Gas near active galactic nuclei: A search for the 4.7micron CO band
Gas near active galactic nuclei: A search for the 4.7micron CO band
复制标题
活跃星系核附近的气体：寻找 4.7 微米 CO 波段
DOI：
10.1051/0004-6361:200400072
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
G. Stacey
中科院分区：
文献类型：
--
作者：
D. Lutz;E. Sturm;R. Genzel;H. Spoon;G. Stacey
为了限制活动星系核周围致密和温暖气体的性质，我们搜索了局部活动星系核的红外空间观测光谱，以寻找一氧化碳4.7微米基频振动带的特征。31AGN的低分辨率光谱为存在宽吸收带设置了上限，该吸收带对应于针对核尘埃连续体的大型温暖和稠密气体的吸收。NGC1068的高分辨率(R~2500)光谱在单条谱线上没有探测到明显的吸收或发射，其3sigma极限为连续谱的7%。局域活动星系核对CO吸收的限制远低于最近斯皮策太空望远镜探测到的被遮挡的超发光红外星系IRAS F00183-7111中致密和温暖气体对CO的强吸收，尽管有证据表明在这两类天体中都有活动星系核附近几秒尺度的致密物质。这表明，这种深吸收与在局部活动星系核中调用的模糊的“环面”物质没有密切的关系，而是高度遮挡的红外星系如IRAS F00183-7111的核周区域的特殊条件的标志。它们可能会反射完全覆盖的几何体，而不是环面几何体。
In order to constrain the properties of dense and warm gas around active galactic nuclei, we have searched Infrared Space Observatory spectra of local active galactic nuclei for the signature of the 4.7micron fundamental ro-vibrational band of carbon monoxide. Low resolution spectra of 31 AGN put upper limits on the presence of wide absorption bands corresponding to absorption by large columns of warm and dense gas against the nuclear dust continuum. High resolution (R~2500) spectra of NGC 1068 detect no significant absorption or emission in individual lines, to a 3sigma limit of 7% of the continuum. The limits set on CO absorption in local AGN are much lower than the recent Spitzer Space Telescope detection of strong CO absorption by dense and warm gas in the obscured ultraluminous infrared galaxy IRAS F00183-7111, despite evidence for dense material on parsec scales near an AGN in both types of objects. This suggests that such deep absorptions are not intimately related to the obscuring `torus' material invoked in local AGN, but rather are a signature of the peculiar conditions in the circumnuclear region of highly obscured infrared galaxies like IRAS F00183-7111. They may reflect fully covered rather than torus geometries.