Conveners
Galactic Diffuse & CR propagation: Galactic Diffuse Emission
- Isabelle Grenier
We discuss the impact that the charged cosmic rays have on the determination of the gamma-ray diffuse galactic emission. We review the implications deriving from present data and outline some future prospects for data and models.
In support of analysis for the Large Area Telescope 4FGL source catalog (see invited contribution by Jean Ballet) we are developing a new model for the Galactic diffuse emission, fit to the same 8-year Pass 8 data set, spanning 50 MeV--1 TeV. Relative to the 4-year Pass 7 model developed for the 3FGL catalog, the new model includes updated distributions of interstellar atomic and molecular...
The recent progress in HI, CO, dust, and gamma-ray observations provides excellent opportunities to probe the properties of the interstellar medium (ISM) at a resolution of a few parsecs inside nearby clouds and to search for biases in the different gas tracers.
The nearby clouds in Galactic anti-center and Chamaleon regions have been studied using jointly the gamma-ray observations of...
The Fermi-LAT discovered giant structures that are barely visible in the EGRET era. The most striking feature is the so-called Fermi bubbles, extending above and below the Galactic center. In addition, Fermi-LAT detected diffuse gamma-ray emissions associated with Loop I. The northern-most part of Loop I is the brightest arm, known as the North Polar Spur (NPS), and is even clearly visible in...
Standard cosmic ray (CR) propagation models that assume neither a time-independent source distribution nor a location-independent diffusion cannot give rise to spatially dependent CR (and hence γ-ray) spectral slopes. Yet, recent observations by Fermi-LAT exhibit a hardening of the γ-ray spectrum between the Sagittarius and Carina tangents, and a further hardening at a few degrees above and...
High-energy gamma rays of interstellar origin are produced by the
interaction of cosmic-ray (CR) particles with the diffuse gas and
radiation fields in the Galaxy. The main features of this emission are
well understood and are reproduced by existing CR propagation models
employing a 2D galactocentric cylindrical symmetric geometry. However,
the high-quality data from instruments like the...
In this contribution we present an interpretation of the most recent data on cosmic-ray electron and positron (CRE) fluxes (from Fermi-LAT, HESS, CALET and AMS-02), with a special focus on the electron contribution from supernova remnants (SNRs). For the first time, we consider together the constraints coming from CRE flux up to 20 TeV, as well as Fermi-LAT dipole upper limits and radio...
Observations in the hard X-ray band found that electrons are accelerated in two magnetic white dwarfs. Protons are found to be accelerated to GeV in the novae by Fermi.These prompted us to analyze the cosmic ray (CR) spectra of electrons, protons, and heavier nuclei observed near Earth including the spectra deduced from the observed hard X-ray and gamma ray spectra. We fit the CR spectra at...
Diffuse gamma-ray emission from local molecular clouds is a powerful probe of the local interstellar gas and cosmic rays. Most of previous LAT studies of the molecular cloud regions assumed that the gamma-ray emitting interstellar gas is decomposed into three components: atomic hydrogen, molecular hydrogen and some excess gas not traced by standard HI and CO surveys. In each phase, uniform gas...
The PICARD code for the numerical solution of the Galactic cosmic-ray propagation problem allows for high resolution 3D models that can acknowledge localised structures within our Galaxy. Using PICARD, we address the impact of different transport physics processes on the flux and distribution of diffuse Galactic gamma rays: we investigate models with a cosmic-ray source distribution aligned...
Cosmic Rays propagate in the Milky Way and interact
with the interstellar medium and magnetic fields. These interactions produce emission that spans the electromagnetic spectrum and is a crucial tool for understanding intensities and spectra of cosmic rays in different regions. Hence observations of this interstellar emission complement information from cosmic ray measurements.
We present...
We present the measurement of the cosmic-ray proton spectrum between 54 GeV and 9.5 TeV using 7 years of Pass 8 flight data from the Fermi Large Area Telescope (LAT). We developed a dedicated proton event selection with an maximum acceptance of 0.25 m^2 sr at 1 TeV. Our analysis yields a large dataset for a spectral measurement with a statistical uncertainty under 1% up to 1 TeV and residual...
The interstellar gas is a key component for understanding cosmic-ray (CR)
physics as it is the target for the generation of secondary CR particles
and the high-energy interstellar emission. Observations of the spectra and
abundances of these secondary particles are used to decipher the
propagation history of CRs and to decode possible signatures of new physics.
Until now, most...
The Orion-Eridanus superbubble, formed from the winds and the explosions of Orion’s massive stars, could be a cosmic-ray acceleration site. Inside the superbubble, the large level of MHD turbulence and the core-collapse supernovae have created a turbulent medium which effect on cosmic rays can be probed comparing their flux and spectrum in the superbubble to the average in nearby interstellar...
High-energy cosmic-ray (CR) protons and electrons interact with the interstellar gas or the interstellar radiation field and produce diffuse gamma rays.
Since the interstellar medium (ISM) is transparent to these high-energy photons,
GeV gamma rays are a powerful probe to study the ISM and Galactic CRs.
Indeed, a significant amount of gas not traced properly by standard radio line surveys...
