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The Initial Mass Function in the Nearest Strong Lenses from SNELLS: Assessing the Consistency of Lensing, Dynamical, and Spectroscopic Constraints

Newman, A.B.; Smith, R.J.; Conroy, C.; Villaume, A.; van Dokkum, P.

The Initial Mass Function in the Nearest Strong Lenses from SNELLS: Assessing the Consistency of Lensing, Dynamical, and Spectroscopic Constraints Thumbnail


Authors

A.B. Newman

C. Conroy

A. Villaume

P. van Dokkum



Abstract

We present new observations of the three nearest early-type galaxy (ETG) strong lenses discovered in the SINFONI Nearby Elliptical Lens Locator Survey (SNELLS). Based on their lensing masses, these ETGs were inferred to have a stellar initial mass function (IMF) consistent with that of the Milky Way, not the bottom-heavy IMF that has been reported as typical for high-σ ETGs based on lensing, dynamical, and stellar population synthesis techniques. We use these unique systems to test the consistency of IMF estimates derived from different methods. We first estimate the stellar M */L using lensing and stellar dynamics. We then fit high-quality optical spectra of the lenses using an updated version of the stellar population synthesis models developed by Conroy & van Dokkum. When examined individually, we find good agreement among these methods for one galaxy. The other two galaxies show 2–3σ tension with lensing estimates, depending on the dark matter contribution, when considering IMFs that extend to 0.08 M ⊙. Allowing a variable low-mass cutoff or a nonparametric form of the IMF reduces the tension among the IMF estimates to <2σ. There is moderate evidence for a reduced number of low-mass stars in the SNELLS spectra, but no such evidence in a composite spectrum of matched-σ ETGs drawn from the SDSS. Such variation in the form of the IMF at low stellar masses (m lesssim 0.3 M ⊙), if present, could reconcile lensing/dynamical and spectroscopic IMF estimates for the SNELLS lenses and account for their lighter M */L relative to the mean matched-σ ETG. We provide the spectra used in this study to facilitate future comparisons.

Citation

Newman, A., Smith, R., Conroy, C., Villaume, A., & van Dokkum, P. (2017). The Initial Mass Function in the Nearest Strong Lenses from SNELLS: Assessing the Consistency of Lensing, Dynamical, and Spectroscopic Constraints. Astrophysical Journal, 845(2), Article 157. https://doi.org/10.3847/1538-4357/aa816d

Journal Article Type Article
Acceptance Date Jul 19, 2017
Online Publication Date Aug 22, 2017
Publication Date Aug 22, 2017
Deposit Date Sep 12, 2017
Publicly Available Date Mar 29, 2024
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 845
Issue 2
Article Number 157
DOI https://doi.org/10.3847/1538-4357/aa816d
Related Public URLs https://arxiv.org/abs/1612.00065v2

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Copyright Statement
© 2017. The American Astronomical Society. All rights reserved.





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