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Sample records for high-redshift uv background

  1. Extragalactic Backgrounds in the Far UV and Exploring Star Formation at High Redshifts with Gamma-ray Observations

    NASA Technical Reports Server (NTRS)

    Stecker, Floyd W.

    2006-01-01

    The determination of the intergalactic photon densities from the FIR to the UV which is produced by stellar emission and dust reradiation at various redshifts can provide an independent measure of the star formation history of the universe. Using recent Spitzer and GALEX data in conjunction with other observational inputs, Stecker, Malkan and Scully have calculated the intergalactic photon density as a function of both energy and redshift for 0 < zeta < 6 for photon energies from 0.003 eV to the Lyman limit cutoff at 13.6 eV in a ACDM universe with Omega(sub Lambda) = 0.7 and Omega(sub m) = 0.3. Their results are based on backwards evolution models for galaxies which were developed by Malkan and Stecker previously. The calculated background SEDs at zeta = 0 are in good agreement with the present observational data and limits. The calculated intergalactic photon densities as a function of redshift were used to predict to extend the absorption of high energy 7-rays in intergalactic space from sources such as blazars and quasars, this absorption being produced by interactions the y-rays with the intergalactic FIR-UV photons having the calculated densities. The results are in excellent agreement with absorption features found in the low gamma-ray spectra of Mkn 421, Mkn 501 at, zeta = 0.03 and PKS

  2. UV Properties and Evolution of High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Buzzoni, Alberto

    I assess the problem of morphological and photometric evolution of high-redshift galaxies in the ultraviolet wavelength range. My discussion will partly rely on a new set of template galaxy models, in order to infer the expected changes along the Hubble morphological sequence at the different cosmic epochs. The impact of evolution on the faint-end galaxy luminosity function at z~1 and beyond will also be evaluated and briefly discussed. See http://www.merate.mi.astro.it/~eps/home.html for more info and model retrieval.

  3. 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.

  4. ON THE EFFECT OF THE COSMIC MICROWAVE BACKGROUND IN HIGH-REDSHIFT (SUB-)MILLIMETER OBSERVATIONS

    SciTech Connect

    Da Cunha, Elisabete; Groves, Brent; Walter, Fabian; Decarli, Roberto; Rix, Hans-Walter; Weiss, Axel; Bertoldi, Frank; Carilli, Chris; Daddi, Emanuele; Sargent, Mark; Maiolino, Roberto; Riechers, Dominik; Smail, Ian

    2013-03-20

    Modern (sub-)millimeter interferometers enable the measurement of the cool gas and dust emission of high-redshift galaxies (z > 5). However, at these redshifts the cosmic microwave background (CMB) temperature is higher, approaching, and even exceeding, the temperature of cold dust and molecular gas observed in the local universe. In this paper, we discuss the impact of the warmer CMB on (sub-)millimeter observations of high-redshift galaxies. The CMB affects the observed (sub-)millimeter dust continuum and the line emission (e.g., carbon monoxide, CO) in two ways: (1) it provides an additional source of (both dust and gas) heating and (2) it is a non-negligible background against which the line and continuum emission are measured. We show that these two competing processes affect the way we interpret the dust and gas properties of high-redshift galaxies using spectral energy distribution models. We quantify these effects and provide correction factors to compute what fraction of the intrinsic dust (and line) emission can be detected against the CMB as a function of frequency, redshift, and temperature. We discuss implications on the derived properties of high-redshift galaxies from (sub-)millimeter data. Specifically, the inferred dust and molecular gas masses can be severely underestimated for cold systems if the impact of the CMB is not properly taken into account.

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

    NASA Astrophysics Data System (ADS)

    Holzbauer, Lauren Nicole

    The first stars to light up our universe are as yet unseen, but there have been many attempts to elucidate their properties. The characteristics of these stars (`Population/Pop III' stars) that we do know lie mostly within theory; they formed out of metal-free hydrogen and helium gas contained in dark matter minihalos at redshifts z 20-30. The extent to which Pop III star formation reached into later times is unknown. Current and near future instruments are incapable of resolving individual Pop III stars. Consequently, astronomers must devise creative means with which to indirectly predict and measure and their properties. In this thesis, we will investigate a few of those means. We use a new method to model fluctuations of the Lyman-Werner (LW) and Lyman-alpha radiation backgrounds at high redshift. At these early epochs the backgrounds are symptoms of a universe newly lit with its first stars. LW photons (11.5-13.6 eV) are of particular interest because they dissociate molecular hydrogen, the primary coolant in the first minihalos that is necessary for star formation. By using a variation of the `halo model', which describes the spatial distribution and clustering of halos, we can efficiently generate power spectra for these backgrounds. Spatial fluctuations in the LW and (indirectly) the Lyman-alpha BG can tell us about the transition from primordial star formation to a more metal-enriched mode that marks the beginning of the second generation of stars in our Universe. The Near Infrared Background (NIRB) has for some time been considered a potential tool with which to indirectly observe the first stars. Ultraviolet (UV) emission from these stars is redshifted into the NIR band, making the NIRB amenable for hunting Pop III stellar signatures. There have been several measurements of the NIRB and subsequent theoretical studies attempting to explain them in recent years. Though controversial, residual levels of the mean NIRB intensity and anisotropies have been

  6. Constraints on the Extragalactic Background Light from Gamma-Ray Observations of High-Redshift Quasars

    NASA Astrophysics Data System (ADS)

    Madau, Piero; Phinney, E. Sterl

    1996-01-01

    We propose to use the detectability of energetic y-rays in the 10-200 GeV range from high-redshift quasars to set limits on the energy density and era of formation of the extragalactic background light (EBL) in the near-ultraviolet, optical, and near-infrared portion of the spectrum. We study a variety of EBL models based on recent estimates of the density of starlight at the present epoch, a detailed modeling of the transfer of ionizing radiation through the intergalactic medium and of the spectral energy distribution of young galaxies, and simple parameterizations of the star formation history. We demonstrate that a cosmic background of optical photons which is comparable to the integrated EBL contributed by ordinary galaxies and originates as near-ultraviolet radiation at redshift z ˜ 2 will make the universe optically thick to γ-ray photons above ˜30 GeV through electron-positron pair production. We also show that a detection by the EGRET instrument aboard the Compton Observatory of ≥15 GeV photons from the quasar 1633+382 (Mattox et al. 1993) would rule out models in which a diffuse optical background with an energy density several times in excess that of known galaxies was formed at z ˜ 2 by a new class of sources. The universe to intermediate redshifts is optically thin to pair production below ˜10 GeV.

  7. 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.

  8. Mid-UV Imaging of Nearby Early to Mid-Type Galaxies as Templates for High Redshift Galaxy Classifications

    NASA Astrophysics Data System (ADS)

    Chiarenza, C. A. T.; Windhorst, R. A.; Taylor, V. A.; Odewahn, S. C.; Conselice, C. J.; MacKenty, J.; de Jong, R. S.; de Grijs, R.; Eskridge, P. B.; Frogel, J. A.; Gallagher, J. S.; Kobulnicky, H.; Hibbard, J. E.; Matthews, L. D.; O'Connell, R. W.

    2000-12-01

    Current samples of high redshift galaxies are primarily observed in their restframe mid-UV. They often resemble nearby late type galaxies, but are they really physically similar classes of objects? To explore this question we did a systematic imaging survey with the HST/WFPC2 of 37 nearby galaxies in two mid-UV bands. Our sample is carefully selected for size and surface brightness over a wide range of Hubble types and inclinations. All objects (will) have ground based UBVRIJ(H)K images, and 15 have far UV UIT images. The mid-UV is the missing keystone. With it we can examine the distribution of star formation and its history, dust, the SED's of star forming regions, and differentiate between age and metallicity. Our first results from this Cycle 9 project are: (1) Early type galaxies can show significant changes from the mid-UV to the red. Some are quite dim in the UV, reflecting their old stellar population. Others become point sources in the mid-UV (LINER's, Seyferts). This raises the question to what extent the apparently strong cosmological evolution of weak AGN in early type galaxies is due to ``morphological K-correction.'' (2) Mid type spirals and star forming galaxies can appear as later or different types in the mid-UV. Dust lanes are well traceable comparing F300W to F814W. We see a considerable range in scale and surface brightness of individual star-forming regions. We acknowledge NASA ADP grant NAG-6740, ASU NASA Space Grants, and NASA grants GO-8645.01-99A and AR-8765.01-99A from STScI. Based on observations with the VATT: the Alice P. Lennon Telescope and the Thomas J. Bannan Astrophysics Facility.

  9. Fluctuations in the high-redshift Lyman-Werner background: close halo pairs as the origin of supermassive black holes

    NASA Astrophysics Data System (ADS)

    Dijkstra, Mark; Haiman, Zoltán; Mesinger, Andrei; Wyithe, J. Stuart B.

    2008-12-01

    The earliest generation of stars and black holes must have established an early `Lyman-Werner' background (LWB) at high redshift, prior to the epoch of reionization. Because of the long mean free path of photons with energies hν < 13.6eV, the LWB was nearly uniform. However, some variation in the LWB is expected due to the discrete nature of the sources, and their highly clustered spatial distribution. In this paper, we compute the probability distribution function (PDF) of the LW flux that irradiates dark matter (DM) haloes collapsing at high redshift (z ~ 10). Our model accounts for (i) the clustering of DM haloes, (ii) Poisson fluctuations in the number of corresponding star-forming galaxies and (iii) scatter in the LW luminosity produced by haloes of a given mass (calibrated using local observations). We find that >99 per cent of the DM haloes are illuminated by an LW flux within a factor of 2 of the global mean value. However, a small fraction, ~10-8 to 10-6, of DM haloes with virial temperatures Tvir >~ 104 K have a close luminous neighbour within <~10 kpc, and are exposed to an LW flux exceeding the global mean by a factor of >20, or to J21,LW > 103 (in units of 10-21 erg s-1 Hz-1 sr-1 cm-2). This large LW flux can photodissociate H2 molecules in the gas collapsing due to atomic cooling in these haloes, and prevent its further cooling and fragmentation. Such close halo pairs therefore provide possible sites in which primordial gas clouds collapse directly into massive black holes (MBH ~ 104-6Msolar), and subsequently grow into supermassive (MBH >~ 109Msolar) black holes by z ~ 6.

  10. Probing the High-Redshift Universe Using Fluctuations in the Cosmic Microwave and Infrared Backgrounds

    NASA Astrophysics Data System (ADS)

    Smidt, Joseph Michael

    Background (CIB) continues to be one of the best probes of physics at the early stages of the universe. If the CMB were a purely Gaussian field, all statistical information would be contained in the power spectrum or two-point correlation function. However, non-Gaussianities ensure that new physics may be extracted from higher n-point correlation functions including the bispectrum and trispectrum of the CMB. In this thesis discuss new estimators we have formulated to probe primordial non-Gaussianity in the bispectrum and trispectrum of CMB data and the constraints we have made using WMAP data while discussing implications for inflationary models. I discuss how these same methods may be used to probe CMB Lensing. Finally, I discuss how upcoming measurements of near and far-infrared CIB fluctuations may be used to constrain the redshift of reionization and clustering of various populations of galaxies. Some preliminary results involving CANDELS, Spitzer SDWFS, CIBER and Herschel datasets is presented.

  11. Dust Attenuation in UV-selected Starbursts at High Redshift and Their Local Counterparts: Implications for the Cosmic Star Formation Rate Density

    NASA Astrophysics Data System (ADS)

    Overzier, Roderik A.; Heckman, Timothy M.; Wang, Jing; Armus, Lee; Buat, Veronique; Howell, Justin; Meurer, Gerhardt; Seibert, Mark; Siana, Brian; Basu-Zych, Antara; Charlot, Stéphane; Gonçalves, Thiago S.; Martin, D. Christopher; Neill, James D.; Rich, R. Michael; Salim, Samir; Schiminovich, David

    2011-01-01

    We present a new analysis of the dust obscuration in starburst galaxies at low and high redshifts. This study is motivated by our unique sample of the most extreme UV-selected starburst galaxies in the nearby universe (z < 0.3), found to be good analogs of high-redshift Lyman break galaxies (LBGs) in most of their physical properties. We find that the dust properties of the Lyman break analogs (LBAs) are consistent with the relation derived previously by Meurer et al. (M99) that is commonly used to dust-correct star formation rate (SFR) measurements at a very wide range of redshifts. We directly compare our results with high-redshift samples (LBGs, "BzK," and submillimeter galaxies at z ~ 2-3) having IR data either from Spitzer or Herschel. The attenuation in typical LBGs at z ~ 2-3 and LBAs is very similar. Because LBAs are much better analogs to LBGs compared to previous local star-forming samples, including M99, the practice of dust-correcting the SFRs of high-redshift galaxies based on the local calibration is now placed on a much more solid ground. We illustrate the importance of this result by showing how the locally calibrated relation between UV measurements and extinction is used to estimate the integrated, dust-corrected SFR density at z ~= 2-6.

  12. High redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Mccarthy, Patrick J.

    1993-01-01

    High redshift galaxies that host powerful radio sources are examined. An overview is presented of the content of radio surveys: 3CR and 3CRR, 4C and 4C/USS, B2/1 Jy, MG, MRC/1Jy, Parkes/PSR, B3, and ESO Key-Project. Narrow-line radio galaxies in the visible and UV, the source of ionization and excitation of the emission lines, emission-line luminosities, morphology of the line-emitting gas, physical properties and energetics, kinematics of the line-emitting gas, and implications from the emission lines are discussed. The morphologies and environments of the host galaxies, the alignment effect, and spectral energy distributions and ages are also examined.

  13. A Novel Approach to Constrain the Escape Fraction and Dust Content at High Redshift Using the Cosmic Infrared Background Fractional Anisotropy

    NASA Astrophysics Data System (ADS)

    Fernandez, Elizabeth R.; Dole, Herve; Iliev, Ilian T.

    2013-02-01

    The Cosmic Infrared Background (CIB) provides an opportunity to constrain many properties of the high-redshift (z > 6) stellar population as a whole. This background, specifically from 1 to 200 μm, should contain information about the era of reionization and the stars that are responsible for these ionizing photons. In this paper, we look at the fractional anisotropy (δI/I) of this high-redshift population, where δI is the ratio of the magnitude of the fluctuations and I is the mean intensity. We show that this can be used to constrain the escape fraction of the population as a whole, because the magnitude of the fluctuations of the CIB depends on the escape fraction, while the mean intensity does not. This results in lower values of the escape fraction producing higher values of the fractional anisotropy. This difference is predicted to be larger at longer wavelength bands (above 10 μm), albeit it is also much harder to observe in that range. We show that the fractional anisotropy can also be used to separate a dusty from a dust-free population. Finally, we discuss the constraints provided by current observations on the CIB fractional anisotropy.

  14. Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Pérez-Fournon, I.; Balcells, M.; Moreno-Insertis, F.; Sánchez, F.

    2010-08-01

    Participants; Group photograph; Preface; Acknowledgements; 1. Galaxy formation and evolution: recent progress R. Ellis; 2. Galaxies at high redshift M. Dickinson; 3. High-redshift galaxies: the far-infrared and sub-millimeter view A. Franceschini; 4. Quasar absorption lines J. Bechtold; 5. Stellar population synthesis models at low and high redshift G. Bruzual A.; 6. Elliptical galaxies K. C. Freeman; 7. Disk galaxies K. C. Freeman; 8. Dark matter in disk galaxies K. C. Freeman.

  15. Mapping the Dark Matter From UV Light at High Redshift: An Empirical Approach to Understand Galaxy Statistics

    SciTech Connect

    Lee, Kyoung-Soo; Giavalisco, Mauro; Conroy, Charlie; Wechsler, Risa H; Ferguson, Henry C.; Somerville, Rachel S.; Dickinson, Mark E.; Urry, Claudia M.; /Yale Ctr. Astron. Astrophys.

    2009-08-03

    We present a simple formalism to interpret the observations of two galaxy statistics, the UV luminosity function (LF) and two-point correlation functions for star-forming galaxies at z {approx} 4, 5 and 6 in the context of {Lambda}CDM cosmology. Both statistics are the result of how star formation takes place in dark matter halos, and thus are used to constrain how UV light depends on halo properties, in particular halo mass. The two physical quantities we explore are the star formation duty cycle, and the range of UV luminosity that a halo of mass M can have (mean and variance). The former directly addresses the typical duration of star formation activity in halos while the latter addresses the averaged star formation history and regularity of gas inflow into these systems. In the context of this formalism, we explore various physical models consistent with all the available observational data, and find the following: (1) the typical duration of star formation observed in the data is {approx}< 0.4 Gyr (1{sigma}), (2) the inferred scaling law between the observed L{sub UV} and halo mass M from the observed faint-end slope of the luminosity functions is roughly linear out to M {approx} 10{sup 11.5} - 10{sup 12} h{sup -1} M{sub {circle_dot}} at all redshifts probed in this work, and (3) the observed L{sub UV} for a fixed halo mass M decreases with time, implying that the star formation efficiency (after dust extinction) is higher at earlier times. We explore several different physical scenarios relating star formation to halo mass, but find that these scenarios are indistinguishable due to the limited range of halo mass probed by our data. In order to discriminate between different scenarios, we discuss the possibility of using the bright-faint galaxy cross-correlation functions and more robust determination of luminosity-dependent galaxy bias for future surveys.

  16. Effect of primordial non-Gaussianities on the far-UV luminosity function of high-redshift galaxies: implications for cosmic reionization

    NASA Astrophysics Data System (ADS)

    Chevallard, Jacopo; Silk, Joseph; Nishimichi, Takahiro; Habouzit, Melanie; Mamon, Gary A.; Peirani, Sébastien

    2015-01-01

    Understanding how the intergalactic medium (IGM) was reionized at z ≳ 6 is one of the big challenges of current high-redshift astronomy. It requires modelling the collapse of the first astrophysical objects (Pop III stars, first galaxies) and their interaction with the IGM, while at the same time pushing current observational facilities to their limits. The observational and theoretical progress of the last few years have led to the emergence of a coherent picture in which the budget of hydrogen-ionizing photons is dominated by low-mass star-forming galaxies, with little contribution from Pop III stars and quasars. The reionization history of the Universe therefore critically depends on the number density of low-mass galaxies at high redshift. In this work, we explore how changes in the cosmological model, and in particular in the statistical properties of initial density fluctuations, affect the formation of early galaxies. Following Habouzit et al. (2014), we run five different N-body simulations with Gaussian and (scale-dependent) non-Gaussian initial conditions, all consistent with Planck constraints. By appealing to a phenomenological galaxy formation model and to a population synthesis code, we compute the far-UV galaxy luminosity function down to MFUV = -14 at redshift 7 ≤ z ≤ 15. We find that models with strong primordial non-Gaussianities on ≲ Mpc scales show a far-UV luminosity function significantly enhanced (up to a factor of 3 at z = 14) in low-mass galaxies. We adopt a reionization model calibrated from state-of-the-art hydrodynamical simulations and show that such scale-dependent non-Gaussianities leave a clear imprint on the Universe reionization history and electron Thomson scattering optical depth τe. Although current uncertainties in the physics of reionization and on the determination of τe still dominate the signatures of non-Gaussianities, our results suggest that τe could ultimately be used to constrain the statistical properties

  17. Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Bauer, F. E.

    2014-10-01

    Recent years have seen tremendous progress in finding and charactering star-forming galaxies at high redshifts across the electromagnetic spectrum, giving us a more complete picture of how galaxies evolve, both in terms of their stellar and gas content, as well as the growth of their central supermassive black holes. A wealth of studies now demonstrate that star formation peaked at roughly half the age of the Universe and drops precariously as we look back to very early times, and that their central monsters apparently growth with them. At the highest-redshifts, we are pushing the boundaries via deep surveys at optical, X-ray, radio wavelengths, and more recently using gamma-ray bursts. I will review some of our accomplishments and failures. Telescope have enabled Lyman break galaxies to be robustly identified, but the UV luminosity function and star formation rate density of this population at z = 6 - 8 seems to be much lower than at z = 2 - 4. High escape fractions and a large contribution from faint galaxies below our current detection limits would be required for star-forming galaxies to reionize the Universe. We have also found that these galaxies have blue rest-frame UV colours, which might indicate lower dust extinction at z > 5. There has been some spectroscopic confirmation of these Lyman break galaxies through Lyman-α emission, but the fraction of galaxies where we see this line drops at z > 7, perhaps due to the onset of the Gunn-Peterson effect (where the IGM is opaque to Lyman-α).

  18. X-Ray Background at High Redshifts from Pop III Remnants: Results from Pop III Star Formation Rates in the Renaissance Simulations

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Ahn, Kyungjin; Norman, Michael L.; Wise, John H.; O'Shea, Brian W.

    2016-11-01

    Due to their long mean free paths, X-rays are expected to have global impacts on the properties of the intergalactic medium (IGM) by their large-scale heating and ionizing processes. At high redshifts, X-rays from Population (Pop) III binaries might have important effects on cosmic reionization and the Lyα forest. As a continuation of our previous work on Pop III binary X-rays, we use the Pop III distribution and evolution from the Renaissance Simulations, a suite of self-consistent cosmological radiation hydrodynamics simulations of the formation of the first galaxies, to calculate the X-ray luminosity density and background over the redshift range 20≥slant z≥slant 7.6. As we find that Pop III star formation continues at a low, nearly constant rate to the end of reionization, X-rays are being continuously produced at significant rates compared to other possible X-ray sources, such as AGNs and normal X-ray binaries during the same period of time. We estimate that Pop III binaries produce approximately 6 eV of energy in the X-rays per hydrogen atom. We calculate the X-ray background for different monochromatic photon energies. KeV X-rays redshift and accumulate to produce a strong X-ray background spectrum extending to roughly 500 eV. The X-ray background is strong enough to heat the IGM to ˜1000 K and to ionize a few percent of the neutral hydrogen. These effects are important for an understanding of the neutral hydrogen hyperfine transition 21 cm line signatures, the Lyα forest, and the Thomson optical depth to the CMB.

  19. 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.

  20. High redshift blazars .

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.

    Blazars are sources whose jet is pointing at us. Since their jets are relativistic, the flux is greatly amplified in the direction of motion, making blazars the most powerful persistent objects in the Universe. This is true at all frequencies, but especially where their spectrum peaks. Although the spectrum of moderate powerful sources peaks in the ˜GeV range, extremely powerful sources at high redshifts peak in the ˜MeV band. This implies that the hard X-ray band is the optimal one to find powerful blazars beyond a redshift of ˜4. First indications strongly suggest that powerful high-z blazars harbor the most massive and active early black holes, exceeding a billion solar masses. Since for each detected blazars there must exist hundreds of similar, but misaligned, sources, the search for high-z blazars is becoming competitive with the search of early massive black holes using radio-quiet quasars. Finding how the two populations of black holes (one in jetted sources, the other in radio-quiet objects) evolve in redshift will shed light on the growth of the most massive black holes and possibly on the feedback between the central engine and the rest of the host galaxy.

  1. Dust in the High Redshift Universe

    NASA Astrophysics Data System (ADS)

    Meurer, G. R.

    2004-05-01

    This paper reviews the dust content of the high redshift (z > 2) universe. Studies of the various ``species'' in the high-z ``zoo'' show that almost all have strong evidence for containing dust. The one exception, where the evidence is not yet convincing, is in quasar absorption line systems, particularly those with low column density. These may not even be associated with galaxies. The high-z galaxy types which do show evidence for dust are all strongly star forming. Hence, as seen locally, star formation and dust in the distant universe are also strongly correlated. It is beyond debate that star formation at z ˜ 3 is dominated by dusty systems who emit most of their bolometric flux in the rest-frame FIR. What is not clear is whether these systems are totally invisible at shorter wavelengths, or whether a large fraction are visible in the rest-frame UV as Lyman Break Galaxies. The issue may not be settled until the sub-mm background is definitively resolved.

  2. 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

  3. High Resolution Science with High Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Windhorst, R.

    I will first review high resolution science that has been done with the Hubble Space Telescope on high redshift galaxies Next I will review the capabilities of the 6 5 meter James Webb Space Telescope JWST which is an optimized infrared telescope that can deploy automatically in space slated for launch to a halo L2 orbit in 2013 I will outline how the JWST can go about measuring First Light Reionization and Galaxy Assembly building on lessons learned from the Hubble Space Telescope I will show what more nearby galaxies observed in their restframe UV--optical light may look like to JWST at high redshifts Last I will summarize the Generation-X mission concept for an X-ray telescope designed to study the very early universe with 1000-times greater sensitivity than current facilities Gen-X will study the first generations of stars and black holes in the epoch z 10-20 the evolution of black holes and galaxies from high z to the present the chemical evolution of the universe and the properties of matter under extreme conditions This requires an effective area of 100 m 2 at 1 keV an angular resolution of 0 1 HPD over 0 1-10 keV

  4. Element abundances at high redshift

    NASA Technical Reports Server (NTRS)

    Meyer, David M.; Welty, D. E.; York, D. G.

    1989-01-01

    Abundances of Si(+), S(+), Cr(+), Mn(+), Fe(_), and Zn(+) are considered for two absorption-line systems in the spectrum of the QSO PKS 0528 - 250. Zinc and sulfur are underabundant, relative to H, by a factor of 10 compared to their solar and Galactic interstellar abundances. The silicon-, chromium-, iron-, and nickel-to-hydrogen ratios are less than the solar values and comparable to the local interstellar ratios. A straightforward interpretation is that nucleosynthesis in these high-redshift systems has led to only about one-tenth as much heavy production as in the gas clouds around the sun, and that the amount of the observed underabundances attributable to grain depletion is small. The dust-to-gas ratio in these clouds is less than 8 percent of the Galactic value.

  5. 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.

  6. High-redshift Fermi blazars

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Tagliaferri, G.; Foschini, L.; Ghirlanda, G.; Tavecchio, F.; Della Ceca, R.; Haardt, F.; Volonteri, M.; Gehrels, N.

    2011-02-01

    With the release of the first-year Fermi catalogue, the number of blazars detected above 100 MeV lying at high redshift has been largely increased. There are 28 blazars at z > 2 in the `clean' sample. All of them are flat spectrum radio quasars. We study and model their overall spectral energy distribution in order to find the physical parameters of the jet-emitting region, and for all of them, we estimate their black hole masses and accretion rates. We then compare the jet with the accretion disc properties, setting these sources in the broader context of all the other bright γ-ray or hard X-ray blazars. We confirm that the jet power correlates with the accretion luminosity. We find that the high-energy emission peak shifts to smaller frequencies as the observed luminosity increases, according to the blazar sequence, making the hard X-ray band the most suitable for searching the most-luminous and distant blazars.

  7. Simulating high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Salvaterra, Ruben; Ferrara, Andrea; Dayal, Pratika

    2011-06-01

    Recent observations have gathered a considerable sample of high-redshift galaxy candidates and determined the evolution of their luminosity function (LF). To interpret these findings, we use cosmological SPH simulations including, in addition to standard physical processes, a detailed treatment of the Pop III-Pop II transition in early objects. The simulated high-z galaxies match remarkably well the amplitude and slope of the observed LF in the redshift range 5 < z < 10. The LF shifts towards fainter luminosities with increasing redshift, while its faint-end slope keeps an almost constant value, α≈-2. The stellar populations of high-z galaxies have ages of 100-300 (40-130) Myr at z= 5 (z= 7-8), implying an early (z > 9.4) start of their star formation activity; the specific star formation rate is almost independent of galactic stellar mass. These objects are enriched rapidly with metals and galaxies identified by HST/WFC3 (?) show metallicities ≈0.1 Z⊙ even at z= 7-8. Most of the simulated galaxies at z≈ 7 (noticeably the smallest ones) are virtually dust-free, and none of them has an extinction larger than E(B-V) = 0.01. The bulk (50 per cent) of the ionizing photons is produced by objects populating the faint end of the LF (?), which JWST will resolve up to z= 7.3. Pop III stars continue to form essentially at all redshifts; however, at z= 6 (z= 10) the contribution of Pop III stars to the total galactic luminosity is always less than 5 per cent for ? (?). The typical high-z galaxies closely resemble the GRB host galaxy population observed at lower redshifts, strongly encouraging the use of GRBs to detect the first galaxies.

  8. 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.

  9. Probing the EBL evolution at high redshifts using 22 GRBs detected with the Fermi-LAT

    NASA Astrophysics Data System (ADS)

    Amitbhai Desai, Abhishek; Ajello, Marco; Omodei, Nicola; Hartmann, Dieter; Fermi-LAT Collaboration

    2017-01-01

    The extragalactic background light (EBL) is the collective emission of all the stars and galaxies over the history of the universe. The most efficient method to study the EBL is through the imprint it leaves via photon-photon annihilation in the spectra of distant gamma-ray sources. Here we present a combined analysis of a sample of 22 Gamma Ray Bursts (GRBs) detected by Fermi Large Area Telescope. GRBs are short-lived, bright, high-energy sources detected up to very high redshifts. This allows us to probe the EBL at much higher redshifts than before. We report the first constrain on the EBL when the Universe was one fourth of its present age (z=1.8). This will be discussed in the context of the generation of the UV-optical background and the star-formation activity of the Universe.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. DUST ATTENUATION IN HIGH REDSHIFT GALAXIES: 'DIAMONDS IN THE SKY'

    SciTech Connect

    Scoville, Nick; Capak, Peter; Steinhardt, Charles; Faisst, Andreas; Kakazu, Yuko; Li, Gongjie

    2015-02-20

    We use observed optical to near-infrared spectral energy distributions (SEDs) of 266 galaxies in the COSMOS survey to derive the wavelength dependence of the dust attenuation at high redshift. All of the galaxies have spectroscopic redshifts in the range z = 2-6.5. The presence of the C IV absorption feature, indicating that the rest-frame UV-optical SED is dominated by OB stars, is used to select objects for which the intrinsic, unattenuated spectrum has a well-established shape. Comparison of this intrinsic spectrum with the observed broadband photometric SED then permits derivation of the wavelength dependence of the dust attenuation. The derived dust attenuation curve is similar in overall shape to the Calzetti curve for local starburst galaxies. We also see the 2175 Å bump feature which is present in the Milky Way and Large Magellanic Cloud extinction curves but not seen in the Calzetti curve. The bump feature is commonly attributed to graphite or polycyclic aromatic hydrocarbons. No significant dependence is seen with redshift between sub-samples at z = 2-4 and z = 4-6.5. The 'extinction' curve obtained here provides a firm basis for color and extinction corrections of high redshift galaxy photometry.

  15. Powerful Quasar Outflows at High Redshifts

    NASA Astrophysics Data System (ADS)

    Aljanahi, Sara; Robert Scott Barrows

    2017-01-01

    Powerful quasar outflows can be driven by radiation pressure or radio jets, and they are capable of effecting the evolution of their host galaxies, particularly at high-redshifts (z~2)) when the quasar density peaks. We present a multi-wavelength analysis of 131 quasar outflows at high-redshifts (0.8high-redshift nature of this sample has pushed the systematic study of quasar outflows closer to the epoch in which quasar feedback is likely to have been important in galaxy evolution.

  16. Moderate resolution spectrophotometry of high redshift quasars

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  17. 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.

  18. 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.

  19. The Physical Conditions of Atomic Gas at High Redshift

    NASA Astrophysics Data System (ADS)

    Neeleman, Marcel

    In this thesis we provide insight into the chemical composition, physical conditions and cosmic distribution of atomic gas at high redshift. We study this gas in absorption against bright background quasars in absorption systems known as Damped Ly-alpha Systems (DLAs). These systems contain the bulk of the atomic gas at high redshift and are the likely progenitors of modern-day galaxies. In Chapter 2, we find that the atomic gas in DLAs obeys a mass-metallicity relationship that is similar to the mass-metallicity relationship seen in star-forming galaxies. The evolution of this relationship is linear with redshift, allowing for a planar equation to accurately describe this evolution, which provides a more stringent constraint on simulations modeling DLAs. Furthermore, the concomitant evolution of the mass-metallicity relationship of atomic gas and star-forming galaxies suggests an intimate link between the two. We next use a novel way to measure the physical conditions of the gas by using fine-structure line ratios of singly ionized carbon and silicon. By measuring the density of the upper and lower level states, we are able to determine the temperature, hydrogen density and electron density of the gas. We find that the conditions present in this high redshift gas are consistent with the conditions we see in the local interstellar medium (ISM). A few absorbers have higher than expected pressure, which suggests that they probe the ISM of star-forming galaxies. Finally in Chapter 4, we measure the cosmic neutral hydrogen density at redshifts below 1.6. Below this redshift, the Ly-alpha line of hydrogen is absorbed by the atmosphere, making detection difficult. Using the archive of the Hubble Space Telescope, we compile a comprehensive list of quasars for a search of DLAs at redshift below 1.6. We find that the incidence rate of DLAs and the cosmic neutral hydrogen density is smaller than previously measured, but consistent with the values both locally and at

  20. 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).

  1. 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.

  2. High-Redshift Astrophysics Using Every Photon

    NASA Astrophysics Data System (ADS)

    Breysse, Patrick; Kovetz, Ely; Rahman, Mubdi; Kamionkowski, Marc

    2017-01-01

    Large galaxy surveys have dramatically improved our understanding of the complex processes which govern gas dynamics and star formation in the nearby universe. However, we know far less about the most distant galaxies, as existing high-redshift observations can only detect the very brightest sources. Intensity mapping surveys provide a promising tool to access this poorly-studied population. By observing emission lines with low angular resolution, these surveys can make use of every photon in a target line to study faint emitters which are inaccessible using traditional techniques. With upcoming carbon monoxide experiments in mind, I will demonstrate how an intensity map can be used to measure the luminosity function of a galaxy population, and in turn how these measurements will allow us to place robust constraints on the cosmic star formation history. I will then show how cross-correlating CO isotopologue lines will make it possible to study gas dynamics within the earliest galaxies in unprecedented detail.

  3. Unveiling high redshift structures with Planck

    NASA Astrophysics Data System (ADS)

    Welikala, Niraj

    2012-07-01

    The Planck satellite, with its large wavelength coverage and all-sky survey, has a unique potential of systematically detecting the brightest and rarest submillimetre sources on the sky. We present an original method based on a combination of Planck and IRAS data which we use to select the most luminous submillimetre high-redshift (z>1-2) cold sources over the sky. The majority of these sources are either individual, strongly lensed galaxies, or represent the combined emission of several submillimetre galaxies within the large beam of Planck. The latter includes, in particular, rapidly growing galaxy groups and clusters. We demonstrate our selection method on the first 5 confirmations that include a newly discovered over-density of 5 submillimetre-bright sources which has been confirmed with Herschel/SPIRE observations and followed up with ground-based observations including VLT/XSHOOTER spectroscopy. Using Planck, we also unveil the nature of 107 high-redshift dusty, lensed submillimetre galaxies that have been previously observed over 940 square degrees by the South Pole Telescope (SPT). We stack these galaxies in the Planck maps, obtaining mean SEDs for both the bright (SPT flux F _{220 GHz} > 20 mJy) and faint (F _{220 GHz} < 20 mJy) galaxy populations. These SEDs and the derived mean redshifts suggest that the bright and faint sources belong to the same population of submillimetre galaxies. Stacking the lensed submillimetre galaxies in Planck also enables us to probe the z~1 environments around the foreground lenses and we obtain estimates of their clustering. Finally, we use the stacks to extrapolate SPT source counts to the Planck HFI frequencies, thereby estimating the contribution of the SPT sources at 220 GHz to the galaxy number counts at 353 and 545 GHz.

  4. Understanding the dark matter-light connection at high redshifts

    NASA Astrophysics Data System (ADS)

    Lee, Kyoung-Soo

    Deep, wide-field surveys have enhanced our understanding of galaxy formation and its close connection to the large-scale structures of dark matter in the universe. At high redshifts ( z > 2), in particular, where it is not possible to observe dark matter structures in other methods such as gravitational lensing or galaxy rotation curves, study of galaxy clustering provides a unique view into the formation of galaxies in large look-back times. In this thesis, I present a clustering study of star-forming galaxies at high redshifts ( z ~ 3- 5), observed and selected from two of the deepest multi-wavelength photometric data to date. First, I show that the UV luminosity (or star formation rate) of these galaxies scales closely with the degree of spatial clustering at all cosmic epochs probed from these surveys. In conjunction with the current, well- established theoretical framework of cold dark matter cosmology, this implies that star formation rate is primarily determined by the total mass of the virialized dark matter structures, or dark matter halos. In addition, I show that the measures of galaxy correlation function exhibits a strong upturn on small scales, which cannot be explained with the clustering of halos hosting these galaxies alone. This strongly suggests that multiple galaxies can share a single massive dark matter halo. A simple scaling law between the number of galaxy occupants and halo mass is sufficient to successfully reproduce the observed shape of the correlation function. However, there is uncertainty in drawing physical parameters of the halo-galaxy association which depends on the assumed form of the scaling law, or the halo occupation distribution (HOD). Physical interpretations are further exacerbated by the unknown degree of "fairness" that color-selected galaxies represent. I present an alternative approach which requires precise measurements of both the luminosity function and correlation function (of various luminosity thresholds). By

  5. Feedback in high redshift radio galaxies

    NASA Astrophysics Data System (ADS)

    De Breuck, Carlos; Nesvadba, Nicole; Lehnert, Matthew; Best, Philip

    High redshift radio galaxies are among the best objects to study AGN feedback in action, as they are among the most massive galaxies (1011 - 1012 M ) hosting powerful radio-loud AGN. I will present near-infrared imaging spectroscopy of a sample of over 50 radio galaxies at 2 < z < 5 using SINFONI at the VLT. We identify kpc-sized outflows of few x 1010 M of ionized gas, located along the radio source axis. Velocity fields are consistent with bipolar outflows, with total velocity offsets of 1000 km/s. FWHMs 1000 km/s suggest strong turbulence. The geometry is consistent with the radio source driving these outflows. Over the lifetime of the radio source (˜ 107 yr), these outflows can eject up to 1011 M of gas out of the gravitational potential of the host galaxy. Such mass loss would be sufficient to terminate star formation within the host galaxy. I will also present results from an ongoing follow-up programme to study the molecular gas in these high z radio galaxies using the IRAM interferometer. In several sources, we find a remarkable deficit in cold molecular relative to ionized gas, which may imply that significant fractions of the interstellar medium of these galaxies are participating in the winds.

  6. Survey For Very High-Redshift Quasars

    NASA Astrophysics Data System (ADS)

    Lemley, S.; MacAlpine, G.

    1997-12-01

    I will present the results from the deep, three color survey for very high redshift quasars. The survey involved direct imaging through Gunn gri filters using a 2048 x 2048 STIS ccd chip and Cerro Tololo's Curtis Scmidt Telescope. Quasar candidates in the range 4.0 < z < 5.4 were selected based on the detection of the Lyman alpha line and the strong drop in the spectrum blueward of this. Because of this response, quasars are clearly located away from the stellar locus on g - r vs. r - i diagrams. Quasar candidates in this redshift range have large values of g - r and small values of r - i. To confirm the candidates as quasars, the multi-fiber spectroscope Hydra, located on the WIYN telescope, was used. To date, spectral confirmation has been completed for ten degrees out of the approximately fifteen square degress of survey area. Several quasars were discovered, and I will present their spectra and information on the viability of this technique.

  7. 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.

  8. 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.

  9. 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

  10. High-redshift Fermi blazars observed by GROND and Swift

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Nardini, M.; Tagliaferri, Greiner, J.; Schady, P.; Rau, A.; Foschini, L.; Tavecchio, F.; Ghirlanda, G.; Sbarrato, T.

    2013-01-01

    We observed five γ-ray-loud blazars at redshift greater than 2 with the X-Ray Telescope (XRT) and the UltraViolet and Optical Telescope (UVOT) on-board the Swift satellite, and the Gamma-Ray burst Optical Near-Infrared Detector (GROND) instrument. These observations were quasi-simultaneous, usually within a few hours. For four of these blazars, the near-IR to UV data show the presence of an accretion disc, and we could reliably estimate its accretion rate and black hole mass. One of them, PKS 1348+007, was found in an extraordinarily high IR-optical state, almost two orders of magnitude brighter than at the epoch of the Sloan Digital Sky Survey observations. For all the five quasars, the physical parameters of the jet-emitting zone, derived by applying a one-zone emission model, are similar to that found for the bulk of other γ-ray-loud quasars. With our observations, we have X-ray data for the full sample of blazars at z > 2 present in the Fermi 2-year (2LAC) catalogue. This allows us to have a rather complete view of the spectral energy distribution of all high-redshift Fermi blazars, and to draw some conclusions about their properties, and especially about the relation between the accretion rate and the jet power.

  11. The problematic growth of dust in high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Ferrara, A.; Viti, S.; Ceccarelli, C.

    2016-11-01

    Dust growth via accretion of gas species has been proposed as the dominant process to increase the amount of dust in galaxies. We show here that this hypothesis encounters severe difficulties that make it unfit to explain the observed UV and IR properties of such systems, particularly at high redshifts. Dust growth in the diffuse ISM phases is hampered by (a) too slow accretion rates, (b) too high dust temperatures, and (c) the Coulomb barrier that effectively blocks accretion. In molecular clouds these problems are largely alleviated. Grains are cold (but not colder than the CMB temperature, TCMB ≈ 20 K at redshift z = 6). However, in dense environments accreted materials form icy water mantles, perhaps with impurities. Mantles are immediately (≲1 yr) photo-desorbed as grains return to the diffuse ISM at the end of the cloud lifetime, thus erasing any memory of the growth. We conclude that dust attenuating stellar light at high-z must be ready-made stardust largely produced in supernova ejecta.

  12. 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

  13. Studies of Resolved Stellar Clumps in High-Redshift Galaxy Analogs

    NASA Astrophysics Data System (ADS)

    Messa, Matteo Maria; Adamo, Angela; Östlin, Göran; Hayes, Matthew; Melinder, Jens

    2015-08-01

    The Lyman-alpha reference sample (LARS) is a sample of 14 local high-redshift analogues observed with the Hubble Space Telescope (HST). These local galaxies (z = 0.028 - 0.19) have been selected to have moderately high EW(Hα) to ensure the selection of star-forming systems and far UV luminosities ranging from log(LFUV) = 9.2 to 10.7 LSUN, comparable to those of high-redshift Lyα emitters and Lyman Break Galaxies. The survey is providing fundamental insights into Lyα emission process, allowing the investigation of Lyα radiation transport and photon escape.In this poster, we present the statistical study of the spatially resolved stellar cluster complexes and of the main star-forming regions of the LARS sample. The exquisite multiband HST coverage and the proximity of the galaxies of the sample allow us to derive the physical properties of these stellar clumps, such as ages, masses, extinction, and sizes. Using the UV fluxes, we constraint which fraction of the current star formation is condensed in these compact regions. We try to quantify their contribution to the total ionizing photon budget derived from total Hα fluxes. The properties of these cluster complexes are compared to clump properties detected in high-redshift galaxies.

  14. Detecting Massive, High-Redshift Galaxy Clusters Using the Thermal Sunyaev-Zel'dovich Effect

    NASA Astrophysics Data System (ADS)

    Adams, Carson; Steinhardt, Charles L.; Loeb, Abraham; Karim, Alexander; Staguhn, Johannes; Erler, Jens; Capak, Peter L.

    2017-01-01

    We develop the thermal Sunyaev-Zel'dovich (SZ) effect as a direct astrophysical measure of the mass distribution of dark matter halos. The SZ effect increases with cosmological distance, a unique astronomical property, and is highly sensitive to halo mass. We find that this presents a powerful methodology for distinguishing between competing models of the halo mass function distribution, particularly in the high-redshift domain just a few hundred million years after the Big Bang. Recent surveys designed to probe this epoch of initial galaxy formation such as CANDELS and SPLASH report an over-abundance of highly massive halos as inferred from stellar ultraviolet (UV) luminosities and the stellar mass to halo mass ratio estimated from nearby galaxies. If these UV luminosity to halo mass relations hold to high-redshift, observations estimate several orders of magnitude more highly massive halos than predicted by hierarchical merging and the standard cosmological paradigm. Strong constraints on the masses of these galaxy clusters are essential to resolving the current tension between observation and theory. We conclude that detections of thermal SZ sources are plausible at high-redshift only for the halo masses inferred from observation. Therefore, future SZ surveys will provide a robust determination between theoretical and observational predictions.

  15. Galaxies at High Redshift and Reionization

    NASA Astrophysics Data System (ADS)

    Bunker, A.; Stanway, E.; Ellis, R.; Lacy, M.; McMahon, R.; Eyles, L.; Stark, D.; Chiu, K.

    2008-08-01

    The quest to discover the most distant galaxies has developed rapidly in the last decade. We are now exploring redshifts of 6 and beyond, when the universe was less than a billion years old, an epoch when the previously neutral intergalactic medium was reionized. The continuing discovery of galaxies at progressively higher and higher redshifts has been driven by the availability of large telescopes on the ground and in space, improvements in detector technology, and new search strategies. Over the past 4 years, the Lyman-break technique has been shown to be effective in isolating z˜ 6 star-forming i'-drop galaxies through spectroscopic confirmation with large ground-based telescopes (Keck, Gemini, and the ESO VLTs). Narrow-band imaging, notably with the wide field of the Subaru telescope, has also produced samples of Lyman-α emitters at these redshifts. Analysis of the Hubble Ultra Deep Field (HUDF---the deepest images obtained so far, and likely to remain so until the James Webb Space Telescope, JWST), has enabled us to explore the faint end of the luminosity function, which may contribute the bulk of the total star formation. The discovery of this i'-drop galaxy population has been used to infer the global star-formation-rate density at this epoch (z˜ 6), and we are now beginning to constrain the contribution to reionization of the UV flux from these galaxies. Infrared data from the Spitzer Space Telescope have been used to determine the spectral energy distributions (SEDs) from the rest-frame UV to the optical of some i'-drops and constrain the previous star-formation histories, masses, and ages of these sources. The indications are that much of the stellar mass of these galaxies might have formed in vigorous bursts at z>6. The next big advances would be to test the population-synthesis modelling of these z˜ 6 galaxies through spectroscopy of the rest-frame optical (rather than crude broad-band SEDs) and also to push the observational horizon for galaxies

  16. Radiative transfer in a clumpy universe: The colors of high-redshift galaxies

    NASA Technical Reports Server (NTRS)

    Madau, Piero

    1995-01-01

    We assess the effects of the stochastic attenuation produced by intervening QSO absorption systems on the broadband colors of galaxies at cosmological distances. We compute the H I opacity of a clumpy universe as a function of redshift, including scattering in resonant lines, such as Lyman alpha, Lyman beta, Lyman gamma, and higher order members, and Lyman-continuum absorption. Both the numerous, optically thin Lyman-alpha forest clouds and the rarer, optically thick Lyman limit systems are found to contribute to the obscuration of background sources. We study the mean properties of primeval galaxies at high redshift in four broad optical passbands, U(sub n), B, G, and R. Even if young galaxies radiated a significant amount of ionizing photons, the attenuation due to the accumulated photoelectric opacity along the path is so severe that sources beyond z approximately 3 will drop out of the U(sub n) image together. We also show that the observed B-R color of distant galaxies can be much redder than expected from a stellar population. At z approximately 3.5, the blanketing by discrete absorption lines in the Lyman series is so effective that background galaxies appear, on average, 1 mag fainter in B. By z approximately 4, the observed B magnitude increment due to intergalactic absorption exceeds 2 mag. By modeling the intrinsic UV spectral energy distribution of star-forming galaxies with a stellar population synthesis code, we show that the (B-R)(sub AB) approximately 0 criterion for identifying 'flat-spectrum,' metal-producing galaxies is biased against objects at z greater than 3. The continuum blanketing from the Lyman series produces a characteristic staircase profile in the transmitted power. We suggest that this cosmic Lyman decrement might be used as a tool to identify high-z galaxies.

  17. 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.

  18. Local analogs of high-redshift galaxies: Interstellar medium conditions

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    Local analog galaxies play an important role in understanding the properties of high-redshift galaxies. We present a method to select a type of local analog that closely resembles the ionized interstellar medium conditions in high-redshift galaxies. These galaxies are selected based on their locations in the [O III]/Hβ versus [N II]/Hα nebular emission-line diagnostic diagram. 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. We find that the high sSFR and SFR surface density can enhance the electron densities and the ionization parameters, but still cannot fully explain the difference in ISM condition between nearby galaxies and the local analogs/high-redshift galaxies.

  19. Dark-ages reionization and galaxy-formation simulation - VII. The sizes of high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Liu, Chuanwu; Mutch, Simon J.; Poole, Gregory B.; Angel, P. W.; Duffy, Alan R.; Geil, Paul M.; Mesinger, Andrei; Wyithe, J. Stuart B.

    2017-03-01

    We investigate high-redshift galaxy sizes using a semi-analytic model constructed for the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulation project. Our fiducial model, including strong feedback from supernovae and photoionization background, accurately reproduces the evolution of the stellar mass function and ultraviolet (UV) luminosity function. Using this model, we study the size-luminosity relation of galaxies and find that the effective radius scales with UV luminosity as Re ∝ L0.25 at z ∼ 5-9. We show that recently discovered very luminous galaxies at z ∼ 7 and 11 lie on our predicted size-luminosity relations. We find that a significant fraction of galaxies at z > 8 will not be resolved by James Webb Space Telescope, but Giant Magellan Telescope will have the ability to resolve all galaxies in haloes above the atomic cooling limit. We show that our fiducial model successfully reproduces the redshift evolution of average galaxy sizes at z > 5. We also explore galaxy sizes in models without supernova feedback. The no-supernova feedback models produce galaxy sizes that are smaller than observations. We therefore confirm that supernova feedback plays an important role in determining the size-luminosity relation of galaxies and its redshift evolution during reionization.

  20. 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.

  1. 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.

  2. Escape fraction of ionizing photons from high-redshift galaxies in cosmological SPH simulations

    NASA Astrophysics Data System (ADS)

    Yajima, Hidenobu; Choi, Jun-Hwan; Nagamine, Kentaro

    2011-03-01

    Combing the three-dimensional radiative transfer (RT) calculation and cosmological smoothed particle hydrodynamics (SPH) simulations, we study the escape fraction of ionizing photons (fesc) of high-redshift galaxies at z= 3-6. Our simulations cover the halo mass range of Mh= 109-1012 M⊙. We post-process several hundred simulated galaxies with the Authentic Radiative Transfer (ART) code to study the halo mass dependence of fesc. In this paper, we restrict ourselves to the transfer of stellar radiation from local stellar population in each dark matter halo. We find that the average fesc steeply decreases as the halo mass increases, with a large scatter for the lower-mass haloes. The low-mass haloes with Mh˜ 109 M⊙ have large values of fesc (with an average of ˜0.4), whereas the massive haloes with Mh˜ 1011 M⊙ show small values of fesc (with an average of ˜0.07). This is because in our simulations, the massive haloes show more clumpy structure in gas distribution, and the star-forming regions are embedded inside these clumps, making it more difficult for the ionizing photons to escape. On the other hand, in low-mass haloes, there are often conical regions of highly ionized gas due to the shifted location of young star clusters from the centre of dark matter halo, which allows the ionizing photons to escape more easily than in the high-mass haloes. By counting the number of escaped ionizing photons, we show that the star-forming galaxies can ionize the intergalactic medium at z= 3-6. The main contributor to the ionizing photons is the haloes with Mh≲ 1010 M⊙ owing to their high fesc. The large dispersion in fesc suggests that there may be various sizes of H II bubbles around the haloes even with the same mass in the early stages of reionization. We also examine the effect of UV background radiation field on fesc using simple, four different treatments of UV background.

  3. The High-Redshift Clustering of Photometrically Selected Quasars

    NASA Astrophysics Data System (ADS)

    Timlin, John

    2017-01-01

    We present the data from the Spitzer IRAC Equatorial Survey (SpIES) along with our first high-redshift (2.9high-redshift quasars. Using the infrared data from SpIES and SHELA, and the deep optical data from SDSS, we employ the multi-dimensional Bayesian selection algorithm outlined in Richards et al. 2015 to identify ~5000 high-redshift quasar candidates in this field. We then combine these candidates with spectroscopically confirmed high-redshift quasars and measure the redshift space correlation function and the projected correlation function. Finally, using these results, we compute the linear bias to try to constrain quasar feedback models akin to those in Hopkins et al. 2007.

  4. Life On The Edge: A Measurement Of The Cosmic UV Background At Z 0

    NASA Astrophysics Data System (ADS)

    Uson, Juan M.; Adams, J. J.; Hill, G. J.; MacQueen, P. J.

    2012-01-01

    We have used the VIRUS-P integral-field spectrometer on the University of Texas McDonald Observatory 2.7m telescope to observe the edge of the superthin spiral galaxy UGC7321. We detect faint Hα emission as expected from the exposure of the peripheral neutral Hydrogen gas traced by its 21cm radio emission to the metagalactic UV background. Observations of the intensity of the UV background and its redshift evolution are important to the theory and simulations of the evolution of large scale structure in the Universe as the UV background controls the cooling and collapse of small halos and is itself determined by the global histories of quasar and star formation. We have used dithered expositions with three pointings that fill in the gaps in the VIRUS-P detector for essentially full spatial coverage over a field of view of 1.6‧ x 1.6‧ and a spectral resolution of R = 3860 from 6040 Å to 6740 Å that allows us to resolve bright OH sky lines and geocoronal Hα from our target wavelength of 6574 Å. The Hα layer appears rather thin, with a peak surface brightness of Σ = 1.4 x 10-19 erg s-1 cm-2 arcsec-2 Å-1 for spectra smoothed with a 15″ spatial kernel. This leads to a measurement of the cosmic UV background induced HI photoionization rate Γ = 3.4 x 10-14 s-1 ( 5σ, preliminary absolute calibration). Contrary to past observational attempts, our measurements covered a large, two-dimensional on-sky area. We reach flux limits that are 50 times fainter than the sky background with significant smoothing over spatial elements and applying a sky background model that accounts for variations in the spectral resolution of our instrument. At this writing, we are continuing with the analysis of the data. Final results will be announced at the meeting.

  5. 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.

  6. The Formation of Massive Primordial Stars in the Presence of Moderate UV Backgrounds

    NASA Astrophysics Data System (ADS)

    Latif, M. A.; Schleicher, D. R. G.; Bovino, S.; Grassi, T.; Spaans, M.

    2014-09-01

    Radiative feedback produced by stellar populations played a vital role in early structure formation. In particular, photons below the Lyman limit can escape the star-forming regions and produce a background ultraviolet (UV) flux, which consequently may influence the pristine halos far away from the radiation sources. These photons can quench the formation of molecular hydrogen by photodetachment of H-. In this study, we explore the impact of such UV radiation on fragmentation in massive primordial halos of a few times 107 M ⊙. To accomplish this goal, we perform high resolution cosmological simulations for two distinct halos and vary the strength of the impinging background UV field in units of J 21 assuming a blackbody radiation spectrum with a characteristic temperature of T rad = 104 K. We further make use of sink particles to follow the evolution for 10,000 yr after reaching the maximum refinement level. No vigorous fragmentation is observed in UV-illuminated halos while the accretion rate changes according to the thermal properties. Our findings show that a few 102-104 solar mass protostars are formed when halos are irradiated by J 21 = 10-500 at z > 10 and suggest a strong relation between the strength of the UV flux and mass of a protostar. This mode of star formation is quite different from minihalos, as higher accretion rates of about 0.01-0.1 M ⊙ yr-1 are observed by the end of our simulations. The resulting massive stars are potential cradles for the formation of intermediate-mass black holes at earlier cosmic times and contribute to the formation of a global X-ray background.

  7. The formation of massive primordial stars in the presence of moderate UV backgrounds

    SciTech Connect

    Latif, M. A.; Schleicher, D. R. G.; Bovino, S.; Grassi, T.; Spaans, M.

    2014-09-01

    Radiative feedback produced by stellar populations played a vital role in early structure formation. In particular, photons below the Lyman limit can escape the star-forming regions and produce a background ultraviolet (UV) flux, which consequently may influence the pristine halos far away from the radiation sources. These photons can quench the formation of molecular hydrogen by photodetachment of H{sup –}. In this study, we explore the impact of such UV radiation on fragmentation in massive primordial halos of a few times 10{sup 7} M {sub ☉}. To accomplish this goal, we perform high resolution cosmological simulations for two distinct halos and vary the strength of the impinging background UV field in units of J {sub 21} assuming a blackbody radiation spectrum with a characteristic temperature of T {sub rad} = 10{sup 4} K. We further make use of sink particles to follow the evolution for 10,000 yr after reaching the maximum refinement level. No vigorous fragmentation is observed in UV-illuminated halos while the accretion rate changes according to the thermal properties. Our findings show that a few 10{sup 2}-10{sup 4} solar mass protostars are formed when halos are irradiated by J {sub 21} = 10-500 at z > 10 and suggest a strong relation between the strength of the UV flux and mass of a protostar. This mode of star formation is quite different from minihalos, as higher accretion rates of about 0.01-0.1 M {sub ☉} yr{sup –1} are observed by the end of our simulations. The resulting massive stars are potential cradles for the formation of intermediate-mass black holes at earlier cosmic times and contribute to the formation of a global X-ray background.

  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.; 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.

  9. HUBBLE SPACE TELESCOPE Imaging of the Host Galaxies of High-RedshiftRadio-loud Quasars

    NASA Astrophysics Data System (ADS)

    Lehnert, Matthew D.; van Breugel, Wil J. M.; Heckman, Timothy M.; Miley, George K.

    1999-09-01

    We present rest-frame UV and Lyα images of spatially resolved structures (``hosts'') around five high-redshift radio-loud quasars obtained with the WFPC2 camera on the Hubble Space Telescope (HST). The quasars were imaged with the PC1 through the F555W (``V''-band) filter, which at the redshifts of the quasars (2.1high redshift have prominent host galaxies that appeared to have properties similar to those of high-redshift radio galaxies. Our HST observations allow a more detailed investigation of quasar host morphologies and a comparison with similar HST studies of radio galaxies by others. Using several methods to measure and quantify the host properties we find that all five quasars are extended and that this ``fuzz'' contains ~5%-40% of the total continuum flux and 15%-65% of the Lyα flux within a radius of about 1.5". The rest-frame UV luminosities of the hosts are log λPλ~11.9-12.5 Lsolar (assuming no internal dust extinction), comparable to the luminous radio galaxies at similar redshifts and a factor 10 higher than both radio-quiet field galaxies at z~2-3 and the most UV-luminous low-redshift starburst galaxies. The Lyα luminosities of the hosts are log LLyα~44.3-44.9 ergs s-1, which are also similar to the those of luminous high-redshift radio galaxies and considerably larger than the Lyα luminosities of high-redshift field galaxies. To generate the Lyα luminosities of the hosts would require roughly a few percent of the total observed ionizing luminosity of the quasar. The UV continuum morphologies of the hosts appear complex and knotty at the relatively high surface brightness levels of our exposures (about 24 V mag arcsec-2). In two quasars we find evidence for foreground galaxies that confuse the

  10. 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.

  11. Searching for Extreme High Redshift Galaxies with HST Grism Spectroscopy

    NASA Astrophysics Data System (ADS)

    Weaver, John R.; Maseda, Michael

    2017-01-01

    With ever increasing capability, we are now able to push galaxy evolution studies to extreme high redshift (z>6). At these early times, the first galaxies begin forming stars but some of their light is quickly absorbed by the neutral intergalactic medium. The result is that the La line of hydrogen is lost. But, with the recent upgrades to HST, we can now utilize the unique multiplexing capacity of slitless grism spectroscopy to explore large samples of candidate systems. By taking near-IR spectra for for every object in the field-of-view simultaneously, we can begin searching for galaxies with a favorable circumgalactic gas distribution where La emission may be obtained. In this study we build on the work of 3D-HST to search for extreme high redshift galaxies (6high redshift galaxies. Follow-up of confirmed candidates will strengthen existing samples of distant galaxies and constrain properties of the early universe.

  12. High-redshift major mergers weakly enhance star formation

    NASA Astrophysics Data System (ADS)

    Fensch, J.; Renaud, F.; Bournaud, F.; Duc, P.-A.; Agertz, O.; Amram, P.; Combes, F.; Di Matteo, P.; Elmegreen, B.; Emsellem, E.; Jog, C. J.; Perret, V.; Struck, C.; Teyssier, R.

    2017-02-01

    Galaxy mergers are believed to trigger strong starbursts. This is well assessed by observations in the local Universe. However, the efficiency of this mechanism has poorly been tested so far for high-redshift, actively star-forming, galaxies. We present a suite of pc-resolution hydrodynamical numerical simulations to compare the star formation process along a merging sequence of high- and low-redshift galaxies, by varying the gas mass fraction between the two models. We show that, for the same orbit, high-redshift gas-rich mergers are less efficient than low-redshift ones at producing starbursts; the star formation rate excess induced by the merger and its duration are both around 10 times lower than in the low gas fraction case. The mechanisms that account for the star formation triggering at low redshift - the increased compressive turbulence, gas fragmentation, and central gas inflows - are only mildly, if not at all, enhanced for high gas fraction galaxy encounters. Furthermore, we show that the strong stellar feedback from the initially high star formation rate in high-redshift galaxies does not prevent an increase of the star formation during the merger. Our results are consistent with the observed increase of the number of major mergers with increasing redshift being faster than the respective increase in the number of starburst galaxies.

  13. 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.

  14. 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.

