Day 1494

Wednesday.

1810.11924
The discovery of a gravitationally lensed quasar at z=6.51
Fan, et al

SL provides a powerful probe of the physical pervertier of quasars and their host galaxies.  A high fraction of the most luminous high-redshift quasars was predicted to be lensed due to magnification bias.  However, no multiple imaged quasar was found at z>5 in previous surveys.  Report the discovery of J043947.08+1634157, a strongly lensed quasar at z=6.551, the first such object detected at the epoch of reionization, and the brightest quasar yet known at z>5.  High-resolution HST imaging reveals a multiple imaged system with a maximum image separation theta ~ 0.2", best explained by a model of 3 quasar images lensed by a low luminosity galaxy at z~0.7, with a magnification factor of ~50.  The existence of this source suggests that a significant population of strongly lensed, high redshift quasars could have been missed by previous surveys, as standard color selection techniques would fail when the quasar color is contaminated by the lensing galaxy.


1810.11985
A redshift survey of the nearby galaxy cluster bell 2107: Global rotation of the cluster and its connection t large-scale structures in the universe
Song, et al

Study the rotational motion of the galaxy cluster Abell 2107 at z=0.04 and its connection to nearby large-scale structures using a large amount of spectroscopic redshift data. By combining 978 new redshirts from the MMT/Hectospec observations with data in the literature, construct a large sample of 1968 galaxies with measured redshifts at cluster centric radius R<60'.  The sample has high (80%) and spatially uniform completeness at r-band apparent magnitude m_r,Petro,0<19.1.  First apply the caustic method to the sample and identify 285 member galaxies of Abell 2107 at R<60'.  Then the rotation amplitude and the position angle of rotation axis are measured.  Find that the member galaxies show strong global rotation at R<20' (v_rot/sigma_v~0.6) with a significance of >3.8sigma, which is confirmed by 2 independent methods.  The rotation becomes weaker in outer regions.  There are at least 5 filamentary structures that are connected to the cluster and that consist of known galaxy groups.  These structures are smoothly connected to the cluster, which seem to be inducing the global rotation of the cluster through inflow of galaxies.


1810.12296
Selection functions of large spectroscopic surveys
Mints, Hekker

Introduce a method to estimate the selection for a given spectroscopic survey.  Apply this method to a large sample of public spectra surveys.  Apply a median division lining algorithm to bin observed stars in the color-magnitude space.  This approach produces lower uncertainties and lower biases of the selection function estimate as compared to traditionally used 2d-histograms.  Run a set of simulations to verify the method and calibrate the one free parameter it contains.  These simulations also allow precision and accuracy testing of the method.  Produce and publish estimated values and uncertainties of selection functions for large sample of public spectra surveys. Publicly release the code used to produce the selection function estimates.  The effect of the selection function on distance modulus and metallicity distributions of stars in surveys is important for surveys with small and largely inhomogeneous spatial coverage.  For surveys with contiguous spatial coverage, the effect of the selection function is almost negligible.


1810.12302
Most lensed quasars at z>6 are missed by current surveys
Pacucci, Loeb

The discovery of the first SL (mu~50) quasar at z>6 (Fan+2018) represents a breakthrough in the understanding of the early Universe.  Derive the theoretical consequences of the new discovery.  Predict that the observed population of z>6 quasars should contain many mildly magnified (mu<~10) sources, with image separations below the resolution threshold.  Additionally, current selection criteria should have missed a substantial population of lensed z>6 quasars, due to the contamination of the drop-out photometric bounds by lens galaxies.  Quantify the fraction of undetected quasars as a function of the slope of the bright end of the quasar luminosity function, beta.  For beta <~3.6, predict that the undetected lensed quasars could reach half of the population, whereas for beta >~ 4.5 the vast majority of the z>6 quasar population is lensed and still undetected.  Argue that this predicted population of lensed z>6 quasars would be misclassified and mixed up with low-z galaxies.  This would significancy affect the z>6 quasar luminosity function and inferred black hole mass distributions, with profound implications for the UV, X-ray and infrared cosmic backgrounds and the growth of early quasars.


1810.12312
The impact of photometric redshift errors on lensing statistics in ray-tracing simulations
Abruzzo, Haiman

WL surveys are reaching sensitivities at which uncertainties in the galaxy redshift distributions n(z) from photo-z errors degrade cosmological constraints.  Use ray-tracing simulations and a simple treatment of photo-z errors to assess cosmological parameter biases from uncertainties in n(z) in an LSST-like survey.  Use the power spectrum and the abundance of lensing peaks to infer cosmological parameters, and find that the former is somewhat more resilient to photo-z errors.  Place conservative lower limits on the survey size at which different types of photo-z errors degrade LCDM (wCDM) parameter constraints by 50%.  A residual constant photo-z bias of |dz|<0.003(1+z), satisfying the current LSST requirement, does not significantly degrade constraints for surveys smaller than ~1300 (~490) square degrees using lensing peaks and ~6500 (~4900) square degrees using the power spectrum.  Adopting a recent prediction for LSST's full photo-z PDF, find that simply approximating n(z) with the photo-z galaxy distribution directly computed from this PDF would degrade surveys as small as ~60 (~65) square degrees using lensing peaks or the power spectrum.  Assuming that the centroid bias in each tomographic redshift bin can be removed from the photo-z galaxy distribution, using lensing peaks or the power spectrum still degrades surveys larger than ~200 (~255) or ~248 (~315) square degrees.  These results imply that the expected broad photo-z PDF significantly biases parameters, which needs to be further mitigated using more sophisticated photo-z treatments.

Day 1493

Tuesday.

1810.11030
Distinguishing standard and modified gravity cosmologies with machine learning
Peel, et al

Present a convolutional neural network to identify distinct cosmological scenarios based on the weak-lensing maps they produce.  Modified gravity models with massive neutrinos can mimic the standard concordance model in terms of Gaussian weak-lensing observables, limiting a deeper understanding of what causes cosmic acceleration.  Demonstrate that a network trained on simulated clean convergence maps, condensed into a novel representation, can discriminate between such degenerate models with 83%-100% accuracy.  The method outperforms conventional statistics by up to 40% and is more robust to noise.


1810.11658
Dark energy versus modified gravity: impacts on measuring neutrino mass
Zhao, et al

Compare the impacts of smooth dark energy, modified gravity, and interacting dark energy on the cosmological limits on the total mass of active neutrinos.  Consider the wCDM model, the f(R) model, and the interacting vacuum energy models with the forms of Q=beta H rho_Lambda and Q=beta Rho_c.  In the cosmological fits, use the Planck 2015 temperature and polarization data, in combination with other low-redshift observations, including the baryon acoustic oscillations, type Ia SNe, and the Hubble constant measurement, as well as the large-scale structure observations involving weak lensing and redshift-space distortion.  The Planck lensing measurement is also employed.  Find that, compared to the LCDM model, the wCDM model favors a higher upper limit on neutrino mass.  The f(R) model has a quite consistent neutrino mass with that in LCDM.  For the interacting dark energy model, the Q=beta H rho_c model favors a higher upper limit on neutrino mass, but the Q=beta H rho_Lambda model gives an identical neutrino mass with the case of LCDM.  Looking at the correlation between the model parameter and the neutrino mass, find that only when the model parameter is correlated with the neutrino mass, the model would have a significant influence on the measurement of the neutrino mass, otherwise the values of the neutrino mass are largely consistent with that given by LCDM.

