-line galaxies (Ly α and H α emitters) are used to probe the environments at high redshifts. Radio galaxies are predicted to be hosted by more massive haloes than quasars, and this is imprinted on the amplitude of galaxy overdensities and cross-correlation functions. We find that Ly α radiative transfer and active galactic nucleus feedback indirectly affect the clustering on small scales and also the stellar masses, star formation rates and gas metallicities of galaxies in dense environments. We also investigate the relation between protoclusters associated with radio galaxies and quasars, and their present-day cluster descendants. The progenitors of massive clusters associated with radio galaxies and quasars allow us to determine an average protocluster size in a simple way. Overdensities within the protoclusters are found to correlate with the halo descendant masses. We present scaling relations that can be applied to observational data. By computing projection effects due to the wavelength resolution of modern spectrographs and narrow-band filters, we show that the former have enough spectral resolution to map the structure of protoclusters, whereas the latter can be used to measure the clustering around radio galaxies and quasars over larger scales to determine the mass of dark matter haloes hosting them.

  3. Detectability of cold streams into high-redshift galaxies by absorption lines

    NASA Astrophysics Data System (ADS)

    Goerdt, Tobias; Dekel, Avishai; Sternberg, Amiel; Gnat, Orly; Ceverino, Daniel

    2012-08-01

    Cold gas streaming along the dark matter filaments of the cosmic web is predicted to be the major source of fuel for disc buildup, violent disc instability and star formation in massive galaxies at high redshift. We investigate to what extent such cold gas is detectable in the extended circumgalactic environment of galaxies via Lyα absorption and selected low-ionization metal absorption lines. We model the expected absorption signatures using high-resolution zoom-in adaptive mesh refinement cosmological simulations. In the post-processing, we distinguish between self-shielded gas and unshielded gas. In the self-shielded gas, which is optically thick to Lyman continuum radiation, we assume pure collisional ionization for species with an ionization potential greater than 13.6 eV. In the optically-thin, unshielded gas, these species are also photoionized by the metagalactic radiation. In addition to absorption of radiation from background quasars, we compute the absorption line profiles of radiation emitted by the galaxy at the centre of the same halo. We predict the strength of the absorption signal for individual galaxies without stacking. We find that the Lyα absorption profiles produced by the streams are consistent with observations of absorption and emission Lyα profiles in high-redshift galaxies. Due to the low metallicities in the streams, and their low covering factors, the metal absorption features are weak and difficult to detect.

  4. Probing the very high redshift universe with the broadband emission of GRBS

    NASA Astrophysics Data System (ADS)

    Inoue, S.; Omukai, K.; Ciardi, B.; Miniati, F.

    Due to their high luminosities and close association with massive stars, gamma-ray bursts hold the promise of being unique and crucial probes of the very high redshift universe. The following topics will be discussed. 1) Dispersion in the low frequency radio emission of GRBs may offer an important probe of the cosmic reionization history. The observational prospects can be particularly interesting for facilities such as LOFAR, if GRBs emit strong, coherent radio emission (Inoue 2004, MNRAS, 348, 999). 2) Due to the contribution of the reverse shock, GRBs at a few hours after the burst are brightest in the millimeter to infrared band, with peak fluxes reaching ˜ mJy from z ˜ 5--30. Atomic and molecular absorption lines in these bands are potentially observable by telescopes such as ALMA, providing an important probe of early star-forming regions (Inoue, Omukai & Ciardi, in prep). 3) The possibility of probing the high redshift UV background utilizing gamma-ray absorption in the GeV-TeV emission of GRBs is briefly discussed (Inoue & Miniati, in prep).

  5. High efficiency SNAP survey for Lyman alpha emitters at low redshift

    NASA Astrophysics Data System (ADS)

    McCandliss, Stephan

    2014-10-01

    The goal of this proposal is to provide the first statistically significant survey of star-forming galaxies with Lyman alpha emission at redshifts 0.02 < z < 0.24. It will provide an overall assessment of the evolution in Lyman alpha luminosity at the lowest redshifts and allowed detailed studies of the physical processes that shape the Lyman alpha profile and govern escape in multi-phase, kinematic media. It will also provide a serendipitous search for star-forming galaxies with high LyC escape fractions that are analogous to those commonly invoked as being responsible for initiating and sustaining the epoch of reionization. The SNAP survey proposed here employing the G140L mode of COS offers a highly efficient means to examine the Lyman alpha emission properties of our candidate emitters and to inform our choice of objects that could warrant deeper integrations in future observations. These data have high UV legacy value and will be of broad interest to the star-forming galaxy community, so we have elected to waive the proprietary period.

