Modelling the spectral energy distribution of dust obscured Starburst-AGN

1. Modelling the spectral energy distribution of dust obscured Starburst-AGN Yunkun Han Supervisor: Zhangwen Han & Fenghui Zhang Group of Binary Population Synthesis Yunnan Astronomical Observatory

2. We are still new in this field!Suggestions are highly welcome!

3. Outline • Dust obscured star formation • Dust obscured BH accretion • Starburst-AGN composite systems • Modelling the spectral energy distribution of dust obscured Starburst-AGN • Some preliminary results

4. Dust obscured star formation The mess of Star Clusters, HII Regions & Dust Star formation takes place in heavily obscured environments. Primary radiation is then reprocessed by dust and re-emitted in the IR band.

5. Dust obscured BH accretion Dusty torus absorb high energy emissions from nuclear center and re-emit them in the IR The synthesis models of the X-ray background require most AGN in the Universe to be obscured (Ueda et al. 2003; Gilliet al. 2007). Most of the accretion power in the Universe is absorbed and then re-emitted in the infrared (IR) bands (Fabian & Iwasawa 1999).

6. Starburst-AGN connection • During the last decade, the hypothesis that AGNs are closely related to galaxy formation and evolution has been supported by a growing body of observational evidence. • The relationship between star formation and super-massive black hole growth is central to our understanding of galaxy formation and evolution.

7. M–σ and M–L relations in galactic bulges Gültekin (2009) Suggesting a connection between the growth of the central black hole through accretion and the growth of the spheroid through star formation.

8. SFR vs. black hole accretion rate SFR from the compilation of Hopkins (2004) Black hole accretion rate based on LADE Model of Aird (2010) SFR at high z from Bouwens (2007) 1σ uncertainty in the model From Aird et al. (2010)

9. Hierarchical Galaxy Formation

10. Starburst-AGN composite systems Star-forming and SMBH accretion are ongoing together Representing an importantphasein galaxy evolution Ideallaboratoryfor examining the physical relationship of star-forming and AGN activities.

11. Hyperluminous infrared galaxies (HLIRG) • Galaxies with IR luminosity • Among the most luminous objects in the Universe. • Exhibit extreme star-formation rates, and most of them show evidence of harbouring powerful AGN.

12. Ultraluminous infrared galaxies (ULIRG) • Galaxies with IR luminosity • About half harbour simultaneously an AGN and starburst activity. (Genzel et al. 1998) • The fraction that hosting an AGN increases with increasing IR luminosity (Veilleux et al. 1995, 1999). • Most likely triggered by mergers of galaxies • (Farrah et al. 2001; Veilleux et al. 2002)

13. Dust rich quasars (SDSS J1148+5251,former most distant quasar)

14. SED observation SED fitting SED Modeling Physical properties of galaxies Analysis of galaxy SEDs • The interplay between the fitting routines and the available data and models. • Useful results can be obtained only if the model are as or more precise than the effect on the data of the property to be measured (Walcher et al. 2010).

15. Difficulties that we are facing • Non-linear problem: dust attenuation, line emission, and dust emission • Very large number of parameters, and with many possible degeneracies: starburst-gas/dust-AGN geometry • Multi-wavelength SEDs

16. Analysis of galaxy SED with Bayesian fitting method 1) Build a pre-computed discrete library of model SEDs 2) Calculate for each model SED 3) The probability of the data given the model (Kauffmann et al. (2003) 4) Contruct the probability density function (PDF) of any physical parameter by summing over all values of the other parameters:

17. Modelling the SEDs of dust obscured Starburst-AGN • Use STARBURST 99 to provide the intrinsic stellar SEDs • Use a parameterized AGN spectrum • Use CLOUDY to compute, dust absorption, and re-emission in the mid- and far-IR (absorption & emission line also included).

18. Dust obscured starburst-AGN

19. Gas & dust (SBnh, SBNH) Gas & dust (AGNnh, AGNNH) Starburst Old stars A simple Model AGN

20. Intrinsic stellar SEDs(STARBURST 99) Star formation law: continuous star formation with SFR=1000 A Saltpeter IMF with power-law index between 0.1 and 120 solar mass. Padova tracks with TP-AGB stars added.

21. AGN T =150,000k, a(ox) = -1.4, a(uv)=-0.5 a(x)=-1

22. SFR=1000 starburst age Cloudy model Input AGN SED Input Starburst SED

23. Log I_SB: -4 to 4 Log SB_age: 4 to 7 Log SBnh: 2 to 6 Log SBNH: 20 to 24 Log AGNU: -3 to 3 Log AGNnh: 2 to 6 Log AGNNH: 20 to 24 Ratio_AGN_SB: 0 to 2 Model gridsRegular vs. Monte Carlo Starburst AGN Regular grids (390625) Monte Carlo grids (2000) Select grids in parameter space randomly by 8 independent random number generator ≈7.4 years With my PC!

24. A HLIRG sample(Ruiz et al. 2007) Selected from the Rowan-Robinson (2000) sample of HLIRG Multi-wavelength SED ,standard empiricalAGN and SBtemplate -fitting approach (Ruiz et al. 2010) Class A: 1) very luminous quasars ( objects with negligible SB contribution) 2) young galaxies going through their maximal star-formation period (objects with signifiant SB emission)

25. A HLIRG sample(Ruiz et al. 2007) Class B: show an IR excess that cannot be modelled with any combination of pure AGN and pure SB templates. The feedback between accretion and star formation processes modifies the SED of class B HLIRG in a way that cannot be replicated by just a simple addition of independentpure AGN and pure SB templates. Sharing many properties with ULIRG (high X-ray absorption, strong star formation, signs of mergers and interactions), so they could be just the high luminosity tail of this population.

26. Class A HLIRG (1)

27. Class A HLIRG (2)

28. Class B HLIRG (1)

29. Class B HLIRG (2)

30. SED of J1148+5251 (Dwek et al. 20007)

31. Best fit

32. Starburst age

33. Luminosity

34. L_AGN/L_SB

35. SBnh

36. SBNH

37. AGNU

38. AGNnh

39. AGNNH

40. Open issues in understanding composite galaxies • What are the respective contributions of starburst and AGN to the total energy output of a given composite galaxy? • A deeply obscured AGN is hard to be distinguished from a similarly obscured starburst by the usual indicators. • In systems where the two are comparable, their additive effects are non-linear (Hopkins et al. 2010). • What can be well constrained by SED fitting methods?

41. Thank you!