J/ApJ/850/15 Mass-to-light ratios in low-mass early-type gal. (Pechetti+, 2017)
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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
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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 ATLAS^3D^ galaxies. We
    consider all ATLAS^3D^ galaxies with 9.7<log(M*/M_{sun}_)<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 ATLAS^3D^ 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
    3.3{sigma}. 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 ATLAS^3D^ 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
    ATLAS^3D^ 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, ATLAS^3D^
                             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
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   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 {sigma}-c
  55- 55 I1     ---       r_Sigma-c  [1/2] Source for {sigma}-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). 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).
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 ATLAS^3D^ 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).
Note (5): Central velocity dispersions derived from reference as follows:
    1 = ATLAS^3D^ kinematic data;
    2 = van den Bosch+ (1998MNRAS.293..343V).
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Byte-by-byte Description of file: table3.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 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)
  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-{sigma} (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). They were calculated by co-adding all
    SAURON spectra within an effective ellipse of area {pi}Re^2^, 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-{sigma} 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/{sigma}-e^2^.
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

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(End)                    Prepared by [AAS], Emmanuelle Perret [CDS]  19-Jun-2018