%0 Generic %1 newman2016initial %A Newman, Andrew B. %A Smith, Russell J. %A Conroy, Charlie %A Villaume, Alexa %A van Dokkum, Pieter %D 2016 %K IMF lensing variation %T The Initial Mass Function in the Nearest Strong Lenses from SNELLS: Assessing the Consistency of Lensing, Dynamical, and Spectroscopic Constraints %U http://arxiv.org/abs/1612.00065 %X 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.

@misc{newman2016initial, 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, 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.}, added-at = {2016-12-02T10:01:58.000+0100}, author = {Newman, Andrew B. and Smith, Russell J. and Conroy, Charlie and Villaume, Alexa and van Dokkum, Pieter}, biburl = {https://www.bibsonomy.org/bibtex/26e15a83d1c144273c7cddf483bda8cce/miki}, description = {[1612.00065] The Initial Mass Function in the Nearest Strong Lenses from SNELLS: Assessing the Consistency of Lensing, Dynamical, and Spectroscopic Constraints}, interhash = {aa0c8c58678a7b8f056c2763ea51671a}, intrahash = {6e15a83d1c144273c7cddf483bda8cce}, keywords = {IMF lensing variation}, note = {cite arxiv:1612.00065Comment: Submitted to ApJ}, timestamp = {2016-12-02T10:01:58.000+0100}, title = {The Initial Mass Function in the Nearest Strong Lenses from SNELLS: Assessing the Consistency of Lensing, Dynamical, and Spectroscopic Constraints}, url = {http://arxiv.org/abs/1612.00065}, year = 2016 }