# Distribution of Galaxy sizes (star count)

First off, I realize how hard this is to even come close to estimating, but I'm trying to get a "general feel" for the distribution of galaxies by star count. I realize everything from rogue stars to super massive galaxies with trillions of stars exist... but I'd really love to see an estimated percentage of galaxies in the observable universe with:

• <10^5 stars
• 10^5 - 10^6 stars
• 10^6 - 10^7 stars
• 10^7 - 10^8 stars
• 10^8 - 10^9 stars
• 10^9 - 10^10 stars
• 10^10 - 10^11 stars
• 10^11 - 10^12 stars
• 10^12 - 10^13 stars... etc.

Does anyone know where I could find some estimates on this... Or even on galactic mass

• Richard Mushotzky has a nice page on the luminosity function of galaxies. astro.umd.edu/~richard/ASTRO620/LumFunction-pp.pdf Sep 23, 2023 at 12:52
• @eshaya how was this function obtained? Is it empirical or is it derived from some physical considerations?
– dtn
Jan 11 at 3:57
• The Luminosity Function is derived empirically by measuring the brightness of all galaxies within a certain distance from us. It requires good distance determination to groups and clusters. Jan 11 at 14:50

So most galaxies would fall on the lower end of star count and galactic mass. I'd estimate that well over 98% have $$<10^9$$, while the remaining few have $$>10^{10}$$. But as I said, it's hard to come up with an accurate ratio since we don't really know how many compact galaxies exist, simply because they are hard to observe. So take that figure with a grain of salt since it came from some generalizations.