2003ApJ...596..362K


Query : 2003ApJ...596..362K

2003ApJ...596..362K - Astrophys. J., 596, 362-382 (2003/October-2)

Molecular counterparts of ultracompact H II regions with extended envelopes.

KIM K.-T. and KOO B.-C.

Abstract (from CDS):

We have carried out 13CO J=1-0, CS, and C34S J=2-1 and J=3-2 line observations of molecular clouds associated with 16 ultracompact (UC) H II regions with extended envelopes. The molecular clouds are the ones that give birth to rich stellar clusters and/or very massive (O7-O4) stars. Our data show that the clouds are very clumpy and of irregular morphology. They usually have much larger masses, velocity dispersions, and fractions of dense gas than molecular clouds that form early B or late O stars. This is compatible with earlier findings that more massive stars form in more massive cores. The IR luminosity-to-mass ratio has a mean value of 9 L/Mand is little correlated with the cloud mass. Most molecular clouds have star formation efficiencies of 1%-2%. We find size-line width and size-density relations in the forms of Δv∝D0.4 and n(H2)∝D–1.2. 13CO cores are in general associated with compact H II regions regardless of the presence of UC H II regions therein. In contrast, CS cores are preferentially associated with compact H II regions that contain UC H II regions. As with the fact that the compact H II regions containing UC H II regions are more compact than those not associated with UC H II regions, these indicate that the former may be in an earlier evolutionary phase than the latter. The diffuse extended envelopes of H II regions often develop in the direction of decreasing molecular gas density. Based on detailed comparison of molecular line data with radio continuum and recombination line data, the extended ionized envelopes are likely the results of champagne flows in at least 10 sources in our sample. Together these results appear to support a published suggestion that the extended emission around UC H II regions can be naturally understood by combining the champagne flow model with the hierarchical structure of molecular clouds, taking into account various inclinations and low resolutions of our data. In addition, the blister model seems to be still applicable to most H II regions, even though massive stars usually form in the interiors rather than on the surfaces of molecular clouds. This is possible because massive star-forming clouds have hierarchical structure and irregular morphology.

Abstract Copyright:

Journal keyword(s): ISM: H II Regions - ISM: Clouds - ISM: Molecules - Radio Lines: ISM - Stars: Formation

Simbad objects: 31

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Number of rows : 31
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 M 42 HII 05 35 01.5 -05 26 24           ~ 3951 0
2 NAME Ori A MoC 05 38 -07.1           ~ 2881 0
3 NAME Horsehead Nebula DNe 05 40 59.0 -02 27 30           ~ 490 0
4 LDN 1630 DNe 05 45.5 -00 59           ~ 373 0
5 Ass Gem OB 1 As* 06 09.8 +21 35           ~ 181 0
6 NAME Rosette Molecular Cloud MoC 06 34.7 +04 02           ~ 250 0
7 GAL 005.88-00.41 HII 18 00 30.388 -24 04 00.20           ~ 320 0
8 W 28a1 HII 18 00 50.018 -23 20 32.53           ~ 5 0
9 [WC89] 008.14+0.23 HII 18 03 00.9 -21 48 10           ~ 10 0
10 M 8 HII 18 03 37 -24 23.2           ~ 595 1
11 NAME Her 36SE SB* 18 03 40.3201232304 -24 22 42.857540472 10.26 11.022 10.372 10.267   O8V+ 187 0
12 GAL 005.97-01.17 HII 18 03 40.501 -24 22 44.46           ~ 33 0
13 * 9 Sgr Em* 18 03 52.4450051016 -24 21 38.632254012 5.08 5.97 5.97 5.72 5.70 O4V((f))z 530 0
14 [WC89] 010.30-0.15B HII 18 08 55.95 -20 05 55.4           ~ 29 0
15 GAL 010.15-00.34 HII 18 09 21.5680 -20 19 27.720           ~ 74 0
16 GAL 010.2-00.3 HII 18 09 24.6 -20 19 29           ~ 78 1
17 W 31 SFR 18 10 28.6 -19 55 51           ~ 252 0
18 IRAS 18097-1825A cor 18 12 40 -18 24.4           ~ 61 0
19 [WC89] 012.43-0.05 HII 18 12 54.593 -18 11 08.33           ~ 5 0
20 M 16 OpC 18 18 45 -13 47.5   6.58 6.0     ~ 999 2
21 NGC 6618 OpC 18 20 47 -16 10.3           ~ 1567 0
22 [CKW87] 183109.3-080954 HII 18 33 52.5 -08 07 32           ~ 31 0
23 [WAM82] 023.955+0.152 HII 18 34 24.9 -07 54 50           ~ 70 1
24 GAL 023.46-00.20 HII 18 34 44.91 -08 31 07.4           ~ 12 0
25 ISOGAL-P J183802.9-062347 Y*? 18 38 02.80 -06 23 47.0           ~ 29 0
26 GAL 027.28+00.15 HII 18 40 35 -04 57.7           ~ 28 0
27 CORNISH G029.9559-00.0168 Y*O 18 46 04.18 -02 39 21.3           ~ 358 0
28 GAL 035.05-00.52 HII 18 57 09.044 +01 39 03.37           ~ 20 0
29 GAL 037.55-00.11 HII 19 00 15.7 +04 03 13           ~ 40 0
30 W 49 SFR 19 10 20 +09 07.7           ~ 550 1
31 W 51 SNR 19 23 50 +14 06.0           ~ 1230 1

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2022.11.26-09:50:26

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