2011A&A...527A.122H


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.11CEST19:53:42

2011A&A...527A.122H - Astronomy and Astrophysics, volume 527A, 122-122 (2011/3-1)

Excitation of H2 in photodissociation regions as seen by Spitzer.

HABART E., ABERGEL A., BOULANGER F., JOBLIN C., VERSTRAETE L., COMPIEGNE M., PINEAU DES FORETS G. and LE BOURLOT J.

Abstract (from CDS):

We present spectroscopic observations obtained with the infrared Spitzer Space Telescope, which provide insight into the H2 physics and gas energetics in photodissociation regions (PDRs) of low to moderate far-ultraviolet (FUV) fields and densities. We analyze data on six well known Galactic PDRs (L1721, California, N7023E, Horsehead, rho Oph, N2023N), sampling a poorly explored range of excitation conditions (χ∼5-103), relevant to the bulk of molecular clouds in galaxies. Spitzer observations of H2 rotational lines are complemented with H2 data, including ro-vibrational line measurements, obtained with ground-based telescopes and ISO, to constrain the relative contributions of ultraviolet pumping and collisions to the H2 excitation. The data analysis is supported by model calculations with the Meudon PDR code. The observed column densities of rotationally excited H2 are observed to be much higher than PDR model predictions. In the lowest excitation PDRs, the discrepancy between the model and the data is about one order of magnitude for rotational levels J≥3. We discuss whether an enhancement in the H2 formation rate or a local increase in photoelectric heating, as proposed for brighter PDRs in former ISO studies, may improve the data-model comparison. We find that an enhancement in the H2 formation rates reduces the discrepancy, but the models still fall short of the data. This large disagreement suggests that our understanding of the formation and excitation of H2 and/or of PDRs energetics is still incomplete. We discuss several explanations, which could be further tested using the Herschel Space Telescope.

Abstract Copyright:

Journal keyword(s): ISM: molecules - ISM: general - ISM: lines and bands - ISM: clouds - evolution - infrared: ISM

Simbad objects: 20

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Number of rows : 20

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 IC 63 HII 00 59 01.37 +60 53 17.8   13.33       ~ 83 1
2 * ksi Per ** 03 58 57.9022917 +35 47 27.713205 3.190 4.080 4.060 3.88 3.89 O7.5III(n)((f)) 789 0
3 NGC 1499 HII 04 03 18 +36 25.3           ~ 151 0
4 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 3479 0
5 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 716 0
6 NAME sigma Orionis Cluster MGr 05 38 42 -02 36.0           ~ 486 0
7 NAME Horsehead Nebula DNe 05 40 59.0 -02 27 30           ~ 445 0
8 NGC 2023 RNe 05 41 37.9 -02 15 52           ~ 570 1
9 HD 37903 Em* 05 41 38.3889407943 -02 15 32.476182358 7.32 7.94 7.83 7.64 7.52 B3IV 323 1
10 LDN 1630 DNe 05 45.5 -00 59           ~ 350 0
11 HD 102065 pr* 11 43 36.9449447212 -80 29 00.508433432   6.67 6.61     B9IV 57 0
12 NAME Cha Dark Cloud SFR 11 55 -78.0           ~ 557 1
13 * nu. Sco ** 16 11 59.73568 -19 27 38.5361 3.42 4.05 4.00 3.90 3.87 B2V 354 0
14 NAME Upper Sco Association As* 16 12 -23.4           ~ 1021 1
15 LDN 1721 DNe 16 14 28.1 -18 54 44           ~ 24 0
16 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3027 0
17 NGC 7023 RNe 21 01 36.9 +68 09 48           ~ 630 0
18 HD 200775 Ae* 21 01 36.9184805541 +68 09 47.770037306 7.34 7.754 7.427 8.13   B2Ve 508 0
19 SH 2-140 OpC 22 19 07.8 +63 17 07           ~ 634 2
20 IRAS 22176+6303 Y*O 22 19 17.978 +63 18 52.92           ~ 589 0

    Equat.    Gal    SGal    Ecl

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2020.07.11-19:53:42

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