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Title: The Heavy Metal Survey: Star Formation Constraints and Dynamical Masses of 21 Massive Quiescent Galaxies at z = 1.3–2.3

In this paper, we present the Heavy Metal Survey, which obtained ultradeep medium-resolution spectra of 21 massive quiescent galaxies at 1.3 <z< 2.3 with Keck/LRIS and MOSFIRE. With integration times of up to 16 hr per band per galaxy, we observe numerous Balmer and metal absorption lines in atmospheric windows. We successfully derive spectroscopic redshifts for all 21 galaxies, and for 19 we also measure stellar velocity dispersions (σv), ages, and elemental abundances, as detailed in an accompanying paper. Except for one emission-line active galactic nucleus, all galaxies are confirmed as quiescent through their faint or absent Hαemission and evolved stellar spectra. For most galaxies exhibiting faint Hα, elevated [Nii]/Hαsuggests a non-star-forming origin. We calculate dynamical masses (Mdyn) by combiningσvwith structural parameters obtained from the Hubble Space Telescope COSMOS(-DASH) survey and compare them with stellar masses (M*) derived using spectrophotometric modeling, considering various assumptions. For a fixed initial mass function (IMF), we observe a strong correlation betweenMdyn/M*andσv. This correlation may suggest that a varying IMF, with high-σvgalaxies being more bottom heavy, was already in place atz∼ 2. When implementing theσv-dependent IMF found in the cores of nearby early-type galaxiesandcorrecting for biases in our stellar mass and size measurements, we find a low scatter inMdyn/M*of 0.14 dex. However, these assumptions result in unphysical stellar masses, which exceed the dynamical masses by 34%. This tension suggests that distant quiescent galaxies do not simply grow inside-out into today’s massive early-type galaxies and the evolution is more complicated.

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DOI PREFIX: 10.3847
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Journal Name:
The Astrophysical Journal
Medium: X Size: Article No. 36
Article No. 36
Sponsoring Org:
National Science Foundation
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