What the study found
Weakly cored three-dimensional stellar profiles can be consistent with cuspy dark matter halos, but strongly cored three-dimensional profiles cannot. The authors also found that weak and strong three-dimensional cores look very similar when projected onto the sky, making it difficult to rule out a dark matter cusp from photometric data alone.
Why the authors say this matters
The study suggests that cored surface density profiles in nearby dwarf galaxies should not be treated as strong evidence against cuspy dark matter halos. The authors conclude that current data and analysis techniques make it hard to use photometry alone to distinguish between cored and cuspy dark matter distributions.
What the researchers tested
The researchers examined photometric data from dwarf spheroidal and ultra-faint dwarf galaxies. They tested a range of spherically symmetric stellar profiles, classifying them as "strong" or "weak" cores and cusps using the central slope (b_0) and logarithmic slope (γ_0), and checked which profiles led to unphysical negative distribution functions when placed in a cuspy halo, treating isotropic and anisotropic kinematics separately.
What worked and what didn't
Weakly cored stellar profiles in three dimensions, defined by b_0 > 0 and γ_0 = 0, could work with cuspy dark matter profiles. Strong three-dimensional cores, defined by b_0 = γ_0 = 0, did not. In projection, however, both weak and strong three-dimensional cores produced nearly indistinguishable inner profiles, and the authors found that ultra-faint dwarf galaxies and Fornax were consistent with both cases.
What to keep in mind
The abstract does not describe detailed limitations beyond the difficulty of ruling out a cusp from photometric data alone. The conclusions are limited to the systems and analysis described, including dwarf spheroidal and ultra-faint dwarf galaxies and the specific profile classes tested.
Key points
- Weakly cored three-dimensional stellar profiles can fit within cuspy dark matter halos.
- Strongly cored three-dimensional stellar profiles cannot be embedded in a cuspy halo without issues in the authors' tests.
- Weak and strong three-dimensional cores appear nearly the same in projected photometric data.
- Ultra-faint dwarf galaxies were consistent with both weak and strong three-dimensional cores.
- The same conclusion was reached for Fornax, a well-studied dwarf spheroidal galaxy.
Disclosure
- Research title:
- Cored stellar profiles can still match cuspy dark matter halos
- Image credit:
- Photo by NASA Hubble Space Telescope on Unsplash
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