Day 1355

Friday.

1712.09736
Removing the impact of correlated PSF uncertainties in weak lensing
Lu, Zhang, et al

Accurate reconstruction of the spatial distributions of the PSF is crucial for high precision cosmic shear measurements.  Nevertheless, current methods are not good at recovering the PSF fluctuations of high spatial frequencies.  In general, the residual PSF fluctuations are spatially correlated, therefore can significantly contaminate the correlation functions of the WL signals.  Propose a method to correct for this contamination statistically, without any assumptions on the PSF and galaxy morphologies or their spatial distribution.  Demonstrate the idea with the data from the W2 field of CFHTLenS.

Day 1354

Wednesday.  Thursday.  Friday.  Monday.  (Tuesday.)  Wednesday.  (Thursday.)

1712.08234
The elusive origin of Mercury
Ebel, Stewart

The MESSENGER mission sought to discover what physical processes determined Mercury's high metal to silicate ratio.  Instead, the mission has discovered multiple anomalous characteristics about the innermost planet.  The lack of FeO and the reduced oxidation state of Mercury's crust and mantle are more extreme than nearly all other known materials in the solar system.  In contrast, moderately volatile elements are present in abundances comparable to the other terrestrial planets.  No single process using Mercury's formation is able to explain all of these observations.  Here, review the current ideas for the origin of Mercury's unique features.  Gaps in understanding the innermost regions of the solar nebular limit testing different hypothesis.  Even so, all proposed models are incomplete and need further development in order to unravel Mercury's remaining secrets.

Day 1353

Friday.  Monday.  Tuesday.

1712.05800
The Hubble constant from SN Refsdal
Vega-Ferrero, Diego, Miranda, Bernstein

HST observations from Dec 11 2015 detected the expected fifth counter image of SN Refsdal at z=1.49.  In this letter, compare the time delay predictions from numerous models with the measured value derived by Kelly et al (2016) from very early data in the light curve of the SN Refsdal, and find a best value for H0=66±12 km/s/Mpc (68% CL), in excellent agreement with predictions from CMB and recent WL data + BAO + BBN (from DES).  This is the first constraint on H0 derived from time delays between multiple lensed SN images, and the first with a galaxy cluster lens, so subject to systematic effects different from other time-delay H0 estimates.  Additional time delay measurements from new multiply-image See will allow derivation of competitive constraints on H0.


1712.06209
Dark Energy Survey Year 1 results: measurement of the Baryon Acoustic Oscillation scale in the distributions of galaxies to redshift 1
DES Collaboration

Present angular diameter distance measurements obtained by locating the BAO scale in the distribution of galaxies selected from DES.  Consider a sample of >1.3 million galaxies distributed over a footprint of 1318 deg^2 with 0.6<z<1 and a typical redshift uncertainty of 0.03(1+z).  This sample was selected, as full described in a companion paper, using a color/magnitude selection that optimizes trade-offs between number density and z uncertainty.  Investigate the BAO signal in the projected clustering using 3 conventions, the angular separation, the co-moving transverse separation, and spherical harmonics.  Further, compare results obtained from template based and machine learning photo-z determinations.  Use 1800 sims that approximate the sample in order to produce covariance matrices and all validation of the distance scale measurement methodology.  Measure the angular diameter distance, D_A, at the effective z of the sample divided by the true physical scale of the BAO feature, r_d.  Obtain close to a 4% distance measurement of D_A(z_eff=0.81)/r_d = 10.75±0.43.  These results are consistent with the flat LCDM concordance cosmological model supported by numerous other recent experimental results.

Day 1352

Thursday.

1712.04923
The skewed weak lensing likelihood: why biases arise, despite data and theory being sound
Sellentin, Heymans, Harnois-Déraps

Derive the essential so f the skewed WL likelihood via a simple Hierarchical Model.  The likelihood passes 4 objective and cosmology-independent tests which a standard Gaussian likelihood fails.  Demonstrate that sound WL analysis are naturally biased low, and this does not indicate any new physics such as deviations from LCDM.  Mathematically, the biases arise because noisy 2pt functions follow skewed distributions. This form of bias is already known from CMB analyses, where the low multiples have asymmetric error bars.  WL is more strongly affected by this asymmetry as galaxies form a discrete set of shear tracer particles, in contrast to a smooth shear field.  Demonstrate that the biases can be up to 30% of the standard deviation per data point, dependent on the properties of the WL survey.  The likelihood provides a versatile framework with which to address this bias in future WL analyses.

Day 1351

Wednesday.

1712.03986
Can gravitational microlensing detect extragalactic exoplanets?  Self-lensing models of the Small Magellanic Cloud
Mroz, Poleski

Use 3D distributions of classical Cepheids and RR Lyrae stars in SMC to model the stellar density distribution of a young and old stellar population in that galaxy.  Use these models to estimate the microlensing self-lensing optical depth to the SMC, which is in excellent agreement with the observations.  Thus, estimate the total stellar mass of the SMC of about 1.0e9Msun under assumption that all microlensing events toward this galaxy are caused by self-lensing.  Also calculate the expected event rates and estimate that future large-scale surveys, like the LSST, will be able to detect up to a few dozen microlensing events in the SMC annually.  If the planet frequency in the SMC is similar to that in the MW, a few extragalactic planets can be detected over the course of the LSST survey, provided significant changes in the SMC observing strategy are devised.  A relatively small investment of LSST resources can give a unique probe of the population of extragalactic exoplanets.


