On using large scale correlation of the Ly-α forest and redshifted 21-cm signal to probe HI distribution during the post reionization era

Abstract

Abstract. We investigate the possibility of detecting the 3D cross correlation power spectrum of the Ly-α forest and HI 21 cm signal from the post reionization epoch. The crosscorrelation signal is directly dependent on the dark matter power spectrum and is sensitive to the 21-cm brightness temperature and Ly-α forest biases. These bias parameters dictate the strength of anisotropy in redshift space. We find that the cross-correlation power spectrum can be detected using 400 hrs observation with SKA-mid (phase 1) and a futuristic BOSS like experiment with a quasar (QSO) density of 30 deg −2 at a peak SNR of 15 for a single field experiment at redshift z = 2.5. We also study the possibility of constraining various bias parameters using the cross power spectrum. We find that with the same experiment 1σ conditional errors on the 21-cm linear redshift space distortion parameter β T and β F corresponding to the Ly-α forest are ∼ 2.7% and ∼ 1.4% respectively for 10 independent pointings of the SKA-mid (phase 1). This prediction indicates a significant improvement over existing measurements. We claim that the detection of the 3D cross correlation power spectrum will not only ascertain the cosmological origin of the signal in presence of astrophysical foregrounds but will also provide stringent constraints on large scale HI biases. This provides an independent probe towards understanding cosmological structure formation.

MODELING THE Lyα FOREST IN COLLISIONLESS SIMULATIONS

“…The high quasar density in the BOSS survey allows for themeasurement ofthe 3DPS, which can be exploited to improve cosmological constrains and/or constrain IGM thermal properties McQuinn & White 2011). Finally, our technique could help themodeling of the cross-correlation between the Lyα forest and theH I 21 cm signal (Guha Sarkar & Datta 2015), as well as between CMB lensing and Lyα forest (Vallinotto et al 2009(Vallinotto et al , 2011. Figure 14.…”

Prospects of probing quintessence with H i 21-cm intensity mapping survey

“…Astrophysical foregrounds from galactic and extra galactic sources are several orders of magnitude larger than the signal (Ghosh et al 2011) and significant amount of foreground subtraction is required for a statistical detection of the signal (Di Matteo et al 2002;Santos et al 2005;Gleser et al 2008;Liu et al 2009;Ghosh et al 2011;Alonso et al 2015). The cross correlation of the redshifted 21 cm signal with other cosmological probes like the Lyman-alpha forest and Lyman-Break galaxies, has been proposed (Guha Sarkar et al 2011;Guha Sarkar & Datta 2015;Villaescusa-Navarro et al 2015) to cope with the effect of foreground residuals. Further man made Radio frequency interferences and other systematic effects like calibration errors shall also have to be tackled before obtaining the pristine cosmological signal.…”

“…But the collective diffuse HI 21-cm radiation from all the clouds without resolving the individual DLAs is expected to form a background in radio observations at frequencies < 1420MHz. Intensity mapping of this background radiation can yield enormous cosmological information regarding the background evolution of the Universe as well as the structure formation in the post-reionization epoch (Wyithe & Loeb 2007;Visbal et al 2009;Chang et al 2008;Bharadwaj et al 2009;Mao et al 2008;Wyithe 2008;Bull et al 2015;Guha Sarkar & Datta 2015). The upcoming Square Kilometer Array (SKA) in various phases has a dominant science goal of mapping out the large scale distribution of neutral hydrogen over a wide range of redshifts.…”

Cosmology and Astrophysics using the Post-Reionization HI

“…The aliasing term P 1D F is obtained by integrating the 3D power spectrum and the pixel noise contribution σ 2 is obtained by assuming that the spectra are measured at an average 3 − σ level. The details of the analysis maybe found in Guha Sarkar & Datta (2015). The Cramer-Rao bound on the error are given by δqi = F −1 ii and δDV /DV = 1 3 (4F −1 11 + 4F −1 12 + F −1 22 ) 0.5 .…”

“…Another way is to detect only the integrated HI emission of galaxies at each sky location without attempting to resolve the individual objects, a technique known as HI intensity mapping (Bharadwaj & Sethi 2001;Chang et al 2010;Masui et al 2013;Lah et al 2009). There has been recent surge of investigations aimed towards understanding dark energy using future SKA observations (Guha Sarkar & Datta 2015;Hussain et al 2016;Bull et al 2015b;Zhao et al 2015;Santos et al 2015;Bull et al 2015a).…”