The Search for the Missing Baryons at Low Redshift

By J. Bregman. 2007

287 citations recorded by the source corpus.

At low redshift, only about one-tenth of the known baryons lie in galaxies or the hot gas seen in galaxy clusters and groups. Models posit that these “missing baryons” are in gaseous form in overdense filaments that connect the much denser virialized groups and clusters. About 30% is cool (<10 5 K) and is detected in Lyα absorption studies, but about half is predicted to lie in the 10 5 –10 7 K regime. Gas is detected in the 2–5 × 10 5 K range through OVI absorption studies (7% of the baryons) and possibly near 10 5 K from broad Lyα absorption (20% of the baryons). Hotter gas (0.5–2 × 10 6 K) is detected at zero redshift by OVII and OVIII Kα X-ray absorption, and the OVII line strengths seem to correlate with the Galactic soft X-ray background, so it is probably produced by Galactic halo gas, rather than a Local Group medium. There are no compelling detections of the intergalactic hot gas (0.5–10 × 10 6 K) either in absorption or emission and these upper limits are consistent with theoretical models. Claimed X-ray absorption lines are not confirmed, while most of the claims of soft emission are attributable to artifacts of background subtraction and field-flattening. The missing baryons should become detectable with moderate improvements in instrumental sensitivity.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/e335a3a9ad740184de493404d6ffcd4eaac05ca2

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Citations in the corpus

GIANT GAMMA-RAY BUBBLES FROM FERMI-LAT: ACTIVE GALACTIC NUCLEUS ACTIVITY OR BIPOLAR GALACTIC WIND? (2010, background): “The study of the Fermi bubbles may provide hints of hot gas feedback from the Galaxy, the search for the missing baryons (Bregman 2007) and the puzzle of high-velocity clouds.”
STRUCTURE AND FORMATION OF ELLIPTICAL AND SPHEROIDAL GALAXIES (2008, background): “After all, there are strong reasons to believ that a warm-hot intergalactic medium surrounds even small galaxies (e. g., Danforth & Shull 2008; see Bregman 2007 for a review).”
Gaseous Galaxy Halos (2012, background): “As discussed further in §4, the amount of hot gas in the halo is below that predicted by cosmological simulations (see also Bregman, 2007), but its extent makes it relevant to studies of large scale Galactic winds and/or shock-heated IGM.”
CMB-S4 Science Case, Reference Design, and Project Plan (2019, background): “, the empirical fact that low-redshift galaxies (such as the Milky Way) have a baryon deficit relative to the cosmological abundance determined from the CMB and BBN [383].”
The Evolution of the Intergalactic Medium (2015, background): “Limits on WHIM emission from the soft X-ray background are currently on the upper end of model forecasts, and there have been purported detections of field O vii absorption with Chandra and XMM-Newton (Bregman 2007).”
A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers (2007, background): “…some redshifted X-ray absorption lines have been reported (e.g., Fang et al. 2002; Mathur et al. 2003; Nicastro et al. 2005), the reliability of the detections has been debated (Kaastra et al. 2006; Rasmussen et al. 2002,2007; Bregman 2007; but see also Fang et al. 2007; Williams et al. 2007).”
GIANT SPARKS AT COSMOLOGICAL DISTANCES? (2014, background): “The primary result of that manuscript was that, if the frequency dependent arrival time was due to propagation, then the Sparker had to be located beyond the Local Group.”
Gusty, gaseous flows of FIRE: Galactic winds in cosmological simulations with explicit stellar feedback (2015, background): “…the entire budget of ‘missing baryons’ in the CGM and IGM have generally come up short, particularly if it is required that the gas would be at least as hot as the virial temperature of L* galaxies (Bregman 2007; Anderson & Bregman 2010; Shull, Smith & Danforth 2012; Anderson, Bregman & Dai 2013).”
Why does the environmental influence on group and cluster galaxies extend beyond the virial radius (2012, background): “Furthermore, it is extremely difficultto even detectthe hot gas haloes of the nearest galaxies (Bregman 2007), let alone measure their structural properties around more distant galaxies falling into groups and clusters.”
On why the iron K-shell absorption in AGN is not a signature of the local warm/hot intergalactic medium (2008, background): “The cosmological requirement that half the baryons in the Universe are in a warm/hot intergalactic medium (WHIM) has motivatedUV and X–ray absorption line studies to detect this otherwise invisible gas, using absorption against a bright AGN to probe the line of sight material (Bregman 2007).”
RADIATION PRESSURE FROM MASSIVE STAR CLUSTERS AS A LAUNCHING MECHANISM FOR SUPER-GALACTIC WINDS (2010, unknown): “1013M⊙) is yet smaller (Bregman 2007).”
THE BARYON CENSUS IN A MULTIPHASE INTERGALACTIC MEDIUM: 30% OF THE BARYONS MAY STILL BE MISSING (2011, background): “Of the remaining 80-90% of cosmological baryons, approximately half can be accounted for in the low-z IGM (Shull 2003; Bregman 2007; Danforth & Shull 2008; Danforth 2009) including the warm-hot IGM (or WHIM).”
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).”
HUBBLE/COS OBSERVATIONS OF THE Lyα FOREST TOWARD THE BL Lac OBJECT 1ES 1553+113 (2010, background): “1ES1553+113 is one of the brightest X-ray sources on the sky and has been suggested as a sight line that could be efficiently probed for WHIM absorption in O VII.”
THE BARYON CONTENT OF COSMIC STRUCTURES (2009, background): “Dust and hot gas do not contribute significantly to the total (Bregman 2007; Anderson & Bregman 2009).”
The formation of disc galaxies in a ΛCDM universe (2010, background): “…strong feedback is employed, the discs can be destroyed by internal processes as too much material is ejected into the halo, preventing efficient disc reformation from cold gas, and possibly violating the upper bounds of halo gas found in X-ray surveys [see Bregman (2007) and references within].”
CHARACTERIZING THE CIRCUMGALACTIC MEDIUM OF NEARBY GALAXIES WITH HST/COS AND HST/STIS ABSORPTION-LINE SPECTROSCOPY (2012, background): “Specifically, we estimate that low impact parameter, low ∆v, high metallicity clouds plausibly associated with “galactic fountains” account for & 0.3 M⊙ yr −1 of gas infall rate in Milky Way size galaxies.”
DO HOT HALOS AROUND GALAXIES CONTAIN THE MISSING BARYONS? (2010, background): “Observational evidence for the existence of the WHIM has subsequently begun to accrue, primarily through detections with ultraviolet and X-ray telescopes of highly ionized oxygen absorption lines (for a recent review, see Bregman 2007).”
THE COS-HALOS SURVEY: RATIONALE, DESIGN, AND A CENSUS OF CIRCUMGALACTIC NEUTRAL HYDROGEN (2013, background): “Third, the baryonic mass in the CGM may be a significant reservoir of cosmic baryons, which are undercounted at low redshift (Persic & Salucci 1992; Fukugita et al. 1998; Cen & Ostriker 1999; Prochaska et al. 2011b) but which may reside in diffuse ionized gas within galaxy halos (Bregman 2007).”