Day 1445

Thursday.  Friday.

1807.08819
The Andromeda galaxy's most important merger about 2 billion years ago as M32's likely progenitor
D'Souza, Bell

Although the proximity of the Andromeda galaxy (M31) offers an opportunity to understand how mergers affect galaxies, uncertainty remains about M31's most important mergers.  Previous studies focused individually on the giant stellar stream or the impact of M32 on M31's disk, thereby suggesting many substantial satellite interactions.  Yet models of M31's disk heating and the similarity between the stellar populations of different tidal substructures in M31's outskirts both suggested a single large merger.  M31's stellar halo (its outer low-surface-brightness regions) is built up from the tidal debris of satellites and provides information about its important mergers.  Here, use cosmo models of galaxy formation to show that M31's massive and metal-rich stellar halo, containing intermediate-age stars, dramatically narrows the range of allowed interactions, requiring a single dominant merger with a large galaxy (with stellar mass  about 2.5e10 Msun, the third largest member of the Local Group) about 2 Gyr ago.  This single event explains many observations that were previously considered separately: M31's compact and metal-rich satellite M32 is likely to be the stripped core of the disrupted galaxy, its rotating inner stellar halo contains most of the merger debris, and the giant stellar stream is likely to have been thrown out during the merger.  This interaction may explain M31's global burst of star formation about 2 Gyr about in which approximately a fifth of its stars were formed.  Moreover, M31's disk and bulge were already in place, suggesting that mergers of this magnitude need not dramatically affect galaxy structure.


1807.09195
Constraints on cosmology and baryonic feedback with the deep lens survey using galaxy-galaxy and galaxy-mass power spectra
Soon, Jee, Tyson, Schmidt, Wittman, Choi

Present cosmological parameter measurements from DLS using galaxy-mass and galaxy-galaxy power spectra in the multipole range ell=250~2000.  Measure gg power spectra from two lens bins centered at z~0.27 and 0.54 and galaxy-mass power spectra by cross-correlating the positions of galaxies in these two lens bins with galaxy shapes in 2 source bins centered at z~0.64 and 1.1.  Marginalize over a baryonic feedback process using a single-parameter representation and a sum of neutrino masses, as well as photometric z and shear calibration systematic uncertainties.  For a flat LCDM cosmology, determine S8==sigma_8 sqrt(Omega_m/0.3)=0.818+0.031-0.039, in good agreement with the previous DLS cosmic shear and the Planck CMB measurements.  Without the baryonic feedback marginalization, S8 decreases by ~0.05 because the DM-only power spectrum lacks the suppression at the highest ell due to AGN feedback.  Together with the Planck CMB measurement, constrain the baryonic feedback parameter to A_baryon=1.07+0.29-0.37, which suggests an interesting possibility that the actual AGN feedback might be stronger that the recipe used in the OWLS simulations.  The interpretation is limited by the validity of this one-parameter representation of the baryonic feedback effect.


1807.09540
Beyond the traditional line-of-sight approach of cosmological angular statistics
Schöneberg, et al

Present a new efficient method to compute the angular power spectra of large-scale structure observables that circumvents the numerical integration over Bessel functions, expanding on a recently proposed algorithm based on FFTlog.  This new approach has better convergence properties.  The method is explicitly implemented in the CLASS code for the case of number count C_ell's (including redshift-space distortions, weak lensing, and all other relativistic corrections) and cosmic shear C_ell's.  In both cases the approach speeds up the calculation of the exact C_ell's (without the Limber approximation) by a factor of order 400 at a fixed precision target of 0.1%.


1807.09645
Ultra-high-energy cosmic rays
Anchordoqui

In this report, review the important progress made in recent years towards understanding the experimental data on ultra-high-energy (E>~1e9 GeV) cosmic rays.  Begin with a general survey of the available data, including a description of the energy spectrum, the nuclear composition, and the distribution of arrival directions.  At this point, also give a synopsis of experimental techniques.  After that, introduce the fundamentals of cosmic ray acceleration and energy loss during propagation, with a view of discussing the conjectured nearby sources.  Next, survey the state of the art regarding the high- and ultra-high-energy cosmic neutrinos which should be produced in association with the observed cosmic rays.  These neutrinos can constitute key messengers identifying currently unknown cosmic accelerators, possibly in the distant universe, because their propagation is not influenced by background photon or magnetic fields.  Subsequently, summarize the collider data to ultra-high energies and the main EM processes that govern the longitudinal shower evolution.  Armed with these two principal shower ingredients and motivation from the underlying physics, describe the different methods proposed to distinguish the primary particle species.  In the end, explore how ultra-high-energy cosmic rays can be used as proves of beyond standard model physics models.


1807.09796
Galaxy two-point correlation function in general relativity
Scaccabarozzi, Yoo, Biern

Perform theoretical and numerical studies of the full relativistic two-point galaxy correlation function, considering the linear-order scalar and tensor perturbation contributions and the wide-angle effects.  Using the gauge-invariant relativistic description of galaxy clustering and accounting for the contributions at the observer position, demonstrate that the complete theoretical expression is devoid of any long-mode contributions from scalar or tensor perturbations and it lacks the infrared divergences in agreement with the equivalence principle.  Using the full gauge-invariant expression, numerically compute the galaxy 2pt correlation function and study the individual contributions in the conformal Newtonian gauge.  Find that several terms at the observer position that are missing in the standard formalism dominate over the other relativistic contributions in the conformal Newtonian gauge.  Compared to the standard theoretical predictions, the relativistic effects in galaxy clustering result in a few percent-level systematic errors beyond the scale of the baryonic acoustic oscillation.  This theoretical and numerical studies provide a comprehensive understanding the relativistic effects in the galaxy 2pt correlation function.


