Cold neutral hydrogen gas in galaxies

Abstract

This review summarizes recent studies of the cold neutral hydrogen gas associated with galaxies probed via the HI 21-cm absorption line. HI 21-cm absorption against background radio-loud quasars is a powerful tool to study the neutral gas distribution and kinematics in foreground galaxies from kilo-parsec to parsec scales. At low redshifts (z<0.4), it has been used to characterize the distribution of high column density neutral gas around galaxies and study the connection of this gas with the galaxy's optical properties. The neutral gas around galaxies has been found to be patchy in distribution, with variations in optical depth observed at both kilo-parsec and parsec scales. At high redshifts (z>0.5), HI 21-cm absorption has been used to study the neutral gas in metal or Lyman-alpha absorption-selected galaxies. It has been found to be closely linked with the metal and dust content of the gas. Trends of various properties like incidence, spin temperature and velocity width of HI 21-cm absorption with redshift have been studied, which imply evolution of cold gas properties in galaxies with cosmic time. Upcoming large blind surveys of HI 21-cm absorption with next generation radio telescopes are expected to determine accurately the redshift evolution of the number density of HI 21-cm absorbers per unit redshift and hence understand what drives the global star formation rate density evolution.

Review article published in Journal of Astrophysics and Astronomy. Based on results presented in arXiv:1601.00971, arXiv:1610.05316, arXiv:1611.07034 and arXiv:1703.00457

References in corpus (29)

• Cosmic Star Formation History
• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• The Circumgalactic Medium
• High-Resolution Rotation Curves and Galaxy Mass Models from THINGS
• Cold gas accretion in galaxies
• The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-Redshift Circumgalactic Medium
• Measurement of 21 cm brightness fluctuations at z ~ 0.8 in cross-correlation
• What is Driving the HI Velocity Dispersion?
• The cold gaseous halo of NGC 891
• Characterizing the Circumgalactic Medium of Nearby Galaxies with HST/COS and HST/STIS Absorption-Line Spectroscopy
• The COS-Dwarfs Survey: The Carbon Reservoir Around sub-L* Galaxies
• FIGGS: Faint Irregular Galaxies GMRT Survey - Overview, observations and first results
• Molecular hydrogen in high-redshift Damped Lyman-alpha systems: The VLT/UVES database
• The HI content of star-forming galaxies at z = 0.24
• Reconciling the Metallicity Distributions of Gamma-ray Burst, Damped Lyman-alpha, and Lyman-break Galaxies at z=3
• WSRT Ultra-Deep Neutral Hydrogen Imaging of Galaxy Clusters at z=0.2, a Pilot Survey of Abell 963 and Abell 2192
• HIGHz: A Survey of the Most HI-Massive Galaxies at z~0.2
• Neutral hydrogen (HI) gas content of galaxies at $z\approx 0.32$
• Multi-phase Circum-Galactic Medium probed with MUSE and ALMA
• A study of the circum-galactic medium at z ~ 0.6 using DLA-galaxies
• Probing the Physical Conditions of Atomic Gas at High Redshift
• HI 21-cm absorption survey of quasar-galaxy pairs: Distribution of cold gas around z<0.4 galaxies
• A GBT Survey for HI 21 cm Absorption in the Disks and Halos of Low-Redshift Galaxies
• Incidence of HI 21-cm absorption in strong FeII systems at $0.5<z<1.5$
• Distribution of Cold ($\lesssim 300$K) Atomic Gas in Galaxies: Results from the GBT HI Absorption Survey Probing the Inner Halos ($\rho <20$kpc) of Low-z Galaxies
• Parsec-scale HI absorption structure in a low-redshift galaxy seen against a Compact Symmetric Object
• Thirty-six New, High-Probability, Damped Ly-alpha Absorbers at Redshift 0.42 < z < 0.70
• Cold parsec-scale gas in a zabs~0.1 sub-DLA with disparate H2 and 21-cm absorption
• Discovery of CO absorption at z=0.05 in G0248+430

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