- ID:
- ivo://nasa.heasarc/gmrtas150m
- Title:
- Giant Metrewave Radio Telescope All-Sky 150-MHz Radio Source Catalog
- Short Name:
- GMRTAS150M
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains results from the first full release of a survey of the 150-MHz radio sky, observed with the Giant Metrewave Radio Telescope (GMRT) between April 2010 and March 2012 as part of the TIFR GMRT Sky Survey (TGSS) project. Aimed at producing a reliable compact source survey, the authors' automated data-reduction pipeline efficiently processed more than 2000 hours of observations with minimal human interaction. Through application of innovative techniques such as image-based flagging, direction-dependent calibration of ionospheric phase errors, correcting for systematic offsets in antenna pointing, and improving the primary beam model, the authors created good quality images for over 95% of the 5,336 pointings. This data release covers 36,900 deg<sup>2</sup> (or 3.6 pi steradians) of the sky between -53 and +90 degrees Declination, which is 90% of the total sky. The majority of pointing images has a noise level below 5 mJy/beam (the median RMS background noise is 3.5 mJy per beam), with an approximate resolution of 25" x 25" (or 25" x 25"/cos(Dec-19<sup>o</sup>) for pointings south of 19 degrees Declination). The authors have produced a catalog of 0.62 Million radio sources with flux densities ranging from 11.1 mJy to 9.22 kJy that are derived from an initial, high-reliability source extraction at the 7-sigma level. For the bulk of the survey, the measured overall astrometric accuracy is better than 2 arcseconds in Right Ascension and Declination, while the flux density accuracy is estimated at approximately 10%. Within the scope of the TGSS Alternative Data Release (TGSS ADR) project, the source catalog, as well as 5,336 mosaic images (5 x 5 degree<sup>2</sup>) and an image cutout service, are made publicly available as a service to the astronomical community. (The TGSS images and cutout server are available through the project website at <a href="http://tgssadr.strw.leidenuniv.nl/">http://tgssadr.strw.leidenuniv.nl/</a>). In addition to enabling a wide range of different scientific investigations, the authors anticipate that these survey products will provide a solid reference for various new low-frequency radio aperture array telescopes (LOFAR, LWA, MWA, SKA-low), and can play an important role in characterizing the epoch-of-reionization (EoR) foreground. The TGSS ADR project aims at continuously improving the quality of the survey data products. Near-future improvements include replacement of bright source snapshot images with archival targeted observations, using new observations to fill the holes in sky coverage and to replace very poor quality observational data, and an improved flux calibration strategy for less severely affected observational data. This table was created by the HEASARC in February 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/598/A78">CDS Catalog J/A+A/598/A78</a> file table3.dat. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/gmrtelain2
- Title:
- Giant Metrewave Radio Telescope ELAIS-N2 Field 610-MHz Radio Source Catalog
- Short Name:
- GMRTELAIN2
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a source catalog based on observations of the European Large-Area ISO Survey-North 2 (ELAIS-N2) field taken at 610 MHz with the Giant Metrewave Radio Telescope (GMRT). Thirteen pointings were observed, covering a total area of ~ 6 square degrees with a resolution of 6.5 x 5 arcsec<sup>2</sup>, position angle of +70 degrees. The rms noise at the center of the pointings is typically ~ 85 microJansky (µJy) before correction for the GMRT primary beam . The techniques used for data reduction and production of a mosaicked image of the region are described in the reference paper, where the final mosaic, along with a catalog of 1310 sources detected above a 6-sigma threshold, are presented. The survey complements existing radio and infrared data that are available for this region. For further details of the surveys and data analysis procedures, please refer to the published paper. This table contains the ELAIS-N2 catalog of 1310 detected 610-MHz radio sources. This table was created by the HEASARC in February 2012 based the source catalog of the Cambridge GMRT Survey of the ELAIS-N2 region which was obtained from the University of Cambridge Astrophysics Group Surveys and Catalogs website at <a href="http://www.mrao.cam.ac.uk/facilities/surveys/gmrt/elais-n2/">http://www.mrao.cam.ac.uk/facilities/surveys/gmrt/elais-n2/</a> file GMRT_EN2_dr1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/gmrtelain1