1807.10163
Dark Energy Survey Year 1 results: measurement of the galaxy angular power spectrum
Camacho, et al

Use data from the Y1 observations of the DES collaboration to measure the galaxies angular power spectrum (APS), and search for its BAO feature using a template-fitting method. Test the methodology in a sample of 1800 DES Y1-like mock catalogs.  The APS is measured with the pseudo-C_ell method, using pixelized maps constructed from the mock catalogs and the DES mask.  The covariance matrix of the C_ell's in these tests are also obtained from the mock catalogs.  Use templates to model the measured spectra and estimate template parameters firstly from the C_ell's of the mocks using two different methods, a maximum likelihood estimator and a MCMC, finding consistent results with a good reduced chi^2.  Robustness tests are performed to estimate the impact of different choices of settings used in the analysis.  After these tests on mocks, apply the method to a galaxy sample constructed from DES Y1 data specifically for LSS studies.  This catalog comprises galaxies within an effective area of 1318 deg^2 and 0.6<z<1.0.  Fit the observed spectra with the optimized templates, considering models with and without BAO features.  Find that the DES Y1 data favors a model with BAO at the 2.6 sigma CL wit ha best-fit shift parameter of alpha=1.023±0.047.  However, the goodness-of-fit is somewhat poor, with chi^2/dof = 1.49.  Identify a possible cause of this issue and show that using a theoretical covariance matrix obtained from C_ell's that are better adjusted to data results in an improved value of chi^2/dof = 1.36, which is similar to the value obtained with the real-space analysis.  The results correspond to a distance meausrement of D_A(z_eff=0.81)/r_d = 10.65±0.49, consistent with the main DES BAO findings.  This is a companion paper to the main DES BAO article showing the details of the harmonic space analysis.

Day 1444

Wednesday.

1807.08794
Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert
IceCube Collaboration

A high-energy neutrino event detected by IceCube on 22 Sept. 2017 was coincident in direction and time with a gamma-ray flare from the blazar TXS 0506+056.  Prompted by the association, investigate 9.5 years of IceCube neutrino observations to search for excess emission at the position of the blazar.  Found an excess of high-energy neutrino events with respect to atmospheric backgrounds at that position between September 2014 and March 2015.  Allowing for time-variable flux, this constitutes 3.5 sigma evidence for neutrino emission from the direction of TXS 0506+056, independent of and prior to the 2017 caring episode.  This suggests that blazers are the first identifiable sources of the high-energy astrophysical neutrino flux.


1807.08816
Multi-messenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A
IceCube, Fermi-Lat, MAGIC, AGILE, ASAS-SN, HAWC, HESS, INTEGRAL, anata, Kiso, Kapteyn, Liverpool telescope, Subaru, Swift/NuSTAR, VERITAS, VLA/17B-403 teams

An extensive multi-wavelength campaign followed the event, ranging from radio frequencies to gamma-rays.  These observations characterize the variability and energetics of the blazar and include the first detection of TXS 0506+056 in very-high-energy gamma-rays.  This observation of a neutrino in spatial coincidence with a gamma-ray emitting blazar during an active phase suggests that blazers may be a source of high-energy neutrinos.


1807.09004
A dark matter hurricane: measuring the S1 stream with dark matter detectors
O'Hare, McCabe, et al

The recently discovered S1 stream passes through the Solar neighborhood on a low inclination, counter-rotating the orbit.  The progenitor of S1 is a dwarf galaxy with a total mass comparable to the present-day Fornax dwarf spheroidal, so the stream is expected to have a significant DM component.  Compute the effects of the S1 stream on WIMP and axion detectors as a function of the density of its unmeasured dark component.  In WIMP detectors the S1 stream supplies more high energy nuclear recoils so will marginally improve DM detection prospects.  Find that even if S1 comprises less than 10% of the local density, multi-ton xenon WIMP detectors can distinguish the S1 stream from the bulk halo in the relatively narrow mass range between 5 and a 25 GeV.  In directional WIMP detectors such as CYGNUS, S1 increases DM detection prospects more substantially since it enhances the anisotropy of the WIMP signal.  Finally, show that axion haloscopes possess by far the greatest potential sensitivity to the S1 stream.  Once the axion mass has been discovered, the distinctive velocity distribution of S1 can easily be extracted from the axion power spectrum.

Day 1443

Monday.  Tuesday.

1807.08249
Cosmological parameters from weak cosmological lensing
Kilbinger

In this manuscript of the habilitation à dirge des recherchen (HDR), the author presents some of his work over the last 10 years.  The main topic of this thesis is cosmic shear, the distortion of images of distant galaxies due to WL by the LSS in the Universe.  Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure.  Review the principles of WL and show how cosmic shear is interpreted in a cosmological context.  Then, give an overview of WL measurements, and present observational results from CFHTLenS, as well as the implications for cosmology.  Conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations.  (also see 1411.0115)


1807.08732
Cosmological constraints from noisy convergence maps through deep learning
Fluri, Kacprzak, Lucci, Refregier, Amara, Hofmann

Deep learning is a powerful analysis technique that has recently been proposed as a method to constrain cosmo parameters from WL mass maps.  Due to its ability to learn relevant features from the data, it is able to extract more information from the mass maps than the commonly used PS, and thus achieve better precision for cosmo parameter measurement.  Explore the advantage of Convolutional Neural Networks (CNN) over the power spectrum for varying levels of shape noise and different smoothing scales applied to the maps.  Compare the cosmo constraints from the two methods in the Omega_m-sigma_8 plane for sets of 400 deg^2 convergence maps.  Find that, for a shape noise level corresponding to 8.53 galaxies/arcmin^2 and the smoothing scale of sigma_s=2.34 arcmin, the network is able to generate 45% tighter constraints.  For smaller smoothing scale of sigma_s=1.17 the improvement can reach ~50%, while for larger smoothing scale of sigma_s=5.85, the improvement decreases to 19%.  The advantage generally decreases when the noise level and smoothing scales increase.  Present a new training strategy to train the neural network with noise data, as well as considerations for practical applications of the deep learning approach.

Day 1442

Friday.

1807.06664
SOFIA/HAWC+ detection of a gravitationally lensed starburst galaxy at $z$=1.03
Ma, et al

Present the detection at 89 um (observed frame) of the Herschel-Selected gravitationally lensed starburst galaxy HATLASJ1429-0028 (also know as G15v2.19) in 15 minutes with the High-resolution Airborne Wideband Camera-plus (HAWC+) onboard SOFIA.  The spectacular lensing system consists of an edge-on foreground disk galaxy at z=0.22 and a nearly complete Einstein ring of an intrinsic ultra-luminous infrared galaxy at z=1.03.  Is this high IR luminosity powered by pure SF or also an AGN?  Previous nebular line diagnostics indicate that it is SF dominated.  Perform a 27-band multi-wavelength SED including the new SOFIA/HAWC+ data to constrain the fractional AGN contribution to the total IR luminosity.  The AGN fraction in the IR turns out to be negligible.  In addition, J1429-0028 serves as a testbed for comparing SED results from different models/templates and SED codes (MAGPHYS, SED3FIT, and CIGALE).  Stress that SFH is the dominant source of uncertainty in the derived M* (as high as a factor of ~10) even in the case of extensive photometric coverage.  Furthermore, the detection of a source at z~1 with SOFIA/HAWC+ demonstrates the potential of utilizing this facility for distant galaxy studies including the decomposition of SF/AGN components, which cannot be accomplished with other current facilities.


