Day 1472

Monday.

1809.10744
Studying the solar system with the international pulsar timing array
Cabllero, et al

Pulsar-timing analyses are sensitive to errors in the solar-system ephemerides (SSEs) that timing models utilize to estimate the location of the solar-system barycentre, the quasi-inertial reference frame to which all recorded pulse times-of-arrival are referred.  Any error in the SSE will affect all pulsars, therefore pulsar timing arrays (PTAs) are a suitable tool to search for such errors and impose independent constraints on relevant physical parameters.  Employ the first data release of the international pulsar timing array to constrain the masses of the planet-moon systems and to search for possible unmodelled objects (UMOs) in the solar system.  Employ ten SSEs from 2 independent research groups, derive and compare mass constrains of planetary systems, and derive the first PTA mass constraints on asteroid-belt objects.  Constrains on planetary-system masses have been improved by factors of up to 20 from the previous relevant study using the same assumptions, with the mass of the Jovian system measured at 9.5479179(3)e-4 Msun.  The mass of the dwarf planet Ceres is measured at 4.7(4)e-10 Msun.  Also present the first sensitivity curves using real data that place generic limits on the masses of UMOs, which can also be used as upper limits on the mass of putative exotic objects.  For example, upper limits on dark-matter clumps are comparable to published limits using independent methods.  While the constraints on planetary masses derived with all employed SSEs are consistent, note and discuss differences in the associated timing residuals and UMO sensitivity curves.


1809.10747
Constraining neutrinos mass with tomographic weak lensing one-point probability distribution function and power spectrum
Liu, Madhavacheril

Study the constraints on neutrino mass sum (M_nu) from the 1pt probability distribution function (PDF) and power spectrum of weak lensing measurements for an LSST-like survey, using the MassiveNuS simulations.  The PDF provides access to non-Gaussian information beyond the power spectrum.  It is particularly sensitive to nonlinear growth on small scales, where massive neutrinos also have the largest effect.  Find that tomography helps improve the constraint on M_nu by 14% and 32% for the power spectrum and the PDF, respectively, compared to a single redshift bin.  The PDF alone outperformed the power spectrum in constraining M_nu.  When the two statistics are combined, the constraint is further tightened by 35%.  Conclude that WL PDF is complementary to the PS and has the potential to become a powerful tool for constraining neutrino mass.

Day 1471

Friday.

1809.10230
Microlensing path parameterization for Earth-like exoplanet detection around solar mass stars
de Almeida, do Nascimento

Propose a new parameterization of the impact parameter u0 and impact angle alpha for microlensing systems composed by an Earth-like Exoplanet around a Solar mass star at 1 AU.  Present the caustic topology of such system, as well as the related light curves generated by using such a new parameterization.  Based on the same density of points and accuracy of regular methods, obtain results 5 times faster for discovering Earth-like exoplanet.  In this big data revolution of photometric astronomy, the method will impact future missions like WFIRST (NASA) and Euclid (ESA) and their data pipelines, providing a rapid and deep detection of exoplanets for this specific class of microlensing event that might otherwise be lost.

Day 1470

Thursday.

1809.09116
The aftermath of the great collision between our galaxy and the Large Magellanic Cloud
Cautun, et al

The MW offers a uniquely detailed view of galactic structure and is often regarded as a prototypical spiral galaxy.  But recent observations indicate that the MW is atypical: it has an undersized supermassive black hole at its centre; it is surrounded by a very low mass, excessively metal-poor stellar halo; and it has an unusually large nearby satellite galaxy, the LMC.  Here, show that the LMC is on a collision course with the MW with which it will merge in 2.4+1.2-0.8 Gyrs (68% CL).  This catastrophic and long-overdue event will restore the MW to normality.  Using the EAGLE galaxy formation simulation, show that, as a result of the merger, the central supermassive black hole will increase in mass by up to a factor of 8.  The Galactic stellar halo will undergo an equally impressive transformation, becoming 5x more massive.  The additional stars will come predominantly from the disrupted LMC, but a sizable number will be ejected onto the halo from the stellar disc.  The post-merger stellar halo will have the median metallicity of the LMC, [Fe/H]=-0.5 dex, which is typical of other galaxies of similar mass to the MW.  At the end of this exceptional event, the MW will become a true benchmark for spiral galaxies, at least temporarily.


1809.10045
Weak lensing constraints on splash back around massive clusters
Contigiani, Hoekstra, Bahé

The splash back radius r_sp separates the physical regimes of collapsed and infalling material around massive DM haloes.  In cosmo sims, this location is associated with a steepening of the spherically averaged density profile rho(r).  In this work, measure the splash back feature in the stacked WL signal of 27 massive clusters from the CCCP with a careful control of residual systematics effects.  Find that the shear introduced by the presence of additional structure along the line of sight significantly affects the noise at large cluster centric distances.  Do not detect a significant steepening, but are able to constrain both r_sp=3.6+1.2-0.7 comoving Mpc and the value of the logarithmic slope gamma=log(rho) / log(r) at this point, gamma(r_sp)=-4.2+1.0-1.8.

Day 1469

Wednesday.

1809.09019
No evidence for modifications of gravity from galaxy motions on cosmological scales
He, Guzzo, Li, Baugh

The recent discovery of gravitational waves marks the culmination of a sequence of successful tests of GR since its formulation in 1915.  Yet these tests remain confined to the scale of stellar systems or the strong gravity regime.  A departure from GR on larger, cosmological scales has been advocated by the proponents of modified gravity theories as an alternative to the Cosmological Constant to account for the observed cosmic expansion history.  While indistinguishable in these terms by construction, such models on the other hand yield distinct values for the linear growth rate of density perturbations and, as a consequence, for the associated galaxy peculiar velocity field.  Measurements of the resulting anisotropy of galaxy clustering, when spectroscopic redshifts are used to derive distances, have thus been proposed as a powerful probe of the validity of GR on cosmological scales.  However, despite significant effort in modeling such redshift space distortions, systematic errors remain comparable to current statistical uncertainties.  Here, present the results of a different forward modeling approach, which fully exploits the sensitivity of the galaxy velocity field to modifications of GR.  Use state-of-the-art, high-resolution N-body sims of a standard GR and a compelling f(R) model, one of GR's simplest variants, to build simulated catalogues of stellar-mass-selected galaxies through a robust match to the SDSS observations.  Find that, well within the uncertainty of this technique, f(R) fails to reproduce the observed z-space clustering on scales 1-10 Mpc/h.  Instead, the standard LCDM GR model agrees impressively well with the data.  This results provides a strong confirmation, on cosmological scales, of the robustness of Einstein's GR.


