A Wide-area GMRT 610~MHz survey of ELAIS N1 field

TL;DR

This paper presents a detailed 610 MHz radio survey of the ELAIS N1 field using GMRT, revealing numerous sources, including giant radio sources and relics, with implications for understanding low-frequency radio populations and source evolution.

Contribution

The survey provides the first wide-area, high-sensitivity 610 MHz map of ELAIS N1, discovering new giant radio sources and relics, and offers extensive multi-wavelength data for source characterization.

Findings

Detected 6,400 sources, mostly compact, with a median flux of 4.5 mJy.

Discovered six giant radio sources, three at redshift ~1 or higher.

Identified several candidate relic sources.

Abstract

In this paper we present a wide-area 610 MHz survey of the ELAIS\,N1 field with the GMRT, covering an area of 12.8 deg$^2$ at a resolution of 6 arcsec and with an rms noise of $\sim 40$ $\mu$Jy beam$^{-1}$. This is equivalent to $\sim 20$ $\mu$Jy beam$^{-1}$ rms noise at 1.4 GHz for a spectral index of $-0.75$. The primary goal of the survey was to study the polarised sky at sub-mJy flux densities at $<$ GHz frequencies. In addition, a range of other science goals, such as investigations in to the nature of the low-frequency $\mu$Jy source populations and alignments of radio jets. A total of 6,400 sources were found in this region, the vast majority of them compact. The sample jointly detected by GMRT at 610 MHz and by VLA FIRST at 1.4\,GHz has a median spectral index of $-0.85 \pm 0.05$ and a median 610 MHz flux density of 4.5 mJy. This region has a wealth of ancillary data which is useful to characterize the detected sources. The multi-wavelength cross matching resulted optical/IR counterparts to $\sim 90$ per~cent of the radio sources, with a significant fraction having at least photometric redshift. Due to the improved sensitivity of this survey over preceding ones, we have discovered six giant radio sources (GRS), with three of them at $z \sim 1$ or higher. This implies that the population of GRS may be more abundant and common than known to date and if true this has implications for the luminosity function and the evolution of radio sources. We have also identified several candidate extended relic sources.