Towards $21$-cm intensity mapping at $z=2.28$ with uGMRT using the tapered gridded estimator -- IV. Wideband analysis

• DOI: 10.48550/arxiv.2403.06736
• Publication Date: 2024-03-11
• Authors: Khandakar Asif Elahi; Somnath Bharadwaj; Srijita Pal; Abhik Ghosh; Sk. Saiyad Ali; Samir Choudhuri; Arnab Chakraborty; Abhirup Datta; Nirupam Roy; Madhurima Choudhury; Prasun Dutta
• Keywords: Wideband; Intensity

We present a Wideband Tapered Gridded Estimator (TGE), which incorporates baseline migration and variation of the primary beam pattern for neutral hydrogen (${\rm H\hspace{0.5mm}}{\scriptsize {\rm I}}$) 21-cm intensity mapping (IM) with large frequency bandwidth radio-interferometric observations. Here we have analysed $394-494 \, MHz}$ $(z = 1.9 - 2.6)$ uGMRT data to estimate Multi-frequency Angular Power Spectrum (MAPS) $C_\ell(\Delta\nu)$ from removed foregrounds using polynomial fitting (PF) Gaussian Process Regression (GPR) methods developed in our earlier work. Using residual mean squared brightness temperature fluctuation $\Delta^2(k)$, find that this is consistent $0 \pm 2 \sigma$ several $k$ bins. The resulting $2\sigma$ upper limit $\Delta^2(k) < (4.68)^2 \rm{mK^2}$ at $k=0.219\,\rm{Mpc^{-1}}$ nearly $15$ times tighter than limits obtained smaller ($24.4 MHz}$) same data. $[\Omega_{{\rm I}}} b_{{\rm I}}}] 1.01 \times 10^{-2}$ within an order magnitude value expected independent estimates ${\rm I}}$ mass density $\Omega_{{\rm I}}}$ bias $b_{{\rm I}}}$. techniques used here can be applied other telescopes frequencies, including $\sim 150 Epoch Reionization