1809.09148
Cosmology from cosmic shear power spectra with Subaru Hyper SUprime-Cam first-year data
Hikage, Oguri, Hamana, More, Mandelbaum, Takada, Köhlinger, Miyatake, et al

Measure cosmic WL shear power spectra with HSC survey first-year shear catalog covering 137 deg^2 of the sky.  Thanks to the high effective galaxy number density of 16.5 arcmin^{-2} even after conservative cuts such as i<24.5 and photometric z cut of 0.3 <= z <= 1.5, obtain a high significance measurement of the cosmic shear power spectra in 4 tomographic z bins, achieving a total S/N of 16 in the multipole range 300 <= ell <= 1900.  Carefully account for various uncertainties in the analysis including the intrinsic alignment of galaxies, scatters and biases in photometric z's, residual uncertainties in the shear measurement, and modeling of the matter PS.  The accuracy of the PS measurement method as well as the analytic model of the covariance matrix are tested against realistic mock shear catalogs.  For a flat LCDM model, find S_8 == sigma_8 (Omega_m/0.3)^alpha = 0.800+0.029-0.028 for alpha = 0.45 (S_8=0.780+0.030-0.033 for alpha=0.5) from the HSC tomographic cosmic shear analysis alone.  In comparison with Planck CMB constraints, the results prefer slightly lower values of S_8, although metrics such as the Bayesian evidence ratio test do not show significant evidence for discordance between these results.  Study the effect of possible additional systematic errors that are unaccounted in the fiducial cosmic shear analysis, and find that they can shift the best-fit values of S_8 by up to ~0.6 sigma.  The full HSC survey data will contain several times more area, and will lead to significantly improved cosmological constraints.


1809.09540
The effects of calibration on the bias of shear measurements
Gillis, Taylor

Forthcoming large-scale surveys will soon attempt to measure cosmic shear to an unprecedented level of accuracy, requiring a similarly high level of accuracy in the shear measurements of galaxies.  Factors such as pixelisation, imperfect PSF correction, and pixel noise can all directly or indirectly lead to biases in shear measurements, and so it can be necessary for shear measurement methods to be calibrated against internal, external, or simulated data to minimize bias.  It is thus important to understand the nature of this calibration.  In this paper, show that a typical calibration procedure will on average leave no residual additive bias, but will leave a residual multiplicative bias.    Additionally, the errors on the post-calibration bias parameters will be changed, and on average increased, from the errors on the pre-calibration measurements of these parameters, but that this is generally worth the benefit in decreasing the expected value of the multiplicative bias.  Find that in most typical cases, it is worthwhile to apply a first-order bias correction, while a higher-order bias correction is only worthwhile for methods with intrinsically high multiplicative bias (>10%) or when the simulation size is very small (<1e6 simulated galaxies).

Day 1468

Tuesday.

1809.08243
First resolution of micro lensed images
Dong, et al

Employ VLTI GRAVITY to resolve, for the first time, the two images generated by a gravitational microlens.  The measurements of the image separation theta_-,+=3.78±0.05 mas, and hence the Einstein radius theta_E=1.87±0.03 mas, are precise.  This demonstrates the robustness of the method, provided that the source is bright enough for GRAVITY (K <~ 10.5) and the image separation is of order or larger than the fringe spacing.  When theta_E is combined with a measurement of the "microlens parallax" pi_E, the two will together yield the lens mass and lens-source relative parallax and proper motion.  Because the source parallax and proper motion are well measured by Gaia, this means that the lens characteristics will be fully determined, whether or not it proves to be luminous.  This method can be a powerful probe of dark, isolated objects, which are otherwise quite difficult to identify, much less characterize.  The measurement contradicts Einstein's (1936) prediction that "the luminous circle [i.e., microlnsed image] cannot be distinguished" from a star.


1809.08344
The Elephant in the room: the importance of where and when massive stars form in molecular clouds
Grudic, Hopkins

Most simulations of galaxies and massive giant molecular clouds (GMCs) cannot explicitly resolve the formation (or predict the MS masses) of individual stars.  So they must use some prescription for the amount of feedback from an assumed population of massive stars (e.g. sampling the IMF).  Perform a methods study of simulations of a star-forming GMC with stellar feedback from UV radiation, varying only the prescription for determining the luminosity of each stellar mass element formed (according to different IMF sampling schemes).  Show that different prescriptions can lead to widely varying (factor of ~3) SF efficiencies (on GMC scales) even though the average mass-to-light ratios agree.  Discreteness of sources is important: radiative feedback from fewer, more-luminous sources has a greater effect for a given total luminosity.  These differences can dominate over other, more widely-recognized differences between similar literature GMC-scale studies (e.g. numerical methods, cloud initial conditions, presence of magnetic fields).  Moreover the differences in these methods are not purely numerical: some make different implicit assumptions about where and how massive stars form, and this remains deeply uncertain in SF theory.

Day 1467

Monday.

1809.07960
The AMBRE Project: r-process elements in the Milky Way thin and thick disks
Guiglion, et al

The chemical evolution of neutron capture elements in the MW disc is still a matter of debate.  Aim to understand the chemical evolution of r-process elements in MW disc.  Focus on 3 pure r-process elements Eu, Gd, and Dy.  Using high-resolution FEROS, HARPS, and UVES spectra from the ESO archive, perform a homogeneous analysis on 6500 FGK MW stars, thanks to the automatic optimization pipeline GAUGUIN.  Present abundances of Ba (5057 stars), Eu (6268 stars), Gd (5431 stars) and Dy (5479 stars).  Chemically characterize the thin and the thick disks, and a metal-rich alpha-rich population.  Find that the [Eu/Fe] ratio follows a continuous sequence from the thin disc to the thick disc as a function of the metallicity.  In thick disc stars, the [Eu/Ba] ratio is found to be constant, while the [Gd/Ba] and [Dy/Ba] ratios decrease as a function of the metallicity. These observations clearly indicate a different nucleosynthesis history in the thick disc between Eu and Gd-Dy.  Also find that the alpha-rich metal-rich stars are also enriched in r-process elements (like thick disc stars), but their [Ba/Fe] is very different from thick disc stars.  Finally, find that the [r/alpha] ratio tends to decrease with metallicity, indicating that SNe of different properties probably contribute differently to the synthesis of r-process elements and alpha-elements.  Provide average abundance trends for [Ba/Fe] and [Eu/Fe] with rather small dispersions, and for the first time for [Gd/Fe] and [Dy/Fe].  This data may help to constrain chemical evolution models of MW r- and s-process elements and the yields of massive stars.  Including yields of neutron-star or BH mergers is now crucial if we want to quantitatively compare observations to Galactic chemical evolution models.


