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B They found some missing mass, Hideki Tanimura Institute of S

  1. Oct 10, 2017 #1
    "...There are the longstanding challenges with pinpointing dark energy and dark matter, two invisible components that together make up more than 95 percent of the cosmos. But there is also the lesser-known problem of missing baryon particles.

    Baryons are subatomic particles that include protons and neutrons, which form the nuclei of atoms. Baryonic matter — part of what we consider “normal matter” in the universe — makes up everything we are familiar with: stars, planets, the chair you are sitting on, the device you are using to read this, and you.

    So there was understandable excitement this week when it emerged that two separate teams of researchers may have found this “missing” baryonic matter. ..."


    From, https://www.seeker.com/space/astron...es-missing-normal-matter-has-begun-to-unravel
  2. jcsd
  3. Oct 10, 2017 #2


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    To avoid confusion, these observations have nothing to do with dark matter (or dark energy).

    The cosmic microwave background observations predict that we should see a certain amount of normal matter in the modern universe. To date, we've only detected a small fraction of that predicted amount, for the simple reason that most of the matter hasn't collapsed into galaxies but still exists as a very thin gas between the galaxies.

    The observations described in the article are talking about detections of this predicted thin gas.
  4. Oct 12, 2017 #3
    A Search for Warm/Hot Gas Filaments Between Pairs of SDSS Luminous Red Galaxies
    Hideki Tanimura, Gary Hinshaw, Ian G. McCarthy, Ludovic Van Waerbeke, Yin-Zhe Ma, Alexander Mead, Alireza Hojjati, Tilman Tröster
    (Submitted on 15 Sep 2017)
    We search the Planck data for a thermal Sunyaev-Zel'dovich (tSZ) signal due to gas filaments between pairs of Luminous Red Galaxies (LRG's) taken from the Sloan Digital Sky Survey Data Release 12 (SDSS/DR12). We identify ∼260,000 LRG pairs in the DR12 catalog that lie within 6-10 h−1Mpc of each other in tangential direction and within 6 h−1Mpc in radial direction. We stack pairs by rotating and scaling the angular positions of each LRG so they lie on a common reference frame, then we subtract a circularly symmetric halo from each member of the pair to search for a residual signal between the pair members. We find a statistically significant (5.3σ) signal between LRG pairs in the stacked data with a magnitude Δy=(1.31±0.25)×10−8. The uncertainty is estimated from two Monte Carlo null tests which also establish the reliability of our analysis. Assuming a simple, isothermal, cylindrical filament model of electron over-density with a radial density profile proportional to rc/r (as determined from simulations), where r is the perpendicular distance from the cylinder axis and rc is the core radius of the density profile, we constrain the product of over-density and filament temperature to be δc×(Te/107K)×(rc/0.5h−1Mpc)=2.7±0.5. To our knowledge, this is the first detection of filamentary gas at over-densities typical of cosmological large-scale structure. We compare our result to the BAHAMAS suite of cosmological hydrodynamic simulations (McCarthy et al. 2017) and find a slightly lower, but marginally consistent Comptonization excess, Δy=(0.84±0.24)×10−8.


    Missing baryons in the cosmic web revealed by the Sunyaev-Zel'dovich effect
    Anna de Graaff, Yan-Chuan Cai, Catherine Heymans, John A. Peacock
    (Submitted on 29 Sep 2017 (this version), latest version 5 Oct 2017 (v2))
    Observations of galaxies and galaxy clusters in the local universe can account for only 10% of the baryon content inferred from measurements of the cosmic microwave background and from nuclear reactions in the early Universe. Locating the remaining 90% of baryons has been one of the major challenges in modern cosmology. Cosmological simulations predict that the 'missing baryons' are spread throughout filamentary structures in the cosmic web, forming a low density gas with temperatures of 105−107 K. Previous attempts to observe this warm-hot filamentary gas via X-ray emission or absorption in quasar spectra have proven difficult due to its diffuse and low-temperature nature. Here we report a 5.1σ detection of warm-hot baryons in stacked filaments through the thermal Sunyaev-Zel'dovich (SZ) effect, which arises from the distortion in the cosmic microwave background spectrum due to ionised gas. The estimated gas density in these 15 Megaparsec-long filaments is approximately 6 times the mean universal baryon density, and overall this can account for ∼30% of the total baryon content of the Universe. This result establishes the presence of ionised gas in large-scale filaments, and suggests that the missing baryons problem may be resolved via observations of the cosmic web.


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