THE STRUCTURE OF THE MILKY WAY'S HOT GAS HALO

By M. Miller, J. Bregman. 2013

155 citations recorded by the source corpus.

The Milky Way's million degree gaseous halo contains a considerable amount of mass that, depending on its structural properties, can be a significant mass component. In order to analyze the structure of the Galactic halo, we use XMM-Newton Reflection Grating Spectrometer archival data and measure O vii Kα absorption-line strengths toward 26 active galactic nuclei, LMC X-3, and two Galactic sources (4U 1820-30 and X1735-444). We assume a β-model as the underlying gas density profile and find best-fit parameters of n○ = 0.46 cm−3, rc = 0.35 kpc, and β = 0.71. These parameters result in halo masses ranging between M(18 kpc) = 7.5 and M(200 kpc) = 3.8 assuming a gas metallicity of Z = 0.3 Z☉, which are consistent with current theoretical and observational work. The maximum baryon fraction from our halo model of fb = 0.07 is significantly smaller than the universal value of fb = 0.171, implying the mass contained in the Galactic halo accounts for 10%–50% of the missing baryons in the Milky Way. We also discuss our model in the context of several Milky Way observables, including ram pressure stripping in dwarf spheroidal galaxies, the observed X-ray emission measure in the 0.5–2 keV band, the Milky Way's star formation rate, spatial and thermal properties of cooler gas (∼105 K), and the observed Fermi bubbles toward the Galactic center. Although the metallicity of the halo gas is a large uncertainty in our analysis, we place a lower limit on the halo gas between the Sun and the Large Magellanic Cloud (LMC). We find that Z ≳ 0.2 Z☉ based on the pulsar dispersion measure toward the LMC.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a0bb23a56778fde6d8f3f33f6498cacaf56d1242

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In Astronomy and Astrophysics

1. Joss Bland-Hawthorn
2. O. Gerhard
3. A. Beck
4. Marcus C. Beck
5. M. Miller
6. B. Gaensler
7. J. Bregman
8. Klaus Dolag

In Instrumentation

1. O. Gerhard
2. Joss Bland-Hawthorn
3. A. Beck
4. Marcus C. Beck
5. B. Gaensler
6. J. Bregman
7. Klaus Dolag
8. M. Miller

Citations in the corpus

• CONSTRAINING THE MILKY WAY'S HOT GAS HALO WITH O vii AND O viii EMISSION LINES (2014, methodology): “Here, we take the optically thin electron density distribution from Miller & Bregman (2013) and convert it to an oxygen density distribution using a solar oxygen abundance of log(NO) = 8.74 from Holweger (2001).”
• The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “A new all-sky catalog of OVII and OVIII emission lines (Henley & Shelton 2012) has been studied by Miller & Bregman (2013, 2015).”
• 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).”