Gamma-ray emission from spectrally resolved cosmic rays in galaxies

Abstract

Cosmic rays (CRs) are ubiquitous in the interstellar medium (ISM) of nearby galaxies, but many of their properties are not well-constrained. Gamma-ray observations provide a powerful tool in this respect, allowing us to constrain both the interaction of CR protons with the ISM and their transport properties. To help better understand the link between observational signatures and CR physics, we use a series of magneto-hydrodynamical (MHD) AREPO simulations of isolated galaxies performed using spectrally-resolved CR transport in every computational cell, with subsequent gamma-ray emission calculated using the CRAYON+ (Cosmic RAY emissiON) code. In each of our simulated halos, modelling the energy-dependent spatial diffusion of CRs leads to a more extended distribution of high-energy (~100 GeV) gamma rays compared to that predicted by a 'grey' steady-state model, which is especially visible in the corresponding emission maps and radial profiles. Despite this, the total gamma-ray spectra can often be well approximated by the steady-state model, although recovering the same spectral index typically requires a minor variation of the energy dependence of the diffusion coefficient. Our simulations reproduce the observed spectral indices and gamma-ray spectra of nearby star-forming galaxies and also match recent observations of the far infrared--gamma-ray relation. We find, however, that the spectrally resolved model yields marginally smaller luminosities for lower star formation rates compared to grey simulations of CRs. Our work highlights the importance of modelling spectrally resolved CR transport for an accurate prediction of spatially resolved high-energy gamma-ray emission, as will be probed by the upcoming Cherenkov Telescope Array observatory.

arXiv comment18 pages, 11 figures, submitted to MNRAS, comments are welcome!

References in corpus (80)