1712.03997
The extended Baryon Oscillation Spectroscopic Survey (eBOSS): testing a new approach to measure the evolution of the structure growth
Ruggeri, Percival, Mueller, Gil-Marin, Zhu, Padmanabhan, Zhao

eBOSS is one of the first of a new generation of galaxy z surveys that will cover a large range in z with sufficient resolution to measure the BAO signal.  For surveys covering a large redshift range, cosmological evolution can no longer be ignored, meaning that either the z shells analyzed have to be significantly narrower than the survey, or averaging over evolving quantities must be allowed.  Both have the potential to remove signal: analyzing small volumes increases the size of the Fourier window function, reducing the large-scale information, while averaging over evolving quantities can, if not performed carefully, remove differential information.  It will be important to measure cosmo evolution from these surveys to explore and discriminate between models.  Apply a method to optimally extract this differential information to mock catalogues designed to mimic the eBOSS quasar sample.  By applying a set of weights to extract z space distortion measurements as a function of z, demonstrate an analysis that does not invoke the problems discussed above.  Show that the estimator gives unbiased constraints.

Day 1350

Tuesday.

1712.03255
Painting galaxies into dark matter haloes using machine learning
Agarwal, Davé, Bassett

Use machine learning (ML0 to populate large DM-only sims with baryonic galaxies.  The ML framework takes input halo properties including halo mass, environment, spin, and recent growth history, and outputs central galaxy and overall halo baryonic properties including stellar mass, SFR, metallicity, and neutral hydrogen mass.  Apply this to the MUFASA cosmo hydro sim, and show that it recovers the mean trends of output quantities with halo mass highly accurately, including following the shape drop in SFR and gas in quenched massive galaxies.  However, the scatter around the mean relations is under-predicted.  Examining galaxies individually, at z=0 the stellar mass and metallicity are accurately recovered (sigma ~< 0.2 dex), but SFR and HI show larger scatter (sigma >~0.3 dex); these values improved somewhat at z=1,2.  ML quantitatively recovers second parameter trends in galaxy properties, e.g. that galaxies with higher gas content and lower metallicity have higher SFR at a given M*.  Testing various ML algorithms, find that none performs significantly better than the others.  Ensembling the algorithms does not fare better, likely because of correlations between the algorithms and the fact that none of the algorithms predict the large observed scatter around the mean properties.  For the random forest, find that halo mass and nearby (~200 kpc) environment are the most important predictive variables followed by growth history.  Find that halo spin and ~Mpc scale environment are not.  Finally, study the impact of additional inputting key baryonic properties M*, SFR, and Z, as would be available e.g. from an equilibrium model, and show that particularly providing the SFR enables HI to be recovered substantially more accurately.


1712.03644
Galaxy and Mass Assembly (GAMA): Blue spheroids within 87 Mpc
Mahajan, et al

Sample of 428 galaxies of various morphologies in 0.002<z<0.02 (8-87 Mpc) with panchromatic data from GAMA.  Find that BSph galaxies are structurally very similar to their passively-evolving red counterparts, but their SF and other properties such as color, age and metallicity are more like SF spirals than spheroids.  Show that BSph galaxies are statistically distinguishable from other spheroids as well as spirals in the multi-dimensional space mapped by luminosity-weighted age, metallicity, dust mass and sSFR.  Use HI data to reveal that some of the BSphs are further developing their disks, hence their blue colors.  They may eventually become spiral galaxies --- if sufficient gas accretion occurs --- or more likely fade into low-mass red galaxies.

Day 1349

Monday.

1712.02886
Cosmological constraints from galaxy clustering in the presence of massive neutrinos
Zennaro, Bel, Dossett, Carbone, Guzzo

The clustering ratio is defined as the ratio between the correlation function and the variance of the smoothed overdensity field.  In LCDM cosmologies not accounting for massive neutrinos, it has already been proved to be independent from bias and redshift space distortions on a range of linear scales.  It therefore allows for a direct comparison of measurements (from galaxies in z space) to predictions (for matter in real space).  In this paper, first extend the applicability of such properties of the clustering ratio to cosmologies that include massive neutrinos, by performing tests against simulated data.  Then investigate the constraining power of the clustering ratio when cosmological parameters such as the total neutrino mass and the equation of state of dark energy are left free.  Analyze the joint posterior distribution of the parameters that must satisfy, at the same time, the measurements of the galaxy clustering ratio in the SDSS DR12, and the angular power spectrum of temperature and polarization anisotropies of the CMB measured by the Planck satellite.  Find the clustering ratio to be very sensitive to the CDM density parameter, but nut very much so to the total neutrino mass.  Lastly, forecast the constraining per the clustering ratio will achieve with forthcoming surveys, predicting the amplitude of its errors in a Euclid-like galaxy survey.  In this case, find it is expected to improve the constraint at 95% level on the CDM density by 40% and on the total neutrino mass by 14%.


