Modification of the 21-cm power spectrum by X-rays during the epoch of reionization

Details Modification of the 21-cm power spectrum by X-rays during the epoch of reionization Modification of the 21-cm power spectrum by X-rays during the epoch of reionization

Jun 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009mnras.396.1106w&link_type=abstract

Monthly Notices of the Royal Astronomical Society, Volume 396, Issue 2, pp. 1106-1118.

Astronomy and Astrophysics

Astronomy

4

Galaxies: High Redshift, Intergalactic Medium

Scientific paper

We incorporate a contribution to reionization from X-rays within analytic and seminumerical simulations of the 21-cm signal arising from neutral hydrogen during the epoch of reionization. The relatively long X-ray mean free path (MFP) means that ionizations due to X-rays are not subject to the same density bias as UV ionizations, resulting in a substantive modification to the statistics of the 21-cm signal. We explore the impact that X-ray ionizations have on the power spectrum (PS) of 21-cm fluctuations by varying both the average X-ray MFP and the fractional contribution of X-rays to reionization. In general, prior to the epoch when the intergalactic medium (IGM) is dominated by ionized regions (HII regions), X-ray-induced ionization enhances fluctuations on spatial scales smaller than the X-ray MFP, provided that X-ray heating does not strongly suppress galaxy formation. Conversely, at later times when HII regions dominate, small-scale fluctuations in the 21-cm signal are suppressed by X-ray ionization. Our modelling also shows that the modification of the 21-cm signal due to the presence of X-rays is sensitive to the relative scales of the X-ray MFP and the characteristic size of HII regions. We therefore find that X-rays imprint an epoch and scale-dependent signature on the 21-cm PS, whose prominence depends on fractional X-ray contribution. The degree of X-ray heating of the IGM also determines the extent to which these features can be discerned. We further show that the presence of X-rays smoothes out the shoulder-like signature of HII regions in the 21-cm PS. For example, a 10 per cent contribution to reionization from X-rays translates to a 20-30 per cent modulation in the 21-cm PS across the scale of HII regions. We show that the Murchison Widefield Array will have sufficient sensitivity to detect this modification of the PS, so long as the X-ray photon MFP falls within the range of scales over which the array is most sensitive (~0.1Mpc-1). In cases in which this MFP takes a much smaller value, an array with larger collecting area would be required. As a result, an X-ray contribution to reionization has the potential to substantially complicate analysis of the 21-cm PS. On the other hand, a combination of precision measurements and modelling of the 21-cm PS promises to provide an avenue for investigating the role and contribution of X-rays during reionization.

Affiliated with

Also associated with

No associations

Rating

Modification of the 21-cm power spectrum by X-rays during the epoch of reionization does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Modification of the 21-cm power spectrum by X-rays during the epoch of reionization, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Modification of the 21-cm power spectrum by X-rays during the epoch of reionization will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1632320