1810.05745
Fast generation of covariance matrices for weak lensing
Sgier, Referier, Amara, Nicola
Upcoming weak lensing surveys will probe large fractions of the sky with unprecedented accuracy. To infer cosmological constraints, a large ensemble of survey simulations are required to accurately model cosmological observables and their covariances. Develop a parallelized multi-lens-plane pipeline called UFalcon, designed to generate full-sky weak lensing maps from light cones within a minimal runtime. It makes use of L-PICOLA, an approximate numerical code, which provides a fast and accurate alternative to cosmological N-body sims. The UFalcon maps are constructed by nesting 2 simulations covering a redshift-range from z=0.1 to 1.5 without replicating the simulation volume. Compute the convergence and projected overdensity maps for L-PICOLA in the light cone or snapshot mode. The generation of such a map, including the L-PICOLA simulation, takes about 3 hrs wall time on 220 cores. Use the maps to calculate the spherical harmonic power spectra, which is compared to theoretical predictions and to UFalcon results generated using the full N-body code GADGET-2. Then compute the covariance matrix of the full-sky spherical harmonic power spectra using 150 UFalcon maps based on L-PICOLA in light cone mode. Consider the PDF, the higher-order moments and the variance of the smoothed field variance to quantify the accuracy of the covariance matrix, which is found to be a few percent for scales ell~1e2 to 1e3. Test the impact of this level of accuracy on cosmological constraints using an optimistic survey configurations, and find that the final results are robust to this level of uncertainty. The speed and accuracy of the developed pipeline provides a basis to also include further important features such as masking, varying noise and will allow to compute covariance matrices for models beyond LCDM.
1801.xxxxx
Observation of new properties of secondary cosmic rays Lithium, Beryllium, and Boron by the Alpha Magnetic Spectrometer on the International Space Station
Aguilar, et al
Report on the observation of new properties of secondary cosmic rays Li, Be, and B measured in the rigidity (momentum per unit charge) range 1.9 GV to 3.3 TV with a total of 5.4x106 nuclei collected by AMS during the first 5 years of operation aboard the ISS. The Li and B fluxes have an identical rigidity dependence above 7 GV and all 3 fluxes have an identical rigidity dependence above 30 GV with the Li/Be flux ratio of 2.0±0.1. The 3 fluxes deviate from a single power law above 200 GV in an identical way. This behavior of secondary CRs has also been observed in the AMS measurement of primary CRs He, C, and O but the rigidity dependences of primary CRs and of secondary CRs are distinctly different. In particular, above 200 GV, the secondary CRs harden more than the primary CRs.
1801.05814
Finding mountains with molehills: the detectability of Exotophography
McTier, Kipping
Consider whether these is any prospect of remotely detecting exoplanet topography. A simple approach to detect and quantify topographical features on the surfaces of exoplanets using transit light curves --- if a planet rotates as it transits its parent star, its changing silhouette yields a time-varying transit depth, which can be observed as an apparent and anomalous increase in the photometric scatter. Using elevation data for several rocky bodies in the Solar System, quantify each world's surface integrated release with a "bumpiness" factor, and calculate the corresponding photometric scatter expected during a transit. Describe the kinds of observations that would be necessary to detect topography in the ideal case of Mars transiting a nearby white dwarf star. If such systems have a conservative occurrence rate of 10%, estimate that the upcoming Colossus or OWL telescopes would be able to detect topography with <20 hours of observing time, which corresponds to ~400 transits with a duration of 2 minutes and orbital period of ~10 hours.
1801.07202
Dependence of the onset of the runaway greenhouse effect on the latitudinal surface water distribution of Earth-like planets.
Kodama, et al
The results indicate that the inner edge of the habitable zone is not a single shape boundary, but a border whose location varies depending on planetary surface condition, such as the amount of surface water. Since land planets have wider habitable zones and less cloud cover, land planets would be good targets for future observations investigating planetary habitability.
1801.07260
Does the Hubble constant tension call for new physics?
