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Paper: Suppressed Star Formation in Massive z ∼ 2.3 Galaxies
Volume: 379, Cosmic Frontiers
Page: 146
Authors: Kriek, M.; van Dokkum, P.; Franx, M.
Abstract: The past few years have seen a tremendous increase in our knowledge of the galaxy population at 2 < z < 3. Recently it was found that red galaxies make up more than 2/3 of the most massive galaxies in this redshift range. As most of these galaxies are beyond the limits of optical spectroscopy they are underrepresented in available samples of high redshift galaxies. To obtain a full spectroscopic census of the universe at z ~ 2.3 we have started a near-infrared (NIR) spectroscopic survey of a K-selected sample with GNIRS on Gemini-South. Up to now our sample contains 20 galaxies in the redshift range 2.0 < z < 2.7. Our results are surprising as they show that most galaxies at z ~ 2.3 look different from previous high-redshift galaxy samples, obtained with optical spectroscopy. 9 of the 20 galaxies in our sample have no detected emission lines, show strong Balmer breaks, and are best fit by stellar population models with low star formation rates (SFRs). Furthermore, we identify active galactic nuclei (AGNs) in several emission line galaxies. Our results suggest that in a significant part of the massive galaxies at z ~ 2.3 the star formation is already strongly suppressed, and that this suppression may be related to an AGN phase.
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