The Origin of the Hot Gas in the Galactic Halo: Confronting Models with XMM-Newton Observations

The Astrophysical Journal (Impact Factor: 6.28). 05/2010; DOI: 10.1088/0004-637X/723/1/935
Source: arXiv

ABSTRACT We compare the predictions of three physical models for the origin of the hot halo gas with the observed halo X-ray emission, derived from 26 high-latitude XMM-Newton observations of the soft X-ray background between $l=120\degr$ and $l=240\degr$. These observations were chosen from a much larger set of observations as they are expected to be the least contaminated by solar wind charge exchange emission. We characterize the halo emission in the XMM-Newton band with a single-temperature plasma model. We find that the observed halo temperature is fairly constant across the sky (~1.8e6-2.3e6 K), whereas the halo emission measure varies by an order of magnitude (~0.0005-0.006 cm^-6 pc). When we compare our observations with the model predictions, we find that most of the hot gas observed with XMM-Newton does not reside in isolated extraplanar supernova remnants -- this model predicts emission an order of magnitude too faint. A model of a supernova-driven interstellar medium, including the flow of hot gas from the disk into the halo in a galactic fountain, gives good agreement with the observed 0.4-2.0 keV surface brightness. This model overpredicts the halo X-ray temperature by a factor of ~2, but there are a several possible explanations for this discrepancy. We therefore conclude that a major (possibly dominant) contributor to the halo X-ray emission observed with XMM-Newton is a fountain of hot gas driven into the halo by disk supernovae. However, we cannot rule out the possibility that the extended hot halo of accreted material predicted by disk galaxy formation models also contributes to the emission. Comment: 20 pages, 14 figures. New version accepted for publication in ApJ. Changes include new section discussing systematic errors (Section 3.2), improved method for characterizing our model spectra (4.2.2), changes to discussion of other observations (5.1). Note that we can no longer rule out possibility that extended hot halo of accreted material contributes to observed halo emission (see 5.2.1)

  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper extends the theoretical development of a quantized Newtonian-gravity model of gravitational eigenstates based on the application of Schrödinger’s equation to the weak regions of deep gravitational wells such as those of galaxies and galactic clusters. We present quantitative results from the mathematical techniques that were derived to deal with high-n, high-l states, that have interesting astronomical properties, including extremely long lifetimes and low interaction rates with photons and localized particles. Other factors that contribute to the weak-interaction properties of certain eigenstates are the effective wavefunction amplitude, and the spatial oscillation frequency (SOF). It is seen that, for the weakest interacting states, the mechanisms preventing a transfer to an eigenspectral state mix appropriate to visible particles fall into two categories: 1) the lack of a suitable overlapping state and 2) differences in the SOF and amplitude of the initial and final state.
    Gravitation and Cosmology 01/2012; 18(4). · 0.49 Impact Factor

Full-text (2 Sources)

Available from
Jun 1, 2014