Journal article

Evidence of a Bottom-heavy Initial Mass Function in Massive Early-type Galaxies from Near-infrared Metal Lines

David J Lagattuta, Jeremy R Mould, Duncan A Forbes, Andrew J Monson, Nicola Pastorello, S Eric Persson

The Astrophysical Journal | IOP PUBLISHING LTD | Published : 2017

Abstract

We present new evidence for a variable stellar initial mass function (IMF) in massive early-type galaxies, using high-resolution, near-infrared spectroscopy from the Folded-port InfraRed Echellette spectrograph (FIRE) on the Magellan Baade Telescope at Las Campanas Observatory. In this pilot study, we observe several gravity-sensitive metal lines between 1.1 and 1.3 μm in eight highly luminous () nearby galaxies. Thanks to the broad wavelength coverage of FIRE, we are also able to observe the Ca ii triplet feature, which helps with our analysis. After measuring the equivalent widths (EWs) of these lines, we notice mild to moderate trends between EW and central velocity dispersion (σ), with s..

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University of Melbourne Researchers

Grants

Awarded by ERC


Awarded by Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO)


Awarded by ARC


Funding Acknowledgements

The authors wish to thank the referee for thoroughly reading the manuscript and providing several useful comments that greatly improved the quality of the paper. Thanks to Rob Simcoe for assistance with the FIRE pipeline. France Allard provided invaluable advice on synthetic stellar spectra. We also thank Blesson Mathew and Nidia Morrell for their contributions. We appreciate the use of Charlie Conroy's FSPS and Michele Cappellari's pPXF codes. D.J.L. acknowledges support from the ERC starting grant 336736-CALENDS. Parts of this research were conducted by the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020. D.A.F. thanks the ARC for financial support via DP130100388.