arXiv subjects

Arnab Chakraborty

Publications and source records attributed to Arnab Chakraborty.

At least 37 records · Page 2Linked to original sources

arXiv2024

Holographic Beam Measurements of the Canadian Hydrogen Intensity Mapping Experiment (CHIME)

We present the first results of the holographic beam mapping program for the Canadian Hydrogen Intensity Mapping Experiment (CHIME). We describe the implementation of the holographic technique as adapted for CHIME, and introduce the processing pipeline which prepares the raw holographic timestreams for analysis of beam features. We use data from six bright sources across the full 400-800\,MHz observing band of CHIME to provide measurements of the co-polar and cross-polar beam response of CHIME in both amplitude and phase for the 1024 dual-polarized feeds instrumented on CHIME. In addition, we present comparisons with independent probes of the CHIME beam which indicate the presence of polarized beam leakage in CHIME. Holographic measurements of the CHIME beam have already been applied in science with CHIME, e.g. in estimating detection significance of far sidelobe FRBs, and in validating the beam models used for CHIME's first detections of \tcm emission (in cross-correlation with measurements of large-scale structure from galaxy surveys and the Lyman-$α$ forest). Measurements presented in this paper, and future holographic results, will provide a unique data set to characterize the CHIME beam and improve the experiment's prospects for a detection of BAO.

astro-ph.IM↗

arXiv2024

Parity nonconservation induced by spacetime geometry

The interaction of fermion spin with spacetime can be non-universal, leading to a new interaction beyond the Standard Model, independent of gravitation. Fermions generate spacetime torsion, which can be integrated out in favor of a four-fermion interaction in a torsion-free background. This is a current-current interaction which involves all fermions and generically has different coupling constants for different chiralities and species of fermions. It does not vanish when curvature goes to zero, so accelerator experiments should be able to see its effect. We calculate the contribution of this geometrical interaction to parity nonconservation in $e^-e^-$ and $e^-D$ scattering and compare with known observations. This provides an estimate of an upper bound on the coupling constants, suggesting that the strength of the ``new physics'' can be as large as only one order of magnitude smaller than that of weak interactions.

hep-ph↗

arXiv2024

BBE-LSWCM: A Bootstrapped Ensemble of Long and Short Window Clickstream Models

We consider the problem of developing a clickstream modeling framework for real-time customer event prediction problems in SaaS products like QBO. We develop a low-latency, cost-effective, and robust ensemble architecture (BBE-LSWCM), which combines both aggregated user behavior data from a longer historical window (e.g., over the last few weeks) as well as user activities over a short window in recent-past (e.g., in the current session). As compared to other baseline approaches, we demonstrate the superior performance of the proposed method for two important real-time event prediction problems: subscription cancellation and intended task detection for QBO subscribers. Finally, we present details of the live deployment and results from online experiments in QBO.

cs.LG↗

arXiv2024

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

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

astro-ph.CO↗

arXiv2024

A numerical investigation on turbulent convective flow characteristics over periodic grooves of different curvatures

Heat transfer augmentation is an essential requirement in all heat transfer devices, such as heat exchangers used in biomedical applications, electronic cooling, solar air heaters, nuclear reactor cores, and gas turbine blade cooling etc. Extended surfaces, protrusions, dimples, internal ribs or, grooves are among the few which are incorporated in the last three decades with the goal of heat transfer augmentation for the better performance of the thermal device. However, considering the usefulness, its relative scarcity in literature, and other advantages of grooved surfaces, we have considered this as a method of heat transfer augmentation here. This makes its necessary to investigate the physics due to turbulence and thermal behavior over periodic grooves (or, ribs) is the prime importance of the present paper. In this work, numerical simulations of turbulent forced convection are carried out by introducing curvatures at sharp corners of a periodic grooved channel at the lower wall. A heat source of constant magnitude is supplied in the bottom wall while the upper wall is insulated. Computations were performed using k-epsilon(RNG) model in RANS formulation implemented in finite volume-based solver in the commercial package ANSYS Fluent 19.2. The simulations are performed over varying Reynolds numbers of 6000-36000 where ratio of the height of the channel and breadth of the groove, groove pitch ratio, and depth ratio kept constant as 1, 2, and 0.5 respectively. Assessment of coefficient of heat transfer, frictional losses, and magnitude of heat enhancement are systematically carried out over varying radius of curvatures on grooves. The insertion of curvatures improves the overall heat transfer by a reasonable magnitude of 12% with an overall 5% increment in the magnitude of heat transfer enhancement. Further, the magnitude of heat transfer increases with increase in curvature radius.

