21 research outputs found
Ultramassive black holes in the most massive galaxies: versus
[Abridged] We investigate the nature of the relations between black hole (BH)
mass () and the central velocity dispersion () and, for
core-S\'ersic galaxies, the size of the depleted core (). Our sample
of 144 galaxies with dynamically determined 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 ( kpc) and large-core
galaxies ( kpc), we find that correlates
remarkably well with such that (rms scatter in log of
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
relation with
dex, however, at the high-mass end large-core
galaxies (four with measured ) are offset upward from this relation
by (, explaining the previously reported
steepening of the relation for massive galaxies. Large-core
spheroids have magnitudes mag, half-light radii Re 10
kpc and are extremely massive . Furthermore, these
spheroids tend to host ultramassive BHs ()
tightly connected with their rather than . The less popular
relation exhibits 62% less scatter in log than the 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
() 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 and the host galaxy
total UV [3.6] color (, Pearson's r = )
for a sample of 67 galaxies (20 early-type galaxies and 47 late-type galaxies)
with directly measured in the GALEX/SG 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 relations for the two morphological types have slopes that differ at
level. Early-type galaxies define a red sequence in the 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 , it follows that the
SMBH masses for late-type galaxies exhibit a steeper dependence on sSFR than
those for early-type galaxies. The and
relations for the sample galaxies reveal a
comparable level of vertical scatter in the log direction, roughly
more than the vertical scatter of the relation.
Our 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 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 + 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 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 in the
spheroid, scoured by SMBH binaries with final mass such that
. We propose a three-phase formation
scenario for NGC 5322 where a few () "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 K and the
low-power radio jets ( W Hz) which
extend 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 4 ) 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