REQUIEM-HST will provide strong observational constraints on massive quiescent galaxies at cosmic noon, reconstructing the formation history of their inner cores through resolved emission- and absorption- line diagnostics.
Joint Bayesian Analysis of Hubble Space Telescope Grism Spectroscopy and Imaging. The full framework of the REQUIEM2D software developed by PhD student Mo Akhshik to perform a two dimensional analysis of Hubble grism and imaging data using priors on the star formation history (SFH) and accounting for dust and metallicity uncertainties. See Akhshik et al. (2020) for more details on the methodology and mock tests on Illustris Simulation SFHs.
Over the last decade, nature’s telescopes (i.e., massive clusters of galaxies that strong gravitationally lens background galaxies) have provided bountiful insights into the formation and evolution of “typical” galaxies at 1 < z < 6, resulting in rich samples of star-forming galaxies (e.g., Livermore et al., 2015; Ma et al., 2015). What has remained largely elusive are strongly lensed massive quiescent galaxies, as only a handful of strongly lensed quiescent galaxies at z > 1 have been studied to date (Muzzin et al., 2012; Geier et al., 2013; Newman et al., 2015; Toft et al., 2017; Ebeling et al., 2018; Newman et al., 2018). With the REQUIEM-HST Survey, a 60-orbit medium Cycle 26 proposal (HST-GO-15663, PI: UConn PhD student, Mo Akhshik), we propose to analyze the first comprehensive sample of eight lensed quiescent galaxies by combining HST/G141 grism spectroscopy with existing HST and Spitzer (and soon ALMA) data, probing a broad range in stellar mass and redshift. We will use strong gravitational lensing to resolve the past (formation) and present (quenching) of massive z ~ 2 galaxies, both major unsolved problems.
REQUIEM2D framework reveals rare rejuvenation in quenched galaxy at cosmic noon. Adapted from Akhshik et al. (2020), demonstrating the requiem2d Bayesian framework to model the stellar population gradients of distant quiescent galaxies. Without the grism spectroscopy and/or the resolved photometric analysis, we would have missed that MRG-S0851 has recently experienced a central rejuvenation episode (Akhshik et al. 2021).
Relevant Publications:
Recent Star Formation in a Massive Slowly Quenched Lensed Quiescent Galaxy at z = 1.88 Akhshik, M., Whitaker, K., Leja, J., Mahler, G., Sharon, K., Brammer, G., Toft, S., Bezanson, R., Man, A., Nelson, E., Pacifici, C., Wellons, S., Williams, C., 2021, Astrophysical Journal Letters, 907, 8.
REQUIEM-2D Methodology: Spatially Resolved Stellar Populations of Massive Lensed Quiescent Galaxies from Hubble Space Telescope 2D Grism Spectroscopy Akhshik, M., Whitaker, K., Brammer, G., Mahler, G., Sharon, K., Leja, J., Bayliss, M., Bezanson, R., Gladders, M., Man, A., Nelson, E., Rigby, J., Rizzo, F., Toft, S., Wellons, S., Williams, C., 2020, Astrophysical Journal, 900, 184.