Giant Metrewave Radio Telescope Explained

The Giant Metrewave Radio Telescope (GMRT), located near Narayangaon, Pune in India, is an array of thirty fully steerable parabolic radio telescopes of 45 metre diameter, observing at metre wavelengths. It is the largest and most sensitive radio telescope array in the world at low frequencies.[1] It is operated by the National Centre for Radio Astrophysics (NCRA), a part of the Tata Institute of Fundamental Research, Mumbai. It was conceived and built under the direction of Govind Swarup during 1984 to 1996.[2] It is an interferometric array with baselines of up to 25km (16miles).[3] [4] [5] It was recently upgraded with new receivers, after which it is also known as the upgraded Giant Metrewave Radio Telescope (uGMRT).[6]

Location

The Giant Metrewave Radio Telescope (GMRT) Observatory is located about 80 km north of Pune at Khodad. A nearby town is Narayangaon which is around 9 km from the telescope site. The office of National Centre for Radio Astrophysics (NCRA) is located in the Savitribai Phule Pune University campus.

Science and observations

One of the aims for the telescope during its development was to search for the highly redshifted 21-cm line radiation from primordial neutral hydrogen clouds in order to determine the epoch of galaxy formation in the universe.[7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30]

Astronomers from all over the world regularly use this telescope to observe many different astronomical objects such as the Sun, Jupiter, exoplanets, magnetically active stars, microquasars or binary stars with a compact object (neutron star or black hole) as companion, pulsars, supernovae, supernovae remnants (SNR) HII regions, galaxies, quasars, radio galaxies, clusters of galaxies, cluster radio relics and halos, high-z galaxies, solar winds, Inter-galactic HI absorption lines, diffuse radio emission from filaments of galaxies, possible signs of time-variation of fundamental constants, variation of gas content with cosmic epoch, epoch of reionisation etc. .

GMRT has produced an all sky survey named TIFR GMRT Sky Survey (TGSS). Nearly 90% of the sky has been imaged at the frequency of 150 MHz (wavelength 2m), with an angular resolution of 25 arc second and rms noise of 5 mili Jansky per beam. Source Catalogue and FITS image files for the scientific community are freely available.[31] General public and citizen scientists can see 150 MHz image of any, supernova remnant, spiral galaxy or radio galaxy with its name or position at the RAD@home RGB-maker web-tool. Power and versatility of the GMRT has led to a renaissance in the field of low frequency radio astronomy.[32]

From this, TGSS survey, data, in August 2018, the most distant known radio galaxy : TGSS J1530+1049, located at a distance of 12 billion light years, was discovered by GMRT.[33] [34]

In February 2020, it helped in the observation of evidence of the largest known explosion in the history of the universe, the Ophiuchus Supercluster explosion.[35]

In January 2023, the telescope picked up a radio signal (21 cm line emission from neutral atomic hydrogen gas) which originated from 8.8 billion light years away.[36]

Activities

Each year on National Science Day the observatory invites the public and pupils from schools and colleges in the surrounding area to visit the site where they can listen to explanations of radio astronomy, receiver technology and astronomy from the engineers and astronomers who work there. Nearby schools/colleges are also invited to put their individual science experiments in exhibition and the best one in each level (primary, secondary school and Jr. college) are awarded.

Visitors are allowed into GMRT only on Fridays in two sessions - Morning (1100 hrs - 1300 hrs) and Evening (1500 hrs to 1700 hrs).

