Ghara, R.; Giri, S. K.; Mellema, G.; Ciardi, B.; Zaroubi, S.; Iliev, I. T.; Koopmans, L. V. E.; Chapman, E.; Gazagnes, S.; Gehlot, B. K.; Ghosh, A .; Jelić, Vibor; Mertens, F. G.; Mondal, R.; Schaye, J.; Silva, M. B.; Asad, K. M. B.; Kooistra, R.; Mevius, M.; Offringa, A. R.; Pandey, V. N.; Yatawatta, S.
(2020)
Constraining the intergalactic medium at z ≈ 9.1 using LOFAR Epoch
of Reionization observations.
Monthly notices of the Royal Astronomical Society, 493
(4).
pp. 47284747.
ISSN 00358711
Abstract
We derive constraints on the thermal and ionization states of the intergalactic medium (IGM) at redshift ≈ 9.1 using new upper limits on the 21cm power spectrum measured by the LOFAR radio telescope and a prior on the ionized fraction at that redshift estimated from recent cosmic microwave background (CMB) observations. We have used results from the reionization simulation code GRIZZLY and a Bayesian inference framework to constrain the parameters which describe the physical state of the IGM. We find that, if the gas heating remains negligible, an IGM with ionized fraction ≳0.13 and a distribution of the ionized regions with a characteristic size ≳ 8 h1 comoving megaparsec (Mpc) and a full width at halfmaximum (FWHM) ≳16 h1 Mpc is ruled out. For an IGM with a uniform spin temperature TS ≳ 3 K, no constraints on the ionized component can be computed. If the largescale fluctuations of the signal are driven by spin temperature fluctuations, an IGM with a volume fraction ≲0.34 of heated regions with a temperature larger than CMB, average gas temperature 7160 K, and a distribution of the heated regions with characteristic size 3.570 h1 Mpc and FWHM of ≲110 h1 Mpc is ruled out. These constraints are within the 95 per cent credible intervals. With more stringent future upper limits from LOFAR at multiple redshifts, the constraints will become tighter and will exclude an increasingly large region of the parameter space.
Actions (login required)

View Item 
6122
UNSPECIFIED