Day 1492

Monday.

1810.11027
On the dissection of degenerate cosmologies with machine learning
Merten, Giocoli, et al

Based on the DUSTGRAIN-pathfinder suite of simulations, investigate observational degeneracies between 9 models of modified gravity and massive neutrinos.  3 types of machine learning techniques are tested for their ability to discriminate lensing convergence maps by extracting dimensional reduced representation of the data.  Classical map descriptors such as the power spectrum, peak counts and Minkowski functional are combined into a joint feature vector and compared to the descriptors and statistics that are common to the field of digital image processing.  To learn new features directly from the data, use a Convolutional Neural Network (CNN).  For the mapping between feature vectors and the predictions of their underlying model, implement 2 different classifiers; one based on a nearest-neighbour search and one that is based on a fully connected neural network.  Find that the neural network provides a much more robust classification than the nearest-neighbor approach and that the CNN provides the most discriminating representation of the data.  It achieves the cleanest separation between the different models and the highest classification success rate of 59% for a single source redshift.  Once the tomographic CNN analysis is preformed, the total classification accuracy increases significantly to 76% with no observational degeneracies remaining.  Visualizing the filter response of the CNN at different network depths provides us with the unique opportunity to learn from very complex models and to understand better why they perform so well.


1810.11040
The effect of dark matter-dark radiation interactions on halo abundance -- a Press-Schechter approach
Sameie, et al

Study halo mass functions with the PS formalism for interaction DM models, where matter PS are damped due to dark acoustic oscillations in the early universe.  After adopting a smooth window function, calibrate the analytical model with numerical simulations from the "Effective theory of structure formation" (ETHOS) project and fix the model parameters in the high mass regime, M_h >~ 3e10 Msun.  Also perform high- resolution cosmological simulations with halo masses down to M_h~1e8 Msun to cover a wide mass range for comparison.  Although the model is calibrated with ETHOS1 and CDM simulations for high halo masses at z=0, it successfully reproduces simulations for 2 other ETHOS models in the low mass regime at low and high redshifts.  As an application, compare the cumulative number density of haloes to that of observed galaxies at z=6, and find the interacting DM models with a kinetic decoupling temperature below 0.5 keV is favored.  Also perform the abundance-matching analysis and derive the stellar-halo mass relation for these models at z=4.  Suppression in halo abundance leads to less massive haloes that host observed galaxies in the stellar mass range M*~=1e5-1e7 Msun.

Day 1491

Friday.

1810.10552
Non-parametric cosmology with cosmic shear
Taylor, Kitching, McEwen

Present a method to measure the growth of structure and the background geometry of the Universe -- which no a priori assumption about the underlying cosmological model.  Using CFHTLenS shear data, simultaneously reconstruct the lensing amplitude, the linear intrinsic alignment amplitude, the redshift evolving matter power spectrum, P(k,z), and the co-moving distance, r(z).  Find that lensing predominately constrains a single global power spectrum amplitude and several co-moving distance bins.  The approach can localize precise scales and redshifts where LCDM fails -- if any.  Find that below z=0.4, the measured co-moving distance r(z) is higher than that expected from the Planck LCDM cosmology by ~1.5 sigma, while at higher redshifts, the reconstruction is fully consistent; this is precisely what we would expect if the reported discrepancy between high and low-redshift measurements of H_0 is physical.  To validate the reconstruction, compare LCDM parameter constraints form the standard cosmic shear likelihood analysis to those found by fitting to the non-parametric information and find good agreement.


1810.10547
The end of cosmic growth
Linder, Polarski

The growth of large scale structure is a battle between gravitational attraction and cosmic acceleration.  Investigate the future behavior of cosmic growth under both GR and modified gravity during prolonged acceleration, deriving analytic asymptotic behaviors and showing that gravity generally loses and growth ends.  Also note the 'why now' problem is equally striking when viewed in terms of the shut down of growth.  For many models inside GR the gravitational growth index \gamma also shows today as a unique time between constant behavior in the past and a higher asymptotic value in the future.  Interestingly, while f(R) models depart in this respect dramatically from GR today and in the recent past, their growth indices are identical in the asymptotic future and past.


1810.10553
Impact of weak lensing mass calibration on eROSITA galaxy cluster cosmological studies -- a forecast
Grandis, Mohr, et al

Forecast the impact of WL cluster mass calibration on the cosmo constraints that will be derived using the X-ray selected galaxy cluster counts from the upcoming eROSITA survey.  To this end, produce a realistic mock cluster catalog within a fiducial cosmology, where each cluster has an observed eROSITA count rate, redshift and gravitational WL tangential shear profile.  The shear profiles are produced to mimic either those from the DES or the future Euclid and LSST surveys.  Using a count rate selection, generate a baseline cosmology catalog that contains 13k clusters over 14,892 deg^2 of extragalactic sky.  Low mass clusters are excluded from this sample using raised count rate thresholds at low redshift.  Analyze the mock cluster sample using a prototype of the eROSITA cosmo analysis pipeline.  Forecast parameter uncertainties for Omega_M, sigma* and w are 0.23 (0.016), 0.038 (0.012), and 0.085 (0.074), respectively, when adopting DES WL (Euclid+LSST WL).  Explore the parameter sensitivities in the experiment and identify a degeneracy between the distance--redshift relation and the parameters of the observable--mass scaling relation that ultimately limits the impact of the WL calibration on the w constraints, and show how this degeneracy can be broken by the inclusion of BAO measurements from DESI, allowing a determination of w to 0.047.  If Planck CMB priors are included, Omega_m and sigma_8 can be determined to 0.005 and 0.007, respectively, while putting an upper limit on the summed neutrino mass sum m_nu< 0.211 eV (at 95%).  Finally, show that if systematic uncertainties at the group mass scale can be controlled, an expanded eROSITA sample with 43k objects with Euclid+LSST WL analysis would determine Omega_m and sigma_8 to 0.007 and w to 0.056.

Day 1490

Thursday.

1810.09466
The circular velocity curve of the Milky Way from 5 to 25 kpc
Eilers, Hogg, Rix, Ness

Measure the circular velocity curve v_c(R) for the MW with the highest precision to date across Galactocentric distances of 5<=R<=25 kpc.  The analysis draws on the 6-dimensional phase-space coordinates of >~23k luminous red-giant stars, for which the previously determined precise parallaxes using a data-driven model that combines spectral data from APOGEE with photometric information from WISE, 2MASS, and Gaia. Derive the circular velocity curve with the Jeans equation assuming an axisymmetric gravitational potential.  At the location of the Sun, determine the circular velocity with its formal uncertainty to be v_c(Rsun) = 229.0±0.2 km/s with systematic uncertainties at the ~5% level.  Find that the velocity curve is gently but significantly declining at -1.7±0.1 km/s/kpc, with a systematic uncertainty of 0.46 km/s/kpc, beyond the inner 5 kpc.  Exclude the inner 5 kpc from the analysis due to the presence of the Galactic bar, which strongly influences the kinematic structure and requires modeling in a non-axisymmetric potential. Combining the results with external measurement of the mass distribution for the baryonic components of the MW from other studies, estimate the Galaxy's dark halo mass within the viral radius to be M_vir=7.25±0.26e11 Msun and a local dark matter density of rho_dm(Sun) = 0.30±0.03 GeV/cm^3.


