From SLAC Today:
Attempting to model and measure the distribution of 300 million galaxies is not a job for the faint of heart. That’s exactly the challenge that has been undertaken by Risa Wechsler, associate professor of physics and astrophysics at SLAC and Stanford, who was recently named fellow of the American Physical Society. Wechsler was elected for her pioneering work in understanding galaxy formation and for her leadership in large survey projects.
“If you study that many galaxies you can learn something about how they evolve over time, as well as how they trace the underlying matter distribution,” Wechsler said. “I work at the interface of galaxy formation and the formation of structure in the universe as a whole.”
See full article here.
A new paper led by undergraduate thesis student Benjamin Lehmann and graduate student Yao-Yuan Mao. We present a new method for abundance matching galaxies to dark matter halos, which includes a free parameter that can account for the concentration dependence of the galaxy-halo connection, and thus naturally can account for different levels of assembly bias. We show that this parameter can be constrained with clustering data, and that low redshift clustering measurements from SDSS prefer a moderate amount of concentration dependence --- more than would be indicated by matching galaxy luminosity to the peak halo mass, and less than would be indicated by matching to the peak halo circular velocity. We use new large high-resolution simulation boxes to show that statistical constraints on these models have been limited primarily by sample variance in the limited-size simulations, and not in the data.
See more here: http://arxiv.org/abs/1510.05651
Scientists on the Dark Energy Survey, using one of the world’s most powerful digital cameras, have discovered eight more faint celestial objects hovering near our Milky Way galaxy. Signs indicate that they—like the objects found by the same team earlier this year—are likely dwarf satellite galaxies, the smallest and closest known form of galaxies.
Read more at
New article from Symmetry Magazine about our trillion particle simulations:
A small team of astrophysicists and computer scientists have created some of the highest-resolution snapshots yet of a cyber version of our own cosmos. Called the Dark Sky Simulations, they’re among a handful of recent simulations that use more than 1 trillion virtual particles as stand-ins for all the dark matter that scientists think our universe contains.
They’re also the first trillion-particle simulations to be made publicly available, not only to other astrophysicists and cosmologists to use for their own research, but to everyone. The Dark Sky Simulations can now be accessed through a visualization program in coLaboratory, a newly announced tool created by Google and Project Jupyter that allows multiple people to analyze data at the same time.
Read more at
News, papers, and tidbits from Risa and her Galaxy Formation and Cosmology Group at KIPAC / Stanford University.