12 research outputs found
Detection of Enhanced Central Mass-to-Light Ratios in Low-Mass Early-Type Galaxies: Evidence for Black Holes?
We present dynamical measurements of the central mass-to-light ratio ()
of a sample of 27 low-mass early-type ATLAS galaxies. We consider all
ATLAS galaxies with 9.7log(MM10.5 in our
analysis, selecting out galaxies with available high-resolution Hubble Space
Telescope (HST) data, and eliminating galaxies with significant central color
gradients or obvious dust features. We use the HST images to derive mass models
for these galaxies and combine these with the central velocity dispersion
values from ATLAS data to obtain a central dynamical estimate.
These central dynamical s are higher than dynamical s derived at
larger radii and stellar population estimates of the galaxy centers in
80\% of galaxies, with a median enhancement of 14\% and a
statistical significance of 3.3. We show that the enhancement in the
central is best described either by the presence of black holes in these
galaxies or by radial IMF variations. Assuming a black hole model, we derive
black hole masses for the sample of galaxies. In two galaxies, NGC 4458 and NGC
4660, the data suggests significantly over-massive BHs, while in most others
only upper limits are obtained. We also show that the level of
enhancements we see in these early-type galaxy nuclei are consistent with the
larger enhancements seen in ultracompact dwarf galaxies (UCDs), supporting the
scenario where massive UCDs are created by stripping galaxies of these masses.Comment: Accepted to ApJ, 17 pages, 13 figure
Kinematic differences between multiple populations in Galactic globular clusters
The formation process of multiple populations in globular clusters is still
up for debate. Kinematic differences between the populations are particularly
interesting in this respect, because they allow us to distinguish between
single-epoch formation scenarios and multi-epoch formation scenarios. We
analyze the kinematics of 25 globular clusters and aim to find kinematic
differences between multiple populations to constrain their formation process.
We split red-giant branch (RGB) stars in each cluster into three populations
(P1, P2, P3) for the type-II clusters and two populations (P1 and P2) otherwise
using Hubble photometry. We derive the rotation and dispersion profiles for
each cluster and its populations by using all stars with radial velocity
measurements obtained from MUSE spectroscopy. Based on these profiles, we
calculate the rotation strength in terms of ordered-over-random motion
evaluated at the half-light radius of the
cluster. We detect rotation in all but four clusters. For NGC~104, NGC~1851,
NGC~2808, NGC~5286, NGC~5904, NGC~6093, NGC~6388, NGC~6541, NGC~7078 and
NGC~7089 we also detect rotation for P1 and/or P2 stars. For NGC~2808, NGC~6093
and NGC~7078 we find differences in between
P1 and P2 that are larger than . Whereas we find that P2 rotates
faster than P1 for NGC~6093 and NGC~7078, the opposite is true for NGC~2808.
However, even for these three clusters, the differences are still of low
significance. We find that the strength of rotation of a cluster generally
scales with its median relaxation time. For P1 and P2, the corresponding
relation is very weak at best. We observe no correlation between the difference
in rotation strength between P1 and P2 and cluster relaxation time. The MUSE
stellar radial velocities that this analysis is based on are made publicly
available
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
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 color--mass-to-light
ratio (\ml) 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, \Msun~and
\Msun~(3 errors), respectively.
However, for NGC 205, the improved models suggest the presence of a BH for the
first time, with a best-fit mass of
\Msun~(3 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 of the Eddington rate. We
also discuss the color--\mleff~relations in our nuclei and find that the slopes
of these vary significantly between nuclei. Nuclei with significant young
stellar populations have steeper color--\mleff~relations than some previously
published galaxy color--\mleff~relations.Comment: 31 pages, 19 figures, 6 tables, Accepted to Ap
The Black Hole in the Most Massive Ultracompact Dwarf Galaxy M59-UCD3
We examine the internal properties of the most massive ultracompact dwarf
galaxy (UCD), M59-UCD3, by combining adaptive optics assisted near-IR integral
field spectroscopy from Gemini/NIFS, and Hubble Space Telescope (HST) imaging.