1810.09456
Dark Energy Survey Year 1 Results: methods for cluster cosmology and application to the SDSS
Constant, et al

Perform the first blind analysis of cluster abundance data.  Specifically, derive cosmo constraints from the abundance and WL signal of red mapper clusters of richness lambda >= 20 in the range 0.1<z<0.3 as measured in SDSS.  Simultaneously fit for cosmological parametersand the richness--mass relation of the clusters.  For a flat LCDM cosmo model with massive neutrinos, find S_8 == sigma8(Omega_m/0.3)^0.5 = 0.79+0.05-0.04.  This value is both consistent and competitive with that derived from cluster catalogues selected in different wavelengths.  The result is also consistent with the combined probes analyses by DES and KiDS, and with CMB anisotropies as measured by Planck.  Demonstrate that the cosmological posteriors are robust against variation of the richness-mass relation model and to systematics associated with the calibration of the selection function.  In combination with BAO and BBN data, constrain the Hubble rate to be h=0.66±0.02, independent of the CMB.  Further work aimed at improving the understanding of the scatter of the richness-mass relation has the potential to significantly improve the precision of the cosmo posteriors.  The methods described in this work were developed for use in the forthcoming analysis of cluster abundances in the DES.  The SDSS analysis constitutes the first part of a staged-unblinding analysis of the full DES data set.

Day 1489

Wednesday.

1810.0896
Challenging a Newtonian prediction through Gaia wide binaries
Hernandez, et al

Under Newtonian dynamics, the relative motion of the components of a binary star should follow Kepler's laws and show a Delta v ~ delta r^{-1/2} scaling with separation, Delta r.  Once orientation effects and a distribution of ellipticities are accounted for, dynamical evolution can be modeled to include the effects of Galactic tides and stellar mass perturbers, over the lifetime of the solar neighborhood.  This furnishes a prediction for the relative velocity between the components of a binary and their projected separation.  Taking a carefully selected small sample of 83 solar neighborhood wide binaries from the work of Shaya & Olling (2011) for the Hipparcos catalogue, identify these same stars in the recent Gaia DR2, to test the prediction mentioned using the latest and most accurate astrometry available.  The results are consistent with the Newtonian prediction for projected separations below 7000 AU, but inconsistent with it at large separations, where accelerations are expected to be lower than the critical a0=1.2e-10 m/s^2 value of MONDian gravity.  This result challenges Newtonian gravity at low accelerations and shows clearly the appearance of gravitational anomalies of the type usually attributed to dark matter at galactic scales, now at much smaller stellar scales.


1810.09505
What does a successful postdoctoral fellowship publication record look like?
Pepper, et al

Obtaining a prize postdoctoral fellowship in astronomy and astrophysics involves a number of factors, many of which cannot be quantified.  One criterion that can be measured is the publication record of an applicant.  The publication records of pst fellowship recipients may, therefore, provide some quantitative guidance for future prospective applicants.  Investigate the publication patterns of recipients of the NASA prize postdoctoral fellowships in the Hubble, Einstein, and Sagan programs from 2014 through 2017, using the NASA ADS reference system.  Tabulated their publications at the point where fellowship applications were submitted, and find that the 133 fellowship recipients in that time frame had a median of 6±2 first-author publications, and 14±6 co-authored publications.  The full range of first author papers is 1 to 15, and for all papers ranges from 2 to 76, indicating very diverse publication patterns.  Thus, while fellowship recipients generally have strong publication records, the distribution of both first-author and co-authored papers is quite broad; there is no apparent threshold of publications necessary to obtain these fellowships.  Also examined the post-PhD publication rates for each of the three fellowship programs, between male and female recipients, across the four years of the analysis and find no consistent trends.  Hope that these findings will prove a useful reference to future junior scientists.


1810.09702
A new method for calibration of gain variation in detector system
Goda, Matsuo

Transit spectroscopy of habitable planets orbiting late-type stars requires high relative spectro-photometric accuracy between wavelengths during transit/eclipse observation.  The spectra-photometric signal is not affected only by image movement and deformation due to wavefront error but also by electrical variation in the detector system.  These time-variation components, coupled to the transit signal, distort the measurements of atmospheric composition in transit spectroscopy.  Propose a new concept for improvement of spectra-photometric accuracy through the calibration of the time-variation components in the detector system by developing densified pupil spectroscopy that provides multiple spectra of the star-planet system.  Owing to a group of pixels exposed by the object light (i.e., science pixels), pixel-to-pixel variations can be smoothed out through an averaging operation, thus only common time-variation components per the science pixels remain.  In addition, considering that the detector plane is optically conjugated to the pupil plane, a pupil mask can completely block astronomical light incoming into residual pixels.  The common time-variation components are reconstructed with the residual pixels and reduced into a random term.  Applying the densified pupil spectrograph with a mid-infrared detector system to a large space cryogenic telescope such as the Origins Space Telescope, show that the system nearly achieves photon-noise limited performance and detects absorption features through transmission spectroscopy and secondary eclipse of terrestrial planets orbiting M-type stars at 10 pc with 60 transit observations.  Thus, the proposed method contributes to the measurement of planetary habitability and biosignatures of the nearby transiting habitable candidates.

Day 1488

Tuesday.

1810.08629
Quantifying baryon effects on the matter power spectrum and the weak lensing shear correlation
Schneider, Teyssier, Stadel, Chisari, Le Brun, Amara, Refregier

Feedback processes from baryons are expected to strongly affect weak-lensing observables of current and future cosmological surveys.  In this paper, present a new parameterization of halo profiles based on gas, stellar, and DM density components.  This parameterization is then used to modify outputs of gravity-only N-body simulations (following the prescriptions of Schneider and Teyssier) in order to mimic baryon effects on the matter density field.  The resulting baryon correction model relies on a few well motivated physical parameters and is able to reproduce the clustering signal of hydrodynamical sims at 3% accuracy or better at z=0.  A detailed study of the baryon suppression effects on the matter PS and the WL shear correlation reveals that the signal is dominated by 2 parameters describing the slope of the gas profile in haloes and the maximum radius of gas ejection.  Show that these parameters can be constrained with the observed gas fraction of galaxy groups and clusters from X-ray data.  Based on these observations, predict a beyond percent effect on the power spectrum above k=0.2=1.0 h/Mpc with a maximum suppression of 15-25 percent around k~10 h/Mpc.  As a result, the weak lensing angular shear power spectrum is suppressed by 10-20 % at scales beyond ell~200-1000 and the shear correlations xi_+ and xi_- are affected  at the 10-25 % level below 5 and 50 arcminutes, respectively.  The relatively large uncertainties of these predictions are a result of the poorly known hydrostatic mass bias of current X-ray observations as well as the generic difficulty to observe the low density gas outside of haloes.

Day 1487

Monday.

