1. Black Holes in Nearby Galaxies Claire Max NGAO Team Meeting March 7, 2007

2. Outline General principles of black hole mass measurements Potential benefits of NGAO, and science requirements (first cut)

3. General Principles Equate kinetic energy of rotation with gravitational potential energy: Spatial resolution matters: need to resolve R’s as small as possible. Width of PSF gives an upper limit on black hole mass (can’t “see” any closer). PSF stability matters: R must be well determined

4. Estimate radius of black hole’s “gravitational sphere of influence” Equate kinetic energy, gravitational potential energy Example: 200 km/sec, 2 x 10 8 solar masses, a BH = 50 pc Within this distance from the black hole, gas and stars “feel” the black hole’s gravity To measure the black hole’s mass, must be able to resolve a BH Keck AO today resolves 30 pc at z = 0.02, 50 pc at z = 0.05. NGAO will resolve even smaller distances (e.g. using Ca triplet at 8498 Å, 8542 Å, 8662 Å).

5. Two general types of measurements: 1) Keplerian circular velocities Assume material is in isotropic, circular Keplerian rotation around the black hole. Measure radial velocities (component of velocity in and out of plane of the sky). Examples: water masers in NGC 4258 (mm wave); orbits of individual stars in Galactic Center

6. Two general types of measurements: 2) Velocity dispersions Measure velocity dispersion as function of position (e.g. Sauron IFU) Issues: –Stellar velocity dispersions in elliptical galaxies: velocities are not isotropic. Need to model the orbits in some detail. Challenging. –Gas velocity dispersions: gas velocity fields are often quite disordered due to non-gravitational forces. –Increased spatial resolution helps in both cases. Ca triplet helps a lot. NGC 3377, Sauron IFU

7. Additional Considerations May need to use IFU together with set of long-slit spectra, to unravel gravitational field of the larger scale galaxy Alternatively, can use a wider field mode of the IFU Necessary for non-ideal galaxies: –Kinematically decoupled cores –Bars –Warps –Merger remnants 40 arc sec

8. NGAO benefits and science requirements Benefits of using Calcium Triplet (8500 - 8660 Å) with decent wavefront error –At a given distance from us, can measure lower black hole masses –At given black hole mass, can detect BH in more distant galaxies Key performance metrics: –Low wavefront error –Operation at 8500 Å –Stable PSFs

9. Science and Instrument Requirements AO system: –Wavefront error low enough to give “good” performance at I band (needs to be quantified in simulations, work is in progress) –Stable PSF in near IR (needs to be quantified further) Instruments: single IFUs –I band out to K band –Field of view: Narrow mode (a few arc sec) to resolve gravitational sphere of influence. Possibly a wide mode as well (up to 30 arc sec) to map galaxy kinematics on larger scales. –Velocity resolution not a key driver: a few 10’s of km/sec (OSIRIS today can do this). (Need to quantify requirement.) Instruments: long slit spectroscopy –Key if wide field mode of IFU is not available –Slit length up to 30 arc sec, configurable at arbitrary angles