• Star Formation in Galaxies Along the Hubble Sequence
• The many lives of active galactic nuclei: cooling flows, black holes and the luminosities and colours of galaxies
• Star Formation in the Milky Way and Nearby Galaxies
• E pur si muove: Galiliean-invariant cosmological hydrodynamical simulations on a moving mesh
• Cosmological SPH simulations: A hybrid multi-phase model for star formation
• The Cosmic Baryon Budget
• Constraints on the relationship between stellar mass and halo mass at low and high redshift
• The IRAS Revised Bright Galaxy Sample (RBGS)
• Estimating Star Formation Rates from Infrared and Radio Luminosities: The Origin of the Radio-Infrared Correlation
• The GALEX Ultraviolet Atlas of Nearby Galaxies
• Theoretical Challenges in Galaxy Formation
• Incremental Fermi Large Area Telescope Fourth Source Catalog
• The Arepo public code release
• GeV Observations of Star-forming Galaxies with \textit{Fermi} LAT
• Improving the convergence properties of the moving-mesh code AREPO
• Parametrization of gamma-ray production cross-sections for pp interactions in a broad proton energy range from the kinematic threshold to PeV energies
• Toward a Unification of Star Formation Rate Determinations in the Milky Way and Other Galaxies
• Simulations of magnetic fields in isolated disk galaxies
• The death of massive stars - II. Observational constraints on the progenitors of type Ibc supernovae
• Magnetohydrodynamics on an unstructured moving grid
• Cosmic ray acceleration and escape from supernova remnants
• A connection between star formation activity and cosmic rays in the starburst galaxy M 82
• Global cosmic-ray related luminosity and energy budget of the Milky Way
• The Physics of the FIR-Radio Correlation: I. Calorimetry, Conspiracy, and Implications
• Simulating cosmic ray physics on a moving mesh
• On The GeV & TeV Detections of the Starburst Galaxies M82 & NGC 253
• Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV gamma ray emission
• The Starburst Contribution to the Extra-Galactic Gamma-Ray Background
• Effect of environment on galaxies mass-size distribution: unveiling the transition from outside-in to inside-out evolution
• The GALEX view of the Herschel Reference Survey - Ultraviolet structural properties of nearby galaxies
• AMS-02 beryllium data and its implication for cosmic ray transport
• Theoretical modelling of the diffuse emission of gamma-rays from extreme regions of star formation: The case of Arp 220
• Cosmic-ray hydrodynamics: Alfvén-wave regulated transport of cosmic rays
• The effects of cosmic rays on the formation of Milky Way-mass galaxies in a cosmological context
• A New Numerical Scheme for Cosmic Ray Transport
• Non-linear diffusion of cosmic rays escaping from supernova remnants - I. The effect of neutrals
• High energy gamma-ray emission from the starburst nucleus of NGC 253
• The $\gamma$-ray Emission of Star-Forming Galaxies
• Cosmicflows-4: The Catalog of ~10000 Tully-Fisher Distances
• Winds, Clumps, and Interacting Cosmic Rays in M82
• The transport of cosmic rays in self-excited magnetic turbulence
• Cosmic ray transport and radiative processes in nuclei of starburst galaxies
• Multi-messenger model for the starburst galaxy M82
• Semi-implicit anisotropic cosmic ray transport on an unstructured moving mesh
• A cosmic ray current driven instability in partially ionised media
• Simulating Gamma-ray Emission in Star-forming Galaxies
• The starburst galaxy NGC 253 revisited by H.E.S.S. and Fermi-LAT
• Diffuse Hard X-ray Emission in Starburst Galaxies as Synchrotron from Very High Energy Electrons
• Measurement of the Mass and Stellar Population Distribution in M82 with the LBT
• High Energy Emission from the Starburst Galaxy NGC253
• Cosmic rays and non-thermal emission in simulated galaxies: III. probing cosmic ray calorimetry with radio spectra and the FIR-radio correlation
• The non-linear infrared-radio correlation of low-z galaxies: implications for redshift evolution, a new radio SFR recipe, and how to minimize selection bias
• Simulating radio synchrotron emission in star-forming galaxies: small-scale magnetic dynamo and the origin of the far infrared-radio correlation
• Non-linear diffusion of cosmic rays escaping from supernova remnants - II. Hot ionized media
• Cosmic-Ray Diffusion Suppression in Star-forming Regions Inhibits Clump Formation in Gas-rich Galaxies
• Cosmic rays and non-thermal emission in simulated galaxies. II. $\gamma$-ray maps, spectra and the far infrared-$\gamma$-ray relation
• Properties of Nearby Starburst Galaxies Based on their Diffuse Gamma-ray Emission
• Evolution of cosmic ray electron spectra in magnetohydrodynamical simulations
• Spectrally resolved cosmic ray hydrodynamics -- I. Spectral scheme
• The complete census of optically selected AGNs in the Coma Supercluster: the dependence of AGN activity on the local environment
• Cosmic rays and non-thermal emission in simulated galaxies. I. Electron and proton spectra compared to Voyager-1 data
• Search for gamma-ray emission from star-forming galaxies with Fermi LAT
• Pericentric passage-driven star formation in satellite galaxies and their hosts: CLUES from Local Group simulations
• Revealing a Ring-like Cluster Complex in a Tidal Tail of the Starburst Galaxy NGC 2146
• The impact of magnetic fields on cosmological galaxy mergers. I: Reshaping gas and stellar discs
• The gamma-ray / infrared luminosity correlation of star-forming galaxies
• On the shape of the gamma-ray spectrum around the "${\pi }^0$-bump"
• Cosmic Rays, Gamma-Rays, and Neutrinos in the Starburst Nuclei of Arp 220
• Dynamical Effects of Cosmic Rays on the Medium Surrounding Their Sources
• A finite volume method for two-moment cosmic-ray hydrodynamics on a moving mesh
• Grammage of cosmic rays in the proximity of supernova remnants embedded in a partially ionized medium
• Evidence of AGN activity in the gamma-ray emission from two starburst galaxies
• Emission from Dust in Galaxies: Metallicity Dependence
• Interstellar gamma-ray emission from cosmic rays in star-forming galaxies
• Breaking the Radio - Gamma-Ray Connection in Arp 220
• Observable Signatures of Cosmic Rays Transport in Starburst Galaxies on Gamma-ray and Neutrino Observations
• A radiative transfer model for the spiral galaxy M33
• Cosmic-ray current-driven instabilities -- revisiting environmental conditions
• Spectrally resolved cosmic rays -- III. Dynamical impact and properties of the circumgalactic medium
• Comparing different closure relations for cosmic ray hydrodynamics

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• The dynamical impact of cosmic rays in the Rhea magnetohydrodynamics simulations
• Constraining the hadronic properties of star-forming galaxies above $1\mathrm{GeV}$ with 15-years Fermi-LAT data
• Exploring magnetised galactic outflows in starburst dwarf galaxies NGC 3125 and IC 4662
• Starburst-Driven Galactic Outflows -- Unveiling the Suppressive Role of Cosmic Ray Halos
• Bayesian approach to equipartition estimation of magnetic field strength
• Energetic Particles in the Central Starburst, Disc, and Halo of NGC253
• CHILLING: Continuum Halos in LVHIS Local Irregular Nearby Galaxies - Radio continuum spectral behavior of dwarf galaxies
• MEDUSA I. Tracing magnetic field structures in tidal arms of the dwarf-dwarf merger NGC 1487