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Full-Text Articles in Physical Sciences and Mathematics
Ly Alpha Emission From Cosmic Structure. I. Fluorescence, Ja Kollmeier, Z Zheng, R Dave, A Gould, N Katz, J Miralda-Escude, Dh Weinberg
Ly Alpha Emission From Cosmic Structure. I. Fluorescence, Ja Kollmeier, Z Zheng, R Dave, A Gould, N Katz, J Miralda-Escude, Dh Weinberg
Astronomy Department Faculty Publication Series
We present predictions for the fluorescent Lyα emission signature arising from photoionized, optically thick structures in smoothed particle hydrodynamic cosmological simulations of a ΛCDM universe using a Monte Carlo Lyα radiative transfer code. We calculate the expected Lyα image and two-dimensional spectra for gas exposed to a uniform ultraviolet ionizing background as well as gas exposed additionally to the photoionizing radiation from a local quasar, after correcting for the self-shielding of hydrogen. As a test of our numerical methods and for application to current observations, we examine simplified analytic structures that are uniformly or anisotropically illuminated. We compare these results …
The Dearth Of Chemically Enriched Warm-Hot Circumgalactic Gas, Y Yao, Qd Wang, Sv Penton, Tm Tripp, Jm Shull, Jt Stocke
The Dearth Of Chemically Enriched Warm-Hot Circumgalactic Gas, Y Yao, Qd Wang, Sv Penton, Tm Tripp, Jm Shull, Jt Stocke
Astronomy Department Faculty Publication Series
The circumgalactic medium (CGM) around galaxies is believed to record various forms of galaxy feedback and contain a significant portion of the "missing baryons" of individual dark matter halos. However, clear observational evidence for the existence of the hot CGM is still absent. We use intervening galaxies along 12 background active galactic nuclei (AGNs) as tracers to search for X-ray absorption lines produced in the corresponding CGM. Stacking Chandra grating observations with respect to galaxy groups and different luminosities of these intervening galaxies, we obtain spectra with signal-to-noise ratios of 46-72 per 20 mÅ spectral bin at the expected O …
Pressure Support Versus Thermal Broadening In The Lyman Alpha Forest - I. Effects Of The Equation Of State On Longitudinal Structure, Ms Peeples, Dh Weinberg, R Dave, Ma Fardal, N Katz
Pressure Support Versus Thermal Broadening In The Lyman Alpha Forest - I. Effects Of The Equation Of State On Longitudinal Structure, Ms Peeples, Dh Weinberg, R Dave, Ma Fardal, N Katz
Astronomy Department Faculty Publication Series
In the low-density intergalactic medium that gives rise to the Lyman α (Lyα) forest, gas temperature and density are tightly correlated. The velocity scale of thermal broadening and the Hubble flow across the gas Jeans scale are of similar magnitude (HλJ∼σth). To separate the effects of gas pressure support and thermal broadening on the Lyα forest, we compare spectra extracted from two smoothed particle hydrodynamics simulations evolved with different photoionization heating rates (and thus different Jeans scales) and from the pressureless dark matter distribution, imposing different temperature–density relations on the evolved particle distributions. The …
Feedback From Galactic Stellar Bulges And Hot Gaseous Haloes Of Galaxies, Sk Tang, Qd Wang, Y Lu, Hj Mo
Feedback From Galactic Stellar Bulges And Hot Gaseous Haloes Of Galaxies, Sk Tang, Qd Wang, Y Lu, Hj Mo
Astronomy Department Faculty Publication Series
We demonstrate that the feedback from stellar bulges can, in principle, play an essential role in shaping the halo gas of galaxies with substantial bulge components by conducting 1D hydrodynamical simulations. The feedback model we consider consists of two distinct phases: (i) an early starburst during the bulge formation and (ii) a subsequent long-lasting mass and energy injection from stellar winds of low-mass stars and Type Ia supernovae. An energetic outward blastwave is initiated by the starburst and maintained and enhanced by the long-lasting stellar feedback. For a Milky Way like galactic bulge, this blastwave heats up the circum-galactic medium …
X-Raying The Intergalactic O Vi Absorbers, Y Yao, Tm Tripp, Qd Wang, Cw Danforth, Cr Canizares, Jm Shull, Hl Marshall, L Song
X-Raying The Intergalactic O Vi Absorbers, Y Yao, Tm Tripp, Qd Wang, Cw Danforth, Cr Canizares, Jm Shull, Hl Marshall, L Song
Astronomy Department Faculty Publication Series
The observed intergalactic O VI absorbers at z>0 have been regarded as a significant reservoir of the "missing baryons." However, to fully understand how these absorbers contribute to the baryon inventory, it is crucial to determine whether the systems are collisionally ionized or photoionized (or both). Using the identified intergalactic O VI absorbers as tracers, we search for the corresponding X-ray absorption lines, which are useful for finding the missing baryons and for revealing the nature of the O VI absorbers. Stacking the Chandra grating spectra along six AGN sight lines, we obtain three spectra with signal-to-noise ratios of …
