论文标题
光谱法揭示的四个蓝色尘埃刺激星系的极端性质
Extreme nature of four blue-excess dust-obscured galaxies revealed by optical spectroscopy
论文作者
论文摘要
我们报告了由Subaru Hyper Suprime-CAM鉴定的四个蓝色口气的星系（Bludogs）的光谱观察结果。 BluDOGs are a sub-class of dust-obscured galaxies (DOGs, defined with the extremely red color $(i-[22])_{\rm AB} \geq 7.0$; Toba et al. 2015), showing a significant flux excess in the optical $g$- and $r$-bands over the power-law fits to the fluxes at the longer wavelengths. Noboriguchi等。 （2019年）提出，Bludogs可能对应于富含气体的主要合并方案所涉及的爆发阶段。然而，由于缺乏光谱信息，因此无法理解Bludog的详细特性。在这项工作中，我们使用Subaru/Focas和VLT/Fors2对四个Bludog进行了深层光谱观察。获得的光谱显示出宽阔的发射线，具有极大的等效宽度，并且在CIV线轮廓中有蓝色机翼。红移在2.2和3.3之间。 CIV线的平均平均值等效宽度为$ 160 \ PM33 $ $ \ MATHRM {\ MATHRING {a}} $，$ \ SIM $ 7 $ 7倍，比典型的1型Quasar的平均值高7倍。它们的速度配置文件的FWHM在1990年至4470 $ {\ rm km \ s^{ - 1}} $之间，其不对称参数为0.05和0.25。如此强大的CIV线显着影响宽带的幅度，这部分是蓝色频谱能量分布中蓝色过量的起源。他们估计的超质量黑洞质量为$ 1.1 \ times10^8 <m _ {\ rm bh}/m_ \ odot <5.5 \ times 10^8 $。 Bludog的推断Eddington比率高于1（$ 1.1 <λ_ {\ rm Edd} <3.8 $），这表明Bludogs处于超大型黑洞的快速发展阶段。
We report optical spectroscopic observations of four blue-excess dust-obscured galaxies (BluDOGs) identified by Subaru Hyper Suprime-Cam. BluDOGs are a sub-class of dust-obscured galaxies (DOGs, defined with the extremely red color $(i-[22])_{\rm AB} \geq 7.0$; Toba et al. 2015), showing a significant flux excess in the optical $g$- and $r$-bands over the power-law fits to the fluxes at the longer wavelengths. Noboriguchi et al. (2019) has suggested that BluDOGs may correspond to the blowing-out phase involved in a gas-rich major merger scenario. However the detailed properties of BluDOGs are not understood because of the lack of spectroscopic information. In this work, we carry out deep optical spectroscopic observations of four BluDOGs using Subaru/FOCAS and VLT/FORS2. The obtained spectra show broad emission lines with extremely large equivalent widths, and a blue wing in the CIV line profile. The redshifts are between 2.2 and 3.3. The averaged rest-frame equivalent widths of the CIV lines are $160\pm33$ $\mathrm{\mathring{A}}$, $\sim$7 times higher than the average of a typical type-1 quasar. The FWHMs of their velocity profiles are between 1990 and 4470 ${\rm km\ s^{-1}}$, and their asymmetric parameters are 0.05 and 0.25. Such strong CIV lines significantly affect the broad-band magnitudes, which is partly the origin of the blue excess seen in the spectral energy distribution of BluDOGs. Their estimated supermassive black hole masses are $1.1\times10^8 < M_{\rm BH}/M_\odot < 5.5 \times 10^8$. The inferred Eddington ratios of the BluDOGs are higher than 1 ($1.1< λ_{\rm Edd} < 3.8$), suggesting that the BluDOGs are in a rapidly evolving phase of supermassive black holes.