1712.02967
Emerging spatial curvature can resolve the conflict between high-redshift (CMB) and low-redshift (distance ladder) measurements of $H_0$
Bolejko

The measurements of the Hubble constant reveal a tension between high-redshift (CMB) and low-z (distance ladder) constraints.  So far neither observational systematics nor new physics has been successfully implemented to explain this tension away.  This paper present a new solution to the Hubble constant problem.  It uses a relativistic simulation of the large scale structure of the Universe (the Simsilun Simulation) together with the ray-tracing algorithm.  The Simsilun simulation allows for relativistic and nonlinear evolution of cosmic structures, which results with a phenomenon of emerging spatial curvature, where the spatial curvature evolves from spatial flatness of the early universe towards slightly curved present-day universe.  This phenomenon speeds up the expansion rate compared to the spatially flat LCDM model.  The results of the ray-tracing analysis show that the universe which starts with initial conditions consistent with the Planck constraints should have the Hubble constant H_0=72.5±2.1 km/s/Mpc.  If the relativistic corrections are not included then the results of the simulation and ray-tracing point towards H_0=68.1±2.0 km/s/Mpc.  Thus, the inclusion of relativistic effects that lead to emergence of the spatial curvature can explain why the low-z measurements favor higher values compared to high-z constraints and alleviate the tension between the CMB and distance ladder measurements of the Hubble constant.

Day 1348

Friday.

1712.02411
The BAHAMAS project: the CMB--large-scale structure tension and the roles of massive neutrinos and galaxy formation
McCarthy, Bird, Schaye, Harnois-Deraps, Font, van Waerbeke

Recent studies have presented evidence for tension between the constraints on Omega_m and sigma_8 from the CMB and measurements of LSS.  This tension can potentially be resolved by appealing to extensions of the standard model of cosmology and/or untreated systematic errors in the modeling of LSS, of which baryonic physics has been frequently suggested.  Revisit this tension using, for the first time, carefully-calibrated cosmological hydrodynamical simulations, which thus capture the back reaction of the baryons on the total matter distribution.  Extend the BAHAMAS simulations to include a treatment of massive neutrinos, which currently represents the best motivated extension to the standard model.  Make synthetic thermal SZ effect, WL, and CMB lensing maps and compare to observed auto-and cross-power spectra from a wide range of recent observational surveys.  Conclude that i) in general there is tension between the primary CMB and LSS when adopting the standard model with minimal neutrino mass; ii) after calibrating feedback processes to match the gas fractions of clusters, the remaining uncertainties in the baryonic physics modeling are insufficient to reconcile this tension; and iii) invoking a non-minimal neutrino mass, typically of 0.2-0.4 eV (depending on the priors on the other relevant cosmological parameters and the datasets being modeled), can resolve the tension.  This solution is fully consistent with separate constraints on the summed neutrino mass from the primary CMB and BAO, given the internal tensions in the Planck primary CMB dataset.

Day 1347

Wednesday.  Thursday.

1712.01846
Testing gravity on cosmological scales with cosmic shear, cosmic microwave background anisotropies, and redshift-space distortions
Ferté, Kirk, Liddle, Zuntz

Use a range of cosmological data to constrain phenomenological modifications to GR on cosmological scales, through modifications to the Poisson and lensing equations.  Include CMB anisotropies measurements from the Planck satellite, cosmic shear from CFHTLenS and DES-SV, and z-space distortions from BOSS DR12 and the 6dF galaxy survey.  Find no evidence of departures from GR, with the modified gravity parameters constrained to Sigma=-0.01-0.04+0.05 and m=-0.06±0.18.  Also forecast the sensitivity of the full five-year DES and of an LSST-like experiment to those parameters, showing a substantial expected improvement in the constrain on Sigma.


1712.01989
Using velocity dispersion to estimate halo mass: is the Local Group in tension with $\Lambda$ CDM?
Elahi, Power, Lagos, Poulton, Robotham

Satellite galaxies are commonly used as tracers to measure the line-of-sight velocity dispersion (sigma_LOS) of the DM halo associated with their central galaxy, and thereby to estimate the halo's mass.  Recent observational dispersion estimates of the Local Group, including the MW and M31, suggest sigma~50 km/s, which is surprisingly low when compared to the theoretical expectations of sigma~100s km/s for systems of their mass.  Does this pose a problem for LCDM?  Explore this tension using the SURVS suite of N-body sims, containing over 10k (sub)halos with well tracked orbits.  Test how well a central galaxy's host halo velocity dispersion can be recovered yb sampling sigma_LOS of sub haloes and surrounding haloes.  The results demonstrate that sigma_LOS is a biased mass proxy.  Define an optimal window in v_LOS and projected distance D_p -- 0.5<~ D_p/R_vir <~1.0 and v_LOS <~0.5 V_esc, where R_vir is the viral radius and V_esc is the escape velocity -- such that the scatter in LOS to halo dispersion is minimized - sigma_LOS=0.5±0.1 sigma_v,H.  Argue that this window should be used to measureLoS dispersions as a proxy for mass, as it minimizes scatter in the sigma_LOS-M_vir relation.  This bias also naturally explains the results from McConnachie 2012, who used similar cuts when estimating sigma_LOS,LG.  Conclude that the LG's velocity dispersion does not pose a problem for LCDM and has a mass of logM_LG,M_sun=11.99+0.26-0.63.

Day 1346

Tuesday.

