2004 Mar 25 Sgr A* at 30 Must Sgr A* be a Super-Massive Black Hole? Mark J. Reid Harvard-Smithsonian CfA Andreas Brunthaler MPIfR/JIVE

2004 Mar 25 Sgr A* at 30 Sgr A* Where is it? Does it move? Karl Menten Reinhard Genzel Thomas Ott Rainer Schoedel Andreas Eckart Andreas Brunthaler

2004 Mar 25Sgr A* at 30 Discovery of Galactic Center Shapley (1918): Shapley (1918): Globular Clusters “point” to Globular Clusters “point” to Galactic Center Galactic Center R o = 13 kpc R o = 13 kpc

2004 Mar 25Sgr A* at 30 Early Radio Observations Piddington & Minnett (1951); Haddock, Mayer & Sloanaker (1954); McGee & Bolton (1954) Sgr A

2004 Mar 25Sgr A* at 30 History of Sgr A* Balick & Brown (1974) Discover Sgr A*: Balick & Brown (1974) Discover Sgr A*: “Intense Sub-Arcsecond Structure” “Intense Sub-Arcsecond Structure” Lo et al (1985) Sgr A* < 20 AU Lo et al (1985) Sgr A* < 20 AU Backer et al (1993) < 3 AU Backer et al (1993) < 3 AU Rogers et al (1994) < 1 AU Rogers et al (1994) < 1 AU

2004 Mar 25Sgr A* at 30 VLA Images of Sgr A J-H Zhao Sgr A*

2004 Mar 25Sgr A* at 30 IR Image of GC 1-3 um image Where is Sgr A*?

2004 Mar 25Sgr A* at 30 6 Questions: Is Sgr A* at the center of the stellar cluster? Is Sgr A* at the center of the stellar cluster? Is the stellar cluster tied to Sgr A*? Is the stellar cluster tied to Sgr A*? Is Sgr A* at the dynamical center of the Galaxy? Is Sgr A* at the dynamical center of the Galaxy? Does Sgr A* have a peculiar motion? Does Sgr A* have a peculiar motion? Does Sgr A* have all the mass sensed by stars? Does Sgr A* have all the mass sensed by stars? Could exotic dark matter dominate the G. C. mass? Could exotic dark matter dominate the G. C. mass?

2004 Mar 25Sgr A* at 30 Radio/IR frame alignment Use stars visible in both Radio and IR Use stars visible in both Radio and IR Red Giants with masers Red Giants with masers Compare Radio and IR positions: Compare Radio and IR positions: Solve for IR plate scale & rotation Solve for IR plate scale & rotation Align IR with Radio to find Sgr A* Align IR with Radio to find Sgr A*

2004 Mar 25Sgr A* at 30 VLA positions for stars 7 SiO masers <12” of SgrA* ~0.1 – 1 Jy Positions to ~ 3 mas mas/yr motions in few years

2004 Mar 25Sgr A* at 30 VLBA proper motions (Reid et al 2003) Sub-mas positions mas/yr motions in 3 months

2004 Mar 25Sgr A* at 30 Stellar positions & motions 7 SiO maser stars positions ~ 3 mas motions ~ 100 km/s

2004 Mar 25Sgr A* at 30 VLT with Adaptive Optics “3-color”: u m 8.2 m VLT telescope CONICA (IR camera) NAOS (adaptive optics) 60 mas resolution

2004 Mar 25Sgr A* at 30 Where was Sgr A* in mas accuracy Between stars: S1, S2 & S3 Sgr A* < 9 mJy

2004 Mar 25Sgr A* at 30 Where was Sgr A* in 2002 Sgr A* position: 10 mas Reid et al (2003) Star “S2” seen at pericenter passage V ~ 5000 km/s !! Orbit determined Schoedel et al (2002)

2004 Mar 25Sgr A* at 30 S2’s orbit 15 year period e = 0.87 Pericenter only 15 mas from Sgr A* ! (120 AU = 17 l-h) (Schoedel et al 2002)

2004 Mar 25Sgr A* at 30 Stellar Orbits 6 stars with orbits Enclosed mass: 4 x 10 6 M sun < 100 AU radius Schoedel etal 02,03 Ghez et al 03 Sgr A* within 100 AU Reid et al 03

2004 Mar 25Sgr A* at 30 Question 1: Is Sgr A* at the center of the stellar cluster? Is Sgr A* at the center of the stellar cluster? Yes… to better than 10 mas Yes… to better than 10 mas

