Probing star formation with galactic cosmic rays

Peršić, M.; Rephaeli, Yoel

doi:10.1111/j.1365-2966.2009.16218.x

Cited by 33 publications

(22 citation statements)

References 67 publications

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“…Our present analysis does not tightly constrain the CR calorimetry scenario for ULIRGs. Energy-independent CR transport should also be examined as a potentially important energy-loss mechanism for CR nuclei in starburst galaxies (see in this context Persic & Rephaeli 2012). Our observations suggest that a substantial fraction of CR energy escapes into intergalactic space for most galaxies since CR nuclei are expected to dominate the CR energy budget, but that some starburst systems such as M82, NGC 253, NGC 1068, and NGC 4945 have substantially higher calorimetic efficiencies relative to the Milky Way.…”

Section: Physics Of Cosmic Rays In Star-forming Galaxiesmentioning

confidence: 85%

GeV OBSERVATIONS OF STAR-FORMING GALAXIES WITH THEFERMILARGE AREA TELESCOPE

Ackermann¹,

Ajello²,

Allafort³

et al. 2012

ApJ

364

557

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Recent detections of the starburst galaxies M82 and NGC 253 by gamma-ray telescopes suggest that galaxies rapidly forming massive stars are more luminous at gamma-ray energies compared to their quiescent relatives. Building upon those results, we examine a sample of 69 dwarf, spiral, and luminous and ultraluminous infrared galaxies at photon energies 0.1-100 GeV using 3 years of data collected by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). Measured fluxes from significantly detected sources and flux upper limits for the remaining galaxies are used to explore the physics of cosmic rays in galaxies. We find further evidence for quasi-linear scaling relations between gamma-ray luminosity and both radio continuum luminosity and total infrared luminosity which apply both to quiescent galaxies of the Local Group and lowredshift starburst galaxies (conservative P-values 0.05 accounting for statistical and systematic uncertainties). The normalizations of these scaling relations correspond to luminosity ratios of log(L 0.1−100 GeV /L 1.4 GHz ) = 1.7 ± 0.1 (statistical) ± 0.2 (dispersion) and log(L 0.1−100 GeV /L 8−1000 µm ) = −4.3 ± 0.1 (statistical) ± 0.2 (dispersion) for a galaxy with a star formation rate of 1 M ⊙ yr −1 , assuming a Chabrier initial mass function. Using the relationship between infrared luminosity and gamma-ray luminosity, the collective intensity of unresolved star-forming galaxies at redshifts 0 < z < 2.5 above 0.1 GeV is estimated to be 0.4-2.4 ×10 −6 ph cm −2 s −1 sr −1 (4-23% of the intensity of the isotropic diffuse component measured with the LAT). We anticipate that ∼ 10 galaxies could be detected by their cosmic-ray induced gamma-ray emission during a 10-year Fermi mission.

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Section: Physics Of Cosmic Rays In Star-forming Galaxiesmentioning

confidence: 85%

GeV OBSERVATIONS OF STAR-FORMING GALAXIES WITH THEFERMILARGE AREA TELESCOPE

Ackermann¹,

Ajello²,

Allafort³

et al. 2012

ApJ

364

557

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“…It is also interesting that – given the play afforded by observational uncertainty – we have no strong evidence from the overall energetics and the FIR luminosity for (or against) any strong biasing of the IMF of the GC stellar population (cf. Persic & Rephaeli 2010; Papadopoulos 2010; Papadopoulos et al 2011). CR electrons accelerated in the HESS region lose ≲10 per cent of their power to synchrotron emission there, generating thereby the diffuse, non‐thermal radio emission detected across the same region. Protons lose ≲1 per cent of their power to pp collisions on ambient gas in the inner few degrees.…”

