Large Steerable Radio Telescope at Ootacamund, India

Swarup, G.; Sarma, N. V. G.; Joshi, M. N.; Kapahi, V. K.; Bagri, D. S.; Damle, S. H.; Ananthakrishnan, S.; Balasubramanian, V.; Bhave, S. S.; Sinha, Rajesh Kumar

doi:10.1038/physci230185a0

Cited by 130 publications

(72 citation statements)

References 10 publications

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“…It operates at a fixed centre frequency of 327 MHz. It has 1056 dipoles arranged North-South along the focal line of the semi parabolic cylinder, and as the result of which it is not sensitive to the other (East-West) component of polarization (for further details refer Swarup et al 1971, Sarma et al 1975a., 1975b, Kapahi et al 1975.…”

Section: Sample Selection and Observationmentioning

confidence: 99%

Scatter broadening of pulsars in the direction of the Gum nebula

Mitra

Ramachandran

2001

A&A

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Abstract. We have measured the scatter broadening of pulsars in the direction of the Gum nebula. For the first time, our observations show clear variations of scattering properties across the Gum nebula. The IRAS-Vela shell is shown to be a high scattering region. Our revised estimations of distances to these pulsars are consistently less by a factor of 2-3, which has very important consequences for the deduced values of radio luminosity and transverse velocity of pulsars.

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Section: Sample Selection and Observationmentioning

confidence: 99%

Scatter broadening of pulsars in the direction of the Gum nebula

Mitra

Ramachandran

2001

A&A

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“…A new programmable backend has been added to the existing capability. For details, please see (Swarup et al, 1971;Kapahi et al, 1975;Sarma et al, 1975;Joshi et al, 1988;Chengalur, 2014, 2017). OWFA has the potential of detecting HI at z 3 and also measuring the power spectrum (Ali & Bharadwaj, 2014).…”

Section: Methodsologymentioning

confidence: 99%

Prospects of Detecting HI using Redshifted 21-cm Radiation at z∼3

Gehlot

Bagla

2017

J Astrophys Astron

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Distribution of cold gas in the post-reionization era provides an important link between distribution of galaxies and the process of star formation. Redshifted 21 cm radiation from the Hyperfine transition of neutral Hydrogen allows us to probe the neutral component of cold gas, most of which is to be found in the interstellar medium of galaxies. Existing and upcoming radio telescopes can probe the large scale distribution of neutral Hydrogen via HI intensity mapping. In this paper we use an estimate of the HI power spectrum derived using an ansatz to compute the expected signal from the large scale HI distribution at z ∼ 3. We find that the scale dependence of bias at small scales makes a significant difference to the expected signal even at large angular scales. We compare the predicted signal strength with the sensitivity of radio telescopes that can observe such radiation and calculate the observation time required for detecting neutral Hydrogen at these redshifts. We find that OWFA (Ooty Wide Field Array) offers the best possibility to detect neutral Hydrogen at z ∼ 3 before the SKA (Square Kilometer Array) becomes operational. We find that the OWFA should be able to make a 3 σ or a more significant detection in 2000 hours of observations at several angular scales. Calculations done using the Fisher matrix approach indicate that a 5σ detection of the binned HI power spectrum via measurement of the amplitude of the HI power spectrum is possible in 1000 hours (Sarkar, Bharadwaj and Ali, 2017).

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“…This makes the telescope's long axis parallel to the Earth's rotation axis (Swarup et al 1971;Sarma et al 1975) and enables the telescope to observe the same part of the sky with a single rotation. The telescope has a feed system that consists of 1056 half-wavelength dipoles which are placed almost end-to-end along the length of the cylinder.…”

Section: The Ooty Wide Field Array (Owfa)mentioning

confidence: 99%

“…The Ooty Radio Telescope (ORT) (Swarup et al 1971;Sarma et al 1975) is currently being upgraded to operate as a linear radio-interferometric array the Ooty Wide Field Array (OWFA) (Prasad & Subrahmanya 2011a,b;Subrahmanya et al 2017a). The primary science goals of OWFA have been outlined in Subrahmanya et al (2017b), and the measurement of the z = 3.35 post-reionization H i 21-cm power spectrum is one of its major objectives.…”

Section: Introductionmentioning

confidence: 99%

“…Single dish antennas are also being considered (BINGO 5 ; Battye et al 2012Battye et al , 2016 to measure the BAO using 21-cm IM observations. The Giant Metrewave Radio Telescope (GMRT 6 ; Swarup et al 1991) is capable of functioning at several different frequencies from 150 MHz to 1420 MHz, which correspond to measuring the H i radiation from the redshift range 0 z 8.5. The prospects of detecting the H i signal using the GMRT have been studied in earlier works (Bharadwaj & Pandey 2003;.…”

Section: Introductionmentioning

confidence: 99%

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An analytical method to simulate the H i 21-cm visibility signal for intensity mapping experiments

Sarkar

Bharadwaj

Marthi

2017

Monthly Notices of the Royal Astronomical Society

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Simulations play a vital role in testing and validating H i 21-cm power spectrum estimation techniques. Conventional methods use techniques like N-body simulations to simulate the sky signal which is then passed through a model of the instrument. This makes it necessary to simulate the H i distribution in a large cosmological volume, and incorporate both the light-cone effect and the telescope's chromatic response. The computational requirements may be particularly large if one wishes to simulate many realizations of the signal. In this paper we present an analytical method to simulate the H i visibility signal. This is particularly efficient if one wishes to simulate a large number of realizations of the signal. Our method is based on theoretical predictions of the visibility correlation which incorporate both the light-cone effect and the telescope's chromatic response. We have demonstrated this method by applying it to simulate the H i visibility signal for the upcoming Ooty Wide Field Array Phase I.

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Large Steerable Radio Telescope at Ootacamund, India

Cited by 130 publications

References 10 publications

Scatter broadening of pulsars in the direction of the Gum nebula

Scatter broadening of pulsars in the direction of the Gum nebula

Prospects of Detecting HI using Redshifted 21-cm Radiation at z∼3

An analytical method to simulate the H i 21-cm visibility signal for intensity mapping experiments

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