Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/48181

Title

The mass-metallicity gradient relation of early-type galaxies

Author(s)

Spolaor, Max;  Proctor, Robert N.;  Forbes, Duncan A.;  Couch, Warrick J.

Abstract

We present a newly observed relation between galaxy mass and radial metallicity gradients of early-type galaxies. Our sample of 51 early-type galaxies encompasses a comprehensive mass range from dwarfs to brightest cluster galaxies. The metallicity gradients are measured out to one effective radius by comparing nearly all of the Lick absorption-line indices to recent models of single stellar populations. The relation shows very different behavior at low and high masses, with a sharp transition being seen at a mass of ∼3.5 × 1010M (velocity dispersion of ∼140 km s−1,MB ∼ −19). Low-mass galaxies form a tight relation with mass, such that metallicity gradients become shallower with decreasing mass and positive at the very low mass end. Above the mass transition point several massive galaxies have steeper gradients, but a clear downturn is visible marked by a broad scatter. The results are interpreted in comparison with competing model predictions.We find that an early star-forming collapse could have acted as the main mechanism for the formation of low-mass galaxies, with star formation efficiency increasing with galactic mass. The high-mass downturn could be a consequence of merging and the observed larger scatter a natural result of different merger properties. These results suggest that galaxies above the mass threshold of ∼3.5×1010M might have formed initially by mergers of gas-rich disk galaxies and then subsequently evolved via dry merger events. The varying efficiency of the dissipative merger-induced starburst and feedback processes have shaped the radial metallicity gradients in these high-mass systems.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing

Source

Astrophysical Journal Letters, Vol. 691, no. 2 (Feb 2009), pp. L138-L141

Publication year

2009

Keyword(s)

Black holes;  Brightest cluster;  Chemical enrichment;  Dwarf galaxies;  Elliptic galaxies;  Evolution;  Formation history;  Kinematics;  Lenticular galaxies;  Star formation;  Stellar content;  Stellar population models;  Supernovae

Publisher

Institute of Physics Publishing

ISSN

0004-637X

Publisher URL

http://dx.doi.org/10.1088/0004-637x/691/2/l138

Copyright

Copyright © 2009 The American Astronomical Society. All rights reserved. Publisher does not officially support author/institution self-archiving of either the postprint (final, revised accepted draft) or published version of full text.

Peer reviewed