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Full-Text Articles in Physical Sciences and Mathematics
Baryon Dynamics, Dark Matter Substructure, And Galaxies, Dh Weinberg, S Colombi, R Dave, N Katz
Baryon Dynamics, Dark Matter Substructure, And Galaxies, Dh Weinberg, S Colombi, R Dave, N Katz
Astronomy Department Faculty Publication Series
By comparing a collisionless cosmological N-body simulation (DM) to a smoothed particle hydrodynamics simulation (SPH) with the same initial conditions, we investigate the correspondence between dark matter subhalos produced by collisionless dynamics and galaxies produced by dissipative gas dynamics in a dark matter background. When galaxies in the SPH simulation fall into larger groups and become satellites, they retain local dark matter concentrations (SPH subhalos) whose mass is typically 5 times the galaxy baryonic mass (compared to the simulation's universal ratio Ωdm/Ωb 7.5). The more massive subhalos of the SPH simulation generally have corresponding subhalos of …
Spectroscopic Confirmation Of An Extreme Starburst At Redshift 4.547, P Capak, Cl Carilli, N Lee, T Aldcroft, H Aussel, E Schinnerer, Gw Wilson, Min Yun, A Blain, M Giavalisco, O Ilbert, J Kartaltepe, Ks Lee, H Mccracken, B Mobasher, M Salvato, S Sasaki, Ks Scott, K Sheth, Y Shioya, D Thompson, M Elvis, Db Sanders, Nz Scoville, Y Tanaguchi
Spectroscopic Confirmation Of An Extreme Starburst At Redshift 4.547, P Capak, Cl Carilli, N Lee, T Aldcroft, H Aussel, E Schinnerer, Gw Wilson, Min Yun, A Blain, M Giavalisco, O Ilbert, J Kartaltepe, Ks Lee, H Mccracken, B Mobasher, M Salvato, S Sasaki, Ks Scott, K Sheth, Y Shioya, D Thompson, M Elvis, Db Sanders, Nz Scoville, Y Tanaguchi
Astronomy Department Faculty Publication Series
We report the spectroscopic confirmation of a submillimeter galaxy (SMG) at z = 4.547 with an estimated LIR = (0.5-2.0) × 1013 L. The spectra, mid-IR, and X-ray properties indicate the bolometric luminosity is dominated by star formation at a rate of >1000 M yr−1. Multiple, spatially separated components are visible in the Lyα line with an observed velocity difference of up to 380 km s−1 and the object morphology indicates a merger. The best-fit spectral energy distribution and spectral line indicators suggest the object is 2-8 Myr old and contains >1010 M …
Ongoing Assembly Of Massive Galaxies By Major Merging In Large Groups And Clusters From The Sdss, Dh Mcintosh, Yc Guo, J Hertzberg, N Katz, Hj Mo, Fc Van Den Bosch, Xh Yang
Ongoing Assembly Of Massive Galaxies By Major Merging In Large Groups And Clusters From The Sdss, Dh Mcintosh, Yc Guo, J Hertzberg, N Katz, Hj Mo, Fc Van Den Bosch, Xh Yang
Astronomy Department Faculty Publication Series
We investigate the incidence of major mergers creating massive (Mstar > 1011 M⊙) galaxies in present-day (z≤ 0.12) groups and clusters. Using a volume-limited sample of 845 groups with dark matter halo masses above 2.5 × 1013 M⊙, we isolate 221 galaxy pairs with ≤1.5 r-band magnitude differences, ≤30 kpc projected separations and combined masses above 1011 M⊙. We fit the r-band images of each pair as the line-of-sight projection of symmetric models and identify 38 mergers by the presence of residual asymmetric structure associated with …
Multiwavelength Study Of Massive Galaxies At Z Similar To 2. I. Star Formation And Galaxy Growth, E Daddi, M Dickinson, G Morrison, R Chary, A Cimatti, D Elbaz, D Frayer, A Renzini, A Pope, Dm Alexander, Fe Bauer, M Giavalisco, M Huynh, J Kurk, M Mignoli
Multiwavelength Study Of Massive Galaxies At Z Similar To 2. I. Star Formation And Galaxy Growth, E Daddi, M Dickinson, G Morrison, R Chary, A Cimatti, D Elbaz, D Frayer, A Renzini, A Pope, Dm Alexander, Fe Bauer, M Giavalisco, M Huynh, J Kurk, M Mignoli
Astronomy Department Faculty Publication Series
No abstract provided.
