We investigate an infrared-excess source called G2 or Dusty S-cluster Object (DSO) moving on a highly eccentric orbit around the Galaxy's central black hole, Sgr A*. We use, for the first time, near-infrared polarimetric imaging data to determine the nature and the properties of the DSO, and obtain an improved K_s-band identification of this source in median polarimetry images of different observing years. The source starts to deviate from the stellar confusion in 2008, and it does not show any flux density variability over the years we analyzed it. We measure the polarization degree and angle of the DSO between 2008 and 2012 and conclude, based on the significance analysis on polarization parameters, that it is an intrinsically polarized source (>20%) with a varying polarization angle as it approaches Sgr A* position. DSO shows a near-infrared excess of K_s-L' > 3 that remains compact close to the pericenter of its orbit. Its observed parameters and the significant polarization obtained in this work show that the DSO might be a dust-enshrouded young star, forming a bow shock as it approaches the super massive black hole. The significantly high measured polarization degree indicates that it has a non-spherical geometry and it can be modelled as a combination of a bow shock with a bipolar wind of the star. We use a 3D radiative transfer model that can reproduce the observed properties of the source such as the total flux density and the polarization degree. We obtain that the change of the polarization angle can be due to an intrinsic change in the source structure. Accretion disc precession of the young star in the gravitational field of the black hole can lead to the change of the bipolar outflow and therefore the polarization angle variation. It might also be the result of the source interaction with the ambient medium.
Closing the gap: Follow-up observations of peculiar dusty objects close to Sgr A* using ERIS
Astronomical Institute, Czech Academy of Sciences（捷克科学院天文研究所）；Indiana University（印第安纳大学）；Charles University, Faculty of Mathematics and Physics（查理大学数学物理学院）
The magnetic fields of the dusty nuclei and molecular outflows of Arp 220
University of South Carolina（南卡罗来纳大学）；Institut de Ciències de l’Espai (ICE-CSIC)（太空科学研究所）；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究学院）；Instituto de Astrofísica de Andalucía, Consejo Superior de Investigaciones Científicas (CSIC)（安达卢西亚天体物理研究所，西班牙高等科研理事会）；School of Sciences, European University Cyprus（塞浦路斯欧洲大学理学院）；Departament de Física Quàntica i Astrofísica (FQA), Universitat de Barcelona（巴塞罗那大学量子物理与天体物理学系）；Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona（巴塞罗那大学宇宙科学研究所）
The Geometry of the Infrared and X-ray Obscurer in a Dusty Hyperluminous Quasar
利用Spitzer和Herschel的红外数据、Nustar、Swift、Suzaku和Chandra的X射线数据以及Palomar的光谱，我们研究了IRAS 09104+4109中活动星系核遮蔽体的几何结构。红外数据意味着一个总的休息帧1-1000 $μ$米光度的$5.5\times10^{46}$ erg的$^{-1}$，并需要一个活动星系核环面和星爆模型。活动星系核环的各向异性校正红外光度为$4.9\times10^{46}$ erg s $^{-1}$，视角和半张角都约为$36$度，星爆的恒星形成率为$(110\pm34)$ M $_{\odot}$ yr $^{-1}$，年龄为$<50$ Myr。这些结果与09104的两个发光活动时期相一致：一个大约在百万年前，另一个正在进行中。X射线数据表明光子指数为$Γ\simeq 1.8$，视线柱为$N_{\rm H} \simeq 5\times10^{23}$ cm $^{-2}$。这与反射占主导地位的硬X射线光谱相反，后者意味着更高的$N_{\rm H}$和光度。X射线和红外线数据与活动星系核的热光度值$L_{\rm bol}\sim(0.5-2.5)\times10^{47}$ erg s $^{-1}$一致。X射线和红外线数据进一步与活动星系核中视线“掠过”环面的共线活动星系核遮蔽物相一致。这也与光学光谱一致，它显示了日冕…
Scattering from Dusty Outflows in Hot Dust-Obscured Galaxies with Blue Excess Emission
Astronomical Observatory（天文台）；Department of Physics and Astronomy, Universiteit Gent（根特大学物理与天文学系）；Instituto de Alta Investigación, Universidad de Tarapacá（塔拉帕卡大学高等研究院）；Department of Physics and Astronomy, University of Leicester（莱斯特大学物理与天文学系）；Institute of Astrophysics, Foundation for Research and Technology-Hellas (FORTH)（希腊研究与技术基金会天体物理研究所）；School of Sciences, European University Cyprus（塞浦路斯欧洲大学理学院）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；Centro de Astrobiología (CAB), CSIC-INTA（CSIC-INTA天体生物学中心）；Department of Physics, Northwestern College（西北学院物理系）；School of Physics, Korea Institute for Advanced Study（韩国高等研究院物理学院）；Max Planck Institut für Radio Astronomie（马克斯·普朗克射电天文研究所）；Centro de Astrofísica y Tecnologias Afines（天体物理学及相关技术中心）
