1 / 23

Searching for SMBH Binary using VLBI Phase-referencing Observations

the 7th Sino-German Workshop on “Galaxies, Super-massive Black Holes and the Cosmic Web” @ Shanghai, China, September 25-28, 2006. Searching for SMBH Binary using VLBI Phase-referencing Observations. Zhi-Qiang Shen Shanghai Astronomical Observatory. Summary.

walterwoods
Download Presentation

Searching for SMBH Binary using VLBI Phase-referencing Observations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. the 7th Sino-German Workshop on “Galaxies, Super-massive Black Holes and the Cosmic Web” @ Shanghai, China, September 25-28, 2006 Searching for SMBH Binary using VLBI Phase-referencing Observations Zhi-Qiang Shen Shanghai Astronomical Observatory

  2. Summary • with differential VLBI astrometry, the uncertainty in the determination of relative positions can be as small as ~10 as • in principle, this can be used to search for orbital motion of SMBH binary candidates • in practice, such kind of observations is still challenging • even though, it is time to start!

  3. Many galaxies are assumed to have the black holes in their centers. The black hole masses vary from million to dozens of billion Solar mass. Because of the small size we cannot observe the black hole itself, but can register the emission of the accretion disk, rotating around the black hole. Black holes in galaxy centers

  4. Two underlying facts • BHB should be common in galaxies • Most galaxies harbor SMBHs at the dynamic center of their hosts • Most galaxies merge with others (in less than a Hubble time), an essential part of the galaxy formation process, which will be enhanced in clusters and groups of galaxies

  5. Observational evidence for BHB • (semi-)periodic changes in lightcurves (Pursimo et al. 2000 A&AS)

  6. Observational evidence for BHB • wiggled/curved pattern of pc-scale jets (4C73.18: Roos et al. 1993 ApJ) (BL Lac: Tateyama et al. 1998 ApJ)

  7. Observational evidence for BHB • X-shaped (winged) radio lobes/jets (Leahy & Williams 1984 MNRAS) 25-kpc in radius

  8. The most direct evidence for a massive BHB would be some manifestation of the Keplerian motion, which has a period

  9. VLBI –the best tool for high-resolution E0 Galaxy; 14.7 Mpc; 3x109 Msun; Rs ~0.001 ly or 4 as Resolution: 3.3 mas x 1.2 mas

  10. distant reference source(s) target source (BBH candidate) VLBI Phase-Referencing Observations • in-beam style, (λ/D=6cm/25m~8’) • dual-beam style, • fast-switching/nodding style, • spectral-line style • switching angle: angular separation • residual phase errors  separation • switching time (,z,Cn,v)

  11. Mauna KeaHawaii Owens ValleyCalifornia BrewsterWashington North LibertyIowa HancockNew Hampshire Kitt PeakArizona Pie TownNew Mexico Fort DavisTexas Los AlamosNew Mexico St. CroixVirgin Islands VLBA

  12. 3C138(z=0.759) ref src 0528+134 (z=2.06) ~ 4 deg 15 GHz (Shen et al. 2005 ApJ;2006 Submitted)

  13. Gal Plane UN beam 1.11 mas x 0.32 mas @ 9o Super-resolution 0.2 mas Intrinsic size along E-W: 0.126 mas = 1.01 au =12.6 Rsc @3.5mm (Shen et al. 2005 Nature) Intrinsic brightness temperature Tb> 1.2 x 1010 K => (non-thermal origin) Mass density > 6.5 × 1021 M◉ pc-3 (1012 x NGC 4258) => (SMBH hypothesis) Best Fit • M = 4.00.3 x 106 M⊙ within a radius of 15 mas = 120 AU = 1500 Rsc (Schödel et al. 2002, Nature; Eisenhauer et al. 2003 ApJ; Ghez et al. 2005 ApJ) Sgr A* MSgrA* > 4 x 105 M⊙ (Reid & Brunthaler 2004 ApJ)

  14. W3(OH) • 12 GHz methanol (CH3OH) maser astrometry (Xu et al. 2006 Science) distance = 1.95  0.04 kpc parallax = 0.512  0.010 mas (accuracy ~ 10 as!) • 22 GHz water (H2O) maser astrometry with an accuracy of 17 as (Hachisuka et al. 2006 ApJ)

  15. W3(OH) as seen from the Earth appears at a certain angular position on the sky plane.

  16. Sources of Systematic Uncertainty: 1. Geometric Errors a. Inaccurate antenna positions b. Movement of antennas c. Polar motion d. Tidal effects e. Ocean loading f. Positions of target and calibrator

  17. 2. Instrumental Errors a. Clock b. Axis-Offsets c. Structural Changes 3. Troposphere(sec(z)) Static: dry,wet components(highly variable) Seasonally averaged & latitude-dependent Dynamic (no model) 4. Ionosphere(sec(z)) Static and Dynamic (no model, highly variable) Day/night ~ 5 –10 times

  18. 10 as vs. 1016-1017 cm • 0.01 < r < 1 pc, or, 3 1016 < r < 3 1018 cm • 24 < theta < 2400 as @ D=85 Mpc(3C 66B, z=0.0215) • 20 < theta < 2000 as @ D=100 Mpc • 2 < theta < 200 as @ D=1 Gpc

  19. radio core vs. BH location 3C 66B (Sudou et al. 2003 Science)

  20. A tentative sample Some other famous sources include: 3C120, OJ287, 3C273, BL Lac, Mrk 501

  21. Summary • with differential VLBI astrometry, the uncertainty in the determination of relative positions can be as small as ~10 as • in principle, this can be used to search for orbital motion of SMBH binary candidates • in practice, such kind of observations is still challenging • even though, it is time to start! • In time, we should be able to detect them. • Let us go for it! Collaborations are welcome!

More Related