Extragalactic Source Counts in the 20-50 keV Energy Band from the Deep Observation of the Coma Region by INTEGRAL IBIS
Extragalactic Source Counts in the 20-50 keV Energy Band from the Deep Observation of the Coma Region by INTEGRAL IBIS
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INTEGRAL IBIS 对后发区的深度观测得出 20-50 keV 能带的河外源计数
DOI：
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发表时间：
2004
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通讯作者：
R. Sunyaev
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作者：
R. Krivonos;A. Vikhlinin;E. Churazov;A. Lutovinov;S. Molkov;R. Sunyaev
我们使用 INTEGRAL 上的 IBIS 仪器对后发星团区域的深度 500 ks 硬 X 射线观测中的偶然源进行了分析。除了后发星团之外，最终的 20-50 keV 图像还包含 12 个统计显着性大于 4 σ 的偶然源。我们使用这些数据（在校正预期的错误检测数量之后）将 20-50 keV 能带中的河外源计数扩展到 1.0 × 10-11 ergs s-1 cm-2 (≃1 mcrab) 的极限通量。与之前使用 HEAO 1 A-4 仪器获得的该能带结果相比，灵敏度提高了 10 倍以上。导出的源计数与欧几里得关系 N(> f) ∝ f-3/2 一致。大部分已确定的偶然源是低红移、z < 0.02 的活动星系核 (AGN)，大部分为 Seyfert 1 型。硬 X 射线源的表面密度为 (1.4 ± 0.5) × 10-2 deg-2，高于 10-11 ergs-1 cm-2 的通量阈值。这些源直接占 20-50 keV 能带的宇宙 X 射线背景的约 3%。鉴于我们样本的红移深度较低，我们预计红移较高的类似源占硬 X 射线背景的很大一部分。我们的场只覆盖天空的3%；对其他河外 INTEGRAL 观测的系统分析可以产生更大的源样本，因此至关重要。
We present the analysis of serendipitous sources in a deep, 500 ks, hard X-ray observation of the Coma Cluster region with the IBIS instrument on board INTEGRAL. In addition to the Coma Cluster, the final 20-50 keV image contains 12 serendipitous sources with statistical significance >4 σ. We use these data (after correcting for expected number of false detections) to extend the extragalactic source counts in the 20-50 keV energy band down to a limiting flux of 1.0 × 10-11 ergs s-1 cm-2 (≃1 mcrab). This is a more than a factor of 10 improvement in sensitivity compared to the previous results in this energy band obtained with the HEAO 1 A-4 instrument. The derived source counts are consistent with the Euclidean relation N(> f) ∝ f-3/2. A large fraction of identified serendipitous sources are low-redshift, z < 0.02, active galactic nuclei (AGNs), mostly of Seyfert 1 type. The surface density of hard X-ray sources is (1.4 ± 0.5) × 10-2 deg-2 above a flux threshold of 10-11 ergs s-1 cm-2. These sources directly account for ~3% of the cosmic X-ray background in the 20-50 keV energy band. Given the low redshift depth of our sample, we expect that similar sources at higher redshifts account for a significant fraction of the hard X-ray background. Our field covers only 3% of the sky; a systematic analysis of other extragalactic INTEGRAL observations can produce much larger source samples and is, therefore, critically important.