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The eMERGE Survey - I: Very Large Array 5.5 GHz observations of the GOODS-North Field

Guidetti, D.; Bondi, M.; Prandoni, I.; Muxlow, T.W.B.; Beswick, R.; Wrigley, N.; Smail, I.; McHardy, I.; Thomson, A.P.; Radcliffe, J.; Argo, M.K.

The eMERGE Survey - I: Very Large Array 5.5 GHz observations of the GOODS-North Field Thumbnail


Authors

D. Guidetti

M. Bondi

I. Prandoni

T.W.B. Muxlow

R. Beswick

N. Wrigley

I. McHardy

A.P. Thomson

J. Radcliffe

M.K. Argo



Abstract

We present new observations of the GOODS-N field obtained at 5.5 GHz with the Karl G. Jansky Very Large Array. The central region of the field was imaged to a median rms of 3 μJy beam−1 with a resolution of 0.5 arcsec. From a 14-arcmin diameter region, we extracted a sample of 94 radio sources with signal-to-noise ratio greater than 5. Near-IR identifications are available for about ∼88 per cent of the radio sources. We used different multiband diagnostics to separate active galactic nuclei (AGNs), both radiatively efficient and inefficient, from star-forming galaxies. From our analysis, we find that about 80 per cent of our radio-selected sample is AGN dominated, with the fraction rising to 92 per cent when considering only the radio sources with redshift >1.5. This large fraction of AGN-dominated radio sources at very low flux densities (the median flux density at 5.5 GHz is 42 μJy), where star-forming galaxies are expected to dominate, is somewhat surprising and at odds with other results. Our interpretation is that both the frequency and angular resolution of our radio observations strongly select against radio sources whose brightness distribution is diffuse on a scale of several kpc. Indeed, we find that the median angular sizes of the AGN-dominated sources is around 0.2–0.3 arcsec against 0.8 arcsec for star-forming galaxies. This highlights the key role that high frequency radio observations can play in pinpointing AGN-driven radio emission at μJy levels. This work is part of the eMERGE legacy project.

Citation

Guidetti, D., Bondi, M., Prandoni, I., Muxlow, T., Beswick, R., Wrigley, N., …Argo, M. (2017). The eMERGE Survey - I: Very Large Array 5.5 GHz observations of the GOODS-North Field. Monthly Notices of the Royal Astronomical Society, 471(1), 210-226. https://doi.org/10.1093/mnras/stx1162

Journal Article Type Article
Acceptance Date May 10, 2017
Online Publication Date Jul 15, 2017
Publication Date Jul 15, 2017
Deposit Date Aug 21, 2017
Publicly Available Date Mar 29, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 471
Issue 1
Pages 210-226
DOI https://doi.org/10.1093/mnras/stx1162
Publisher URL http://ukads.nottingham.ac.uk/abs/2017MNRAS.471..210G

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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2017. The Authors.
Published by Oxford University Press on behalf of the Royal Astronomical Society.





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