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Hot Halos of Local Galaxies Detected by the Sunyaev-Zeldovich Effect

Presentation #104.04 in the session ISM/Galaxies - Poster Session.

Published onMay 03, 2024
Hot Halos of Local Galaxies Detected by the Sunyaev-Zeldovich Effect

Most of the baryons in galaxies are not accounted for by the stars and warm/cool gas, with models predicting that the missing gas either escaped as a galactic wind, or is bound in an extensive hot halo (~106 K) that extends to the virial radius, or beyond. This gas can be detected near the galaxy in X-rays, but at larger radius, the preferred signature is through electron scattering of CMB photons – the Sunyaev-Zeldovich effect. We have developed improved SZ maps through the use of neural networks, which allow us to investigate a stack of 12 local spiral galaxies (D < 10 Mpc) to greater accuracy than previously possible. We detect the SZ signal to at least 0.6Rvirial and with a radial profile steeper than the density decline, which probably indicates a temperature decrease as well. The hot gas mass within the virial radius may close the baryon census or still require significant gas in the 1-2Rvirial range. The uncertainty lies with the poorly determined temperature profile at large radius, where a steeper decline leads to a greater baryon mass.

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