2002A&A...392..781L


Query : 2002A&A...392..781L

2002A&A...392..781L - Astronomy and Astrophysics, volume 392, 781-789 (2002/9-4)

Detection of molecular hydrogen in a near Solar-metallicity damped Lyman-α system at zabs≃2 toward Q0551-366.

LEDOUX C., SRIANAND R. and PETITJEAN P.

Abstract (from CDS):

We report the detection of H2, CI, CI*, CI** and ClI lines in a near Solar-metallicity ([Zn/H]=-0.13) damped Lyman-α (DLA) system at zabs=1.962 observed on the line of sight to the quasar Q0551-366. The iron-peak elements, X=Fe, Cr and Mn are depleted compared to zinc, [X/Zn]~-0.8, probably because they are tied up onto dust grains. Among the three detected H2-bearing clouds, spanning 55km/s in velocity space, we derive a total molecular hydrogen column density N(H2)=2.6x1017cm–2 and a mean molecular fraction f=2N(H2)/(2N(H2)+N(HI))=1.7x10–3. The depletion of heavy elements (S, Si, Mg, Mn, Cr, Fe, Ni and Ti) in the central component is similar to that observed in the diffuse neutral gas of the Galactic halo. This depletion is approximately the same in the six Ci-detected components independently of the presence or absence of H2. The gas clouds in which H2 is detected always have large densities, nH>30cm–3, and low temperatures, T01≲100K. This shows that presence of dust, high particle density and/or low temperature is required for molecules to be present. The photo-dissociation rate derived in the components where H2 is detected suggests the existence of a local UV radiation field similar in strength to the one in the Galaxy. Star formation therefore probably occurs near these H2-bearing clouds.

Abstract Copyright:

Journal keyword(s): cosmology: observations - galaxies: halos - galaxies: ISM - quasars: absorption lines - quasars: individual: Q0551-366

Nomenclature: [LSP2002] QSO J0552-3637 abs N.NNN N=1. Tables 3-5: [LSP2002] QSO J0552-3637 abs N.NNNNN N=11.

Errata: erratum vol. 396, p. 429 (2002)

Simbad objects: 8

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Number of rows : 8
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 QSO J0003-2603 QSO 00 03 22.9531962024 -26 03 18.304471908   18 17.53     ~ 291 0
2 LBQS 0013-0029 QSO 00 16 02.4050159808 -00 12 25.077257064   18.67 18.36     ~ 194 0
3 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 11178 1
4 QSO B0347-383 QSO 03 49 43.6603590912 -38 10 30.825444900     17.3     ~ 191 0
5 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 17478 0
6 QSO B0551-36 QSO 05 52 46.1824785360 -36 37 27.608212524   17.72 17.57     ~ 97 0
7 QSO B0841+129 BLL 08 44 24.2445546984 +12 45 46.526286780   18.28 18.5     ~ 119 0
8 LBQS 1232+0815 QSO 12 34 37.5514444464 +07 58 43.367750796     18.4     ~ 125 0

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