The Ages of Galaxy Bulges and Disks from Optical and Near Infrared Colours

Peletier, R. F.; Balcells, M.
Bibliographical reference

New light on galaxy evolution. The IAU Symposium 171, held at Max Planck Haus in Heidelberg, Germany from 25th-30th June 1995. Edited by Ralf Bender and Roger L. Davies. Published by Kluwer Academic Publishers, p. 29.

Advertised on:
0
1996
Number of authors
2
IAC number of authors
0
Citations
1
Refereed citations
0
Description
For a sample of bright nearby early-type galaxies we have obtained surface photometry in bands ranging from U to K. Since the galaxies have inclinations larger than 50 deg. it is easy to separate bulges and disks. By measuring the colours in special regions, we minimize the effects of extinction, and by looking at B-K colour gradients we can show that for these type of spirals the colours mainly give information about stellar populations, and not extinction. We find that the differences between bulges and disks in all colours is very small, and using simple population models we can show that on the average the age difference between the bulge and the disk at 2 scale length is smaller than 30%, and much smaller if part of the difference is caused by a gradient in metallicity.