Spatially Extended 21 cm Signal from Strongly Clustered UV and X-Ray Sources in the Early Universe

Abstract

We present our prediction for the local 21 cm differential brightness temperature ($\delta T_b$) from a set of strongly clustered sources of Population III (Pop III) and II (Pop II) objects in the early Universe, by a numerical simulation of their formation and radiative feedback. These objects are located inside a highly biased environment, which is a rare, high-density peak ("Rarepeak") extending to $\sim 7$ comoving Mpc. We study the impact of ultraviolet (UV) and X-ray photons on the intergalactic medium (IGM) and the resulting $\delta T_b$, when Pop III stars are assumed to emit X-ray photons by forming X-ray binaries very efficiently. We parameterize the rest-frame spectral energy distribution (SED) of X-ray photons, which regulates X-ray photon-trapping, IGM-heating, secondary Lyman-alpha pumping and the resulting morphology of $\delta T_b$. A combination of emission ($\delta T_b>0$) and absorption ($\delta T_b<0$) regions appears in varying amplitudes and angular scales. The boost of the signal by the high-density environment ($\delta \sim 0.64$) and on a relatively large scale combine to make Rarepeak a discernible, spatially-extended ($\theta \sim 10^{\prime }$) object for 21 cm observation at $13\lesssim z\lesssim 17$, which is found to be detectable as a single object by SKA with integration time of $\sim 1000$ hours. Power spectrum analysis by some of the SKA precursors (LOFAR, MWA, PAPER) of such rare peaks is found difficult due to the rarity of these peaks, and the contribution only by these rare peaks to the total power spectrum remains subdominant compared to that by all astrophysical sources.

Accepted for publication in ApJ; Major revision done on the cosmological 21-cm line transfer, allowing for generic cases with peculiar motion of gas and non-negligible optical depth

References in corpus (7)

• The Formation of Population III Binaries from Cosmological Initial Conditions
• The Global 21 Centimeter Background from High Redshifts
• 21 cm fluctuations from inhomogeneous X-ray heating before reionization
• Simulating Cosmic Reionization at Large Scales II: the 21-cm Emission Features and Statistical Signals
• Formation of massive protostars in atomic cooling haloes
• The rich complexity of 21-cm fluctuations produced by the first stars
• Heating the IGM by X-rays from Population III Binaries in High Redshift Galaxies

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• Formation of the first galaxies in the aftermath of the first supernovae
• X-ray Background at High Redshifts from Pop III Remnants: Results from Pop III star formation rates in the Renaissance Simulations
• Cosmic Reionization May Still Have Started Early and Ended Late: Confronting Early Onset with CMB Anisotropy and 21 cm Global Signals
• Distortion of the luminosity function of high-redshift galaxies by gravitational lensing
• A Global Semi-Analytic Model of the First Stars and Galaxies Including Dark Matter Halo Merger Histories
• Maximal X-ray feedback in the pre-reionization universe
• The mass distribution of the first stars can be determined via the 21-cm signal
• Linear Polarization of the 21 cm Line from the Epoch of Reionization