arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1002.4712astro-ph.HE
收藏

局部康普顿厚AGN分数的再评价

Re-evaluating the Local Compton-thick AGN Fraction

A. Malizia, J. B. Stephen, L. Bassani, A. J. Bird, F. Panessa, P. Ubertini

摘要:

我们研究了在INTEGRAL/IBIS观测的20-40 keV波段中选取的88个活动星系核的NH分布。我们发现,吸收源(NH > 10^22 cm^-2)的比例为43%,而康普顿厚度的活动星系核仅占样品的7%。虽然这些估计与以前的软伽马射线调查完全兼容,但它们似乎与光学选择样本报告的结果相反。这种明显的差异可以解释为由于康普顿厚物体中的高能通量减少而导致的选择偏差,从而使它们在我们的灵敏度极限下不可见。考虑到这一点,我们估计,高度吸收的源的分数实际上是在密切的协议与光学选择的样品。此外,我们表明,在我们的样品中的吸收源的测量分数从80%下降到20-30%的红移的函数与所有康普顿厚的活动星系核具有z<0.015。我们的结论是,在低红移仓,我们看到几乎整个活动星系核人口,从未吸收至少轻度康普顿厚的对象,而在总样本中,我们失去了大量吸收的“同行”的遥远,因此暗淡的来源很少或根本没有吸收。因此,把这个低z仓作为唯一能够提供1型和2型活动星系核中“真实”吸收分布的仓,我们估计康普顿厚天体所占的比例大于24%

英文摘要:

We study the NH distribution in a complete sample of 88 AGN selected in the 20-40 keV band from INTEGRAL/IBIS observations. We find that the fraction of absorbed (NH > 10^22 cm^-2) sources is 43% while Compton thick AGN comprise 7% of the sample. While these estimates are fully compatible with previous soft gamma-ray surveys, they would appear to be in contrast with results reported from an optically selected sample. This apparent difference can be explained as being due to a selection bias caused by the reduction in high energy flux in Compton thick objects rendering them invisible at our sensitivity limit. Taking this into account we estimate that the fraction of highly absorbed sources is actually in close agreement with the optically selected sample. Furthermore we show that the measured fraction of absorbed sources in our sample decreases from 80% to ~20-30% as a function of redshift with all Compton thick AGN having z<0.015. We conclude that in the low redshift bin we are seeing almost the entire AGN population, from unabsorbed to at least mildly Compton thick objects, while in the total sample we lose the heavily absorbed 'counterparts' of distant and therefore dim sources with little or no absorption. Taking therefore this low z bin as the only one able to provide the 'true' distribution of absorption in type 1 and 2 AGN, we estimate the fraction of Compton thick objects to be >24%

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