See also

External links

Notes and References

  1. Web site: The Giant Metrewave Radio Telescope . NCRA website . en-us.
  2. http://www.gmrt.ncra.tifr.res.in/news/gs.html Prof. Govind Swarup: The Father of Radio Astronomy in India
  3. Ananthakrishnan. S.. The giant meterwave radio telescope.. Journal of Astrophysics and Astronomy. 1995. 16. 433. 27 June 2015.
  4. 10.1088/1009-9271/5/S1/87 . Ishwara-Chandra . C H . Rao . A Pramesh . Pandey . 2005 . Mamta . Manchanda . R K . Durouchoux . Philippe . Low Frequency Radio Observations of GRS1915+105 with GMRT. Chinese Journal of Astronomy and Astrophysics. 5 . S1. 87–92. 2005ChJAS...5...87I. astro-ph/0512061 .
  5. Swarup, G., Ananthkrishnan, S., Kapahi, V.K., Rao, A.P., Subrahamanya, C.R., and Kulkarni, V.K. (1991) "The Giant Metrewave Radio Telescope", Current Science, vol. 60, pages 90-105.
  6. Gupta . Y. . Ajithkumar . B. . Kale . H. S. . Nayak . S. . Sabhapathy . S. . Sureshkumar . S. . Swami . R. V. . Chengalur . J. N. . Ghosh . S. K. . Ishwara-Chandra . C. H. . Joshi . B. C. . Kanekar . N. . Lal . D. V. . Roy . S. . 2017-08-25 . The Upgraded GMRT:Opening New Windows on the Radio Universe . Current Science . 113 . 4 . 707 . 10.18520/cs/v113/i04/707-714 . 2017CSci..113..707G . 0011-3891.
  7. Kapahi. V. K.. Ananthakrishnan. S.. Astronomy with the giant metrewave radio telescope (GMRT).. Bulletin of the Astronomical Society of India. 1995. 23. 267. 27 June 2015. 1995BASI...23..265K.
  8. Bharadwaj. Somnath. Nath. Biman B.. Sethi. Shiv K.. 2001-03-01. Using HI to probe large scale structures at z~3. Journal of Astrophysics and Astronomy. en. 22. 1. 21–34. 10.1007/BF02933588. 0250-6335. astro-ph/0003200. 2001JApA...22...21B. 14407741 .
  9. Bharadwaj. S.. Nath. B. B.. Sethi. S. K.. 2002. Probing Large Scale Structures in HI with GMRT. The Universe at Low Radio Frequencies. 199. 108–109. 2002IAUS..199..108B. 10.1017/s0074180900168640. free.
  10. Bharadwaj. Somnath. Sethi. Shiv K.. 2001-12-01. HI fluctuations at large redshifts: I-visibility correlation. Journal of Astrophysics and Astronomy. en. 22. 4. 293–307. 10.1007/BF02702273. 0973-7758. 2001JApA...22..293B. astro-ph/0203269. 14605700 .
  11. Bharadwaj. Somnath. Pandey. Sanjay K.. 2003-03-01. HI Fluctuations at Large Redshifts: II - the Signal Expected for the GMRT. Journal of Astrophysics and Astronomy. 24. 1–2. 23–35. 10.1007/BF03012189. 0250-6335. astro-ph/0307303. 2003JApA...24...23B. 18496656 .
  12. Bharadwaj. Somnath. Srikant. P. S.. 2004-03-01. HI Fluctuations at Large Redshifts: III - Simulating the Signal Expected at GMRT. Journal of Astrophysics and Astronomy. 25. 1–2. 67–80. 10.1007/BF02702289. 0250-6335. 2004JApA...25...67B. astro-ph/0402262. 8964798 .
  13. Pandey. Sanjay K.. Bharadwaj. Somnath. Saiyad Ali. S. K.. 2006-02-11. Probing the bispectrum at high redshifts using 21-cm H i observations. Monthly Notices of the Royal Astronomical Society. en. 366. 1. 213–218. 10.1111/j.1365-2966.2005.09847.x. free . 0035-8711. astro-ph/0510118. 2006MNRAS.366..213S . 7600009 .
  14. Choudhury. T. Roy. Bharadwaj. Somnath. Datta. Kanan K.. 2007-12-01. Detecting ionized bubbles in redshifted 21-cm maps. Monthly Notices of the Royal Astronomical Society. en. 382. 2. 809–818. 10.1111/j.1365-2966.2007.12421.x. free . 0035-8711. 2007MNRAS.382..809D. astro-ph/0703677.