1809.08126
Dense matter equation of state for neutron star mergers
Lalit, et al

In simulations of binary neutron star mergers, the dense matter equation of state (EOS) is required over wide ranges of density and temperature as well as under conditions in which neutrinos are trapped, and the effects of magnetic fields and rotation prevail.  Here, assess the status of dense matter theory and point out the success and limitations of approaches currently in use.  A comparative study of the excluded volume (EV) and viral approaches for the np alpha system using the equation of state of Akmal, Pandharipande and Ravenhall for interacting nucleons is presented in the sub-nuclear density regime.  Owing to the excluded volume of the alpha-particles, their mass fraction vanishes in the EV approach below the baryon density 0.1 fm^{-3}, whereas it continues to rise due to the predominantly attractive interactions in the viral approach.  The EV approach of Lattimer et al. is extended here to include clusters of light nuclei such as d, 3H and 3He ain addition to alpha particles.  Results of the relevant state variables from this development are presented and enable comparisons with related by slightly different approaches in the literature.  Also comment on some of the sweet and sour aspects of the supra-nuclear EOS.  The extent to which the gravitational and baryon masses vary due to thermal effects, neutrino trapping, magnetic fields and rotation are summarized from earlier studies in which the effects from each of these sources were considered separately.  Increases of about 25% (50%) occur for rigid (differential) rotation with comparable increases occurring in the presence of magnetic fields only for fields in excess of 1e18 Gauss.  Comparatively smaller changes occur due to thermal effects and neutrino trapping.  Some future studies to gain further insight into the outcome of dynamical simulations are suggested.

Day 1466

Tuesday.  Wednesday.  Thursday.  Friday.

1809.06424
The effect of assembly bias on redshift space distortions
Padilla, Contreras, Zehavi, Baugh, Norberg

Study potential systematic effects of assembly bias on cosmological parameter constraints from redshift space distortion measurements.  Use a semi-analytic galaxy formation model applied to the Millennium N-body WMAP-7 simulation to study the effects of halo assembly bias on the redshift space distortions of the galaxy correlation function.  Look at the pairwise velocities of galaxies living in haloes with concentrations and ages in the upper and lower quintiles, and find that the velocity differences between these are consistent with those reported for real-space clustering analyses, i.e. samples with higher clustering also exhibit stronger infall pairwise motions.  This can also be seen in the monopole and quadrupole of the redshift-space correlation function.  Find that regardless of the method of measurement, the changes in the beta parameter due to different secondary halo parameters fully tracks the change in the bias parameter.  Hence, assembly bias does not introduce detectable systematics in the inferred logarithmic growth factor.


1809.06634
On the degeneracy between baryon feedback and massive neutrinos as probed by matter clustering and weak lensing
Parimbelli, Viel, Sefusatti

Massive neutrinos, due to their free streaming, produce a suppression in the matter PS at intermediate and small scales which could be probed by galaxy clustering and/or weak lensing observables.  This effect happens at scales that are also influenced by baryon feedback, i.e., galactic winds or AGN feedback, which in realistic hydrodynamic sims has also been show to produce a suppression of power.  Leaving aside for the moment the complex issue of galaxy bias, focus here on matter clustering and tomographic WL, investigate the possible degeneracy between baryon feedback and neutrinos showing that it is not likely to degrade significantly the measurement of neutrino mass in future surveys.  To do so, generate mock data sets and fit them using MCMC technique and explore degeneracies between feedback parameters and neutrino mass.  Model baryon feedback through fitting functions, while massive neutrinos are accounted for, also in the non-linear regime, using Halofit calibrated against accurate N-body neutrino simulations.  In the error budget, include the uncertainty in the modeling of nonlinearities.  For both matter clustering and WL, always recover the input neutrino mass within ~0.25 sigma CL.  Finally, also take into account the intrinsic alignment effect in the WL mock data.  Even in this case, able to recover the right parameters: in particular, find a significant degeneracy pattern between M_nu and the IA parameter A_IA.


1809.06960
Strange messenger: a new history of hydrogen on Earth, as told by Xenon
Zahnle, Gacesa, Catling

Atmospheric Xe is strongly mass fractionated, the result of a process that apparently continued through the Archean and perhaps beyond.  Previous models that explain Xe fractionation by hydrodynamic H escape cannot gracefully explain how Xe escaped and Ar and Kr did not, nor allow Xe to escape in the Archean.  Here show that Xe is the only noble gas that can escape as an ion in a photo-ionized H wind, possible in the absence of a geomagnetic field or along polar magnetic field lines that open into interplanetary space.  To quantify the hypothesis, construct new 1D models of hydrodynamic diffusion-limited H escape from highly-irradiated CO_2-H_2-H atmospheres.  The models reveal 3 minimum requirements for Xe escape: solar EUV irradiation needs to exceed 10x that of the modern Sun; the total H mixing ratio in the atmosphere needs to exceed 1% (equiv. to 0.5% CH_4); and transport amongst the ions in the lower ionosphere needs to lift the Xe ions to the base of the outflowing H corona.  The long duration of Xe escape implies that, if a constant process, Earth lost the H from at least one ocean of water, roughly evenly split between the Hadean and the Archean.  However, to account for both Xe's fractionation and also its depletion with respect to Kr and primordial 244Pu, Xe escape must have been limited to small apertures or short episodes, which suggests that Xe escape was restricted to polar windows by a geomagnetic fields, or dominated by outbursts of high solar activity, or limited to transient episodes of abundant H, or a combination of these.  Xe escape stopped when the H (or methane) mixing ratio became too small, or EUV radiation from the aging Sub became too weak, or charge exchange between Xe^+ and O_2 rendered Xe neutral.


