2004A&A...426..195K


C.D.S. - SIMBAD4 rel 1.7 - 2021.02.26CET20:52:38

2004A&A...426..195K - Astronomy and Astrophysics, volume 426, 195-200 (2004/10-4)

The structure of the Onsala1 star forming region.

KUMAR M.S.N., TAFALLA M. and BACHILLER R.

Abstract (from CDS):

We present new high-sensitivity high-resolution mm-wave observations of the Onsala1 ultra-compact HII region that bring to light the internal structure of this massive star forming cloud. The 1.2mm continuum map obtained with the IRAM 30-m radiotelescope (∼11" resolution) shows a centrally peaked condensation of 1' size (∼0.5pc at the assumed distance of 1.8kpc) which has been further investigated at higher resolution in the 3mm continuum and in the emission lines of H13CO+ J= 1-0 and SiO J= 2-1 with the IRAM Plateau de Bure interferometer. The 3mm data, with a resolution of ∼5"x4", display an unresolved continuum source at the peak of the extended 1.2 mm emission and closely associated with the ultra-compact HII region. The H13CO+map traces the central condensation in good agreement with previous NH3 maps of Zheng et al. (1985ApJ...293..522Z). However, the velocity field of this central condensation, which was previously thought to arise in a rapidly rotating structure, is better explained in terms of the dense and compact component of a bipolar outflow. This interpretation is confirmed by SiO and CO observations of the full region. In fact, our new SiO data unveil the presence of multiple (at least 4) outflows in the region. In particular, there is an important center of outflow activity in the region about 1' north of the UCHII region. Indeed the different outflows are related to different members of the Onsala1 cluster. The data presented here support a scenario in which massive star formation begin much later in the evolution of a cluster and/or the phases of UCHII regions last for much longer than 105yr.

Abstract Copyright:

Journal keyword(s): stars: formation - ISM: jets and outflows - HII regions - ISM: clouds

Simbad objects: 9

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Number of rows : 9

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME OMC-1 MoC 05 35 14 -05 22.4           ~ 1038 2
2 3C 345 QSO 16 42 58.8100340220 +39 48 36.999540578   16.81 16.59 16.84   ~ 1574 2
3 IRAS 20081+3132 * 20 10 06.8473113162 +31 41 37.000322873           ~ 2 0
4 [KCW94] 069.540-00.975 HII 20 10 09.0 +31 31 35           ~ 167 1
5 IRAS 20081+3122 Y*O 20 10 09.036 +31 31 34.14           ~ 170 0
6 Onsala 1 Mas 20 10 09.2036 +31 31 36.090           ~ 179 0
7 QSO J2015+371 BLL 20 15 28.7298087 +37 10 59.514637     21.82 21.4   ~ 254 2
8 QSO B2023+336 BLL 20 25 10.84210 +33 43 00.2144       0   ~ 134 1
9 EM* MWC 349 ** 20 32 45.499080 +40 39 36.74124   15.88 13.15 12.13   Bep 720 0

    Equat.    Gal    SGal    Ecl

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