Browsing by Author "McAlpine, K."
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Item Evolution of faint radio sources in the VIDEO-XMM3 field(OUP, 2013) McAlpine, K.; Jarvis, Matt; Bonfield, David G.It has been speculated that low luminosity radio-loud AGN have the potential to serve as an important source of AGN feedback, and may be responsible for suppressing star-formation activity in massive elliptical galaxies at late times. As such the cosmic evolution of these sources is vitally important to understanding the significance of such AGN feedback processes and their influence on the global star-formation history of the universe. In this paper we present a new investigation of the evolution of faint radio sources out to z~2.5. We combine a 1 square degree VLA radio survey, complete to a depth of 100 μJy, with accurate 10 band photometric redshifts from the VIDEO and CFHTLS surveys. The results indicate that the radio population experiences mild positive evo- lution out to z~1.2 increasing their space density by a factor of ~3, consistent with results of several previous studies. Beyond z=1.2 there is evidence of a slowing down of this evolution. Star-forming galaxies drive the more rapid evolution at low redshifts, z<1.2, while more slowly evolving AGN populations dominate at higher redshifts resulting in a decline in the evolution of the radio luminosity function at z>1.2. The evolution is best fit by pure luminosity evolution with star-forming galaxies evolving as (1 + z)2.47±0.12 and AGN as (1 + z)1.18±0.21.Item The VISTA Deep Extragalactic Observations (VIDEO) survey(Oxford University Press, 2013) Jarvis, Matt; Bonfield, David G.; Bruce, V.A.; Zwart, J.; Geach, J.E.; McAlpine, K.; McLure, R.J.; Gonzalez-Solares, Eduardo A.; Irwin, M.; Lewis, J.; Kupcu Yoldas, A.; Andreon, S.; Cross, N.J.G.; Emerson, J.P.; Dalton, G.; Dunlop, J.S.; Hodgkin, S. T.; Le Fevre, O.; Karouzos, M.; Meisenheimer, K.; Oliver, S.; Rawlings, S.; Simpson, Chris; Smail, I.; Smith, Daniel J.B.; Sullivan, M.; Sutherland, W.; White, S.V.In this paper we describe the first data release of the the Visible and Infrared Survey Telescope for Astronomy (VISTA) Deep Extragalactic Observations (VIDEO) survey. VIDEO is a 12 degree2 survey in the near-infrared Z,Y ,J,H andKs bands, specifically designed to enable the evolution of galaxies and large structures to be traced as a function of both epoch and environment from the present day out to z=4, and active galactic nuclei (AGN) and the most massive galaxies up to and into the epoch of reionization. With its depth and area, VIDEO will be able to fully explore the period in the Universe where AGN and starburst activity were at their peak and the first galaxy clusters were beginning to virialize. VIDEO therefore offers a unique data set with which to investigate the interplay between AGN, starbursts and environment, and the role of feedback at a time when it was potentially most crucial. We provide data over the VIDEO-XMM3 tile, which also covers the Canada-France- Hawaii-Telescope Legacy Survey Deep-1 field (CFHTLS-D1). The released VIDEO data reach a 5 AB-magnitude depth of Z = 25:7, Y = 24:5, J = 24:4, H = 24:1 and Ks = 23:8 in 2 arcsec diameter apertures (the full depth of Y = 24:6 will be reached within the full integration time in future releases). The data are compared to previous surveys over this field and we find good astrometric agreement with the Two-Micron All Sky Survey, and source counts in agreement with the recently released UltraVISTA survey data. The addition of the VIDEO data to the CFHTLS-D1 optical data increases the accuracy of photometric redshifts and significantly reduces the fraction of catastrophic outliers over the redshift range 0 < z < 1 from 5.8 to 3.1 per cent in the absence of an iband luminosity prior. However, we expect the main improvement in photometric redshifts will come in the redshift range 1 < z < 4 due to the sensitivity to the Balmer and 4000°A breaks provided by the near-infrared VISTA filters. All images and catalogues presented in this paper are publicly available through ESO’s phase 3 archive and the VISTA Science Archive.