Mörtsell, Dhawan
The LCDM model represents the current standard model in cosmology. Within this, there is a tension between the value of the Hubble constant, H0, inferred from local distance indicators and the angular scale of fluctuations n the CMB. Investigate whether the tension is significant enough to warrant new physics in the form of modifying or adding energy components to the standard cosmological model. Find that late term DE explanations are slightly disfavored whereas a pre-CMB decoupling extra DE component has a marginally positive Bayesian evidence. A constant equation of state of the additional early energy density is constrained to 0.086+0.04-0.03. Although this value deviates significantly from 1/3, valid for dark radiation, the latter is not disfavored based on the Bayesian evidence. If the tension persists, future estimates of H0 at the 1% level will be able to decisively determine which of the proposed explanations is favored.
1801.07262
Cosmological distance indicators
Suyu, et al
Review 3 distance measurement techniques beyond the local universe: (1) gravitational lens time delays, (2) baryon acoustic oscillation (BAO), and (3) HI intensity mapping. Describe the principles and theory behind each method, the ingredients needed for measuring such distances, the current observational results, and future prospects. Time delays from strongly lensed quasars currently provide constraints on H0 with <4% uncertainty, and with 1% within reach from ongoing surveys and efforts. Recent exciting discoveries of strong lensed SNe hold great promise for time-delay cosmography. BAO features have been detected in redshift surveys up to z<~0.8 with galaxies and z~2 with Ly-alpha forest, providing precise distance measurements and H0 with <2% uncertainty in flat LCDM. Future BAO surveys will probe the distance scale with percent-level precision. HI intensity mapping has great potential to map BAO distances at z~0.8 and beyond with precisions of a few percent. The next years ahead will be exciting as various cosmological probes reach 1% uncertainty in determining H0, to assess the current tension in H0 measurements that could indicate new physics.
1801.07333
Life beyond the Solar System: space weather and its impact on habitable worlds
Airapetian, et al
The search of life in the Universe is a fundamental problem of astrobiology and a major priority for NASA. A key area of major progress since the NASA Astrobiology Strategy 2015 (NAS15) has been a shift from the exoplanet discovery phase to a phase of characterization and modeling of the physics and chemistry of exoplanetary atmospheres, and the development of observational strategies for the search for life in the Universe by combining expertise from four NASA science disciplines including heliophysics, astrophysics, planetary science and Earth science. The NASA Nexus for Exoplanetary System Science (NExSS) has provided an efficient environment for such interdisciplinary studies. Solar flares, coronal mass ejections and solar energetic particles produce disturbances in interplanetary space collectively referred to as space weather, which interacts with the Earth upper atmosphere and causes dramatic impact on space and ground-based technological systems. Exoplanets within close in habitable zones around M dwarfs and other active stars are exposed to extreme ionizing radiation fluxes, thus making exoplanetary space weather (ESW) effects a crucial factor of habitability. In this paper, describe the recent developments and provide recommendations in this interdisciplinary effort with the focus on the impacts of ESW on habitability, and the prospects for future progress in searching for signs of life in the Universe as the outcome of the NExSS workshop held in Nov 29-Dec 2, 2016, New Orleans, LA. This is one of five Life Beyond the Solar System white papers submitted by NExSS to the National Academy of Sciences in support of the Astrobiology Science Strategy for the Search for Life in the Universe.
1801.07810
Life Beyond the Solar System: Observation and Modeling of Exoplanet Environments
Del Genio, et al
Describe recent developments in these other [other than planetary science, heliophysics, Earth science, probably] disciplines, wit ha focus on exoplanet properties and environments, and the prospects for future progress that will be achieved by integrating emerging knowledge from astrophysics with insights from these fields.
1801.07811
Life Beyond the Solar System: Technology Needs
Siegler, et al
Outlines the key technology challenges pertaining to the remote search for life in extrasolar planetary systems.
1801.08240
First release of high-redshift super luminous supernovae from the Subaru High-~sUpernova Campaign (SHIZUCA). I. Photometric properties
Moriya, Tanaka, et al
Report the first discoveries of high-z She from SHIZUCA, a transient survey using Subaru/HSC. Report the discovery of 3 SNe at spectroscopically-confirmed redshifts of 2.399, 1.965, and 1.851, and two supernova candidates with host galaxy photometric redshifts of 3.2 and 4.2, respectively. In this paper, present their photometric properties, and the spectroscopic properties of the confirmed high-z SNe are presented in the accompanying paper (Curtin+2018). The SNe with the confirmed z of z~2 have rest UV peak magnitudes of around -21 mag, which make them super luminous SNe. The discovery of 3 SNe at z~2 roundly corresponds to an event rate of ~900 Gpc^-3 yr^-1, which is already consistent with the total super luminous SN rate estimated by extrapolating the local rate based on the cosmic SFH. Adding unconfirmed super luminous SN candidates would increase the event rate. The super luminous SN candidates at the redshift of around 3 and 4 indicate minimum SSN rates of ~400 Gpc^-3 yr^-1 (z~3) and ~500 Gpc^-3 yr^-1 (z~4). Because we have only performed a pilot search for high-z SN so far and have not completed selecting all the high-z SN candidates, these rates are lower limits. The initial results demonstrate the amazing capability of HSC to discover high-z SNe.