1712.00677
The $H_0$ and $\sigma_8$ tensions and the scale invariant spectrum
Benetti, Graef, Alcaniz

In a previous communication showed that a joint analysis of CMB data and the current measurement of the local expansion rate favors a model with a scale invariant spectrum HZ over the minimal LambdaCDM scenario provided that the effective number of relativistic degrees of freedom, N_eff, is taken as a free parameter.  Such a result is basically obtained due to the HST value of the Hubble constant, H0=73.24±1.74 km/s/Mpc (68% CL), as the CMB data alone discard the HZ+N_eff model.  Although such a model is not physically motivated by current scenarios of the early universe, observations pointing to a scale invariant spectrum may indicate that the origin of cosmic perturbations lies in an unknown physical process.  Here, extend the previous results performing a Bayesian analysis using joint CMB, HST and BAO measurements.  In order to take into account the well-known tension on the value of the fluctuation amplitude parameter, sigma_8, also consider Cluster Number counts (CN) and WL data.  Use two different sample of BAO data, which are obtained using 2pt spatial (BAO 2PCF) and angular (BAO 2PACF) correlation functions.  The results show that a joint CMB+HST+BAO 2PACF favors the former model, even when an extended dataset with NC [CN?] and WL is considered.

Day 1345

Monday.

1712.00058
The dynamics of stellar disks in live dark-matter halo
Fujii, et al

Recent developments in computer hardware and software enables researchers to simulate the self-gravitating evolution of galaxies at a resolution comparable to the actual number of stars.  Present the results of a series of such simulations.  Perform N-body sims of disk galaxies at with 100 and 500 million particles over a wide range of initial conditions.  The calculations include a live bulge, disk, and DM halo, each of which is represented by self-gravitating particles in the N-body code.  The simulations are performed using the gravitational N-body tree-code Bonsai running on the Piz Daint supercomputer.  Find that the time scale over which the bar forms increase exponentially with decreasing disk-mass fraction.  The effective criterion for bar formation is obtained in the simulations for a disk-to-halo mass-fractions >~0.25.  These results can be explained with the swing-amplification theory.  The conditions for the formation of m=2 spirals is consistent with that for the formation of the bar, which also is an m=2 phenomenon.  Further argue that the 2-armed structures in grand-design spiral galaxies is a transitional phenomenon, and that these galaxies evolve to barred galaxies on a dynamical timescale.  The resulting barred galaxies have rich morphology, which is also present in the Hubble sequence.  Explain the sequence of spiral-galaxies in the Hubble diagram by the bulge-to-disk mass fraction, and the sequence of barred-spiral galaxies is a consequence of secular evolution.


1712.00094
Strong orientation dependence of surface mass density profiles of dark haloes at large scales
Osato, et al

Study the dependence of surface mass density profiles, which can be directly measured by weak gravitational lensing, on the orientation of haloes with respect to the line-of-sight direction, using a suite of N-body simulations.  Find that, when major axes of haloes are aligned with the line-of-sight direction, SMD profiles have higher amplitudes than those averaged over all halo orientations, over all scales from 0.1 to 100 Mpc/h studied.  While the orientation dependence at small scales is ascribed to the halo triaxiality, the results indicate even stronger orientation dependence in the so-called 2-halo regime, up to 100 Mpc/h.  The orientation dependence for the 2-halo term is well approximated by a constant shift of the amplitude and therefore a shift in the halo bias parameter value.  The halo bias from the 2-halo term can be overestimated or underestimated by up to ~30% depending on the viewing angle, which translates into the bias in estimated halo masses by up to a factor of 2 from halo bias measurements.  The orientation dependence at large scales originates from the anisotropic halo-matter correlation function, which has an elliptical shape with the axis ratio of ~0.55 up to 100 Mpc/h.  Discuss potential impacts of halo orientation bias on other observables such as optically selected cluster samples and a clustering analysis of large-scale structure tracers such as quasars.

Day 1344

Thursday.  Friday.


1711.10999
KiDS+2dFLenS+GAMA: testing the cosmological model with the $E_{\rm G}$ statistic
Amon, Blake, Heymans, et al

Present a new measurement of E_G, which combines measurements of WL, GC and z-space distortions.  This statistic was proposed as a consistency test of GR that is insensitive to linear, deterministic galaxy bias and the matter clustering amplitude.  Combine deep imaging data from KiDS with overlapping spectroscopy from 2dFLenS, BOSS DR12 and GAMA and find E_G(z=0.27)=0.43±0.13 (GAMA), E_G(z=0.31)=0.27±0.08 (LOWZ+2dFLOZ) and E_G(z=0.55)=0.26±0.07 (CMASS+2dFHIZ).  demonstrate that the existing tension in the value of the matter density parameter hinders the robustness of this statistic as solely a test of GR.  Find that the E_G measurements, as well as existing ones in the literature, favor a lower matter density cosmology than the CMB.  For a flat LCDM universe, find Omega_m(z=0)=0.25±0.03.  With this paper, publicly release the 2dFLenS dataset at http://2dflens.swin.edu.au.

Day 1343

Monday.  Tuesday.  Wednesday.

1711.09882
The shape of galaxy dark matter haloes in massive galaxy clusters: insights from strong gravitational lensing
Jauzac, Harvey, Massey

Assess how much unused strong lensing information is available in the deep HST imaging and VLT/MUSE spectroscopy of the Frontier Field clusters.  As a pilot study, analyze galaxy cluster MACS J0416.1-2403 (z=0.397, M(R<200 kpc)=1.6e14 Msun), which has 141 multiple images with spectroscopic redshifts.  Find that many additional parameters in a cluster mass model can be constrained, and that adding even small amounts of extra freedom to a model can dramatically improve its figures of merit.  Use this information to constrain the distribution of DM around cluster member galaxies, simultaneously with the cluster's large-scale mass distribution.  Find tentative evidence that some galaxies' dark matter has surprisingly similar ellipticity to their stars (unlike in the field, where it is more spherical), but that its orientation is often misaligned.  When non-coincident DM and baryonic haloes are allowed, the model improves by 35%.  This technique may provide a new way to investigate the processes and timescales on which DM is stripped from galaxies as they fall into a massive cluster.  The preliminary conclusions will be made more robust by analyzing the remaining 5 Frontier Field clusters.