1810.08430
An application of machine learning techniques to galaxy cluster mass estimation using the MACSIS simulations
Armitage, Kay, Barnes

ML techniques, in particular supervised regression algorithms, are a promising new way to use multiple observables to predict a cluster's mass or any other key features.  To investigate this approach, use the MACSIS sample of simulated Hydro galaxy clusters to train a variety of ML models, mimicking different datasets.  Find that compared to predicting the cluster mass from the sigma-M relation, the scatter in the predicted-to-true mass ratio is reduced by a factor of 4, from 0.130±0.004 dex ~ 35% to 0.031±0.001 dex ~ 7% when using the same, interloper contaminated, spectroscopic galaxy sample.  Interestingly, omitting line-of-sight galaxy velocities from the training set has no effect on the scatter the the galaxies are taken from within r_200c. Also train ML models to reproduce estimated masses derived from the mock X-ray and WL analyses.  While the WL masses can be recovered with a similar scatter to that when training on the true mass, the hydrostatic mass suffers from significantly higher scatter of ~0.13 dex ~35%.  Training models using dark matter only simulations does not significantly increase the scatter in predicted cluster mass compared to training on simulated clusters with hydrodynamics.  In summary, find ML techniques to offer a powerful method to predict masses for large samples of clusters, a vital requirement for cosmological analysis with future surveys.


1810.08513
Indirect detection of extrasolar planets via Astrometry
Butler, Matthews

Radio wavelength astrometry of stars and other objects has a long and productive history. The use of that technique to determine whether stars have planets around them would cover a nearly unique part of the parameter space for detection of those systems.  Namely, astrometric observations are most sensitive to systems with large planets in moderately wide orbits (a few to ~10 AU), because it is those systems that produce large reflex motion of the star, in a short enough measurement period (years to tens of years).  In addition, astrometric observations are most sensitive to systems with planets in close orbits (less than ~1 AU), which are nearly edge-on.  Describe here, using the Hipparcos and Gaia star catalogs, how ngVLA could use this technique on hundreds of stars, some tens of which are solar analogs, to determine whether these stars have planets orbiting them.

Day 1486

Friday. 

1810.08185
The physics of Lyman-alpha escape from high-redshift galaxies
Smith, et al

Lyman-alpha (Lya) photons from ionizing sources and cooling radiation undergo a complex resonant scattering process that generates unique spectral signatures in high-z galaxies.  Present a detailed Lya radiative transfer study of a cosmological zoom-in simulation from the Feedback in Realistic Environments (FIRE) project.  Focus on the time, spatial, and angular properties of the Lya emission over a redshift range of z=5-7, after escaping the galaxy and being transmitted through the intergalactic medium (IGM).  Over this epoch, the target galaxy has an average stellar mass of M_star ~ 5e8 Msun.  Find that many of the interesting features of the Lya one can be understood in terms of the galaxy's SFH.  The time variability, spatial morphology, and anisotropy of Lya properties are consistent with current observations.  For example, the rest frame equivalent width has a EW_Lya,0>20A duty cycle of 62% with a non-negligible number of sightlines with >100A, associated with outflowing regions of a starburst with greater coincident UV continuum absorption, as these conditions generate the redder, narrower (or single peaked) line profiles.  The lowest equivalent widths correspond to cosmo filaments, which have little impact on UV continuum photons but efficiently trap Lya and produce bluer, broader lines with less transmission through the IGM.  Also show that in dense self-shielding low-metallicity filaments and satellites Lya radiation pressure can be dynamically important.  Finally, despite a significant reduction in surface brightness with increasing redshift, Lya detection and spectroscopy of high-z galaxies with the upcoming JWST is feasible.

Day 1485

Thursday.

1810.06686
Science with the ngVLA: H$_2$O Megamaser Cosmology
Braatz, et al

In combination with observations of the CMB, a measurement of the Hubble Constant provides a direct test of the standard LCDM cosmo model and a powerful constraint on the equation of state of DE.  Observations of circumnuclear water vapor megamasers at 22 GHz in nearby active galaxies can be used to measure their distances, geometrically, and thereby provide a direct, one step measurement of the Hubble Constant.  The measurement is independent of distance ladders and standard candles.  With present-day instrumentation, the Megamaser Cosmology Project is expected to reach a ~4% measurement using the megamaser technique, based on distances to fewer than 10 megamaser systems.  A goal of the observational cosmology community is to reach a percent-level measurement of H0 from several independent astrophysical measurements to minimize the systematics.  The ngVLA will provide the sensitivity at 22 GHz required to discover and measure the additional megamaser disks that will enable an H0 measurement at the ~1% level.


1810.06561
Measurement of the primordial helium abundance from the intergalactic medium
Cooke, Fumagalli

Almost every helium atom in the Universe was created just a few minutes after the BB through a process commonly referred to as BBN.  The amount of He that was made during BBN is determined by the combination of particle physics and cosmology.  The current leading measures of the primordial He abundance (Y_P) are based on the relative strengths of H I and He I emission lines emanating from SF regions in local metal-poor galaxies. As the statistical errors on these measurements improve, it is essential to test for systematics by developing independent techniques.  Here, report the first determination of the primordial He abundance based on a near-pristine intergalactic gas cloud that is seen in absorption against the light of a background quasar.  This gas cloud, observed when the Universe was just 1/3 of its present age (z_abs=1.724), has a metal content ~100 times less than the Sun and ~30% less metals than the most metal-poor H II region currently known where a determination of the primordial He abundance is afforded, conclude that the He abundance of this intergalactic gas cloud is Y=0.250+0.033-0.025, which agrees with the Standard Model primordial value, Y_P=0.24672±0.00017.  The determination of the primordial He abundance is not yet as precise as that derived using metal-poor galaxies, but the method has the potential to offer a competitive test of physics beyond the Standard Model during BBN.


1810.07200
Testing MOG theory in the Milky Way
Negrelli, et al

Perform a test of John Moffat's Modified Gravity theory (MOG) within the MW, adopting the well known "Rotation Curve" method.  Use the dynamics of observed tracers within the disk to determine the gravitational potential as a function of galactocentric distance, and compare that with the potential that is expected to be generated by the visible component only (stars and gas) under different "flavors" of the MOG theory, making use of a state-of-the-art setup for both the observed tracers and baryonic morphology.  The analysis shows that in both the original and the modified version (considering a self-consistent evaluation of the MW mass), the theory fails to reproduce the observed rotation curve.  Conclude that in none of its present formulation, the MOG theory s able to explain the observed Rotation Curve of the MW.


1810.07628
$H_0$ tension: response to Riess et al arXiv:1810.03526
Shanks, Hogarth, Metcalfe

Riess+2018 have claimed there exist seven problems in the analyses presented by Shanks+2018 where it is argued that there is enough uncertainty in Cepheid distances and local peculiar velocity fields to explain the current tension in H0.  Here, take each of the Riess+2018 points in turn and suggest that either they do no apply or that the necessary caveats are already made by Shanks+2018.  Conclude that the main point to be inferred from the analyses still stands which is that previous claims by Riess+ that Gaia parallaxes confirm their Cepheid scale are, at best, premature in advance of fur their improvements in the Gaia astrometric solution.


