Overview of Radio Astronomy Overview of Radio Astronomy activities at NCRA activities at NCRA

Yashwant Gupta

National Centre for Radio AstrophysicsPune India

India-South Africa Astronomy Workshop Capetown 7 Aug 2012

Introduction 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 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 ObjectivesORT & GMRT : Scientific Objectives

The ORT is primarily used for :The ORT is primarily used for : Interplanetary scintillations, solar wind and space weather studiesInterplanetary 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 planetsThe Sun, extrasolar planets Pulsars : rapidly rotating neutron starsPulsars : rapidly rotating neutron stars Other Galactice objects like : supernova remnants, microquasars etcOther Galactice objects like : supernova remnants, microquasars etc Other explosive events like Gamma Ray BurstsOther explosive events like Gamma Ray Bursts Ionized and neutral Hydrogen gas clouds (in our Galaxy and in other Ionized and neutral Hydrogen gas clouds (in our Galaxy and in other

galaxies)galaxies) Radio properties of different kinds of galaxies; galaxy clustersRadio properties of different kinds of galaxies; galaxy clusters Radio galaxies at large distances in the UniverseRadio galaxies at large distances in the Universe Cosmology and the Epoch of ReionizationCosmology 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…GMRT : Some Pulsar Results…

Some pulsar related resultsfrom 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)

Finding New Pulsars Using The GMRTFinding 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 pulsarLocating the new pulsar

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

MAPPING CONCURRENTLY WITH PHASED ARRAY OBSERVATIONS !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 G21.5-0.9

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 Simultaneous Multi-frequency Pulsar ObservationsObservations

Simultaneous Multi-frequency pulsar Simultaneous Multi-frequency pulsar observations provide a very powerful tool to observations provide a very powerful tool to study several aspects of pulsar emission study several aspects of pulsar emission properties properties

““Local MFO” : The GMRT has the unique Local MFO” : The GMRT has the unique ability to observe simultaneously at more than ability to observe simultaneously at more than one frequency, using the “sub-array” mode – one frequency, using the “sub-array” mode – upto 4 frequency observations have been upto 4 frequency observations have been carried out – the data from the different carried out – the data from the different frequencies is completely time synchronised !frequencies is completely time synchronised !

““Global MFO” : We have participated in Global MFO” : We have participated in coordinated multi-frequency observations coordinated multi-frequency observations with other observatories, contributing at 2 or with other observatories, contributing at 2 or 3 wavebands 3 wavebands

Dual frequency observations : DM variations of PPTA MSPs

Simultaneous Simultaneous dual frequency dual frequency observations at observations at 325 & 610 MHz325 & 610 MHz

DM accuracies DM accuracies of 1 part in 10^5of 1 part in 10^5

Ujjwal Kumar Ujjwal Kumar et al.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 Decoding the nature of pulsar emission

Mitra, Gil & Melikidze 2009

Strong single pulses from 10 pulsars with the GMRT, showing extremely high Strong single pulses from 10 pulsars with the GMRT, showing extremely high linear polarization with the position angle following locally the mean PA traverselinear polarization with the position angle following locally the mean PA traverse

Must consist exclusively of a single polarization mode Must consist exclusively of a single polarization mode extraordinary wave extraordinary wave excited by coherent curvatureexcited by coherent curvature

Acetaldehyde from Sgr B2Acetaldehyde from Sgr B2

The CHThe CH33CHO emission at 1065 MHz CHO emission at 1065 MHz

appears to be masedappears to be mased

CHCH33CHO emission is coincident with CHO emission is coincident with

HCHO absorptionHCHO absorption

Emission is seen in both the low & high Emission is seen in both the low & high resolution images, made from a single resolution images, made from a single GMRT observationsGMRT observations

Emission on both large scales and fine Emission on both large scales and fine scales appears correlated with shocksscales appears correlated with shocks

GMRT maps are the only direct images GMRT maps are the only direct images of wide spread emission from a large of wide spread emission from a large organic molecueorganic molecue

Chengalur & Kanekar 2003

Moving to some results from Moving to some results from outside our Galaxy…outside our Galaxy…

Drawf Galaxy Drawf Galaxy NGC 3741 (MNGC 3741 (MB B ~ -13.13 mag)~ -13.13 mag)

