scholarly journals X-Ray and Gamma-Ray Observations of the Fermi Bubbles and NPS/Loop I Structures

Galaxies ◽  
2018 ◽  
Vol 6 (1) ◽  
pp. 27 ◽  
Author(s):  
Jun Kataoka ◽  
Yoshiaki Sofue ◽  
Yoshiyuki Inoue ◽  
Masahiro Akita ◽  
Shinya Nakashima ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Galactic Halo ◽  
Galactic Center ◽  
Galactic Disk ◽  
Radio Continuum ◽  
X Ray ◽  
The North ◽  
Metal Abundance ◽  
Gamma Ray Emission ◽  
Halo Gas

The Fermi bubbles were possibly created by large injections of energy into the Galactic Center (GC), either by an active galactic nucleus (AGN) or by nuclear starburst more than ~10 Myr ago. However, the origin of the diffuse gamma-ray emission associated with Loop I, a radio continuum loop spanning across 100° on the sky, is still being debated. The northern-most part of Loop I, known as the North Polar Spur (NPS), is the brightest arm and is even clearly visible in the ROSAT X-ray sky map. In this paper, we present a comprehensive review on the X-ray observations of the Fermi bubbles and their possible association with the NPS and Loop I structures. Using uniform analysis of archival Suzaku and Swift data, we show that X-ray plasma with kT~0.3 keV and low metal abundance (Z~0.2 Z◉) is ubiquitous in both the bubbles and Loop I and is naturally interpreted as weakly shock-heated Galactic halo gas. However, the observed asymmetry of the X-ray-emitting gas above and below the GC has still not been resolved; it cannot be fully explained by the inclination of the axis of the Fermi bubbles to the Galactic disk normal. We argue that the NPS and Loop I may be asymmetric remnants of a large explosion that occurred before the event that created the Fermi bubbles, and that the soft gamma-ray emission from Loop I may be due to either π0 decay of accelerated protons or electron bremsstrahlung.

scholarly journals Understanding the diffuse gamma ray emission of the milky way - from supernova remnants to dark matter

2019 ◽  
pp. 17-22
Author(s):  
Jovana Petrovic ◽  
Tijana Prodanovic ◽  
Milos Kovacevic
Keyword(s):  
Dark Matter ◽  
Supernova Remnants ◽  
Milky Way ◽  
Gamma Ray ◽  
Galactic Center ◽  
Galactic Disk ◽  
High Energy ◽  
Data Sets ◽  
Source Population ◽  
Gamma Ray Emission

Diffuse gamma ray emission from the Galactic center at 2-3 GeV, as well as the 12 TeV gamma ray excess in the Galactic disk, remain open for debate and represent the missing puzzles in the complete picture of the high-energy Milky Way sky. Our papers emphasize the importance of understanding all of the populations that contribute to the diffuse gamma background in order to discriminate between the astrophysical sources such as supernova remnants and pulsars, and something that is expected to be seen in gamma rays and is much more exotic - dark matter. We analyze two separate data sets that have been measured in different energy ranges from the ?Fermi-LAT? and ?Milagro? telescopes, using these as a powerful tool to limit and test our analytical source population models. We model supernova remnants and pulsars, estimating the number of still undetected ones that contribute to the diffuse background, trying to explain both the Galactic center and the 12 TeV excess. Furthermore, we aim to predict the number of soon to be detected sources with new telescopes, such as the ?HAWC?.

scholarly journals Cosmic-Ray Production and X-Ray and Gamma-Ray Emission from the Galactic Center

2009 ◽  
Vol 78 (Suppl.A) ◽  
pp. 133-137
Author(s):  
V. A. Dogiel ◽  
K.-S. Cheng ◽  
D. O. Chernyshov ◽  
V. Tatischeff ◽  
C.-M. Ko ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Galactic Center ◽  
Cosmic Ray ◽  
X Ray ◽  
Gamma Ray Emission

Non-Blazar Gamma-Ray Variables in the Galactic Plane: A New Class of Gamma-Ray Sources

1998 ◽  
Vol 11 (2) ◽  
pp. 771-774
Author(s):  
Marco Tavani
Keyword(s):  
Strong Evidence ◽  
Gamma Ray ◽  
Galactic Center ◽  
Galactic Plane ◽  
Time Variable ◽  
Radio Pulsars ◽  
X Ray ◽  
New Class ◽  
Gamma Ray Emission

AbstractWe discuss recent detections of time-variable gamma-ray sources near the Galactic plane. A new bright gamma-ray transient was detected by EGRET in June 1995 near the Galactic center (GRO J1838-04). Also one of the most interesting unidentified gamma-ray sources in the plane, 2CG 135+1, was recently shown to be variable. Both GRO J1838-04 and 2CG 135+1 share many characteristics: variability of the gamma-ray flux within days/weeks, occasional peak gamma-ray emission of comparable flux (˜ 4 x 10-6ph cm-2s-1), absence of radio-loud spectrally-flat AGNs or prominent radio pulsars within their error boxes, lack of strong X-ray and/or hard X-ray counterparts. These characteristics do not match those of either gamma-ray blazars or isolated pulsars. Therefore, GRO J1838-04 and 2CG 135+1 provide strong evidence for the existence of a new class of variable gamma-ray sources.

