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Overview of Radio Astronomy activities at NCRA

Overview of Radio Astronomy activities at NCRA. Yashwant Gupta National Centre for Radio Astrophysics Pune India. India-South Africa Astronomy Workshop Capetown 7 Aug 2012. Introduction.

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Overview of Radio Astronomy activities at NCRA

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  1. Overview of Radio Astronomy activities at NCRA Yashwant Gupta National Centre for Radio Astrophysics Pune India India-South Africa Astronomy Workshop Capetown 7 Aug 2012

  2. Introduction • Radio Astronomy activities at NCRA can be broadly categorised into : • Research programs using the ORT and the GMRT • Technology improvements at the facilities, including the upgrades • SKA and related activities • Outreach and user community development programs

  3. NCRA major facilities : ORT & GMRT • The ORT & GMRT are the main observational facilities at NCRA, with many interesting science results • Both the ORT (age : 40 yrs) and the GMRT (age : 10 yrs) are undergoing major upgrades at present

  4. ORT & GMRT : Scientific Objectives • The ORT is primarily used for : • Interplanetary scintillations, solar wind and space weather studies • The GMRT is a powerful instrument for a wide range of studies : • The Sun, extrasolar planets • Pulsars : rapidly rotating neutron stars • Other Galactice objects like : supernova remnants, microquasarsetc • Other explosive events like Gamma Ray Bursts • Ionized and neutral Hydrogen gas clouds (in our Galaxy and in other galaxies) • Radio properties of different kinds of galaxies; galaxy clusters • Radio galaxies at large distances in the Universe • Cosmology and the Epoch of Reionization • All sky surveys such as the 150 MHz TGSS

  5. GMRT : Some Pulsar Results…

  6. Some pulsar related results from the GMRT • Pulsar discoveries : e.g. NGC1851A (Freire et al 2004), J1833-1034 in G21.5-0.9 (Gupta et al 2005), pulsars from 610 survey (Joshi et al. 2009), Fermi LAT pulsar discoveries (ongoing!) • Pulsar timing : multiple glitches from J1833-1034 (Roy et al, in press) • Pulsar polarisation and clues to emission mechanism : e.g. Mitra et al (2007), Johnston et al (2008), Mitra et al (2009) • Simultaneous multi-frequency observations : e.g. Kramer et al (2003), Loehmer et al (2004), Ahuja et al (2005), Bhat et al (2007) • Single pulse studies : e.g. Gupta et al (2004), Bhattacharyya et al (2007, 2010), Backus, Mitra & Rankin (2011) • Off-pulse emission from pulsars : Basu, Athreya & Mitra (2011)

  7. Finding New Pulsars Using The GMRT Discovery of the first new pulsar with the GMRT : a binary millisecond pulsar in the Globular Cluster NGC 1851 Very interesting variation period with epoch ! Binary pulsar with very eccentric orbit (e = 0.89) ! Freire, Gupta, Ransom & Ishwar-Chandra (2004)

  8. Locating the new pulsar MAPPING CONCURRENTLY WITH PHASED ARRAY OBSERVATIONS ! NGC1851 : A relatively bring GC (Mv = -8.3) with a very condensed core and high central luminosity density GMRT radio map of NGC1851 made from data simultaneous with phased array acquisition

  9. Targeted searches using phased array mode of the GMRT : supernova remnants • Central core of GMRT used in phased array mode to cover the target SNR • 62 ms young pulsar in SNR G21.5-0.9 Timing observations show frequent, low-amplitude glitches Distinct population of young pulsars with reduced glitch activity parameter Gupta et al (2005) Roy, Gupta & Lewandowski (in press)

  10. Fermi LAT Pulsars with the GMRT Total of 6 new MSPs discovered in follow-up radio searches of Fermi LAT sources, using the GMRT, in the last 1.5 years First Fermi LAT discovery with the GMRT Bhattacharyya et al (in preparation) GMRT Fermi Search Team : Bhaswati Bhattacharyya, Jayanta Roy, Yashwant Gupta & Dipankar Bhatacharya

  11. Fermi LAT Pulsars with the GMRT Of the 6 MSPs make an interesting bunch : there are black widows, isolated MSPs, wide profile pulsars… Black-widow system with shortest binary period : 2.8 hr Bhattacharyya et al (in preparation) GMRT Fermi Search Team : Bhaswati Bhattacharyya, Jayanta Roy, Yashwant Gupta & Dipankar Bhatacharya

  12. Fermi LAT Pulsars with the GMRT Of the 6 MSPs make an interesting bunch : there are black widows, isolated MSPs, wide profile pulsars… MSP with very wide profile Bhattacharyya et al (in preparation) GMRT Fermi Search Team : Bhaswati Bhattacharyya, Jayanta Roy, Yashwant Gupta & Dipankar Bhatacharya