physics.flu-dyn↗

arXiv2023

Towards $21$-cm intensity mapping at $z=2.28$ with uGMRT using the tapered gridded estimator III: Foreground removal

Neutral hydrogen (HI) $21$-cm intensity mapping (IM) is a promising probe of the large-scale structures in the Universe. However, a few orders of magnitude brighter foregrounds obscure the IM signal. Here we use the Tapered Gridded Estimator (TGE) to estimate the multi-frequency angular power spectrum (MAPS) $C_{\ell}(Δν)$ from a $24.4\,\rm{MHz}$ bandwidth uGMRT Band $3$ data at $432.8\,\rm{MHz}$. In $C_{\ell}(Δν)$ foregrounds remain correlated across the entire $Δν$ range, whereas the $21$-cm signal is localized within $Δν\le[Δν]$ (typically $0.5-1\,\rm{MHz}$). Assuming the range $Δν>[Δν]$ to have minimal $21$-cm signal, we use $C_{\ell}(Δν)$ in this range to model the foregrounds. This foreground model is extrapolated to $Δν\leq[Δν]$, and subtracted from the measured $C_{\ell}(Δν)$. The residual $[C_{\ell}(Δν)]_{\rm res}$ in the range $Δν\le[Δν]$ is used to constrain the $21$-cm signal, compensating for the signal loss from foreground subtraction. $[C_{\ell}(Δν)]_{\rm{res}}$ is found to be noise-dominated without any trace of foregrounds. Using $[C_{\ell}(Δν)]_{\rm res}$ we constrain the $21$-cm brightness temperature fluctuations $Δ^2(k)$, and obtain the $2σ$ upper limit $Δ_{\rm UL}^2(k)\leq(18.07)^2\,\rm{mK^2}$ at $k=0.247\,\rm{Mpc}^{-1}$. We further obtain the $2σ$ upper limit $ [Ω_{\rm HI}b_{\rm HI}]_{\rm UL}\leq0.022$ where $Ω_{\rm HI}$ and $b_{\rm HI}$ are the comoving HI density and bias parameters respectively. Although the upper limit is nearly $10$ times larger than the expected $21$-cm signal, it is $3$ times tighter over previous works using foreground avoidance on the same data.

astro-ph.CO↗

arXiv2023

A Detection of Cosmological 21 cm Emission from CHIME in Cross-correlation with eBOSS Measurements of the Lyman-$α$ Forest

We report the detection of 21 cm emission at an average redshift $\bar{z} = 2.3$ in the cross-correlation of data from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) with measurements of the Lyman-$α$ forest from eBOSS. Data collected by CHIME over 88 days in the $400-500$~MHz frequency band ($1.8 < z < 2.5$) are formed into maps of the sky and high-pass delay filtered to suppress the foreground power, corresponding to removing cosmological scales with $k_\parallel \lesssim 0.13\ \text{Mpc}^{-1}$ at the average redshift. Line-of-sight spectra to the eBOSS background quasar locations are extracted from the CHIME maps and combined with the Lyman-$α$ forest flux transmission spectra to estimate the 21 cm-Lyman-$α$ cross-correlation function. Fitting a simulation-derived template function to this measurement results in a $9σ$ detection significance. The coherent accumulation of the signal through cross-correlation is sufficient to enable a detection despite excess variance from foreground residuals $\sim6-10$ times brighter than the expected thermal noise level in the correlation function. These results are the highest-redshift measurement of \tcm emission to date, and set the stage for future 21 cm intensity mapping analyses at $z>1.8$.