HI gas disk ~ 8.3 times Holmberg radius HI gas disk ~ 8.3 times Holmberg radius

The most extended HI disk knownThe most extended HI disk known

MHI ~ 2 х 108 MO

Begum, Chengalur & Karachentsev 2005

NGC 3741 : Dark MatterNGC 3741 : Dark Matter

Rotation curve measured out Rotation curve measured out to 38 optical disk scale to 38 optical disk scale lengthslengths

Dynamical mass to light Dynamical mass to light ratio ~ 107ratio ~ 107

NGC 3741 is one of the “darkest” known irregulars

Begum, Chengalur & Karachentsev 2005

Several new DLA systems Several new DLA systems have been discovered with have been discovered with the GMRT in the past few the GMRT in the past few yearsyears

9 new detections in 400 9 new detections in 400 hours survey with the hours survey with the GMRT in the 610 MHz GMRT in the 610 MHz band band

Damped Lyman Alpha (DLA) systems Damped Lyman Alpha (DLA) systems

Neeraj Gupta et al 2007

Mapping 21 cm absorption in DLAs Mapping 21 cm absorption in DLAs towards extended radio sources – size, towards extended radio sources – size,

kinematics of high z galaxieskinematics of high z galaxies

Kanekar & Chengalur 2008

Detection of Molecular gas at Detection of Molecular gas at

intermediate redshifts using the GMRTintermediate redshifts using the GMRT

Kanekar & Chengalur have Kanekar & Chengalur have detected OH absorption in 3 detected OH absorption in 3 radio sources with GMRT, in radio sources with GMRT, in addition to that detected earlier addition to that detected earlier by Chengalur with WSRT in by Chengalur with WSRT in the lensing galaxy towards the lensing galaxy towards 1830-211.1830-211.

Good correlation between NGood correlation between NOHOH & N& NHCO+HCO+ which indicates that which indicates that OH may be a good tracer of HOH may be a good tracer of H2 2

at cosmological distances. at cosmological distances. OH [1665 & 1667 MHz]B 1504+377Zabs=0.67345

Kanekar and Chengalur (2002)

Transient Sources : Gamma Ray Burst Transient Sources : Gamma Ray Burst GRB030329GRB030329

Resmi & Bhattacharya 2006

Data at 1280 and 610 MHz Data at 1280 and 610 MHz with the GMRT, compared with the GMRT, compared with the “refreshed jet” model with the “refreshed jet” model of the afterglowof the afterglow

Jet becomes sub-relativistic ~ Jet becomes sub-relativistic ~ 60 days after burst60 days after burst

Longest ever radio follow-up Longest ever radio follow-up and lowest radio frequency and lowest radio frequency observations of a GRBobservations of a GRB

Sample results : Polarization Sample results : Polarization

610 MHz, 30 hrs, 15 microJy RMS 610 MHz, 30 hrs, 15 microJy RMS courtesy : Russ Taylor & team , July 2011 courtesy : Russ Taylor & team , July 2011

Polarized Intensity Polarized Intensity Total Intensity Total Intensity

EN1DEEP06 : GMRT Deep Polarization Field EN1DEEP06 : GMRT Deep Polarization Field

EoR Experiment at the GMRT

EoR project at the GMRT led by Ue-Li Pen (CITA)EoR project at the GMRT led by Ue-Li Pen (CITA)First published results establish interesting new limits on EoR signal First published results establish interesting new limits on EoR signal strength strength

Paciga et al, 2011 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 Expected Performance Figures (for array mode)(for array mode)

200200250250350350 25002500

Incoherent Array search sensitivity for 10 Incoherent Array search sensitivity for 10 min (uJy)min (uJy)

400400350350250250125125Max Bandwidth (MHz)Max Bandwidth (MHz)

125-125-250250

Phased Array search sensitivity for 10 min Phased Array search sensitivity for 10 min (uJy)(uJy)

Phased Array Beam FoV (arcsec) Phased Array Beam FoV (arcsec)

Incoherent Array Beam FoV (deg)Incoherent Array Beam FoV (deg)

353540406060400400

225599 2020

0.40.40.80.81.41.43.23.2

1000-1000-14501450

550-550-900900

250-250-500500

Frequency Band (MHz)Frequency Band (MHz)

Thank You Thank You