2005A&A...437..947V


C.D.S. - SIMBAD4 rel 1.7 - 2021.02.26CET18:36:39

2005A&A...437..947V - Astronomy and Astrophysics, volume 437, 947-956 (2005/7-3)

Very compact radio emission from high-mass protostars. II. Dust disks and ionized accretion flows.

VAN DER TAK F.F.S. and MENTEN K.M.

Abstract (from CDS):

This paper reports 43 GHz imaging of the high-mass protostars W 33A, AFGL 2591 and NGC 7538 IRS9 at ∼0.04'' and ∼0.6'' resolution. In each case, weak (∼mJy-level), compact (O∼100AU) emission is detected, which has an elongated shape (axis ratio ∼3). However, for AFGL 2591 and NGC 7538 IRS9, the emission is single-peaked, while for the highest-luminosity source, W 33A, a ``mini-cluster'' of three sources is detected. The derived sizes, flux densities, and broad-band radio spectra of the sources support recent models where the initial expansion of H II regions around very young O-type stars is prevented by stellar gravity. In these models, accretion flows onto high-mass stars originate in large-scale molecular envelopes and become ionized close to the star. These models reproduce our observations of ionized gas as well as the structure of the molecular envelopes of these sources on 103-104AU scales derived previously from single-dish sub-millimeter continuum and line mapping. For AFGL 2591, the 43GHz flux density is also consistent with dust emission from a disk recently seen in near-infrared ``speckle'' images. However, the alignment of the 43 GHz emission with the large-scale molecular outflow argues against an origin in a disk for AFGL 2591 and NGC 7538 IRS9. In contrast, the outflow from W 33A does not appear to be collimated. Together with previously presented case studies of W 3 IRS5 and AFGL 2136, our results indicate that the formation of stars and stellar clusters with luminosities up to ∼105L proceeds through accretion and produces collimated outflows as in the solar-type case, with the ``additional feature'' that the accretion flow becomes ionized close to the star. Above ∼105L, clusters of H II regions appear, and outflows are no longer collimated, possibly as the result of mergers of protostars or pre-stellar cores.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - stars: formation - instrumentation: high angular resolution - ISM: H II regions

Nomenclature: Fig.2, Table 1: [VM2005] W33A QN (Nos Q1-Q3).

Simbad objects: 16

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Number of rows : 16

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 W3 IRS 5 Y*O 02 25 40.54 +62 05 51.4           B1 330 0
2 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2049 1
3 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3839 2
4 W 33a Y*O 18 14 39.0 -17 52 03           ~ 593 0
5 [VM2005] W33A Q3 Rad 18 14 39.4153 -17 52 01.293           ~ 1 0
6 [VM2005] W33A Q1 mm 18 14 39.46 -17 52 00.5           ~ 18 0
7 [VM2005] W33A Q2 Rad 18 14 39.4891 -17 52 00.557           ~ 1 0
8 QSO J1820-2528 QSO 18 20 57.84869182 -25 28 12.5836842   18.56       ~ 82 0
9 RAFGL 2136 SFR 18 22 26.8740 -13 30 17.177           ~ 254 0
10 ICRF J183220.8-103511 G 18 32 20.83647 -10 35 11.1968           ~ 71 1
11 QSO J2015+371 BLL 20 15 28.7298087 +37 10 59.514637     21.82 21.4   ~ 254 2
12 NAME Cyg X Cld 20 28 41 +41 10.2           ~ 643 1
13 RAFGL 2591 Y*O 20 29 25.03656 +40 11 20.3316           ~ 573 0
14 NGC 7538 OpC 23 13 37 +61 30.0           ~ 834 0
15 IRAS 23118+6110 Y*O 23 14 01.63 +61 27 20.2           ~ 349 0
16 NAME Galactic Molecular Ring PoG ~ ~           ~ 39 0

    Equat.    Gal    SGal    Ecl

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