A Combined Model for the X‐Ray to Gamma‐Ray Emission of Cygnus X‐1

1998 ◽  
Vol 502 (1) ◽  
pp. 428-436 ◽  
Author(s):  
Igor V. Moskalenko ◽  
Werner Collmar ◽  
Volker Schonfelder
Keyword(s):  
Gamma Ray ◽  
Combined Model ◽  
X Ray ◽  
Gamma Ray Emission

scholarly journals Discovery of recombining plasma inside the extended gamma-ray supernova remnant HB9

2019 ◽  
Vol 489 (3) ◽  
pp. 4300-4310 ◽  
Author(s):  
A Sezer ◽  
T Ergin ◽  
R Yamazaki ◽  
H Sano ◽  
Y Fukui
Keyword(s):  
Supernova Remnant ◽  
Gamma Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Large Area ◽  
Imaging Spectrometer ◽  
X Ray ◽  
East Region ◽  
X Ray Imaging ◽  
Collisional Ionization

ABSTRACT We present the results from the Suzaku X-ray Imaging Spectrometer observation of the mixed-morphology supernova remnant (SNR) HB9 (G160.9+2.6). We discovered recombining plasma (RP) in the western Suzaku observation region and the spectra here are well described by a model having collisional ionization equilibrium (CIE) and RP components. On the other hand, the X-ray spectra from the eastern Suzaku observation region are best reproduced by the CIE and non-equilibrium ionization model. We discuss possible scenarios to explain the origin of the RP emission based on the observational properties and concluded that the rarefaction scenario is a possible explanation for the existence of RP. In addition, the gamma-ray emission morphology and spectrum within the energy range of 0.2–300 GeV are investigated using 10 yr of data from the Fermi Large Area Telescope (LAT). The gamma-ray morphology of HB9 is best described by the spatial template of radio continuum emission. The spectrum is well fit to a log-parabola function and its detection significance was found to be 25σ. Moreover, a new gamma-ray point source located just outside the south-east region of the SNR’s shell was detected with a significance of 6σ. We also investigated the archival H i and CO data and detected an expanding shell structure in the velocity range of $-10.5$ and $+1.8$ km s−1 that is coinciding with a region of gamma-ray enhancement at the southern rim of the HB9 shell.

scholarly journals The magnetic structure of our Galaxy: a review of observations

2008 ◽  
Vol 4 (S259) ◽  
pp. 455-466 ◽  
Author(s):  
JinLin Han
Keyword(s):  
Magnetic Fields ◽  
Magnetic Structure ◽  
Large Scale ◽  
Galactic Halo ◽  
Galactic Center ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Dust Emission ◽  
Measure Data ◽  
Radio Sources

AbstractThe magnetic structure in the Galactic disk, the Galactic center and the Galactic halo can be delineated more clearly than ever before. In the Galactic disk, the magnetic structure has been revealed by starlight polarization within 2 or 3 kpc of the Solar vicinity, by the distribution of the Zeeman splitting of OH masers in two or three nearby spiral arms, and by pulsar dispersion measures and rotation measures in nearly half of the disk. The polarized thermal dust emission of clouds at infrared, mm and submm wavelengths and the diffuse synchrotron emission are also related to the large-scale magnetic field in the disk. The rotation measures of extragalactic radio sources at low Galactic latitudes can be modeled by electron distributions and large-scale magnetic fields. The statistical properties of the magnetized interstellar medium at various scales have been studied using rotation measure data and polarization data. In the Galactic center, the non-thermal filaments indicate poloidal fields. There is no consensus on the field strength, maybe mG, maybe tens of μG. The polarized dust emission and much enhanced rotation measures of background radio sources are probably related to toroidal fields. In the Galactic halo, the antisymmetric RM sky reveals large-scale toroidal fields with reversed directions above and below the Galactic plane. Magnetic fields from all parts of our Galaxy are connected to form a global field structure. More observations are needed to explore the untouched regions and delineate how fields in different parts are connected.

scholarly journals Cygnus OB2 at all wavelengths

2003 ◽  
Vol 212 ◽  
pp. 505-514 ◽  
Author(s):  
Jürgen Knödlseder
Keyword(s):  
Star Formation ◽  
Gamma Ray ◽  
Current Knowledge ◽  
Radio Continuum ◽  
Electromagnetic Spectrum ◽  
Text Book ◽  
Nearby Star ◽  
X Ray ◽  
Stellar Cluster ◽  
Star Formation Regions

The Cygnus X region is one of the most nearby star formation regions within our Galaxy, that is recognised by prominent emission throughout the entire electromagnetic spectrum, from radio to gamma-ray waves. The centre is populated by the peculiar stellar cluster Cyg OB2, traditionally classified as OB association, but in the light of modern data more likely the prototype of a young globular cluster within our own Galaxy. Heavily shredded by dense molecular clouds this object has been less thoroughly studied than other, more distant star formation complexes in the Milky Way. I will review our current knowledge about this object, by exposing its properties and that of its environment throughout the entire electromagnetic spectrum. Particular emphasis will be given to infrared, radio-continuum, X-ray, and gamma-ray line observations that find in Cyg OB2 a text-book case for multiwavelength studies.

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