Accretion, Feedback And Galaxy Bimodality: A Comparison Of The Galics Semi-Analytic Model And Cosmological Sph Simulations, A Cattaneo, J Blaizot, Dh Weinberg, D Keres, S Colombi, R Dave, J Devriendt, B Guiderdoni, N Katz
Accretion, Feedback And Galaxy Bimodality: A Comparison Of The Galics Semi-Analytic Model And Cosmological Sph Simulations, A Cattaneo, J Blaizot, Dh Weinberg, D Keres, S Colombi, R Dave, J Devriendt, B Guiderdoni, N Katz
Astronomy Department Faculty Publication Series
We compare the galaxy population of a smoothed particle hydrodynamics (SPH) simulation to those predicted by the GalICS (Galaxies In Cosmological Simulations) N-body + semi-analytic model and a stripped down version of GalICS that omits the effects of supernova and active galactic nucleus (AGN) feedback. The SPH simulation and the no-feedback GalICS model make similar predictions for the baryonic mass functions of galaxies and for the dependence of these mass functions on environment and redshift. The two methods also make similar predictions for the galaxy content of dark matter haloes as a function of halo mass and for the …
Evidence For A Population Of High-Redshift Submillimeter Galaxies From Interferometric Imaging, Jd Younger, Gg Fazio, Js Huang, Min Yun, Gw Wilson, Mln Ashby, Ma Gurwell, K Lai, Ab Peck, Gr Petitpas, Dj Wilner, D Iono, K Kohno, R Kawabe, Dh Hughes, I Aretxaga, T Webb, A Martinez-Sansigre, S Kim, Ks Scott, J Austermann, T Perera, Jd Lowenthal, E Schinnerer, V Smolcic
Evidence For A Population Of High-Redshift Submillimeter Galaxies From Interferometric Imaging, Jd Younger, Gg Fazio, Js Huang, Min Yun, Gw Wilson, Mln Ashby, Ma Gurwell, K Lai, Ab Peck, Gr Petitpas, Dj Wilner, D Iono, K Kohno, R Kawabe, Dh Hughes, I Aretxaga, T Webb, A Martinez-Sansigre, S Kim, Ks Scott, J Austermann, T Perera, Jd Lowenthal, E Schinnerer, V Smolcic
Astronomy Department Faculty Publication Series
We have used the Submillimeter Array to image a flux-limited sample of seven submillimeter galaxies, selected by the AzTEC camera on the JCMT at 1.1 mm, in the COSMOS field at 890 μ m with ~2'' resolution. All of the sources—two radio-bright and five radio-dim—are detected as single point sources at high significance (>6 σ), with positions accurate to ~0.2'' that enable counterpart identification at other wavelengths observed with similarly high angular resolution. All seven have IRAC counterparts, but only two have secure counterparts in deep HST ACS imaging. As compared to the two radio-bright sources in the sample, …
The Morphological Diversities Among Star-Forming Galaxies At High Redshifts In The Great Observatories Origins Deep Survey, S Ravindranath, M Giavalisco, Hc Ferguson, C Conselice, N Katz, M Weinberg, J Lotz, M Dickinson, Sm Fall, B Mobasher, C Papovich
The Morphological Diversities Among Star-Forming Galaxies At High Redshifts In The Great Observatories Origins Deep Survey, S Ravindranath, M Giavalisco, Hc Ferguson, C Conselice, N Katz, M Weinberg, J Lotz, M Dickinson, Sm Fall, B Mobasher, C Papovich
Astronomy Department Faculty Publication Series
We used the deep, multiwavelength images obtained by the Great Observatories Origins Deep Survey (GOODS) to identify ~4700 Lyman break galaxies (LBGs) at z > 2.5, and 292 starburst galaxies at z ~ 1.2. We present the results from morphological analysis based on light profile shape and ellipticity for ~1333 of the most luminous LBGs. About 40% of LBGs at z ~ 3 have exponential profiles, ~30% of the galaxies have steep (r1/4-like) profiles, and ~30% of LBGs have multiple cores of disturbed morphologies suggestive of close pairs or mergers. The fraction of spheriod-like LBGs decrease by about 15% from z …
Galaxy Merger Statistics And Inferred Bulge-To-Disk Ratios In Cosmological Sph Simulations, Ah Maller, N Katz, D Keres, R Dave, Dh Weinberg
Galaxy Merger Statistics And Inferred Bulge-To-Disk Ratios In Cosmological Sph Simulations, Ah Maller, N Katz, D Keres, R Dave, Dh Weinberg
Astronomy Department Faculty Publication Series
