Day 1362

Wednesday.

1801.08001
Curvature from strong gravitational lensing: a spatially closed Universe or systematics?
Li, et al

Model-independent constraints on the spatial curvature are not only closely related to important problems such as the evolution of the Universe and properties of DE, but also provide a test of the validity of the fundamental Copernican principle.  In this paper, with the distance sum rule in the Friedmann-Lemaitre-Robertson-Walker metric, achieve model-independent measurements of the spatial curvature from the latest type Ia SNe and SL observations.  Find that a spatially closed Universe is preferred.  Moreover, by considering different kinds of velocity dispersion and subsample, study possible factors which might affect model-independent estimations for the spatial curvature from SL observations.  It is suggested that the combination of observational data from different surveys might cause a systematic bias and the tension between the spatially flat Universe and SL observations is alleviated when the subsample only from the Sloan Lens ACS Survey is used or a more complex treatment for the density profile of lenses is considered.


1801.08559
The impact of baryons on the matter power spectrum from the Horizon-AGN cosmological hydrodynamical simulation
Chisari, et al

Accurate cosmology from upcoming WL surveys relies on knowledge of the total matter power spectrum at percent level at scales k<10 h/Mpc, for which modeling the impact of baryonic physics is crucial.  Compare measurements of the total matter power spectrum from the Horizon cosmological hydrodynamical simulations.  A DM-only run, one with full baryonic physics, and another lacking AGN feedback.  Baryons cause a suppression of power at k~=10 h/Mpc of <15% at z=0, and an enhancement of a factor of a few at smaller scales due to the more efficient cooling and SF.  The results are sensitive to the presence of the highest mass haloes in the simulation and the distribution of DM is also impacted up to a few percent.  The redshift evolution of the effect is non-monotonic throughout z=0-5 due to an interplay between AGN feedback and gas pressure, and the growth of structure.  Investigate the effectiveness of the "baryonic correction model" proposed by Schneider & Teyssier (2015) in describing the results.  Require a different redshift evolution and propose an alternative fitting function with 4 free parameters that reproduces the results within 5%.  Compared to other simulations, find the impact of baryonic processes on the total matter power spectrum to be smaller at z=0.  Nevertheless, the results also suggest that AGN feedback is not strong enough in the simulation.  Total matter power spectra from the Horizon simulations are made publicly available at https://www.horizon-simulation.org/catalogues.html.


1801.09070
Fast cosmic web simulations with generative adversarial networks
Rodriguez, et al

DM in the universe evolves through gravity to form a complex network of haloes, filaments, sheets and voids, that is known as the cosmic web.  Computational models of the underlying physical processes, such as classical N-body simulations, are extremely resource intensive, as they track the action of gravity in an expanding universe using billions of particles as tracers of the cosmic matter distribution.  Therefore, upcoming cosmology experiments will face a computational bottleneck that may limit the exploitation of their full scientific potential.  To address this challenge, demonstrate the application of a machine learning technique called Generative Adversairal Networks (GAN) to learn models that can efficiently generate new, physical realistic realizations of the cosmic web.  The training set is a small, representative sample of 2D image snapshots from N-body sims of size 500 and 100 Mpc.  Show that the GAN-produced results are qualitatively and quantitatively very similar to the originals.  Generation of a new cosmic web realization with a GAN takes a fraction of a second, compared to the many hours needed by the N-body technique.  Anticipate that GANs will therefore play an important role in providing extremely fast and precise simulations of cosmic web in the era of large cosmological surveys, such as Euclid and LSST.

Day 1361

Thursday (1/18) - Wednesday (1/24), Thursday, Friday.  Monday, Tuesday.

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.

Day 1360

Wednesday (1/10) - Wednesday (1/17).

1801.02634
The Astropy Project: building an inclusive, open-science project and status of the v2.0 software
Price-Whelan, et al

The Astropy project supports and fosters the development of open-source and openly-developed Python packages that provide commonly-needed functionality to the astronomical community.  A key element of the Astropy project is the core package Astropy, which serves as the foundation for more specialized projects and packages.  In this article, provide and overview of the organization of the Astropy project and summarize key features in the core package as of the recent major release, version 2.0.  Then describe the project infrastructure designed to facilitate and support development for a broader ecosystem of inter-operable packages.  Conclude with a future outlook of planned new features and directions for the broader Astropy project.


