Number density distribution of near-infrared sources on a sub-degree scale in the Galactic center: Comparison with the Fe <scp>xxv</scp> Kα line at 6.7 keV

Uchiyama

et al. 2016

ApJ

Self Cite

This paper reports detailed K-shell line profiles of iron (Fe) and nickel (Ni) of the Galactic Center X-ray Emission (GCXE), Galactic Bulge X-ray Emission (GBXE), Galactic Ridge X-ray Emission (GRXE), magnetic Cataclysmic Variables (mCVs), non-magnetic Cataclysmic Variables (non-mCVs), and coronally Active Binaries (ABs). For the study of the origin of the GCXE, GBXE, and GRXE, the spectral analysis is focused on equivalent widths of the Fe I-Kα, Fe XXV-Heα, and Fe XXVI-Lyα lines. The global spectrum of the GBXE is reproduced by a combination of the mCVs, non-mCVs, and ABs spectra. On the other hand, the GRXE spectrum shows significant data excesses at the Fe I-Kα and Fe XXV-Heα line energies. This means that additional components other than mCVs, non-mCVs, and ABs are required, which have symbiotic phenomena of cold gas and very high-temperature plasma. The GCXE spectrum shows larger excesses than those found in the GRXE spectrum at all the K-shell lines of iron and nickel. Among them the largest ones are the Fe I-Kα, Fe XXV-Heα, Fe XXVI-Lyα, and Fe XXVI-Lyβ lines. Together with the fact that the scale heights of the Fe I-Kα, Fe XXV-Heα, and Fe XXVI-Lyα lines are similar to that of the central molecular zone (CMZ), the excess components would be related to high-energy activity in the extreme envelopment of the CMZ.

Section: Galactic Center X-ray Emission (Gcxe)supporting

confidence: 66%

Origin of the Galactic Diffuse X-Ray Emission: Iron K-Shell Line Diagnostics

Uchiyama

et al. 2016

ApJ

Self Cite

“…Numerous, brighter star-forming regions that are more energetically active (Tyler et al 2004, Yasui et al 2015 can affect the production, destruction and distribution of dust and also the ionization of the DIG. This can result in a more prominent and extended DIG component.…”

Section: Modeling the Impact Of Geometrymentioning

confidence: 99%

“…On the other hand, the DIG scale height and intensity are correlated with the number and brightness of HII regions and star formation activity (Dettmar 1990, Rand 1996, Wang et al 1999, Collins et al 2000, Oey et al 2007. Numerous, brighter star-forming regions that are more energetically active (Tyler et al 2004, Yasui et al 2015 can affect the production, destruction and distribution of dust and also the ionization of the DIG. This can result in a more prominent and extended DIG component.…”

Section: Modeling the Impact Of Geometrymentioning

confidence: 99%

Attenuation Modified by DIG and Dust as Seen in M31

Tomičić

Kreckel

Groves

et al. 2017

ApJ

The spatial distribution of dust in galaxies affects the global attenuation, and hence inferred properties, of galaxies. We trace the spatial distribution of dust in five fields (at 0.6-0.9 kpc scale) of M31 by comparing optical attenuation with the total dust mass distribution. We measure the attenuation from the Balmer decrement using Integral Field Spectroscopy and the dust mass from Herschel far-IR observations. Our results show that M31's dust attenuation closely follows a foreground screen model, contrary to what was previously found in other nearby galaxies. By smoothing the M31 data we find that spatial resolution is not the cause for this difference. Based on the emission line ratios and two simple models, we conclude that previous models of dust/gas geometry need to include a weakly or non-attenuated diffuse ionized gas (DIG) component. Due to the variation of dust and DIG scale heights with galactic radius, we conclude that different locations in galaxies will have different vertical distributions of gas and dust and therefore different measured attenuation. The difference between our result in M31 with that found in other nearby galaxies can be explained by our fields in M31 lying at larger galactic radii than the previous studies that focused on the centers of galaxies.

“…At present, our models employ ISRFs and magnetic field energy densities that are not consistent with multiwavelength observations of the CMZ. Specifically, radio surveys find that 50-200µG magnetic fields permeate the CMZ [31,47], while stellar populations spanning the inner few degrees [126,127] and the dense nuclear star clusters surrounding Sgr A* indicate ISRF energy densities in the inner 10 pc which are several orders of magnitude higher than current Galprop models [99,128,129]. A realistic model of diffuse γ-ray emission will need to investigate both:…”

Section: When Including a Gce Template Fits In The Innermentioning

confidence: 99%

Improved cosmic-ray injection models and the Galactic Center gamma-ray excess

Carlson¹,

Linden²,

Profumo³

2016

Phys. Rev. D

Fermi-LAT observations of the Milky Way Galactic Center (GC) have revealed a sphericallysymmetric excess of GeV γ rays extending to at least 10• from the dynamical center of the Galaxy. A critical uncertainty in extracting the intensity, spectrum, and morphology of this excess concerns the accuracy of astrophysical diffuse γ-ray emission models near the GC. Recently, it has been noted that many diffuse emission models utilize a cosmic-ray injection rate far below that predicted based on the observed star formation rate in the Central Molecular Zone. In this study, we add a cosmic-ray injection component which non-linearly traces the Galactic H2 density determined in three-dimensions, and find that the associated γ-ray emission is degenerate with many properties of the GC γ-ray excess. Specifically, in models that utilize a large sideband (40• × 40• surrounding the GC) to normalize the best-fitting diffuse emission models, the intensity of the GC excess decreases by approximately a factor of 2, and the morphology of the excess becomes less peaked and less spherically symmetric. In models which utilize a smaller region of interest (15• ) the addition of an excess template instead suppresses the intensity of the best-fit astrophysical diffuse emission, and the GC excess is rather resilient to changes in the details of the astrophysical diffuse modeling. In both analyses, the addition of a GC excess template still provides a statistically significant improvement to the overall fit to the γ-ray data. We also implement advective winds at the GC, and find that the Fermi-LAT data strongly prefer outflows of order several hundred km/s, whose role is to efficiently advect low-energy cosmic rays from the inner few kpc of the Galaxy. Finally, we perform numerous tests of our diffuse emission models, and conclude that they provide a significant improvement in the physical modeling of the multi-wavelength non-thermal emission from the GC region.