1807.06870
Detecting domain walls in laboratory experiments
Llinares, Brax

The inherently unstable nature of domain walls makes their detection in laboratory experiments extremely challenging.  Propose a method to stabilize domain walls in a particular modified gravity model inside a cavity.  Suggest 2 ways in which the walls could be detected once stabilized: studying the trajectories of Ultra Cold Neutrons (UCN's) either via the defection angle of a neutron beam induced by the attraction towards the wall or through the time difference of these particles passing through the wall.  Give realistic estimates for these effects and expect that they should be detectable experimentally.


1807.06875
A Bayesian method for combining theoretical and simulated covariance matrices for large-scale structure surveys
Hall, Taylor

Accurate and precise covariance matrices will be important in enabling planned cosmological surveys to detect new physics.  Standard methods imply either the need for many N-body sims in order to obtain an accurate estimate, or a precise theoretical model.  Combine these approaches by constructing a likelihood function conditions on simulated and theoretical covariances, consistently propagating noise from the finite number of simulations and uncertainty in the theoretical model itself using an informative Invers-Wishart prior.  Unlike standard methods, the approach allows the required number of simulations to be less than the number of summary statistics.  Recover the linear 'shrinkage' covariance estimator in the context of a Beysian data model, and test the marginal likelihood on simulated mock power spectrum estimates.  Conduct a thorough investigation into the impact of prior confidence in different choices of covariance models on the quality of model fits and parameter variances.  In a simplified setting find that the number of simulations required can be reduced if one is willing to accept a mild degradation in the quality of model fits, finding that even weakly informative priors can help to reduce the simulation requirements.  Identify the correlation matrix of the summary statistics as a key quantity requiring careful modeling.  The approach can be easily generalized to any covariance model or set of summary statistics, and elucidates the role of hybrid estimators in cosmological inference.


1807.07084
A quantification of the butterfly effect in cosmological simulations and implications for galaxy scaling relations
Genel, et al

Study the chaotic-like behavior of cosmo sims by quantifying how minute perturbations grow over time and manifest as macroscopic differences in galaxy properties.  When the same setup is run multiple times, the results produced by the code Arepo, are binary identical.  However, when pairs of 'shadow' simulations are run that are identical except for random minute initial displacements to particle positions (e.g. of order 1e-7 pc), the results diverge from each other at the individual galaxy level (while the statistical properties of the ensemble of galaxies are unchanged).  After cosmological times, the global properties of pairs of 'shadow' galaxies that are matched between the simulations differ from each other generally at a level of ~2-25%, depending on the considered physical quantity.  Perform these experiments using cosmo volumes of (25-50 Mpc/h)^3 evolved either purely with DM, or with baryons and SF but no feedback, or using the full feedback model of the IllustrisTNG project.  The runs cover 4 resolution levels spanning a factor of 512 in mass.  Find that without feedback the differences between shadow galaxies generally become smaller as the resolution increases, but with the IllustrisTNG model the results are mostly covering towards a 'floor'.  This hints at the role of feedback in setting the chaotic properties of galaxy formation.  Importantly, compare the macroscopic differences between shadow galaxies to the overall scatter in various galaxy scaling relations, and conclude that for the star formation-mass and the Tully-Fisher relations, the chaotic behavior of the simulations contributes significantly to the overall scatter.  Discuss the implications for galaxy formation theory in general and for cosmological simulations in particular.


1807.07435
A multi messenger view of galaxies and quasars from now to mid-century
D'Onofrio, Marziani

I the next 30 years, a new generation of space and ground-based telescopes will permit to obtain multi-frequency observations of faint sources and, for the first time in human history, to achieve a deep, almost synoptical monitoring of the whole sky.  Gravitational wave observatories will detect a Universe of unseen BHs in the merging process over a broad spectrum of mass.  Computing facilities will permit new high-resolution simulations with a deeper physical analysis of the main phenomena occurring at different scales.  Given these development lines, first sketch a panorama of the main instrumental developments expected in the next 30 years, dealing not only with EM radiation, but also from a multi-messenger perspective that includes GWs, neutrinos, and CRs.  Then present how the new instrumentation will make it possible to foster advances in the present understanding of galaxies and quasars.  Focus on selected scientific themes that are hotly debated today, in some cases advancing conjectures on the solution of major problems that may become solved in the next 30 years.


1807.07548
The maximum angular-diameter distance in cosmology
Melia, Yennapureddy

Unlike other observational signatures in cosmology, the angular-diameter distance d_A(z) uniquely reaches a maximum (at z_max) and then shrinks to zero towards the big bang.  The location of this turning point depends sensitively on the model, but has been difficult to measure.  In this paper, estimate and use z_max inferred from quasar cores: (1) by employing a sample of 140 objects yielding a much reduced dispersion due to pre-constrained limits on their spectral index and luminosity, (2) by reconstructing d_A(z) using Gaussian processes, and (3) comparing the predictions of 7 different cosmologies and showing that the measured value of z_max can effectively discriminate between them.  Find that z_max=1.70±0.20 --- an important new probe of the Universe's geometry.  The most strongly favored model is R_h=ct, followed by Planck LCDM.  Several others, including Milne, Einstein-de Sitter and Static tired light are stonily rejected.  According to these results, the R_h=ct universe, which predicts z_max=1.718, has a ~92.8% probability of being the correct cosmology.  For consistency, also carry out model selection based on d_A(z) itself.  This test confirms that R_h=ct and Planck LCDM are among the few models that account for angular-size data better than those that are disfavored by z_max.  The d_A(z) comparison, however, is less discerning than that with z_max, due to the additional free parameter, H_0.  Find that H_0=63.4±1.2 km/s/Mpc for R_h=ct, and 69.9±1.5 km/s/Mpc for LCDM.  Both are consistent with previously measured values in each model, though they differ from each other by over 4 sigma.  In contrast, model selection based on z_max is independent of H0.

