The Effects of X-rays on Star Formation

and Black Hole Growth in Young

Galaxies

Ayçin Aykutalp (Kapteyn), John Wise (Georgia), Rowin Meijerink (Kapteyn/Leiden)

Marco Spaans (Kapteyn, Netherlands)

BHs

Many galaxies contain BHs : MBH~10-3 Mbulge

Need accretion onto seed BHs and the formation of Pop III and PopII/I at early times

Even z~6 SMBHs of 109 M exist

Possible evolution in Magorrian rel. at high z (Walter ea 04)

BHs produce UV and X-ray radiation: feedback

Seed BHs formed as remnants of Pop III stars or through singular collapse in primordial atomic cooling halos. The latter requires a strong UV background (103-5 J21) and/or Lyman α trapping (Bromm & Loeb 03, Spaans & Silk 06, Shang ea 08, Dijsktra ea 08, Inayoshi & Omukai 12)

XDRs σ ~ E-3

1keV 1022 cm-2 penetration Secondary

Ionizations Dominate

FX =84 L44 r100-2 erg

cm-2 s-1

X-ray flux over 1-100 keV with a power law E-0.9

think of a Seyfert AGN at 100 pc

E > 1 keV

Heating: X-ray photo-ionization fast electrons; 10-50% H and H2 vib excitation; UV emission (Ly α, Lyman-Werner)

Cooling: [FeII] 1.26, 1.64; [OI] 63; [CII] 158; [SiII] 35 μm; CO

thermal H2 vib; gas-dust

1 keV photon penetrates 1022 cm-2 of NH

XDRs

Heating efficiency 10-50%

X-rays penetrate further than UV

High opacity of metal-rich gas Large energy deposition rate (~FX/nH)

X-rays ionize and drive the ion-molecule chemistry, hence the H2 formation

Simulations-1

Box size of 3 Mpc/h

3.6 pc proper resolution

Include X-ray chemistry by porting XDR code (Meijerink&Spaans 05): dust & ion-molecule chemistry, heating, cooling (escape probability for lines); pre-computed tables in nH, NH, FX, and Z/Z (176 species, more than 1000 reactions)

Employ Moray (Wise et. al. 12): UV and X-ray radiation transport (polychromatic spectrum) around the seed BH and every star particle

XDR (metallicity dependent) + Enzo non-equilibrium chemistry (9 species) run in parallel

Simulations-2

Consider singular collapse scenario for UV backgrounds of 103 J21 and 105 J21, which facilitate destruction of H2 and suppresses fragmentation

Introduce seed BH M=5 x 104 M at z=15

BH at 10% Eddington (Kim et. al. 11 prescrip.) produces UV (90%) and X-ray (10%)

Star formation recipes for Pop III (H2 > 5 x 10-4) and Pop II/I (Z > 10-3.5 Z) from z=30

SN feedback, metal enrichment followed

Density-temperature (left) and column density-radius (right) profiles for zero and solar metallicity cases at z=14.95 (top) and z=14.54 (bottom).

High opacity effect of metal enriched gas

Solar

Solar

SolarZero

Zero Zero

Zero

Solar

H2 Fraction

Low (103 J21) and high (105 J21) UV bg. cases at z=14.95 (left), 14.86 (middle), and 14.78 (right).

Low

High

Pop III stars

Low UV bg, at z=14.95!!!

Metallicity

z=14.78

Accretion rate

High UV bg case: 105 J21 Low UV bg case: 103 J21

BH growth

Strong UV background prevents growth to a SMBH!

X-ray feedback/BH growth self-regulating

X-ray Flux

X-ray flickering

z=14.95

z=13.22

z=14.39

z=12.86

z=12.15 z=12.00

HII region

High UV bg case, at z=12.86

Conclusions X-rays important & metals boost X-ray opacity

heating

Weaker 103 J21 UV background allows Pop III star formation and enrich the medium with metals

X-ray feedback/BH growth is self-regulating

Singular collapse scenario does not yield SMBHs at z=6 for 105 J21 UV background

Interesting though for slowly evolving dwarfs today, unless there is later time UV weakening and/or metal enrichment

For low UV bg, 105 M MBH grows at 10-3 M/yr, doubles in mass in Edd. time (usual suspects for SMBHs at z=6)

Discussion

3 Mpc/h box size: Merger rate, maximum halo mass underestimated

No Jets included

Self-shielding approximated locally

No UV background evolution

The simulations are still running!!!