The XMM-Newton serendipitous survey III. The AXIS X-ray source counts and angular clustering
The XMM-Newton serendipitous survey III. The AXIS X-ray source counts and angular clustering
复制标题
XMM-牛顿偶然调查 III。
DOI：
10.1051/0004-6361:20066271
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发表时间：
2007
影响因子：
6.5
通讯作者：
Carrera F
中科院分区：
文献类型：
--
作者：
Carrera F
最近的结果将x射线背景（XRB）总强度向上修正至~10 keV以下，因此需要准确地确定源计数。关于x射线选择源的聚类也有相互矛盾的结果。目的研究了软（0.5-2 keV）、硬（2-10 keV）、XID （0.5-4.5 keV）和超硬（4.5-7.5 keV）四个能量带的x射线源计数，以评价不同通量的x射线源对x射线背景的贡献。我们还研究了这些波段中x射线源的角聚类。方法saxis （AnXMM-NewtonInternational Survey）是对36个高银河系纬度dexmm - newton观测数据的调查，覆盖北部天空4.8°2，包含1433个偶然的x射线源，检测到5-σ显著性。这项调查与xmm -牛顿目录具有相似的深度，因此可以作为探索它们可能性的探路者。我们将此调查与浅层和深层调查相结合，并使用最大似然技术拟合源计数。仅使用AXIS源，我们使用一种新颖的鲁棒技术研究了角相关。结果我们的源计数结果在软带、XID带、超硬带和硬带上与大多数以前的样品兼容。我们在硬带方面的成绩比以前有所改善。在这项工作中使用的调查中，XRB在软、硬、XID和超硬波段的分离率分别为87%、85%、60%和25%。我们的源计数外推到零通量不足以使XRB强度饱和。只有星系和/或被吸收的AGN可以贡献剩余的未解决的XRB强度。在误差范围内，我们的结果与最近修订的XRB软带和硬带强度是一致的。对XRB的最大贡献来自源计数中断后约十年内的通量（~10-14cgs），在软带和硬带中达到总通量的~50%。角聚类（广泛分布在天空中，不局限于几个深场）在软波段和XID波段以99-99.9%的显著性被检测到，而在硬波段和超硬波段没有检测到（可能是由于源数量较少）。我们不能确认在硬谱硬源中检测到明显更强的聚类。结论像AXIS这样的中深度巡天对于确定10 keV以下宇宙x射线发射的演化是必不可少的。
ContextRecent results have revised upwards the total X-ray background (XRB) intensity below ~10 keV, therefore an accurate determination of the source counts is needed. There are also contradictory results on the clustering of X-ray selected sources.AimsWe have studied the X-ray source counts in four energy bands: soft (0.5–2 keV), hard (2–10 keV), XID (0.5–4.5 keV) and ultra-hard (4.5–7.5 keV) in order to evaluate the contribution of sources at different fluxes to the X-ray background. We have also studied the angular clustering of X-ray sources in those bands.MethodsAXIS (AnXMM-NewtonInternational Survey) is a survey of 36 high Galactic latitudeXMM-Newtonobservations covering 4.8 deg2in the Northern sky and containing 1433 serendipitous X-ray sources detected with 5-σsignificance. This survey has similar depth to theXMM-Newtoncatalogues and therefore serves as a pathfinder to explore their possibilities. We have combined this survey with shallower and deeper surveys, and fitted the source counts with a Maximum Likelihood technique. Using only AXIS sources we have studied the angular correlation using a novel robust technique.ResultsOur source counts results are compatible with most previous samples in the soft, XID, ultra-hard and hard bands. We have improved on previous results in the hard band. The fractions of the XRB resolved in the surveys used in this work are 87%, 85%, 60% and 25% in the soft, hard, XID and ultra-hard bands, respectively. Extrapolation of our source counts to zero flux is not sufficient to saturate the XRB intensity. Only galaxies and/or absorbed AGN could contribute the remaining unresolved XRB intensity. Our results are compatible, within the errors, with recent revisions of the XRB intensity in the soft and hard bands. The maximum fractional contribution to the XRB comes from fluxes within about a decade of the break in the source counts (~10-14cgs), reaching ~50% of the total in the soft and hard bands. Angular clustering (widely distributed over the sky and not confined to a few deep fields) is detected at 99–99.9% significance in the soft and XID bands, with no detection in the hard and ultra-hard band (probably due to the smaller number of sources). We cannot confirm the detection of significantly stronger clustering in the hard-spectrum hard sources.ConclusionsMedium depth surveys such as AXIS are essential to determine the evolution of the X-ray emission in the Universe below 10 keV.