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The colours of Virgo dEs as seen by SDSS

Published online by Cambridge University Press:  08 November 2005

Thorsten Lisker
Affiliation:
Astronomical Institute, University of Basel, Switzerland; email: [email protected]
Eva K. Grebel
Affiliation:
Astronomical Institute, University of Basel, Switzerland; email: [email protected]
Bruno Binggeli
Affiliation:
Astronomical Institute, University of Basel, Switzerland; email: [email protected]
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Abstract

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A colour analysis of a carefully selected sample of over 200 Virgo cluster dEs and 8 giant ellipticals (Es) in the SDSS yields the following results: a) the nucleated dEs (dENs) follow a tight colour-magnitude relation (CMR) which does not broaden significantly at fainter ($M_r \ge -15$) magnitudes, b) the CMR of dENs smoothly transitions to the CMR of Es, but the latter changes its slope at about $M_r \approx -20$, c) the brighter dENs are consistent with ages of $t \ge 5\rm{Gyr}$ and a decrease of metallicity towards fainter magnitudes, but a possible additional luminosity-age relation is not ruled out, d) it is crucial to treat dS0s separately from dEs since their different colour properties would otherwise bias the comparison of nucleated and non-nucleated dEs (dEnoNs), e) the dEnoNs show a weak trend towards bluer colours than dENs.

Type
Contributed Papers
Copyright
© 2005 International Astronomical Union