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   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

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

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

GMRT : Some Pulsar Results…

Some pulsar related results from the GMRT   Pulsar discoveries : e.g. NGC1851A (Freire et al 2004), J in G (Gupta et al 2005), pulsars from 610 survey (Joshi et al. 2009), Fermi LAT pulsar discoveries (ongoing!)   Pulsar timing : multiple glitches from J (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)

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 Freire, Gupta, Ransom & Ishwar-Chandra (2004) Very interesting variation period with epoch ! Binary pulsar with very eccentric orbit (e = 0.89) !

Locating the new pulsar NGC1851 : A relatively bring GC (M v = -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 MAPPING CONCURRENTLY WITH PHASED ARRAY OBSERVATIONS !

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

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 GMRT Fermi Search Team : Bhaswati Bhattacharyya, Jayanta Roy, Yashwant Gupta & Dipankar Bhatacharya First Fermi LAT discovery with the GMRT Bhattacharyya et al (in preparation)

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

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

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)

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)

Simultaneous Multi-frequency Pulsar Observations 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

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.

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)

Decoding the nature of pulsar emission Mitra, Gil & Melikidze 2009  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

Acetaldehyde from Sgr B2  The CH 3 CHO emission at 1065 MHz appears to be mased  CH 3 CHO 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

Moving to some results from outside our Galaxy…

Drawf Galaxy NGC 3741 (M B ~ mag) HI gas disk ~ 8.3 times Holmberg radius  The most extended HI disk known M HI ~ 2 х 10 8 M O Begum, Chengalur & Karachentsev 2005

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

 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 Damped Lyman Alpha (DLA) systems Neeraj Gupta et al 2007

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

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  Good correlation between N OH & N HCO+ which indicates that OH may be a good tracer of H 2 at cosmological distances. OH [1665 & 1667 MHz] B Z abs = Kanekar and Chengalur (2002)

Transient Sources : Gamma Ray Burst GRB Transient Sources : Gamma Ray Burst GRB Resmi & Bhattacharya 2006  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

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

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

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

Expected Performance Figures (for array mode) Expected Performance Figures (for array mode) Incoherent Array search sensitivity for 10 min (uJy) Max Bandwidth (MHz) Phased Array search sensitivity for 10 min (uJy) Phased Array Beam FoV (arcsec) Incoherent Array Beam FoV (deg) Frequency Band (MHz)

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