J/A+A/600/L10 Massive cluster progenitors from ATLASGAL (Csengeri+, 2017)
ALMA survey of massive cluster progenitors from ATLASGAL.
Limited fragmentation at the early evolutionary stage of massive clumps.
Csengeri T., Bontemps S., Wyrowski F., Motte F., Menten K.M., Beuther H.,
Bronfman L., Commercon B., Chapillon E., Duarte-Cabral A., Fuller G.A.,
Henning T., Leurini S., Longmore S., Palau A., Peretto N., Schuller F.,
Tan J.C., Testi L., Traficante A., Urquhart J.S.
<Astron. Astrophys. 600, L10 (2017)>
=2017A&A...600L..10C 2017A&A...600L..10C (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Millimetric/submm sources ; Morphology
Keywords: stars: formation - stars: massive - submillimeter: ISM
Abstract:
The early evolution of massive cluster progenitors is poorly
understood. We investigate the fragmentation properties from 0.3pc to
0.06pc scales of a homogenous sample of infrared-quiet massive clumps
within 4.5kpc selected from the ATLASGAL survey. Using the ALMA 7m
array we detect compact dust continuum emission towards all targets
and find that fragmentation, at these scales, is limited. The mass
distribution of the fragments uncovers a large fraction of cores above
40M☉, corresponding to massive dense cores (MDCs) with masses up
to ∼400M☉. Seventy-seven percent of the clumps contain at most 3
MDCs per clump, and we also reveal single clumps/MDCs. The most
massive cores are formed within the more massive clumps and a high
concentration of mass on small scales reveals a high core formation
efficiency. The mass of MDCs highly exceeds the local thermal Jeans
mass, and we lack the observational evidence of a survey efficiently
high level of turbulence or strong enough magnetic fields to keep the
most massive MDCs in equilibrium. If already collapsing, the observed
fragmentation properties with a high core formation efficiency are
consistent with the collapse setting in at parsec scales.
Description:
We present observations carried out in Cycle 2 with the ALMA 7m array
using 9 to 11 of the 7m antennas with baselines ranging between 8.2m
(9.5kλ) to 48.9m (53.4kλ). We used a low-resolution
wide-band set-up in Band 7, yielding 4x1.75GHz effective bandwidth
with a spectral resolution of 976.562kHz. The four basebands were
centred on 347.331, 345.796, 337.061, and 335.900GHz, respectively.
The primary beam at this frequency is 28.9". Each source was observed
for ∼5.4min in total. The system temperature, Tsys, varies between
100-150K. The targets were split into five observing groups according
to Galactic longitude.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 91 100 Summary of physical properties of the sample
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See also:
J/A+A/570/A65 : ATLASGAL massive clumps CO depletion (Giannetti+, 2014)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Source Source name (LLL.llll+B.bbbb-MMN)
20 A1 --- n_Source [*] Note on Source (1)
22- 30 F9.5 deg RAdeg Right ascension (J2000)
32- 40 F9.5 deg DEdeg Declination (J2000)
42- 45 F4.2 Jy/beam Fnu Peak flux at 345GHz
47- 51 F5.2 Jy Snu Integrated flux density at 345GHz
53- 57 F5.2 arcsec ThetaA FWHM major axis
59- 63 F5.2 arcsec ThetaB FWHM minor axis
65- 68 F4.2 arcsec Beam Beam size as the geometric mean of the
beam major and minor axes
70- 73 F4.2 arcsec FWHM Beam convolved angular source size
75- 78 F4.2 kpc Dist Distance from Csengeri et al.
(2017, in prep.)
80- 85 F6.2 Msun Mcore Core mass as described in the main text
87- 91 F5.2 g/cm2 Sigmacore Core surface density as described in the
main text
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Note (1): * for unresolved sources.
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History:
From electronic version
(End) Patricia Vannier [CDS] 31-Mar-2017