- Title:
- Giant Metrewave Radio Telescope ELAIS-N1 Field 610-MHz Radio Source Catalog
- Short Name:
- GMRTELAIN1
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a source catalog based on observations of the European Large-Area ISO Survey-North 1 (ELAIS-N1) field taken at 610 MHz with the Giant Metrewave Radio Telescope. Nineteen pointings were observed, covering a total area of ~ 9 square degrees with a resolution of 6 x 5 arcsec<sup>2</sup>, position angle of +45 degrees. Four of the pointings were deep observations with an rms of ~ 40 microJansky (µJy) before primary beam correction, with the remaining fifteen pointings having an rms of ~ 70 uJy. The techniques used for data reduction and production of a mosaicked image of the region are described in the reference paper, where the final mosaic, along with a catalog of 2500 sources detected above a 6-sigma threshold, are presented. This work complements the large amount of optical and infrared data already available on the region. In their paper, the authors calculate 610-MHz source counts down to 270 uJy, and find further evidence for the turnover in differential number counts below 1 mJy, previously seen at both 610 MHz and 1.4 GHz. For further details of the surveys and data analysis procedures, please refer to the published paper. This table contains the ELAIS-N1 catalog of 2500 detected 610-MHz radio sources. This table was created by the HEASARC in February 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/383/75">CDS Catalog J/MNRAS/383/75</a> file catalog.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/gmrt4f150m
- Title:
- Giant Metrewave Radio Telescope Field I 150-MHz Radio Source Catalog
- Short Name:
- GMRT4F150M
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- Foreground removal is a major challenge for detecting the redshifted 21-cm neutral hydrogen (HI) signal from the Epoch of Reionization. The authors have used 150-MHz Giant Metrewave Radio Telescope (GMRT) observations to characterize the statistical properties of the foregrounds in four different fields of view. The observational data were used to assess point source subtraction. Considering the brightest source (~1 Jy) in each field, the authors find that the residual artefacts are less than 1.5% in the most sensitive field (FIELD I). Considering all the sources in the fields, they find that the bulk of the image is free of artefacts, the artefacts being localized to the vicinity of the brightest sources. The authors have used FIELD I, which has an rms noise of 1.3 mJy beam<sup>-1</sup>, to study the properties of the radio source population to a limiting flux of 9 mJy. The differential source count is well fitted with a single power law of slope -1.6. They find there is no evidence for flattening of the source counts towards lower flux densities which suggests that source population is dominated by the classical radio-loud active galactic nuclei. The authors have observed FIELD I in GMRT Time Allocation Committee (GTAC) cycle 15 in 2008 January, whereas FIELD II and FIELD III were observed in cycle 17 during 2010 February. These target fields were selected at high Galactic latitudes (b > 10<sup>o</sup>) which were up at night time during the GTAC cycles 15 and 17, and which contain relatively few bright sources (>= 0.3 Jy) in the 1400 MHz NRAO VLA Sky Survey (NVSS). Finally, FIELD IV was observed in cycle 8 (2005 June). Full details of these 4 observations are given in Table 1 of the reference paper. This table contains the 150-MHz source catalog for the most sensitive observation, namely the 9.8-hour observation of Field I (centered on J2000.0 RA and Dec of 5<sup>h</sup> 30<sup>m</sup> 00<sup>s</sup>, +60<sup>o</sup> 00' 00"), which was made on 2008 January 8. This table was created by the HEASARC in September 2013 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/426/3295">CDS Catalog J/MNRAS/426/3295</a> file tablea1.dat This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/gmrtha325m
- Title:
- Giant Metrewave Radio Telescope Herschel-ATLAS/GAMA Flds 325-MHz Source Catalog
- Short Name:
- GMRTHA325M