1711.10017
The effect of baryons in the cosmological lensing PDFs
Castro, et al

Understanding the effect of baryonic matter on the LSS is one of the challenges to be faced in cosmology.  In this work, thoroughly study the effect of baryonic physics on different lensing statistics.  Making use of the Magnetic Pathfinder suite of sims, show that on angular resolutions already achieved ongoing surveys the influence of luminous matter on the 1pt lensing statistics of point sources is significant, enhancing the probability of magnified objects with mu>3 by a factor of 2 and the occurrence of multiple-images by a factor of 6-30 depending on the source redshift.  Also discuss the dependence of the lensing statistics on the angular resolution of surveys.  The results and methodology were carefully tested in order to guarantee that the uncertainties are much smaller than the effects here presented.


1711.10018
Deriving galaxy cluster velocity anisotropy profiles from a joint analysis of dynamical and weak lensing data
Stark, Miller, Halenka

Present an analytic approach to lift the mass-anisotropy degeneracy in clusters of galaxies by utilizing the line-of-sight velocity dispersion of clustered galaxies jointly with WL-inferred masses.  More specifically, solve the spherical Jeans equation by assuming a simple relation between the line-of-sight velocity dispersion and the radial velocity dispersion and recast the Jeans equation as a Bernoulli differential equation which has a well-known analytic solution.  First test the method in cosmological N-body simulations and then derive the anisotropy profiles for 35 archival data galaxy with an average redshift of <z_c>=0.25.  The resulting profiles yield a weighted average global value of <beta(0.2<=r/r200<=1)>=0.35±0.28(stat)±0.15(sys).  This indicates that clustered galaxies tend to globally fall on radially anisotropic orbits.  Note that this is the first attempt to derive velocity anisotropy profiles for a cluster sample of this size utilizing joint dynamical and WL data.

Day 1342

Thursday.

1711.07985
Declining rotation curves at $z=2$: a natural phenomenon in $\Lambda$CDM cosmology
Teklu, et al

Selecting disk galaxies from the cosmological, hydrodynamical sim Magneticum Pathfinder, show that almost half of the poster child disk galaxies at z=2 show significantly declining rotation curves and low DM fractions, very similar to recently reported observations.  These galaxies do not show any anomalous behavior, reside in standard DM haloes and typically grow significantly in mass until z=0, where they span all morphological classes, including disk galaxies matching present day rotation curves and observed DM fractions.  The findings demonstrate that declining rotation curves and low DM fractions in rotation dominated galaxies at z=2 appear naturally within the LCDM paradigm and reflect the complex baryonic physics, which plays a role at the peak epoch of SF.  In addition, find that dispersion dominated galaxies at z=2, which host a significant gas disk, exhibit similar shaped rotation curves as the disk galaxy population, rendering it difficult to differentiate between these two populations with currently available observation techniques.

Day 1341

Tuesday.  Wednesday.

1711.06692
Influence of XUV Irradiation from Sgr A* on planetary habitability and occurrence of panspermia near the Galactic center
Chen, Forbes, Loeb

Find that, out to ~20 pc from Sgr A*, the XUV flux emitted during its quasar phase can remove several percent of a planet's H/He envelope by mass; in many cases, this removal results in bare rocky cores, many of which situated in the habitable zones (HZs) of G-type stars.  The erosion of sub-neptune sized planets may be one of the most prevalent channels by which terrestrial super-Earths are created near the GalacticCenter.  As such, the planet population demographics may be quite different close to Sgr A* than in the Galaxy's outskirts.  The high stellar densities in this region (about seven orders of magnitude greater than the solar neighborhood) imply that the distance between neighboring rocky worlds is short (500-5000AU).  The proximity between potentially habitable terrestrial planets may enable the onset of widespread interstellar panspermia near the nuclei of galaxies.  More generally, predict these phenomena to be ubiquitous for planets in nuclear star clusters (NSCs) and ultra-compact dwarfs (UCDs).


1711.06801
Whole planet coupling between climate, mantle, and core: implications for the evolution of rocky planets
Foley, Driscoll

Earth's climate, mantle, and core interact over geologic timescales.  Climate influences whether plate tectonics can take place on a planet, with cool climates being favorable for plate tectonics because they enhance stresses in the lithosphere, suppress plate boundary annealing, and promote hydration and weakening of the lithosphere.  Plate tectonics plays a vital role in the long-term carbon cycle, which helps to maintain a temperate climate.  Plate tectonics provides long-term cooling of the core, which is vital for generating a magnetic field, and the magnetic field is capable of shielding atmospheric volatiles from the solar wind.  Coupling between climate, mantle, and core can potentially explain the divergent evolution of Earth and Venus.  As Venus lies too close to the sun for liquid water to exist, there is no long-term carbon cycle and thus an extremely hot climate.  Therefore plate tectonics cannot operate and a long-lived core dynamo cannot be sustained due to insufficient core cooling.  On planets within the habitable zone where liquid water is possible, a wide range of evolutionary scenarios can take place depending on initial atmospheric composition, bulk volatile content, or the timing of when plate tectonics initiates, among other factors.  Many of these evolutionary trajectories would render the planet uninhabitable.  However, there is still significant uncertainty over the nature of the coupling between climate, mantle, and core.  Future work is needed to constrain potential evolutionary scenarios and the likelihood of an Earth-like evolution.


