Improved Dynamical Constraints on the Masses of the Central Black Holes in Nearby Low-mass Early-type Galactic Nuclei and the First Black Hole Determination for NGC 205

Abstract

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 HST /STIS spectroscopy to fit the star formation histories of the nuclei in these galaxies, and use these measurements to create local colormass-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 +1.84 −1.53 × 10 5 M and 6.31 +1.06 −2.74 × 10 5 M (3σ errors), respectively. However, for NGC 205, the improved models suggests the presence of a BH for the first time, with a best-fit mass of 6.8 +95.6 −6.7 × 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 10 −5 of the Eddington rate. We also discuss the color-M/L eff 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/L eff relations than some previously published galaxy color-M/L eff relations.

A consistency test for determining whether ultracompact dwarf galaxies could be the remnant nuclei of threshed galaxies

“…gives an expected black hole mass in NGC 205 equal to 6.4 × 10 3 M if M nc = 1.4 × 10 6 M , or M bh = 1.2 × 10 4 M if M nc = 1.8 × 10 6 M . This expectation from equations established a few years ago is in remarkable agreement withNguyen et al (2019) who report a dynamically-determined black hole mass in NGC 205 of 6.8 +95.6 −6.7 ×10 3 M (±3σ uncertainty), consistent with the upper limit of 3.8 × 10 3 M (±3σ uncertainty) fromValluri et al (2005).…”

“…index (seeGraham & Driver 2005, for a review of the Sérsic model) of the inner component is 3.3. This compares favourably with the Sérsic index of the nuclear star cluster in the Milky Way (n = 3) and in M32 (n = 2.3)(Graham & Spitler (2009); see alsoNguyen et al (2019) who report n = 2.7 ± 0.3 for M32).Pluggingin M bh = (2.2 ± 0.4) × 10 7 M (Seth et al 2014) into equation 4, and assuming an intrinsic scatter of 0.5 dex in the log M nc direction, gives log(M nc /M ) = 7.42 ± 0.53, or M nc = (2.6 +6.3 −1.8 ) × 10 7 M . This predicted nuclear cluster mass is just 2.65 times smaller than the stellar mass of the inner component in M60-UCD1 (= 6.9 × 10 7 M ), i.e.…”

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.…”

Radio jets from AGNs in dwarf galaxies in the COSMOS survey: mechanical feedback out to redshift ∼3.4

“…Given that obtaining a dynamical mass measurement of an IMBH in a dwarf galaxy is currently limited to slightly beyond the Local Group (e.g. Gebhardt et al 2001;Nguyen et al 2017Nguyen et al , 2018Nguyen et al , 2019, most IMBH searches in dwarf galaxies have focused on finding accretion signatures from low-mass AGN (M BH 10 6 E-mail: marmezcua.astro@gmail.com † Subaru fellow M ) either in the form of high-ionisation optical and infrared emission lines (e.g. Satyapal et al 2008;Sartori et al 2015;Marleau et al 2017), broad optical emission lines and reverberation mapping techniques (e.g.…”