Passive Evolution Calculator

Version 1.1 (9/6/07)

P. G. van Dokkum & M. Franx, 2001, ApJ, 553, 90

This calculator provides the redshift evolution of the luminosities and colors of early-type galaxies for a range of rest-frame filters. In its simplest form it gives the evolution of a single age stellar population formed at a given redshift. However, it can also allow for morphological evolution in the galaxy population ("progenitor bias") and complex star formation histories of individual galaxies.

The calculator is based on the paper given above, with various updates. The most important update is that the powerlaw relations between age and luminosity are now derived from the Bruzual & Charlot (2003) models. Parameters listed in green are identical to those used in the paper. Actually reading the paper may not be required, as the Help links below may contain sufficient information.


: single stellar population; all early-types formed at z>>1
: early start of star formation; mild morphological evolution
: early start of star formation; strong morphological evolution

Formation redshift (start of star formation in all galaxies): Help
Corresponding time, as fraction of Hubble time: tstart =

Characteristic timescale for transformation: τ = Help
Time interval for morphological transformation to early-type: Help
Fraction of today's early-type galaxies formed by z=1: Help

Form of star formation history of individual galaxies: f* = Help

Rest-frame filters

Filter for luminosity evolution:

κ: Help

Filters for color evolution:

κ1 - κ2: - =


Number of objects in Monte-Carlo simulation: Help

(Explorer only; help for other browsers)

If you use this calculator please refer to the paper listed at the top of this page.