We construct merger trees for galaxies identified in a cosmological hydrodynamic simulation and use them to characterize predicted merger rates as a function of redshift, galaxy mass, and merger mass ratio. At z = 0.3, we find a mean rate of 0.054 mergers per galaxy per Gyr above a 1 : 2 mass ratio threshold for massive galaxies (baryonic mass above 6.4 × 1010 M), but only 0.018 Gyr-1 for lower mass galaxies. The mass ratio distribution is R for the massive galaxy sample, so high-mass mergers dominate the total merger growth rate. The predicted rates increase …
Probing Galaxy Formation With He Ii Cooling Lines, Yj Yang, Ai Zabludoff, R Dave, Dj Eisenstein, Pa Pinto, N Katz, Dh Weinberg, Ej Barton
Probing Galaxy Formation With He Ii Cooling Lines, Yj Yang, Ai Zabludoff, R Dave, Dj Eisenstein, Pa Pinto, N Katz, Dh Weinberg, Ej Barton
Astronomy Department Faculty Publication Series
Using high-resolution cosmological simulations, we study hydrogen and helium gravitational cooling radiation from gas accretion by young galaxies. We focus on the He II cooling lines, which arise from gas with a different temperature history (Tmax ~ 105 K) than H I line-emitting gas. We examine whether three major atomic cooling lines, H I λ1216, He II λ1640, and He II λ304, are observable, finding that Lyα and He II λ1640 cooling emission at z = 2-3 are potentially detectable with deep narrowband (R > 100) imaging and/or spectroscopy from the ground. While the expected strength of …
On The Origin Of Cold Dark Matter Halo Density Profiles, Y Lu, Hj Mo, N Katz, Md Weinberg
On The Origin Of Cold Dark Matter Halo Density Profiles, Y Lu, Hj Mo, N Katz, Md Weinberg
Astronomy Department Faculty Publication Series
N-body simulations predict that cold dark matter (CDM) halo-assembly occurs in two phases: (i) a fast-accretion phase with a rapidly deepening potential well; and (ii) a slow-accretion phase characterized by a gentle addition of mass to the outer halo with little change in the inner potential well. We demonstrate, using one-dimensional simulations, that this two-phase accretion leads to CDM haloes of the Navarro, Frenk & White (NFW) form and provides physical insight into the properties of the mass-accretion history that influence the final profile. Assuming that the velocities of CDM particles are effectively isotropized by fluctuations in the gravitational potential …
Interferometric 890 Mu M Images Of High-Redshift Submillimeter Galaxies, D Iono, Ab Peck, A Pope, C Borys, D Scott, Dj Wilner, M Gurwell, Ptp Ho, Min Yun, S Matsushita, Gr Petitpas, Js Dunlop, M Elvis, A Blain, E Le Floc'h
Interferometric 890 Mu M Images Of High-Redshift Submillimeter Galaxies, D Iono, Ab Peck, A Pope, C Borys, D Scott, Dj Wilner, M Gurwell, Ptp Ho, Min Yun, S Matsushita, Gr Petitpas, Js Dunlop, M Elvis, A Blain, E Le Floc'h
Astronomy Department Faculty Publication Series
We present high-resolution 890 μm images of two 20 mJy submillimeter galaxies, SMM J123711+622212 and MIPS J142824.0+352619, obtained using the Submillimeter Array (SMA). Using submillimeter interferometric observations with an angular resolution of 25, the coordinates of these high-redshift sources are determined with an accuracy of 02. The new SMA data on SMM J123711+622212 reveal an unresolved submillimeter source offset to the east by 08 from an optical galaxy found in deep HST images, suggesting either a large galaxy with a dusty central region or an interacting galaxy system. The SMA image of hyperluminous (LFIR = 3.2 × 10 …
How Do Galaxies Get Their Gas?, D Keres, N Katz, Dh Weinberg, R Dave
How Do Galaxies Get Their Gas?, D Keres, N Katz, Dh Weinberg, R Dave
Astronomy Department Faculty Publication Series
We examine the temperature history of gas accreted by forming galaxies in smoothed particle hydrodynamics simulations. About half of the gas follows the track expected in the conventional picture of galaxy formation, shock heating to roughly the virial temperature of the galaxy potential well (T∼ 106 K for a Milky Way type galaxy) before cooling, condensing and forming stars. However, the other half radiates its acquired gravitational energy at much lower temperatures, typically T < 105 K, and the histogram of maximum gas temperatures is clearly bimodal. The ‘cold mode’ of gas accretion dominates for low-mass galaxies (baryonic …