1801.03009
Predicting the binary black hole population of the Milky Way with cosmological simulation
Lamberts, et al

Binary BHs are the primary endpoint of massive stellar evolution.  Their properties provide a unique opportunity to constraint binary evolution, which is still poorly understood.  In this paper, predict the inventory of binary BHs and their merger products in/around the MW, and detail their main properties.  Present the first combination of a high-res cosmo sim of a MW-mass galaxy with a binary population synthesis model.  The hydrodynamicsimulation, taken from the FIRE project, provides a cosmologically realistic SFH for the galaxy and its stellar halo and satellites.  Apply a metallicity-dependent evolutionary model to the star particles to produce individual binary BHs.  Find that a million binary BHs have merged in the model Milky Way, and 3 million binary are still present, with an average mass of 28 Msun per binary.  Because the BH progenitors are biased towards low metallicity stars, half reside in the stellar halo and satellites and 40% of the binaries were formed outside the main galaxy.  This trend increases with the masses of the BHs.  The numbers and mass distribution of the merged systems is compatible with the LIGO/Virgo detections.  Observations of these BHs will be challenging, both with EM methods and LISA.  Find that a cosmologically realistic SFH, with self-consistent metal enrichment and Galactic accretion history, are key ingredients for determining binary BH rates that can be compared with observations to constrain massive binary evolution.


1801.03103
A candidate $z/sim10$ galaxy strongly lensed into a spatially resolved arc
Salmon, Coe, et al

The most distant galaxies known are at z~10-11, observed 400-500 Myr after the Big Bang.  The view z~10-11 candidates discovered to date have been exceptionally small -- barely resolved, if at all, by HST.  Here, present the discovery of SPT0615-JD, a fortuitous z~10 (z_poht-9.9±0.6) galaxy candidate stretched into an arc over ~2.5" by the effects of SL.  Discovered in the Reionization Lensing Cluster Survey (RELICS) Hubble Treasury program wand companion S-RELICS Spitzer program, this candidate has a lensed H-band magnitude of 25.7±0.1 AB mag.  With a magnification of mu~4-7 estimated from the lens models, the de-lensed intrinsic magnitude is 27.6±0.3 AB mag, and the half-light radius is r_e<0.8 kpc, both consistent with other z>9 candidates.  The inferred stellar mass [log (M*/Msun)]=9.7^0.7_-0.5 and SFR log [SFR/Msun yr^-1]=1.3+0.2_-0.3 indicate that this candidate is a typical SF galaxy on the z>6 SFR-M* relation.  Note that three independent lens models predict two counter images, at least one of which should be of a similar magnitude to the arc, but these counter images are not yet detected.  Counterimages would not be expected if the arc were at lower redshift.  However, the only spectral energy distributions capable of fitting the Hubble and Spitzer photometry well at lower redshifts require unphysical combinations of z~2 galaxy properties.  The unprecedented lensed size of the z~10 candidate offers the potential for the JWST to study the geometric and kinematic properties of a galaxy observed 500 Myr after the Big Bang.


1801.03555
Galactic Reddening in 3D from stellar photometry - An improved map
Green, Schlafly, Finkbeiner, Nix, et al

Present a new 3D map of interstellar dust reddening, covering 3 quarters of the sky (declinations greater than -30 deg) out to a distance of several kilo parsecs.  The map is based on high-quality stellar photometry of 800 million stars from Pan-STARRS 1 and 2MASS.  Divide the sky into sightlines containing a few hundred stars each, and then infer stellar distances and types, along with the line-of-sight dust distribution.  The new map incorporates a more accurate average extinction law and an additional 1.5 years of Pan-STARRS 1 data, tracing dust to greater extinctions and at higher angular resolutions than the previous map.  Out of the plane of the Galaxy, the map agrees well with 2D reddening maps derived from FIR dust emission.  After accepting for a 15% difference in scale, find a mean scatter of 10% between the map and the Planck FIR emission-based dust map, out to a depth of 0.8 mag in E(r-z), with the level of agreement varying over the sky.  The map can be downloaded at http://argonaut.skymaps.info, or by it sDOI: 10.7910/DVN/LCYHJG.


