A multiwavelength investigation of the temperature of the cold neutral medium

Abstract

We present measurements of the H I spin temperatures (T_s) of the Cold Neutral Medium (CNM) towards radio sources that are closely aligned with stars for which published H_2 ortho-para temperatures (T_{01}) are available from UV observations. Our sample consists of 18 radio sources close to 16 nearby stars. The transverse separation of the lines of sight of corresponding the UV and radio observations varies from 0.1 to 12.0 pc at the distance of the star. The ultraviolet (UV) measurements do not have velocity information, so we use the velocities of low ionization species (e.g Na I, K I, C I) observed towards these same stars to make a plausible identification of the CNM corresponding to the H_2 absorption. We then find that T_{01} and T_s match within observational uncertainties for lines-of-sight with H_2 column density above 10^{15.8} cm^{-2}, but deviate from each other below this threshold. This is consistent with the expectation that in the CNM T_s tracks the kinetic temperature due to collisions and that T_{01} is driven towards the kinetic temperature by proton exchange reactions.

6 pages, 2 tables, 2 figures. Accepted for publication in MNRAS Letters. Abstract modified. The definitive version is available at http://www.blackwell-synergy.com

References in corpus (4)

• The Millennium Arecibo 21-CM Absorption Line Survey. II. Properties of the Warm and Cold Neutral Media
• The Millennium Arecibo 21-cm Absorption Line Survey. I. Techniques and Gaussian Fits
• New Temperatures of Diffuse Interstellar Gas: Thermally Unstable Gas
• Spatial and Temporal Variations in Small-Scale Galactic HI Structure Toward 3C~138

Cited by in corpus (38)

• The 21-SPONGE HI Absorption Survey I: Techniques and Initial Results
• 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
• Excitation mechanisms in newly discovered H2-bearing Damped Lyman-alpha clouds: systems with low molecular fractions
• CO-dark molecular gas at high redshift: very large H${}_2$ content and high pressure in a low metallicity damped Lyman-alpha system
• Physical conditions in the neutral interstellar medium at z=2.43 toward Q2348-011
• 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
• A complete sample of 21-cm absorbers at z~1.3: Giant Metrewave Radio Telescope Survey Using MgII Systems
• The temperature of the diffuse HI in the Milky Way I: High resolution HI 21 cm absorption studies
• Molecular hydrogen in the z = 2.66 damped Lyman-alpha absorber toward Q J0643-5041
• The temperature of the diffuse HI in the Milky Way II: Gaussian decomposition of the HI 21 cm absorption spectra
• Detection of 21-cm, H2 and Deuterium absorption at z>3 along the line-of-sight to J1337+3152
• Analysis of Molecular Hydrogen Absorption toward QSO B0642-5038 for a Varying Proton-to-Electron Mass Ratio
• X-shooter observations of strong H${}_2$-bearing DLAs at high redshift
• Parsec-scale structures and diffuse bands in a translucent interstellar medium at z 0.079
• An HST/COS survey of molecular hydrogen in DLAs & sub-DLAs at z < 1: Molecular fraction and excitation temperature
• Molecular gas and star formation in an absorption-selected galaxy: Hitting the bull's eye at z = 2.46
• Efficient ortho-para conversion of H2 on interstellar grain surfaces
• Excitation temperature of the warm neutral medium as a new probe of the Lyman-α radiation field
• Molecular Hydrogen Absorption from the Halo of a z ~ 0.4 Galaxy
• Connecting X-ray absorption and 21cm neutral hydrogen absorption in obscured radio AGN
• Turbulence measurements from HI absorption spectra
• Mapping kiloparsec-scale structures in the extended HI disc of the galaxy UGC 00439 by HI 21-cm absorption
• Dissecting cold gas in a high-redshift galaxy using a lensed background quasar
• New constraints on the physical conditions in H${}_2$-bearing GRB-host damped Lyman-$\alpha$ absorbers
• Estimating kinetic temperature from H I 21 cm absorption studies: correction for the turbulence broadening
• Multicomponent H2 in DLA at zabs = 2.05: physical conditions through observations and numerical models
• HI 21-cm absorption from $z\sim 0.35$ strong MgII absorbers
• Cold parsec-scale gas in a zabs~0.1 sub-DLA with disparate H2 and 21-cm absorption
• A detection of H${}_2$ in a high velocity cloud toward the Large Magellanic Cloud
• Probing galaxy evolution through HI 21-cm emission and absorption: current status and prospects with the Square Kilometre Array
• Molecular hydrogen from z = 0.0963 DLA towards the QSO J1619+3342
• Cold neutral hydrogen gas in galaxies
• C II radiative cooling of the Galactic diffuse interstellar medium: Insight about the star formation in Damped Lyman-alpha systems
• Properties of atomic hydrogen gas in the Galactic plane from THOR 21-cm absorption spectra: a comparison with the high latitude gas
• New HI observations of KK 69. Is KK 69 a dwarf galaxy in transition?
• On the Dusty Proximate Damped Lyman-α System toward Q2310-3358 at z = 2.40
• HI 21-cm Absorption Associated with Foreground Galaxies on Top of Quasars
• Research on the Interstellar Medium and Star Formation in the Galaxy: An Indian Perspective