arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1107.3148astro-ph.COastro-ph.HE
收藏

“揭示了钱德拉深场南部z=0.5-1处的一群严重模糊的活跃星系核

"Revealing a Population of Heavily Obscured Active Galactic Nuclei at z=0.5-1 in the Chandra Deep Field-South

B. Luo, W. N. Brandt, Y. Q. Xue, D. M. Alexander, M. Brusa, F. E. Bauer, A. Comastri, A. C. Fabian, R. Gilli, B. D. Lehmer, D. A. Rafferty, D. P. Schneider, C. Vignali

摘要:

我们在Chandra Deep Field-South(CDF-S)和Extended Chandra Deep Field-South中选择了242个X射线未探测到的天体,这些天体的红外恒星形成率(SFR)远高于(3.2倍或更多)校正尘埃消光后从紫外线确定的SFR,从而确定了一个数值上显著的z~0.5-1的严重遮蔽AGN种群。利用4 Ms Chandra数据对23个候选星系进行了X射线叠加分析,发现了一个有效幂律光子指数为Gamma=0.6 - 0.4 ^{+0.3}的硬X射线信号,表明活动星系核对这些星系的贡献很大。基于蒙特卡罗模拟,我们得出结论,74+-25%的选定星系拥有模糊的活动星系核,其中约95%是严重模糊的,约80%是康普顿厚度(CT; NH>1.5x10^{24} cm^{-2})。在我们的样本中,被严重遮蔽的天体具有中等的内在X射线光度[2-10 keV波段~(0.9-4)x10^{42} erg/s]。CT活动星系核的空间密度为(1.6 ± 0.5)× 10 ^{-4} Mpc^{-3}。在10-30 keV波段,z~0.5-1的CT天体预计贡献XRB总通量的~1%,根据布居合成模型,它们占所有CT活动星系核在这一能量波段预计发射的~5-15%。在6- 8 keV波段,23个被严重遮蔽的候选星系的叠加信号占未分辨XRB通量的5%以下,而在该波段未分辨的~25%的XRB可能可以用CDF-S中未探测到的光学星系的叠加分析(2.5 sigma叠加信号)来解释。我们讨论的前景,以确定这种严重模糊的对象使用未来的硬X射线天文台。

英文摘要:

(abridged) We identify a numerically significant population of heavily obscured AGNs at z~0.5-1 in the Chandra Deep Field-South (CDF-S) and Extended Chandra Deep Field-South by selecting 242 X-ray undetected objects with infrared-based star formation rates (SFRs) substantially higher (a factor of 3.2 or more) than their SFRs determined from the UV after correcting for dust extinction. An X-ray stacking analysis of 23 candidates in the central CDF-S region using the 4 Ms Chandra data reveals a hard X-ray signal with an effective power-law photon index of Gamma=0.6_{-0.4}^{+0.3}, indicating a significant contribution from obscured AGNs. Based on Monte Carlo simulations, we conclude that 74+-25% of the selected galaxies host obscured AGNs, within which ~95% are heavily obscured and ~80% are Compton-thick (CT; NH>1.5x10^{24} cm^{-2}). The heavily obscured objects in our sample are of moderate intrinsic X-ray luminosity [ ~ (0.9-4)x10^{42} erg/s in the 2-10 keV band]. The space density of the CT AGNs is (1.6+-0.5)x10^{-4} Mpc^{-3}. The z~0.5-1 CT objects studied here are expected to contribute ~1% of the total XRB flux in the 10-30 keV band, and they account for ~5-15% of the emission in this energy band expected from all CT AGNs according to population-synthesis models. In the 6--8 keV band, the stacked signal of the 23 heavily obscured candidates accounts for <5% of the unresolved XRB flux, while the unresolved ~25% of the XRB in this band can probably be explained by a stacking analysis of the X-ray undetected optical galaxies in the CDF-S (a 2.5 sigma stacked signal). We discuss prospects to identify such heavily obscured objects using future hard X-ray observatories.

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。

↑