1801.03941
Full-sky ray-tracing simulation of weak lensing using  ELUCID simulations: exploring galaxy intrinsic alignment and cosmic shear correlations
Wei, et al

The IA of galaxies is an important systematic effect in WL surveys, which can affect the derived cosmological parameters.  One direct way to distinguish different alignment models and quantify their effects on the measurement is to produce mock WL surveys. In this work, use full-sky ray-tracing technique to produce mock images of galaxies from the ELUCID N-body sims run with the WMAP9 cosmology.  The model assumes that the shape of central elliptical galaxy follows that of the DM halo, and spiral galaxy follows the halo spin. Using the mock galaxy images, a combination of galaxy intrinsic shape and the gravitational shear, compare the predicted tomographic shear correlation to the results of KiDS and DLS.  It is found that the predictions stay between the KiDS and DLS results.  Rule out a model in which the satellite galaxies are radially aligned with the center galaxy, otherwise the shear-correlations on small scales are too high.  Most importantly, find that although the IA of spiral galaxies is very weak, they induce a positive correlation between the gravitational shear signal and the intrinsic galaxy orientation (GI).  This is because the spiral galaxy is tangentially aligned with the nearby large-scale overdensity, contrary to the radial alignment of elliptical galaxy.  The results explain the origin of detected positive GI term from the WL surveys.  Conclude that in future analysis, the GI model must include the dependence on galaxy types in more detail.  And the full-sky mock data introduced in this work can be available if you are interesting.  :D


1801.xxxxx
The CosmicWatch desktop muon detector: a self-contained, pocket sized particle detector
Axani, Frankiewicz, Conrad

The CosmicWatch Desktop Muon Detector is a self-contained, hand-held cosmic ray muon detector that is valuable for astro/particle physics research applications and outreach.  The material cost of each detector is under $100 and it takes a novice student approximately four hours to build their first detector.  The detectors are powered via a USB connection and the data can either be recorded directly to a computer or to a microSD card.  Arduino- and Python-based software is provided to operate the detector and an online application to plot the data in real-time.  In this paper, describe the various design features, evaluate the performance, and illustrate the detectors capabilities by providing several example measurements.

Day 1359

Tuesday.

1801.01883
Evidence for radial variations in the stellar mass-to-light ratio of massive galaxies from weak and strong lensing
Sonnenfeld, Leauthaud, et al

The IMF for massive galaxies can be constrained by combining stellar dynamics with strong gravitational lensing.  However, this method is limited by degeneracies between the density profile of DM and the stellar mass-to-light ratio.  In this work, reduce this degeneracy by combining WL together with SL and stellar kinematics.  The analysis is based on two galaxy samples: 45 SL from the SLACS survey and 1700 massive quiescent galaxies from the SDSS main spectroscopic sample with WL measurements from the HSC survey.  Use a Bayesian hierarchical approach to jointly model all 3 observables.  Fit the data with models of varying complexity and show that model with a radial gradient in the stellar mass-to-light ratio is required to simultaneously describe both galaxy samples.  Models with no gradient result in too small dark matter masses when fitted to the SL sample, at odds with WL constraints.  The measurements are unable to determine whether M*/L gradients are due to variations in stellar population parameters at fixed IMF, or to gradients in the IMF itself.  The inclusion of M*/L gradients decreases dramatically the inferred IMF normalization, compared to previous lensing-based studies. The main effect of strong lensing selection is to shift the stellar mass distribution towards the high mass end, while the halo mass and stellar IMF distribution at fixed stellar mass are not significantly affected.


