标题： 无核球星系中的黑洞：对NGC 3367和NGC 4536的XMM-Newton研究 显示英文标题

标题： Black Holes in Bulgeless Galaxies: An XMM-Newton Investigation of NGC 3367 and NGC 4536

摘要： 大多数在本地宇宙中通过光学方法识别的活动星系核（AGNs）位于具有显著核心的宿主星系中，这支持了黑洞形成和增长与星系核心构建基本相关的假设。 然而，最近使用斯皮策望远镜对一组光学“正常”的晚型星系进行的中红外光谱研究揭示了几个天体中存在高电离的[NeV]线，为这些星系中存在AGNs提供了有力证据。 我们介绍了最近使用XMM-Newton获得的对两个此类天体的后续X射线观测，这两个天体是光学上正常的晚型星系NGC 3367和NGC 4536。 在这两项观测中都检测到了这两个天体。 详细的光谱分析表明，对于这两个星系，2-10 keV发射主要由幂律主导，X射线光度在10^39 - 10^40 ergs s^-1范围内，这与低光度AGNs一致。 虽然有可能X射线双星占观测到的X射线光度的一部分，但我们认为这一部分可以忽略不计。 因此，这些观测增加了越来越多的证据，表明仅使用光学观测时，宿主AGNs的晚型星系比例被显著低估。 中红外[NeV]光度与X射线光度的比较表明，这两个星系中存在额外的高度吸收的X射线源，并且NGC 3367中的黑洞质量范围为10^5 - 10^7 M_solar，NGC 4536中的黑洞质量范围为10^4 - 10^6 M_solar。 显示英文摘要

摘要： The vast majority of optically identified active galactic nuclei (AGNs) in the local Universe reside in host galaxies with prominent bulges, supporting the hypothesis that black hole formation and growth is fundamentally connected to the build-up of galaxy bulges. However, recent mid-infrared spectroscopic studies with Spitzer of a sample of optically "normal" late-type galaxies reveal remarkably the presence of high-ionization [NeV] lines in several sources, providing strong evidence for AGNs in these galaxies. We present follow-up X-ray observations recently obtained with XMM-Newton of two such sources, the late-type optically normal galaxies NGC 3367 and NGC 4536. Both sources are detected in our observations. Detailed spectral analysis reveals that for both galaxies, the 2-10 keV emission is dominated by a power law with an X-ray luminosity in the 10^39 - 10^40 ergs s^-1 range, consistent with low luminosity AGNs. While there is a possibility that X-ray binaries account for some fraction of the observed X-ray luminosity, we argue that this fraction is negligible. These observations therefore add to the growing evidence that the fraction of late-type galaxies hosting AGNs is significantly underestimated using optical observations alone. A comparison of the mid-infrared [NeV] luminosity and the X-ray luminosities suggests the presence of an additional highly absorbed X-ray source in both galaxies, and that the black hole masses are in the range of 10^5 - 10^7 M_solar for NGC 3367 and 10^4 - 10^6 M_solar for NGC 4536.