Related papers: Local Column Density Distribution Function from HI…
We investigate the metallicity dependence of HI surface densities in star-forming regions along many lines of sight within 70 nearby galaxies, probing kpc to 50 pc scales. We employ HI, SFR, stellar mass, and metallicity (gradient)…
We discuss the effects of gravitational collapse on the shape of absorption line profiles for low column density (log N(HI) < 14) Lyman Alpha forest clouds and argue by comparison with cosmological simulations that Lyman alpha forest…
We report new HST and ground-based observations of a damped Lyman-alpha absorption system toward the QSO 0850+4400. The redshift of the absorption system is z = 0.163770 and the neutral hydrogen column density of the absorption system is…
We have conducted an HI 21 cm emission-line survey of six loose groups of galaxies chosen to be analogs to the Local Group. The survey was conducted using the Parkes Multibeam instrument and the Australia Telescope Compact Array (ATCA) over…
Cosmological simulations with gas dynamics suggest that the Lyman-alpha forest is produced mainly by "small scale structure" --- filaments and sheets that are the high redshift analog of today's galaxy superclusters. There is no sharp…
Observations show that galaxies in galaxy clusters are strongly influenced by their environment. There is growing evidence that some galaxies in groups show similar properties to galaxies in clusters, such as redder colours and gas…
We use a high-resolution cosmological simulation to predict the distribution of HI Ly-alpha emission from the low-redshift (z<0.5) intergalactic medium (IGM). Our simulation can be used to reliably compute the emission from optically thin…
Despite the existence of well-defined relationships between cold gas and star formation, there is evidence that some galaxies contain large amounts of HI that do not form stars efficiently. By systematically assessing the link between HI…
We use cosmological hydrodynamic simulations with stellar feedback from the FIRE project to study the physical nature of Lyman limit systems (LLSs) at z<1. At these low redshifts, LLSs are closely associated with dense gas structures…
We consider the incidence of HI absorption in intrinsically small sub-galactic sized extragalactic sources selected from sources classified as Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources. We find that the…
We present spatial correlations of galaxies and IGM HI in the COSMOS/UltraVISTA 1.62 deg$^2$ field. Our data consist of 13,415 photo-$z$ galaxies at $z\sim2-3$ with $K_s<23.4$ and the Ly$\alpha$ forest absorptions in the background quasar…
We develop a method to calculate the column density distribution of the Lyman-alpha forest for column densities in the range $10^{12.5} - 10^{14.5} cm^{-2}$. The Zel'dovich approximation, with appropriate smoothing, is used to compute the…
We present a detailed analysis of a high resolution spectrum of the damped Ly$\alpha$ system at $z_{\rm abs}$~=~2.8112toward PKS~0528-250. The absorption redshift is slightly larger than the emission redshift of the quasar. We estimate the…
We analyze the equivalent widths of HI Ly-$\alpha$ ($W_{Ly\alpha}$) absorption from the inner (R < 160 kpc) circumgalactic medium (CGM) of 85 galaxies at $z \sim 0$ with stellar masses $M*$ ranging $\rm{8 \leq log M* / M_{\odot} \leq…
Detecting HI using redshifted Ly-alpha absorption lines is 1e6 times more sensitive than using the 21cm emission line. We review recent discoveries of HI Ly-alpha absorbers made with the Hubble Space Telescope (HST) which have allowed us a…
Systematic effects on HI and Halpha long-slit observations make a measurement of the inner slope of the dark matter density distribution difficult to determine. Halos with constant density cores and ones with r^-1 profiles both appear…
I explore the hypothesis that Ly$\alpha$ absorption at low redshift is caused by the outer regions of extended galaxy disks, including those of dwarf and low surface brightness galaxies. McGaugh (1996) has shown that the distribution of…
We present high S/N measurements of the H I Ly alpha absorption line toward 16 Galactic targets which are at distances between approximately 190 and 2200 pc, all beyond the wall of the Local Bubble. We describe the models used to remove…
Knowledge of the evolution of the low column density end of the Ly alpha forest (12.8 < log N_HI < 16.0 cm^-2) can provide substantial insight for models of structure formation and studies of the evolution of the ionizing background. Here…
We measure the z=0 B-band optical luminosity function (LF) for galaxies selected in a blind HI survey. The total LF of the HI selected sample is flat, with Schechter parameters M*=-19.38_{-0.62}^{+1.02} + 5 log h mag and…