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Giant Metrewave Radio Telescope LBDS-Lynx Region 150-MHz Radio Source Catalog

Metadata Updated: October 30, 2025

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 .

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Dates

Metadata Created Date April 11, 2025
Metadata Updated Date October 30, 2025

Metadata Source

Harvested from NASA Data.json

Additional Metadata

Resource Type Dataset
Metadata Created Date April 11, 2025
Metadata Updated Date October 30, 2025
Publisher High Energy Astrophysics Science Archive Research Center
Maintainer
Identifier ivo://nasa.heasarc/gmrtlbdsly
Data Last Modified 2025-09-10
Category Astrophysics
Public Access Level public
Bureau Code 026:00
Metadata Context https://project-open-data.cio.gov/v1.1/schema/catalog.jsonld
Schema Version https://project-open-data.cio.gov/v1.1/schema
Catalog Describedby https://project-open-data.cio.gov/v1.1/schema/catalog.json
Harvest Object Id 8a835519-1eaa-4104-bad5-ad3bf9672f1b
Harvest Source Id 58f92550-7a01-4f00-b1b2-8dc953bd598f
Harvest Source Title NASA Data.json
Homepage URL https://heasarc.gsfc.nasa.gov/W3Browse/all/gmrtlbdsly.html
Program Code 026:000
Source Datajson Identifier True
Source Hash 08abaa33998d6aeddc12e810aa186bdbf8c70bf78fad8e42cc2127fba4e8ad89
Source Schema Version 1.1

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