1810.07265
Gravitational lenses at high-resolution telescopes
Barnacka

The inner regions of active galaxies host the most extreme and energetic phenomena in the universe including, relativistic jets, SMBH binaries, and recoiling SMBHs.  However, many of these sources cannot be resolved with direct observations.  Review how strong gravitational lensing can be used to elucidate the structures of these sources from radio frequencies up to very high energy gamma rays.  The deep gravitational potentials surrounding galaxies act as natural gravitational lenses.  These gravitational lenses split background sources into multiple images, each with a gravitationally-induced time delay.  These time delays and positions of lensed images depend on the source location, and thus, can be used to infer the spatial origins of the emission.  For example, using gravitationally-induced time delays improves angular resolution of modern gamma-ray instruments by six orders of magnitude, and provides evidence that gamma-ray outbursts can be produced at even thousands of light years from a SMBH, and that the compact radio emission does not always trace the position of the SMBH.  These findings provide unique physical information about the central structure of active galaxies, force us to revise the models of operating particle acceleration mechanisms, and challenge the assumptions about the origin of compact radio emission.  Future surveys, including LSST, SKA and Euclid, will provide observations for hundreds of thousands of gravitationally lensed sources, which will allow us to apply strong gravitational lensing to study the multi-wavelength structure for large ensembles of sources.  This large ensemble of gravitationally lensed active galaxies will allow elucidation of the physical origins of multi-wavelength emissions, their connections to SMBHs, and their cosmic evolution.

Day 1484

Wednesday.

1810.05649
Observable tests of self-interacting dark matter in galaxy clusters: cosmological simulations with SIDM and baryons
Robertson, et al

Present BAHAMAS-SIDM, the first large-volume, (400/h Mpc)^3, cosmological simulations including both self-interacting dark matter (SIDM) and baryonic physics.  These simulations are important for two primary reasons: 1) they include the effects of baryons on the DM distribution 2) the baryon particles can be used to make mock observables that can be compared directly with observations.  As is well known, SIDM haloes are systematically less dense in their centre, and rounder, than CDM haloes.  Here, find that these changes are not reflected in the distribution of gas or stars within galaxy clusters, or in their X-ray luminosities.  However, gravitational lensing observables can discriminate between DM models, and present a menu of tests that future surveys could use to measure the SIDM interaction strength.  Ray-trace the simulated galaxy clusters to produce strong lensing maps.  Including baryons boosts the lensing strength of clusters that produce no critical curves in SIDM-only simulations.  Comparing the Einstein radii of the simulated clusters with those observed in the CLASH survey, find that sigma/m<1cm^2/g at velocities around 1000 km/s.


1810.05765
A giant protocluster of galaxies at redshift 5.7
Jiang, et al

Galaxy clusters trace the large structures of the Universe and provide ideal laboratories for studying galaxy evolution and cosmology.  Clusters with extended X-ray emission have been discovered at redshifts up to z~2.5.  Meanwhile, there has been growing interest in hunting for protoclusters, the progenitors of clusters, at higher redshifts.  It is, however, very challenging to find the largest protoclusters at early times when they start to assemble.  Here, report a giant protoclusters of galaxy at z=5.7, when the Universe was only one billion years old.  This protocluster occupies a volume of about 35x35x35 cubic co-moving megaparsecs.  It is embedded in an even larger overdense region with at least 41 spectroscopically confirmed, luminous Lyman-alpha emitting galaxies (LAEs), including several previously reported LAEs.  Its LAE density is 6.6 times the average density at z~5.7.  It is the only one of its kind in an LAE survey in four square degrees on the sky.  Such a large structure is also rarely seen in current cosmological simulations.  This protocluster will collapse into a galaxy cluster with a mass of (3.6±0.9)e15 Msun, comparable to those of the most massive clusters or protoclusters known to date.


1810.05976
Relativistic electron scattering and bing bang nucleosynthesis
Sasankan et al

Big band nucleosynthesis (BBN) is a valuable tool to constrain the physics of the early universe and is the only probe of the radiation dominated epoch.  A fundamental assumption in BBN is that the nuclear velocity distributions obey Maxwell Boltzmann statistics as they do in stars  In this letter, however, point out that there is a fundamental difference between stellar reaction rates and BBN reaction rates.  Specifically, the BBN epoch is characterized by a dilute baryon plasma for which the velocity distribution of nuclei is mainly determined by the dominant Coulomb scattering with mildly relativistic electrons.  This modifies the nuclear velocity distributions and significantly alters the thermonuclear reaction rates, and hence, the light element abundances.  Show that this novel result alters all previous calculations of light element abundances from BBN, and indeed exacerbates the discrepancies between BBN and inferred primordial light-element abundances possibly suggesting the need for new physics in the early universe.

Day 1483

Tuesday.

1810.05168
The signal of decaying dark matter with hydrodynamical simulations
Lovell, et al

DM articles may decay, emitting photons.  Drawing on the EAGLE family of hydrodynamic simulations of galaxy formation -- including the APOSTLE and C-EAGLE simulations -- assess the systematic uncertainties and scatter on the decay flux from different galaxy classes, from MW satellites to galaxy clusters, and compare the results to studies of the 3.55 keV line.  Demonstrate that previous detections and non-detections of this line are consistent with a DM interpretation.  For example, in the simulations the width of the DM decay one for Perseus-Analogue galaxy clusters lies in the range 1300-1700 km/s.  Therefore, the non-detection of the 3.55 keV line in the centre of the Perseus cluster by the Hitomi collaboration is consistent with detections by other instruments.  Also consider trends with stellar and halo mass and evaluate the scatter in the expected fluxes arising from the anisotropic halo mass distribution and from object-to-object variations.  Provide specific predictions for observations with XMM-Newton and with the planned X-ray telescopes XRISM and ATHENA.  If future detections of unexplained X-ray lines match the predictions, including line widths, there is strong evidence that we have discovered the DM. 


1810.05216
BICEP2 / Keck Array x: Constraints on primordial gravitational waves using Planck, WMAP, and New BICEP2/Keck observations through the 2015 season
Keck Array, BICEP2 collaborations, et al

Present results from an analysis of all data taken by the BICEP2/Keck CMB polarization experiments up to and including the 2015 observing season.  This includes the first Keck Array observations at 220 GHz and additional observations at 95 & 150 GHz.  The Q/U maps reach depths of 5.2, 2.9 and 26 mu K_cmb arcmin at 95,150 and 220 GHz respectively over an effective area of ~400 square degrees.  The 220 GHz maps achieve a signal-to-noise on polarized dust emission approximately equal to that of Planck at 353 GHz.  Take auto- and cross-spectra between these maps and publicly available WMAP and Planck maps at frequencies from 23 to 353 GHz.  Evaluate the joint likelihood of the spectra versus a multicomponent model of lensed-LCDM+r+dust+synchrotron+noise.  The foreground model has seven parameters, and impose priors on some of these using external information from Planck and WMAP derived from larger regions of sky.  The model is shown to be an adequate description of the data at the current noise levels.  The likelihood analysis yields the constraint r_0.05<0.07 at 95% confidence, which tightens to r_0.05<0.06 in conjunction with Planck temperature measurements and other data.  The lensing signal is detected at 8.8 sigma significance.  Running maximum likelihood search on simulations, obtain unbiased results and find that sigma(r)=0.020.  These are the strongest constrains to date on primordial gravitational waves.