  15. A physical model for the evolving ultraviolet luminosity function of high redshift galaxies and their contribution to the cosmic reionization

    SciTech Connect

    Cai, Zhen-Yi; Lapi, Andrea; Bressan, Alessandro; De Zotti, Gianfranco; Danese, Luigi; Negrello, Mattia

    2014-04-10

    We present a physical model for the evolution of the ultraviolet (UV) luminosity function of high-redshift galaxies, taking into account in a self-consistent way their chemical evolution and the associated evolution of dust extinction. Dust extinction is found to increase fast with halo mass. A strong correlation between dust attenuation and halo/stellar mass for UV selected high-z galaxies is thus predicted. The model yields good fits of the UV and Lyman-α (Lyα) line luminosity functions at all redshifts at which they have been measured. The weak observed evolution of both luminosity functions between z = 2 and z = 6 is explained as the combined effect of the negative evolution of the halo mass function; of the increase with redshift of the star formation efficiency due to the faster gas cooling; and of dust extinction, differential with halo mass. The slope of the faint end of the UV luminosity function is found to steepen with increasing redshift, implying that low luminosity galaxies increasingly dominate the contribution to the UV background at higher and higher redshifts. The observed range of the UV luminosities at high z implies a minimum halo mass capable of hosting active star formation M {sub crit} ≲ 10{sup 9.8} M {sub ☉}, which is consistent with the constraints from hydrodynamical simulations. From fits of Lyα line luminosity functions, plus data on the luminosity dependence of extinction, and from the measured ratios of non-ionizing UV to Lyman-continuum flux density for samples of z ≅ 3 Lyman break galaxies and Lyα emitters, we derive a simple relationship between the escape fraction of ionizing photons and the star formation rate. It implies that the escape fraction is larger for low-mass galaxies, which are almost dust-free and have lower gas column densities. Galaxies already represented in the UV luminosity function (M {sub UV} ≲ –18) can keep the universe fully ionized up to z ≅ 6. This is consistent with (uncertain) data

  16. 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

  17. 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

  18. VLP - High-Redshift AGNs and the X-SERVS Survey

    NASA Astrophysics Data System (ADS)

    Brandt, W.

    2016-06-01

    In the first part of this talk, I will review how X-ray observations of high-redshift AGNs at z = 4-7 have played a critical role in understanding their basic demographics as well as their physical processes; e.g., accretion rates, jet emission, X-ray absorption by nuclear material and winds. Since 2000, XMM-Newton and Chandra have provided new X-ray detections for more than 120 such objects, and well-defined samples of z > 4 AGNs now allow reliable basic X-ray population studies. I will point out key remaining areas of uncertainty, highlighting where further XMM-Newton and Chandra observations can advance understanding. I will then describe the X-SERVS project which aims to go ``beyond COSMOS'' via a 12 deg^2 survey of three prime sky regions: W-CDF-S, XMM-LSS, and ELAIS-S1. The X-SERVS survey will allow outstanding studies of the detected AGNs and groups/clusters by powerfully leveraging multiple intensive radio-to-UV surveys: ATLAS/HerMES/SERVS/VIDEO/DES/HSC/PS1MD/VOICE/CSI/PRIMUS. We aim to dramatically advance studies of SMBH growth across the full range of cosmic environments, links between SMBH accretion and star formation, exceptional AGNs at high redshifts, protoclusters, etc. The targeted X-SERVS fields will have extraordinary legacy value as MOONS massive spectroscopy fields, prime ALMA fields, and DES/LSST deep-drilling fields.

  19. The Main Sequences of Star-forming Galaxies and Active Galactic Nuclei at High Redshift

    NASA Astrophysics Data System (ADS)

    Mancuso, C.; Lapi, A.; Shi, J.; Cai, Z.-Y.; Gonzalez-Nuevo, J.; Béthermin, M.; Danese, L.

    2016-12-01

    We provide a novel, unifying physical interpretation on the origin, average shape, scatter, and cosmic evolution for the main sequences of star-forming galaxies and active galactic nuclei (AGNs) at high redshift z≳ 1. We achieve this goal in a model-independent way by exploiting: (i) the redshift-dependent star formation rate functions based on the latest UV/far-IR data from HST/Herschel, and related statistics of strong gravitationally lensed sources; (ii) deterministic evolutionary tracks for the history of star formation and black hole accretion, gauged on a wealth of multiwavelength observations including the observed Eddington ratio distribution. We further validate these ingredients by showing their consistency with the observed galaxy stellar mass functions and AGN bolometric luminosity functions at different redshifts via the continuity equation approach. Our analysis of the main sequence for high-redshift galaxies and AGNs highlights that the present data are consistently interpreted in terms of an in situ coevolution scenario for star formation and black hole accretion, envisaging these as local, time-coordinated processes.

  20. Broadband and Narrowband Search for z < 1 Analogs of High Redshift Star Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Rosenwasser, Benjamin; Barger, Amy J.; Wold, Isak; Lauchlan Cowie, Lennox

    2017-01-01

    Studies of high redshift (z > 6) galaxies rely on extreme broadband colors from Spitzer/IRAC to select samples of low-mass star forming galaxies. These broadband excess searches are biased towards galaxies with the strongest emission lines, and the extent to which existing studies miss fainter galaxies with lower star formation rates remains unknown. Using both broadband (BB) and narrowband (NB) imaging from the HyperSuprimeCam (HSC) and SuprimeCam (SC) on the Subaru Telescope, we have performed a search for z < 1 strong emission line galaxies, which are analogs of the high redshift population. The search was performed over roughly 4 square degrees centered on the COSMOS field, and the narrowband filters allow us to probe fainter emission lines than the broadband searches. We carried out spectral followup of our BB excess and NB excess samples using WIYN/Hydra to measure redshifts and line ratios in order to understand the biases in the different selection techniques. We also investigate the rest frame UV properties of our sample using data from GALEX. This study demonstrates the effectiveness of using broadband colors to select intermediate redshift emission line galaxies.

  1. Detecting Relativistic X-Ray Jets in High-redshift Quasars

    NASA Astrophysics Data System (ADS)

    McKeough, Kathryn; Siemiginowska, Aneta; Cheung, C. C.; Stawarz, Łukasz; Kashyap, Vinay L.; Stein, Nathan; Stampoulis, Vasileios; van Dyk, David A.; Wardle, J. F. C.; Lee, N. P.; Harris, D. E.; Schwartz, D. A.; Donato, Davide; Maraschi, Laura; Tavecchio, Fabrizio

    2016-12-01

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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Structure of the Universe at Small and High Redshifts

    NASA Astrophysics Data System (ADS)

    Doroshkevich, A.; Turchaninov, V.

    1998-12-01

    The approximate theoretical description of the formation and evolution of the structure of the universe proposed by Demianski and Doroshkevich (1998) is compared with observed and simulated matter distribution at small and high redshifts. It is found that for the CDM-like power spectrum and suitable parameters of the cosmological model the effective matter compression reaches at small redshifts the observed scales Rwall ~20 - 25h^{-1}Mpc with the typical mean separation of wall-like elements DSLSS 50 - 70h^{-1}Mpc. We show that the same theoretical model explains well both the redshift, temperature and NHI distributions of absorption lines observed in the spectra of quasars at redshifts 2 <= z <= 3.5. The models with 0.3 <= Omega_m <= 0.5 give better description of the observed structure parameters.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Mapping metals at high redshift with far-infrared lines

    NASA Astrophysics Data System (ADS)

    Pallottini, A.; Gallerani, S.; Ferrara, A.; Yue, B.; Vallini, L.; Maiolino, R.; Feruglio, C.

    2015-10-01

    Cosmic metal enrichment is one of the key physical processes regulating galaxy formation and the evolution of the intergalactic medium (IGM). However, determining the metal content of the most distant galaxies has proven so far almost impossible; also, absorption line experiments at z ≳ 6 become increasingly difficult because of instrumental limitations and the paucity of background quasars. With the advent of Atacama Large Millimeter/submillimeter Array (ALMA), far-infrared emission lines provide a novel tool to study early metal enrichment. Among these, the [C II] line at 157.74 μm is the most luminous line emitted by the interstellar medium of galaxies. It can also resonant scatter comic microwave background (CMB) photons inducing characteristic intensity fluctuations (ΔI/ICMB) near the peak of the CMB spectrum, thus allowing to probe the low-density IGM. We compute both [C II] galaxy emission and metal-induced CMB fluctuations at z ˜ 6 by using adaptive mesh refinement cosmological hydrodynamical simulations and produce mock observations to be directly compared with ALMA Band 6 data (νobs ˜ 272 GHz). The [C II] line flux is correlated with MUV as log (F_peak/μ Jy)= -27.205 -2.253 M_UV -0.038 M_UV^2. Such relation is in very good agreement with recent ALMA observations of MUV < -20 galaxies by e.g. Maiolino et al. and Capak et al. We predict that a MUV = -19 (MUV = -18) galaxy can be detected at 4σ in ≃40 (2000) h, respectively. CMB resonant scattering can produce ≃ ± 0.1 μJy/beam emission/absorptions features that are very challenging to be detected with current facilities. The best strategy to detect these signals consists in the stacking of deep ALMA observations pointing fields with known MUV ≃ -19 galaxies. This would allow to simultaneously detect both [C II] emission from galactic reionization sources and CMB fluctuations produced by z ˜ 6 metals.

  15. 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}.

  16. Close Companions to Two High-redshift Quasars

    NASA Astrophysics Data System (ADS)

    McGreer, Ian D.; Fan, Xiaohui; Strauss, Michael A.; Haiman, Zoltàn; Richards, Gordon T.; Jiang, Linhua; Bian, Fuyan; 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 AB = 23.6) located 2'' (12 kpc projected) from the quasar with strong Lyα emission (EW0 ≈ 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 AB = 25) at a separation of 0.''9. The red i 775 - Y 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. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs #12184 and #12493. Observations were also made with the LBT and MMT.

  17. The formation and evolution of high-redshift dusty galaxies

    NASA Astrophysics Data System (ADS)

    Ma, Jingzhe; Gonzalez, Anthony H.; Ge, Jian; Vieira, Joaquin D.; Prochaska, Jason X.; Spilker, Justin; Strandet, Maria; Ashby, Matthew; Noterdaeme, Pasquier; Lundgren, Britt; Zhao, Yinan; Ji, Tuo; Zhang, Shaohua; Caucal, Paul; SPT SMG Collaboration

    2017-01-01

    Star formation and chemical evolution are among the biggest questions in galaxy formation and evolution. High-redshift dusty galaxies are the best sites to investigate mass assembly and growth, star formation rates, star formation history, chemical enrichment, and physical conditions. My thesis is based on two populations of high-redshift dusty galaxies, submillimeter galaxies (SMGs) and quasar 2175 Å dust absorbers, which are selected by dust emission and dust absorption, respectively.For the SMG sample, I have worked on the gravitationally lensed dusty, star-forming galaxies (DSFGs) at 2.8 < z < 5.7, which were first discovered by the South Pole Telescope (SPT) and further confirmed by ALMA. My thesis is focused on the stellar masses and star formation rates of these objects by means of multi-wavelength spectral energy distribution (SED) modelling. The data include HST/WFC3, Spitzer/IRAC, Herschel/PACS, Herschel/SPIRE, APEX/Laboca and SPT. Compared to the star-forming main sequence (MS), these DSFGs have specific SFRs that lie above the MS, suggesting that we are witnessing ongoing strong starburst events that may be driven by major mergers. SPT0346-52 at z = 5.7, the most extraordinary source in the SPT survey for which we obtained Chandra X-ray and ATCA radio data, was confirmed to have the highest star formation surface density of any known galaxy at high-z.The other half of my thesis is focused on a new population of quasar absorption line systems, 2175 Å dust absorbers, which are excellent probes of gas and dust properties, chemical evolution and physical conditions in the absorbing galaxies. This sample was selected from the SDSS and BOSS surveys and followed up with the Echelle Spectrographs and Imager on the Keck-II telescope, the Red & Blue Channel Spectrograph on the Multiple Mirror Telescope, and the Ultraviolet and Visible Echelle Spectrograph onboard the Very Large Telescope. We found a correlation between the presence of the 2175 Å bump and other

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. A Survey for Very High-Redshift Quasars

    NASA Astrophysics Data System (ADS)

    Lemley, Shelley R.

    1995-12-01

    I have been conducting a deep, three color survey for very high redshift quasars and will present information on how my candidates, which are awaiting spectroscopic confirmation, have been selected. The survey involves direct imaging through Gunn gri filters using a 2048 x 2048 STIS ccd chip and Cerro Tololo's Curtis Scmidt Telescope. Quasar candidates in the range 4.2 < z < 5.4 have been selected based on the detection of the Lyman alpha line and the strong drop in the spectrum blueward of this. Because of this response, quasars are clearly located away from the stellar locus on g - r vs. r - i diagrams. Quasar candidates with z ~ 4.5 have large values of g - r and values of r - i near zero. The z>5 candidates have large r - i values and g - r values near zero. Before beginning the survey, test observations using this selection method were made of two known quasars with redshifts of 4.5 and 4.7. The quasars were successfully relocated by the technique and several candidates, which will also be observed for spectroscopic confirmation, were selected from those two fields. To date, 13 square degrees have been surveyed.

  4. Tracing high redshift cosmic web with quasar systems

    NASA Astrophysics Data System (ADS)

    Einasto, Maret

    2016-10-01

    We study the cosmic web at redshifts 1.0 <= <= 1.8 using quasar systems based on quasar data from the SDSS DR7 QSO catalogue. Quasar systems were determined with a friend-of-friend (FoF) algorithm at a series of linking lengths. At the linking lengths l <= 30 h -1 Mpc the diameters of quasar systems are smaller than the diameters of random systems, and are comparable to the sizes of galaxy superclusters in the local Universe. The mean space density of quasar systems is close to the mean space density of local rich superclusters. At larger linking lengths the diameters of quasar systems are comparable with the sizes of supercluster complexes in our cosmic neighbourhood. The richest quasar systems have diameters exceeding 500h Mpc. Very rich systems can be found also in random distribution but the percolating system which penetrate the whole sample volume appears in quasar sample at smaller linking length than in random samples showing that the large-scale distribution of quasar systems differs from random distribution. Quasar system catalogues at our web pages (http://www.aai.ee/maret/QSOsystems.html) serve as a database to search for superclusters of galaxies and to trace the cosmic web at high redshifts.

  5. Radio Selected Clusters of Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Wing, Joshua; Blanton, Elizabeth

    2010-08-01

    Previous studies have shown that three-component radio sources exhibiting some degree of bending between components are likely to be found in galaxy clusters. Often this radio emission is associated with a cD type galaxy at the center of a cluster. We have cross-correlated the Sloan Digital Sky Survey (SDSS) with samples selected from the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) catalog and measured the richness of the cluster environments surrounding three- component sources exhibiting both bent and straight lobes. This has lead to the discovery and classification of a large number of galaxy clusters out to a redshift of z ~ 0.5. For both bent- and straight- lobed sources without an optical counterpart it is likely that the radio emission is associated with a galaxy fainter than m_r=22 (the limiting magnitude of the SDSS) and at a redshift higher than z~0.8. We propose to observe a small sub-sample of these sources with the FLAMINGOS instrument on the Mayall 4-m telescope in an attempt to discover if these sources are located in high redshift (z≳0.8) galaxy clusters. In our visually-selected bent radio source sample, 78% of sources with counterparts in the SDSS are associated with clusters.

  6. Dusty Star Forming Galaxies and Supermassive Black Holes at High Redshifts: In- Situ Coevolution

    NASA Astrophysics Data System (ADS)

    Mancuso, Claudia

    2016-10-01

    We have exploited the continuity equation approach and the star-formation timescales derived from the observed 'main sequence' relation (Star Formation Rate vs Stellar Mass), to show that the observed high abundance of galaxies with stellar masses ≥ a few 10^10 M⊙ at redshift z ≥ 4 implies the existence of a galaxy population featuring large star formation rates (SFRs) ψ ≥ 10^2 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-InfraRed (FIR) 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, elucidating that the number density at z ≤ 8 for SFRs ψ ≥ 30 M⊙ yr^-1 cannot be estimated relying on the UltraViolet (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 AzTEC-LABOCA, SCUBA-2 and ALMA-SPT surveys are already digging into it. We substantiate how an observational strategy based on a color preselection in the far-IR or (sub-)mm band with Herschel and SCUBA-2, supplemented by photometric data via on-source observations with ALMA, can allow 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-)mm observations by ALMA and NIKA2. The same could be done with radio observations by SKA and its precursors. In particular we have worked out predictions for the radio counts of star-forming galaxies down to nJy levels, along with redshift distributions down to the detection limits of the phase 1 Square Kilometer Array MID telescope (SKA1-MID) and of its precursors. To do that we

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

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

    SciTech Connect

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

    2014-12-01

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

  9. Suppression of cucumber powdery mildew by UV-B is affected by background light quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Brief (5-10 min) exposure to UV-B radiation (280-300 nm) suppressed powdery mildew (Podosphaera xanthii) on Cucumis sativus. The effect was enhanced by red light (600-660 nm), but offset by blue light (420-500 nm) and UV-A (300-420 nm). Compared to untreated controls, 2 h red light from specific lig...

  10. Strongly time-variable ultraviolet metal-line emission from the circum-galactic medium of high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Sravan, Niharika; Faucher-Giguère, Claude-André; van de Voort, Freeke; Kereš, Dušan; Muratov, Alexander L.; Hopkins, Philip F.; Feldmann, Robert; Quataert, Eliot; Murray, Norman

    2016-11-01

    We use cosmological simulations from the Feedback In Realistic Environments project, which implement a comprehensive set of stellar feedback processes, to study ultraviolet (UV) metal-line emission from the circum-galactic medium of high-redshift (z = 2-4) galaxies. Our simulations cover the halo mass range Mh ˜ 2 × 1011-8.5 × 1012 M⊙ at z = 2, representative of Lyman break galaxies. Of the transitions we analyse, the low-ionization C III (977 Å) and Si III (1207 Å) emission lines are the most luminous, with C IV (1548 Å) and Si IV (1394 Å) also showing interesting spatially extended structures. The more massive haloes are on average more UV-luminous. The UV metal-line emission from galactic haloes in our simulations arises primarily from collisionally ionized gas and is strongly time variable, with peak-to-trough variations of up to ˜2 dex. The peaks of UV metal-line luminosity correspond closely to massive and energetic mass outflow events, which follow bursts of star formation and inject sufficient energy into galactic haloes to power the metal-line emission. The strong time variability implies that even some relatively low-mass haloes may be detectable. Conversely, flux-limited samples will be biased towards haloes whose central galaxy has recently experienced a strong burst of star formation. Spatially extended UV metal-line emission around high-redshift galaxies should be detectable by current and upcoming integral field spectrographs such as the Multi Unit Spectroscopic Explorer on the Very Large Telescope and Keck Cosmic Web Imager.

  11. 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.

  12. STAR FORMATION IN HIGH-REDSHIFT CLUSTER ELLIPTICALS

    SciTech Connect

    Wagner, Cory R.; Brodwin, Mark; Snyder, Gregory F.; Gonzalez, Anthony H.; Mancone, Conor L.; Stanford, S. A.; Alberts, Stacey; Pope, Alexandra; Stern, Daniel; Eisenhardt, Peter R. M.; Zeimann, Gregory R.; Chary, Ranga-Ram; Dey, Arjun; Moustakas, John

    2015-02-20

    We measure the star formation rates (SFRs) of massive (M {sub *} > 10{sup 10.1} M {sub ☉}) early-type galaxies (ETGs) in a sample of 11 high-redshift (1.0 < z < 1.5) galaxy clusters drawn from the IRAC Shallow Cluster Survey (ISCS). We identify ETGs visually from Hubble Space Telescope imaging and select likely cluster members as having either an appropriate spectroscopic redshift or red-sequence color. Mid-infrared SFRs are measured using Spitzer 24 μm data for isolated cluster galaxies for which contamination by neighbors, and active galactic nuclei, can be ruled out. Cluster ETGs show enhanced specific star formation rates (sSFRs) compared to cluster galaxies in the local universe, but have sSFRs more than four times lower than that of field ETGs at 1 < z < 1.5. Relative to the late-type cluster population, isolated ETGs show substantially quenched mean SFRs, yet still contribute 12% of the overall star formation activity measured in 1 < z < 1.5 clusters. We find that new ETGs are likely being formed in ISCS clusters; the fraction of cluster galaxies identified as ETGs increases from 34% to 56% from z ∼ 1.5 → 1.25. While the fraction of cluster ETGs that are highly star-forming (SFR ≥ 26 M {sub ☉} yr{sup –1}) drops from 27% to 10% over the same period, their sSFRs are roughly constant. All these factors taken together suggest that, particularly at z ≳ 1.25, the events that created these distant cluster ETGs—likely mergers, at least among the most massive—were both recent and gas-rich.

  13. 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.

  14. Galaxy Evolution at High Redshift: Obscured Star Formation, GRB Rates, Cosmic Reionization, and Missing Satellites

    NASA Astrophysics Data System (ADS)

    Lapi, A.; Mancuso, C.; Celotti, A.; Danese, L.

    2017-01-01

    We provide a holistic view of galaxy evolution at high redshifts z ≳ 4, which incorporates the constraints from various astrophysical/cosmological probes, including the estimate of the cosmic star formation rate (SFR) density from UV/IR surveys and long gamma-ray burst (GRBs) rates, the cosmic reionization history following the latest Planck measurements, and the missing satellites issue. We achieve this goal in a model-independent way by exploiting the SFR functions derived by Mancuso et al. on the basis of an educated extrapolation of the latest UV/far-IR data from HST/Herschel, and already tested against a number of independent observables. Our SFR functions integrated down to a UV magnitude limit MUV ≲ ‑13 (or SFR limit around 10‑2 M⊙ yr‑1) produce a cosmic SFR density in excellent agreement with recent determinations from IR surveys and, taking into account a metallicity ceiling Z ≲ Z⊙/2, with the estimates from long GRB rates. They also yield a cosmic reionization history consistent with that implied by the recent measurements of the Planck mission of the electron scattering optical depth τes ≈ 0.058 remarkably, this result is obtained under a conceivable assumption regarding the average value fesc ≈ 0.1 of the escape fraction for ionizing photons. We demonstrate via the abundance-matching technique that the above constraints concurrently imply galaxy formation becoming inefficient within dark matter halos of mass below a few 108 M⊙ pleasingly, such a limit is also required so as not to run into the missing satellites issue. Finally, we predict a downturn of the Galaxy luminosity function faintward of MUV ≲ ‑12, and stress that its detailed shape, to be plausibly probed in the near future by the JWST, will be extremely informative on the astrophysics of galaxy formation in small halos, or even on the microscopic nature of the dark matter.

  15. 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.

  16. MASSIVE CLUMPS IN LOCAL GALAXIES: COMPARISONS WITH HIGH-REDSHIFT CLUMPS

    SciTech Connect

    Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Dewberry, J.; Putko, J.; Teich, Y.; Popinchalk, M.; Sanchez Almeida, J.; Munoz-Tunon, C.

    2013-09-01

    Local UV-bright galaxies in the Kiso survey include clumpy systems with kiloparsec-size star complexes that resemble clumpy young galaxies in surveys at high redshift. We compare clump masses and underlying disks in several dozen galaxies from each of these surveys to the star complexes and disks of normal spirals. Photometry and spectroscopy for the Kiso and spiral sample come from the Sloan Digital Sky Survey. We find that the largest Kiso clumpy galaxies resemble Ultra Deep Field (UDF) clumpies in terms of the star formation rates, clump masses, and clump surface densities. Clump masses and surface densities in normal spirals are smaller. If the clump masses are proportional to the turbulent Jeans mass in the interstellar medium, then for the most luminous galaxies in the sequence of normal:Kiso:UDF, the turbulent speeds and surface densities increase in the proportions 1.0:4.7:5.0 and 1.0:4.0:5.1, respectively, for fixed restframe B-band absolute magnitude. For the least luminous galaxies in the overlapping magnitude range, the turbulent speed and surface density trends are 1.0:2.7:7.4 and 1.0:1.4:3.0, respectively. We also find that while all three types have radially decreasing disk intensities when measured with ellipse-fit azimuthal averages, the average profiles are more irregular for UDF clumpies (which are viewed in their restframe UV) than for Kiso galaxies (viewed at g-band), and major axis intensity scans are even more irregular for the UDF than Kiso galaxies. Local clumpy galaxies in the Kiso survey appear to be intermediate between UDF clumpies and normal spirals.

  17. The Progenitors of the Compact Early-type Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Williams, Christina C.; Giavalisco, Mauro; Cassata, Paolo; Tundo, Elena; Wiklind, Tommy; Guo, Yicheng; Lee, Bomee; Barro, Guillermo; Wuyts, Stijn; Bell, Eric F.; Conselice, Christopher J.; Dekel, Avishai; Faber, Sandra M.; Ferguson, Henry C.; Grogin, Norman; Hathi, Nimish; Huang, Kuang-Han; Kocevski, Dale; Koekemoer, Anton; Koo, David C.; Ravindranath, Swara; Salimbeni, Sara

    2014-01-01

    We use GOODS and CANDELS images to identify progenitors of massive (M > 1010 M ⊙) compact early-type galaxies (ETGs) at z ~ 1.6. Because merging and accretion increase the size of the stellar component of galaxies, if the progenitors are among known star-forming galaxies, these must be compact themselves. We select candidate progenitors among compact Lyman-break galaxies at z ~ 3 on the basis of their mass, star-formation rate (SFR), and central stellar density, and we find that these account for a large fraction of, and possibly all, compact ETGs at z ~ 1.6. We find that the average far-UV spectral energy distribution (SED) of the candidates is redder than that of the non-candidates, but the optical and mid-IR SED are the same, implying that the redder UV of the candidates is inconsistent with larger dust obscuration and consistent with more evolved (aging) star formation. This is in line with other evidence suggesting that compactness is a sensitive predictor of passivity among high-redshift massive galaxies. We also find that the light distribution of both the compact ETGs and their candidate progenitors does not show any extended "halos" surrounding the compact "core,"both in individual images and in stacks. We argue that this is generally inconsistent with the morphology of merger remnants, even if gas rich, as predicted by N-body simulations. This suggests that the compact ETGs formed via highly dissipative, mostly gaseous accretion of units whose stellar components are very small and undetected in the Hubble Space Telescope images, with their stellar mass assembling in situ, and that they have not experienced any major merging until the epoch of observations at z ~ 1.6.

  18. The progenitors of the compact early-type galaxies at high redshift

    SciTech Connect

    Williams, Christina C.; Giavalisco, Mauro; Lee, Bomee; Cassata, Paolo; Tundo, Elena; Conselice, Christopher J.; Wiklind, Tommy; Guo, Yicheng; Barro, Guillermo; Faber, Sandra M.; Koo, David C.; Bell, Eric F.; Dekel, Avishai; Ferguson, Henry C.; Grogin, Norman; Koekemoer, Anton; Hathi, Nimish; Huang, Kuang-Han; Kocevski, Dale; and others

    2014-01-01

    We use GOODS and CANDELS images to identify progenitors of massive (M > 10{sup 10} M {sub ☉}) compact early-type galaxies (ETGs) at z ∼ 1.6. Because merging and accretion increase the size of the stellar component of galaxies, if the progenitors are among known star-forming galaxies, these must be compact themselves. We select candidate progenitors among compact Lyman-break galaxies at z ∼ 3 on the basis of their mass, star-formation rate (SFR), and central stellar density, and we find that these account for a large fraction of, and possibly all, compact ETGs at z ∼ 1.6. We find that the average far-UV spectral energy distribution (SED) of the candidates is redder than that of the non-candidates, but the optical and mid-IR SED are the same, implying that the redder UV of the candidates is inconsistent with larger dust obscuration and consistent with more evolved (aging) star formation. This is in line with other evidence suggesting that compactness is a sensitive predictor of passivity among high-redshift massive galaxies. We also find that the light distribution of both the compact ETGs and their candidate progenitors does not show any extended 'halos' surrounding the compact 'core,' both in individual images and in stacks. We argue that this is generally inconsistent with the morphology of merger remnants, even if gas rich, as predicted by N-body simulations. This suggests that the compact ETGs formed via highly dissipative, mostly gaseous accretion of units whose stellar components are very small and undetected in the Hubble Space Telescope images, with their stellar mass assembling in situ, and that they have not experienced any major merging until the epoch of observations at z ∼ 1.6.

  19. 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

  20. Calan Tololo Survey: Bright Quasars at High Redshifts

    NASA Astrophysics Data System (ADS)

    Maza, Jose; Ruiz, Maria Teresa; Gonzalez, Luis E.; Wischnjewsky, Marina

    An objective prism survey has been started at Cerro Tololo Inter-American Observatory using the thin UV prism (1,360 Å/mm at Hγ and 1,740 Å/mm at Hβ) on the Curtis Schmidt telescope. Unfiltered baked IIIaJ plates exposed 90 minutes have been obtained for 163 fields. Unwiden spectra taken in good seeing reach B ≅ 19. This survey is an extension of the original Tololo survey (Smith 1975; Smith, Aguirre and Zemelman 1986).

  1. 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.

  2. Dissecting High-Redshift Galaxies with GRBs: Three Hosts at z 6 Observed with HST

    NASA Astrophysics Data System (ADS)

    McGuire, J. T. W.

    2016-10-01

    The first detection of three GRB hosts at z 6 is presented, along with their comparison to Lyman-break galaxies, potential star formation histories and a brief look at their impact on the high-redshift galaxy luminosity function.

  3. 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.

  4. First detection of CO in a high-redshift damped Lyman-α system

    NASA Astrophysics Data System (ADS)

    Srianand, R.; Noterdaeme, P.; Ledoux, C.; Petitjean, P.

    2008-05-01

    We present the first detection of carbon monoxide (CO) in a damped Lyman-α system (DLA) at z_abs = 2.41837 toward SDSS J143912.04+111740.5. We also detected H2 and HD molecules. The measured total column densities (in log units) of H i, H2, and CO are 20.10±0.10, 19.38±0.10, and 13.89±0.02, respectively. The molecular fraction, f = 2N(H2)/(N(H i)+2N(H2)) = 0.27^+0.10-0.08, is the highest among all known DLAs. The abundances relative to solar of S, Zn, Si, and Fe are -0.03±0.12, +0.16±0.11, -0.86±0.11, and -1.32±0.11, respectively, indicating a high metal enrichment and a depletion pattern onto dust-grains similar to the cold ISM of our Galaxy. The measured N(CO)/N(H2) = 3×10-6 is much less than the conventional CO/H2 ratio used to convert the CO emission into gaseous mass but is consistent with what is measured along translucent sightlines in the Galaxy. The CO rotational excitation temperatures are higher than those measured in our Galactic ISM for similar kinetic temperature and density. Using the C i fine structure absorption lines, we show that this is a consequence of the excitation being dominated by radiative pumping by the cosmic microwave background radiation (CMBR). From the CO excitation temperatures, we derive T_CMBR = 9.15±0.72 K, while 9.315±0.007 K is expected from the hot big-bang theory. This is the most precise high-redshift measurement of T_CMBR and the first confirmation of the theory using molecular transitions at high redshift. Based on observations carried out at the European Southern Observatory (ESO), under programme 278.A-5062 with the UVES echelle spectrograph installed at the ESO Very Large Telescope (VLT), unit Kueyen, on Mount Paranal in Chile.

  5. New Gapless COS G140L Mode Proposed for Background-limited Far-UV Observations

    NASA Astrophysics Data System (ADS)

    Redwine, Keith; McCandliss, Stephan R.; Zheng, Wei; Fleming, Brian; France, Kevin; Osterman, Steven; Howk, J. Christopher; Anderson, Scott F.; Gäensicke, Boris T.

    2016-10-01

    Here we describe the observation and calibration procedure for a new G140L observing mode for the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope (HST). This mode, CENWAV = 800, is designed to move the far-UV band fully onto the Segment A detector, allowing for more efficient observation and analysis by simplifying calibration management between the two channels, and reducing the astigmatism in this wavelength region. We also describe some of the areas of scientific interest for which this new mode will be especially suited.

  6. 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.

  7. The superluminous supernova PS1-11ap: bridging the gap between low and high redshift

    NASA Astrophysics Data System (ADS)

    McCrum, M.; Smartt, S. J.; Kotak, R.; Rest, A.; Jerkstrand, A.; Inserra, C.; Rodney, S. A.; Chen, T.-W.; Howell, D. A.; Huber, M. E.; Pastorello, A.; Tonry, J. L.; Bresolin, F.; Kudritzki, R.-P.; Chornock, R.; Berger, E.; Smith, K.; Botticella, M. T.; Foley, R. J.; Fraser, M.; Milisavljevic, D.; Nicholl, M.; Riess, A. G.; Stubbs, C. W.; Valenti, S.; Wood-Vasey, W. M.; Wright, D.; Young, D. R.; Drout, M.; Czekala, I.; Burgett, W. S.; Chambers, K. C.; Draper, P.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Metcalfe, N.; Price, P. A.; Sweeney, W.; Wainscoat, R. J.

    2014-01-01

    We present optical photometric and spectroscopic coverage of the superluminous supernova (SLSN) PS1-11ap, discovered with the Pan-STARRS1 Medium Deep Survey at z = 0.524. This intrinsically blue transient rose slowly to reach a peak magnitude of Mu = -21.4 mag and bolometric luminosity of 8 × 1043 erg s-1 before settling on to a relatively shallow gradient of decline. The observed decline is significantly slower than those of the SLSNe-Ic which have been the focus of much recent attention. Spectroscopic similarities with the lower redshift SN2007bi and a decline rate similar to 56Co decay time-scale initially indicated that this transient could be a candidate for a pair instability supernova (PISN) explosion. Overall the transient appears quite similar to SN2007bi and the lower redshift object PTF12dam. The extensive data set, from 30 d before peak to 230 d after, allows a detailed and quantitative comparison with published models of PISN explosions. We find that the PS1-11ap data do not match these model explosion parameters well, supporting the recent claim that these SNe are not pair instability explosions. We show that PS1-11ap has many features in common with the faster declining SLSNe-Ic, and the light-curve evolution can also be quantitatively explained by the magnetar spin-down model. At a redshift of z = 0.524, the observer-frame optical coverage provides comprehensive rest-frame UV data and allows us to compare it with the SLSNe recently found at high redshifts between z = 2 and 4. While these high-z explosions are still plausible PISN candidates, they match the photometric evolution of PS1-11ap and hence could be counterparts to this lower redshift transient.

  8. EXPLORING THE CHEMICAL LINK BETWEEN LOCAL ELLIPTICALS AND THEIR HIGH-REDSHIFT PROGENITORS

    SciTech Connect

    Leja, Joel; Van Dokkum, Pieter G.; Momcheva, Ivelina; Nelson, Erica; Brammer, Gabriel; Skelton, Rosalind E.; Whitaker, Katherine E.; Andrews, Brett H.; Franx, Marijn; Patel, Shannon G.; Kriek, Mariska; Van der Wel, Arjen; Bezanson, Rachel; Conroy, Charlie; Förster Schreiber, Natascha

    2013-12-01

    We present Keck/MOSFIRE K-band spectroscopy of the first mass-selected sample of galaxies at z ∼ 2.3. Targets are selected from the 3D-Hubble Space Telescope Treasury survey. The six detected galaxies have a mean [N II]λ6584/Hα ratio of 0.27 ± 0.01, with a small standard deviation of 0.05. This mean value is similar to that of UV-selected galaxies of the same mass. The mean gas-phase oxygen abundance inferred from the [N II]/Hα ratios depends on the calibration method, and ranges from 12+log(O/H){sub gas} = 8.57 for the Pettini and Pagel calibration to 12+log(O/H){sub gas} = 8.87 for the Maiolino et al. calibration. Measurements of the stellar oxygen abundance in nearby quiescent galaxies with the same number density indicate 12+log(O/H){sub stars} = 8.95, similar to the gas-phase abundances of the z ∼ 2.3 galaxies if the Maiolino et al. calibration is used. This suggests that these high-redshift star forming galaxies may be progenitors of today's massive early-type galaxies. The main uncertainties are the absolute calibration of the gas-phase oxygen abundance and the incompleteness of the z ∼ 2.3 sample: the galaxies with detected Hα tend to be larger and have higher star formation rates than the galaxies without detected Hα, and we may still be missing the most dust-obscured progenitors.

  9. Exploring the Chemical Link Between Local Ellipticals and Their High-Redshift Progenitors

    NASA Technical Reports Server (NTRS)

    Leja, Joel; Van Dokkum, Pieter G.; Momcheva, Ivelina; Brammer, Gabriel; Skelton, Rosalind E.; Whitaker, Katherine E.; Andrews, Brett H.; Franx, Marijn; Kriek, Mariska; Van Der Wel, Arjen; Bezanson, Rachel; Conroy, Charlie; Schreiber, Natascha Foerster; Nelson, Erica; Patel, Shannon G.

    2013-01-01

    We present Keck/MOSFIRE K-band spectroscopy of the first mass-selected sample of galaxies at z approximately 2.3. Targets are selected from the 3D-Hubble Space Telescope Treasury survey. The six detected galaxies have a mean [N II]lambda6584/H-alpha ratio of 0.27 +/- 0.01, with a small standard deviation of 0.05. This mean value is similar to that of UV-selected galaxies of the same mass. The mean gas-phase oxygen abundance inferred from the [N II]/Halpha ratios depends on the calibration method, and ranges from 12+log(O/H)(sub gas) = 8.57 for the Pettini & Pagel calibration to 12+log(O/H)(sub gas) = 8.87 for the Maiolino et al. calibration. Measurements of the stellar oxygen abundance in nearby quiescent galaxies with the same number density indicate 12+log(O/H)(sub stars) = 8.95, similar to the gas-phase abundances of the z approximately 2.3 galaxies if the Maiolino et al. calibration is used. This suggests that these high-redshift star forming galaxies may be progenitors of today's massive early-type galaxies. The main uncertainties are the absolute calibration of the gas-phase oxygen abundance and the incompleteness of the z approximately 2.3 sample: the galaxies with detected Ha tend to be larger and have higher star formation rates than the galaxies without detected H-alpha, and we may still be missing the most dust-obscured progenitors.

  10. XMM-Newton analysis of a newly discovered, extremely X-ray luminous galaxy cluster at high redshift

    NASA Astrophysics Data System (ADS)

    Thoelken, S.; Schrabback, T.

    2016-06-01

    Galaxy clusters, the largest virialized structures in the universe, provide an excellent method to test cosmology on large scales. The galaxy cluster mass function as a function of redshift is a key tool to determine the fundamental cosmological parameters and especially measurements at high redshifts can e.g. provide constraints on dark energy. The fgas test as a direct cosmological probe is of special importance. Therefore, relaxed galaxy clusters at high redshifts are needed but these objects are considered to be extremely rare in current structure formation models. Here we present first results from an XMM-Newton analysis of an extremely X-ray luminous, newly discovered and potentially cool core cluster at a redshift of z=0.9. We carefully account for background emission and PSF effects and model the cluster emission in three radial bins. Our preliminary results suggest that this cluster is indeed a good candidate for a cool core cluster and thus potentially of extreme value for cosmology.

  11. 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.

  12. Reconciling the Stellar and Nebular Spectra of High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  13. The Connection Between Reddening, Gas Covering Fraction, and the Escape of Ionizing Radiation at High Redshift

    NASA Astrophysics Data System (ADS)

    Reddy, Naveen A.; Steidel, Charles C.; Pettini, Max; Bogosavljević, Milan; Shapley, Alice E.

    2016-09-01

    Using a large sample of spectroscopically confirmed z∼ 3 galaxies, we establish an empirical relationship between reddening (E(B-V)), neutral gas covering fraction ({f}{{cov}}({{H}} {{I}})), and the escape of ionizing (Lyman continuum, LyC) photons. Our sample includes 933 galaxies at z∼ 3,121 of which have deep spectroscopic observations (≳ 7 hr) at 850≲ {λ }{{rest}}≲ 1300 Å with the Low Resolution Imaging Spectrograph on Keck. The high covering fraction of outflowing optically thick {{H}} {{I}} indicated by the composite spectra of these galaxies implies that photoelectric absorption, rather than dust attenuation, dominates the depletion of LyC photons. By modeling the composite spectra as the combination of an unattenuated stellar spectrum including nebular continuum emission with one that is absorbed by {{H}} {{I}} and reddened by a line-of-sight extinction, we derive an empirical relationship between E(B-V) and {f}{{cov}}({{H}} {{I}}). Galaxies with redder UV continua have larger covering fractions of {{H}} {{I}} characterized by higher line-of-sight extinctions. We develop a model which connects the ionizing escape fraction with E(B-V), and which may be used to estimate the ionizing escape fraction for an ensemble of galaxies. Alternatively, direct measurements of the escape fraction for our sample allow us to constrain the intrinsic LyC-to-UV flux density ratio to be < S(900 \\mathring{{A}} )/S(1500 \\mathring{{A}} ){> }{{int}}≳ 0.20, a value that favors stellar population models that include weaker stellar winds, a flatter initial mass function, and/or binary evolution. Last, we demonstrate how the framework discussed here may be used to assess the pathways by which ionizing radiation escapes from high-redshift galaxies. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous

  14. 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

  15. Expanding the Gamma-ray Universe: High Redshift Fermi-LAT Blazars

    NASA Astrophysics Data System (ADS)

    Ojha, Roopesh; Paliya, Vaidehi; Gasparrini, Dario; Ajello, Marco; Cutini, Sara; Fermi-LAT Collaboration

    2017-01-01

    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 Fermi-LAT sample. These blazars appear to host very massive black holes and could shed light on the origin and growth of black holes in the early Universe. We present the latest high redshift blazar detections in the LAT and discuss some of their implications.

  16. 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.

  17. The SFR of high redshift galaxies: mid-IR vs SED fitting

    NASA Astrophysics Data System (ADS)

    Santini, P.; Fontana, A.; Grazian, A.

    2009-05-01

    In this work we compare two distinct techniques to estimate the star formation rate (SFR) in high redshift galaxies: mid-infrared emission and SED fitting analysis. We used the multiwavelength GOODS-MUSIC catalog to estimate the total infrared luminosity, which is a SFR indicator arising from dust reprocessed emission, and the star formation rate from the overall SED shape using the 14 bands photometry. We will apply the two methods to a couple of physical topics: the selection of a sample of quiescent galaxies at high redshift and the measure of the star formation rate.

  18. Stellar Populations, Outflows, and Morphologies of High-Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Kornei, Katherine Anne

    Understanding the regulation and environment of star formation across cosmic time is critical to tracing the build-up of mass in the Universe and the interplay between the stars and gas that are the constituents of galaxies. Three studies are presented in this thesis, each examining a different aspect of star formation at a specific epoch. The first study presents the results of a photometric and spectroscopic survey of 321 Lyman break galaxies (LBGs) at z ˜ 3 to investigate systematically the relationship between Lyalpha emission and stellar populations. Lyalpha equivalent widths were calculated from rest-frame UV spectroscopy and optical/near-infrared/Spitzer photometry was used in population synthesis modeling to derive the key properties of age, dust extinction, star formation rate (SFR), and stellar mass. Using a variety of statistical tests, we find that Lyalpha equivalent width and age, SFR, and dust extinction, respectively, are significantly correlated in the sense that objects with strong Lyalpha emission also tend to be older, lower in star formation rate, and less dusty than objects with weak Lyalpha emission, or the line in absorption. We accordingly conclude that, within the LBG sample, objects with strong Lyalpha emission represent a later stage of galaxy evolution in which supernovae-induced outflows have reduced the dust covering fraction. The second study focuses specifically on galactic-scale outflowing winds in 72 star-forming galaxies at z ˜ 1 in the Extended Groth Strip. Galaxies were selected from the DEEP2 survey and follow-up LRIS spectroscopy was obtained covering SiII, CIV, FeII, MgII, and MgI lines in the rest-frame ultraviolet. Using GALEX, HST, and Spitzer imaging available for the Extended Groth Strip, we examine galaxies on a per-object basis in order to better understand both the prevalence of galactic outflows at z ˜ 1 and the star-forming and structural properties of objects experiencing outflows. Gas velocities, measured from

  19. 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⊙).

  20. 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.

  1. 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.

  2. CO Linewidths and the Black Hole - Bulge Relationship for High Redshift QSOs

    NASA Astrophysics Data System (ADS)

    Menezes, K. L.; Shields, G. A.; Massart, C. A.; vanden Bout, P.

    2005-10-01

    Supermassive black holes in galactic nuclei have masses MBH related to the mass and velocity dispersion σ* of the host galaxy. We examine the MBH - σ* in high redshift QSOs, deriving MBH from the broad emission-line widths and σ* from the radio CO lines. At redshifts z = 4 to 6, gigantic black holes appear to exist in relatively modest galaxies.

  3. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data

    SciTech Connect

    Fan, X.; Strauss, M.A.; Schneider, D.P.; Gunn, J.E.; Lupton, R.H.; Yanny, B.; Anderson, S.F.; Anderson, J.E. Jr.; Annis, J.; Bahcall, N.A.; Bakken, J.A.; Bastian, S.; Berman, E.; Boroski, W.N.; Briegel, C.; Briggs, J.W.; Brinkmann, J.; Carr, M.A.; Colestock, P.L.; Connolly, A.J.; Crocker, J.H.; Csabai, I. |; Davis, J.E.; and others

    1999-07-01

    We present photometric and spectroscopic observations of 15 high-redshift quasars (z{gt}3.6) discovered from {approximately}140 deg{sup 2} of five-color ({ital u}{prime}, {ital g}{prime}, {ital r}{prime}, {ital i}{prime}, and {ital z}{prime}) imaging data taken by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. The quasars are selected by their distinctive colors in SDSS multicolor space. Four of the quasars have redshifts higher than 4.6 (z=4.63, 4.75, 4.90, and 5.00, the latter being the highest redshift quasar yet known). In addition, two previously known z{gt}4 objects were recovered from the data. The quasars all have i{sup *} {lt}20 and have luminosities comparable to that of 3C 273. The spectra of the quasars have similar features (strong, broad emission lines and substantial absorption blueward of the Ly{alpha} emission line) seen in previously known high-redshift quasars. Although the photometric accuracy and image quality fail to meet the final survey requirements, our success rate for identifying high-redshift quasars (17 quasars from 27 candidates) is much higher than that of previous multicolor surveys. However, the numbers of high-redshift quasars found is in close accord with the number density inferred from previous surveys. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}

  4. The Rest-frame Submillimeter Spectrum of High-redshift, Dusty, Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Spilker, J. S.; Marrone, D. P.; Aguirre, J. E.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bradford, C. M.; Bothwell, M. S.; Brodwin, M.; Carlstrom, J. E.; Chapman, S. C.; Crawford, T. M.; de Breuck, C.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Gullberg, B.; Hezaveh, Y.; Holzapfel, W. L.; Husband, K.; Ma, J.; Malkan, M.; Murphy, E. J.; Reichardt, C. L.; Rotermund, K. M.; Stalder, B.; Stark, A. A.; Strandet, M.; Vieira, J. D.; Weiß, A.; Welikala, N.

    2014-04-01

    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 12CO, [C I], and H2O, we also detect several faint transitions of 13CO, HCN, HNC, HCO+, 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 13CO brightness in these objects is comparable to that of the only other z > 2 star-forming galaxy in which 13CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO+, and CN is consistent with a warm, dense medium with T kin ~ 55 K and n_{H_2} \\gtrsim 10^{5.5} cm-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.

  5. 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.

  6. The High-Redshift Quasar Luminosity Function from Multi-Epoch Imaging Surveys

    NASA Astrophysics Data System (ADS)

    AlSayyad, Yusra

    Upcoming time-domain imaging surveys such as the LSST will detect over a million high-redshift z > 4 quasars, making complete spectroscopic followup unfeasible. Statistical estimates such as luminosity functions and clustering measurements will require purely photometric methods for classifying quasars, estimating redshifts and estimating selection functions. We validate these methods and constrain the optical, type I quasar luminosity function (QLF) at 3.75 < z < 4.5 for -27.5 < M1450 3.75) and constraint on the characteristic luminosity (M*1450 = -26.7) from a single, uniformly-selected survey at z 4. We used the Sloan Digital Sky Survey (SDSS) repeated imaging of the 275 sq. deg. equatorial region of the sky (-50 < R.A. < +60; -1.26 < Dec. < +1.26), known as Stripe 82, to select a statistical sample of z 4 quasars. We extracted 40 million lightcurves from the imaging using forced photometry on all u, g, r, i, z epochs at the positions of sources detected on a deep i-band co-add. We developed a classification method based on photometric information alone (colors and variability metrics derived from these new multi-band lightcurves), which we validated with a spectroscopically complete 55 sq. deg. sub-region augmented with 102 new spectroscopic observations of quasars at z > 3.4 with i < 22.5. We demonstrate that selection functions for ensemble classifiers can be estimated by building generative models of empirical distributions of quasars previously selected with a diverse set of selection criteria. The z 4 QLF contributes to our understanding of supermassive black hole growth and cosmic reionization of both H I and He II which likely began at z 4 as a result of hard UV emissivity from quasars. The resulting QLF measurement is consistent with the previous lower number densities reported from deep, narrow-field surveys (COSMOS); it is not consistent with higher number densities reported from the NDWFS-DLS and CANDELS GOODS-S fields. In the context of recent 2

  7. Evolution of the dust-to-metals ratio in high-redshift galaxies probed by GRB-DLAs

    NASA Astrophysics Data System (ADS)

    Wiseman, P.; Schady, P.; Bolmer, J.; Krühler, T.; Yates, R. M.; Greiner, J.; Fynbo, J. P. U.

    2017-02-01

    Context. Several issues regarding the nature of dust at high redshift remain unresolved: its composition, its production and growth mechanisms, and its effect on background sources. Aims: We provide a more accurate relation between dust depletion levels and dust-to-metals ratio (DTM), and to use the DTM to investigate the origin and evolution of dust in the high-redshift Universe via gamma-ray burst damped Lyman-alpha absorbers (GRB-DLAs). Methods: We use absorption-line measured metal column densities for a total of 19 GRB-DLAs, including five new GRB afterglow spectra from VLT/X-Shooter. We use the latest linear models to calculate the dust depletion strength factor in each DLA. Using these values we calculate total dust and metal column densities to determine a DTM. We explore the evolution of DTM with metallicity, and compare it to previous trends in DTM measured with different methods. Results: We find significant dust depletion in 16 of our 19 GRB-DLAs, yet 18 of the 19 have a DTM significantly lower than the Milky Way. We find that DTM is positively correlated with metallicity, which supports a dominant ISM grain-growth mode of dust formation. We find a substantial discrepancy between the dust content measured from depletion and that derived from the total V-band extinction, AV, measured by fitting the afterglow SED. We advise against using a measurement from one method to estimate that from the other until the discrepancy can be resolved. Based on observations collected at the European Southern Observatory, Paranal, Chile, Program IDs: 088.A-0051(B), 089.A-0067(B), 091.C-0934, 094.A-0134(A).

  8. Investigating the Gas Kinematics of High-Redshift Active Galactic Nuclei with Double-Peaked Narrow Emission Lines

    NASA Astrophysics Data System (ADS)

    Barrows, Robert S.; Stern, D.; Lacy, C. H. S.; Kennefick, J.; Kennefick, D.; Seigar, M.

    2012-05-01

    Pairs of supermassive black holes (SMBHs) are a natural consequence of galaxy mergers, and these systems are observable when both SMBHs are accreting as active galactic nuclei (AGN). Observational evidence for these AGN pairs (dual AGN) has dramatically increased recently through a combination of spectroscopic selection of candidates from double-peaked optical emission lines and follow-up morphological data. The primary motivation for compiling a sample of dual AGN is for their use in tracing galaxy mergers and in constraining the link between galaxy mergers and AGN enhancement. Therefore, this phenomenon should be investigated at higher redshifts when galaxy mergers were more frequent. Motivated by our detailed analysis of a candidate dual AGN at a relatively high redshift (z=1.175), we have compiled a sample of analogous sources at z>0.80 identified from double-peaked UV emission lines in the Sloan Digital Sky Survey (SDSS). The double-peaked profile can be mimicked by gas-kinematics around a single AGN, including large-scale outflows, which are known to affect the velocity profiles of high-ionization UV emission lines. Through emission line diagnostics, we have taken advantage of access to rest-frame UV emission lines in SDSS quasar spectra, allowing us to investigate the kinematics of the ionized gas. In particular, for each of these sources we have put constraints on the likelihood of a correlation between peak velocity-offset and ionization potential. Such tests will aid in determining which double-peaked emission line sources are most likely the result of an outflow and which are strong dual AGN candidates. This study will both increase the sample size of candidate dual AGN for follow-up observations and extend the sample to higher redshifts.

  9. Spatially Resolved Emission of a High-redshift DLA Galaxy with the Keck/OSIRIS IFU

    NASA Astrophysics Data System (ADS)

    Jorgenson, Regina A.; Wolfe, Arthur M.

    2014-04-01

    We present the first Keck/OSIRIS infrared IFU observations of a high-redshift damped Lyα (DLA) galaxy detected in the line of sight to a background quasar. By utilizing the Laser Guide Star Adaptive Optics to reduce the quasar point-spread function to FWHM ~ 0.''15, we were able to search for and map the foreground DLA emission free from the quasar contamination. We present maps of the Hα and [O III] λλ5007, 4959 emission of DLA 2222-0946 at a redshift of z ~ 2.35. From the composite spectrum over the Hα emission region, we measure a star formation rate of 9.5 ± 1.0 M ⊙ yr-1 and a dynamical mass of M dyn = 6.1 × 109 M ⊙. The average star formation rate surface density is langΣSFRrang = 0.55 M ⊙ yr-1 kpc-2, with a central peak of 1.7 M ⊙ yr-1 kpc-2. Using the standard Kennicutt-Schmidt relation, this corresponds to a gas mass surface density of Σgas = 243 M ⊙ pc-2. Integrating over the size of the galaxy, we find a total gas mass of M gas = 4.2 × 109 M ⊙. We estimate the gas fraction of DLA 2222-0946 to be f gas ~ 40%. We detect [N II] λ6583 emission at 3σ significance with a flux corresponding to a metallicity of 75% solar. Comparing this metallicity with that derived from the low-ion absorption gas ~6 kpc away, ~30% solar, indicates possible evidence for a metallicity gradient or enriched in/outflow of gas. Kinematically, both Hα and [O III] emission show relatively constant velocity fields over the central galactic region. While we detect some red and blueshifted clumps of emission, they do not correspond with rotational signatures that support an edge-on disk interpretation. 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.

  10. Spatially resolved emission of a high-redshift DLA galaxy with the Keck/OSIRIS IFU

    SciTech Connect

    Jorgenson, Regina A.; Wolfe, Arthur M.

    2014-04-10

    We present the first Keck/OSIRIS infrared IFU observations of a high-redshift damped Lyα (DLA) galaxy detected in the line of sight to a background quasar. By utilizing the Laser Guide Star Adaptive Optics to reduce the quasar point-spread function to FWHM ∼ 0.''15, we were able to search for and map the foreground DLA emission free from the quasar contamination. We present maps of the Hα and [O III] λλ5007, 4959 emission of DLA 2222–0946 at a redshift of z ∼ 2.35. From the composite spectrum over the Hα emission region, we measure a star formation rate of 9.5 ± 1.0 M {sub ☉} yr{sup –1} and a dynamical mass of M {sub dyn} = 6.1 × 10{sup 9} M {sub ☉}. The average star formation rate surface density is (Σ{sub SFR}) = 0.55 M {sub ☉} yr{sup –1} kpc{sup –2}, with a central peak of 1.7 M {sub ☉} yr{sup –1} kpc{sup –2}. Using the standard Kennicutt-Schmidt relation, this corresponds to a gas mass surface density of Σ{sub gas} = 243 M {sub ☉} pc{sup –2}. Integrating over the size of the galaxy, we find a total gas mass of M {sub gas} = 4.2 × 10{sup 9} M {sub ☉}. We estimate the gas fraction of DLA 2222–0946 to be f {sub gas} ∼ 40%. We detect [N II] λ6583 emission at 3σ significance with a flux corresponding to a metallicity of 75% solar. Comparing this metallicity with that derived from the low-ion absorption gas ∼6 kpc away, ∼30% solar, indicates possible evidence for a metallicity gradient or enriched in/outflow of gas. Kinematically, both Hα and [O III] emission show relatively constant velocity fields over the central galactic region. While we detect some red and blueshifted clumps of emission, they do not correspond with rotational signatures that support an edge-on disk interpretation.

  11. Bayesian Multiscale Analysis of X-Ray Jet Features in High Redshift Quasars

    NASA Astrophysics Data System (ADS)

    McKeough, Kathryn; Siemiginowska, A.; Kashyap, V.; Stein, N.

    2014-01-01

    X-ray emission of powerful quasar jets may be a result of the inverse Compton (IC) process in which the Cosmic Microwave Background (CMB) photons gain energy by interactions with the jet’s relativistic electrons. However, there is no definite evidence that IC/CMB process is responsible for the observed X-ray emission of large scale jets. A step toward understanding the X-ray emission process is to study the Radio and X-ray morphologies of the jet. We implement a sophisticated Bayesian image analysis program, Low-count Image Reconstruction and Analysis (LIRA) (Esch et al. 2004; Conners & van Dyk 2007), to analyze jet features in 11 Chandra images of high redshift quasars (z ~ 2 - 4.8). Out of the 36 regions where knots are visible in the radio jets, nine showed detectable X-ray emission. We measured the ratios of the X-ray and radio luminosities of the detected features and found that they are consistent with the CMB radiation relationship. We derived a range of the bulk lorentz factor (Γ) for detected jet features under the CMB jet emission model. There is no discernible trend of Γ with redshift within the sample. The efficiency of the X-ray emission between the detected jet feature and the corresponding quasar also shows no correlation with redshift. This work is supported in part by the National Science Foundation REU and the Department of Defense ASSURE programs under NSF Grant no.1262851 and by the Smithsonian Institution, and by NASA Contract NAS8-39073 to the Chandra X-ray Center (CXC). This research has made use of data obtained from the Chandra Data Archive and Chandra Source Catalog, and software provided by the CXC in the application packages CIAO, ChIPS, and Sherpa. We thank Teddy Cheung for providing the VLA radio images. Connors, A., & van Dyk, D. A. 2007, Statistical Challenges in Modern Astronomy IV, 371, 101 Esch, D. N., Connors, A., Karovska, M., & van Dyk, D. A. 2004, ApJ, 610, 1213

  12. 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

  13. Damped Ly alpha absorbers at high redshift: Large disks or galactic building blocks?

    NASA Technical Reports Server (NTRS)

    Haehnelt, Martin G.; Steinmetz, Matthias; Rauch, Michael

    1997-01-01

    The nature of the physical structures giving rise to damped Lyman alpha absorption systems (DLAS) at high redshifts is investigated. The proposal that rapidly rotating large disks are the only viable explanation for the observed asymmetric profiles of low ionization absorption lines is examined. Using hydrodynamic simulations of galaxy formation, it is demonstated that irregular protogalactic clumps can reproduce the observed velocity width distribution and asymmetries of the absorption profiles equally well. The velocity broadening in the simulated clumps is due to a mixture of rotation, random motions, infall and merging. The observed velocity width correlates with the virial velocity for the dark matter halo of the forming protogalactic clump. The typical virial velocity of the halos required to lead to the DLAS population is approximately 100 km/s. It is concluded that the evidence that DLAS at high redshift are related to large, rapidly rotating disks, is not compelling.

  14. The Black Hole-Bulge Relationship for QSOs at High Redshift

    NASA Astrophysics Data System (ADS)

    Shields, G. A.; Menezes, K. L.; Massart, C. A.; Vanden Bout, P.

    2006-04-01

    We examine the black hole mass-galaxy bulge relationship in high-redshift QSOs. Black hole masses are derived from broad emission lines, and the host galaxy stellar velocity dispersion σ* is estimated from the widths of the radio CO emission lines. At redshifts z>3, the CO line widths are narrower than expected for the black hole mass, indicating that these giant black holes reside in undersized bulges by an order of magnitude or more. The largest black holes (MBH>109 Msolar) evidently grow rapidly in the early universe without commensurate growth of their host galaxies. CO line widths offer a unique opportunity to study AGN host galaxy dynamics at high redshift.

  15. From Nearby Low Luminosity AGN to High Redshift Radio Galaxies: Science Interests with Square Kilometre Array

    NASA Astrophysics Data System (ADS)

    Kharb, P.; Lal, D. V.; Singh, V.; Bagchi, J.; Ishwara Chandra, C. H.; Hota, A.; Konar, C.; Wadadekar, Y.; Shastri, P.; Das, M.; Baliyan, K.; Nath, B. B.; Pandey-Pommier, M.

    2016-12-01

    We present detailed science cases that a large fraction of the Indian AGN community is interested in pursuing with the upcoming Square Kilometre Array (SKA). These interests range from understanding low luminosity active galactic nuclei in the nearby Universe to powerful radio galaxies at high redshifts. Important unresolved science questions in AGN physics are discussed. Ongoing low-frequency surveys with the SKA pathfinder telescope GMRT, are highlighted.

  16. 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.

  17. 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.

  18. New quasar surveys with WIRO: Searching for high redshift (z~6) quasar candidates

    NASA Astrophysics Data System (ADS)

    Haze Nunez, Evan; Bassett, Neil; Deam, Sophie; Dixon, Don; Griffith, Emily; Harvey, William Bradford; Lee, Daniel; Lyke, Bradley; Parziale, Ryan; Witherspoon, Catherine; Myers, Adam D.; Findlay, Joseph; Kobulnicky, Henry A.; Dale, Daniel A.

    2017-01-01

    High redshift quasars (z~6) are of great interest to fundamental astronomy due to the information they hold about the early universe. With their low number density in the sky, however, they are elusive objects. Reported here is our search for these high redshift quasars using the Wyoming Infrared Observatory (WIRO) 2.3m telescope. We search for potential candidates that have been detected by surveys such as WISE, which have been mostly redshifted out of the optical. The main emission feature of these quasars (the Lyman-Alpha line at ~1216 Angstroms rest-frame) would be redshifted to the z-band or beyond. This means that the quasars should have very low levels of i-band flux. These objects are known as i-dropouts. By imaging the quasars in the i-band and running photometric analysis on our fields, candidates can be identified or rejected by whether or not they appear in our fields. We also provide an analysis of the colors of our candidate high-redshift quasars.This work is supported by the National Science Foundation under REU grant AST1560461

  19. 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.

