A spherical harmonic analysis of the Ooty Wide Field Array (OWFA) visibility signal

Chatterjee, Suman; Bharadwaj, Somnath

doi:10.1093/mnras/sty942

Cited by 7 publications

(5 citation statements)

References 38 publications

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“…The possibility of detecting the HI 21-cm signal using OWFA has been studied extensively [29,[73][74][75][76]. Detailed foreground predictions [29,77] and calibration issues [70] for OWFA have also been addressed.…”

Section: Predictions For the Ooty Wide Field Array (Owfa)mentioning

confidence: 99%

Constraining warm dark matter power spectrum using the cross-correlation of HI 21 cm signal and the Lyman-α forest

Sarkar¹,

Pal²,

Sarkar³

2019

J. Cosmol. Astropart. Phys.

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We have considered the prospects for measuring the cross Warm Dark Matter (WDM) power spectrum of the redshifted HI 21-cm signal and the Lyman-α forest and thereby constraining WDM mass using observations with upcoming radio-interferometers—the Ooty Wide Field Array (OWFA) and SKA1-mid, and a spectroscopic survey of the quasars. We have considered a quasar survey with a mean observed quasar number density of n̄Q = 48 deg−2 over a collecting area of 14455 deg2, and a mean spectroscopic SNR = 5. Our analysis with OWFA shows that it is possible to measure the WDM power spectrum in several k-bins at k ⩽ 0.45 Mpc−1 with SNR > 5 using observations of 200 hours each in 100 different fields-of-view for mWDM = 0.25 keV . Considering the possibility of the joint measurement of the parameters, the warm dark matter density parameter ΩWDM, and the dark energy density parameter ΩΛ0, we find that the relative error on the 1−σ measurement of the parameter ΩWDM is ∼ 0.8 for a fiducial mWDM = 0.25 keV . However, we find that OWFA is not sensitive towards measuring the suppression of the WDM power spectrum, and therefore, cannot be used to constrain the WDM mass. Considering the analysis with SKA I mid, we find that for a fiducial mWDM= 0.25 keV, the suppression in the cross power spectrum can be measured at ∼ 10 − σ around k ∼ 0.2 Mpc−1 for a total observing time of 20000 hours distributed uniformly over 50 independent pointings where we have binned the available k-range as Δ k = k/5.

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Section: Predictions For the Ooty Wide Field Array (Owfa)mentioning

confidence: 99%

Constraining warm dark matter power spectrum using the cross-correlation of HI 21 cm signal and the Lyman-α forest

Sarkar¹,

Pal²,

Sarkar³

2019

J. Cosmol. Astropart. Phys.

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“…Considering S (Ua, νn), the H i signal contribution to the model visibilities, we have simulated these using the flat-sky approximation (FSA). An earlier work (Chatterjee & Bharadwaj 2018b) has carried out a full spherical harmonic analysis for OWFA to find that the differences from the FSA are at most within 10% at the few smallest baselines and they are much smaller at the other larger baselines. Using ∆n = θ which is now a 2D vector on the plane of the sky, eq.…”

Section: Visibility Simulationsmentioning

confidence: 99%

Simulated Predictions for HI at $z = 3.35$ with the Ooty Wide Field Array (OWFA) -- II: Foreground Avoidance

Chatterjee,

Bharadwaj,

Marthi

2019

Preprint

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Considering the upcoming OWFA, we use simulations of the foregrounds and the z = 3.35 H i 21-cm intensity mapping signal to identify the (k ⊥ , k ) modes where the expected 21-cm power spectrum P (k ⊥ , k ) is substantially larger than the predicted foreground contribution. Only these uncontaminated k-modes are used for measuring P (k ⊥ , k ) in the "Foreground Avoidance" technique. Though the foregrounds are largely localised within a wedge. we find that the small leakage beyond the wedge surpasses the 21-cm signal across a significant part of the (k ⊥ , k ) plane. The extent of foreground leakage is extremely sensitive to the frequency window function used to estimate P (k ⊥ , k ). It is possible to reduce the leakage by making the window function narrower, however this comes at the expense of losing a larger fraction of the 21-cm signal. It is necessary to balance these competing effects to identify an optimal window function. Considering a broad class of cosine window functions, we identify a six term window function as optimal for 21-cm power spectrum estimation with OWFA. Considering only the k-modes where the expected 21-cm power spectrum exceeds the predicted foregrounds by a factor of 100 or larger, a 5 σ detection of the binned power spectrum is possible in the k ranges 0.18 k 0.3 Mpc −1 and 0.18 k 0.8 Mpc −1 with 1, 000 − 2, 000 hours and 10 4 hours of observation respectively.

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“…While HI intensity mapping is being used to study the EoR and cosmic dawn by a variety of meter wavelength instruments, including LOFAR [10], MWA [11], HERA [12], PAPER [13], and LWA [14], this paper focuses on measurements of the post-reionization epoch. Several dedicated instruments have been constructed, or are under development, to detect the 21 cm signal: CHIME [15], Tianlai [8,[16][17][18][19], HIRAX [20], OWFA [21], and BINGO [22]. Other instruments are being designed and built to test the technique, including BMX and PAON-4 [23,24].…”

Section: Introductionmentioning

confidence: 99%

The Tianlai Cylinder Pathfinder array: System functions and basic performance analysis

Zuo

et al. 2020

Sci. China Phys. Mech. Astron.

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The Tianlai Cylinder Pathfinder is a radio interferometer array designed to test techniques for 21 cm intensity mapping in the post-reionization Universe, with the ultimate aim of mapping the large scale structure and measuring cosmological parameters such as the dark energy equation of state. Each of its three parallel cylinder reflectors is oriented in the north-south direction, and the array has a large field of view. As the Earth rotates, the northern sky is observed by drift scanning. The array is located in Hongliuxia, a radio-quiet site in Xinjiang, and saw its first light in September 2016. In this first data analysis paper for the Tianlai cylinder array, we discuss the subsystem qualification tests, and present basic system performance obtained from preliminary analysis of the commissioning observations during 2016-2018. We show typical interferometric visibility data, from which we derive the actual beam profile in the east-west direction and the frequency band-pass response. We describe also the calibration process to determine the complex gains for the array elements, either using bright astronomical point sources, or an artificial on site calibrator source, and discuss the instrument response stability, crucial for transit interferometry. Based on this analysis, we find a system temperature of about 90 K, and we also estimate the sensitivity of the array.

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A spherical harmonic analysis of the Ooty Wide Field Array (OWFA) visibility signal

Cited by 7 publications

References 38 publications

Constraining warm dark matter power spectrum using the cross-correlation of HI 21 cm signal and the Lyman-α forest

Constraining warm dark matter power spectrum using the cross-correlation of HI 21 cm signal and the Lyman-α forest

Simulated Predictions for HI at $z = 3.35$ with the Ooty Wide Field Array (OWFA) -- II: Foreground Avoidance

The Tianlai Cylinder Pathfinder array: System functions and basic performance analysis

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