1711.06863
Chasing the peak: optimal statistics for weak shear analysis
Smit, Kuijken

WL analyses are fundamentally limited by the intrinsic, non-Gaussian distribution of galaxy shapes.  Explore alternate statistics for samples of ellipticity measurements that are unbiased, efficient, and robust.  Take the non-linear mapping of gravitational shear and the effect of noise into account.  Then discuss how the distribution of individual galaxy shapes in the observed field of view can be modeled by fitting Fourier modes to the shear pattern directly.  Simulate samples of galaxy ellipticities, using both theoretical distributions and real data for ellipticities and noise; determine the possible bias Delta e, the efficiency eta and the robustness of the least absolute deviations, the biweight, and the convex hull peeling estimators, compared to the canonical weighted mean.  Using these statistics for regression, show the applicability of direct Fourier mode fitting.  These estimators can be unbiased in the absence of noise, and decrease noise bias by more than ~30%.  The convex hull peeling estimator distribution is centered around the underlying shear, and its bias least affected by noise.  The least absolute deviations estimator is found to be the most efficient estimator in almost all cases, except in the Gaussian case, where it's still competitive (0.83<eta<5.1) and therefore robust.  These results hold when fitting Fourier modes, where amplitudes of variation in ellipticity are determined to the order of 1e-3.  The peak of the ellipticity distribution is a direct tracer of the underlying shear and unaffected by noise; show that estimators that are sensitive to a central cusp perform more efficiently, potentially reducing uncertainties by more than 50% and significantly decreasing noise bias.


1711.07297
Models of gravitational lens candidates from Space Warps CFHTLS
Küng, Saha, et al

Report modeling follow-up of recently-discovered gravitational-lens candidates in CFHTLS.  Lens modeling was done by a small group of specially-interested volunteers from the SpaceWarps citizen-science community who originally found the candidate lenses.  Models are categorized according to 7 diagnostics indicating (a) the image morphology and how clear or indistinct it is, (b) whether the mass map and synthetic lensed image appear to be plausible, and (c) how the lens-model mass compares with the stellar mass and the abundance-matched halo mass.  The lensing masses range from ~1e11 Msun to >1e13 Msun.  Preliminary estimates of the stellar masses show a smaller spread in stellar mass (except for two lenses): a factor of a few below or above ~1e11 Msun.  Therefore, expect the stellar-to-total mass fraction to decline sharply as lensing mass increases.  The most massive system with a convincing model is J1434+522 (SW05).  The two low-mass outliers are J0206-095 (SW19) and J2217+015 (SW42); if these two are indeed lenses, they probe an interesting regime of very low SF efficiency.  Some improvements to the modeling software (SpaghettiLens), and discussion of strategies regarding scaling to future surveys with more and frequent discoveries, are included.


1711.07467
Complete super-sample lensing covariance n the response approach
Barreira, Krause, Schmidt

Derive the complete SSC of the matter and WL convergence power spectra using the PS response formalism to accurately describe the coupling of super-to-intra survey modes.  The SSC term is completely characterized by the survey window function, the NL matter PS and the full first-order NL power spectrum response function, which describes the response to SS density and tidal field perturbations.  Separate universe simulations can efficiently measure these responses in the NL regime of structure formation, which is necessary for lensing applications.  Under the Limber and flat-sky approximations, show that the tidal contributions, which have not been included in cosmological analyses so far, represent a significant fraction (~20-25%) of the total SSC, even for an isotropic survey footprint on the sky.  The SSC is the dominant off-diagonal contribution to the total lensing covariance for survey sky fractions f_sky <~0.3, making it important to include these tidal terms in cosmic shear analyses.


1711.07919
A quadruply lensed SN Ia: gaining a time-delay...losing a standard candle
Yahalomi, Schechter, Wambsganss

Investigate the flux ratio anomalies between macro-model predictions and the observed rightness of the SN iPDF16geu, as published in a recent paper by More+ 2017.  This group suggested that these discrepancies are, qualitatively, likely due to microlensing.  Analyze the plausibility of attributing this discrepancy to microlensing, and find that the discrepancy is too large to be due to microlensing alone.  This is true whether one assumes knowledge of the luminosity of the SN or allows the luminosity to be a free parameter.  Varying the dark/stellar ratio likewise doesn't help.  In addition, other macro-models with quadruplicity from external shear or ellipticity do not significantly improve to model.  Finally, microlensing also makes it difficult to accurately determine the standard candle brightness of the SN, as the likelihood plot for the intrinsic magnitude of the source (for a perfect macro-model) has a FWHM of 0.73 magnitudes.  As such, the error for the standard candle brightness is quite large.  This reduces the utility of the standard candle nature of type Ia SN.

Day 1340

Monday.

1711.06267
There is no missing satellites problem
Kim, Peter, Hargis

A critical challenge to the CDM paradigm is that there are fewer satellites observed around the MW than found in simulations of DM substructure.  Show that there is a match between the observed satellite counts corrected by the detection efficiency of the SDSS (for luminosities L<~340 L_sun) and the number of luminous satellites predicted by CDM, assuming an empirical relation between stellar mass and halo mass.  The "missing satellites problem", cast in terms of number counts is thus solved, and imply that luminous satellites inhabit sub halos as smalls 1e7-8 Msun.  The total number of MW satellites depends sensitively on the spatial distribution of satellites.  Also show that WDM models with a thermal relic mass smaller than 4 keV are robustly ruled out, and that limits of m_WDM <~ 8keV from the MW are probable in the near future.  Similarly stringent constraints can be placed on any DM model that leads to a suppression of the matter power spectrum on ~1e7 Msun scales.  Measurements of completely dark halos below 1e8 Msun, achievable with substructure lensing, are the next frontier for tests of CDM.


