J/A+A/588/A29 Star formation in massive clumps in Milky Way (Heyer+, 2016)
The rate and latency of star formation in dense, massive clumps in the
Milky Way.
Heyer M., Gutermuth R., Urquhart J.S., Csengeri T., Wienen M., Leurini S.,
Menten K., Wyrowski F.
<Astron. Astrophys. 588, A29 (2016)>
=2016A&A...588A..29H 2016A&A...588A..29H (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; YSOs ; Stars, masses ; Interstellar medium
Keywords: stars: formation - stars: protostars - infrared: stars -
submillimeter: ISM - Galaxy: disk
Abstract:
Newborn stars form within the localized, high density regions of
molecular clouds. The sequence and rate at which stars form in dense
clumps and the dependence on local and global environments are key
factors in developing descriptions of stellar production in galaxies.
We seek to observationally constrain the rate and latency of star
formation in dense massive clumps that are distributed throughout the
Galaxy and to compare these results to proposed prescriptions for
stellar production. A sample of 24 micron based Class I protostars are
linked to dust clumps that are embedded within molecular clouds
selected from the APEX Telescope Large Area Survey of the Galaxy. We
determine the fraction of star-forming clumps that imposes a
constraint on the latency of star formation in units of a clump's
lifetime. Protostellar masses are estimated from models of
circumstellar environments of young stellar objects from which star
formation rates are derived. Physical properties of the clumps are
calculated from 870 micron dust continuum emission and NH3 line
emission.
Linear correlations are identified between the star formation rate
surface density, Sigma_SFR and the quantities SigmaH2/tauff and
SigmaH2/taucross, suggesting that star formation is regulated at the
local scales of molecular clouds. The measured fraction of star
forming clumps is 23%. Accounting for star formation within clumps
that are excluded from our sample due to 24 micron saturation, this
fraction can be as high as 31%, which is similar to previous results.
Dense, massive clumps form primarily low mass (<1-2M☉) stars with
emergent 24 micron fluxes below our sensitivity limit or are incapable
of forming any stars for the initial 70% of their lifetimes. The low
fraction of star forming clumps in the Galactic center relative to
those located in the disk of the Milky Way is verified.
Description:
We exploit the information within two surveys of the Galactic plane -
the APEX Telescope Large Area Survey of the Galaxy, (ATLASGAL;
Schuller et al., 2009A&A...504..415S 2009A&A...504..415S; Csengeri et al., 2014, Cat.
J/A+A/565/A75) and the Spitzer MIPSGAL survey of 24um emission (Carey
et al., 2009PASP..121...76C 2009PASP..121...76C).
We examine dust sources (hereafter, clumps) from ATLASGAL within the
Galactic longitudes 60°>l> 300° and latitudes, |b|<1°.
There are 9494 ATLASGAL sources located within these boundaries.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 82 290 Protostellar mass and errors
table3.dat 119 219 Properties of star forming ATLASGAL clumps
table4.dat 104 298 Properties of non star forming ATLASGAL clumps
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See also:
J/A+A/549/A45 : ATLASGAL Compact Source Catalog: 330<l<21 (Contreras+, 2013)
J/A+A/568/A41 : ATLASGAL Compact Source Catalog: 280<l<60 (Urquhart+, 2014)
J/AJ/149/64 : MIPSGAL 24µm point source catalog (Gutermuth+, 2015)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- MIPSGAL MIPSGAL name (MGLLL.llll+BB.bbbb)
21- 38 A18 --- ATLASGAL ATLASGAL name (AGALLLL.lll+BB.bbb)
41- 48 E8.2 Lsun LIR Infrared luminosity
51- 55 F5.2 Msun Mstar Protostellar Mass
58- 62 F5.2 Msun Mlow2 Protostellar Mass at -2sigma
64- 68 F5.2 Msun Mlow1 Protostellar Mass at -1sigma
71- 75 F5.2 Msun Mhigh1 Protostellar Mass at +1sigma
78- 82 F5.2 Msun Mhigh2 Protostellar Mass at +2sigma
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- ATLASGAL ATLASGAL name (AGALLLL.lll+BB.bbb)
21- 25 F5.2 kpc Dist Distance (G1)
28- 32 F5.2 kpc e_Dist 1 sigma distance error
35 I1 --- r_Dist [1/2] Reference for Dist (G2)
39- 43 I5 Msun MClump Clump mass
47- 51 I5 Msun e_MClump 1 sigma MClump error
56- 59 I4 Msun/pc2 SigmaH2 Clump mass surface density
64- 67 I4 Msun/pc2 e_SigmaH2 1 sigma SigmaH2 error
72- 75 I4 Msun/pc2/Myr SigmaSFR SFR surface density (1)
80- 83 I4 Msun/pc2/Myr e_SigmaSFR 1 sigma SigmaSFR error
90- 91 I2 --- Mcorr Mimf/Mstar,T
95- 99 F5.2 10+4cm-3 nclump Clump mean density
102-105 F4.2 10+6yr tauff Clump free-fall time
111-113 I3 10+6yr tauorb Clump orbital time
116-119 F4.2 10+6yr taucross Clump crossing time (G3)
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Note (1): Values of SigmaSFRlimit<0.5M☉/pc^2/Myr are rounded to 0.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- ATLASGAL ATLASGAL Name
21- 25 F5.2 kpc Dist Distance (G1)
28- 32 F5.2 kpc e_Dist 1 sigma Dist error
35 I1 --- r_Dist [1/2] Reference for Distance (G2)
39- 43 I5 Msun MClump Clump Mass
47- 51 I5 Msun e_MClump 1 sigma MClump error
56- 59 I4 Msun/pc2 SigmaH2 Clump Mass surface density
64- 67 I4 Msun/pc2 e_SigmaH2 1 sigma SigmaH2 error
74- 75 I2 Msun/pc2/Myr SigmaSFRlim 2 sigma upper limit SFR
surface density
78- 83 F6.2 10+4cm-3 nclump Clump mean density
87- 90 F4.2 10+6yr tauff Clump free-fall time
96- 98 I3 10+6yr tauorb Clump orbital time
101-104 F4.2 10+6yr taucross Clump crossing time (G3)
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Global notes:
Note (G1): Reid et al., (2009ApJ...700..137R 2009ApJ...700..137R) Galactic rotation parameters
Note (G2): References as follows:
1 = Wienen et al., 2015A&A...579A..91W 2015A&A...579A..91W
2 = Ellsworth-Bowers et al., 2015, Cat. J/ApJ/799/29, and J/ApJ/805/157
Note (G3): taucross value equal to 0 implies there are no available velocity
dispersion measurements for this ATLASGAL clump.
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Acknowledgements:
Mark Heyer, mark.heyer(at)gmail.com
(End) Patricia Vannier [CDS] 26-Jan-2016