J/ApJ/850/15 Mass-to-light ratios in low-mass early-type gal. (Pechetti+, 2017)
Detection of enhanced central mass-to-light ratios in low-mass early-type
galaxies: evidence for black holes?
Pechetti R., Seth A., Cappellari M., McDermid R., den Brok M., Mieske S.,
Strader J.
<Astrophys. J., 850, 15 (2017)>
=2017ApJ...850...15P 2017ApJ...850...15P
ADC_Keywords: Galaxies, nearby; Velocity dispersion; Stars, masses; Black holes
Keywords: galaxies: elliptical and lenticular, cD ; galaxies: formation ;
galaxies: kinematics and dynamics ; quasars: supermassive black holes
Abstract:
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*/M☉)<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.
Description:
In this study, we combine central velocity dispersion values of the
galaxies from the ATLAS3D survey (Cappellari+ 2011, J/MNRAS/413/813),
with high-resolution mass models derived from HST images to obtain the
central M/Ls of these galaxies.
We use the optical integral field spectroscopic observations for the
ATLAS3D galaxies taken from SAURON Integral Field Unit (IFU) on the
William Herschel Telescope (WHT).
We downloaded the HST imaging using the Hubble Legacy Archive,
including imaging from the Wide Field and Planetary Camera 2 (WFPC2),
Advanced Camera for Survey (ACS)/Wide Field Channel (WFC), ACS/High
Resolution Camera (HRC), and Wide Field Camera 3 (WFC3)/ultraviolet
and visible light (UVIS).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 35 237 Multi-Gaussian Expansion (MGE) parameters of all
27 galaxies
table2.dat 84 27 Mass-to-light ratios, central velocity dispersions
and HST imaging data of all 27 galaxies
table3.dat 105 27 Black hole masses, sphere of influence, ATLAS3D
and HST pixel sizes of all 27 galaxies
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
VII/237 : HYPERLEDA. I. Catalog of galaxies (Paturel+, 2003)
J/ApJ/621/673 : Line indices for 124 early-type galaxies (Thomas+, 2005)
J/ApJS/182/216 : Surface photometry of Virgo ellipticals (Kormendy+, 2009)
J/ApJ/714/25 : AMUSE-Virgo survey. II. (Gallo+, 2010)
J/MNRAS/413/813 : ATLAS3D project. I. (Cappellari+, 2011)
J/MNRAS/443/1151 : AIMSS Project. I. Compact Stellar Systems (Norris+, 2014)
J/ApJ/798/54 : "Under-massive" black hole candidates (Graham+, 2015)
J/ApJ/826/L32 : Black hole masses in megamaser disk galaxies (Greene+, 2016)
J/MNRAS/458/2221 : ATLAS3D Project. XXXI (Nyland+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy's name from LEDA,
Paturel+ (2003, VII/237)
11- 15 A5 --- Filt Filter in which the MGE components
are derived (F475W, F606W, F702W, F814W)
17- 22 F6.3 [Lsun/pc2] log(I) [-0.3/6] Surface brightness of each Gaussian
24- 29 F6.3 [arcsec] log(Sig) [-1.8/1.7] Width of each Gaussian
31- 35 F5.3 --- q [0.1/1] Axis ratio of each Gaussian
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name Galaxy's name from LEDA,
Paturel+ (2003, VII/237)
11- 15 F5.2 Msun/Lsun M/L-c [1.3/11.2] Central M/L derived using
JAM models (1)
17- 21 F5.2 Msun/Lsun b_M/L-c [0.9/10.2] Lower bound on M/L-cen (1)
23- 27 F5.2 Msun/Lsun B_M/L-c [1.7/12.1] Upper bound on M/L-cen (1)
29- 33 F5.2 Msun/Lsun M/L-dyn [0.9/10.5] Dynamical M/L derived from
outer parts of galaxies (2)
35- 35 I1 --- q_M/L-dyn [0/3]? Quality flag for M/L-dyn
(3=good) (3)
37- 40 F4.2 Msun/Lsun M/L-pop [1.3/4.3] Stellar population M/L derived
from nuclear spectra (4)
42- 47 F6.2 km/s Sigma-c [49.8/317.1] Central velocity dispersions
49- 53 F5.2 km/s e_Sigma-c [2/10.6] Uncertainty in σ-c
55- 55 I1 --- r_Sigma-c [1/2] Source for σ-c (5)
57- 65 A9 --- Camera HST camera used for mass models
67- 71 A5 --- Filt1 Filter used for mass models
(F475W, F606W, F702W, F814W)
73- 84 A12 --- Filt2 Filters used for colors
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Note (1): Central M/L derived using Jeans Anisotropic Models (JAM) models
(Cappellari+, 2008MNRAS.390...71C 2008MNRAS.390...71C). All the values are in SDSS r-band.