astro-ph.CO↗

arXiv2023

Towards $21$-cm intensity mapping at $z=2.28$ with uGMRT using the tapered gridded estimator II: Cross-polarization power spectrum

Neutral hydrogen ($\rm{HI}$) $21$-cm intensity mapping (IM) offers an efficient technique for mapping the large-scale structures in the universe. We introduce the 'Cross' Tapered Gridded Estimator (Cross TGE), which cross-correlates two cross-polarizations (RR and LL) to estimate the multi-frequency angular power spectrum (MAPS) $C_{\ell}(Δν)$. We expect this to mitigate several effects like noise bias, calibration errors etc., which affect the 'Total' TGE which combines the two polarizations. Here we apply the Cross TGE on a $24.4 \,\rm{MHz}$ bandwidth uGMRT Band $3$ data centred at $432.8 \,\rm{MHz}$ aiming $\rm{HI}$ IM at $z=2.28$. The measured $C_{\ell}(Δν)$ is modelled to yield maximum likelihood estimates of the foregrounds and the spherical power spectrum $P(k)$ in several $k$ bins. Considering the mean squared brightness temperature fluctuations, we report a $2σ$ upper limit $Δ_{UL}^{2}(k) \le (58.67)^{2} \, {\rm mK}^{2}$ at $k=0.804 \, {\rm Mpc}^{-1}$ which is a factor of $5.2$ improvement on our previous estimate based on the Total TGE. Assuming that the $\rm{HI}$ traces the underlying matter distribution, we have modelled $C_{\ell}(Δν)$ to simultaneously estimate the foregrounds and $[Ω_{\rm{HI}} b_{\rm{HI}}] $ where $Ω_{\rm{HI}}$ and $b_{\rm{HI}}$ are the $\rm{HI}$ density and linear bias parameters respectively. We obtain a best fit value of $[Ω_{\rm{HI}}b_{\rm{HI}}]^2 = 7.51\times 10^{-4} \pm 1.47\times 10^{-3}$ which is consistent with noise. Although the $2σ$ upper limit $[Ω_{\rm{HI}}b_{\rm{HI}}]_{UL} \leq 0.061$ is $\sim 50$ times larger than the expected value, this is a considerable improvement over earlier works at this redshift.

astro-ph.CO↗

arXiv2023

Detection of HI 21 cm emission from a strongly lensed galaxy at z~1.3

We report the first $5σ$ detection of HI 21 cm emission from a star-forming galaxy at redshift $z\sim1.3$ (nearly 9 billion years ago) using upgraded Giant Metrewave Radio Telescope (uGMRT). This is the highest redshift HI detection in emission from an individual galaxy to date. The emission is strongly boosted by the gravitational lens, an early type elliptical galaxy, at redshift $z \sim 0.13$. The measured HI mass of the galaxy is $\rm M_{HI} = (0.90 \pm 0.14 \pm 0.05) \times 10^{10}M_{\odot}$, which is almost twice the inferred stellar mass of the galaxy, indicating an extended structure of the HI gas inside the galaxy. By fitting two-dimensional Gaussian to the HI signal at the peak of the spectral line, we find the source to be marginally resolved with the position angle consistent with the emission being tangential to the critical curve of the lens mass distribution. This indicates that the solid angle of the approaching HI line flux comes very close to the inner lens caustic and results in very high magnification. These results, for the first time, demonstrate the feasibility of observing high redshift HI in a lensed system with a modest amount of telescope time and open up exciting new possibilities for probing the cosmic evolution of neutral gas with existing and upcoming low-frequency radio telescopes in the near future.

astro-ph.GA↗

arXiv2022

Probing early universe through redshifted 21-cm signal: Modelling and observational challenges

