THE SMALL-SCALE DISTRIBUTION OF EMISSION FROM THE 6.7-GHZ TRANSITION OF METHANOL IN SGR B2

被引:29
作者
HOUGHTON, S [1 ]
WHITEOAK, JB [1 ]
机构
[1] CSIRO,AUSTRALIA TELESCOPE NATL FACIL,EPPING,NSW 2121,AUSTRALIA
关键词
MASERS; STARS; FORMATION; ISM; INDIVIDUAL; SGR B2; KINEMATICS AND DYNAMICS; MOLECULES; RADIO LINES;
D O I
10.1093/mnras/273.4.1033
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The Australia Telescope Compact Array has been used to map the distribution of emission from the 6.7-GHz 5(1)-6(0)A(+) transition of methanol over the HII region/molecular cloud complex Sgr B2. Images obtained with restored beamwidths of 3 arcsec and lower reveal the presence of 11 methanol maser locations, seven of which are near maser positions for other molecules: Methanol absorption has been detected in two well-known clouds, with velocities near 65 and 80 km s(-1), which observations of other molecules have shown to be associated with Sgr B2. Although other transitions, including the 2(0)-3(-1)E transition of methanol at 12.2 GHz, have shown that the 65 km s(-1) cloud extends over all the continuum emission, the 6.7-GHz absorption is confined to the north and west, with optical depths of around unity. No absorption was found to be associated with a third known cloud with a velocity near 50 km s(-1). We suggest that 6.7-GHz absorption occurs only in the regions of higher temperature in the molecular clouds. Assumed cloud temperatures of 20 K yield methanol column densities as high as 7.5 x 10(18) cm(-2).
引用
收藏
页码:1033 / 1040
页数:8
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