The Role of Quenching Time in the Evolution of the Mass-size Relation of Passive Galaxies from the Wisp Survey
Zanella, A.; Scarlata, C.; Malkan, M.; Teplitz, H.; Atek, H.; Siana, B.; Henry, A.; Bunker, A. J.; Martin, C.; Dalla Bontà, E.; Corsini, E. M.; Bedregal, A. G.; Rafelski, M.; Rutkowski, M. J.; Dai, Y. S.; . Colbert, J.
United States, Italy, France, United Kingdom, Japan
Abstract
We analyze how passive galaxies at z ∼ 1.5 populate the mass-size plane as a function of their stellar age, to understand if the observed size growth with time can be explained with the appearance of larger quenched galaxies at lower redshift. We use a sample of 32 passive galaxies extracted from the Wide Field Camera 3 Infrared Spectroscopic Parallel (WISP) survey with spectroscopic redshift 1.3 ≲ z ≲ 2.05, specific star formation rates lower than 0.01 Gyr-1, and stellar masses above 4.5 × 1010 M ⊙. All galaxies have spectrally determined stellar ages from fitting of their rest-frame optical spectra and photometry with stellar population models. When dividing our sample into young (age ≤2.1 Gyr) and old (age >2.1 Gyr) galaxies we do not find a significant trend in the distributions of the difference between the observed radius and that predicted by the mass-size relation. This result indicates that the relation between the galaxy age and its distance from the mass-size relation, if it exists, is rather shallow, with a slope α ≳ -0.6. At face value, this finding suggests that multiple dry and/or wet minor mergers, rather than the appearance of newly quenched galaxies, are mainly responsible for the observed time evolution of the mass-size relation in passive galaxies.
Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.