The redshifted 21-cm radiation from the atomic hydrogen (HI) provides an excellent direct probe to study the evolution of HI in IGM and thus reveal the nature of the first luminous objects, their evolution and role during Cosmic Dawn (CD) and Epoch of Reionization (EoR), and formation and evolution of the structures thereafter. Direct mapping of the HI density during the CD-EoR is rather difficult with the current and future instruments due to large foreground and other observational contamination. The first detection of this redshifted HI signal is planned through statistical estimators. Given the utmost importance of the detection and analysis of the redshifted 21-cm signal, physics of CD-EoR is one of the objectives of the upcoming SKA-Low telescope. This paper summarizes the collective effort of Indian astronomers to understand the origin of the redshifted 21-cm signal, sources of first ionizing photons, their propagation through the IGM, various cosmological effects on the expected 21-cm signal, various statistical measures of the signal like power spectrum, bispectrum, etc. A collective effort on detection of the signal by developing estimators of the statistical measures with rigorous assessment of their expected uncertainties, various challenges like that of the large foreground emission and calibration issues are also discussed. Various versions of the detection methods discussed here have also been used in practice with the GMRT with successful assessment of the foreground contamination and upper limits on the matter density in EoR and post-EoR. The collective efforts compiled here has been a large part of the global effort to prepare proper observational technique and analysis procedure for the first light of the CD-EoR through the SKA-Low.

astro-ph.CO↗

arXiv2022

Synthetic Observations with the Square Kilometre Array (SKA) -- development towards an end-to-end pipeline

Detection of the redshifted 21-cm signal of neutral hydrogen from the Cosmic Dawn and the Epoch of Reionization is one of the final frontiers of modern observational cosmology. The inherently faint signal makes it susceptible to contamination by several sources like astrophysical foregrounds and instrumental systematics. Nevertheless, developments achieved in the recent times will combine to make signal detection possible with the upcoming Square Kilometer Array (SKA), both statistically and via tomography. This review describes an indigenously developed end-to-end pipeline that simulates sensitive interferometric observations. It mainly focuses on the requirements for \hi detection in interferometers. In its present form, it can mimic the effects of realistic point source foregrounds and systematics- calibration error and position error on 21-cm observations. The performance of the pipeline is demonstrated for test cases with 0.01\% calibration error and position error. Its performance is consistent across telescope, foreground, and signal models. The focus of the simulation pipeline during the initial stages was for EoR science. But since this is a general interferometric simulation pipeline, it will be helpful to the entire SKA user community, irrespective of the science goals.

astro-ph.IM↗

arXiv2022

Detecting galaxies in a large H{\sc i}~spectral cube

The upcoming Square Kilometer Array (SKA) is expected to produce humongous amount of data for undertaking H{\sc i}~science. We have developed an MPI-based {\sc Python} pipeline to deal with the large data efficiently with the present computational resources. Our pipeline divides such large H{\sc i}~21-cm spectral cubes into several small cubelets, and then processes them in parallel using publicly available H{\sc i}~source finder {\sc SoFiA-$2$}. The pipeline also takes care of sources at the boundaries of the cubelets and also filters out false and redundant detections. By comapring with the true source catalog, we find that the detection efficiency depends on the {\sc SoFiA-$2$} parameters such as the smoothing kernel size, linking length and threshold values. We find the optimal kernel size for all flux bins to be between $3$ to $5$ pixels and $7$ to $15$ pixels, respectively in the spatial and frequency directions. Comparing the recovered source parameters with the original values, we find that the output of {\sc SoFiA-$2$} is highly dependent on kernel sizes and a single choice of kernel is not sufficient for all types of H{\sc i}~galaxies. We also propose use of alternative methods to {\sc SoFiA-$2$} which can be used in our pipeline to find sources more robustly.

astro-ph.IM↗

arXiv2022

Benchmarking the Semi-Stochastic CC(P;Q) Approach for Singlet-Triplet Gaps in Biradicals

We recently proposed a semi-stochastic approach to converging high-level coupled-cluster (CC) energetics, such as those obtained in the CC calculations with singles, doubles, and triples (CCSDT), in which the deterministic CC($P$;$Q$) framework is merged with the stochastic configuration interaction Quantum Monte Carlo propagations [J. E. Deustua, J. Shen, and P. Piecuch, Phys. Rev. Lett. 119, 223003 (2017)]. In this work, we investigate the ability of the semi-stochastic CC($P$;$Q$) methodology to recover the CCSDT energies of the lowest singlet and triplet states and the corresponding singlet-triplet gaps of biradical systems using methylene, ${\rm (HFH)}^{-}$, cyclobutadiene, cyclopentadienyl cation, and trimethylenemethane as examples.

