Archived Data
Current Research Projects
1. Galaxy Nuclear Dynamics
Using HST observations, the STIS/GTO team and the Nuker team are seeking to determine the implications of the correlation between the masses of black holes in galactic nuclei with the properties of the host galaxies within which they are embedded. The plot below shows the relationship between black hole mass and host galaxy luminosity and velocity dispersion at the effective radius. The plot on the right is especially remarkable because it shows a very tight correlation between black hole mass and the shape of the host galaxy's gravitational potential. This implies that the major events in the formation of galaxy spheroids also control the growth of the galaxy's black hole. Supermassive black holes are therefore fundamentally important components in the centers of massive galaxies. They are not just rare, exotic objects that perhaps they were once thought to be.
2. The Supermassive Black Hole Paradigm in Radio-Quiet AGNs
By mapping the stellar dynamics in the nuclei of Seyfert galaxies and LINERs using HST, we are measuring the masses of nuclear black holes to compare with the masses derived from other techniques such as the kinematics of nuclear gas disks and reverberation mapping. The main uncertainty in these other techniques is that the motion of gas in a galactic nucleus can be affected by non-gravitational forces, whereas stars reliably map the central gravitational potential. Agreement between these three methods could therefore validate methods relying on gas dynamics, implying that these methods could be extended to higher redshift where galaxies are too distant to employ stellar dynamics.
3. Masses and Spins of Black Holes in Seyfert Galaxies
Using HST, Andrew Wilson (Dept. of Astronomy, U. Maryland-College Park), Gary Bower, and Pierre Ferruit (Centre de Recherche Astronomique de Lyon) have discovered a nuclear gas disk in MCG-6-30-15. We have obtained a STIS spectrum of this gas disk, and we are analyzing the gas kinematics to determine the mass of its nuclear black hole. This galaxy is important because it is a type 1 Seyfert nucleus with a very broad Fe K-alpha emission profile at 6.4 keV. The profile for this galaxy is the best-studied case among about 20 known cases. From this profile, attempts have been made to measure the metric (or spin) of its black hole. This could be the first black hole for which both the mass and spin will be measured. Knowledge of both quantities in an AGN could have a profound impact on several issues, including the geometry and efficiency of accretion, the formation of radio jets, and the evolutionary history of the angular momentum of the black hole itself.
4. The Kinematics of Seyfert Galaxy Narrow-Line Regions
Gary Bower is a member of a team led by D. Michael Crenshaw (Catholic University of America and NASA/GSFC) to analyze the kinematics of gas clouds near the nucleus of Seyfert galaxies using slitless spectroscopy with HST/STIS. This technique provides entire spatial coverage of the NLR in a short exposure, rather than being limited to a single axis as is the case for slit spectroscopy. The main goal of this program is to understand the dynamical effects of radio jets and winds outflowing from the central engine.
Links to other Astronomy sites:
NOAO
KPNO
CTIO
NASA/GSFC
AURA
NSF/Physical Sciences
AAS
ESO
My lovely wife
Donna Bower,
who is the Sr. Business Manager at the
Dept.
of Aerospace and Mechanical Engineering at the
University of Arizona.
Other useful links:
Last modified: 2 April 2001
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