  20. MORPHOLOGY AND SIZE DIFFERENCES BETWEEN LOCAL AND HIGH-REDSHIFT LUMINOUS INFRARED GALAXIES

    SciTech Connect

    Rujopakarn, Wiphu; Rieke, George H.; Eisenstein, Daniel J.; Juneau, Stephanie

    2011-01-10

    We show that the star-forming regions in high-redshift luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and submillimeter galaxies (SMGs) have similar physical scales to those in local normal star-forming galaxies. To first order, their higher infrared (IR) luminosities result from higher luminosity surface density. We also find a good correlation between the IR luminosity and IR luminosity surface density in starburst galaxies across over five orders of magnitude of IR luminosity from local normal galaxies to z {approx} 2 SMGs. The intensely star-forming regions of local ULIRGs are significantly smaller than those in their high-redshift counterparts and hence diverge significantly from this correlation, indicating that the ULIRGs found locally are a different population from the high-redshift ULIRGs and SMGs. Based on this relationship, we suggest that luminosity surface density should serve as a more accurate indicator for the IR emitting environment, and hence the observable properties, of star-forming galaxies than their IR luminosity. We demonstrate this approach by showing that ULIRGs at z {approx} 1 and a lensed galaxy at z {approx} 2.5 exhibit aromatic features agreeing with local LIRGs that are an order of magnitude less luminous, but have similar IR luminosity surface density. A consequence of this relationship is that the aromatic emission strength in star-forming galaxies will appear to increase at z>1 for a given IR luminosity compared to their local counterparts.

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

    PubMed

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

    2011-01-13

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

  2. Searching for the Progenitors of High-redshift Compact Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Williams, Christina; Giavalisco, M.; Cassata, P.; Guo, Y.

    2012-05-01

    High-redshift galaxy surveys have revealed a population of very massive and already evolved early-type galaxies at z > 1, which appear to be ultra-compact in size relative to local galaxies of similar stellar mass. The compactness and stellar masses of these galaxies, which are already in place at high-redshift, pose challenges for theories in which mergers drive the evolution of galaxies. We investigate the properties of Lyman Break Galaxies at z > 3 in CANDELS, among whom must be the progenitor population of these ultra-compact early-type galaxies, to assess the extent to which they were also ultra-compact while building up their stellar mass. Since merging and accretion generally increase the size of galaxies, the progenitors of the ultra-compact ellipticals must be compact star-forming galaxies themselves. Using rest-frame optical imaging from HST and SED fitting, we study the evolution in the mass-radius relation using their morphologies and stellar masses. We also discuss the implications that these ultra-compact star-forming galaxies have on theories of galaxy evolution and the quenching of star-formation at high-redshift.

  3. Seeding High Redshift QSOs by Collisional Runaway in Primordial Star Clusters

    NASA Astrophysics Data System (ADS)

    Katz, Harley; Sijacki, Debora; Haehnelt, Martin

    2015-08-01

    The formation and evolution of high mass galaxies across cosmic time is believed to be fundamentally related to the activity and growth of their constituent supermassive black holes. Such black holes with masses of over a billion solar masses were in place in galaxies when the Universe was less than ten percent of its current age, leaving in doubt whether known mechanisms of forming black holes could be responsible for seeding these massive objects and posing the question of how such objects impacted the early Universe. We study a channel, whereby the runaway stellar collisions in high redshift, metal poor, star clusters result in very massive stars of up to ~1000 M⊙, which can then directly collapse into intermediate mass black holes. We present novel, high resolution, hydrodynamical, zoom-in simulations, with non-equilibrium cooling to follow the detailed chemical properties, collapse, and evolution of a pair high redshift dwarf galaxies which subsequently produce a metal enriched, dense, gaseous clump. We then use the spatial configuration of this flattened, asymmetrical birth cloud to set the initial conditions for simulations of an initially non-spherical star cluster with a direct summation code. We find that, for a variety of different parameters, collisional runaway is a promising mechanism to produce large numbers of high redshift seeds required for the formation of super massive black holes by z=6.

  4. Were Progenitors of Local L* Galaxies Lyα Emitters at High Redshift?

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

    The Lyα emission has been observed from galaxies over a redshift span z ~ 0-8.6. However, the evolution of high-redshift Lyα emitters (LAEs), and the link between these populations and local galaxies, remains poorly understood. Here, we investigate the Lyα properties of progenitors of a local L* galaxy by combining cosmological hydrodynamic simulations with three-dimensional radiative transfer calculations using the new ART2 code. We find that the main progenitor (the most massive one) of a Milky-Way-like galaxy has a number of Lyα properties close to those of observed LAEs at z ~ 2-6, but most of the fainter ones appear to fall below the detection limits of current surveys. The Lyα 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 Lyα line profiles characteristic of gas inflow, and that the Lyα emission by excitation cooling increases with redshift, and becomes dominant at z >~ 6. Our results suggest that some observed LAEs at z ~ 2-6 with luminosity of L Lyα ~ 1042-1043 erg s-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. A multi-wavelength imaging study of a large sample of galaxies at z˜2: Implications for star formation and dust properties at high redshift

    NASA Astrophysics Data System (ADS)

    Shivaei, Irene; Reddy, N.

    2014-01-01

    From a unique sample of 262 UV-selected galaxies with spectroscopic redshifts at z˜2 and rest-UV through Spitzer/IRAC near-IR photometry, we investigate their star-formation rates and dust attenuation based on multiple diagnostics. The sample includes galaxies at redshifts 2.08≤z≤2.51, where H-alpha falls in the K-band, and where the H-alpha flux can be estimated by comparing the K-band photometry to stellar population model fits to the UV- to near-IR photometry. This technique has the advantage of being immune to uncertain corrections for slit loss that can affect spectroscopic measurements of H-alpha. Comparing the H-alpha SFRs with those from the UV shows a general agreement between the two tracers if we assume that the nebular lines are attenuated by the same amount as the stellar continuum. We use the H-alpha, UV, and Spitzer/MIPS 24 micron data (where available) to examine the bolometric SFRs and recipes for dust corrections at high redshift.

  6. The first detection of [OIII] emission from high-redshift damped Lyman-α galaxies

    NASA Astrophysics Data System (ADS)

    Weatherley, S. J.; Warren, S. J.; Møller, P.; Fall, S. M.; Fynbo, J. U.; Croom, S. M.

    2005-04-01

    We present the detection of [OIII] emission lines from the galaxies responsible for two high-redshift z > 1.75 damped Lyman-α (DLA) absorption lines. We find two sources of [OIII] emission corresponding to the z= 1.92 DLA absorber towards the quasar Q2206-1958, and we also detect [OIII] emission from the galaxy responsible for the z= 3.10 DLA absorber towards the quasar 2233.9+1381. These are the first detections of rest-frame optical emission lines from high-redshift DLA galaxies. Unlike the Lyα line, the [OIII] line provides a measure of the systemic velocity of the galaxy. We compare the [OIII] redshifts with the velocity profile of the low-ionization metal lines in these two absorbers, with the goal of distinguishing between the model of Prochaska and Wolfe of DLA absorbers as large rapidly rotating cold thick discs, and the standard hierarchical cold dark matter model of structure formation, in which DLAs arise in protogalactic fragments. We find some discrepancies with the predictions of the former model. Furthermore, the image of the DLA galaxy towards Q2206-1958 shows a complex disturbed morphology, which is more in accord with the hierarchical picture. We use the properties of the rest-frame optical emission lines to further explore the question posed by Møller et al.: are high-redshift DLA galaxies Lyman-break galaxies (LBGs) selected by gas cross-section? The measured velocity dispersions of the DLA galaxies are in agreement with this picture, while the data on the [OIII] luminosities and the velocity differences between the Lyα and [OIII] lines are inconclusive, as there are insufficient LBG measurements overlapping in luminosity. Finally, we estimate the star formation rates in these two DLA galaxies, using a variety of diagnostics, and include a discussion of the extent to which the [OIII] line is useful for this purpose.

  7. 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.

  8. Why do high-redshift galaxies show diverse gas-phase metallicity gradients?

    NASA Astrophysics Data System (ADS)

    Ma, Xiangcheng; Hopkins, Philip F.; Feldmann, Robert; Torrey, Paul; Faucher-Giguère, Claude-André; Kereš, Dušan

    2017-01-01

    Recent spatially resolved observations of galaxies at z ˜ 0.6-3 reveal that high-redshift galaxies show complex kinematics and a broad distribution of gas-phase metallicity gradients. To understand these results, we use a suite of high-resolution cosmological zoom-in simulations from the Feedback in Realistic Environments (FIRE) project, which include physically motivated models of the multi-phase ISM, star formation, and stellar feedback. Our simulations reproduce the observed diversity of kinematic properties and metallicity gradients, broadly consistent with observations at z ˜ 0-3. Strong negative metallicity gradients only appear in galaxies with a rotating disk, but not all rotationally supported galaxies have significant gradients. Strongly perturbed galaxies with little rotation always have flat gradients. The kinematic properties and metallicity gradient of a high-redshift galaxy can vary significantly on short time-scales, associated with starburst episodes. Feedback from a starburst can destroy the gas disk, drive strong outflows, and flatten a pre-existing negative metallicity gradient. The time variability of a single galaxy is statistically similar to the entire simulated sample, indicating that the observed metallicity gradients in high-redshift galaxies reflect the instantaneous state of the galaxy rather than the accretion and growth history on cosmological time-scales. We find weak dependence of metallicity gradient on stellar mass and specific star formation rate (sSFR). Low-mass galaxies and galaxies with high sSFR tend to have flat gradients, likely due to the fact that feedback is more efficient in these galaxies. We argue that it is important to resolve feedback on small scales in order to produce the diverse metallicity gradients observed.

  9. Observational Signatures of High-Redshift Quasars and Local Relics of Black Hole Seeds

    NASA Astrophysics Data System (ADS)

    Reines, Amy E.; Comastri, Andrea

    2016-10-01

    Observational constraints on the birth and early evolution of massive black holes come from two extreme regimes. At high redshift, quasars signal the rapid growth of billion-solar-mass black holes and indicate that these objects began remarkably heavy and/or accreted mass at rates above the Eddington limit. At low redshift, the smallest nuclear black holes known are found in dwarf galaxies and provide the most concrete limits on the mass of black hole seeds. Here, we review current observational work in these fields that together are critical for our understanding of the origin of massive black holes in the Universe.

  10. Molecular gas in the halo fuels the growth of a massive cluster galaxy at high redshift.

    PubMed

    Emonts, B H C; Lehnert, M D; Villar-Martín, M; Norris, R P; Ekers, R D; van Moorsel, G A; Dannerbauer, H; Pentericci, L; Miley, G K; Allison, J R; Sadler, E M; Guillard, P; Carilli, C L; Mao, M Y; Röttgering, H J A; De Breuck, C; Seymour, N; Gullberg, B; Ceverino, D; Jagannathan, P; Vernet, J; Indermuehle, B T

    2016-12-02

    The largest galaxies in the universe reside in galaxy clusters. Using sensitive observations of carbon monoxide, we show that the Spiderweb galaxy-a massive galaxy in a distant protocluster-is forming from a large reservoir of molecular gas. Most of this molecular gas lies between the protocluster galaxies and has low velocity dispersion, indicating that it is part of an enriched intergalactic medium. This may constitute the reservoir of gas that fuels the widespread star formation seen in earlier ultraviolet observations of the Spiderweb galaxy. Our results support the notion that giant galaxies in clusters formed from extended regions of recycled gas at high redshift.

  11. 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

  12. 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.

  13. Molecular gas in the halo fuels the growth of a massive cluster galaxy at high redshift

    NASA Astrophysics Data System (ADS)

    Emonts, B. H. C.; Lehnert, M. D.; Villar-Martín, M.; Norris, R. P.; Ekers, R. D.; van Moorsel, G. A.; Dannerbauer, H.; Pentericci, L.; Miley, G. K.; Allison, J. R.; Sadler, E. M.; Guillard, P.; Carilli, C. L.; Mao, M. Y.; Röttgering, H. J. A.; De Breuck, C.; Seymour, N.; Gullberg, B.; Ceverino, D.; Jagannathan, P.; Vernet, J.; Indermuehle, B. T.

    2016-12-01

    The largest galaxies in the universe reside in galaxy clusters. Using sensitive observations of carbon monoxide, we show that the Spiderweb galaxy—a massive galaxy in a distant protocluster—is forming from a large reservoir of molecular gas. Most of this molecular gas lies between the protocluster galaxies and has low velocity dispersion, indicating that it is part of an enriched intergalactic medium. This may constitute the reservoir of gas that fuels the widespread star formation seen in earlier ultraviolet observations of the Spiderweb galaxy. Our results support the notion that giant galaxies in clusters formed from extended regions of recycled gas at high redshift.

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

    PubMed

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

    2004-09-30

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

  15. Detecting the integrated Sachs-Wolfe effect with high-redshift 21-cm surveys

    NASA Astrophysics Data System (ADS)

    Raccanelli, Alvise; Kovetz, Ely; Dai, Liang; Kamionkowski, Marc

    2016-04-01

    We investigate the possibility of detecting the integrated Sachs-Wolfe (ISW) effect by cross-correlating 21-cm surveys at high redshifts with galaxies in a way similar to the usual CMB-galaxy cross-correlation. The high-redshift 21-cm signal is dominated by CMB photons that travel freely without interacting with the intervening matter, and hence its late-time ISW signature should correlate extremely well with that of the CMB at its peak frequencies. Using the 21-cm temperature brightness instead of the CMB would thus be a further check of the detection of the ISW effect, measured by different instruments at different frequencies and suffering from different systematics. We also study the ISW effect on the photons that are scattered by HI clouds. We show that a detection of the unscattered photons is achievable with planned radio arrays, while one using scattered photons will require advanced radio interferometers, either an extended version of the planned Square Kilometre Array or futuristic experiments such as a lunar radio array.

  16. 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.

  17. AWAKENING OF THE HIGH-REDSHIFT BLAZAR CGRaBS J0809+5341

    SciTech Connect

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

    2015-04-20

    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 × 10{sup 45} erg s{sup −1} and 10{sup 8.4} M{sub ⊙}, 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.

  18. 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.

  19. The search for high-redshift supernovae and the image reduction

    NASA Astrophysics Data System (ADS)

    Kim, Matthew Yongsok

    1999-11-01

    The absolute peak magnitudes of Type Ia supernovae are tightly bound and their small variation shows a strong correlation with their lightcurve widths and spectral features. This correlation can be used to calibrate Type Ia supernovae peak magnitudes, making Type Ia supernovae one of the most powerful cosmological distance indicators. The Supernova Cosmology Project has developed a new search technique for detecting Type Ia supernovae at high redshift and found more than 70 supernovae at 0.3 < z < 1.2. We have used these high-redshift Type Ia supernovae to measure the cosmological parameters, ΩM, and ΩΛ , of the standard big bang model. By analyzing the redshift-apparent brightness relationship on a sample of the first 42 supernovae at 0.3 < z < .85, we have succeeded in putting a significant constraint, on the cosmological parameters. In this paper, I will discuss our supernova detection technique and the image reduction process we have used in our project.

  20. 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.

  1. 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.

  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. THE MID-INFRARED ENVIRONMENTS OF HIGH-REDSHIFT RADIO GALAXIES

    SciTech Connect

    Galametz, Audrey; Stern, Daniel; De Breuck, Carlos; Vernet, Joeel; Hatch, Nina; Mayo, Jack; Miley, George; Rettura, Alessandro; Seymour, Nick; Adam Stanford, S.

    2012-04-20

    Taking advantage of the impressive sensitivity of Spitzer to detect massive galaxies at high redshift, we study the mid-infrared environments of powerful, high-redshift radio galaxies at 1.2 < z < 3. Galaxy cluster member candidates were isolated using a single Spitzer/IRAC mid-infrared color criterion, [3.6]-[4.5] > -0.1 (AB), in the fields of 48 radio galaxies at 1.2 < z < 3. Using a counts-in-cell analysis, we identify a field as overdense when 15 or more red IRAC sources are found within 1' (i.e., 0.5 Mpc at 1.2 < z < 3) of the radio galaxy to the 5{sigma} flux density limits of our IRAC data (f{sub 4.5} = 13.4 {mu}Jy). We find that radio galaxies lie preferentially in medium to dense regions, with 73% of the targeted fields denser than average. Our (shallow) 120 s data permit the rediscovery of previously known clusters and protoclusters associated with radio galaxies as well as the discovery of new promising galaxy cluster candidates at z > 1.2.

  4. The high-redshift galaxy population in hierarchical galaxy formation models

    NASA Astrophysics Data System (ADS)

    Kitzbichler, M. G.; White, S. D. M.

    2007-03-01

    We compare observations of the high-redshift galaxy population to the predictions of the galaxy formation model of Croton et al. and De Lucia & Blaizot. This model, implemented on the Millennium Simulation of the concordance Lambda cold dark matter cosmogony, introduces `radio mode' feedback from the central galaxies of groups and clusters in order to obtain quantitative agreement with the luminosity, colour, morphology and clustering properties of the present-day galaxy population. Here we construct deep light cone surveys in order to compare model predictions to the observed counts and redshift distributions of distant galaxies, as well as to their inferred luminosity and mass functions out to redshift 5. With the exception of the mass functions, all these properties are sensitive to modelling of dust obscuration. A simple but plausible treatment agrees moderately well with most of the data. The predicted abundance of relatively massive (~M*) galaxies appears systematically high at high redshift, suggesting that such galaxies assemble earlier in this model than in the real Universe. An independent galaxy formation model implemented on the same simulation matches the observed mass functions slightly better, so the discrepancy probably reflects incomplete or inaccurate galaxy formation physics rather than problems with the underlying cosmogony.

  5. Imaging of Three Possible Low-redshift Analogs to High-redshift Compact Red Galaxies

    NASA Astrophysics Data System (ADS)

    Shih, Hsin-Yi; Stockton, Alan

    2011-05-01

    As part of a larger program to identify and characterize possible low-redshift analogs to massive compact red galaxies found at high redshift, we have examined the morphologies of three low-redshift compact galaxies drawn from the sample of Trujillo et al. Using deeper and higher resolution images, we have found faint and relatively extensive outer structures in addition to the compact cores identified in the earlier measurements. One object appears to have a small companion that may be involved in an ongoing minor merger of the sort that could be responsible for building up the outer parts of these galaxies. The ages of the dominant stellar populations in these objects are found to be around 2-4 Gyr, in good agreement with the previous estimates. The presence of diffuse outer structures in these galaxies indicates that truly compact and massive red galaxies are exceedingly rare at low redshift. The relatively young stellar populations suggest that the accretion of the extensive outer material must occur essentially universally on relatively short timescales of a few billion years or less. These results confirm and extend previous suggestions that the driving mechanism behind the size evolution of high-redshift compact galaxies cannot be highly stochastic processes such as major mergers, which would inevitably leave a non-negligible fraction of survivors at low redshift.

  6. CLASH: EXTREME EMISSION-LINE GALAXIES AND THEIR IMPLICATION ON SELECTION OF HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Huang, Xingxing; Wang, Junxian; Shu, Xinwen; Zheng, Wei; Ford, Holland; Lemze, Doron; Moustakas, John; Van der Wel, Arjen; Zitrin, Adi; Frye, Brenda L.; Bartelmann, Matthias; Benítez, Narciso; Infante, Leopoldo; and others

    2015-03-01

    We utilize the Cluster Lensing And Supernova survey with Hubble observations of 25 clusters to search for extreme emission-line galaxies (EELGs). The selections are carried out in two central bands: F105W (Y {sub 105}) and F125W (J {sub 125}), as the flux of the central bands could be enhanced by the presence of [O III] λλ4959, 5007 at redshifts of ∼0.93-1.14 and 1.57-1.79, respectively. The multiband observations help to constrain the equivalent widths (EWs) of emission lines. Thanks to cluster lensing, we are able to identify 52 candidates down to an intrinsic limiting magnitude of 28.5 and to a rest-frame [O III] λλ4959, 5007 EW of ≅ 3700 Å. Our samples include a number of EELGs at lower luminosities that are missed in other surveys, and the extremely high EW can only be found in such faint galaxies. These EELGs can mimic a dropout feature similar to that of high-redshift galaxies and contaminate the color-color selection of high-redshift galaxies when the signal-to-noise ratio is limited or the band coverage is incomplete.

  7. Ly-alpha emission from disk absorption systems at high redshift - Star formation in young galaxy disks

    NASA Technical Reports Server (NTRS)

    Smith, Harding E.; Cohen, Ross D.; Burns, Joseph E.; Moore, David J.; Uchida, Barbara A.

    1989-01-01

    Narrow-band imaging observations are reported which were made in an attempt to detect Ly-alpha emission from high-redshift candidate galaxy disk systems discovered as high column density absorbers of background QSOs. For four systems with z = 2.3-2.8, no emission is detected to a limit of about 10 to the -16th ergs/sq cm/s, corresponding to luminosity limits of about 10 exp 42-43 ergs/s for the material producing the absorption. The inferred Ly-alpha luminosities lie one to two orders of magnitude below estimates of the Ly-alpha luminosities for active star-forming epochs of many prescriptions for galaxy formation and also considerably below measured Ly-alpha luminosities for other candidate young galaxies detected in radio surveys. A limiting star-formation rate in these systems of about 2-7 solar masses/yr is set; the limit may be about 10 times larger with small but observationally allowable amounts of dust.

  8. 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

  9. Supermassive Black Hole Mass and Spiral Galaxy Pitch Angle at Intermediate to High Redshift

    NASA Astrophysics Data System (ADS)

    Hughes, John A.; Barrows, R. S.; Berrier, J. C.; Davis, B. L.; Kennefick, D.; Kennefick, J. D.; Lacy, C. H. S.; Seigar, M. S.; Shields, D. W.; Zoldak, K. A.

    2012-01-01

    A possible correlation between spiral galaxy pitch angle (P) and the mass of the central supermassive black hole (SMBH) of the galaxy (M) was reported (Seigar et al. 2008) from a sample of 27 nearby galaxies. Here we investigate the extension of this result to intermediate and high redshifts. We have selected AGN showing spiral structure in their host galaxies from the GOODS fields and from a sample of AGN with reverberation mapping SMBH mass estimates. After careful measure of the pitch angle of these galaxies, we compare the mass found from the M-P relation to that reported from reverberation mapping or estimated from their MgII profiles. By extending the sample to higher redshift, we demonstrate how the M-P relationship can be used to estimate the mass of SMBHs in the center of galaxies with imaging data alone, a useful tool in the study of galaxy evolution.

  10. 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.

  11. VizieR Online Data Catalog: KMOS AGN Survey at High redshift (KASHz) (Harrison+, 2016)

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    KASHz is designed to ultimately obtain spatially resolved emission-line kinematics of ~(100-200) high-redshift (z~0.6-3.6) AGN. For our target selection we make use of deep X-ray surveys performed in extragalactic fields (COSMOS, see Scoville et al., 2007, Cat. J/ApJS/171/1; CDF-S, see Giacconi et al. 2001ApJ...551..624G and Xue et al., 2011, Cat. J/ApJS/195/10 (CDFS); UDS, SXDS: see Furusawa et al. 2008, Cat. J/ApJS/176/1 (UDS) and SSA22, see Steidel et al. 1998ApJ...492..428S). (1 data file).

  12. A Detailed Study of Two Optically Selected, High-Redshift Clusters of Galaxies

    NASA Technical Reports Server (NTRS)

    Lubin, Lori M.

    2000-01-01

    We are obtaining detailed X-ray spectral and structural data for two distant, optically-selected clusters of galaxies which are known X-ray emitters, CL1324+3011 at z = 0.76 and CL,1604+4304 at z = 0.90. These observations will allow us to place accurate constraints on the temperature, surface-brightness profile, and mass fraction of the intracluster medium in rich, optically-selected clusters at very high redshift. The two target clusters are the most well-studied systems at z greater than 0.7 in the optical and infrared regimes; therefore, with the addition of the XMM data, we plan to study the specifies of the relationship between the X-ray and optical properties and their implications for galaxy and cluster evolution.

  13. Gamma-ray bursts: cosmic rulers for the high-redshift universe?

    PubMed

    Speirits, Fiona C; Hendry, Martin A; Gonzalez, Alejandro

    2007-05-15

    The desire to extend the Hubble Diagram to higher redshifts than the range of current Type 1a Supernovae observations has prompted investigation into spectral correlations in gamma-ray bursts (GBRs), in the hope that standard candle-like properties can be identified. In this paper, we discuss the potential of these new 'cosmic rulers' and highlight their limitations by investigating the constraints that current data can place on an alternative Cosmological model in the form of Conformal Gravity. By fitting current Type 1a Supernovae and GRB data to the predicted luminosity distance redshift relation of both the standard Concordance Model and the Conformal Gravity, we show that currently neither model is strongly favoured at high redshift. The scatter in the current GRB data testifies to the further work required if GRBs are to cement their place as effective probes of the cosmological distance scale.

  14. A high-redshift IRAS galaxy with huge luminosity - Hidden quasar or protogalaxy?

    NASA Technical Reports Server (NTRS)

    Rowan-Robinson, M.; Broadhurst, T.; Oliver, S. J.; Taylor, A. N.; Lawrence, A.; Mcmahon, R. G.; Lonsdale, C. J.; Hacking, P. B.; Conrow, T.

    1991-01-01

    An emission line galaxy with the enormous far-IR luminosity of 3 x 10 to the 14th solar has been found at z = 2.286. The spectrum is very unusual, showing lines of high excitation but with very weak Lyman-alpha emission. A self-absorbed synchrotron model for the IR energy distribution cannot be ruled out, but a thermal origin seems more plausible. A radio-quiet quasar embedded in a very dusty galaxy could account for the IR emission, as might a starburst embedded in 1-10 billion solar masses of dust. The latter case demands so much dust that the object would probably be a massive galaxy in the process of formation. The presence of a large amount of dust in an object of such high redshift implies the generation of heavy elements at an early cosmological epoch.

  15. The detection of FIR emission from high-redshift star-forming galaxies in the ECDF-S

    NASA Astrophysics Data System (ADS)

    Davies, L. J. M.; Bremer, M. N.; Stanway, E. R.; Lehnert, M. D.

    2013-08-01

    fact the most actively star-forming systems. All of our z ˜ 3 samples fall on the `main sequence' of star-forming galaxies at z ˜ 3 and our detected sub-samples are likely to represent the high obscuration end of the LBGs population at their epoch. We compare the FIR properties of our sub-samples with various other galaxy populations, finding that our stellar mass selected sample shows some similar FIR characteristics to Submillimeter Galaxies (SMGs) at the same epoch and therefore potentially represents the low FIR luminosity end of the high-redshift FIR luminosity function.

  16. Infrared-faint radio sources in the SERVS deep fields. Pinpointing AGNs at high redshift

    NASA Astrophysics Data System (ADS)

    Maini, A.; Prandoni, I.; Norris, R. P.; Spitler, L. R.; Mignano, A.; Lacy, M.; Morganti, R.

    2016-12-01

    Context. Infrared-faint radio sources (IFRS) represent an unexpected class of objects which are relatively bright at radio wavelength, but unusually faint at infrared (IR) and optical wavelengths. A recent and extensive campaign on the radio-brightest IFRSs (S1.4 GHz≳ 10 mJy) has provided evidence that most of them (if not all) contain an active galactic nuclei (AGN). Still uncertain is the nature of the radio-faintest IFRSs (S1.4 GHz≲ 1 mJy). Aims: The scope of this paper is to assess the nature of the radio-faintest IFRSs, testing their classification and improving the knowledge of their IR properties by making use of the most sensitive IR survey available so far: the Spitzer Extragalactic Representative Volume Survey (SERVS). We also explore how the criteria of IFRSs can be fine-tuned to pinpoint radio-loud AGNs at very high redshift (z > 4). Methods: We analysed a number of IFRS samples identified in SERVS fields, including a new sample (21 sources) extracted from the Lockman Hole. 3.6 and 4.5 μm IR counterparts of the 64 sources located in the SERVS fields were searched for and, when detected, their IR properties were studied. Results: We compared the radio/IR properties of the IR-detected IFRSs with those expected for a number of known classes of objects. We found that IR-detected IFRSs are mostly consistent with a mixture of high-redshift (z ≳ 3) radio-loud AGNs. The faintest ones (S1.4 GHz 100 μJy), however, could be also associated with nearer (z 2) dust-enshrouded star-burst galaxies. We also argue that, while IFRSs with radio-to-IR ratios >500 can very efficiently pinpoint radio-loud AGNs at redshift 2 < z < 4, lower radio-to-IR ratios ( 100-200) are expected for higher redshift radio-loud AGNs.

  17. A WISE Search for the Most Massive High-Redshift Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Gonzalez, Anthony

    We propose a comprehensive program to detect and characterize the most massive galaxy clusters at z>1 over half the sky. The foundation for this program is the Preliminary Release data from the NASA Wide-field Infrared Survey Explorer (WISE). WISE is an all-sky infrared survey mission for which the first 23,600 sq. deg. of data are publicly available, providing images and photometric catalogs at 3.4, 4.6, 12, and 22 microns. The shortest wavelength band achieves a 5-sigma depth of 50 microJansky, which is sufficient to detect L* galaxies out to a z~1 (8 Gyr lookback time). Our team has developed a modified version of a cluster detection algorithm developed by Papovich (2008) that employs color selection in the two bluest bands (3.4 and 4.6 microns) to isolate galaxies at z>1 and identify galaxy clusters as overdensities of galaxies brighter than L*. The technique has been been tested using WISE data for a small (3,000 sq. deg.) subfield and optimized to enable an efficient search over the full Preliminary Release area. Within this subfield we find candidates that appear comparable to the most massive z>1 systems known. As a continuation of this pilot study, we propose to conduct a search over the full PR area (excluding the galactic plane) for high-redshift clusters. We will use multiwavelength observations of known and newly confirmed clusters to understand the mass and redshift selection function. The cluster sample resulting from this program is designed to be optimal for investigations of the Gaussianity of the initial density perturbations after inflation, the evolution of massive galaxies in the most overdense environments during their epoch of star formation and mass assembly, and the high-redshift Universe by employing the clusters as gravitational telescopes.

  18. COSMIC RAYS CAN DRIVE STRONG OUTFLOWS FROM GAS-RICH HIGH-REDSHIFT DISK GALAXIES

    SciTech Connect

    Hanasz, M.; Kowalik, K.; Wóltański, D.; Lesch, H.; Naab, T.; Gawryszczak, A.

    2013-11-10

    We present simulations of the magnetized interstellar medium (ISM) in models of massive star-forming (40 M {sub ☉} yr{sup –1}) disk galaxies with high gas surface densities (Σ{sub gas} ∼ 100 M {sub ☉} pc{sup –2}) similar to observed star-forming high-redshift disks. We assume that type II supernovae deposit 10% of their energy into the ISM as cosmic rays (CRs) and neglect the additional deposition of thermal energy or momentum. With a typical Galactic diffusion coefficient for CRs (3 × 10{sup 28} cm{sup 2} s{sup –1}), we demonstrate that this process alone can trigger the local formation of a strong low-density galactic wind maintaining vertically open field lines. Driven by the additional pressure gradient of the relativistic fluid, the wind speed can exceed 10{sup 3} km s{sup –1}, much higher than the escape velocity of the galaxy. The global mass loading, i.e., the ratio of the gas mass leaving the galactic disk in a wind to the star formation rate, becomes of order unity once the system has settled into an equilibrium. We conclude that relativistic particles accelerated in supernova remnants alone provide a natural and efficient mechanism to trigger winds similar to observed mass-loaded galactic winds in high-redshift galaxies. These winds also help in explaining the low efficiencies for the conversion of gas into stars in galaxies, as well as the early enrichment of the intergalactic medium with metals. This mechanism may be at least of similar importance to the traditionally considered momentum feedback from massive stars and thermal and kinetic feedback from supernova explosions.

  19. 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.

  20. 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.

  1. Nocturnal atmospheric uv background measurements in the 300-400 nm band with baby 2001: a balloon borne experiment to flight on board of a transmediterranean balloon.

    NASA Astrophysics Data System (ADS)

    Giarrusso, S.; Agnetta, G.; Biondo, B.; Catalano, O.; Cusumano, G.; Gugliotta, G.; La Rosa, G.; Maccarone, M.C.; Mangano, A.; Russo, F.; Sacco, B.

    In the framework of the EUSO project (an experiment approved by ESA to be accommodate on board of the ISS) we present a new balloon borne experimental apparatus, named BABY 2001 that is devoted to systematic and exhaustive observations of the UV nocturnal atmospheric background. The BABY 2001 experiment is foreseen to flight on the 3rd 4th week of July 2001 from the Milo-Trapani base on board of a transmediterranean balloon, looking downward from about 40 km of altitude the dark nocturnal atmosphere over the sea. The apparatus used for the BABY 2001 experiment was designed and built at the IFCAI-CNR in Palermo. The instrument is composed by 8 filtered and collimated fast photomultipliers, two of them detecting the UV light in the 300-400 nm wavelengths band and the others in the three narrow bands centered at the emission lines of the atmospheric Nitrogen molecules.

  2. 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

  3. Investigating the Local and High Redshift Universe With Deep Survey Data and Ground-Based Spectroscopy

    NASA Astrophysics Data System (ADS)

    Masters, Daniel Charles

    Large multiwavelength surveys are now driving the frontiers of astronomical research. I describe results from my work using data from two large astronomical surveys: the Cosmic Evolution Survey (COSMOS), which has obtained deep photometric and spectroscopic data on two square degrees of the sky using many of the most powerful telescopes in the world, and the WFC3 Infrared Spectroscopic Parallels (WISP) Survey, which uses the highly sensitive slitless spectroscopic capability of the Hubble Space Telescope Wide Field Camera 3 to detect star-forming galaxies over most of the universe's history. First I describe my work on the evolution of the high-redshift quasar luminosity function, an important observational quantity constraining the growth of the supermassive black holes in the early universe. I show that the number density of faint quasars declines rapidly above z ˜ 3. This result is discussed in the context of cosmic reionization and the coevolution of galaxies and their central black holes. Next I present results of a multi-year campaign of near-infrared spectroscopy with FIRE, a world-class near-infrared spectrometer on the Magellan Baade 6.5 meter telescope in Chile, targeting emission-line galaxies at z ˜ 2 discovered with the Hubble Space Telescope. Our results showed that the typical emission-line galaxy at this redshift has low-metallicity, low dust obscuration, high ionization parameter, and little evidence for significant active galactic nucleus (AGN) contribution to the emission lines. We also find evidence that high redshift star-forming galaxies have enhanced nitrogen abundances. This result has interesting implications for the nature of the star formation in such galaxies -- in particular, it could mean that a large fraction of such galaxies harbor substantial populations of Wolf-Rayet stars, which are massive, evolved stars ejecting large amounts of enriched matter into the interstellar medium. Finally, I will discuss the discovery of three

  4. 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.

  5. The evolution of the diffuse cosmic ultraviolet background constrained by the Hubble Space Telescope observations of 3C 273

    NASA Technical Reports Server (NTRS)

    Ikeuchi, Satoru; Turner, Edwin L.

    1991-01-01

    Results are presented of recent HST UV spectroscopy of 3C 273, which revealed more low-redshift Lyman-alpha absorption lines (IGM clouds) than expected from the extrapolation from high-redshift (not less than 1.6) observations. It is shown on the basis of the standard pressure confined cloud model of the Lyman-alpha forest that this result indicates a sharp drop in the diffuse cosmic UV background from 2 to 0 redshift. It is predicted that the H I optical depth will drop slowly or perhaps even increase with decreasing redshift at less than 2 redshift. The implied constraints on the density and pressure of the diffuse IGM at 0 redshift are also derived. The inferred evolution of the diffuse UV flux bears a striking resemblance to the most recent direct determinations of the volume emissivity of the quasar population.

  6. Swift multi-wavelength observations of the high-redshift Blazar S5 0836+710 (4C 71.07)

    NASA Astrophysics Data System (ADS)

    Vercellone, Stefano; Romano, Patrizia; Raiteri, Claudia Maria; Acosta Pulido, Jose; Villata, Massimo; Carnerero Martin, Maria Isabel

    2016-04-01

    We present the preliminary results of a year-long Swift monitoring campaign of the high-redshift (z=2.172) flat-spectrum radio quasar (FSRQ) S5 0836+710 (4C 71.07). The campaign, based on one observation per month, 5 ks each observation, for 12 months, allowed us to investigate the synchrotron and nuclear emission contributions to the optical-UV frequency range of its spectral energy distribution and the X-ray spectral variations along a baseline of a year. We obtained a high-accuracy determination of UVOT magnitudes, an X-ray photon index with an uncertainty of the order of 5%, and well-sampled light curves both in the optical-UV and X-ray energy bands to study their possible modulations and correlations. Our study allowed us to exploit the unique Swift capabilities in terms of both simultaneous energy coverage and schedule flexibility. The Swift monitoring campaign was supported by observations by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) Collaboration, which provided radio, near-infrared, and optical photometric data as well as optical polarimetry. Moreover, a spectroscopic monitoring was obtained at the William Herschel Telescope (WHT) and the Nordic Optical Telescope (NOT). All these observations will allow us to obtain a comprehensive picture of the jet as well as of the nuclear source emission.

  7. Gamma-Ray Bursts from the Swift Burst Alert Telescope: Instrumental Sensitivity and Implication on the High-Redshift GRBs

    NASA Astrophysics Data System (ADS)

    Lien, A.; Sakamoto, T.; Barthelmy, S. D.; Baumgartner, W. H.; Cannizzo, J. K.; Chen, K.; Collins, N. R.; Cummings, J. R.; Gehrels, N.; Graziani, C.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Stamatikos, M.; Troja, E.; Ukwatta, T. N.

    2016-10-01

    We present the analyses of the Swift/BAT GRBs for the past 11years. In particular, we discuss the instrumental sensitivity and selection effects of the BAT GRB detections, and its implication on the observations of high-redshift bursts.

  8. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data. II. The Spring Equatorial Stripe

    SciTech Connect

    Fan, Xiaohui; Strauss, Michael A.; Schneider, Donald P.; Gunn, James E.; Lupton, Robert H.; Anderson, Scott F.; Voges, Wolfgang; Margon, Bruce; Annis, James; Bahcall, Neta A.

    2000-01-01

    This is the second paper in a series aimed at finding high-redshift quasars from five-color (u{sup '} g{sup '} r{sup '} i{sup '} z{sup '}) imaging data taken along the Celestial Equator by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. In this paper, we present 22 high-redshift quasars (z>3.6) discovered from {approx}250 deg2 of data in the spring Equatorial Stripe, plus photometry for two previously known high-redshift quasars in the same region of the sky. Our success rate in identifying high-redshift quasars is 68%. Five of the newly discovered quasars have redshifts higher than 4.6 (z=4.62, 4.69, 4.70, 4.92, and 5.03). All the quasars have i{sup *} <20.2 with absolute magnitude - 28.8

  9. THE GEOMETRY EFFECTS OF AN EXPANDING UNIVERSE ON THE DETECTION OF COOL NEUTRAL GAS AT HIGH REDSHIFT

    SciTech Connect

    Curran, S. J.

    2012-03-20

    Recent high-redshift surveys for 21 cm absorption in damped Ly{alpha} absorption systems (DLAs) take the number of published searches at z{sub abs} > 2 to 25, the same number as at z{sub abs} < 2, although the detection rate at high redshift remains significantly lower (20% compared to 60%). Using the known properties of the DLAs to estimate the unknown profile widths of the 21 cm non-detections and including the limits via a survival analysis, we show that the mean spin temperature/covering factor degeneracy at high redshift is, on average, double that of the low-redshift sample. This value is significantly lower than the previous factor of eight for the spin temperatures and is about the same factor as in the angular diameter distance ratios between the low- and high-redshift samples. That is, without the need for the several pivotal assumptions, which lead to an evolution in the spin temperature, we show that the observed distribution of 21 cm detections in DLAs can be accounted for by the geometry effects of an expanding universe. That is, as yet there is no evidence of the spin temperature of gas-rich galaxies evolving with redshift.

  10. GRB afterglows: Dust extinction properties from the low to high redshift universe

    NASA Astrophysics Data System (ADS)

    Zafar, Tayyaba

    2016-11-01

    Long-duration Gamma-ray bursts (GRBs) are excellent probes to study dust extinction due to their occurrence in star-forming regions and having simple synchrotron emission spectra. Inclusion of spectroscopic data to the GRB X-ray to the infrared spectral energy distribution (SED) could better define the continuum and confirm extinction feature. A preliminary SED analysis of GRB afterglows targeted with the VLT/X-Shooter spectrograph finds that all the 60% of extinguished bursts fit-well with featureless extinction curves. The longer wavelength coverage from ultraviolet to the near-infrared of X-Shooter helps to derive individual extinction curves and determine the total-to-selective extinction, RV precisely, suggesting extinction curves steeper (with a mean of RV = 2.66 ± 0.10) than the Small Magellanic Cloud. Moreover, addition of more data to the study of dust-to-metals ratios in GRB afterglows, quasar absorbers, and multiply lensed galaxies still shows the dust-to-metals ratios close to the Galactic value (with a mean value of log - 21.2cm-2mag-1), hinting short time delay between metals and dust formation. Such studies demonstrate the strength of using GRB afterglows to study dust origin and its properties the from low to high redshift Universe.

  11. HIghZ: A search for HI absorption in high-redshift radio galaxies

    NASA Astrophysics Data System (ADS)

    Allison, J.; Callingham, J.; Sadler, E.; Wayth, R.; Curran, S.; Mahoney, E.

    2017-01-01

    We will use the unique low-frequency spectral capability of the MWA to carry out a pilot survey for neutral gas in the interstellar medium of the most distant (z>5) radio galaxies in the Universe. Through detection of the HI 21-cm line in absorption we aim to place stringent lower limits on the source redshift, confirming its location in the early Universe. Our sample makes use of the excellent wide-band spectral information available from the recently completed MWA GLEAM survey, from which we have selected a sample of ultra-steep peaked-spectrum radio sources that have a spectral turnover below 300 MHz. These sources should be ideal candidates for high-redshift compact radio galaxies since they have (a) spectral peaks that turnover below 1GHz and (b) very steep (alpha < -1.0) spectral indices that are consistent with the high density environments expected for radio galaxies in the early Universe. Using the MWA, we aim to verify this hypothesis through the detection of significant column densities of cold HI. This pathfinder project will provide important technical information that will inform future absorption surveys both with the MWA and, ultimately, the SKA-LOW telescope.

  12. H-ATLAS: a candidate high redshift cluster/protocluster of star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Clements, D. L.; Braglia, F.; Petitpas, G.; Greenslade, J.; Cooray, A.; Valiante, E.; De Zotti, G.; O'Halloran, B.; Holdship, J.; Morris, B.; Pérez-Fournon, I.; Herranz, D.; Riechers, D.; Baes, M.; Bremer, M.; Bourne, N.; Dannerbauer, H.; Dariush, A.; Dunne, L.; Eales, S.; Fritz, J.; Gonzalez-Nuevo, J.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Leeuw, L. L.; Maddox, S.; Michałowski, M. J.; Negrello, M.; Omont, A.; Oteo, I.; Serjeant, S.; Valtchanov, I.; Vieira, J. D.; Wardlow, J.; van der Werf, P.

    2016-09-01

    We investigate the region around the Planck-detected z = 3.26 gravitationally lensed galaxy HATLAS J114637.9-001132 (hereinafter HATLAS12-00) using both archival Herschel data from the H-ATLAS survey and using submm data obtained with both LABOCA and SCUBA2. The lensed source is found to be surrounded by a strong overdensity of both Herschel-SPIRE sources and submm sources. We detect 17 bright (S870 > ˜7 mJy) sources at >4σ closer than 5 arcmin to the lensed object at 850/870 μm. 10 of these sources have good cross-identifications with objects detected by Herschel-SPIRE which have redder colours than other sources in the field, with 350 μm flux >250 μm flux, suggesting that they lie at high redshift. Submillimeter Array (SMA) observations localise one of these companions to ˜1 arcsec, allowing unambiguous cross identification with a 3.6 and 4.5 μm Spitzer source. The optical/near-IR spectral energy distribution of this source is measured by further observations and found to be consistent with z > 2, but incompatible with lower redshifts. We conclude that this system may be a galaxy cluster/protocluster or larger scale structure that contains a number of galaxies undergoing starbursts at the same time.

  13. NEARBY CLUMPY, GAS RICH, STAR-FORMING GALAXIES: LOCAL ANALOGS OF HIGH-REDSHIFT CLUMPY GALAXIES

    SciTech Connect

    Garland, C. A.; Pisano, D. J.; Rabidoux, K.; Low, M.-M. Mac; Kreckel, K.; Guzmán, R. E-mail: djpisano@mail.wvu.edu E-mail: mordecai@amnh.org E-mail: guzman@astro.ufl.edu

    2015-07-10

    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.

  14. Constraining high-redshift X-ray sources with next generation 21-cm power spectrum measurements

    NASA Astrophysics Data System (ADS)

    Ewall-Wice, Aaron; Hewitt, Jacqueline; Mesinger, Andrei; Dillon, Joshua S.; Liu, Adrian; Pober, Jonathan

    2016-05-01

    We use the Fisher matrix formalism and seminumerical simulations to derive quantitative predictions of the constraints that power spectrum measurements on next-generation interferometers, such as the Hydrogen Epoch of Reionization Array (HERA) and the Square Kilometre Array (SKA), will place on the characteristics of the X-ray sources that heated the high-redshift intergalactic medium. Incorporating observations between z = 5 and 25, we find that the proposed 331 element HERA and SKA phase 1 will be capable of placing ≲ 10 per cent constraints on the spectral properties of these first X-ray sources, even if one is unable to perform measurements within the foreground contaminated `wedge' or the FM band. When accounting for the enhancement in power spectrum amplitude from spin temperature fluctuations, we find that the observable signatures of reionization extend well beyond the peak in the power spectrum usually associated with it. We also find that lower redshift degeneracies between the signatures of heating and reionization physics lead to errors on reionization parameters that are significantly greater than previously predicted. Observations over the heating epoch are able to break these degeneracies and improve our constraints considerably. For these two reasons, 21-cm observations during the heating epoch significantly enhance our understanding of reionization as well.

  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. The gas distribution in the high-redshift cluster MS 1054-0321

    NASA Astrophysics Data System (ADS)

    Mirakhor, M. S.; Birkinshaw, M.

    2016-04-01

    We investigate the gas mass distribution in the high-redshift cluster MS 1054-0321 using Chandra X-ray and One Centimetre Receiver array Sunyaev-Zel'dovich (SZ) effect data. We use a superposition of offset β-type models to describe the composite structure of MS 1054-0321. We find gas mass fractions f_{gas}^{X {-}ray} = 0.087_{-0.001}^{+0.005} and f_{gas}^SZ=0.094_{-0.001}^{+0.003} for the (main) eastern component of MS 1054-0321 using X-ray or SZ data, but f_{gas}^{X {-}ray}=0.030_{-0.014}^{+0.010} for the western component. The gas mass fraction for the eastern component is in agreement with some results reported in the literature, but inconsistent with the cosmic baryon fraction. The low-gas mass fraction for the western component is likely to be a consequence of gas stripping during the ongoing merger. The gas mass fraction of the integrated system is 0.060_{-0.009}^{+0.004}: we suggest that the missing baryons from the western component are present as hot diffuse gas which is poorly represented in existing X-ray images. The missing gas could appear in sensitive SZ maps.

  17. The high-redshift gamma-ray burst GRB 140515A

    DOE PAGES

    Melandri, A.; Bernardini, M. G.; D'Avanzo, P. D.; ...

    2015-09-09

    High-redshift gamma-ray bursts (GRBs) offer several advantages when studying the distant Universe, providing unique information about the structure and properties of the galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge of this kind of distant events. We present the multi-wavelength analysis of the high-zSwift GRB GRB 140515A (z = 6.327). The best estimate of the neutral hydrogen fraction of the intergalactic medium towards the burst is xHI ≤ 0.002. The spectral absorption lines detected for this event are the weakest lines ever observed in GRB afterglows, suggesting that GRB 140515A exploded in amore » very low-density environment. Its circum-burst medium is characterised by an average extinction (AV ~ 0.1) that seems to be typical of z ≥ 6 events. The observed multi-band light curves are explained either with a very hard injected spectrum (p = 1.7) or with a multi-component emission (p = 2.1). In the second case a long-lasting central engine activity is needed in order to explain the late time X-ray emission. Furthermore, the possible origin of GRB 140515A in a Pop III (or in a Pop II star with a local environment enriched by Pop III) massive star is unlikely.« less

  18. The high-redshift gamma-ray burst GRB 140515A

    SciTech Connect

    Melandri, A.; Bernardini, M. G.; D'Avanzo, P. D.; Sanchez-Ramirez, R.; Nappo, F.; Nava, L.; Japelj, J.; de Ugarte Postigo, A.; Oates, S.; Campana, S.; Covino, S.; D'Elia, V.; Ghirlanda, G.; Gafton, E.; Ghisellini, G.; Gnedin, N.; Goldoni, P.; Gorosabel, J.; Libbrecht, T.; Malesani, D.; Salvaterra, R.; Thone, C. C.; Vergani, S. D.; Xu, D.; Tagliaferri, G.

    2015-09-09

    High-redshift gamma-ray bursts (GRBs) offer several advantages when studying the distant Universe, providing unique information about the structure and properties of the galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge of this kind of distant events. We present the multi-wavelength analysis of the high-zSwift GRB GRB 140515A (z = 6.327). The best estimate of the neutral hydrogen fraction of the intergalactic medium towards the burst is xHI ≤ 0.002. The spectral absorption lines detected for this event are the weakest lines ever observed in GRB afterglows, suggesting that GRB 140515A exploded in a very low-density environment. Its circum-burst medium is characterised by an average extinction (AV ~ 0.1) that seems to be typical of z ≥ 6 events. The observed multi-band light curves are explained either with a very hard injected spectrum (p = 1.7) or with a multi-component emission (p = 2.1). In the second case a long-lasting central engine activity is needed in order to explain the late time X-ray emission. Furthermore, the possible origin of GRB 140515A in a Pop III (or in a Pop II star with a local environment enriched by Pop III) massive star is unlikely.

  19. The discovery of high-redshift supernovae and their cosmological implications

    SciTech Connect

    Kim, Alex G.

    1997-09-01

    In this thesis the author discusses the methodology for doing photometry from procedure of extracting supernova counts from images that contain combined supernova plus galaxy flux, to standard star calibration, to additional instrumental corrections that arise due to the multiple telescopes used for observations. He discusses the different sources of photometric error and their correlations, and the construction of the covariance matrix for all the points in the light curve. He then describes the K corrections which account for the redshifting of spectra that are necessary to compare the photometry of the high-redshift data with those from nearby (z < 0.1) supernovae. Finally, he uses the first seven of the supernovae to test the hypothesis that they live in an under-dense bubble where the locally measured Hubble constant differs significantly from the true Hubble constant. He also uses the data to place limits on the value of the Hubble constant. Discussions of several other important aspects of the data analysis are or will be included in other papers. These topics include a description of how the covariance matrix is used to generate light-curve fits, a discussion of non-photometric systematic errors that also effect the measurements, and a discussion of the application of the supernovae to address other scientific/cosmological problems.

  20. The Origin and Evolution of Interstellar Dust in the Local and High-Redshift Universe

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2011-01-01

    In this talk I will begin by reviewing our current state of knowledge regarding the origin and evolution of dust in the local solar neighborhood. Using chemical evolution models, I will discuss their many different input parameters and their uncertainties. An important consequence of these models is the delayed injection of dust from AGB stars, compared to supernova-condensed dust, into the interstellar medium. I will show that these stellar evolutionary effects on dust composition are manifested in the infrared spectra of local galaxies. The delayed production of dust in AGB stars has also important consequences for the origin of the large amount of dust detected in high-redshift galaxies, when the universe was less that - 1 Gyr old. Supernovae may have been the only viable dust sources in those galaxies. Recent observations of SN1987a show a significant mass of dust in the ejecta of this SN. Is that production rate high enough to account for the observed dust mass in these galaxies? If not, what are the alternative viable sources of dust, and how do they depend on the nature of the galaxy (starburst or AGN) and its star formation history.

  1. The Origin and Evolution of Interstellar Dust in the Local and High-redshift Universe

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2012-01-01

    In this talk I will begin by reviewing our current state of knowledge regarding the origin and evolution of dust in the local solar neighborhood. using chemical evolution models, I will discuss their many different input parameters and their uncertainties. An important consequence of these models is the delayed injection of dust from AGB stars, compared to supernova-condensed dust, into the interstellar medium. I will show that these stellar evolutionary effects on dust composition are manifested in the infrared spectra of local galaxies. The delayed production of dust in AGB stars has also important consequences for the origin of the large amount of dust detected in high-redshift galaxies, when the universe was less that approx. 1 Gyr old. Supernovae may have been the only viable dust sources in those galaxies. Recent observations of sN1987a show a significant mass of dust in the ejecta of this SN. Is that production rate high enough to account for the observed dust mass in these galaxies? If not, what are the alternative viable sources of dust, and how do they depend on the nature of the galaxy (starburst or AGN) and its star formation history .

  2. Extended radio jets in the high-redshift quasars 3C 9 and 280.1

    NASA Astrophysics Data System (ADS)

    Swarup, G.; Sinha, R. P.; Saikia, D. J.

    1982-10-01

    Total intensity and polarization observations made with the VLA at 5 GHz of two high-redshift quasars 3C 9 and 280.1 are presented. They appear to have extended one-sided radio jets, which are the most luminous yet to be reported. The jet in 3C 280.1 which was observed with rather higher resolution is discussed in greater detail. This jet has no prominent hotspot at its end and shows several wiggles along its path. The magnetic field is nearly aligned with the axis of the jet and appears to bend along with it. Several possible explanations for the morphological features of the jet are considered, and it is suggested that they are likely to be due to hydrodynamic instabilities. In this scenario, the observed wiggles in the jet are attributed to the onset of helical modes of large wavelength. The absence of a prominent hotspot at the end of the jet may be understood if the energy in the beam is gradually dissipated in shocks and small-wavelength perturbations.

  3. Inflow velocities of cold flows streaming into massive galaxies at high redshifts

    NASA Astrophysics Data System (ADS)

    Goerdt, Tobias; Ceverino, Daniel

    2015-07-01

    We study the velocities of the accretion along streams from the cosmic web into massive galaxies at high redshift with the help of three different suites of AMR hydrodynamical cosmological simulations. The results are compared to free-fall velocities and to the sound speeds of the hot ambient medium. The sound speed of the hot ambient medium is calculated using two different methods to determine the medium's temperature. We find that the simulated cold stream velocities are in violent disagreement with the corresponding free-fall profiles. The sound speed is a better albeit not always correct description of the cold flows' velocity. Using these calculations as a first order approximation for the gas inflow velocities vinflow = 0.9 vvir is given. We conclude from the hydrodynamical simulations as our main result that the velocity profiles for the cold streams are constant with radius. These constant inflow velocities seem to have a `parabola-like' dependency on the host halo mass in units of the virial velocity that peaks at Mvir = 1012 M⊙ and we also propose that the best-fitting functional form for the dependency of the inflow velocity on the redshift is a square root power-law relation: v_inflow ∝ √{z + 1} v_vir.

  4. Physical properties of high-redshift WFC3 galaxies at z=7-10

    NASA Astrophysics Data System (ADS)

    Nagamine, Kentaro

    2010-09-01

    Over the past decade, large samples of Ly-break galaxies {LBGs} have been assembled at z=3-6. The observers are now pushing the forefront of galaxy formation study into the range of z=7-9 utilizing the new data from the WFC3 camera. However, due to the faintness of the sources at these redshifts, it is difficult to derive the physical parameters such as stellar mass and star formation histories of the candidate galaxies. Therefore, it would be helpful to obtain predictions on these quantities from theoretical models using self-consistent, cosmological hydrodynamic simulations of galaxy formation. In the proposed work, we will examine the physical properties of high-redshift star-forming galaxies at z=7-10 using cosmological hydrodynamic simulations. In the first step, we will develop a model for estimating the variable extinction values of individual galaxies based on their metal column densities. We will also examine the spectro-photometric properties, stellar masses, star formation histories, and spatial correlations, and provide feedback to the WFC3 observations. The second step of our project is to perform the radiative transfer calculations of stellar radiation from high-z galaxies using the Authentic Radiative Transfer {ART} code. This exact RT calculation will allow us to check the accuracy of our earlier results from part {1}, and to develop a better model of dust distribution in cosmological simulations.

  5. 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

  6. 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

  7. The Great Observatories Origins Deep Survey High Redshift Search for Supernovae

    NASA Astrophysics Data System (ADS)

    Strolger, L.-G.; Riess, A. G.; Dahlen, T.; GOODS SN Searchers; HHZS Team

    2003-05-01

    We have recently concluded the Hubble Higher-z Supernova Team's search for high redshift supernovae in conjunction with the Great Observatories Origins Deep Survey (GOODS). Using the Advanced Camera for Surveys (ACS), we have surveyed ˜170 sq. arcmin fields about the CDF-S and HSF-N on five epochs each, with ˜45 day baselines. These deep observations have allowed us to discover ˜40 supernovae in the range of 0.2=1. A cosmic evolution of SN Ia luminosity or ``grey dust'' would cause SNe Ia to be systematically fainter at higher-z and thus show a different sign and shape on the Hubble diagram. We are also investigating the rate of SNe at /line{z}˜=0.8-1.0, the relation to the local rates, comparisons of host environments to low redshift host environments, and the implications of each to SN progenitors, star formation rate history, and possibly to cosmology.

  8. Characterization and Modeling of Contamination for Lyman Break Galaxy Samples at High Redshift

    NASA Astrophysics Data System (ADS)

    Vulcani, Benedetta; Trenti, Michele; Calvi, Valentina; Bouwens, Rychard; Oesch, Pascal; Stiavelli, Massimo; Franx, Marijn

    2017-02-01

    The selection of high-redshift sources from broadband photometry using the Lyman-break galaxy (LBG) technique is a well established methodology, but the characterization of its contamination for the faintest sources is still incomplete. We use the optical and near-IR data from four (ultra)deep Hubble Space Telescope legacy fields to investigate the contamination fraction of LBG samples at z∼ 5{--}8 selected using a color–color method. Our approach is based on characterizing the number count distribution of interloper sources, that is, galaxies with colors similar to those of LBGs, but showing detection at wavelengths shorter than the spectral break. Without sufficient sensitivity at bluer wavelengths, a subset of interlopers may not be properly classified, and contaminate the LBG selection. The surface density of interlopers in the sky gets steeper with increasing redshift of LBG selections. Since the intrinsic number of dropouts decreases significantly with increasing redshift, this implies increasing contamination from misclassified interlopers with increasing redshift, primarily by intermediate redshift sources with unremarkable properties (intermediate ages, lack of ongoing star formation and low/moderate dust content). Using Monte-Carlo simulations, we estimate that the CANDELS deep data have contamination induced by photometric scatter increasing from ∼ 2 % at z∼ 5 to ∼ 6 % at z∼ 8 for a typical dropout color ≥slant 1 mag, with contamination naturally decreasing for a more stringent dropout selection. Contaminants are expected to be located preferentially near the detection limit of surveys, ranging from 0.1 to 0.4 contaminants per arcmin2 at {J}125 = 30, depending on the field considered. This analysis suggests that the impact of contamination in future studies of z> 10 galaxies needs to be carefully considered.

  9. Outflows driven by quasars in high-redshift galaxies with radiation hydrodynamics

    NASA Astrophysics Data System (ADS)

    Bieri, Rebekka; Dubois, Yohan; Rosdahl, Joakim; Wagner, Alexander; Silk, Joseph; Mamon, Gary A.

    2017-01-01

    The quasar mode of active galactic nuclei (AGN) in the high-redshift Universe is routinely observed in gas-rich galaxies together with large-scale AGN-driven winds. It is crucial to understand how photons emitted by the central AGN source couple to the ambient interstellar medium to trigger large-scale outflows. By means of radiation-hydrodynamical simulations of idealized galactic discs, we study the coupling of photons with the multiphase galactic gas, and how it varies with gas cloud sizes, and the radiation bands included in the simulations, which are ultraviolet, optical, and infrared (IR). We show how a quasar with a luminosity of 1046 erg s- 1 can drive large-scale winds with velocities of 10^2-10^3 km s^{-1} and mass outflow rates around 103 M⊙ yr- 1 for times of the order of a few million years. IR radiation is necessary to efficiently transfer momentum to the gas via multiscattering on dust in dense clouds. However, IR multiscattering, despite being extremely important at early times, quickly declines as the central gas cloud expands and breaks up, allowing the radiation to escape through low gas density channels. The typical number of multiscattering events for an IR photon is only about a quarter of the mean optical depth from the centre of the cloud. Our models account for the observed outflow rates of ˜500-1000 M⊙ yr- 1 and high velocities of ˜ 103 km s- 1, favouring winds that are energy driven via extremely fast nuclear outflows, interpreted here as being IR radiatively driven winds.

  10. 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.

  11. The coevolution of supermassive black holes and massive galaxies at high redshift

    SciTech Connect

    Lapi, A.; Raimundo, S.; Aversa, R.; Cai, Z.-Y.; Celotti, A.; De Zotti, G.; Danese, L.; Negrello, M.

