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

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	A SEARCH FOR INFALL EVIDENCE IN EGOs. I. THE NORTHERN SAMPLE
	Chen, Xi 1; Shen, Zhi-Qiang 1; Li, Jing-Jing 2; Xu, Ye2 ; He, Jin-Hua 3
刊名	ASTROPHYSICAL JOURNAL
	2010-02-10
卷号	710 期号:1 页码:150-169
关键词	ISM: kinematics and dynamics ISM: molecules radio lines: ISM stars: formation
ISSN号	0004-637X
英文摘要	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.
学科主题	Astronomy & Astrophysics
WOS标题词	Science & Technology ; Physical Sciences
类目[WOS]	Astronomy & Astrophysics
研究领域[WOS]	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
收录类别	SCI
语种	英语
WOS记录号	WOS:000273850800016
公开日期	2011-11-23
内容类型	期刊论文
源URL	[http://159.226.72.40/handle/332002/1225]
专题	紫金山天文台_紫金山天文台青海观测站
作者单位	1.Chinese Acad Sci, Shanghai Astron Observ, Key Lab Res Galaxies & Cosmol, Shanghai 200030, Peoples R China 2.Chinese Acad Sci, Purple Mt Observ, Nanjing 210008, Peoples R China 3.Chinese Acad Sci, Natl Astron Observ, Yunnan Observ, Kunming 650011, Peoples R China
推荐引用方式 GB/T 7714	Chen, Xi,Shen, Zhi-Qiang,Li, Jing-Jing,et al. A SEARCH FOR INFALL EVIDENCE IN EGOs. I. THE NORTHERN SAMPLE[J]. ASTROPHYSICAL JOURNAL,2010,710(1):150-169.
APA	Chen, Xi,Shen, Zhi-Qiang,Li, Jing-Jing,Xu, Ye,&He, Jin-Hua.(2010).A SEARCH FOR INFALL EVIDENCE IN EGOs. I. THE NORTHERN SAMPLE.ASTROPHYSICAL JOURNAL,710(1),150-169.
MLA	Chen, Xi,et al."A SEARCH FOR INFALL EVIDENCE IN EGOs. I. THE NORTHERN SAMPLE".ASTROPHYSICAL JOURNAL 710.1(2010):150-169.