2018A&A...615A.158T


C.D.S. - SIMBAD4 rel 1.7 - 2021.06.13CEST05:10:39

2018A&A...615A.158T - Astronomy and Astrophysics, volume 615A, 158-158 (2018/7-1)

Unveiling the remarkable photodissociation region of Messier 8.

TIWARI M., MENTEN K.M., WYROWSKI F., PEREZ-BEAUPUITS J.P., WIESEMEYER H., GUSTEN R., KLEIN B. and HENKEL C.

Abstract (from CDS):


Aims. Messier 8 (M8) is one of the brightest HII regions in the sky. We collected an extensive dataset comprising multiple sub- millimeter spectral lines from neutral and ionized carbon and from CO. Based on this dataset, we aim to understand the morphology of M8 and that of its associated photodissociation region (PDR) and to carry out a quantitative analysis of the physical conditions of these regions such as kinetic temperatures and volume densities.
Methods. We used the Stratospheric Observatory For Infrared Astronomy (SOFIA), the Atacama Pathfinder Experiment (APEX) 12 m, and the Institut de Radioastronomie Millimetrique (IRAM) 30 m telescopes to perform a comprehensive imaging survey of the emission from the fine structure lines of [CII] and [CI] and multiple rotational transitions of carbon monoxide (CO) isotopologs within 1.3x1.3pc around the dominant Herschel 36 (Her 36) system, which is composed of at least three massive stars. To further explore the morphology of the region, we compared archival infrared, optical, and radio images of the nebula with our newly obtained fine structure line and CO data, and in particular with the velocity information these data provide. We performed a quantitative analysis, using both LTE and non-LTE methods to determine the abundances of some of the observed species, kinetic temperatures, and volume densities.
Results. Bright CO, [CII] and [CI] emission have been found toward the HII region and the PDR in M8. Our analysis places the bulk of the molecular material in the background of the nebulosity illuminated by the bright stellar systems Her 36 and 9 Sagitarii. Since the emission from all observed atomic and molecular tracers peaks at or close to the position of Her 36, we conclude that the star is still physically close to its natal dense cloud core and heats it. A veil of warm gas moves away from Her 36 toward the Sun and its associated dust contributes to the foreground extinction in the region. One of the most prominent star forming regions in M8, the Hourglass Nebula, is particularly bright due to cracks in this veil close to Her 36. We obtain H2 densities ranging from ∼104-106cm–3 and kinetic temperatures of 100-150 K in the bright PDR caused by Her 36 using radiative transfer modeling of various transitions of CO isotopologs.

Abstract Copyright: © ESO 2018

Journal keyword(s): ISM: general - ISM: individual objects: M8 - submillimeter: ISM - HII regions - ISM: clouds

VizieR on-line data: <Available at CDS (J/A+A/615/A158): list.dat fits/*>

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 - 2021
#notes
1 V* R Dor AB* 04 36 45.59127 -62 04 37.7974 7.84 6.98 5.40 2.71 -0.44 M8III:e 301 0
2 NAME OMC-1 MoC 05 35 14 -05 22.4           ~ 1059 2
3 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2079 1
4 M 42 HII 05 35 17.3 -05 23 28           ~ 3803 0
5 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 762 0
6 RAFGL 5254 C* 09 13 53.9380628049 -24 51 25.223261483           C-rich 49 0
7 NAME Car-Sgr Arm PoG 15 00 -40.0           ~ 442 1
8 NAME Galactic Center gam 17 45 39.60213 -29 00 22.0000           ~ 12252 0
9 QSO J1800-241 QSO 18 00 30.3936762615 -24 04 02.811037080           ~ 5 0
10 NGC 6523 Cl* 18 03.2 -24 23           ~ 184 1
11 M 8 HII 18 03 37 -24 23.2           ~ 564 1
12 CD-24 13806 ** 18 03 40.321 -24 22 42.86 10.26 10.88 10.30 10.27   O7:V 182 2
13 GAL 005.97-01.17 HII 18 03 40.501 -24 22 44.46           ~ 33 0
14 NAME Hourglass Nebula ISM 18 03 41.1 -24 22 37           ~ 74 2
15 * 9 Sgr Em* 18 03 52.4455370104 -24 21 38.639393923 5.08 5.97 5.97 5.72 5.70 O4V((f))z 522 0
16 NGC 6530 OpC 18 04 31 -24 21.5           ~ 363 0
17 NAME M 8E Y*O 18 04 53.26 -24 26 42.3           ~ 58 0
18 HD 165052 SB* 18 05 10.5506202440 -24 23 54.850635234 6.16 6.98 6.87 7.77   O5.5:Vz+O8:V 253 1
19 NAME M 17 SW SFR 18 20 23.1 -16 11 43           ~ 255 0
20 NGC 6618 OpC 18 20 47 -16 10.3           ~ 1517 0

    Equat.    Gal    SGal    Ecl

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2021.06.13-05:10:39

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