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Axions that couple to electromagnetism are produced in the early Universe by, among other channels, freeze-in via the Primakoff process. For sufficiently large axion masses, the same coupling causes the axions to decay into two photons,…

High Energy Physics - Phenomenology · Physics 2025-10-24 Ziwen Yin , Hanyu Cheng , Eleonora Di Valentino , Naomi Gendler , David J. E. Marsh , Luca Visinelli

In this first of several application papers, we investigate the mechanics of reionization from stellar sources in high-z galaxies, the utility of various clumping factors on estimating the recombination time in the IGM, and the photon…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-17 Geoffrey C. So , Michael L. Norman , Daniel R. Reynolds , Robert P. Harkness

Optical diagnostic diagrams are powerful tools to separate different ionizing sources in galaxies. However, the model-constraining power of the most widely-used diagrams is very limited and challenging to visualize. In addition, there have…

Astrophysics of Galaxies · Physics 2020-10-28 Xihan Ji , Renbin Yan

In this work we present a study of the strong optical collisional emission lines of Ne and Ar in an heterogeneous sample of ionized gaseous nebulae for which it is possible to derive directly the electron temperature and hence the chemical…

We have constructed a 3D photoionisation model of a planetary nebula (PN) similar in structure to NGC 7009 with its outer pair of knots (also known as FLIERs --fast, low-ionization emission regions). The work is motivated by the fact that…

Astrophysics · Physics 2009-11-13 Denise R. Goncalves , ; Barbara Ercolano , ; A. Carnero , ; A. Mampaso , R. Corradi

(Abridged) We examine standard methods of measuring nebular chemical abundances, including estimates based on direct T_e measurements, and also bright-line diagnostics. We use observations of 4 LMC HII regions whose ionizing stars have…

Astrophysics · Physics 2009-10-31 M. S. Oey , J. C. Shields

The dynamically-driven double-degenerate double-detonation model has emerged as a promising progenitor candidate for Type Ia supernovae. In this scenario, the primary white dwarf ignites due to dynamical interaction with a companion white…

High Energy Astrophysical Phenomena · Physics 2026-05-06 J. M. Pollin , S. A. Sim , L. J. Shingles , R. Pakmor , F. P. Callan , C. E. Collins , F. K. Roepke , L. A. Kwok , A. Holas , S. Srivastav

Active galactic nuclei (AGN) can launch outflows of ionized gas that may influence galaxy evolution, and quantifying their full impact requires spatially resolved measurements of the gas masses, velocities, and radial extents. We previously…

Ever since the pioneering study of Spitzer, it has been widely recognized that grains play an important role in the heating and cooling of photo-ionized environments. A detailed code is necessary to model grains in a photo-ionized medium.…

Astrophysics · Physics 2009-11-10 P. A. M. van Hoof , J. C. Weingartner , P. G. Martin , K. Volk , G. J. Ferland

We use the photon flux and absorption tracer algorithm presented in Katz et al.~2018, to characterise the contribution of haloes of different mass and stars of different age and metallicity to the reionization of the Universe. We employ a…

Cosmology and Nongalactic Astrophysics · Physics 2018-12-05 Harley Katz , Taysun Kimm , Martin G. Haehnelt , Debora Sijacki , Joakim Rosdahl , Jeremy Blaizot

UV, visible, and near-infrared spectroscopy is used to study the transitions of neutral oxygen leading to the emission of broad OI $\lambda$8446, $\lambda$11287 and $\lambda$1304 in Active Galactic Nuclei. From the strength of the former…

Astrophysics · Physics 2009-11-07 A. Rodriguez-Ardila , S. M. Viegas , M. G. Pastoriza , L. Prato , Carlos J. Donzelli

Aims: Temperature uncertainties plague our understanding of abundance variations within the ISM. Using the PHANGS-MUSE large program, we develop and apply a new technique to model the strong emission lines arising from HII regions in 19…

Magnetic spin-down of a millisecond neutron star has been proposed as the power source of hydrogen-poor "superluminous" supernovae (SLSNe-I). However, producing an unambiguous test that can distinguish this model from alternatives, such as…

High Energy Astrophysical Phenomena · Physics 2015-06-16 Brian D. Metzger , Indrek Vurm , Romain Hascoet , Andrei M. Beloborodov

We apply a recently developed theoretical model of helium emission to observations of both the Orion Nebula and a sample of extragalactic H II regions. In the Orion analysis, we eliminate some weak and blended lines and compare theory and…

Astrophysics · Physics 2008-11-26 R. L. Porter , G. J. Ferland , K. B. MacAdam

The discrepancy between abundances computed using optical recombination lines (ORLs) and collisionally excited lines (CELs) is a major unresolved problem in nebular astrophysics. We show here that the largest abundance discrepancies are…

Solar and Stellar Astrophysics · Physics 2015-06-23 Romano Corradi , Jorge García-Rojas , David Jones , Pablo Rodríguez-Gil

Opacity determines radiation transport through material media. In a plasma source the primary contributors to atomic opacity are bound-bound line transitions and bound-free photoionization into the continuum. We review the theoretical…

Solar and Stellar Astrophysics · Physics 2023-03-08 Anil Pradhan

Optical emission-line ratios in star-forming galaxies at $z \sim 3$-8, such as [OIII]/H$\beta$ and [OIII]/[OII], are strongly offset from those at $z \sim 0$-2, pointing to more extreme ionization and ISM conditions in the early Universe.…

We present a study of the impact of photoionization feedback from young massive stars on the turbulent statistics of star-forming molecular clouds. This feedback is expected to alter the density structure of molecular clouds and affect…

Astrophysics of Galaxies · Physics 2020-11-09 Nina S. Sartorio , Bert Vandenbroucke , Diego Falceta-Goncalves , Kenneth Wood

In the context of observations of the rest-frame ultraviolet and optical emission from distant galaxies, we explore the emission-line properties of photoionization models of active and inactive galaxies. Our aim is to identify new…

Astrophysics of Galaxies · Physics 2016-01-20 Anna Feltre , Stephane Charlot , Julia Gutkin

The light curves of Type Ia Supernovae (SN Ia) are powered by gamma-rays emitted by the decay of radioactive elements such as $^{56}$Ni and its decay products. These gamma-rays are downscattered,absorbed, and eventually reprocessed into the…