2009A&A...500..845M


Query : 2009A&A...500..845M

2009A&A...500..845M - Astronomy and Astrophysics, volume 500, 845-860 (2009/6-3)

Prestellar and protostellar cores in Orion B9.

MIETTINEN O., HARJU J., HAIKALA L.K., KAINULAINEN J. and JOHANSSON L.E.B.

Abstract (from CDS):

Dense molecular cores are studied to gain insight into the processes causing clouds to fragment and form stars. In this study, we concentrate on a region that is assumed to represent an early stage of clustered star-formation in a giant molecular cloud. We aim to determine the properties and spatial distribution of dense cores in the relatively quiescent Ori B9 cloud, and to estimate their ages and dynamical timescales. The cloud was mapped in the 870µm continuum with APEX/LABOCA, and selected positions were observed in the lines of N2H+ and N2D+ using IRAM-30m. These were used together with our previous H2D+ observations to derive the degree of deuteration and some other chemical characteristics. Archival far-infrared Spitzer/MIPS maps were combined with the LABOCA map to distinguish between prestellar and protostellar cores, and to estimate the evolutionary stages of protostars. Twelve dense cores were detected at 870µm continuum in the Ori B9 cloud. The submm cores constitute ∼4% of the total mass of the Ori B9 region. There is an equal number of prestellar and protostellar cores. Two of the submm sources, which we call SMM 3 and SMM 4, are previously unknown Class 0 candidates. There is a high likelihood of the core masses and mutual separations representing the same distributions as observed in other parts of Orion. We found a moderate degree of deuteration in N2H+ (0.03-0.04). There is, furthermore, evidence of N2H+ depletion in the core SMM 4. These features suggest that the cores have reached chemical maturity. We derive a relatively high degree of ionization (∼10–7) in the clump associated with IRAS 05405-0117. The ambipolar diffusion timescales for two of the cores are ∼70-100 times longer than the free-fall time. The distribution and masses of dense cores in Ori B9 are similar to those observed in more active regions of Orion, where the statistical core properties have been explained by turbulent fragmentation. The 50/50 proportions of prestellar and protostellar cores imply that the duration of the prestellar phase is comparable to the free-fall time. However, on the basis of chemical data of the IRAS 05405-0117 region, this timescale could be questioned. A possible explanation is that this survey samples only the densest, i.e., dynamically most advanced cores.

Abstract Copyright:

Journal keyword(s): stars: formation - ISM: clouds - ISM: molecules - radio continuum: ISM - radio lines: ISM - submillimeter

Nomenclature: Fig. 1, Table 2: [MHH2009c] SMM N (Nos 1-7).

CDS comments: Fig. 6 IRAS 05045-0117 is a probable misprint for IRAS 05405-0117.

Simbad objects: 45

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Number of rows : 45
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 NAME Per Region reg 03 37 00.0 +31 15 00           ~ 258 0
2 NAME [BM89] L1498 PoC 04 10 51.4 +25 09 58           ~ 187 0
3 LDN 1498 DNe 04 11.0 +24 58           ~ 271 0
4 IRAS 04191+1523 Y*O 04 22 00.43944 +15 30 21.2148           ~ 195 0
5 QSO B0420-0127 QSO 04 23 15.80072217 -01 20 33.0656073   17.50 17.00 16.28   ~ 1149 3
6 Barnard 217 DNe 04 27 46.5 +26 17 52           ~ 89 0
7 LDN 1521F DNe 04 28 39.3 +26 51 43           ~ 195 1
8 Bad 16 Y*O 04 30 50.2774891944 +23 00 08.757461592       14.95   F1 139 0
9 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 4099 0
10 Barnard 220 DNe 04 41 38.8 +26 00 42           ~ 133 0
11 NAME [BM89] L1517B cor 04 55 18.8 +30 38 04           ~ 139 0
12 LDN 1512 MoC 05 04 09.7 +32 43 09           ~ 166 0
13 LDN 1544 DNe 05 04 16.6 +25 10 48           ~ 805 0
14 NAME [BM89] L1544 cor 05 04 22.5 +25 11 36           ~ 436 1
15 NAME Ori Complex Cld 05 35.3 -05 23           ~ 405 0
16 NAME Ori A MoC 05 38 -07.1           ~ 2899 0
17 NGC 2023 RNe 05 41 37.9 -02 15 52           ~ 611 1
18 NAME Ori B MoC 05 41 43.0 -01 54 44           ~ 1303 0
19 NGC 2024 Cl* 05 41 43 -01 50.5           ~ 1123 1
20 HH 92 HH 05 42 21.1 -01 18 29           ~ 16 0
21 IRAS 05399-0121 Y*O 05 42 27.68 -01 20 01.0           ~ 40 0
22 [MHH2009c] SMM 1 smm 05 42 30.5 -01 20 45           ~ 8 0
23 NAME Ori B9 Cloud Cld 05 42 30.5 -01 20 33           ~ 21 0
24 HGBS J054233.1-012539 cor 05 42 32.9 -01 25 28           ~ 4 0
25 [MHH2009c] SMM 3 smm 05 42 44.4 -01 16 03           ~ 9 0
26 IRAS 05405-0117 Y*O 05 43 03.05688 -01 16 29.2404           G3-M4 33 0
27 [MHH2009c] SMM 4 smm 05 43 03.9 -01 15 44           ~ 6 0
28 [MHH2009c] SMM 5 smm 05 43 04.5 -01 17 06           ~ 4 0
29 NAME Orion B9-SMM 6 cor 05 43 05.1 -01 18 38           ~ 9 0
30 [HHL2006] OriB9 E smm 05 43 05.2 -01 16 23           ~ 2 0
31 [HHL2006] OriB9 N smm 05 43 05.7 -01 14 41           ~ 4 0
32 [MHH2009c] SMM 7 smm 05 43 22.1 -01 13 46           ~ 7 0
33 2MASS J05434630-0104439 Y*O 05 43 46.30656 -01 04 43.9644           ~ 7 1
34 HH 212 HH 05 43 51.41 -01 02 53.1           ~ 358 1
35 IRAS 05413-0104 IR 05 43 51.5 -01 02 52           ~ 81 0
36 LDN 1630 DNe 05 45.5 -00 59           ~ 373 0
37 M 78 RNe 05 46 45.8 +00 04 45   8.0       ~ 366 0
38 NGC 2071 RNe 05 47 10 +00 18.0           ~ 631 1
39 NAME Orion Molecular Cloud MoC 05 56 -01.8           ~ 1025 1
40 LDN 183 MoC 15 54 12.2 -02 49 42           ~ 729 1
41 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3448 1
42 LDN 57 DNe 17 22 38.2 -23 49 34           ~ 302 1
43 NAME Serpens Cloud SFR 18 29 49 +01 14.8           ~ 1049 2
44 IRAS 20293+3952 HII 20 31 11.040 +40 03 10.69           ~ 70 0
45 LDN 1262 MoC 23 25 47 +74 17.6           ~ 132 0

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2023.02.04-10:10:29

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