1809.07255
Shape of dark matter haloes in the Illustris Simulation: effects of baryons
Chua, Pillepich, Vogelsberger, Hernquist

Study the effect of baryonic processes on the shapes of DM haloes from Illustris, a suite of hydro (Illustris) and DM-only (Illustris-Dark) cosmo sims performed with the moving-mesh code (arepo).  DM halo shapes are determined using an interactive method based on the inertia tensor for a wide range of z=0 masses (M_200=[1e11, 3e14] Msun).  Convergence tests shows that the local DM shape profiles are converged only for r>9 epsilon, epsilon being the Plummer-equivalent softening length, larger than expected. Haloes from non-radiative sims (i.e. neglecting radiative processes, SF, and feedback) exhibit no alteration in shapes from their DM-only counterparts: thus moving-mesh hydrodynamics alone is insufficient to cause differences in DM shapes.  With the full galaxy-physics implementation, condensation of baryons results in significantly rounder and more oblate haloes, with the median minor-to-major axis ratio <c/a>~0.7, almost invariant throughout the halo and across halo masses.  This somewhat improves the agreement between simulation predictions and observational estimates of the MW halo shape.  Consistently, the velocity anisotropy of DM is also reduced in Illustris, across halo masses and radii.  Within the inner halo (r-0.15 R_200), both s and q (intermediate-to-major axis ratio) exhibit non-monotonicity with galaxy mass, peaking at m*~1e[10.5-11] Msun, which is found due to the strong dependence of inner halo shape with galaxy formation efficiency.  Baryons in Illustris affect the correlation of halo shape with halo properties, leading to a positive correlation of sphericity of MW-mass haloes with halo formation time and concentration, the latter being mildly more pronounced than in Illustris-Dark.


1809.07341
Survey of Gravitationally-lensed Objects in HST Imaging (SuGOHI).  II. Environments and line-of-sight structure of strong gravitational lens galaxies to z~0.8
Wong, et al

Investigate the local and line-of-sight overdensities of strong GLs using wide-area multi band imaging from the HSC Subaru Strategic Program.  Present 41 new definite or probable lens candidates discovered in DR2 of the survey.  Using a combined sample of 87 galaxy-scale lenses out to a lens redshift of z_L~0.8, compare galaxy number counts in lines of sight toward known and newly-discovered lenses in the survey to those of a control sample consisting of random line-of-sight.  Also compare the local overdensity of lens galaxies to a sample of "twin" galaxies that have a similar redshift and velocity dispersion to test whether lenses lie in different environments from similar non-lens galaxies.  Find that lens fields contain higher number counts of galaxies compared to the control fields, but this effect arises from the local environment of the lens.  Once galaxies in the lens plane are removed, the lens lines of sight are consistent with the control sample.  The local environments of the lenses are overdense compared to the control sample, and are slightly overdense compared to those of the twin sample, although the significance is marginal.  There is no significant evidence of the evolution of the local overdensity of lens eivnormnents with redshift.

Day 1465

Tuesday.  Wednesday.  Thursday.  Friday.  Monday.

1809.02654
WFIRST Exoplanet mass measurement method finds a planetary mass of 39±8 M_oplus for OGLE-2012-BLG-0950Lb
Bhattacharaya, et al

Present analysis of the simultaneous high resolution images from HST and Keck AO system of the planetary event OGLE-2012-BLG-0950 that determine that the system consists of a 058±0.04 M_odot host star orbited by a 39±8 M_oplus planet at a projected separation of 2.54±0.23 AU.  The planetary system is located at a distance of 2.19±0.23 kpc from Earth.  This is the second microlens planet beyond the snow line with a mass measured to be in the mass range 20-80 M_oplus. The runaway gas accretion process of the core accretion model predicts few planets in this mass range, because giant planets are thought to be growing rapidly at these masses and they rarely complete growth at this mass.  So, this result suggests that the core accretion theory may need revision.  This analysis also demonstrates the techniques that will be used to measure the masses of planets and their host stars by the WFIRST exoplanet microlensing survey: one-dimentional microlensing parallax combined with the separation and brightness measurement of the unresolved source and host stars to yield multiple redundant constraints on the masses and distance of the planetary system.


1809.03373
The WIRCam Ultra Deep Survey (WUDS) I. Survey overview a UV luminosity functions at z~5 and z~6
Pello, Hudelot, Laporte, Melier, McCracken, et al

The aim of this paper is to introduce WUDS, a NIR photometric public survey carried out at CFHT in the field of CFHTLS-D3 field (Groth strip).  WUDS includes 4 NIR bands (Y, J, H and K_s) over a field of view of ~400 arcmin^2.  The typical depth of WUDS data reaches between ~26.8 in Y and J, and ~26 in H and K_s (AB, 3 sigma in 1.3 arcsec aperture).  The area and depth of this survey were specifically tailored to set strong constraints on the cosmic star formation rate and the luminosity function brighter or around L* in the z~6-10 redshift domain, although these data are also useful for a variety of extragalactic projects.  This first paper is intended to present the properties of WUDS: catalog building, completeness and depth, number counts, photometric redshifts, and global properties of the galaxy populations.  Have concentrated on the study of galaxy samples at z~[4.5-7] in this field.  UV luminosity functions were derived at z~5 and z~6 combined determination of M* and Phi* with increased accuracy.  The results of the luminosity function are consistent with a small evolution of both M* and Phi* between z=5 and z=6, irrespective of the method used to derive them, either photometric redshifts applied to blindly-selected dropout samples or the classical Lyman Break Galaxy color-preselected samples.  The results lend support to higher Phi* determinations at z=6 than usually reported.  The selection and combined analysis of different galaxy samples at z>7 will be presented in a forthcoming paper.  WUDS is intended to provide a robust database in the NIR of the selection of targets for detailed spectroscopic studies, in particular for the MIR/GTC GOYA Survey (Abridged).


