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10.02.2023 / 10:00 / Zeuthen, Zoom
Astroparticle SeminarHot Extended Galaxy Halos around Local L* Galaxies from Sunyaev–Zeldovich Measurements
Andrew Taylor | DESY
Most of the baryons in L* galaxies are unaccounted for and are predicted to lie in hot gaseous halos (T ∼ 106.5 K) that may extend beyond R200. A hot gaseous halo will produce a thermal Sunyaev–Zeldovich signal that is proportional to the product of the gas mass and the mass-weighted temperature. To best detect this signal, we used a Needlet Independent Linear Combination all-sky Planck map that we produced from the most recent Planck data release, also incorporating WMAP data. The sample is 12 L* spiral galaxies with distances of 3−10 Mpc, which are spatially resolved so that contamination from the optical galaxy can be excluded. One galaxy, NGC 891, has a particularly strong SZ signal, and when excluding it, the stack of 11 galaxies is detected at about 4σ (declining with radius) and is extended to at least 250 kpc (≈R200) at >99% confidence. The gas mass within a spherical volume to a radius of 250 kpc is 9.8 ± 2.8 × 1010 M⊙, for Tavg = 3 × 106 K. This is about 30% of the predicted baryon content of the average galaxy (3.1 × 1011 M⊙), and about equal to the mass of stars, disk gas, and warm halo gas. The remaining missing baryons (≈1.4 × 1011 M⊙, 40%–50% of the total baryon content) are likely to be hot and extend to the 400–500 kpc volume, if not beyond. The result is higher than predictions, but within the uncertainties.
More Information: https://confluence.desy.de/display/DESYAstroparticlePublic/Astroparticle+Seminar