Day 1441

Thursday.

1807.05217
Persistence characterization of teledyne H2RG detectors
Tulloch

Image persistence is a major problem in IR detectors, potentially seriously limiting data quality in many observational regimes.  The problem manifests itself as remnant images that can persist for several days after a deep exposure.  In this study, the persistence behavior of three 5.3 um cutoff H2RGs has been characterized using a low-background cryostat with LED light sources.  Persistence charge de-trapping was measured over several hours following a wide range of exposure levels and exposure times.  This data was then analyzed to yield charge trapping and de-trapping spectra which present graphically the trap density as a function of their time constants.  These spectra show the detector behavior in a very direct way and offer a natural metric for comparing different devices.  It is hoped that the trap time constant spectra for each detector can be used in an analysis pipeline to remove persistence artifacts based on the recent exposure history of the detector.  The study confirmed that the charge traps responsible for persistence must be present in the depletion region fo the pixel, however, two trap populations were revealed.  One of these captures charge within milliseconds and then releases it over many hours.  The second population is less problematic with fairly similar trapping and de-trapping time constants.  Large differences in persistence magnitude and trap spectra have been found even between devices with near-consecutive serial numbers.  Lower temperatures results in lower persistence both in terms of total trapped chart and the time taken for that charge to decay.  Limiting the full-well by reducing pixel bias voltage also had a beneficial effect.  Previously proposed mitigation techniques including "global reset de-trapping" and "night light" illumination were tried but found to be ineffective.


1807.05667
A standard siren measurement of the Hubble constant from GW170817 without the electromagnetic counterpart
Fishbach, et al

Perform a statistical standard siren analysis of GW170817.  The analysis does not utilize knowledge of NGC 4993 as the unique host galaxy of the optical counterpart to GW170817.  Instead, consider each galaxy within the GW170817 localization region as a potential host; combining the H0 values from all the galaxies provides a final measurement of H0.  Explore the dependence of the results on the galaxy thresholds, as well as the impact of weighting the galaxies by stellar mass and SFR.  Considering all galaxies brighter than 0.01 L*_B (containing ~99% of the total blue luminosity) as equally likely to host a BNS merger, find H0=76+48-23 km/s/Mpc (maximum a posteriori and 68.3% highest density posterior interval; all results are from publicly available LIGO/Virgo sky maps using approximations to the line-of-sight distance distributions).  Restricting only to galaxies brighter than 0.626 L*_B (containing ~50% of the total blue luminosity) tightens the measurement to H0=77+37-18 km/s/Mpc.  Show that the weighting the host galaxies by stellar mass or SFR provides entirely consistent results with potentially tighter constraints.  While these statistical estimates are inferior to the value from the counterpart standard siren measurement utilizing NGC 4993 as the unique host, the analysis is a proof-of-principle demonstration of the statistical approach first proposed by Bernard Schutz over 30 years ago.  This method is of particular promise in the case of binary BHs, since they are not expected to have optical counterparts, and they occur at sufficient rate that the combined statistical standard siren measurements from many events may offer precision measurements of the luminosity distance-redshift relation to high (z<~1) redshift.


1807.06025
The distance of the dark matter deficient galaxy NGC1052-DF2
van Dokkum, Danieli, Cohen, Conroy

Recently have inferred that the galaxy NGC1052-DR2 has little of no dark matter and a rich system of unusual globular clusters.  Assumed that the galaxy is a satellite of the luminous elliptical galaxy NGC1052vat ~20 Mpc, on the basis of its surface brightness fluctuations (SBF) distance of 19.0±1.7 Mpc, its radial velocity of ~1800 km/s, and its projected position.  Trujillo+ 2018 proposed a much closer distance of 13 Mpc, based largely on ta putative detection of the tip of the red giant branch (TRGB) in the color-magnitude diagram (CMD) and a recalibration of the SBF measurement.  Here, analyze the CMD using both fully population galaxy models and other galaxies in the HST sample, and demonstrate the Trujillo+ almost certainly confused blends for individual red giants in their analysis.  These blends produce a "phantom" TRGB ~2 times brighter than the true TRGB, leading to a ~1.4 times smaller inferred distance.  The large population of unblended stars on the red giant branch expected for distances of ~13 Mpc is not detected in the HST data.  Also provide a new distance measurement to NGC1052-DR2 that is free of calibration uncertainties, by anchoring it to a satellite of the megamaser host galaxy NGC4258.  From a megamaser-TRGB-SBF distance ladder, obtain D-18.7 ±1.7 Mpc, consistent with the previous measurement and with the distance to NGC1052.


1807.06658
All transverse motion is peculiar: connection the proper motions of galaxies to the matter power spectrum
Darling, Truebenbach

In an isotropic and homogenous Hubble expansion, all transverse motion is peculiar.  Like the radial peculiar velocities of galaxies, transverse peculiar velocities are a means to trace the density of matter that does not rely on light tracing mass.  Unlike radial peculiar velocity measurements that require precise redshift-independent distances in order to distinguish between the Hubble expansion and the observed redshift, transverse peculiar velocities can be measured using redshifts alone as a proxy for distance.  Extragalactic proper motions can therefore directly measuring peculiar velocities and probe the matter power spectrum.  Develop 2pt transverse velocity correlation statistics and demonstrate their dependence on the matter power spectrum.  Predict the power in these correlation statistics as a function of the physical separation, angular separation, and distance of pairs of galaxies and demonstrate that the effect of large scale structure on transverse motions is best measured for pairs of objects with comoving separations less than about 50 Mpc.  Transverse peculiar velocities induced by large scale structure should be observable as proper motions using long baseline radio interferometry or space-based optical astrometry.

Day 1440

Wednesday.