1809.03502
The cosmic microwave background and the stellar initial mass function
Jermyn, Steinhardt, Tout

Argue that an increased temperature in SF clouds alters the stellar IMF to be more bottom-light than in the MW.  At z>~6, heating from CMB radiation produces this effect in all galaxies, and it is also present at lower z in galaxies with very high SFRs.  A failure to account for it means that at present, photometric template fitting likely overestimates stellar masses and SFRs for the highest-z and highest-SFR galaxies.  In addition this may resolve several outstanding problems in the chemical evolution of galactic halos.


1809.03525
Neutron star mergers might not b the only source of r-Process elements in the Milky Way
Côté, et al

Probing the origin of r-process elements in the universe represents a multi-disciplinary challenge.  Review the observational evidence that probe the properties of process sites, and address them using galactic chemical evolution simulations, binary population synthesis models, and nucleosynthesis calculations.  The motivation is to define which astrophysical sites have significantly contributed to the total mass of r-pcocess elements present in our Galaxy.  Found discrepancies with the neutron star (NS-NS) merger scenario.  Assuming they are the only site, the decreasing trend of [Eu/Fe] at [Fe/H] >-1 in the disk of the MW cannot be reproduced while accounting for the delay-time distribution (DTD) of coalescence times (~t^{-1}) derived from short gamma-ray bursts and population synthesis models.  Steeper DTD functions (~t^{-1.5}) or power laws combined with a strong burst of mergers before the onset of Type Ia SNe can reproduce the [Eu/Fe] trend, but this scenario is inconsistent with the similar fraction of short gamma-ray bursts and Type Ia SNe occurring in early-type galaxies, and reduces the probability of detecting GW170817 in an early-type galaxy.  One solution is to assume an extra production site of Eu that would be active in the early universe, but would fade away with increasing metallicity.  If this is correct, NS-NS mergers would contribute to about 2/3 of the total amount of Eu currently present in the Milky Way.  A rare class of SNe could be this additional source of the r-process, but hydrodynamic simulations still need to ensure the conditions for a robust r-process pattern.


1809.03602
The dependence of intrinsic alignment of galaxies on wavelength using KiDS and GAMA
Georgia, Johnston, Hoekstra, et al

The outer regions of galaxies are more susceptible to the tidal interactions that lead to intrinsic alignments of galaxies.  The resulting alignment signal may therefore depend the passband if the colors of galaxies vary spatially.  To quantify this, measure the shapes of galaxies with spec-zs from the GAMA survey using deep gri imaging data from KiDS.  The performance of the moment-based shape measurement algorithm DEIMOS was assessed using dedicated image simulations, which showed that the ellipticities could be determined with an accuracy better than 1% in all bands.  Additional tests for potential systematic errors did not reveal any issues.  Measure a significant difference of the alignment signal between the g, r and i-band observations.  This difference exceeds the amplitude of the linear alignment model on scales below 2 Mpc/h.  Separating the sample into central/satellite and red/blue galaxies, find that the difference is dominated by red satellite galaxies.


1809.03924
Weak lensing beyond shear
Fleury, Larena, Uzan

When a luminous source is extended, tis distortions by WL are richer than a mere combination of magnification and shear.  In a recent work, proposed an elegant formalism based on complex analysis to describe and calculate such distortions.  The present article further elaborates this finite-beam approach, and applies it to a realistic cosmological model.  In particular, the cosmic correlations of image distortions beyond shear are predicted for the first time.  These constitute new WL observables, sensitive to very-small-scale features of the distribution of matter in the Universe.  While the major part of the analysis is performed in the approximation of circular sources, a general method for extending it to noncircular sources is presented, and applied to the astrophysically relevant case of elliptic sources.


1809.04375
The PAU survey: Early demonstration of photometric redshift performance n the COSMOS field
Eriksen, et al

The PAU Survey (PAUS) is an innovative photometric survey with 40 narrow bands at the William Herschel Telescope (WHT).  The narrow bands are spaced at 100 A intervals covering the range 4500A to 8500A and, in combination with standard broad bands, enable excellent redshift precision.  This paper describes the technique, galaxy templates and additional photometric calibration used to determine early photometric redshifts from PAUS.  Using BCNz2, a new photometric redshift code developed for this purpose, characterize the photometric z performance using PAUS data on the COSMOS fields.  Comparison to secure spectra from zCOSMOS DR3 shows that PAUS achieves sigma_68/(1+z) = 0.0037 to i_AB <22.5 when selecting the best 50% of the sources based on a photometric redshift quality cut.  Furthermore, a higher photo-z precision (sigma_68/(1+z)~0.001) is obtained for a bright and high quality selection, which is driven by the identification of emission lines.  Conclude that PAUS meets its design goals, opening up a hitherto uncharted regime of deep, wide and dense galaxy survey with precise redshifts that will provide unique insights into the formation, evolution and clustering of galaxies, as well as their intrinsic alignments.


1809.04597
Neutron star mergers are the dominant source of the r-process in the Early evolution of dwarf galaxies
Duggan, Kirby, Andrievsky, Korotin

There are many candidate sites of the r-process: core-collapse SNe (including rare magneto rotational core-collapse SNe), NS mergers, and NS/BH mergers.  the chemical enrichment of galaxies --- specifically dwarf galaxies --- helps distinguish between these sources based on the continual build-up of r-process elements.  This technique can distinguish between the r-process candidate sites by the clearest observational difference --- how quickly these events occur after the stars are created.  The existence of several nearby dwarf galaxies allows robust measurement of chemical abundance for galaxies with different SFHs.  Dwarf galaxies are especially useful because simple chemical evolution models can be used to determine the sources of r-process material.  Measured the r-process element Barium with Keck/DEIMOS medium-resolution spectroscopy.  Present the largest sample of Ba abundances (almost 250 stars) in dwarf galaxies ever assembled.  Measure [Ba/Fe] as a function of [Fe/H] in this sample and compare with existing [alpha/Fe] measurements.  Found that a large contribution of Ba needs to occur at more delayed timescales than core-collapse SNe in order to explain the observed abundances, namely the significantly more positive trend of the r-process component of [Ba/Fe] vs. [Fe/H] seen for [Fe/H] <~ -1.6 when compared pt the [Mg/Fe] vs. [Fe/H] trend. Conclude that NS mergers are the most likely source of r-process enrichment in dwarf galaxies at early times.