A Search For Dust Emission In The Leo Intergalactic Cloud, Caroline Bot, George Helou, William B. Latter, Jérémie Puget, Stephen Schneider, Yervant Terzian
A Search For Dust Emission In The Leo Intergalactic Cloud, Caroline Bot, George Helou, William B. Latter, Jérémie Puget, Stephen Schneider, Yervant Terzian
Astronomy Department Faculty Publication Series
We present a search for infrared dust emission associated with the Leo cloud, a large intergalactic cloud in the M96 group. Mid-infrared and far-infrared images were obtained with the InfraRed Array Camera and the Multiband Imaging Photometer for Spitzer on the Spitzer Space Telescope. Our analysis of these maps is done at each wavelength relative to the H i spatial distribution. We observe a probable detection at 8 μm and a marginal detection at 24 μm associated with the highest H i column densities in the cloud. At 70 and 160 μm, upper limits on the dust emission are …
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 …
Simulation Of Soft X-Ray Emission Lines From The Missing Baryons, Tt Fang, Rac Croft, Wt Sanders, J Houck, R Dave, N Katz, Dh Weinberg, L Hernquist
Simulation Of Soft X-Ray Emission Lines From The Missing Baryons, Tt Fang, Rac Croft, Wt Sanders, J Houck, R Dave, N Katz, Dh Weinberg, L Hernquist
Astronomy Department Faculty Publication Series
We study the soft X-ray emission (0.1-1 keV) from the warm-hot intergalactic medium (WHIM) in a hydrodynamic simulation of a cold dark matter universe. Our main goal is to investigate how such emission can be explored with a combination of imaging and spectroscopy and to motivate future X-ray missions. We first present high-resolution images of the X-ray emission in several energy bands in which emission from different ion species dominates. We pick three different areas to study the high-resolution spectra of X-rays from the WHIM: (1) a galaxy group, (2) a filament, and (3) an underluminous region. By taking into …
Warm-Hot Gas In And Around The Milky Way: Detection And Implications Of Ovii Absorption Toward Lmc X-3, Qd Wang, Y Yao, Tm Tripp, Tt Fang, W Cui, F Nicastro, S Mathur, Rj Williams, L Song, R Croft
Warm-Hot Gas In And Around The Milky Way: Detection And Implications Of Ovii Absorption Toward Lmc X-3, Qd Wang, Y Yao, Tm Tripp, Tt Fang, W Cui, F Nicastro, S Mathur, Rj Williams, L Song, R Croft
Astronomy Department Faculty Publication Series
X-ray absorption lines of highly ionized species such as O VII at about zero redshift have been firmly detected in the spectra of several active galactic nuclei. However, the location of the absorbing gas remains a subject of debate. To separate the Galactic and extragalactic contributions to the absorption, we have obtained Chandra LETG-HRC and Far Ultraviolet Spectroscopic Explorer observations of the black hole X-ray binary LMC X-3. We clearly detect the O VII Kα absorption line with an equivalent width of 20(14, 26) mÅ (90% confidence range). The Ne IX Kα absorption line is also detected, albeit marginally. A …
X-Ray Absorption By The Low-Redshift Intergalactic Medium: A Numerical Study Of The Lambda Cold Dark Matter Model, Xl Chen, Dh Weinberg, N Katz, R Dave
X-Ray Absorption By The Low-Redshift Intergalactic Medium: A Numerical Study Of The Lambda Cold Dark Matter Model, Xl Chen, Dh Weinberg, N Katz, R Dave
Astronomy Department Faculty Publication Series
Using a hydrodynamic simulation of a cold dark matter universe with a cosmological constant, we investigate the "X-ray forest" absorption imprinted on the spectra of background quasars by the intervening intergalactic medium (IGM), at redshift z 0. In agreement with previous studies, we find that O VII and O VIII produce the strongest absorption features. The strong oxygen absorbers that might be detectable with Chandra or XMM-Newton arise in gas with T ~ 105.5-106.5 K and overdensities δ 100 that are characteristic of galaxy groups. Future X-ray missions could detect weaker oxygen absorption produced by gas with …
Comparing Simulations And Observations Of The Ly Alpha Forest. I. Methodology, Ce Petry, Cd Impey, N Katz, Dh Weinberg, Le Hernquist
Comparing Simulations And Observations Of The Ly Alpha Forest. I. Methodology, Ce Petry, Cd Impey, N Katz, Dh Weinberg, Le Hernquist
Astronomy Department Faculty Publication Series
We describe techniques for comparing spectra extracted from cosmological simulations and observational data, using the same methodology to link Lyα properties derived from the simulations with properties derived from observational data. The eventual goal is to measure the coherence or clustering properties of Lyα absorbers using observations of quasar pairs and groups. We quantify the systematic underestimate in opacity that is inherent in the continuum-fitting process of observed spectra over a range of resolution and signal-to-noise ratio (S/N). We present an automated process for detecting and selecting absorption features over the range of resolution and S/N of typical observational data …
