2008A&A...483..485N


Query : 2008A&A...483..485N

2008A&A...483..485N - Astronomy and Astrophysics, volume 483, 485-493 (2008/5-4)

Modeling of diffuse molecular gas applied to HD 102065 observations.

NEHME C., LE BOURLOT J., BOULANGER F., PINEAU DES FORETS G. and GRY C.

Abstract (from CDS):

We model a diffuse molecular cloud present along the line of sight to the star HD 102065. We compare our modeling with observations to test our understanding of physical conditions and chemistry in diffuse molecular clouds. We analyze an extensive set of spectroscopic observations which characterize the diffuse molecular cloud observed toward HD 102065. Absorption observations provide the extinction curve, H2, CI, CO, CH, and CH+ column densities and excitation. These data are complemented by observations of C+, CO and dust emission. Physical conditions are determined using the Meudon PDR model of UV illuminated gas. We find that all observational results, except column densities of CH, CH+ and H2 in its excited (J≥2) levels, are consistent with a cloud model implying a Galactic radiation field (G∼0.4 in Draine's unit), a density of 80cm–3 and a temperature (60-80K) set by the equilibrium between heating and cooling processes. To account for excited (J≥2) H2 levels column densities, an additional component of warm (∼250K) and dense (nH≥104cm–3) gas within 0.03pc of the star would be required. This solution reproduces the observations only if the ortho-to-para H2 ratio at formation is ∼1. In view of the extreme physical conditions and the unsupported requirement on the ortho-to-para ratio, we conclude that H2 excitation is most likely to be accounted for by the presence of warm molecular gas within the diffuse cloud heated by the local dissipation of turbulent kinetic energy. This warm H2 is required to account for the CH+ column density. It could also contribute to the CH abundance and explain the inhomogeneity of the CO abundance indicated by the comparison of absorption and emission spectra.

Abstract Copyright:

Journal keyword(s): astrochemistry - ISM: clouds - ISM: molecules - ISM: structure - ISM: individual objects : Chamaeleon clouds - stars: individual: HD 102065

Simbad objects: 7

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Number of rows : 7
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 * bet Pic PM* 05 47 17.0876901 -51 03 59.441135 4.13 4.03 3.86 3.74 3.58 A6V 1908 1
2 HD 100546 Be* 11 33 25.4408872296 -70 11 41.241297948   6.71 6.30   6.64 A0VaekB8_lB 807 1
3 HD 102065 Y*O 11 43 36.9451657872 -80 29 00.511110852   6.67 6.61     B9IV 65 0
4 [DB2002b] G300.23-16.89 DNe 11 54 31 -79 27.8           ~ 45 1
5 NAME Chamaeleon Region SFR 11 55 -78.0           ~ 808 0
6 * zet Oph Be* 16 37 09.5400587698 -10 34 01.509742704 1.73 2.58 2.56 2.46 2.50 O9.2IVnn 1840 0
7 HD 163296 Ae* 17 56 21.2881851168 -21 57 21.871819008 7.00 6.93 6.85 6.86 6.67 A3VaekA1mA1 1113 0

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