The Triangulum Extended (TREX) Survey: The Stellar Disk Dynamics of M33 as a Function of Stellar Age

Abstract Triangulum (M33) is a low-mass, relatively undisturbed spiral galaxy that offers new regime in which to test models of dynamical heating. In spite its proximity, M33's heating history has not yet been well-constrained. this work, we present the TREX Survey, largest stellar spectroscopic survey across disk M33. We kinematics as function age study past and ongoing measure line-of-sight velocities for ?4500 stars. Using subset, divide stars into broad bins using Hubble Space Telescope Canada–France–Hawaii photometric catalogs: massive main-sequence helium-burning (?80 Myr), intermediate-mass asymptotic branch (?1 Gyr), low-mass red giant (?4 Gyr). compare dynamics gas existing H i , CO, ? kinematics. find M33 low-velocity dispersion (?16 km s ?1 ), unlike Milky Way Andromeda galaxies, there no strong trend velocity age. The youngest are dynamically hot oldest hotter than predicted by most M33-like simulated analogs Illustris. young highly structured, with large fairly localized. cause high-velocity evident from observations presented here.