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Spatially resolved variations of the IMF mass normalisation in early-type galaxies as probed by molecular gas kinematics

Davis, Timothy and McDermid, Richard M. 2017. Spatially resolved variations of the IMF mass normalisation in early-type galaxies as probed by molecular gas kinematics. Monthly Notices of the Royal Astronomical Society 464 (1) , pp. 453-468. 10.1093/mnras/stw2366

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Abstract

We here present the first spatially-resolved study of the IMF in external galaxies derived using a dynamical tracer of the mass-to-light ratio. We use the kinematics of relaxed molecular gas discs in seven early-type galaxies (ETGs) selected from the ATLAS3D survey to dynamically determine mass-to-light ratio (M/L) gradients. These M/L gradients are not very strong in the inner parts of these objects, and galaxies that do show variations are those with the highest specific star formation rates. Stellar population parameters derived from star formation histories are then used in order to estimate the stellar initial mass function function (IMF) mismatch parameter, and shed light on its variation within ETGs. Some of our target objects require a light IMF, otherwise their stellar population masses would be greater than their dynamical masses. In contrast, other systems seem to require heavier IMFs to explain their gas kinematics. Our analysis again confirms that IMF variation seems to be occurring within massive ETGs. We find good agreement between our IMF normalisations derived using molecular gas kinematics and those derived using other techniques. Despite this, we do not see find any correlation between the IMF normalisation and galaxy dynamical properties or stellar population parameters, either locally or globally. In the future larger studies which use molecules as tracers of galaxy dynamics can be used to help us disentangle the root cause of IMF variation.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Uncontrolled Keywords: galaxies: elliptical and lenticular, cD ISM: molecules galaxies: ISM galaxies: evolution galaxies: kinematics and dynamics
Publisher: Oxford University Press
ISSN: 0035-8711
Funders: STFC
Date of First Compliant Deposit: 21 September 2016
Date of Acceptance: 14 September 2016
Last Modified: 06 Jun 2017 16:46
URI: http://orca.cf.ac.uk/id/eprint/94696

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