1998A&AS..133...29H


C.D.S. - SIMBAD4 rel 1.7 - 2020.05.26CEST05:34:29

1998A&AS..133...29H - Astron. Astrophys., Suppl. Ser., 133, 29-49 (1998/November-2)

A survey of molecular line emission towards ultracompact HII regions.

HATCHELL J., THOMPSON M.A., MILLAR T.J. and MacDONALD G.H.

Abstract (from CDS):

We have used the JCMT to survey molecular line emission towards 14 ultracompact HII regions (G5.89, G9.62, G10.30, G10.47, G12.21, G13.87, G29.96, G31.41, G34.26, G43.89, G45.12, G45.45, G45.47, and G75.78). For each source, we observed up to ten 1GHz bands between 200 and 350GHz, covering lines of more than 30 species including multiple transitions of CO isotopes, CH3OH, CH3CCH, CH3CN and HCOOCH3, and sulphuretted molecules. The number of transitions detected varied by a factor of 20 between sources, which were chosen following observations of high-excitation ammonia (Cesaroni et al., 1994A&A...288..903C) and methyl cyanide (Olmi et al., 1993A&A...276..489O). In half our sample (the line-poor sources), only C17O, C18O, SO, C34S and CH3OH were detected. In the line-rich sources, we detected over 150 lines, including high excitation lines of CH3CN, HCOOCH3, C2H5CN, CH3OH, and CH3CCH. We have calculated the physical conditions of the molecular gas. To reproduce the emission from the line-rich sources requires both a hot, dense compact core and an ambient cloud consisting of less dense, cooler gas. The hot cores, which are less than 0.1 pc in size, reach densities of at least 108cm–3 and temperatures of more than 80K. The line-poor sources can be modelled without a hot core by a 20-30K, 105cm–3 cloud. We find no correlation between the size of the HII region and the current physical conditions in the molecular environment. A comparison with chemical models (Millar et al. 1997) confirms that grain surface chemistry is important in hot cores.

Abstract Copyright:

Journal keyword(s): ISM: molecules - ISM: clouds - ISM: HII regions - radio lines: ISM - stars: formation - molecular processes

VizieR on-line data: <Available at CDS (J/A+AS/133/29): tab10-17.dat table18.dat tables.tex>

Status at CDS:  

Simbad objects: 14

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Number of rows : 14

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 GAL 005.88-00.41 HII 18 00 30.388 -24 04 00.20           ~ 295 0
2 GAL 009.62+00.19 HII 18 06 13.9 -20 31 44           ~ 186 0
3 GAL 010.47+00.03 HII 18 08 38.4 -19 51 52           ~ 108 0
4 [WC89] 010.30-0.15B HII 18 08 55.924 -20 05 54.64           ~ 28 0
5 IRAS 18097-1825A cor 18 12 40.3094 -18 24 20.782           ~ 45 0
6 GAL 013.87+00.28 HII 18 14 35.8 -16 45 31           ~ 34 0
7 GAL 029.96-00.02 Y*O 18 46 03.7 -02 39 21           ~ 331 1
8 IRAS 18449-0115 cor 18 47 34.4947 -01 12 40.269           ~ 307 0
9 OH 34.26 +0.15 SFR 18 53 18.54 +01 14 57.9           ~ 457 0
10 Caswell OH 045.12+00.13 HII 19 13 27.845 +10 53 36.74           ~ 111 0
11 GAL 045.5+00.0 HII 19 14 20.8 +11 09 04           ~ 138 0
12 [GPD88] 045.454+0.060 HII 19 14 21.3 +11 09 13           ~ 150 1
13 GAL 043.89-00.78 HII 19 14 26.16 +09 22 34.0           ~ 49 0
14 NAME Cygnus 2N HII 20 21 44.1 +37 26 40           ~ 109 1

    Equat.    Gal    SGal    Ecl

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