2005A&A...433..955C


Query : 2005A&A...433..955C

2005A&A...433..955C - Astronomy and Astrophysics, volume 433, 955-977 (2005/4-3)

Star formation in RCW 108: Triggered or spontaneous?

COMERON F., SCHNEIDER N. and RUSSEIL D.

Abstract (from CDS):

We present visible, near infrared and mm-wave observations of RCW 108, a molecular cloud complex in the Ara OB1 association that is being eroded by the energetic radiation of two O-type stars in the nearby cluster NGC 6193. The western part of the RCW 108 molecular cloud, for which we derive a mass of ∼8000M, contains an embedded compact HII region, IRAS 16362-4845, ionized by an aggregate of early-type stars for which we estimate a mass of ∼210M. The spectral type of the earliest star is O9, as confirmed by the visible spectrum of the compact HII region. We notice a lack of stars later than A0 in the aggregate, at least having the moderate reddenings that are common among its B-type stars, and we speculate that this might be a consequence of the extreme youth of the aggregate. We also note the existence of a dense ionized clump (n>104cm–3) appearing near the main ionizing star of the compact HII region. We examine the distribution of stars displaying infrared excesses projected across the molecular cloud. While many of them are located in the densest (n∼104–5cm–3) area of the molecular cloud near the position of IRAS 16362-4845, we also find a group concentrating towards the edge of the cloud that faces NGC 6193, as well as some other stars beyond the edge of the molecular cloud. The intense ionizing radiation field by the O stars in NGC 6193 is a clear candidate trigger of star formation in the molecular cloud, and we suggest that the existence and arrangement of stars in this region of the molecular cloud supports a scenario in which their formation may be a consequence of this. However, infrared excess stars are also present in some areas of the opposite side of the cloud, where no obvious candidate external trigger is identified. The existence of such tracers of recent star formation scattered across the more massive molecular cloud associated with IRAS 16362-4845, and the low star formation efficiency that we derive, indicate that it is in a state to still form stars. This is in contrast to the less massive cloud (∼660M) close to NGC 6193, which seems to be more evolved and mostly already recycled into stars, and whose internal kinematics show hints of having been perturbed by the presence of the massive stars formed out of it.

Abstract Copyright:

Journal keyword(s): ISM: HIIregions - ISM: individual objects: RCW 108 - ISM: clouds - infrared: ISM

Nomenclature: Table 2: [CSR2005] Star NN (Nos 1-25).

CDS comments: paragr. 6.1: IRAS 16362-4849 is a misprint for IRAS 16362-4845.

Simbad objects: 43

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Number of rows : 43
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NAME Trapezium Cluster As* 05 35 16.5 -05 23 14           ~ 1558 1
2 M 42 HII 05 35 17.3 -05 23 28           ~ 3938 0
3 NAME Ori A MoC 05 38 -07.1           ~ 2871 0
4 NAME Rosette Molecular Cloud MoC 06 34.7 +04 02           ~ 249 0
5 NGC 2899 PN 09 27 03.02 -56 06 21.1     12.40     G0 149 0
6 MR 35 s*b 11 08 40.0634208096 -60 42 51.721320060   12.33 10.20 11.66   LBV 124 0
7 LAWD 37 WD* 11 45 42.9169346379 -64 50 29.461957832 11.08 11.725 11.513 11.34 11.163 DQ 248 0
8 Ass Ara OB 1 As* 16 39.5 -46 46           ~ 92 0
9 [AMR2003] E PoC 16 39.9 -48 55           ~ 2 0
10 2MASS J16395830-4851452 * 16 39 58.30 -48 51 45.3           ~ 2 0
11 2MASS J16395849-4852048 Y*? 16 39 58.4996983224 -48 52 04.907013672           ~ 5 0
12 [CSR2005] Star 3 * 16 39 58.8 -48 51 59           ~ 1 0
13 2MASS J16395900-4851336 * 16 39 59.00 -48 51 33.7           B5 1 0
14 2MASS J16395952-4851374 Y*? 16 39 59.522 -48 51 37.43           O 4 0
15 [CSR2005] Star 6 * 16 39 59.7 -48 51 56           ~ 1 0
16 [WSB2008] 124 Y*? 16 39 59.80 -48 52 00.0           ~ 2 0
17 [CSR2005] Star 8 * 16 39 59.8 -48 51 39           ~ 1 0
18 2MASS J16395989-4851528 Y*O 16 39 59.8850263800 -48 51 52.966762776           ~ 3 0
19 [CSR2005] Star 10 * 16 40 00.00 -48 51 42.0   15.26 14.56     ~ 5 0
20 NGC 6188 ISM 16 40 -48.5           ~ 16 0
21 CD-48 11039 * 16 40 00.0882315576 -48 46 58.371343032   11.32 10.92 11.092   B3V 24 0
22 GUM 53 HII 16 40 00.1 -48 51 45           ~ 91 1
23 [CSR2005] Star 11 * 16 40 00.1 -48 51 45           ~ 1 0
24 MSX6C G336.4917-01.4741 Y*O 16 40 00.1261535856 -48 51 40.386823308           ~ 8 0
25 IRAS 16362-4845 MoC 16 40 00.1 -48 51 45           ~ 16 2
26 WRAY 19-47 * 16 40 00.2386287349 -48 51 59.613334188     14.90     ~ 3 0
27 [CSR2005] Star 14 * 16 40 00.3 -48 51 56           A0 2 0
28 [WSB2008] 116 Y*? 16 40 00.40 -48 51 43.0           ~ 2 0
29 [CSR2005] Star 15 * 16 40 00.4 -48 51 46           ~ 2 0
30 2MASS J16400072-4851388 * 16 40 00.727 -48 51 38.83           ~ 3 0
31 2MASS J16400125-4851454 Y*O 16 40 01.260 -48 51 45.46           ~ 3 0
32 2MASS J16400155-4851484 Y*O 16 40 01.55 -48 51 48.4           ~ 6 0
33 2MASS J16400163-4851532 Y*O 16 40 01.6438916520 -48 51 53.318643084           ~ 3 0
34 [CSR2005] Star 21 * 16 40 01.7 -48 51 04           ~ 1 0
35 2MASS J16400170-4851390 * 16 40 01.706 -48 51 39.04           ~ 3 0
36 [CSR2005] Star 24 * 16 40 01.9 -48 51 48           ~ 1 0
37 [CSR2005] Star 25 * 16 40 02.2 -48 51 05           ~ 1 0
38 NGC 6193 OpC 16 41 17 -48 46.6           ~ 143 0
39 HD 150135 * 16 41 19.4443334664 -48 45 47.568769200 6.19 7.00 6.88 7.33   O6.5V((f))z 117 0
40 HD 150136 SB* 16 41 20.4155898816 -48 45 46.730465028 4.98 5.78 5.65 6.93   O3.5-4III(f*)+O6IV 181 0
41 [AMR2003] O PoC 16 41.5 -48 49           ~ 1 0
42 HD 150248 PM* 16 41 49.7935085784 -45 22 07.512832956   7.66 7.03     G3V+? 82 0
43 [YSM99] 78 MoC ~ ~           ~ 1 0

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2022.10.05-20:11:12

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