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Register a new userThe prospects for observing [OIII] 52 micron emission from galaxies during the Epoch of Reionization
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The [OIII] 88 $mu$m fine structure emission line has been detected into the Epoch of Reionization (EoR) from star-forming galaxies at redshifts $6 < z lesssim 9$ with ALMA. These measurements provide valuable information regarding the properties of the interstellar medium (ISM) in the highest redshift galaxies discovered thus far. The [OIII] 88 $mu$m line observations leave, however, a degeneracy between the gas density and metallicity in these systems. Here we quantify the prospects for breaking this degeneracy using future ALMA observations of the [oiii] 52 $mu$m line. Among the current set of ten [OIII] 88 $mu$m emitters at $6 < z lesssim 9$, we forecast 52 $mu$m detections (at 6-$sigma$) in SXDF-NB1006-2, B14-6566, J0217-0208, and J1211-0118 within on-source observing times of 2-10 hours, provided their gas densities are larger than about $n_{mathrm{H}} gtrsim 10^2-10^3$ cm$^{-3}$. Other targets generally require much longer integration times for a 6-$sigma$ detection. Either successful detections of the 52 $mu$m line, or reliable upper limits, will lead to significantly tighter constraints on ISM parameters. The forecasted improvements are as large as $sim 3$ dex in gas density and $sim 1$ dex in metallicity for some regions of parameter space. We suggest SXDF-NB1006-2 as a promising first target for 52 $mu$m line measurements. We discuss how such measurements will help in understanding the mass metallicity relationship during the EoR.
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We present a study of the impact of a bright quasar on the redshifted 21cm signal during the Epoch of Reionization (EoR). Using three different cosmological radiative transfer simulations, we investigate if quasars are capable of substantially changing the size and morphology of the H II regions they are born in. We choose stellar and quasar luminosities in a way that is favourable to seeing such an effect. We find that even the most luminous of our quasar models is not able to increase the size of its native H II region substantially beyond those of large H II regions produced by clustered stellar sources alone. However, the quasar H II region is found to be more spherical. We next investigate the prospects of detecting such H II regions in the redshifted 21cm data from the Low Frequency Array (LOFAR) by means of a matched filter technique. We find that H II regions with radii ~ 25 comoving Mpc or larger should have a sufficiently high detection probability for 1200 hours of integration time. Although the matched filter can in principle distinguish between more and less spherical regions, we find that when including realistic system noise this distinction can no longer be made. The strong foregrounds are found not to pose a problem for the matched filter technique. We also demonstrate that when the quasar position is known, the redshifted 21cm data can still be used to set upper limits on the ionizing photon rate of the quasar. If both the quasar position and its luminosity are known, the redshifted 21 cm data can set new constrains on quasar lifetimes.
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The neutral hydrogen (HI) and its 21 cm line are promising probes to the reionization process of the intergalactic medium (IGM). To use this probe effectively, it is imperative to have a good understanding on how the neutral hydrogen traces the underlying matter distribution. Here we study this problem using semi-numerical modeling by combining the HI in the IGM and the HI from halos during the epoch of reionization (EoR), and investigate the evolution and the scale-dependence of the neutral fraction bias as well as the 21 cm line bias. We find that the neutral fraction bias on large scales is negative during reionization, and its absolute value on large scales increases during the early stage of reionization and then decreases during the late stage. During the late stage of reionization, there is a transition scale at which the HI bias transits from negative on large scales to positive on small scales, and this scale increases as the reionization proceeds to the end.
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