1810.6146
The origin of magnetism in white dwarfs
Ferrario

The absence of magnetic white dwarfs with a non-degenerate low-mass stellar companion in a wide binary is still very intriguing and at odds with the hypothesis that magnetic white dwarfs are the progenies of the magnetically peculiar Ap/Bp stars.  On the other hand, we cannot resort to a process that impedes the generation of a strong magnetic field in the main or pre-main sequence progenitors of white dwarfs if they are in a multiple stellar system, because such a process would also prevent the formation of magnetic cataclysmic variables consisting of a magnetic white dwarf accreting mass from a low-mass companion.  This is the reason why it has been proposed that fields in white dwarfs may be linked to their binary and are generated through a dynamo mechanism during common envelope evolution.


1810.06200
Intergalactic $\gamma$-ray propagation: basic ideas, processes, and constraints
Dzhatdoev, et al

Review extragalactic gamma-ray propagation models with emphasis on the EM cascade process in the magnetized expanding Universe.  Consider cascades initiated by primary protons of ultra-high energy accelerated by blazers and show that the observable spectrum is similar to the universal spectrum of a purely EM cascade.  Also present a detailed calculation of the observable energy distribution for the case of EM cascades developing from relatively nearby (<20 Mpc) sources.  Finally, calculate the point-like source differential sensitivity of a novel liquid Argon time projection chamber gamma-ray telescope and show that its sensitivity is several times better than the Fermi LAT sensitivity in the 100 MeV -- 100 GeV energy range.

Day 1482

Monday.

1810.01847
Black Hole entropy and soft hair
Halo, Hawking, Perry, Strominger

A set of infinitesimal Virasoro_L (*) Virasoro_R diffeomorphisms are presented which act non-trivially on the horizon of a generic Kerr black hole with spin J.  The covariant phase space formalism provides a formula for the Virasoro charges as surface integrals on the horizon.  Integrability and associativity of the charge algebra are shown to require the inclusion of Wald-Zoupas' counterterms.  A counter term satisfying the known consistency requirement is constructed and yields central charges c_L=c_R=12J.  Assuming the existence of a quantum Hilbert space on which these charges generate the symmetries, as well as the applicability of the Cardy formula, the central charges reproduce the macroscopic area-entropy law for generic Kerr black holes.


1810.05183
The effects of galaxy assembly bias on the inference of growth rate from redshift-space distortions
McCarthy, Zheng, Guo

The large scale z-space distortion (RSD) in galaxy clustering can probe f sigma_8, a combination of the cosmic structure growth rate and the matter fluctuation amplitude, which can constrain DE models and test theories of gravity.  While the RSD on small scales (e.g. a few to tends of h^{-1} Mpc) can further tighten the f sigma_8 constraints, galaxy assembly bias, if not correctly modeled, may introduce systematic uncertainties.  Using a mock galaxy catalogue with built-in assembly bias, perform a preliminary study on how assembly bias may affect the f sigma_8 inference.  Find good agreement on scales down to 8-9 h^{-1} Mpc between a f sigma_8 metric from the z-space 2pt correlation function with the central-only mock catalogue and that with the shuffled catalogue free of assembly bias, implying that f sigma_8 information can be extracted on such scales even with assembly bias.  Then apply the halo occupation distribution (HOD) and 3 sub halo clustering and abundance matching (SCAM) models to model the z-space clustering with the mock.  Only the SCAM model based on v_peak (used to create the mock) can reproduce the f sigma_8 metric, and the other 3 could not.  However, the f sigma_8 metrics determined from central galaxies from all the models are able to match the expected one down to 8 h^{-1} Mpc.  The results suggest that halo models with no or incorrect assembly bias prescription could still be used to model the RSD down to scales of ~8 h^{-1} Mpc to tighten the f sigma_8 constraint, with a sample of central galaxies or with a flexible satellite occupation prescription.


1810.05225
Inherently stable effective field theory for dark energy and modified gravity
Lombriser, et al

The growing wealth of cosmo observations places increasingly more stringent constraints on DE and alternative gravity models.  Particularly successful in efficiently probing the vast model space has been the effective field theory of dark energy and modified gravity, providing a unified framework for generalized cosmological predictions.  However, the optimal parameterization of the free time-dependent function inherent to the formalism is still unresolved.  It should respect a multitude of requirements, ranging from simplicity, generality and representativity of known theories to computational efficiency.  But in particular, for theoretical soundness, the parameter space should adhere to strict stability requirements.  Recently proposed an inherently stable effective field theory with physical basis of Planck mass evolution, sound speed of the scalar field fluctuations, kinetic coefficient, and background expansion, which covers Horndeski models with luminal speed of gravity.  Here, devise a parameterization of these basis functions that can straightforwardly be configured to evade theoretical pathologies such as ghost or gradient instabilities or to accommodate further theoretical priors such as subliminal scalar sound speed.  The parameterisation is simple yet general, conveniently represents a broad range of known DE and gravitational theories, and with a simple additional approximation can be rendered numerically highly efficient.  Finally, by operating in the new basis, show that there are no general limitations from stability requirements on the current values that can be assumed by the phenomenological modification of the Poisson equation and the gravitational slip besides the exclusion of anti-gravity.  The inherently stable effective field theory is ready for implementation in parameter estimation analyses employing linear cosmological observations.

Day 1481

Friday.

1810.04955
Forecasts of cosmological constraints from Type Ia supernovae including the weak-lensing convergence
Hada, Futamase

Investigate how the cosmological constraints from SNe Ia are improved by including the effects of weak-lensing convergence. To do so, introduce the lognormal function as the convergence of PDF modeling the lensing scatter of SN Ia magnitude, and apply a sample selection for SNeIa to avoid strongly lensed samples.  Comparing with the contribution of other uncertainties (e.g., the intrinsic magnitude scatter), find that the lensing effect is dominant at z>1.  Then forecasting the parameter constraints for the Wide-Field InfraRed Survey Telescope survey, show that considering the WL effect, the constraints on the density parameters Omega_m or Omega_Lambda, and the DE EoS w are improved, especially for SNeIa samples at higher redshift z>1.  Furthermore, see that the degeneracy between the total mass of neutrino Sigma m_nu and the (cold) DM density parameters Omega_c can be resolved, and when marginalizing these two parameters, obtain the upper bound on the total mass of neutrinos: Sigma m_nu < 0.6 eV.


1810.04966
How does an incomplete sky coverage affect the Hubble Constant variance?
Bengaly, Andrade, Alcaniz

Address the ~=3.8 sigma tension between local and the CMB measurements of the Hubble Constant using simulated SNIa data sets.  Probe its directional dependence by means of a hemispherical comparison through the entire celestial sphere.  Perform MC simulations assuming isotropic and non-uniform distributions of data points, the latter coinciding with the real data.  This allows incorporation of observational features, such as the sample incompleteness, in the cosmic variance estimation.  Obtain that this tension can be alleviated, at best, to 2.4 sigma for isotropic datasets, and 1.8 sigma for the anisotropic ones, showing how much the incomplete sky coverage affects H0 variance.  Also find that the H0 variance is largely reduced if the datasets are augmented to 4 and 10 times the current size.  Future surveys will be able to tell whether the Hubble Constant tension happens due to unaccounted cosmic variance, or whether it is an actual indication of physics beyond the standard cosmological model.

Day 1480

Thursday.

Particles for Justice
www.particlessforjustice.org

A statement "in the strongest possible terms" against Alessandro Strumia, a well known particle theorist, whose talk on 28. Sept. 2018 at CERN argued that the primary explanation for the discrepancies between men and women in theoretical physics is that women are inherently less capable.


