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A potential role for wet minor mergers in the size-mass evolution of quiescent galaxies

Published onJun 01, 2020
A potential role for wet minor mergers in the size-mass evolution of quiescent galaxies

Quiescent and early-type galaxies are often considered “red and dead”, having long ago ended significant star formation. Yet, star formation may still occur in these galaxies if, for example, cold gas is be accreted via (minor) wet mergers. It remains unclear the extent to which the observed size-mass evolution of these galaxies is associated with this merger activity. We test for a possible link between recent star formation and this size-mass growth by studying a rare sample of quiescent galaxies which have also experienced a minor (≪1% of stellar mass) recent star formation episode. We select our sample on massive (M > 1010 solar masses) galaxies at intermediate redshift (0.5 < z < 1.5) from the GOODS-North field having UVJ colors consistent with “quiescent” galaxies. Of this sample, ~100 galaxies have already been observed in the rest-frame far-UV (HST WFC3/UV F275W) as part of the ongoing UVCANDELS survey. Notably, we find that ETGs with F275W emission, which reveals young stars (<100Myr) in these optically quiescent galaxies, are comparatively isolated in space, whereas those without this emission are more often found with neighboring galaxies. This may suggest a link between star formation in ETGs and their local environment. We measure sizes for galaxies in the rest-frame UV/optical and discuss the evolution of the size-mass relation for these massive quiescent galaxies.

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