The Serendipitous XMM-Newton Cluster Athens Survey (SEXCLAS): sample selection and the cluster log N-log S
The Serendipitous XMM-Newton Cluster Athens Survey (SEXCLAS): sample selection and the cluster log N-log S
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偶然的 XMM-牛顿聚类雅典调查 (SEXCLAS)：样本选择和聚类 log N-log S
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
T. Gaga
中科院分区：
文献类型：
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作者：
V. Kolokotronis;A. Georgakakis;S. Basilakos;S. Kitsionas;M. Plionis;I. Georgantopoulos;T. Gaga
在本文中，作为x射线识别（XID）计划的一部分，我们利用xmm -牛顿档案观测和五波段光学光度跟踪观测（r约为23等）偶然识别出x射线星团候选者。我们的样品覆盖了大约2.1°(2)（15个XMM-Newton场）的区域，总共包括21个（19个偶然的+两个目标）扩展的x射线源，其极限f(x) （0.5-2 keV）近似于6 x 10(-15) erg s(-1) cm(-2)，在XMM-Newton图像上有很高的概率（> 99.9%）被扩展。在21个x射线星团中，14个是首次发现的，而7个在文献中得到了光谱证实。利用这些领域的光学数据，我们发现大于或接近68%的x射线星团候选与光学星系过密度有关。我们还尝试用光度法来约束候选星团的红移。因此，我们在每个x射线选择的候选星团附近构建了星系的光度红移分布，并根据场星系的背景分布寻找具有统计意义的红移峰。我们的大多数星团的光度或光谱红移范围在0.4 <z <0.6。对已确认的星团的光度估计和光谱红移估计的比较表明，我们的简单方法在z近似于0.5的范围内是稳健的。对于高z的星团，需要更深入的光学数据来估计可靠的光度红移。利用19个偶然x射线选择的候选星团的样本，我们估计它们的表面密度低至f(x) (0.5-2 keV)，近似于6 x 10(-15) erg s(-1) cm(-2)，并发现它与之前和最近的研究相当一致。
In this paper we serendipitously identify X-ray cluster candidates using XMM-Newton archival observations complemented by five-band optical photometric follow-up observations (r approximate to 23 mag) as part of the X-ray Identification (XID) programme. Our sample covers an area of approximate to 2.1 deg(2) (15 XMM-Newton fields) and comprises a total of 21 (19 serendipitous + two target) extended X-ray sources to the limit f(x) (0.5-2 keV) approximate to 6 x 10(-15) erg s(-1) cm(-2), with a high probability (> 99.9 per cent) of being extended on the XMM-Newton images. Of the 21 X-ray clusters, 14 are detected for the first time while seven are spectroscopically confirmed in the literature. Exploiting the optical data available for these fields we discover that greater than or similar to 68 per cent of the X-ray cluster candidates are associated with optical galaxy overdensities. We also attempt to constrain the redshifts of our cluster candidates using photometric methods. We thus construct the photometric redshift distribution of galaxies in the vicinity of each X-ray selected cluster candidate and search for statistically significant redshift peaks against that of the background distribution of field galaxies. Most of our clusters have photometric or spectroscopic redshifts in the range 0.4 <z <0.6. Comparison of photometric with spectroscopic redshift estimates for the confirmed clusters suggests that our simple method is robust out to z approximate to 0.5. For clusters at higher z, deeper optical data are required to estimate reliable photometric redshifts. Using the sample of the 19 serendipitous X-ray selected cluster candidates, we estimate their surface density down to f(x) (0.5-2 keV) approximate to 6 x 10(-15) erg s(-1) cm(-2) and find it to be in fair agreement with previous and recent studies.