Re: Galaxies without dark matter halos?

Ulf Torkelsson <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> This is wrong.  The Hubble scheme for classification of galaxies is
> purely morphological.  It does not depend on any form of distances.
> As long as you can get a good picture of a galaxy you can determine
> its Hubble typ.

We are not discussing the Hubble morphological classification scheme.  We
are discussing the theoretical relationship between galactic type and
absolute luminosity.  Absolute luminosity is not included in the Hubble
classification.

> colonel_hack is then providing a brief, but accurate description of the
> calibration of the Tully-Fisher and Faber-Jackson relations in modern
> times, and nowhere in that process do you need to put in Hubble's
> constant.  On the contrary these relations can be and have been used
> to determine Hubble's constant.

Any calibration of a distance scale needs something to calibrate with.
There are between 20 and 40 galaxies containing resolvable Cepheid variables
(depending on study).  Galaxies beyond this range use the Hubble constant.
The Tully-Fisher scheme was calibrated using "nearer"
Hubble-constant-determined distances, in order to avoid them in the far
distances.

Now, can you provide a more recent paper that uses something else to
calibrate Tully-Fisher?

greywolf42
ubi dubium ibi libertas

[Mod. notes:
1) Quoted text trimmed, please do this yourself
2) Try Sakai et al 2000 ApJ 529 698 -- one of a number of references
anyone should be able to find on even a cursory ADS search -- mjh]