QUIET BHs in GALACTIC NUCLEI Random motions of stars measure random speeds, look for cusps example: Milky Way nucleus, M87 Organized rotation of stars example: Andromeda Galaxy (30 million ) Rotation of gas clouds example: M87 Disk traced in masers example: NGC 4258 (36 million ) ANDROMEDA GALAXY - M31 BH mass: 30 million Suns M32: BH=3million ANDROMEDA GALAXY - M31 Estimated BH mass: 30 million solar masses SOMBRERO GALAXY - 1/2 billion solar masses Sombrero Galaxy M billion solar masses NGC 4258 BH = 36 million Suns MOST ACCURATE MEASUREMENT: MASER= M icrowave A mplification by S timulated E mission of R adiation MASERS IN NGC 4258 NGC 4258: 36 million solar masses IS BH MASS RELATED TO GALAXY BULGE MASS? Claim: Is this correlation real or an artifact of observational limitations? WHY QUIET? Need supply of gas for activity need ~ 1 solar mass/yr for quasar/luminous Seyfert Probably comes from: interstellar debris gas dumped into nucleus during galaxy mergers Gas more plentiful in early stages of galaxy evolution? Accounts for prevalence of quasars at high redshift? THE MILKY WAY million solar masses Infrared picture of the Galaxys Center (Genzel et al., Germany) From Ghez et al Prof. Andrea Ghez, UCLA SgrA* Chandra image (2/00) ENERGY CHAIN IS BROKEN: GRAVITY MOTION HEAT RADIATION (X-rays, UV) matter swirling inward friction THE NEW ENERGY CHAIN: GRAVITY MOTION HEAT Are black holes fussy eaters? ISSUES OF BH FORMATION/GROWTH Insignificant growth once formed? Did BHs and galaxies form together? Infrequent major mergers? rapid spin or Frequent minor mergers? slow spin Grow by swallowing gas? luminous (Were all galaxies once quasars?) or Grow by swallowing stars? less luminous? BLACK HOLE BINARIES Galaxy mergers black hole binaries How long does it take them to merge? Do we see any galaxies with two active nuclei? FLARES FROM TIDALLY SHREDDED STARS Must occur for BHs < a billion solar masses more massive stars swallowed whole Estimate once per 10,000 yrs for Milky Way nucleus conditions We should see one per year if we study more than 10,000 MW-like galaxies but what do they look like?