S20B0098abst
S20B0098
At present, we still do not fully understand why some massive galaxies abruptly switch off their star formation in the early Universe, and what causes their rapid transition to the red sequence. Recently-quenched ‘post-starburst’ (PSB) galaxies are key to understanding this transition phase, but few have been spectroscopically identified at high redshift (z > 1). Fortunately, our new photometric PCA technique has enabled us to identify >1500 candidate PSBs in the UDS field at 0.5<z<3. From optical spectroscopy at VLT (24 PSBs), we have already confirmed the nature of these candidates at z < 1.4, but spectroscopic confirmation at higher redshift remains lacking, with implications for >700 candidates. We request a pilot study to obtain near-infrared spectra for 4 candidate PSBs at z∼2, to confirm their nature and the validity of the PCA technique at these redshifts for the first time. We will also age-date their stellar populations using absorption line diagnostics (e.g. Balmer lines), and use Mg/Fe ratios to measure the duration of the star formation episode prior to quenching. The remaining slits will be assigned to lower-z PSBs (z<1.8) and phot-z selected galaxies at similar redshifts as a control sample for comparison.
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