Study of the High Redshift radio galaxies in radio deep fields

Abstract

The High Redshift radio galaxies are some of the rarest objects in the known Universe. These objects have several distinct constituents which interact with each other in various forms and thereby enabling us to investigate them in the multi-wavelength data regime of the electromagnetic spectrum. We study these High Redshift radio galaxies (HzRG’s) in the European Large- Area ISO Survey(ELAIS North 1) field which is at 16h:10m:1.2s and +54deg:30m:36s in the J2000 epoch. We have recent observations for this field with the upgraded Giant Meter-wave Radio Telescope; uGMRT at 300-500 MHz. This catalogue was compiled by our group in which there were 2528 sources at 400 MHz. A comparison and analysis of this compiled radio catalogue with the corresponding optical and Infra-Red catalogue from other surveys is put forth. From these multi-wavelength data we elucidate the correlation between the redshift and spectral index of the matched sources in the ELAIS North 1 field. This correlation is established for both redshifts; photometric and spectroscopic. The work also undertakes the administration of the USS criterion: Ultra Steep Spectra sources on this correlation. However, in the literature there is no homogeneous definition of this threshold cutoff as when administered in the radio sources. This work also delves into the study of a particular High Redshift radio galaxy in the regime of z > 5. This High Redshift radio galaxy; having Right Ascension and Declination at 9h:24m:19.92s and-22d:01m:41.5s, was discovered in 1999. This source was observed with GMRT at 150MHz, 325MHz and 1 GHz frequencies and the radio data is analyzed with the peeling scheme SPAM: Source Peeling and Atmospheric Modeling. We analyzed the multi-frequency data of this source and details of that is mentioned here. We also introduce this High Redshift radio galaxy in our correlation. Finally, these High Redshifts radio galaxies are used as laboratories for scrutinizing the early Universe and are the progenitors biggest clusters that we observe today. The discovery of these galaxies at the regimes of z > 5 can be a daunting one. However with the recent discovery of one such most Highly Redshifted radio galaxy at z = 5.72 in 2018 seems to propose an endeavour to hunt for these galaxies and henceforth pushing the known redshift bar beyond.