    2014-02-20

    We exploit the recent, wide samples of far-infrared (FIR) selected galaxies followed up in X-rays and of X-ray/optically selected active galactic nuclei (AGNs) followed up in the FIR band, along with the classic data on AGNs and stellar luminosity functions at high redshift z ≳ 1.5, to probe different stages in the coevolution of supermassive black holes (BHs) and host galaxies. The results of our analysis indicate the following scenario: (1) the star formation in the host galaxy proceeds within a heavily dust-enshrouded medium at an almost constant rate over a timescale ≲ 0.5-1 Gyr and then abruptly declines due to quasar feedback, over the same timescale; (2) part of the interstellar medium loses angular momentum, reaches the circum-nuclear regions at a rate proportional to the star formation, and is temporarily stored in a massive reservoir/proto-torus wherefrom it can be promptly accreted; (3) the BH grows by accretion in a self-regulated regime with radiative power that can slightly exceed the Eddington limit L/L {sub Edd} ≲ 4, particularly at the highest redshifts; (4) for massive BHs, the ensuing energy feedback at its maximum exceeds the stellar one and removes the interstellar gas, thus stopping the star formation and the fueling of the reservoir; (5) afterward, if the latter has retained enough gas, a phase of supply-limited accretion follows, exponentially declining with a timescale of about two e-folding times. We also discuss how the detailed properties and the specific evolution of the reservoir can be investigated via coordinated, high-resolution observations of star-forming, strongly lensed galaxies in the (sub-)mm band with ALMA and in the X-ray band with Chandra and the next-generation X-ray instruments.

  12. 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.

  13. 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.

  14. Giant clumps in the FIRE simulations: a case study of a massive high-redshift galaxy

    NASA Astrophysics Data System (ADS)

    Oklopčić, Antonija; Hopkins, Philip F.; Feldmann, Robert; Kereš, Dušan; Faucher-Giguère, Claude-André; Murray, Norman

    2017-02-01

    The morphology of massive star-forming galaxies at high redshift is often dominated by giant clumps of mass ˜108-109 M⊙ and size ˜100-1000 pc. Previous studies have proposed that giant clumps might have an important role in the evolution of their host galaxy, particularly in building the central bulge. However, this depends on whether clumps live long enough to migrate from their original location in the disc or whether they get disrupted by their own stellar feedback before reaching the centre of the galaxy. We use cosmological hydrodynamical simulations from the FIRE (Feedback in Realistic Environments) project which implement explicit treatments of stellar feedback and interstellar medium physics to study the properties of these clumps. We follow the evolution of giant clumps in a massive (M* ˜ 1010.8 M⊙ at z = 1), discy, gas-rich galaxy from redshift z ≳ 2 to z = 1. Even though the clumpy phase of this galaxy lasts over a gigayear, individual gas clumps are short-lived, with mean lifetime of massive clumps of ˜20 Myr. During that time, they turn between 0.1 per cent and 20 per cent of their gas into stars before being disrupted, similar to local giant molecular clouds. Clumps with M ≳ 107 M⊙ account for ˜20 per cent of the total star formation in the galaxy during the clumpy phase, producing ˜1010 M⊙ of stars. We do not find evidence for net inward migration of clumps within the galaxy. The number of giant clumps and their mass decrease at lower redshifts, following the decrease in the overall gas fraction and star formation rate.

  15. 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 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.

  16. THE FAINT END OF THE CLUSTER-GALAXY LUMINOSITY FUNCTION AT HIGH REDSHIFT

    SciTech Connect

    Mancone, Conor L.; Baker, Troy; Gonzalez, Anthony H.; Ashby, Matthew L. N.; Snyder, Greg; Stanford, Spencer A.; Brodwin, Mark; Eisenhardt, Peter R. M.; Stern, Daniel; Wright, Edward L.

    2012-12-20

    We measure the faint-end slope of the galaxy luminosity function (LF) for cluster galaxies at 1 < z < 1.5 using Spitzer IRAC data. We investigate whether this slope, {alpha}, differs from that of the field LF at these redshifts, and with the cluster LF at low redshifts. The latter is of particular interest as low-luminosity galaxies are expected to undergo significant evolution. We use seven high-redshift spectroscopically confirmed galaxy clusters drawn from the IRAC Shallow Cluster Survey to measure the cluster-galaxy LF down to depths of M* + 3 (3.6 {mu}m) and M* + 2.5 (4.5 {mu}m). The summed LF at our median cluster redshift (z = 1.35) is well fit by a Schechter distribution with {alpha}{sub 3.6{mu}m} = -0.97 {+-} 0.14 and {alpha}{sub 4.5{mu}m} = -0.91 {+-} 0.28, consistent with a flat faint-end slope and is in agreement with measurements of the field LF in similar bands at these redshifts. A comparison to {alpha} in low-redshift clusters finds no statistically significant evidence of evolution. Combined with past studies which show that M* is passively evolving out to z {approx} 1.3, this means that the shape of the cluster LF is largely in place by z {approx} 1.3. This suggests that the processes that govern the buildup of the mass of low-mass cluster galaxies have no net effect on the faint-end slope of the cluster LF at z {approx}< 1.3.

  17. Probing the Physical Properties of High-Redshift Lyman-Alpha Emitters with Spitzer

    NASA Astrophysics Data System (ADS)

    Finkelstein, Keely; Finkelstein, Steven; Rhoads, James E.; Malhotra, Sangeeta

    2015-08-01

    Abstract: Studies of Lyman Alpha emitting galaxies (LAEs) offer insight into an understanding of early galaxies and the build-up of galaxies at early times. To better understand these objects and constrain their stellar properties, we have observed a sample of 162 z=4.5 and 14 z=5.7 LAEs with deep Spitzer IRAC 3.6 and 4.5 micron imaging from the Spitzer Lyman Alpha Survey. This is by far the largest sample of high-redshift LAEs imaged with Spitzer, which probes rest-frame optical wavelengths at these redshifts, dramatically improving constraints on the stellar masses and star-formation rates. By fitting the spectral energy distributions of individual LAEs using ground-based optical, HST near-IR, and Spitzer mid-IR imaging, we show that our sample of LAEs has a wide range of stellar properties. For individual LAEs detected with IRAC, stellar mass ranges from 5x10^8 - 10^11 solar masses. In addition, we find a correlation between stellar mass and star formation rate (SFR), similar to trends measured at lower redshift (e.g. Noeske et al. 2007; Daddi et al. 2007). However for this sample of higher redshift LAEs, the LAE sequence is elevated compared to continuum-selected galaxies at the same redshift, meaning that for a given stellar mass, the LAEs tend to have higher star formation rates. However, a subset of massive LAEs sits on the continuum-selected galaxy trend, tentatively implying that there may be two mechanisms for Lyman alpha escape.

  18. Far Infrared Spectroscopy of the Nearby Analogues of High-Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Hayes, Matthew

    2014-10-01

    We propose far infrared emission line spectroscopy of a sample of 23 local star-forming galaxies, drawn from the Lyman alpha Reference Sample (LARS), for which we have unrivalled high-resolution imaging and spectroscopy from HST, and 21cm HI observations from VLA+GMRT. Moreover the galaxies are selected as the close analogues of the high-redshift Lyman-break galaxies and Spitzer+Herschel selected galaxies found in extragalactic deep fields. The science goal of LARS is to determine what governs the escape of Lyman alpha (Lya) photons from galaxies, and thereby aid interpretation of high-z observations where Lya is the most used spectral probe. However given its clean selection and multiwavelength nature, LARS can equally well improve our understanding of FIR line observations of high-z galaxies. The target emission lines in this proposal are [CII], [OI], and [OIII] at 158, 63, and 88 micron, respectively. The motivations are that these lines: 1. are of increasing interest at high-z as new sensitive submm/radio interferometers come online 2. are proposed quantitative tracers of star formation rates, but their utility must be proven in appropriately analogous well-studied galaxies 3. when combined with models of photodissociation regions, enable estimates of the density and mass of PDR gas and provide vital constraints on our Lya radiative transfer models of galaxies. 4. provide uniquely robust estimates of nebular extinction and metallicity when combined with our optical IFU data. Astrophysical applications are many, especially when combined with the array of existing data. Specifically they will provide vital constraints on ISM structure, that are required for understanding the emission of the cosmologically vital Lya emission line. Moreover, SFR calibrations will be tested in star forming environments that resemble those of early galaxies and the legacy value of the sample is hard to overstate.

  19. Investigating the properties of gamma ray bursts and gravitational wave standard sirens as high redshift distance indicators

    NASA Astrophysics Data System (ADS)

    Speirits, Fiona Claire

    In a discipline commonly faulted for ad hoc assumptions and models with very little discriminating observational evidence, cosmologists are continually trying, and in many cases succeeding, to improve both the data and models. However, the desire to support currently favoured models often dominates research and may lead to a systematic bias being introduced in favour of a model before a strong body of supporting evidence has been accumulated. This is perhaps most evident in literature supporting the viability of Gamma Ray Bursts as cosmological distance indicators, where aside from subjective data-selection, the basic statistical methods are at best questionable and at worst incorrect. To this end, we construct a simple cosmology-independent illustration of the effect that the application of these methods has on parameter estimation and discuss the correct method to apply to current data. We also investigate the constraints potential future Gamma Ray Burst data may place on alternatives to the status quo Concordance Model in the shape of Conformal Gravity and Unified Dark Matter through a widely applicable and transferable Bayesian model comparison technique and the development of a representative mock data set. Finally, we investigate gravitational wave standard sirens as an alternative high-redshift distance indicator. We first illustrate their strong diagnostic potential through a Bayesian model comparison between the standard Unified Dark Matter model and a variant in which the dark component is redshift dependent. By drawing mock data from a known cosmological model, thus fixing the expected values of the model parameters, we find that while 182 Type 1a Supernovae are readily confused between constant and evolving models, just 2 standard sirens are able to successfully identify the correct model. Having established standard sirens as an effective tool in cosmological model comparison, we then address the potential confusion of models with dynamical dark energy

  20. A PARAMETRIC STUDY OF POSSIBLE SOLUTIONS TO THE HIGH-REDSHIFT OVERPRODUCTION OF STARS IN MODELED DWARF GALAXIES

    SciTech Connect

    White, Catherine E.; Somerville, Rachel S.; Ferguson, Henry C.

    2015-02-01

    Both numerical hydrodynamic and semi-analytic cosmological models of galaxy formation struggle to match observed star formation histories of galaxies in low-mass halos (M {sub H} ≲ 10{sup 11} M {sub ☉}), predicting more star formation at high redshift and less star formation at low redshift than observed. The fundamental problem is that galaxies' gas accretion and star formation rates are too closely coupled in the models: the accretion rate largely drives the star formation rate. Observations point to gas accretion rates that outpace star formation at high redshift, resulting in a buildup of gas and a delay in star formation until lower redshifts. We present three empirical adjustments of standard recipes in a semi-analytic model motivated by three physical scenarios that could cause this decoupling: (1) the mass-loading factors of outflows driven by stellar feedback may have a steeper dependence on halo mass at earlier times, (2) the efficiency of star formation may be lower in low-mass halos at high redshift, and (3) gas may not be able to accrete efficiently onto the disk in low-mass halos at high redshift. These new recipes, once tuned, better reproduce the evolution of f {sub *}≡ M {sub *}/M {sub H} as a function of halo mass as derived from abundance matching over redshifts z = 0 to 3, though they have different effects on cold gas fractions, star formation rates, and metallicities. Changes to gas accretion and stellar-driven winds are promising, while direct modification of the star formation timescale requires drastic measures that are not physically well motivated.

  1. The Cycle of Dust in the Milky Ways: Clues from the High-Redshift and the Local Universe

    NASA Technical Reports Server (NTRS)

    Dwek, Eli

    2008-01-01

    Massive amount of dust has been observed at high-redshifts when the universe was a mere 900 Myr old. The formation and evolution of dust is there dominated by massive stars and interstellar processes. In contrast, in the local universe lower mass stars, predominantly 2-5 Msun AGB stars, play the dominant role in the production of interstellar dust. These two extreme environments offer fascinating clues about the evolution of dust in the Milky Way galaxy

  2. Tests of the Accelerating Universe with Near-Infrared Observations of a High-Redshift Type IA Supernova

    NASA Astrophysics Data System (ADS)

    Riess, Adam G.; Filippenko, Alexei V.; Liu, Michael C.; Challis, Peter; Clocchiatti, Alejandro; Diercks, Alan; Garnavich, Peter M.; Hogan, Craig J.; Jha, Saurabh; Kirshner, Robert P.; Leibundgut, B.; Phillips, M. M.; Reiss, David; Schmidt, Brian P.; Schommer, Robert A.; Smith, R. Chris; Spyromilio, J.; Stubbs, Christopher; Suntzeff, Nicholas B.; Tonry, John; Woudt, Patrick; Brunner, Robert J.; Dey, Arjun; Gal, Roy; Graham, James; Larkin, James; Odewahn, Steve C.; Oppenheimer, Ben

    2000-06-01

    We have measured the rest-frame B-, V-, and I-band light curves of a high-redshift type Ia supernova (SN Ia), SN 1999Q (z=0.46), using the Hubble Space Telescope (HST) and ground-based near-infrared detectors. A goal of this study is the measurement of the color excess, EB-I, a sensitive indicator of interstellar or intergalactic dust, which could affect recent cosmological measurements from high-redshift SNe Ia. Our observations disfavor a 30% opacity of SN Ia visual light by dust as an alternative to an accelerating universe. This statement applies to both Galactic-type dust (rejected at the 3.4 σ confidence level) and grayer dust (grain size >0.1 μm, rejected at the 2.3-2.6 σ confidence level) as proposed by Aguirre. The rest-frame I-band light curve shows the secondary maximum 1 month after the B maximum typical of nearby SNe Ia of normal luminosity, providing no indication of evolution as a function of redshift out to z~0.5. An expanded set of similar observations could improve the constraints on any contribution of extragalactic dust to the dimming of high-redshift SNe Ia.

  3. High-redshift blazar identification for Swift J1656.3-3302

    NASA Astrophysics Data System (ADS)

    Masetti, N.; Mason, E.; Landi, R.; Giommi, P.; Bassani, L.; Malizia, A.; Bird, A. J.; Bazzano, A.; Dean, A. J.; Gehrels, N.; Palazzi, E.; Ubertini, P.

    2008-03-01

    We report on the high-redshift blazar identification of a new gamma-ray source, Swift J1656.3-3302, detected with the BAT imager onboard the Swift satellite and the IBIS instrument on the INTEGRAL satellite. Follow-up optical spectroscopy has allowed us to identify the counterpart as an R˜ 19 mag source that shows broad Lyman-α, Si iv, He ii, C iv, and C iii] emission lines at redshift z = 2.40 ± 0.01. Spectral evolution is observed in X-rays when the INTEGRAL/IBIS data are compared to the Swift/BAT results, with the spectrum steepening when the source gets fainter. The 0.7-200 keV X-ray continuum, observed with Swift/XRT and INTEGRAL/IBIS, shows the power law shape typical of radio loud (broad emission line) active galactic nuclei (with a photon index Γ ˜ 1.6) and a hint of spectral curvature below ~2 keV, possibly due to intrinsic absorption (NH ˜ 7× 10 22 cm-2) local to the source. Alternatively, a slope change (Δ Γ ˜ 1) around 2.7 keV can describe the X-ray spectrum equally well. At this redshift, the observed 20-100 keV luminosity of the source is ~1048 erg s-1 (assuming isotropic emission), making Swift J1656.3-3302 one of the most X-ray luminous blazars. This source is yet another example of a distant gamma-ray loud quasar discovered above 20 keV. It is also the farthest object, among the previously unidentified INTEGRAL sources, whose nature has been determined a posteriori through optical spectroscopy. Partly based on X-ray observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation of Russia and the USA, and on optical observations collected at ESO (La Silla, Chile) under programme 079.A-0171(A).

  4. 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.

  5. 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

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

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  7. High-redshift formation and evolution of central massive objects - II. The census of BH seeds

    NASA Astrophysics Data System (ADS)

    Devecchi, B.; Volonteri, M.; Rossi, E. M.; Colpi, M.; Portegies Zwart, S.

    2012-04-01

    We present results of simulations aimed at tracing the formation of nuclear star clusters (NCs) and black hole (BH) seeds in the framework of the current Λcold dark matter (ΛCDM) cosmogony. These BH seeds are considered to be progenitors of the supermassive BHs that inhabit today's galaxies. We focus on two mechanisms for the formation of BHs at high redshifts: as end-products of (1) Population III stars in metal-free haloes, and (2) runaway stellar collisions in metal-poor NCs. Our model tracks the chemical, radiative and mechanical feedback of stars on the baryonic component of the evolving haloes. This procedure allows us to evaluate when and where the conditions for BH formation are met, and to trace the emergence of BH seeds arising from the dynamical channel, in a cosmological context. BHs start to appear already at redshift ˜30 as remnants of Population III stars. The efficiency of this mechanism begins decreasing once feedbacks become increasingly important. Around redshift z˜ 15, BHs mostly form in the centre of mildly metal-enriched haloes inside dense NCs. The seed BHs that form along the two pathways have at birth a mass of around 100-1000 M⊙. The occupation fraction of BHs is a function of both halo mass and mass growth rate: at a given redshift, heavier and faster growing haloes have a higher chance to form a native BH, or to acquire an inherited BH via merging of another system. With decreasing z, the probability of finding a BH shifts towards progressively higher mass halo intervals. This is due to the fact that, at later cosmic times, low-mass systems rarely form a seed, and already formed BHs are deposited into larger mass systems due to hierarchical mergers. Our model predicts that at z= 0, all haloes above 1011 M⊙ should host a BH (in agreement with observational results), most probably inherited during their lifetime. Haloes less massive than 109 M⊙ have a higher probability to host a native BH, but their occupation fraction decreases

  8. 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.

  9. The ratio of CO to total gas mass in high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Mashian, Natalie; Sternberg, Amiel; Loeb, Abraham

    2013-11-01

    Walter et al. have recently identified the J = 6 - 5, 5 - 4, and 2 - 1 CO rotational emission lines, and [C II] fine-structure emission line from the star-forming interstellar medium (ISM) in the high-redshift submillimetre source HDF 850.1, at z = 5.183. We employ large velocity gradient (LVG) modelling to analyse the spectra of this source assuming the [C II] and CO emissions originate from (i) separate virialized regions, (ii) separate unvirialized regions, (iii) uniformly mixed virialized regions and (iv) uniformly mixed unvirialized regions. We present the best-fitting set of parameters, including for each case the ratio α between the total hydrogen/helium gas mass and the CO(1-0) line luminosity. We also present computations of the ratio of H2 mass to [C II] line luminosity for optically thin conditions, for a range of gas temperatures and densities, for direct conversion of [C II] line luminosities to `CO-dark' H2 masses. For HDF 850.1 we find that a model in which the CO and C+ are uniformly mixed in gas that is shielded from ultraviolet radiation requires a cosmic ray or X-ray ionization rate of ζ ≈ 3 × 10-14 s-1, plausibly consistent with the large star formation rate (˜103 M⊙ yr-1) observed in this source. Enforcing the cosmological constraint posed by the abundance of dark matter haloes in the standard Λ cold dark matter (ΛCDM) cosmology and taking into account other possible contributions to the total gas mass, we find that the two models in which the virialization condition is enforced can be ruled out at the ≳2σ level, while the model assuming mixed unvirialized regions is less likely. We conclude that modelling HDF 850.1's ISM as a collection of unvirialized molecular clouds with distinct CO and C+ layers, for which α = 1.2 M⊙ (K km s-1 pc2)-1 for the CO to H2 mass-to-luminosity ratio (similar to the standard ultraluminous infrared galaxy value), is most consistent with the ΛCDM cosmology.

  10. VIMOS Ultra-Deep Survey (VUDS): IGM transmission towards galaxies with 2.5 < z < 5.5 and the colour selection of high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Thomas, R.; Le Fèvre, O.; Le Brun, V.; Cassata, P.; Garilli, B.; Lemaux, B. C.; Maccagni, D.; Pentericci, L.; Tasca, L. A. M.; Zamorani, G.; Zucca, E.; Amorin, R.; Bardelli, S.; Cassarà, L.; Castellano, M.; Cimatti, A.; Cucciati, O.; Durkalec, A.; Fontana, A.; Giavalisco, M.; Grazian, A.; Hathi, N. P.; Ilbert, O.; Paltani, S.; Pforr, J.; Ribeiro, B.; Schaerer, D.; Scodeggio, M.; Sommariva, V.; Talia, M.; Tresse, L.; Vanzella, E.; Vergani, D.; Capak, P.; Charlot, S.; Contini, T.; Cuby, J. G.; de la Torre, S.; Dunlop, J.; Fotopoulou, S.; Koekemoer, A.; López-Sanjuan, C.; Mellier, Y.; Salvato, M.; Scoville, N.; Taniguchi, Y.; Wang, P. W.

    2017-01-01

    The observed UV rest-frame spectra of distant galaxies are the result of their intrinsic emission combined with absorption along the line of sight produced by the inter-galactic medium (IGM). Here we analyse the evolution of the mean IGM transmission Tr(Lyα) and its dispersion along the line of sight for 2127 galaxies with 2.5 < z < 5.5 in the VIMOS Ultra Deep Survey (VUDS). We fitted model spectra combined with a range of IGM transmission to the galaxy spectra using the spectral fitting algorithm GOSSIP+. We used these fits to derive the mean IGM transmission towards each galaxy for several redshift slices from z = 2.5 to z = 5.5. We found that the mean IGM transmission defined as Tr(Lyα) = e- τ (with τ as the HI optical depth) is 79%, 69%, 59%, 55%, and 46% at redshifts 2.75, 3.22, 3.70, 4.23, and 4.77, respectively. We compared these results to measurements obtained from quasar lines of sight and found that the IGM transmission towards galaxies is in excellent agreement with quasar values up to redshift z 4. We found tentative evidence for a higher IGM transmission at z ≥ 4 compared to results from QSOs, but a degeneracy between dust extinction and IGM prevents us from firmly concluding whether the internal dust extinction for star-forming galaxies at z > 4 takes a mean value significantly in excess of E(B-V) > 0.15. Most importantly, we found a large dispersion of IGM transmission along the lines of sight towards distant galaxies with 68% of the distribution within 10 to 17% of the median value in δz = 0.5 bins, similar to what is found on the lines of sight towards QSOs. We demonstrate that taking this broad range of IGM transmission into account is important when selecting high-redshift galaxies based on their colour properties (e.g. LBG or photometric redshiftselection) because failing to do so causes a significant incompleteness in selecting high-redshift galaxy populations. We finally discuss the observed IGM properties and speculate that the broad

  11. Large-scale opacity fluctuations in the Lyα forest: evidence for QSOs dominating the ionizing UV background at z ∼ 5.5-6?

    NASA Astrophysics Data System (ADS)

    Chardin, Jonathan; Puchwein, Ewald; Haehnelt, Martin G.

    2017-03-01

    Lyα forest data probing the post-reionization Universe show surprisingly large opacity fluctuations over rather large (≥50 h-1 comoving Mpc) spatial scales. We model these fluctuations using a hybrid approach utilizing the large-volume Millennium simulation to predict the spatial distribution of QSOs combined with smaller scale full hydrodynamical simulation performed with RAMSES and post-processed with the radiative transfer code ATON. We produce realistic mock absorption spectra that account for the contribution of galaxies and QSOs to the ionizing UV background. These improved models confirm our earlier findings that a significant ( ≳ 50 per cent) contribution of ionizing photons from QSOs can explain the large reported opacity fluctuations on large scales. The inferred QSO luminosity function is thereby consistent with recent estimates of the space density of QSOs at this redshift. Our simulations still somewhat struggle, however, to reproduce the very long (110 h-1 comoving Mpc) high-opacity absorption through observed in ULAS J0148+0600, perhaps suggesting an even later end of reionization than assumed in our previously favoured model. Medium-deep/medium area QSO surveys as well as targeted searches for the predicted strong transverse QSO proximity effect would illuminate the origin of the observed large-scale opacity fluctuations. They would allow us to substantiate whether UV fluctuations due to QSO are indeed primarily responsible, or whether significant contributions from other recently proposed mechanisms such as large-scale fluctuations in temperature and mean free path (even in the absence of rare bright sources) are required.

  12. Measurements of Extragalactic Background Light from the Far UV to the Far IR from Deep Ground- and Space-based Galaxy Counts

    NASA Astrophysics Data System (ADS)

    Driver, Simon P.; Andrews, Stephen K.; Davies, Luke J.; Robotham, Aaron S. G.; Wright, Angus H.; Windhorst, Rogier A.; Cohen, Seth; Emig, Kim; Jansen, Rolf A.; Dunne, Loretta

    2016-08-01

    We combine wide and deep galaxy number-count data from the Galaxy And Mass Assembly, COSMOS/G10, Hubble Space Telescope (HST) Early Release Science, HST UVUDF, and various near-, mid-, and far-IR data sets from ESO, Spitzer, and Herschel. The combined data range from the far UV (0.15 μm) to far-IR (500 μm), and in all cases the contribution to the integrated galaxy light (IGL) of successively fainter galaxies converges. Using a simple spline fit, we derive the IGL and the extrapolated IGL in all bands. We argue that undetected low-surface-brightness galaxies and intracluster/group light are modest, and that our extrapolated-IGL measurements are an accurate representation of the extragalactic background light (EBL). Our data agree with most earlier IGL estimates and with direct measurements in the far IR, but disagree strongly with direct estimates in the optical. Close agreement between our results and recent very high-energy experiments (H.E.S.S. and MAGIC) suggests that there may be an additional foreground affecting the direct estimates. The most likely culprit could be the adopted model of zodiacal light. Finally we use a modified version of the two-component model to integrate the EBL and obtain measurements of the cosmic optical background (COB) and cosmic infrared background of {24}-4+4 nW m-2 sr-1 and {26}-5+5 nW m-2 sr-1 respectively (48%:52%). Over the next decade, upcoming space missions such as Euclid and the Wide Field Infrared Space Telescope will have the capacity to reduce the COB error to <1%, at which point comparisons to the very high-energy data could have the potential to provide a direct detection and measurement of the reionization field.

  13. PROBING HIGH-REDSHIFT GALAXY FORMATION AT THE HIGHEST LUMINOSITIES: NEW INSIGHTS FROM DEIMOS SPECTROSCOPY

    SciTech Connect

    Lee, Kyoung-Soo; Dey, Arjun; Cooper, Michael C.; Reddy, Naveen; Jannuzi, Buell T.

    2013-07-01

    We present Keck DEIMOS spectroscopic observations of the most UV-luminous star-forming galaxies at redshifts 3.2 < z < 4.6. Our sample, selected in the Booetes field of the NOAO Deep Wide-Field Survey, contains galaxies with luminosities of L* {approx}< L{sub UV} {approx}< 7 L* and is one of the largest samples to date of the most UV-luminous galaxies at these redshifts. Our spectroscopic data confirm 41 candidates as star-forming galaxies at 3.2 < z < 4.6 and validate the relatively clean selection of the photometric candidates with a contamination rate of 11%-28%. We find that the fraction of Ly{alpha} emitting galaxies increases with decreasing UV luminosity. None of the 12 galaxies with M{sub UV} < -22 (i.e., L{sub UV} > 3 L*) exhibit strong Ly{alpha} emission. We find strong evidence of large-scale outflows, transporting the neutral/ionized gas in the interstellar medium away from the galaxy. Galaxies exhibiting both interstellar absorption and Ly{alpha} emission lines show a significant offset between the two features, with a relative velocity of 200-1150 km s{sup -1}. We find tentative evidence that this measure of the outflow velocity increases with UV luminosity and/or stellar mass. The luminosity- and mass-dependent outflow strengths suggest that the efficiency of feedback and enrichment of the surrounding medium depend on these galaxy parameters. We also stack the individual spectra to construct composite spectra of the absorption-line-only and Ly{alpha}-emitting subsets of the UV luminous galaxies at z {approx_equal} 3.7. The composite spectra are very similar to those of lower-redshift and lower-luminosity Lyman break galaxy (LBG) samples, but with some subtle differences. Analyses of the composite spectra suggest that the UV luminous LBGs at z {approx_equal} 3.7 may have a higher covering fraction of absorbing gas, and may be older (or have had more prolonged star formation histories) than their lower-redshift and lower-luminosity counterparts. In

  14. The Diversity of Diffuse Lyα Nebulae around Star-forming Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Xue, Rui; Lee, Kyoung-Soo; Dey, Arjun; Reddy, Naveen; Hong, Sungryong; Prescott, Moire K. M.; Inami, Hanae; Jannuzi, Buell T.; Gonzalez, Anthony H.

    2017-03-01

    We report the detection of diffuse Lyα emission, or Lyα halos (LAHs), around star-forming galaxies at z ≈ 3.78 and 2.66 in the NOAO Deep Wide-Field Survey Boötes field. Our samples consist of a total of ∼1400 galaxies, within two separate regions containing spectroscopically confirmed galaxy overdensities. They provide a unique opportunity to investigate how the LAH characteristics vary with host galaxy large-scale environment and physical properties. We stack Lyα images of different samples defined by these properties and measure their median LAH sizes by decomposing the stacked Lyα radial profile into a compact galaxy-like and an extended halo-like component. We find that the exponential scale-length of LAHs depends on UV continuum and Lyα luminosities, but not on Lyα equivalent widths or galaxy overdensity parameters. The full samples, which are dominated by low UV-continuum luminosity Lyα emitters (M UV ≳ ‑21), exhibit LAH sizes of 5–6 kpc. However, the most UV- or Lyα-luminous galaxies have more extended halos with scale-lengths of 7–9 kpc. The stacked Lyα radial profiles decline more steeply than recent theoretical predictions that include the contributions from gravitational cooling of infalling gas and from low-level star formation in satellites. However, the LAH extent matches what one would expect for photons produced in the galaxy and then resonantly scattered by gas in an outflowing envelope. The observed trends of LAH sizes with host galaxy properties suggest that the physical conditions of the circumgalactic medium (covering fraction, H i column density, and outflow velocity) change with halo mass and/or star formation rates.

  15. Local Turbulent Disks: analogs of high-redshift vigorously star-forming disks and laboratories for galaxy assembly?

    NASA Astrophysics Data System (ADS)

    Damjanov, Ivana

    2012-10-01

    Kinematical investigations at redshifts 1high-redshift galaxies exhibit very high internal velocity dispersions. Dynamical data collected with integral field spectrographs {IFS} suggest that the level of rotational support in these systems follows a trend in mass, with compact dispersion-dominated Lyman Break Galaxies at lower stelar masses and large dynamically unstable turbulent disks at stellar masses larger than 10^10 solar masses. The high velocity dispersion of these young disks results in a large characteristic scale for star-forming clusters thereby also explaining their 'clump cluster' morphology. Galaxies like these were thought to be absent from the local Universe. As part of a IFS campaign to observe the most H-alpha luminous galaxies in SDSS, we have discovered a sample of very rare objects seemingly identical to these high-z turbulent disks. In this proposal we seek imaging in H-alpha of thirteen local disk galaxies in our sample, using the ACS tunable-wavelength ramp filters. Our goal is to measure the size distribution of the star-forming complexes in these objects, with ten times the typical physical resolution of HST observations of high-z galaxies, in order to test the idea that they are indeed dynamically unstable turbulent disks caught in the process of formation. In synergy with existing high resolution HST imaging of the local analogs of low-mass dispersion-dominated galaxies at high redshift {Lyman Break Analogs}, our proposed observations of the local counterparts to large turbulent disks at high redshift will help to paint a complete picture of local analogs of high-z star-forming galaxies.

  16. 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

  17. Narrowband selected high-redshift galaxy candidates contaminated by lower redshift [OIII] ultra-strong emitter line galaxies

    NASA Astrophysics Data System (ADS)

    Pénin, Aurélie; Cuby, Jean-Gabriel; Clément, Benjamin; Hibon, Pascale; Kneib, Jean-Paul; Cassata, Paolo; Ilbert, Olivier

    2015-05-01

    Context. Lyman-break galaxies (LBG) and narrowband (NB) surveys have been successful at detecting large samples of high-redshift galaxies. Both methods are subject to contamination from low-redshift interlopers. Aims: Our aim is to investigate the nature of low-redshift interlopers in NB Lyman-α emitters (LAE) searches. Methods: From previous HAWK-I NB imaging at z ~ 7.7, we identify three objects that would have been selected as high-redshift LAEs had our optical data been one magnitude shallower (but still one to two magnitudes fainter than the near infrared data). We follow up these objects in spectroscopy with X-Shooter at the VLT. Results: Despite low quality data due to bad weather conditions, for each of the three objects we identify one, and only one emission line, in the spectra of the objects that we identify as the [OIII]5007 Å line. From this result, combined with spectral energy density fitting and tests based on line ratios of several populations of galaxies, we infer that the three objects are ultra-strong line emitters at redshifts ~1.1. Conclusions: From this work and the literature we remark that the [OIII] line appears to be a common source of contamination in high-redshift LBG and LAE samples and we suggest that efforts be made to characterize with high accuracy the [OIII] luminosity function out to redshift ~3 or higher. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programmes ID 385.A-1025(A) and 181.A-0485.

  18. Deep imaging of high redshift QSO fields below the Lyman limit. II - Number counts and colors of field galaxies

    NASA Technical Reports Server (NTRS)

    Steidel, Charles C.; Hamilton, Donald

    1993-01-01

    We present an analysis of the number counts and colors of faint galaxies to about 26.5 mag in the fields of two high Galactic latitude, very-high-redshift QSOs. We concentrate on the general properties of the field galaxies at faint magnitudes. In particular, we readdress the faint galaxy number counts and colors as a function of apparent magnitude and we reexamine the possible contribution of very-high-redshift galaxies to the faint samples. We find that the number counts to R = 26 are well fitted by the relation log N(m) = 0.31R + C. The G-band counts for the same galaxies are consistent with the same slope fainter than G about 23.5, but exhibit a much steeper slope at brighter magnitudes. At R = 25.5, the differential number counts have reached about 1.2 x 10 exp 5/sq deg; the same surface density of galaxies is reached at G = 26.5. We confirm the existence of a gradual 'blueing' trend of the field galaxies toward fainter apparent magnitude; however, the blueing trend appears to extend only as faint as G about 24, fainter than which both the (G-R) and (U sub n-G) colors appear to level off. The mean colors of faint galaxies are considerably redder than flat spectrum. There are essentially no objects to R = 26 which have spectral energy distributions which are bluer than flat spectrum. The potential contribution of very-high-redshift galaxies may have been underestimated in previous analyses; the current data are consistent with the same population of relatively luminous galaxies at z about 3 as exist at z about 0.7.

  19. PKS 2123-463: A Confirmed Gamma-ray Blazar at High Redshift

    NASA Technical Reports Server (NTRS)

    DAmmando, F.; Rau, A.; Schady, P.; Finke, J.; Orienti, M.; Greiner, J.; Kann, D. A.; Ojha, R.; Foley, A. R.; Stevens, J.; Blanchard, J. M.; Edwards, P. G.; Kadler, M.; Lovell, J. E. J.

    2012-01-01

    The flat spectrum radio quasar (FSRQ) PKS 2123-463 was associated in the First Fermi-LAT source catalog with the gamma-ray source 1FGL J2126.1-4603, but when considering the full first two years of Fermi observations, no gamma-ray source at a position consistent with this FSRQ was detected, and thus PKS 2123-463 was not reported in the Second Fermi-LAT source catalog. On 2011 December 14 a gamma-ray source positionally consistent with PKS 2123-463 was detected in flaring activity by Fermi-LAT. This activity triggered radio-to-X-ray observations by the Swift, GROND, ATCA, Ceduna, and KAT-7 observatories. Results of the localization of the gamma-ray source over 41 months of Fermi-LAT operation are reported here in conjunction with the results of the analysis of radio, optical, UV and X-ray data collected soon after the gamma-ray flare. The strict spatial association with the lower energy counterpart together with a simultaneous increase of the activity in optical, UV, X-ray and gamma-ray bands led to a firm identification of the gamma-ray source with PKS 2123-463. A new photometric redshift has been estimated as z = 1.46 +/- 0.05 using GROND and Swift/UVOT observations, in rough agreement with the disputed spectroscopic redshift of z = 1.67. We fit the broadband spectral energy distribution with a synchrotron/external Compton model. We find that a thermal disk component is necessary to explain the optical/UV emis- sion detected by Swift/UVOT. This disk has a luminosity of 1.8x1046 erg s-1, and a fit to the disk emission assuming a Schwarzschild (i.e., nonrotating) black hole gives a mass of 2 x 109 M(solar mass). This is the first black hole mass estimate for this source.

  20. MILLIMETER OBSERVATIONS OF A SAMPLE OF HIGH-REDSHIFT OBSCURED QUASARS

    SciTech Connect

    Martinez-Sansigre, Alejo; Karim, Alexander; Schinnerer, Eva E-mail: karim@mpia.d

    2009-11-20

    quasars must have higher cool-dust masses and are therefore often found at an earlier evolutionary phase than those of unobscured quasars. For one source at z = 2.767, we detect the CO(3-2) transition, with S{sub CO}DELTAnu = 630 +- 50 mJy km s{sup -1}, corresponding to L{sub CO(3-2)} = 3.2 x10{sup 7} L{sub sun}, or a brightness-temperature luminosity of L'{sub CO(3-2)} = 2.4 x 10{sup 10} K km s{sup -1} pc{sup 2}. For another source at z = 4.17, the lack of detection of the CO(4-3) line suggests the line to have a brightness-temperature luminosity L'{sub CO(4-3)} < 1 x 10{sup 10} K km s{sup -1} pc{sup 2}. Under the assumption that in these objects the high-J transitions are thermalized, we can estimate the molecular gas contents to be M{sub H{sub 2}}=1.9x10{sup 10} M {sub sun} and <8 x 10{sup 9} M{sub sun}, respectively. The estimated gas depletion timescales are tau{sub g} = 4 Myr and <16 Myr, and low gas-to-dust mass ratios of M{sub g}/M {sub d} = 19 and <20 are inferred. These values are at the low end but consistent with those of other high-redshift galaxies.

  1. Cosmic reionization on computers. Ultraviolet continuum slopes and dust opacities in high redshift galaxies

    SciTech Connect

    Khakhaleva-Li, Zimu; Gnedin, Nickolay Y.

    2016-03-30

    In this study, we compare the properties of stellar populations of model galaxies from the Cosmic Reionization On Computers (CROC) project with the exiting UV and IR data. Since CROC simulations do not follow cosmic dust directly, we adopt two variants of the dust-follows-metals ansatz to populate model galaxies with dust. Using the dust radiative transfer code Hyperion, we compute synthetic stellar spectra, UV continuum slopes, and IR fluxes for simulated galaxies. We find that the simulation results generally match observational measurements, but, perhaps, not in full detail. The differences seem to indicate that our adopted dust-follows-metals ansatzes are not fully sufficient. While the discrepancies with the exiting data are marginal, the future JWST data will be of much higher precision, rendering highly significant any tentative difference between theory and observations. It is, therefore, likely, that in order to fully utilize the precision of JWST observations, fully dynamical modeling of dust formation, evolution, and destruction may be required.

  2. Cosmic reionization on computers. Ultraviolet continuum slopes and dust opacities in high redshift galaxies

    DOE PAGES

    Khakhaleva-Li, Zimu; Gnedin, Nickolay Y.

    2016-03-30

    In this study, we compare the properties of stellar populations of model galaxies from the Cosmic Reionization On Computers (CROC) project with the exiting UV and IR data. Since CROC simulations do not follow cosmic dust directly, we adopt two variants of the dust-follows-metals ansatz to populate model galaxies with dust. Using the dust radiative transfer code Hyperion, we compute synthetic stellar spectra, UV continuum slopes, and IR fluxes for simulated galaxies. We find that the simulation results generally match observational measurements, but, perhaps, not in full detail. The differences seem to indicate that our adopted dust-follows-metals ansatzes are notmore » fully sufficient. While the discrepancies with the exiting data are marginal, the future JWST data will be of much higher precision, rendering highly significant any tentative difference between theory and observations. It is, therefore, likely, that in order to fully utilize the precision of JWST observations, fully dynamical modeling of dust formation, evolution, and destruction may be required.« less

  3. The Star Formation History of Local Starbursts as Benchmark for High Redshifts

    NASA Astrophysics Data System (ADS)

    Schmitt, Henrique R.; Calzetti, Daniela; Armus, Lee

    2001-08-01

    We propose to use the WIYN telescope and MIMO to obtain broad band B and R, and narrow band H(alpha) and H(beta) images for a sample of 13 local starburst galaxies detected by ISO at 170-200(micron) and for which we are obtaining ultraviolet (1600Å) images with an approved HST/STIS program. With these observations we will complete the ground based portion of this project. This sample spans a wide range in the luminosity, star formation rate, metallicity and morphology parameters, and will be used as a low-redshift benchmark to explore the relationship between the Lyman-break and the SCUBA galaxies at z~3. The broad- band ground-based and HST images will be used to characterize the stellar populations and determine the ages of the star forming regions of these galaxies, while the H(alpha)/H(beta) ratio will be used to determine the reddening and gas morphology of these regions. We will study the conditions for the escape of UV light from a dusty galaxy, as a function of the sample parameters. The H(alpha) and UV HST images will be combined to derive a relative empirical calibration between these two star formation indicators. We will measure the fraction of nuclear and disk emission, the fraction of star formation in massive clusters and the properties of those star clusters, the structural properties of star forming bars, rings, and tidally-driven star formation in IR-bright galaxies.

  4. The Star Formation History of Local Starbursts as Benchmark for High Redshifts

    NASA Astrophysics Data System (ADS)

    Schmitt, Henrique R.; Calzetti, Daniela; Armus, Lee

    2001-02-01

    We propose to use the WIYN telescope and MIMO to obtain broad band B and R, and narrow band H(alpha) and H(beta) images for a sample of 22 local starburst galaxies detected by ISO at 170-200(micron) and for which we are obtaining ultraviolet (1600Å) images with an approved HST/STIS program. This sample spans a wide range in the luminosity, star formation rate, metallicity and morphology parameters, and will be used as a low-redshift benchmark to explore the relationship between the Lyman-break and the SCUBA galaxies at z~3. The broad-band ground- based and HST images will be used to characterize the stellar populations and determine the ages of the star forming regions of these galaxies, while the H(alpha)/H(beta) ratio will be used to determine the reddening and gas morphology of these regions. We will study the conditions for the escape of UV light from a dusty galaxy, as a function of the sample parameters. The H(alpha) and UV HST images will be combined to derive a relative empirical calibration between these two star formation indicators. We will measure the fraction of nuclear and disk emission, the fraction of star formation in massive clusters and the properties of those star clusters, the structural properties of star forming bars, rings, and tidally-driven star formation in IR-bright galaxies.

  5. COSMIC REIONIZATION ON COMPUTERS. ULTRAVIOLET CONTINUUM SLOPES AND DUST OPACITIES IN HIGH REDSHIFT GALAXIES

    SciTech Connect

    Khakhaleva-Li, Zimu; Gnedin, Nickolay Y. E-mail: gnedin@fnal.gov

    2016-04-01

    We compare the properties of stellar populations of model galaxies from the Cosmic Reionization On Computers (CROC) project with the exiting ultraviolet (UV) and IR data. Since CROC simulations do not follow cosmic dust directly, we adopt two variants of the dust-follows-metals ansatz to populate model galaxies with dust. Using the dust radiative transfer code Hyperion, we compute synthetic stellar spectra, UV continuum slopes, and IR fluxes for simulated galaxies. We find that the simulation results generally match observational measurements, but, perhaps, not in full detail. The differences seem to indicate that our adopted dust-follows-metals ansatzes are not fully sufficient. While the discrepancies with the exiting data are marginal, the future James Webb Space Telescope (JWST) data will be of much higher precision, rendering highly significant any tentative difference between theory and observations. It is, therefore, likely, that in order to fully utilize the precision of JWST observations, fully dynamical modeling of dust formation, evolution, and destruction may be required.

  6. New Constraints on ΩM, ΩΛ, and w from an Independent Set of 11 High-Redshift Supernovae Observed with the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Knop, R. A.; Aldering, G.; Amanullah, R.; Astier, P.; Blanc, G.; Burns, M. S.; Conley, A.; Deustua, S. E.; Doi, M.; Ellis, R.; Fabbro, S.; Folatelli, G.; Fruchter, A. S.; Garavini, G.; Garmond, S.; Garton, K.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D. E.; Hardin, D.; Hook, I.; Howell, D. A.; Kim, A. G.; Lee, B. C.; Lidman, C.; Mendez, J.; Nobili, S.; Nugent, P. E.; Pain, R.; Panagia, N.; Pennypacker, C. R.; Perlmutter, S.; Quimby, R.; Raux, J.; Regnault, N.; Ruiz-Lapuente, P.; Sainton, G.; Schaefer, B.; Schahmaneche, K.; Smith, E.; Spadafora, A. L.; Stanishev, V.; Sullivan, M.; Walton, N. A.; Wang, L.; Wood-Vasey, W. M.; Yasuda, N.

    2003-11-01

    We report measurements of ΩM, ΩΛ, and w from 11 supernovae (SNe) at z=0.36-0.86 with high-quality light curves measured using WFPC2 on the Hubble Space Telescope (HST). This is an independent set of high-redshift SNe that confirms previous SN evidence for an accelerating universe. The high-quality light curves available from photometry on WFPC2 make it possible for these 11 SNe alone to provide measurements of the cosmological parameters comparable in statistical weight to the previous results. Combined with earlier Supernova Cosmology Project data, the new SNe yield a measurement of the mass density ΩM=0.25+0.07-0.06(statistical)+/-0.04 (identified systematics), or equivalently, a cosmological constant of ΩΛ=0.75+0.06-0.07(statistical)+/-0.04 (identified systematics), under the assumptions of a flat universe and that the dark energy equation-of-state parameter has a constant value w=-1. When the SN results are combined with independent flat-universe measurements of ΩM from cosmic microwave background and galaxy redshift distortion data, they provide a measurement of w=-1.05+0.15-0.20(statistical)+/-0.09 (identified systematic), if w is assumed to be constant in time. In addition to high-precision light-curve measurements, the new data offer greatly improved color measurements of the high-redshift SNe and hence improved host galaxy extinction estimates. These extinction measurements show no anomalous negative E(B-V) at high redshift. The precision of the measurements is such that it is possible to perform a host galaxy extinction correction directly for individual SNe without any assumptions or priors on the parent E(B-V) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with P(ΩΛ>0)>0.99, a result consistent with previous and current SN analyses that rely on the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution. Based in part on

  7. PKS 2123-463: A Confirmed Gamma-ray Blazar at High Redshift

    NASA Technical Reports Server (NTRS)

    D'Ammando, F.; Rau, A.; Schady, P.; Finke, J.; Orienti, M.; Greiner, J.; Kann, D. A.; Ojha, R.; Foley, A. R.; Stevens, J.; Blanchard, J. M.; Edwards, P. G.; Kadler, M.; Lovell, J. E.

    2013-01-01

    The flat spectrum radio quasar (FSRQ) PKS 2123-463 was associated in the first Fermi- Large Area Telescope (LAT) source catalogue with the gamma-ray source 1FGL J2126.1-4603, but when considering the full first two years of Fermi observations, no gamma-ray source at a position consistent with this FSRQ was detected, and thus PKS 2123-463 was not reported in the second Fermi-LAT source catalogue. On 2011 December 14 a gamma-ray source positionally consistent with PKS 2123-463 was detected in flaring activity by Fermi-LAT. This activity triggered radio-to-X-ray observations by the Swift,Gamma-ray Optical/Near-Infrared Detector (GROND), Australia Telescope Compact Array (ATCA), Ceduna and Seven Dishes Karoo Array Telescope (KAT-7) observatories. Results of the localization of the gamma-ray source over 41 months of Fermi-LAT operation are reported here in conjunction with the results of the analysis of radio, optical, ultraviolet (UV) and X-ray data collected soon after the gamma-ray flare. The strict spatial association with the lower energy counterpart together with a simultaneous increase of the activity in optical, UV, X-ray and gamma-ray bands led to a firm identification of the gamma-ray source with PKS 2123-463. A new photometric redshift has been estimated as z = 1.46 plus or minus 0.05 using GROND and Swift Ultraviolet/Optical Telescope (UVOT) observations, in rough agreement with the disputed spectroscopic redshift of z = 1.67.We fit the broad-band spectral energy distribution with a synchrotron/external Compton model. We find that a thermal disc component is necessary to explain the optical/UV emission detected by Swift/UVOT. This disc has a luminosity of approximately 1.8 x 10(exp 46) erg s(exp -1), and a fit to the disc emission assuming a Schwarzschild (i.e. non-rotating) black hole gives a mass of approximately 2 x 10(exp 9) solar mass. This is the first black hole mass estimate for this source.

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

    SciTech Connect

    Hezaveh, Yashar D.

    2014-08-20

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

  9. The hard X-ray luminosity function of high-redshift (3 < z ≲ 5) active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Vito, F.; Gilli, R.; Vignali, C.; Comastri, A.; Brusa, M.; Cappelluti, N.; Iwasawa, K.

    2014-12-01

    We present the hard-band (2-10 keV) X-ray luminosity function (HXLF) of 0.5-2 keV band selected active galactic nuclei (AGN) at high redshift. We have assembled a sample of 141 AGN at 3 < z ≲ 5 from X-ray surveys of different size and depth, in order to sample different regions in the LX - z plane. The HXLF is fitted in the range log LX ˜ 43-45 with standard analytical evolutionary models through a maximum likelihood procedure. The evolution of the HXLF is well described by a pure density evolution, with the AGN space density declining by a factor of ˜10 from z = 3 to 5. A luminosity-dependent density evolution model, which, normally, best represents the HXLF evolution at lower redshift, is also consistent with the data, but a larger sample of low-luminosity (log LX < 44), high-redshift AGN is necessary to constrain this model. We also estimated the intrinsic fraction of AGN obscured by a column density log NH ≥ 23 to be 0.54 ± 0.05, with no strong dependence on luminosity. This fraction is higher than the value in the Local Universe, suggesting an evolution of the luminous (LX > 1044 erg s-1) obscured AGN fraction from z = 0 to z > 3.

  10. 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.

  11. 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.

  12. Imaging Cold Gas to 1 kpc scales in high-redshift galaxies with the ngVLA

    NASA Astrophysics Data System (ADS)

    Casey, Caitlin; Narayanan, Desika; Dave, Romeel; Hung, Chao-Ling; Champagne, Jaclyn; Carilli, Chris Luke; Decarli, Roberto; Murphy, Eric J.; Popping, Gergo; Riechers, Dominik; Somerville, Rachel S.; Walter, Fabian

    2017-01-01

    The next generation Very Large Array (ngVLA) will revolutionize our understanding of the distant Universe via the detection of cold molecular gas in the first galaxies. Its impact on studies of galaxy characterization via detailed gas dynamics will provide crucial insight on dominant physical drivers for star-formation in high redshift galaxies, including the exchange of gas from scales of the circumgalactic medium down to resolved clouds on mass scales of ~10^5 M_sun. In this study, we employ a series of high-resolution, cosmological, hydrodynamic zoom simulations from the MUFASA simulation suite and a CASA simulator to generate mock ngVLA observations. Based on a direct comparison between the inferred results from our mock observations and the cosmological simulations, we investigate the capabilities of ngVLA to constrain the mode of star formation, dynamical mass, and molecular gas kinematics in individual high-redshift galaxies using cold gas tracers like CO(1-0) and CO(2-1). Using the Despotic radiative transfer code that encompasses simultaneous thermal and statistical equilibrium in calculating the molecular and atomic level populations, we generate parallel mock observations of high-J transitions of CO and C+ from ALMA for comparison. The factor of 100 times improvement in mapping speed for the ngVLA beyond the Jansky VLA and the proposed ALMA Band 1 will make these detailed, high-resolution imaging and kinematic studies routine at z=2 and beyond.

  13. A LINK TO THE PAST: USING MARKOV CHAIN MONTE CARLO FITTING TO CONSTRAIN FUNDAMENTAL PARAMETERS OF HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Pirzkal, N.; Rothberg, B.; Koekemoer, Anton; Nilsson, Kim K.; Finkelstein, S.; Malhotra, Sangeeta; Rhoads, James

    2012-04-01

    We have developed a new method for fitting spectral energy distributions (SEDs) to identify and constrain the physical properties of high-redshift (4 < z < 8) galaxies. Our approach uses an implementation of Bayesian based Markov Chain Monte Carlo that we have dubbed '{pi}MC{sup 2}'. It allows us to compare observations to arbitrarily complex models and to compute 95% credible intervals that provide robust constraints for the model parameters. The work is presented in two sections. In the first, we test {pi}MC{sup 2} using simulated SEDs to not only confirm the recovery of the known inputs but to assess the limitations of the method and identify potential hazards of SED fitting when applied specifically to high-redshift (z > 4) galaxies. In the second part of the paper we apply {pi}MC{sup 2} to thirty-three 4 < z < 8 objects, including the spectroscopically confirmed Grism ACS Program for Extragalactic Science Ly{alpha} sample (4 < z < 6), supplemented by newly obtained Hubble Space Telescope/WFC3 near-IR observations, and several recently reported broadband selected z > 6 galaxies. Using {pi}MC{sup 2}, we are able to constrain the stellar mass of these objects and in some cases their stellar age and find no evidence that any of these sources formed at a redshift larger than z = 8, a time when the universe was Almost-Equal-To 0.6 Gyr old.

  14. SMA observations on faint submillimeter galaxies with S {sub 850} < 2 mJy: Ultra dusty low-luminosity galaxies at high redshift

    SciTech Connect

    Chen, Chian-Chou; Cowie, Lennox L.; Barger, Amy J.; Williams, Jonathan P.; Wang, Wei-Hao

    2014-07-01

    We obtained Submillimeter Array (SMA) observations of eight faint (intrinsic 850 μm fluxes < 2 mJy) submillimeter galaxies (SMGs) discovered in SCUBA images of the massive lensing cluster fields A370, A2390, and A1689 and detected five. In total, we obtain five SMA detections, all of which have de-lensed fluxes <1 mJy with estimated total infrared luminosities 10{sup 10}-10{sup 12} L {sub ☉}, comparable to luminous infrared galaxies and normal star-forming galaxies. Based on the latest number counts, these galaxies contribute ∼70% of the 850 μm extragalactic background light and represent the dominant star-forming galaxy population in the dusty universe. However, only 40{sub −16}{sup +30}% of our faint SMGs would be detected in deep optical or near-infrared surveys, which suggests many of these sources are at high redshifts (z ≳ 3) or extremely dusty, and they are not included in current star formation history estimates.

  15. LOW-METALLICITY STAR FORMATION IN HIGH-REDSHIFT GALAXIES AT z {approx} 8

    SciTech Connect

    Taniguchi, Y.; Shioya, Y.; Trump, J. R.

    2010-12-01

    Based on the recent very deep near-infrared imaging of the Hubble Ultra Deep Field with WFC3 on the Hubble Space Telescope, five groups published the most probable samples of galaxies at z {approx} 8, selected by the so-called dropout method or photometric redshift; e.g., Y{sub 105}-dropouts (Y{sub 105} - J{sub 125} > 0.8). These studies are highly useful for investigating both the early star formation history of galaxies and the sources of cosmic re-ionization. In order to better understand these issues, we carefully examine whether there are low-z interlopers in the samples of z {approx} 8 galaxy candidates. We focus on the strong emission-line galaxies at z {approx} 2 in this paper. Such galaxies may be selected as Y{sub 105}-dropouts since the [O III] {lambda}5007 emission line is redshifted into the J{sub 125} band. We have found that the contamination from such low-z interlopers is negligibly small. Therefore, all objects found by the five groups are free from this type of contamination. However, it remains difficult to extract real z {approx} 8 galaxies because all the sources are very faint and the different groups have found different candidates. With this in mind, we construct a robust sample of eight galaxies at z {approx} 8 from the objects found by the five groups: each of these eight objects has been selected by at least two groups. Using this sample, we discuss their UV continuum slope. We also discuss the escape fraction of ionizing photons adopting various metallicities. Our analysis suggests that massive stars forming in low-metallicity gas (Z {approx} 5 x 10{sup -4} Z{sub sun}) can be responsible for the completion of cosmic re-ionization if the escape fraction of the ionizing continuum from galaxies is as large as 0.5, and this is consistent with the observed blue UV continua.

  16. Cosmic Metal Production and the Contribution of QSO Absorption Systems to the Ionizing Background

    NASA Technical Reports Server (NTRS)

    Madau, Piero; Shull, J. Michael

    1996-01-01

    The recent discovery by Cowie et al. (1995) and Tytler et al. (1995) of metals in the Ly alpha clouds shows that the intergalactic medium (IGM) at high redshift is contaminated by the products of stars and suggests that ionizing photons from massive star formation may be a significant contributor to the UV background radiation at early epochs. We assess the validity of the stellar photoionization hypothesis. Based on recent computations of metal yields and 0-star Lyman continuum (Lyc) fluxes, we find that 0.2 percent of the rest-mass energy of the metals produced is radiated as Lyc. By modeling the transfer of ionizing radiation through the IGM and the rate of chemical enrichment, we demonstrate that the background intensity of photons at 1 ryd that accompanies the production of metals in the Ly alpha forest clouds may be significant, approaching 0.5 x 10(exp -21) ergs cm squared s(-1) Hz(-1) sr(-1) at z approximately equals 3 if the Lyc escape fraction is greater than of equal to 0.25. Together with quasars, massive stars could then, in principle, provide the hydrogen and helium Lyc photons required to ionize the universe at high redshifts. We propose that observations of the He2 Gunn-Peterson effect and of the metal ionization states of the Ly alpha forest and Lyman-limit absorbers should show the signature of a stellar spectrum. We also note that the stellar photoionization model fails if a large fraction of the UV radiation emitted from stars cannot escape into the IGM, as suggested by the recent Hopkins Ultraviolet Telescope observations by Leitherer et al. (1995) of low-redshift starburst galaxies, or if most of the metals observed at z is approximately 3 were produced at much earlier epochs.

  17. Scintillation noise power spectrum and its impact on high-redshift 21-cm observations

    NASA Astrophysics Data System (ADS)

    Vedantham, H. K.; Koopmans, L. V. E.

    2016-05-01

    Visibility scintillation resulting from wave propagation through the turbulent ionosphere can be an important source of noise at low radio frequencies (ν ≲ 200 MHz). Many low-frequency experiments are underway to detect the power spectrum of brightness temperature fluctuations of the neutral-hydrogen 21-cm signal from the Epoch of Reionization (EoR: 12 ≳ z ≳ 7, 100 ≲ ν ≲ 175 MHz). In this paper, we derive scintillation noise power spectra in such experiments while taking into account the effects of typical data processing operations such as self-calibration and Fourier synthesis. We find that for minimally redundant arrays such as LOFAR and MWA, scintillation noise is of the same order of magnitude as thermal noise, has a spectral coherence dictated by stretching of the snapshot uv-coverage with frequency, and thus is confined to the well-known wedge-like structure in the cylindrical (two-dimensional) power spectrum space. Compact, fully redundant (dcore ≲ rF ≈ 300 m at 150 MHz) arrays such as HERA and SKA-LOW (core) will be scintillation noise dominated at all baselines, but the spatial and frequency coherence of this noise will allow it to be removed along with spectrally smooth foregrounds.

  18. Limits to Seeing High-Redshift Galaxies Due to Planck-Scale-Induced Blurring

    NASA Astrophysics Data System (ADS)

    Steinbring, Eric

    2015-08-01

    Carefully accounting for cosmological surface-brightness dimming and K-corrections are two important steps in teasing out the underlying properties of evolving high-z galaxy populations. Another potential effect is worthy of scrutiny simply because of its profound physical implications, if seen. In the last decade or so there has been debate over the possibility that the fuzzy quantum nature of spacetime might decohere wavefronts emanating from very distant sources. Consequences of that could be "blurred" or "faded" images of compact structures in galaxies, primarily at z>1 for their emitted X-rays and gamma-rays, but perhaps even in UV through optical light at higher redshift. So far there are only inconclusive hints of this from z~4 active-galactic nucleii and gamma-ray bursts viewed with Fermi and Hubble Space Telescope. If correct though, that would impose a significant, fundamental resolution limit for galaxies out to z~8 in the era of the James Webb Space Telescope and the next generation of ground-based telescopes using adaptive optics. I consider what to look for (and maybe not see).

  19. UNDERSTANDING PHYSICAL CONDITIONS IN HIGH-REDSHIFT GALAXIES THROUGH C I FINE STRUCTURE LINES: DATA AND METHODOLOGY

    SciTech Connect

    Jorgenson, Regina A.; Wolfe, Arthur M.; Prochaska, J. Xavier

    2010-10-10

    We probe the physical conditions in high-redshift galaxies, specifically, the damped Ly{alpha} systems (DLAs) using neutral carbon (C I) fine structure lines and molecular hydrogen (H{sub 2}). We report five new detections of C I and analyze the C I in an additional two DLAs with previously published data. We also present one new detection of H{sub 2} in a DLA. We present a new method of analysis that simultaneously constrains both the volume density and the temperature of the gas, as opposed to previous studies that a priori assumed a gas temperature. We use only the column density of C I measured in the fine structure states and the assumption of ionization equilibrium in order to constrain the physical conditions in the gas. We present a sample of 11 C I velocity components in six DLAs and compare their properties to those derived by the global C II* technique. The resulting median values for this sample are (n(H I)) = 69 cm{sup -3}, (T) = 50 K, and (log(P/k)) = 3.86 cm{sup -3} K, with standard deviations, {sigma}{sub n(H{sub i})} = 134 cm{sup -3}, {sigma}{sub T} = 52 K, and {sigma}{sub log(P/k)} = 3.68 cm{sup -3} K. This can be compared with the integrated median values for the same DLAs: (n(H I)) = 2.8 cm{sup -3}, (T) = 139 K, and (log(P/k)) = 2.57 cm{sup -3} K, with standard deviations {sigma}{sub n(H{sub i})} = 3.0 cm{sup -3}, {sigma}{sub T} = 43 K, and {sigma}{sub log(P/k)} = 0.22 cm{sup -3} K. Interestingly, the pressures measured in these high-redshift C I clouds are similar to those found in the Milky Way. We conclude that the C I gas is tracing a higher-density, higher-pressure region, possibly indicative of post-shock gas or a photodissociation region on the edge of a molecular cloud. We speculate that these clouds may be direct probes of the precursor sites of star formation in normal galaxies at high redshift.