  6. Short-term optical variability of high-redshift quasi-stellar objects

    NASA Astrophysics Data System (ADS)

    Bachev, R.; Strigachev, A.; Semkov, E.

    2005-04-01

    In this paper we present the results of a search for short-term variability in the optical band of selected high-luminosity, high-redshift radio-quiet quasars. Each quasar has been monitored typically for 2-4 h with a time resolution of 2-5 min and a photometric accuracy of about 0.01-0.02 mag. As a result of the significant redshift (z > 2), the covered wavelength range falls into the ultraviolet region (typically 1500-2500 Å). We have found no statistical evidence for any continuum variations larger than 0.01-0.02 mag for any of the monitored objects. Our results suggest that the presence of a short-term variability in radio-quiet quasars is unlikely even in the ultraviolet region, contrary to reports by other authors. This conclusion holds true at least for high-luminosity (large black hole mass and accretion rate?) objects. The results are consistent with the idea that significant short-term (less than 1 h) variations in active galactic nuclei, where observed, should be attributed primarily to processes in a relativistic jet.

  7. The MaGICC volume: reproducing statistical properties of high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Kannan, Rahul; Stinson, Greg S.; Macciò, Andrea V.; Brook, Chris; Weinmann, Simone M.; Wadsley, James; Couchman, Hugh M. P.

    2014-02-01

    We present a cosmological hydrodynamical simulation of a representative volume of the Universe, as part of the Making Galaxies in a Cosmological Context (MaGICC) project. MaGICC uses a thermal implementation for supernova and early stellar feedback. This work tests the feedback model at lower resolution across a range of galaxy masses, morphologies and merger histories. The simulated sample compares well with observations of high-redshift galaxies (z ≥ 2) including the stellar mass-halo mass (M⋆-Mh) relation, the galaxy stellar mass function (GSMF) at low masses (M⋆ < 5 × 1010 M⊙) and the number density evolution of low-mass galaxies. The poor match of M⋆-Mh and the GSMF at high masses (M⋆ ≥ 5 × 1010 M⊙) indicates that supernova feedback is insufficient to limit star formation in these haloes. At z = 0, our model produces too many stars in massive galaxies and slightly underpredicts the stellar mass around L⋆ mass galaxy. Altogether our results suggest that early stellar feedback, in conjunction with supernova feedback, plays a major role in regulating the properties of low-mass galaxies at high redshift.

  8. EXTENDED Ly{alpha} EMISSION FROM INTERACTING GALAXIES AT HIGH REDSHIFTS

    SciTech Connect

    Yajima, Hidenobu; Li Yuexing; Zhu Qirong

    2013-08-20

    Recent observations have discovered a population of extended Ly{alpha} sources, dubbed Ly{alpha} blobs (LABs), at high redshift z {approx} 2-6.6. These LABs typically have a luminosity of L {approx} 10{sup 42}-10{sup 44} erg s{sup -1}, and a size of tens of kiloparsecs, with some giant ones reaching up to D {approx} 100 kpc. However, the origin of these LABs is not well understood. In this paper, we investigate a merger model for the formation of LABs by studying Ly{alpha} emission from interacting galaxies at high redshifts by means of a combination of hydrodynamics simulations with three-dimensional radiative transfer calculations. Our galaxy simulations focus on a set of binary major mergers of galaxies with a mass range of 3-7 Multiplication-Sign 10{sup 12} M{sub Sun} in the redshift range z {approx} 3-7, and we use the newly improved ART{sup 2} code to perform the radiative transfer calculations, which couple multi-wavelength continuum, ionization of hydrogen, and Ly{alpha} line emission. We find that intense star formation and enhanced cooling induced by gravitational interaction produce strong Ly{alpha} emission from these merging galaxies. The Ly{alpha} emission appears to be extended due to the extended distribution of sources and gas. During the close encounter of galaxy progenitors when the star formation rate peaks at {approx}10{sup 3} M{sub Sun} yr{sup -1}, our model produces LABs with luminosity of L {approx} 10{sup 42}-10{sup 44} erg s{sup -1}, and size of D {approx} 10-20 kpc at z > 6 and D {approx} 20-50 kpc at z {approx} 3, in broad agreement with observations in the same redshift range. Our results suggest that merging galaxies may produce some typical LABs as observed, but the giant ones may be produced by mergers more massive than those in our model, or a combination of mergers and cold accretion from filaments on a large scale.