physics.chem-ph↗

arXiv2022

Characterization of the John A. Galt telescope for radio holography with CHIME

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) will measure the 21 cm emission of astrophysical neutral hydrogen to probe large scale structure at redshifts z=0.8-2.5. However, detecting the 21 cm signal beneath substantially brighter foregrounds remains a key challenge. Due to the high dynamic range between 21 cm and foreground emission, an exquisite calibration of instrument systematics, notably the telescope beam, is required to successfully filter out the foregrounds. One technique being used to achieve a high fidelity measurement of the CHIME beam is radio holography, wherein signals from each of CHIME's analog inputs are correlated with the signal from a co-located reference antenna, the 26 m John A. Galt telescope, as the 26 m Galt telescope tracks a bright point source transiting over CHIME. In this work we present an analysis of several of the Galt telescope's properties. We employ driftscan measurements of several bright sources, along with background estimates derived from the 408 MHz Haslam map, to estimate the Galt system temperature. To determine the Galt telescope's beam shape, we perform and analyze a raster scan of the bright radio source Cassiopeia A. Finally, we use early holographic measurements to measure the Galt telescope's geometry with respect to CHIME for the holographic analysis of the CHIME and Galt interferometric data set.

astro-ph.IM↗

arXiv2022

Large Eddy Simulations of turbulent convective flow through a periodic groove channel

The use of extended surfaces find wide range of applications in heat transfer devices for achieving heat transfer augmentation like gas turbine blade cooling and nuclear reactor core since the last few decades. So, understanding the underlying flow physics physics and the transport phenomenon governing the heat transfer enhancement is the goal of the present study. In the present investigation, numerical computations of turbulent forced convection through a periodic groove channel are carried out using large eddy simulations. The lower wall of the grooved channel is provided with constant heat flux while upper wall insulated. Computations were carried out using WMLES model in LES formulation implemented in a finite volume based solver ANSYS Fluent 19.2. The simulations are performed over varying Reynolds numbers range of 3000-30000 at different ratios groove width to channel height (B/H) in the range 0.75-1.75. The groove pitch ratio, and depth ratio kept constant of magnitude 2 and 0.5 respectively. Estimation of coefficient of heat transfer, associated frictional losses, and magnitude of heat enhancement are systematically carried out and compared with reported results in literature obtained using RANS framework reported in literature. The results obtained using LES show improvements in the heat transfer rate by a reasonable magnitude of 45% while the associated frictional losses decreased by an average magnitude of 40% compared to results obtained using RANS formulation in the aforementioned range of Re. Further, a maximum magnitude of 64% improvement in the thermal enhancement factor is achieved using LES for a B/H ratio of 0.75. Two correlations are proposed to calculate the friction factor and thermal enhancement factor for a given Re, Nu and (B/H) ratio, with a R-squared value of 0.94 and 0.96 respectively based on the obtained simulated results.

physics.flu-dyn↗

arXiv2022

Towards 21-cm Intensity Mapping at $z=2.28$ with uGMRT using the Tapered Gridded Estimator I: Foreground Avoidance