1807.06205
Planck 2018 results. I. Overview and the cosmological legacy of Planck
Planck Collaboration, et al

ESA's Planck satellite, which was dedicated to studying the early Universe and its subsequent evolution, was launched on 14 Man 2009.  It scanned the microwave and submillimetre sky continuously between 12 Aug. 2009 and 23 Oct 2013, producing deep, high-resolution, all-sky maps in 9 frequency bands from 30 to 857 GHz.  This paper presents the cosmological legacy of Planck, which currently provides the strongest constraints on the parameters of the standard cosmological model and some f the tightest limits available on deviations from that model.  The 6 parameter LCDM model continues to provide an excellent fit to the CMB data at high and low z, describing the cosmo information in over a billion map pixels with just 6 parameters.  With 18 peaks in the T and polarization angular power spectra constrained well, Planck m causers 5 of the 6 parameters to better than 1% (simultaneously), with the best-determined parameter (theta-*) now known to 0.03%.  Describe the multi-component sky as seed by Planck, the success of the LCDM model, and the connection to lower-redshift probes of structure formation.  Also give a comprehensive summary of the major changes introduced in the 2018 release.  The Planck data, alone and in combination with other probes, provide stringent constraints on the models of the early Universe and the LSS within which all astrophysical objects form and evolve.  Discuss some lessons learned from the Planck mission, and highlight areas ripe for further experimental advances.


1807.06209
Planck 2018 results. VI.  Cosmological parameters
Planck Collaboration, et al

Present cosmo parameter realists from the final full-mission Planck measurement of the CMB anisotropies.  Find good consistency with the standard spatially-flat 6-parameter LCDM cosmology having a power-law spectrum of adiabatic scalar perturbations (denoted "base LCDM" in this paper), from polarization, temperature, and lensing, separately and in combination.  A combined analysis gives DM density Omega_c h^2 = 0.120 ± 0.001, baryon density Omega_b h^2 = 0.0224±0.0001, scale spectral index n_s=0.965 ± 0.004, and optical depth tau=0.054±0.007 (in this abstract quote 68% CL on measured parameters and 95% on upper limits).  The angular acoustic scale is measured to 0.03% precision, with 100 theta_*=1.0411±0.0003.  These results are only weakly dependent on the cosmological model and remain stable, with somewhat increased errors, in many commonly considered extensions.  Assuming the base LCDM cosmology, the inferred late-universe parameters are: H_0=(67.4±0.5) km/s/Mpc; Omega_m=0.315±0.007; and sigma_8=0.811±0.006.  Find no compelling evidence for extensions to the base LCDM model.  Combining with BAO, constrain the effective extra relativistic degrees of freedom to be N_eff = 2.99±0.17, and the neutrino mass is tightly constrained to sum m_nu<0.12 eV.  The CMB spectra continue to prefer higher lensing amplitudes than predicted in based LCDM at over 2 sigma, which pulls some parameters that affect the lensing amplitude away from the base LCDM model; however, this is not supported by the lensing reconstruction or (in models that also change the background geometry) BAO data.

Day 1439

Friday.  Monday.  Tuesday.

Science
Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A
The IceCube Collaboration, Fermi-LAT, MAGIC, AGILE, ASAS-SN, HAWC, H.E.S.S., INTEGRAL, et al

Previous detections of individual astrophysical sources of neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified.  On 22 September 2017, detected a high-energy neutrino, IceCube-170922A, with an energy of ~290 tera-electronvolts.  Its arrival direction was consistent with the location of a known gamma-ray blazar, TXS 0506+056, observed to be in a flaring state.  An extensive multi wavelength campaign followed, ranging from radio frequencies to gamma-rays.  These observations characterize the variability and energetics of the blazar and include the detection of TXS 0506+056 in very-high-energy gamma-rays.  This observation of a neutrino in spatial coincidence with a gamma-ray-emitting blazar during an active phase suggests that blazers may be a source of high-energy neutrinos. 


1807.04275
Interpretation of the coincident observation of a high energy neutrino and a bright flare
Gao

On 22 Sept 2017, the IceCube Neutrino Observatory reported a muon track from a neutrino with a very good positional accuracy.  The alert triggered a number of astronomical follow-up campaigns, and the Fermi gamma-ray telescope found as counterpart an object named TS50506+056 in a very bright, flaring state; this observation may be the first direct evidence for an extragalactic source of very high-energy cosmic rays.  While this and subsequent observations provide the observational picture across the EM spectrum, answering where in the spectrum signatures of CRs arise and what the source properties must be, given the observational constraints, requires a self-consistent description of the processes at work.  Here, perform a detailed time-dependent modeling of these relevant processes and study a set of self-consistent models for the source.  Find a slow but over-proportional increase of the neutrino flux during the flare compared to the production enhancement of energetic CRs.  Also demonstrate that interactions of energetic CR ions result in predominantly hard X-ray emission, strongly constraining the expected number of neutrinos, and to a lesser degree in TeV gamma rays.  Optical photons and GeV-scale gamma rays are predominantly radiated by electrons.  The results indicate that especially future X-ray and TeV-scale gamma-ray observations of nearby objects can be used to identify more such events.


1807.04277 (https://www.nature.com/articles/s41550-018-0508-y)
Gravitational lensing detection of an extremely dense environment around a galaxy cluster
Sereno, Giocoli, et al

Galaxy clusters form at the highest density nodes of the cosmic web.  The clustering of massive haloes is enhanced relative to the general mass distribution and matter beyond the viral region is strongly correlated to the halo mass (halo bias).  Clustering can be further enhanced depending on halo properties other than mass (secondary bias).  The questions of how much and why the regions surrounding rich clusters are over-dense are still unanswered.  Here, report the analysis of the environment bias in a sample of very massive clusters, selected through the Sunyaev-Zel'dovich effect by the Planck mission.  Present the first detection of the correlated DM associated to a single cluster, PSZ2 G099.86+58.45.  The system is extremely rare in the current paradigm of structure formation.  The gravitational lensing signal was traced up to 30 Mpc with high S/N ratio ~3.4.  The measured shear is very large and points at environment matter density in notable excess of the cosmological mean.  The boosting of the correlated DM density around high mass haloes can be very effective.  Together with ensemble studies of the large scale structure, lensing surveys can picture the surroundings of single haloes.