1711.06273
Exploring the brighter fatter effect with the hyper suprime-cam
Coulton, Armstrong, Smith, Lupton, Spergel

The brighter fatter effect has been postulated to arise due to the build up of a transverse electric field, produced as photo-charges accumulate in the pixels' potential wells.  Investigate the brighter fatter effect in HSC by examine flat fields and moments of stars.  Observe deviations from the expected linear relation in the photon transfer curve, luminosity dependent correlations between pixels in flat field images and a luminosity dependent PSF in stellar observations.  Under the key assumptions of translation invariance and Maxwell's equations in thequasi-static limit, give a first-principles proof that the effect can be parameterized by a translationally invariant scalar kernel.  Describe how this kernel can be estimated from flat fields and discuss how this kernel has been used to remove the brighter fatter distortions in HSC images.  Find that the correction restores the expected linear relation in the photon transfer curves and significantly reduces, but does not completely remove, the luminosity dependence of the PSF over a wide range of magnitudes.

Day 1339

Friday.

1711.05761
Interstellar communication. III. Optimal frequency to maximize data rate
Hippke, Forgan

The optimal frequency for interstellar communication, using "Earth 2017" technology, was derived in papers I and II of this series.  The framework included models for the loss of photons from diffraction (free space), interstellar extinction, and atmospheric transmission.  A major limit of current technology is the focusing of wavelengths lambda < 300 nm (UV).  When this technological constraint is dropped, a physical bound is found at lambda ~ 1 nm (E~keV) for distances out to kpc.  While shorter wavelengths may produce tighter beams and thus higher data rates, the physical limit comes from surface roughness of focusing devices at the atomic level.  This limit can be surpassed by beam-forming with EM fields, e.g. using a free electron laser, but such methods are not energetically competitive.  Current lasers are not yet cost efficient at nm wavelengths, with a gap of two orders of magnitude, but future technological progress may converge on the physical optimum.  Recommend expanding SETI efforts towards targeted (at us) monochromatic (or narrow band) X-ray emission at 0.5-2 keV energies.


1711.06029
Measuring the hydrostatic mass bias in galaxy clusters by combining Sunyaev-Zel'dovich and CMB lensing data
Hurier, Angulo

The cosmological parameters preferred by the CMB primary anisotropies predict many more galaxy clusters than those that have been detected via the tSZ effect.  This tension has attracted considerable attention since it could be evidence of physics beyond the simplest LCDM model.  However, an accurate and robust calibration of the mass-observable relation for clusters is necessary for the comparison, which has been proven difficult to obtain so far.  Here, present new constraints on the mass-pressure relation by combining tSZ and CMB lensing measurements about optically-selected clusters.  Consequently, the galaxy cluster sample is independent from the data employed to derive cosmological constraints.  Estimate an average hydrostatic mass bias of b=0.26±0.07, with no significant mass nor z evolution.  This value greatly reduces the tension between the predictions of LCDM and the observed abundance of tSZ clusters while being in agreement with recent estimations from tSZ clustering.  On the other hand, the value for b is higher than the predictions from hydro-dynamical simulations.  This suggests the existence of mechanisms driving large departures from hydrostatic equilibrium and that are not included in state-of-the-art simulations, and/or unaccounted systematic errors such as biases in the cluster catalogue due to the optical selection.

Day 1338

Monday.  Tuesday, network issues at Cornell (arXiv).  Wednesday.  Thursday.

1711.05272
The stellar populations of two ultra-diffuse galaxies from optical and near-infrared photometry
Pandya, et al

Present observational constraints on the stellar populations of 2 UDGs using optical through NIR data, from Spitzer IRAC 3.6um and 4.5um imaging, archival optical imaging, and with a Bayesian SED fitting framework.  3 samples : 1 field UDG, 1 cluster UDG, and one cluster dwarf elliptical.  All 3 galaxies have NIR colors that are significantly different form each other.  The Virgo UDG is old (~7.7 Gyr) and significantly metal poor (Z/Zsun <~ -1.0).  The field UDG is probably younger than the Virgo UDG, with an extended SFH and an age posterior extending down to ~3 Gyr.  The stellar metallicity of the field UDG is sub-solar, but higher than that of the Virgo UDG, with Z/Zsun=-0.63+0.35-0.62; in the case of exactly zero diffuse interstellar dust, the field UDG may even have solar metallicity.  The spectroscopically confirmed globular clusters of the Virgo UDG have similar optical-NIR colors as the UDG itself, with empirical color relations suggesting sub-solar metallicities and supporting the metal-poor nature of it.  With it and several Coma UDGs, a general picture is emerging where cluster UDGs may be "failed" galaxies, but the field UDG seems more consistent with a stellar feedback-induced expansion scenario.