1801.01886
Weak lensing peaks in simulated light-cones: Investigating the coupling between dark matter and dark energy
Giocoli, et al

In this paper, study the statistical properties of WL peaks in light-cones generated from numerical simulations.  Focus on interacting DE cosmological models, characterized by a coupling term between DE and DM which allows studies of how such an interaction affects a particular second-order WL statistics.  Cosmological models characterized by a a larger population of massive clusters tend to also have more numerous high signal-to-noise peaks; however structural properties like e.g. the halo concentration play an important role: models characterized by the same number of haloes possess more WL peaks if their haloes are more concentrated.  The various cosmological models exhibit large differences in peaks for high values of the S/N ratio, due to intervening massive haloes along the LoS, demonstrating a clear connection between peaks in the convergence field and galaxy clusters with M200>=1e14 Msun/h.  The most extreme model under investigation shows a difference of about 20% with respect to the reference LCDM model and a clearly different behavior with respect to the LCDM model with the same power spectrum normalization, proving that different expansion histories and growth rates produce a clear signature on peak properties.  The analysis underscores the point that WL peak statistics represent an important tool for disentangling DE models by accurately tracing the structure formation processes as a function of the comic time.  Stress its complementary to cosmic shear measurements.

Day 1358

Friday.  Monday.

1801.01120
New parallaxes of galactic Cepheids from spatially scanning the Hubble Space Telescope: Implications for the Hubble constant
Riess, et al

New parallax measurements of 7 long-period (>10 ays) MW Cepheids using astrometry from spatial scanning of WFC3 on HST.  Observations were obtained at 6 month intervals over 4 years.  The distances are 1.7--3.6 kpc with a mean precision of 45 microarcseconds and a best of 29 microarcseconds (SNR=14).  The accuracy of the parallaxes is demonstrated through independent analyses of >100 reference stars.  This raises to 10 the number of long-period Cepheids in the hosts of 19 SNeIa.  This sample addresses two outstanding systematic uncertainties affecting prior comparisons of MW and extragalactic Cepheids used to calibrate H0: their dissimilarity of ladder gives a ratio (or independent scale for H0) of 1.034±0.036, consistent with no change and inconsistent at the 3.3 sigma level with a ratio of 0.91 needed to match the value predicted by Planck+LCDM.  Using these data instead to augment the Riess+2016 measurement of H0 improves the precision to 2.3%, yielding 73.45±1.66 km/s/Mpc, and tension with Planck+LCDM increases to 3.7 sigma.  The future combination of Gaia parallaxes and HST spatial scanning photometry of 50 MW Cepheids can support a <1% calibration of H0.


1801.01257
Testing weak equivalence principle with strongly lensed cosmic transients
Yu, Wang

Compare the time delays between lensed images seen in different energy bands, or in gravitational waves (GWs) and their electromagnetic (EM) counterparts in strongly lensed cosmic transients, to robustly test for WEP.  If the time delay of cosmic transient can be measured with accuracy about 0.1s, show that the upper limit on the differences of the parameterized post-Newtonian parameter gamma values is Delta gamma <1e-7 with a one-month strong lensing time delay event.  This accuracy of WEP can be improved by a a factor of 1e7, if the leasing is a galaxy cluster and the strongly lensed cosmic transients have much shorter duration, such as fast radio bursts.


1801.01474
Galactic effects on habitability
Kaib

The galactic environment has been suspected to influence planetary habitability in many ways.  Very metal-poor regions of the Galaxy (those largely devoid of atoms more massive than H and He) are thought to be unable to form habitable planets.  Moreover, if such planets do form, the young system is subjected to close stellar passages while it resides in its stellar birth cluster.  Various potential hazards remain after clusters disperse.  For instance, central galactic regions may present risks to habitability via nearby supernovae, GRBs, and frequent comet showers.  In addition, planets residing within very wide binary star systems are affected by the Galaxy, as local gravitational perturbations from the Galaxy can increase the binary's eccentricity until it destabilizes the planets it hosts.  Here, review the most recent work on the main galactic influences over planetary habitability.  Although there must be some metallicity limit below which rocky planets cannot form, recent exoplanet surveys show that they form around stars with a very large range of metallicities.  Once formed, the probability of star clusters destabilizing planetary systems only becomes high for rare, extremely long-lived clusters.  Regarding threats to habitability from supernovae, GRBs, and comet showers, many recent studies suggest that their hazards are more limited than originally thought.  Finally, denser regions of the Galaxy enhance the threat that very wide binary companions pose to planetary habitability, but the probability that a very wide binary star disrupts habitability will always be substantially below 100% for any environment.  While some MW regions must be more hospitable to habitable planets than others, it is difficult to state that habitable planets are confined to any well-defined regions of the Galaxy or that any other particular region of the Galaxy is uninhabitable.


