# 2010A&A...524A..91M

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 Query : 2010A&A...524A..91M

2010A&A...524A..91M - Astronomy and Astrophysics, volume 524, A91-91 (2010/12-1)

Physical properties of dense cores in Orion B9.

MIETTINEN O., HARJU J., HAIKALA L.K. and JUVELA M.

Abstract (from CDS):

We aim to determine the physical and chemical properties of the starless and protostellar cores in Orion B9, which represents a relatively quiescent star-forming region in Orion B. We observed the NH3 (J,K)=(1,1) and (2,2) inversion lines and the N2H+(3-2) rotational lines, with the Effelsberg 100-m and APEX telescopes, respectively, towards the submillimetre peak positions in Orion B9. These data are used in conjunction with our APEX/LABOCA 870µm dust continuum data of the region. The gas kinetic temperature in the cores derived from the NH3 data is between ∼9.4-13.9K. The non-thermal velocity dispersion is subsonic in most of the cores. The non-thermal linewidth in protostellar cores appears to increase with increasing bolometric luminosity. The core masses, ∼2-8M, are very likely drawn from the same parent distribution as the core masses in Orion B North. Based on the virial parameter analysis, starless cores in the region are likely to be gravitationally bound, and thus prestellar. Some of the cores have a lower radial velocity than the systemic velocity of the region, suggesting that they are members of the low-velocity part'' of Orion B. The observed core-separation distances deviate from the corresponding random-like model distributions. The distances between the nearest neighbours are comparable to the thermal Jeans length. The fractional abundances of NH3 and N2H+ in the cores are ∼1.5-9.8x10–8 and ∼0.2-5.9x10–10, respectively. The NH3 abundance appears to decrease with increasing H2 column and number densities. The NH3/N2H+ column density ratio is larger in starless cores than in cores with embedded protostars. The core population in Orion B9 is comparable in physical properties to those in nearby low-mass star-forming regions. The Orion B9 cores also seem to resemble cores found in isolation rather than those associated with clusters. Moreover, because the cores may not be randomly distributed within the region (contrary to what was suggested in our Paper I), it is unclear whether the origin of cores could be explained by turbulent fragmentation. On the other hand, many of the core properties conform to the picture of dynamic core evolution. The Orion B9 region has probably been influenced by the feedback from the nearby Ori OB 1b group, and the fragmentation of the parental cloud into cores could be caused by gravitational instability.

Journal keyword(s): stars: formation - ISM: clouds - ISM: individual objects: Orion B - ISM: molecules - radio lines: ISM

Full paper

 Number of rows : 35
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 QSO B0420-0127 QSO 04 23 15.8007747432 -01 20 33.063518580   17.50 17.00 16.28   ~ 1138 3
2 NAME Per B AGN 04 37 04.37510272 +29 40 13.8184969   21.7       ~ 498 2
3 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 4012 0
4 Ass Ori OB 1b As* 05 34.0 -01 30           ~ 254 0
5 NGC 2023 RNe 05 41 37.9 -02 15 52           ~ 602 1
6 NAME Ori B MoC 05 41 43.0 -01 54 44           ~ 1286 0
7 NGC 2024 Cl* 05 41 43 -01 50.5           ~ 1116 1
8 HH 92 HH 05 42 21.1 -01 18 29           ~ 16 0
9 IRAS 05399-0121 Y*O 05 42 27.68 -01 20 01.0           ~ 40 0
10 [MHH2009c] SMM 1 smm 05 42 30.5 -01 20 45           ~ 8 0
11 NAME Ori B9 Cloud Cld 05 42 30.5 -01 20 33           ~ 20 0
12 HGBS J054233.1-012539 cor 05 42 32.9 -01 25 28           ~ 4 0
13 ICRF J054236.1+495107 Sy1 05 42 36.1380355416 +49 51 07.232213736   18.45 17.80 17.210   ~ 1401 1
14 [MHH2009c] SMM 3 smm 05 42 44.4 -01 16 03           ~ 9 0
15 IRAS 05405-0117 Y*O 05 43 03.05688 -01 16 29.2404           G3-M4 30 0
16 [MHH2009c] SMM 4 smm 05 43 03.9 -01 15 44           ~ 6 0
17 [MHH2009c] SMM 5 smm 05 43 04.5 -01 17 06           ~ 4 0
18 NAME Orion B9-SMM 6 cor 05 43 05.1 -01 18 38           ~ 8 0
19 [HHL2006] OriB9 N smm 05 43 05.7 -01 14 41           ~ 4 0
20 [MHH2009c] SMM 7 smm 05 43 22.1 -01 13 46           ~ 7 0
21 2MASS J05434630-0104439 Y*O 05 43 46.30656 -01 04 43.9644           ~ 7 1
22 HH 212 HH 05 43 51.41 -01 02 53.1           ~ 346 1
23 IRAS 05413-0104 IR 05 43 51.5 -01 02 52           ~ 81 0
24 LDN 1630 DNe 05 45.5 -00 59           ~ 371 0
25 M 78 RNe 05 46 45.8 +00 04 45   8.0       ~ 363 0
26 NGC 2071 RNe 05 47 10 +00 18.0           ~ 627 1
27 * alf Ori s*r 05 55 10.30536 +07 24 25.4304 4.38 2.27 0.42 -1.17 -2.45 M1-M2Ia-Iab 1577 0
28 RAFGL 865 C* 06 04 00.04728 +07 25 52.0104           C-rich 98 0
29 3C 213 Rad 09 00 48.30 +18 32 12.0   19.5       ~ 14 1
30 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4117 2
31 NAME rho Oph Cloud B1 PoC 16 27 10.5 -24 29 30           ~ 53 1
32 NAME rho Oph B2 Cloud PoC 16 27 27.9 -24 26 29           ~ 82 1
33 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3396 1
34 NAME the Pipe Nebula DNe 17 30 -25.0           ~ 373 1
35 NGC 7027 PN 21 07 01.571952 +42 14 10.47120   10.358 8.831 10.157   ~ 2408 1

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2022.09.28-08:47:07