1801.08547
Inferring binary and trinity stellar populations
Widmark, Leistest, Hogg
Multiple stellar systems are ubiquitous in the MW, but are often unresolved and seen as single objects in spectroscopic, photometric, and astrometric surveys. Yet, modeling them is essential for developing a full understanding of large surveys such as Gaia, and connecting them to stellar and Galactic models. In this paper, address this problem by jointly fitting the Gaia and 2MASS photometric and astrometric data using a data-driven Bayesian hierarchical model that includes populations of binary and trinity systems. This allows us to classify observations into singles, binaries and trinities, in a robust and efficient manner, without resorting to external models. Able to identify multiple systems and, in some cases, make strong predictions for the properties of its unresolved stars. Will be able to compare such predictions with Gaia DR4, which will contain astrometric identification and analysis of binary systems.
1801.08945
Improving weak lensing mass map reconstructions using Gaussian and sparsity proiors: application to DES SV
Jeffrey, Abdallah, Lahav, Lanusse, Starck, et al
Mapping the underlying density field, including non-visible DM, using WL measurements is now a standard tool in cosmology. Due to its importance to the science results of current and upcoming surveys, the quality of the convergence reconstruction methods should be well understood. Compare 3 different mass map reconstruction methods: KS (Kaiser-Squires), Wiener filter, and GLIMPSE. KS is a direct inversion method, taking no account of survey masks or noise. The Wiener filter is well motivated for Gaussian density fields in a Bayesian framework. The GLIMPSE method uses sparsity, with the aim of reconstructing nonlinearities in the density field. Compare these methods with a series of tests on the public DES SV data and on realistic DES simulations. The Wiener filter and GLIMPSE methods offer substantial improvement on the standard smoothed KS with a range of metrics. For both the Wiener filter and GLIMPSE convergence reconstructions, present a 12% improvement in Pearson correlation with the underlying truth from simulations. To compare the mapping methods abilities to find mass peaks, measure the difference between peak counts from simulated LCDM shear catalogs and catalogues with no mass fluctuations. This is a standard data vector when inferring cosmology from peak statistics. The maximum S/N value of these peak statistic data vectors was increased by a factor of 3.5 for the Wiener filter and by a factor of 9 using GIMPSE. With simulations, measure the reconstruction of the harmonic phases, showing that the concentration of the phase residuals is improved 17% by GLIMPSE and 18% by the Wiener filter. Show that the correlation between the reconstructions from data and the foreground redMaPPer clusters is increased 18% by the Wiener filter and 32% by GLIMPSE.
1801.09146
Different is more : the value of finding an inhabited planet that is far from earth 2.0
Lenardic, Seales
The search for an inhabited planet, other than our own, is a driver of planetary exploration in out solar system and beyond. Using information from our own planet to inform search strategies allows for a targeted search. It is, however, worth considering some span in the strategy and in a priori expectation. An inhabited Earth-like planet is one that would be similar to Earth in ways that extend beyond having biota. To facilitate analysis, introduce a metric that extends from zero, for an inhabited planet that is like Earth in all other regards (i.e., zero differences), toward positive or negative values for planets that differ from Earth. The analysis shows how assessment of life potential in our galaxy changes more significantly if we find an inhabited planet that is less Earth-like (i.e., it quantifies how probability assessments improve with deviations from Earth-likeness). Discovering such planets could also provide a test of the strong form of the Gaia hypothesis - a test that has proved difficult using only the Earth as a laboratory. Lastly, discuss how an Earth2.0 narrative, that has been presented to the public as a search strategy, comes with nostalgia-laden philosophical baggage that does not best serve exploration.
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