1711.05276
Disruption of dark matter substructure: fact or fiction?
van den Bosch, Ogiya, Hahn, Burkert

Use both analytical estimates and idealized numerical simulations to investigate whether the DM substructure disruption in N-body sims is mainly physical (tidal heating and stripping) or numerical (i.e., artificial).  Show that, contrary to naive expectation, sub haloes that experience a tidal shock Delta E that exceeds the smbhalo's binding energy, E_b, do not undergo disruption, even when Delta E/E_b is as large as 100.  Along the same line, and contrary to existing claims in the literature, instantaneously stripping matter from the outskirts of a DM subhalo also does not result in its complete disruption, even when the instantaneous remnant has positive binding energy.  In addition, show that today heating due to high-speed (impulsive) encounters with other sub haloes ('harassment'), is negligible compared to the tidal effects due to the host halo.  Hence conclude that in the absence of baryonic processes, the complete, physical disruption of CDM substructure is extremely rare, and that most disruption in numerical simulations therefore must be artificial.  Discuss various processes that have been associated with numerical over merging, and conclude that inadequate force-softening is the most likely culprit.

Day 1337

Friday.

1711.03234
SDSS-V: Pioneering Panoptic spectroscopy
Kollmeier, et al

SDSS-V will be an all-sky, multi-epoch spectroscopic survey of over 6M objects.  It is designed to decode the history of the Milky Way, trace the emergence of the chemical elements, reveal the inner workings of stars, and investigate the origin of planets.  It will also create an integral-field spectroscopic map of the gas in the Galaxy and the Local Group that is 1000x larger than the current state of the art and at high enough spatial resolution to reveal the self-regulation mechanisms of galactic ecosystems.  SDSS-V will pioneer systematic, spectroscopic monitoring across the whole sky, revealing changes on timescales from 20 minutes to 20 years.  The survey will thus track the flickers, flares, and radical transformations of the most luminous persistent objets in the universe: massive black holes growing at the centers of galaxies.  The scope and flexibility of SDSS-V will be unique among extant and future spectroscopic surveys: it is all-sky, with matched survey infrastructures in both hemispheres; it provides near-IR and optical multi-object fiber spectroscopy that is rapidly reconfigurable to serve high target densities, targets of opportunity, and time-domain monitoring; and it provides optical, ultra-wide-field integral field spectroscopy.  SDSS-V, with its programs anticipated to start in 2020, will be well-timed to multiply the scientific output from major space missions (e.g., TESS, Gaia, eROSITA) and ground-based projects.  SDSS-V builds on the 25-year heritage of SDSS's advances in data analysis, collaboration infrastructure, and product deliverables.  The project is now refining its science scope, optimizing the survey strategies, and developing new hardware that builds on the SDSS-IV infrastructure.  Present here an overview of the current state of these developments as the worldwide consortium of institutional and individual members are sought to be built.

Day 1336

Thursday.

1711.02677
Scale dependence of galaxy biasing investigated by weak gravitational lensing: an assessment using semi-analytic galaxies and simulated lensing data
Simon, Hilbert

Galaxies are biased tracers of the matter density on cosmological scales.  For future tests of galaxy models, refine and assess a method to measure galaxy biasing as function of physical scale k with WL.  This method enables reconstruction of the galaxy bias factor b(k) as well as the galaxy-matter correlation r(k) on physical scales between 0.01 h/Mpc <~ k <~ 10 h/Mpc for redshift-binned lens galaxies below z <~0.6.  In the refinement, account for an intrinsic alignment of source ellipticities, and correct for the lensing magnification of the angular number density of the lens galaxies to improve the accuracy of the reconstructed r(k).  For simulated data, the reconstructions achieve an accuracy of 3-7% (68% CL) over the above k-range for a survey area and a typical depth of contemporary ground-based surveys.  Realistically the accuracy is, however, probably reduced to about 10-15%, mainly by systematic errors in the assumed intrinsic source alignments, the fiducial cosmology, and the z distributions of lens and source galaxies (in that order).  Furthermore, the reconstruction technique employs physical templates for b(k) and r(k) that elucidate the impact of central galaxies and the halo-occupation statistics of satellite galaxies on the scale-dependence of galaxy bias, which is discussed in the paper.  In a first demonstration, apply this method to previous measurements in the Garching-Bonn-Deep Survey and give a physical interpretation of the lens population.


1711.02780
Mining the Kilo-Degree Survey for solar system objects
Mahlke, et al

The search for minor bodies in the solar system promises insights into its formation history.  Wide imaging surveys offer the opportunity to serendipitously discover and identify these traces of planetary formation and evolution.  Aim to present a method to acquire position, photometry, and proper motion measurements of solar system objects in surveys using dithered image sequences.  The application of this method on KiDS is demonstrated.  Optical images of 346 sq deg fields of the sky are searched in up to 4 filters using the AstrOmatic software suite to reduce the pixel to catalog data.  The solar system objects within the acquired sources are selected based on a set of criteria depending on their number of observation, motion, and size.  The Virtual Observatory SkyBoT tool is used to identify known objects.  Observed 20,221 SSO candidates, with an estimate false-positive content of less than 0.05%.  Of these SSO candidates, 53.4% are identified by  SkyBoT.  KiDS can detect previously unknown SSOs because of its depth and coverage at high ecliptic altitude, including parts of the Souther Hemisphere.  Thus, expect the large fraction of the 46.6% of unidentified objects to be truly new SSOs.  The method is applicable to a variety of dithered surveys such as DES, LSST, and Euclid.  It offers a quick and easy-to-implement search for solar system objects.  SkyBoT can then be used to estimate the completeness of the recovered sample.