The LOFAR Two-metre Sky Survey: IV. First Data Release: Photometric redshifts and rest-frame magnitudes

Duncan, Kenneth J.; Sabater, J.; Röttgering, H.J.A.; Jarvis, M.J.; Smith, D.J.B.; Best, P.N.; Callingham, J.R.; Cochrane, R.; Croston, J.H.; Hardcastle, M.J.

doi:10.1051/0004-6361/201833562

The LOFAR Two-metre Sky Survey: IV. First Data Release: Photometric redshifts and rest-frame magnitudes

Kenneth J. Duncan
(
- Leiden Observ.
)
,
J. Sabater
(
- Edinburgh U., Inst. Astron.
)
,
H.J.A. Röttgering
(
- Leiden Observ.
)
,
M.J. Jarvis
(
- U. Oxford, Astrophys. Dept.
)
,
D.J.B. Smith
(
- Hertfordshire U.
)

Nov 19, 2018

17 pages

Published in:

Astron.Astrophys. 622 (2019) A3

Published: Feb 1, 2019

e-Print:

1811.07928 [astro-ph.GA]

DOI:

10.1051/0004-6361/201833562 (publication)

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Abstract: (EDP Sciences)

The LOFAR Two-metre Sky Survey (LoTSS) is a sensitive, high-resolution 120–168 MHz survey of the Northern sky. The LoTSS First Data Release (DR1) presents 424 square degrees of radio continuum observations over the HETDEX Spring Field (10h45m00s < right ascension < 15h30m00s and 45°00′00″ < declination < 57°00′00″) with a median sensitivity of 71 μJy beam−1 and a resolution of 6″. In this paper we present photometric redshifts (photo-z) for 94.4% of optical sources over this region that are detected in the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) 3π steradian survey. Combining the Pan-STARRS optical data with mid-infrared photometry from the Wide-field Infrared Survey Explorer, we estimate photo-zs using a novel hybrid photometric redshift methodology optimised to produce the best possible performance for the diverse sample of radio continuum selected sources. For the radio-continuum detected population, we find an overall scatter in the photo-z of 3.9% and an outlier fraction (|zphot−zspec|/(1 + zspec) > 0.15) of 7.9%. We also find that, at a given redshift, there is no strong trend in photo-z quality as a function of radio luminosity. However there are strong trends as a function of redshift for a given radio luminosity, a result of selection effects in the spectroscopic sample and/or intrinsic evolution within the radio source population. Additionally, for the sample of sources in the LoTSS First Data Release with optical counterparts, we present rest-frame optical and mid-infrared magnitudes based on template fits to the consensus photometric (or spectroscopic when available) redshift.Key words: radio continuum: galaxies / galaxies: active / galaxies: distances and redshifts⋆ LoTSS.⋆⋆ The catalogue is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/622/A1

Note:

16 figures, 1 table and 18 pages. This paper is part of the LOFAR surveys Data Release 1 and has been accepted for publication in a special edition of A&A that will appear in Feb 2019, Volume 622. The catalogues and images from the data release will be publicly available at http://www.lofar-surveys.org upon publication of the volume

radio continuum: galaxies
galaxies: active
galaxies: distances and redshifts

References(57)

Figures(23)