The UVJ Selection of Quiescent and Star Forming Galaxies: Separating Early and Late-Type Galaxies and Isolating Edge-on Spirals

TL;DR

This study uses HST imaging to analyze galaxy structures in the UVJ diagram at 0.6<z<0.9, revealing how galaxy color, morphology, and inclination relate to star formation activity and dust effects.

Contribution

It demonstrates the effectiveness of the UVJ diagram in distinguishing galaxy types and links UVJ positions to morphology, dust, and inclination effects at intermediate redshift.

Findings

Quiescent galaxies are concentrated with high Sersic indices and smooth structures.

Star-forming galaxies show a broad range of Sersic indices and structures.

Galaxy inclination influences UVJ colors, with edge-on systems appearing redder due to dust reddening.

Abstract

We utilize for the first time HST ACS imaging to examine the structural properties of galaxies in the rest-frame U-V versus V-J diagram (i.e., the UVJ diagram) using a sample at 0.6<z<0.9 that reaches a low stellar mass limit (log M/Msun>10.25). The use of the UVJ diagram as a tool to distinguish quiescent galaxies from star forming galaxies (SFGs) is becoming more common due to its ability to separate red quiescent galaxies from reddened SFGs. Quiescent galaxies occupy a small and distinct region of UVJ color space and we find most of them to have concentrated profiles with high Sersic indices (n>2.5) and smooth structure characteristic of early-type systems. SFGs populate a broad, but well-defined sequence of UVJ colors and are comprised of objects with a mix of Sersic indices. Interestingly, most UVJ-selected SFGs with high Sersic indices also display structure due to dust and star formation typical of the n<2.5 SFGs and late-type systems. Finally, we find that the position of a SFG on the sequence of UVJ colors is determined to a large degree by the mass of the galaxy and its inclination. Systems that are closer to edge-on generally display redder colors and lower [OII]3727 luminosity per unit mass as a consequence of the reddening due to dust within the disks. We conclude that the two main features seen in UVJ color space correspond closely to the traditional morphological classes of early and late-type galaxies.