Identifying Gamma-Ray Burst Progenitors
Using a clever technique, the authors identify a sub-population of rotating Wolf-Rayet stars.
Bars Rejuvenating Bulges?
Paper title: Bars rejuvenating bulges? Evidence from stellar population analysis Authors: Paula Coelho and Dimitri A. Gadotti First author’s affiliation:Núcleo de Astrofísica Teórica, Universidade Cruzeiro do Sul, São Paulo, Brasil SummaryAs you may recall from Nathan Sanders’ April post, some spiral galaxies have central bulges with high concentrations of stars. Coelho and Gadotti examine a sample of 575 of these galaxies to investigate whether the presence or absence of a bar (a bar-shaped overdensity of stars) influences the rate of star formation in the central bulge. Astronomers expect to see a higher star formation rate in the bulges of barred galaxies because bars can transport gas from the outer regions of the galaxy into the center and supply fuel for growing stars. Previous detections of star-formation indicators (such as enhanced Hα emission) have indicated that the current star formation rates are higher in barred spirals than in unbarred spirals, but Coelho and Gadotti take the alternative approach of determining the ages of the stellar populations in the bulges. They find that the bulges of barred galaxies are systematically younger than the bulges of unbarred galaxies, which is consistent with the expectation that bars should promote star formation. The Galaxy SampleIn a previous paper, Gadotti derived stellar masses, bulge stellar masses, bar properties, and other parameters for a sample of face-on galaxies observed by Sloan Digital Sky Survey (SDSS). All of the galaxies had stellar masses above 10^10 solar masses and redshifts between 0.02 and 0.07. Selecting face-on galaxies reduced the effect of dust and simplified the process of identifying bars and bulges in the galaxies. In this paper, Coelho...
Quasars, the Lyman Alpha Forest, and the Reionization of the Universe
While high-redshift quasars are very interesting objects in their own right, their incredible luminosities allow them to act as background light sources that illuminate the intervening universe on our line of sight. One could think of quasars as giant flashlights that the universe uses to make really interesting spectroscopic shadow puppets back here on Earth.
Intro to Astro – Confessions of a Novice Research Student
I’m a fourth year undergraduate from the University of Southampton, UK, studying for my masters at the Harvard-Smithsonian Centre for Astrophysics. With my summer reading completed, and a new exoplanet waiting to be discovered, I stepped off the plane into Boston Logan Int. this September and eagerly exchanged a drizzly English summer for a beautiful New English Autumn.
The First High Redshift Quasar from Pan-STARRS
Morganson et al. announce the discovery of the first quasar discovered by Pan-STARRS. The newly detected quasar is a Broad Absorption Line quasar at a redshift of 5.73 +/- 0.02 with a z band magnitude of 19.4, a luminosity of 3.8×1047 erg/s, and an estimated black hole mass of 6.9×109 solar masses.
A Star That Should Not Exist
Astronomers have discovered an extremely metal-poor, low mass star located in the Galactic Halo. SDSS J102915+172927 appears to have fewer metals than ever predicted for stars of this mass since many models of star formation suggest that a star with these properties should not have even formed in the early universe.