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arXiv 2003.05513astro-ph.GA
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在COSMOS巡天中被遮蔽和未遮蔽的X射线选择活动星系核的宿主星系特性和环境

Host galaxy properties and environment of obscured and unobscured X-ray selected Active Galactic Nuclei in the COSMOS survey

Carlos Guillermo Bornancini, Diego García Lambas

摘要:

我们分析了从COSMOS巡天中选出的活动星系核(AGN)和类星体(QSO)的不同光度和光谱特性,这些活动星系核和类星体是根据它们的中红外幂律和X射线发射来选择的。我们使用一组恒星形成星系作为对照样本与结果进行比较。我们考虑了模糊源(HR > -0.2)和非模糊源(HR < -0.2)的样本,包括$L_X$ < $10^{44}$ erg s $^{-1}$的活动星系核,以及1.4 < z < 2.5的类星体($L_X$ > $10^{44}$ erg s $^{-1}$)。我们还研究了这些样本的典型环境,通过评估邻近星系的数量密度和邻近属性,如颜色,恒星质量和恒星形成率。我们发现,不同类型活动星系核的紫外/光学和中红外颜色分布有很大的不同。此外,我们得到的大多数活动星系核和类星体是更紧凑的SF星系的样本相比。一般来说,我们发现不同活动星系核样本的恒星质量分布是相似的,在未遮蔽和遮蔽的类星体之间仅得到$Δ\overline{\mathrm{log}M}=0.3$ dex($M_{\odot}$)的差异。在小尺度($r_p$ < 100 kpc)上,活动星系核和类星体存在于不同的局域环境中。我们的研究结果支持以前的研究结果,活动星系核类型与环境相关。这些差异和活动星系核主体性质的差异,排除了最简单的统一模型,即遮蔽纯粹是一种取向效应。

英文摘要:

We analyse different photometric and spectroscopic properties of active galactic nuclei (AGNs) and quasars (QSOs) selected by their mid-IR power-law and X-ray emission from the COSMOS survey. We use a set of star-forming galaxies as a control sample to compare with the results. We have considered samples of obscured (HR > -0.2) and unobscured (HR < -0.2) sources including AGNs with $L_X$ < $10^{44}$ erg s$^{-1}$, as well as QSOs ($L_X$ > $10^{44}$ erg s$^{-1}$) with 1.4 < z < 2.5. We also study the typical environment of these samples, by assessing neighbouring galaxy number density and neighbour properties such as colour, stellar mass and star formation rate. We find that the UV/optical and mid-infrared colour distribution of the different AGN types differ significantly. Also, we obtain most of AGNs and QSOs to be more compact when compared to the sample of SF galaxies. In general we find that the stellar mass distribution of the different AGN sample are similar, obtaining only a difference of $Δ\overline{\mathrm{log}M}=0.3$ dex ($M_{\odot}$) between unobscured and obscured QSOs. Obscured and unobscured AGNs and QSOs reside in different local environment at small ($r_p$ < 100 kpc) scales. Our results support previous findings where AGN type correlates with environment. These differences and those found in AGN host properties cast out the simplest unified model in which obscuration is purely an orientation effect.

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