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arXiv 0704.2818astro-ph
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Seyfert星系中央区的致密星暴

Compact starburst in the central regions of Seyfert galaxies

Kotaro Kohno, Koichiro Nakanishi, Masatoshi Imanishi

摘要:

我们利用野边山毫米波阵对本宇宙中Seyfert星系和星暴星系的CO(1- 0)、HCN(1- 0)和HCO $^+$(1- 0)线进行了高分辨率的“3D”成像观测。我们探测到了这些赛弗特星系中相当一部分的发光HCN(1- 0)发射(我们的子样本中有12个),这表明其中一些塞弗特星系,如NGC 3079,NGC 3227,NGC 4051,NGC 6764和NGC 7479,确实伴随着紧凑的核星暴,给出了HCN(1- 0)光度与恒星形成星系中恒星形成速率之间的紧密相关性。然而,我们认为,这些塞弗特星系中的一些星系,包括NGC 1068,NGC 1097,NGC 5033和NGC 5194,HCN(1- 0)发射的升高并不意味着那里存在大规模的恒星爆发。这是因为这些Seyfert核显示出异常高的HCN(1- 0)/HCO $^+$(1- 0)比(2- 3),这在我们的样本中的星爆核中从未观察到。这可能是由于在这些塞弗特星系中心的X射线主导区(XDR)中HCN分子过多。

英文摘要:

We have conducted a high-resolution ``3D'' imaging survey of the CO(1--0), HCN(1--0), and HCO$^+$(1--0) lines toward the central a few kpc regions of the Seyfert and starburst galaxies in the local universe using the Nobeyama Millimeter Array. We detected luminous HCN(1--0) emissions toward a considerable fraction of these Seyfert galaxies (10 of 12 in our sub-sample), which indicated that some of these Seyfert galaxies, such as NGC 3079, NGC 3227, NGC 4051, NGC 6764, and NGC 7479, are indeed accompanied with compact nuclear starburst, given the tight correlation between the HCN(1--0) luminosity and the star formation rate among star-forming galaxies. However, we suggest that the elevated HCN(1--0) emission from some of these Seyfert galaxies, including NGC 1068, NGC 1097, NGC 5033, and NGC 5194, does not signify the presence of massive starbursts there. This is because these Seyfert nuclei show abnormally high HCN(1--0)/HCO$^+$(1--0) ratios (2--3), which were never observed in the starburst nuclei in our sample. This could be attributed to the overabundance of HCN molecules in the X-ray dominated regions (XDRs) at the centers of these Seyfert galaxies.

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