Day 912

Thursday.


1506.07173
The brightest Ly$\alpha$ emitter: Pop III or Black Hole?
Pallottini, et al

CR7 is the brightest z-6.6 LAE known to date, and spectroscopic follow-up by Sobral+2015 suggests that CR7 might host Pop III stars.  Examine this interpretation using cosmo hydro sims.  Several simulated galaxies show the same "Pop III wave" pattern observed in CR7.  However, to reproduce the extreme CR7 Lya/HeII 1640 line luminosities (L_alpha/HeII) a top-heavy IMF and a massive (>1e7 Msun) PopIII burst with age <2Myr are required.  Assuming that the observed properties of Lya and HeII emission are typical for Pop III, predict that in the COSMOS/UDS/SA22 fields, 14 out of the 30 LAEs at z=6.6 with L_a>1e43.3 erg/s should also host Pop III stars producing an observable L_HeII>1e42.7 erg/s.  As an alternate explanation, explore the possibility that CR7 is instead powered by accretion onto a Direct Collapse Black Hole (DCBH).  The model predicts L_a, L_HeII, and X-ray luminosities that are in agreement with the observations.  In any case, the observed properties of CR7 in ideate that this galaxy is most likely powered by sources formed from pristine gas.  Propose that further X-ray observations can distinguish between the two above scenarios.


1506.07185
The importance of 56Ni in shaping the light curves of type II supernovae
Nakar, Poznanski, Katz

What intrinsic property shape the light curves of Type II SNe [core-collapse SNe]?  To address this question, derive observational measures that are robust (i.e., insensitive to detailed radiative transfer) and constrain the contribution from 56Ni, as well as a combination of the ejecta mass, progenitor radius, and explosion energy.  By applying the methods to a sample of type II SNe from the literature, find that 56Ni contribution is often significant.  It is typically the source of about 20% of the radiated energy during the photospheric phase, and in extreme cases it even dominates.  Find that the 56Ni relative contribution is anti-correlated with the luminosity decline rate, while it is not significantly correlated with other properties of the light curve.  When added to other clues, this in turn suggests that the flat plateaus often observed i type II SNe are not a generic feature of the cooling envelope emission, and that without 56Ni many of the SNe that are classified as II-P would have shown a decline rate that is steeper by up to 1 mag/100 d.  Furthermore, contrary to previous suggestions, find that SNe with faster decline have at least comparable, and possibly larger, ejecta mass compared to those with flat plateaus.


1506.07366
Angular spectra of the intrinsic galaxy ellipticity field, their observability and their impact on lensing in tomographic surveys
Schaefer, Merkel

Subject of this paper: intrinsic ellipticity correlations between galaxies, their statistical properties, their observability with future surveys and their interference with WL measurements.  Using an angular momentum-based, quadratic intrinsic alignment model, derive correlation functions of the ellipticity components and project them to yield the four non-zero angular ellipticity spectra C_E(ell), C_B(ell), C_C(ell) and C_S(ell) in their generalization to tomographic surveys.  For a Euclid-like survey, these spectra would have amplitudes smaller than the WL effect on nonlinear structures, but would constitute an important systematic.  Computing estimation basis for cosmological parameters derived from an alignment-contaminated survey suggests biases of +5sigma_w for the DE EoS parameter w, -20sigma_Omega_m for the matter density Omega_m and -12sigma_sigma8 for the spectrum normalization sigma_8.  IA yield a signal which is easily observable with a survey similar to Euclid: while not independent, significances for estimates of each of the four spectra reach values of tens of sigma if WL and shape noise are considered as noise sources, which suggests relative uncertainties on alignment parameters at the percent level.