by Courtney Dressing | Nov 10, 2011 | Daily Paper Summaries
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...
by Chris Faesi | Oct 27, 2011 | Daily Paper Summaries
Blue stragglers are stars that, given their mass, should have already evolved beyond the main sequence, and their existence has been a mystery to astronomers for decades. These stars must somehow have gained mass during their main sequence lifetimes; stellar collisions and mass transfer were proposed as the most likely mechanisms that could cause this to happen. A unique combination of observations, simulations, and statistical analysis was recently used to constrain their formation process.
by Nathan Sanders | Oct 3, 2011 | Daily Paper Summaries
What aspects of a star’s life are affected by its rate of rotation? Just about everything!
by Courtney Dressing | Sep 15, 2011 | Daily Paper Summaries
Wolfgang & Laughlin combine observations from the HARPS radial velocity survey and the Kepler transit survey to investigate the mass-radius-period distribution of exoplanets. They find that most small planets are rocky.
by Anna Rosen | Sep 12, 2011 | Daily Paper Summaries
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.
by Courtney Dressing | Sep 1, 2011 | Daily Paper Summaries
How do the planet candidates discovered by Kepler compare to the planets detected by radial velocity surveys? Can we combine the Kepler radii with the RV masses to determine whether small planets are rocky Super-Earths or gaseous mini-Neptunes?
