2022, Pechetti, Renuka, Seth, Anil, Kamann, Sebastian, Caldwell, Nelson, Strader, Jay, den Brok, Mark, Luetzgendorf, Nora, Neumayer, Nadine, Voggel, Karina

We investigate the presence of a central black hole (BH) in B023-G078, M31's most massive globular cluster. We present high-resolution, adaptive-optics assisted, integral-field spectroscopic kinematics from Gemini/NIFS that show a strong rotation (∼20 km s-1) and a velocity dispersion rise toward the center (37 km s-1). We combine the kinematic data with a mass model based on a two-component fit to HST ACS/HRC data of the cluster to estimate the mass of a putative BH. Our dynamical modeling suggests a >3σ detection of a BH component of (1σ uncertainties). The inferred stellar mass of the cluster is , consistent with previous estimates, thus the BH makes up 1.5% of its mass. We examine whether the observed kinematics are caused by a collection of stellar mass BHs by modeling an extended dark mass as a Plummer profile. The upper limit on the size scale of the extended mass is 0.56 pc (95% confidence), which does not rule out an extended mass. There is compelling evidence that B023-G078 is the tidally stripped nucleus of a galaxy with a stellar mass >109 M o˙, including its high-mass, two-component luminosity profile, color, metallicity gradient, and spread in metallicity. Given the emerging evidence that the central BH occupation fraction of >109 M o˙ galaxies is high, the most plausible interpretation of the kinematic data is that B023-G078 hosts a central BH. This makes it the strongest BH detection in a lower-mass (<107 M o˙) stripped nucleus, and one of the few dynamically detected intermediate-mass BHs.

2019, Nguyen, Dieu D., Seth, Anil C., Neumayer, Nadine, Iguchi, Satoru, Cappellari, Michelle, Strader, Jay, Chomiuk, Laura, Tremou, Evangelia, Pacucci, Fabio, Nakanishi, Kouichiro, Bahramian, Arash, Nguyen, Phuong M., den Brok, Mark, Ahn, Christopher C., Voggel, Karina T., Kacharov, Nikolay, Tsukui, Takafumi, Ly, Cuc K., Dumont, Antoine, Pechetti, Renuka

We improve the dynamical black hole (BH) mass estimates in three nearby low-mass early-type galaxies: NGC 205, NGC 5102, and NGC 5206. We use new Hubble Space Telescope (HST)/STIS spectroscopy to fit the star formation histories of the nuclei in these galaxies, and use these measurements to create local color–mass-to-light ratio (M/L) relations. We then create new mass models from HST imaging and combined with adaptive optics kinematics, we use Jeans dynamical models to constrain their BH masses. The masses of the central BHs in NGC 5102 and NGC 5206 are both below one million solar masses and are consistent with our previous estimates, ${9.12}_{-1.53}^{+1.84}\times {10}^{5}$ M⊙ and ${6.31}_{-2.74}^{+1.06}\times {10}^{5}$ M⊙ (3σ errors), respectively. However, for NGC 205, the improved models suggest the presence of a BH for the first time, with a best-fit mass of ${6.8}_{-6.7}^{+95.6}\times {10}^{3}$ M⊙ (3σ errors). This is the least massive central BH mass in a galaxy detected using any method. We discuss the possible systematic errors of this measurement in detail. Using this BH mass, the existing upper limits of both X-ray, and radio emissions in the nucleus of NGC 205 suggest an accretion rate lesssim10−5 of the Eddington rate. We also discuss the color–M/Leff relations in our nuclei and find that the slopes of these vary significantly between nuclei. Nuclei with significant young stellar populations have steeper color–M/Leff relations than some previously published galaxy color–M/Leff relations.