1807.04300
The blazar TXS 0506_056 associated with a high-energy neutrino: insights into extragalactic jets and cosmic ray acceleration
Ahnen, et al

A neutrino with energy of ~290 eV, IceCube-170922A, was detected in coincidence with the BL Lac object TXS 0506_056 during enhanced gamma-ray activity, with chance coincidence being rejected at ~3 sigma level.  Monitored the object in the VHE band with the MAGIC telescopes for ~41 hours from 1.3 to 40.4 days after the neutrino detection.  Day-timescale variability is clearly resolved.  Interpret the quasi-simultaneous neutrino and broadband EM observations with a novel open-zone left-hadronic model, based on interactions of e- and p+ co-accelerated in the jet with external photons originating from a slow-moving plasma sheath surrounding the faster jet spine.  Can reproduce the multi wavelength spectra of TXS 0506+056 with neutrino rate and energy compatible with IceCube-170922A, and with plausible values for the jet power of ~1e45 - 4e46 erg/s.  The steep spectrum observed by MAGIC is concordant with internal gamma-gamma absorption above a few tens of GeV entailed by photohadronic production of a ~290 TeV neutrino, corroborating a genuine connection between the multi-messenger signals.  In contrast to previous predictions of predominantly hadronic emission from neutrino sources, the gamma-rays can be mostly ascribed to inverse Compton up-scattering of external photons by accelerated electrons.  The X-ray and VHE bands provide crucial constraints on the emission from both accelerated electrons and protons.  Infer that the maximum energy of protons in the jet co-moving frame can be in the range ~1e14 to 1e18 eV.


1807.04461
Dissecting the region around IceCube-170922: the blazar TXS 0506+056 as the first cosmic neutrino source
Padovani, et al

Present the dissection in space, time and energy of the region around the IceCube-170922A neutrino alert.  This study is motivated by: (1) the first association between a neutrino alert and a blazar in a flaring state, TXS 0506+056; (2) the evidence of a neutrino flaring activity during 2014-2015 from the same direction; (3) the lack of an accompanying simultaneous gamma-ray enhancement from the same counterpart; (4) the contrasting flaring activity of a neighboring bright gamma-ray source, the blazar PKS 0502+049, during 2014-2015.  The study makes use of multi-wavelength archival data accessed through Open Universe tools and includes a new analysis of Fermi-LAT data.  Find that PKS 0502+049 contaminates the gamma-ray emission region at low energies but TXS 0506+056 dominates the sky above a few GeV.  TXS 0506+056, which is a very strong (top percent) radio and gamma-ray source, is in a high gamma-ray state during the neutrino alert but in a low through hard gamma-ray state in coincidence with the neutrino flare.  Both states can be reconciled with the energy associated with the neutrino emission and, in particular during the low/hard state, there is evidence that TXS 0506+056 has undergone a hadronic flare with very important implications for blazar modeling.  All multi-messenger diagnostics reported here support a single coherent picture in which TXS 0506+056, a very high gamma-ray blazar, is the only counterpart of all the neutrino emissions in the region and therefore the most plausible first non-stellar neutrino and, hence, cosmic ray source.


1807.04468
On measuring the Galactic dark matter halo with hypervelocity stars
Contigiani, Rossi, Marchetti

HVSs travel from the Galactic Centre to the DM halo of the MW, where they are observed with velocities in excess of the Galactic escape speed.  Their trajectories make them a unique probe of the still poorly constrained DM component of the Galaxy.  In this paper, present a new method to constrain the Galactic potential with HVSs.  The likelihood is constructed by efficiently calculating the local HVS density at any point of the Galaxy by back-propagating the phase space position and quantifying the ejection probability along the orbit.  This method is particularly suited to the data from the ESA mission Gaia.  Therefore, to showcase the method, apply it to a simulated Gaia sample of ~200 stars in Galactic potentials with 3 different dark matter components, parameterized by a spheroidal NFW profile.  Find that individual HVSs exhibit a degeneracy in the scale mass-scale radius plane (M_s-r_s) and are able to measure only the combination alpha=M_s/r_s^2, likewise a degeneracy is also present between alpha and the spheroidal axis-ratio q.  When the whole sample is considered, both parameters are nailed down with sub-percentage precision (~1% and 0.1% for alpha and q respectively) and no systematic bias is observed.  This remarkable power to constrain deviations from a symmetric halo is a consequence of the Galactocentric origin of HVSs.  To compare the results with other probes, break the degeneracy in the scale parameters and impose a mass concentration relation.  The result is a competitive precision on the viral mass M200 of about 10%.


1807.04493
Different stellar rotation in the two main sequences of the young globular cluster NGC1818: first direct spectroscopic evidence
Marino, et al

Present a spectroscopic analysis of MS stars in the young globular cluster NGC1818 (age~40 Myrs) in the LMC.  The photometric survey on MC clusters has revealed that NGC1818, similarly to the other young objects with age 600 Myrs, displays not only an extended MS Turn-Off (eMSTO), as observed in intermediate-age clusters (age~1-2 Gyrs), but also a split MS.  The most straightforward interpretation of the double MS is the presence of two stellar populations; a sequence of slowly-rotating stars lying on the blue-MS and a sequence of fast rotators, with rotation close to the breaking speed, defining a red-MS.  Report the first direct spectroscopic measurements of projected rotational velocities vsini for the double MS, eMSTO and Be stars of a young cluster.  The analysis of line profiles includes non-LTE effects, required for correctly deriving v sini values.  The results suggest that: (i) the mean rotation for blue- and red-MS stars is vsini=71±10 km/s (sigma=37 km/s) and vsini=202±23 km/s (sigma=91 km/s), respectively; (ii) eMSTO stars have different vsini, which are generally lower than those inferred for red-MS stars, and (iii) as expected, Be stars display the highest vsini values.  This analysis supports the idea that distinct rotational velocities play an important role in the appearance of multiple stellar populations in the color-magnitude diagrams of young clusters, and poses new constraints to the current scenarios.