Theoretical Models Of The Halo Occupation Distribution: Separating Central And Satellite Galaxies, Z Zheng, Aa Berlind, Dh Weinberg, Aj Benson, Cm Baugh, S Cole, R Dave, Cs Frenk, N Katz, Cg Lacey
Theoretical Models Of The Halo Occupation Distribution: Separating Central And Satellite Galaxies, Z Zheng, Aa Berlind, Dh Weinberg, Aj Benson, Cm Baugh, S Cole, R Dave, Cs Frenk, N Katz, Cg Lacey
Astronomy Department Faculty Publication Series
The halo occupation distribution (HOD) describes the relation between galaxies and dark matter at the level of individual dark matter halos. The properties of galaxies residing at the centers of halos differ from those of satellite galaxies because of differences in their formation histories. Using a smoothed particle hydrodynamics (SPH) simulation and a semianalytic (SA) galaxy formation model, we examine the separate contributions of central and satellite galaxies to the HOD, more specifically to the probability P(N|M) that a halo of virial mass M contains N galaxies of a particular class. In agreement with earlier …
Interpreting The Relationship Between Galaxy Luminosity, Color, And Environment, Aa Berlind, Mr Blanton, Dw Hogg, Dh Weinberg, R Dave, Dj Eisenstein, N Katz
Interpreting The Relationship Between Galaxy Luminosity, Color, And Environment, Aa Berlind, Mr Blanton, Dw Hogg, Dh Weinberg, R Dave, Dj Eisenstein, N Katz
Astronomy Department Faculty Publication Series
We study the relationship between galaxy luminosity, color, and environment in a cosmological simulation of galaxy formation. Using a simple prescription to assign colors and luminosities to simulated galaxies, we compare the predicted relationship with that observed for SDSS galaxies and find that the model successfully predicts most of the qualitative features seen in the data, but also shows some interesting differences. Specifically, the simulation predicts that the local density around bright red galaxies is a strong increasing function of luminosity, but does not depend much on color at fixed luminosity. Moreover, we show that these trends are due to …
Galaxy Clustering And Galaxy Bias In A Lambda Cdm Universe, Dh Weinberg, R Dave, N Katz, L Hernquist
Galaxy Clustering And Galaxy Bias In A Lambda Cdm Universe, Dh Weinberg, R Dave, N Katz, L Hernquist
Astronomy Department Faculty Publication Series
We investigate galaxy clustering and the correlations between galaxies and mass in the ΛCDM cosmological model (inflationary cold dark matter with Ωm = 0.4, ΩΛ = 0.6, h = 0.65, n = 0.95, and σ8 = 0.8), using a large, smoothed particle hydrodynamics simulation (SPH; with 2 × 1443 particles in a 50 h-1 Mpc cube). Simulated galaxies can be unambiguously identified as clumps of stars and cold gas a few kpc to a few tens of kpc across, residing in extended halos of hot gas and dark matter; the space density of the resolved …
The Canada-Uk Deep Submillimetre Survey - Viii. Source Identifications In The 3-Hour Field, D Clements, S Eales, K Wojciechowski, T Webb, S Lilly, L Dunne, R Ivison, H Mccracken, Min Yun, A James, M Brodwin, O Le Fevre, W Gear
The Canada-Uk Deep Submillimetre Survey - Viii. Source Identifications In The 3-Hour Field, D Clements, S Eales, K Wojciechowski, T Webb, S Lilly, L Dunne, R Ivison, H Mccracken, Min Yun, A James, M Brodwin, O Le Fevre, W Gear
Astronomy Department Faculty Publication Series
We present optical, near-infrared (IR) and radio observations of the 3-hour field of the Canada–UK Deep Submillimetre Survey (CUDSS). Of the 27 submillimetre sources in the field, nine have secure identifications with either a radio source or a near-IR source. We show that the percentage of sources with secure identifications in the CUDSS is consistent with that found for the bright ‘8-mJy’ submillimetre survey, once allowance is made for the different submillimetre and radio flux limits. Of the 14 secure identifications in the two CUDSS fields, eight are very red objects (VROs) or extremely red objects (EROs), five have colours …
The Halo Occupation Distribution And The Physics Of Galaxy Formation, Aa Berlind, Dh Weinberg, Aj Benson, Cm Baugh, S Cole, R Dave, Cs Frenk, A Jenkins, N Katz, Cg Lacey
