by Elisa Chisari | Feb 2, 2013 | Daily Paper Summaries
Dust is really ubiquitous in the Universe: it is everywhere from our Solar System to stars and the interstellar medium. However, the observations of dust in galaxies fall short of the prediction of how much dust there is in the Universe. In this work, the authors try to alleviate this problem by estimating the amount of dust present in clouds of gas that inhabit galaxy halos while they look for clues regarding the origin of these clouds.
by Dan Gifford | Oct 2, 2012 | Daily Paper Summaries
Title: Spatial Anisotropy of Galaxy Kinematics in Sloan Digital Sky Survey Galaxy ClustersFirst Author: Skielboe, A.Galaxy clusters are beautifully simple, but also fantastically complicated structures. For many years, astronomers have treated these systems as spherical cows, but simulations and observations have repeatedly shown that clusters exhibit triaxial rather than spherical shapes with nice relaxed dynamics (are virialized). Many cluster mass estimators assume spherically symmetric velocity fields (i.e. you measure the same velocities of cluster galaxies regardless of which side you observe from), but if the shape is anisotropic it’s probable the velocities are as well. This makes it crucial to measure the degree of triaxiality of clusters in observations to constrain its impact on mass estimates.The authors sought to show that velocity anisotropy exists by testing for an azimuthal (angle on the sky) dependence of the projected velocity dispersion. To do this, they used a stacked sample of galaxy clusters from the Sloan Digital Sky Survey (SDSS). Stacking is a common technique of taking many clusters with a similar property (in this case galaxy richness or number which is a proxy for mass) and adding them together to make a composite system with many hundreds more galaxies than any one system alone. This gives much better statistics and makes a result more robust.Because the authors are looking for azimuthal variations, they fit each cluster with an ellipse and stack them with their major axes aligned. They then estimate the projected velocity dispersion for galaxies closer to the stacked minor axis, and a separate velocity dispersion for galaxies closer to the major axis. Because they have a stacked sample with...
by Dan Gifford | Aug 7, 2012 | Daily Paper Summaries
Need to improve a relationship between 2 parameters? Why not try adding a 3rd!
by Maria Drout | Jul 23, 2012 | Daily Paper Summaries
Scientists search for signatures of pair-instability supernovae in thousands of Sloan Digital Sky Survey Stars.
by Nathan Sanders | Jul 9, 2012 | Daily Paper Summaries
The current and next generation of large scale spectroscopic surveys could provide new clues in the hunt for the carriers producing mysterious interstellar absorption features.
by Alice Olmstead | Jun 6, 2012 | Daily Paper Summaries
The discovery of a population of red spiral galaxies has caused astronomers to questions the relation between galaxy color and morphology: a closer look at their star formation rates reveals a clearer picture.
