Kinematics of disk galaxies with known masses of their supermassive black holes. Observations

Astronomy Reports (Impact Factor: 0.94). 07/2010; 54(7):578-589. DOI: 10.1134/S1063772910070024


This is the first paper in a project aimed at analyzing relations between the masses of supermassive black holes or nuclear
clusters in galaxies and the kinematic features of the host galaxies. We present long-slit spectroscopic observations of galaxies
obtained on the 6-m telescope of the Special Astrophysical Observatory using the SCORPIO focal reducer. Radial profiles of
the line-of-sight velocities and velocity dispersions of the stellar populations were obtained for seven galaxies with known
masses of their supermassive black holes (Mkn 79, Mkn 279, NGC 2787, NGC 3245, NGC 3516, NGC 7457, and NGC 7469), and also
for one galaxy with a nuclear cluster (NGC 428). Velocity profiles of the emitting gas were obtained for some of these galaxies
as well. We present preliminary galactic rotation curves derived from these data.

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    ABSTRACT: Stellar velocity dispersion data at galactocentric distance of two disk radial scale lengths (R = 2h), available in the literature allowed us to determine the upper limits of disk local surface densities at a given R and (by extrapolation) total masses of disks proceeding from the marginal gravitational stability condition. A comparison of the obtained disk masses with the photometric estimates based on the stellar population models indicates the absence of strong dynamical overheating inmost spiral galaxies and hence the absence of significant major merging events, which were able to heat dynamically the inner parts of disks. The same conclusion is valid for some of S0 galaxies. However, a significant part of the latter possesses stellar velocity dispersion, which exceeds the threshold value needed for gravitational stability. Dynamically overheated disks occur both among paired and isolated galaxies. Disk to total mass ratios within R = 4h found for marginally stable disks in most cases lie in the range 0.5–0.8 with the absence of the clearly defined correlation of this ratio with color index or morphological type. Keywordsgalactic disks–gravitational stability
    Full-text · Article · Jun 2011 · Astronomy Letters
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    ABSTRACT: In this paper, we present the results of a wide-field imaging study of the globular cluster (GC) system of the field S0 galaxy NGC 7457. To derive the global properties of the GC system, we obtained deep BVR images with the WIYN 3.5 m telescope and Minimosaic Imager and studied the GC population of NGC 7457 to a projected radius of ~30 kpc. Our ground-based data were combined with archival and published Hubble Space Telescope data to probe the properties of the GC system close to the galaxy center and reduce contamination in the GC candidate sample from foreground stars and background galaxies. We performed surface photometry of NGC 7457 and compared the galaxy's surface brightness profile with the surface density profile of the GC system. The profiles have similar shapes in the inner 1' (3.9 kpc), but the GC system profile appears to flatten relative to the galaxy light at larger radii. The GC system of NGC 7457 is noticeably elliptical in our images; we measure = 0.66 ± 0.14 for the GC distribution, which is consistent with our measured ellipticity of the galaxy light. We integrated the radial surface density profile of the GC system to derive a total number of GCs, N GC = 210 ± 30. The GC specific frequencies normalized by the galaxy luminosity and mass are SN = 3.1 ± 0.7 and T = 4.8 ± 1.1, respectively. Comparing the derived GC system properties and other empirical data for NGC 7457 to S0 formation scenarios suggests that this field S0 galaxy may have formed in an unequal-mass merger.
    Full-text · Article · Jun 2011 · The Astrophysical Journal
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    ABSTRACT: The statistical relation between the masses of supermassive black holes (SMBHs) in disk galaxies and the kinematic properties of their host galaxies is analyzed. Velocity estimates for several galaxies obtained earlier at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and the data for other galaxies taken from the literature are used. The SMBH masses correlate well with the rotational velocities at a distance of R ≈ 1 kpc, V 1, which characterize the mean density of the central region of the galaxy. The SMBH masses correlate appreciably weaker with the asymptotic velocity at large distances from the center and the angular velocity at the optical radius R 25. We have found for the first time a correlation between the SMBH mass and the total mass of the galaxy within the optical radius R 25, M 25, which includes both baryonic and “dark” mass. The masses of the nuclear star clusters in disk galaxies (based on the catalog of Seth et al.) are also related to the dynamical mass M 25; the correlations with the luminosity and rotational velocity of the disk are appreciably weaker. For a given value of M 25, the masses of the central cluster are, on average, an order of magnitude higher in S0-Sbc galaxies than in late-type galaxies, or than the SMBH masses. We suggest that the growth of the SMBH occurs in the forming “classical” bulge of the galaxy over a time < 109 yr, during a monolithic collapse of gas in the central region of the protogalaxy. The central star clusters form on a different time scale, and their stellar masses continue to grow for a long time after the growth of the central black hole has ceased, if this process is not hindered by activity of the nucleus.
    No preview · Article · Jul 2011 · Astronomy Reports
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