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The baryonic mass function of galaxies
1University of Cambridge Institute of Astronomy Madingley Road, Cambridge CB3 0HA, UK. jir22@ast.cam.ac.uk
Summary
This study quantifies the baryonic mass function of galaxies, revealing most cosmic baryons reside outside galaxies in the intergalactic medium. We determined the cosmological density of baryons within galaxies to be Omega(b,gal)=0.0035.
Area of Science:
- Cosmology
- Astrophysics
- Galaxy Formation and Evolution
Background:
- The Big Bang produced approximately 5% baryonic matter, with only a fraction incorporated into galaxies as stars or gas.
- Understanding the distribution of baryonic mass in galaxies is crucial for cosmological models and galaxy formation theories.
Purpose of the Study:
- To measure the baryonic mass function of galaxies, detailing mass distribution across galaxy types and sizes.
- To constrain current cosmology by analyzing baryonic mass within galaxies.
Main Methods:
- Utilized data from astronomical surveys like the Sloan Digital Sky Survey (optical) and HIPASS (radio).
- Integrated the measured baryonic mass function to calculate the cosmological density of baryons in galaxies.
Main Results:
- Determined the cosmological density of baryons in galaxies to be Omega(b,gal)=0.0035, with most (Omega(*)=0.0028) in stars.
- Found that approximately 80% of baryonic mass within galaxies is in stars, with only 20% in gas.
- Estimated that about 90% of all baryons in the universe are located outside galaxies, likely in the intergalactic medium.
Conclusions:
- The majority of cosmic baryons are not found within galaxies but in the warm/hot intergalactic medium.
- Directly observing and theoretically understanding the intergalactic baryonic medium presents a significant challenge for future astronomical research.