its bulge velocity dispersion but is significantly lower than that expected from its bulge luminosity.'
author:
- '[Ning Jiang (蒋凝)]{}, Luis C. Ho, Xiao-Bo Dong (董小波), Huan Yang (杨欢) and Junxian Wang (王俊贤)'
title: 'UM 625 Revisited: Multiwavelength Study of A Seyfert 1 Galaxy with a Low-mass Black Hole'
---

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Introduction
============

Supermassive black holes (BHs), with masses in the range of $10^{6}-10^{10}$ [$M_{\odot}$]{} as measured via stellar and gas kinematics, have been convincingly inferred to be present in the centers of nearby inactive massive galaxies and are generally believed to reside in all galaxies with a spheroidal stellar component (see Kormendy & Ho 2013 for a review). Moreover, there are tight relations between the BH mass ([$M_\mathrm{BH}$]{}) and the properties of the spheroidal component (namely, ellipticals and the bulges of disk galaxies), including stellar velocity dispersion ($\sigma_\star$; Ferrarese & Merritt 2000, Gebhardt et al. 2000a), luminosity ($L_{\rm bulge}$; Kormendy & Richstone 1995; Magorrian et al. 1998; Marconi & Hunt 2003), and mass ($M_{\rm bulge}$; Häring & Rix 2004).

However, the situation is far from clear in the low-mass regime (${\ensuremath{M_\mathrm{BH}}}\lesssim 10^6$ [$M_{\odot}$]{}) because such BHs are largely beyond the reach of current capabilities for direct dynamical measurement. A 