The Halo Occupation Distribution And The Physics Of Galaxy Formation, Aa Berlind, Dh Weinberg, Aj Benson, Cm Baugh, S Cole, R Dave, Cs Frenk, A Jenkins, N Katz, Cg Lacey
Astronomy Department Faculty Publication Series
The halo occupation distribution (HOD) describes the bias between galaxies and dark matter by specifying (1) the probability P(N|M) that a halo of virial mass M contains N galaxies of a particular class and (2) the relative spatial and velocity distributions of galaxies and dark matter within halos. We calculate and compare the HODs predicted by a smoothed particle hydrodynamics (SPH) simulation of a ΛCDM cosmological model (cold dark matter with a cosmological constant) and by a semianalytic galaxy formation model applied to the same cosmology. Although the two methods predict different galaxy mass functions, …
The Influence Of Omega(B) On High-Redshift Structure, Jp Gardner, N Katz, L Hernquist, Dh Weinberg
The Influence Of Omega(B) On High-Redshift Structure, Jp Gardner, N Katz, L Hernquist, Dh Weinberg
Astronomy Department Faculty Publication Series
We analyze high-redshift structure in three hydrodynamic simulations that have identical initial conditions and cosmological parameters and differ only in the value of the baryon density parameter, Ωb = 0.02, 0.05, and 0.125. Increasing Ωb does not change the fraction of baryons in the diffuse (unshocked) phase of the intergalactic medium, but it increases cooling rates and therefore transfers some baryons from the shocked intergalactic phase to the condensed phase associated with galaxies. Predictions of Lyα forest absorption are almost unaffected by changes in Ωb at velocity scales greater than 5 km s-1 (our resolution limit), …
The Canada-Uk Deep Submillimeter Survey. Vii. Optical And Near-Infrared Identifications For The 14 Hour Field, Tma Webb, Sj Lilly, Dl Clements, S Eales, Min Yun, M Brodwin, L Dunne, Wk Gear
The Canada-Uk Deep Submillimeter Survey. Vii. Optical And Near-Infrared Identifications For The 14 Hour Field, Tma Webb, Sj Lilly, Dl Clements, S Eales, Min Yun, M Brodwin, L Dunne, Wk Gear
Astronomy Department Faculty Publication Series
We present the multiwavelength identifications for 23 sources in the Canada-UK Deep Submillimeter Survey (CUDSS) 14h field. The identifications have been selected on the basis of radio and near-infrared data, and we argue that, to our observational limits, both are effective at selecting the correct counterparts of the SCUBA sources. We discuss the properties of these identifications and find that they are very red in near-infrared color, with many classified as extremely red objects, and show disturbed morphologies. Using the entire CUDSS catalog of 50 sources, we use a combination of spectroscopic redshifts (four objects), 1.4 GHz : 850 …
High-Redshift Galaxies In Cold Dark Matter Models, Dh Weinberg, L Hernquist, N Katz
High-Redshift Galaxies In Cold Dark Matter Models, Dh Weinberg, L Hernquist, N Katz
Astronomy Department Faculty Publication Series
We use hydrodynamic cosmological simulations to predict the star formation properties of high-redshift galaxies (z = 2-6) in five variants of the inflationary cold dark matter scenario, paying particular attention to z = 3, the redshift of the largest "Lyman break galaxy" (LBG) samples. Because we link the star formation timescale to the local gas density, the rate at which a galaxy forms stars is governed mainly by the rate at which it accretes cooled gas from the surrounding medium. At z = 3, star formation in most of the simulated galaxies is steady on ~200 Myr timescales, and …
Cooling Radiation And The Ly Alpha Luminosity Of Forming Galaxies, Ma Fardal, N Katz, Jp Gardner, L Hernquist, Dh Weinberg, R Dave
Cooling Radiation And The Ly Alpha Luminosity Of Forming Galaxies, Ma Fardal, N Katz, Jp Gardner, L Hernquist, Dh Weinberg, R Dave
Astronomy Department Faculty Publication Series
