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The SINFONI Nearby Elliptical Lens Locator Survey: discovery of two new low-redshift strong lenses and implications for the initial mass function in giant early-type galaxies

Smith, R.J.; Lucey, J.R.; Conroy, C.

The SINFONI Nearby Elliptical Lens Locator Survey: discovery of two new low-redshift strong lenses and implications for the initial mass function in giant early-type galaxies Thumbnail


Authors

C. Conroy



Abstract

We present results from a blind survey to identify strong gravitational lenses among the population of low-redshift early-type galaxies. The SINFONI Nearby Elliptical Lens Locator Survey (SNELLS) uses integral-field infrared spectroscopy to search for lensed emission line sources behind massive lens candidates at z < 0.055. From 27 galaxies observed, we have recovered one previously known lens (ESO 325−G004) at z = 0.034, and discovered two new systems, at z = 0.031 and 0.052. All three lens galaxies have high velocity dispersions (σ > 300 km s− 1) and α-element abundances ([Mg/Fe] > 0.3). From the lensing configurations we derive total J-band mass-to-light ratios of 1.8 ± 0.1, 2.1 ± 0.1 and 1.9 ± 0.2 within the ∼2 kpc Einstein radius. Correcting for estimated dark matter contributions, and comparing to stellar population models with a Milky Way (Kroupa) initial mass function (IMF), we determine the ‘mass excess factor’, α. Assuming the lens galaxies have ‘old’ stellar populations (10 ± 1 Gyr), the average IMF mass factor is 〈α〉 = 1.10 ± 0.08 ± 0.10, where the first error is random and the second is systematic. If we instead fit the stellar populations from 6dF optical survey spectra, all three galaxies are consistent with being old, but the age errors are 3–4 Gyr, due to limited signal-to-noise ratio. The IMF constraints are therefore looser in this case, with 〈α〉 = 1.23+0.16−0.13±0.10. Our results are thus consistent with a Kroupa IMF (α = 1.00) on average, and strongly reject very heavy IMFs with α ≳ 2. A Salpeter IMF (α = 1.55) is inconsistent at the 3.5σ level if the galaxies are old, but cannot be excluded using age constraints derived from the currently available optical spectra.

Citation

Smith, R., Lucey, J., & Conroy, C. (2015). The SINFONI Nearby Elliptical Lens Locator Survey: discovery of two new low-redshift strong lenses and implications for the initial mass function in giant early-type galaxies. Monthly Notices of the Royal Astronomical Society, 449(4), 3441-3457. https://doi.org/10.1093/mnras/stv518

Journal Article Type Article
Acceptance Date Mar 6, 2015
Online Publication Date Apr 9, 2015
Publication Date Jun 1, 2015
Deposit Date Sep 21, 2015
Publicly Available Date Mar 29, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 449
Issue 4
Pages 3441-3457
DOI https://doi.org/10.1093/mnras/stv518
Keywords Gravitational lensing: strong, Stars: luminosity function, mass function, Galaxies: elliptical and lenticular, cD, Galaxies: stellar content.

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Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.





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