The Low and High values include the errors from velocity dispersions and
2.5% systematic error.
Note (2): Dynamical M/L derived by dynamically fitting the outer regions of
the galaxy (>2", within 1 Re). We assume an error of 6% on all of these
M/L as given in Cappellari+ (2013MNRAS.432.1862C 2013MNRAS.432.1862C).
Note (3): Quality flag for M/L-dyn as follows:
0 = low-quality JAM fit due to barred galaxies, dust or uncertain
deprojection due to a low inclination of the galaxy.
3 = a good JAM fit to the data.
Note (4): Stellar population M/L derived by fitting the ATLAS3D central
spectrum of a galaxy assuming a Kroupa IMF. We assume an error of 6% on
all of these M/L as given in Cappellari+ (2013MNRAS.432.1862C 2013MNRAS.432.1862C).
Note (5): Central velocity dispersions derived from reference as follows:
1 = ATLAS3D kinematic data;
2 = van den Bosch+ (1998MNRAS.293..343V 1998MNRAS.293..343V).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name Galaxy's name from LEDA,
Paturel+ (2003, VII/237)
11- 15 F5.3 km/s sigma-e [1.7/2.4] Effective stellar velocity
dispersion (6)
17- 22 F6.3 [Msun] logM* [9.8/10.6] Galaxy mass, log,
Cappellari+ (2013MNRAS.432.1709C 2013MNRAS.432.1709C)
24- 31 E8.2 Msun MBH-dyn [0/778000000] Best-fit BH masses using
(M/L)-dyn (7)
33- 40 E8.2 Msun b_MBH-dyn [0/557000000] Lower bound on MBH-dyn (7)
42- 49 E8.2 Msun B_MBH-dyn [26400000/998000000] Upper bound on MBH-dyn (7)
51- 58 E8.2 Msun MBH-pop [0/1290000000] Best-fit BH masses using
(M/L)-pop (8)
60- 67 E8.2 Msun b_MBH-pop [0/1070000000] Lower bound on MBH-pop (8)
69- 76 E8.2 Msun B_MBH-pop [14600000/1510000000] Upper bound on MBH-pop (8)
78- 85 E8.2 Msun MBH-pre [173000/545000000] Expected BH masses from
MBH-σ (9)
87- 92 F6.2 pc rSOI [7.2/263.7] Sphere of Influence predicted using
MBH-dyn (10)
94- 99 F6.2 pc Pixel1 [50/187] Pixel size, ATLAS-3D (11)
101-105 F5.2 pc Pixel2 [2.6/11.1] Pixel size, HST (12)
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Note (6): Effective stellar velocity dispersion adopted from
Cappellari+ (2013MNRAS.432.1709C 2013MNRAS.432.1709C). They were calculated by co-adding all
SAURON spectra within an effective ellipse of area πRe2, where Re is
the effective radius.
Note (7): Best-fit BH masses derived using (M/L)-dyn as the true stellar M/L
in our JAM models.
Note (8): Best-fit BH masses derived using (M/L)-pop as the true stellar M/L
in our JAM models.
Note (9): Expected BH masses from the MBH-σ relationship from
Equation∼2. Galaxies NGC4458 and NGC4660 are highly significant
detections.
Note (10): Sphere of influence calculated from the derived BH masses
(MBH-dyn) using rSOI=G*MBH/σ-e2.
Note (11): Pixel size of ATLAS^3D kinematic data for our sample of galaxies
that were derived using the distances from
Cappellari+ (2011, J/MNRAS/413/813).
Note (12): Pixel size of HST images for our sample of galaxies that were
derived using the distances from Cappellari+ (2011, J/MNRAS/413/813).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Jun-2018