Angular Momentum and Galaxy Formation Revisited: Effects of Variable Mass-to-light Ratios

TL;DR

This study revises the relation between galaxy angular momentum and stellar mass by incorporating variable mass-to-light ratios, confirming that different galaxy types follow nearly parallel j_*--M_* sequences with improved accuracy.

Contribution

It introduces a method to estimate stellar mass using B-V color-dependent mass-to-light ratios, refining the angular momentum-mass relation for various galaxy types.

Findings

Galaxies follow nearly parallel j_*--M_* sequences with a slope of ~0.6.

The offset between galaxy types is about a factor of 5, larger than previous estimates.

Results tighten constraints on angular momentum loss in galactic disks.

Abstract

We rederive the relation between the specific angular momentum j_* and the mass M_* of the stellar matter in galaxies of different morphological types. This is a revision of the j_*--M_* diagram presented in our recent comprehensive study of galactic angular momentum. In that work, we estimated j_* from kinematic and photometric data that extended to large radii and M_* from near-infrared luminosities L_K with an assumed universal mass-to-light ratio M_*/L_K. However, recent stellar population models show large variations in M_*/L_K correlated with B-V color. In the present work, we use this correlation to estimate M_*/L_K and hence M_* from the measured B-V and L_K. Our revised j_*--M_* diagram is similar to our previous one; both disk-dominated and elliptical galaxies follow nearly parallel sequences with j_* \propto M_*^\alpha\ and \alpha = 0.6 +/- 0.1. However, the offset between the sequences is now a factor of about 5, some 30% larger than before (and close to the offset found by Fall in 1983). Thus, our new results place even tighter constraints on the loss of specific angular momentum by galactic disks over their lifetimes.