Browsing by Subject "bulge mass relation"
Now showing 1 - 3 of 3
- Results Per Page
- Sort Options
Item Is There A Black Hole In NGC 4382?(2011-11) Gultekin, Kayhan; Richstone, Douglas O.; Gebhardt, Karl; Faber, S. M.; Lauer, Tod R.; Bender, Ralf; Kormendy, John; Pinkney, Jason; Gebhardt, KarlWe present Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph observations of the galaxy NGC 4382 (M85) and axisymmetric models of the galaxy to determine mass-to-light ratio (Gamma(V)) and central black hole mass (M-BH). We find Gamma(V) = 3.74 +/- 0.1 M-circle dot/L-circle dot and M-BH = 1.3(-1.2)(+5.2) x 10(7) M-circle dot at an assumed distance of 17.9 Mpc, consistent with no black hole. The upper limit, M-BH < 9.6 x 10(7) M-circle dot (2 sigma) or M-BH < 1.4 x 10(8)(3 sigma), is consistent with the current M-sigma relation, which predicts M-BH = 8.8 x 10(7) M-circle dot at sigma(e) = 182 km s(-1), but low for the current M-L relation, which predicts M-BH = 7.8 x 10(8) M-circle dot at L-V = 8.9 x 10(10) L-circle dot, (V). HST images show the nucleus to be double, suggesting the presence of a nuclear eccentric stellar disk, analogous to the Tremaine disk in M31. This conclusion is supported by the HST velocity dispersion profile. Despite the presence of this non-axisymmetric feature and evidence of a recent merger, we conclude that the reliability of our black hole mass determination is not hindered. The inferred low black hole mass may explain the lack of nuclear activity.Item Nuclear Star Clusters From Clustered Star Formation(2011-03) Agarwal, Meghann; Milosavljevic, Milos; Agarwal, MeghannPhotometrically distinct nuclear star clusters (NSCs) are common in late-type disk and spheroidal galaxies. The formation of NSCs is inevitable in the context of normal star formation in which a majority of stars form in clusters. A young, mass-losing cluster embedded in an isolated star-forming galaxy remains gravitationally bound over a period determined by its initial mass and the galactic tidal field. The cluster migrates radially toward the center of the galaxy and becomes integrated in the NSC if it reaches the center. The rate at which the NSC grows by accreting young clusters can be estimated from empirical cluster formation rates and dissolution times. We model cluster migration and dissolution and find that the NSCs in late-type disks and in spheroidals could have assembled from migrating clusters. The resulting stellar nucleus contains a small fraction of the stellar mass of the galaxy; this fraction is sensitive to the high-mass truncation of the initial cluster mass function (ICMF). The resulting NSC masses are consistent with the observed values, but generically, the final NSCs are surrounded by a spatially more extended excess over the inward-extrapolated exponential (or Sersic) law of the outer galaxy. We suggest that the excess can be related to the pseudobulge phenomenon in disks, though perhaps not all of the pseudobulge mass assembles this way. Comparison with observed NSC masses can be used to constrain the truncation mass scale of the ICMF and the fraction of clusters suffering prompt dissolution. We infer truncation mass scales of less than or similar to 10(6) M-circle dot (greater than or similar to 10(5) M-circle dot) without (with 90%) prompt dissolution. Since the NSC assembly is collisionless and non-dissipative, no relation to the process responsible for central black hole assembly in more massive galaxies is expected.Item Orbit-Based Dynamical Models Of The Sombrero Galaxy (NGC 4594)(2011-09) Jardel, John R.; Gebhardt, Karl; Shen, Juntai T.; Fisher, David B.; Kormendy, John; Kinzler, Jeffry; Lauer, Tod R.; Richstone, Douglas; Gultekin, Kayhan; Jardel, John R.; Gebhardt, Karl; Kinzler, JeffryWe present axisymmetric, orbit-based models to study the central black hole (BH), stellarmass-to-light ratio (M/L), and dark matter (DM) halo of NGC 4594 (M104, the Sombrero Galaxy). For stellar kinematics, we use published high-resolution kinematics of the central region taken with the Hubble Space Telescope, newly obtained Gemini long-slit spectra of the major axis, and integral field kinematics from the Spectroscopic Areal Unit for Research on Optical Nebulae instrument. At large radii, we use globular cluster kinematics to trace the mass profile and apply extra leverage to recovering the DM halo parameters. We find a BH of mass M-center dot = (6.6 +/- 0.4) x 10(8) M-circle dot and determine the stellar M/L-I = 3.4 +/- 0.05 (uncertainties are the 68% confidence band marginalized over the other parameters). Our best-fit DM halo is a cored logarithmic model with asymptotic circular speed V-c = 376 +/- 12 km s(-1) and core radius r(c) = 4.7 +/- 0.6 kpc. The fraction of dark to total mass contained within the half-light radius is 0.52. Taking the bulge and disk components into account in our calculation of sigma(e) puts NGC 4594 squarely on the M-sigma relation. We also determine that NGC 4594 lies directly on the M-L relation.