The e-MERGE Survey (e-MERLIN Galaxy Evolution Survey): overview and survey description
Guidetti, D.; Bondi, M.; Prandoni, I.; Muxlow, T. W. B.; Thomson, A. P.; Argo, M. K.; Ivison, R. J.; Smail, Ian; Sargent, M. T.; Ibar, E.; Murphy, E. J.; Venturi, T.; Kneib, Jean-Paul; Jarvis, M. J.; Swinbank, A. M.; Pearson, Chris; Serjeant, Stephen; Coppin, K.; Simpson, J. M.; Koopmans, L. V. E.; Richards, A. M. S.; Garrett, M. A.; Röttgering, H. J. A.; Beswick, R. J.; Biggs, A. D.; Chapman, S. C.; Morabito, L. K.; Pérez-Torres, M. A.; Knudsen, Kirsten K.; Bacon, David; McHardy, I. M.; Simpson, C.; Garrington, S. T.; Best, P. N.; Chen, H.; Radcliffe, J. F.; Wrigley, N. H.; Varenius, E.; Garratt, T. K.; Njeri, A.
United Kingdom, South Africa, Germany, Italy, Canada, China, Netherlands, Chile, Switzerland, France, Sweden, United States, Spain, Taiwan
Abstract
We present an overview and description of the e-MERGE Survey (e-MERLIN Galaxy Evolution Survey) Data Release 1 (DR1), a large program of high-resolution 1.5-GHz radio observations of the GOODS-N field comprising ∼140 h of observations with enhanced-Multi-Element Remotely Linked Interferometer Network (e-MERLIN) and ∼40 h with the Very Large Array (VLA). We combine the long baselines of e-MERLIN (providing high angular resolution) with the relatively closely packed antennas of the VLA (providing excellent surface brightness sensitivity) to produce a deep 1.5-GHz radio survey with the sensitivity ( ${\sim}1.5\, \mu$ Jy beam-1), angular resolution (0.2-0.7 arcsec) and field-of-view (∼15 × 15 arcmin2) to detect and spatially resolve star-forming galaxies and active galactic nucleus (AGN) at $z$ ≳ 1. The goal of e-MERGE is to provide new constraints on the deep, sub-arcsecond radio sky which will be surveyed by SKA1-mid. In this initial publication, we discuss our data analysis techniques, including steps taken to model in-beam source variability over an ∼20-yr baseline and the development of new point spread function/primary beam models to seamlessly merge e-MERLIN and VLA data in the uv plane. We present early science results, including measurements of the luminosities and/or linear sizes of ∼500 galaxies selected at 1.5 GHz. In combination with deep Hubble Space Telescope observations, we measure a mean radio-to-optical size ratio of re-MERGE/rHST ∼ 1.02 ± 0.03, suggesting that in most high-redshift galaxies, the ∼GHz continuum emission traces the stellar light seen in optical imaging. This is the first in a series of papers that will explore the ∼kpc-scale radio properties of star-forming galaxies and AGN in the GOODS-N field observed by e-MERGE DR1.