Characterizing EoR foregrounds: a study of the Lockman Hole region at 325 MHz

Mazumder, Aishrila; Chakraborty, Arnab; Datta, Abhirup; Choudhuri, Samir; Roy, Nirupam; Wadadekar, Yogesh; Ishwara‐Chandra, C. H.

doi:10.1093/mnras/staa1317

Cited by 17 publications

(9 citation statements)

References 91 publications

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“…tions of the ELAIS-N1 at 400 MHz [Chakraborty et al, 2019] and Lockman Hole at 325 MHz [Mazumder et al, 2020[Mazumder et al, , 2022a. The AGNs dominate the flux densities ≥1 mJy while SFGs dominate at the sub-mJy level.…”

Section: Foregroundsmentioning

confidence: 96%

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

Mazumder¹,

Datta²,

Rao³

et al. 2022

Preprint

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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.

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Section: Foregroundsmentioning

confidence: 96%

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

Mazumder¹,

Datta²,

Rao³

et al. 2022

Preprint

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“…Additionally, it reduces computational load by using gridded visibilities, and internally subtracts out the positive-definite noise bias to produce unbiased estimates of the measured quantities. The TGE has been used to characterise the angular power spectrum 𝐶 ℓ of the foregrounds at EoR frequencies (Choudhuri et al 2017(Choudhuri et al , 2020 as well as post-EoR frequencies (Chakraborty et al 2019a,b;Mazumder et al 2020). Bharadwaj et al (2018) further developed upon this to introduce a MAPS-based TGE which first estimates the MAPS, and, from it, the PS, effectively dealing with the missing frequency channels in the visibility data while preserving all the qualities mentioned above.…”

Section: Introductionmentioning

confidence: 99%

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

Elahi¹,

Bharadwaj²,

Ghosh³

et al. 2023

Preprint

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Neutral hydrogen (H ) 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 ℓ (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 MHz bandwidth uGMRT Band 3 data centred at 432.8 MHz aiming H IM at 𝑧 = 2.28. The measured 𝐶 ℓ (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 2 𝑈 𝐿 (𝑘) ≤ (58.67) 2 mK 2 at 𝑘 = 0.804 Mpc −1 which is a factor of 5.2 improvement on our previous estimate based on the Total TGE. Assuming that the H traces the underlying matter distribution, we have modelled 𝐶 ℓ (Δ𝜈) to simultaneously estimate the foregrounds and [Ω H 𝑏 H ] where Ω H and 𝑏 H are the H density and linear bias parameters respectively. We obtain a best fit value of [Ω H 𝑏 H ] 2 = 7.51 × 10 −4 ± 1.47 × 10 −3 which is consistent with noise. Although the 2𝜎 upper limit [Ω H 𝑏 H ] 𝑈 𝐿 ≤ 0.061 is ∼ 50 times larger than the expected value, this is a considerable improvement over earlier works at this redshift.

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“…The most sensitive operational interferometers like the GMRT, MWA, LOFAR, HERA have all set upper limits on the power spectrum (PS) amplitude of the signal (Paciga et al 2011;Beardsley et al 2016;Gehlot et al 2019;Trott et al 2020;Mertens et al 2020;The HERA Collaboration et al 2022) but and no confirmed detection of the cosmological H 21cm signal. The cosmological signal is prone to contamination due to bright astrophysical foregrounds (Bharadwaj & Saiyad Ali 2005;Jelić et al 2008Jelić et al , 2010Zahn et al 2011;Chapman et al 2015;Choudhuri et al 2017;Chakraborty et al 2019;Mazumder et al 2020). Other sources of contamination are Earth's ionosphere and several instrumental systematics.…”

Section: Introductionmentioning

confidence: 99%

Observing the reionization: effect of calibration and position errors on realistic observation conditions

Mazumder

Datta

Chakraborty

et al. 2022

Monthly Notices of the Royal Astronomical Society

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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 ⪆ 5″ 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.

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Characterizing EoR foregrounds: a study of the Lockman Hole region at 325 MHz

Cited by 17 publications

References 91 publications

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

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

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

Observing the reionization: effect of calibration and position errors on realistic observation conditions

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