Nearby Early-type Galactic Nuclei at High Resolution: Dynamical Black Hole and Nuclear Star Cluster Mass Measurements

Abstract

We present a detailed study of the nuclear star clusters (NSCs) and massive black holes (BHs) of four of the nearest low-mass early-type galaxies: M32, NGC 205, NGC 5102, and NGC 5206. We measure dynamical masses of both the BHs and NSCs in these galaxies using Gemini/NIFS or VLT/SINFONI stellar kinematics, Hubble Space Telescope (HST ) imaging, and Jeans Anisotropic Models. We detect massive BHs in M32, NGC 5102, and NGC 5206, while in NGC 205, we find only an upper limit. These BH mass estimates are consistent with previous measurements in M32 and NGC 205, while those in NGC 5102 & NGC 5206 are estimated for the first time, and both found to be <10 6 M . This adds to just a handful of galaxies with dynamically measured sub-million M central BHs. Combining these BH detections with our recent work on NGC 404's BH, we find that 80% (4/5) of nearby, low-mass (10 9 − 10 10 M ; σ ∼ 20 − 70 km s −1 ) early-type galaxies host BHs. Such a high occupation fraction suggests the BH seeds formed in the early epoch of cosmic assembly likely resulted in abundant seeds, favoring a low-mass seed mechanism of the remnants, most likely from the first generation of massive stars. We find dynamical masses of the NSCs ranging from 2 − 73 × 10 6 M and compare these masses to scaling relations for NSCs based primarily on photometric mass estimates. Color gradients suggest younger stellar populations lie at the centers of the NSCs in three of the four galaxies (NGC 205, NGC 5102, and NGC 5206), while the morphology of two are complex and are best-fit with multiple morphological components (NGC 5102 and NGC 5206). The NSC kinematics show they are rotating, especially in M32 and NGC 5102 (V /σ ∼ 0.7).

Probing Massive Black Hole Binary Populations with LISA

“…Along the same lines, Illustris, and simulations like it, do not access the scales needed to examine populations of dwarf galaxies. As evidence mounts that dwarf galaxies house MBHs in their center in both observations (Reines et al 2013;Moran et al 2014;Satyapal et al 2014;Lemons et al 2015;Sartori et al 2015;Pardo et al 2016;Nguyen et al 2018Nguyen et al , 2019 and simulations (Volonteri et al 2008;van Wassenhove et al 2010;Bellovary et al 2019), we must improve models since these dwarf galaxy sources are enitrely missing from our analysis. Due to the prevalence of dwarf galaxies as well as the general understanding that dwarf galaxies consistently merge into larger "host" galaxies over time, missing the dwarf galaxy MBHs could deflate our rate calculations significantly.…”

Accelerated orbital decay of supermassive black hole binaries in merging nuclear star clusters

“…As a result, dense NSCs are formed and the SMBHs are embedded in them (Van Wassenhove et al 2014) during the last phase of the galaxy merger. Furthermore, recent searches for SMBHs in dwarf galaxies have successfully found them (Nguyen et al 2018), and classic analytic estimates of the SMBHB hardening timescales suggest a more rapid evolution than expected in dwarf galaxies in the presence of NSCs due to the increased stellar densities (Biava et al 2019).…”

A Deep View into the Nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. II. Kinematic Characterization of the Stellar Populations

“…Where detailed measurements of kinematics are possible, rotation seems to be a common dynamical ingredient of NSCs (Feldmeier et al 2014;Nguyen et al 2018) and is also commonly found in a high fraction of GCs (van de Ven et al 2006;Bellazzini et al 2012;Bianchini et al 2013;Kacharov et al 2014;Fabricius et al 2014;Kimmig et al 2015;Bellini et al 2017;Kamann et al 2018;Bianchini et al 2018;Sollima et al 2019). The presence of internal rotation can be an indicator of their formation mechanism (Mastrobuono-Battisti & Perets 2013, 2016Hénault-Brunet et al 2015;Gavagnin et al 2016;Khoperskov et al 2018;Mastrobuono-Battisti et al 2019a) and can give important clues on their long-term dynamical evolution (e.g., Einsel & Spurzem 1999;Tiongco et al 2018).…”