J/A+A/417/115 High-mass protostellar candidates (Williams+, 2004)
The circumstellar environments of HMPOs. I: Submillimetre continuum emission.
Williams S.J., Fuller G.A., Sridharan T.K.
<Astron. Astrophys. 417, 115 (2004)>
=2004A&A...417..115W 2004A&A...417..115W
ADC_Keywords: YSOs ; Interstellar medium ; Infrared sources
Keywords: stars: formation - stars: circumstellar matter - ISM: clouds -
ISM: dust
Abstract:
We present maps of the 850µm and 450µm continuum emission
seen towards a sample of 68 high-mass protostellar candidates with
luminosities ranging from 102.5L☉ to ∼105L☉. Most of
these candidate high-mass stars are in the earliest stages of
evolution, and have not yet developed an ultra-compact HII region. We
observe a variety of continuum emission morphologies, from compact
symmetric sources through to multiple cores embedded in long filaments
of emission. We find on average there is a 65% probability of an IRAS
point-source having a companion detection at submillimetre
wavelengths. The ratio of integrated flux to peak flux for our
detections shows no strong dependence on distance, suggesting the
emission we have observed is primarily from scale-free envelopes with
power-law density structures. Assuming a near kinematic distance
projection, the clumps we detect vary in mass from ∼1M☉ to over
1000M☉, with a mean clump mass of 330M☉, column density of
9x1023cm-2^ and diameter of ∼0.6pc. The high luminosity and low mass
of the smallest clumps suggests they are accompanied by a minimal
number of stellar companions, while the most massive clumps may be
examples of young protogroups and protoclusters. We measure the
spectral index of the dust emission (α) and the spectral index
of the dust grain opacity (β) towards each object, finding clumps
with morphologies suggestive of strong temperature gradients, and of
grain growth in their dense inner regions. We find a mean value for
beta of 0.9, significantly smaller than observed towards ultra-compact
HII regions.
Description:
The sample of High-Mass Protostellar Objects (HMPOs was observed at
850µm and 450µm between March 2000 and June 2000 using the
Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk
Maxwell Telescope. The position and measured flux of the detections
resolved by our JCMT observations. Positions are measured from the
450µm "jiggle" maps wherever possible. Unless otherwise stated,
450µm detections without corresponding 850µm detections arise
from the increased resolution of the 450µm observations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 82 112 Position and flux of submm detections
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See also:
II/125 : IRAS catalogue of Point Sources, Version 2.0 (IPAC 1986)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- WFS Source identifier
5- 14 A10 --- IRAS Associated IRAS point source (II/125)
16- 17 I2 h RAh Right ascension (J2000)
19- 20 I2 min RAm Right ascension (J2000)
22- 25 F4.1 s RAs Right ascension (J2000)
27 A1 --- DE- Declination sign
28- 29 I2 deg DEd Declination (J2000)
31- 32 I2 arcmin DEm Declination (J2000)
34- 35 I2 arcsec DEs Declination (J2000)
37- 41 F5.2 Jy P850um ? Peak 850µm flux, in Jy/beam
43- 46 F4.2 Jy e_P850um ? 1-sigma uncertainty in P850um, in Jy/beam
48- 51 F4.1 Jy I850um ? Integrated 850µm flux
53- 55 F3.1 Jy e_I850um ? 1-sigma uncertainty in I850um
57- 60 F4.1 Jy P450um ? Peak 450µm flux, in Jy/beam
62- 64 F3.1 Jy e_P450um ? 1-sigma uncertainty in P450um, in Jy/beam
66- 70 F5.1 Jy I450um ? Integrated 450µm flux
72- 75 F4.1 Jy e_I450um ? 1-sigma uncertainty in I450um
77- 80 F4.1 --- Y ? Ratio of integrated/peak flux at 850µm
82 I1 --- Note [1/2]? Problematic detections (1)
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Note (1): Notes:
1 = 850 micron emission falls on a noisy bolometer
2 = 2-sigma detection at 450 microns
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Acknowledgements:
Stewart Williams
(End) Stewart Williams [UMIST], Patricia Bauer [CDS] 16-Mar-2004