Day 550

Thursday.  Friday.

1311.5008
Type Ia supernovae from merging white dwarfs I. Prompt Detonations
Moll, Raskin, Kasen, Woosley

Merging WDs are possible progenitor of SNe Ia.  Numerical methods suggest that a detonation might be initiated before the stars have coalesced to form a single compact object.  Study such "peri-merger" detonations by sims, molding the disruption and nucleosynthesis of the stars until the ejecta reach the coasting phase.  Synthetic light curves and spectra are generated for comparison with observations.  3 models are considered with primary masses 0.96 Msun, 1.06 Msun, and 1.2 Msun.  Of these, the 0.96 Msun dwarf merging with an 0.81 Msun companion, with a Ni56 yield of 0.58 Msun, is the most promising candidate for reproducing common SNe Ia.  The more massive mergers produce unusually luminous SNe Ia with peak luminosities approaching those attributed to "super-Chandrasekhar" mass SNe Ia.  While the synthetic light curves and spectra of some of the models resemble observed SNe Ia, the significant asymmetry of the ejecta leads to large orientation effects.  The peak bolometric luminosity varies by >2x with the viewing angle, and the velocities of the spectral absorption features are lower when observed from angles where the light curve is brightest.  The largest orientation effects are seen in the UV, where the flux varies by more than an order of magnitude.  Despite the large variation with viewing angle, the set of 3 models roughly obeys a width-luinosity relation, with the brighter light curves declining more slowly in the B-band.  Spectral features due to unburned carbon from the secondary star are also seen in some cases.

1311.5042
Exploring hot gas at junctions of galaxy filaments with Suzaku
Mitsuishi et al

Search for hot gases associated with the junctions of galaxy filaments; find X-ray sources in all 5 regions and analyzed 2 bright sources in each field (previously undetected).  Spectral analysis indicates that 3 sources originate from x-ray diffuse halos associated with optically bright galaxies or groups of galaxies with kT~0.6-0.8 keV.  Other 3 sources are possibly group- and cluster-scale X-ray haloes with temperatures of ~1 keV and ~4 keV, respectively while the others are compact object origins such as AGNs.  All the 3 observed intracluster media within the junctions of the galaxy filaments previously found are involved in ongoing mergers.  Thus, demonstrate that deep X-ray observations at the filament junctions identified by galaxy surveys are a powerful mean to explore growing haloes in a hierarchical structure undetected so far.

1311.5223
Lyman-{\alpha} forest and cosmic weak lensing in a warm dark matter universe
Markovic, Viel

Review the current state of the theory of LSS in WDM: focus on the NL modeling of the matter PS and on the mass function of DM haloes.  Describe the results of N-body sims with WDM and mention the effects that could be induced by baryonic physics.  Also examine the halo model of LSS and its recently suggested modifications for a WDM cosmology, which account for the small scale smoothness of the initial matter density field and better fit the results of N-body sims.  Having describe the theoretical models, discuss the current lower limits on the WDM particle mass, m_w, which correspond to upper limits on the WDM temperature under the assumption that the particles are thermal relics.  The best such constraints come from the Lya forest and exclude all masses below 3.3 keV at the 2 sigma confidence level.  Finally review the forecasts for future lensing surveys, which will be of the same order of magnitude as the already existing constraints from the Lya forest data but explore a different redshift regime.

1311.5224
Consistent use of Type Ia supernovae highly magnified by galaxy clusters to constrain the cosmological parameters
Zitrin, Redlich, Broadhurst

Discuss how SNe Ia strongly magnified by FG galaxy clusters should be self-consistently treated when used in samples fitted for the cosmological parameters.  While the cluster lens magnification of a SN can be well constrained from sets of multiple images of various BG galaxies with measured redshifts, its value is typically dependent on the fiducial set of cosmological parameters used to construct the mass model to begin with [yikes].  In such cases, one should not naively demagnify the observed SN luminosity by the model magnification into the expected Hubble diagram, which would then create a bias, but take into account the cosmological parameters a-priori chosen to construct the mass model.  Quantify the effect and found that a systematic error of typically a few percent, up to a few-dozen precent, per magnified SN, may be propagated onto a cosmological parameter fit, unless the cosmology assumed for the mass model is taken into account (the bias can be even larger if the SN is lying very near the critical curves).  Also simulate how such a bias propagates onto the cosmological parameter fit using the Union2.1 sample, supplemented with strongly magnified SNe.  The resulting bias on the deduced cosmological parameters is generally at the few percent level, if only few biased SNe are included, and increasing with the number of lensed SNe and their redshift.  Samples containing magnified SNe Ia, e.g., from ongoing cluster surveys, should readily account for this possible bias.