2016/01/31 by Liang Wang, Aaron A. Dutton, Gregory S. Stinson +4 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Baryon #Dark matter #Dwarf galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Halo #Mass fraction #Milky Way #Omega #Physics #Virial mass #Virial theorem #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stx066
11 pages, 8 figures, 1 table accepted for publication by MNRAS
arxiv created 2017/01/12 · openalex publication_date 2017/01/13 · arxiv updated 2017/01/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We use the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) galaxy formation simulations to make predictions for the baryonic budget in present day galaxies ranging from dwarf (M200 ∼ 1010 M⊙) to Milky Way (M200 ∼ 1012 M⊙) masses. The sample is made of 88 independent high-resolution cosmological zoom-in simulations. NIHAO galaxies reproduce key properties of observed galaxies, such as the stellar mass versus halo mass and cold gas versus stellar mass relations. Thus they make plausible predictions for the baryon budget. We present the mass fractions of stars, cold gas (T < 104 K), cool gas (104 < T < 105 K), warm-hot gas (105 < T < 5 × 106 K) and hot gas (T > 5 × 106 K), inside the virial radius, R200. Compared to the predicted baryon mass, using the dark halo mass and the universal baryon fraction, fb ≡ Ωb/Ωm = 0.15, we find that all of our haloes are missing baryons. The missing mass has been relocated past 2 virial radii, and cool gas dominates the corona at low mass (M200 ≲ 3 × 1011 M⊙) while the warm-hot gas dominates at high mass (M200 ≳ 3 × 1011 M⊙). Haloes of mass M200 ∼ 1010 M⊙ are missing ∼90 per cent of their baryons. More massive haloes (M200 ∼ 1012 M⊙) retain a higher fraction of their baryons, with ∼30 per cent missing, consistent with recent observational estimates. Moreover, these more massive haloes reproduce the observed fraction of cold, warm-hot and hot gases. The fraction of cool gas we predict (0.11 ± 0.06) is significantly lower than the observation from COS-Halos (0.3-0.47), but agrees with the alternative analysis of Stern et al. (2016).