  9. A K{sub S} AND IRAC SELECTION OF HIGH-REDSHIFT EXTREMELY RED OBJECTS

    SciTech Connect

    Wang, Wei-Hao; Barger, Amy J.; Cowie, Lennox L.

    2012-01-10

    In order to find the most extreme dust-hidden high-redshift galaxies, we select 196 extremely red objects in the K{sub S} and Infrared Array Camera (IRAC) bands (KIEROs, [K{sub s} - 4.5 {mu}m]{sub AB} > 1.6) in the 0.06 deg{sup 2} Great Observatories Origins Deep Surveys-North (GOODS-N) region. This selection avoids the Balmer breaks of galactic spectra at z < 4 and picks up red galaxies with strong dust extinction. The photometric redshifts of KIEROs are between 1.5 and 5, with {approx}70% at z {approx} 2-4. KIEROs are very massive, with M{sub *} {approx} 10{sup 10}-10{sup 12} M{sub Sun }. They are optically faint and usually cannot be picked out by the Lyman break selection. On the other hand, the KIERO selection includes approximately half of the known millimeter and submillimeter galaxies in the GOODS-N. Stacking analyses in the radio, millimeter, and submillimeter all show that KIEROs are much more luminous than average 4.5 {mu}m-selected galaxies. Interestingly, the stacked fluxes for Advanced Camera for Surveys (ACS)-undetected KIEROs in these wave bands are 2.5-5 times larger than those for ACS-detected KIEROs. With the stacked radio fluxes and the local radio-FIR correlation, we derive mean infrared luminosities of (2-7) Multiplication-Sign 10{sup 12} L{sub Sun} and mean star formation rates (SFRs) of 400-1200 M{sub Sun} yr{sup -1} for KIEROs with redshifts. We do not find evidence of a significant subpopulation of passive KIEROs. The large stellar masses and SFRs imply that KIEROs are z > 2 massive galaxies in rapid formation. Our results show that a large sample of dusty ultraluminous sources can be selected in this way and that a large fraction of high-redshift star formation is hidden by dust.

  10. Infrared to x-ray spectral energy distributions of high redshift quasars

    NASA Technical Reports Server (NTRS)

    Bechtold, Jill; Elvis, Martin; Fiore, Fabrizio; Kuhn, Olga; Cutri, Roc M.; Mcdowell, Jonathan C.; Rieke, Marcia; Siemiginowska, Aneta; Wilkes, Belinda J.

    1994-01-01

    We have observed 14 quasars with z greater than 2.8 with the ROSAT-PSPC, and detected 12 of them, including the z=4.11 quasar 0000-263. We present the first x-ray spectrum of a radio quiet quasar with z greater than 3, 1946+768. Its x-ray spectrum is consistent with a power law with spectral index alpha(sub E)=1.8(sup +2.1, sub -1.4) and no evidence for absorption in excess of the galactic column (alpha(sub E)=1.00(sup +0.28, sub -0.32) assuming N(sub H)=N(sub H)(Gal)). A Position Sensitive Proportional Counter (PSPC) hardness ratio is used to constrain the x-ray spectral properties of the quasars for which there were less than 100 photons detected. For the radio quiet quasars, (alpha(sub E)) approximately equals 1.2, if one assumes that there is no absorption in excess of the galactic column. We combine the x-ray data with new ground based optical and near-IR spectrophotometry obtained at the Steward 2.3 m and Multiple Mirror Telescope, and data from the literature. The spectral energy distributions are compared to those of low redshift objects. For the radio quiet quasars with z greater than 2.5, the mean (alpha(sub ox)) is approximately 1.8. This is larger than the mean for quasars with z less than 2.5, but consistent with the expected value for quasars with the high optical luminosities of the objects in this sample. For the radio-loud quasars, (alpha(sub ox)) is approximately 1.4, independent of redshift. This is smaller than the expected value for the optically luminous, high redshift objects in this sample, if they are mostly GHz peaked radio sources and hence comparable to steep-spectrum, compact radio sources at lower redshift. Finally, we compare the spectral energy distributions of two representative objects to the predicted spectrum of a thin accretion disk in the Kerr geometry, and discuss the uncertainties in deriving black hole masses and mass accretion rates.