The post-reionization $(z \le 6)$ neutral hydrogen (HI) 21-cm intensity mapping signal holds the potential to probe the large scale structures, study the expansion history and constrain various cosmological parameters. Here we apply the Tapered Gridded Estimator (TGE) to estimate $P(k_{\perp},k_{\parallel})$ the power spectrum of the $z = 2.28$ $(432.8\, {\rm MHz})$ redshifted 21-cm signal using a $24.4\,{\rm MHz}$ sub-band drawn from uGMRT Band 3 observations of European Large-Area ISO Survey-North 1 (ELAIS-N1). The TGE allows us to taper the sky response which suppresses the foreground contribution from sources in the periphery of the telescope's field of view. We apply the TGE on the measured visibility data to estimate the multi-frequency angular power spectrum (MAPS) $C_{\ell}(Δν)$ from which we determine $P(k_{\perp},k_{\parallel})$ using maximum-likelihood which naturally overcomes the issue of missing frequency channels (55 \% here). The entire methodology is validated using simulations. For the data, using the foreground avoidance technique, we obtain a $2\,σ$ upper limit of $Δ^2(k) \le (133.97)^2 \, {\rm mK}^{2}$ for the 21-cm brightness temperature fluctuation at $k = 0.347 \, \textrm{Mpc}^{-1}$. This corresponds to $[Ω_{\rm HI}b_{\rm HI}] \le 0.23$, where $Ω_{\rm HI}$ and $b_{\rm HI}$ respectively denote the cosmic \HI mass density and the \HI bias parameter. A previous work has analyzed $8 \, {\rm MHz}$ of the same data at $z=2.19$, and reported $Δ^{2}(k) \le (61.49)^{2} \, {\rm mK}^{2}$ and $[Ω_{\rm HI} b_{\rm HI}] \le 0.11$ at $k=1 \, {\rm Mpc}^{-1}$. The upper limits presented here are still orders of magnitude larger than the expected signal corresponding to $Ω_{\rm HI} \sim 10^{-3}$ and $b_{\rm HI} \sim 2 $.

astro-ph.CO↗

arXiv2022

A study on the Clustering Properties of Radio-Selected sources in the Lockman Hole Region at 325 MHz

Studying the spatial distribution of extragalactic source populations is vital in understanding the matter distribution in the Universe. It also enables understanding the cosmological evolution of dark matter density fields and the relationship between dark matter and luminous matter. Clustering studies are also required for EoR foreground studies since it affects the relevant angular scales. This paper investigates the angular and spatial clustering properties and the bias parameter of radio-selected sources in the Lockman Hole field at 325 MHz. The data probes sources with fluxes $\gtrsim$0.3 mJy within a radius of 1.8$^\circ$ around the phase center of a $6^\circ \times 6^\circ$ mosaic. Based on their radio luminosity, the sources are classified into Active Galactic Nuclei (AGNs) and Star-Forming Galaxies (SFGs). Clustering and bias parameters are determined for the combined populations and the classified sources. The spatial correlation length and the bias of AGNs are greater than SFGs -- indicating that more massive haloes host the former. This study is the first reported estimate of the clustering property of sources at 325 MHz, intermediate between the preexisting studies at high and low-frequency bands. It also probes a well-studied deep field at an unexplored frequency with moderate depth and area. Clustering studies require such observations along different lines of sight, with various fields and data sets across frequencies to avoid cosmic variance and systematics. Thus, an extragalactic deep field has been studied in this work to contribute to this knowledge.

astro-ph.CO↗

arXiv2022

Observing the Reionization : Effect of Calibration and Position Errors on Realistic Observation Conditions

Observation of the redshifted 21-cm signal from Cosmic Dawn and Epoch of Reionization is a challenging endeavor in observational cosmology. Presence of orders of magnitude brighter astrophysical foregrounds and various instrumental systematics increases the complexity of these observations. This work presents an end-to-end pipeline dealing with synthetic interferometric data of sensitive radio observations . The mock sky model includes the redshifted 21-cm signal and astrophysical foregrounds. The effects of calibration error and position error in the extraction of the redshifted 21-cm power spectrum has been simulated. The effect of the errors in the image plane detection of the cosmological signal has also been studied. A comparative analysis for array configurations like the SKA1-Low, MWA and HERA has been demonstrated. The calibration error tolerance of the arrays, under some assumptions about the nature of the systematic components, is optimally found to be $\sim 0.01\%$ for the detection of the signal. For position errors, an offset of $\gtrapprox 5\arcsec$ makes the residual foregrounds obscure the target signal. These simulations also imply that in the SKA-1 Low performs marginally better than the others in the image domain, while the same is true for MWA in the power spectrum domain. This is one of the first studies that compares performance of various radio telescopes operating under similar observing conditions towards detecting the cosmological signal. This end-to-end pipeline can also be extended to study effects of chromatic primary beam, radio frequency inferences, foregrounds with spectral features, etc.

astro-ph.CO↗