The Milky Way’s bright satellites as an apparent failure of ΛCDM

By M. Boylan-Kolchin, James S. Bullock, M. Kaplinghat. 2011

658 citations recorded by the source corpus.

We use the Aquarius simulations to show that the most massive subhaloes in galaxy-mass dark matter (DM) haloes in Λ cold dark matter (ΛCDM) are grossly inconsistent with the dynamics of the brightest Milky Way dwarf spheroidal galaxies. While the best-fitting hosts of the dwarf spheroidals all have , ΛCDM simulations predict at least 10 subhaloes with Vmax > 25 km s−1. These subhaloes are also among the most massive at earlier times, and significantly exceed the reionization suppression mass back to z∼ 10. No ΛCDM-based model of the satellite population of the Milky Way explains this result. The problem lies in the satellites’ densities: it is straightforward to match the observed Milky Way luminosity function, but doing so requires the dwarf spheroidals to have DM haloes that are a factor of ∼5 more massive than is observed. Independent of the difficulty in explaining the absence of these dense, massive subhaloes, there is a basic tension between the derived properties of the bright Milky Way dwarf spheroidals and ΛCDM expectations. The inferred infall masses of these galaxies are all approximately equal and are much lower than standard ΛCDM predictions for systems with their luminosities. Consequently, their implied star formation efficiencies span over two orders of magnitude, from 0.2 to 20 per cent of baryons converted into stars, in stark contrast with expectations gleaned from more massive galaxies. We explore possible solutions to these problems within the context of ΛCDM and find them to be unconvincing. In particular, we use controlled simulations to demonstrate that the small stellar masses of the bright dwarf spheroidals make supernova feedback an unlikely explanation for their low inferred densities.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/44f2ad14530b3f23f714df62d53ea9d920f15c74

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Citations in the corpus

Is there a "too big to fail" problem in the field? (2014, methodology): “In addition, the AM procedure in Ferrero et al. is performed on the basis of stellar mass, as is the case in all previous works assessing the TBTF problem (Boylan-Kolchin et al. 2011; Tollerud et al. 2014; Garrison-Kimmel et al. 2014).”
FIRE in the field: Simulating the threshold of galaxy formation (2016, background): “…convergence is important: if we compare the observed central Vcirc (at the half-light radii) of the 9 brightest dSph satellites of the MW (from Boylan-Kolchin et al. 2012), we see that the low-resolution run is consistent with at least two satellites while the highest-resolution run is…”
The formation of disc galaxies in high-resolution moving-mesh cosmological simulations (2013, background): “On the other hand, using the space motion of the Leo I dwarf spheroidal galaxy, Boylan-Kolchin et al. (2012) put a strong lower limit on the Milky Way’s mass, finding a median MW mass of 1.6×1012 M , rather similar to several of our candidate systems.”
Self-Interacting Dark Matter from a Non-Abelian Hidden Sector (2014, methodology): “too-big-to-fail problem [53].”
THE AVERAGE STAR FORMATION HISTORIES OF GALAXIES IN DARK MATTER HALOS FROM z = 0–8 (2012, background): “At the present day, the transition between merger-dominated buildup (at high mass) and star formation-dominatedbuildup (at low mass) occurs at roughly the mass of the Milky Way.”
Forged in FIRE: cusps, cores and baryons in low-mass dwarf galaxies (2015, background): “…into stars (Klypin et al. 1999) and they also must be significantly less dense in their centers than predicted in dissipationless LCDM simulations (Boylan-Kolchin et al. 2011, 2012; Ferrero et al. 2012; Garrison-Kimmel et al. 2014; Tollerud et al. 2014; Klypin et al. 2014; Papastergis et al.…”
“Non-cold” dark matter at small scales: a general approach (2017, background): “Moreover, the dynamical properties of massive MW satellites are not reproduced in simulations (too-big-to-fail problem [8, 9]).”