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Compact galaxies and the size-mass galaxy distribution from a colour-selected sample at 0.04 < z < 0.15 supplemented by ugrizYJHK photometric redshifts

Baldry, IK, Sullivan, T, Rani, R and Turner, S (2020) Compact galaxies and the size-mass galaxy distribution from a colour-selected sample at 0.04 < z < 0.15 supplemented by ugrizYJHK photometric redshifts. Monthly Notices of the Royal Astronomical Society, 500 (2). pp. 1557-15574. ISSN 0035-8711

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The size-mass galaxy distribution is a key diagnostic for galaxy evolution. Massive compact galaxies are of particular interest as potential surviving relics of a high-redshift phase of star formation. Some compact galaxies at low redshift could be nearly unresolved in SDSS imaging and thus not included in galaxy samples. To overcome this, a sample was selected from the 9-band combination of SDSS and UKIDSS photometry to r < 17.8. This was done in two stages: first using colour-colour selection, and then by obtaining accurate photometric redshifts using scaled flux matching (SFM). Compared to spectroscopic redshifts, SFM obtained a 1-sigma scatter of 0.0125 with only 0.3% outliers (|D ln(1+z)| > 0.06). A sample of 163186 galaxies was obtained with 0.04 < z < 0.15 over 2300 deg^2 using a combination of spec-z and photo-z. Following Barro et al., log S_1.5 = log M_* - 1.5 log r_50 was used in order assess the completeness and number density of massive compact galaxies (log M_* > 10, log S_1.5 > 10.5). The spectroscopic completeness was 76% for compact galaxies compared to 92% for normal-size galaxies. This difference is primarily attributed to SDSS fibre collisions and not the completeness of the main galaxy sample selection. Using environmental overdensities, this confirms that compact quiescent galaxies are significantly more likely to be found in high-density environments compared to normal-size galaxies. By comparison with a high-redshift sample from 3D-HST, log S_1.5 distribution functions show significant evolution, with this being a compelling way to compare with simulations such as EAGLE. The number density of compact quiescent galaxies drops by a factor of about 30 from z ~ 2 to log (n / Mpc^-3) = -5.3 +- 0.4 in the SDSS-UKIDSS sample. The uncertainty is dominated by the steep cut off in log S_1.5, which is demonstrated conclusively using this complete sample.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2020 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: astro-ph.GA; astro-ph.GA
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 27 Oct 2020 09:45
Last Modified: 25 Apr 2022 16:00
DOI or ID number: 10.1093/mnras/staa3327
URI: https://researchonline.ljmu.ac.uk/id/eprint/13571
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