THE BARYON CENSUS IN A MULTIPHASE INTERGALACTIC MEDIUM: 30% OF THE BARYONS MAY STILL BE MISSING

By J. Michael Shull, Britton D. Smith, C. Danforth. 2011

341 citations recorded by the source corpus.

Although galaxies, groups, and clusters contain ∼10% of the baryons, many more reside in the photoionized and shocked-heated intergalactic medium (IGM) and in the circumgalactic medium (CGM). We update the baryon census in the (H i) Lyα forest and warm-hot IGM (WHIM) at 105–6 K traced by O vi λ1032, 1038 absorption. From Enzo cosmological simulations of heating, cooling, and metal transport, we improve the H i and O vi baryon surveys using spatially averaged corrections for metallicity (Z/Z☉) and ionization fractions (fH i, fO vi). Statistically, the O vi correction product correlates with column density, (Z/Z☉)fO vi ≈ (0.015)(NO vi/1014 cm−2)0.70, with an NO vi-weighted mean of 0.01, which doubles previous estimates of WHIM baryon content. We also update the Lyα forest contribution to baryon density out to z = 0.4, correcting for the (1  +  z)3 increase in absorber density, the (1  +  z)4.4 rise in photoionizing background, and cosmological proper length dℓ/dz. We find substantial baryon fractions in the photoionized Lyα forest (28% ± 11%) and WHIM traced by O vi and broad-Lyα absorbers (25% ± 8%). The collapsed phase (galaxies, groups, clusters, CGM) contains 18% ± 4%, leaving an apparent baryon shortfall of 29%  ±  13%. Our simulations suggest that ∼15% reside in hotter WHIM (T ⩾ 106 K). Additional baryons could be detected in weaker Lyα and O vi absorbers. Further progress requires higher-precision baryon surveys of weak absorbers, down to minimum column densities NH i ⩾ 1012.0 cm−2, NO vi ⩾ 1012.5 cm−2, NO vii ⩾ 1014.5 cm−2, using high signal-to-noise data from high-resolution UV and X-ray spectrographs.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/0c5ab4aaa35c9298c92202a6ec67a18a6078fe13

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Citations in the corpus

• COSMIC REIONIZATION AFTER PLANCK: COULD QUASARS DO IT ALL? (2015, methodology): “Following the results of cosmological hydrodynamical simulations by Shull et al. (2012) (see also Finlator et al. 2012), we define the characteristic hydrogen recombination timescale as trec,H = [(1 + χ)〈nH〉(1 + z) 3〈αB(T )〉CRR] −1, (4) where αB is the case-B radiative recombination rate…”
• Bimodality of low-redshift circumgalactic O VI in non-equilibrium EAGLE zoom simulations (2016, background): “105 K at lower densities (e.g. Shull et al. 2012).”
• The ESO UVES advanced data products quasar sample: II. Cosmological evolution of the neutral gas mass density (2013, background): “Another 5± 3% may reside in condensed gas phase in the circumgalactic medium (CGM) within the virial radius of galaxies (Shull et al. 2012).”
• Hubble Tension: The Evidence of New Physics (2023, background): “[197] provided an estimation of fIGM ≈ 0.”
• Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions (2011, background): “It is estimated [160, 421] that the observed baryons in clusters only account for about 4% of those produced during BBN (Figure 40).”
• Mapping stellar content to dark matter haloes using galaxy clustering and galaxy–galaxy lensing in the SDSS DR7 (2015, background): “In particular, what fraction of baryons are condensed into stars as opposed to spreading out in the form of gas and dust in and outside of galaxies (Cen & Ostriker 1999; McGaugh et al. 2010; Putman et al. 2012; Shull et al. 2012)?”
• The Evolution of the Intergalactic Medium (2015, background): “In addition, ξion equals 4000 for an empirically motivated stellar initial mass function (IMF), although with factor of two theoretical uncertainty (Shull et al. 2012).”
• CHARACTERIZING THE CIRCUMGALACTIC MEDIUM OF NEARBY GALAXIES WITH HST/COS AND HST/STIS ABSORPTION-LINE SPECTROSCOPY (2012, methodology): “…stars and disk gas as a function of galaxy mass is beyond the scope of this paper; therefore, these collapsed baryon reservoirs are included with the stars in Table 8 and are assumed to total 20% of the baryon inventory (Fukugita et al. 1998; Shull et al. 2012) for all three luminosity sub-samples.”
• LOCATING THE “MISSING” BARYONS WITH EXTRAGALACTIC DISPERSION MEASURE ESTIMATES (2013, background): “…constraints on the locations of the rest (the majority) of the cosmic baryons are weaker, as they reside at densities and temperatures that do not afford significant absorption or emission, except sometimes from highly ionized states of oxygen (Cen & Ostriker 1999; Bregman 2007; Shull et al. 2012).”
• Highly charged ions: Optical clocks and applications in fundamental physics (2018, background): “Since the epoch of reionization – roughly 13 billion years ago – atomic matter in the universe mostly appears as ions (Shull et al., 2012).”