Day 532

Monday.

1310.4824
A tidally-stripped stellar component of the Magellanic bridge
Nidever, et al

SMC stellar photometry (R=4deg, 4.2 kpc) used to study the LoS depth with red clump (RC) stars.  [absolute luminosities of stars in the red clump are fairly independent of stellar composition or age, so that consequently they make good standard candles for estimating astronomical distances both within the galaxy and to nearby galaxies and clusters.  from wikipedia.  (only for ~2 Msun stars?)]  The RC LF is affected little by young (<1 Gyr) blue-loop stars in these regions because their MS counterparts are not observed in the color-magnitude diagrams.  The SMC's eastern side is found to have a large LoS depth (~23 kpc), while the western side has a much shallower depth (~10 kpc), consistent with previous photographic plate photometry results.  Use a model SMC RC LF to deconvolve the observed RC magnitudes and construct the density function in distance for the fields.  Three of the eastern fields show a distance bimodality with one component at the "systemic" ~67kpc SMC distance and a second component at ~55 kpc.  Data are not reproduced well by the various extant Magellanic Cloud and Stream simulations.  However, the models predict that the known HI Magellanic Bridge (stretching from the SMC eastward towards the LMC) has a decreasing distance with angle from the SMC and should be seen in both the gaseous and stellar components.  From comparison with these models, conclude that the most likely explanation for the newly identified ~55 kpc stellar structure in the eastern SMC is a stellar counterpart of the HI Magellanic Bridge that was tidally stripped from the SMC ~200 Myr ago during a close encounter with the LMC.  This discovery has important implications for microlensing surveys of the SMC.

1310.4830
Strong lens time delay challenge: I. Experimental design
Dobler, Fassnacht, Treu, Marshall, Liao, Hojjati, Linder, Rumbaugh

LSST monitoring ~1000 SL systems or multiply imaged quasars; need to assess capability to measure time delays to provide input to future feasibility studies.  Time delay challenge (TDC) offered as a test.  TDC0 for practice (small number of data sets); TDC1 launches Dec.1 2013, consisting of 1000 light curves, a sample designed to provide the statistical power to make meaningful statements about the sub-percent accuracy required to provide competitive DE constraints in the LSST era.