| 1. |
- Rey, Martin P., et al.
(författare)
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EDGE – Dark matter or astrophysics? Breaking dark matter heating degeneracies with H I rotation in faint dwarf galaxies
- 2024
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711. ; 529:3, s. 2379-2398
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Tidskriftsartikel (refereegranskat)abstract
- Low-mass dwarf galaxies are expected to reside within dark matter haloes that have a pristine, ‘cuspy’ density profile within their stellar half-light radii. This is because they form too few stars to significantly drive dark matter heating through supernova-driven outflows. Here, we study such simulated faint systems (104 ≤ M* ≤ 2 × 106 M) drawn from high-resolution (3 pc) cosmological simulations from the ‘Engineering Dwarf Galaxies at the Edge of galaxy formation’ (EDGE) project. We confirm that these objects have steep and rising inner dark matter density profiles at z = 0, little affected by galaxy formation effects. But five dwarf galaxies from the suite also showcase a detectable H I reservoir (MH I ≈ 105 − 106 M), analogous to the observed population of faint, H I-bearing dwarf galaxies. These reservoirs exhibit episodes of ordered rotation, opening windows for rotation curve analysis. Within actively star-forming dwarfs, stellar feedback easily disrupts the tenuous H I discs (vφ,g ≈ 10 km s−1), making rotation short-lived (≪ 150 Myr) and more challenging to interpret for dark matter inferences. In contrast, we highlight a long-lived (≥ 500 Myr) and easy-to-interpret H I rotation curve extending to ≈ 2 r1/2,3D in a quiescent dwarf, that has not formed new stars since z = 4. This stable gas disc is supported by an oblate dark matter halo shape that drives high-angular momentum gas flows. Our results strongly motivate further searches for H I in rotation curves in the observed population of H I-bearing low-mass dwarfs, that provide a key regime to disentangle the respective roles of dark matter microphysics and galaxy formation effects in driving dark matter heating.
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| 2. |
- Goater, Alex, et al.
(författare)
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EDGE : The direct link between mass growth history and the extended stellar haloes of the faintest dwarf galaxies
- 2024
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711. ; 527:2, s. 2403-2412
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-f aint dw arf galaxies (UFDs) are commonly found in close proximity to the Milky Way and other massive spiral galaxies. As such, their projected stellar ellipticity and extended light distributions are often thought to owe to tidal forces. In this paper, we study the projected stellar ellipticities and faint stellar outskirts of tidally isolated ultra-faints drawn from the 'Engineering Dwarfs at Galaxy Formation's Edge' (EDGE) cosmological simulation suite. Despite their tidal isolation, our simulated dwarfs exhibit a wide range of projected ellipticities (0.03 < ϵ < 0.85), with many possessing anisotropic extended stellar haloes that mimic tidal tails, but owe instead to late-time accretion of lower mass companions. Furthermore, we find a strong causal relationship between ellipticity and formation time of a UFD, which is robust to a wide variation in the feedback model. We show that the distribution of projected ellipticities in our suite of simulated EDGE dwarfs matches well with a sample of 19 Local Group dwarf galaxies and a sample of 11 isolated dwarf galaxies. Given ellipticity in EDGE arises from an ex-situ accretion origin, the agreement in shape indicates the ellipticities of some observed dwarfs may also originate from a non-tidal scenario. The orbital parameters of these observed dwarfs further support that they are not currently tidally disrupting. If the baryonic content in these galaxies is still tidally intact, then the same may be true for their dark matter content, making these galaxies in our Local Group pristine laboratories for testing dark matter and galaxy formation models.
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