As part of a continuing project using planetary nebulae (PNe) to study the chemical evolution and formation history of M31 (see accompanying poster by Balick et al.), we obtained spectra of eight PNe in the fall of 2013 with the OSIRIS spectrograph on the GTC. All of these PNe are located outside M31’s inner disk and bulge. Spectral coverage

The incidence and properties of present-day dwarf galaxies hosting massive black holes (BHs) can provide important constraints on the origin of high-redshift BH seeds. Here we present high-resolution X-ray and radio observations of the low-metallicity, star-forming, dwarf-galaxy system Mrk 709 with the Chandra X-ray Observatory and the Karl G

Dwarf elliptical galaxies (dEs) are the most common galaxy class in dense environments, outnumbering all other classes combined. Their low masses make them ideal test beds for studying different mechanisms that shape galaxies, since both external influences and internal feedback mechanisms are far more extreme in dwarfs than in massive galaxies

The Tolman test for surface brightness (SB) dimming was originally proposed as a test for the expansion of the universe. The test, which is independent of the details of the assumed cosmology, is based on comparisons of the SB of identical objects at different cosmological distances. Claims have been made that the Tolman test provides compelling

Modern astronomic telescopes take advantage of multi-conjugate adaptive optics, in which wavefront sensors play a key role. A single sensor capable of measuring wavefront phases at any angle of observation would be helpful when improving atmospheric tomographic reconstruction. A new sensor combining both geometric and plenoptic arrangements is

We present the first release of the X-shooter Spectral Library (XSL). This release contains 237 stars. The spectra in this release span a wavelength range of 3000-10 200 Å and have been observed at a resolving power of R ≡ λ/ Δλ ~ 10 000. The spectra were obtained at ESO's 8-m Very Large Telescope (VLT). The sample contains O-M, long-period