J/MNRAS/452/217 HI cosmological mass density at z=5 (Crighton+, 2015) ================================================================================ The neutral hydrogen cosmological mass density at z = 5. Crighton N.H.M., Murphy M.T., Prochaska J.X., Worseck G., Rafelski M., Becker G.D., Ellison S.L., Fumagalli M., Lopez S., Meiksin A., O'meara J.M. =2015MNRAS.452..217C (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: QSOs ; Redshifts Keywords: quasars: absorption lines - cosmological parameters Abstract: We present the largest homogeneous survey of z>4.4 damped Ly{alpha} systems (DLAs) using the spectra of 163 QSOs that comprise the Giant Gemini GMOS (GGG) survey. With this survey we make the most precise high-redshift measurement of the cosmological mass density of neutral hydrogen, Omega_HI_. At such high redshift, important systematic uncertainties in the identification of DLAs are produced by strong intergalactic medium absorption and QSO continuum placement. These can cause spurious DLA detections, result in real DLAs being missed or bias the inferred DLA column density distribution. We correct for these effects using a combination of mock and higher resolution spectra, and show that for the GGG DLA sample the uncertainties introduced are smaller than the statistical errors on Omega_HI_. We find Omega_HI_=0.98^+0.20^_-0.18_x10^-3^ at =4.9, assuming a 20 percent contribution from lower column density systems below the DLA threshold. By comparing to literature measurements at lower redshifts, we show that Omega_HI_ can be described by the functional form Omega_HI_(z){prop.to}(1+z)^0.4^. This gradual decrease from z=5 to 0 is consistent with the bulk of HI gas being a transitory phase fuelling star formation, which is continually replenished by more highly ionized gas from the intergalactic medium and from recycled galactic winds. Description: Our main data sample consists of Gemini Multi-Object Spectrograph (GMOS) spectra for the 163 QSOs which comprise the Giant Gemini GMOS (GGG) survey (Worseck et al., 2014, Cat. J/MNRAS/445/1745). We also use a smaller sample of 59 QSOs with higher resolution spectra, listed in Table 1. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 43 59 Higher resolution spectra used in our analysis table3.dat 44 163 Redshift limits used to calculate the redshift search path for DLAs for each QSO -------------------------------------------------------------------------------- See also: J/MNRAS/445/1745 : Giant Gemini GMOS survey. I. (Worseck+, 2014) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 A4 --- --- [SDSS] 6- 24 A19 --- SDSS QSO SDSS name (JHHMMSS.ss+DDMMSS.s) 26- 29 F4.2 --- zem QSO emission redshift 31- 34 A4 --- Inst Instrument used to take the spectrum 36- 39 F4.1 --- S/N Median S/N per pixel over rest-frame wavelengths 1240-1280{AA} 41- 43 A3 --- GGG? [Yes/No ] Whether the QSO is in the GGG sample -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 A4 --- --- [SDSS] 5- 23 A19 --- SDSS QSO SDSS name (JHHMMSS.ss+DDMMSS.s) 26- 30 F5.3 --- zmin Start redshift for the DLA search 33- 37 F5.3 --- zmax End redshift for the DLA search 40- 44 F5.3 --- zem QSO emission redshift -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Patricia Vannier [CDS] 13-Jan-2016