1810.04307
Galactic Panspermia
Ginsburg, Lingam, Loeb

Present an analytic model to estimate the total number of rocky or icy objects that could be captured by planetary systems within the MW galaxy and result in panspermia should they harbor life.  Estimate the capture rate of objects ejected from planetary systems over the entire phase space as well as time.  The final expression for the capture rate depends upon the velocity dispersion as well as the characteristic biological survival time and the size of the captured object.  Further take into account the number of stars that an interstellar object traverses, asl well as the scale height and length of the MW's disk.  The likelihood of Galactic panspermia is strongly dependent upon the survival lifetime of the putative organisms as well as the velocity of the transporter.  Velocities between 10-100 km/s result in the highest probabilities.  However, given large enough survival lifetimes, even hypervelocity objects traveling at over 1000 kms have a significant chance of capture, thereby increasing the likelihood of panspermia.  Thus, show that panspermia is not exclusively relegated to solar-system sized scales, and the entire MW could potentially be exchanging biotic components across vast distances.


1810.04480
Gravitationally lensed quasars in Gaia: III. 22 new lensed quasars from Gaia Data Release 2
Lemon, Auger, McMahon

Report the discovery and spectroscopic confirmation of 22 new gravitationally lensed quasars found using Gaia DR2.  The selection was made using several techniques: multiple Gaia detections around objects in quasars candidate catalogues, modeling of unWISE coadd pixels using Gaia astrometry, and Gaia detections offset from photometric and spectroscopic galaxies.  Spectra of 33 candidates were obtained with the William Herschel Telescope, 22 of which are lensed quasars, 2 highly probably lensed quasars, 5 nearly identical quasar pairs, 1 inconclusive system, and 3 contaminants.  Of the 3 confirmed quadruply imaged systems, J2145+6345 is a 2.1 arc second separation quad with 4 bright images (G=16.86, 17.26, 18.34, 18.56), making it ideal for time delay monitoring.  Analyzing this new sample alongside known lenses in the Pan-STARRS footprint, and comparing to expected numbers of lenses, show that, as expected, there are bias towards systems with bright lensing galaxies and low source redshifts.  Discuss possible techniques to remove this bias from future searches.  A |b|>20 complete sample of lensed quasars detected by Gaia and with image separations above 1 arc second will provide a valuable statistical sample of around 350 systems.  Currently only 96 known lenses satisfy these criteria, yet promisingly, the unWISE modeling technique is able to recover all of these with simple WISE-Gaia color cuts that remove ~80% of previously followed-up contaminants.  Finally, provide an online database of known lenses, quasar pairs, and contaminant systems.

Day 1479

Wednesday.

1810.03227
Parkes Pulsar Timing Array constraints on ultralight scalar-field dark matter
Porayko et al

It is widely accepted that day matter contributes about a quarter of the critical mass-energy density in our Universe.  The nature of dark matter is currently unknown, with the mass of possible constituents spanning nearly one hundred orders of magnitude.  The ultralight scalar fieldwork matter, consisting of extremely light bosons with m~1e-22 eV and often called "fuzzy" dark matter, provides intriguing solutions to some challenges at sub-galactic scales for the standard cold dark matter model.  As shown by Khmelnitsky and Rubakov, such a scalar field in the Galaxy would produce an oscillating gravitational potential with nanohertz frequencies, resulting in periodic variations in the times of arrival of radio pulses from pulsars.  The Parkes Pulsar Timing Array (PPTA) has been monitoring 20 millisecond pulsars at 2 to 3 weeks intervals for more than a decade.  In addition to the detection of nanohertz gravitational waves, PPTA offers the opportunity for direct searches for fuzzy dark matter in an astrophysical feasible range of masses.  Analyze the latest PPTA data set which includes timing observations for 26 pulsars made between 2004 and 2016.  Perform a search in this data set for evidence of ultralight dark matter in the Galaxy using Bayesian and Frequentist methods. No statistically significant detection has been made.  Therefore place upper limits on the local DM density.  The limits, improving on previous searches by a factor of 2 to 5, constrain the DM density of ultralight bosons with m<=1e-23 eV to be below 6 GeV/cm^3 with 95 % CL in the Earth neighborhood.  Finally, discuss the project of probing the astrophysical favored mass range m>~1e-22 eV with next-generation pulsar timing facilities.

Day 1478

Tuesday.

1810.02441
Dark Energy Survey Year 1 Results: Cross-correlation between DES Y1 galaxy weak lensing and SPT+Planck CMB weak lensing
Omori, et al

Cross-correlate galaxy weak lensing measurements from DES Y1 data with a CMB weak lensing map derived from SPT and Planck data, with an effective overlapping area of 1289 deg^2.  With the combined measurements from 4 source galaxy redshift bins, reject the hypothesis of no lensing wit ha significance of 10.8 sigma.  When employing angular scale cuts, the significance is reduced to 6.8 sigma, which remains the highest S/N measurement of its kind to date.  Fit the amplitude of the correlation functions while fixing the cosmo parameters to a fiducial LCDM model, finding A=0.99±0.17.  Additionally use the correlation function meausremetns to constrain shear calibration bias, obtaining constraints that are consistent with previous DES analyses.  Finally, when performing a cosmological analysis under the LCDM model, obtain the marginalized constraints of Omega_m=0.261+0.070-0.051 and S_8==sigma_8 sqrt(Omega_m/0.3)=0.660+0.085-0.100.  These measurements are used in a companion work that presents cosmological constraints from the joint analysis of 2pt functions among galaxies, galaxy shears, and CMB lensing using DES, SPT and Planck data.


1810.03363

Nonscanning large-area Raman imaging for ex vivo/in vivo skin cancer discrimination
Schmälzin, et al

Imaging Raman spectroscopy can be used to identify cancerous tissue.  Traditionally, a step-by-step scanning of the sample if applied to generate a Raman image, which, however, is too slow for routine examination of patients.  By transferring the technique of integral field spectroscopy (IFS) from astronomy to Raman imaging, it becomes possible to record entire Raman images quickly within a single exposure, without the need for a tedious scanning procedure.  An IFS-based Raman imaging setup is presented, which is capable of measuring skin ex vivo or in vivo.  It is demonstrated how Raman images of healthy and cancerous skin biopsies were recorded and analyzed.


1810.03526
Seven problems with the claims related to the Hubble tension in arXiv:1810.02595
Riess, et al

Shanks+(2018) arXiV:1810.02595 make two claims that they argue bring the local measurement and early Universe prediction of H0 into agreement: A) they claim that Gaia DR2 parallax measurements show the geometric calibration of the Cepheid distance scale used to measure H0 to be grossly in error and B) that we live near the middle of an enormous void, further biasing the local measurement of the Hubble constant.  Show that the first claim is caused by 5 erroneous uses of the data: in decreasing order of importance: 1) the use of a distance indicator, main sequence fitting of cluster stars, which is unrelated to the calibration of Cepheids and therefore has no bearing on current measurements of H0; 2) the use of Gaia data for Cepheids that fully saturate the detector, producing unreliable parallaxes; 3) the use of a fixed parallax offset which is known to depend on source magnitude and color but which is derived for sources with extremely different colors and magnitudes; 4) ignoring the uncertainty in this offset; and 5) ignoring the other geometric sources of Cepheid calibration, the distance of the LMC for detected eclipsing binaries and the masers in NGC 4258, which are independent of MW parallaxes.  Just resolving the first 2 of these issues by not using unrelated or saturated data leads to no inconsistency between Gaia parallaxes and the current Cepheid distance scale.  The second claim can be refuted 6) because of the increase in chi-squared that the alleged void would entail in SN measurement in the Hubble flow, and 7) because it would represent a 6 sigma fluctuation of cosmic variance between the local and globally measured expansion, requiring us to live in an exceedingly special location.

