The lack of observed major mergers at high-redshift has prompted discussion of inside-out growth, that is, galaxies building up their stellar populations by cold gas accretion, starting in the inner regions and gradually moving outwards. This picture is far from settled, however, and so the authors of this paper set out to investigate whether or not the observations match the theory.
AU Mic is a low mass star that undergoes unpredictable brightening events, called flares. It’s located just 10pc and has a circumstellar disk. In this paper, Wilner et al. report on observations of the disk at millimeter wavelengths and find evidence for a planetesimal ring.
Gamma ray bursts are high-energy events generally associated with supernova explosions in other galaxies. Though it is possible to study these events via the gamma photons that arrive here on Earth, energetic neutrinos are better suited to probe the optically-thick afterglow of gamma ray bursts and provide a more detailed description of the processes involved. This paper delves into the details of studying these neutrinos.
A specific class of elliptical galaxies called compact ellipticals, or cEs, are unusually compressed. Some speculate that these galaxies are petite because their outer layers have been stripped away by a neighboring galaxy; however, an alternative theory claims that these are regular elliptical galaxies that simply formed small and never contained stars in their outer regions. In order to differentiate between these two models, Howley et al. 2012 measured the dynamics of individual stars in one of our nearest neighbors, the compact elliptical M32.
The basis for something called the “G dwarf problem” is the comparison between observations and a simple model for chemical evolution in a galaxy. To cut to the chase, there are fewer very metal poor G dwarfs than are predicted by this basic understanding. This discrepancy has been shown to hold for the Milky Way as well as for other galaxies. It also holds for K dwarfs in the Milky Way – and now for M dwarfs as well.
This paper considers the fate of red giants and clouds of dark gas that wander in front of the relativistic jets within AGN. Numerical simulations are performed under varying jet conditions for obstacles of homogeneous and inhomogeneous composition.