We use the multi-band HST imaging to create a mass model that suggests and
accounts for the presence of multiple stellar populations and structural
components. We combine these mass models with kinematics measurements from
Gemini/NIFS to find a best-fit stellar mass-to-light ratio () and black
hole (BH) mass using Jeans Anisotropic Models (JAM), axisymmetric Schwarzschild
models, and triaxial Schwarzschild models. The best fit parameters in the JAM
and axisymmetric Schwarzschild models have black holes between 2.5 and 5.9
million solar masses. The triaxial Schwarzschild models point toward a similar
BH mass, but show a minimum at a BH mass of . Models with a BH
in all three techniques provide better fits to the central profiles,
and thus we estimate the BH mass to be
M (estimated 1 uncertainties). We also present deep radio
imaging of M59-UCD3 and two other UCDs in Virgo with dynamical BH mass
measurements, and compare these to X-ray measurements to check for consistency
with the fundamental plane of BH accretion. We detect faint radio emission in
M59cO, but find only upper limits for M60-UCD1 and M59-UCD3 despite X-ray
detections in both these sources. The BH mass and nuclear light profile of
M59-UCD3 suggests it is the tidally stripped remnant of a 10
M galaxy.Comment: 17 pages, 14 figures, 5 table
Nearby Early-type Galactic Nuclei at High Resolution: Dynamical Black Hole and Nuclear Star Cluster Mass Measurements
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 the 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 and NGC 5206 are estimated for the first time and both found to be <106 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}\mbox{--}{10}^{10} M ⊙; {\sigma }_{\star }\sim 20\mbox{--}70 km s−1) early-type galaxies host BHs. Such a high occupation fraction suggests that 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 to 73 × 106 M ⊙ and compare these masses to scaling relations for NSCs based primarily on photometric mass estimates. Color gradients suggest that 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 best fit with multiple morphological components (NGC 5102 and NGC 5206). The NSC kinematics show they are rotating, especially in M32 and NGC 5102 ()
Detection of a 100,000 M ⊙ black hole in M31's Most Massive Globular Cluster: A Tidally Stripped Nucleus
International audienceAbstract We investigate the presence of a central black hole (BH) in B023-G078, M31's most massive globular cluster. We present high-resolution, adaptive-optics assisted, integral-field spectroscopic kinematics from Gemini/NIFS that show a strong rotation (∼20 km s −1 ) and a velocity dispersion rise toward the center (37 km s −1 ). We combine the kinematic data with a mass model based on a two-component fit to HST ACS/HRC data of the cluster to estimate the mass of a putative BH. Our dynamical modeling suggests a >3 σ detection of a BH component of 9.1 − 2.8 + 2.6 × 10 4 M ⊙ (1 σ uncertainties). The inferred stellar mass of the cluster is 6.22 − 0.05 + 0.03 × 10 6 M ⊙ , consistent with previous estimates, thus the BH makes up 1.5% of its mass. We examine whether the observed kinematics are caused by a collection of stellar mass BHs by modeling an extended dark mass as a Plummer profile. The upper limit on the size scale of the extended mass is 0.56 pc (95% confidence), which does not rule out an extended mass. There is compelling evidence that B023-G078 is the tidally stripped nucleus of a galaxy with a stellar mass >10 9 M ⊙ , including its high-mass, two-component luminosity profile, color, metallicity gradient, and spread in metallicity. Given the emerging evidence that the central BH occupation fraction of >10 9 M ⊙ galaxies is high, the most plausible interpretation of the kinematic data is that B023-G078 hosts a central BH. This makes it the strongest BH detection in a lower-mass (<10 7 M ⊙ ) stripped nucleus, and one of the few dynamically detected intermediate-mass BHs
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Detection of a 100,000 M-circle dot black hole in M31's Most Massive Globular Cluster: A Tidally Stripped Nucleus
We investigate the presence of a central black hole (BH) in B023-G078, M31's most massive globular cluster. We present high-resolution, adaptive-optics assisted, integral-field spectroscopic kinematics from Gemini/NIFS that show a strong rotation (∼20 km s-1) and a velocity dispersion rise toward the center (37 km s-1). We combine the kinematic data with a mass model based on a two-component fit to HST ACS/HRC data of the cluster to estimate the mass of a putative BH. Our dynamical modeling suggests a >3σ detection of a BH component of (1σ uncertainties). The inferred stellar mass of the cluster is , consistent with previous estimates, thus the BH makes up 1.5% of its mass. We examine whether the observed kinematics are caused by a collection of stellar mass BHs by modeling an extended dark mass as a Plummer profile. The upper limit on the size scale of the extended mass is 0.56 pc (95% confidence), which does not rule out an extended mass. There is compelling evidence that B023-G078 is the tidally stripped nucleus of a galaxy with a stellar mass >109 M o˙, including its high-mass, two-component luminosity profile, color, metallicity gradient, and spread in metallicity. Given the emerging evidence that the central BH occupation fraction of >109 M o˙ galaxies is high, the most plausible interpretation of the kinematic data is that B023-G078 hosts a central BH. This makes it the strongest BH detection in a lower-mass (<107 M o˙) stripped nucleus, and one of the few dynamically detected intermediate-mass BHs
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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
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 Hubble Space Telescope (HST)/STIS spectroscopy to fit the star formation histories of the nuclei in these galaxies, and use these measurements to create local color–mass-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, M⊙ and M⊙ (3σ errors), respectively. However, for NGC 205, the improved models suggest the presence of a BH for the first time, with a best-fit mass of 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 lesssim10−5 of the Eddington rate. We also discuss the color–M/Leff 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/Leff relations than some previously published galaxy color–M/Leff relations