1807.04565
The escape speed curve of the Galaxy obtained from Gaia DR2 implies a heavy Milky Way
Monari, et al

Measure the escape speed curve of the MW based on the analysis of the velocity distribution of ~2850 counter-rotating halo stars from Gaia DR2.  The distances were estimated through the StarHorse code, and only stars with distance errors smaller than 10% were used in the study.  The escape speed curve is measured at Galactocentric radii ranging from ~5 kpc to~10.5 kpc.  The local Galactic escape at the Sun's position is estimated to be v_e (r_sun)=580 ± 63 km/s, and it rises towards the Galactic center.  Defined as the minimum speed required to reach three viral radii, the estimate of the escape speed as a function of radius implies, for a NFW profile and local circular velocity of 240 km/s, a dark matter mass M_200=1.28+0.68-0.50 e12 Msun and a high concentration c_200=11.09+2.94-1.79.  Assuming the mass-concentration relation of LCDM, get M_200=1.55-0.51+0.64 e12 Msun, c_200=7.93-0.27+0.33, for a local circular velocity of 228 km/s.


1807.04607
VERITAS observations of the BL Lac object TXS 0506+056
Abeysekara, et al

On 2017 Sept. 22, the IceCube Neutrino Observatory reported the detection of the high-energy neutrino event /icnu, of potential astrophysical origin.  It was soon determined that the neutrino direction was consistent with the location of the gamma-ray blazar txs, which was in an elevated gamma-ray emission state as measured by the Fermi satellite.  VERITAS observations of the neutrino/blazar region started on 2017 Sept 23 in response to the neutrino alert and continued through 2018 February 6.  While no significant very-high-energy (VHE; E>100 GeV) emission was observed for the blazar by VERITAS in the 2 week period immediately following the IceCube alert, TXS 0506+056 was detected by VERITAS with a significance of 5.8 sigma in the full 35-hour data set.  The average photon flux of the source during this period was (8.9±1.6)e-12 /cm^2/s, or 1.6% of the CrabNebular flux, above an energy threshold of 100 GeV, with a soft spectral index of 4.8±1.3.


1807.04672
Bias due to neutrinos must not uncorrect'd go
Vagnozzi, et al

In cosmologies with massive neutrinos, the galaxy bias defined with respect to the total matter field (CDM, baryons, and non-relativistic neutrinos) depends on the sum of the neutrino masses M_nu, and becomes scale-dependent even on large scales.  This effect has been usually neglected given the sensitivity of current surveys, but becomes a severe systematic for future surveys aiming to provide the first detection of non-zero M_nu.  The effect can be corrected for by defining the bias with respect to the density field of CDM and baryons instead of the total matter field.  In this work, provide a simple prescription for correctly mitigating the neutrino-induced scale-dependent bias effect in a practical way.  Clarify a number of subtleties regarding how to properly implement this correction in the presence of z-space distortions and non-linear evolution of perturbations.  Perform a MCMC analysis on simulated galaxy clustering data that match the expected sensitivity of the Euclid survey.  Find that the neutrino-induced scale-dependent bias can lead to important shifts in both the inferred mean value of M_nu, as well as its uncertainty.  Show how these shifts propagate to other cosmological parameters correlated with M_nu, such as the CDM physical density Omega_cdm h^2 and the scalar spectral index n_s.  In conclusion, find that correctly accounting for the neutrino-induced scale-dependent bias will be of crucial importance for future galaxy clustering analyses.  Encourage the cosmology community to correctly account for this effect using the simple prescription presented in this work.  The tools necessary to easily correct for the neutrino-induced scale-dependent bias will be made publicly available in an upcoming release of the Boltzmann solver CLASS.


1807.04748
Blazar flares as an origin of high-energy cosmic neutrinos?
Murase, Oikonomou, Petropoulou

Consider implications of high-energy neutrino emission from blazar flares, including the recent event IceCube-170922A and the 2014-2015 neutrino flare that could originate from TXS 0506+056.  First, discuss their contribution to the diffuse neutrino intensity taking into account various observational constraints, and show that blazar flares like those of TXS 0506+056 can make <(1-10)% of the total neutrino intensity.  Even though blazars are likely to be subdominant in the diffuse neutrino intensity at sub-PeV energies, energetic flares can still be detected with a rate of <1 per year.  Also argue that the neutrino output of blazers can be dominated by flares in the standard leptonic scenario for their gamma-ray emission.  Second, consider multi-messenger constraints on the source modeling.  Show that luminous neutrino flares should be accompanied by luminous broadband cascade emission, emerging also in X rays and gamma rays.  This implies that not only gamma-ray telescopes like Fermi but also X-ray sky monitors such as Swift and MAXI are critical to test the canonical picture based on the single-zone modeling.  Also suggest 2-zone models that can avid the X-ray constraints.


1807.05180
Predictably missing satellites: sub halo abundance in Milky Way-like haloes
Fielder, Mao, Newman, Zentner, Licquia

On small scales there have been a number of claims of discrepancies between the standard CDM model and observations.  The 'missing satellites problem' infamously describes the overabundance of sub haloes from CDM simulations compared to the number of satellites observed in the MW.  A variety of solutions to this discrepancy have been proposed; however, the impact of the specific properties of the MW halo relative to the typical halo of its mass have yet to be explored.  Motivated by recent studies that identified ways in which the MW is atypical (e.g., Licquia+0215), investigate how the properties of DM haloes with mass comparable to the Galaxy's --- including concentration, spin, shape and scale factor of the last major merger --- correlate with the sub halo abundance.  Using zoom-in simulations of MW-like haloes, build 2 models of sub halo abundance as functions of host halo properties and conclude that the MW should be expected to have 22-44% fewer sub haloes with low maximum rotation velocities (V_max^sat) ~ 10 km/s at the 95% confidence level and up to 72% fewer than average sub haloes with high rotation velocities (V_max^sat >~ 30 km/s, comparable to the Magellatnic Clouds) than would be expected for a typical halo of the MW's mass.  Concentration is the most informative single parameter for predicting sub halo abundance.  The results imply that models tuned to explain the missing satellites problem assuming typical sub halo abundances for the Galaxy will be overcorrecting.


1807.04877
Gravitational waves from ultrashort period exoplanets
Cunha, Silva, Lima

In the last two decades, thousands of extrasolar planets were discovered based on different observational techniques, and their number must increase substantially in virtue of the ongoing and near-future approved missions and facilities.  It is shown that interesting signatures of binary systems from nearby exoplanets and their parent stars can also be obtained measuring the pattern of gravitational waves that will be made available by the new generation of detectors including the space-based LISA observatory.  As an example, a subset of exoplanets with extremely short periods (less than 80 min) is discussed.  All of them have gravitational luminosity, L_GW ~1e30 erg/s, strain h~1e-22, frequencies f_gw>1e-4 Hz, and as such as within the standard sensitivity curve of LISA.  The analysis suggests that the emitted gravitational wave pattern may also provide an efficient tool to discover ultrashort period exoplanets.


