2002A&A...391..675G


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.13CEST01:05:29

2002A&A...391..675G - Astronomy and Astrophysics, volume 391, 675-680 (2002/8-4)

H2 formation and excitation in the diffuse interstellar medium.

GRY C., BOULANGER F., NEHME C., PINEAU DES FORETS G., HABART E. and FALGARONE E.

Abstract (from CDS):

We use far-UV absorption spectra obtained with FUSE towards three late B stars to study the formation and excitation of H2 in the diffuse ISM. The data interpretation relies on a model of the chemical and thermal balance in photon-illuminated gas. The data constrain well the n R product between gas density and H2 formation rate on dust grains: nR=1 to 2.2x10–15s–1. For each line of sight the mean effective H2 density n, assumed uniform, is obtained by the best fit of the model to the observed N(J=1)/N(J=0) ratio, since the radiation field is known. Combining n with the n R values, we find similar H2 formation rates for the three stars of about R=4x10–17cm3/s. Because the target stars do not interact with the absorbing matter we can show that the H2 excitation in the J>2 levels cannot be accounted for by the UV pumping of the cold H2 but implies collisional excitation in regions where the gas is much warmer. The existence of warm H2 is corroborated by the fact that the star with the largest column density of CH+ has the largest amount of warm H2.

Abstract Copyright:

Journal keyword(s): ISM: molecules - ISM: clouds - ISM: lines and bands - ISM: individual objects: chamaeleon - ultraviolet: ISM - stars: individual: HD 102065, HD 108927, HD 96675

Simbad objects: 5

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Number of rows : 5

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 NGC 891 H2G 02 22 32.907 +42 20 53.95 11.08 10.81 9.93 7.86   ~ 1521 2
2 HD 96675 pr* 11 05 57.8104415475 -76 07 48.883424761   7.82 7.68   8.48 B6IV/V 68 0
3 HD 102065 pr* 11 43 36.9449447212 -80 29 00.508433432   6.67 6.61     B9IV 57 0
4 NAME Cha Dark Cloud SFR 11 55 -78.0           ~ 557 1
5 HD 108927 * 12 32 19.7295088681 -78 11 38.855613888   7.83 7.76     B5V 29 0

    Equat.    Gal    SGal    Ecl

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2020.07.13-01:05:29

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