%0 Generic %1 leier2015strong %A Leier, Dominik %A Ferreras, Ignacio %A Saha, Prasenjit %A Charlot, Stéphane %A Bruzual, Gustavo %A La Barbera, Francesco %D 2015 %K imf population stellar variation %T Strong Gravitational Lensing and the Stellar IMF of Early-type Galaxies %U http://arxiv.org/abs/1512.00462 %X The stellar initial mass function is an important ingredient in galaxy formation, mainly linking the luminosity of a galaxy to its stellar mass, and driving chemical enrichment. In recent years there has been an ongoing discussion about systematic variations of the IMF in early-type galaxies and its connection with possible drivers such as velocity dispersion or metallicity. Strong gravitational lensing over galaxy scales in combination with photometric and spectroscopic data provides a powerful method to constrain the stellar mass-to-light ratio and hence the functional form of the IMF. We combine photometric and spectroscopic constraints from the latest set of population synthesis models of Charlot & Bruzual, including a varying IMF, with a non-parametric analysis of the lensing mass in a sample of 18 early-type lens galaxies from the SLACS survey, with velocity dispersions in the range 200-300 km/s. We find that very bottom-heavy IMFs are excluded. However, the upper limit to the IMF slope ($2.2$ for a bimodal IMF, taking into account a 20-30% contribution to the lensing mass from dark matter, where $\mu=1.3$ corresponds to a Kroupa-like IMF) is compatible at the $1\sigma$ level with the constraints imposed by gravity-sensitive line strengths. A two-segment power law parameterisation of the IMF (keeping its index at the high mass end fixed at the Salpeter value) is more constrained ($\Gammałesssim1.5$, where $\Gamma$ is the power index at the low-mass end). Furthermore we find that for a standard Milky Way-like IMF to be applicable a significant amount of dark matter is required within an effective radius. Our results reveal a large scatter regarding possible values of the IMF slope, suggesting that the recent lenses of Smith et al. - who find a Milky Way-like IMF in a few massive lensing early-type galaxies - may be explained by such a scatter. (Abridged)

@misc{leier2015strong, abstract = {The stellar initial mass function is an important ingredient in galaxy formation, mainly linking the luminosity of a galaxy to its stellar mass, and driving chemical enrichment. In recent years there has been an ongoing discussion about systematic variations of the IMF in early-type galaxies and its connection with possible drivers such as velocity dispersion or metallicity. Strong gravitational lensing over galaxy scales in combination with photometric and spectroscopic data provides a powerful method to constrain the stellar mass-to-light ratio and hence the functional form of the IMF. We combine photometric and spectroscopic constraints from the latest set of population synthesis models of Charlot & Bruzual, including a varying IMF, with a non-parametric analysis of the lensing mass in a sample of 18 early-type lens galaxies from the SLACS survey, with velocity dispersions in the range 200-300 km/s. We find that very bottom-heavy IMFs are excluded. However, the upper limit to the IMF slope ($\mu \lesssim 2.2$ for a bimodal IMF, taking into account a 20-30% contribution to the lensing mass from dark matter, where $\mu=1.3$ corresponds to a Kroupa-like IMF) is compatible at the $1\sigma$ level with the constraints imposed by gravity-sensitive line strengths. A two-segment power law parameterisation of the IMF (keeping its index at the high mass end fixed at the Salpeter value) is more constrained ($\Gamma\lesssim1.5$, where $\Gamma$ is the power index at the low-mass end). Furthermore we find that for a standard Milky Way-like IMF to be applicable a significant amount of dark matter is required within an effective radius. Our results reveal a large scatter regarding possible values of the IMF slope, suggesting that the recent lenses of Smith et al. - who find a Milky Way-like IMF in a few massive lensing early-type galaxies - may be explained by such a scatter. (Abridged)}, added-at = {2015-12-03T12:27:58.000+0100}, author = {Leier, Dominik and Ferreras, Ignacio and Saha, Prasenjit and Charlot, Stéphane and Bruzual, Gustavo and La Barbera, Francesco}, biburl = {https://www.bibsonomy.org/bibtex/29bbff36882e3d3475feb250e2aeb1a43/miki}, description = {[1512.00462] Strong Gravitational Lensing and the Stellar IMF of Early-type Galaxies}, interhash = {cffc8d1300d924f8f081a7b86d9be445}, intrahash = {9bbff36882e3d3475feb250e2aeb1a43}, keywords = {imf population stellar variation}, note = {cite arxiv:1512.00462Comment: submitted to MNRAS, 17 pages, 12 figures, 3 tables}, timestamp = {2015-12-03T12:27:58.000+0100}, title = {Strong Gravitational Lensing and the Stellar IMF of Early-type Galaxies}, url = {http://arxiv.org/abs/1512.00462}, year = 2015 }