Detection of Thermal Sunyaev–Zel’dovich Effect in the Circumgalactic Medium of Low-mass Galaxies—A Surprising Pattern in Self-similarity and Baryon Sufficiency

Abstract

We report on the measurement of the thermal Sunyaev–Zel’dovich (tSZ) effect in the circumgalactic medium (CGM) of 641,923 galaxies with M _⋆ = 10 ^9.8–11.3 M _⊙ at z 2 σ steeper than the self-similarity relation and the deviation from the same that has been reported previously in higher-mass halos. We calculate the baryon fraction of the galaxies, f _b , assuming the CGM to be at the virial temperature that is derived from M _200 . The baryon fraction f _b exhibits a nonmonotonic trend with mass, with M _⋆ = 10 ^10.9–11.2 M _⊙ galaxies being baryon-sufficient.

Keywords

• Circumgalactic medium
• Hot ionized medium
• Hot intergalactic medium
• Sunyaev-Zeldovich effect
• Millimeter astronomy
• Cosmic microwave background radiation