Stellar feedback is often cited as the biggest uncertainty in galaxy formation models today. This uncertainty stems from a dearth of observational constraints as well as the great dynamic range between the small scales ( 1 pc) where the feedback originates and the large scales of galaxies ( 1 kpc) that are shaped by this feedback. To bridge this divide, in this paper we aim to assess observatio...

it is inferred from the symmetrical and luminous x-ray emission of fossil groups that they are mature, relaxed galaxy systems. cosmological simulations and observations focusing on their dark halo and inter-galactic medium properties confirm their early formation. recent photometric observations suggest that, unlike the majority of non-fossil brightest group galaxies (bggs), the central early-t...

A new estimate of the Galactic interstellar radiation field between 0.1 µm and 1000 µm Cosmic-ray electrons and positrons propagating in the Galaxy produce diffuse gamma-rays via the inverse Compton (IC) process. The low energy target photon populations with which the cosmic-rays interact during propagation are produced by stars, this stellar light being reprocessed by Galactic dust. Detailed m...

Radiation pressure from the absorption and scattering of starlight by dust grains may be a crucial feedback mechanism in starburst galaxies and the self-gravitating parsec-scale disks that accompany the fueling of active galactic nuclei. I review the case for radiation pressure in both optically-thin and highly optically-thick contexts. I describe the conditions for which Eddington-limited star...

We compare models of line-driven winds from accretion discs and single spherical stars. We look at the problem of scaling mass-loss rates and velocities of stellar and disc winds with model parameters. We find that stellar and disc winds driven by radiation, within the CAK framework, are very similar as far as mass-loss rates and velocities are concerned. Thus we can use analytic results for st...

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We use the stellar census of OB associations in the Large Magellanic Cloud (LMC) to predict the Hα luminosities of the host HII regions, based on results from stellar atmosphere models. These values are compared to the observed HII region luminosities, yielding an estimate for the mean fraction of H-ionising photons that escape the local nebulae in this sample. We formally estimate that, overal...

We examine various ways in which disk accretion can heat an accreting star. These include 1) radiation emitted from the disk surface which is intercepted by the stellar surface, 2) radiative flux directly across the disk–star interface, and 3) advection of thermal energy from the disk into the star. For each of these, the physics of the boundary layer between the disk and the star is crucial to...