(CO)-C-12, (CO)-C-13 and (CO)-O-18 observations along the major axes of nearby bright infrared galaxies

	(CO)-C-12, (CO)-C-13 and (CO)-O-18 observations along the major axes of nearby bright infrared galaxies
	Tan, Qing-Hua 1,2,3; Gao, Yu1 ; Zhang, Zhi-Yu 1,2; Xia, Xiao-Yang 3
刊名	RESEARCH IN ASTRONOMY AND ASTROPHYSICS
	2011-07-01
卷号	11 期号:7 页码:787-810
关键词	galaxies: ISM ISM: clouds ISM: molecules radio lines: ISM
英文摘要	We present simultaneous observations of (CO)-C-12, (CO)-C-13 and (CO)-O-18 J=1-0 emission in 11 nearby (cz <1000 km s(-1)) bright infrared galaxies. Both (CO)-C-12 and (CO)-C-13 are detected in the centers of all the galaxies, except for (CO)-C-13 in NGC 3031. We have also detected (CO)-O-18, CSJ=2-1 and HCO+ J=1-0 emission in the nuclear regions of M82 and M51. These are the first systematical extragalactic detections of (CO)-C-12 and its isotopes from the PMO 14 m telescope. We have conducted half-beam-spaced mapping of M82 over an area of 4' x 2.5' and major axis mapping of NGC 3627, NGC 3628, NGC 4631 and M51. The radial distributions of (CO)-C-12 and (CO)-C-13 in NGC 3627, NGC 3628 and M51 can be well fitted by an exponential profile. The (CO)-C-12/(CO)-C-13 intensity ratio, R, decreases monotonically with the galactocentric radius in all mapped sources. The average R in the center and disk of the galaxies are 9.9 +/- 3.0 and 5.6 +/- 1.9, respectively, much lower than the peculiar R(similar to 24) found in the center of M82. The intensity ratios of (CO)-C-13/(CO)-O-18, (CO)-C-13/HCO+ and (CO)-C-13/CS (either our or literature data) show little variation with galactocentric radius, in sharp contrast with the greatly varied R. This supports the notion that the observed gradient in R could be the result of the variations of the physical conditions across the disks. The H-2 column density derived from (CO)-O-18 shows that the Galactic standard conversion factor (X-factor) overestimates the amount of the molecular gas in M82 by a factor of similar to 2.5. These Observations suggest that the X-factor in active star-forming regions (i.e., nuclear regions) should be lower than that in normal star-forming disks and the gradient in R can be used to trace the variations of the X-factor.
WOS标题词	Science & Technology ; Physical Sciences
类目[WOS]	Astronomy & Astrophysics
研究领域[WOS]	Astronomy & Astrophysics
关键词[WOS]	DENSE MOLECULAR GAS ; STAR-FORMATION ; SPIRAL GALAXIES ; CARBON-MONOXIDE ; CO SURVEY ; ULTRALUMINOUS GALAXIES ; PHYSICAL CONDITIONS ; IRREGULAR GALAXIES ; GALACTIC-CENTER ; COLUMN DENSITY
收录类别	SCI
语种	英语
WOS记录号	WOS:000293037500005
内容类型	期刊论文
源URL	[http://libir.pmo.ac.cn/handle/332002/15976]
专题	紫金山天文台_期刊（老文献）
作者单位	1.Chinese Acad Sci, Purple Mt Observ, Nanjing 210008, Peoples R China 2.Chinese Acad Sci, Grad Sch, Beijing 100039, Peoples R China 3.Tianjin Normal Univ, Tianjin Astrophys Ctr, Tianjin 300384, Peoples R China
推荐引用方式 GB/T 7714	Tan, Qing-Hua,Gao, Yu,Zhang, Zhi-Yu,et al. (CO)-C-12, (CO)-C-13 and (CO)-O-18 observations along the major axes of nearby bright infrared galaxies[J]. RESEARCH IN ASTRONOMY AND ASTROPHYSICS,2011,11(7):787-810.
APA	Tan, Qing-Hua,Gao, Yu,Zhang, Zhi-Yu,&Xia, Xiao-Yang.(2011).(CO)-C-12, (CO)-C-13 and (CO)-O-18 observations along the major axes of nearby bright infrared galaxies.RESEARCH IN ASTRONOMY AND ASTROPHYSICS,11(7),787-810.
MLA	Tan, Qing-Hua,et al."(CO)-C-12, (CO)-C-13 and (CO)-O-18 observations along the major axes of nearby bright infrared galaxies".RESEARCH IN ASTRONOMY AND ASTROPHYSICS 11.7(2011):787-810.