A new astrophysical solution to the Too Big To Fail problem

Insights from the moria simulations

¹ Astronomical Observatory, Ghent University, Krijgslaan 281, S9, 9000 Gent, Belgium
e-mail: robbert.verbeke@ugent.be; sven.derijcke@ugent.be
² Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
e-mail: papastergis@astro.rug.nl
³ Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia
⁴ IIT Roorkee, Haridwar Highway, Roorkee, Uttarakhand 247667, India

Received: 9 March 2017
Accepted: 7 July 2017

Abstract

Aims. We test whether or not realistic analysis techniques of advanced hydrodynamical simulations can alleviate the Too Big To Fail problem (TBTF) for late-type galaxies. TBTF states that isolated dwarf galaxy kinematics imply that dwarfs live in halos with lower mass than is expected in a Λ cold dark matter universe. Furthermore, we want to identify the physical mechanisms that are responsible for this observed tension between theory and observations.

Methods. We use the moria suite of dwarf galaxy simulations to investigate whether observational effects are involved in TBTF for late-type field dwarf galaxies. To this end, we create synthetic radio data cubes of the simulated moria galaxies and analyse their H i kinematics as if they were real, observed galaxies.

Results. We find that for low-mass galaxies, the circular velocity profile inferred from spatially resolved H i kinematics often underestimates the true circular velocity profile, as derived directly from the enclosed mass. Fitting the H i kinematics of moria dwarfs with a theoretical halo profile results in a systematic underestimate of the mass of their host halos. We attribute this effect to the fact that the interstellar medium of a low-mass late-type dwarf is continuously stirred by supernova explosions into a vertically puffed-up, turbulent state to the extent that the rotation velocity of the gas is simply no longer a good tracer of the underlying gravitational force field. If this holds true for real dwarf galaxies as well, it implies that they inhabit more massive dark matter halos than would be inferred from their kinematics, solving TBTF for late-type field dwarf galaxies.