A SEARCH FOR INFALL EVIDENCE IN EGOs. I. THE NORTHERN SAMPLE

doi:10.1088/0004-637X/710/1/150

YNAO OpenIR > 大样本恒星演化研究组

	A SEARCH FOR INFALL EVIDENCE IN EGOs. I. THE NORTHERN SAMPLE
	Chen, X 1; Shen, ZQ 1; Li, JJ 2; Xu, Y 2; He JH(何金华)3 ; Chen, X (reprint author), Chinese Acad Sci, Shanghai Astron Observ, Key Lab Res Galaxies & Cosmol, Shanghai 200030, Peoples R China.
发表期刊	ASTROPHYSICAL JOURNAL
	2010-02-10
卷号	710 期号:1 页码:150-169
DOI	10.1088/0004-637X/710/1/150
产权排序	第3完成单位
收录类别	SCI
关键词	Ism: Kinematics And Dynamics Ism: Molecules Radio Lines: Ism Stars: Formation
摘要	We report the first systematic survey of molecular lines ( including IICO(+) (1-0) and (12)CO, (13)CO, C(18)O (1-0) lines at the 3 mm band) toward a new sample of 88 massive young stellar object (MYSO) candidates associated with ongoing outflows ( known as extended green objects or EGOs) identified from the Spitzer GLIMPSE survey in the northern hemisphere with the Purple Mountain Observatory 13.7 m radio telescope. By analyzing the asymmetries of the optically thick line HCO(+) for 69 of 72 EGOs with HCO+ detection, we found 29 sources with "blue asymmetric profiles" and 19 sources with "red asymmetric profiles." This results in a blue excess of 0.14, seen as a signature of collapsing cores in the observed EGO sample. We found that the sources not associated with infrared dark clouds (IRDCs) show a higher blue excess (0.41) than those associated with IRDCs (-0.08), and "possible" outflow candidates show a higher blue excess (0.29) than "likely" outflow candidates (0.05). A higher blue excess (0.19) and a lower blue excess (0.07) were also measured in ultracompact H II regions and 6.7 GHz class II methanol maser sources, respectively. These suggest that the relatively small blue excess ( 0.14) in our full sample is due to the fact that the observed EGOs are mostly dominated by outflows and at an earlier evolutionary phase associated with IRDCs and 6.7 GHz methanol masers. The physical properties of clouds surrounding EGOs derived from CO lines are similar to those of massive clumps wherein the massive star-forming cores associated with EGOs possibly embedded. The infall velocities and mass infall rates derived for 20 infall candidates are also consistent with the typical values found in MYSOs. Thus, our observations further support the speculation of Cyganowski et al. that EGOs trace a population with ongoing outflow activity and at the active rapid accretion stage of massive protostellar evolution from a statistical view, although there may be limitations due to a single-pointing survey with a large beam.
项目资助者	National Natural Science Foundation of China [10803017, 10573029, 10621303, 10625314, 10633010, 10673024, 10733030, 10821302] ; Knowledge Innovation Program of the Chinese Academy of Sciences [KJCX2-YW-T03] ; National Key Basic Research Development Program of China [2007CB815405, 2007CB815403]
语种	英语
学科领域	Astronomy & Astrophysics
文章类型	Article
ISSN	0004-637X
URL	查看原文
WOS记录号	WOS:000273850800016
WOS研究方向	Astronomy & Astrophysics
WOS类目	Astronomy & Astrophysics
关键词[WOS]	INFRARED-DARK CLOUDS ; MASSIVE STAR-FORMATION ; YOUNG STELLAR OBJECTS ; H-II REGIONS ; EXTENDED GREEN OBJECTS ; METHANOL MASER SURVEY ; PROTOSTELLAR COLLAPSE ; DENSE CORES ; PHYSICAL-PROPERTIES ; MOLECULAR OUTFLOWS
引用统计	被引频次：46[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
条目标识符	http://ir.ynao.ac.cn/handle/114a53/4508
专题	大样本恒星演化研究组
通讯作者	Chen, X (reprint author), Chinese Acad Sci, Shanghai Astron Observ, Key Lab Res Galaxies & Cosmol, Shanghai 200030, Peoples R China.
作者单位	1.Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China 2.Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China 3.National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China
推荐引用方式 GB/T 7714	Chen, X,Shen, ZQ,Li, JJ,et al. A SEARCH FOR INFALL EVIDENCE IN EGOs. I. THE NORTHERN SAMPLE[J]. ASTROPHYSICAL JOURNAL,2010,710(1):150-169.
APA	Chen, X,Shen, ZQ,Li, JJ,Xu, Y,He JH,&Chen, X .(2010).A SEARCH FOR INFALL EVIDENCE IN EGOs. I. THE NORTHERN SAMPLE.ASTROPHYSICAL JOURNAL,710(1),150-169.
MLA	Chen, X,et al."A SEARCH FOR INFALL EVIDENCE IN EGOs. I. THE NORTHERN SAMPLE".ASTROPHYSICAL JOURNAL 710.1(2010):150-169.

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