1809.04599
Dark Energy Survey Year 1 results: the effect of intra-cluster light on photometric redshifts for weak gravitational lensing
Gruen, et al

Study the effect of diffuse intra-cluster light on the critical surface mass density estimated from photo-zs of lensing source galaxies, and the resulting bias in a WL measurement of galaxy cluster mass.  Under conservative assumptions, find the bias to be negligible for imaging surveys like the DES with a recommended scale cut of >=200 kpc distance from cluster centers.  For significantly deeper source catalogs from present and future surveys like LSST, more conservative scale and source magnitude cuts or a correction of the effect may be necessary to achieve percent level lensing measurement accuracy, especially at the massive end of the cluster population.


1809.04921
On the role of magnetic fields in star formation
Nixon, Pringle

Magnetic fields are observed in SF regions.  However simulations of the late stages of SF that do not include magnetic fields provide a good fit to the properties of young stars including the IMF and the multiplicity.  Argue here that the simulations that do include magnetic fields are unable to capture the correct physics, in particular the high value of the magnetic Prandtl number, and the low value of the magnetic diffusivity.  The artificially high (numerical and uncontrolled) magnetic diffusivity leads to a large magnetic flux pervading the SF regions.  Argue further that in reality the dynamics of high magnetic Prandtl number turbulence may lead to local regions of magnetic energy dissipation through reconnection, meaning that the regions of molecular clouds which are forming stars might be essentially free of magnetic fields.  Thus the simulations that ignore magnetic fields on the scales on which the properties of stellar masses, stellar multiplicities and planet-forming disks are determined, may be closer to reality than those which include magnetic fields, but can only do so in an unrealistic parameter regime.


1809.05128
Nuclear processes in other universes: Varying the strength of the weak force
Howe, Grohs, Adams

Motivated by the possibility that the laws of physics could be different in other regions of space-time, consider nuclear processes in universes where the weak interaction is either stronger or weaker than observed.  Focus on the physics of both BBN and stellar evolution.  For sufficiently ineffective weak interactions, neutrons do not decay during BBN and the baryon-to-photon ratio "eta" must be smaller in order for protons to survive without becoming incorporated into larger nuclei.  For stronger weak interactions, neutron decay before the onset of BBN, and the early universe is left with nearly a pure H composition.  Then consider stellar structure and evolution for the different nuclear compositions resulting from BBN, a wide range of weak force strengths, and the full range of stellar masses for a given universe.  Delineate the range of this parameter space that supports working stars, along with a determination of the dominant nuclear reactions over the different regimes.  Deuterium burning dominates the energy generation in stars when the weak force is sufficiently weak, whereas proton-proton burning into He-3 dominates for the regime where the weak force is much stronger than in our universe.  Although stars in these universes are somewhat different, they have comparable surface temperatures, luminosities, radii, and lifetimes, so that a wide range of such universes remain potentially habitable.


1809.05437
Fast and easy super-sample covariance of large scale structure observables
Lacasa, Grain

Present a numerically cheap approximation to SSC of large scale structure cosmological probes, first in the case of angular power spectra.  It necessitates no new elements besides those used for the prediction of the considered probes, thus relieving analysis pipelines from having to develop a full SSC modeling, and reducing the computational load.  The approximation is asymptotically exact for fine redshift bins Delta z -> 0.  Furthermore show how it can be implemented at the level of a Gaussian likelihood or a Fisher matrix forecast, as a fast correction to the Gaussian case without needing to build large covariance matrices.  Numerical application to a Euclid-like survey show that, compared to a full SSC computation, the approximation recovers nicely the S/N ratio as well as Fisher forecasts on cosmological parameters of the wCDM cosmological model.  In the case of photometric galaxy clustering with Euclid-like specifications, find that sigma_8, n_s and the DE EoS w are particularly heavily affected.  Finally show how to generalize the approximation for probes other than angular spectra (correlation functions, number counts and bispectra), and at the likelihood level, allowing for the latter to be non-Gaussian if need be.

Day 1464

Monday.

1809.02180
Astrophysical validation
Calder, Townsley

Present examples of validating components of an astrophysical simulation code.  Problems of stellar astrophysics are multi-dimensional and involve physics acting on large ranges of length and time scales that are impossible to include in macroscopic models on present computational resources.  Simulating these events thus necessitates the development of sub-grid-scale models and the capacity to post-process simulations with higher-fildelity methods.  Present an overview of the problem of validating astrophysical models and simulations illustrated with two examples.  First, present a study aimed at validating hydrodynamics with high energy density laboratory experiments probing shocks and fluid instabilities.  Second, present an effort at validating code modules for use in both macroscopic simulations of astrophysical events and for post processing Lagrangian tracer particles to calculate detailed abundances from thermonuclear reactions occurring during an event.


1809.02340
Can the $H_0$ tension be resolved in extensions to $\Lambda$CDM cosmology?
Guo, Zhang, Zhang

Investigate whether there is an extension to the base LCDM cosmology that can resolve the tension between the Planck observation of the CMB anisotropies and the local measurement of H0.  Consider various plausible extended models in this work, and use the Planck 2015 observations, combined with BAO data, the JLA type Ia SNe data, and the local measurement of H0 (by Riess+ 2016) to make an analysis.  Find that the holographic DE plus sterile neutrino model can reduce the tension to be at the 1.11 sigma level, but this model is obviously not favored by the current observations.  Among these extended models, the LCDM+N_eff model is the most favored by the current observations, and this model can reduce the tension to be at the 1.89 sigma level.  By a careful test, conclude that none of these extended models can convincingly resolve the H0 tension.

Day 1463

Friday.

1809.01945
Minimal Re-computation for exploratory data analysis in astronomy
Nikolic, et al

Present a technique to automatically minimize the re-computation when a data analysis program is iteratively changed, or added to, as is often the case in exploratory data analysis in astronomy.  A typical example is flagging and calibration of demanding or unusual observations where visual inspection suggests improvement to the processing strategy.  The technique is based on memoization and referentially transparent tasks.  Describe the implementation of this technique for the CASA radio astronomy data reduction package.  Also propose a technique for optimizing efficiency of storage of memoized intermediate data products using copy-on-write and block level de-duplication and measure their practical efficiency.  Find the minimal recompilation technique improves the efficiency of data analysis while reducing the possibility for user error and improving the reproducibility of the final result.  It also aids exploratory data analysis on batch-schedule cluster computer systems.