Section: Discussionmentioning

confidence: 99%

Wild at Heart: the particle astrophysics of the Galactic Centre

Crocker¹,

Jones²,

Aharonian³

et al. 2011

Monthly Notices of the Royal Astronomical Society

126

209

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We consider the high‐energy astrophysics of the inner ∼200 pc of the Galaxy. Our modelling of this region shows that the supernovae exploding here every few thousand years inject enough power to (i) sustain the steady‐state, in situ population of cosmic rays (CRs) required to generate the region’s non‐thermal radio and TeV γ‐ray emission; (ii) drive a powerful wind that advects non‐thermal particles out of the inner Galactic Centre; (iii) supply the low‐energy CRs whose Coulombic collisions sustain the temperature and ionization rate of the anomalously warm envelope detected throughout the Central Molecular Zone; (iv) accelerate the primary electrons which provide the extended, non‐thermal radio emission seen over ∼150 pc scales above and below the plane (the Galactic Centre lobe); and (v) accelerate the primary protons and heavier ions which, advected to very large scales (up to ∼10 kpc), generate the recently identified Wilkinson Microwave Anisotropy Probe (WMAP) haze and corresponding Fermi haze/bubbles. Our modelling bounds the average magnetic field amplitude in the inner few degrees of the Galaxy to the range 60 < B/μ G < 40 0 (at 2σ confidence) and shows that even TeV CRs likely do not have time to penetrate into the cores of the region’s dense molecular clouds before the wind removes them from the region. This latter finding apparently disfavours scenarios in which CRs – in this starburst‐like environment – act to substantially modify the conditions of star formation. We speculate that the wind we identify plays a crucial role in advecting low‐energy positrons from the Galactic nucleus into the bulge, thereby explaining the extended morphology of the 511 keV line emission. We present extensive appendices reviewing the environmental conditions in the Galactic Centre, deriving the star formation and supernova rates there, and setting out the extensive prior evidence that exists, supporting the notion of a fast outflow from the region.

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“…As for Γ π 0 →γγ in Eq. (7), it is the product of the flux Φ p of CR protons (averaged over the volume of the galaxy) and the cross section for the production of gamma rays [142,143]. The distribution and propagation of CR protons is governed by the diffuse-loss equation, which depends on their injection rate, diffusion, energy losses and possible inelastic interactions (see Ref.…”

Section: Star-forming Galaxiesmentioning

confidence: 99%

The nature of the Diffuse Gamma-Ray Background

2015

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We review the current understanding of the diffuse gamma-ray background (DGRB). The DGRB is what remains of the total measured gamma-ray emission after the subtraction of the resolved sources and of the diffuse Galactic foregrounds. It is interpreted as the cumulative emission of sources that are not bright enough to be detected individually. Yet, its exact composition remains unveiled. Well-established astrophysical source populations (e.g. blazars, misaligned AGNs, star-forming galaxies and millisecond pulsars) all represent guaranteed contributors to the DGRB. More exotic scenarios, such as dark matter annihilation or decay, may contribute as well. In this review, we describe how these components have been modeled in the literature and how the DGRB can be used to provide valuable information on each of them. We summarize the observational information currently available on the DGRB, paying particular attention to the most recent measurement of its intensity energy spectrum by the Fermi LAT Collaboration. We also discuss the novel analyses of the auto-correlation angular power spectrum of the DGRB and of its cross-correlation with tracers of the large-scale structure of the Universe. New data sets already (or soon) available are expected to provide further insight on the nature of this emission. By summarizing where we stand on the current knowledge of the DGRB, this review is intended both as a useful reference for those interested in the topic and as a means to trigger new ideas for further research

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Probing star formation with galactic cosmic rays

Cited by 33 publications

References 67 publications

GeV OBSERVATIONS OF STAR-FORMING GALAXIES WITH THEFERMILARGE AREA TELESCOPE

GeV OBSERVATIONS OF STAR-FORMING GALAXIES WITH THEFERMILARGE AREA TELESCOPE

Wild at Heart: the particle astrophysics of the Galactic Centre

The nature of the Diffuse Gamma-Ray Background

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