  20. Gemini Spectroscopy of Supernovae from the Supernova Legacy Survey: Improving High-Redshift Supernova Selection and Classification

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

    We present new techniques for improving the efficiency of supernova (SN) classification at high redshift using 64 candidates observed at Gemini North and South during the first year of the Supernova Legacy Survey (SNLS). The SNLS is an ongoing 5 year project with the goal of measuring the equation of state of dark energy by discovering and following over 700 high-redshift SNe Ia using data from the Canada-France-Hawaii Telescope Legacy Survey. We achieve an improvement in the SN Ia spectroscopic confirmation rate: at Gemini 71% of candidates are now confirmed as SNe Ia, compared to 54% using the methods of previous surveys. This is despite the comparatively high redshift of this sample, in which the median SN Ia redshift is z=0.81 (0.155<=z<=1.01). These improvements were realized because we use the unprecedented color coverage and light curve sampling of the SNLS to predict whether a candidate is a SN Ia and to estimate its redshift, before obtaining a spectrum, using a new technique called the ``SN photo-z.'' In addition, we have improved techniques for galaxy subtraction and SN template χ2 fitting, allowing us to identify candidates even when they are only 15% as bright as the host galaxy. The largest impediment to SN identification is found to be host galaxy contamination of the spectrum-when the SN was at least as bright as the underlying host galaxy the target was identified more than 90% of the time. However, even SNe in bright host galaxies can be easily identified in good seeing conditions. When the image quality was better than 0.55", the candidate was identified 88% of the time. Over the 5 year course of the survey, using the selection techniques presented here, we will be able to add ~170 more confirmed SNe Ia than would be possible using previous methods. APC, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France. DSM/DAPNIA, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France.

  1. The Red Sequence of High-Redshift Clusters: A Comparison with Cosmological Galaxy Formation Models

    NASA Astrophysics Data System (ADS)

    Menci, N.; Rosati, P.; Gobat, R.; Strazzullo, V.; Rettura, A.; Mei, S.; Demarco, R.

    2008-10-01

    We compare the results from a state-of-the-art semianalytic model of galaxy formation with spectrophotometric observations of distant galaxy clusters observed in the range 0.8 <= z<= 1.3. We investigate the properties of their red sequence (RS) galaxies and compare them with those of the field at the same redshift. In our model we find that (1) a well-defined, narrow RS is obtained already by z ≈ 1.2; this is found to be more populated than the field RS, analogously to what is observed and predicted at z = 0; (2) the predicted U-V rest-frame colors and scatter of the cluster RS at z = 1.2 have average values of 1 and 0.15, respectively, with a cluster-to-cluster variance of ≈0.2 and ≈0.06, respectively. The scatter of the RS of cluster galaxies is ≈5 times smaller than the corresponding field value; (3) when the RS galaxies are considered, the mass growth histories of field and cluster galaxies at z ≈ 1.2 are similar, with 90% of the stellar mass of RS galaxies at z = 1.2 already formed at cosmic times t = 2.5 Gyr, and 50% at t = 1 Gyr; and (4) the predicted distribution of stellar ages of RS galaxies at z = 1.2 peaks at 3.7 Gyr for both cluster and field populations; however, for the latter the distribution is significantly skewed toward lower ages. When compared with observations, the above findings show an overall consistency, although the average value ΔU - V ≈ 0.07 of the observed cluster RS scatter at z ≈ 1.2 is smaller than the corresponding model central value. We discuss the physical origin and the significance of the above results in the framework of cosmological galaxy formation.

  2. Atomic Data for Zn II: Improving Spectral Diagnostics of Chemical Evolution in High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Kisielius, Romas; Kulkarni, Varsha P.; Ferland, Gary J.; Bogdanovich, Pavel; Som, Debopam; Lykins, Matt L.

    2015-05-01

    Damped Lyα (DLA) and sub-DLA absorbers in quasar spectra provide the most sensitive tools for measuring the element abundances of distant galaxies. The estimation of abundances from absorption lines depends sensitively on the accuracy of the atomic data used. We have started a project to produce new atomic spectroscopic parameters for optical and UV spectral lines using state-of-the-art computer codes employing a very broad configuration interaction (CI) basis. Here we report our results for Zn ii, an ion used widely in studies of the interstellar medium (ISM) as well as DLAs and sub-DLAs. We report new calculations of many energy levels of Zn ii and the line strengths of the resulting radiative transitions. Our calculations use the CI approach within a numerical Hartree-Fock framework. We use both nonrelativistic and quasi-relativistic one-electron radial orbitals. We have incorporated the results of these atomic calculations into the plasma simulation code Cloudy and applied them to a lab plasma and examples of a DLA and a sub-DLA. Our values of the Zn ii λ λ 2026, 2062 oscillator strengths are higher than previous values by 0.10 dex. The Cloudy calculations for representative absorbers with the revised Zn atomic data imply ionization corrections lower than calculated earlier by 0.05 dex. The new results imply that Zn metallicities should be lower by 0.1 dex for DLAs and by 0.13-0.15 dex for sub-DLAs than in past studies. Our results can be applied to other studies of Zn ii in the Galactic and extragalactic ISM.

  3. Errata: A Wide-Field Multicolor Survey for High-Redshift Quasars, Z >= 2.2. III. The Luminosity Function

    NASA Astrophysics Data System (ADS)

    Warren, Stephen J.; Hewett, Paul C.; Osmer, Patrick S.

    1995-01-01

    In the paper "A Wide-Field Multicolor Survey for High-Redshift Quasars, z >= 2.2. III. The Luminosity Function" by Stephen. Warren, Paul C. Hewett and Patrick S. Osmer (ApJ, 421,412 [1994]), two equations should be corrected: On page 419, column one, line 11, the expression following the words "the error,, should have an opening parenthesis just before the integral sign, to read: [{SIGMA} 1/({integral} ρ(z)dV_a_)^2^]^1/2^. On page 421, equation (15) is missing the asterisk (*) in the M_c_^*^ term just prior to (β + 1); that is, the exponent in the second term the denominator should read: 0.4(M_c_ - M_c_^*^)(β + 1). The authors wish to draw these errors to the attention of any readers who will be using the expression and equation.

  4. Comparing High-redshift Galaxy Dropouts in GOODS-S from SelfCal and MultiDrizzle Maps

    NASA Astrophysics Data System (ADS)

    Cooper, Jennifer; Cooray, Asantha R.; Nayyeri, Hooshang

    2017-01-01

    A subset of the multi-wavelength CANDELS survey is utilized to compare results of high-redshift photometric dropout galaxies from two different image processing techniques in the GOODS-S region. The maps used are the publicly available CANDELS mosaics and SelfCal, which is a self-calibration method that removes anisotropy offsets that are introduced from combining frames taken at different times. The identified dropout sources for redshifts 4 and larger from each dataset are compared to Lyman-break galaxy catalogs. Preliminary results indicate a low match rate for sources between the SelfCal maps and published catalogs, which could be attributed to differing map depth and processing techniques.

  5. The spectral slope and escape fraction of bright quasars at z ˜ 3.8: the contribution to the cosmic UV background

    NASA Astrophysics Data System (ADS)

    Cristiani, Stefano; Serrano, Luisa Maria; Fontanot, Fabio; Vanzella, Eros; Monaco, Pierluigi

    2016-11-01

    We use a sample of 1669 quasars (r < 20.15, 3.6 < z < 4.0) from the Baryon Oscillation Spectroscopic Survey to study the intrinsic shape of their continuum and the Lyman continuum photon escape fraction (fesc,q), estimated as the ratio between the observed flux and the expected intrinsic flux (corrected for the intergalactic medium absorption) in the wavelength range 865-885 Å rest frame. Modelling the intrinsic quasar (QSO) continuum shape with a power law, Fλ ∝ λ-γ, we find a median γ = 1.30 (with a dispersion of 0.38, no dependence on the redshift and a mild intrinsic luminosity dependence) and a mean fesc,q = 0.75 (independent of the QSO luminosity and/or redshift). The fesc,q distribution shows a peak around zero and a long tail of higher values, with a resulting dispersion of 0.7. If we assume for the QSO continuum a double power-law shape (also compatible with the data) with a break located at λbr = 1000 Å and a softening Δγ = 0.72 at wavelengths shorter than λbr, the mean fesc,q rises to 0.82. Combining our γ and fesc,q estimates with the observed evolution of the active galactic nucleus (AGN) luminosity function (LF), we compute the AGN contribution to the UV ionizing background (UVB) as a function of redshift. AGN brighter than one-tenth of the characteristic luminosity of the LF are able to produce most of it up to z ˜ 3, if the present sample is representative of their properties. At higher redshifts, a contribution of the galaxy population is required. Assuming an escape fraction of Lyman continuum photons from galaxies between 5.5 and 7.6 per cent, independent of the galaxy luminosity and/or redshift, a remarkably good fit to the observational UVB data up to z ˜ 6 is obtained. At lower redshift, the extrapolation of our empirical estimate agrees well with recent UVB observations, dispelling the so-called Photon Underproduction Crisis.

  6. INTERPRETING THE GLOBAL 21 cm SIGNAL FROM HIGH REDSHIFTS. I. MODEL-INDEPENDENT CONSTRAINTS

    SciTech Connect

    Mirocha, Jordan; Harker, Geraint J. A.; Burns, Jack O.

    2013-11-10

    The sky-averaged (global) 21 cm signal is a powerful probe of the intergalactic medium (IGM) prior to the completion of reionization. However, so far it has been unclear whether it will provide more than crude estimates of when the universe's first stars and black holes formed, even in the best case scenario in which the signal is accurately extracted from the foregrounds. In contrast to previous work, which has focused on predicting the 21 cm signatures of the first luminous objects, we investigate an arbitrary realization of the signal and attempt to translate its features to the physical properties of the IGM. Within a simplified global framework, the 21 cm signal yields quantitative constraints on the Lyα background intensity, net heat deposition, ionized fraction, and their time derivatives without invoking models for the astrophysical sources themselves. The 21 cm absorption signal is most easily interpreted, setting strong limits on the heating rate density of the universe with a measurement of its redshift alone, independent of the ionization history or details of the Lyα background evolution. In a companion paper, we extend these results, focusing on the confidence with which one can infer source emissivities from IGM properties.

  7. Approximate Bayesian Computation for astronomical model analysis: a case study in galaxy demographics and morphological transformation at high redshift

    NASA Astrophysics Data System (ADS)

    Cameron, E.; Pettitt, A. N.

    2012-09-01

    'Approximate Bayesian Computation' (ABC) represents a powerful methodology for the analysis of complex stochastic systems for which the likelihood of the observed data under an arbitrary set of input parameters may be entirely intractable - the latter condition rendering useless the standard machinery of tractable likelihood-based, Bayesian statistical inference [e.g. conventional Markov chain Monte Carlo (MCMC) simulation]. In this paper, we demonstrate the potential of ABC for astronomical model analysis by application to a case study in the morphological transformation of high-redshift galaxies. To this end, we develop, first, a stochastic model for the competing processes of merging and secular evolution in the early Universe, and secondly, through an ABC-based comparison against the observed demographics of massive (Mgal > 1011 M⊙) galaxies (at 1.5 < z < 3) in the Cosmic Assembly Near-IR Deep Extragalatic Legacy Survey (CANDELS)/Extended Groth Strip (EGS) data set we derive posterior probability densities for the key parameters of this model. The 'Sequential Monte Carlo' implementation of ABC exhibited herein, featuring both a self-generating target sequence and self-refining MCMC kernel, is amongst the most efficient of contemporary approaches to this important statistical algorithm. We highlight as well through our chosen case study the value of careful summary statistic selection, and demonstrate two modern strategies for assessment and optimization in this regard. Ultimately, our ABC analysis of the high-redshift morphological mix returns tight constraints on the evolving merger rate in the early Universe and favours major merging (with disc survival or rapid reformation) over secular evolution as the mechanism most responsible for building up the first generation of bulges in early-type discs.

  8. The effects of the small-scale DM power on the cosmological neutral hydrogen (HI) distribution at high redshifts

    NASA Astrophysics Data System (ADS)

    Sarkar, Abir; Mondal, Rajesh; Das, Subinoy; Sethi, Shiv. K.; Bharadwaj, Somnath; Marsh, David J. E.

    2016-04-01

    The particle nature of dark matter remains a mystery. In this paper, we consider two dark matter models—Late Forming Dark Matter (LFDM) and Ultra-Light Axion (ULA) models—where the matter power spectra show novel effects on small scales. The high redshift universe offers a powerful probe of their parameters. In particular, we study two cosmological observables: the neutral hydrogen (HI) redshifted 21-cm signal from the epoch of reionization, and the evolution of the collapsed fraction of HI in the redshift range 2 < z < 5. We model the theoretical predictions of the models using CDM-like N-body simulations with modified initial conditions, and generate reionization fields using an excursion set model. The N-body approximation is valid on the length and halo mass scales studied. We show that LFDM and ULA models predict an increase in the HI power spectrum from the epoch of reionization by a factor between 2-10 for a range of scales 0.1 < k < 4 Mpc-1. Assuming a fiducial model where a neutral hydrogen fraction bar xHI = 0.5 must be achieved by z = 8, the reionization process allows us to put approximate bounds on the redshift of dark matter formation zf > 4 × 105 (for LFDM) and the axion mass ma > 2.6 × 10-23 eV (for ULA). The comparison of the collapsed mass fraction inferred from damped Lyman-α observations to the theoretical predictions of our models lead to the weaker bounds: zf > 2 × 105 and ma > 10-23 eV. These bounds are consistent with other constraints in the literature using different observables; we briefly discuss how these bounds compare with possible constraints from the observation of luminosity function of galaxies at high redshifts. In the case of ULAs, these constraints are also consistent with a solution to the cusp-core problem of CDM.

  9. CONTAMINATION OF BROADBAND PHOTOMETRY BY NEBULAR EMISSION IN HIGH-REDSHIFT GALAXIES: INVESTIGATIONS WITH KECK'S MOSFIRE NEAR-INFRARED SPECTROGRAPH

    SciTech Connect

    Schenker, Matthew A; Ellis, Richard S; Konidaris, Nick P; Stark, Daniel P

    2013-11-01

    Earlier work has raised the potential importance of nebular emission in the derivation of the physical characteristics of high-redshift Lyman break galaxies. Within certain redshift ranges, and especially at z ≅ 6-7, such lines may be strong enough to reduce estimates of the stellar masses and ages of galaxies compared with those derived assuming the broadband photometry represents stellar light alone. To test this hypothesis at the highest redshifts where such lines can be probed with ground-based facilities, we examine the near-infrared spectra of a representative sample of 28 3.0 < z < 3.8 Lyman break galaxies using the newly commissioned MOSFIRE near-infrared spectrograph at the Keck I telescope. We use these data to derive the rest-frame equivalent widths (EWs) of [O III] emission and show that these are comparable with estimates derived using the spectral energy distribution (SED) fitting technique introduced for sources of known redshift by Stark et al. Although our current sample is modest, its [O III] EW distribution is consistent with that inferred for Hα based on SED fitting of Stark et al.'s larger sample of 3.8 < z < 5 galaxies. For a subset of survey galaxies, we use the combination of optical and near-infrared spectroscopy to quantify kinematics of outflows in z ≅ 3.5 star-forming galaxies and discuss the implications for reionization measurements. The trends we uncover underline the dangers of relying purely on broadband photometry to estimate the physical properties of high-redshift galaxies and emphasize the important role of diagnostic spectroscopy.

  10. THERMAL AND RADIATIVE ACTIVE GALACTIC NUCLEUS FEEDBACK HAVE A LIMITED IMPACT ON STAR FORMATION IN HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Roos, Orianne; Juneau, Stéphanie; Bournaud, Frédéric; Gabor, Jared M.

    2015-02-10

    The effects of active galactic nuclei (AGNs) on their host galaxies depend on the coupling between the injected energy and the interstellar medium (ISM). Here, we model and quantify the impact of long-range AGN ionizing radiation—in addition to the often considered small-scale energy deposition—on the physical state of the multi-phase ISM of the host galaxy and on its total star formation rate (SFR). We formulate an AGN spectral energy distribution matched with observations, which we use with the radiative transfer (RT) code Cloudy to compute AGN ionization in a simulated high-redshift disk galaxy. We use a high-resolution (∼6 pc) simulation including standard thermal AGN feedback and calculate RT in post-processing. Surprisingly, while these models produce significant AGN-driven outflows, we find that AGN ionizing radiation and heating reduce the SFR by a few percent at most for a quasar luminosity (L {sub bol} = 10{sup 46.5} erg s{sup –1}). Although the circumgalactic gaseous halo can be kept almost entirely ionized by the AGN, most star-forming clouds (n ≳ 10{sup 2} {sup –} {sup 3} cm{sup –3}) and even the reservoirs of cool atomic gas (n ∼ 0.3-10 cm{sup –3})—which are the sites of future star formation (SF; 100-200 Myr), are generally too dense to be significantly affected. Our analysis ignores any absorption from a putative torus, making our results upper limits on the effects of ionizing radiation. Therefore, while the AGN-driven outflows can remove substantial amounts of gas in the long term, the impact of AGN feedback on the SF efficiency in the interstellar gas in high-redshift galaxies is marginal, even when long-range radiative effects are accounted for.

  11. The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular Gas Reservoirs in High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Decarli, Roberto; Walter, Fabian; Aravena, Manuel; Carilli, Chris; Bouwens, Rychard; da Cunha, Elisabete; Daddi, Emanuele; Elbaz, David; Riechers, Dominik; Smail, Ian; Swinbank, Mark; Weiss, Axel; Bacon, Roland; Bauer, Franz; Bell, Eric F.; Bertoldi, Frank; Chapman, Scott; Colina, Luis; Cortes, Paulo C.; Cox, Pierre; Gónzalez-López, Jorge; Inami, Hanae; Ivison, Rob; Hodge, Jacqueline; Karim, Alex; Magnelli, Benjamin; Ota, Kazuaki; Popping, Gergö; Rix, Hans-Walter; Sargent, Mark; van der Wel, Arjen; van der Werf, Paul

    2016-12-01

    We study the molecular gas properties of high-z galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets an ˜1 arcmin2 region in the Hubble Ultra Deep Field (UDF), a blind survey of CO emission (tracing molecular gas) in the 3 and 1 mm bands. Of a total of 1302 galaxies in the field, 56 have spectroscopic redshifts and correspondingly well-defined physical properties. Among these, 11 have infrared luminosities {L}{IR}\\gt {10}11 {L}⊙ , i.e., a detection in CO emission was expected. Out of these, 7 are detected at various significance in CO, and 4 are undetected in CO emission. In the CO-detected sources, we find CO excitation conditions that are lower than those typically found in starburst/sub-mm galaxy/QSO environments. We use the CO luminosities (including limits for non-detections) to derive molecular gas masses. We discuss our findings in the context of previous molecular gas observations at high redshift (star formation law, gas depletion times, gas fractions): the CO-detected galaxies in the UDF tend to reside on the low-{L}{IR} envelope of the scatter in the {L}{IR}{--}{L}{CO}\\prime relation, but exceptions exist. For the CO-detected sources, we find an average depletion time of ˜1 Gyr, with significant scatter. The average molecular-to-stellar mass ratio ({M}{{H}2}/M *) is consistent with earlier measurements of main-sequence galaxies at these redshifts, and again shows large variations among sources. In some cases, we also measure dust continuum emission. On average, the dust-based estimates of the molecular gas are a factor ˜2-5× smaller than those based on CO. When we account for detections as well as non-detections, we find large diversity in the molecular gas properties of the high-redshift galaxies covered by ASPECS.

  12. Precise Strong Lensing Mass Modeling of Four Hubble Frontier Field Clusters and a Sample of Magnified High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Kawamata, Ryota; Oguri, Masamune; Ishigaki, Masafumi; Shimasaku, Kazuhiro; Ouchi, Masami

    2016-03-01

    We conduct precise strong lensing mass modeling of four Hubble Frontier Field (HFF) clusters, Abell 2744, MACS J0416.1-2403, MACS J0717.5+3745, and MACS J1149.6+2223, for which HFF imaging observations are completed. We construct a refined sample of more than 100 multiple images for each cluster by taking advantage of the full-depth HFF images, and conduct mass modeling using the glafic software, which assumes simply parametrized mass distributions. Our mass modeling also exploits a magnification constraint from the lensed SN Ia HFF14Tom for Abell 2744 and positional constraints from the multiple images S1-S4 of the lensed supernova SN Refsdal for MACS J1149.6+2223. We find that our best-fitting mass models reproduce the observed image positions with rms errors of ˜0.″4, which are smaller than rms errors in previous mass modeling that adopted similar numbers of multiple images. Our model predicts a new image of SN Refsdal with a relative time delay and magnification that are fully consistent with a recent detection of reappearance. We then construct catalogs of z ˜ 6-9 dropout galaxies behind the four clusters and estimate magnification factors for these dropout galaxies with our best-fitting mass models. The dropout sample from the four cluster fields contains ˜120 galaxies at z ≳ 6, about 20 of which are predicted to be magnified by a factor of more than 10. Some of the high-redshift galaxies detected in the HFF have lensing-corrected magnitudes of MUV ˜ -15 to -14. Our analysis demonstrates that the HFF data indeed offer an ideal opportunity to study faint high-redshift galaxies. All lensing maps produced from our mass modeling will be made available on the Space Telescope Science Institute website (https://archive.stsci.edu/prepds/frontier/lensmodels/).

  13. THE RELATION BETWEEN EJECTA VELOCITY, INTRINSIC COLOR, AND HOST-GALAXY MASS FOR HIGH-REDSHIFT TYPE Ia SUPERNOVAE

    SciTech Connect

    Foley, Ryan J.

    2012-04-01

    Recently, using a large low-redshift sample of Type Ia supernovae (SNe Ia), we discovered a relation between SN Ia ejecta velocity and intrinsic color that improves the distance precision of SNe Ia and reduces potential systematic biases related to dust reddening. No SN Ia cosmological results have yet made a correction for the 'velocity-color' relation. To test the existence of such a relation and constrain its properties at high redshift, we examine a sample of 75 SNe Ia discovered and observed by the Sloan Digital Sky Survey-II Supernova Survey and Supernova Legacy Survey. From each spectrum, we measure ejecta velocities at maximum brightness for the Ca H and K and Si II {lambda}6355 features, v{sup 0}{sub CaHandK} and v{sup 0}{sub SiII}, respectively. Using SN light curve parameters, we determine the intrinsic B{sub max} - V{sub max} for each SN. Similar to what was found at low redshift, we find that SNe Ia with higher ejecta velocity tend to be intrinsically redder than SNe Ia with lower ejecta velocity. The distributions of ejecta velocities for SNe Ia at low and high redshift are similar, indicating that current cosmological results should have little bias related to the velocity-color relation. Additionally, we find a slight (2.4{sigma} significant) trend between SN Ia ejecta velocity and host-galaxy mass such that SNe Ia in high-mass host galaxies tend to have lower ejecta velocities as probed by v{sup 0}{sub CaHandK}. These results emphasize the importance of spectroscopy for SN Ia cosmology.

  14. The Connection between Stellar Populations and the Baryon Cycle and Ionizing Escape Fractions of Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Reddy, Naveen; Steidel, Charles

    2016-08-01

    We propose Spitzer IRAC 3.6 micron observations to cover the three remaining fields of a large spectroscopic survey of galaxies, AGN, and QSOs in the same cosmic volumes at z~2-3. The IRAC data will be used to probe the stellar populations in these galaxies and to understand how galaxy properties (e.g., stellar masses, ages, reddening, star-formation rates) depend on the flow of baryons into and out of galaxies, as well as identify those properties of galaxies that are conducive to the escape of ionizing radiation at high redshift. The dense spectroscopic sampling of the targeted fields have provided unique insights into metal enrichment as a function of galactocentric radius and the statistical correlation between galaxies and metals in the inter-galactic medium. Our goal is to quantify how the distribution of metals in the circum-galactic and inter-galactic media (CGM/IGM) depend on the stellar masses, ages, and star formation rates of galaxies. Moreover, in an effort to clarify the role of galaxies in reionizing the Universe (and keeping it ionized), we wish to understand the types of stellar populations (e.g., stellar masses, ages) that influence the propensity of galaxies to leak ionizing radiation. Our preliminary observations suggest that bluer galaxies with lower star-formation rates have larger escape fractions, but the results are tentative without the inclusion of the IRAC data proposed here. A modest investment of just 13.1 hours (including overhead), divided among the three fields will cover a total of approximately 200 spectroscopically-confirmed z~2-3 galaxies that span two orders of magnitude in bolometric luminosity and stellar mass. The proposed IRAC imaging will allow us to fully leverage the existing spectroscopic samples that form the backbone of our survey of the baryon cycle and escaping ionizing radiation at high redshift.

  15. Contamination of Broadband Photometry by Nebular Emission in High-redshift Galaxies: Investigations with Keck's MOSFIRE Near-infrared Spectrograph

    NASA Astrophysics Data System (ADS)

    Schenker, Matthew A.; Ellis, Richard S.; Konidaris, Nick P.; Stark, Daniel P.

    2013-11-01

    Earlier work has raised the potential importance of nebular emission in the derivation of the physical characteristics of high-redshift Lyman break galaxies. Within certain redshift ranges, and especially at z ~= 6-7, such lines may be strong enough to reduce estimates of the stellar masses and ages of galaxies compared with those derived assuming the broadband photometry represents stellar light alone. To test this hypothesis at the highest redshifts where such lines can be probed with ground-based facilities, we examine the near-infrared spectra of a representative sample of 28 3.0 < z < 3.8 Lyman break galaxies using the newly commissioned MOSFIRE near-infrared spectrograph at the Keck I telescope. We use these data to derive the rest-frame equivalent widths (EWs) of [O III] emission and show that these are comparable with estimates derived using the spectral energy distribution (SED) fitting technique introduced for sources of known redshift by Stark et al. Although our current sample is modest, its [O III] EW distribution is consistent with that inferred for Hα based on SED fitting of Stark et al.'s larger sample of 3.8 < z < 5 galaxies. For a subset of survey galaxies, we use the combination of optical and near-infrared spectroscopy to quantify kinematics of outflows in z ~= 3.5 star-forming galaxies and discuss the implications for reionization measurements. The trends we uncover underline the dangers of relying purely on broadband photometry to estimate the physical properties of high-redshift galaxies and emphasize the important role of diagnostic spectroscopy.

  16. Dark Matter annihilations in halos and high-redshift sources of reionization of the universe

    NASA Astrophysics Data System (ADS)

    Poulin, Vivian; Serpico, Pasquale D.; Lesgourgues, Julien

    2015-12-01

    It is well known that annihilations in the homogeneous fluid of dark matter (DM) can leave imprints in the cosmic microwave background (CMB) anisotropy power spectrum. However, the relevance of DM annihilations in halos for cosmological observables is still subject to debate, with previous works reaching different conclusions on this point. Also, all previous studies used a single type of parameterization for the astrophysical reionization, and included no astrophysical source for the heating of the intergalactic medium. In this work, we revisit these problems. When standard approaches are adopted, we find that the ionization fraction does exhibit a very particular (and potentially constraining) pattern, but the currently measurable τreio is left almost unchanged: in agreement with most of the previous literature, for plausible halo models we find that the modification of the signal with respect to the one coming from annihilations in the smooth background is tiny, below cosmic variance within currently allowed parameter space. However, if different and probably more realistic treatments of the astrophysical sources of reionization and heating are adopted, a more pronounced effect of the DM annihilation in halos is possible. We thus conclude that within currently adopted baseline models the impact of the virialised DM structures cannot be uncovered by CMB power spectra measurements, but a larger impact is possible if peculiar models are invoked for the redshift evolution of the DM annihilation signal or different assumptions are made for the astrophysical contributions. A better understanding (both theoretical and observational) of the reionization and temperature history of the universe, notably via the 21 cm signal, seems the most promising way for using halo formation as a tool in DM searches, improving over the sensitivity of current cosmological probes.

  17. Dark Matter annihilations in halos and high-redshift sources of reionization of the universe

    SciTech Connect

    Poulin, Vivian; Serpico, Pasquale D.; Lesgourgues, Julien E-mail: Pasquale.Serpico@lapth.cnrs.fr

    2015-12-01

    It is well known that annihilations in the homogeneous fluid of dark matter (DM) can leave imprints in the cosmic microwave background (CMB) anisotropy power spectrum. However, the relevance of DM annihilations in halos for cosmological observables is still subject to debate, with previous works reaching different conclusions on this point. Also, all previous studies used a single type of parameterization for the astrophysical reionization, and included no astrophysical source for the heating of the intergalactic medium. In this work, we revisit these problems. When standard approaches are adopted, we find that the ionization fraction does exhibit a very particular (and potentially constraining) pattern, but the currently measurable τ{sub reio} is left almost unchanged: in agreement with most of the previous literature, for plausible halo models we find that the modification of the signal with respect to the one coming from annihilations in the smooth background is tiny, below cosmic variance within currently allowed parameter space. However, if different and probably more realistic treatments of the astrophysical sources of reionization and heating are adopted, a more pronounced effect of the DM annihilation in halos is possible. We thus conclude that within currently adopted baseline models the impact of the virialised DM structures cannot be uncovered by CMB power spectra measurements, but a larger impact is possible if peculiar models are invoked for the redshift evolution of the DM annihilation signal or different assumptions are made for the astrophysical contributions. A better understanding (both theoretical and observational) of the reionization and temperature history of the universe, notably via the 21 cm signal, seems the most promising way for using halo formation as a tool in DM searches, improving over the sensitivity of current cosmological probes.

  18. Unveiling the nature of dark matter with high redshift 21 cm line experiments

    SciTech Connect

    Evoli, C.; Mesinger, A.; Ferrara, A. E-mail: andrei.mesinger@sns.it

    2014-11-01

    Observations of the redshifted 21 cm line from neutral hydrogen will open a new window on the early Universe. By influencing the thermal and ionization history of the intergalactic medium (IGM), annihilating dark matter (DM) can leave a detectable imprint in the 21 cm signal. Building on the publicly available 21cmFAST code, we compute the 21 cm signal for a 10 GeV WIMP DM candidate. The most pronounced role of DM annihilations is in heating the IGM earlier and more uniformly than astrophysical sources of X-rays. This leaves several unambiguous, qualitative signatures in the redshift evolution of the large-scale (k ≅ 0.1 Mpc{sup -1}) 21 cm power amplitude: (i) the local maximum (peak) associated with IGM heating can be lower than the other maxima; (ii) the heating peak can occur while the IGM is in emission against the cosmic microwave background (CMB); (iii) there can be a dramatic drop in power (a global minimum) corresponding to the epoch when the IGM temperature is comparable to the CMB temperature. These signatures are robust to astrophysical uncertainties, and will be easily detectable with second generation interferometers. We also briefly show that decaying warm dark matter has a negligible role in heating the IGM.

  19. Z > 6 Galaxy Signatures in the Infrared Background and the 21-cm background

    NASA Astrophysics Data System (ADS)

    Cooray, A.

    2006-08-01

    We will discuss the signatures of the high-redshift galaxy formation in the near-infrared background. Ionizing sources at high redshift generically imprint a distinctive Lyman-cutoff feature and a unique spatial anisotropy signature to the IRB, both of which may be detectable in a short rocket flight. We will discuss the Cosmic Infrared Background ExpeRiment (CIBER), a rocket-borne instrument to probe the absolute spectrum and spatial anisotropy of the extragalactic InfraRed Background (IRB) optimized for detection of the integrated spatial anisotropies in the IR background from high-redshift galaxies. We will also discuss the signatures of first galaxies in the low radio frequency 21-cm background from the neutral Hydrogen distribution at z > 6; When combined with arcminute-scale temperature anisotropy and the polarization of the cosmic microwave background, the 21-cm background will allow a determination of inhomogeneous distribution of Lyman-alpha photons from first galaxies. We will discuss these and other possibilities to understand the first galaxy population with IR, 21-cm, and CMB backgrounds.

  20. THE ORIGIN OF [O II] IN POST-STARBURST AND RED-SEQUENCE GALAXIES IN HIGH-REDSHIFT CLUSTERS

    SciTech Connect

    Lemaux, B. C.; Lubin, L. M.; Kocevski, D.; Shapley, A.; Gal, R. R.; Squires, G. K.

    2010-06-20

    We present the first results from a near-IR spectroscopic campaign of the Cl1604 supercluster at z {approx} 0.9 and the cluster RX J1821.6+6827 at z {approx} 0.82 to investigate the nature of [O II] {lambda}3727 emission in cluster galaxies at high redshift. Of the 401 members in Cl1604 and RX J1821+6827 confirmed using the Keck II/DEIMOS spectrograph, 131 galaxies have detectable [O II] emission with no other signs of current star formation activity, as well as strong absorption features indicative of a well-established older stellar population. The combination of these features suggests that the primary source of [O II] emission in these galaxies is not a result of star formation processes, but rather due to the presence of a low-ionization nuclear emission-line region (LINER) or Seyfert component. Using the NIRSPEC spectrograph on the Keck II 10 m telescope, 19 such galaxies were targeted, as well as 6 additional [O II]-emitting cluster members that exhibited signs of ongoing star formation activity. Nearly half ({approx}47%) of the 19 [O II]-emitting, absorption-line-dominated galaxies exhibit [O II] to H{alpha} equivalent width (EW) ratios higher than unity, the typical observed value for star-forming galaxies, with an EW distribution similar to that observed for LINERs at low redshift. A majority ({approx}68%) of these 19 galaxies are classified as LINER/Seyfert based primarily on the emission-line ratio of [N II] {lambda}6584 and H{alpha}. The fraction of LINER/Seyferts increases to {approx}85% for red [O II]-emitting, absorption-line-dominated galaxies. The LINER/Seyfert galaxies in our Cl1604 sample exhibit average L([O II])/L(H{alpha}) ratios that are significantly higher than that observed in populations of star-forming galaxies, suggesting that [O II] is a poor indicator of star formation in a significant fraction of high-redshift cluster members. From the prevalence of [O II]-emitting, absorption-line-dominated galaxies in both systems and the fraction

  1. The effects of the small-scale DM power on the cosmological neutral hydrogen (HI) distribution at high redshifts

    SciTech Connect

    Sarkar, Abir; Sethi, Shiv K.; Mondal, Rajesh; Bharadwaj, Somnath; Das, Subinoy; Marsh, David J.E. E-mail: rm@phy.iitkgp.ernet.in E-mail: sethi@rri.res.in E-mail: david.marsh@kcl.ac.uk

    2016-04-01

    The particle nature of dark matter remains a mystery. In this paper, we consider two dark matter models—Late Forming Dark Matter (LFDM) and Ultra-Light Axion (ULA) models—where the matter power spectra show novel effects on small scales. The high redshift universe offers a powerful probe of their parameters. In particular, we study two cosmological observables: the neutral hydrogen (HI) redshifted 21-cm signal from the epoch of reionization, and the evolution of the collapsed fraction of HI in the redshift range 2 < z < 5. We model the theoretical predictions of the models using CDM-like N-body simulations with modified initial conditions, and generate reionization fields using an excursion set model. The N-body approximation is valid on the length and halo mass scales studied. We show that LFDM and ULA models predict an increase in the HI power spectrum from the epoch of reionization by a factor between 2–10 for a range of scales 0.1 < k < 4 Mpc{sup −1}. Assuming a fiducial model where a neutral hydrogen fraction x-bar {sub HI} = 0.5 must be achieved by z = 8, the reionization process allows us to put approximate bounds on the redshift of dark matter formation z{sub f} > 4 × 10{sup 5} (for LFDM) and the axion mass m{sub a} > 2.6 × 10{sup −23} eV (for ULA). The comparison of the collapsed mass fraction inferred from damped Lyman-α observations to the theoretical predictions of our models lead to the weaker bounds: z{sub f} > 2 × 10{sup 5} and m{sub a} > 10{sup −23} eV. These bounds are consistent with other constraints in the literature using different observables; we briefly discuss how these bounds compare with possible constraints from the observation of luminosity function of galaxies at high redshifts. In the case of ULAs, these constraints are also consistent with a solution to the cusp-core problem of CDM.

  2. Twenty-Three High-Redshift Supernovae from the Institute for Astronomy Deep Survey: Doubling the Supernova Sample at z > 0.7

    NASA Astrophysics Data System (ADS)

    Barris, Brian J.; Tonry, John L.; Blondin, Stéphane; Challis, Peter; Chornock, Ryan; Clocchiatti, Alejandro; Filippenko, Alexei V.; Garnavich, Peter; Holland, Stephen T.; Jha, Saurabh; Kirshner, Robert P.; Krisciunas, Kevin; Leibundgut, Bruno; Li, Weidong; Matheson, Thomas; Miknaitis, Gajus; Riess, Adam G.; Schmidt, Brian P.; Smith, R. Chris; Sollerman, Jesper; Spyromilio, Jason; Stubbs, Christopher W.; Suntzeff, Nicholas B.; Aussel, Hervé; Chambers, K. C.; Connelley, M. S.; Donovan, D.; Henry, J. Patrick; Kaiser, Nick; Liu, Michael C.; Martín, Eduardo L.; Wainscoat, Richard J.

    2004-02-01

    We present photometric and spectroscopic observations of 23 high-redshift supernovae (SNe) spanning a range of z=0.34-1.03, nine of which are unambiguously classified as Type Ia. These SNe were discovered during the IfA Deep Survey, which began in 2001 September and observed a total of 2.5 deg2 to a depth of approximately m~25-26 in RIZ over 9-17 visits, typically every 1-3 weeks for nearly 5 months, with additional observations continuing until 2002 April. We give a brief description of the survey motivations, observational strategy, and reduction process. This sample of 23 high-redshift SNe includes 15 at z>=0.7, doubling the published number of objects at these redshifts, and indicates that the evidence for acceleration of the universe is not due to a systematic effect proportional to redshift. In combination with the recent compilation of Tonry et al. (2003), we calculate cosmological parameter density contours that are consistent with the flat universe indicated by the cosmic microwave background (Spergel et al. 2003). Adopting the constraint that Ωtotal=1.0, we obtain best-fit values of (Ωm,ΩΛ)=(0.33,0.67) using 22 SNe from this survey augmented by the literature compilation. We show that using the empty-beam model for gravitational lensing does not eliminate the need for ΩΛ>0. Experience from this survey indicates great potential for similar large-scale surveys while also revealing the limitations of performing surveys for z>1 SNe from the ground. CFHT: Based in part on observations obtained at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. CTIO: Based in part on observations taken at the Cerro Tololo Inter-American Observatory. Keck: Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership

  3. Breaking through the high redshift bottleneck of Observational Hubble parameter Data: the Sandage-Loeb signal Scheme

    NASA Astrophysics Data System (ADS)

    Yuan, Shuo; Zhang, Tong-Jie

    2015-02-01

    We propose a robust scheme to measure the Hubble parameter H(z) at high redshifts by detecting the Sandage-Loeb signal (SL signal) which can be realized by the next generation extremely large telescope. It will largely extend the current observational Hubble parameter data (OHD) towards the redshift range of z in [2.0,5.0] where other dark energy probes is difficult to provide useful information of the cosmic expansion. To quantify the capability of such future measurement to constrain cosmological models, we simulate observational data for a CODEX (COsmic Dynamics and EXo-earth experiment)-like survey. We find that the SL signal scheme brings the redshift upper-limit of OHD from zmax = 2.3 to 0zmax simeq 5., provides more accurate constraints on different dark energy models, and greatly changes the degeneracy direction of the parameters. For the ΛCDM case, the accuracy of Ωm is improved by 58% and the degeneracy between Ωm and ΩΛ is rotated to the vertical direction of Ωm - ΩΛ plane; for the wCDM case, the accuracy of w is improved by 15%. The Fisher matrix forecast on different time-dependent w(z) cosmological model is also performed.

  4. Discovery of an Obscured Broad-Line Region in the High-Redshift Radio Galaxy MRC 2025-218.

    PubMed

    Larkin; McLean; Graham; Becklin; Figer; Gilbert; Levenson; Teplitz; Wilcox; Glassman

    2000-04-10

    This Letter presents infrared spectra taken with the newly commissioned near-infrared spectrometer (NIRSPEC) on the Keck II telescope of the high-redshift radio galaxy MRC 2025-218 (z=2.63). These observations represent the deepest infrared spectra of a radio galaxy to date and have allowed for the detection of Hbeta, [O iii] lambdalambda4959, 5007, [O i] lambda6300, Halpha, [N ii] lambdalambda6548, 6583, and [S ii] lambdalambda6716, 6713. The Halpha emission is very broad (FWHM=9300 km s-1) and luminous (2.6x1044 ergs s-1), and it is very comparable to the line widths and strengths of radio-loud quasars at the same redshift. This strongly supports active galactic nucleus unification models linking radio galaxies and quasars, although we discuss some of the outstanding differences. The line [O iii] lambda5007 is extremely strong and has extended emission with large relative velocities toward the nucleus. We also derive that if the extended emission is due to star formation, each knot has a star formation rate comparable to a Lyman-break galaxy at the same redshift.

  5. NOMADS : Physical Origins And Conditions Of Line-emitting Gas From High-redshift (1 < z < 3) Galaxies

    NASA Astrophysics Data System (ADS)

    Wright, Shelley; Ma, C.; Larkin, J.; Graham, J.

    2011-01-01

    We present results from NOMADS (Near-infrared OSIRIS Metallicity, AGN, and Dynamics Survey) of spatially resolved rest-frame optical emission lines (e.g., Hβ, [O III], Hα, and [N II]) for nine star forming galaxies at a redshift range of 1 < z < 3. These results are part of an on-going survey to study the chemical abundances, dynamics, and role of weak active galactic nuclei (AGN) in galaxies that have been used previously in metallicity studies at high-redshift. Using 0.1" spatial scale with the integral field spectrograph OSIRIS coupled to the Keck Adaptive Optics system we can identify, localize, and quantify any contribution from AGN activity in these measurements and map two-dimensional chemical abundances on sub-kiloparsec scales. We present metallicity gradients and kinematics for several high-z galaxies and place constraints on the formation mechanisms of these young, star forming galaxies. In addition, we find that a few of these systems do harbor weak non-thermal activity and we will discuss the role of AGN in galaxy formation. We acknowledge funding support from NASA STScI HF-51265.01.

  6. Escape of about five per cent of Lyman-alpha photons from high-redshift star-forming galaxies.

    PubMed

    Hayes, Matthew; Ostlin, Göran; Schaerer, Daniel; Mas-Hesse, J Miguel; Leitherer, Claus; Atek, Hakim; Kunth, Daniel; Verhamme, Anne; de Barros, Stéphane; Melinder, Jens

    2010-03-25

    The Lyman-alpha (Lyalpha) emission line is the primary observational signature of star-forming galaxies at the highest redshifts, and has enabled the compilation of large samples of galaxies with which to study cosmic evolution. The resonant nature of the line, however, means that Lyalpha photons scatter in the neutral interstellar medium of their host galaxies, and their sensitivity to absorption by interstellar dust may therefore be greatly enhanced. This implies that the Lyalpha luminosity may be significantly reduced, or even completely suppressed. Hitherto, no unbiased empirical test of the escaping fraction (f(esc)) of Lyalpha photons has been performed at high redshifts. Here we report that the average f(esc) from star-forming galaxies at redshift z = 2.2 is just 5 per cent by performing a blind narrowband survey in Lyalpha and Halpha. This implies that numerous conclusions based on Lyalpha-selected samples will require upwards revision by an order of magnitude and we provide a benchmark for this revision. We demonstrate that almost 90 per cent of star-forming galaxies emit insufficient Lyalpha to be detected by standard selection criteria. Both samples show an anti-correlation of f(esc) with dust content, and we show that Lyalpha- and Halpha-selection recovers populations that differ substantially in dust content and f(esc).

  7. THE THICK DISKS OF SPIRAL GALAXIES AS RELICS FROM GAS-RICH, TURBULENT, CLUMPY DISKS AT HIGH REDSHIFT

    SciTech Connect

    Bournaud, Frederic; Martig, Marie; Elmegreen, Bruce G.

    2009-12-10

    The formation of thick stellar disks in spiral galaxies is studied. Simulations of gas-rich young galaxies show formation of internal clumps by gravitational instabilities, clump coalescence into a bulge, and disk thickening by strong stellar scattering. The bulge and thick disks of modern galaxies may form this way. Simulations of minor mergers make thick disks too, but there is an important difference. Thick disks made by internal processes have a constant scale height with galactocentric radius, but thick disks made by mergers flare. The difference arises because in the first case, perpendicular forcing and disk-gravity resistance are both proportional to the disk column density, so the resulting scale height is independent of this density. In the case of mergers, perpendicular forcing is independent of the column density and the low-density regions get thicker; the resulting flaring is inconsistent with observations. Late-stage gas accretion and thin-disk growth are shown to preserve the constant scale heights of thick disks formed by internal evolution. These results reinforce the idea that disk galaxies accrete most of their mass smoothly and acquire their structure by internal processes, in particular through turbulent and clumpy phases at high redshift.

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

    NASA Astrophysics Data System (ADS)

    Shemmer, Ohad; Trakhtenbrot, B.; Anderson, S. F.; Brandt, W. N.; Diamond-Stanic, A. M.; Fan, X.; Lira, P.; Netzer, H.; Plotkin, R. M.; Richards, G. T.; Schneider, D. P.; Strauss, M. A.

    2011-01-01

    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 we 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/LEdd=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+0.24-0.22which supports the virial L/LEdd 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.

  9. Observations of High-Redshift X-Ray Selected Clusters with the Sunyaev-Zel'dovich Array

    NASA Technical Reports Server (NTRS)

    Muchovej, Stephen; Carlstrom, John E.; Cartwright, John; Greer, Christopher; Hawkins, David; Hennessey, Ryan; Joy, Marshall; Lamb, James; Leitch, Erik M.; Loh, Michael; Miller, Amber D.; Mroczkowski, Tony; Pryke, Clem; Reddall, Ben; Runyan, Marcus; Sharp, Matthew; Woody, David

    2006-01-01

    We report measurements of the Sunyaev-Zel'dovich (SZ) effect in three high redshift (0.89 less than or equal to z less than or equal to 1.03), X-ray selected galaxy clusters. The observations were obtained at 30 GHz during the commissioning period of a new, eight-element interferometer - the Sunyaev-Zel'dovich Array (SZA) - built for dedicated SZ effect observations. The SZA observations are sensitive to angular scales larger than those subtended by the virial radii of the clusters. Assuming isothermality and hydrostatic equilibrium for the intracluster medium, and gas-mass fractions consistent with those for clusters at moderate redshift, we calculate electron temperatures, gas masses, and total cluster masses from the SZ data. The SZ-derived masses, integrated approximately to the virial radii, are 1.9 (sup +0.5)(sub -0.4) x 10(exp 14) solar mass for Cl J1415.1+3612, 3.4 (sup +0.6)(sub -0.5) x 10(exp 14) solar mass for Cl J1429.0+4241 and 7.2 (sup +1.3)(sub -0.9) x 10(exp 14) solar mass for Cl J1226.9+3332. The SZ-derived quantities are in good agreement with the cluster properties derived from X-ray measurements.

  10. The Argo simulation - I. Quenching of massive galaxies at high redshift as a result of cosmological starvation

    NASA Astrophysics Data System (ADS)

    Feldmann, Robert; Mayer, Lucio

    2015-01-01

    Observations show a prevalence of high-redshift galaxies with large stellar masses and predominantly passive stellar populations. A variety of processes have been suggested that could reduce the star formation in such galaxies to observed levels, including quasar mode feedback, virial shock heating, or galactic winds driven by stellar feedback. However, the main quenching mechanisms have yet to be identified. Here we study the origin of star formation quenching using Argo, a cosmological, hydrodynamical zoom-in simulation that follows the evolution of a massive galaxy at z ≥ 2. This simulation adopts the same subgrid recipes of the Eris simulations, which have been shown to form realistic disc galaxies, and, in one version, adopts also a mass and spatial resolution identical to Eris. The resulting galaxy has properties consistent with those of observed, massive (M* ˜ 1011 M⊙) galaxies at z ˜ 2 and with abundance matching predictions. Our models do not include active galactic nuclei (AGN) feedback indicating that supermassive black holes likely play a subordinate role in determining masses and sizes of massive galaxies at high-z. The specific star formation rate (sSFR) of the simulated galaxy matches the observed M*-sSFR relation at early times. This period of smooth stellar mass growth comes to a sudden halt at z = 3.5 when the sSFR drops by almost an order of magnitude within a few hundred Myr. The suppression is initiated by a levelling off and a subsequent reduction of the cool gas accretion rate on to the galaxy, and not by feedback processes. This `cosmological starvation' occurs as the parent dark matter halo switches from a fast collapsing mode to a slow accretion mode. Additional mechanisms, such as perhaps radio mode feedback from an AGN, are needed to quench any residual star formation of the galaxy and to maintain a low sSFR until the present time.

  11. A simple model to link the properties of quasars to the properties of dark matter haloes out to high redshift

    NASA Astrophysics Data System (ADS)

    Croton, Darren J.

    2009-04-01

    We present a simple model of how quasars occupy dark matter haloes from z = 0 to 5 using the observed mBH-σ relation and quasar luminosity functions. This provides a way for observers to statistically infer host halo masses for quasar observations using luminosity and redshift alone. Our model is deliberately simple and sidesteps any need to explicitly describe the physics. In spite of its simplicity, the model reproduces many key observations and has predictive power: (i) model quasars have the correct luminosity function (by construction) and spatial clustering (by consequence); (ii) we predict high-redshift quasars of a given luminosity live in less massive dark matter haloes than the same luminosity quasars at low redshifts; (iii) we predict a factor of ~5 more 108.5Msolar black holes at z ~ 2 than is currently observed; (iv) we predict a factor of ~20 evolution in the amplitude of the mBH-Mhalo relation between z = 5 and the present day; (v) we expect luminosity-dependent quasar lifetimes of between tQ ~ 107 and 108yr, but which may become as short as 105-6yr for quasars brighter than L* and (vi) while little luminosity-dependent clustering evolution is expected at z <~ 1, increasingly strong evolution is predicted for L > L* quasars at higher redshifts. These last two results arise from the narrowing distribution of halo masses that quasars occupy as the Universe ages. We also deconstruct both `downsizing' and `upsizing' trends predicted by the model at different redshifts and space densities. Importantly, this work illustrates how current observations cannot distinguish between more complicated physically motivated quasar models and our simple phenomenological approach. It highlights the opportunities such methodologies provide.

  12. Absorption-line Spectroscopy of Gravitationally Lensed Galaxies: Further Constraints on the Escape Fraction of Ionizing Photons at High Redshift

    NASA Astrophysics Data System (ADS)

    Leethochawalit, Nicha; Jones, Tucker A.; Ellis, Richard S.; Stark, Daniel P.; Zitrin, Adi

    2016-11-01

    The fraction of ionizing photons escaping from high-redshift star-forming galaxies is a key obstacle in evaluating whether galaxies were the primary agents of cosmic reionization. We previously proposed using the covering fraction of low-ionization gas, measured via deep absorption-line spectroscopy, as a proxy. We now present a significant update, sampling seven gravitationally lensed sources at 4 < z < 5. We show that the absorbing gas in our sources is spatially inhomogeneous, with a median covering fraction of 66%. Correcting for reddening according to a dust-in-cloud model, this implies an estimated absolute escape fraction of ≃19% ± 6%. With possible biases and uncertainties, collectively we find that the average escape fraction could be reduced to no less than 11%, excluding the effect of spatial variations. For one of our lensed sources, we have sufficient signal-to-noise ratio to demonstrate the presence of such spatial variations and scatter in its dependence on the Lyα equivalent width, consistent with recent simulations. If this source is typical, our lower limit to the escape fraction could be reduced by a further factor ≃2. Across our sample, we find a modest anticorrelation between the inferred escape fraction and the local star formation rate, consistent with a time delay between a burst and leaking Lyman continuum photons. Our analysis demonstrates considerable variations in the escape fraction, consistent with being governed by the small-scale behavior of star-forming regions, whose activities fluctuate over short timescales. This supports the suggestion that the escape fraction may increase toward the reionization era when star formation becomes more energetic and burst-like.

  13. Rapid, Machine-learned Resource Allocation: Application to High-redshift Gamma-Ray Burst Follow-up

    NASA Astrophysics Data System (ADS)

    Morgan, A. N.; Long, James; Richards, Joseph W.; Broderick, Tamara; Butler, Nathaniel R.; Bloom, Joshua S.

    2012-02-01

    As the number of observed gamma-ray bursts (GRBs) continues to grow, follow-up resources need to be used more efficiently in order to maximize science output from limited telescope time. As such, it is becoming increasingly important to rapidly identify bursts of interest as soon as possible after the event, before the afterglows fade beyond detectability. Studying the most distant (highest redshift) events, for instance, remains a primary goal for many in the field. Here, we present our Random Forest Automated Triage Estimator for GRB redshifts (RATE GRB-z ) for rapid identification of high-redshift candidates using early-time metrics from the three telescopes onboard Swift. While the basic RATE methodology is generalizable to a number of resource allocation problems, here we demonstrate its utility for telescope-constrained follow-up efforts with the primary goal to identify and study high-z GRBs. For each new GRB, RATE GRB-z provides a recommendation—based on the available telescope time—of whether the event warrants additional follow-up resources. We train RATE GRB-z using a set consisting of 135 Swift bursts with known redshifts, only 18 of which are z > 4. Cross-validated performance metrics on these training data suggest that ~56% of high-z bursts can be captured from following up the top 20% of the ranked candidates, and ~84% of high-z bursts are identified after following up the top ~40% of candidates. We further use the method to rank 200 + Swift bursts with unknown redshifts according to their likelihood of being high-z.

  14. THE XMM CLUSTER SURVEY: THE BUILD-UP OF STELLAR MASS IN BRIGHTEST CLUSTER GALAXIES AT HIGH REDSHIFT

    SciTech Connect

    Stott, J. P.; Collins, C. A.; Hilton, M.; Capozzi, D.; Sahlen, M.; Lloyd-Davies, E.; Hosmer, M.; Liddle, A. R.; Mehrtens, N.; Romer, A. K.; Miller, C. J.; Stanford, S. A.; Viana, P. T. P.; Davidson, M.; Hoyle, B.; Kay, S. T.; Nichol, R. C.

    2010-07-20

    We present deep J- and K{sub s} -band photometry of 20 high redshift galaxy clusters between z = 0.8 and1.5, 19 of which are observed with the MOIRCS instrument on the Subaru telescope. By using near-infrared light as a proxy for stellar mass we find the surprising result that the average stellar mass of Brightest Cluster Galaxies (BCGs) has remained constant at {approx}9 x 10{sup 11} M {sub sun} since z {approx} 1.5. We investigate the effect on this result of differing star formation histories generated by three well-known and independent stellar population codes and find it to be robust for reasonable, physically motivated choices of age and metallicity. By performing Monte Carlo simulations we find that the result is unaffected by any correlation between BCG mass and cluster mass in either the observed or model clusters. The large stellar masses imply that the assemblage of these galaxies took place at the same time as the initial burst of star formation. This result leads us to conclude that dry merging has had little effect on the average stellar mass of BCGs over the last 9-10 Gyr in stark contrast to the predictions of semi-analytic models, based on the hierarchical merging of dark matter halos, which predict a more protracted mass build-up over a Hubble time. However, we discuss that there is potential for reconciliation between observation and theory if there is a significant growth of material in the intracluster light over the same period.

  15. THE MOST METAL-POOR DAMPED Lyα SYSTEMS: AN INSIGHT INTO DWARF GALAXIES AT HIGH-REDSHIFT

    SciTech Connect

    Cooke, Ryan J.; Pettini, Max; Jorgenson, Regina A.

    2015-02-10

    In this paper we analyze the kinematics, chemistry, and physical properties of a sample of the most metal-poor damped Lyα systems (DLAs), to uncover their links to modern-day galaxies. We present evidence that the DLA population as a whole exhibits a ''knee'' in the relative abundances of the α-capture and Fe-peak elements when the metallicity is [Fe/H] ≅ –2.0, assuming that Zn traces the buildup of Fe-peak elements. In this respect, the chemical evolution of DLAs is clearly different from that experienced by Milky Way halo stars, but resembles that of dwarf spheroidal galaxies in the Local Group. We also find a close correspondence between the kinematics of Local Group dwarf galaxies and of high-redshift metal-poor DLAs, which further strengthens this connection. On the basis of such similarities, we propose that the most metal-poor DLAs provide us with a unique opportunity to directly study the dwarf galaxy population more than ten billion years in the past, at a time when many dwarf galaxies were forming the bulk of their stars. To this end, we have measured some of the key physical properties of the DLA gas, including their neutral gas mass, size, kinetic temperature, density, and turbulence. We find that metal-poor DLAs contain a warm neutral medium with T {sub gas} ≅ 9600 K predominantly held up by thermal pressure. Furthermore, all of the DLAs in our sample exhibit a subsonic turbulent Mach number, implying that the gas distribution is largely smooth. These results are among the first empirical descriptions of the environments where the first few generations of stars may have formed in the universe.

  16. QUEST FOR COSMOS SUBMILLIMETER GALAXY COUNTERPARTS USING CARMA AND VLA: IDENTIFYING THREE HIGH-REDSHIFT STARBURST GALAXIES

    SciTech Connect

    Smolcic, V.; Navarrete, F.; Bertoldi, F.; Aravena, M.; Sheth, K.; Ilbert, O.; Yun, M. S.; Salvato, M.; Finoguenov, A.; McCracken, H. J.; Diener, C.; Aretxaga, I.; Hughes, D.; Wilson, G.; Riechers, D. A.; Capak, P.; Scoville, N. Z.; Karim, A.; Schinnerer, E.

    2012-05-01

    We report on interferometric observations at 1.3 mm at 2''-3'' resolution using the Combined Array for Research in Millimeter-wave Astronomy. We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F{sub 1m} > 5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, {approx}10''-30'', resolution. All three sources-AzTEC/C1, Cosbo-3, and Cosbo-8-are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but with that farther away from it. This illustrates the need for intermediate-resolution ({approx}2'') mm-observations to identify the correct counterparts of single-dish-detected SMGs. All of our three sources become prominent only at NIR wavelengths, and their mm-to-radio flux based redshifts suggest that they lie at redshifts z {approx}> 2. As a proof of concept, we show that photometric redshifts can be well determined for SMGs, and we find photometric redshifts of 5.6 {+-} 1.2, 1.9{sup +0.9}{sub -0.5}, and {approx}4 for AzTEC/C1, Cosbo-3, and Cosbo-8, respectively. Using these we infer that these galaxies have radio-based star formation rates of {approx}> 1000 M{sub Sun} yr{sup -1}and IR luminosities of {approx}10{sup 13} L{sub Sun} consistent with properties of high-redshift SMGs. In summary, our sources reflect a variety of SMG properties in terms of redshift and clustering, consistent with the framework that SMGs are progenitors of z {approx} 2 and today's passive galaxies.

  17. RAPID, MACHINE-LEARNED RESOURCE ALLOCATION: APPLICATION TO HIGH-REDSHIFT GAMMA-RAY BURST FOLLOW-UP

    SciTech Connect

    Morgan, A. N.; Richards, Joseph W.; Butler, Nathaniel R.; Bloom, Joshua S.; Long, James; Broderick, Tamara

    2012-02-20

    As the number of observed gamma-ray bursts (GRBs) continues to grow, follow-up resources need to be used more efficiently in order to maximize science output from limited telescope time. As such, it is becoming increasingly important to rapidly identify bursts of interest as soon as possible after the event, before the afterglows fade beyond detectability. Studying the most distant (highest redshift) events, for instance, remains a primary goal for many in the field. Here, we present our Random Forest Automated Triage Estimator for GRB redshifts (RATE GRB-z ) for rapid identification of high-redshift candidates using early-time metrics from the three telescopes onboard Swift. While the basic RATE methodology is generalizable to a number of resource allocation problems, here we demonstrate its utility for telescope-constrained follow-up efforts with the primary goal to identify and study high-z GRBs. For each new GRB, RATE GRB-z provides a recommendation-based on the available telescope time-of whether the event warrants additional follow-up resources. We train RATE GRB-z using a set consisting of 135 Swift bursts with known redshifts, only 18 of which are z > 4. Cross-validated performance metrics on these training data suggest that {approx}56% of high-z bursts can be captured from following up the top 20% of the ranked candidates, and {approx}84% of high-z bursts are identified after following up the top {approx}40% of candidates. We further use the method to rank 200 + Swift bursts with unknown redshifts according to their likelihood of being high-z.

  18. Quest for COSMOS Submillimeter Galaxy Counterparts using CARMA and VLA: Identifying Three High-redshift Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Smolčić, V.; Navarrete, F.; Aravena, M.; Ilbert, O.; Yun, M. S.; Sheth, K.; Salvato, M.; McCracken, H. J.; Diener, C.; Aretxaga, I.; Riechers, D. A.; Finoguenov, A.; Bertoldi, F.; Capak, P.; Hughes, D.; Karim, A.; Schinnerer, E.; Scoville, N. Z.; Wilson, G.

    2012-05-01

    We report on interferometric observations at 1.3 mm at 2''-3'' resolution using the Combined Array for Research in Millimeter-wave Astronomy. We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F 1 mm > 5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, ~10''-30'', resolution. All three sources—AzTEC/C1, Cosbo-3, and Cosbo-8—are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but with that farther away from it. This illustrates the need for intermediate-resolution (~2'') mm-observations to identify the correct counterparts of single-dish-detected SMGs. All of our three sources become prominent only at NIR wavelengths, and their mm-to-radio flux based redshifts suggest that they lie at redshifts z >~ 2. As a proof of concept, we show that photometric redshifts can be well determined for SMGs, and we find photometric redshifts of 5.6 ± 1.2, 1.9+0.9 - 0.5, and ~4 for AzTEC/C1, Cosbo-3, and Cosbo-8, respectively. Using these we infer that these galaxies have radio-based star formation rates of >~ 1000 M ⊙ yr-1and IR luminosities of ~1013 L ⊙ consistent with properties of high-redshift SMGs. In summary, our sources reflect a variety of SMG properties in terms of redshift and clustering, consistent with the framework that SMGs are progenitors of z ~ 2 and today's passive galaxies.

