Neutral chlorine and molecular hydrogen at high redshift

Abstract

Chlorine and molecular hydrogen are known to be tightly linked together in the cold phase of the local interstellar medium through rapid chemical reactions. We present here the first systematic study of this relation at high redshifts using H${}_2$-bearing damped Ly$\alpha$ systems (DLAs) detected along quasar lines of sight. Using high-resolution spectroscopic data from VLT/UVES and Keck/HIRES, we report the detection of ClI in 9 DLAs (including 5 new detections) out of 18 high-$z$ DLAs with $N($H${}_2)\ge 10^{17.3}$cm${}^{-2}$ (including a new H${}_2$ detection at $z=3.09145$ towards J2100$-$0641) and present upper limits for the remaining 9 systems. We find a $\sim$5$\sigma$ correlation between $N$(ClI) and $N$(H${}_2$) with only $\sim$0.2dex dispersion over the range 18.1$<$log$N$(H${}_2$)$<$20.1, thus probing column densities 10 times lower those seen towards nearby stars, roughly following the relation $N$(ClI$)\approx 1.5\times 10^{-6}\times N($H${}_2)$. This relation between column densities is surprisingly the same at low and high redshift suggesting that the physical and chemical conditions are similar for a given H${}_2$ (or ClI) column density. In turn, the $N({Cl$\,$I})/N({\rm H_2})$ ratio is found to be uncorrelated with the overall metallicity in the DLA. Our results confirm that neutral chlorine is an excellent tracer of molecule-rich gas and show that the molecular fraction or/and metallicity in the H${}_2$-bearing component of DLA could possibly be much higher than the line-of-sight average values usually measured in DLAs.

arXiv comment5 pages, 3 figures, Accepted for publication in A&A Letters

References in corpus (33)

• The chemical composition of the Sun
• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• On the (Non)Evolution of HI Disks over Cosmic Time
• Metallicity Evolution of Damped Lyman-alpha Systems out to z~5
• Evolution of the cosmological mass density of neutral gas from Sloan Digital Sky Survey II - Data Release 7
• The VLT-UVES survey for molecular hydrogen in high-redshift damped Lyman-alpha systems
• Molecular hydrogen in high-redshift Damped Lyman-alpha systems: The VLT/UVES database
• The evolution of the Cosmic Microwave Background Temperature: Measurements of TCMB at high redshift from carbon monoxide excitation
• The VLT-UVES survey for molecular hydrogen in high-redshift damped Lyman-alpha systems: Physical conditions in the neutral gas
• The chemistry of interstellar molecules containing the halogen elements
• First detection of CO in a high-redshift DLA
• A translucent interstellar cloud at z=2.69: CO, H2 and HD in the line-of-sight to SDSS J123714.60+064759.5
• Keck telescope constraint on cosmological variation of the proton-to-electron mass ratio
• The spin temperature of high-redshift damped Lyman-$\alpha$ systems
• Herschel/HIFI discovery of interstellar chloronium (H${}_2$Cl${}^{+}$)
• The elemental abundance pattern in a galaxy at z=2.626
• Metallicity as a criterion to select H2 bearing Damped Lyman-alpha systems
• Excitation mechanisms in newly discovered H2-bearing Damped Lyman-alpha clouds: systems with low molecular fractions
• On the sizes of z>2 Damped Lyman-alpha Absorbing Galaxies
• Understanding Physical Conditions in High Redshift Galaxies through C I Fine Structure Lines: Data and Methodology
• Physical conditions in the neutral interstellar medium at z=2.43 toward Q2348-011
• Partial coverage of the Broad Line Region of Q1232+082 by an intervening H2-bearing cloud
• Molecular Hydrogen in a Damped Lyman-alpha System at z_abs=4.224
• Molecular hydrogen in the z = 2.66 damped Lyman-alpha absorber toward Q J0643-5041
• Molecular hydrogen absorption systems in Sloan Digital Sky Survey
• Metallicities, dust and molecular content of a QSO-Damped Lyman-α system reaching log N (H i) = 22: An analog to GRB-DLAs
• HD/H2 Molecular Clouds in the Early Universe: The Problem of Primordial Deuterium
• Parsec-scale structures and diffuse bands in a translucent interstellar medium at z 0.079
• Direct Evidence of Cold Gas in DLA 0812+32B
• Revisiting the Chlorine Abundance in Diffuse Interstellar Clouds from Measurements with the Copernicus Satellite
• A cold component and the complex velocity structure of DLA1331+170
• Variations in the D/H ratio of extended sightlines from FUSE observations
• Chlorine in the Galactic ISM: Revised f-values with FUSE and STIS

Cited by in corpus (23)

• The warm, the excited, and the molecular gas: GRB 121024A shining through its star-forming galaxy
• Discovery of a Perseus-like cloud in the early Universe: HI-to-H2 transition, carbon monoxide and small dust grains at zabs=2.53 towards the quasar J0000+0048
• CO-dark molecular gas at high redshift: very large H${}_2$ content and high pressure in a low metallicity damped Lyman-alpha system
• Search for a drifting proton--electron mass ratio from H${}_2$
• VLT/UVES observations of extremely strong intervening damped Lyman-alpha systems: Molecular hydrogen and excited carbon, oxygen and silicon at log N(HI)=22.4
• X-shooter observations of strong H${}_2$-bearing DLAs at high redshift
• Cold gas and a Milky Way-type 2175 Å bump in a metal-rich and highly depleted absorption system
• The elusive HI-> H2 transition in high-z damped Lyman-alpha systems
• Near Infrared spectroscopic observations of high redshift C~{\sc i} absorbers
• Chlorine-bearing molecules in molecular absorbers at intermediate redshifts
• The 2175 Å extinction feature in the optical afterglow spectrum of GRB 180325A at z=2.25
• Physical conditions in three high-z H2-bearing DLAs: implications for grain size
• New constraints on the physical conditions in H${}_2$-bearing GRB-host damped Lyman-$\alpha$ absorbers
• Quasar 2175 Å dust absorbers II: Correlation analysis and relationship with other absorption line systems
• Constraint on a varying proton-to-electron mass ratio from H2 and HD absorption at z = 2.34
• Physical conditions in diffuse interstellar medium of local and high redshift galaxies: measurements based on excitation of H${}_2$ rotational and CI fine-structure levels
• Multicomponent H2 in DLA at zabs = 2.05: physical conditions through observations and numerical models
• Down-the-barrel observations of a multiphase quasar outflow at high redshift: VLT/X-shooter spectroscopy of the proximate molecular absorber at z=2.631 towards SDSS J001514+184212
• Estimation of physical conditions in the cold phase of the ISM in the sub-DLA system at z = 2.06 in the spectrum of the quasar J2123-0050
• A Reexamination of Phosphorus and Chlorine Depletions in the Diffuse Interstellar Medium
• Proximate molecular quasar absorbers: Chemical enrichment and kinematics of the neutral gas
• Neutral carbon in diffuse interstellar medium: abundance matching with H2 for DLAs at high redshifts
• Multi-phase gas properties of extremely strong intervening DLAs towards quasars