A Study in Blue: The Baryon Content of Isolated Low-mass Galaxies
Abstract
We study the baryon content of low-mass galaxies selected from the Sloan Digital Sky Survey (SDSS DR8), focusing on galaxies in isolated environments where the complicating physics of galaxy-galaxy interactions are minimized. We measure neutral hydrogen (HI) gas masses and line widths for 148 isolated galaxies with stellar mass between 107 and {10}9.5{M}⊙ . We compare isolated low-mass galaxies to more massive galaxies and galaxies in denser environments by remeasuring HI emission lines from the Arecibo Legacy Fast ALFA survey 40% data release. All isolated low-mass galaxies either have large atomic gas fractions or large atomic gas fractions cannot be ruled out via their upper limits. We measure a median atomic gas fraction of {f}{gas}=0.81+/- 0.13 for our isolated low-mass sample with no systems below 0.30. At all stellar masses, the correlations between galaxy radius, baryonic mass, and velocity width are not significantly affected by environment. Finally, we estimate a median baryon to total dynamical mass fraction of {f}{baryon,{disk}}=0.15+/- 0.17. We also estimate two different median baryon to halo mass fractions using the results of semi-analytic models ({f}{baryon,{halo}}=0.04+/- 0.06) and abundance matching ({f}{baryon,{halo}}=0.04+/- 0.02). Baryon fractions estimated directly using HI observations appear independent of environment and maximum circular velocity, while baryon fractions estimated using abundance matching show a significant depletion of baryons at low maximum circular velocities.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2015
- DOI:
- 10.1088/0004-637X/809/2/146
- arXiv:
- arXiv:1505.04819
- Bibcode:
- 2015ApJ...809..146B
- Keywords:
-
- galaxies: dwarf;
- galaxies: evolution;
- galaxies: ISM;
- galaxies: kinematics and dynamics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Re-submitted to ApJ. Updated with referee's comments. 20 pages. Figure 4 and 5 illustrate our key results. Table 1 presents a small sample of isolated galaxies. Table 3 presents scaling relation fits