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Title

The early-type galaxies NGC 1407 and NGC 1400 II: star formation and chemical evolutionary history

Author(s)

Spolaor, Max;  Forbes, Duncan A.;  Proctor, Robert N.;  Hau, George K. T.;  Brough, Sarah

Abstract

We present a possible star formation and chemical evolutionary history for two early-type galaxies NGC 1407 and NGC 1400. They are the two brightest galaxies of the NGC 1407 (or Eridanus-A) group, one of the 60 groups studied as part of the Group Evolution Multi-wavelength Study. Our analysis is based on new high signal-to-noise ratio spatially resolved integrated spectra obtained at the ESO 3.6-m telescope, out to ∼0.6 (NGC 1407) and ∼1.3 (NGC 1400) effective radii. Using Lick/IDS indices, we estimate luminosity-weighted ages, metallicities and α-element abundance ratios. Colour radial distributions from HST/ACS and Subaru Suprime-Cam multiband wide-field imaging are compared to colours predicted from spectroscopically determined ages and metallicities using single stellar population (SSP) models. The galaxies formed over half of their mass in a single short-lived burst of star formation (≥100 M⊙ yr−1) at redshift z≥ 5. This likely involved an outside–in mechanism with supernova-driven galactic winds, as suggested by the flatness of the α-element radial profiles and the strong negative metallicity gradients. Our results support the predictions of the revised version of the monolithic collapse model for galaxy formation and evolution. We speculate that, since formation, the galaxies have evolved quiescently and that we are witnessing the first infall of NGC 1400 in the group.

Publication type

Journal article

Research centre

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

Source

Monthly Notices of the Royal Astronomical Society, Vol. 385, no. 2 (Feb 2008), pp. 675-686

Publication year

2008

Keyword(s)

Abundances;  Galaxies;  Galaxy evolution;  Galaxy formation;  NGC 1400;  NGC 1407;  Stars

Publisher

Wiley-Blackwell Publishing

ISSN

0035-8711

Publisher URL

http://dx.doi.org/10.1111/j.1365-2966.2008.12892.x

Copyright

Copyright © 2008 Royal Astronomical Society. Author's final draft reproduced here in accordance with the copyright policy of the publisher.

Full text

Peer reviewed