We examine the cooling radiation from forming galaxies in hydrodynamic simulations of the LCDM model (cold dark matter with a cosmological constant), focusing on the Lyα line luminosities of high-redshift systems. Primordial composition gas condenses within dark matter potential wells, forming objects with masses and sizes comparable to the luminous regions of observed galaxies. As expected, the energy radiated in this process is comparable to the gravitational binding energy of the baryons, and the total cooling luminosity of the galaxy population peaks at z 2. However, in contrast to the classical picture of gas cooling from the ~106 K …
Simulations Of Damped Ly Alpha And Lyman Limit Absorbers In Different Cosmologies: Implications For Structure Formation At High Redshift, Jp Gardner, N Katz, L Hernquist, Dh Weinberg
Simulations Of Damped Ly Alpha And Lyman Limit Absorbers In Different Cosmologies: Implications For Structure Formation At High Redshift, Jp Gardner, N Katz, L Hernquist, Dh Weinberg
Astronomy Department Faculty Publication Series
We use hydrodynamic cosmological simulations to study damped Lyα (DLA) and Lyman limit (LL) absorption at redshifts z = 2-4 in five variants of the cold dark matter scenario: COBE-normalized (CCDM), cluster-normalized (SCDM), and tilted (n = 0.8) Ωm = 1 models, as well as open (OCDM) and flat (LCDM) Ωm = 0.4 models. Our standard simulations resolve the formation of dense concentrations of neutral gas in halos with circular velocity vc ≥ vc,res 140 km s-1 for Ωm = 1 and 90 km s-1 for Ωm = 0.4, …
The Effects Of Gasdynamics, Cooling, Star Formation, And Numerical Resolution In Simulations Of Cluster Formation, Gf Lewis, A Babul, N Katz, T Quinn, L Hernquist, Dh Weinberg
The Effects Of Gasdynamics, Cooling, Star Formation, And Numerical Resolution In Simulations Of Cluster Formation, Gf Lewis, A Babul, N Katz, T Quinn, L Hernquist, Dh Weinberg
Astronomy Department Faculty Publication Series
We present the analysis of a suite of simulations of a Virgo-mass galaxy cluster. Undertaken within the framework of standard cold dark matter cosmology, these simulations were performed at differing resolutions and with increasingly complex physical processes, with the goal of identifying the effects of each on the evolution of the cluster. We focus on the cluster at the present epoch and examine properties including the radial distributions of density, temperature, entropy, and velocity. We also map "observable" projected properties such as the surface mass density, X-ray surface brightness, and Sunyaev-Zeldovich signature. We identify significant differences between the simulations, which …
The Low-Redshift Ly Alpha Forest In Cold Dark Matter Cosmologies, R Dave, L Hernquist, N Katz, Dh Weinberg
The Low-Redshift Ly Alpha Forest In Cold Dark Matter Cosmologies, R Dave, L Hernquist, N Katz, Dh Weinberg
Astronomy Department Faculty Publication Series
We study the physical origin of the low-redshift Lyα forest in hydrodynamic simulations of four cosmological models, all variants of the cold dark matter scenario. Our most important conclusions are insensitive to the cosmological model, but they depend on our assumption that the UV background declines at low redshift in concert with the declining population of quasar sources. We find that the expansion of the universe drives rapid evolution of dN/dz (the number of absorbers per unit redshift above a specified equivalent width threshold) at z1.7, but that at lower redshift the fading of the UV background …
Constraining The Metallicity Of The Low-Density Ly Alpha Forest Using O Vi Absorption, R Dave, U Hellsten, L Hernquist, N Katz, Dh Weinberg
Constraining The Metallicity Of The Low-Density Ly Alpha Forest Using O Vi Absorption, R Dave, U Hellsten, L Hernquist, N Katz, Dh Weinberg
Astronomy Department Faculty Publication Series
We present a systematic search for O VI (1032, 1037 Å) absorption in a Keck High-Resolution Echelle Spectrometer spectrum of the z = 3.62 quasar Q1422+231, with the goal of constraining the metallicity and ionization state of the low-density intergalactic medium (IGM). Comparison of C IV absorption measurements to models of the Lyα forest based on cosmological simulations shows that absorbers with NH I 1014.5 cm-2 have a mean carbon abundance [C/H] -2.5, assuming a metagalactic photoionizing background with the spectral shape predicted by Haardt and Madau in 1996. In these models, lower column density absorption arises …