Showing papers by "Stephen E. Schneider published in 2002"

The Arecibo* Dual-Beam Survey: The H I Mass Function of Galaxies

Abstract: We use the H I-selected galaxy sample from the Arecibo Dual-Beam Survey of Rosenberg and Schneider to determine the shape of the H I mass function of galaxies in the local universe using both the stepwise maximum likelihood and the 1/tot methods. Our survey region spanned all 24 hours of right ascension at selected declinations between 8° and 29° covering ~430 deg2 of sky in the main beam. The survey is not as deep as some previous Arecibo surveys, but it has a larger total search volume and samples a much larger area of the sky. We conducted extensive tests on all aspects of the galaxy detection process, allowing us to empirically correct for our sensitivity limits, unlike the previous surveys. The mass function for the entire sample is quite steep, with a power-law slope of α ≈ -1.5. We find indications that the slope of the H I mass function is flatter near the Virgo Cluster, suggesting that evolutionary effects in high-density environments may alter the shape of the H I mass function. These evolutionary effects may help to explain differences in the H I mass function derived by different groups. We are sensitive to the most massive sources (log M > 5 × 1010 M☉) over most of the declination range, ~1 sr, and do not detect any massive low surface brightness galaxies. These statistics restrict the population of Malin 1-like galaxies to less than 5.5 × 10-6 Mpc-3.

The Contribution of HI-rich Galaxies to the Damped Lyman-alpha Absorber Population at z=0

Abstract: We present a study of the expected properties of the low redshift damped Lyman-alpha absorber population determined from a sample of HI-selected galaxies in the local universe. Because of a tight correlation between the HI mass and HI cross-section, which we demonstrate spans all galaxy types, we can use our HI-selected sample to predict the properties of the absorption line systems. We use measurements of the number density and HI cross-section of galaxies to show that the total HI cross-section at column densities sufficient to produce damped Lyman-alpha absorption is consistent with no evolution of the absorber population. We also find that the dN/dz distribution is dominated by galaxies with HI masses near 10^9 Msolar. However, because of the large dispersion in the correlation between HI mass and stellar luminosity, we find that the distribution of dN/dz as a function of L_J is fairly flat. Additionally, we examine the line widths of the HI-selected galaxies and show that there may be evolution in the kinematics of HI-rich galaxies, but it is not necessary for the higher redshift population to contain a greater proportion of high mass galaxies than we find locally.

The Contribution of HI-rich Galaxies to the Damped Absorber Population at z = 0

Abstract: We present a study of HI-rich galaxies in the local universe selected from blind emission-line surveys. These galaxies represent the emission-line counterparts of local damped Lyman-alpha systems. We find that the HI cross-section of galaxies is drawn from a large range of galaxy masses below M_star, 66% of the area comes from galaxies in the range 8.5 < Log M_star < 9.7. Both because of the low mass galaxy contribution, and because of the range of galaxy types and luminosities at any given HI mass, the galaxies contributing to the HI cross-section are not exclusively L_star spirals, as is often expected. The optical and near infrared counterparts of these galaxies cover a range of types (from spirals to irregulars), luminosities (from L_star to <0.01 L_star), and surface brightnesses. The range of optical and near infrared properties as well as the kinematics for this population are consistent with the properties for the low-z damped Lyman-alpha absorbers. We also show that the number of HI-rich galaxies in the local universe does not preclude evolution of the low-z damped absorber population, but it is consistent with no evolution.

A study of 2MASS low surface brightness galaxies

Abstract: A study is being made of a sample of about 4,000 Low Surface Brightness (LSB) galaxies detected in the 2MASS all-sky near-infrared survey. These objects have similar central K-band surface brightnesses as optically selected LSBs. About 1,000 of them were observed in H i, and one third of these were detected. BVRI CCD photometry was obtained of 65 objects. These multi-wavelength data provide us with important information on a large, homogenous sample of LSB galaxies (e.g., colors, gas content). They will be used to construct models of the star formation histories and evolution of LSBs, and for a study of their Tully-Fisher (TF) relation, particularly to search for deviations from the ‘classical’ TF relation.