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NATURE OF W51e2: MASSIVE CORES AT DIFFERENT PHASES OF STAR FORMATION
Shi, Hui1; Zhao, Jun-Hui2; Han, J. L.1
2010-02-10
Source PublicationASTROPHYSICAL JOURNAL
Volume710Issue:1Pages:843-852
AbstractWe present high-resolution continuum images of the W51e2 complex processed from archival data of the Submillimeter Array (SMA) at 0.85 and 1.3 mm and the Very Large Array at 7 and 13 mm. We also made line images and profiles of W51e2 for three hydrogen radio recombination lines (RRLs; H26 alpha, H53 alpha, and H66 alpha) and absorption of two molecular lines of HCN(4-3) and CO(2-1). At least four distinct continuum components have been detected in the 3 '' region of W51e2 from the SMA continuum images at 0.85 and 1.3 mm with resolutions of 0.'' 3 x 0.'' 2 and 1.'' 4 x 0.'' 7, respectively. The west component, W51e2-W, coincides with the ultracompact HII region reported from previous radio observations. The H26 alpha line observation reveals an unresolved hyper-compact ionized core (< 0.'' 06 or < 310 AU) with a high electron temperature of 1.2x10(4) K, with the corresponding emission measure EM > 7 x 10(10) pc cm(-6) and the electron density N(e) > 7 x 10(6) cm(-3). The inferred Lyman continuum flux implies that the HII region W51e2-W requires a newly formed massive star, an O8 star or a cluster of B-type stars, to maintain the ionization. W51e2-E, the brightest component at 0.85 mm, is located 0.'' 9 east from the hyper-compact ionized core. It has a total mass of similar to 140 M(circle dot) according to our spectral energy distribution analysis and a large infall rate of > 1.3 x 10(-3) M(circle dot) yr(-1) inferred from the absorption of HCN. W51e2-E appears to be the accretion center in W51e2. Given the fact that no free-free emission and no RRLs have been detected, the massive core of W51e2-E appears to host one or more growing massive proto-stars. Located 2 '' northwest from W51e2-E, W51e2-NW is detected in the continuum emission at 0.85 and 1.3 mm. No continuum emission has been detected at lambda >= 7 mm. Along with the maser activities previously observed, our analysis suggests that W51e2-NW is at an earlier phase of star formation. W51e2-N is located 2 '' north of W51e2-E and has only been detected at 1.3 mm with a lower angular resolution (similar to 1 ''), suggesting that it is a primordial, massive gas clump in the W51e2 complex.
KeywordHii Regions Ism: Individual Objects (W51e2) Stars: Formation
DOI10.1088/0004-637X/710/1/843
Indexed BySCI
Language英语
WOS IDWOS:000273850800066
Citation statistics
Cited Times:23[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Identifierhttp://ir.bao.ac.cn/handle/114a11/7780
Collection射电天文研究部
Affiliation1.Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China
2.Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA
Recommended Citation
GB/T 7714
Shi, Hui,Zhao, Jun-Hui,Han, J. L.. NATURE OF W51e2: MASSIVE CORES AT DIFFERENT PHASES OF STAR FORMATION[J]. ASTROPHYSICAL JOURNAL,2010,710(1):843-852.
APA Shi, Hui,Zhao, Jun-Hui,&Han, J. L..(2010).NATURE OF W51e2: MASSIVE CORES AT DIFFERENT PHASES OF STAR FORMATION.ASTROPHYSICAL JOURNAL,710(1),843-852.
MLA Shi, Hui,et al."NATURE OF W51e2: MASSIVE CORES AT DIFFERENT PHASES OF STAR FORMATION".ASTROPHYSICAL JOURNAL 710.1(2010):843-852.
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