[seminar] Astro Journal Club on 2 March

[Oskari Miettinen]

Dear all,

Our Astro Journal Club will be held on Wednesday at 3:00 pm in the seminar
room F-201 of the Physics Department. This time we will discuss about
topological lensing.

Presenter: Dinko Milakovic
Paper title: A Search for Nontoroidal Topological Lensing in the Sloan
Digital Sky Survey Quasar Catalog
Authors: Fujii, H., and Yoshii, Y.

Summary:
Flat space models with multiply connected topology, which have compact
dimensions, are tested against the distribution of high-redshift (z >= 4)
quasars of the Sloan Digital Sky Survey (SDSS). When the compact
dimensions are smaller in size than the observed universe, topological
lensing occurs, in which multiple images of single objects (ghost images)
are observed. We improve on the recently introduced method to identify
ghost images by means of four-point statistics. Our method is valid for
any of the 17 multiply connected flat models, including nontoroidal ones
that are compacted by screw motions or glide reflection. Applying the
method to the data revealed one possible case of topological lensing
caused by sixth-turn screw motion, however, it is consistent with the
simply connected model by this test alone. Moreover, simulations suggest
that we cannot exclude the other space models despite the absence of their
signatures. This uncertainty mainly originates from the patchy coverage of
SDSS in the south Galactic cap, and this situation will be improved by
future wide-field spectroscopic surveys.

Link to the paper: http://adsabs.harvard.edu/abs/2013ApJ...773..152F

Hope to see you all on Wednesday!

Cheers,
Oskari