  15. Chengalur. Jayaram N.. Bharadwaj. Somnath. Ali. Sk Saiyad. 2008-04-21. Foregrounds for redshifted 21-cm studies of reionization: Giant Meter Wave Radio Telescope 153-MHz observations. Monthly Notices of the Royal Astronomical Society. en. 385. 4. 2166–2174. 10.1111/j.1365-2966.2008.12984.x. free . 0035-8711. 2008MNRAS.385.2166A. 0801.2424. 13541850 .
  16. Choudhury. T. Roy. Bharadwaj. Somnath. Majumdar. Suman. Datta. Kanan K.. 2008-12-21. Simulating the impact of H i fluctuations on matched filter search for ionized bubbles in redshifted 21-cm maps. Monthly Notices of the Royal Astronomical Society. en. 391. 4. 1900–1912. 10.1111/j.1365-2966.2008.14008.x. free . 0035-8711. 2008MNRAS.391.1900D. 0805.1734. 15646124 .
  17. Choudhury. T. Roy. Bharadwaj. Somnath. Datta. Kanan K.. 2009-10-01. The optimal redshift for detecting ionized bubbles in Hi 21-cm maps. Monthly Notices of the Royal Astronomical Society: Letters. en. 399. 1. L132–L136. 10.1111/j.1745-3933.2009.00739.x. free . 1745-3925. 2009MNRAS.399L.132D. 0906.0360. 8941846 .
  18. Choudhury. T. Roy. Datta. Kanan K.. Bharadwaj. Somnath. Majumdar. Suman. 2011-05-11. The impact of anisotropy from finite light traveltime on detecting ionized bubbles in redshifted 21-cm maps. Monthly Notices of the Royal Astronomical Society. en. 413. 2. 1409–1418. 10.1111/j.1365-2966.2011.18223.x. free . 0035-8711. 2011MNRAS.413.1409M. 1006.0430. 8869385 .
  19. Ghosh. Abhik. Bharadwaj. Somnath. Ali. Sk. Saiyad. Chengalur. Jayaram N.. 2011-03-01. GMRT observation towards detecting the post-reionization 21-cm signal. Monthly Notices of the Royal Astronomical Society. 411. 4. 2426–2438. 10.1111/j.1365-2966.2010.17853.x. free . 0035-8711. 2011MNRAS.411.2426G. 1010.4489. 119230101 .
  20. Ghosh. Abhik. Bharadwaj. Somnath. Ali. Sk. Saiyad. Chengalur. Jayaram N.. 2011-12-01. Improved foreground removal in GMRT 610 MHz observations towards redshifted 21-cm tomography. Monthly Notices of the Royal Astronomical Society. 418. 4. 2584–2589. 10.1111/j.1365-2966.2011.19649.x. free . 0035-8711. 2011MNRAS.418.2584G. 1108.3707. 118437718 .
  21. Choudhury. T. Roy. Bharadwaj. Somnath. Majumdar. Suman. 2012-11-11. Constraining quasar and intergalactic medium properties through bubble detection in redshifted 21-cm maps. Monthly Notices of the Royal Astronomical Society. en. 426. 4. 3178–3194. 10.1111/j.1365-2966.2012.21914.x. free . 0035-8711. 2012MNRAS.426.3178M. 1111.6354. 118436604 .
  22. Chengalur. Jayaram N.. Ali. Sk Saiyad. Bharadwaj. Somnath. Prasad. Jayanti. Ghosh. Abhik. 2012-11-11. Characterizing foreground for redshifted 21 cm radiation: 150 MHz Giant Metrewave Radio Telescope observations. Monthly Notices of the Royal Astronomical Society. en. 426. 4. 3295–3314. 10.1111/j.1365-2966.2012.21889.x. free . 0035-8711. 2012MNRAS.426.3295G. 1208.1617. 54662482 .
  23. Ghosh. A.. Prasad. J.. Bharadwaj. S.. Ali. Sk. S.. Chengalur. J. N.. 2013-04-01. VizieR Online Data Catalog: Complete 150MHz GMRT source catalogue (Ghosh+, 2012). VizieR On-line Data Catalog. 742. 2013yCat..74263295G.
  24. Ali. Sk Saiyad. Ghosh. Abhik. Bharadwaj. Somnath. Choudhuri. Samir. 2014-12-21. Visibility-based angular power spectrum estimation in low-frequency radio interferometric observations. Monthly Notices of the Royal Astronomical Society. en. 445. 4. 4351–4365. 10.1093/mnras/stu2027. free . 0035-8711. 2014MNRAS.445.4351C. 1409.7789.
