Journal Article

Keck spectroscopy of the faint dwarf elliptical galaxy population in the Perseus Cluster core: mixed stellar populations and a flat luminosity function

Samantha J. Penny and Christopher J. Conselice

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 383, issue 1, pages 247-257
Published in print January 2008 | ISSN: 0035-8711
Published online December 2007 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2007.12535.x
Keck spectroscopy of the faint dwarf elliptical galaxy population in the Perseus Cluster core: mixed stellar populations and a flat luminosity function

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We present the result of a photometric and Keck low-resolution imaging spectrometer (LRIS) spectroscopic study of dwarf galaxies in the core of the Perseus Cluster, down to a magnitude of MB=−12.5. Spectra were obtained for 23 dwarf-galaxy candidates, from which we measure radial velocities and stellar population characteristics from absorption line indices. From radial velocities obtained using these spectra, we confirm 12 systems as cluster members, with the remaining 11 as non-members. Using these newly confirmed cluster members, we are able to extend the confirmed colour–magnitude relation for the Perseus Cluster down to MB=−12.5. We confirm an increase in the scatter about the colour–magnitude relationship below MB=−15.5, but reject the hypothesis that very red dwarfs are cluster members. We measure the faint-end slope of the luminosity function between MB=−18 and −12.5, finding α=−1.26 ± 0.06, which is similar to that of the field. This implies that an overabundance of dwarf galaxies does not exist in the core of the Perseus Cluster. By comparing metal and Balmer absorption line indices with α-enhanced single stellar population models, we derive ages and metallicities for these newly confirmed cluster members. We find two distinct dwarf elliptical populations: an old, metal-poor population with ages ∼8 Gyr and metallicities [Fe/H] < −0.33, and a young, metal-rich population with ages <5 Gyr and metallicities [Fe/H] > −0.33. Dwarf galaxies in the Perseus Cluster are therefore not a simple homogeneous population, but rather exhibit a range in age and metallicity.

Keywords: galaxies: clusters: general; galaxies: clusters: individual: Perseus Cluster; galaxies: dwarf; galaxies: luminosity function, mass function

Journal Article.  8396 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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