Rainer Schödel & Andreas Eckart Universität zu Köln. Stellar Dynamics Star Formation/Young Stars

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1 Rainer Schödel & Andreas Eckart Universität zu Köln The Center of the Milky Way Stellar Dynamics Star Formation/Young Stars Variable emission from Sgr A*

2 e.g. Eckart & Genzel (1996); Ghez et al. (1998); Genzel et al. (2000); Eckart et al. (2002); Schödel et al. (2003) Proper Motions of Stars near Sgr A* April 1994 Juli 2001 N E 10 (0.39 pc)

3 The orbit of S2 proper motion data + spectroscopic line of sight velocity Orbital Elements + BH Mass/Location + GC Distance! 1. M 0 = 3.6 ± 0.6x10 6 M sol 2. R 0 = 7.9 ± 0.4 kpc 1st direct measurement P = 15.6 yr 50mas 2 light days 3. Center of attraction within < 0.16 mpc of formal radio position of Sgr A* 4. Closest approach to Sgr A*: 0.55 mpc or 15.6 lh Schödel et al. (2002, 2003); Ghez et al. (2003); Eisenhauer et al. (2003)

4 Weighing the central cusp Non-Keplerian orbit fitting: <10% of dark mass is extended Mouawad et al., 2004, astro-ph/

5 The Nature of SgrA*

6 Cluster of Dark Objects? log 10 M h /M sun Based on Maoz 1998 log 10 R h [M sun pc -3 ] T = 10 4 yr Milky Way T = 10 6 yr Milky Way NGC 4258 M 31 would have M 32 a lifetime < 10 5 years! NGC 4594 T = 10 8 yr T = yr Any cluster of realistic astrophysical objects with the mass and density found at the GC T = yr M 87 NGC 3377 NGC 4486B

7 Flares: Duration Size at 7 mm Flares: T var Sgr A*: Scales R plummer R neutrino 5 AU = 70 R S mpc R S BH-cluster < 10 7 yr Any non BH Model: Accretion of matter over life time of galaxy should eventually lead to collapse and BH formation!

8 Stellar Dynamics near SgrA*: Evidence for recent star formation

9 Overall rotation of early type stars early K<14.7 early K< clockwise J z /J z (max) 0 radial 0 0 v z (km/s) counter clockwise p SgrA* (arcsec) Dec-offset (") Genzel et al. 2003, Ap.J., Ott et al (1000 proper motions, 200 3Dvels )

10 Rotating disks of early type stars x(arcsec) x(arcsec) z (arcsec) y (arcsec) 0 z (arcsec) SPIFFI spectroscopy: The two disks have very similar shortlived stellar populations (LBV, Wolf-Rayet ) y (arcsec) Coeval formation Genzel et al. 2003, Ap.J (astro-ph ) Levin & Beloorodov, Ap.J. 2003

Anisotropy of SgrA*-cluster stars radial motion tangential Stars in Sgr A* cluster (r < 50 mpc from black hole) show radial anisotropy and appear not dynamically

11 Anisotropy of SgrA*-cluster stars radial motion tangential Stars in Sgr A* cluster (r < 50 mpc from black hole) show radial anisotropy and appear not dynamically relaxed. Many stars near SgrA* are indeed OB main sequence stars!!! Eisenhauer et al. in preparation radial motion tangential Genzel et al. 2000, Schödel et al. 2003

12 II. IRS13N NACO imaging of a new source complex IRS 13 is a dense complex of bright stars ~40 mpc in diameter,, ~150 mpc from SgrA* of unknown nature

13 NACO L-band L Adaptive Optics NIR 3.8 µm science verification data 500mas 23 light days

14 HKL-imaging of the IRS13N complex with NACO Eckart et al. 2003

15 HKL-colors of sources in the IRS13N complex IRS 13N sources may be sources weakly interacting with the ISM (bow shocks) or very young stars (Herbig Ae/Be)! κ L=10e2-10e4 Lsol M=2-8 Msol Eckart et al. 2004

16 Variable Emission from SgrA*

Dynamical Model for Accretion Ineraction between the starburst and the black hole Massloss from stars 10 3 M o yr 1 radiation efficiency of SgrA* 10 8 Bower et al.

17 Dynamical Model for Accretion Ineraction between the starburst and the black hole Massloss from stars 10 3 M o yr 1 radiation efficiency of SgrA* 10 8 Bower et al. 2003: RM of linear polarized flux rules out large accretion rates < Quataert 2003: hydrodynamic calculations show that all the mass gets blown away in a central wind. 5 Available for accretion: 10 yr M o 1

18 SgrA* NIR flares! T = 0 min NACO/VLT, 8/9 May 2003, 1.7 µm NACO/VLT, , 2 µm T = 38 min

Genzel et al. 2003, Nature; Ghez et al., 2003 SgrA* NIR flares! Detected at 1.7 + 2.2 µm (VLT); 3.8 µm (VLT+Keck) Similar to X-ray flares (Baganoff et al.

19 Genzel et al. 2003, Nature; Ghez et al., 2003 SgrA* NIR flares! Detected at µm (VLT); 3.8 µm (VLT+Keck) Similar to X-ray flares (Baganoff et al., 2001) position within < 10 mas (0.4 mpc) from Sgr A* Frequency: 3-6/day! Factors 1.5 (3.8 µm) to 6 (1.7 µm ) Time scales origin <10 R S of 3.6x10 6 M sol BH!