2004 Mar 25Sgr A* at 30 Radio/IR frame alignment Compare Radio(SiO) and IR positions: Compare Radio(SiO) and IR positions: Solve for IR plate scale & rotation Solve for IR plate scale & rotation Align IR with Radio to find Sgr A* Align IR with Radio to find Sgr A* Compare Radio(SiO) and IR velocities: Compare Radio(SiO) and IR velocities: SiO velocities relative to Sgr A* SiO velocities relative to Sgr A* Tie IR velocities to Sgr A* Tie IR velocities to Sgr A*

2004 Mar 25Sgr A* at 30 Velocity Alignment East,North proper motions in mas/yr East,North proper motions in mas/yr Star Radio Infrared Difference IRS , , (0.7),+1.9 (1.2) IRS , , (1.0),-0.9 (3.5) IRS , , (0.5),-2.0 (0.8) IRS , , (0.4),+0.1 (1.0) Unweighted mean (sem) +0.8 (0.8),-0.25(1.0) 1 mas/yr ~ 40 km/s Central star cluster moves with Sgr A* to ~70 km/s

2004 Mar 25Sgr A* at 30 Question 2: Is the stellar cluster tied to Sgr A*? Is the stellar cluster tied to Sgr A*? Yes… to better than 70 km/s Yes… to better than 70 km/s

2004 Mar 25Sgr A* at 30 Proper Motion of Sgr A* Sun’s Galactic Orbit: 225 Myr period kpc = 6 mas/yr

2004 Mar 25Sgr A* at 30 Sgr A*’s apparent motion Relative to 2 Quasars Sun’s Galactic Orbit: 220 km/s at 8.0 kpc = 6 mas/yr in Gal plane (Kassim, Frail & Briggs)

2004 Mar 25Sgr A* at 30 Project History 1979: Proposal to US VLBI Network 1979: Proposal to US VLBI Network –“To Study Feasibility of Detecting Proper Motion of the Galactic Center” –15 GHz; OVRO, HRAS, GB, Haystack –Failed: Scatter broadened Sgr A* Scatter broadened Sgr A* Limited sensitivity Limited sensitivity Needed VLBA ! Needed VLBA !

2004 Mar 25Sgr A* at 30 Sgr A*’s Apparent Motion Moves mostly along Galactic Plane Slight deviation from V SUN Gal Plane Best Fit

2004 Mar 25Sgr A* at 30 Eastward Motion Sgr A* drifts smoothly QSOs don’t move

2004 Mar 25Sgr A* at 30 Northward Motion Sgr A* drifts smoothly QSO don’t move NB: error bars larger than eastward positions

2004 Mar 25Sgr A* at 30 Sgr A* motion Galactic Coords: Motion in Galactic Plane:  o /R o = /- 0.9 km/s/kpc Compare to (A-B)/R o = /- 0.9 km/s/kpc (Feast & Whitelock 1997) Motion out of Galactic Plane: Very small…

2004 Mar 25Sgr A* at 30 Question 3: Is Sgr A* at the dynamical center of the Galaxy? Is Sgr A* at the dynamical center of the Galaxy? Yes… to within our knowledge of  o /R o Yes… to within our knowledge of  o /R o

2004 Mar 25Sgr A* at 30 Sgr A* motion toward Galactic Pole Solar Motion 7 km/s Sgr A*s peculiar motion /- 0.8 km/s

2004 Mar 25Sgr A* at 30 Question 4: Does Sgr A* have a peculiar motion? Does Sgr A* have a peculiar motion? No … less than 1.6 km/s (out of Plane) No … less than 1.6 km/s (out of Plane)

2004 Mar 25Sgr A* at 30 Estimating Sgr A*’s Mass Chatterjee, Hernquist & Loeb (2002) Chatterjee, Hernquist & Loeb (2002) mass estimator:  mass estimator:  M lim ~ G M(R) m / R V 2 M lim ~ G M(R) m / R V 2 Set M(R) = 4 x 10 6 for R = 100 AU Set M(R) = 4 x 10 6 for R = 100 AU m = 3 M sun m = 3 M sun V < 1.6 km/s V < 1.6 km/s get M > 3.5 x 10 6  sun get M > 3.5 x 10 6  sun

2004 Mar 25Sgr A* at 30 If Sgr A* is not a SMBH… 1) Tight binary black hole Decays by Grav Radiation 2) Theoretically “flexible” eg, density power law:  r 

2004 Mar 25Sgr A* at 30 If Sgr A* is not a SMBH… V >> 1 km/s for any dark matter distribution, unless M dark ~ 0 Would be easily observed, except…

2004 Mar 25Sgr A* at 30 If Sgr A* is not a SMBH… Accel >> cm/s 2 Would be easily observed, EXCEPT…

2004 Mar 25Sgr A* at 30 Sgr A* “orbital period” Measured V (& A) not sensitive to P<16 yrs Essentially all dark mass distributions give P<16 yrs But still detectable …

