A quartet of black holes and a missing duo: probing the low end of the MBH–σ relation with the adaptive optics assisted integral-field spectroscopy

Abstract

We present mass estimates of supermassive black holes in six nearby fast rotating early-type galaxies (NGC 4339, NGC 4434, NGC 4474, NGC 4551, NGC 4578 and NGC 4762) with effective stellar velocity dispersion around 100 km/s. We use near-infrared laser-guide adaptive optics observations with the GEMINI/NIFS to derive stellar kinematics in the galactic nuclei, and SAURON observations from the ATLAS 3D Survey for large-scale kinematics. We build axisymmetric Jeans Anisotropic Models and axisymmetric Schwarzschild dynamical models. Both modelling approaches recover consistent orbital anisotropies and black hole masses within 1 − 2σ confidence level, except for one galaxy for which the difference is just above the 3σ level. Two black holes (NGC 4339 and NGC 4434) are amongst the largest outliers from the current black hole mass -velocity dispersion relation, with masses of (4.3 +4.8 −2.3 ) × 10 7 and (7.0 +2.0 −2.8 ) × 10 7 M , respectively (3σ confidence level). The black holes in NGC 4578 and NGC 4762 lie on the scaling relation with masses of (1.9 +0.6 −1.4 ) × 10 7 and (2.3 +0.9 −0.6 ) × 10 7 M , respectively (3σ confidence level). For two galaxies (NGC 4474 and NGC 4551) we are able to place upper limits on their black holes masses (< 7×10 6 and < 5×10 6 M , respectively, 3σ confidence level). The kinematics for these galaxies clearly indicate central velocity dispersion drops within a radius of 35 pc and 80 pc, respectively. These drops cannot be associated with cold stellar structures and our data do not have the resolution to exclude black holes with masses an order of magnitude smaller than the predictions. Parametrizing the orbital distribution in spherical coordinates, the vicinity of the black holes is characterized by isotropic or mildly tangential anisotropy.

The MASSIVE Survey. XV. A Stellar Dynamical Mass Measurement of the Supermassive Black Hole in Massive Elliptical Galaxy NGC 1453

“…These pairs of definitions are only expected to differ when there is significant contribution from the ordered flow velocity term v φ 2 . For reference, differing definitions and symbols were used in the literature, e.g., β from Thomas et al (2014), β r from Peletier et al (2007), and σ r /σ t from Walsh et al (2015) all excluded the v φ 2 term, while β rot from Krajnović et al (2018) and Thomas et al (2014) and σ r /σ t from Gebhardt et al (2003) included this term.…”

A catalogue of nuclear stellar velocity dispersions of nearby galaxies from Hα STIS spectra to constrain supermassive black hole masses

“…with JWST) or from the ground while being assisted by adaptive optics (AO), such as those presented by Krajnović et al (2018), who indeed also found evidence for undermassive SBH in two nearby early-type galaxies. AO assisted integral-field observations would also allow to establish if our nuclear σ * dip can be explained by the presence of a central dynamically cold component such as a nuclear disc, although we note that in that case the presence of a SBH would be betrayed by an increased central stellar rotation (as also discussed by Krajnović et al 2018). Theoretical works indicate that assessing the fraction of undermassive black holes in nearby galaxies would be quite important to constrain the processes driving the mass growth of SBHs and how they settled in galactic nuclei (Volonteri et al 2011).…”

“…For instance NGC 4435 would be an ideal target for future near-infrared observations from either space (e.g. with JWST) or from the ground while being assisted by adaptive optics (AO), such as those presented by Krajnović et al (2018), who indeed also found evidence for undermassive SBH in two nearby early-type galaxies. AO assisted integral-field observations would also allow to establish if our nuclear σ * dip can be explained by the presence of a central dynamically cold component such as a nuclear disc, although we note that in that case the presence of a SBH would be betrayed by an increased central stellar rotation (as also discussed by Krajnović et al 2018).…”

“…The relationship between M• and the stellar velocity dispersion σ * of the spheroidal component is currently the tightest correlation discovered so far (Beifiori et al 2012;Kormendy & Ho 2013;van den Bosch 2016), although there are open issues about its slope (Saglia et al 2016), whether the SBHs in barred and ordinary galaxies and/or classical and pseudobulges follow the same correlation (Graham 2016), and the role of the over and undermassive SBHs with respect to those tracing the correlation (Savorgnan & Graham 2015, Krajnović et al 2018. In fact, there is still the need of increasing the statistics of M• in some specific physical ranges.…”

“…The finding of low M• outliers, or even ruling out the presence of a SBH is a more challenging task given to the detection threshold imposed by the angular resolution of present telescopes. Yet, remarkable low M• outlier examples do exist, such as the radio-loud elliptical NGC 4335 (Verdoes Kleijn et al 2002) and the barred lenticular NGC 4435 (Coccato et al 2006), where M• was constrained from the central ionised-gas kinematics observed with HST, or the lenticular NGC 4474 and elliptical NGC 4551, where stringent M• limits were derived from stellar dynamical models and groundbased integral-field observations assisted by adaptive optics (Krajnović et al 2018). The merging galaxies NGC 1316 (Nowak et al 2008) and NGC 4382 have also quite small M• for their galaxy luminosities but in these cases it is not clear if this could be linked to the merger physics and to limitations in search techniques.…”