Day 91

Tuesday.  STILL no apartment yet.  Almost done with the proposal.


AIfA Bachelor Kolloquium
AIfA 0.002 28 Sept. 2011, 11am
Extinktion im interstellaren medium in M33
Karsten Spiekermann


The extinction in ISM of M33, one of the 3 spiral galaxies in the Local Group, is determined for (from?) the HII regions NGC 595 and NGC 604.  For this purpose, NIR Paschen-alpha images from the WIYN High Resolution Infrared Camera (WHIRC) were reduced and combined with the H-alpha maps of KPNO Schmidt-Telescope.


* Lyman-alpha: 2 => 1 transition emission (122 nm)
* Balmer-alpha: 3 => 2 transition (656 nm)
* Paschen-alpha: 4 => 3 transition (1870 nm)


1109.5175
Nonlinear color-metallicity relations of globular clusters. II.  A test on the nonlinearity scenario for color bimodality using the u-band colors: The case of M87 (NCG 4486)
Yoon, Sohn, Lee, Kim, Cho, Chung, Blakeslee

Optical color distribution of globular clusters in most large elliptical galaxies are bimodal.  Linear relationship between GC colors and metallicities assumed.  However, recent observations and modeling of GCs suggest color-metallicity relations (CMRs) are inflected, and hence nonlinear.  The nonlinearity could produce bimodal color distributions from a broad underlying metallicity spread, even if [metallicity] is unimodal.    ...Color bimodality is still an open question.  Propose new photometric technique to probe possible nonlinear nature of CMRs.  A color distribution of GCs is a "projected" distribution of their metallicities.  Form of CMRs hinges on which color is used, shape of color distributions varies depending on the colors.  Among the optical colors, the u-band related colors (u-g and u-z) are theoretically predicted to exhibit significantly less inflected CMRs than other preferred CMRs.  Case study: HST archival u-band photometry for the M87 GC system with confirmed color bimodality.  Show u-band color distributions are significantly different from that of g-z, and consistent with model predictions.  With more u-band measurements, this methods will uspport or rule out the non-linear CMR scenario for the origin of GC color bimodality with high confidence.




1109.5175
Interpolating masked weak lensing signal with Karhunen-Loeve analysis
Vanderplas, Connoley, Jain, Jarvis


A WL systematic limitaion: incomplete coverage and pixel-level masking.  Method: use 2-d KL eigenmodes of shear to interpolate noisy shear measurements across masked regions.  Explore this method with simulated shear catalogs, using statistics of high-convergence regions in the resulting map.  Find: not only minimizes the bias due to masked regions in the field, but also reduced spurious peak counts from shape noise by a factor of ~3 in the cosmologically sensitive regime.  (!!!)  Indicates KO reconstruction of masked shear not only useful for creating robust convergence maps from shear catalogs, but also offer promise of improved parameters constraints within studies of shear peak statistics.  


* maybe we can use this with cluster mass estimates too...???