Details

Autor(en) / Beteiligte

• Read, J. I
• Agertz, O
• Collins, M. L. M

Titel

Dark matter cores all the way down

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2016-07, Vol.459 (3), p.2573-2590

Ort / Verlag

London: Oxford University Press

Erscheinungsjahr

2016

Link zum Volltext

Quelle

Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals

Beschreibungen/Notizen

• We use high-resolution simulations of isolated dwarf galaxies to study the physics of dark matter cusp-core transformations at the edge of galaxy formation: M 200 = 107–109 M⊙. We work at a resolution (∼4 pc minimum cell size; ∼250 M⊙ per particle) at which the impact from individual supernovae explosions can be resolved, becoming insensitive to even large changes in our numerical ‘sub-grid’ parameters. We find that our dwarf galaxies give a remarkable match to the stellar light profile; star formation history; metallicity distribution function; and star/gas kinematics of isolated dwarf irregular galaxies. Our key result is that dark matter cores of size comparable to the stellar half-mass radius r 1/2 always form if star formation proceeds for long enough. Cores fully form in less than 4 Gyr for the M 200 = 108 M⊙ and ∼14 Gyr for the 109 M⊙ dwarf. We provide a convenient two parameter ‘coreNFW’ fitting function that captures this dark matter core growth as a function of star formation time and the projected stellar half-mass radius. Our results have several implications: (i) we make a strong prediction that if Λcold dark matter is correct, then ‘pristine’ dark matter cusps will be found either in systems that have truncated star formation and/or at radii r > r 1/2; (ii) complete core formation lowers the projected velocity dispersion at r 1/2 by a factor of ∼2, which is sufficient to fully explain the ‘too-big-to-fail problem’; and (iii) cored dwarfs will be much more susceptible to tides, leading to a dramatic scouring of the sub-halo mass function inside galaxies and groups.