An ALMA Gas-dynamical Mass Measurement of the Supermassive Black Hole in the Local Compact Galaxy UGC 2698
An ALMA Gas-dynamical Mass Measurement of the Supermassive Black Hole in the Local Compact Galaxy UGC 2698
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DOI：
10.3847/1538-4357/ac0f78
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发表时间：
2021-04
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通讯作者：
J. Cohn;J. Walsh;Benjamin D. Boizelle;A. Barth;K. Gebhardt;K. Gültekin;A. Yıldırım;D. Buote;J. Darling;A. Baker;L. Ho;Kyle M. Kabasares
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作者：
J. Cohn;J. Walsh;Benjamin D. Boizelle;A. Barth;K. Gebhardt;K. Gültekin;A. Yıldırım;D. Buote;J. Darling;A. Baker;L. Ho;Kyle M. Kabasares
利用0.“14分辨率的阿塔卡玛大型毫米/亚毫米阵列（阿尔马）CO（2−1）观测了UGC 2698（一个局部致密星系）的环核气盘。圆盘呈现出规则的自转，在星系中心附近的投影速度高达450 km s−1。我们将气体动力学模型与阿尔马数据立方体拟合，假设CO发射来自一个动态冷的薄盘，并测量出UGC 2698中超大质量黑洞（BH）的质量为M BH =（2.46 ± 0.07 [1σ统计]-0.78 +0.70 [系统]）× 109 M。UGC 2698是附近早期星系样本的一部分，可能是z 102红块遗迹。先前对样本中三个星系的恒星动力学模型发现BH质量与BH质量-恒星速度色散（M BH − σ）关系一致，但相对于BH质量-凸起光度（M BH − L bul）关系过大，这表明BH可能在其宿主星系之前获得大部分质量。然而，UGC 2698与M BH − σ和M BH − L bul都是一致的。由于UGC 2698在本地致密星系样本中具有最大的恒星质量和有效半径，它可能经历了更近的合并，使其符合BH标度关系。另外，考虑到先前测量的三个致密星系是M BH − L bul的异常值，而UGC 2698不是，在关系的低采样高质量端可能存在显著的散射。对致密星系样本的额外气体动力学M BH测量将提高我们对BH-星系共同演化的理解。
We present 0.″14 resolution Atacama Large Millimeter/submillimeter Array (ALMA) CO(2−1) observations of the circumnuclear gas disk in UGC 2698, a local compact galaxy. The disk exhibits regular rotation with projected velocities rising to 450 km s−1 near the galaxy center. We fit gas-dynamical models to the ALMA data cube, assuming the CO emission originates from a dynamically cold, thin disk, and measured the mass of the supermassive black hole (BH) in UGC 2698 to be M BH = (2.46 ± 0.07 [1σ statistical] −0.78+0.70 [systematic]) × 109 M ⊙. UGC 2698 is part of a sample of nearby early-type galaxies that are plausible z ∼ 2 red nugget relics. Previous stellar-dynamical modeling for three galaxies in the sample found BH masses consistent with the BH mass−stellar velocity dispersion (M BH − σ ⋆) relation but over-massive relative to the BH mass−bulge luminosity (M BH − L bul) correlation, suggesting that BHs may gain the majority of their mass before their host galaxies. However, UGC 2698 is consistent with both M BH − σ ⋆ and M BH − L bul. As UGC 2698 has the largest stellar mass and effective radius in the local compact galaxy sample, it may have undergone more recent mergers that brought it in line with the BH scaling relations. Alternatively, given that the three previously measured compact galaxies are outliers from M BH − L bul, while UGC 2698 is not, there may be significant scatter at the poorly sampled high-mass end of the relation. Additional gas-dynamical M BH measurements for the compact galaxy sample will improve our understanding of BH−galaxy co-evolution.