No Cepheids in elliptical galaxies?

I've been reading the Astronomy special cosmology issue "Origin & Fate
of the Universe" (very interesting).
A line in Marcia Bartusiak's article on "Going the distance" caught my
eye, when she said elliptical galaxies don't contain Cepheids.
Why not?
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Elliptical Galaxies contain Type II Cephids.
They are about 1.5 magnitudes fainter than
type I Cephids with the same period, and
their light curve is differently shaped.

Jonathan Silverlight wrote
in message ...
I've been reading the Astronomy special cosmology issue "Origin & Fate
of the Universe" (very interesting).
A line in Marcia Bartusiak's article on "Going the distance" caught my
eye, when she said elliptical galaxies don't contain Cepheids.
Why not?

Well, they may have a few, but certainly a smaller number than disk
galaxies.

The reason is that Cepheids are the late (non-Main sequence) evolutionary
stages of very massive stars (O, B and A). These stars have short
lifetimes. Hence, to see Cepheids in a galaxy, the galaxy must be actively
creating new stars. Creating new stars requires a lot of free gas (not
already contained in stars). And elliptical galaxies have less free gas
than disk galaxies do.

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