  25. Choudhuri. Samir. Bharadwaj. Somnath. Ali. Sk. Saiyad. 2014. Foreground simulation and power spectrum estimation for 610 MHz GMRT observations. Astronomical Society of India Conference Series. 13. 315–317. 2014ASInC..13..315C.
  26. Ghosh. Abhik. Roy. Nirupam. Ali. Sk Saiyad. Chatterjee. Suman. Bharadwaj. Somnath. Choudhuri. Samir. 2016-12-21. The visibility-based tapered gridded estimator (TGE) for the redshifted 21-cm power spectrum. Monthly Notices of the Royal Astronomical Society. en. 463. 4. 4093–4107. 10.1093/mnras/stw2254. free . 0035-8711. 1609.01732. 2016MNRAS.463.4093C.
  27. Ali. Sk. Saiyad. Bharadwaj. Somnath. Choudhuri. Samir. Ghosh. Abhik. Roy. Nirupam. 2016-11-28. Prospects of Measuring the Angular Power Spectrum of the Diffuse Galactic Synchrotron Emission with SKA1 Low. Journal of Astrophysics and Astronomy. en. 37. 4. 35. 10.1007/s12036-016-9413-x. 0973-7758. 2016JApA...37...35A. 1610.08184. 55989492 .
  28. Ghosh. Abhik. Intema. Huib T.. Roy. Nirupam. Ali. Sk Saiyad. Bharadwaj. Somnath. Choudhuri. Samir. 2017-09-01. The angular power spectrum measurement of the Galactic synchrotron emission in two fields of the TGSS survey. Monthly Notices of the Royal Astronomical Society: Letters. en. 470. 1. L11–L15. 10.1093/mnrasl/slx066. free . 1745-3925. 1704.08642. 2017MNRAS.470L..11C.
  29. Chatterjee. Suman. Bharadwaj. Somnath. 2019-02-01. On the prospects of measuring the cosmic dawn 21-cm power spectrum using the upgraded Giant Metrewave Radio Telescope (uGMRT). Monthly Notices of the Royal Astronomical Society. 483. 2. 2269–2274. 10.1093/mnras/sty3242. free . 0035-8711. 2019MNRAS.483.2269C. 1804.00515.
  30. Dutta. Prasun. Choudhuri. Samir. Pal. Srijita. Bharadwaj. Somnath. 2019-03-11. A Tapered Gridded Estimator (TGE) for the multifrequency angular power spectrum (MAPS) and the cosmological H i 21-cm power spectrum. Monthly Notices of the Royal Astronomical Society. en. 483. 4. 5694–5700. 10.1093/mnras/sty3501. free . 0035-8711. 1812.08801. 2019MNRAS.483.5694B.
  31. Intema . H. T. . Jagannathan . P. . Mooley . K. P. . Frail . D. A. . February 2017 . The GMRT 150 MHz all-sky radio survey: First alternative data release TGSS ADR1 . Astronomy & Astrophysics . 598 . A78 . 10.1051/0004-6361/201628536 . 1603.04368 . 2017A&A...598A..78I . 15961445 . 0004-6361.
  32. Kembhavi . Ajit K. . Chengalur . Jayaram N. . 2023-04-19 . Govind Swarup. 23 March 1929—7 September 2020 . Biographical Memoirs of Fellows of the Royal Society . 75 . 455–478 . en . 10.1098/rsbm.2022.0049 . 0080-4606. free .
  33. Netherlands Research School for Astronomy . Astronomers report the most distant radio galaxy ever discovered . Phys.org . Science X Network . 23 July 2023 . 10.1093/mnras/sty1996 . 8 Aug 2018. free . 1887/71688 . free .
  34. Web site: Telescope In Pune Discovers Most Distant Radio Galaxy Ever Found. NDTV.com. 2019-06-13.
  35. Web site: Astronomers detect biggest explosion in the history of the Universe. ScienceDaily. en. 2020-02-27.
  36. Web site: Indian astronomer captures radio signal that originated 8 billion years ago . 20 January 2023 .

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