Day 1765

Tuesday.

2010.01138

Dark Energy Survey Year 1 Results: cosmological constraints from cluster abundances, weak lensing, and galaxy correlations

Combining multiple observational probes is a powerful technique to provide robust and precise constraints on cosmological parameters. In this letter, we present the first joint analysis of cluster abundances and auto/cross correlations of three cosmic tracer fields measured from the first year data of the Dark Energy Survey: galaxy density, weak gravitational lensing shear, and cluster density split by optical richness. From a joint analysis of cluster abundances, three cluster cross-correlations, and auto correlations of galaxy density, we obtain Ωm=0.305+0.055−0.038 and σ8=0.783+0.064−0.054. This result is consistent with constraints from the DES-Y1 galaxy clustering and weak lensing two-point correlation functions for the flat nuΛ  CDM model. We thus combine cluster abundances and all two-point correlations from three cosmic tracer fields and find improved constraints on cosmological parameters as well as on the cluster observable--mass scaling relation. This analysis is an important advance in both optical cluster cosmology and multi-probe analyses of upcoming wide imaging surveys.

2010.01346

Period change of binary pulsars due to the accretion of dark matter particles

Hassani, et al

As binary systems move inside galaxies, they interact with the dark matter halo. This interaction leads to the accretion of dark matter particles inside binary components. The accretion of dark matter particles increases the mass of the binary components and then, the total mass of the system. Increased mass by this way can affect other physical parameters of the systems, like orbital periods of the systems. In this work, we estimated the period change of some known compact binary systems due to the accretion of dark matter particles inside them. Our conclustion is that, for WIMP particles with masses in the range $\simeq 10 \: GeV.c^{-2}$ and dark matter density as high as the dark matter density around the sun, period change due to accretion of dark matter partices is negligible compared to the period change due to the emission of gravitaional waves from the systems.

2010.02133

Spectropolarimetry of primitive phototrophs as global surface biosignatures

Sparks, et al

Photosynthesis is an ancient metabolic process that began on the early Earth, offering plentiful energy to organisms that utilize it, to the extent that they can achieve global significance. The potential exists for similar processes to operate on habitable exoplanets and result in observable biosignatures. Prior to the advent of oxygenic photosynthesis, the most primitive phototrophs, anoxygenic phototrophs, dominated surface environments on the planet. Here, we characterize surface polarization biosignatures associated with a diverse sample of anoxygenic phototrophs and cyanobacteria, examining both pure cultures and microbial communities from the natural environment. Polarimetry is a tool that can be used to measure the chiral signature of biomolecules. Chirality is considered a universal, agnostic biosignature that is independent of a planet's biochemistry, receiving considerable interest as a target biosignature for life detection missions. In contrast to preliminary indications from earlier work, we show that there is a diversity of distinctive circular polarization signatures, including the magnitude of the polarization, associated with the variety of chiral photosynthetic pigments and pigment complexes of anoxygenic and oxygenic phototrophs. We also show that the apparent death and release of pigments from one of the phototrophs is accompanied by an elevation of the reflectance polarization signal by an order of magnitude, which may be significant for remotely detectable environmental signatures. This work and others suggest circular polarization signals up to ~1% may occur, significantly stronger than previously anticipated circular polarization levels. We conclude that global surface polarization biosignatures may arise from anoxygenic and oxygenic phototrophs, which have dominated nearly 80% of the history of our rocky, inhabited planet.