Day 1462

Thursday.

1803.03266
Dark haloes around neutron stars and gravitational waves
Nelson, Reddy, Zhou

Find that a class of models of MeV-GeV DM in which DM interacts strongly can be constrained by the observation of gravitational waves from neutron star mergers.  Trace amounts of dark matter, either produced during the SN or accreted later, can alter the structure of NSs and influence their tidal polarizability.  Focus on models of DM interacting by the exchange of light vector gauge bosons that couple to a conserved dark charge.  In these models, dark matter accumulated in NSs can extend to large radii and enhance their tidal polarizability.  Gravitational waves detected from the first binary NS merger GW170817 places useful constraints on such not-so compact objects.  Dark haloes, if present, also predict a greater variability of NS tidal polarizabilities than expected for ordinary NSs.


1809.01146
Modeling baryonic physics in future weak lensing surveys
Huang, Eifler, Mandelbaum, Dodelson

Modifications of the matter power spectrum due to baryonic physics are one of the major theoretical uncertainties in cosmological WL measurements.  Developing robust mitigation schemes for this source of systematic uncertainty increases the robustness of cosmological constraints, and may increase their precision if they enable the use of information from smaller scales.  Here, explore the performance of two mitigation schemes for baryonic effects in WL cosmic shear: the PCA method and the halo-model approach in HMcode.  Construct mock tomographic shear power spectra from four hydrodynamical simulations, and run simulated likelihood analyses with CosmiLike assuming LSST-like survey statistics.  With an angular scale cut of ell_max<2000, both methods successfully remove the biases in cosmo parameters due to the various baryonic physics scenarios, with the PCA method causing less degradation in the parameter constraints than HMcode.  For a more aggressive ell_max=5000, the PCA method performs well for all but one baryonic physics scenario, requiring additional training simulations to account for the extreme baryonic physics scenario of Illustris; HMcode exhibits tensions in the 2D poster distributions of cosmoloigal parameters due to lack of freedom in describing the PS for k>10/h Mpc.  Investigate variants of the PCA method and improve the bias mitigation through PCA by accounting for the noise properties in the data via Cholesky decomposition of the covariance matrix.  The improved PCA method allows for retention of more statistical constraining power while effectively mitigating baryonic uncertainties even for a broad range of baryonic physics scenarios.


1809.01171
The causes of the red sequence, the blue cloud, the green valley and the green mountain
Eals, et al

The galaxies found in optical surveys fall in two distinct regions of a diagram of optical color versus absolute magnitude: the red sequence and the blue cloud with the green valley in between.  Show that the galaxies found in a submillimetre survey have almost the opposite distribution in this diagram, forming a 'green mountain'.  Show that these distinctive distributions follow naturally from a single, continuous, curved Galaxy Sequence in a diagram of specific star-formation rate versus stellar mass without there being the need for a separate star-forming galaxy MS and region of passive galaxies.  The cause of the red sequence and the blue cloud is the geometric mapping between stellar mass/sSFR and absolute magnitude/colour, which distorts a continuous Galaxy Sequence in the diagram of intrinsic properties into a bimodal distribution in the diagram of observed properties.  The cause of the green mountain is Malmquist bias in the submillimetre waveband, with submillimetre surveys tending to select galaxies on the curve of the Galaxy Sequence, which have the highest ratios of submillimetre-to-optical luminosity.  Thiseffect, working in reverse, causes galaxies on the curve of the Galaxy Sequence to be underrepresented in optical samples, deepening the green valley.  The green valley is therefore not evidence (1) for there being two distinct populations of galaxies, (2) for galaxies in this region evolving more quickly than galaxies in the blue cloud and the red sequence, (c) [3?] for rapid quenching processes in the galaxy population.


1809.01274
H0LiCOW - IX. Cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 and a new measurement of the Hubble constant
Birrer, Treu, et al

Present a blind time-delay strong lensing (TDSL) cosmographic analysis of the doubly imaged quasar SDSS 1206+4332.  Combine the relative time delay between the quasar images, HST imaging, the Keck stellar velocity dispersion of the lensing galaxy, and wide-field photometric and spectroscopic data of the field to constrain two angular diameter distance relations.  The combined analysis is performed by forward modeling the individual data sets through a Bayesian hierarchical framework, and it is kept blind until the very end to prevent experimenter bias.  After unblinding, the inferred distances imply a Hubble constant H0=68.8+5.4-5.1 km/s/Mpc, assuming a flat Lambda CDM cosmology with uniform prior on Omega_m in [0.05,0.5].  The precision of the cosmographic measurement with the doubly imaged quasar SDSS 1206+4332 is comparable with those of quadruply imaged quasars and opens the path to perform on selected doubles the same analysis as anticipated for quads.  The analysis is based on a completely independent lensing code than the previous 3 H0LiCOW systems and the new measurement is fully consistent with those.  Provide the analysis scripts paired with the publicly available software to facilitate independent analysis.  The consistency between blind measurements with independent codes provides an important sanity check on lens modeling systematics.  By combining the likelihoods of the 4 systems under the same prior, obtain H0=72.5+2.1-2.3 km/s/Mpc.  This measurement is independent of the distance ladder and other cosmological probes.

Day 1461

Tuesday = Labor Day.  Wednesday.


1809.00180
The distances to Novae as seen by Gaia
Schaefer

The Gaia spacecraft has just released a large set of parallaxes, including 41 novae for which the fractional error is <30%.  Use these to evaluate the accuracy and bias of the many prior methods for getting nova-distances.  The best of the prior methods is the geometrical parallaxes from HST for just four novae, although the real error bars are 3x larger than stated.  The canonical method for prior nova-distnces has been the expansion parallaxes from the novel shells, but this method is found to have real 1-sigma uncertainty of 0.95 mag in the distance modulus, and the prior quoted error bars are on average 3.6x worse than advertised.  The many variations on the maximum-magnitude-rate-of-decline (MMRD) relation are all found to be poor, too poor to be usable, and even to be non-applicable for 5-out-of-7 samples of nova, so the MMRD should no longer be used.  The prior method of using various measures of the extinction from the interstellar medium have been notoriously bad, but now a new version by Ozdonmez and coworkers has improved this to an unbiased method with 1-sigma uncertainty of 1.14 mag in the distance modulus.  For the future, recommend in order (1) using the Gaia parallax, () using the catalog of Ozdonmez, (3) using M_max=-7.0±1.4 mag as an empirical method of poor accuracy, and (4) if none of these methods is available, then to not use the nova for purposes where a distance is needed.


