Day 1320

Tuesday.

1710.02530
Unique signatures of Population III stars in the global 21-cm signal
Mirocha, et al

Investigate the effects of Pop III stars on the sky-averaged 21-cm background radiation, which traces the collective emission from all sources of UV and X-ray photons before reionization incomplete.  While UV photons from PopIII stars can in principle shift the onset of radiative coupling of the 21-cm transition -- and potentially reionization -- to early times, find that the remnants of PopIII stars are likely to have a more discernible impact on the 21-cm signal than PopIII stars themselves.  The X-rays from such sources preferentially heat the IGM at early times, which elongates the epoch of reheating and results in a more gradual transition from an absorption signal to emission.  This gradual heating gives rise to broad, asymmetric wings in the absorption signal, which stand in contrast to the relatively sharp, symmetric signals that arise in models treating PopII sources only.  A stronger signature of PopIII, in which the position of the absorption minimum becomes inconsistent with PopII-only models, requires extreme SF events that may not be physically plausible, lending further credence to predictions of relatively high frequency absorption troughs, nu_min ~ 100 MHz.  As a result, though the trough location alone may not be enough to indicate the presence of PopIII, the asymmetric wings should arise even if only a few PopIII stars form in each halo before the transition to PopII star formation occurs, provided that the PopIII IMF is sufficiently top-heavy and at least some PopIII stars form in binaries.


1710.03075
The inner mass power spectrum of galaxies using strong gravitational lensing: beyond linear approximation
Chatterjee, Koopmans

In the last decade the detection of individual massive dark matter sub-haloes has been possible using potential correction formalism in SL imaging.  Propose a statistical formalism to relate SL surface brightness anomalies to the lens potential fluctuations arising from DM distribution in the lens galaxy.  Consider these fluctuations as a Gaussian random field in addition to the unperturbed smooth lens model.  This is very similar to WL formalism and show that in this way, can measure the power spectrum of these perturbations to the potential.  Test the method by applying it to simulated mock lenses of different geometries and by performing an MCMC analysis of the theoretical power spectra.  This method can measure density fluctuations in early type galaxies on scales of 1-10 kpc at typical rms-levels of a percent, using a single lens system observed with the HST with typical S/N ratios obtained in a single orbit.