  13. Localising the Fermi LAT Pulsars with the GMRT GMRT as an interferometer offers unique opportunity to quickly localise the position of the detected pulsar with good accuracy : • First, make a quick map of the FoV however, many point-like sources ! • Record raw voltages for the source and making multiple phased array beams at different possible point source locations, and check for the pulsar ! Jayanta Roy et al. (submitted)

  14. Localising the Fermi LAT Pulsars with the GMRT GMRT as an interferometer offers unique opportunity to quickly localise the position of the detected pulsar with good accuracy : • First, make a quick map of the FoV • Record raw voltages for the source and making multiple phased array beams at different possible point source locations, and check for the pulsar • Even better : Gated Correlator : Make On-pulse & Off-pulse maps and subtract !! Jayanta Roy et al. (in preparation)

  15. Simultaneous Multi-frequency Pulsar Observations • Simultaneous Multi-frequency pulsar observations provide a very powerful tool to study several aspects of pulsar emission properties • “Local MFO” : The GMRT has the unique ability to observe simultaneously at more than one frequency, using the “sub-array” mode – upto 4 frequency observations have been carried out – the data from the different frequencies is completely time synchronised ! • “Global MFO” : We have participated in coordinated multi-frequency observations with other observatories, contributing at 2 or 3 wavebands

  16. Dual frequency observations : DM variations of PPTA MSPs Simultaneous dual frequency observations at 325 & 610 MHz DM accuracies of 1 part in 10^5 Ujjwal Kumar et al.

  17. New Results : Off-pulse emission from pulsars Using gated interferometer to make images for on-pulse and off-pulse regions for some well known pulsars Basu, Athreya & Mitra (2011)

  18. Decoding the nature of pulsar emission • Strong single pulses from 10 pulsars with the GMRT, showing extremely high linear polarization with the position angle following locally the mean PA traverse • Must consist exclusively of a single polarization mode  extraordinary wave excited by coherent curvature Mitra, Gil & Melikidze 2009

  19. Acetaldehyde from Sgr B2 • The CH3CHO emission at 1065 MHz appears to be mased • CH3CHO emission is coincident with HCHO absorption • Emission is seen in both the low & high resolution images, made from a single GMRT observations • Emission on both large scales and fine scales appears correlated with shocks GMRT maps are the only direct images of wide spread emission from a large organic molecue Chengalur & Kanekar 2003

  20. Moving to some results from outside our Galaxy…

  21. Drawf Galaxy NGC 3741 (MB ~ -13.13 mag) HI gas disk ~ 8.3 times Holmberg radius The most extended HI disk known MHI ~ 2 х 108 MO Begum, Chengalur & Karachentsev 2005

  22. NGC 3741 : Dark Matter • Rotation curve measured out to 38 optical disk scale lengths • Dynamical mass to light ratio ~ 107 NGC 3741 is one of the “darkest” known irregulars Begum, Chengalur & Karachentsev 2005

  23. Damped Lyman Alpha (DLA) systems • Several new DLA systems have been discovered with the GMRT in the past few years • 9 new detections in 400 hours survey with the GMRT in the 610 MHz band Neeraj Gupta et al 2007

  24. Mapping 21 cm absorption in DLAs towards extended radio sources – size, kinematics of high z galaxies Kanekar & Chengalur 2008

  25. Detection of Molecular gas at intermediate redshifts using the GMRT • Kanekar & Chengalur have detected OH absorption in 3 radio sources with GMRT, in addition to that detected earlier by Chengalur with WSRT in the lensing galaxy towards 1830-211. • Good correlation between NOH & NHCO+ which indicates that OH may be a good tracer of H2 at cosmological distances. OH [1665 & 1667 MHz]B 1504+377Zabs=0.67345 Kanekar and Chengalur (2002)

  26. Transient Sources : Gamma Ray Burst GRB030329 • Data at 1280 and 610 MHz with the GMRT, compared with the “refreshed jet” model of the afterglow • Jet becomes sub-relativistic ~ 60 days after burst • Longest ever radio follow-up and lowest radio frequency observations of a GRB Resmi & Bhattacharya 2006

  27. Sample results : Polarization EN1DEEP06 : GMRT Deep Polarization Field 610 MHz, 30 hrs, 15 microJy RMS courtesy : Russ Taylor & team , July 2011 Total Intensity Polarized Intensity

  28. EoR Experiment at the GMRT • EoR project at the GMRT led by Ue-Li Pen (CITA) • First published results establish interesting new limits on EoR signal strength Paciga et al, 2011

  29. Upgraded GMRT : Expected Performance Expected performance of the upgraded GMRT compared to other major facilities in the world, present and projected

  30. Frequency Band (MHz) 125-250 250-500 550-900 1000-1450 Max Bandwidth (MHz) 125 250 350 400 Incoherent Array Beam FoV (deg) 3.2 1.4 0.8 0.4 Incoherent Array search sensitivity for 10 min (uJy) 2500 350 250 200 Phased Array Beam FoV (arcsec) 20 9 5 2 Phased Array search sensitivity for 10 min (uJy) 400 60 40 35 Expected Performance Figures (for array mode)

  31. Thank You

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