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arXiv 1102.4270astro-ph.HE
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XRT GRB深油气田(SwiftFT)中的快速偶然勘探I. X射线目录和数量计数

The Swift Serendipitous Survey in deep XRT GRB fields (SwiftFT) I. The X-ray catalog and number counts

S. Puccetti, M. Capalbi, P. Giommi, M. Perri, G. Stratta, L. Angelini, D. N. Burrows, S. Campana, G. Chincarini, G. Cusumano, N. Gehrels, A. Moretti, J. Nousek,… 展开作者

S. Puccetti, M. Capalbi, P. Giommi, M. Perri, G. Stratta, L. Angelini, D. N. Burrows, S. Campana, G. Chincarini, G. Cusumano, N. Gehrels, A. Moretti, J. Nousek, J. P. Osborne, G. Tagliaferri

摘要:

我们在超过370个Swift-XRT场中搜寻了X射线偶然源,这些场集中在2004年至2008年期间探测到的伽马射线暴上,观测到的总曝光量从10 ks到超过1 Ms。这定义了深XRT伽玛射线暴场中的Swift-Serendipitous调查,与现有调查相比,这是相当广泛的(~33平方度)和中等深度,在0.5至2 keV的能量范围内,最微弱的通量极限为7.2 e-16 erg cm^-2 s^-1。由于XRT的稳定点扩散函数和小的渐晕校正因子,该测量具有高度的均匀性,此外,由于伽马射线暴在天空中完全不相关的部分爆炸,因此在天空中完全随机。在本文中,我们介绍了高银河纬度样本的样本和X射线计数,在宽通量范围内(即,0.5-2 keV波段为7.2e-16至~5e-13 erg cm^-2 s^-1,2-10 keV波段为3.4e-15至~ 6 e-13 erg cm^-2 s^-1)。我们检测到9387个点状源,而7071个点状源被发现在高银河系纬度(即>=20度)。由于大面积和深通量极限的结合,探测到的大量源使这一调查成为研究活动星系核演化的一个新的重要工具。特别是,大面积允许发现罕见的高光度物体,如QSO 2,这是其他调查中采样不足,为光度函数亮端增加了宝贵的信息。高银河系纬度logN-logS关系是很好地确定在所有的流量覆盖范围,它是很好地与以前的结果在1西格玛置信水平一致。通过硬X射线颜色分析,我们发现在深XRT伽玛暴场中的Swift偶发巡天对活动星系核的取样相对较清晰,在2-10(0.3-3 keV)波段的活动星系核中有约37%(约15%)的源被遮蔽。

英文摘要:

We searched for X-ray serendipitous sources in over 370 Swift-XRT fields centered on gamma ray bursts detected between 2004 and 2008 and observed with total exposures ranging from 10 ks to over 1 Ms. This defines the Swift Serendipitous Survey in deep XRT GRB fields, which is quite broad compared to existing surveys (~33 square degrees) and medium depth, with a faintest flux limit of 7.2e-16 erg cm^-2 s^-1 in the 0.5 to 2 keV energy range. The survey has a high degree of uniformity thanks to the stable point spread function and small vignetting correction factors of the XRT, moreover is completely random on the sky as GRBs explode in totally unrelated parts of the sky. In this paper we present the sample and the X-ray number counts of the high Galactic-latitude sample, estimated with high statistics over a wide flux range (i.e., 7.2e-16 to ~5e-13 erg cm^-2 s^-1 in the 0.5-2 keV band and 3.4e-15 to ~6e-13 erg cm^-2 s^-1 in the 2-10 keV band). We detect 9387 point-like sources, while 7071 point-like sources are found at high Galactic-latitudes (i.e. >=20 deg). The large number of detected sources resulting from the combination of large area and deep flux limits make this survey a new important tool for investigating the evolution of AGN. In particular, the large area permits finding rare high-luminosity objects like QSO2, which are poorly sampled by other surveys, adding precious information for the luminosity function bright end. The high Galactic-latitude logN-logS relation is well determined over all the flux coverage, and it is nicely consistent with previous results at 1 sigma confidence level. By the hard X-ray color analysis, we find that the Swift Serendipitous Survey in deep XRT GRB fields samples relatively unobscured and mildly obscured AGN, with a fraction of obscured sources of ~37% (~15%) in the 2-10 (0.3-3 keV) band.

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