1. Elizabeth J. McGrath, Aurora Y. Kesseli, Arjen van der Wel, Eric Bell, Guillermo Barro and the CANDELS Collaboration QUIESCENT DISKS IN THE EARLY UNIVERSE

2. Red sequence in place at z~2 Growth in quiescent population (red symbols) is dramatic since z~2 Galaxies evolve from mostly low Sersic index (open symbols) to higher Sersic (filled symbols) FORMATION OF THE RED SEQUENCE Bell et al. (2012)

3. Strongest correlation is between Sersic index and quenched fraction for all redshift ranges. High Sersic = bulge dominated (?) Consistent with merger formation scenario SEARCH FOR A QUENCHING PARAMETER Bell et al. (2012)

4. Previous studies have found strong evidence for massive, quiescent disks, even without large central bulges (including spectroscopic confirmation of their quiescence): QUIESCENT DISKS McGrath et al. (2007, 2008) n=1.49 z=1.412 ACS NIC2 Model Residuals

5. CANDELS Large area near-IR WFC3 survey. Particularly well-suited to the study of quenched or “passive” galaxies at z~2 that are essentially invisible at shorter, rest-frame UV wavelengths. ACSWFC3 z = 1.6 vz YJ H

6. DETAILED MORPHOLOGY STUDIES Real galaxies aren’t as simple as pure disks or pure ellipticals. By convention, Sersic n 2.5 = spheroidal With good data we can decompose an image of a galaxy into its subcomponents

7. POINT SPREAD FUNCTION “Hybrid” PSF Stacked stars within 2.5” Central and outermost pixels replaced with TinyTim model Drizzled in same manner as data Available at candels.ucolick.org or by email: emcgrath@colby.edu

8. UVJ SELECTION OF QUIESCENT GALAXIES AT Z > 1 a la Labbé et al. (2005); Wuyts et al. (2007); Williams et al. (2009) GOODS-S from CANDELS

9. QUIESCENT DISKS z = 1.29 n = 4.0 z = 1.68 n = 2.4 z = 1.69 n = 1.9 z = 1.61 n = 2.6 z = 0.90 n = 2.6 Closer inspection of “high-Sersic”, massive, quiescent galaxies has revealed a number of disk-dominated galaxies. B/T = 0.30 B/T = 0.25 B/T = 0.33 B/T = 0.19

10. Results from Bruce et al. (2014) in the UDS + COSMOS: 1 10 11 M sun HOW COMMON ARE THESE QUIESCENT DISKS? Bruce et al. (2014) 29% of all quiescent galaxies have B/T < 0.5.

11. Expanding the sample with CANDELS/ GOODS-S: Defined to be disks if B/T < 0.5 Redshift bins spaced equally in time. HOW COMMON ARE QUIESCENT DISKS? 30% are disk- dominated at z~2 Quiescent galaxies with M > 10 10 M o EJM, Kesseli, et al., in prep. 10 5 4 3 Time (Gyr)

12. SUMMARY A significant fraction of quenched galaxies at high-z appear to be disk dominated. Spheroid formation may not be the trigger that quenches star-formation, but just an end result. (In)consistent with merger paradigm? Compare number density of quiescent disks to predictions from SAMs (e.g., Somerville et al. mock galaxy catalogs with B/T ratios). In-situ vs. ex-situ processes for star-formation quenching? disk instabilities environment (e.g., halo quenching)