Ultramassive black holes in the most massive galaxies: MBH−σM_{\rm BH}-\sigma versus MBH−RbM_{\rm BH}-R_{\rm b}

[Abridged] We investigate the nature of the relations between black hole (BH) mass ($M_{\rm BH}$) and the central velocity dispersion ($\sigma$) and, for core-S\'ersic galaxies, the size of the depleted core ($R_{\rm b}$). Our sample of 144 galaxies with dynamically determined $M_{\rm BH}$ encompasses 24 core-S\'ersic galaxies, thought to be products of gas-poor mergers, and reliably identified based on high-resolution HST imaging. For core-S\'ersic galaxies -- i.e., combining normal-core ($R_{\rm b} < 0.5$ kpc) and large-core galaxies ($R_{\rm b} \gtrsim 0.5$ kpc), we find that $M_{\rm BH}$ correlates remarkably well with $R_{\rm b}$ such that $M_{\rm BH} \propto R_{\rm b}^{1.20 \pm 0.14}$ (rms scatter in log $M_{\rm BH}$ of $\Delta_{\rm rms} \sim 0.29$ dex), confirming previous works on the same galaxies except three new ones. Separating the sample into S\'ersic, normal-core and large-core galaxies, we find that S\'ersic and normal-core galaxies jointly define a single log-linear $M_{\rm BH}-\sigma$ relation $M_{\rm BH} \propto \sigma^{ 4.88 \pm 0.29}$ with $\Delta_{\rm rms} \sim 0.47$ dex, however, at the high-mass end large-core galaxies (four with measured $M_{\rm BH}$) are offset upward from this relation by ($2.5-4) \times \sigma_{\rm s}$, explaining the previously reported steepening of the $M_{\rm BH}-\sigma$ relation for massive galaxies. Large-core spheroids have magnitudes $M_{V} \le -23.50$ mag, half-light radii Re $>$ 10 kpc and are extremely massive $M_{*} \ge 10^{12}M_{\odot}$. Furthermore, these spheroids tend to host ultramassive BHs ($M_{\rm BH} \ge 10^{10}M_{\odot}$) tightly connected with their $R_{\rm b}$ rather than $\sigma$. The less popular $M_{\rm BH}-R_{\rm b}$ relation exhibits $\sim$ 62% less scatter in log $M_{\rm BH}$ than the $M_{\rm BH}- \sigma$ relations.Comment: 11 pages, 4 figures, accepted (2020, November 27) for publication in Ap

The (black hole mass)-(color) relations for early- and late-type galaxies: red and blue sequences

[Abridged] Tight correlations between supermassive black hole (SMBH) mass ($M_{\rm BH}$) and the properties of the host galaxy have useful implications for our understanding of the growth of SMBHs and evolution of galaxies. Here, we present newly observed correlations between $M_{\rm BH}$ and the host galaxy total UV$-$ [3.6] color ($\mathcal{C_{\rm UV,tot}}$, Pearson's r = $0.6-0.7$) for a sample of 67 galaxies (20 early-type galaxies and 47 late-type galaxies) with directly measured $M_{\rm BH}$ in the GALEX/S$^{4}$G survey. The colors are carefully measured in a homogeneous manner using the galaxies' FUV, NUV and 3.6 \micron magnitudes and their multi-component structural decompositions in the literature. We find that more massive SMBHs are hosted by (early- and late-type) galaxies with redder colors, but the $M_{\rm BH}- \mathcal{C_{\rm UV,tot}}$ relations for the two morphological types have slopes that differ at $\sim 2 \sigma$ level. Early-type galaxies define a red sequence in the $M_{\rm BH}- \mathcal{C_{\rm UV,tot}}$ diagrams, while late-type galaxies trace a blue sequence. Within the assumption that the specific star formation rate of a galaxy (sSFR) is well traced by $L_{\rm UV}/L_{\rm 3.6}$, it follows that the SMBH masses for late-type galaxies exhibit a steeper dependence on sSFR than those for early-type galaxies. The $M_{\rm BH}- \mathcal{C_{\rm UV,tot}}$ and $M_{\rm BH}-L_{\rm 3.6,tot}$ relations for the sample galaxies reveal a comparable level of vertical scatter in the log $M_{\rm BH}$ direction, roughly $5\%-27\%$ more than the vertical scatter of the $M_{\rm BH}-\sigma$ relation. Our $M_{\rm BH}- \mathcal{C_{\rm UV,tot}}$ relations suggest different channels of SMBH growth for early- and late-type galaxies, consistent with their distinct formation and evolution scenarios.Comment: 27 pages, 8 figures, 6 tables, accepted for publication in Ap

