Séminaire/Seminar Galaxies |
| « Constraining Dark Matter through 3D dispersion profiles of Classical Dwarf Galaxies » |
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Eduardo Vitral |
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Astrophysical evidence strongly supports that dark matter constitutes the majority of the Universe's matter. Its elusive nature remains a critical puzzle from cosmology to particle physics. Classical dwarf galaxies orbiting the Milky Way are pivotal for further progress.
They are dark matter dominated, and the kinematics of its many visible stars trace the gravitational potential, thus providing clues to the dark matter distribution. Traditional analyses of line-of-sight (LOS) velocities have led to the "cusp-core problem": a discrepancy between the steep density profiles predicted by simulations versus the flatter profiles observed. Resolving this requires analyzing transverse velocities or proper motions, necessitating long time-baseline observations (>10 years) with high-resolution observatories like the Hubble Space Telescope (HST). We present unprecedented radially-resolved 3D velocity dispersion profiles for the Draco dwarf spheroidal, that we obtained by combining four epochs of imaging over 18 years with LOS velocities from the literature. Using oblate axisymmetric Jeans equations, we infer radial velocity anisotropy along the symmetry axis, but tangential anisotropy on average. The analysis reveals that the galaxy's mass profile is consistent with ?CDM predictions, suggesting that Draco's dark halo has remained largely unaffected by baryonic processes due to its low stellar mass and ancient star formation history. We discuss our ongoing efforts to now apply similar methods to other galaxies, specifically Ursa Minor and Sculptor, to elucidate the variation in dark matter distributions amongst galaxies. Moreover, we discuss our ongoing efforts to expand the HST proper motion analyses using JWST observations of additional fields and epochs. |
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jeudi 21 novembre 2024 - 11:30 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |