THE GALACTIC CENSUS OF HIGH- AND MEDIUM-MASS PROTOSTARS. I. CATALOGS AND FIRST RESULTS FROM MOPRA HCO+ MAPS

被引:58
作者
Barnes, Peter J. [1 ]
Yonekura, Yoshinori [2 ]
Fukui, Yasuo [3 ]
Miller, Andrew T. [4 ]
Muehlegger, Martin [4 ,5 ]
Agars, Lawrence C. [4 ]
Miyamoto, Yosuke [3 ]
Furukawa, Naoko [3 ]
Papadopoulos, George [4 ,6 ]
Jones, Scott L. [4 ,7 ]
Hernandez, Audra K. [1 ]
O'Dougherty, Stefan N. [1 ]
Tan, Jonathan C. [1 ]
机构
[1] Univ Florida, Dept Astron, Gainesville, FL 32611 USA
[2] Ibaraki Univ, Ctr Astron, Mito, Ibaraki 3108512, Japan
[3] Nagoya Univ, Dept Astrophys, Chikusa Ku, Nagoya, Aichi 4648602, Japan
[4] Univ Sydney, Sch Phys A28, Sydney, NSW 2006, Australia
[5] Max Planck Inst Extraterr Phys, D-85748 Garching, Germany
[6] Univ Sydney, Sch Math & Stat F07, Sydney, NSW 2006, Australia
[7] Univ NSW, Sch Elect Engn & Telecommun, Sydney, NSW 2052, Australia
关键词
astrochemistry; ISM: kinematics and dynamics; ISM: molecules; radio lines: ISM; stars: formation; STAR-FORMING REGIONS; PROTOSTELLAR CANDIDATES; SOUTHERN-HEMISPHERE; EMBEDDED CLUSTERS; MOLECULAR CORES; DUST CONTINUUM; DENSE CLUMPS; GAS; EVOLUTION; SEARCH;
D O I
10.1088/0067-0049/196/1/12
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The Census of High- and Medium-mass Protostars (CHaMP) is the first large-scale, unbiased, uniform mapping survey at sub-parsec-scale resolution of 90 GHz line emission from massive molecular clumps in the Milky Way. We present the first Mopra (ATNF) maps of the CHaMP survey region (300 degrees > l > 280 degrees) in the HCO+ J = 1 -> 0 line, which is usually thought to trace gas at densities up to 10(11) m(-3). In this paper, we introduce the survey and its strategy, describe the observational and data reduction procedures, and give a complete catalog of moment maps of the HCO+ J = 1 -> 0 emission from the ensemble of 303 massive molecular clumps. From these maps we also derive the physical parameters of the clumps, using standard molecular spectral-line analysis techniques. This analysis yields the following range of properties: integrated line intensity 1-30 K km s(-1), peak line brightness 1-7 K, linewidth 1-10 km s(-1), integrated line luminosity 0.5-200 K km s(-1) pc(2), FWHM size 0.2-2.5 pc, mean projected axial ratio 2, optical depth 0.08-2, total surface density 30-3000 M-circle dot pc(-2), number density (0.2-30) x 10(9) m(-3), mass 15-8000 M-circle dot, virial parameter 1-55, and total gas pressure 0.3-700 pPa. We find that the CHaMP clumps do not obey a Larson-type size-linewidth relation. Among the clumps, there exists a large population of subthermally excited, weakly emitting (but easily detectable) dense molecular clumps, confirming the prediction of Narayanan et al. These weakly emitting clumps comprise 95% of all massive clumps by number, and 87% of the molecular mass, in this portion of the Galaxy; their properties are distinct from the brighter massive star-forming regions that are more typically studied. If the clumps evolve by slow contraction, the 95% of fainter clumps may represent a long-lived stage of pressure-confined, gravitationally stable massive clump evolution, while the CHaMP clump population may not engage in vigorous massive star formation until the last 5% of their lifetimes. The brighter sources are smaller, denser, more highly pressurized, and closer to gravitational instability than the less bright sources. Our data suggest that massive clumps approach critical Bonnor-Ebert-like states at constant density, while others' suggest that lower-mass clumps reach such states at constant pressure. Evidence of global gravitational collapse of massive clumps is rare, suggesting that this phase lasts <1% of the clumps' lifetime.
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页数:38
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