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a source list from a 325-MHz survey undertaken with the Giant Metrewave Radio Telescope (GMRT). This survey covers a large part of the three equatorial fields at 9, 12 and 14.5 h of Right Ascension from the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) in the area also covered by the Galaxy And Mass Assembly (GAMA) survey. The full data set, after some observed pointings were removed during the data reduction process, comprises 212 GMRT pointings covering ~90 deg<sup>2</sup> of sky. A list of the central coordinates of the images from which the sources listed in this catalog are derived is available at <a href="http://gmrt-gama.extragalactic.info/GMRT_GAMA_IMAGE_CENTERS">http://gmrt-gama.extragalactic.info/GMRT_GAMA_IMAGE_CENTERS</a>. The images themselves are available at <a href="http://gmrt-gama.extragalactic.info/">http://gmrt-gama.extragalactic.info/</a>. The authors have imaged and catalogued the data using a pipeline that automates the process of flagging, calibration, self-calibration and source detection for each of the survey pointings. The resulting images have resolutions of between 14 and 24 arcseconds and minimum rms noise (away from bright sources) of ~1 mJy beam<sup>-1</sup>, and the catalogue contains 5263 sources brighter than the local 5 sigma values. In the reference paper, the authors investigate the spectral indices of those GMRT sources which are also detected at 1.4 GHz and find them to agree broadly with previously published results; there is no evidence for any flattening of the radio spectral index below S<sub>1.4</sub> = 10 mJy. This work adds to the large amount of available optical and infrared data in the H-ATLAS equatorial fields and will facilitate further study of the low-frequency radio properties of star formation and AGN activity in galaxies out to z ~1. This table was created by the HEASARC in December 2013 based on electronic versions of the 3 catalogs that comprise Table 3 from the reference paper which were obtained from the MNRAS web site. Some of the values for the name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/gmrt1hxcsf
- Title:
- Giant Metrewave Radio Telescope 1h XMM/Chandra Survey Fld 610-MHz Source Catalog
- Short Name:
- GMRT1HXCSF
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of a deep 610-MHz survey of the 1<sup>hr</sup> XMM-Newton/Chandra survey area with the Giant Metre-wave Radio Telescope (GMRT). The resulting maps have a resolution of ~7 arcseconds and an rms noise limit of 60 µJy (µJy). To a 5-sigma detection limit of 300 uJy, the authors detect 223 sources within a survey area of 64 arcminutes in diameter. They compute the 610-MHz source counts and compare them to those measured at other radio wavelengths. The well-known flattening of the Eucidean-normalized 1.4-GHz source counts below ~ 2 mJy, usually explained by a population of starburst galaxies undergoing luminosity evolution, is seen at 610 MHz. In 2004 August, the 1<sup>hr</sup> field (centered at (J2000.0) RA, Dec = 01<sup>h</sup> 45<sup>m</sup> 27<sup>s</sup>, -04<sup>o</sup> 34' 42") was observed for approximately 4.5 hours at 610 MHz with the GMRT. Observations were carried out in dual band, spectral line mode, the former to maximize bandwidth and the latter to minimize chromatic aberration. Two sidebands, each of 128 spectral channels of 125 kHz, were centred on 602 and 618 MHz to give a total of 32 MHz bandwidth, with two independent circular polarizations recorded. Sources were extracted with the AIPS task SAD. A conservative peak flux density detection limit of 5 sigma (i.e. 300 uJy) was used to minimize the number of noise spikes spuriously detected as sources. In the areas surrounding the five brightest sources, detection was performed separately with higher detection thresholds to account for the higher rms noise. Within the 20% power radius of the GMRT primary beam at 610 MHz (32 arcminutes), 213 sources were discovered above a 5-sigma peak flux density detection limit of 300 uJy. In order to determine the success of the SAD source extraction, both the science images and the residual noise maps were carefully inspected. There were eight extended sources where the Gaussian model fit by SAD inadequately described the data: these are marked by source_flag = 'a' in this table. The characteristics of these sources were determined using the AIPS task TVSTAT, and contour plots of them are shown in Fig. 1 of the reference paper. Five of these appear to contain two peaks joined by extended emission, that is, they are double-lobe sources. This table was created by the HEASARC in June 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/378/995">CDS Catalog J/MNRAS/378/995</a> file table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/gmrtj0916
