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arXiv · 2107.14281

Hot Extended Galaxy Halos Around Local L* Galaxies From Sunyaev-Zeldovich Measurements

Joel N. Bregman·Edmund Hodges-Kluck·Zhijie Qu·Cameron Pratt·Jiang-Tao Li·Yansong Yun
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Abstract

Most of the baryons in L* galaxies are unaccounted for and are predicted to lie in hot gaseous halos (T ~ 3E6 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 4sigma (declining with radius) and is extended to at least 250 kpc (~R_{200}) at > 99% confidence. The gas mass within a spherical volume to a radius of 250 kpc is 9.8 +/- 2.8 E10 Msun, for Tavg = 3E6 K. This is about 30% of the cosmic baryon content of the average galaxy (3.1E11 Msun), and about equal to the mass of stars, disk gas, and warm halo gas. The remaining missing baryons (~ 1.4E11 Msun, 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.

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Joel N. Bregman, Edmund Hodges-Kluck, Zhijie Qu, Cameron Pratt, Jiang-Tao Li, Yansong Yun. 2022-03-23. Hot Extended Galaxy Halos Around Local L* Galaxies From Sunyaev-Zeldovich Measurements. https://doi.org/10.3847/1538-4357%2Fac51de

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