Supermassive black hole formation at high redshift

Transcription

1 Supermassive black hole formation at high redshift Muhammad Latif Institut d'astrophysique de Paris, France Marta Volonteri, Dominik Schleicher, Melanie Habouzit,Tilman Hartwig, Kazu Omukai, Jens Niemeyer, Wolfram Schmidt, Marco Spaans, Caroline Van Borm, Stefano Bovino, Tommaso Grassi

2 High z Quasars Supermassive black holes of ~10 9 solar masses have been observed at z>6 (Venemans +15) The highest-redshift quasar at z=7.085 hosts a SMBH of 2x10 9 M (Mortlock et al. 2011) The most massive black hole has a mass of 1.3 x M at z=6.3 (Wu et al. Nature 2015) Wu et al. Nature 2015

3 Direct collapse scenario Provides massive seeds of M Key requirement is to have large inflow rate of > 0.1 M /yr Isothermal direct collapse with T~ 8000 K Primordial gas composition Requires strong LW flux to quench H 2 formation See recent review by Latif & Ferrara 2016 (arxiv: ) s Regan et al 2009

4 Supergiant protostar stellar+radius+: R * +(+R! ) TH+12 HIburning+starts HIburning+starts ZAMS stellar+mass +M * +(+M! ) " The+protostar+never+contracts+to+reach+the+ZAMS+stage,+but largely+expands+with+very+rapid+accredon,++>+0.01+m! /yr.+ " large+radius+ +low+effecdve+temperature+ +weak+uv+feedback+ Hoskawa et al. 2012, Schleicher, ML et al., A&A, 2013

5 Thermodynamics of primordial gas J>J crit H atomic cooling J<J crit H 2 molecular cooling Omukai 01, Also see Latif et. al 2014 MNRAS

6 Cosmological simulations Latif et al. 2013, 2014, 2015

7 Global properties of simulated halos Successes of Isothermal DC Latif et al 2013, MNRAS, 433, 1607L

8 Simulations exploring the direct collapse te of Simulations Collapse Latif et al 2013occurs MNRAS isothermally with T~ 8000 K L Provides large inflow rates of ~1M /yr Latif et al. 2013, MNRAS, 433, 1607L

9 Impact of H - cooling & Realistic opacities Latif, Schleicher & Hartwig, 2016, MNRAS, 458, 233L

10 Masses of protostars/sinks s s Employed sink particles and followed the evolution for 200,000 yrs Massive sinks of about 10 5 M are Latif et al. 2013, MNRAS, 436, 2989L formed

11 Fraction of metal free halos Latif et al ApJ L, See Habouzit, et al 2016

12 Estimates of J crit from 3D simulations Latif et al 2014 ArXiv: L Latif et al. MNRAS , Also see Agarwal et al. 2016

13 Number density of DCBHs Habouzit,Volonteri, ML et al. 2016, Also see Dijkstra et al. 2014

14 massive stars are favoured to reproduce the observations. 10 The Zcrit model yields larger masses of low-metallicity gas down to smaller redshifts and consequently allows primory CONSISTENT dial star formation at later times. Hence, more massive stars can also survive to contribute to the Heii luminosity at z = The Zcrit model produces the highest Heii luminosities, 10 Sobral et al 2015, Pallottini et al. 2015, Agarwal et al which are still more than 10 orders of magnitude below the observed value of erg s 1. Even for a higher t [Myr] halo mass, the final luminosities are too small. We note Figure 4. Mean cosmic Pop III SFR for all four models per that the corresponding Lyα luminosity for Pop III stars in a comoving volume. The primordial SFR peaks around redshift 20, 1012 M halo is of the order erg s 1, which is and decreases at z < 12. about 7 orders of magnitude below the observed value. -6 CR7: Potential host for a DCBH? What mostlyet limits the Heii luminosity is the mass of T. Hartwig al. Pop III stars that survive until z = 6.6. To show this effect, we plot the stellar mass distribution of primordial stars in 10 Figure 7. The more massive the stars, the shorter the lifefiducial times and the smaller the probability that they survive long 1->100 Zcrit enough to be present down to z = 6.6. For M < 2 M this merger plot represents the IMF, since the lifetimes of these stars are long enough for them to survive until z = 6.6. For higher masses we see that the Zcrit model is the most likely one to 108 also contain stars that are 10 M since it has the largest amount of gas available for star formation down to lower Prime target for JWST! redshifts. But even these stars are not massive enough to contribute significantly to the Heii luminosity, due to the steep dependence of the Heii luminosity on the stellar mass 107 (see also Table 1). We also test more extreme models for the Pop III IMF with a mass range from Mmin = 10 M to Mmax = 1000 M and find significantly fewer primordial stars at z = 6.6 and also a smaller Heii line luminosity than in the fiducial model. For Mmin " 50 M there are no Pop III starscomparison at all that might contribute to the Heii luminosity at Figure 17. of the three different models, regardin z = 6.6, such within a few the metallicity of because clump A at massive z = 6.6stars andexplode the mass of the stel Myr asor SNe. Hartwig, al MNRAS,The resubmitted t [Myr] lar population ofml theetbh, respectively. grey shaded are 9 Mprist [M ] z 10 9

15 Growth of a DCBH 3D RT+ hydro simulations Include both UV & X-ray feedback (0.1eV-1.1 KeV) from a BH Accretion Rate [M O /yr] M BH [10 4 M O ] Time [Myrs] Time [Myrs] Latif et al. in preparation

16 Summary Direct isothermal collapse provides massive seeds of about 10 5 M Large accretion rates of ~0.1 M /yr are found in numerical simulations Direct collapse model seems feasible Difficult to grow a DCBH 10 4 M in an atomic cooling halo Radiative feedback from active BH limits its growth

17 Thank you!