- Title:
- Giant Metrewave Radio Telescope J0916+6348 Field Radio Source Catalog
- Short Name:
- GMRTJ0916
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a catalog based on deep multifrequency observations made using the Giant Metrewave Radio Telescope (GMRT) at 153, 244, 610 and 1260 MHz of a field centred on J0916+6348, to search for evidence of fossil radio lobes which could be due to an earlier cycle of episodic activity of the parent galaxy, as well as haloes and relics in clusters of galaxies. The authors do not find any unambiguous evidence of episodic activity in a list of 374 sources, suggesting that such activity is rare even in relatively deep low-frequency observations. The authors examine the spectra of all the sources by combining their observations with those from the Westerbork Northern Sky Survey (WENSS), NRAO (National Radio Astronomy Observatories) VLA (Very Large Array) Sky Survey (NVSS) and the Faint Images of the Radio Sky at Twenty-Centimeters Survey (FIRST). Considering only those which have measurements at a minimum of 3 different frequencies, they find that almost all sources are consistent with a straight spectrum with a median spectral index alpha ~ 0.8 (S<sub>nu</sub> ~ nu<sup>-alpha</sup>) which appears steeper than theoretical expectations of the injection spectral index. The authors identify 14 very-steep-spectrum sources with alpha >~ 1.3. This table contains the list of 317 sources (out of the 374 sources which were within 1.5 degrees of the phase center at 153 MHz and had peak brightnesses at least 6 times larger than the local rms value) which were detected at a minimum of 3 frequencies out of the 6 frequencies (153, 244, 327, 610, 1260 and 1400 MHz) which were utilized in this study. The new observations were made on 2005 December 12 at 153 MHz, 2005 November 26 at 244 MHz and 610 MHz, and on 2008 April 22 at 1260 MHz, on the Giant Metrewave Radio Telescope (Pune, India). This table was created by the HEASARC in March 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/392/1403">CDS Catalog J/MNRAS/392/1403</a> file table2.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/gmrtlbdsly
- Title:
- Giant Metrewave Radio Telescope LBDS-Lynx Region 150-MHz Radio Source Catalog
- Short Name:
- GMRTLBDSLY
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- It has been known for nearly three decades that high-redshift radio galaxies exhibit steep radio spectra, and hence ultrasteep spectrum radio sources provide candidates for high-redshift radio galaxies. Nearly all radio galaxies with z > 3 have been found using this redshift-spectral index correlation. The authors have started a program with the Giant Metrewave Radio Telescope (GMRT) to exploit this correlation at flux density levels about 10 to 100 times deeper than the known high-redshift radio galaxies which were identified primarily using the already available radio catalogs. In their program, they have obtained deep, high-resolution radio observations at 150 MHz with the GMRT for several "deep" fields which are well studied at higher radio frequencies and in other bands of the electromagnetic spectrum, with the aim to detect candidate high-redshift radio galaxies. In their paper, they present results from the deep 150-MHz observations of the LBDS (Leiden-Berkeley Deep Survey) Lynx field, which has been already imaged at 327, 610 and 1412 MHz with the Westerbork Synthesis Radio Telescope (WSRT) and at 1400 and 4860 MHz with the Very Large Array (VLA). The counterparts for the 150-MHz sources at higher radio frequencies were searched within a 20-arcsec radius from the 150-MHz position. The 150-MHz image made with the GMRT has an rms noise of ~ 0.7 mJy beam<sup>-1</sup> and a resolution of ~ 19 x 15 arcsec<sup>2</sup>. It is the deepest low-frequency image of the LBDS-Lynx field. The source catalog of this field at 150 MHz has 765 sources down to ~ 20% of the primary beam response, covering an area of about 15 deg<sup>2</sup>. The spectral index was estimated by cross-correlating each source detected at 150 MHz with the available observations at 327, 