20 Radio to X-ray Spectrum of Sgr A* To understand the accretion and emission mechanisms simultaneous multi-wavelength observations are necessary. First successful simultaneous observation of NIR/X-ray flare and quasi-quiescent emission in 2003 Eckart, Baganoff, Morris, Schödel et al. 2004, A&A, in press

21 Simultaneous NIR / X-ray Measurements June 2003 Chandra data

22 NACO DDT Observations DDT time on June 19, 2003 NACO VLT UT4 AO locked on IRS7 (NIR) Ks filter science observations zenith seeing 0.8 Strehl ~20% NIR source to within about 10mas at the dynamical position of SgrA* Observations in parallel to Chandra measurements of SgrA* Eckart, Baganoff, Morris, Bautz, Brandt, Garmire, Genzel, Ott, Ricker, Straubmeier, Viehmann, Schödel, Bower, and Goldston A&A in press

23 First Simultaneous NIR/X-ray Flare First simultaneous detection of Sgr A* NIR/X-ray (quiescent and flaring state!) The NIR data started 0.38 minutes before the midpoint of the highest X-ray data point (10min bins).

24 Cross-Correlation of NIR/X-ray Data Cross-correlation of NIR (40sec bins) and X-ray data (10min bins). This implies a delay of less than minutes for the decaying part of the flare including the peak of the X-ray emission.

25 First simultaneous weak flare and models E (ev) R IA F % p = 1 p o w e r la w R IA F % p = 3.5 p o w e r la w R IA F + S S C je t-d is k Need for local spectral indices! ν L ν (3.8x10 33 erg/s) few RS diameter B-fields up to 20 G similar to what is expected by RIAF models ν (Hz) Radio: Zhao, Falcke, Bower, Aitken, et al X-ray: Baganoff et al. 2001, 2003, Goldwurm et al. 2003, Porquet et al. 2003, NIR: Genzel et al. 2003, Ghez et al models: Markoff, Falcke, Liu, Melia, Narayan, Quataert, Yuan et al SSC model after Marscher (1983) and Gould (1979) Data and model Eckart, Baganoff, Morris et al. 2004

26 Fine Structure of the Flares A Measurement of the Black Hole Spin?

27 NIR flares: quasi-periodicity K t o =4 h 47 m 46 s (UT) 12 8 S1 SgrA* 0.5 K-band flares June15th & 16th dereddened flux density (mjy) K t o =3 h 01 m 07 s (UT) S1 x normalized FFT amplitude T=16.5±2.5 min SgrA* June 16 S1 June16 all SgrA* June x10-4 5x x10-3 5x frequency (Hz) t-t o (min) Genzel et al. 2003, Nature

Detection of Cyclic Accretion Disk Modes? Cyclic modes associated with accretion disks are well known QPO from (Nowak & Lehr 1998): Kepler orbital motion Lense-Thirring Precission vertical and.

28 Detection of Cyclic Accretion Disk Modes? Cyclic modes associated with accretion disks are well known QPO from (Nowak & Lehr 1998): Kepler orbital motion Lense-Thirring Precission vertical and... radial epicyclic oscillation modes They depend on the dimensionless spin parameter a=j/m and are of the order of a few 100Hz for 10 solar mass stellar BHs and about 0.6mHz for the GC MBH. Aschenbach et al. (2004a,b) derive ~3.3 million solar masses and a~0.992 as possible solutions for the Galactic Center. If emission is not associated with LSO then17min period may represend a lower frequency mde. ~4min static ~30min prograde ~60min retrograde for 3.6x10**6Msol

29 Spin measurement of Sgr A*? Period at last stable orbit for 3.6 x10 6 M sol non-rotation Schwarzschild BH: 27 min Orbital frequency is shortest one of all expected frequencies near a BH. Interpretation of ~17 min quasi-periodicity: Result from NIR flares: Emission from accreting matter on a prograde orbit near LSO of spinning (Kerr) BH at about half maximum spin. Melia et al. 2001, Bardeen, Press, Teukolsky 1972 normalized FFT amplitude Genzel et al., NATURE K-band flares June15th & 16th T=16.5±2.5 min SgrA* June 16 S1 June16 all SgrA* June x10-4 5x x10-3 5x frequency (Hz)

30 Detection of Cyclic Accretion Disk Modes? Analysing the two strongest X-ray bursts Aschenbach et al report the detection of cyclic modes associated with accretion disks. Chandra Oct XMM Oct Baganoff et al Porquet et al. 2003

31 July 2004 run In collaboration with F. Baganoff (MIT), M. Morris (UCLA), R Genzel (MPE) and others NIR/X-ray flare activity of SgrA* is a persistant feature! A second simultaneous NIR/X-ray detection of a flare and a further indication of flare fine structure.

32 New indications for persisting fine structure S1 SgrA*

33 July 2004: Detection of a Rising Flare Flank X-ray flare: 07:07:03:12: :07:03:54: :07:03:00:55-07:07:04:00:00

34 to be continued

35 2003/2004: Detection of Rising and Decaying Flare Flanks

The Centre of the Milky Way: Stellar Dynamics, Potential Star Formation, and Variable NIR Emission from Sgr A*

Mem. S.A.It. Vol. 76, 65 c SAIt 2005 Memorie della The Centre of the Milky Way: Stellar Dynamics, Potential Star Formation, and Variable NIR Emission from Sgr A* R. Schödel, and A. Eckart I.Physikalisches