Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Column density distribution and cosmological mass density of neutral gas: Sloan Digital Sky Survey-III Data Release 9

P. Noterdaeme, P. Petitjean, W. C. Carithers, I. Pâris, A. Font-Ribera, S. Bailey, E. Aubourg, D. Bizyaev, G. Ebelke, H. Finley, J. Ge, E. Malanushenko, V. Malanushenko, J. Miralda-Escudé, A. D. Myers, D. Oravetz, K. Pan, M. M. Pieri, N. P. Ross, D. P. Schneider, A. Simmons, D. G. York

TL;DR

This paper presents the first results of a large DLA survey in SDSS-III BOSS Data Release 9, delivering the largest catalog of DLAs to date and enabling precise measurements of the neutral gas content across $2 < z < 3.5$. Using automated DLA detection calibrated with realistic mocks, the authors derive the HI column-density distribution $f(N_{\rm HI},\chi)$ at $\langle z \rangle = 2.5$ and quantify the cosmological mass density of neutral gas $\Omega_{\rm g}^{\rm DLA}$. They find the high-column-density tail extends beyond $\log N(\mathrm{H\,I}) \sim 22$ with a slope near $-3.5$, and that very high column density systems contribute non-negligibly to $\Omega_{\rm g}^{\rm DLA}$. After correcting for systematics with mock spectra, $\Omega_{\rm g}^{\rm DLA}$ shows only mild evolution from $z \sim 3.5$ to $z \sim 2.3$, implying a relatively stable neutral gas reservoir over a large fraction of cosmic time. The results provide a powerful dataset to test models of galaxy formation and the gas supply for star formation across cosmic history.

Abstract

We present the first results from an ongoing survey for Damped Lyman-alpha systems (DLAs) in the spectra of z>2 quasars observed in the course of the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey (SDSS) III. Our full (non-statistical) sample, based on Data Release 9, comprises 12,081 systems with log N(HI)>=20, out of which 6,839 have log N(HI)>=20.3. This is the largest DLA sample ever compiled, superseding that from SDSS-II by a factor of seven. Using a statistical sub-sample and estimating systematics from realistic mock data, we probe the N(HI) distribution at <z> = 2.5. Contrary to what is generally believed, the distribution extends beyond 10^22 cm^-2 with a moderate slope of index\approx-3.5. This result matches surprisingly well the opacity-corrected distribution observed at z = 0. The cosmological mass density of neutral gas in DLAs is found to be Omega_g_DLA~10^-3, evolving only mildly over the past 12 billion years.

Column density distribution and cosmological mass density of neutral gas: Sloan Digital Sky Survey-III Data Release 9

TL;DR

This paper presents the first results of a large DLA survey in SDSS-III BOSS Data Release 9, delivering the largest catalog of DLAs to date and enabling precise measurements of the neutral gas content across . Using automated DLA detection calibrated with realistic mocks, the authors derive the HI column-density distribution at and quantify the cosmological mass density of neutral gas . They find the high-column-density tail extends beyond with a slope near , and that very high column density systems contribute non-negligibly to . After correcting for systematics with mock spectra, shows only mild evolution from to , implying a relatively stable neutral gas reservoir over a large fraction of cosmic time. The results provide a powerful dataset to test models of galaxy formation and the gas supply for star formation across cosmic history.

Abstract

We present the first results from an ongoing survey for Damped Lyman-alpha systems (DLAs) in the spectra of z>2 quasars observed in the course of the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey (SDSS) III. Our full (non-statistical) sample, based on Data Release 9, comprises 12,081 systems with log N(HI)>=20, out of which 6,839 have log N(HI)>=20.3. This is the largest DLA sample ever compiled, superseding that from SDSS-II by a factor of seven. Using a statistical sub-sample and estimating systematics from realistic mock data, we probe the N(HI) distribution at <z> = 2.5. Contrary to what is generally believed, the distribution extends beyond 10^22 cm^-2 with a moderate slope of index\approx-3.5. This result matches surprisingly well the opacity-corrected distribution observed at z = 0. The cosmological mass density of neutral gas in DLAs is found to be Omega_g_DLA~10^-3, evolving only mildly over the past 12 billion years.

Paper Structure

This paper contains 8 sections, 3 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Method
  3. Detection of DLAs
  4. Statistical sample
  5. Mocks
  6. The column density distribution at $\left< z \right>=2.5$
  7. Cosmological mass density of neutral gas
  8. Conclusion

Figures (3)

  • Figure 1: Redshift sensitivity function $g(z)$ of our full DR9 sample (dotted) and statistical sample (black) compared to that of DR7 (Noterdaeme09dla, grey).
  • Figure 2: Column density distribution functions from synthetic (left) and real data (centre) at $\left< z \right>=2.5$. Horizontal bars represent the bin over which $f(N_{\rm HI},\chi)$ is calculated and vertical error bars represent Poissonian uncertainty. The difference between output and input mock distributions is shown at the bottom of panel a. The double power-law and $\Gamma$-function fits to the DR7 distribution (Noterdaeme09dla, $\left< z \right>=2.9$) are shown as red dashed lines. $f(N_{\rm HI},\chi)(z=0)$ are taken from Braun12 and Zwaan05. Right: The contribution of DLAs in a given $N(\ion{H}{i})$ range to the total mass census of neutral gas. DR9 values are corrected for systematics.
  • Figure 3: Cosmological mass density of neutral gas in DLAs as a function of redshift (Z05: Zwaan05, B12: Braun12, R06: Rao06, PW09: Prochaska09a, DR9: this work).