  19. Pressure distribution of the high-redshift cluster of galaxies CL J1226.9+3332 with NIKA

    NASA Astrophysics Data System (ADS)

    Adam, R.; Comis, B.; Macías-Pérez, J.-F.; Adane, A.; Ade, P.; André, P.; Beelen, A.; Belier, B.; Benoît, A.; Bideaud, A.; Billot, N.; Blanquer, G.; Bourrion, O.; Calvo, M.; Catalano, A.; Coiffard, G.; Cruciani, A.; D'Addabbo, A.; Désert, F.-X.; Doyle, S.; Goupy, J.; Kramer, C.; Leclercq, S.; Martino, J.; Mauskopf, P.; Mayet, F.; Monfardini, A.; Pajot, F.; Pascale, E.; Perotto, L.; Pointecouteau, E.; Ponthieu, N.; Revéret, V.; Ritacco, A.; Rodriguez, L.; Savini, G.; Schuster, K.; Sievers, A.; Tucker, C.; Zylka, R.

    2015-04-01

    The thermal Sunyaev-Zel'dovich (tSZ) effect is expected to provide a low scatter mass proxy for galaxy clusters since it is directly proportional to the cluster thermal energy. The tSZ observations have proven to be a powerful tool for detecting and studying them, but high angular resolution observations are now needed to push their investigation to a higher redshift. In this paper, we report high angular (<20 arcsec) resolution tSZ observations of the high-redshift cluster CL J1226.9+3332 (z = 0.89). It was imaged at 150 and 260 GHz using the NIKA camera at the IRAM 30-m telescope. The 150 GHz map shows that CL J1226.9+3332 is morphologically relaxed on large scales with evidence of a disturbed core, while the 260 GHz channel is used mostly to identify point source contamination. NIKA data are combined with those of Planck and X-ray from Chandra to infer the cluster's radial pressure, density, temperature, and entropy distributions. The total mass profile of the cluster is derived, and we find M500 = 5.96+1.02-0.79 × 1014M⊙ within the radius R500 = 930+50-43 kpc, at a 68% confidence level. (R500 is the radius within which the average density is 500 times the critical density at the cluster's redshift.) NIKA is the prototype camera of NIKA2, a KIDs (kinetic inductance detectors) based instrument to be installed at the end of 2015. This work is, therefore, part of a pilot study aiming at optimizing tSZ NIKA2 large programs. The FITS file of the published maps is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/576/A12

  20. GRB 120521C at z ∼ 6 and the properties of high-redshift γ-ray bursts

    SciTech Connect

    Laskar, Tanmoy; Berger, Edo; Zauderer, B. Ashley; Margutti, Raffaella; Fong, Wen-fai; Tanvir, Nial; Wiersema, Klaas; Levan, Andrew; Perley, Daniel; Menten, Karl; Hrudkova, Marie

    2014-01-20

    We present optical, near-infrared, and radio observations of the afterglow of GRB 120521C. By modeling the multi-wavelength data set, we derive a photometric redshift of z ≈ 6.0, which we confirm with a low signal-to-noise ratio spectrum of the afterglow. We find that a model with a constant-density environment provides a good fit to the afterglow data, with an inferred density of n ≲ 0.05 cm{sup –3}. The radio observations reveal the presence of a jet break at t {sub jet} ≈ 7 d, corresponding to a jet opening angle of θ{sub jet} ≈ 3°. The beaming-corrected γ-ray and kinetic energies are E {sub γ} ≈ E{sub K} ≈ 3 × 10{sup 50} erg. We quantify the uncertainties in our results using a detailed Markov Chain Monte Carlo analysis, which allows us to uncover degeneracies between the physical parameters of the explosion. To compare GRB 120521C to other high-redshift bursts in a uniform manner we re-fit all available afterglow data for the two other bursts at z ≳ 6 with radio detections (GRBs 050904 and 090423). We find a jet break at t {sub jet} ≈ 15 d for GRB 090423, in contrast to previous work. Based on these three events, we find that γ-ray bursts (GRBs) at z ≳ 6 appear to explode in constant-density environments, and exhibit a wide range of energies and densities that span the range inferred for lower redshift bursts. On the other hand, we find a hint for narrower jets in the z ≳ 6 bursts, potentially indicating a larger true event rate at these redshifts. Overall, our results indicate that long GRBs share a common progenitor population at least to z ∼ 8.

  1. GOODS-HERSCHEL: SEPARATING HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI AND STAR-FORMING GALAXIES USING INFRARED COLOR DIAGNOSTICS

    SciTech Connect

    Kirkpatrick, Allison; Pope, Alexandra; Charmandaris, Vassilis; Daddi, Emmanuele; Elbaz, David; Pannella, Maurilio; Aussel, Herve; Dasyra, Kalliopi; Leiton, Roger; Scott, Douglas; Magnelli, Benjamin; Popesso, Paola; Altieri, Bruno; Coia, Daniela; Valtchanov, Ivan; Dannerbauer, Helmut; Dickinson, Mark; Kartaltepe, Jeyhan; Magdis, Georgios

    2013-02-15

    We have compiled a large sample of 151 high-redshift (z = 0.5-4) galaxies selected at 24 {mu}m (S {sub 24} > 100 {mu}Jy) in the GOODS-N and ECDFS fields for which we have deep Spitzer IRS spectroscopy, allowing us to decompose the mid-infrared spectrum into contributions from star formation and activity in the galactic nuclei. In addition, we have a wealth of photometric data from Spitzer IRAC/MIPS and Herschel PACS/SPIRE. We explore how effective different infrared color combinations are at separating our mid-IR spectroscopically determined active galactic nuclei from our star-forming galaxies. We look in depth at existing IRAC color diagnostics, and we explore new color-color diagnostics combining mid-IR, far-IR, and near-IR photometry, since these combinations provide the most detail about the shape of a source's IR spectrum. An added benefit of using a color that combines far-IR and mid-IR photometry is that it is indicative of the power source driving the IR luminosity. For our data set, the optimal color selections are S {sub 250}/S {sub 24} versus S {sub 8}/S {sub 3.6} and S {sub 100}/S {sub 24} versus S {sub 8}/S {sub 3.6}; both diagnostics have {approx}10% contamination rate in the regions occupied primarily by star-forming galaxies and active galactic nuclei, respectively. Based on the low contamination rate, these two new IR color-color diagnostics are ideal for estimating both the mid-IR power source of a galaxy when spectroscopy is unavailable and the dominant power source contributing to the IR luminosity. In the absence of far-IR data, we present color diagnostics using the Wide-field Infrared Survey Explorer mid-IR bands which can efficiently select out high-z (z {approx} 2) star-forming galaxies.

  2. GALAXY EVOLUTION IN OVERDENSE ENVIRONMENTS AT HIGH REDSHIFT: PASSIVE EARLY-TYPE GALAXIES IN A CLUSTER AT z {approx} 2

    SciTech Connect

    Strazzullo, V.; Gobat, R.; Daddi, E.; Onodera, M.; Carollo, M.; Dickinson, M.; Renzini, A.; Arimoto, N.; Cimatti, A.; Finoguenov, A.; Chary, R.-R.

    2013-08-01

    We present a study of galaxy populations in the central region of the IRAC-selected, X-ray-detected galaxy cluster Cl J1449+0856 at z = 2. Based on a sample of spectroscopic and photometric cluster members, we investigate stellar populations and the morphological structure of cluster galaxies over an area of {approx}0.7 Mpc{sup 2} around the cluster core. The cluster stands out as a clear overdensity both in redshift space and in the spatial distribution of galaxies close to the center of the extended X-ray emission. The cluster core region (r < 200 kpc) shows a clearly enhanced passive fraction with respect to field levels. However, together with a population of massive, passive galaxies mostly with early-type morphologies, the cluster core also hosts massive, actively star-forming, often highly dust reddened sources. Close to the cluster center, a multi-component system of passive and star-forming galaxies could represent the future brightest cluster galaxy still forming. We observe a clear correlation between passive stellar populations and an early-type morphology, in agreement with field studies at similar redshift. Passive early-type galaxies in this cluster are typically a factor of 2-3 smaller than similarly massive early types at z {approx} 0. On the other hand, these same objects are on average larger by a factor of {approx}2 than field early-types at similar redshift, lending support to recent claims of an accelerated structural evolution in high-redshift dense environments. These results point toward the early formation of a population of massive galaxies, already evolved both in their structure and stellar populations, coexisting with still actively forming massive galaxies in the central regions of young clusters 10 billion years ago.

  3. How AGN and SN Feedback Affect Mass Transport and Black Hole Growth in High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Prieto, Joaquin; Escala, Andrés; Volonteri, Marta; Dubois, Yohan

    2017-02-01

    Using cosmological hydrodynamical simulations, we study the effect of supernova (SN) and active galactic nucleus (AGN) feedback on the mass transport (MT) of gas onto galactic nuclei and the black hole (BH) growth down to redshift z∼ 6. We study the BH growth in relation to the MT processes associated with gravity and pressure torques and how they are modified by feedback. Cosmological gas funneled through cold flows reaches the galactic outer region close to freefall. Then torques associated with pressure triggered by gas turbulent motions produced in the circumgalactic medium by shocks and explosions from SNe are the main source of MT beyond the central ∼100 pc. Due to high concentrations of mass in the central galactic region, gravitational torques tend to be more important at high redshift. The combined effect of almost freefalling material and both gravity and pressure torques produces a mass accretion rate of order ∼ 1 {M}ȯ yr‑1 at approximately parsec scales. In the absence of SN feedback, AGN feedback alone does not affect significantly either star formation or BH growth until the BH reaches a sufficiently high mass of ∼ {10}6 {M}ȯ to self-regulate. SN feedback alone, instead, decreases both stellar and BH growth. Finally, SN and AGN feedback in tandem efficiently quench the BH growth, while star formation remains at the levels set by SN feedback alone, due to the small final BH mass, ∼few times {10}5 {M}ȯ . SNe create a more rarefied and hot environment where energy injection from the central AGN can accelerate the gas further.

  4. Dark-ages Reionization and Galaxy formation simulation - I. The dynamical lives of high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Poole, Gregory B.; Angel, Paul W.; Mutch, Simon J.; Power, Chris; Duffy, Alan R.; Geil, Paul M.; Mesinger, Andrei; Wyithe, Stuart B.

    2016-07-01

    We present the Dark-ages Reionization and Galaxy formation Observables from Numerical Simulations (DRAGONS) programme and Tiamat, the collisionless N-body simulation programme upon which DRAGONS is built. The primary trait distinguishing Tiamat from other large simulation programme is its density of outputs at high redshift (100 from z = 35 to z = 5; roughly one every 10 Myr) enabling the construction of very accurate merger trees at an epoch when galaxy formation is rapid and mergers extremely frequent. We find that the friends-of-friends halo mass function agrees well with the prediction of Watson et al. at high masses, but deviates at low masses, perhaps due to our use of a different halo finder or perhaps indicating a break from `universal' behaviour. We then analyse the dynamical evolution of galaxies during the Epoch of Reionization finding that only a small fraction (˜20 per cent) of galactic haloes are relaxed. We illustrate this using standard relaxation metrics to establish two dynamical recovery time-scales: (i) haloes need ˜1.5 dynamical times following formation, and (ii) ˜2 dynamical times following a major (3:1) or minor (10:1) merger to be relaxed. This is remarkably consistent across a wide mass range. Lastly, we use a phase-space halo finder to illustrate that major mergers drive long-lived massive phase-space structures which take many dynamical times to dissipate. This can yield significant differences in the inferred mass build-up of galactic haloes and we suggest that care must be taken to ensure a physically meaningful match between the galaxy formation physics of semi-analytic models and the halo finders supplying their input.

  5. Measurements of the UV Nocturnal Atmospheric Background in the 300-400 nm Wavelength Band with the Experiment BaBy during a Transmediterranean Balloon Flight

    NASA Astrophysics Data System (ADS)

    Giarrusso, S.; Gugliotta, G.; Agnetta, G.; Assis, P.; Biondo, B.; Catalano, O.; Celi, F.; Cusumano, G.; D'Ali Staiti, G.; Raffaele, R.Di.; Espirito-Santo, M.C.; Gabriele, M.; Rosa, G.La; Maccarone, M.C.; Mangano, A.; Mineo, T.; Pimenta, M.; Russo, F.; Sacco, B.; Santangelo, A.; Scarsi, P.; Tome, B.

    2003-07-01

    We present new results of U V no cturnal atmospheric background measured with the balloon borne experiment BaBy that performed a trans-Mediterranean flight on July 11 2002. The experiment looked downwards from about 40 km of altitude the dark no cturnal atmosphere over the sea in a moonless night. It is composed of 8 filtered and collimated fast PMTs detecting the U V light in the 300-400 nm wavelength band and in the 3 narrow bands centered at the emission lines of the atmospheric Nitrogen molecules. Both single photon counting and charge integration methods are used in pairs of PMTs with the same filter. The background measured over the sea is about 300 photons m-2 sr-1 ns-1 in the 300-400 nm wavelength band. Introduction The Backround Bypass, BaBy, experiment is a scientific support activity to the evaluation of the sensitivity of EUSO [3], devoted to the observation of the Extreme Energy Cosmic Rays from space by detecting U V fluorescence light. One of the fundamental information in EUSO design is the U V no cturnal atmospheric background level whose main sources are: light pollution from cities, planes and ships, naturally occurring bioluminescence, lightning flashes, reflected moonlight and starlight, auroral flashes, low energy cosmic ray air showers and atmospheric chemical reactions. Since 1998, no cturnal atmospheric U V background measurements, in the wavelength interval (300-400 nm) relevant for EUSO, have been performed by

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  7. LMT imaging of the Extended Groth Strip: a search for the high-redshift tail of the sub-mm galaxy population

    NASA Astrophysics Data System (ADS)

    Aretxaga, Itziar

    2015-08-01

    The combination of short and long-wavelength deep (sub-)mm surveys can effectively be used to identify high-redshift sub-millimeter galaxies (z>4). Having star formation rates in excess of 500 Msun/yr, these bright (sub-)mm sources have been identified with the progenitors of massive elliptical galaxies undergoing rapid growth. With this purpose in mind, we are surveying a 20 sq. arcmin field within the Extended Groth Strip with the 1.1mm AzTEC camera mounted at the Large Millimeter Telescope that overlaps with the deep 450/850um SCUBA-2 Cosmology Legacy Survey and the CANDELS deep NIR imaging. The improved beamsize of the LMT (8”) over previous surveys aids the identification of the most prominent optical/IR counterparts. We discuss the high-redshift candidates found.

  8. Physical conditions of the interstellar medium of high-redshift, strongly lensed submillimetre galaxies from the Herschel-ATLAS

    NASA Astrophysics Data System (ADS)

    Valtchanov, I.; Virdee, J.; Ivison, R. J.; Swinyard, B.; van der Werf, P.; Rigopoulou, D.; da Cunha, E.; Lupu, R.; Benford, D. J.; Riechers, D.; Smail, Ian; Jarvis, M.; Pearson, C.; Gomez, H.; Hopwood, R.; Altieri, B.; Birkinshaw, M.; Coia, D.; Conversi, L.; Cooray, A.; de Zotti, G.; Dunne, L.; Frayer, D.; Leeuw, L.; Marston, A.; Negrello, M.; Portal, M. Sanchez; Scott, D.; Thompson, M. A.; Vaccari, M.; Baes, M.; Clements, D.; Michałowski, M. J.; Dannerbauer, H.; Serjeant, S.; Auld, R.; Buttiglione, S.; Cava, A.; Dariush, A.; Dye, S.; Eales, S.; Fritz, J.; Ibar, E.; Maddox, S.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Smith, D. J. B.; Temi, P.; Carpenter, J.; Bolatto, A.; Gurwell, M.; Vieira, J. D.

    2011-08-01

    We present Herschel-Spectral and Photometric Imaging Receiver (SPIRE) Fourier transform spectrometer (FTS) and radio follow-up observations of two Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS)-detected strongly lensed distant galaxies. In one of the targeted galaxies H-ATLAS J090311.6+003906 (SDP.81), we detect [O III] 88 μm and [C II] 158 μm lines at a signal-to-noise ratio of ˜5. We do not have any positive line identification in the other fainter target H-ATLAS J091305.0-005343 (SDP.130). Currently, SDP.81 is the faintest submillimetre galaxy with positive line detections with the FTS, with continuum flux just below 200 mJy in the 200-600 μm wavelength range. The derived redshift of SDP.81 from the two detections is z = 3.043 ± 0.012, in agreement with ground-based CO measurements. This is the first detection by Herschel of the [O III] 88 μm line in a galaxy at redshift higher than 0.05. Comparing the observed lines and line ratios with a grid of photodissociation region (PDR) models with different physical conditions, we derive the PDR cloud density n ≈ 2000 cm-3 and the far-ultraviolet ionizing radiation field G0≈ 200 (in units of the Habing field - the local Galactic interstellar radiation field of 1.6 × 10-6 W m-2). Using the CO-derived molecular mass and the PDR properties, we estimate the effective radius of the emitting region to be 500-700 pc. These characteristics are typical for star-forming, high-redshift galaxies. The radio observations indicate that SDP.81 deviates significantly from the local far-infrared/radio (FIR/radio) correlation, which hints that some fraction of the radio emission is coming from an active galactic nucleus (AGN). The constraints on the source size from millimetre-wave observations put a very conservative upper limit of the possible AGN contribution to less than 33 per cent. These indications, together with the high [O III]/FIR ratio and the upper limit of [O I] 63 μm/[C II] 158 μm, suggest that

  9. Properties of z ~ 3-6 Lyman break galaxies. II. Impact of nebular emission at high redshift

    NASA Astrophysics Data System (ADS)

    de Barros, S.; Schaerer, D.; Stark, D. P.

    2014-03-01

    Context. To gain insight on the mass assembly and place constraints on the star formation history (SFH) of Lyman break galaxies (LBGs), it is important to accurately determine their properties. Aims: We estimate how nebular emission and different SFHs affect parameter estimation of LBGs. Methods: We present a homogeneous, detailed analysis of the spectral energy distribution (SED) of ~1700 LBGs from the GOODS-MUSIC catalogue with deep multi-wavelength photometry from the U band to 8 μm to determine stellar mass, age, dust attenuation, and star formation rate. Using our SED fitting tool, which takes into account nebular emission, we explore a wide parameter space. We also explore a set of different star formation histories. Results: Nebular emission is found to significantly affect the determination of the physical parameters for the majority of z ~ 3-6 LBGs. We identify two populations of galaxies by determining the importance of the contribution of emission lines to broadband fluxes. We find that ~65% of LBGs show detectable signs of emission lines, whereas ~35% show weak or no emission lines. This distribution is found over the entire redshift range. We interpret these groups as actively star-forming and more quiescent LBGs, respectively. We find that it is necessary to considerer SED fits with very young ages (<50 Myr) to reproduce some colours affected by strong emission lines. Other arguments favouring episodic star formation and relatively short star formation timescales are also discussed. Considering nebular emission generally leads to a younger age, lower stellar mass, higher dust attenuation, higher star formation rate, and a large scatter in the SFR-M⋆ relation. Our analysis yields a trend of increasing specific star formation rate with redshift, as predicted by recent galaxy evolution models. Conclusions: The physical parameters of approximately two thirds of high redshift galaxies are significantly modified when we account for nebular emission. The

  10. The high-redshift gamma-ray burst GRB 140515A. A comprehensive X-ray and optical study

    NASA Astrophysics Data System (ADS)

    Melandri, A.; Bernardini, M. G.; D'Avanzo, P.; Sánchez-Ramírez, R.; Nappo, F.; Nava, L.; Japelj, J.; de Ugarte Postigo, A.; Oates, S.; Campana, S.; Covino, S.; D'Elia, V.; Ghirlanda, G.; Gafton, E.; Ghisellini, G.; Gnedin, N.; Goldoni, P.; Gorosabel, J.; Libbrecht, T.; Malesani, D.; Salvaterra, R.; Thöne, C. C.; Vergani, S. D.; Xu, D.; Tagliaferri, G.

    2015-09-01

    High-redshift gamma-ray bursts (GRBs) offer several advantages when studying the distant Universe, providing unique information about the structure and properties of the galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge of this kind of distant events. We present the multi-wavelength analysis of the high-zSwift GRB GRB 140515A (z = 6.327). The best estimate of the neutral hydrogen fraction of the intergalactic medium towards the burst is xHI ≤ 0.002. The spectral absorption lines detected for this event are the weakest lines ever observed in GRB afterglows, suggesting that GRB 140515A exploded in a very low-density environment. Its circum-burst medium is characterised by an average extinction (AV ~ 0.1) that seems to be typical of z ≥ 6 events. The observed multi-band light curves are explained either with a very hard injected spectrum (p = 1.7) or with a multi-component emission (p = 2.1). In the second case a long-lasting central engine activity is needed in order to explain the late time X-ray emission. The possible origin of GRB 140515A in a Pop III (or in a Pop II star with a local environment enriched by Pop III) massive star is unlikely. Based on observations collected at the European Southern Observatory, ESO, the VLT/Kueyen telescope, Paranal, Chile (proposal code: 093.A-0069), on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias (programme 49-008), and on observations made with the Italian 3.6-m Telescopio Nazionale Galileo (TNG), operated by the Fundación Galileo Galilei of the INAF (Instituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias (programme A26TAC_63).Appendix A is available in electronic form at

  11. High-energy properties of the high-redshift flat spectrum radio quasar PKS 2149-306

    NASA Astrophysics Data System (ADS)

    D'Ammando, F.; Orienti, M.

    2016-01-01

    We investigate the γ-ray and X-ray properties of the flat spectrum radio quasar PKS 2149-306 at redshift z = 2.345. A strong γ-ray flare from this source was detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope satellite in 2013 January, reaching on January 20 a daily peak flux of (301 ± 36) × 10-8 ph cm-2 s-1 in the 0.1-100 GeV energy range. This flux corresponds to an apparent isotropic luminosity of (1.5 ± 0.2) × 1050 erg s-1, comparable to the highest values observed by a blazar so far. During the flare the increase of flux was accompanied by a significant change of the spectral properties. Moreover significant flux variations on a 6-h time-scale were observed, compatible with the light crossing time of the event horizon of the central black hole. The broad-band X-ray spectra of PKS 2149-306 observed by Swift-XRT and NuSTAR are well described by a broken power-law model, with a very hard spectrum (Γ1 ˜ 1) below the break energy, at E break = 2.5-3.0 keV, and Γ2 ˜ 1.4-1.5 above the break energy. The steepening of the spectrum below ˜3 keV may indicate that the soft X-ray emission is produced by the low-energy relativistic electrons. This is in agreement with the small variability amplitude and the lack of spectral changes in that part of the X-ray spectrum observed between the two NuSTAR and Swift joint observations. As for the other high-redshift FSRQ detected by both Fermi-LAT and Swift-BAT, the photon index of PKS 2149-306 in hard X-ray is 1.6 or lower and the average γ-ray luminosity higher than 2 × 1048 erg s-1.

  12. Uv Imaging of Circumnuclear Starburst Rings

    NASA Astrophysics Data System (ADS)

    Colina, Luis

    1996-07-01

    We propose to obtain F218W WFPC images of a well defined sample of nearby galaxies with face-on circumnuclear starburst rings, and covering different levels of activity from pure starbursts to Seyfert 1 {AGNs}. These high resolution images will allow to generate for the first time an homogeneous database with the UV properties of about 60 individual circumnuclear star-forming knots. The use of the database will allow for the first time a direct and quantitative determination of basic ultraviolet properties of individual nuclear/circumnuclear star-forming knots, and of the entire starburst ring, such as: {a} their size and structure, {b} their UV luminosity function and, {c} their contribution to the UV energy output in composite AGN+starburst galaxies. The database will help in our understanding of high redshift blue galaxies, thought to be star-forming galaxies, where the flux detected in optical filters corresponds to flux emitted at UV {1500-3000Angstrom} rest frame wavelengths. The requested UV images will be combined with ROSAT/HRI images to characterize for the first time the high energy end, i.e. UV to soft X-rays, of circumnuclear starburst rings.

  13. HerMES: a search for high-redshift dusty galaxies in the HerMES Large Mode Survey - catalogue, number counts and early results

    NASA Astrophysics Data System (ADS)

    Asboth, V.; Conley, A.; Sayers, J.; Béthermin, M.; Chapman, S. C.; Clements, D. L.; Cooray, A.; Dannerbauer, H.; Farrah, D.; Glenn, J.; Golwala, S. R.; Halpern, M.; Ibar, E.; Ivison, R. J.; Maloney, P. R.; Marques-Chaves, R.; Martinez-Navajas, P. I.; Oliver, S. J.; Pérez-Fournon, I.; Riechers, D. A.; Rowan-Robinson, M.; Scott, Douglas; Siegel, S. R.; Vieira, J. D.; Viero, M.; Wang, L.; Wardlow, J.; Wheeler, J.

    2016-10-01

    Selecting sources with rising flux densities towards longer wavelengths from Herschel/Spectral and Photometric Imaging Receiver (SPIRE) maps is an efficient way to produce a catalogue rich in high-redshift (z > 4) dusty star-forming galaxies. The effectiveness of this approach has already been confirmed by spectroscopic follow-up observations, but the previously available catalogues made this way are limited by small survey areas. Here we apply a map-based search method to 274 deg2 of the Herschel Multi-tiered Extragalactic Survey (HerMES) Large Mode Survey and create a catalogue of 477 objects with SPIRE flux densities S500 > S350 > S250 and a 5σ cut-off S500 > 52 mJy. From this catalogue we determine that the total number of these `red' sources is at least an order of magnitude higher than predicted by galaxy evolution models. These results are in agreement with previous findings in smaller HerMES fields; however, due to our significantly larger sample size we are also able to investigate the shape of the red source counts for the first time. We have obtained spectroscopic redshift measurements for two of our sources using the Atacama Large Millimeter/submillimeter Array. The redshifts z = 5.1 and 3.8 confirm that with our selection method we can indeed find high-redshift dusty star-forming galaxies.

  14. Herschel-ATLAS Galaxy Counts and High-redshift Luminosity Functions: The Formation of Massive Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Lapi, A.; González-Nuevo, J.; Fan, L.; Bressan, A.; De Zotti, G.; Danese, L.; Negrello, M.; Dunne, L.; Eales, S.; Maddox, S.; Auld, R.; Baes, M.; Bonfield, D. G.; Buttiglione, S.; Cava, A.; Clements, D. L.; Cooray, A.; Dariush, A.; Dye, S.; Fritz, J.; Herranz, D.; Hopwood, R.; Ibar, E.; Ivison, R.; Jarvis, M. J.; Kaviraj, S.; López-Caniego, M.; Massardi, M.; Michałowski, M. J.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Serjeant, S.; Smith, D. J. B.; Temi, P.; Wardlow, J.; van der Werf, P.

    2011-11-01

    Exploiting the Herschel Astrophysical Terahertz Large Area Survey Science Demonstration Phase survey data, we have determined the luminosity functions (LFs) at rest-frame wavelengths of 100 and 250 μm and at several redshifts z >~ 1, for bright submillimeter galaxies with star formation rates (SFRs) >~ 100 M ⊙ yr-1. We find that the evolution of the comoving LF is strong up to z ≈ 2.5, and slows down at higher redshifts. From the LFs and the information on halo masses inferred from clustering analysis, we derived an average relation between SFR and halo mass (and its scatter). We also infer that the timescale of the main episode of dust-enshrouded star formation in massive halos (M H >~ 3 × 1012 M ⊙) amounts to ~7 × 108 yr. Given the SFRs, which are in the range of 102-103 M ⊙ yr-1, this timescale implies final stellar masses of the order of 1011-1012 M ⊙. The corresponding stellar mass function matches the observed mass function of passively evolving galaxies at z >~ 1. The comparison of the statistics for submillimeter and UV-selected galaxies suggests that the dust-free, UV bright phase is >~ 102 times shorter than the submillimeter bright phase, implying that the dust must form soon after the onset of star formation. Using a single reference spectral energy distribution (SED; the one of the z ≈ 2.3 galaxy SMM J2135-0102), our simple physical model is able to reproduce not only the LFs at different redshifts >1 but also the counts at wavelengths ranging from 250 μm to ≈1 mm. Owing to the steepness of the counts and their relatively broad frequency range, this result suggests that the dispersion of submillimeter SEDs of z > 1 galaxies around the reference one is rather small. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  15. Atomic data for S II—toward better diagnostics of chemical evolution in high-redshift galaxies

    SciTech Connect

    Kisielius, Romas; Bogdanovich, Pavel; Kulkarni, Varsha P.; Ferland, Gary J.; Lykins, Matt L.

    2014-01-01

    Absorption-line spectroscopy is a powerful tool used to estimate element abundances in both the nearby and distant universe. The accuracy of the abundances thus derived is naturally limited by the accuracy of the atomic data assumed for the spectral lines. We have recently started a project to perform new extensive atomic data calculations used for optical/UV spectral lines in the plasma modeling code Cloudy using state of the art quantal calculations. Here, we demonstrate our approach by focussing on S II, an ion used to estimate metallicities for Milky Way interstellar clouds as well as distant damped Lyman-alpha (DLA) and sub-DLA absorber galaxies detected in the spectra of quasars and gamma-ray bursts. We report new extensive calculations of a large number of energy levels of S II, and the line strengths of the resulting radiative transitions. Our calculations are based on the configuration interaction approach within a numerical Hartree-Fock framework, and utilize both non-relativistic and quasirelativistic one-electron radial orbitals. The results of these new atomic calculations are then incorporated into Cloudy and applied to a lab plasma, and a typical DLA, for illustrative purposes. The new results imply relatively modest changes (≈0.04 dex) to the metallicities estimated from S II in past studies. These results will be readily applicable to other studies of S II in the Milky Way and other galaxies.

  16. Extragalactic Backgrounds after Planck

    NASA Astrophysics Data System (ADS)

    Dore, Olivier

    Among the potentially most important results of cosmology in the last decade is the realization that the star formation rate at redshifts greater than 1 is higher than at present by about an order of magnitude, and that half of the energy produced since the surface of last scattering has been absorbed and reemitted by dust. Most of the light produced by stars at high redshifts thus reaches us in the far infrared. This radiation is referred to as the cosmic infrared background (CIB) and is emitted primarily by dusty, star-forming galaxies at redshift z=1-4. Embedded in far infrared emission of the CIB is the history of star formation, dust production, and the growth of large scale structures. Our research project aims at shedding new light on several extragalactic backgrounds investigated by NASA surveys, in light of recent observational progresses in mapping the CIB. Most lately, two new missions, Planck and Herschel, released ground-breaking measurements of the CIB. These measurements are an order of magnitude deeper and wider than previous ones, and they are literally revolutionizing the field. Our understanding of these data is now advanced enough for us to leverage our measurement of the CIB in Planck and Herschel, in order to extract new scientific insights from past missions. We propose to combine Planck and Herschel public data with archival data from WISE, GALEX, Chandra and Fermi. Not only original, the impact of our research project should be immediate. Using the CIB as a full sky, bright, high redshift reference extragalactic background, we will exploit the underlying physical connection among these various cosmological datasets. We expect new insights about the CIB, but also about the multiple extragalactic backgrounds probed in combination with it. In particular, we will investigate the cosmic star formation history at a period where it peaks, and because the clustering of matter is driven by dark matter, the measurement of the CIB clustering also

  17. Heating the intergalactic medium by X-rays from population III binaries in high-redshift galaxies

    SciTech Connect

    Xu, Hao; Norman, Michael L.; Ahn, Kyungjin; Wise, John H.; O'Shea, Brian W. E-mail: mlnorman@ucsd.edu E-mail: jwise@gatech.edu

    2014-08-20

    Due to their long mean free path, X-rays are expected to have an important impact on cosmic reionization by heating and ionizing the intergalactic medium (IGM) on large scales, especially after simulations have suggested that Population III (Pop III) stars may form in pairs at redshifts as high as 20-30. We use the Pop III distribution and evolution from a self-consistent cosmological radiation hydrodynamic simulation of the formation of the first galaxies and a simple Pop III X-ray binary model to estimate their X-ray output in a high-density region larger than 100 comoving (Mpc){sup 3}. We then combine three different methods—ray tracing, a one-zone model, and X-ray background modeling—to investigate the X-ray propagation, intensity distribution, and long-term effects on the IGM thermal and ionization state. The efficiency and morphology of photoheating and photoionization are dependent on the photon energies. The sub-kiloelectronvolt X-rays only impact the IGM near the sources, while the kiloelectronvolt photons contribute significantly to the X-ray background and heat and ionize the IGM smoothly. The X-rays just below 1 keV are most efficient in heating and ionizing the IGM. We find that the IGM might be heated to over 100 K by z = 10 and the high-density source region might reach 10{sup 4} K, limited by atomic hydrogen cooling. This may be important for predicting the 21 cm neutral hydrogen signals. On the other hand, the free electrons from X-ray ionizations are not enough to contribute significantly to the optical depth of the cosmic microwave background to the Thomson scattering.

  18. Heating the Intergalactic Medium by X-Rays from Population III Binaries in High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Ahn, Kyungjin; Wise, John H.; Norman, Michael L.; O'Shea, Brian W.

    2014-08-01

    Due to their long mean free path, X-rays are expected to have an important impact on cosmic reionization by heating and ionizing the intergalactic medium (IGM) on large scales, especially after simulations have suggested that Population III (Pop III) stars may form in pairs at redshifts as high as 20-30. We use the Pop III distribution and evolution from a self-consistent cosmological radiation hydrodynamic simulation of the formation of the first galaxies and a simple Pop III X-ray binary model to estimate their X-ray output in a high-density region larger than 100 comoving (Mpc)3. We then combine three different methods—ray tracing, a one-zone model, and X-ray background modeling—to investigate the X-ray propagation, intensity distribution, and long-term effects on the IGM thermal and ionization state. The efficiency and morphology of photoheating and photoionization are dependent on the photon energies. The sub-kiloelectronvolt X-rays only impact the IGM near the sources, while the kiloelectronvolt photons contribute significantly to the X-ray background and heat and ionize the IGM smoothly. The X-rays just below 1 keV are most efficient in heating and ionizing the IGM. We find that the IGM might be heated to over 100 K by z = 10 and the high-density source region might reach 104 K, limited by atomic hydrogen cooling. This may be important for predicting the 21 cm neutral hydrogen signals. On the other hand, the free electrons from X-ray ionizations are not enough to contribute significantly to the optical depth of the cosmic microwave background to the Thomson scattering.

  19. A Giant Metrewave Radio Telescope search for associated H I 21 cm absorption in high-redshift flat-spectrum sources

    NASA Astrophysics Data System (ADS)

    Aditya, J. N. H. S.; Kanekar, Nissim; Kurapati, Sushma

    2016-02-01

    We report results from a Giant Metrewave Radio Telescope search for `associated' redshifted H I 21 cm absorption from 24 active galactic nuclei (AGNs), at 1.1 < z < 3.6, selected from the Caltech-Jodrell Bank Flat-spectrum (CJF) sample. 22 out of 23 sources with usable data showed no evidence of absorption, with typical 3σ optical depth detection limits of ≈0.01 at a velocity resolution of ≈30 km s-1. A single tentative absorption detection was obtained at z ≈ 3.530 towards TXS 0604+728. If confirmed, this would be the highest redshift at which H I 21 cm absorption has ever been detected. Including 29 CJF sources with searches for redshifted H I 21 cm absorption in the literature, mostly at z < 1, we construct a sample of 52 uniformly selected flat-spectrum sources. A Peto-Prentice two-sample test for censored data finds (at ≈3σ significance) that the strength of H I 21 cm absorption is weaker in the high-z sample than in the low-z sample; this is the first statistically significant evidence for redshift evolution in the strength of H I 21 cm absorption in a uniformly selected AGN sample. However, the two-sample test also finds that the H I 21 cm absorption strength is higher in AGNs with low ultraviolet or radio luminosities, at ≈3.4σ significance. The fact that the higher luminosity AGNs of the sample typically lie at high redshifts implies that it is currently not possible to break the degeneracy between AGN luminosity and redshift evolution as the primary cause of the low H I 21 cm opacities in high-redshift, high-luminosity AGNs.

  20. Constraining the population of radio-loud active galactic nuclei at high redshift with the power spectrum of the 21 cm Forest

    NASA Astrophysics Data System (ADS)

    Ewall-Wice, Aaron; Dillon, Joshua S.; Mesinger, Andrei; Hewitt, Jacqueline N.

    2014-06-01

    The 21 cm forest, the absorption by the intergalactic medium (IGM) towards a high redshift radio-loud source, is a probe of the thermal state of the IGM. To date, the literature has focused on line-of-sight spectral studies of a single quasar known to have a large redshift. We instead examine many sources in a wide field of view, and show that the imprint from the 21 cm forest absorption of these sources is detectible in the power spectrum. The properties of the power spectrum can reveal information on the population of the earliest radio loud sources that may have existed during the pre-reionization epoch at z>10.Using semi-numerical simulations of the IGM and a semi-empirical source population, we show that the 21 cm forest dominates, in a distinctive region of Fourier space, the brightness temperature power spectrum that many contemporary experiments aim to measure. In particular, the forest dominates the diffuse emission on smaller spatial scales along the line of sight. Exploiting this separation, one may constrain the IGM thermal history, such as heating by the first X-ray sources, on large spatial scales and the absorption of radio loud active galactic nuclei on small ones.Using realistic simulations of noise and foregrounds, we show that planned instruments on the scale of the Hydrogen Epoch of Reionization Array (HERA) with a collecting area of one tenth of a square kilometer can detect the 21cm forest in this small spatial scale region with high signal to noise. We develop an analytic toy model for the signal and explore its detectability over a large range of thermal histories and potential high redshift source scenarios.

  1. Modelling UV sky for future UV missions

    NASA Astrophysics Data System (ADS)

    Sreejith, A. G.; Safanova, M.; Mohan, R.; Murthy, Jayant

    Software simulators are now widely used in all areas of science, especially in application to astronomical missions: from instrument design to mission planning, and to data interpretation. We present a simulator to model the diffuse ultraviolet sky, where the different contributors are separately calculated and added together to produce a sky image of the size specified by the instrument requirements. Each of the contributors to the background, instrumental dark current, airglow, zodiacal light and diffuse galactic light, is dependent on various factors. Airglow is dependent on the time of day, zodiacal light on the time of year, angle from the Sun and from the ecliptic, and diffuse UV emission depends on the look direction. To provide a full description of any line of sight, we have also added stars. The diffuse UV background light can dominate in many areas of the sky and severely impact space telescopes viewing directions due to over brightness. The simulator, available as a downloadable package and as a simple web-based tool, can be applied to separate missions and instruments. For demonstration, we present the example used for two UV missions: the UVIT instrument on the Indian ASTROSAT mission to be launched in the next year and a prospective wide-field mission to search for transients in the UV.

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

    NASA Technical Reports Server (NTRS)

    Chen, Andrew; Ritz, Steven

    1999-01-01

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

  3. UV spectroscopy of young star clusters

    NASA Astrophysics Data System (ADS)

    Maraston, Claudia

    We propose to take spectra of young star clusters (t < 1 Gyr) in the Magellanic Clouds. These data will serve to improve and extend the calibration of the UV spectral index system for stellar population models, which we have built with IUE spectra from the data bases of Fanelli et al. (1992) and Cassatella et al. (1987). We have developed evolutionary population synthesis models of the most relevant absorption features of stellar systems with ages in the range 1 Myr to 1 Gyr, covering the most important elements including C, Si, Fe and Mg (Nieves & Maraston 2004). The new data will allow the calibration of these spectral indices for different chemical abundances and ages. The calibrated stellar population models will provide an important tool to interpret spectra of high redshift galaxies

  4. A cosmic web filament revealed in Lyman-α emission around a luminous high-redshift quasar.

    PubMed

    Cantalupo, Sebastiano; Arrigoni-Battaia, Fabrizio; Prochaska, J Xavier; Hennawi, Joseph F; Madau, Piero

    2014-02-06

    Simulations of structure formation in the Universe predict that galaxies are embedded in a 'cosmic web', where most baryons reside as rarefied and highly ionized gas. This material has been studied for decades in absorption against background sources, but the sparseness of these inherently one-dimensional probes preclude direct constraints on the three-dimensional morphology of the underlying web. Here we report observations of a cosmic web filament in Lyman-α emission, discovered during a survey for cosmic gas fluorescently illuminated by bright quasars at redshift z ≈ 2.3. With a linear projected size of approximately 460 physical kiloparsecs, the Lyman-α emission surrounding the radio-quiet quasar UM 287 extends well beyond the virial radius of any plausible associated dark-matter halo and therefore traces intergalactic gas. The estimated cold gas mass of the filament from the observed emission-about 10(12.0 ± 0.5)/C(1/2) solar masses, where C is the gas clumping factor-is more than ten times larger than what is typically found in cosmological simulations, suggesting that a population of intergalactic gas clumps with subkiloparsec sizes may be missing in current numerical models.

  5. Structure formation simulations with momentum exchange: alleviating tensions between high-redshift and low-redshift cosmological probes

    NASA Astrophysics Data System (ADS)

    Baldi, Marco; Simpson, Fergus

    2017-02-01

    Persisting tensions between the cosmological constraints derived from low-redshift probes and the ones obtained from temperature and polarization anisotropies of the cosmic microwave background (CMB) - although not yet providing compelling evidence against the Λcold dark matter model - seem to consistently indicate a slower growth of density perturbations as compared to the predictions of the standard cosmological scenario. Such behaviour is not easily accommodated by the simplest extensions of General Relativity, such as f(R) models, which generically predict an enhanced growth rate. In this work, we present the outcomes of a suite of large N-body simulations carried out in the context of a cosmological model featuring a non-vanishing scattering cross-section between the dark matter and the dark energy fields, for two different parametrizations of the dark energy equation of state. Our results indicate that these dark scattering models have very mild effects on many observables related to large-scale structures formation and evolution, while providing a significant suppression of the amplitude of linear density perturbations and the abundance of massive clusters. Our simulations therefore confirm that these models offer a promising route to alleviate existing tensions between low-redshift measurements and those of the CMB.

  6. Supermassive black hole pairs in clumpy galaxies at high redshift: delayed binary formation and concurrent mass growth

    NASA Astrophysics Data System (ADS)

    Tamburello, Valentina; Capelo, Pedro R.; Mayer, Lucio; Bellovary, Jillian M.; Wadsley, James W.

    2017-01-01

    Massive gas-rich galaxy discs at z ˜ 1-3 host massive star-forming clumps with typical baryonic masses in the range 107-108 M⊙ which can affect the orbital decay and concurrent growth of supermassive black hole (BH) pairs. Using a set of high-resolution simulations of isolated clumpy galaxies hosting a pair of unequal-mass BHs, we study the interaction between massive clumps and a BH pair at kiloparsec scales, during the early phase of the orbital decay. We find that both the interaction with massive clumps and the heating of the cold gas layer of the disc by BH feedback tend to delay significantly the orbital decay of the secondary, which in many cases is ejected and then hovers for a whole gigayear around a separation of 1-2 kpc. In the envelope, dynamical friction is weak and there is no contribution of disc torques: these lead to the fastest decay once the orbit of the secondary BH has circularized in the disc mid-plane. In runs with larger eccentricities the delay is stronger, although there are some exceptions. We also show that, even in discs with very sporadic transient clump formation, a strong spiral pattern affects the decay time-scale for BHs on eccentric orbits. We conclude that, contrary to previous belief, a gas-rich background is not necessarily conducive to a fast BH decay and binary formation, which prompts more extensive investigations aimed at calibrating event-rate forecasts for ongoing and future gravitational-wave searches, such as with Pulsar Timing Arrays and the future evolved Laser Interferometer Space Antenna.

  7. 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

  8. The KMOS AGN Survey at High redshift (KASHz): the prevalence and drivers of ionized outflows in the host galaxies of X-ray AGN

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    We present the first results from the KMOS (K-band Multi-Object Spectrograph) AGN (active galactic nuclei) Survey at High redshift (KASHz), a VLT/KMOS integral-field spectroscopic (IFS) survey of z ≳ 0.6 AGN. We present galaxy-integrated spectra of 89 X-ray AGN (L2-10 keV = 1042-1045 erg s-1), for which we observed [O III] (z ≈ 1.1-1.7) or Hα emission (z ≈ 0.6-1.1). The targets have X-ray luminosities representative of the parent AGN population and we explore the emission-line luminosities as a function of X-ray luminosity. For the [O III] targets, ≈50 per cent have ionized gas velocities indicative of gas that is dominated by outflows and/or highly turbulent material (i.e. overall line widths ≳600 km s-1). The most luminous half (i.e. LX > 6 × 1043 erg s-1) have a ≳2 times higher incidence of such velocities. On the basis of our results, we find no evidence that X-ray obscured AGN are more likely to host extreme kinematics than unobscured AGN. Our KASHz sample has a distribution of gas velocities that is consistent with a luminosity-matched sample of z < 0.4 AGN. This implies little evolution in the prevalence of ionized outflows, for a fixed AGN luminosity, despite an order-of-magnitude decrease in average star formation rates over this redshift range. Furthermore, we compare our Hα targets to a redshift-matched sample of star-forming galaxies and despite a similar distribution of Hα luminosities and likely star formation rates, we find extreme ionized gas velocities are up to ≈10 times more prevalent in the AGN-host galaxies. Our results reveal a high prevalence of extreme ionized gas velocities in high-luminosity X-ray AGN and imply that the most powerful ionized outflows in high-redshift galaxies are driven by AGN activity.

  9. Predicting UV sky for future UV missions

    NASA Astrophysics Data System (ADS)

    Safonova, M.; Mohan, R.; Sreejith, A. G.; Murthy, Jayant

    2013-02-01

    Software simulators are now widely used in all areas of science, especially in application to astronomical missions: from instrument design to mission planning, and to data interpretation. We present a simulator to model the diffuse ultraviolet sky, where the different contributors are separately calculated and added together to produce a sky image of the size specified by the instrument requirements. Each of the contributors to the background, instrumental dark current, airglow, zodiacal light and diffuse Galactic light, depends on different factors. Airglow is dependent on the time of day; zodiacal light depends on the time of year, angle from the Sun and from the ecliptic; diffuse UV emission depends on the line of sight. To provide a full description of the sky along any line of sight, we have also added stars. The UV background light can dominate in many areas of the sky and severely limit viewing directions due to overbrightness. The simulator, available as a downloadable package and as a web-based tool, can be applied to preparation of real space missions and instruments. For demonstration, we present the example use for the two near-future UV missions: UVIT instrument on the Indian Astrosat mission and a new proposed wide-field (∼1000 square degrees) transient explorer satellite.

  10. Uv Throughput

    NASA Astrophysics Data System (ADS)

    Casertano, Stefano

    1995-07-01

    GRW+70d5824 is observed shortly before and after a DECON through all the UV filters in each chip and through F160BW crossed with F130LP, F185LP, and F165LP (where applicable) to determine the wavelength dependence of the throughput across the bandpass (hence color terms). Based on no particular cycle 4 program, this program is designed to better characterize the spectral response curve in the UV, and the spectral shape introduced by the contamination. Overall discrepencies between the updated synthetic photometric products and the results of this test should be 1-2% rms. This does not mean that the UV throughput will be known to this accuracy primarily because of uncertainties in the flux calibration of the standard used (5%) uncertainties in the UV flatfields (maybe 3% near the chip center), and time dependent contamination corrections (3% error), and uncertainties in the CTE correction (2%). The derived UV absolute photometry accuracy at the center of the chips should therefore be about 10%. After pipeline processing, each image will be reduced by aperture photometry. The throughput curves and their normalizations can be updated by trial and error. Expected to run 8/95. NOTE: crossed filters exposures should be observed in ALL chips after decontamination, but just in WF3 before decontamination.

  11. UV Throughput

    NASA Astrophysics Data System (ADS)

    Baggett, Sylvia

    1996-07-01

    This proposal has 2 main sections: 1} GRW+70d5824 is observed shortly before and after a DECON through all the UV filters in each chip and through F160BW crossed with F130LP, F185LP, and F165LP {where applicable}. 2} BD+75D325 is observed in a subset of chips and uv filters {including Lyman alpha}, shortly before and after a Decon; to be done before SMOV. These observations will be used to determine the wavelength dependence of the throughput across the bandpass {hence color terms}. Based on the Cycle 5 UV Throughput proposal {6186} and the Cycle 4 Lyman alpha throughput proposal {5778}, this program is designed to better characterize the spectral response curve in the UV, and the spectral shape introduced by the contamination as well as provide baseline measurements in preparation for SMOV 1997. The Lyman alpha observations will provide a measure of possible contamination on the pickoff mirror. The UV throughput should be measured to better than 3%. Accuracy in the Lyman alpha throughput is expected to be between 5% and 10%, due to the residual uncertainty of the red leak correction determined from observations of F122M crossed with F130LP. Results will be presented at TIPS, in WFPC2 ISR, and used to update SYNPHOT tables if necessary. NOTE: crossed filters exposures should be observed in ALL chips after decontamination, but just in WF3 before decontamination.

  12. Star formation and obscuration in AGN: A sub-mm study of high-redshift mid-IR selected type-2 QSOs

    NASA Astrophysics Data System (ADS)

    Violino, Giulio; Stevens, Jason; Coppin, Kristen; Geach, James

    2016-08-01

    The AGN unification model describes unobscured and obscured AGN (AGN1 and AGN2) as identical sources, with their different observed properties explained solely by orientation effects; as a result, it predicts no difference in the host galaxies. As an alternative, a second scenario has been proposed in which type-2 AGN represent an earlier stage in the life of AGN characterized by dust-enshrouded host galaxies which contribute to the obscuration and higher star formation activity, at least at earlier epochs. To test this scenario we employ Herschel data at three different wavelengths (250, 350, 500 um) to study the far-IR-to-submm properties of a sample of mid-IR selected type 2 QSOs at high redshift (1.5

  13. Mid-UV HST Imaging of Nearby Late-Type, Irregular, and Peculiar Galaxies

    NASA Astrophysics Data System (ADS)

    Taylor, V. A.; Windhorst, R. A.; Chiarenza, C. A. T.; Odewahn, S. C.; Conselice, C. J.; MacKenty, J.; de Jong, R. S.; de Grijs, R.; Eskridge, P. B.; Frogel, J. A.; Gallagher, J. S.; Kobulnicky, H.; Hibbard, J. E.; Matthews, L. D.; O'Connell, R. W.

    2000-12-01

    Distant galaxies observed by HST appear to have primarily late-type, irregular, or peculiar morphologies. However, because of their high redshift they are observed in their restframe mid-UV. Nearby galaxies can look dramatically different in the rest-frame mid- and far-UV. We must therefore ask if these high redshift morphologies are due to real evolutionary effects or band-pass shifting and surface brightness dimming at high redshift. To address this, we have conducted a survey with HST of 37 nearby galaxies of various Hubble types and inclinations in two mid-UV bands. Most of these galaxies have supporting ground based data in UBVRJHK. A comparison of the photometric properties of these galaxies in these different band-passes will lead to a better ability to separate true evolutionary effects from the morphological K-correction. We will present and discuss preliminary results from the HST survey and ground-based observations in UBVR. Our preliminary results suggest that the late-types imaged so far are a heterogeneous mixture. More than half of the few irregulars/peculiars/mergers show a mid-UV F300W morphology that is similar to I-band F814W, but with important differences due to recognizable dust-lanes blocking out UV light, star-formation ``ridges,'' and hot stars or star-clusters that are mostly visible in F300W but not in F814W. Others yield significantly different classifications in F300W and F814W. We acknowledge NASA grant GO-8645.01-99A from STScI and the NASA Space Grant. This project is based on observations with the VATT: the Alice P. Lennon Telescope and the Thomas J. Bannan Astrophysics Facility.

  14. Cosmology from High Redshift Supernovae

    NASA Astrophysics Data System (ADS)

    Garnavich, Peter

    The discovery of a correlation between the light curve shape and intrinsic b rightness has made Type Ia supernovae exceptionally accurate distance indicators out to cosmologically interesting redshifts. Ground-based searches and follow-up as well as Hubble S pace Telescope observations of Type Ia supernovae have produced a significant number of object s with redshifts between 0.3 and 1.0. The distant SNe, when combined with a local samp le analyzed in the same way, provide reliable constraints on the deceleration and age of th e Universe. Early this year, an analysis of a handful of Type Ia events indicated that the deceleration was too small for gravitating matter alone to make a flat Universe. A larger sa mple of supernovae gives the surprising result that the Universe is accelerating, implying the exi stence of a cosmological constant or some other exotic form of energy. The success of this research has depended on the development of algorithms and software to register, scale and subtract CCD images taken weeks apart and to search for var iable objects. A good fraction of the point-sources identified are asteroids, variable stars, or AGN, so spectra are needed to confirm the identification as a Type Ia supernova and obt ain a redshift. The best candidates are followed photometrically to construct light curves. The steps to transform the observed light curves into cosmologically interestin g results will also be described.

  15. X-ray emission from high-redshift miniquasars: self-regulating the population of massive black holes through global warming

    NASA Astrophysics Data System (ADS)

    Tanaka, Takamitsu; Perna, Rosalba; Haiman, Zoltán.

    2012-10-01

    Observations of high-redshift quasars at z ≳6 imply that supermassive black holes (SMBHs) with masses M≳109 M were in place less than 1 Gyr after the big bang. If these SMBHs assembled from 'seed' BHs left behind by the first stars, then they must have accreted gas at close to the Eddington limit during a large fraction (>rsim 50 per cent) of the time. A generic problem with this scenario, however, is that the mass density in M ˜ 106 M⊙ SMBHs at z ˜ 6 already exceeds the locally observed SMBH mass density by several orders of magnitude; in order to avoid this overproduction, BH seed formation and growth must become significantly less efficient in less massive protogalaxies through some form of feedback, while proceeding unabated in the most massive galaxies that formed first. Using Monte Carlo realizations of the merger and growth history of BHs, we show that X-rays from the earliest accreting BHs can provide such a feedback mechanism, on a global scale. Our calculations paint a self-consistent picture of BH-made climate change, in which the first miniquasars - among them the ancestors of the z ˜ 6 quasar SMBHs - globally warm the intergalactic medium and suppress the formation and growth of subsequent generations of BHs. We present two specific models with global miniquasar feedback that provide excellent agreement with recent estimates of the z = 6 SMBH mass function. For each of these models, we estimate the rate of BH mergers at z > 6 that could be detected by the proposed gravitational-wave observatory eLISA/NGO.

  16. HIGH-REDSHIFT COOL-CORE GALAXY CLUSTERS DETECTED VIA THE SUNYAEV-ZEL'DOVICH EFFECT IN THE SOUTH POLE TELESCOPE SURVEY

    SciTech Connect

    Semler, D. R.; Suhada, R.; Bazin, G.; Bocquet, S.; Desai, S.; Aird, K. A.; Ashby, M. L. N.; Bayliss, M.; Bautz, M.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Brodwin, M.; Cho, H. M.; Clocchiatti, A.; De Haan, T.; Dobbs, M. A.; and others

    2012-12-20

    We report the first investigation of cool-core properties of galaxy clusters selected via their Sunyaev-Zel'dovich (SZ) effect. We use 13 galaxy clusters uniformly selected from 178 deg{sup 2} observed with the South Pole Telescope (SPT) and followed up by the Chandra X-ray Observatory. They form an approximately mass-limited sample (>3 Multiplication-Sign 10{sup 14} M{sub Sun} h {sup -1}{sub 70}) spanning redshifts 0.3 < z < 1.1. Using previously published X-ray-selected cluster samples, we compare two proxies of cool-core strength: surface brightness concentration (c{sub SB}) and cuspiness ({alpha}). We find that c{sub SB} is better constrained. We measure c{sub SB} for the SPT sample and find several new z > 0.5 cool-core clusters, including two strong cool cores. This rules out the hypothesis that there are no z > 0.5 clusters that qualify as strong cool cores at the 5.4{sigma} level. The fraction of strong cool-core clusters in the SPT sample in this redshift regime is between 7% and 56% (95% confidence). Although the SPT selection function is significantly different from the X-ray samples, the high-z c{sub SB} distribution for the SPT sample is statistically consistent with that of X-ray-selected samples at both low and high redshifts. The cool-core strength is inversely correlated with the offset between the brightest cluster galaxy and the X-ray centroid, providing evidence that the dynamical state affects the cool-core strength of the cluster. Larger SZ-selected samples will be crucial in understanding the evolution of cluster cool cores over cosmic time.

  17. The Star Formation History of BCGs to z = 1.8 from the SpARCS/SWIRE Survey: Evidence for Significant In Situ Star Formation at High Redshift

    NASA Astrophysics Data System (ADS)

    Webb, Tracy M. A.; Muzzin, Adam; Noble, Allison; Bonaventura, Nina; Geach, James; Hezevah, Yashar; Lidman, Chris; Wilson, Gillian; Yee, H. K. C.; Surace, Jason; Shupe, David

    2015-12-01

    We present the results of an MIPS-24 μm study of the brightest cluster galaxies (BCGs) of 535 high-redshift galaxy clusters. The clusters are drawn from the Spitzer Adaptation of the Red-Sequence Cluster Survey, which effectively provides a sample selected on total stellar mass, over 0.2 < z < 1.8 within the Spitzer Wide-Area Infrared Extragalactic (SWIRE) Survey fields. Twenty percent, or 106 clusters, have spectroscopically confirmed redshifts, and the rest have redshifts estimated from the color of their red sequence. A comparison with the public SWIRE images detects 125 individual BCGs at 24 μm ≳ 100 μJy, or 23%. The luminosity-limited detection rate of BCGs in similar richness clusters (Ngal > 12) increases rapidly with redshift. Above z ∼ 1, an average of ∼20% of the sample have 24 μm inferred infrared luminosities of LIR > 1012 L⊙, while the fraction below z ∼ 1 exhibiting such luminosities is <1%. The Spitzer-IRAC colors indicate the bulk of the 24 μm detected population is predominantly powered by star formation, with only 7/125 galaxies lying within the color region inhabited by active galactic nuclei (AGNs). Simple arguments limit the star formation activity to several hundred million years and this may therefore be indicative of the timescale for AGN feedback to halt the star formation. Below redshift z ∼ 1, there is not enough star formation to significantly contribute to the overall stellar mass of the BCG population, and therefore BCG growth is likely dominated by dry mergers. Above z ∼ 1, however, the inferred star formation would double the stellar mass of the BCGs and is comparable to the mass assembly predicted by simulations through dry mergers. We cannot yet constrain the process driving the star formation for the overall sample, though a single object studied in detail is consistent with a gas-rich merger.

  18. Star Formation Quenching in High-redshift Large-scale Structure: Post-starburst Galaxies in the Cl 1604 Supercluster at z ~ 0.9

    NASA Astrophysics Data System (ADS)

    Wu, Po-Feng; Gal, Roy R.; Lemaux, Brian C.; Kocevski, Dale D.; Lubin, Lori M.; Rumbaugh, Nicholas; Squires, Gordon K.

    2014-09-01

    The Cl 1604 supercluster at z ~ 0.9 is one of the most extensively studied high-redshift large-scale structures, with more than 500 spectroscopically confirmed members. It consists of eight clusters and groups, with members numbering from a dozen to nearly a hundred, providing a broad range of environments for investigating the large-scale environmental effects on galaxy evolution. Here we examine the properties of 48 post-starburst galaxies in Cl 1604, comparing them to other galaxy populations in the same supercluster. Incorporating photometry from ground-based optical and near-infrared imaging, along with Spitzer mid-infrared observations, we derive stellar masses for all Cl 1604 members. The colors and stellar masses of the K+A galaxies support the idea that they are progenitors of red sequence galaxies. Their morphologies, residual star formation rates, and spatial distributions suggest that galaxy mergers may be the principal mechanism producing post-starburst galaxies. Interaction between galaxies and the dense intracluster medium (ICM) is also effective, but only in the cores of dynamically evolved clusters. The prevalence of post-starburst galaxies in clusters correlates with the dynamical state of the host cluster, as both galaxy mergers and the dense ICM produce post-starburst galaxies. We also investigate the incompleteness and contamination of K+A samples selected by means of Hδ and [O II] equivalent widths. K+A samples may be up to ~50% incomplete due to the presence of LINERs/Seyferts, and up to ~30% of K+A galaxies could have substantial star formation activity.

  19. Star formation quenching in high-redshift large-scale structure: post-starburst galaxies in the Cl 1604 supercluster at z ∼ 0.9

    SciTech Connect

    Wu, Po-Feng; Gal, Roy R.; Lemaux, Brian C.; Kocevski, Dale D.; Lubin, Lori M.; Rumbaugh, Nicholas; Squires, Gordon K.

    2014-09-01

    The Cl 1604 supercluster at z ∼ 0.9 is one of the most extensively studied high-redshift large-scale structures, with more than 500 spectroscopically confirmed members. It consists of eight clusters and groups, with members numbering from a dozen to nearly a hundred, providing a broad range of environments for investigating the large-scale environmental effects on galaxy evolution. Here we examine the properties of 48 post-starburst galaxies in Cl 1604, comparing them to other galaxy populations in the same supercluster. Incorporating photometry from ground-based optical and near-infrared imaging, along with Spitzer mid-infrared observations, we derive stellar masses for all Cl 1604 members. The colors and stellar masses of the K+A galaxies support the idea that they are progenitors of red sequence galaxies. Their morphologies, residual star formation rates, and spatial distributions suggest that galaxy mergers may be the principal mechanism producing post-starburst galaxies. Interaction between galaxies and the dense intracluster medium (ICM) is also effective, but only in the cores of dynamically evolved clusters. The prevalence of post-starburst galaxies in clusters correlates with the dynamical state of the host cluster, as both galaxy mergers and the dense ICM produce post-starburst galaxies. We also investigate the incompleteness and contamination of K+A samples selected by means of Hδ and [O II] equivalent widths. K+A samples may be up to ∼50% incomplete due to the presence of LINERs/Seyferts, and up to ∼30% of K+A galaxies could have substantial star formation activity.