Bar-driven AGN fuelling in SO galaxies with complex central structures

<p>Nuclear stellar bars, rings and/or spirals in disk galaxies are thought to stimulate the inward funnelling of disk materials, fuelling the AGN. However, how such small-scale structures and the central AGN activities are actually related still remains uncertain. Therefore, we performed a detailed analysis of the structures and isophotal properties for three barred S0 galaxies NGC 2681, NGC 3945 and NGC 4371 having small-scale stellar bars, rings and a point source. Building on this and using our imaging of the narrow lines (Hβ, [O III], Hα, [N II], and [S II]) to measure the pertaining emission fluxes, we constructed the standard BPT diagnostic diagrams. Our results favor bar-related AGN fuelling and nuclear gas ionisation. However, we argue that the bar-driven scenario alone cannot account for the formation of these three S0s.</p

The nuclear activity and central structure of the elliptical galaxy NGC 5322

We have analysed a new high-resolution e-MERLIN 1.5 GHz radio continuum map together with $HST$ and SDSS imaging of NGC 5322, an elliptical galaxy hosting radio jets, aiming to understand the galaxy's central structure and its connection to the nuclear activity. We decomposed the composite $HST$ + SDSS surface brightness profile of the galaxy into an inner stellar disc, a spheroid, and an outer stellar halo. Past works showed that this embedded disc counter-rotates rapidly with respect to the spheroid. The $HST$ images reveal an edge-on nuclear dust disc across the centre, aligned along the major-axis of the galaxy and nearly perpendicular to the radio jets. After careful masking of this dust disc, we find a central stellar mass deficit $M_{\rm def}$ in the spheroid, scoured by SMBH binaries with final mass $M_{\rm BH}$ such that $M_{\rm def}/M_{\rm BH} \sim 1.3 - 3.4$. We propose a three-phase formation scenario for NGC 5322 where a few ($2-7$) "dry" major mergers involving SMBHs built the spheroid with a depleted core. The cannibalism of a gas-rich satellite subsequently creates the faint counter-rotating disc and funnels gaseous material directly onto the AGN, powering the radio core with a brightness temperature of $T_{\rm B,core} \sim 4.5 \times 10^{7}$ K and the low-power radio jets ($P_{\rm jets}\sim 7.04 \times 10^{20}$ W Hz$^{-1}$) which extend $\sim 1.6$ kpc. The outer halo can later grow via minor mergers and the accretion of tidal debris. The low-luminosity AGN/jet-driven feedback may have quenched the late-time nuclear star formation promptly, which could otherwise have replenished the depleted core.Comment: 14 pages, 5 figures, accepted for publication in MNRA

A Photometric and Kinematic Analysis of UDG1137+16 (dw1137+16): Probing Ultra-Diffuse Galaxy Formation in a Group Environment

The dominant physical formation mechanism(s) for ultra-diffuse galaxies (UDGs) is still poorly understood. Here, we combine new, deep imaging from the Jeanne Rich Telescope with deep integral field spectroscopy from the Keck II telescope to investigate the formation of UDG1137+16 (dw1137+16). Our new analyses confirm both its environmental association with the low density UGC 6594 group, along with its large size of 3.3 kpc and status as a UDG. The new imaging reveals two distinct stellar components for UDG1137+16, indicating that a central stellar body is surrounded by an outer stellar envelope undergoing tidal interaction. Both the components have approximately similar stellar masses. From our integral field spectroscopy we measure a stellar velocity dispersion within the half-light radius (15 $\pm$ 4 $\mathrm{km\ s^{-1}}$) and find that UDG1137+16 is similar to some other UDGs in that it is likely dark matter dominated. Incorporating literature measurements, we also examine the current state of UDG observational kinematics. Placing these data on the central stellar velocity dispersion -- stellar mass relation, we suggest there is little evidence for UDG1137+16 being created through a strong tidal interaction. Finally, we investigate the constraining power current dynamical mass estimates (from stellar and globular cluster velocity dispersions) have on the total halo mass of UDGs. As most are measured within the half-light radius, they are unable to accurately constrain UDG total halo masses.Comment: Published in MNRAS: 15 pages, 8 figures, 1 appendix; Minor update to match published versio