610, 1400 and 4860 MHz and also using available radio surveys such as the Westerbork Northern Sky Survey (WENSS) at 327 MHz and the NRAO VLA Sky Survey (NVSS) and the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey at 1400 MHz. A total of 639 sources out of 765 (83%) have spectral indices determined. The remaining 17% of the sources are mostly weak radio sources with a median flux density of ~ 9 mJy, or fall in the regions where deep observations at higher frequencies do not exist. The median spectral index of the sample is 0.78. The authors find about 150 radio sources with spectra steeper than 1. About two-thirds of these are not detected in the Sloan Digital Sky Survey (SDSS), hence are strong candidate high-redshift radio galaxies, which need to be further explored with deep infrared imaging and spectroscopy to estimate the redshift. The list of the 98 such steep-spectrum sources lacking SDSS counterparts is given in Table 4 of the published paper. This table was created by the HEASARC in February 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/405/436">CDS Catalog J/MNRAS/405/436</a> file table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/gmrtlhcat2
- Title:
- Giant Metrewave Radio Telescope Lockman Hole 610-MHz Radio Source Catalog 2
- Short Name:
- GMRTLHCAT2
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a source catalog based on further observations of the Lockman Hole field, made with the Giant Metrewave Radio Telescope at 610 MHz with an angular resolution of 6 x 5 arcsec<sup>2</sup>. These complement this group's earlier observations of the central ~ 5 deg<sup>2</sup> of the Lockman Hole (Garn et al. 2008, MNRAS, 387, 1037, the HEASARC Browse table GMRTLHCAT) by covering a further ~ 8 deg<sup>2</sup> area, with an rms noise down to ~ 80 microJansky/beam (µJy/beam). A catalog of 4934 radio sources in both the inner and outer regions of the Lockman Hole is presented in this table. The earlier survey had 12 pointings covering ~ 5 square degrees in the center of the Lockman Hole, and herein a further 26 pointings in the outer parts of the Lockman Hole are added, to cover a total of ~ 14 square degrees. To match the earlier survey, the images were made with a resolution of 6" x 5", at a position angle of +45 degrees. The majority of the new pointings have an rms noise of ~80 µJy/beam before the primary beam correction, but the noise in the west - particularly near the very bright source 3C244.1 - is worse. This table was created by the HEASARC in February 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/BASI/38.103">CDS Catalog J/BASI/38.103</a> file gmrtlh2.cat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/gmrtlhcat
- Title:
- Giant Metrewave Radio Telescope Lockman Hole 610-MHz Radio Source Catalog
- Short Name:
- GMRTLHCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a source catalog based on observations of the Lockman Hole with the Giant Metrewave Radio Telescope (GMRT) taken at 610 MHz (49 cm). Twelve pointings were observed, covering a total area of ~5 deg<sup>2</sup> with a resolution of 6 x 5 arcsec<sup>2</sup>, position angle +45 degrees. The majority of the pointings have an rms noise of ~ 60 µJy/beam (µJy/beam) before correction for the attenuation of the GMRT primary beam. The techniques used for data reduction and the production of a mosaicked image of the region are described in the reference paper, where the final mosaic is presented, along with a catalog of 2845 sources detected above the 6-sigma threshold which is contained in this table. In the paper, radio source counts are calculated at 610 MHz and combined with existing 1.4-GHz source counts, in order to show that pure luminosity evolution of the local radio luminosity functions for active galactic nuclei and starburst galaxies is sufficient to account for the two source counts simultaneously. The 'central region' of the Lockman Hole, consisting of 12 pointings spaced by 36 arcminutes in a hexagonal pattern (shown in Fig. 1 of the reference paper) was observed on 2004 July 24 and 25 using the GMRT. The observations were made in two 16-MHz sidebands centered on 610 MHz, each split into 128 spectral channels, with a 16.9s integration time. This table was created by the HEASARC in February 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/387/1037">CDS Catalog J/MNRAS/387/1037</a> file catalog.dat. This is a service provided by NASA HEASARC .