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

    SciTech Connect

    Schrabback, T.; et al.

    2016-11-11

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

  1. COMPLETE IONIZATION OF THE NEUTRAL GAS: WHY THERE ARE SO FEW DETECTIONS OF 21 cm HYDROGEN IN HIGH-REDSHIFT RADIO GALAXIES AND QUASARS

    SciTech Connect

    Curran, S. J.; Whiting, M. T.

    2012-11-10

    From the first published z {approx}> 3 survey of 21 cm absorption within the hosts of radio galaxies and quasars, Curran et al. found an apparent dearth of cool neutral gas at high redshift. From a detailed analysis of the photometry, each object is found to have a {lambda} = 1216 A continuum luminosity in excess of L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}, a critical value above which 21 cm has never been detected at any redshift. At these wavelengths, and below, hydrogen is excited above the ground state so that it cannot absorb in 21 cm. In order to apply the equation of photoionization equilibrium, we demonstrate that this critical value also applies to the ionizing ({lambda} {<=} 912 A) radiation. We use this to show, for a variety of gas density distributions, that upon placing a quasar within a galaxy of gas, there is always an ultraviolet luminosity above which all of the large-scale atomic gas is ionized. While in this state, the hydrogen cannot be detected or engage in star formation. Applying the mean ionizing photon rate of all of the sources searched, we find, using canonical values for the gas density and recombination rate coefficient, that the observed critical luminosity gives a scale length (3 kpc) similar that of the neutral hydrogen (H I) in the Milky Way, a large spiral galaxy. Thus, this simple yet physically motivated model can explain the critical luminosity (L {sub 912} {approx} L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}), above which neutral gas is not detected. This indicates that the non-detection of 21 cm absorption is not due to the sensitivity limits of current radio telescopes, but rather that the lines of sight to the quasars, and probably the bulk of the host galaxies, are devoid of neutral gas.

  2. First Detections of the [NII] 122 Micrometer Line at High Redshift: Demonstrating the Utility of the Line for Studying Galaxies in the Early Universe

    NASA Technical Reports Server (NTRS)

    Ferkinhoff, Carl; Brisbin, Drew; Nikola, Thomas; Parshley, Stephen C.; Stacey, Gordon J.; Phillips, Thomas G.; Falgarone, Edith; Benford, Dominic J.; Staguhn, Johannes G.; Tucker, Carol E.

    2011-01-01

    We report the first detections of the [NIl] 122 {\\mu} m line from a high redshift galaxy. The line was strongly (> 6{\\sigma}) detected from SMMJ02399-0136, and HI413+ 117 (the Cloverleaf QSO) using the Redshift(z) and Early Universe Spectrometer (ZEUS) on the CSO. The lines from both sources are quite bright with line-to-FIR continuum luminosity ratios that are approx.7.0x10(exp -4) (Cloverleaf) and 2.1x10(exp -3) (SMMJ02399). With ratios 2-10 times larger than the average value for nearby galaxies, neither source exhibits the line-to-continuum deficits seen in nearby sources. The line strengths also indicate large ionized gas fractions, approx.8 to 17% of the molecular gas mass. The [OIII]/[NII] line ratio is very sensitive to the effective temperature of ionizing stars and the ionization parameter for emission arising in the narrow-line region (NLR) of an AGN. Using our previous detection of the [01II] 88 {\\mu}m line, the [OIII]/ [NIl] line ratio for SMMJ02399-0136 indicates the dominant source of the line emission is either stellar HII regions ionized by 09.5 stars, or the NLR of the AGN with ionization parameter 10g(U) = -3.3 to -4.0. A composite system, where 30 to 50% of the FIR lines arise in the NLR also matches the data. The Cloverleaf is best modeled by a superposition of approx.200 M82like starbursts accounting for all of the FIR emission and 43% of the [NIl] line. The remainder may come from the NLR. This work demonstrates the utility of the [NIl] and [OIII] lines in constraining properties of the ionized medium.

  3. First Detections of the [N II] 122 micron Line at High Redshift: Demonstrating the Utility of the Line for Studying Galaxies in the Early Universe

    NASA Technical Reports Server (NTRS)

    Ferkinhoff, Carl; Brisbin, Drew; Nikola, Thomas; Parshley, Stephen C.; Stacey, Gordon J.; Phillips, Thomas G.; Falgarone, Edith; Benford, Dominic J.; Staguhn, Johannes G.; Tucker, Carol E.

    2011-01-01

    We report the first detections of the [N II] 122 micron line from a high-redshift galaxy. The line was strongly (>6(sigma)) detected from SMMJ02399-0136, and H1413 + 117 (the Cloverleaf QSO) using the Redshift (zeta) and Early Universe Spectrometer on the Caltech Submillimeter Observatory. The lines from both sources are quite bright with line to far-infrared (FIR) continuum luminosity ratios that are approx.7.0 x 10(exp -4) (Cloverleaf) and 2.1 x 10(exo -3) (SMMJ02399). With ratios 2-10 times larger than the average value for nearby galaxies, neither source exhibits the line to continuum deficits seen in nearby sources. The line strengths also indicate large ionized gas fractions, approx.8%-17% of the molecUlar gas mass. The [O III]/[N II] line ratio is very sensitive to the effective temperature of ionizing stars and the ionization parameter for emission arising in the narrow-line region (NLR) of an active galactic nucleus (AGN). Using Our previous detection of the [O III] 88 micron line, the [O III]/[N II]line ratio for SMMJ02399-0136 indicates that the dominant source of the line emission is either stellar H II regions ionized by O9.5 stars, or the NLR of the AGN with ionization parameter log(U) = -3.3 to -4.0. A composite system, where 30%-50% of the FIR lines arise in the NLR also matches the data. The Cloverleaf is best modeled by a superposition of approx.200 M82-like starbursts accounting for all of the FIR emission and 43% of the [N II]line. The remainder may come from the NLR. This war!< demonstrates the utility of the [N II] and [O III] lines in constraining properties of the ionized medium.

  4. Evolution of the mass, size, and star formation rate in high redshift merging galaxies. MIRAGE - A new sample of simulations with detailed stellar feedback

    NASA Astrophysics Data System (ADS)

    Perret, V.; Renaud, F.; Epinat, B.; Amram, P.; Bournaud, F.; Contini, T.; Teyssier, R.; Lambert, J.-C.

    2014-02-01

    Context. In Λ-CDM models, galaxies are thought to grow both through continuous cold gas accretion coming from the cosmic web and episodic merger events. The relative importance of these different mechanisms at different cosmic epochs is nevertheless not yet understood well. Aims: We aim to address questions related to galaxy mass assembly through major and minor wet merging processes in the redshift range 1 < z < 2, an epoch that corresponds to the peak of cosmic star formation history. A significant fraction of Milky Way-like galaxies are thought to have undergone an unstable clumpy phase at this early stage. We focus on the behavior of the young clumpy disks when galaxies are undergoing gas-rich galaxy mergers. Methods: Using the adaptive mesh-refinement code RAMSES, we build the Merging and Isolated high redshift Adaptive mesh refinement Galaxies (MIRAGE) sample. It is composed of 20 mergers and 3 isolated idealized disks simulations, which sample disk orientations and merger masses. Our simulations can reach a physical resolution of 7 parsecs, and include star formation, metal line cooling, metallicity advection, and a recent physically-motivated implementation of stellar feedback that encompasses OB-type stars radiative pressure, photo-ionization heating, and supernovae. Results: The star formation history of isolated disks shows a stochastic star formation rate, which proceeds from the complex behavior of the giant clumps. Our minor and major gas-rich merger simulations do not trigger starbursts, suggesting a saturation of the star formation due to the detailed accounting of stellar feedback processes in a turbulent and clumpy interstellar medium fed by substantial accretion from the circumgalactic medium. Our simulations are close to the normal regime of the disk-like star formation on a Schmidt-Kennicutt diagram. The mass-size relation and its rate of evolution in the redshift range 1 < z < 2 matches observations, suggesting that the inside-out growth

  5. THE STAR FORMATION HISTORY OF BCGs TO z = 1.8 FROM THE SpARCS/SWIRE SURVEY: EVIDENCE FOR SIGNIFICANT IN SITU STAR FORMATION AT HIGH REDSHIFT

    SciTech Connect

    Webb, Tracy M. A.; Bonaventura, Nina; Muzzin, Adam; Noble, Allison; Yee, H. K. C.; Geach, James; Hezevah, Yashar; Lidman, Chris; Wilson, Gillian; Surace, Jason

    2015-12-01

    We present the results of an MIPS-24 μm study of the brightest cluster galaxies (BCGs) of 535 high-redshift galaxy clusters. The clusters are drawn from the Spitzer Adaptation of the Red-Sequence Cluster Survey, which effectively provides a sample selected on total stellar mass, over 0.2 < z < 1.8 within the Spitzer Wide-Area Infrared Extragalactic (SWIRE) Survey fields. Twenty percent, or 106 clusters, have spectroscopically confirmed redshifts, and the rest have redshifts estimated from the color of their red sequence. A comparison with the public SWIRE images detects 125 individual BCGs at 24 μm ≳ 100 μJy, or 23%. The luminosity-limited detection rate of BCGs in similar richness clusters (N{sub gal} > 12) increases rapidly with redshift. Above z ∼ 1, an average of ∼20% of the sample have 24 μm inferred infrared luminosities of L{sub IR} > 10{sup 12} L{sub ⊙}, while the fraction below z ∼ 1 exhibiting such luminosities is <1%. The Spitzer-IRAC colors indicate the bulk of the 24 μm detected population is predominantly powered by star formation, with only 7/125 galaxies lying within the color region inhabited by active galactic nuclei (AGNs). Simple arguments limit the star formation activity to several hundred million years and this may therefore be indicative of the timescale for AGN feedback to halt the star formation. Below redshift z ∼ 1, there is not enough star formation to significantly contribute to the overall stellar mass of the BCG population, and therefore BCG growth is likely dominated by dry mergers. Above z ∼ 1, however, the inferred star formation would double the stellar mass of the BCGs and is comparable to the mass assembly predicted by simulations through dry mergers. We cannot yet constrain the process driving the star formation for the overall sample, though a single object studied in detail is consistent with a gas-rich merger.

  6. The Hyperluminous Infrared Quasar 3C 318 and Its Implications for Interpreting Sub-MM Detections of High-Redshift Radio Galaxies

    NASA Technical Reports Server (NTRS)

    Willott, Chris J.; Rawlings, Steve; Jarvis, Matt J.

    1999-01-01

    We present near-infrared spectroscopy and imaging of the compact steep-spectrum radio source 3C 318 which shows it to be a quasar at redshift z = 1.574 (the z = 0.752 value previously reported is incorrect). 3C 318 is an IRAS, ISO and SCUBA source so its new redshift makes it the most intrinsically luminous far-infrared (FIR) source in the 3C catalogue (there is no evidence of strong gravitational lensing effects). Its bolometric luminosity greatly exceeds the 10(exp 13) solar luminosity level above which an object is said to be hyperluminous. Its spectral energy distribution (SED) requires that the quasar heats the dust responsible for the FIR flux, as is believed to be the case in other hyperluminous galaxies, and contributes (at the greater than 10% level) to the heating of the CIA dust responsible for the sub-mm emission. We cannot determine whether a starburst makes an important contribution to the heating of the coolest dust, so evidence for a high star-formation rate is circumstantial being based on the high dust, and hence gas, C-1 mass required by its sub-mm detection. We show that the current sub-mm and FIR data available for the highest-redshift radio galaxies are consistent with SEDs similar to that of 3C 318. This indicates that at least some of this population may be detected in the sub-mm because of dust heated by the quasar nucleus, and that interpreting sub-mm detection as evidence for very high (approx. less than 1000 solar mass/yr) star-formation rates may not always be valid. We show that the 3C318 quasar is slightly reddened (A(sub v) approx. = 0.5), the most likely cause of which is SMC-type dust in the host galaxy. If very distant radio galaxies are reddened in a similar way then we show that only slightly greater amounts of dust could obscure the quasars in these sources. We speculate that the low fraction of quasars amongst the very high redshift (z approx. greater than 3) objects in low-frequency radio-selected samples is the result of

  7. Unexpectedly low UV-sensitivity in a bird, the budgerigar

    PubMed Central

    Chavez, Johanna; Kelber, Almut; Vorobyev, Misha; Lind, Olle

    2014-01-01

    Photoreceptor adaptation ensures appropriate visual responses during changing light conditions and contributes to colour constancy. We used behavioural tests to compare UV-sensitivity of budgerigars after adaptation to UV-rich and UV-poor backgrounds. In the latter case, we found lower UV-sensitivity than expected, which could be the result of photon-shot noise corrupting cone signal robustness or nonlinear background adaptation. We suggest that nonlinear adaptation may be necessary for allowing cones to discriminate UV-rich signals, such as bird plumage colours, against UV-poor natural backgrounds. PMID:25376799

  8. What the UV SED Tells us About Stellar Populations and Galaxies

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.

    2011-01-01

    The UV SED parameter b as in f(sub 1) 1(sup b), is commonly used to estimate fundamental properties of high-redshift galaxies including age and metallicity. However, sources and processes other than age and metallicity can influence the value of b. We use the local starforming dwarf galaxy, I Zw 18, in a case study to investigate uncertainties in age and metallicity inferred from b due errors or uncertainties in: mode of star formation (instantaneous starburst vs. continuous SF), dust extinction, nebular continuous emission (2-photon emission, Balmer continuum flux), and presence of older stars.

  9. Breaking the Curve with CANDELS: A Bayesian Approach to Reveal the Non-Universality of the Dust-Attenuation Law at High Redshift

    NASA Astrophysics Data System (ADS)

    Salmon, Brett; Papovich, Casey; Long, James; Willner, S. P.; Finkelstein, Steven L.; Ferguson, Henry C.; Dickinson, Mark; Duncan, Kenneth; Faber, S. M.; Hathi, Nimish; Koekemoer, Anton; Kurczynski, Peter; Newman, Jeffery; Pacifici, Camilla; Pérez-González, Pablo G.; Pforr, Janine

    2016-08-01

    Dust attenuation affects nearly all observational aspects of galaxy evolution, yet very little is known about the form of the dust-attenuation law in the distant universe. Here, we model the spectral energy distributions of galaxies at z ˜ 1.5-3 from CANDELS with rest-frame UV to near-IR imaging under different assumptions about the dust law, and compare the amount of inferred attenuated light with the observed infrared (IR) luminosities. Some individual galaxies show strong Bayesian evidence in preference of one dust law over another, and this preference agrees with their observed location on the plane of infrared excess (IRX, {L}{TIR}/{L}{UV}) and UV slope (β). We generalize the shape of the dust law with an empirical model, {A}λ ,δ =E{(B-V){k}λ (λ /{λ }V)}δ where k λ is the dust law of Calzetti et al., and show that there exists a correlation between the color excess E(B-V) and tilt δ with δ =(0.62+/- 0.05){log}(E(B-V))+(0.26+/- 0.02). Galaxies with high color excess have a shallower, starburst-like law, and those with low color excess have a steeper, SMC-like law. Surprisingly, the galaxies in our sample show no correlation between the shape of the dust law and stellar mass, star formation rate, or β. The change in the dust law with color excess is consistent with a model where attenuation is caused by scattering, a mixed star-dust geometry, and/or trends with stellar population age, metallicity, and dust grain size. This rest-frame UV-to-near-IR method shows potential to constrain the dust law at even higher redshifts (z\\gt 3).

  10. BLAST: RESOLVING THE COSMIC SUBMILLIMETER BACKGROUND

    SciTech Connect

    Marsden, Gaelen; Chapin, Edward L.; Halpern, Mark; Ngo, Henry; Ade, Peter A. R.; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Moncelsi, Lorenzo; Pascale, Enzo; Bock, James J.; Devlin, Mark J.; Dicker, Simon R.; Klein, Jeff; Gundersen, Joshua O.; Hughes, David H.; Magnelli, Benjamin; Olmi, Luca; Patanchon, Guillaume

    2009-12-20

    The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) has made 1 deg{sup 2}, deep, confusion-limited maps at three different bands, centered on the Great Observatories Origins Deep Survey South Field. By calculating the covariance of these maps with catalogs of 24 mum sources from the Far-Infrared Deep Extragalactic Legacy Survey, we have determined that the total submillimeter intensities are 8.60 +- 0.59, 4.93 +- 0.34, and 2.27 +- 0.20 nW m{sup -2} sr{sup -1} at 250, 350, and 500 mum, respectively. These numbers are more precise than previous estimates of the cosmic infrared background (CIB) and are consistent with 24 mum-selected galaxies generating the full intensity of the CIB. We find that the fraction of the CIB that originates from sources at z >= 1.2 increases with wavelength, with 60% from high-redshift sources at 500 mum. At all BLAST wavelengths, the relative intensity of high-z sources is higher for 24 mum-faint sources than that for 24 mum-bright sources. Galaxies identified as active galactic nuclei (AGNs) by their Infrared Array Camera colors are 1.6-2.6 times brighter than the average population at 250-500 mum, consistent with what is found for X-ray-selected AGNs. BzK-selected galaxies are found to be moderately brighter than typical 24 mum-selected galaxies in the BLAST bands. These data provide high-precision constraints for models of the evolution of the number density and intensity of star-forming galaxies at high redshift.

  11. Primordial helium and the cosmic background radiation

    SciTech Connect

    Steigman, Gary

    2010-04-01

    The products of primordial nucleosynthesis, along with the cosmic microwave background (CMB) photons, are relics from the early evolution of the Universe whose observations probe the standard model of cosmology and provide windows on new physics beyond the standard models of cosmology and of particle physics. According to the standard, hot big bang cosmology, long before any stars have formed a significant fraction ( ∼ 25%) of the baryonic mass in the Universe should be in the form of helium-4 nuclei. Since current observations of {sup 4}He are restricted to low redshift regions where stellar nucleosynthesis has occurred, an observation of high redshift, prestellar, truly primordial {sup 4}He would constitute a fundamental test of the hot, big bang cosmology. At recombination, long after big bang nucleosynthesis (BBN) has ended, the temperature anisotropy spectrum imprinted on the CMB depends on the {sup 4}He abundance through its connection to the electron density and the effect of the electron density on Silk damping. Since the relic abundance of {sup 4}He is relatively insensitive to the universal density of baryons, but is sensitive to a non-standard, early Universe expansion rate, the primordial mass fraction of {sup 4}He, Yp, offers a test of the consistency of the standard models of BBN and the CMB and, provides constraints on non-standard physics. Here, the WMAP seven year data (supplemented by other CMB experiments), which lead to an indirect determination of Yp at high redshift, are compared to the BBN predictions and to the independent, direct observations of {sup 4}He in low redshift, extragalactic HII regions. At present, given the very large uncertainties in the CMB-determined primordial {sup 4}He abundance (as well as for the helium abundances inferred from HII region observations), any differences between the BBN predictions and the CMB observations are small, at a level ∼<1.5σ.

  12. Powerful Activity in the Bright Ages. I. A Visible/IR Survey of High Redshift 3C Radio Galaxies and Quasars

    NASA Astrophysics Data System (ADS)

    Hilbert, B.; Chiaberge, M.; Kotyla, J. P.; Tremblay, G. R.; Stanghellini, C.; Sparks, W. B.; Baum, S.; Capetti, A.; Macchetto, F. D.; Miley, G. K.; O'Dea, C. P.; Perlman, E. S.; Quillen, A.

    2016-07-01

    We present new rest-frame UV and visible observations of 22 high-z (1 < z < 2.5) 3C radio galaxies and QSOs obtained with the Hubble Space Telescope's Wide Field Camera 3 instrument. Using a custom data reduction strategy in order to assure the removal of cosmic rays, persistence signal, and other data artifacts, we have produced high-quality science-ready images of the targets and their local environments. We observe targets with regions of UV emission suggestive of active star formation. In addition, several targets exhibit highly distorted host galaxy morphologies in the rest frame visible images. Photometric analyses reveal that brighter QSOs generally tend to be redder than their dimmer counterparts. Using emission line fluxes from the literature, we estimate that emission line contamination is relatively small in the rest frame UV images for the QSOs. Using archival VLA data, we have also created radio map overlays for each of our targets, allowing for analysis of the optical and radio axes alignment.

  13. Lyα and UV Sizes of Green Pea Galaxies

    NASA Astrophysics Data System (ADS)

    Yang, Huan; Malhotra, Sangeeta; Rhoads, James E.; Leitherer, Claus; Wofford, Aida; Jiang, Tianxing; Wang, Junxian

    2017-03-01

    Green Peas are nearby analogs of high-redshift Lyα-emitting galaxies (LAEs). To probe their Lyα escape, we study the spatial profiles of Lyα and UV continuum emission of 24 Green Pea galaxies using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope. We extract the spatial profiles of Lyα emission from their 2D COS spectra, and of the UV continuum from both 2D spectra and NUV images. The Lyα emission shows more extended spatial profiles than the UV continuum, in most Green Peas. The deconvolved full width at half maximum of the Lyα spatial profile is about 2–4 times that of the UV continuum, in most cases. Because Green Peas are analogs of high z LAEs, our results suggest that most high-z LAEs probably have larger Lyα sizes than UV sizes. We also compare the spatial profiles of Lyα photons at blueshifted and redshifted velocities in eight Green Peas with sufficient data quality, and find that the blue wing of the Lyα line has a larger spatial extent than the red wing in four Green Peas with comparatively weak blue Lyα line wings. We show that Green Peas and MUSE z = 3–6 LAEs have similar Lyα and UV continuum sizes, which probably suggests that starbursts in both low-z and high-z LAEs drive similar gas outflows illuminated by Lyα light. Five Lyman continuum (LyC) leakers in this sample have similar Lyα to UV continuum size ratios (∼1.4–4.3) to the other Green Peas, indicating that their LyC emissions escape through ionized holes in the interstellar medium.

  14. ACTIVE GALACTIC NUCLEI AS MAIN CONTRIBUTORS TO THE ULTRAVIOLET IONIZING EMISSIVITY AT HIGH REDSHIFTS: PREDICTIONS FROM A {Lambda}-CDM MODEL WITH LINKED AGN/GALAXY EVOLUTION

    SciTech Connect

    Giallongo, E.; Menci, N.; Fiore, F.; Castellano, M.; Fontana, A.; Grazian, A.; Pentericci, L.

    2012-08-20

    We have evaluated the contribution of the active galactic nuclei (AGN) population to the ionization history of the universe based on a semi-analytic model of galaxy formation and evolution in the cold dark matter cosmological scenario. The model connects the growth of black holes and of the ensuing AGN activity to galaxy interactions. In the model we have included a self-consistent physical description of the escape of ionizing UV photons; this is based on the blast-wave model for the AGN feedback we developed in a previous paper to explain the distribution of hydrogen column densities in AGNs of various redshifts and luminosities, due to absorption by the host galaxy gas. The model predicts UV luminosity functions for AGNs that are in good agreement with those derived from the observations especially at low and intermediate redshifts (z {approx} 3). At higher redshifts (z > 5), the model tends to overestimate the data at faint luminosities. Critical biases in both the data and in the model are discussed to explain such apparent discrepancies. The predicted hydrogen photoionization rate as a function of redshift is found to be consistent with that derived from the observations. All of the above suggests that we should reconsider the role of the AGNs as the main driver of the ionization history of the universe.

  15. A Wide Area Survey for High-Redshift Massive Galaxies. II. Near-Infrared Spectroscopy of BzK-Selected Massive Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Onodera, Masato; Arimoto, Nobuo; Daddi, Emanuele; Renzini, Alvio; Kong, Xu; Cimatti, Andrea; Broadhurst, Tom; Alexander, Dave M.

    2010-05-01

    Results are presented from near-infrared spectroscopic observations of a sample of BzK-selected, massive star-forming galaxies (sBzKs) at 1.5 < z < 2.3 that were obtained with OHS/CISCO at the Subaru telescope and with SINFONI at the Very Large Telescope. Among the 28 sBzKs observed, Hα emission was detected in 14 objects, and for 11 of them the [N II] λ6583 flux was also measured. Multiwavelength photometry was also used to derive stellar masses and extinction parameters, whereas Hα and [N II] emissions have allowed us to estimate star formation rates (SFRs), metallicities, ionization mechanisms, and dynamical masses. In order to enforce agreement between SFRs from Hα with those derived from rest-frame UV and mid-infrared, additional obscuration for the emission lines (that originate in H II regions) was required compared to the extinction derived from the slope of the UV continuum. We have also derived the stellar mass-metallicity relation, as well as the relation between stellar mass and specific SFR (SSFR), and compared them to the results in other studies. At a given stellar mass, the sBzKs appear to have been already enriched to metallicities close to those of local star-forming galaxies of similar mass. The sBzKs presented here tend to have higher metallicities compared to those of UV-selected galaxies, indicating that near-infrared selected galaxies tend to be a chemically more evolved population. The sBzKs show SSFRs that are systematically higher, by up to ~2 orders of magnitude, compared to those of local galaxies of the same mass. The empirical correlations between stellar mass and metallicity, and stellar mass and SSFR are then compared with those of evolutionary population synthesis models constructed either with the simple closed-box assumption, or within an infall scenario. Within the assumptions that are built-in such models, it appears that a short timescale for the star formation (sime100 Myr) and large initial gas mass appear to be required

  16. Predicting dust extinction properties of star-forming galaxies from Hα/UV ratio

    NASA Astrophysics Data System (ADS)

    Koyama, Yusei; Kodama, Tadayuki; Hayashi, Masao; Shimakawa, Rhythm; Yamamura, Issei; Egusa, Fumi; Oi, Nagisa; Tanaka, Ichi; Tadaki, Ken-ichi; Takita, Satoshi; Makiuti, Sin'itirou

    2015-10-01

    Using star-forming galaxies sample in the nearby Universe (0.02 < z < 0.10) selected from the Sloan Digital Sky Survey (DR7) and Galaxy Evolution Explorer all-sky survey (GR5), we present a new empirical calibration for predicting dust extinction of galaxies from the Hα-to-FUV flux ratio. We find that the Hα dust extinction (AHα) derived with Hα/Hβ ratio (Balmer decrement) increases with increasing Hα/UV ratio as expected, but there remains a considerable scatter around the relation, which is largely dependent on stellar mass and/or Hα equivalent width (EWHα). At fixed Hα/UV ratio, galaxies with higher stellar mass (or galaxies with lower EWHα) tend to be more highly obscured by dust. We quantify this trend and establish an empirical calibration for predicting AHα with a combination of Hα/UV ratio, stellar mass, and EWHα, with which we can successfully reduce the systematic uncertainties accompanying the simple Hα/UV approach by ˜15-30 per cent. The new recipes proposed in this study will provide a convenient tool for predicting dust extinction level of galaxies particularly when Balmer decrement is not available. By comparing AHα (derived with Balmer decrement) and AUV (derived with IR/UV luminosity ratio) for a subsample of galaxies for which AKARI far-infrared photometry is available, we demonstrate that more massive galaxies tend to have higher extra extinction towards the nebular regions compared to the stellar continuum light. Considering recent studies reporting smaller extra extinction towards nebular regions for high-redshift galaxies, we argue that the dust geometry within high-redshift galaxies resembles low-mass galaxies in the nearby Universe.

  17. The cosmic infrared background experiment

    NASA Astrophysics Data System (ADS)

    Bock, James; Battle, John; Cooray, Asantha; Kawada, Mitsunobu; Keating, Brian; Lange, Andrew; Lee, Dae-Hea; Matsumoto, Toshio; Matsuura, Shuji; Pak, Soojong; Renbarger, Tom; Sullivan, Ian; Tsumura, Kohji; Wada, Takehiko; Watabe, Toyoki

    2006-03-01

    The extragalactic background, based on absolute measurements reported by DIRBE and IRTS at 1.2 and 2.2 μm, exceeds the brightness derived from galaxy counts by up to a factor 5. Furthermore, both DIRBE and the IRTS report fluctuations in the near-infrared sky brightness that appear to have an extra-galactic origin, but are larger than expected from local ( z = 1-3) galaxies. These observations have led to speculation that a new class of high-mass stars or mini-quasars may dominate primordial star formation at high-redshift ( z ˜ 10-20), which, in order to explain the excess in the near-infrared background, must be highly luminous but produce a limited amount of metals and X-ray photons. Regardless of the nature of the sources, if a significant component of the near-infrared background comes from first-light galaxies, theoretical models generically predict a prominent near-infrared spectral feature from the redshifted Lyman cutoff, and a distinctive fluctuation power spectrum. We are developing a rocket-borne instrument (the Cosmic Infrared Background ExpeRiment, or CIBER) to search for signatures of primordial galaxy formation in the cosmic near-infrared extra-galactic background. CIBER consists of a wide-field two-color camera, a low-resolution absolute spectrometer, and a high-resolution narrow-band imaging spectrometer. The cameras will search for spatial fluctuations in the background on angular scales from 7″ to 2°, where a first-light galaxy signature is expected to peak, over a range of angular scales poorly covered by previous experiments. CIBER will determine if the fluctuations reported by the IRTS arise from first-light galaxies or have a local origin. In a short rocket flight CIBER has sensitivity to probe fluctuations 100× fainter than IRTS/DIRBE, with sufficient resolution to remove local-galaxy correlations. By jointly observing regions of the sky studied by Spitzer and ASTRO-F, CIBER will build a multi-color view of the near

  18. PKS 1502+106: A high-redshift Fermi blazar at extreme angular resolution. Structural dynamics with VLBI imaging up to 86 GHz

    NASA Astrophysics Data System (ADS)

    Karamanavis, V.; Fuhrmann, L.; Krichbaum, T. P.; Angelakis, E.; Hodgson, J.; Nestoras, I.; Myserlis, I.; Zensus, J. A.; Sievers, A.; Ciprini, S.

    2016-02-01

    Context. Blazars are among the most energetic objects in the Universe. In 2008 August, Fermi/LAT detected the blazar PKS 1502+106, which showed a rapid and strong γ-ray outburst followed by high and variable flux over the next months. This activity at high energies triggered an intensive multi-wavelength campaign that also covered the radio, optical, UV, and X-ray bands, indicating that the flare was accompanied by a simultaneous outburst at optical/UV/X-rays and a delayed outburst at radio bands. Aims: We explore the phenomenology and physical conditions within the ultra-relativistic jet of the γ-ray blazar PKS 1502+106. Additionally, we address the question of the spatial localization of the MeV/GeV-emitting region of the source. Methods: We used ultra-high angular resolution mm-VLBI observations at 43 and 86 GHz complemented by VLBI observations at 15 GHz. We also employed single-dish radio data from the F-GAMMA program at frequencies matching the VLBI monitoring. Results: PKS 1502+106 shows a compact core-jet morphology and fast superluminal motion with apparent speeds in the range 5-22 c. Estimating Doppler factors along the jet yields values of between ~7 up to ~50. This Doppler factor gradient implies an accelerating jet. The viewing angle towards the source differs between the inner and outer jet, with the former at θ ~ 3° and the latter at θ ~ 1°, after the jet bends towards the observer beyond 1 mas. The de-projected opening angle of the ultra-fast magnetically dominated jet is found to be (3.8 ± 0.5)°. A single jet component can be associated with the pronounced flare both at high energies and in radio bands. Finally, the γ-ray emission region is localized at ≤ 5.9 pc away from the jet base. Images as FITS files are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A60

  19. Background-Limited Infrared-Submillimeter Spectroscopy (BLISS)

    NASA Technical Reports Server (NTRS)

    Bradford, Charles Matt

    2004-01-01

    The bulk of the cosmic far-infrared background light will soon be resolved into its individual sources with Spitzer, Astro-F, Herschel, and submm/mm ground-based cameras. The sources will be dusty galaxies at z approximately equal to 1-4. Their physical conditions and processes in these galaxies are directly probed with moderate-resolution spectroscopy from 20 micrometers to 1 mm. Currently large cold telescopes are being combined with sensitive direct detectors, offering the potential for mid-far-IR spectroscopy at the background limit (BLISS). The capability will allow routine observations of even modest high-redshift galaxies in a variety of lines. The BLISS instrument's capabilities are described in this presentation.

  20. NuSTAR AND MULTIFREQUENCY STUDY OF THE TWO HIGH-REDSHIFT BLAZARS S5 0836+710 AND PKS 2149–306

    SciTech Connect

    Tagliaferri, G.; Ghisellini, G.; Covino, S.; Sbarrato, T.; Perri, M.; Giommi, P.; Puccetti, S.; Hayashida, M.; Balokovic, M.; Harrison, F. A.; Madejski, G. M.; Chiang, J.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Hailey, C. J.; Stern, D.; Zhang, W. W.

    2015-07-10

    Powerful blazars are flat-spectrum radio quasars whose emission is dominated by a Compton component peaking between a few hundred keV and a few hundred MeV. We observed two bright blazars, PKS 2149–306 at redshift z = 2.345 and S5 0836+710 at z = 2.172, in the hard X-ray band with the Nuclear Spectroscopic Telescope Array satellite. Simultaneous soft-X-rays and UV–optical observations were performed with the Swift satellite, while near-infrared (near-IR) data were obtained with the Rapid Eye Mount telescope. To study their variability, we repeated these observations for both sources on a timescale of a few months. While no fast variability was detected during a single observation, both sources were variable in the X-ray band, up to 50%, between the two observations, with larger variability at higher energies. No variability was detected in the optical/NIR band. These data, together with Fermi-Large Area Telescope, Wide-field Infrared Survey Explorer, and other literature data, are then used to study the overall spectral energy distributions (SEDs) of these blazars. Although the jet nonthermal emission dominates the SED, it leaves the UV band unhidden, allowing us to detect the thermal emission of the disk and to estimate the black hole mass. The nonthermal emission is well reproduced by a one-zone leptonic model by the synchrotron, self-Compton, and external Compton processes. Our data are better reproduced if we assume that the location of the dissipation region of the jet, R{sub diss}, is in between the torus and the broad-line region. The observed variability is explained by changing a minimum number of model parameters by a very small amount.

  1. UV-CONTINUUM SLOPES AT z {approx} 4-7 FROM THE HUDF09+ERS+CANDELS OBSERVATIONS: DISCOVERY OF A WELL-DEFINED UV COLOR-MAGNITUDE RELATIONSHIP FOR z {>=} 4 STAR-FORMING GALAXIES

    SciTech Connect

    Bouwens, R. J.; Franx, M.; Labbe, I.; Smit, R.; Illingworth, G. D.; Oesch, P.A.; Gonzalez, V.; Magee, D.; Van Dokkum, P.; Carollo, C. M.

    2012-08-01

    Ultra-deep Advanced Camera for Surveys (ACS) and WFC3/IR HUDF+HUDF09 data, along with the wide-area GOODS+ERS+CANDELS data over the CDF-S GOODS field, are used to measure UV colors, expressed as the UV-continuum slope {beta}, of star-forming galaxies over a wide range of luminosity (0.1L*{sub z=3} to 2L*{sub z=3}) at high redshift (z {approx} 7 to z {approx} 4). {beta} is measured using all ACS and WFC3/IR passbands uncontaminated by Ly{alpha} and spectral breaks. Extensive tests show that our {beta} measurements are only subject to minimal biases. Using a different selection procedure, Dunlop et al. recently found large biases in their {beta} measurements. To reconcile these different results, we simulated both approaches and found that {beta} measurements for faint sources are subject to large biases if the same passbands are used both to select the sources and to measure {beta}. High-redshift galaxies show a well-defined rest-frame UV color-magnitude (CM) relationship that becomes systematically bluer toward fainter UV luminosities. No evolution is seen in the slope of the UV CM relationship in the first 1.5 Gyr, though there is a small evolution in the zero point to redder colors from z {approx} 7 to z {approx} 4. This suggests that galaxies are evolving along a well-defined sequence in the L{sub UV}-color ({beta}) plane (a 'star-forming sequence'?). Dust appears to be the principal factor driving changes in the UV color {beta} with luminosity. These new larger {beta} samples lead to improved dust extinction estimates at z {approx} 4-7 and confirm that the extinction is essentially zero at low luminosities and high redshifts. Inclusion of the new dust extinction results leads to (1) excellent agreement between the star formation rate (SFR) density at z {approx} 4-8 and that inferred from the stellar mass density; and (2) to higher specific star formation rates (SSFRs) at z {approx}> 4, suggesting that the SSFR may evolve modestly (by factors of {approx}2) from

  2. Fluctuations In The Cosmic Infrared Background Using the Cosmic Infrared Background ExpeRiment (CIBER).

    NASA Astrophysics Data System (ADS)

    Smidt, Joseph; Arai, T.; Battle, J.; Bock, J. J.; Cooray, A.; Frazer, C.; Hristov, V.; Keating, B.; Kim, M.; Lee, D.; Mason, P.; Matsumoto, T.; Mitchell-Wynne, K.; Nam, U.; Renbarger, T.; Smith, A.; Sullivan, I.; Tsumura, K.; Wada, T.; Zemcov, M.

    2012-01-01

    The clustering properties of faint unresolved sources may be probed by examining the anisotropies they create in the Cosmic Infrared Background (CIB). Using information from fluctuations in the CIB at different wavelengths allows us to disentangle how clustering relates to redshift. In this talk, preliminary measurements of clustering using data from the Cosmic Infrared Background ExpeRiment (CIBER), a rocket-borne experiment designed to detect the signatures of unresolved infrared galaxies during reionization, will be discussed. The CIBER payload contains four instruments including two wide field imagers designed to measure fluctuations in the near IR cosmic infrared background (CIB) at 1.0 and 1.6 microns on scales between 0.2 and 100 arcmin in both bands, where the clustering of high-redshift sources is expected to peak. CIBER observations may be combined with Akari/NEP and Spitzer/NDWFS near-infrared surveys to check systematic errors and to fully characterize the electromagnetic spectrum of CIB fluctuations.

  3. UV water disinfector

    DOEpatents

    Gadgil, A.; Garud, V.

    1998-07-14

    A UV disinfector with a gravity driven feed water delivery system and an air-suspended bare UV lamp are disclosed. The disinfector is hydrodynamically optimized with a laminerizing, perforated baffle wall, beveled treatment chamber, and outlet weir. 7 figs.

  4. UV water disinfector

    DOEpatents

    Gadgil, Ashok; Garud, Vikas

    1998-07-14

    A UV disinfector with a gravity driven feed water delivery system, and an air-suspended bare UV lamp. The disinfector is hydrodynamically optimized with a laminerizing, perforated baffle wall, beveled treatment chamber, and outlet weir.

  5. Índice UV

    EPA Pesticide Factsheets

    Información general sobre el Índice UV que proporciona un pronóstico del riesgo esperado de sobreexposición a la radiación ultravioleta (UV) del sol. El índice UV va acompañado de recomendaciones para protegerse del sol.

  6. Correlated UV Through IR Signature Modeling of Targets and Backgrounds

    DTIC Science & Technology

    1998-11-01

    other high energy sources. In particular, variation of the sources as a function of time, wavelength and aspect angle is discussed, as these variations...sources as a function of time, wavelength and aspect angle is discussed, as these variations may be critical to the discrimination of targets...δt, a, v) = S f (λ, δλ)J (t)A(θ, φ)P(a)V (v)ψ (1) where A(θ, φ) is an aspect angle function that defines the relative magnitude of the source viewed

  7. Ultraviolet background fluctuations with clustered sources

    NASA Astrophysics Data System (ADS)

    Desjacques, Vincent; Dizgah, Azadeh Moradinezhad; Biagetti, Matteo

    2014-11-01

    We develop a count-in-cells approach to the distribution of ultraviolet background fluctuations that includes source clustering. We demonstrate that an exact expression can be obtained if the clustering of ionizing sources follows the hierarchical ansatz. In this case, the intensity distribution depends solely on their two-point correlation function. We show that the void scaling function of high-redshift mock quasars is consistent with the negative binomial form, before applying our formalism to the description of He II-ionizing fluctuations at the end of helium reionization. The model inputs are the observed quasar luminosity function and two-point correlation at z ˜ 3. We find that, for an (comoving) attenuation length ≲55 Mpc, quasar clustering contributes less than 30 per cent of the variance of intensity fluctuations so long as the quasar correlation length does not exceed ˜15 Mpc. We investigate also the dependence of the intensity distribution on the large-scale environment. Differences in the mean He II-ionizing intensity between low- and high-density regions could be a factor of few if the sources are highly clustered. An accurate description of quasar demographics and their correlation with strong absorption systems is required to make more precise predictions.

  8. PROPERTIES OF QSO METAL-LINE ABSORPTION SYSTEMS AT HIGH REDSHIFTS: NATURE AND EVOLUTION OF THE ABSORBERS AND NEW EVIDENCE ON ESCAPE OF IONIZING RADIATION FROM GALAXIES

    SciTech Connect

    Boksenberg, Alec; Sargent, Wallace L. W.

    2015-05-15

    Using Voigt-profile-fitting procedures on Keck High Resolution Spectrograph spectra of nine QSOs, we identify 1099 C IV absorber components clumped in 201 systems outside the Lyman forest over 1.6 ≲ z ≲ 4.4. With associated Si IV, C II, Si II  and N V where available, we investigate the bulk statistical and ionization properties of the components and systems and find no significant change in redshift for C IV and Si IV while C II, Si II  and N V change substantially. The C IV components exhibit strong clustering, but no clustering is detected for systems on scales from 150 km s{sup –1} out to 50,000 km s{sup –1}. We conclude that the clustering is due entirely to the peculiar velocities of gas present in the circumgalactic media of galaxies. Using specific combinations of ionic ratios, we compare our observations with model ionization predictions for absorbers exposed to the metagalactic ionizing radiation background augmented by proximity radiation from their associated galaxies and find that the generally accepted means of radiative escape by transparent channels from the internal star-forming sites is spectrally not viable for our stronger absorbers. We develop an active scenario based on runaway stars with resulting changes in the efflux of radiation that naturally enable the needed spectral convergence, and in turn provide empirical indicators of morphological evolution in the associated galaxies. Together with a coexisting population of relatively compact galaxies indicated by the weaker absorbers in our sample, the collective escape of radiation is sufficient to maintain the intergalactic medium ionized over the full range 1.9 < z ≲ 4.4.

  9. Properties of QSO Metal-line Absorption Systems at High Redshifts: Nature and Evolution of the Absorbers and New Evidence on Escape of Ionizing Radiation from Galaxies

    NASA Astrophysics Data System (ADS)

    Boksenberg, Alec; Sargent, Wallace L. W.

    2015-05-01

    Using Voigt-profile-fitting procedures on Keck High Resolution Spectrograph spectra of nine QSOs, we identify 1099 C IV absorber components clumped in 201 systems outside the Lyman forest over 1.6 <~ z <~ 4.4. With associated Si IV, C II, Si II and N V where available, we investigate the bulk statistical and ionization properties of the components and systems and find no significant change in redshift for C IV and Si IV while C II, Si II and N V change substantially. The C IV components exhibit strong clustering, but no clustering is detected for systems on scales from 150 km s-1 out to 50,000 km s-1. We conclude that the clustering is due entirely to the peculiar velocities of gas present in the circumgalactic media of galaxies. Using specific combinations of ionic ratios, we compare our observations with model ionization predictions for absorbers exposed to the metagalactic ionizing radiation background augmented by proximity radiation from their associated galaxies and find that the generally accepted means of radiative escape by transparent channels from the internal star-forming sites is spectrally not viable for our stronger absorbers. We develop an active scenario based on runaway stars with resulting changes in the efflux of radiation that naturally enable the needed spectral convergence, and in turn provide empirical indicators of morphological evolution in the associated galaxies. Together with a coexisting population of relatively compact galaxies indicated by the weaker absorbers in our sample, the collective escape of radiation is sufficient to maintain the intergalactic medium ionized over the full range 1.9 < z <~ 4.4. 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

  10. A Survey of Luminous High-redshift Quasars with SDSS and WISE. II. the Bright End of the Quasar Luminosity Function at z ≈ 5

    NASA Astrophysics Data System (ADS)

    Yang, Jinyi; Wang, Feige; Wu, Xue-Bing; Fan, Xiaohui; McGreer, Ian D.; Bian, Fuyan; Yi, Weimin; Yang, Qian; Ai, Yanli; Dong, Xiaoyi; Zuo, Wenwen; Green, Richard; Jiang, Linhua; Wang, Shu; Wang, Ran; Yue, Minghao

    2016-09-01

    This is the second paper in a series on a new luminous z ˜ 5 quasar survey using optical and near-infrared colors. Here we present a new determination of the bright end of the quasar luminosity function (QLF) at z ˜ 5. Combining our 45 new quasars with previously known quasars that satisfy our selections, we construct the largest uniform luminous z ˜ 5 quasar sample to date, with 99 quasars in the range of 4.7 ≤ z < 5.4 and -29 < M 1450 ≤ -26.8, within the Sloan Digital Sky Survey (SDSS) footprint. We use a modified 1/V a method including flux limit correction to derive a binned QLF, and we model the parametric QLF using maximum likelihood estimation. With the faint-end slope of the QLF fixed as α = -2.03 from previous deeper samples, the best fit of our QLF gives a flatter bright end slope β = -3.58 ± 0.24 and a fainter break magnitude {M}1450* = -26.98 ± 0.23 than previous studies at similar redshift. Combined with previous work at lower and higher redshifts, our result is consistent with a luminosity evolution and density evolution model. Using the best-fit QLF, the contribution of quasars to the ionizing background at z ˜ 5 is found to be 18%-45% with a clumping factor C of 2-5. Our sample suggests an evolution of radio loud fraction with optical luminosity but no obvious evolution with redshift.

  11. A UV Imaging Survey of IR-Bright Star- Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Calzetti, Daniela

    2000-07-01

    We propose to carry out a UV{ 1, 600 Angstrom} snapshot imaging survey with STIS of all the actively star-forming galaxies detected by ISO at Lambda>170 Mum and closer than cz=9000 km/s. The sample covers a large region in the parameter's space of morphology, luminosity, metallicity, and star formation intensity. The multiwavelength {UV/far-IR} information will be exploited to address open issues on low- and high-redshift star formation and on the dust/star- formation interconnection. The ISO galaxies will be used as low-redshift benchmarks to explore the relationship between the Lyman-break galaxies at z 3 and the SCUBA sources. The conditions for the escape of UV light from a `dusty' galaxy will be investigated as a function of the sample parameters. UV-bright structures will be measured and used to quantify the fractions of nuclear and disk emission, the fraction of star formation in massive clusters and the properties of those star clusters, the structural properties of star forming bars, rings, and tidally-driven star formation in IR-bright galaxies. Given the breadth of scientific applications and the relevance of this unique dataset for upcoming instruments and missions, including mid/far-IR ones like SIRTF, we propose this project as a Service to the Community and will release immediately the UV images in the public domain.

  12. Modelling the UV spectrum of SDSS-III/BOSS galaxies: hints towards the detection of the UV upturn at high-z

    NASA Astrophysics Data System (ADS)

    Le Cras, Claire; Maraston, Claudia; Thomas, Daniel; York, Donald G.

    2016-09-01

    We exploit stellar population models of absorption line indices in the ultraviolet (from 2000 to 3200 Å) to study the spectra of massive galaxies. Our central aim is to investigate the occurrence at high redshift of the UV upturn, i.e. the increased UV emission due to old stars observed in massive galaxies and spiral bulges in the local Universe. We use a large (˜275 000) sample of z ˜ 0.6 massive (M*/M⊙ > 11.5) galaxies using both individual spectra and stacks and employ a suite of models including a UV contribution from old populations, spanning various effective temperatures, fuel consumptions and metallicities. We find that a subset of our indices; Mg I, Fe I, and BL3096, are able to differentiate between old and young UV ages. We find evidence for old stars contributing to the UV in massive galaxies, rather than star formation. The data favour models with low/medium upturn temperatures (10 000-25 000 K) consistent with local galaxies, depending on the assumed metallicity, and with a larger fuel (f ˜ 6.5× 10^{-2} {M}_{⊙}). Models with one typical temperature are favoured over models with a temperature range, which would be typical of an extended horizontal branch. Old UV-bright populations are found in the whole galaxy sample (92 per cent), with a mass fraction peaking around 20-30 per cent. Upturn galaxies are massive and have redder colours, in agreement with findings in the local Universe. We find that the upturn phenomenon appears at z ˜ 1 and its frequency increases towards lower redshift, as expected by stellar evolution of low-mass stars. Our findings will help constrain stellar evolution in the exotic UV upturn phase.

  13. Using photo-ionisation models to derive carbon and oxygen gas-phase abundances in the rest UV

    NASA Astrophysics Data System (ADS)

    Pérez-Montero, Enrique; Amorín, Ricardo

    2017-01-01

    We present a new method to derive oxygen and carbon abundances using the ultraviolet (UV) lines emitted by the gas-phase ionised by massive stars. The method is based on the comparison of the nebular emission-line ratios with those predicted by a large grid of photo-ionisation models. Given the large dispersion in the O/H - C/O plane, our method firstly fixes C/O using ratios of appropriate emission lines and, in a second step, calculates O/H and the ionisation parameter from carbon lines in the UV. We find abundances totally consistent with those provided by the direct method when we apply this method to a sample of objects with an empirical determination of the electron temperature using optical emission lines. The proposed methodology appears as a powerful tool for systematic studies of nebular abundances in star-forming galaxies at high redshift.

  14. High-redshift Universe Science with ALMA

    NASA Astrophysics Data System (ADS)

    Blain, Andrew

    ALMA is the largest ground-based astrophysics facility to date, being build by three major international partners: East Asia, Europe and North America. Within a year it should be de-livering data to the worldwide scientific community, and will offer a greatly enhanced capability to study the origins of galaxies, stars and planets. I will describe some of the unique capabilities of the telescope, and its likely impact on the study of the formation and evolution of galaxies. ALMA will provide unprecedented 100-parcsec-scale images of the earliest galaxies, including systems that are currently 100-1000 times too faint to be detected with existing facilities. It is likely that the commissioning of ALMA will provide the greatest increase in observational capability ever seen for a wide range of different disciplines, and ALMA primary and archived data will be as prized and provide as rich a heritage as that from the great space observatories Hubble, Spitzer and Chandra.

  15. Detecting Dual AGN at High Redshift

    NASA Astrophysics Data System (ADS)

    Barrows, Robert S.

    2012-01-01

    The existence of supermassive black holes (SMBHs) in most, if not all, galaxies, along with observations of galaxy mergers, suggests that pairs of SMBHs should exist for some time in the merger remnant. Observational evidence for these systems at kpc-scale separations (i.e. dual AGN) has dramatically increased recently through a combination of spectral and morphological selections. I discuss observations of CXOXBJ142607.6+353351 (CXOJ1426+35), a candidate dual AGN at z=1.175, and put its properties, including significant obscuration, within the context of other candidate/confirmed dual AGN at lower redshifts. Though dual AGN are expected to be more common at higher redshifts, they are more difficult to detect. Furthermore, adding to the difficulties of detection are a number of other physical mechanisms which can mimic the spectroscopic signature of two Type 2 AGN. In particular, I will discuss the possibility of strong outflows from an AGN. These outflow phenomena can be an important feedback mechanism in galaxies and are apparently common in AGN, making them a viable alternative to the dual AGN scenario. Based on our candidate's luminosity and emission line intensities, we find that an outflow is a possibility. If this is the case, such an outflow would be especially strong and has implications for AGN feedback in galaxies. However, the dual AGN scenario cannot be ruled out, and at z=1.175, the two putative AGN could potentially be resolved with Chandra. Other candidate dual AGN at similar redshifts and with significant obscuration could also be confirmed this way. This research was sponsored by the Strategic University Research Partnership Program, the National Aeronautics and Space Administration and the Arkansas NASA EPSCoR program.

  16. Clustering of Radio Sources at High Redshift

    NASA Astrophysics Data System (ADS)

    Magliocchetti, M.; Maddox, S. J.; Lahav, O.; Wall, J. V.

    1998-12-01

    We investigate the large-scale clustering of radio sources in the FIRST 1.4-GHz survey by analysing their distribution function. We estimate the angular two-point correlation function w(theta), the variance Psi_2, and skewness Psi_3 of the distribution; both w(theta) and Psi_2 show power-law behaviour with an amplitude corresponding a spatial correlation length of r_0 ~10 h^{-1}Mpc. We detect significant skewness in the distribution, the first such detection in radio surveys, consistent with the non-linear gravitational growth of perturbations from primordial Gaussian initial conditions. We also investigate how different theoretical predictions for the normalised variance sigma^2 can match our measurements.

  17. Probing Dark Energy with High Redshift Supernovae

    NASA Astrophysics Data System (ADS)

    Perlmutter, S.

    2003-05-01

    The Hubble diagram of Type Ia Supernovae provides the most direct current measurement of the expansion history of the universe, including the present acceleration and the transition to matter-dominated deceleration. Recent measurements already yield statistical uncertainties small enough that we are close to being limited by systematics. I will review the anticipated improvement in systematics attainable by the next generations of experiments from ground and space that promise a systematics-controlled prize: a detailed expansion history of the universe that can teach us about the nature of the mysterious "dark energy" that accelerates the universe. This work is supported by the U.S. Dept. of Energy, Office of Science, under contract DE-AC03-76SF00098.

  18. Galaxy halo occupation at high redshift

    NASA Astrophysics Data System (ADS)

    Bullock, James S.; Wechsler, Risa H.; Somerville, Rachel S.

    2002-01-01

    We discuss how current and future data on the clustering and number density of z~3 Lyman-break galaxies (LBGs) can be used to constrain their relationship to dark matter haloes. We explore a three-parameter model in which the number of LBGs per dark halo scales like a power law in the halo mass: N(M)=(M/M1)S for M>Mmin. Here, Mmin is the minimum mass halo that can host an LBG, M1 is a normalization parameter, associated with the mass above which haloes host more than one observed LBG, and S determines the strength of the mass-dependence. We show how these three parameters are constrained by three observable properties of LBGs: the number density, the large-scale bias and the fraction of objects in close pairs. Given these three quantities, the three unknown model parameters may be estimated analytically, allowing a full exploration of parameter space. As an example, we assume a ΛCDM cosmology and consider the observed properties of a recent sample of spectroscopically confirmed LBGs. We find that the favoured range for our model parameters is Mmin~=(0.4-8)×1010h- 1Msolar, M1~=(6-10)×1012h- 1Msolar, and 0.9<~S<~1.1. The preferred region in Mmin expands by an order of magnitude, and slightly shallower slopes are acceptable if the allowed range of bg is permitted to span all recent observational estimates. We also discuss how the observed clustering of LBGs as a function of luminosity can be used to constrain halo occupation, although because of current observational uncertainties we are unable to reach any strong conclusions. Our methods and results can be used to constrain more realistic models that aim to derive the occupation function N(M) from first principles, and offer insight into how basic physical properties affect the observed properties of LBGs.

  19. UV-sensitive syndrome.

    PubMed

    Spivak, Graciela

    2005-09-04

    UV-sensitive syndrome (UV(S)S) is a human DNA repair-deficiency disorder with mild clinical manifestations. In contrast to other disorders with photosensitivity, no neurological or developmental abnormalities and no predisposition to cancer have been reported. The cellular and biochemical responses of UV(S)S and Cockayne syndrome (CS) cells to UV light are indistinguishable, and result from defective transcription-coupled repair of photoproducts in expressed genes [G. Spivak, T. Itoh, T. Matsunaga, O. Nikaido, P. Hanawalt, M. Yamaizumi, Ultra violet-sensitive syndrome cells are defective in transcription-coupled repair of cyclobutane pyrimidine dimers, DNA Repair, 1, 2002, 629-643]. The severe neurological and developmental deficiency characteristic of CS may arise from unresolved blockage of transcription at oxidative DNA lesions, which could result in excessive cell death and/or attenuated transcription. We have proposed that individuals with UV(S)S develop normally because they are proficient in repair of oxidative base damage or in transcriptional bypass of these lesions; consistent with this hypothesis, CS-B cells, but not UV(S)S cells, are deficient in host cell reactivation of plasmids containing oxidative base lesions [G. Spivak, P. Hanawalt, Host cell reactivation of plasmids containing oxidative DNA lesions is defective in Cockayne syndrome but normal in UV-sensitive syndrome, 2005, submitted for publication]. In this review, I will summarize the current understanding of the UV-sensitive syndrome and compare it with the Cockayne syndrome.

  20. Swift/UVOT Measurements of the UV Dust Extinction Curve and the Recent Star Formation History of the SMC and M33

    NASA Astrophysics Data System (ADS)

    Hagen, Lea M. Z.; Siegel, Michael; Hoversten, Erik A.; Gronwall, Caryl; Immler, Stefan; Vargas, Angelica

    2017-01-01

    The Swift Ultraviolet/Optical Telescope (UVOT) is uniquely suited to study star formation and dust extinction in nearby galaxies. I will discuss results from the Small Magellanic Cloud (SMC) and M33, for which we have unprecedented observations in three near-UV bands from 1700-3000Å at 2.5" resolution. We combine our UV imaging with archival optical and infrared data to model the spectral energy distributions of individual regions of each galaxy, simultaneously fitting for the dust extinction curve properties, total dust, stellar mass, and age. We have created the first-ever maps of the UV dust extinction curve, which show previously-unconfirmed spatial variation: both the slope and 2175Å bump vary considerably over the face of both the SMC and M33. I will discuss the implications of these results on studies of star formation and galaxy evolution at both low and high redshift.

  1. Efficacy of Inactivation of Human Enteroviruses by Multiple-Wavelength UV LEDs - abstract

    EPA Science Inventory

    Background: Ultraviolet (UV) light has been successfully used for treating a broad suite of pathogens without the concomitant formation of carcinogenic disinfection by-products (DBPs). However, conventional mercury UV lamps have some practical limitations in water treatment appli...

  2. HIRDES UV spectrographs

    NASA Astrophysics Data System (ADS)

    Kappelmann, N.; Barnstedt, J.; Gringel, W.; Werner, K.; Becker-Ross, H.; Florek, S.; Graue, R.; Kampf, D.; Reutlinger, A.; Neumann, C.; Shustov, B.; Sachkov, M.; Panchuk, V.; Yushkin, M.; Moisheev, A.; Skripunov, E.

    2006-06-01

    The World Space Observatory Ultraviolet (WSO/UV) is a multi-national project grown out of the needs of the astronomical community to have future access to the ultraviolet range of the spectrum. The development of the WSO/UV S/C and the telescope is headed by the Russian Federal Space Agency (Roscosmos). The mission is scheduled to be launched in 2010 into the L2 orbit. The WSO/UV consists of a single Ultraviolet Telescope, incorporating a primary mirror of 1.7 m diameter feeding UV spectrometer and UV imagers. The UV spectrometer comprises three different single spectrographs, two high resolution echelle spectrographs - the High Resolution Double Echelle Spectrograph (HIRDES) - and a low dispersion long slit instrument. Within the HIRDES the spectral band (102 - 310 nm) is separated into two echelle spectrographs covering the UV range between 174- and 310 nm (UVES) and VacuumUV range between 102 and 176 nm (VUVES) with a very high spectral resolution of > 50000. Each spectrograph encompass a stand alone optical bench structure with a fully redundant high speed MCP detector system, the optomechanics and a network of mechanisms with different functionalities. The fundamental technical concept is based on the heritage of the two previous ORFEUS SPAS missions. The phase B1 development activities are described in this paper under consideration of performance aspects, design drivers, the related trade offs (e.g. mechanical concepts, material selection etc.) and the critical functional and environmental test verification approach. Furthermore the actual state of the other scientific instruments of the WSO/UV (e.g. UV imagers) project is described.

  3. Constraining the redshifted 21-cm signal with the unresolved soft X-ray background

    NASA Astrophysics Data System (ADS)

    Fialkov, Anastasia; Cohen, Aviad; Barkana, Rennan; Silk, Joseph

    2017-01-01

    We use the observed unresolved cosmic X-ray background (CXRB) in the 0.5-2 keV band and existing upper limits on the 21-cm power spectrum to constrain the high-redshift population of X-ray sources, focusing on their effect on the thermal history of the Universe and the cosmic 21-cm signal. Because the properties of these sources are poorly constrained, we consider hot gas, X-ray binaries and mini-quasars (i.e. sources with soft or hard X-ray spectra) as possible candidates. We find that (1) the soft-band CXRB sets an upper limit on the X-ray efficiency of sources that existed before the end of reionization, which is one-to-two orders of magnitude higher than typically assumed efficiencies, (2) hard sources are more effective in generating the CXRB than the soft ones, (3) the commonly assumed limit of saturated heating is not valid during the first half of reionization in the case of hard sources, with any allowed value of X-ray efficiency, (4) the maximal allowed X-ray efficiency sets a lower limit on the depth of the absorption trough in the global 21-cm signal and an upper limit on the height of the emission peak, while in the 21-cm power spectrum it sets a minimum amplitude and frequency for the high-redshift peaks, and (5) the existing upper limit on the 21-cm power spectrum sets a lower limit on the X-ray efficiency for each model. When combined with the 21-cm global signal, the CXRB will be useful for breaking degeneracies and helping constrain the nature of high-redshift heating sources.

  4. UV, stress and aging.

    PubMed

    Debacq-Chainiaux, Florence; Leduc, Cedric; Verbeke, Alix; Toussaint, Olivier

    2012-07-01

    Skin is a model of choice in studies on aging. Indeed, skin aging can be modulated by internal and external factors, reflecting its complexity. Two types of skin aging have been identified: intrinsic, mainly genetically determined and extrinsic-also called "photo-aging"-resulting on the impact of environmental stress and more precisely of UV rays. Simplified in vitro models, based on cellular senescence, have been developed to study the relationship between UV and aging. These models vary on the cell type (fibroblasts or keratinocytes, normal or immortalized) and the type of UV used (UVA or UVB).

