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

Published online by Cambridge University Press:  25 May 2016

R. F. Peletier  and
M. Balcells
R. F. Peletier
Affiliation:
Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, Netherlands Instituto de Astrofísica de Canarias, Via Lactea s/n, 38200 La Laguna, Tenerife, Spain
M. Balcells
Affiliation:
Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, Netherlands

Abstract

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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° 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.

Type
Spiral Galaxies
Information
Symposium - International Astronomical Union , Volume 171: New Light on Galaxy Evolution , 1996 , pp. 29 - 33
Copyright
Copyright © Kluwer 1996 

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