We investigate the impact of quasars on the ionization of the surrounding intergalactic medium (IGM) with the radiative transfer code CRASH4, now accounting for X-rays and secondary electrons. After comparing with analytic solutions, we post-process a cosmic volume (≈1.5 × 104 Mpc3 h-3) containing a ULAS J1120+0641-like quasar (QSO) hosted by a 5 × 1011M⊙h-1 dark matter (DM) halo. We find that (i) the average H II region (R ~3.2 pMpc in a lifetime tf = 107 yr) is mainly set by UV flux, in agreement with semi-analytic scaling relations; (ii) a largely neutral (x H II < 0.001), warm (T ~103 K) tail extends up to few Mpc beyond the ionization front, as a result of the X-ray flux; and (iii) LyC-opaque inhomogeneities induce a line of sight (LOS) scatter in R as high as few physical Mpc, consistent with the DLA scenario proposed to explain the anomalous size of the ULAS J1120+0641 ionized region. On the other hand, with an ionization rate Nγ,0 ~1057 s-1, the assumed DLA clustering and gas opacity, only one LOS shows an H II region compatible with the observed one.We deduce that either the ionization rate of the QSO is at least one order of magnitude lower or the ULAS J1120+0641 bright phase is shorter than 107 yr.
X-ray ionization of the intergalactic medium by quasars / Graziani, L.; Ciardi, B.; Glatzle, M.. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - 479:4(2018), pp. 4320-4335. [10.1093/mnras/sty1367]
X-ray ionization of the intergalactic medium by quasars
Graziani L.
;
2018
Abstract
We investigate the impact of quasars on the ionization of the surrounding intergalactic medium (IGM) with the radiative transfer code CRASH4, now accounting for X-rays and secondary electrons. After comparing with analytic solutions, we post-process a cosmic volume (≈1.5 × 104 Mpc3 h-3) containing a ULAS J1120+0641-like quasar (QSO) hosted by a 5 × 1011M⊙h-1 dark matter (DM) halo. We find that (i) the average H II region (R ~3.2 pMpc in a lifetime tf = 107 yr) is mainly set by UV flux, in agreement with semi-analytic scaling relations; (ii) a largely neutral (x H II < 0.001), warm (T ~103 K) tail extends up to few Mpc beyond the ionization front, as a result of the X-ray flux; and (iii) LyC-opaque inhomogeneities induce a line of sight (LOS) scatter in R as high as few physical Mpc, consistent with the DLA scenario proposed to explain the anomalous size of the ULAS J1120+0641 ionized region. On the other hand, with an ionization rate Nγ,0 ~1057 s-1, the assumed DLA clustering and gas opacity, only one LOS shows an H II region compatible with the observed one.We deduce that either the ionization rate of the QSO is at least one order of magnitude lower or the ULAS J1120+0641 bright phase is shorter than 107 yr.File | Dimensione | Formato | |
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