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The tilt between accretion disk and stellar disk

The tilt between accretion disk and stellar disk. Shiyin Shen Shanghai Astronomical Observatory Collaborators ： ZhengYi Shao ， Minfeng Gu. Motivation. Correlation between the orientation of stellar disk and accretion disk?. What we know. Inclination of stellar disk Axis ratio b/a

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The tilt between accretion disk and stellar disk

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  1. The tilt between accretion disk and stellar disk Shiyin Shen Shanghai Astronomical Observatory Collaborators：ZhengYi Shao，Minfeng Gu

  2. Motivation Correlation between the orientation of stellar disk and accretion disk?

  3. What we know • Inclination of stellar disk • Axis ratio b/a • Inclination of accretion disk • pc scale, difficult to measure • Tilt between jets and stellar disk (Kpc VS Kpc) • wide distribution, jet avoid lying close to the plane of the dust disks (Schimitt et al. 2002, 20 radio galaxies) • Kpc scale radio jet orient randomly with respect to the host galaxy axes. (Gallimore et al. 2006, 19 objects)

  4. Type II AGNs: accretion disk viewed edge-on. Our test: do the stellar disks of their hosts also more likely be viewed edge-on?

  5. Type II AGNs in SDSS DR7 • BPT diagram • Star forming VS AGN • Kewley et al. 2001 • Theoretical upper limit of starbursts • Kauffmann et al. 2003 • Empirical separation NAGN=109,832

  6. AGNs hosted by spirals • fracDev<0.5: select spiral galaxies • Fcomp = fracDeV FdeV + (1 - fracDeV) Fexp • ~40% of galaxies are spiral • AGNs hosted by spirals • ~30% of AGNs hosted by spirals • b/a of late type galaxies • approximate the inclination of disk Disk height Disk ellipticity NAGN,spiral=32,618

  7. ~32,600 type II AGNs hosted by spiral galaxies spatial correlation betweenaccretion disk and stellar disk distinctive physical properties of AGN host b/a distribution A control sample with the same physical properties as AGN hosts

  8. Control sample of galaxies • The same distributions of • Stellar mass • Redshift • Concentration • D4000 • R50 • FracDev How about b/a? • AGN VS Non-AGNs • AGN VS control Non-AGNs

  9. The AGN hosts indeed biased to low inclinations (b/a)! How to interpret this systematical bias?

  10. Incl= f(b/a| ,,,) (, ) disk structure parameter = C/A :disk height = (1-B/A) : disk ellipticity AGN have the same (, ) distribution as control galaxies! (, ) viewing angle : inclination  : position angle Control galaxies: random AGN hosts: preferred angle? the shape of spiral galaxies

  11. ,  distributions Non-negative least square linear regression

  12. viewing angle of AGN hots • Viewing angle of stellar disk (S, S) • Viewing angle of accretion disk (A, A) • Tilt angle between accretion disk and Tilt stellar disk AS • Opening angle of torus T • Type II AGN: 90-A< T s AS A 2T

  13. Toy model (, ) distribution Random viewing angle of stellar disk (S, S) b/a of galaxy Viewing angle of accretion disk (A0, A0) Tilt angle AS NAGN/NAGN(b/a) 90-A0 < T Type II AGN fraction f2 (, ) distribution Viewing angle of observed AGN (A, A) b/a of AGN host

  14. Model results • IfAS random or T=90 • cosAS: uniform distribution • NAGN/NGAL=1 • Non-random Assumption • cosAS follows Gaussian distribution, with most probable value AS =0, scatter As,m • AS,m=37 deg • T: free parameter • T =58 deg • f2=80%: in excellent agreement with the results in literature!

  15. Summary • We select a sample of 32,618 type II AGNs hosted by spiral galaxies from SDSS DR7. • We build a control sample of galaxies, which are expected to have the same physical properties as the AGN hosts. • By comparing with the control galaxies, we find the AGN hosts are more likely to be viewed as edge-on. • The bias in the axis ratio (inclination) of the AGN hosts can be explained with a simple model that • the opening angle of the torus is ~60 degree • the mean tilt angle between the accretion disk and stellar disk is ~30 degree

  16. Thanks

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