@article{PohlMaciasColemanetal.2022,
  author    = {Pohl, Martin and Macias, Oscar and Coleman, Phaedra and Gordon, Chris},
  title     = {Assessing the impact of hydrogen absorption on the characteristics of the Galactic center excess},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {929},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  number    = {2},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0004-637X},
  doi       = {10.3847/1538-4357/ac6032},
  pages     = {13},
  year      = {2022},
  abstract  = {We present a new reconstruction of the distribution of atomic hydrogen in the inner Galaxy that is based on explicit radiation transport modeling of line and continuum emission and a gas-flow model in the barred Galaxy that provides distance resolution for lines of sight toward the Galactic center. The main benefits of the new gas model are (a) the ability to reproduce the negative line signals seen with the HI4PI survey and (b) the accounting for gas that primarily manifests itself through absorption. We apply the new model of Galactic atomic hydrogen to an analysis of the diffuse gamma-ray emission from the inner Galaxy, for which an excess at a few GeV was reported that may be related to dark matter. We find with high significance an improved fit to the diffuse gamma-ray emission observed with the Fermi-LAT, if our new H i model is used to estimate the cosmic-ray induced diffuse gamma-ray emission. The fit still requires a nuclear bulge at high significance. Once this is included there is no evidence of a dark-matter signal, be it cuspy or cored. But an additional so-called boxy bulge is still favored by the data. This finding is robust under the variation of various parameters, for example, the excitation temperature of atomic hydrogen, and a number of tests for systematic issues.},
  language  = {en}
}
@article{MaciasGordonCrockeretal.2018,
  author    = {Macias, Oscar and Gordon, Chris and Crocker, Roland M. and Coleman, Brendan and Paterson, Dylan and Horiuchi, Shunsaku and Pohl, Martin},
  title     = {Galactic bulge preferred over dark matter for the Galactic centre gamma-ray excess},
  series = {Nature Astronomy},
  volume    = {2},
  journal   = {Nature Astronomy},
  number    = {5},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2397-3366},
  doi       = {10.1038/s41550-018-0414-3},
  pages     = {387 -- 392},
  year      = {2018},
  abstract  = {An anomalous gamma-ray excess emission has been found in the Fermi Large Area Telescope data1 covering the centre of the Galaxy2,3. Several theories have been proposed for this 'Galactic centre excess'. They include self-annihilation of dark-matter particles4, an unresolved population of millisecond pulsars5, an unresolved population of young pulsars6, or a series of burst events7. Here, we report on an analysis that exploits hydrodynamical modelling to register the position of interstellar gas associated with diffuse Galactic gamma-ray emission. We find evidence that the Galactic centre excess gamma rays are statistically better described by the stellar over-density in the Galactic bulge and the nuclear stellar bulge, rather than a spherical excess. Given its non-spherical nature, we argue that the Galactic centre excess is not a dark-matter phenomenon but rather associated with the stellar population of the Galactic bulge and the nuclear bulge.},
  language  = {en}
}