1801.01506
Time Delay lens modeling challenge: I. Experimental Design
Ding, Treu, et al

Following the experience of the past challenge on time delay, where it was shown that time delays can indeed be measured precisely and accurately at the sub-percent level, now present the "Time Delay Lens Modeling Challenge" (TDLMC).  The goal of this challenge is to assess the present capability of lens modeling codes and assumptions and test the level of accuracy of inferred cosmological parameters given realistic mock datasets.  Invite scientists to model a set of simulated HST observations of 50 mock lens systems .  The systems are organized in rungs, with the complexity and realism increasing going up the ladder.  The goal of the challenge is to infer H0 for each rung, given the HST images, the time delay, and a stellar velocity dispersion of the deflector, for a fixed background cosmology.  The TDLMC challenge will start with the mock data release on 2018 January 8th, with a deadline for blind submission of 2018 August 8th.  This first paper gives an overview of the challenge including the data design, and a set of metrics to quantify the modeling performance and challenge details.  After the deadline, the results of the challenge will be presented in a companion paper with all challenge participants as co-authors.

Day 1357

Thursday.

1801.00792
SDSS-IV MaNGA: Galaxy pair fraction and correlated active galactic nuclei
Fu, et al

Identified 105 galaxy pairs at z~0.04 with the MaNGA integral-field spectroscopic data.  The pairs have projected separations between 1kpc and 30 kpc, and are selected to have radial velocity offsets less than 600 km/s and stellar mass ratio between 0.1 and 1.  The pair fraction increases with both the physical size of the IFU and the stellar mass, consistent with theoretical expectations.  Provide the best-fit analytical function of the pair fraction and find that ~3% of M* galaxies are in close pairs.  For both isolated galaxies and paired galaxies, AGN are selected using emission-line ratios and H-alpha equivalent widths measured inside apertures at a fixed physical size.  Find AGNs in ~24% of the paired galaxies and binary AGNs in ~13% of the pairs.  To account for the selection biases in both the pair sample and the MaNGA sample, compare the AGN comoving volume densities with those expected from the mass- and redshift-dependent AGN fractions.  Find a strong (~5x) excess of binary AGNs over random pairing and a mild (~20%) deficit of single AGNs.  The binary AGN excess increases from ~2x to ~6x as the projected separation decreases from 10-30 kpc to 1-10 kpc.  The results indicate that pairing of galaxies preserves the AGN duty cycle in individual galaxies but increases the population of binary AGNs through correlated activities.  Suggest tidally-induced galactic-scale shocks and AGN cross-ionization as two plausible channels to produce low-luminosity narrow-line-selected binary AGNs.

Day 1356

Monday, 2018.  (Tuesday,) Wednesday.

1801.00052
The astrobiology of the Anthropocene
Haqq-Misra, et al

Human influence on the biosphere has been evident at least since the development of widespread agriculture, and some stratigraphers have suggested that the activities of modern civilization indicate a geological epoch transition.  The study of the anthropocene as a geological epoch, and its implication for the future of energy-intensive civilizations, is an emerging transdisciplinary field in which astrobiology can play a leading role.  Habitability research of Earth, Mars, and exoplanets examines extreme cases relevant for understanding climate change as a planetary process.  Energy-intensive civilizations will also face thermodynamic limits to growth, which provides an important constraint for estimating the longevity of human civilization and guiding the search for extraterrestrial intelligence.  Recommend that missions concepts such as LUVOIR, HabEx, and OST be pursued in order to make significant progress toward understanding the future evolution of life on the planet and the possible evolution of technological, energy-intensive life elsewhere in the universe.