The rest-frame UV luminosity function at z≃4 : a significant contribution of AGN to the bright-end of the galaxy population
Monthly Notices of the Royal Astronomical Society Oxford University Press 494:2 (2020) 1771-1783
Abstract:
We measure the rest-frame UV luminosity function (LF) at z ∼ 4 self-consistently over a wide range in absolute magnitude (−27 . MUV . −20). The LF is measured with 46,904 sources selected using a photometric redshift approach over ∼ 6 deg2 of the combined COSMOS and XMM-LSS fields. We simultaneously fit for both AGN and galaxy LFs using a combination of Schechter or Double Power Law (DPL) functions alongside a single power law for the faint-end slope of the AGN LF. We find a lack of evolution in the shape of the bright-end of the LBG component when compared to other studies at z ' 5 and evolutionary recipes for the UV LF. Regardless of whether the LBG LF is fit with a Schechter function or DPL, AGN are found to dominate at MUV < −23.5. We measure a steep faint-end slope of the AGN LF with αAGN = −2.09+0.35 −0.38 (−1.66+0.29 −0.58) when fit alongside a Schechter function (DPL) for the galaxies. Our results suggest that if AGN are morphologically selected it results in a bias to lower number densities. Only by considering the full galaxy population over the transition region from AGN to LBG domination can an accurate measurement of the total LF be attained.Cosmology with Phase 1 of the Square Kilometre Array Red Book 2018: technical specifications and performance forecasts
Publications of the Astronomical Society of Australia Cambridge University Press 37 (2020) e007
Abstract:
We present a detailed overview of the cosmological surveys that we aim to carry out with Phase 1 of the Square Kilometre Array (SKA1) and the science that they will enable. We highlight three main surveys: a medium-deep continuum weak lensing and low-redshift spectroscopic HI galaxy survey over 5 000 deg2; a wide and deep continuum galaxy and HI intensity mapping (IM) survey over 20 000 deg2 from z = 0.35 to 3; and a deep, high-redshift HI IM survey over 100 deg2 from z = 3 to 6. Taken together, these surveys will achieve an array of important scientific goals: measuring the equation of state of dark energy out to z ~ 3 with percent-level precision measurements of the cosmic expansion rate; constraining possible deviations from General Relativity on cosmological scales by measuring the growth rate of structure through multiple independent methods; mapping the structure of the Universe on the largest accessible scales, thus constraining fundamental properties such as isotropy, homogeneity, and non-Gaussianity; and measuring the HI density and bias out to z = 6. These surveys will also provide highly complementary clustering and weak lensing measurements that have independent systematic uncertainties to those of optical and near-infrared (NIR) surveys like Euclid, LSST, and WFIRST leading to a multitude of synergies that can improve constraints significantly beyond what optical or radio surveys can achieve on their own. This document, the 2018 Red Book, provides reference technical specifications, cosmological parameter forecasts, and an overview of relevant systematic effects for the three key surveys and will be regularly updated by the Cosmology Science Working Group in the run up to start of operations and the Key Science Programme of SKA1.The Karl G. Jansky very large array sky survey (VLASS). Science case and survey design
Publications of the Astronomical Society of the Pacific 132:1009 (2020)
Abstract:
© 2020. The Astronomical Society of the Pacific. The Very Large Array Sky Survey (VLASS) is a synoptic, all-sky radio sky survey with a unique combination of high angular resolution (≈2.″5), sensitivity (a 1σ goal of 70 μJy/beam in the coadded data), full linear Stokes polarimetry, time domain coverage, and wide bandwidth (2–4 GHz). The first observations began in 2017 September, and observing for the survey will finish in 2024. VLASS will use approximately 5500 hr of time on the Karl G. Jansky Very Large Array (VLA) to cover the whole sky visible to the VLA (decl. > −40°), a total of 33 885 deg2. The data will be taken in three epochs to allow the discovery of variable and transient radio sources. The survey is designed to engage radio astronomy experts, multi-wavelength astronomers, and citizen scientists alike. By utilizing an “on the fly” interferometry mode, the observing overheads are much reduced compared to a conventional pointed survey. In this paper, we present the science case and observational strategy for the survey, and also results from early survey observations.The faint radio source population at 15.7 GHz – IV. The dominance of core emission in faint radio galaxies
Monthly Notices of the Royal Astronomical Society Oxford University Press 493:2 (2020) 2841-2853
Abstract:
We present 15-GHz Karl G. Jansky Very Large Array observations of a complete sample of radio galaxies selected at 15.7 GHz from the Tenth Cambridge (10C) survey. 67 out of the 95 sources (71 per cent) are unresolved in the new observations and lower frequency radio observations, placing an upper limit on their angular size of ∼2 arcsec. Thus, compact radio galaxies, or radio galaxies with very faint jets, are the dominant population in the 10C survey. This provides support for the suggestion in our previous work that low-luminosity (L<1025W~Hz−1) radio galaxies are core dominated, although higher resolution observations are required to confirm this directly. The 10C sample of compact, high-frequency selected radio galaxies is a mixture of high-excitation and low-excitation radio galaxies and displays a range of radio spectral shapes, demonstrating that they are a mixed population of objects.A lack of evolution in the very bright-end of the galaxy luminosity function from z ≃ 8-10
Monthly Notices of the Royal Astronomical Society Oxford University Press 493:2 (2020) 2059-2084