The main conclusions from this work are as follows:
1. The baryonic density of the universe that resides in galaxies is
b, gal
= 0.0035 ± 0.0003.
This is far less than the value of
b = 0.03
inferred from the CMB or from BBN.
Most of the baryons in the Universe do not reside in galaxies and
probably reside in the warm/hot intergalactic medium.
2. Most of the baryons in galaxies are in stars, not gas, and about
one-half of these stars are in early-type galaxies. We derive the value of
*
= 0.0028 ± 0.0003, assuming stellar mass-to-light ratios derived from
population synthesis models, a Kroupa IMF in discs and irregular
galaxies and stellar mass-to-light ratios derived from dynamical
measurements in bulges and elliptical galaxies.
3. About 15-20% of the baryons in galaxies are in gas. Of this, about one half is in molecular gas, similar to the fraction observed in the Milky Way.
4. About 30% of the atomic gas seen by HIPASS is not present in our atomic gas mass function. We attribute this to gas in galaxies that are missing in the sample that we used to define a scaling between optical luminosities and gas masses.