TY - JOUR
T1 - Detection of enhanced central mass-to-light ratios in low-mass early-type galaxies
T2 - Evidence for Black Holes?
AU - Pechetti, Renuka
AU - Seth, Anil
AU - Cappellari, Michele
AU - McDermid, Richard
AU - Brok, Mark Den
AU - Mieske, Steffen
AU - Strader, Jay
PY - 2017/11/20
Y1 - 2017/11/20
N2 - We present dynamical measurements of the central mass-to-light ratio (M/L) of a sample of 27 low-mass early-type ATLAS3D galaxies. We consider all ATLAS3D galaxies with 9.7 < log(M∗/MΘ) < 10.5 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 ATLAS3D data to obtain a central dynamical M/L estimate. These central dynamical M/Ls are higher than dynamical M/Ls 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 3.3σ. We show that the enhancement in the central M/L is best described either by the presence of black holes in these galaxies or by radial initial mass function 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 suggest significantly overmassive black holes, while in most others only upper limits are obtained. We also show that the level of M/L 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.
AB - We present dynamical measurements of the central mass-to-light ratio (M/L) of a sample of 27 low-mass early-type ATLAS3D galaxies. We consider all ATLAS3D galaxies with 9.7 < log(M∗/MΘ) < 10.5 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 ATLAS3D data to obtain a central dynamical M/L estimate. These central dynamical M/Ls are higher than dynamical M/Ls 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 3.3σ. We show that the enhancement in the central M/L is best described either by the presence of black holes in these galaxies or by radial initial mass function 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 suggest significantly overmassive black holes, while in most others only upper limits are obtained. We also show that the level of M/L 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.
KW - cD
KW - elliptical and lenticular
KW - galaxies
KW - Galaxies
KW - galaxies: formation
KW - kinematics and dynamics
KW - Quasars: supermassive black holes
UR - http://www.scopus.com/inward/record.url?scp=85037706820&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/aa9021
DO - 10.3847/1538-4357/aa9021
M3 - Article
VL - 850
SP - 1
EP - 16
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
ER -