Day 794

Wednesday.

1411.5398
Chitah: strong-gravitational-lens hunter in imaging surveys
Chan, Suyu, ... Marshall, Coupon, Oguri, et al

SL quasars provide means to study galaxy evolution and cosmology.  Current and upcoming imaging surveys will contain thousands of new lensed quasars, augmenting the existing sample by at least 2 orders of magnitudes.  TO find such lens systems, build Chitah that hunts for lensed quasars by modeling the configuration of the multiple quasar images.  Given an image of an object that might be a lensed quasar, Chitah first disentangles the light from the supposed lens galaxy and the right from the multiple quasar images based on color info.  A simple rule is designed to categorize the given object into a potential quad or double lensed quasar system.  The configuration of the identified quasar images is subsequently modeled to classify whether the object is a lensed quasar system.  Test the performance of Chitah using simulated lens systems based on CFHTLS.  For bright quads with large image separations (r_Einstein > 1.1"), a high try-positive rate of >90% and a low cals-positive rate of <3% show that this is a promising approach.  Obtain high true-positive rate for lens systems with r_Einstein > 0.5", so the performance of Chitah is set by the seeing.  Further feed a known gravitational lens system in COSMOS to Chitah, and demonstrate that Chitah is able to classify successfully this real gravitational lens system.  Chita is omnivorous and can hunt in any ground-based imaging surveys.

1411.6724
Dust content, galaxy orientations, and shape noise in imaging surveys
Pattarakijwanich, Schmidt

Show that dust absorption in disk galaxies leads to a color- and orientation-dependent centroid shift which is expected to be observable in multi-band imaging surveys.  This centroid shift is an interesting new probe which contains astrophysical and cosmologically relevant information: it can be used to probe the dust content of a large sample of galaxies, and to reduce the shape noise due to inclination of disk galaxies for WL shear.  Specifically, find that data sets comparable to CFHTLenS, the DES or the HSC survey should probe a dust measurement for several hundred galaxies per square degree.  Conversely, given knowledge of the dust optical depth, this technique will significantly lower the shape noise for the brightest galaxies in the sample (S/N greater than a few hundred), thereby increasing their relative importance for the WL shear measurement.

1411.6628
Primordial star clusters at extreme magnification
Zackrisson, et al

If magnification of ~1000 possible (normally only up to 100), then can probe intrinsically small, high-z objects with very high number densities.  Explore the prospects of detecting compact (<10 pc), high-z (z>7) Pop III star clusters at extreme magnifications in large-area surveys with planned telescopes like Euclid, WFIRST and WISH.  Find that the planned WISH 100 sq. deg ultra deep survey may be able to detect a small number of such objects, provided that the total stellar mass of these star clusters is >1e4 Msun.  If candidates for such lensed Pop III star clusters are found, follow-up spectroscopy of the surrounding nebula wit the JWST or ground based ELT should be able to confirm the Pop III nature of these objects.  Multi band photometry of these objects with JWST also has the potential to confirm that the stellar IMF in these Pop III star clusters is top-heavy, as supported by current simulations.

1411.6807
The Sun and stars: giving light to dark matter
Casanellas, Lopes

Present recent results of use of stars to test new physics, in particular the properties of the hypothetical particles that constitute the dark matter of the Universe.