1809.00282
Constraining dark energy with stacked concave lenses
Dong, Zhang, et al

Low density regions are less affected by the nonlinear structure formation and baryonic physics.  They are ideal places for probing the nature of dark energy, a possible explanation for the cosmic acceleration.  Unlike void lensing, which require identifications of individual voids, study the stacked lensing signals around the low-density-positions (LDP), defined as places that are devoid of foreground bright galaxies in projection.  The method allows a direct comparison with numerical results by drawing correspondence between the bright galaxies with haloes.  It leads to lensing signals that are significant enough for differentiating several dark energy models.  In this work, use the CFHTLenS catalogue to define LDPs, as well as measuring their background lensing signals.  Consider several different definitions of the foreground bright galaxies (redshift range & magnitude cut).  Regarding the cosmological model, run six simulations: the first set of simulations have the same initial conditions, with w_de=-1,-0.5,-0.8,-1.2; the second set of simulations include a slightly different LCDM model and a w(z) model from 2017NatAs...1..627Z.  The lensing results indicate that the models with w_de=-0.5,-0.8 are not favored and the other four models all achieve comparable agreement with the data.


1809.00523
ELUCID. IV: Cosmic variance of galaxy distribution in the local Universe
Chen, Mo, et al

Halo merger trees are constructed from ELUCID, a constrained N-body simulation in SDSS volume.  These merger trees are used to populate DM haloes with galaxies according to an empirical model of galaxy formation.  Mock catalogs in the SDSS sky coverage are constructed, which can be used to study the spatial distribution of galaxies in the low-z Universe.  These mock catalogs are used to quantify the cosmic variance in the galaxy stellar mass function (GSMF) measured from the SDSS survey.  The GSMF estimated from the SDSS magnitude-limited sample can be underestimated significantly by the presence of the under-dense region at z<0.03, so that the low-mass end of the function can be underestimated significantly.  Several existing methods designed to deal with the effects of the cosmic variance in the estimate of GSMF are tested, and none is found to be able to fully account for the cosmic variance.  Propose a method based on the conditional stellar mass functions in DM haloes, which can provide an unbiased estimate of the global GSMF.  The application of the method to the SDSS data shows that the GSMF has a significant upturn at M*<1ee9.5 M_sun/h, which has been missed in many earlier measurements of the local GSMF.

1809.01057
The effect of microlensing on the observed X-ray energy spectra of gravitationally lensed quasars
Krawczynski, et al

The Chandra observations of several gravitationally lensed quasars show evidence for flux and spectral variability of the X-ray emission that is uncorrelated between images and is thought to result from the microlensing by stars in the lensing galaxy.  Report here on the most detailed modeling of such systems to date, including simulations of the emission of the Fe K-alpha fluorescent radiation from the accretion disk with a GRic ray tracing code, the use of realistic microlensing magnification maps derived from inverse ray shooting calculation, and the simulations of the line detection biases.  Use lensing and black hole parameters appropriate for the quadruply lensed quasar RX J1131-1231, and compare the simulated results with the observational results.  The simulations cannot fully reproduce the distribution of the detected line energies indicating that some of the assumptions underlying the simulations are not correct, or that the simulations are missing some important physics.  Conclude by discussing several possible explanations.

Day 1460

Monday.


1808.10460
What fraction of the density fluctuations in the Perseus cluster core is due to gas sloshing rather than AGN feedback?
Walker, Sanders, Fabian

Deep Chandra observations of the core of the Perseus cluster show a plethora of complex structure.  It has been found that when the observed density fluctuations in the intracluster medium are converted into constraints on AGN induced turbulence, the resulting turbulent heating rates are sufficient to balance cooling locally throughout the central 220 kpc.  However while the signatures of AGN feedback (inflated bubbles) dominate the central 60 kpc in X-ray images, beyond this radius the intracluster medium is increasingly shaped by the effects of gas sloshing, which can also produce subtle variations in X-ray surface brightness.  Use mock Chandra observations of gas sloshing simulations to investigate what fraction of the observed density fluctuations in the core of the Perseus galaxy cluster may originate from sloshing rather than AGN included feedback.  Outside 60 kpc, find that the observed level of the density fluctuations is broadly consistent with being produced by sloshing alone.  If this is the case, AGN-generated turbulence is likely to be insufficient in combating cooling outside 60 kpc.


1808.10493
No guaranteed neutrino astronomy without (enough) taus
Fargion, et al

Since 2013, the highest energy IceCube cascade showers overcame the common muon neutrino trans.  This fast flavor changes, above few tens TeV, has been indebt to the injection of the long searched astrophysical neutrino.  However for what concern the recent published ICECUBE 54 neutrino, high energy staring events (HESE) in 2016, as well as the most recent ones of 82 and 103 IceCube events (2017-2018) and the several dozens of thorough-going muon tracks formed around the IceCube, none of them are pointing or clustering toward any expected x, gamma or radio sources: no one in connection to GRB, no toward active BL Lac, neither to AGN source in Fermi catalog.  No clear correlation with nearby mass distribution (Local Group), nor with galactic plane.  Withal, there have not been any record of the expected double bang due to the tau neutrino birth and decay among several events above 200 TeV energy (disregard for a moment the most celebrated recent first correlated, but unique, muon track and the recent two tau possible identification); no any self-clustering events at tens TeV energy raised in most recent searches.  Furthermore, there is a tension between the internal HESE event spectra power index and the external thorough-going muon tracks one. As shown in the conclusions a more mundane (but a bit more abundant) prompt charmed atmospheric neutrino component may pollute and rule the data, explaining most of the present enlisted IceCube puzzles.  Review the last HESE event data shown in early and in most recent papers (and talks in Neutrino 2018) making the case for the simplest conclusions.  believe that most astrophysical neutrino signals are still hidden below the ashes of these new, anyway discovered, prompt atmospheric noise.