2002A&A...389..393L


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.04CEST20:37:04

2002A&A...389..393L - Astronomy and Astrophysics, volume 389, 393-404 (2002/7-2)

Two-phase equilibrium and molecular hydrogen formation in damped Lyman-alpha systems.

LISZT H.

Abstract (from CDS):

Molecular hydrogen is quite underabundant in damped Lyman-α systems at high redshift, when compared to the interstellar medium near the Sun. This has been interpreted as implying that the gas in damped Lyman-α systems is warm like the nearby neutral intercloud medium, rather than cool, as in the clouds which give rise to most H I absorption in the Milky Way. Other lines of evidence suggest that the gas in damped Lyman-α systems - in whole or part - is actually cool; spectroscopy of neutral and ionized carbon, discussed here, shows that the damped Lyman-α systems observed at lower redshift z<2.3 are largely cool, while those seen at z>2.8 are warm (though not devoid of H2). To interpret the observations of carbon and hydrogen we constructed detailed numerical models of H2 formation under the conditions of two-phase thermal equilibrium, like those which account for conditions near the Sun, but with varying metallicity, dust-gas ratio, etc. We find that the low metallicity of damped Lyman-α systems is enough to suppress H2 formation by many orders of magnitude even in cool diffuse clouds, as long as the ambient optical/uv radiation field is not too small. For very low metallicity and under the most diffuse conditions, H2 formation will be dominated by slow gas-phase processes not involving grains, and a minimum molecular fraction in the range 10–8-10–7 is expected.

Abstract Copyright:

Journal keyword(s): quasars: absorption lines - ISM: molecules

Simbad objects: 13

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Number of rows : 13

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 QSO J0003-2603 QSO 00 03 22.9530051057 -26 03 18.306624161   18 17.53     ~ 272 0
2 LBQS 0013-0029 QSO 00 16 02.4050445836 -00 12 25.076529860   18.67 18.36     ~ 175 0
3 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9440 1
4 PHL 957 QSO 01 03 11.2740814277 +13 16 17.810502093   16.97 16.57     ~ 327 0
5 QSO B0347-383 QSO 03 49 43.6605705480 -38 10 30.834942758     17.3     ~ 176 0
6 QSO B0454+0356 QSO 04 56 47.1747689004 +04 00 52.945030656   16.76 16.53 16.26   ~ 227 1
7 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14826 1
8 QSO B0528-2505 QSO 05 30 07.96279681 -25 03 29.8994010   18.17 17.34 17.7   ~ 393 0
9 LBQS 1232+0815 QSO 12 34 37.5507010309 +07 58 43.372966617     18.4     ~ 112 0
10 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3715 1
11 QSO B1331+170 QSO 13 33 35.7826224 +16 49 04.014213   16.84 16.71 16.41   ~ 408 1
12 QSO B1337+11 QSO 13 40 02.5420534525 +11 06 30.176749720     18.7     ~ 103 0
13 QSO J1759+2343 QSO 17 59 00.3579983815 +23 43 46.950857063     18.0 15.76   ~ 82 1

    Equat.    Gal    SGal    Ecl

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2020.07.04-20:37:04

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