Compact galaxies and the size–mass galaxy distribution from a colour-selected sample at 0.04 < z < 0.15 supplemented by ugrizYJHK photometric redshifts. Issue 2 (27th October 2020)

• Record Type: Journal Article
• Authors: Baldry, Ivan K; Sullivan, Tricia; Rani, Raffaele; Turner, Sebastian
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 500:Issue 2(2021)
• Page Start: 1557
• Page End: 1574
• Publication Date: 2020-10-27
• Subjects: galaxies: distances and redshifts -- galaxies: evolution -- galaxies: luminosity function, mass function -- galaxies: structure; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa3327
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: The size–mass galaxy distribution is a key diagnostic for galaxy evolution. Massive compact galaxies are potential surviving relics of a high-redshift phase of star formation. Some of these could be nearly unresolved in Sloan Digital Sky Survey (SDSS) imaging and thus not included in galaxy samples. To overcome this, a sample was selected from the combination of SDSS and UKIRT Infrared Deep Sky Survey (UKIDSS) photometry to r &lt; 17.8. This was done using colour–colour selection, and then by obtaining accurate photometric redshifts (photo-z) using scaled flux matching (SFM). Compared to spectroscopic redshifts (spec-z), SFM obtained a 1σ scatter of 0.0125 with only 0.3 per cent outliers (|Δln (1 + z )| &gt; 0.06). A sample of 163 186 galaxies was obtained with 0.04 &lt; z &lt; 0.15 over $2300\, {\rm deg}^2$ using a combination of spec-z and photo-z. Following Barro et al. log Σ1.5 = log M * − 1.5log r 50, maj was used to define compactness. The spectroscopic completeness was 76 per cent for compact galaxies (log Σ1.5 &gt; 10.5) compared to 92 per cent for normal-sized galaxies. This difference is primarily attributed to SDSS &#39;fibre collisions&#39; 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-sized galaxies. By comparison with a high-redshift sample from 3D- HST, log Σ1.5 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 Σ1.5, which is demonstrated conclusively using this complete sample.