Day 1477

Monday.

1810.02212
Cosmological lensing ratios with DES Y1, SPT and Planck
Prat, et al

Correlations between tracers of the matter density field and gravitational lensing are sensitive to the evolution of the matter power spectrum and the expansion rate across cosmic time.  Appropriately defined ratios of such correlation functions, on the other hand, depend only on the angular diameter distances to the tracer objects an to the gravitational lensing source places.  Because of their simple cosmological dependence, such ratios can exploit available signal-to-noise down to small angular scales, even where directly modeling the correlation functions is difficult.  Present a measurement of lensing ratios using galaxy position and lensing data from the DES, and CMB lensing data from SPT and Planck, obtaining the highest precision lensing ratio measurements to date.  Relative to the concordance LCDM model, find a best lensing ratio amplitude of A=1.1±0.1.  Use the ratio measurement to generate cosmological constraints, focusing on the curvature parameter.  Demonstrate that photometrically selected galaxies can be used to measure lensing ratios, and argue that future lensing ratio measurements with data from a combination of LSST and Stage-4 CMB experiments can be used to place interesting cosmological constraints, even after considering the systematic uncertainties associated with photo-z and galaxy shear estimation.  


1810.02374
Constraining neutrino mass with the tomographic weak lensing bispectrum
Coulton, et al

Explore the effect of massive neutrinos in the WL shear bispectrum ing the Cosmological Mssive Neutrino Simulations.  Find that the primary effect of massive neutrinos is to suppress the amplitude of the bispectrum with limited effect on the bispectrum shape.  The suppression of the bispectrum amplitude is a factor of 2 greater than the suppression of the small scale PS.  For an LSST-like WL survey that observed half f the sky with five tomographic redshift bins, explore the constraining power of the bispectrum on 3 cosmological parameters: the sum of the neutrino mass Sum(m_nu), the matter density Omega_m, and the amplitude of primordial fluctuations A_s.  Bispectrum measurements alone provide similar constraints to the PS measurements and combining the 2 probes leads to significant improvements than using the latter alone.  Find that the joint constraints tighten the PS 95% constraints by ~32% for Sum(m_nu), 13% for Omega_m and 57% for A_s.


1810.02375
The dependence of halo bias on age, concentration and spin
Sato-Polito, et al

Halo bias is the main link between the matter distribution and DM haloes.  In its simplest form, halo bias is determined by halo mass, but there are known additional dependencies on other halo properties which are of consequence for accurate modeling of galaxy clustering.  Present the most precise measurement of these secondary-bias dependencies on halo age, concentration, and spin, for a wide range of halo masses spanning from 1e10.7 to 1e14.7 h^{-1} Msun.  At the high-mass end, find no strong evidence of assembly bias for masses above M_vir ~1e14 h^{-1} Msun.  Secondary bias exists, whoever, for halo concentration and spin, up to cluster-size haloes, in agreement with previous findings.  For halo spin, report 2 different regimes: above M_vir~1e11.5 h^{-1} Msun, haloes with larger values of spin have larger bias, at fixed mass, with the effect reaching almost a factor 2.  This trend reverses below this characteristic mass. In addition to these results, test the performance of a multi-tracer method for the determination of the relative bias between different subsets of haloes.  Show that this method increases significantly the signal-to-noise of the secondary-bias measurement as compared to a traditional approach.  This analysis serves as the basis for follow-up applications of the multi-tracer method to real data.


1810.02499
Dark Energy Survey Year 1 Results: constrains on extended cosmological models from galaxy clustering and weak lensing
DES Collaboration, et al

Present constraints on extension of the minimal cosmological models dominated by DM and DE, LCDM and wCDM, by using a combined analysis of galaxy clustering and WL from DES Y1 in combination with external data.  Consider 4 extensions of the minimal DE-dominated scenarios: 1) nonzero curvature Omega_k, 2) number of relativistic species N_eff different from the standard value of 3.046, 3) time-varying equation-of-state of DE described by the parameters w_0 and w_a (alternative quoted by the values at the pivot redshift, w_p and w_a), and 4) modified gravity described by the parameters mu_0 and Sigma_0 that modify the metric potentials.  Also consider e eternal information from Planck CMB measurements; BAO measurements from SDSS, 6dF, and BOSS; RSD measurements from BOSS; and SN1a information from the Pantheon compilation.  Constraints on curvature and the number of relativistic species are dominated by the external data; when these are combined with DES Y1, find Omega_k=0.0020+0.0037-0.0032 at the 68% CL, and N_eff<3.28 (3.55) ad 68% (95%) CL.  For the time-varying equation-of-state, find the pivot value (w_p, w_a)=(-0.91+0.19-0.23, -0.57+0.93-1.11) at pivot redshift z_p=0.27 from DES alone and (w_p, w_a)=(-1.01+0.04-0.04, -0.28+0.37-0.48) at pivot redshift z_p=0.20 from DES Y1 combined with external data; in either case, find no evidence for the temporal variation of the equation of state.  For modified gravity, find the present-day value of the relevant parameters to be Sigma_0=0.45+0.28-0.29 from DES Y1 alone, and (Sigma_0, mu_0)=(0.06+0.08-0.07, -0.11+0.42-0.46) from DES Y1 combined with external data, consistent with predictions from GR.


1810.02564
Can the CIB constrain the dark energy?
Maniyar, et al

[...]  find that the ISW is not detected with the existing CIB maps over such small sky fractions [~11% of the sky].


1810.02595
GAIA Cepheid parallaxes and 'Local Hole' relieve $H_0$ tension
Shanks, Hogarth, Metcalfe

There has been much discussion of the tension between the values of H0 implied by the distance scale and fits to the microwave background's primordial power spectrum.  While the latter is fitted by standard cosmological models with H0=67.4±0.5 km/s/Mpc, the distance scale gives H_0=73.45±1.66 km/s/Mpc, an ~10%, ~3.5 sigma discrepancy.  Here, first show that GAIA parallax distances of MW Cepheids may be between 7-18% larger than previously estimated, with the potential to produce a corresponding reduction in the value of H_0.  Then, show that the existence of an ~150 h^{-1} Mpc 'Local Hole' in the galaxy distribution around our position implies an outflow of ~500 km/s averaging over direction.  Accounting for this in the recession velocities of SNIa standard candles out to z~0.1 reduces H0 by a further ~1.8%, while maintaining reasonable consistency with the SN Hubble diagram.  Combining this result with even an ~7% increase in the Cepheid distance scale due to GAIA implies an ~9% reduction in the value of the Hubble constant, decreasing from H0 ~ 73.45 to 67.6 km/s/Mpc.  This would leave the distance scale and Planck CMB values entirely consistent, thus potentially relieving the previous H0 tension.