S. K. Sirothia , N. G. Kantharia, C. H. Ishwara-Chandra, Gopal-Krishna

NCRA-TIFR, Pune, India

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The Survey

We are carrying out an extragalactic radio continuum survey at 150 MHz, using the Giant Metrewave Radio Telescope ( GMRT ), covering about 37,000 sq. deg of the sky north of declination of -55 degrees and reaching an rms noise of 5-7 mJy/beam (better than the 7-9 mJy/beam that was expected) at an angular resolution of about 20 arcsec. ( The TGSS was originally planned to be north of declination of -30 degrees). ) When complete, the survey is expected to detect more than 2 million sources.

The above has become possible due to the development of AIPS++ based automated data analysis tools for GMRT data (Sirothia 2009, Ph.D. thesis) which can identify and remove data corrupted by radio frequency interference (RFI) and by other problems. We note that despite being a prime objective conceived for the GMRT, no major low-frequency survey has so far been undertaken with this telescope and this survey when completed will be the first of its kind from GMRT . The proposed GMRT 150 MHz survey will result in more than 4 times improvement both in sensitivity and angular resolution over all existing surveys at this frequency. Also it will be strategically placed in the frequency gap between the two existing prominent radio surveys, namely WENSS (325 MHz) and VLSS (74 MHz), each having only a modest angular resolution of ~1 arcmin. The survey proposed here is expected to fulfill a prominent goal of the GMRT and will prove to be a major database for multi-wavelength astronomy. We are proposing to complete these observations before the solar activity in the current solar cycle peaks around 2012. The analyzed data will be made available to the astronomy community in an expeditious manner (possibly on time scales of a few months from the date of observing). Observatory specific data release policy for large projects will be followed.

Typical GMRT radio sky image at 150 MHz obtained using our AIPS++ data analysis pipeline. (Lower panel) GMRT observes the radio sky.(GMRT photo courtesy: Premkumar).

TGSS Mailing List:
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Comments, brickbats - email to tgss AT ncra.tifr.res.in

Click here to visit our new press release and research publications webpage.


We announce TGSS data release 5. All the images and catalogues released have been made with the modified pipeline and have better sensitivity to extended structure. (30 November 2012)

Apologies to all users who have been waiting for the next TGSS data release. We have not been able to have our October 2012 release. (1 November 2012)

Next data release has been delayed. There was a power cut at NCRA which resulted in a week's downtime for the TGSS computing lab which, in turn, resulted in an effective loss of about three weeks of analysis time. Release delayed to October 2012. (6 September 2012)

TGSS team has a new online book-keeping tool. As the number of imaged and released fields increase; the complexity of book-keeping is also increasing which this tool will help handle. (6 September 2012)

We announce TGSS data release 4 covering about 1 steradian of the southern sky. (20 April 2012)

The next TGSS data release is scheduled for April 2012. (3 April 2012)

All the observations at 150 MHz of the sky accessible to GMRT have been completed. Data analysis is in progress. The data analysis pipeline is being improved to increase sensitivity to faint extended structure. (3 April 2012)

New TGSS images as part of TGSS DR3 are released on 31 October 2011. (31 October 2011)

35 new computers are being added to the TGSS computing lab. (21 October 2011)

We are working towards our next data release. Till date about 270 GB of image data (each FITS image is about 67 MB in size) have been downloaded from our website. (21 October 2011)

TGSS has 100 hours of GMRT time in Observing Cycle 21 to complete the observations of the sky south of -30 degrees. We started the observations for these parts of the sky in Cycle 20. At the end of Cycle 21, the complete sky visible to GMRT will have been observed at 150 MHz for TGSS. (21 October 2011)

Click here to visit our new press release and research publications webpage. (7 September 2011)

NCRA had a press conference on TGSS today. (26 August 2011)

All the pointings covering the sky north of declination -35 degrees have now been observed. (12 August 2011)

The first science result from the TGSS has been published and you can download the paper from here . The paper reports the discovery of a giant double radio relic in a Planck SZ cluster. (12 August 2011)

The TGSS Data Release 2 covering about 2100 square degrees of the southern sky is here. This release includes the fields released in DR1 and all the images are available for download through the image server and FITS file listing. The catalogue for the fields can be browsed through the catalogue browser. Visit the download page for more details. We apologise to users for the delay. (9 June 2011)

GTAC has allocated 280 hours of observing time in GMRT Observing Cycle 20. This also includes time to survey the entire southern sky observable from GMRT in the nighttime during the cycle. (14 April 2011)

We're running late! We ran into a few problems which we are trying to understand and resolve. After all, these are images at 150 MHz and these are snapshot observations in not a very-quiet RFI zone so we're realising that each data release is going to be full of excitement, at least for us! We'll let you know when the next data release is happening. (28 February 2011)

The next TGSS data release is planned for January/February 2011. (5 January 2011)

TGSS has 134 interested users! Thanks to all for registering. We will keep you informed. (8 November 2010)

GMRT Observations in GMRT Cycle 19 are in progress and we have used about 175 hours on the sky. Analysis of data from the GMRT Software Backend is also in progress. (8 November 2010)

For subscribing to the TGSS announcements mailing list visit here . For further information contact us at tgss AT ncra tifr res in . (22 October 2010)

The first TGSS data release which we refer to as the Glimpse release is here! Glimpse covers about 1000 square degrees of the sky imaged with GMRT at 150 MHz. The interested user can download contour plots, grey scale images and FITS files in addition to querying our catalogue browser. (19 October 2010)

GTAC has allocated 770 hours of observing time in GMRT Observing Cycle 19. Observations have begun and you can view the status here. (11 October 2010)

The difference in the rms noise between the GHB, GSB and combined GSB,GHB data is less than 10%. The GSB data is being analysed and will be released. TGSS Observations in Cycle 18 are in progress. Click here for the latest status. (13 August 2010)

We have generated sky images of the same 36 fields of the data observed on 6 June 2010 using data from the the new GMRT software backend (GSB), combined GSB and GHB data and are comparing with the images of the data from the GHB. (30 July 2010)

The analysis pipeline is running on all the computers. Images of 36 pointings observed on 6 June 2010 in Cycle 18 have been generated and are being checked. (5 July 2010)

AIPS++ installed on all computers and the analysis pipeline is running on a few computers churning out images at 150 MHz. (23 June 2010)

The computers required for the data analysis have arrived at NCRA. (21 May 2010)

770 hours of observing time on GMRT alloted by GTAC in Cycle 18 for the GMRT 150 MHz Extragalactic sky survey now named TGSS. (April 2010)

The TGSS computing lab is being setup for quasi-real time data analysis. ( April 2010 )

This page will be regularly updated as results come in so keep looking!

(First Version: January 2010)