Hot Dust-Obscured Galaxies with Excess Blue Light

Hot Dust-Obscured Galaxies (Hot DOGs) are among the most luminous galaxies in the Universe. Powered by highly obscured, possibly Compton-thick, active galactic nuclei (AGNs), Hot DOGs are characterized by SEDs that are very red in the mid-IR yet dominated by the host galaxy stellar emission in the UV and optical. An earlier study identified a sub-sample of Hot DOGs with significantly enhanced UV emission. One target, W0204–0506, was studied in detail and, based on Chandra observations, it was concluded that the enhanced emission was most likely due to either extreme unobscured star-formation (SFR > 1000 M⊙ yr−1) or to light from the highly obscured AGN scattered by gas or dust into our line of sight. Here, we present a follow-up study of W0204–0506 as well as two more Hot DOGs with excess UV emission. For the two new objects we obtained Chandra/ACIS-S observations, and for all three targets we obtained HST/WFC3 F555W and F160W imaging. The analysis of these observations, combined with multi-wavelength photometry and UV/optical spectroscopy suggest that UV emission is most likely dominated by light from the central highly obscured, hyper-luminous AGN that has been scattered into our line of sight, by either gas or dust. We cannot decisively rule out, however, that star-formation or a second AGN in the system may significantly contribute to the UV excess of these targets.

热尘埃遮蔽星系（Hot Dust-Obscured Galaxies，简称Hot DOGs）是宇宙中光度最高的星系之一。这类星系由高度遮蔽、可能为康普顿厚的活动星系核（active galactic nuclei，AGNs）供能，其光谱能量分布（SED）在中红外波段表现为极强的红移特征，而紫外与光学波段则以宿主星系的恒星辐射为主。早期一项研究识别出了紫外辐射显著增强的Hot DOGs子样本。其中目标天体W0204–0506被开展了详细研究，基于钱德拉X射线天文台的观测数据，研究团队得出结论：该天体的增强辐射最有可能源于两种情形之一：一是极端未遮蔽的恒星形成（恒星形成率SFR > 1000 M⊙ yr⁻¹），二是被气体或尘埃散射至我们视线方向的高度遮蔽活动星系核辐射。本文呈现了针对W0204–0506以及另外两例存在紫外辐射超标的Hot DOGs的后续研究。针对这两个新目标，我们获取了钱德拉/ACIS-S观测数据；针对全部三个目标，我们获取了哈勃空间望远镜/宽视场相机3（HST/WFC3）的F555W与F160W波段成像数据。对上述观测数据的分析结合多波段测光与紫外/光学光谱数据表明，这类天体的紫外辐射最有可能源于被气体或尘埃散射至我们视线方向的中心高度遮蔽的超亮活动星系核辐射。不过我们无法明确排除恒星形成或系统内次级活动星系核对这些目标的紫外超额辐射存在显著贡献的可能性。

搜集汇总

背景与挑战

背景概述

该数据集聚焦于热尘埃遮蔽星系（Hot DOGs）中具有过量蓝光（紫外辐射）的子样本，通过多波段观测分析其辐射机制。研究发现，这些星系的紫外辐射可能主要来自高度遮蔽的超亮活动星系核（AGN）的光被气体或尘埃散射到视线方向，但无法完全排除恒星形成或第二个AGN的贡献。数据集包含观测数据和相关分析，旨在揭示这类极端星系的物理性质。