Metal Enrichment Of The Intergalactic Medium In Cosmological Simulations, A Aguirre, L Hernquist, J Schaye, N Katz, Dh Weinberg, J Gardner
Metal Enrichment Of The Intergalactic Medium In Cosmological Simulations, A Aguirre, L Hernquist, J Schaye, N Katz, Dh Weinberg, J Gardner
Astronomy Department Faculty Publication Series
Observations have established that the diffuse intergalactic medium (IGM) at z ~ 3 is enriched to ~10-2.5 solar metallicity and that the hot gas in large clusters of galaxies (ICM) is enriched to - Z at z = 0. Metals in the IGM may have been removed from galaxies (in which they presumably form) during dynamical encounters between galaxies, by ram-pressure stripping, by supernova-driven winds, or as radiation-pressure-driven dust efflux. This study develops a method of investigating the chemical enrichment of the IGM and of galaxies, using already completed cosmological simulations. To these simulations we add dust and (gaseous) …
Enrichment Of The Intergalactic Medium By Radiation Pressure-Driven Dust Efflux, A Aguirre, L Hernquist, N Katz, J Gardner, D Weinberg
Enrichment Of The Intergalactic Medium By Radiation Pressure-Driven Dust Efflux, A Aguirre, L Hernquist, N Katz, J Gardner, D Weinberg
Astronomy Department Faculty Publication Series
The presence of metals in hot cluster gas and in Lyα absorbers, as well as the mass-metallicity relation of observed galaxies, suggest that galaxies lose a significant fraction of their metals to the intergalactic medium (IGM). Theoretical studies of this process have concentrated on metal removal by dynamical processes or supernova-driven winds. Here we investigate the enrichment of the IGM by the expulsion of dust grains from galaxies by radiation pressure. We use already completed cosmological simulations to which we add dust, assuming that most dust can reach the equilibrium point between radiation pressure and gravitational forces. We find that …
Baryons In The Warm-Hot Intergalactic Medium, R Dave, R Cen, Jp Ostriker, Gl Bryan, L Hernquist, N Katz, Dh Weinberg, Ml Norman, B O'Shea
Baryons In The Warm-Hot Intergalactic Medium, R Dave, R Cen, Jp Ostriker, Gl Bryan, L Hernquist, N Katz, Dh Weinberg, Ml Norman, B O'Shea
Astronomy Department Faculty Publication Series
Approximately 30%-40% of all baryons in the present-day universe reside in a warm-hot intergalactic medium (WHIM), with temperatures in the range 105 < T < 107 K. This is a generic prediction from six hydrodynamic simulations of currently favored structure formation models having a wide variety of numerical methods, input physics, volumes, and spatial resolutions. Most of these warm-hot baryons reside in diffuse large-scale structures with a median overdensity around 10-30, not in virialized objects such as galaxy groups or galactic halos. The evolution of the WHIM is primarily driven by shock heating from gravitational perturbations breaking on mildly nonlinear, nonequilibrium …
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 …
The Observability Of Metal Lines Associated With The Ly Alpha Forest, U Hellsten, L Hernquist, N Katz, Dh Weinberg
The Observability Of Metal Lines Associated With The Ly Alpha Forest, U Hellsten, L Hernquist, N Katz, Dh Weinberg
Astronomy Department Faculty Publication Series
We develop a prescription for characterizing the strengths of metal lines associated with Lyα forest absorbers (LYFAs) of a given neutral hydrogen column density NH I and metallicity [O/H]. This line observability index (LOX) is line specific and translates, for weak lines, into a measure of the equivalent width. It can be evaluated quickly for thousands of transitions within the framework of a given model of the Lyα forest, providing a ranking of the absorption lines in terms of their strengths and enabling model builders to select the lines that deserve more detailed consideration, i.e., those that should be …
The Opacity Of The Ly Alpha Forest And Implications For Omega(B) And The Ionizing Background, M Rauch, J Miraldaescude, Wl Sargent, Ta Barlow, Dh Weinberg, L Hernquist, N Katz, R Cen, Jp Ostriker
The Opacity Of The Ly Alpha Forest And Implications For Omega(B) And The Ionizing Background, M Rauch, J Miraldaescude, Wl Sargent, Ta Barlow, Dh Weinberg, L Hernquist, N Katz, R Cen, Jp Ostriker
Astronomy Department Faculty Publication Series
We have measured the distribution function of the flux decrement D = 1 - e-τ caused by Lyα forest absorption from intervening gas in the lines of sight to high-redshift QSOs from a sample of seven high-resolution QSO spectra obtained with the Keck telescope. The observed flux decrement distribution function (FDDF) is compared with the FDDF from two simulations of the Lyα forest: a ΛCDM model (with Ω = 0.4, Λ = 0.6), computed with the Eulerian code of Cen & Ostriker, and a standard cold dark matter (SCDM) model (with Ω = 1), computed with the smoothed particle …