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Ammonia cores in high mass star formation regions
Wu, Y; Zhang, Q; Yu, W; Miller, M; Mao, R; Sun, K; Wang, Y
AbstractWe observed a sample of 35 water masers not coincident with known HII regions and/or low mass young stellar objects (YSOs) with the Effelsberg 100 m telescope in the NH3(J,K) = (1,1), (2,2), (3,3) and (4,4) transitions. Sixteen sources were detected in the NH3 emission. The detection rate is 46%. All these sixteen sources have NH3 (1,1) and (2,2) emission, among which four sources have NH3 (3,3) emission. Comparing with the IRAS and the 2MASS data, we analyzed the relationship between the detection rate and the infrared color, the dust temperature and the source distance. All the detected sources were mapped and 17 cores were obtained (one source IRAS 20215+3725 has two cores). From the detected sources five cores do not coincide with radio continuum or IRAS and MSX point sources. Excluding one core that has no MSX data available, the remaining eleven cores are coincident with IRAS or MSX point sources. The typical size and mass of the cores are 1.6 pc and 1.5 x 10(3) M-circle dot, respectively. The average line widths of the NH3 (1,1) and (2,2) are 1.54 and 1.73 km s(-1). The average kinetic temperature of the gas is about 19 K. These values are much larger than those of low mass cores. The NH3 cores that coincide with IRAS sources (referred to as Group I) have slightly larger line widths (1.65 and 1.75 km s(-1) for the (1,1) and (2,2) lines, respectively) and larger masses (1.8 x 10(3) M-circle dot) than the mean values of the sample. For this type of core the kinetic temperature correlates with the line width. The line width appears to correlate with the bolometric luminosity and the core size. Despite the average luminosity of 2.9 x 10(4) L-circle dot, there is no detectable 6 cm emission. These are candidates for high mass protostars or precursors of UC HII regions. The NH3 cores with peaks onset from infrared sources (referred to as Group II) have an average size of 1.7 pc and an average line width of 1.50 km s(-1) for the (1,1) line. The line width of the (1,1) emission is smaller than that of the group I. The average mass is 9.4 x 10(2) M-circle dot. One possible explanation for the deviation is that the NH3 peak and the infrared source correspond to different clumps. These cores are potential high mass star formation sites and may be at an earlier evolutionary stage than those with IRAS point sources. This type of core is seen in mapping observations, and can be easily missed by single-spectrum observations toward the IRAS position.
KeywordMasers Ism : Clouds Ism : Kinematics And Dynamics Stars : Formation
Subject AreaAstronomy & Astrophysics
WOS HeadingsScience & Technology ; Physical Sciences
Indexed BySCI
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000236707400015
Citation statistics
Cited Times:36[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Affiliation1.Peking Univ, Dept Astron, CAS, PKU Joint Beijing Astrophys Ctr, Beijing 100871, Peoples R China
2.Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA
3.Univ Bonn, Inst Inorgan Chem, D-53117 Bonn, Germany
4.Univ Cologne, Inst Phys 1, D-50937 Cologne, Germany
5.Chinese Acad Sci, Purple Mt Observ, Nanjing 210008, Peoples R China
Recommended Citation
GB/T 7714
Wu, Y,Zhang, Q,Yu, W,et al. Ammonia cores in high mass star formation regions[J]. ASTRONOMY & ASTROPHYSICS,2006,450(2):607-NL_30.
APA Wu, Y.,Zhang, Q.,Yu, W.,Miller, M.,Mao, R.,...&Wang, Y.(2006).Ammonia cores in high mass star formation regions.ASTRONOMY & ASTROPHYSICS,450(2),607-NL_30.
MLA Wu, Y,et al."Ammonia cores in high mass star formation regions".ASTRONOMY & ASTROPHYSICS 450.2(2006):607-NL_30.
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