VLA detection of OH absorption from the elliptical galaxy NGC 1052
VLA detection of OH absorption from the elliptical galaxy NGC 1052
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VLA 检测椭圆星系 NGC 1052 的 OH 吸收
DOI：
10.1051/0004-6361:20011604
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发表时间：
2001
影响因子：
6.5
通讯作者：
J. Rigby
中科院分区：
文献类型：
--
作者：
A. Omar;K. Anantharamaiah;M. Rupen;J. Rigby
给出了椭圆星系NGC1052对OH吸收的VLA观测结果。在1665和1667 MHz的两条OH线都在NGC1052的中心被检测到吸收。两条OH线(τ16 6 7/τ16 6 5)的超精细比为2.6\pm0.8美元，而光学薄云在LTE条件下的激发预期为1.8美元。在T_(Rm)ex=10$K的假设下，OH的柱密度估计为$2.73，(pm0.26)×10^{14}×10 cm-2。两条OH谱线的中心都比星系的系统速度红移了~173 S-1。OH线的速度与HI最强吸收对应的速度一致。我们认为，OH吸收是由于分子云向原子核下落而产生的。OH线虽然较窄，但被发现在更宽广和更平滑的H2O超伽马塞发射范围内。讨论了OH/HI与H2O排放之间可能的联系。
VLA observations of OH absorption towards the elliptical galaxy NGC 1052 are presented. Both OH lines, at 1665 and 1667 MHz, were detected in absorption towards the center of NGC 1052. The hyperfine ratio of the two OH lines ( τ 1667 / τ 1665 ) is $2.6\pm0.8$ as compared to 1.8 expected for the excitation under LTE conditions for an optically thin cloud. The column density of OH is estimated to be $2.73\,(\pm0.26)\times10^{14}$ cm -2 assuming $T_{\rm ex} \sim10$ K. The centers of both the OH lines are redshifted from the systemic velocity of the galaxy by ~173 km s -1 . The velocity of OH line coincides with the velocity corresponding to the strongest HI absorption. We suggest that OH absorption is arising from a molecular cloud falling towards the nucleus. The OH line, though narrower, is found to be within the much broader and smoother H 2 O megamaser emission. The possible link between OH/HI and H 2 O emission is discussed.