Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userExtracting bias using the cross-bispectrum: An EoR and 21 cm-[CII]-[CII] case study
62
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The amplitude of redshifted 21 cm fluctuations during the Epoch of Reionization (EoR) is expected to show a distinctive rise and fall behavior with decreasing redshift as reionization proceeds. On large scales (k <~ 0.1 Mpc^{-1}) this can mostly be characterized by evolution in the product of the mean 21 cm brightness temperature and a bias factor, b_21(z). This quantity evolves in a distinctive way that can help in determining the average ionization history of the intergalactic medium (IGM) from upcoming 21 cm fluctuation data sets. Here we consider extracting <T_21> b_21(z) using a combination of future redshifted 21 cm and [CII] line-intensity mapping data sets. Our method exploits the dependence of the 21 cm-[CII]-[CII] cross-bispectrum on the shape of triangle configurations in Fourier space. This allows one to determine <T_21> b_21(z) yet, importantly, is less sensitive to foreground contamination than the 21 cm auto-spectrum, and so can provide a valuable cross-check. We compare the results of simulated bispectra with second-order perturbation theory: on large scales the perturbative estimate of <T_21> b_21(z) matches the true value to within 10% for <x_i> <~ 0.8. We consider the 21 cm auto-bispectrum and show that this statistic may also be used to extract the 21 cm bias factor. Finally, we discuss the survey requirements for measuring the cross-bispectrum. Although we focus on the 21 cm-[CII]-[CII] bispectrum during reionization, our method may be of broader interest and can be applied to any two fields throughout cosmic history.
rate research
Read More
CII line intensity mapping (LIM) is a potential technique to probe the early galaxies from the Epoch of Reionization (EoR). Several experiments e.g. CONCERTO, TIME, CCAT-p are underway to map the CII LIM signal fluctuations from the EoR, enabling us to estimate the CII power-spectrum and CII$times$21-cm cross-power spectrum. Observed LIM signal will have its time evolution embedded in it along the Line of Sight (LoS) due to the finite travel time of the signal from its origin to the observer. We have investigated this so-called light-cone effect on the observed statistics of our semi-numerically simulated CII signal from the EoR. Using a suit of simulated CII and neutral hydrogen 21-cm maps and corresponding light-cone boxes, we have shown that the light-cone effect can impact the CII power spectrum by more than 15% at large scales ($ksim 0.1, text{Mpc}^{-1}$, at $z=6.8$). We have also observed that the impact of light-cone effect on the CII power spectrum drops with decreasing redshift within the redshift range considered here ($7.2 lesssim z lesssim 6$). The CII$times$21-cm cross-power spectrum is also affected by light-cone, and in our models where reionization ends before $z=6$, we find that the maximum impact on cross-power can reach up to 20%. At $z=6.4$, we find comparatively pronounced variation in the light-cone effect with reionization history on the cross power. Faster reionization histories have a more drastic light-cone effect on cross-power. We conclude that we need to incorporate the light-cone in order to properly model the signal, constrain the EoR-related astrophysical parameters and reionization history using the CII$times$21-cm cross-power spectrum.
With the advent of the first luminous sources at Cosmic Dawn (CD), the redshifted 21-cm signal, from the neutral hydrogen in the Inter-Galactic Medium (IGM), is predicted to undergo a transition from absorption to emission against the CMB. Using simulations, we show that the redshift evolution of the sign and the magnitude of the 21-cm bispectrum can disentangle the contributions from Ly$alpha$ coupling and X-ray heating of the IGM, the two most dominant processes which drive this transition. This opens a new avenue to probe the first luminous sources and the IGM physics at CD.
We introduce simulations aimed at assessing how well weak gravitational lensing of 21cm radiation from the Epoch of Reionization ($z sim 8$) can be measured by an SKA-like radio telescope. A simulation pipeline has been implemented to study the performance of lensing reconstruction techniques. We show how well the lensing signal can be reconstructed using the three-dimensional quadratic lensing estimator in Fourier space assuming different survey strategies. The numerical code introduced in this work is capable of dealing with issues that can not be treated analytically such as the discreteness of visibility measurements and the inclusion of a realistic model for the antennae distribution. This paves the way for future numerical studies implementing more realistic reionization models, foreground subtraction schemes, and testing the performance of lensing estimators that take into account the non-Gaussian distribution of HI after reionization. If multiple frequency channels covering $z sim 7-11.6$ are combined, Phase 1 of SKA-Low should be able to obtain good quality images of the lensing potential with a total resolution of $sim 1.6$ arcmin. The SKA-Low Phase 2 should be capable of providing images with high-fidelity even using data from $zsim 7.7 - 8.3$. We perform tests aimed at evaluating the numerical implementation of the mapping reconstruction. We also discuss the possibility of measuring an accurate lensing power spectrum. Combining data from $z sim 7-11.6$ using the SKA2-Low telescope model, we find constraints comparable to sample variance in the range $L<1000$, even for survey areas as small as $25mbox{ deg}^2$.
We present a novel method to simultaneously characterise the star formation law and the interstellar medium properties of galaxies in the Epoch of Reionization (EoR) through the combination of [CII] 158$mu$m (and its known relation with star formation rate) and CIII]$lambda$1909{AA} emission line data. The method, based on a Markov Chain Monte Carlo algorithm, allows to determine the target galaxy average density, $n$, gas metallicity, $Z$, and burstiness parameter, $kappa_s$, quantifying deviations from the Kennicutt-Schmidt relation. As an application, we consider COS-3018 (z=6.854), the only EoR Lyman Break Galaxy so far detected in both [CII] and CIII]. We show that COS-3018 is a moderate starburst ($kappa_s approx 3$), with $Zapprox 0.4, Z_{odot}$, and $n approx 500, {rm cm^{-3}}$. Our method will be optimally applied to joint ALMA and JWST targets.
The high-redshift 21 cm signal from the Epoch of Reionization (EoR) is a promising observational probe of the early universe. Current- and next-generation radio interferometers such as the Hydrogen Epoch of Reionization Array (HERA) and Square Kilometre Array (SKA) are projected to measure the 21 cm auto power spectrum from the EoR. Another observational signal of this era is the kinetic Sunyaev-Zeldovich (kSZ) signal in the cosmic microwave background (CMB), which will be observed by the upcoming Simons Observatory (SO) and CMB-S4 experiments. The 21 cm signal and the contribution to the kSZ from the EoR are expected to be anti-correlated, the former coming from regions of neutral gas in the intergalactic medium and the latter coming from ionized regions. However, the naive cross-correlation between the kSZ and 21 cm maps suffers from a cancellation that occurs because ionized regions are equally likely to be moving toward or away from the observer and so there is no net correlation with the 21 cm signal. We present here an investigation of the 21 cm-kSZ-kSZ bispectrum, which should not suffer the same cancellation as the simple two-point cross-correlation. We show that there is a significant and non-vanishing signal that is sensitive to the reionization history, suggesting the statistic may be used to confirm or infer the ionization fraction as a function of redshift. In the absence of foreground contamination, we forecast that this signal is detectable at high statistical significance with HERA and SO. The bispectrum we study suffers from the fact that the kSZ signal is sensitive only to Fourier modes with long-wavelength line-of-sight components, which are generally lost in the 21 cm data sets owing to foreground contamination. We discuss possible strategies for alleviating this contamination, including an alternative four-point statistic that may help circumvent this issue.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
