Related papers: A Dramatic Decrease in Carbon Star Formation in M3…

The formation of stars is a key process in the early universe with far reaching consequences for further cosmic evolution. While stars forming from truly primordial gas are thought to be considerably more massive than our Sun, stars in the…

Most galaxies follow well-defined scaling relations of metallicity and stellar mass; however, some outliers at the low mass end of the observed galaxy population exhibit unusually high metallicity for their mass. Understanding how these…

We compute the mass and composition of dust produced by stars with masses in the range 1Msun<M<8 Msun and with a metallicity of Z=0.001 during their AGB and Super AGB phases. Stellar evolution is followed from the pre-main sequence phase…

We investigate the process of self-regulated star formation via photodissociation of hydrogen molecules in low metallicity clouds. We evaluate the influence region's scale of a massive star in low metallicity gas clouds whose temperatures…

Studies both of entire galaxies and of local Galactic star formation indicate a dependency of a molecular cloud's star formation rate (SFR) on its dense gas mass. In external galaxies, such measurements are derived from HCN(1-0)…

We have developed a new procedure to search for carbon-enhanced metal-poor (CEMP) stars from the Hamburg/ESO (HES) prism-survey plates. This method employs an extended line index for the CH G-band, which we demonstrate to have superior…

We have analyzed new HST/ACS and HST/WFC3 imaging in F475W and F814W of two previously-unobserved fields along the M31 minor axis to confirm our previous constraints on the shape of M31's inner stellar halo. Both of these new datasets reach…

We have identified a new class of Asymptotic Giant Branch (AGB) stars in the Small and Large Magellanic Clouds (SMC/LMC) using optical to infrared photometry, light curves, and optical spectroscopy. The strong dust production and…

The characteristic mass of stars at early times may have been higher than today owing to the cosmic microwave background (CMB). This study proposes that (1) the testable predictions of this "CMB-IMF" hypothesis are an increase in the…

We present spectroscopic observations of red giant branch (RGB) stars over a large expanse in the halo of the Andromeda spiral galaxy (M31), acquired with the DEIMOS instrument on the Keck II 10-m telescope. Using a combination of five…

We compare atomic gas, molecular gas, and the recent star formation rate (SFR) inferred from H-alpha in the Small Magellanic Cloud (SMC). By using infrared dust emission and local dust-to-gas ratios, we construct a map of molecular gas that…

We use hierarchical Bayesian regression analysis to investigate star formation laws in the Andromeda galaxy (M31) in both local (30, 155, and 750pc) and global cases. We study and compare the well-known Kennicutt-Schmidt law, the extended…

We investigate the environmental effect on the metal enrichment of star-forming galaxies (SFGs) in the farthest spectroscopically confirmed and X-ray detected cluster, CL~J1449+0856 at $z=1.99$. We combined HST/WFC3~G141 slitless…

We demonstrate that there are systematic scale errors in the [Fe/H] values determined by the Hamburg/ESO Survey (and by inference by the HK Survey in the past) for certain extremely metal poor highly C-enhanced giants. The consequences of…

Stars on the asymptotic giant branch (AGB) lose substantial amounts of matter, to the extent that they are important for the chemical evolution of, and dust production in, the universe. The mass loss is believed to increase gradually with…

We calculate the dust formed around AGB and SAGB stars of metallicity Z=0.008 by following the evolution of models with masses in the range 1M<M<8M throughthe thermal pulses phase, and assuming that dust forms via condensation of molecules…

The bulge carbon stars have been a mystery since their discovery, because they are about 2.5mag too faint to be regarded as genuine AGB stars, if located inside the metal-rich bulge (m-M=14.5mag). Part of the mystery can be solved if these…

Carbon-rich (C-rich) stars can be found at all metallicities and evolutionary stages. They are often the result of mass-transfer from a companion, but some of the most metal-poor C-rich objects are likely carrying the imprint of the…

We determine magnesium isotopic abundances of metal poor dwarf stars from the galactic halo, to shed light on the onset of asymptotic giant branch (AGB) star nucleossynthesis in the galactic halo and constrain the timescale of its…

New wide-field near-infrared (NIR) imaging observations of M33 were obtained from UKIRT. These show a large population of intermediate-age stars considerably improving on previous NIR data. The spatial distribution of super giant stars,…