SAMI-H I: The H I view of the Hα Tully-Fisher relation and data release
Abstract
We present SAMI-H I, a survey of the atomic hydrogen content of 296 galaxies with integral field spectroscopy available from the SAMI Galaxy Survey. The sample spans nearly 4 dex in stellar mass ($M_\star = 10^{7.4}-10^{11.1}~ \rm M_\odot$), redshift z < 0.06, and includes new Arecibo observations of 153 galaxies, for which we release catalogues and H I spectra. We use these data to compare the rotational velocities obtained from optical and radio observations and to show how systematic differences affect the slope and scatter of the stellar-mass and baryonic Tully-Fisher relations. Specifically, we show that $\rm H\alpha$ rotational velocities measured in the inner parts of galaxies (1.3 effective radii in this work) systematically underestimate H I global measurements, with H I/$\rm H\alpha$ velocity ratios that increase at low stellar masses, where rotation curves are typically still rising and $\rm H\alpha$ measurements do not reach their plateau. As a result, the $\rm H\alpha$ stellar mass Tully-Fisher relation is steeper (when M⋆ is the independent variable) and has larger scatter than its H I counterpart. Interestingly, we confirm the presence of a small fraction of low-mass outliers of the $\rm H\alpha$ relation that are not present when H I velocity widths are used and are not explained by 'aperture effects'. These appear to be highly disturbed systems for which $\rm H\alpha$ widths do not provide a reliable estimate of the rotational velocity. Our analysis reaffirms the importance of taking into account differences in velocity definitions as well as tracers used when interpreting offsets from the Tully-Fisher relation, at both low and high redshifts and when comparing with simulations.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2023
- DOI:
- 10.1093/mnras/stac3556
- arXiv:
- arXiv:2212.04728
- Bibcode:
- 2023MNRAS.519.1098C
- Keywords:
-
- galaxies: fundamental parameters;
- galaxies: ISM;
- galaxies: kinematics and dynamics;
- radio lines: galaxies;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 18 pages, 12 figures. Accepted for publication in MNRAS