A new method to determine X-ray luminosity functions of AGN and their evolution with redshift
A new method to determine X-ray luminosity functions of AGN and their evolution with redshift
复制标题
确定活动星系核X射线光度函数及其红移演化的新方法
DOI：
10.1093/mnras/stad007
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发表时间：
2023
影响因子：
4.8
通讯作者：
Alqasim A
中科院分区：
文献类型：
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作者：
Alqasim A
如今，几乎所有大质量星系的中心都含有超大质量黑洞（SMBH）。超大质量黑洞通过吸积周围物质来生长，并在吸积过程中发射 X 射线。为了了解 AGN 群体的宇宙学特性和演化，人们对活动星系核 (AGN) 的 X 射线光度函数 (XLF) 进行了广泛的研究。我们提出了一种新的固定静止框架方法，以更准确地研究 AGN XLF 在宇宙时间内的演化。通常，XLF 是在固定的观察者坐标系能带中构建的，这可能会出现问题，因为它在不同的红移处探测不同的静止坐标系能量。在新方法中，我们通过红移改变观察到的能带，在固定静止帧带中构造 XLF。我们使用 XMM-Newton 和 HEAO 1X 射线数据瞄准静止帧 2–8 keV 能带，其中有七个观察者帧能带随着 0 <z< 3 的红移而变化。我们使用两种技术生成 XLF：一种是构建分箱 XLF，一种是使用最大似然 (ML) 拟合，这利用了完整的未分箱源样本。我们发现两种方法的ML最佳拟合纯光度演化结果彼此一致，这表明使用仅限于高光度AGN的高红移数据进行XLF演化研究对固定观察者框架或静止框架能带的选择不是很敏感，这与我们的预期一致，即高光度AGN通常表现出很少的吸收。我们已经证明了新方法在测量 XLF 演化方面的可行性。
Almost all massive galaxies today are understood to contain supermassive black holes (SMBH) at their centres. SMBHs grew by accreting material from their surroundings, emitting X-rays as they did so. X-ray luminosity functions (XLFs) of active galactic nuclei (AGN) have been extensively studied in order to understand the AGN population’s cosmological properties and evolution. We present a new fixed rest-frame method to achieve a more accurate study of the AGN XLF evolution over cosmic time. Normally, XLFs are constructed in a fixed observer-frame energy band, which can be problematic because it probes different rest-frame energies at different redshifts. In the new method, we construct XLFs in the fixed rest-frame band instead, by varying the observed energy band with redshift. We target a rest-frame 2–8 keV band usingXMM-NewtonandHEAO 1X-ray data, with seven observer-frame energy bands that vary with redshift for 0 <z< 3. We produce the XLFs using two techniques; one to construct a binned XLF, and one using a maximum likelihood (ML) fit, which makes use of the full unbinned source sample. We find that our ML best-fitting pure luminosity evolution results for both methods are consistent with each other, suggesting that performing XLF evolution studies with the high-redshift data limited to high-luminosity AGN is not very sensitive to the choice of fixed observer-frame or rest-frame energy band, which is consistent with our expectation that high-luminosity AGN typically show littleabsorption. We have demonstrated the viability of the new method in measuring the XLF evolution.