2002/02/28 by Michele Cappellari, M. Cappellari, E. K. Verolme +9 · 3 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics #Black hole (networking) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Milky Way #Physics #Satellite galaxy #Star formation #Stellar dynamics #Stellar kinematics #Stellar mass #astro-ph
paper · pdf · doi:10.1086/342653
published as Astrophys.J. 578 (2002) 787 · 51 pages, LaTeX with 19 PostScript figures. Revised version, with three new figures and data tables. To appear in The Astrophysical Journal, 578, 2002 October 20
arxiv created 2002/06/27 · openalex publication_date 2002/10/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The E3 giant elliptical galaxy IC 1459 is the prototypical galaxy with a fast counterrotating stellar core. We obtained one Hubble Space Telescope ( HST ) Space Telescope Imaging Spectrograph (STIS) long-slit spectrum along the major axis of this galaxy and Cerro Tololo Inter-American Observatory (CTIO) spectra along five position angles. The signal-to-noise ratio (S/N) of the ground-based data is such that also the higher order Gauss-Hermite moments ( h 3 - h 6 ) can be extracted reliably. We present self-consistent three-integral axisymmetric models of the stellar kinematics, obtained with Schwarzschild's numerical orbit superposition method. The available data allow us to study the dynamics of the kinematically decoupled core (KDC) in IC 1459, and we find that it consists of stars that are well separated from the rest of the galaxy in phase space. In particular, our study indicates that the stars in the KDC counterrotate in a disk on orbits that are close to circular. We estimate that the KDC mass is ≈0.5% of the total galaxy mass or ≈3 × 10 9 M ☉ . We estimate the central black hole (BH) mass M BH of IC 1459 independently from both its stellar and its gaseous kinematics. Although both tracers rule out models without a central BH, neither yields a particularly accurate determination of the BH mass. The main problem for the stellar dynamical modeling is the fact that the modest S/N of the STIS spectrum and the presence of strong gas emission lines preclude measuring the full line-of-sight velocity distribution (LOSVD) at HST resolution. The main problem for the gasdynamical modeling is that there is evidence that the gas motions are disturbed, possibly as a result of nongravitational forces acting on the gas. These complications probably explain why we find rather discrepant BH masses with the different methods. The stellar kinematics suggest that M BH = (2.6 ± 1.1) × 10 9 M ☉ (3 σ error). The gas kinematics suggests that M BH ≈ 3.5 × 10 8 M ☉ if the gas is assumed to rotate at the circular velocity in a thin disk. If the observed velocity dispersion of the gas is assumed to be gravitational, then M BH could be as high as ~1.0 × 10 9 M ☉ . These different estimates bracket the value M BH = (1.1 ± 0.3) × 10 9 M ☉ predicted by the M BH -σ relation. It will be an important goal for future studies to attempt comparisons of BH mass determinations from stellar and gaseous kinematics for other galaxies. This will assess the reliability of BH mass determinations with either technique. This is essential if one wants to interpret the correlation between the BH mass and other global galaxy parameters (e.g., velocity dispersion) and in particular the scatter in these correlations (believed to be only ~0.3 dex).