  5. UV Signature Mutations †

    PubMed Central

    2014-01-01

    Sequencing complete tumor genomes and exomes has sparked the cancer field's interest in mutation signatures for identifying the tumor's carcinogen. This review and meta-analysis discusses signatures and their proper use. We first distinguish between a mutagen's canonical mutations – deviations from a random distribution of base changes to create a pattern typical of that mutagen – and the subset of signature mutations, which are unique to that mutagen and permit inference backward from mutations to mutagen. To verify UV signature mutations, we assembled literature datasets on cells exposed to UVC, UVB, UVA, or solar simulator light (SSL) and tested canonical UV mutation features as criteria for clustering datasets. A confirmed UV signature was: ≥60% of mutations are C→T at a dipyrimidine site, with ≥5% CC→TT. Other canonical features such as a bias for mutations on the non-transcribed strand or at the 3' pyrimidine had limited application. The most robust classifier combined these features with criteria for the rarity of non-UV canonical mutations. In addition, several signatures proposed for specific UV wavelengths were limited to specific genes or species; non-signature mutations induced by UV may cause melanoma BRAF mutations; and the mutagen for sunlight-related skin neoplasms may vary between continents. PMID:25354245

  6. THE VERY FAINT END OF THE UV LUMINOSITY FUNCTION OVER COSMIC TIME: CONSTRAINTS FROM THE LOCAL GROUP FOSSIL RECORD

    SciTech Connect

    Weisz, Daniel R.; Johnson, Benjamin D.; Conroy, Charlie

    2014-10-10

    We present a new technique to estimate the evolution of the very faint end of the UV luminosity function (LF) out to z ∼ 5. Measured star formation histories (SFHs) from the fossil record of Local Group (LG) galaxies are used to reconstruct the LF down to M {sub UV} ∼–5 at z ∼ 5 and M {sub UV} ∼–1.5 at z < 1. Such faint limits are well beyond the current observational limits and are likely to remain beyond the limits of next-generation facilities. The reconstructed LFs, when combined with direct measurements of the LFs at higher luminosity, are well-fit by a standard Schechter function with no evidence of a break to the faintest limits probed by this technique. The derived faint-end slope, α, steepens from ≈ – 1.2 at z < 1 to ≈ – 1.6 at 4 < z < 5. We test the effects of burstiness in the SFHs and find the recovered LFs to be only modestly affected. Incompleteness corrections for the faintest LG galaxies and the (unlikely) possibility of significant luminosity-dependent destruction of dwarf galaxies between high redshift and the present epoch are important uncertainties. These and other uncertainties can be mitigated with more detailed modeling and future observations. The reconstructed faint end LF from the fossil record can therefore be a powerful and complementary probe of the high-redshift faint galaxies believed to play a key role in the reionization of the universe.

  7. The Atacama Cosmology Telescope: Cross-Correlation of Cosmic Microwave Background Lensing and Quasars

    NASA Technical Reports Server (NTRS)

    Sherwin, Blake D; Das, Sudeep; Haijian, Amir; Addison, Graeme; Bond, Richard; Crichton, Devin; Devlin, Mark J.; Dunkley, Joanna; Gralla, Megan B.; Halpern, Mark; Hill, J. Colin; Hincks, Adam D.; Hughes, John P.; Huffenberger, Kevin; Hlozek, Renee; Kosowsky, Arthur; Louis, Thibaut; Marriage, Tobias A.; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D.; Page, Lyman A.; Reese. Erik D.; Sehgal, Neelima; Sievers, Jon; Sifon, Cristobal; Spergel, David N.; Staggs, Suzanne T.; Switzer, Eric R.; Wollack, Ed.

    2012-01-01

    We measure the cross-correlation of Atacama cosmology telescope cosmic microwave background (CMB) lensing convergence maps with quasar maps made from the Sloan Digital Sky Survey DR8 SDSS-XDQSO photometric catalog. The CMB lensing quasar cross-power spectrum is detected for the first time at a significance of 3.8 sigma, which directly confirms that the quasar distribution traces the mass distribution at high redshifts z > 1. Our detection passes a number of null tests and systematic checks. Using this cross-power spectrum, we measure the amplitude of the linear quasar bias assuming a template for its redshift dependence, and find the amplitude to be consistent with an earlier measurement from clustering; at redshift z ap 1.4, the peak of the distribution of quasars in our maps, our measurement corresponds to a bias of b = 2.5 +/- 0.6. With the signal-to-noise ratio on CMB lensing measurements likely to improve by an order of magnitude over the next few years, our results demonstrate the potential of CMB lensing crosscorrelations to probe astrophysics at high redshifts.

  8. X-Ray Background from Early Binaries

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-11-01

    observed X-ray energy (and the total X-ray background is given by the sum of the curves). The two panels show results from two different calculation methods. [Xu et al. 2016]Xu and collaborators have now attempted to model to the impact of this X-ray production from Pop III binaries on the intergalactic medium and determine how much it could have contributed to reionization and the diffuse X-ray background we observe today.Generating a BackgroundThe authorsestimated the X-ray luminosities from Pop III binaries using the results of a series of galaxy-formation simulations, beginning at a redshift of z 25 and evolving up to z = 7.6. They then used these luminosities to calculate the resulting X-ray background.Xu and collaborators find that Pop III binaries can produce significant X-ray radiation throughout the period of reionization, and this radiation builds up gradually into an X-ray background. The team shows that X-rays from Pop III binaries might actually dominate more commonly assumed sources of the X-ray background at high redshifts (such as active galactic nuclei), and this radiation isstrong enough to heat the intergalactic medium to 1000K and ionize a few percent of the neutral hydrogen.If Pop III binaries are indeed this large of a contributor to the X-ray background and to the local and global heating of the intergalactic medium, then its important that we follow up with more detailed modeling to understand what this means for our interpretation of cosmological observations.CitationHao Xu et al 2016 ApJL 832 L5. doi:10.3847/2041-8205/832/1/L5

  9. UV-extending ghost inflation

    SciTech Connect

    Ivanov, Mikhail M.; Sibiryakov, Sergey E-mail: sergey.sibiryakov@cern.ch

    2014-05-01

    We present a setup that provides a partial UV-completion of the ghost inflation model up to a scale which can be almost as high as the Planck mass. This is achieved by coupling the inflaton to the Lorentz-violating sector described by the Einstein-aether theory or its khronometric version. Compared to previous works on ghost inflation our setup allows to go beyond the study of small perturbations and include the background dynamics in a unified framework. In the specific regime when the expansion of the Universe is dominated by the kinetic energy of the inflaton we find that the model predicts rather high tensor-to-scalar ratio r ∼ 0.02÷0.2 and non-Gaussianity of equilateral type with f{sub NL} in the range from -50 to -5.

  10. An Evaluation of UV-Monitoring Enhanced Skin Cancer Prevention among Farm Youth in Rural Virginia

    ERIC Educational Resources Information Center

    Chen, Yi-Chun; Ohanehi, Donatus C.; Redican, Kerry J.

    2015-01-01

    Background: Health districts in southwest Virginia have one of the highest ultraviolet (UV) radiation exposure and sunburn rate. Due to higher levels of UV exposure, rural farm youth are at higher risk for skin cancer than non-farm youth. Few studies have been published that explore best practices for decreasing UV exposure among this population.…

  11. Degradation of antipyrine by UV, UV/H₂O₂ and UV/PS.

    PubMed

    Tan, Chaoqun; Gao, Naiyun; Deng, Yang; Zhang, Yongji; Sui, Minghao; Deng, Jing; Zhou, Shiqing

    2013-09-15

    Degradation of antipyrine (AP) in water by three UV-based photolysis processes (i.e., direct UV, UV/H₂O₂, UV/persulfate (UV/PS)) was studied. For all the oxidation processes, the AP decomposition exhibited a pseudo-first-order kinetics pattern. Generally, UV/H₂O₂ and UV/PS significantly improved the degradation rate relevant to UV treatment alone. The pseudo-first-order degradation rate constants (kobs) were, to different degrees, affected by initial AP concentration, oxidant dose, pH, UV irradiation intensity, and co-existing chemicals such as humic acid, chloride, bicarbonate, carbonate and nitrate. The three oxidation processes followed the order in terms of treatment costs: UV/PS>UV>UV/H₂O₂ if the energy and chemical costs are considered. Finally, the AP degradation pathways in the UV/H₂O₂ and UV/PS processes are proposed. Results demonstrated that UV/H₂O₂ and UV/PS are potential alternatives to control water pollution caused by emerging contaminants such as AP.

  12. Four papers by the Supernova Cosmology Project: (1) Scheduled discoveries of 7+ high-redshift supernovae -- First cosmology results and bounds on q{sub 0}; (2) K corrections for Type Ia supernovae and a test for spatial variation of the Hubble constant; (3) Observation of cosmological time dilation using Type Ia supernovae as clocks; (4) The Type Ia supernova rate at z {approximately} 0.4

    SciTech Connect

    Perlmutter, S.; Deustua, S.; Gabi, S. |

    1995-06-01

    The 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}. These four presentations 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 the ongoing search.

  13. Biobased Nanoparticles for Broadband UV Protection with Photostabilized UV Filters.

    PubMed

    Hayden, Douglas R; Imhof, Arnout; Velikov, Krassimir P

    2016-12-07

    Sunscreens rely on multiple compounds to provide effective and safe protection against UV radiation. UV filters in sunscreens, in particular, provide broadband UV protection but are heavily linked to adverse health effects due to the generation of carcinogenic skin-damaging reactive oxygen species (ROS) upon solar irradiation. Herein, we demonstrate significant reduction in the ROS concentration by encapsulating an antioxidant photostabilizer with multiple UV filters into biobased ethyl cellulose nanoparticles. The developed nanoparticles display complete broadband UV protection and can form transparent and flexible films. This system therefore shows significant potential toward effective and safe nanoparticle-based UV protective coatings.

  14. ACS UV Contamination Monitor

    NASA Astrophysics Data System (ADS)

    Avila, Roberto

    2013-10-01

    The observations consist of SBC imaging and spectroscopy of the cluster NGC 6681 in order to monitor the temporal evolution of the UV sensitivity.All six filters and the two prisms will be used. Two SBC dark frames will follow the orbits.

  15. Are You UV Safe?

    ERIC Educational Resources Information Center

    Capobianco, Brenda; Thiel, Elizabeth Andrew

    2006-01-01

    Students may be slathered with SPF 30 sunscreen all summer at the beach or pool, but what do they know about ultraviolet (UV) light radiation and absorption? The authors of this article found the perfect opportunity to help students find out the science behind this important health precaution, when they developed a series of practical strategies…

  16. UV-optical from space

    NASA Technical Reports Server (NTRS)

    Illingworth, Garth; Savage, Blair; Angel, J. Roger; Blandford, Roger D.; Boggess, Albert; Bowyer, C. Stuart; Carruthers, George R.; Cowie, Lennox L.; Doschek, George A.; Dupree, Andrea K.

    1991-01-01

    The following subject areas are covered: (1) the science program (star formation and origins of planetary systems; structure and evolution of the interstellar medium; stellar population; the galactic and extragalactic distance scale; nature of galaxy nuclei, AGNs, and QSOs; formation and evolution of galaxies at high redshifts; and cosmology); (2) implementation of the science program; (3) the observatory-class missions (HST; LST - the 6m successor to HST; and next-generation 16m telescope); (4) moderate and small missions (Delta-class Explorers; imaging astrometric interferometer; small Explorers; optics development and demonstrations; and supporting ground-based capabilities); (5) prerequisites - the current science program (Lyman-FUSE; HTS optimization; the near-term science program; data analysis, modeling, and theory funding; and archives); (6) technologies for the next century; and (7) lunar-based telescopes and instruments.

  17. Background sources at PEP

    SciTech Connect

    Lynch, H.; Schwitters, R.F.; Toner, W.T.

    1988-01-01

    Important sources of background for PEP experiments are studied. Background particles originate from high-energy electrons and positrons which have been lost from stable orbits, ..gamma..-rays emitted by the primary beams through bremsstrahlung in the residual gas, and synchrotron radiation x-rays. The effect of these processes on the beam lifetime are calculated and estimates of background rates at the interaction region are given. Recommendations for the PEP design, aimed at minimizing background are presented. 7 figs., 4 tabs.

  18. TAUVEX - UV Space Telescope

    NASA Astrophysics Data System (ADS)

    Topaz, Jeremy; Braun, Ofer; Brosch, Noah

    1993-01-01

    The TAUVEX UV Space Telescope currently under construction by El-Op Ltd. in Israel is designed both for recording images of the sky in the UV region and to serve as the optical monitor for the SODART X-Ray Telescope being built by the Danish Space Research Institute. The two systems, together with several other experiments, will be flown on the S-R-G satellite to be launched by the CIS in 1995. TAUVEX will image a field of about 1 deg simultaneously in three spectral bands. In addition, it will record a selected object in a high-speed time-resolved mode in these bands. The concept and design of TAUVEX is described in this paper.

  19. UV curable materials development

    SciTech Connect

    Parker, B.G.

    1996-12-01

    Adhesives, coatings, and inks were selected for evaluation based on literature search and possible production applications. A differential photocalorimeter was used to measure degree of cure and allow prediction of optimum processing conditions. UV cure equipment were characterized and the ability to size equipment to specific materials cure needs established. Adhesion tests procedures were developed for the adhesives and solvent resistance testing procedures developed for the coatings and inks.

  20. Transverse effects in UV FELs

    SciTech Connect

    Small, D.W.; Wong, R.K.; Colson, W.B.

    1995-12-31

    In an ultraviolet Free Electron Laser (UV FEL), the electron beam size can be approximately the same as the optical mode size. The performance of a UV FEL is studied including the effect of emittance, betatron focusing, and external focusing of the electron beam on the transverse optical mode. The results are applied to the Industrial Laser Consortium`s UV FEL.

  1. Probing Reionization with the Cross-power Spectrum of 21 cm and Near-infrared Radiation Backgrounds

    NASA Astrophysics Data System (ADS)

    Mao, Xiao-Chun

    2014-08-01

    The cross-correlation between the 21 cm emission from the high-redshift intergalactic medium and the near-infrared (NIR) background light from high-redshift galaxies promises to be a powerful probe of cosmic reionization. In this paper, we investigate the cross-power spectrum during the epoch of reionization. We employ an improved halo approach to derive the distribution of the density field and consider two stellar populations in the star formation model: metal-free stars and metal-poor stars. The reionization history is further generated to be consistent with the electron-scattering optical depth from cosmic microwave background measurements. Then, the intensity of the NIR background is estimated by collecting emission from stars in first-light galaxies. On large scales, we find that the 21 cm and NIR radiation backgrounds are positively correlated during the very early stages of reionization. However, these two radiation backgrounds quickly become anti-correlated as reionization proceeds. The maximum absolute value of the cross-power spectrum is |\\Delta ^2_{21,NIR}|\\sim 10^{-4} mK nW m-2 sr-1, reached at l ~ 1000 when the mean fraction of ionized hydrogen is \\bar{x}_{i}\\sim 0.9. We find that Square Kilometer Array can measure the 21 cm-NIR cross-power spectrum in conjunction with mild extensions to the existing CIBER survey, provided that the integration time independently adds up to 1000 and 1 hr for 21 cm and NIR observations, and that the sky coverage fraction of the CIBER survey is extended from 4 × 10-4 to 0.1. Measuring the cross-correlation signal as a function of redshift provides valuable information on reionization and helps confirm the origin of the "missing" NIR background.

  2. Probing reionization with the cross-power spectrum of 21 cm and near-infrared radiation backgrounds

    SciTech Connect

    Mao, Xiao-Chun

    2014-08-01

    The cross-correlation between the 21 cm emission from the high-redshift intergalactic medium and the near-infrared (NIR) background light from high-redshift galaxies promises to be a powerful probe of cosmic reionization. In this paper, we investigate the cross-power spectrum during the epoch of reionization. We employ an improved halo approach to derive the distribution of the density field and consider two stellar populations in the star formation model: metal-free stars and metal-poor stars. The reionization history is further generated to be consistent with the electron-scattering optical depth from cosmic microwave background measurements. Then, the intensity of the NIR background is estimated by collecting emission from stars in first-light galaxies. On large scales, we find that the 21 cm and NIR radiation backgrounds are positively correlated during the very early stages of reionization. However, these two radiation backgrounds quickly become anti-correlated as reionization proceeds. The maximum absolute value of the cross-power spectrum is |Δ{sub 21,NIR}{sup 2}|∼10{sup −4} mK nW m{sup –2} sr{sup –1}, reached at ℓ ∼ 1000 when the mean fraction of ionized hydrogen is x-bar{sub i}∼0.9. We find that Square Kilometer Array can measure the 21 cm-NIR cross-power spectrum in conjunction with mild extensions to the existing CIBER survey, provided that the integration time independently adds up to 1000 and 1 hr for 21 cm and NIR observations, and that the sky coverage fraction of the CIBER survey is extended from 4 × 10{sup –4} to 0.1. Measuring the cross-correlation signal as a function of redshift provides valuable information on reionization and helps confirm the origin of the 'missing' NIR background.

  3. A Correlation between Lyα Spectral Line Profile and Rest-frame UV Morphology

    NASA Astrophysics Data System (ADS)

    U, Vivian; Hemmati, Shoubaneh; Darvish, Behnam; Mobasher, Bahram; Nayyeri, Hooshang; Dickinson, Mark; Stern, Daniel; Spinrad, Hyron; Mallery, Ryan

    2015-12-01

    We explore the relationship between the spectral shape of the Lyα emission and the UV morphology of the host galaxy using a sample of 304 Lyα-emitting BVi-dropouts at 3 < z < 7 in the Great Observatories Origins Deep Survey and Cosmic Evolution Survey fields. Using our extensive reservoir of high-quality Keck DEIMOS spectra combined with Hubble Space Telescope WFC3 data, we measure the Lyα line asymmetries for individual galaxies and compare them to axial ratios measured from observed J- and H-band (restframe UV) images. We find that the Lyα skewness exhibits a large scatter at small elongation (a/b < 2), and this scatter decreases as the axial ratio increases. Comparison of this trend to radiative transfer models and various results from the literature suggests that these high-redshift Lyα emitters are not likely to be intrinsically round and symmetric disks, but they probably host galactic outflows traced by Lyα emitting clouds. The ionizing sources are centrally located, and the optical depth is a good indicator of the absorption and scattering events on the escape path of Lyα photons from the source. Our results find no evidence of evolution in Lyα asymmetry or axial ratio with look-back time.

  4. A CORRELATION BETWEEN Lyα SPECTRAL LINE PROFILE AND REST-FRAME UV MORPHOLOGY

    SciTech Connect

    Vivian U; Hemmati, Shoubaneh; Darvish, Behnam; Mobasher, Bahram; Nayyeri, Hooshang; Mallery, Ryan; Dickinson, Mark; Stern, Daniel; Spinrad, Hyron

    2015-12-10

    We explore the relationship between the spectral shape of the Lyα emission and the UV morphology of the host galaxy using a sample of 304 Lyα-emitting BVi-dropouts at 3 < z < 7 in the Great Observatories Origins Deep Survey and Cosmic Evolution Survey fields. Using our extensive reservoir of high-quality Keck DEIMOS spectra combined with Hubble Space Telescope WFC3 data, we measure the Lyα line asymmetries for individual galaxies and compare them to axial ratios measured from observed J- and H-band (restframe UV) images. We find that the Lyα skewness exhibits a large scatter at small elongation (a/b < 2), and this scatter decreases as the axial ratio increases. Comparison of this trend to radiative transfer models and various results from the literature suggests that these high-redshift Lyα emitters are not likely to be intrinsically round and symmetric disks, but they probably host galactic outflows traced by Lyα emitting clouds. The ionizing sources are centrally located, and the optical depth is a good indicator of the absorption and scattering events on the escape path of Lyα photons from the source. Our results find no evidence of evolution in Lyα asymmetry or axial ratio with look-back time.

  5. The Cosmic Background Radiation circa ν2K

    NASA Astrophysics Data System (ADS)

    Bond, J. Richard; Pogosyan, Dmitry; Prunet, Simon

    We describe the implications of cosmic microwave background (CMB) observations and galaxy and cluster surveys of large scale structure (LSS) for theories of cosmic structure formation, especially emphasizing the recent Boomerang and Maxima CMB balloon experiments. The inflation-based cosmic structure formation paradigm we have been operating with for two decades has never been in better shape. Here we primarily focus on a simplified inflation parameter set, {ωb, ωcdm, Ωtot, ΩΛ, ns, τC, σ8}. Combining all of the current CMB+LSS data points to the remarkable conclusion that the local Hubble patch we can access has little mean curvature (Ωtot = 1.08 +/- 0.06) and the initial fluctuations were nearly scale invariant (ns = 1.03 +/- 0.08), both predictions of (non-baroque) inflation theory. The baryon density is found to be slightly larger than that preferred by independent Big Bang Nucleosynthesis estimates (ωb --- Ωbh2 = 0.030 +/- 0.005 cf. 0.019 +/- 0.002). The CDM density is in the expected range (ωcdm = 0.17+/-0.02). Even stranger is the CMB+LSS evidence that the density of the universe is dominated by unclustered energy akin to the cosmological constant (ΩΛ = 0.66 +/- 0.06), at the same level as that inferred from high redshift supernova observations. We also sketch the CMB+LSS implications for massive neutrinos.

  6. AMiBA: Array for Microwave Background Anisotropy

    NASA Astrophysics Data System (ADS)

    Lo, K. Y.; Chiueh, T.; Martin, R. N.

    2000-12-01

    As part of a 4-year US\\ 15 million Cosmology and Particle Astrophysics (CosPA) Research Excellence Initiative in Taiwan, AMiBA - a 19-element dual-channel 85-105 GHz interferometer array is being specifically built to survey for high redshift clusters of galaxies via the Sunyaev-Zeldovich Effect. In addition, the AMiBA will have full polarization capabilities in order to probe the polarization properties of the Cosmic Microwave Background. The AMiBA, to be sited on Mauna Kea in Hawaii or in Chile, will reach a sensitivity of 1.5 mJy or 7\\mu$K in 1 hour. The project involves scientific and technical collaborations with the Australia Telescope National Facilities (ATNF), the Canadian Institute of Theoretical Astrophysics (CITA), the Physics departments of the Carnegie-Mellon University (CMU) and the University of Pennsylvania (UPenn). The construction of the AMiBA is scheduled to be completed in 2003. Current status of the project will be discussed.

  7. The Cosmic Background Explorer.

    ERIC Educational Resources Information Center

    Gulkis, Samuel; And Others

    1990-01-01

    Outlines the Cosmic Background Explorer (COBE) mission to measure celestial radiation. Describes the instruments used and experiments involving differential microwave radiometers, and a far infrared absolute spectrophotometer. (YP)

  8. Deep X-ray and UV Surveys of Galaxies with Chandra, XMM-Newton, and GALEX

    NASA Technical Reports Server (NTRS)

    Hornschemeier, Ann

    2006-01-01

    Only with the deepest Chandra surveys has X-ray emission from normal and star forming galaxies (as opposed to AGN, which dominate the X-ray sky) been accessible at cosmologically interesting distances. The X-ray emission from accreting binaries provide a critical glimpse into the binary phase of stellar evolution and studies of the hot gas reservoir constrain past star formation. UV studies provide important, sensitive diagnostics of the young star forming populations and provide the most mature means for studying galaxies at 2 < zeta < 4. This talk will review current progress on studying X-ray emission in concert with UV emission from normal/star-forming galaxies at higher redshift. We will also report on our new, deep surveys with GALEX and XMM-Newton in the nearby Coma cluster. These studies are relevant to DEEP06 as Coma is the nearest rich cluster of galaxies and provides an important benchmark for high-redshift studies in the X-ray and UV wavebands. The 30 ks GALEX (note: similar depth to the GALEX Deep Imaging Survey) and the 110 ks XMM observations provide extremely deep coverage of a Coma outskirts field, allowing the construction of the UV and X-ray luminosity function of galaxies and important constraints on star formation scaling relations such as the X-ray-Star Formation Rate correlation and the X-ray/Stellar Mass correlation. We will discuss what we learn from these deep observations of Coma, including the recently established suppression of the X-ray emission from galaxies in the Coma outskirts that is likely associated with lower levels of past star formation and/or the results of tidal gas stripping.

  9. UV Radiation and the Skin

    PubMed Central

    D’Orazio, John; Jarrett, Stuart; Amaro-Ortiz, Alexandra; Scott, Timothy

    2013-01-01

    UV radiation (UV) is classified as a “complete carcinogen” because it is both a mutagen and a non-specific damaging agent and has properties of both a tumor initiator and a tumor promoter. In environmental abundance, UV is the most important modifiable risk factor for skin cancer and many other environmentally-influenced skin disorders. However, UV also benefits human health by mediating natural synthesis of vitamin D and endorphins in the skin, therefore UV has complex and mixed effects on human health. Nonetheless, excessive exposure to UV carries profound health risks, including atrophy, pigmentary changes, wrinkling and malignancy. UV is epidemiologically and molecularly linked to the three most common types of skin cancer, basal cell carcinoma, squamous cell carcinoma and malignant melanoma, which together affect more than a million Americans annually. Genetic factors also influence risk of UV-mediated skin disease. Polymorphisms of the melanocortin 1 receptor (MC1R) gene, in particular, correlate with fairness of skin, UV sensitivity, and enhanced cancer risk. We are interested in developing UV-protective approaches based on a detailed understanding of molecular events that occur after UV exposure, focusing particularly on epidermal melanization and the role of the MC1R in genome maintenance. PMID:23749111

  10. Observations of the diffuse UV radiation field

    NASA Technical Reports Server (NTRS)

    Murthy, Jayant; Henry, R. C.; Feldman, P. D.; Tennyson, P. D.

    1989-01-01

    Spectra are presented for the diffuse UV radiation field between 1250 to 3100 A from eight different regions of the sky, which were obtained with the Johns Hopkins UVX experiment. UVX flew aboard the Space Shuttle Columbia (STS-61C) in January 1986 as part of the Get-Away Special project. The experiment consisted of two 1/4 m Ebert-Fastie spectrometers, covering the spectral range 1250 to 1700 A at 17 A resolution and 1600 to 3100 A at 27 A resolution, respectively, with a field of view of 4 x .25 deg, sufficiently small to pick out regions of the sky with no stars in the line of sight. Values were found for the diffuse cosmic background ranging in intensity from 300 to 900 photons/sq cm/sec/sr/A. The cosmic background is spectrally flat from 1250 to 3100 A, within the uncertainties of each spectrometer. The zodiacal light begins to play a significant role in the diffuse radiation field above 2000 A, and its brightness was determined relative to the solar emission. Observed brightnesses of the zodiacal light in the UV remain almost constant with ecliptic latitude, unlike the declining visible brightnesses, possibly indicating that those (smaller) grains responsible for the UV scattering have a much more uniform distribution with distance from the ecliptic plane than do those grains responsible for the visible scattering.

  11. Correlators in nontrivial backgrounds

    SciTech Connect

    Mello Koch, Robert de; Ives, Norman; Stephanou, Michael

    2009-01-15

    Operators in N=4 super Yang-Mills theory with an R-charge of O(N{sup 2}) are dual to backgrounds which are asymtotically AdS{sub 5}xS{sup 5}. In this article we develop efficient techniques that allow the computation of correlation functions in these backgrounds. We find that (i) contractions between fields in the string words and fields in the operator creating the background are the field theory accounting of the new geometry, (ii) correlation functions of probes in these backgrounds are given by the free field theory contractions but with rescaled propagators and (iii) in these backgrounds there are no open string excitations with their special end point interactions; we have only closed string excitations.

  12. The Athena Background

    NASA Astrophysics Data System (ADS)

    Piro, Luigi; Lotti, Simone; Macculi, Claudio; Molendi, Silvano; Eraerds, Tanja; Laurent, Philippe

    2015-09-01

    Estimating, reducing and controlling the residual particle background is fundamental for achieving the objectives of several science topics of Athena, in particular those connected with background dominated observations of faint and/or diffuse sources. This requires assessing the particle environment in L2, propagating the various particle components throughout the mirror, spacecraft, and instruments via proper modelling and simulations of various physical processes, implementing design and h/w measures at instrument and mission level to reduce the un-rejected background and identifying proper calibration methods to control the background variations. Likewise, an adequate knowledge of the XRB, made of components that may vary spatially or temporally, is required as well. Here we will review the present status of the background knowledge, and summarize the activities on-going within Athena at various levels.

  13. THE UV LUMINOSITY FUNCTION OF STAR-FORMING GALAXIES VIA DROPOUT SELECTION AT REDSHIFTS z {approx} 7 AND 8 FROM THE 2012 ULTRA DEEP FIELD CAMPAIGN

    SciTech Connect

    Schenker, Matthew A.; Ellis, Richard S.; Robertson, Brant E.; Schneider, Evan; Ono, Yoshiaki; Ouchi, Masami; Stark, Daniel P.; McLure, Ross J.; Dunlop, James S.; Bowler, Rebecca A. A.; Curtis-Lake, Emma; Rogers, Alexander B.; Cirasuolo, Michele; Koekemoer, Anton; Charlot, Stephane; Furlanetto, Steven R.

    2013-05-10

    We present a catalog of high-redshift star-forming galaxies selected to lie within the redshift range z {approx_equal} 7-8 using the Ultra Deep Field 2012 (UDF12), the deepest near-infrared (near-IR) exposures yet taken with the Hubble Space Telescope (HST). As a result of the increased near-IR exposure time compared to previous HST imaging in this field, we probe {approx}0.65 (0.25) mag fainter in absolute UV magnitude, at z {approx} 7 (8), which increases confidence in a measurement of the faint end slope of the galaxy luminosity function. Through a 0.7 mag deeper limit in the key F105W filter that encompasses or lies just longward of the Lyman break, we also achieve a much-refined color-color selection that balances high redshift completeness and a low expected contamination fraction. We improve the number of dropout-selected UDF sources to 47 at z {approx} 7 and 27 at z {approx} 8. Incorporating brighter archival and ground-based samples, we measure the z {approx_equal} 7 UV luminosity function to an absolute magnitude limit of M{sub UV} = -17 and find a faint end Schechter slope of {alpha}=-1.87{sup +0.18}{sub -0.17}. Using a similar color-color selection at z {approx_equal} 8 that takes our newly added imaging in the F140W filter into account, and incorporating archival data from the HIPPIES and BoRG campaigns, we provide a robust estimate of the faint end slope at z {approx_equal} 8, {alpha}=-1.94{sup +0.21}{sub -0.24}. We briefly discuss our results in the context of earlier work and that derived using the same UDF12 data but with an independent photometric redshift technique.

  14. Uvs Nuur, Mongolia

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The Uvs Nuur Basin in Mongolia and the Russian Federation is the northernmost of the enclosed basins of Central Asia. It takes its name from Uvs Nuur Lake, a large, shallow and very saline lake, very important for migrating birds. Inscribed as a UNESCO World Heritage Site in 2003, the site is made up of twelve protected areas representing major biomes of eastern Eurasia. The steppe ecosystem supports a rich diversity of birds and the desert is home to a number of rare gerbil, jerboas and the marbled polecat. The mountains are an important refuge for the endangered snow leopard, mountain sheep, and the Asiatic ibex.

    The image covers an area of 46 x 47.8 km, was acquired on September 4, 2001, and is located near 50.3 degrees north latitude, 90.7 degrees east longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  15. The cosmic neutrino background

    NASA Technical Reports Server (NTRS)

    Dar, Arnon

    1991-01-01

    The cosmic neutrino background is expected to consist of relic neutrinos from the big bang, of neutrinos produced during nuclear burning in stars, of neutrinos released by gravitational stellar collapse, and of neutrinos produced by cosmic ray interactions with matter and radiation in the interstellar and intergalactic medium. Formation of baryonic dark matter in the early universe, matter-antimatter annihilation in a baryonic symmetric universe, and dark matter annihilation could have also contributed significantly to the cosmic neutrino background. The purpose of this paper is to review the properties of these cosmic neutrino backgrounds, the indirect evidence for their existence, and the prospects for their detection.

  16. Background Underground at WIPP

    NASA Astrophysics Data System (ADS)

    Esch, Ernst-Ingo; Hime, A.; Bowles, T. J.

    2001-04-01

    Recent interest to establish a dedicated underground laboratory in the United States prompted an experimental program at to quantify the enviromental backgrounds underground at the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico. An outline of this program is provided along with recent experimental data on the cosmic ray muon flux at the 650 meter level of WIPP. The implications of the cosmic ray muon and fast neutron background at WIPP will be discussed in the context of new generation, low background experiments envisioned in the future.

  17. Notification: Background Investigation Services

    EPA Pesticide Factsheets

    Project #OA-FY15-0029, February 26, 2015. The Office of Inspector General (OIG) for the U.S. Environmental Protection Agency (EPA) plans to begin field work for our audit of background investigation services.

  18. The GLAST Background Model

    SciTech Connect

    Ormes, J. F.; Atwood, W.; Burnett, T.; Grove, E.; Longo, F.; McEnery, J.; Ritz, S.; Mizuno, T.

    2007-07-12

    In order to estimate the ability of the GLAST/LAT to reject unwanted background of charged particles, optimize the on-board processing, size the required telemetry and optimize the GLAST orbit, we developed a detailed model of the background particles that would affect the LAT. In addition to the well-known components of the cosmic radiation, we included splash and reentrant components of protons, electrons (e+ and e-) from 10 MeV and beyond as well as the albedo gamma rays produced by cosmic ray interactions with the atmosphere. We made estimates of the irreducible background components produced by positrons and hadrons interacting in the multilayered micrometeorite shield and spacecraft surrounding the LAT and note that because the orbital debris has increased, the shielding required and hence the background are larger than were present in EGRET. Improvements to the model are currently being made to include the east-west effect.

  19. The GLAST Background Model

    SciTech Connect

    Ormes, J.F.; Atwood, W.; Burnett, T.; Grove, E.; Longo, F.; McEnery, J.; Mizuno, T.; Ritz, S.; /NASA, Goddard

    2007-10-17

    In order to estimate the ability of the GLAST/LAT to reject unwanted background of charged particles, optimize the on-board processing, size the required telemetry and optimize the GLAST orbit, we developed a detailed model of the background particles that would affect the LAT. In addition to the well-known components of the cosmic radiation, we included splash and reentrant components of protons, electrons (e+ and e-) from 10 MeV and beyond as well as the albedo gamma rays produced by cosmic ray interactions with the atmosphere. We made estimates of the irreducible background components produced by positrons and hadrons interacting in the multilayered micrometeorite shield and spacecraft surrounding the LAT and note that because the orbital debris has increased, the shielding required and hence the background are larger than were present in EGRET. Improvements to the model are currently being made to include the east-west effect.

  20. Diamond Nanowire for UV Detection

    DTIC Science & Technology

    2010-02-28

    addition to the stated goal of solar - blind , radiation-hard diamond nanowire UV detectors [3]. The use of diamond nanowires in field-effect transistors could...the next phase. As a result, a working diamond nanowire UV detector can be expected within the coming few months. And, a completely new diamond...attractive candidate for use in ultraviolet ( UV ) light detectors and emitters[2]. Of all known materials, it is the hardest, and has the highest

  1. The Austrian UV monitoring network

    NASA Astrophysics Data System (ADS)

    Blumthaler, Mario; Klotz, Barbara; Schwarzmann, Michael; Schreder, Josef

    2017-02-01

    The Austrian UV Monitoring network is operational since 1998 providing a large data set of erythemally weighted UV irradiance recorded with broadband UV biometer at 12 stations distributed all over Austria. In order to obtain high quality data all biometer are recalibrated once a year, the detectors are checked regularly for humidity and quality control is done routinely. The collected data are processed and then published on the website http://www.uv-index.at where the UV-Index of all measurement sites is presented in near real time together with a map of the distribution of the UV-Index over Austria. These UV-Index data together with measurements of global radiation and ozone levels from OMI are used to study long term trends for the stations of the monitoring network. Neither for all weather conditions nor for clear sky conditions is a statistically significant trend found for the UV-Index (with one exception) and for ozone. Furthermore, the radiation amplification factor (RAF) is determined experimentally from the power law correlation between UV-Index and ozone level for the site Innsbruck (577 m above sea level, 47.26°N, 11.38°E) for 19°solar elevation. A value of 0.91 ± 0.05 is found for the RAF for clear sky days with low ground albedo and a value of 1.03 ± 0.08 for days with high ground albedo (snow cover).

  2. Imaging the Spatial Fluctuations in Cosmic IR Background from Reionization with CIBER

    NASA Astrophysics Data System (ADS)

    Frazer, Chris; Bock, J.; Cooray, A.; Kawada, M.; Kim, M.; Lee, D.; Levenson, L.; Matsumoto, T.; Matsumuura, S.; Mitchell-Wynne, K.; Renbarger, T.; Smidt, J.; Sullivan, I.; Arai, T.; Tsumura, K.; Wada, T.; Zemcov, M.

    2011-01-01

    The Cosmic Infrared Background Experiment (CIBER) is a rocket-born absolute photometry imaging and spectroscopy experiment optimized to detect unresolved infrared signatures of first-light galaxies that were present during reionization. The signatures from reionization are theorized to be dominant at the wavelengths upon which CIBER surveys. CIBER consists of two wide field imagers to measure the extragalactic background fluctuations in the H and I-Bands (1.6 and 0.9 microns respectively) of the cosmic infrared background (CIB) as well as two spectrometers designed to take measurements of the foreground zodiacal light and the absolute Extragalactic Background Light (EBL) spectrum They imagers are capable of examining high-redshift (z 10-20) CIB fluctuations which will facilitate in the study of surface densities of sources associated with reionization. Studies of galaxies with similar redshift parameters (z > 6) are largely unaccounted for. The spectrometer configuration consists of one low resolution spectrometer and one narrow band spectrometer. They are respectively designed to take measurements of the absolute Extragalactic Background Light (EBL) spectrum, and foreground zodiacal light. In this poster we present the specifications for both CIBER imagers and detail how the fluctuations from galaxies during reionization will be measured.

  3. Deep UV LEDs

    NASA Astrophysics Data System (ADS)

    Han, Jung; Amano, Hiroshi; Schowalter, Leo

    2014-06-01

    Deep ultraviolet (DUV) photons interact strongly with a broad range of chemical and biological molecules; compact DUV light sources could enable a wide range of applications in chemi/bio-sensing, sterilization, agriculture, and industrial curing. The much shorter wavelength also results in useful characteristics related to optical diffraction (for lithography) and scattering (non-line-of-sight communication). The family of III-N (AlGaInN) compound semiconductors offers a tunable energy gap from infrared to DUV. While InGaN-based blue light emitters have been the primary focus for the obvious application of solid state lighting, there is a growing interest in the development of efficient UV and DUV light-emitting devices. In the past few years we have witnessed an increasing investment from both government and industry sectors to further the state of DUV light-emitting devices. The contributions in Semiconductor Science and Technology 's special issue on DUV devices provide an up-to-date snapshot covering many relevant topics in this field. Given the expected importance of bulk AlN substrate in DUV technology, we are pleased to include a review article by Hartmann et al on the growth of AlN bulk crystal by physical vapour transport. The issue of polarization field within the deep ultraviolet LEDs is examined in the article by Braut et al. Several commercial companies provide useful updates in their development of DUV emitters, including Nichia (Fujioka et al ), Nitride Semiconductors (Muramoto et al ) and Sensor Electronic Technology (Shatalov et al ). We believe these articles will provide an excellent overview of the state of technology. The growth of AlGaN heterostructures by molecular beam epitaxy, in contrast to the common organo-metallic vapour phase epitaxy, is discussed by Ivanov et al. Since hexagonal boron nitride (BN) has received much attention as both a UV and a two-dimensional electronic material, we believe it serves readers well to include the

  4. The Cosmic Background Explorer

    NASA Technical Reports Server (NTRS)

    Gulkis, Samuel; Lubin, Philip M.; Meyer, Stephan S.; Silverberg, Robert F.

    1990-01-01

    The Cosmic Background Explorer (CBE), NASA's cosmological satellite which will observe a radiative relic of the big bang, is discussed. The major questions connected to the big bang theory which may be clarified using the CBE are reviewed. The satellite instruments and experiments are described, including the Differential Microwave Radiometer, which measures the difference between microwave radiation emitted from two points on the sky, the Far-Infrared Absolute Spectrophotometer, which compares the spectrum of radiation from the sky at wavelengths from 100 microns to one cm with that from an internal blackbody, and the Diffuse Infrared Background Experiment, which searches for the radiation from the earliest generation of stars.

  5. Extragalactic background light measurements and applications

    PubMed Central

    Cooray, Asantha

    2016-01-01

    This review covers the measurements related to the extragalactic background light intensity from γ-rays to radio in the electromagnetic spectrum over 20 decades in wavelength. The cosmic microwave background (CMB) remains the best measured spectrum with an accuracy better than 1%. The measurements related to the cosmic optical background (COB), centred at 1 μm, are impacted by the large zodiacal light associated with interplanetary dust in the inner Solar System. The best measurements of COB come from an indirect technique involving γ-ray spectra of bright blazars with an absorption feature resulting from pair-production off of COB photons. The cosmic infrared background (CIB) peaking at around 100 μm established an energetically important background with an intensity comparable to the optical background. This discovery paved the way for large aperture far-infrared and sub-millimetre observations resulting in the discovery of dusty, starbursting galaxies. Their role in galaxy formation and evolution remains an active area of research in modern-day astrophysics. The extreme UV (EUV) background remains mostly unexplored and will be a challenge to measure due to the high Galactic background and absorption of extragalactic photons by the intergalactic medium at these EUV/soft X-ray energies. We also summarize our understanding of the spatial anisotropies and angular power spectra of intensity fluctuations. We motivate a precise direct measurement of the COB between 0.1 and 5 μm using a small aperture telescope observing either from the outer Solar System, at distances of 5 AU or more, or out of the ecliptic plane. Other future applications include improving our understanding of the background at TeV energies and spectral distortions of CMB and CIB. PMID:27069645

  6. Extragalactic background light measurements and applications.

    PubMed

    Cooray, Asantha

    2016-03-01

    This review covers the measurements related to the extragalactic background light intensity from γ-rays to radio in the electromagnetic spectrum over 20 decades in wavelength. The cosmic microwave background (CMB) remains the best measured spectrum with an accuracy better than 1%. The measurements related to the cosmic optical background (COB), centred at 1 μm, are impacted by the large zodiacal light associated with interplanetary dust in the inner Solar System. The best measurements of COB come from an indirect technique involving γ-ray spectra of bright blazars with an absorption feature resulting from pair-production off of COB photons. The cosmic infrared background (CIB) peaking at around 100 μm established an energetically important background with an intensity comparable to the optical background. This discovery paved the way for large aperture far-infrared and sub-millimetre observations resulting in the discovery of dusty, starbursting galaxies. Their role in galaxy formation and evolution remains an active area of research in modern-day astrophysics. The extreme UV (EUV) background remains mostly unexplored and will be a challenge to measure due to the high Galactic background and absorption of extragalactic photons by the intergalactic medium at these EUV/soft X-ray energies. We also summarize our understanding of the spatial anisotropies and angular power spectra of intensity fluctuations. We motivate a precise direct measurement of the COB between 0.1 and 5 μm using a small aperture telescope observing either from the outer Solar System, at distances of 5 AU or more, or out of the ecliptic plane. Other future applications include improving our understanding of the background at TeV energies and spectral distortions of CMB and CIB.

  7. Contribution of the first galaxies to the cosmic far-infrared/sub-millimeter background - I. Mean background level

    NASA Astrophysics Data System (ADS)

    De Rossi, María Emilia; Bromm, Volker

    2017-03-01

    We study the contribution of the first galaxies to the far-infrared/sub-millimeter (FIR/sub-mm) extragalactic background light (EBL) by implementing an analytical model for dust emission. We explore different dust models, assuming different grain-size distributions and chemical compositions. According to our findings, observed reradiated emission from dust in dwarf-size galaxies at z ∼ 10 would peak at a wavelength of ∼ 500 μm with observed fluxes of ∼10-3-10-2 nJy, which is below the capabilities of current observatories. In order to be detectable, model sources at these high redshifts should exhibit luminosities of ≳1012 L⊙, comparable to that of local ultraluminous systems. The FIR/sub-mm-EBL generated by primeval galaxies peaks at ∼ 500 μm, with an intensity ranging from ∼10-4 to 10-3 nW m-2 sr-1, depending on dust properties. These values are ∼3-4 orders of magnitude below the absolute measured cosmic background level, suggesting that the first galaxies would not contribute significantly to the observed FIR/sub-mm-EBL. Our model EBL exhibits a strong correlation with the dust-to-metal ratio, where we assume a fiducial value of D = 0.005, increasing almost proportionally to it. Thus, measurements of the FIR/sub-mm-EBL could provide constraints on the amount of dust in the early Universe. Even if the absolute signal from primeval dust emission may be undetectable, it might still be possible to obtain information about it by exploring angular fluctuations at ∼ 500 μm, close to the peak of dust emission from the first galaxies.

  8. Berkeley Low Background Facility

    SciTech Connect

    Thomas, K. J.; Norman, E. B.; Smith, A. R.; Poon, A. W. P.; Chan, Y. D.; Lesko, K. T.

    2015-08-17

    The Berkeley Low Background Facility (BLBF) at Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California provides low background gamma spectroscopy services to a wide array of experiments and projects. The analysis of samples takes place within two unique facilities; locally within a carefully-constructed, low background laboratory on the surface at LBNL and at the Sanford Underground Research Facility (SURF) in Lead, SD. These facilities provide a variety of gamma spectroscopy services to low background experiments primarily in the form of passive material screening for primordial radioisotopes (U, Th, K) or common cosmogenic/anthropogenic products; active screening via neutron activation analysis for U,Th, and K as well as a variety of stable isotopes; and neutron flux/beam characterization measurements through the use of monitors. A general overview of the facilities, services, and sensitivities will be presented. Recent activities and upgrades will also be described including an overview of the recently installed counting system at SURF (recently relocated from Oroville, CA in 2014), the installation of a second underground counting station at SURF in 2015, and future plans. The BLBF is open to any users for counting services or collaboration on a wide variety of experiments and projects.

  9. Nonthermal cosmic neutrino background

    NASA Astrophysics Data System (ADS)

    Chen, Mu-Chun; Ratz, Michael; Trautner, Andreas

    2015-12-01

    We point out that, for Dirac neutrinos, in addition to the standard thermal cosmic neutrino background (C ν B ), there could also exist a nonthermal neutrino background with comparable number density. As the right-handed components are essentially decoupled from the thermal bath of standard model particles, relic neutrinos with a nonthermal distribution may exist until today. The relic density of the nonthermal (nt) background can be constrained by the usual observational bounds on the effective number of massless degrees of freedom Neff and can be as large as nν nt≲0.5 nγ. In particular, Neff can be larger than 3.046 in the absence of any exotic states. Nonthermal relic neutrinos constitute an irreducible contribution to the detection of the C ν B and, hence, may be discovered by future experiments such as PTOLEMY. We also present a scenario of chaotic inflation in which a nonthermal background can naturally be generated by inflationary preheating. The nonthermal relic neutrinos, thus, may constitute a novel window into the very early Universe.

  10. China: Background Notes Series.

    ERIC Educational Resources Information Center

    Reams, Joanne Reppert

    Concise background information on the People's Republic of China is provided. The publication begins with a profile of the country, outlining the people, geography, economy, and membership in international organizations. The bulk of the document then discusses in more detail China's people, geography, history, government, education, economy, and…

  11. Building Background Knowledge

    ERIC Educational Resources Information Center

    Fisher, Douglas; Ross, Donna; Grant, Maria

    2010-01-01

    Too often, students enter our classrooms with insufficient knowledge of physical science. As a result, they have a difficult time understanding content in texts, lectures, and laboratory activities. This lack of background knowledge can have an impact on their ability to ask questions and wonder--both key components of inquiry. In this article,…

  12. Association of UV Index and Sunscreen Use among White High School Students in the United States

    ERIC Educational Resources Information Center

    Everett Jones, Sherry; O'Malley Olsen, Emily; Michael, Shannon L.; Saraiya, Mona

    2013-01-01

    Background: When used appropriately, sunscreen decreases the amount of ultraviolet (UV) radiation exposure to the skin and is recommended to prevent skin cancer. This study examined the association between annual average UV index and sunscreen use among White, non-Hispanic youth. Methods: The 2007 and 2009 national Youth Risk Behavior Survey…

  13. Sensitization of bleached Stentor to far UV.

    PubMed

    Burchill, B R; Bordy, M; Grene, R B

    1979-10-01

    Stentors are more sensitive to far UV-induced delay of oral regeneration following bleaching of their UV-absorbant cortical pigment granules. This finding supports a subcortical location of UV-sensitive sites.

  14. High-resolution imaging of three new UV-bright lensed arcs

    NASA Astrophysics Data System (ADS)

    Allam, Sahar

    2009-07-01

    We have identified and spectroscopically confirmed three new strongly lensed, UV-bright star-forming galaxies at z 2 that are similar to the well-studied gravitationally lensed Lyman Break Galaxy {LBG} MS1512-cB58, and are of comparable brightness to the ''8 O'Clock Arc'' {Allam et al. 2007} and ''Clone'' systems {Lin et al. 2008}. The 8 O'Clock Arc and Clone have already been awarded 20 orbits for deep WFPC2 and NICMOS imaging in five bands {HST cycle 16, Program 11167, PI: Allam}. Adding these three recently discovered objects thus completes a unique set of the brightest known strongly lensed galaxies at z 2, with magnitudes of r 20-21, and they provide a new window into the detailed study of the properties of high redshift galaxies. We propose 21 orbits for deep WFC3 imaging in five bands {F475W, F606W, F814W, F110W, and F160W} in order to construct detailed lensing models, to probe the mass and light profiles of the lensing galaxies and their environments, and to constrain the spectral energy distributions, star formation histories, and morphologies of the lensed galaxies.

  15. UV clothing and skin cancer.

    PubMed

    Tarbuk, Anita; Grancarić, Ana Marija; Situm, Mirna; Martinis, Mladen

    2010-04-01

    Skin cancer incidence in Croatia is steadily increasing in spite of public and governmental permanently measurements. It is clear that will soon become a major public health problem. The primary cause of skin cancer is believed to be a long exposure to solar ultraviolet (UV) radiation. The future designers of UV protective materials should be able to block totally the ultraviolet radiation. The aim of this paper is to present results of measurements concerning UV protecting ability of garments and sun-screening textiles using transmission spectrophotometer Cary 50 Solarscreen (Varian) according to AS/NZS 4399:1996; to show that standard clothing materials are not always adequate to prevent effect of UV radiation to the human skin; and to suggest the possibilities for its improvement for this purpose.

  16. The Moon in the UV

    NASA Astrophysics Data System (ADS)

    Hendrix, Amanda

    2014-11-01

    While the Moon has been observed in the UV for decades, the real utility of this spectral region for unlocking some of the Moon’s secrets has only recently been understood. Previously the domain of atmospheric studies, the UV has now emerged as an important spectral region for studying surfaces. The ultraviolet regime is very sensitive to both space weathering effects and composition, including hydration. This presentation will cover a review of early UV lunar observations (e.g., Apollo 17, International Ultraviolet Explorer), as well as early laboratory studies that first shone a light on the importance of this spectral region. The Lyman Alpha Mapping Project (LAMP) instrument, currently in orbit on the Lunar Reconnaissance Orbiter (LRO) spacecraft, is providing critical mapping capabilities of UV signatures, including signals from the permanently shadowed regions of the poles. I will discuss some of these exciting results, and extend these to implications for other airless bodies in the solar system.

  17. The MOSDEF Survey: The Strong Agreement Between Hα and UV-To-FIR Star Formation Rates for z ~ 2 Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Shivaei, Irene; Reddy, Naveen; Kriek, Mariska T.; Shapley, Alice E.; Mobasher, Bahram; Coil, Alison L.; Siana, Brian D.; Sanders, Ryan; Price, Sedona; Freeman, William R.; Azadi, Mojegan

    2016-06-01

    We present the first direct comparison between Balmer line and panchromatic SED-based star-formation rates (SFRs) for z ~ 2 galaxies. While dust-corrected SFRs(Hα,Hβ) using Balmer decrements are commonly used at low redshift, it has been argued that Balmer lines may miss optically thick star-forming regions at high redshifts. In order to investigate this possible bias, we compare the SFRs(Hα,Hβ) with independently measured UV-to-far-IR SFRs for star-forming galaxies at z ~ 2. For this comparison we use a sample of galaxies selected from the unique spectroscopic dataset of the MOSFIRE Deep Evolution Field (MOSDEF) survey. The MOSDEF survey is a multi-year project that uses the near-IR MOSFIRE spectrograph on the 10-m Keck I telescope to characterize the gaseous and stellar contents of ~ 1500 rest-frame optically selected galaxies at 1.37 ≤ z ≤ 3.80. In addition to the rest-frame optical spectra, we use data from Spitzer/MIPS 24 μm, Herschel/PACS 100 and 160 μm, and Herschel/SPIRE 250, 350, and 500 μm to measure mid- and far-IR fluxes. We fit the UV-to-far-IR SEDs with the state-of-the-art flexible stellar population synthesis (FSPS) models, which utilize energy balance to fit the stellar and dust emission simultaneously. Comparing the SFR(Hα,Hβ) with the robust UV-to-far-IR SED inferrred SFRs, show us how accurately Balmer decrements predict the obscuration of the nebular lines in order to robustly calculate SFRs for star-forming galaxies at high redshift. Furthermore, we use our data to assess SFR indicators based on modeling the UV-to-mid-IR SEDs or by adding SFR(UV) and SFR(IR), for which the latter is based on the empirical conversions from mid-IR to total IR luminosity. This study shed light on the validity of various SFR indicators, specifically the nebular emission lines, for galaxies at z ~ 2.

  18. Ultraviolet Background Radiation (Preprint)

    DTIC Science & Technology

    1991-03-01

    5.4 Apollo-Soyuz 3 5 5.5 Evidence for Scattering From Dust ? 3 8 5.6 More Evidence For Scattering From Dust ? 4 0 5.7 More Observations 4 2...Emission from cold interstellar dust . This has been observed by IRAS as the 100 u.m cosmic cirrus (64). The existence of such dust at moderate and... DUST 4 6 CONCLUSIONS 4 7 6.1 Spectral Structure in the Diffuse 4 7 Ultraviolet Background 6.2 Is There Light Scattered From Dust ? 4 7 6.3

  19. Cosmic Background Radiation

    NASA Astrophysics Data System (ADS)

    Sidharth, B. G.; Valluri, S. R.

    2015-08-01

    It is shown that a collection of photons with nearly the same frequency exhibits a "condensation" type of phenomenon corresponding to a peak intensity. The observed cosmic background radiation can be explained from this standpoint. We have obtained analogous results by extremization of the occupation number for photons with the use of the Lambert W function. Some of the interesting applications of this function are briefly discussed in the context of graphene which exhibits an interesting two dimensional structure with several characteristic properties and diverse practical applications.

  20. The heliosphere neutrals composition: from Voyager UVS to IMAPS

    NASA Astrophysics Data System (ADS)

    Ben-Jaffel, L.

    2015-12-01

    For the last 35 years, the Voyagers (V) 1 and 2 ultraviolet spectrometers (UVS) data harvest has covered heliosphere sky-background in-situ measurements, stellar spectrophotometry, and outer planets encounters. Their long and ongoing operation period overlaps with many current and past ultraviolet missions, offering unique opportunities for cross-calibration with other spectrometers. Here we revisit the Voyager UVS calibration to assess the intriguing 243% (V1) and 156% (V2) sensitivity enhancements recently proposed. Using the Saturn Lyman-α airglow, observed in-situ by both Voyagers, and remotely by IUE, we match the Voyager values to IUE, taking into account the shape of the Saturn and sky-background Lyman-α lines observed with the Goddard High Resolution Spectrograph onboard the Hubble Space Telescope. For all known ranges of the interplanetary H I density, we show that the V1 and V2 UVS sensitivities at the Lyman-α channels cannot be enhanced by the amounts thus far proposed. Our prescription is to keep the original calibration of the Voyager UVS with an uncertainty that should not exceed 30%, making both instruments some of the most stable EUV/FUV spectrographs of the history of space exploration. This rich heritage from past and current space missions confirms that UV observations of the sky-background are a powerful lever for constraining the neutral composition and large structure of the heliosphere. It also points to the need in the future for fine Doppler-shift measurements and faint emissions detection in order to directly access the microphysical processes that drive the instant shape and composition of the heliosphere that is forced by the magnetized plasmas from solar wind and the local interstellar medium. Future deep space missions should thus include UV capabilities that make use of sensitive, high-resolution technology that allows achieving the highest throughput for extended light sources.

  1. The Backgrounds Data Center

    NASA Technical Reports Server (NTRS)

    Snyder, W. A.; Gursky, H.; Heckathorn, H. M.; Lucke, R. L.; Berg, S. L.; Dombrowski, E. G.; Kessel, R. A.

    1993-01-01

    The Strategic Defense Initiative Organization has created data centers for midcourse, plumes, and backgrounds phenomenologies. The Backgrounds Data Center (BDC) has been designated as the prime archive for data collected by SDIO programs. The BDC maintains a Summary Catalog that contains 'metadata,' that is, information about data, such as when the data were obtained, what the spectral range of the data is, and what region of the Earth or sky was observed. Queries to this catalog result in a listing of all data sets (from all experiments in the Summary Catalog) that satisfy the specified criteria. Thus, the user can identify different experiments that made similar observations and order them from the BDC for analysis. On-site users can use the Science Analysis Facility (SAFE for this purpose. For some programs, the BDC maintains a Program Catalog, which can classify data in as many ways as desired (rather than just by position, time, and spectral range as in the Summary Catalog). For example, data sets could be tagged with such diverse parameters as solar illumination angle, signal level, or the value of a particular spectral ratio, as long as these quantities can be read from the digital record or calculated from it by the ingest program. All unclassified catalogs and unclassified data will be remotely accessible.

  2. PHYSICAL PROPERTIES OF Ly{alpha} EMITTERS AT z {approx} 0.3 FROM UV-TO-FIR MEASUREMENTS

    SciTech Connect

    Oteo, I.; Bongiovanni, A.; Perez Garcia, A. M.; Cepa, J.; Pintos-Castro, I.; Ederoclite, A.; Sanchez-Portal, M.; Altieri, B.; Perez-Martinez, R.; Andreani, P.; Aussel, H.; Daddi, E.; Elbaz, D.; Le Floc'h, E.; Cimatti, A.; and others

    2012-06-01

    The analysis of the physical properties of low-redshift Ly{alpha} emitters (LAEs) can provide clues in the study of their high-redshift analogs. At z {approx} 0.3, LAEs are bright enough to be detected over almost the entire electromagnetic spectrum and it is possible to carry out a more precise and complete study than at higher redshifts. In this work, we examine the UV and IR emission, dust attenuation, star formation rate (SFR), and morphology of a sample of 23 GALEX-discovered star-forming LAEs at z {approx} 0.3 with direct UV (GALEX), optical (ACS), and FIR (PACS and MIPS) data. Using the same UV and IR limiting luminosities, we find that LAEs at z {approx} 0.3 tend to be less dusty, have slightly higher total SFRs, have bluer UV continuum slopes, and are much smaller than other galaxies that do not exhibit Ly{alpha} emission in their spectrum (non-LAEs). These results suggest that at z {approx} 0.3, Ly{alpha} photons tend to escape from small galaxies with low dust attenuation. Regarding their morphology, LAEs belong to Irr/merger classes, unlike non-LAEs. Size and morphology represent the most noticeable difference between LAEs and non-LAEs at z {approx} 0.3. Furthermore, the comparison of our results with those obtained at higher redshifts indicates either that the Ly{alpha} technique picks up different kind of galaxies at different redshifts or that the physical properties of LAEs are evolving with redshift.

  3. Use of UV Sources for Detection and Identification of Explosives

    NASA Technical Reports Server (NTRS)

    Hug, William; Reid, Ray; Bhartia, Rohit; Lane, Arthur

    2009-01-01

    Measurement of Raman and native fluorescence emission using ultraviolet (UV) sources (<400 nm) on targeted materials is suitable for both sensitive detection and accurate identification of explosive materials. When the UV emission data are analyzed using a combination of Principal Component Analysis (PCA) and cluster analysis, chemicals and biological samples can be differentiated based on the geometric arrangement of molecules, the number of repeating aromatic rings, associated functional groups (nitrogen, sulfur, hydroxyl, and methyl), microbial life cycles (spores vs. vegetative cells), and the number of conjugated bonds. Explosive materials can be separated from one another as well as from a range of possible background materials, which includes microbes, car doors, motor oil, and fingerprints on car doors, etc. Many explosives are comprised of similar atomic constituents found in potential background samples such as fingerprint oils/skin, motor oil, and soil. This technique is sensitive to chemical bonds between the elements that lead to the discriminating separability between backgrounds and explosive materials.

  4. Cross-Correlating the Cosmic Infrared and Cosmic X-Ray Background Fluctuations

    NASA Astrophysics Data System (ADS)

    Cooper, Rachel Ann; Cappelluti, Nico; Li, Yanxia; Urry, C. Megan; Guo, Joyce

    2017-01-01

    Studying unresolved (i.e., undetected) sources is a way to probe the faintest, and thus the least understood, source populations. In particular, such studies have suggested a population of high redshift accreting black holes. We present cross-power spectra and coherence between the cosmic infrared and cosmic x-ray background fluctuations, using infrared images from Spitzer Space Telescope and x-ray images from XMM-Newton of the ˜2 square degree area of the COSMOS field. We first masked all known sources and subtracted model images of the masked x-ray sources’ PSF tails so as to isolate the unresolved cosmic backgrounds. We have considered infrared data from two bands, 3.6 and 4.5 μm, and x-ray data from five bands, [0.3-0.5], [0.5-1], [1-2], [0.5-2], and [2-10] keV. We find strong correlation between the cosmic infrared and cosmic x-ray backgrounds, which suggests an origin in a common population, i.e., stars and/or growing black holes.

  5. Star formation history and chemical enrichment in the early Universe: clues from the rest-optical and rest-UV spectra of z~2-3 star-forming galaxies in the Keck Baryonic Structure Survey