2004 Mar 25Sgr A* at 30 Sgr A* orbital excursions Would easily see excursions > 4 AU Sgr A* either i) ~4 x 10 6 M sun ii) “bound” within 4 AU 2 AU

2004 Mar 25Sgr A* at 30 Stars orbiting Sgr A* Consider star orbiting a massive object: MV = mv Add in large number of stars & random fluctuations give: MV 2 ~ mv 2

2004 Mar 25Sgr A* at 30 Effect of Bound Stars on Sgr A* Recipe: 1. Put 4 x 10 6 stars in computer 2. Place SMBH/dark mass at center of mass of system 3. Solve Kepler’s Eq for each star 4. Calculate COM after 8 years 5. Determine position & then velocity of SMBH 6. Repeat as needed to get V rms Standard IMF eccentricities from 0 to 0.99

2004 Mar 25Sgr A* at 30 Sgra A* must be massive… Compare simulated systems with trial measurements Sgr A*’s mass (M sun ) Best est.: 2 x % conf.: 0.3 x 10 6 Very conservative calc.: Ignored effects of DM, clumping, stars > 4 pc

2004 Mar 25Sgr A* at 30 Sgra A* must be massive… Compare simulated systems with trial measurements Sgr A*’s mass (M sun ) Maximum liklihood lower limit: 1.2 x % confidence lower limit: 0.2 x 10 6 Very conservative calculation; ignored effects of… Possible dark cluster of stellar remnants, Stellar clumping/collective effects, Stars beyond 2 pc

2004 Mar 25Sgr A* at 30 Effects of Stellar Remnants 10% of mass <100 AU in stellar remnants Plummer distribution of Mouawad et al 2004 Vz(SgrA*) > 0.3 km/s for 0.01 < a < 2 pc

2004 Mar 25Sgr A* at 30 Question 5: Does Sgr A* have all the gravitational mass? Does Sgr A* have all the gravitational mass? Yes … well, more than ~30% of mass Yes … well, more than ~30% of mass

2004 Mar 25Sgr A* at 30 Exotic Dark Matter ? Could exotic dark matter dominate the G.C. mass? Could exotic dark matter dominate the G.C. mass? Not likely … less than 30% of mass & dropping Not likely … less than 30% of mass & dropping Tied radiative source to the mass… Tied radiative source to the mass… “Fermion ball” can’t give Sgr A*’s SED “Fermion ball” can’t give Sgr A*’s SED First time ~10 6 M sun tied directly to an AGN First time ~10 6 M sun tied directly to an AGN

2004 Mar 25Sgr A* at 30 6 Questions: 6 Answers Is Sgr A* at the center of the stellar cluster? Is Sgr A* at the center of the stellar cluster? Yes … to within 10 milli-arcsec Yes … to within 10 milli-arcsec Is the stellar cluster tied to Sgr A*? Is the stellar cluster tied to Sgr A*? Yes … to within 70 km/s Yes … to within 70 km/s Is Sgr A* at the dynamical center of the Galaxy? Is Sgr A* at the dynamical center of the Galaxy? Yes … to within our knowledge of  o/Ro Yes … to within our knowledge of  o/Ro Does Sgr A* have a peculiar motion? Does Sgr A* have a peculiar motion? No … less than 2 km/s No … less than 2 km/s Does Sgr A* have all the mass sensed by stars? Does Sgr A* have all the mass sensed by stars? Yes … (>30%) Yes … (>30%) Could exotic dark matter dominate the G. C. mass? Could exotic dark matter dominate the G. C. mass? No … (<70% and dropping; can’t give observed SED) No … (<70% and dropping; can’t give observed SED)

2004 Mar 25Sgr A* at 30 Must Sgr A* be a SMBH? Object Density Method Mass & Radius (M sun /pc 3 ) (M sun /pc 3 ) M 87 2 x 10 6 HST: 3x10 9 M sun in 7 pc NGC x 10 9 VLBA : H 2 O 3x10 7 M sun in 0.1 pc Sgr A* 8 x S2’s orbit 4x10 6 M sun in pc Sgr A* 2 x Sgr A*s p.m. 1x10 6 M sun in 0.5 AU SMBH 2 x R sch 4x10 6 M sun in 0.08 AU VLBI (eg, 1 mm -> 20 uas 10 8 kpc

2004 Mar 25Sgr A* at 30 The Utimate Proof/Prize Image SMBH with resolution ~R Sch Show all of the mass is contained within ~3R Sch See how accretion disk, black hole, and jets work