A HUGE RESERVOIR OF IONIZED GAS AROUND THE MILKY WAY: ACCOUNTING FOR THE MISSING MASS?

By A. Gupta, S. Mathur, Y. Krongold, F. Nicastro, M. Galeazzi. 2012

195 citations recorded by the source corpus.

Most of the baryons from galaxies have been “missing” and several studies have attempted to map the circumgalactic medium (CGM) of galaxies in their quest. We report on X-ray observations made with the Chandra X-Ray Observatory probing the warm-hot phase of the CGM of our Milky Way at about 106 K. We detect O vii and O viii absorption lines at z = 0 in extragalactic sight lines and measure accurate column densities using both Kα and Kβ lines of O vii. We then combine these measurements with the emission measure of the Galactic halo from literature to derive the density and the path length of the CGM. We show that the warm-hot phase of the CGM is massive, extending over a large region around the Milky Way, with a radius of over 100 kpc. The mass content of this phase is over 10 billion solar masses, many times more than that in cooler gas phases and comparable to the total baryonic mass in the disk of the Galaxy. The missing mass of the Galaxy appears to be in this warm-hot gas phase.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/15469d973477d358d772313e2059be3ec72ebbab

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Citations in the corpus

A FAST RADIO BURST IN THE DIRECTION OF THE CARINA DWARF SPHEROIDAL GALAXY (2014, background): “Recent estimates for the electron density of the Milky Way ionized halo suggest ne = (2±0.6)×10 −4 cm−3 (Gupta et al. 2012).”
The COS-Halos Survey: Metallicities in the Low-redshift Circumgalactic Medium (2017, background): “Faerman et al. (2017) have recently combined these constraints to build a phenomenological model of the hot Milky Way halo finding MhotCGM ≈ 1.3 × 1011M (see also Gupta et al. 2012).”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “Early attempts to model the corona using X-ray observations assumed (unphysically) that it was isothermal and at a constant density (Bregman & Lloyd-Davies 2007, Gupta et al. 2012).”
CHARACTERIZING THE CIRCUMGALACTIC MEDIUM OF NEARBY GALAXIES WITH HST/COS AND HST/STIS ABSORPTION-LINE SPECTROSCOPY (2012, methodology): “Recently, Gupta et al. (2012) reanalyzed the X-ray spectroscopy of eight bright AGN which all probe the Galaxy halo and Local Group CGM.”
Star formation sustained by gas accretion (2014, background): “A massive (1010 M ) hot (106 K) gas is indeed detected over a large region (100 kpc) around the MW (Gupta et al. 2012).”
The Circumgalactic Medium (2017, background): “The Gupta et al. (2012) claims that the baryon budget is closed for the Milky Way, based on the assumption of an isothermal, uniform density medium, have been questioned by evidence that the gas is neither isothermal nor of uniform density (Wang & Yao 2012).”
The impact of star formation feedback on the circumgalactic medium (2016, background): “The 1011 M⊙ halo gas has a broader range of densities at a given radius, due to the larger impact of stellar feedback on the CGM. mass in different temperature regimes is directly related to many of the best observational constraints we have on the structure of the CGM. X-ray emission and absorption”
Constraints on the distribution and energetics of fast radio bursts using cosmological hydrodynamic simulations (2014, methodology): “…density distributions representative of the Galactic halo, overplotted with observational data and constrain s covering the entire virial radius, as presented by Miller & Bregman (2013), Grcevich & Putman (2009), Blitz & Robishaw (2000), Bregman & Lloyd-Davies (2007) and Gupta et al. (2012).”
THE STRUCTURE OF THE MILKY WAY'S HOT GAS HALO (2013, methodology): “Alternatively, Gupta et al. (2012) found a lower limit on the halo gas mass of >6.1 × 1010 M for L > 139 kpc assuming the gas metallicity is 0.3 Z .”
THE COS-HALOS SURVEY: PHYSICAL CONDITIONS AND BARYONIC MASS IN THE LOW-REDSHIFT CIRCUMGALACTIC MEDIUM (2014, methodology): “Finally, when we add in the detected X-ray halo gas, the fraction is at most 0.08 (but see Gupta et al. 2012; Fang et al. 2013).”
CONSTRAINING THE MILKY WAY'S HOT GAS HALO WITH O vii AND O viii EMISSION LINES (2014, methodology): “These works imply optical depths ranging between ≈ 0.1 - 2.0 depending on the Doppler width assumed for the lines, whether one is observing O VII or O VIII, and which direction one observes (Gupta et al. 2012; Miller & Bregman 2013).”
THE SPACE MOTION OF LEO I: THE MASS OF THE MILKY WAY'S DARK MATTER HALO (2012, background): “…Mvir,MW = 5 × 1011 M , then essentially all of those baryons are accounted for by observed stars and gas in and around the Galaxy; if Mvir,MW = 2.5×1012 M , then a large majority of the MW’s baryons are missing (Fukugita & Peebles 2004; Anderson & Bregman 2010; Gupta et al. 2012; Fang et al. 2013).”