1. Imaging Compact Supermassive Binary Black Holes with VLBI G. B. Taylor (UNM), C. Rodriguez (UNM), R. T. Zavala (USNO) A. B. Peck (CfA), L. K. Pollack (UCSC), H.L. Maness (UCB), and R. W. Romani (Stanford) Black Holes: From Stars to Galaxies IAU General Assembly Prague, Aug 24, 2006

2. Introduction 3C 75 NGC 6240 7 kpc separation 1.4 kpc separation 7 kpc separation 1.4 kpc separation VLA image of 3C 75 at 6 cm (Owen et al. 1985) Chandra image of NGC 6240 (Komossa et al. 2003)

3. Hydra A 10 kpc

4. 1946+708 10 pc

5. C1 C2 0402+379 at 5 GHz (Pollack et al. 2004) 0402+379 at 5 GHz (Pollack et al. 2004) Discovery of 0402+379 by Pollack et al. (2004). Possible explanations for its properties: Background Source Gravitational Lensing Jet Component Binary Supermassive Black Hole System 1.2.3.4. 20 pc

6. VLBA observations were made in 2005 at 0.3, 5, 8, 15, 22, and 43 GHz. We also obtained fully-calibrated 5 GHz VLBI data taken in 1990 (Xu et al. 1995), in 1996 (VCS; Beasley et al. 2002), in three epochs (1994, 1996, and 1999) of the CJ Proper Motion Survey (Britzen et al. 2003) and in 2003 (Maness et al. 2004). The Very Long Baseline Array (VLBA). The Very Long Baseline Array (VLBA).

7. Results Radio Continuum Rodriguez et al. astro-ph/0604042 Naturally weighted 2005 VLBA images of 0402+379 at 0.3, 5, 8, 15, 22, and 43 GHz. C1: 0.183 ± 0.048 pc C2: 0.124 ± 0.035 pc Projected separation between C1 and C2 equal to 7.3 pc Evidence against background source

8. Component Motions Components model for the VLBA observations of 0402+379 Components model for the VLBA observations of 0402+379 Northern jet is moving away from the two central components to the northeast, N1: (0.185 ± 0.008)c N1: (0.185 ± 0.008)c N2: (0.114 ± 0.019)c N2: (0.114 ± 0.019)c Southern jet is moving away to the southwest, though more slowly, S2: (0.0251 ± 0.0085)c S2: (0.0251 ± 0.0085)c S3: (0.056 ± 0.010)c S3: (0.056 ± 0.010)c The results obtained for C2 show no significant motion. A limit of less than 0.088c was obtained. Evidence against jet component

9. Component Variability Light curves of the different components of 0402+379 at 5 GHz. Light curves of the different components of 0402+379 at 5 GHz. Component C1 substantially increases in flux density over the 15 y baseline. Component C2 is also variable. For the southern and northern components, there is no substantial variation in the flux densities over the 15 y baseline. Evidence against lensing

10. In both hotspots of the source, N2 and S2, a steep spectrum was found. For both central components, C1 and C2, the spectrum peaks at ~10 GHz. For both central components, C1 and C2, the spectrum peaks at ~10 GHz. Spectral index distribution between 8 and 22 GHz from the 2005 VLBA observations. Radio Continuum Spectra Evidence against lensing Evidence against jet component

11. HET Spectroscopy The optical spectrum at 5.6 Å spectral resolution taken by the HET Hobby-Eberly Telescope Red shoulder found suggesting two components with velocity separation of 300 km s −1. Spectrum of the core of 0402+379 obtained on 2004 December 11 with the 9.2m Hobby-Eberly telescope (HET).

12. 0402+379 neutral hydrogen in absorption Maness et al 2004 Evidence for Multiple velocity systems Consistent with a merger

13. Binary Supermassive Black Hole System Most likely explanation:

14. Constraints on the Mass of the Black Holes Supermassive Binary Black Hole Orbital Parameters Combining HET and VLBA observations a system mass of 1.5 × 10 8 M Sun was obtained. According to Kepler’s Laws the period of rotation for such a binary system should be ~ 1.5 × 10 5 y, implying a projected velocity between both components of ~ 0.001c. Gravitational Wave Signal Natural gravitational wave frequency (Hughes 2003) is approximately 2 × 10 −13 Hz. A binary black hole on a circular orbitin the final stage of evolution will merge within the time (Peters 1964): A binary black hole on a circular orbit in the final stage of evolution will merge within the time (Peters 1964): Merger time equal to ~10 18 y. Some other loss of angular momentum will be necessary if this system is to merge in less than a Hubble time.

15. VLBI Imaging of Active Galactic Nuclei VLBA Imaging Polarimetry Survey (VIPS) 1127 sources: S > 85 mJy, 65 > dec > 20, |b|>10 at 5 GHz in SDSS northern cap First epoch observations on the VLBA in 2006 Identifications and redshifts from SLOAN, HET, Palomar, … Goals: - Characterize GLAST sources - Study Evolution of Radio Sources - Study AGN environments - Find more supermassive binary black holes http://www.phys.unm.edu/~gbtaylor/VIPS/

16. Some Candidate SBBH Systems from VIPS

17. Conclusions C1 and C2: two active nuclei of a single galaxy. C1 and C2: two active nuclei of a single galaxy. Closest binary black hole system yet discovered. Projected separation of 7.3 pc. Closest binary black hole system yet discovered. Projected separation of 7.3 pc. Total mass of the system: 1.5 × 10 8 M Sun. Total mass of the system: 1.5 × 10 8 M Sun. Gravitational radiation frequency: 2 × 10 −13 Hz. Gravitational radiation frequency: 2 × 10 −13 Hz. Searching for more binary black hole systems. The VLBA Imaging and Polarization Survey (VIPS, Taylor et al. 2005) has imaged 1127 sources. Searching for more binary black hole systems. The VLBA Imaging and Polarization Survey (VIPS, Taylor et al. 2005) has imaged 1127 sources.