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New Results on DLA Systems: Statistics

Published online by Cambridge University Press:  17 August 2016

Sandhya Rao ,
David Turnshek ,
Eric Monier  and
Gendith Sardane
Sandhya Rao
Affiliation:
University of Pittsburgh and the Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), Pittsburgh, PA 15260, USA email: srao@pitt.edu
David Turnshek
Affiliation:
University of Pittsburgh and the Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), Pittsburgh, PA 15260, USA email: srao@pitt.edu
Eric Monier
Affiliation:
The College at Brockport, State University of New York, Brockport, NY 14420, USA
Gendith Sardane
Affiliation:
University of Pittsburgh and the Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), Pittsburgh, PA 15260, USA email: srao@pitt.edu
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Abstract

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The damped Lyman-α absorption-line systems (DLAs) that are observed in quasar spectra arise in neutral-gas-rich regions of intervening galaxies. With the highest neutral hydrogen column densities observed (N(HI) ⩾ 2 × 1020 atoms cm−2), they are known to trace the bulk of the neutral gas content of the Universe, and are thus powerful probes of galaxy formation and evolution. However, DLAs are extremely rare, and since the Lyman-α line falls in the UV for redshifts z < 1.65, not many are known at low redshift due to the limited availability of space data. Our HST surveys for DLAs in strong MgII absorbers have been successful at showing that MgII can be used as an unbiased tracer of DLAs. We present new results on their incidence, or redshift number density, dn/dz, and cosmological neutral gas mass density, ΩDLA, at redshifts 0.11 ⩽ z ⩽ 1.65, and incorporate results from higher and lower redshift studies in the literature to derive the evolution of neutral gas in the Universe.

Keywords

galaxies:evolution(galaxies:) quasars: absorption lines
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , Symposium S319: Galaxies at High Redshift and Their Evolution Over Cosmic Time , August 2015 , pp. 40
Copyright
Copyright © International Astronomical Union 2016 

References

Rao, S., Turnshek, D., & Nestor, D. 2006, ApJ, 636, 4610 Google Scholar
Turnshek, D., et al. 2015, MNRAS, 449, 1536 Google Scholar