A deep Chandra survey of the Groth Strip – II. Optical identification of the X‐ray sources
A deep Chandra survey of the Groth Strip – II. Optical identification of the X‐ray sources
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格罗斯带的深度钱德拉调查 – X 射线源的光学识别。
DOI：
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发表时间：
2006
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通讯作者：
Berkeley
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作者：
A. Georgakakis;K. Nandra;E. Laird;S. Gwyn;C. Steidel;V. Sarajedini;P. Barmby;S. Faber;A. Coil;M. Cooper;M. Davis;J. A. N. I. College;UCOLick;Victoria;Caltech;Florida;Cfa;Steward Observatory;Berkeley
在本文中，我们讨论了单个指向Groth-Westphal带状区域的200ks钱德拉探测到的光源的光学和x射线光谱特性。丰富的光学光度和光谱数据在这个领域是可用的，为x射线种群提供光学识别和红移测定。这里使用的光学光度和光谱学主要来自深河外进化探测器2号（DEEP2）调查，并从文献中获得了额外的红移。这些数据与来自加拿大-法国-夏威夷望远镜遗产巡天的更深（r≈26等）多波段数据（ugriz）相补充，以估计光度红移，并在光学上识别比DEEP2极限（R_(AB)≈24.5等）更暗的源。我们的研究重点是2 - 10 keV选择的样品，包括97个源，极限≈8 × 10^(−1)6 erg s^(−1)cm^(−2)，这是光学识别率（86%）和红移测定分数（63%；光谱和光度）方面最完整的。我们首先构造样品的红移分布，在z≈1处有一个峰。这与不太明亮的活动星系核（agn）演化到z≈1的模型大致一致，而强大的准恒星天体（qso）在更高的红移处达到z≈2的峰值。与适用于整个AGN群体（I型和II型）的宽系qso相似的进化与数据不符。我们还探索了样品的观测到的N_H分布，并估计了被遮挡的AGN的一部分(N_H bbb10 ^（22) cm^(- 2)）为48±9%。这与光度相关的本质N_H分布一致，其中较低亮度的系统包含较高比例的II型AGN，以及I型和II型AGN之间固定比例为2:1的模型。我们进一步将我们的结果与较深和较浅的调查结果进行比较。我们认为，需要光度相关的内禀NH分布参数化，以解释在不同样品中观察到的在广泛通量范围内的模糊AGN的比例。
In this paper, we discuss the optical and X-ray spectral properties of the sources detected in a single 200-ks Chandra pointing in the Groth-Westphal Strip region. A wealth of optical photometric and spectroscopic data are available in this field providing optical identifications and redshift determinations for the X-ray population. The optical photometry and spectroscopy used here are primarily from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) survey with additional redshifts obtained from the literature. These are complemented with the deeper (r ≈ 26 mag) multiwaveband data (ugriz) from the Canada–France–Hawaii Telescope Legacy Survey to estimate photometric redshifts and to optically identify sources fainter than the DEEP2 magnitude limit (R_(AB)≈ 24.5 mag). We focus our study on the 2–10 keV selected sample comprising 97 sources to the limit ≈ 8 × 10^(−1)6 erg s^(−1) cm^(−2), this being the most complete in terms of optical identification rate (86 per cent) and redshift determination fraction (63 per cent; both spectroscopic and photometric). We first construct the redshift distribution of the sample which shows a peak at z≈ 1. This is in broad agreement with models where less luminous active galactic nuclei (AGNs) evolve out to z≈ 1 with powerful quasi-stellar objects (QSOs) peaking at higher redshift, z≈ 2. Evolution similar to that of broad-line QSOs applied to the entire AGN population (both types I and II) does not fit the data. We also explore the observedNH distribution of the sample and estimate a fraction of obscured AGN (N_H > 10^(22) cm^(−2)) of 48 ± 9 per cent. This is found to be consistent with both a luminosity-dependent intrinsic N_H distribution, where less luminous systems comprise a higher fraction of type II AGNs and models with a fixed ratio 2:1 between types I and II AGNs. We further compare our results with those obtained in deeper and shallower surveys. We argue that a luminosity-dependent parametrization of the intrinsic NH distribution is required to account for the fraction of obscured AGN observed in different samples over a wide range of fluxes.