1. The Formation of the HE0450-2958 System 胡剑 清华天体物理中心 Apr. 22, 2005

2. 2 The HE0450 – 2958 system The HE0450-2958 system was first detected by IRAS, identified as an AGN candidate by de Grijp et al. (1987), and spectroscopically identified as a radio quiet QSO by Low et al. (1988). Optical images by Hutchings & Neff (1988) showed a double nucleus separated by 2 ”, and a suggested linear tail along the line of the nuclei, to the SE. Later it was found that the second nucleus, the one to the northwest, was instead a foreground G star (Low et al. 1989). Hutchings & Neff (1988)

3. 3 Zoom in … Canalizo & Stockton 2001

4. 4 Clear … galaxy quasar Foreground G star Gas in the dark galaxy Magain et al. 2005, Nature, 437, 381 By MCS deconvolution technique ( Magain, P., Courbin, F. & Sohy, S. 1998 ApJ, 494, 472 )

5. 5 NLR

6. 6 A NLS1 quasar?

7. 7 A naked quasar? M V =-23 M V >-20.5

8. 8 Explanations of the HE0450-2958 system MBHs merge, then kick out due to gravitational wave (Haehnelt et al. 2005). But v kick <~500 km/s. Slingshot due to a small MBH interact with a MBH binary (Hoffman & Loeb 2006; Haehnelt et al. 2005). But MBH can ’ t carry out NLR. Quasar acceleration due to the asymmetric jet/outflow (Tygan 2006) But no jet/outflow found Hoffman & Loeb 2006

9. 9 Geometric configuration of the system z=0.2863  1 ” =4.3 kpc Projected distance between the galaxy and quasar: 6.9 kpc Companion galaxy: Long axis 3.4 kpc, short axis 2.2 kpc; viewing angle:  =50º Projected relative quasar speed: 40 km/s Projected galaxy circular speed: v 0 sin  =130 km/s Best solution: v 0 =170 km/s,  33º slit direction  disk galaxy

10. 10 Radial velocities obtained from the emission lines along the slit 140 40

11. 11 Mass model of the galaxy Sersic profile:  =  e exp{-d n [(R/R e ) 1/n -1]}, d n =3n-1/3, M B =-9.4log(n)-14.3 Baryon: R e =1.1 kpc, M b =1.27 £ 10 10 M ¯ Dark matter: R e =200 kpc, M DM =2 £ 10 12 M ¯ (M vir =10 12 M ¯ )

12. 12 Trajectory of the high-speed collision system (M QSO /M gal =0)

13. 13 Trajectory of the high-speed collision system (M QSO /M gal =1/3)

14. 14 Ring-like starburst ∆VR∆VR r R

15. 15

16. 16 Star formation rate Schmidt law:  SFR =(2.5±0.7) £ 10 -4 £ (  gas /M ¯ pc -2 ) 1.4±0.15 M ¯ -1 kpc -2

17. 17 Toomre instability and starburst  c =  c/3.36G  c (M ¯ pc -2 )=0.59  (V/km s -1 )/(R/kpc)  SFR » 0.017  gas  gas

18. 18 Constraint on the quasar halo mass M DM <5 £ 10 11 M ¯ Virial velocity =

19. 19 The gas in the quasar halo is disturbed by the galaxy -- formation of the blob Infall speed need to reach the blob center virial speed Gas compression 6 kpc v No shell crossing Shell crossing (dM/dt) infall ~10 M ¯ yr

20. 20 Lower limit of quasar halo mass Gas mass estimation –Gas density: [SII]6717/6713 → n~1000 cm -3 –Blob volume: V~ (1kpc) 3 –Original gas density ~ 1 cm -3 –Gas mass: M gas ~2.5 £ 10 9 M ¯ –M V >-20.5 →M * <1.5 £ 10 10 M ¯ Dark matter halo mass estimation –M DM >1.4 £ 10 11 M ¯ (cosmic baryon fraction 18%) –M DM ~(3-5) £ 10 11 M ¯

21. 21 MBH growth The MBH fuelled by the hot gas (Nulsen & Fabian 2000) –M BH =(9±1) £ 10 7 M ¯ (by Greene & Ho's virial formula) –M=M 0 exp(t/t sal ), t sal =3.9 £ 10 8 (  )(L E /L) yr –If  =0.1, L=L E, t=10 8 yr→M 0 =8.8 £ 10 6 M ¯ –If  =0.1, L=4L E, t=10 8 yr→M 0 =1.0 £ 10 4 M ¯ –If  =0.2, L=L E, t=10 8 yr→M 0 =3.3 £ 10 8 M ¯ –If  =0.2, L=4L E, t=10 8 yr→M 0 =1.7 £ 10 6 M ¯ M BH -M DM relation –M BH /10 8 M ¯ ~0.1(M DM /10 12 M ¯ ) 1.65 (Ferrarese 2002) –M 0 =8.8 £ 10 6 M ¯ →M DM =9.3 £ 10 11 M ¯

22. 22 Discussion We need independent deconvolution method to verify Magain et al. ’ s results. We need X-ray observation to constrain the quasar parameters (spin?). We need model the hot gas accretion history in details.

23. 23 Summary The HE0450-2958 system consists of a ULIRG that experienced a major starburst ~10 8 yr ago, which is triggered by the high speed collision with a smaller DM halo. The quasar host a MBH with mass ~10 8 M ¯ and its narrow-line region absolute magnitude M V >-20.5. The MBH powers the active nucleus at a super-Eddington accretion rate, L/L E ~4, similar to the accretion rates inferred in other NLS1s. HE0450−2958 may not a naked quasar, but a low luminosity galaxy.