Year: 2018
Type: article
Abstract: The baryon content around local galaxies is observed to be much less than is needed in Big Bang nucleosynthesis. Simulations indicate that a significant fraction of these “missing baryons” may be stored in a hot tenuous circumgalactic medium (CGM) around massive galaxies extending to or even beyond the virial radius of their dark matter halos. Previous observations in X-ray and Sunyaev–Zel’dovich (SZ) signals claimed that ∼(1–50)% of the expected baryons are stored in a hot CGM within the virial radius. The large scatter is mainly caused by the very uncertain extrapolation of the hot gas density profile based on the detection in a small radial range (typically within 10%–20% of the virial radius). Here, we report stacking X-ray observations of six local isolated massive spiral galaxies from the CGM-MASS sample. We find that the mean density profile can be characterized by a single power law out to a galactocentric radius of ≈200 kpc (or ≈130 kpc above the 1 σ background uncertainty), about half the virial radius of the dark matter halo. We can now estimate that the hot CGM within the virial radius accounts for (8 ± 4)% of the baryonic mass expected for the halos. Including the stars, the baryon fraction is (27 ± 16)%, or (39 ± 20)% by assuming a flattened density profile at r ≳ 130 kpc. We conclude that the hot baryons within the virial radius of massive galaxy halos are insufficient to explain the “missing baryons.”
Authors: Jiang-Tao Li, Joel N. Bregman, Q. Daniel Wang, Robert A. Crain, Michael E. Anderson
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Awards: GALAXY FORMATION MODELS PREDICT THAT MASSIVE SPIRAL GALAXIES PRODUCE EXTENSIVE HOT GASEOUS HALOS BY EXTERIOR ACCRETION SHOCKS AND GALACTIC FEEDBACK., THE PRESENCE OF NONTHERMAL SYNCHROTRON EMISSION FROM RADIO TO ~100KEV IN YOUNG SHELL-TYPE SNRS IS A STRONG EVIDENCE OF CR ACCELERATION BY SNR BLAST W
OpenAlex ID: W2788561779