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.