Аннотация
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, they 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-$\sigma$ 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 find good agreement
among these methods for one galaxy. The other two galaxies show 2-5$\sigma$
tension, depending on the dark matter contribution, when considering IMFs with
a fixed low-mass cut-off of 0.08 Msol. Allowing a variable cut-off mass reduces
the tension to 1-3$\sigma$ and can reach consistency with the lensing/dynamical
$M_*/L$ if dark matter is assumed to be negligible. Compared to published
scaling relations, the SNELLS lenses are distinctly offset to lower total $M/L$
and lighter IMFs than the mean matched-$\sigma$ ETG, as estimated from lensing
and dynamics. However, their mean spectrum is virtually indistinguishable--at
the 0.3% level--from the mean spectrum of matched-$\sigma$ ETGs drawn from the
SDSS, and the derived IMF and abundance pattern are likewise consistent. This
indicates a puzzling divergence between the masses and stellar population
properties of the SNELLS sample. We discuss some possible resolutions.
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