http://arxiv.org/abs/2203.10105
The ratio of baryonic to dark matter in present-day galaxies constrains galaxy formation theories and can be determined empirically via the baryonic Tully-Fisher relation (BTFR), which compares a galaxy’s baryonic mass (M${bary}$) to its maximum rotation velocity (V${max}$). The BTFR is well-determined at M${bary}>10^8$ M${\odot}$, but poorly constrained at lower masses due to small samples and the challenges of measuring rotation velocities in this regime. For 25 galaxies with high-quality data and M${bary}<\sim10^8$ M${\odot}$, we estimate M${bary}$ from infrared, optical, and HI observations and Vmax from the HI gas rotation. Many of the V${max}$ values are lower limits because the velocities are still rising at the edge of the detected HI disks; consequently, most of our sample has lower velocities than expected from extrapolations of the BTFR at higher masses. To estimate V${max}$, we map each galaxy to a dark matter halo assuming density profiles with and without cores, and find that the cored profiles match the data better. When we compare the V${max}$ values derived from the cored density profiles to our M${bary}$ measurements, we find a turndown of the BTFR at low masses that is consistent with CDM predictions and implying baryon fractions of 1-10% of the cosmic value. Although we are limited by the sample size and assumptions inherent in mapping measured rotational velocities to theoretical rotation curves, our results suggest that the galaxy formation efficiency drops at masses below M${bary}\sim10^8$ M${\odot}$, corresponding to M${200}\sim10^{10}$ M$_{\odot}$.
K. McQuinn, E. Adams, J. Cannon, et. al.
Tue, 22 Mar 22
41/82
Comments: 36 pages, 3 tables, 23 figures
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