|
| | | | |
| | | |
| Stat |
Members: 3645
Articles: 2'506'133
Articles rated: 2609
26 April 2024 |
|
| | | | |
|
Article overview
| |
|
|
Structure of photodissociation fronts in star-forming regions revealed by observations of high-J CO emission lines with Herschel | | C. Joblin
; E. Bron
; C. Pinto
; P. Pilleri
; F. Le Petit
; M. Gerin
; J. Le Bourlot
; A. Fuente
; O. Berne
; J. R. Goicoechea
; E. Habart
; M. Koehler
; D. Teyssier
; Z. Nagy
; J. Montillaud
; C. Vastel
; J. Cernicharo
; M. Roellig
; V. Ossenkopf-Okada
; E. A. Bergin
; | | Date: |
11 Jan 2018 | | Abstract: | The morphology of bright photodissociation regions (PDRs) associated to
massive star formation is a subject of active research. The presence of dense
"clumps" that are immersed in a less dense interclump medium is often proposed
to explain the difficulty of models to predict gas emission line intensities in
these objects. Taking benefit from the Herschel data, we present a
comprehensive view of the modeling of the CO rotational ladder in PDRs,
including the high-J lines that trace warm molecular gas at PDR interfaces. We
observed the 12CO and 13CO ladders in two prototypical PDRs, the Orion Bar and
NGC 7023 NW using the three instruments onboard Herschel: PACS, SPIRE and HIFI.
We also considered line emission from key species in the gas cooling (C+, O,
H2) and other tracers of PDR edges such as OH, CH+ and HCO+. All the
intensities were analyzed using the Meudon PDR code. A grid of models was run
to explore the parameter space of only two parameters: thermal gas pressure and
a global geometry scaling factor. We conclude that the emission in the high-J
CO lines, (up to Jup=23 in the Orion Bar and Jup=19 in NGC 7023), can only
originate from small structures (typically few 1e-3 pc thickness) at high
thermal pressures (Pth~1e8 Kcm-3). The calculated intensities for the others
tracers are consistent with the observations, with evidence for a more extended
diffuse phase for C+. Herschel observations of high-J CO lines allow us to
refine our understanding of the morphology of bright PDR edges, strongly
supporting the presence of thin (typically the arcsecond at the distance of
Orion) high-pressure interfaces. Compiling data from the literature, we found
that the gas thermal pressure in these dense structures increases with the
intensity of the FUV radiation field, following a trend in line with recent
simulations that describe photoevaporation of the illuminated edge of molecular
clouds. | | Source: | arXiv, 1801.3893 | | Services: | Forum | Review | PDF | Favorites | |
|
|
No review found.
Did you like this article?
Note: answers to reviews or questions about the article must be posted in the forum section.
Authors are not allowed to review their own article. They can use the forum section.
browser Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
|
| |
|
|
|
|
News, job offers and information for researchers and scientists:
| |
REGISTER