GMRTLBDSLY ivo://nasa.heasarc/gmrtlbdsly NASA/GSFC HEASARC Ishwara-Chandra et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source 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 . 2010MNRAS.405..436I https://heasarc.gsfc.nasa.gov/W3Browse/all/gmrtlbdsly.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=gmrtlbdsly& GET text/xml 180 99999 true 130.88375 42.60886111 0.0833333333333333 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=gmrtlbdsly GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_gmrtlbdsly&Action=More+Options&Action=Parameter+Search&ConeAdd=1 RADIO CATALOG 0.0833333333333333 Radio public gmrtlbdsly Giant Metrewave Radio Telescope LBDS-Lynx Region 150-MHz Radio S name Source Designation ([ISW2010] GMRT JHHMMSS+DDMMSS) meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable flux_150_mhz GMRT Flux Density at 150MHz mJy phot.flux.density;em.radio.100-200MHz double nullable wsrt_flux_327_mhz WSRT Flux Density at 327MHz mJy phot.flux.density;em.radio.200-400MHz double nullable first_flux_1400_mhz FIRST Flux Density at 1400MHz (VIII/71) mJy phot.flux.density;em.radio.750-1500MHz double nullable spectral_index Spectral Index from the Fit spect.index double nullable bii Galactic Latitude degree pos.galactic.lat double nullable wsrt_flux_a_1412_mhz WSRT Flux Density at 1412MHz from Windhorst et al., 1984, Cat. J/A+AS/58/1 mJy phot.flux.density;em.radio.750-1500MHz double nullable vla_flux_1462_mhz VLA Flux Density at 1462MHz mJy phot.flux.density;em.radio.750-1500MHz double nullable vla_flux_4860_mhz VLA Flux Density at 4860MHz mJy phot.flux.density;em.radio.3-6GHz double nullable wenss_flux_327_mhz WENSS Flux Density at 327MHz (VIII/62) mJy phot.flux.density;em.radio.200-400MHz double nullable wsrt_flux_b_1412_mhz WSRT Flux Density at 1412MHz from Oort, 1987, Cat. J/A+AS/71/221 mJy phot.flux.density;em.radio.750-1500MHz double nullable lii Galactic Longitude degree pos.galactic.lon double nullable nvss_flux_1400_mhz NVSS Flux Density at 1400MHz (VIII/65) mJy phot.flux.density;em.radio.750-1500MHz double nullable wsrt_flux_610_mhz WSRT Flux Density at 610MHz mJy phot.flux.density;em.radio.400-750MHz double nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable