GeV Gamma-Ray Emission from Normal and Starburst Galaxies

Knödlseder, Jürgen

doi:10.1007/978-3-642-35410-6_13

Cited by 5 publications

(5 citation statements)

References 87 publications

(79 reference statements)

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“…The environment of the LMC is distinct from that found in our Galaxy-it is characterized by a low metallicity (lower abundances of gaseous atoms heavier than He; Z LMC ∼ 0.3-0.5 Z e , e.g., Russell & Dopita 1992;Westerlund 1997;Rolleston et al 2002), lower dust-to-gas ratio (e.g., Dufour 1975Dufour , 1984Koornneef 1984;Roman-Duval et al 2014), higher intensity of the interstellar UV radiation (e.g., Browning et al 2003;Welty et al 2006), and lower cosmic-ray density (e.g., Abdo et al 2010;Knödlseder 2013). Metal (such as C, O, and N) abundances are expected to set the electron temperature of H II regions since the collisionally excited lines from metals are the primary cooling mechanism in the ionized gas (e.g., Shaver et al 1983;Balser et al 2011 and references therein).…”

Section: Introductioncontrasting

confidence: 84%

The Detection of Higher-order Millimeter Hydrogen Recombination Lines in the Large Magellanic Cloud

Sewiło,

Tokuda,

Kurtz

et al. 2023

ApJ

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We report the first extragalactic detection of the higher-order millimeter hydrogen recombination lines (Δn > 2). The γ-, ϵ-, and η-transitions have been detected toward the millimeter continuum source N 105–1 A in the star-forming region N 105 in the Large Magellanic Cloud with the Atacama Large Millimeter/submillimeter Array. We use the H40α line, the brightest of the detected recombination lines (H40α, H36β, H50β, H41γ, H57γ, H49ϵ, H53η, and H54η), to determine the electron temperature and study ionized gas kinematics in the region, and the 3 mm free–free continuum emission to determine the physical parameters: the size, emission measure, and electron density. We compare the physical properties of N 105–1 A to a large sample of Galactic compact and ultracompact (UC) H ii regions and conclude that N 105–1 A is similar to the most luminous (L > 105 L ⊙) UC H ii regions in the Galaxy. N 105–1 A is ionized by an O5.5 V star; it is deeply embedded in its natal molecular clump, and likely associated with a (proto)cluster. We incorporate high-resolution molecular line data including CS, SO, SO2, and CH3OH (∼0.12 pc), and HCO+ and CO (∼0.087 pc) to explore the molecular environment of N 105–1 A. Based on the CO data, we find evidence for a cloud–cloud collision that likely triggered star formation in the region. We find no clear outflow signatures, but the presence of filaments and streamers indicates ongoing accretion onto the clump hosting the UC H ii region. Sulfur chemistry in N 105–1 A is consistent with the accretion shock model predictions.

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Section: Introductioncontrasting

confidence: 84%

The Detection of Higher-order Millimeter Hydrogen Recombination Lines in the Large Magellanic Cloud

Sewiło,

Tokuda,

Kurtz

et al. 2023

ApJ

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“…Star forming regions have been thought to be efficient sites for CR acceleration (Knödlseder 2013;Bykov 2014; Aharonian, Yang & de Oña Wilhelmi 2018). Several ISBs have been identified as powerful sources of gamma-rays (hereafter, γ-rays) [The Fermi and H.E.S.S.…”

Section: Introductionmentioning

confidence: 99%

Constraining cosmic ray acceleration in young star clusters using multi-wavelength observations

Gupta

Nath

Sharma

2018

Monthly Notices of the Royal Astronomical Society

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We use 1D and 3D two-fluid cosmic ray (CR) hydrodynamic simulations to investigate the role of CRs in the vicinity of a compact young star cluster. We model a selfgravitating cloud (density profile ρ ∝ r −1 ), include important thermal and non-thermal processes, and explore two different CR injection scenarios. We show that if internal shocks in the wind-driving region are the main site for CR acceleration, then the resulting γ-ray luminosity (L γ ) can reach ≈ 5% of the mechanical luminosity (L w ), independent of the fraction of wind energy (∼ 1 − 20%) injected into CRs. In contrast, if the forward/reverse shock of a bubble is the injection site then L γ increases linearly with the CR injection fraction, as expected analytically. We find that the X-ray luminosity (L x ) in the forward/reverse shock injection scenario is 10 −3 L w , which is ∼ 10 times larger than in the central wind-driving injection case. We predict the corresponding range of the synchrotron radio luminosity. We show how multi-wavelength observations can constrain the CR parameters. Comparing the predicted multi-wavelength luminosities with those of 30 Doradus we identify the reverse shock as the most probable CR injection site, and that thermal conduction is important. We do not find significant dynamical impact of CRs in our models.

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“…For instance, the Cygnus OB association, Westerlund 1, Westerlund 2 in our Galaxy and 30 Doradus in the Large Magellanic Cloud are some of the bright sources of γ-rays from GeV to several TeV energies and have been interpreted as powerful CR accelerators (Abdo et al 2010;Ackermann et al 2011;Abramowski et al 2015;Abeysekara et al 2021). Although star forming regions have been previously discussed as possible sources of CRs (e.g., Knödlseder 2013;Bykov 2014;Aharonian et al 2018), these γ-ray observations have strengthened this hypothesis and they allow us to make more detailed theoretical models, thereby to improve our understanding of CR acceleration in these environments.…”

Section: Introductionmentioning

confidence: 94%

Cosmic rays from massive star clusters : A close look at Westerlund 1

Bhadra,

Gupta,

Nath

et al. 2022

Preprint

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We study the effect of cosmic ray (CR) acceleration in the massive compact star cluster Westerlund 1 in light of its recent detection in γ-rays. Recent observations reveal a 1/r radial distribution of the CR energy density. Here we theoretically investigate whether or not this profile can help to distinguish between (1) continuous CR acceleration in the star cluster stellar wind-driven shocks and (2) discrete CR acceleration in multiple supernovae shocks -which are often debated in the literature. Using idealized two-fluid simulations and exploring different acceleration sites and diffusion coefficients, we obtain the CR energy density profile and luminosity to find the best match for the γ-ray observations. We find that the inferred CR energy density profiles from observations of γ-ray luminosity and mass can be much different from the true radial profile. CR acceleration at either the cluster core region or the wind termination shock can explain the observations, if the diffusion coefficient is κ cr ∼ 10 27 cm 2 s −1 and a fraction of ≈ 10% − 20% of the shock power/post-shock pressure is deposited into the CR component. We also study the possibility of discrete supernovae (SN) explosions being responsible for CR acceleration and find that with an injection rate of 1 SN in every ∼ 0.03 Myr, one can explain the observed γ-ray profile. This multiple SN scenario is consistent with X-ray observations only if the thermal conductivity is close to the Spitzer value.

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GeV Gamma-Ray Emission from Normal and Starburst Galaxies

Cited by 5 publications

References 87 publications

The Detection of Higher-order Millimeter Hydrogen Recombination Lines in the Large Magellanic Cloud

The Detection of Higher-order Millimeter Hydrogen Recombination Lines in the Large Magellanic Cloud

Constraining cosmic ray acceleration in young star clusters using multi-wavelength observations

Cosmic rays from massive star clusters : A close look at Westerlund 1

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