1807.05909
Hypervelocity stars in the Gaia era: runaway B stars beyond the speed limit of classical ejection mechanisms
Irrgang, Kreuzer, Heber

Young massive stars in the halo are supposed to be runaway stars from the Galactic disk.  Possible ejection scenarios are binary supernovaejections (BSE) or dynamical ejections from star clusters (DE).  Hypervelocity stars (HVSs) are extreme runaway stars that are potentially unbound to the Galaxy.  Powerful acceleration mechanisms like the tidal disruption of a binary by a supermassive black hole are required.  Hence, HVSs are believed to originate in the Galactic center (GC).  Gaia DR2 offers the opportunity to study HVSs in a n unprecedented manner.  Revisit the most interesting HVSs, i.e., 15 stars for which proper motions with the HST were obtained in the pre-Gaia era, to unravel their origin.  By carrying out kinematic analyses in 3 different Galactic mass models, kinetic properties are obtained that help to constrain the spatial origins of the HVSs.  While HVSs previously considered unbound remain unbound in 2 Galactic potential, most stars become bound in the most massive Galactic model.  For 9 stars (including 5 unbound candidates), the GC can be rules out as spatial origin at 2 sigma confidence.  Using optical and infrared photometry to determine its spectrophotometric distance, confirm that HVS3 originates in the LMC.  The results suggest that a large fraction of the HVSs are actually disk runaway stars launched close to or beyond Galactic escape velocities.  Population synthesis models predict that only a small fraction of the HVSs stems from BSE.  Furthermore, a maximum ejection velocity of 540 km/s is predicted for BSE and a similar limit has been found for DE.  The ejection velocities of 5 of the non-GC HVSs are close to or above this limit, calling for the existence of another dynamical ejection mechanism (e.g., massive perturbs such as intermediate mass BHs) besides the classical scenarios mentioned above.

Day 1438

Wednesday.  Thursday.


1807.03724
The quasi-linear nearby Universe
Hoffman, et al

The local Universe provides a unique opportunity for testing cosmology and theories of structure formation.  To facilitate this opportunity, present a new method for the reconstruction of the quasi-linear matter density and velocity fields from galaxy peculiar velocities and apply it to the Cosmicflows-2 data.  The method consists of constructing and ensemble of cosmological simulations, constrained by the standard cosmological model and the observational data.  The quasi-linear density field is the geometric mean and variance of the fully non-linear density fields of the simulations.  The main nearby clusters (Virgo, Centaurus, Coma), superclusters (Shapley, Perseus-Pisces) and voids (Dipole Repeller) are robustly reconstructed.  Galaxies are born biased with respect to the underlying DM distribution.  Using the quasi-linear framework, demonstrate that the luminosity-weighted density field derived from the 2M++ redshift compilations is non-linearly biased with respect to the matter density field.  The bias diminishes in the linear regime.


1807.03789
Star cluster ages in the Gaia era
Choi, Conroy, et al

Use the framework developed as part of the MESA Isochrones and Stellar Tracks (MIST) project to assess the utility of several types of observables in jointly measuring the age and 1d stellar model parameters in star clusters.  Begin with a pedagogical overview summarizing the effects of stellar model parameters, such as the He abundance, mass-loss efficiency, and the mixing length parameter, on observational diagnostics including the color-magnitude diagram, mass-radius relation, and surface abundances, amongst others.  Find that these parameters and the stellar age influence observables in qualitatively distinctive, degeneracy-breaking ways.  To assess the current state of affairs, use the recent Gaia DR2 along with data from the literature to investigate 3 well-studies old open clusters -- NGC6819, M67, NGC6791 -- as case studies.  Although there is no obvious tension between the existing observations and the MIST models for NGC6819, there are interesting discrepancies in the cases of M67 and NGC6791.  At this time, parallax zero point uncertainties in Gaia DR2 remain one of the limiting factors in the analysis of these clusters.  With a combination of exquisite photometry, parallax distances, and cluster memberships from Gaia at the end of its mission, anticipate precise and accurate ages for these and other star clusters in the Galaxy.



1807.03793
EasyCritics II.  Testing its efficiency: new gravitational lens candidates in CFHTLenS
Carrasco, et al

Report the results of EasyCritics, a fully automated algorithm for the efficient search of SL regions in wide-field surveys, applied to CFHTLenS.  By using only the photometric information of the brightest elliptical galaxies distributed over a wide redshift range (0.2<~z<~0.9) and without requiring the identification of arcs, the algorithm produces a lensing potential models and catalogs of critical curves of the entire survey area.  Explore several parameter set configurations in order to test the efficiency of the approach.  In a specific configurations, EasyCritics generates only ~1200 possibly super-critical regions in the CFHTLS area, drastically reducing the effective area for inspection from 154 sq. deg to ~0.623 sq. deg, i.e. by more than 2 orders of magnitude.  Among the pre-selected SL regions, identify 32 of the 44 previously known lenses on the group and cluster scale, and discover 9 new promising lens candidates.  The detection rate can be easily improved to ~82% by a simple modification in the parameter set, but at the expense of increasing the total number of possible SL candidates.  Note that EasyCritics is fully complementary to other arc-finders since we characterize lenses instead of directly identifying arcs.  Although future comparisons against numerical simulations are required for fully assessing the efficiency of EasyCritics, the algorithm seems very promising for upcoming surveys covering 1e4 sq deg, such as the Euclid mission and LSST, where the pre-selection of candidates for any kind of SL analysis will be indispensable due to the expected enormous data volume.


1807.03938
Production of Silicon on Mass increasing white dwarfs -- possible origin of high-velocity-features in type Ia supernovae
Kato, Saio, Hachisu

SNe Ia often show high-velocity absorption features (HVFs) in their early phase spectra; however the origin of the HVSs is unknown.  Show that a near-Chandrasekhar-mass WD develops a Si-rich layer on a carbon-oxygen (CO) core before it explodes as an SNIa.  Calculate the nuclear yield in successive He shell flashes for 1.0 Msun, 1.2 Msun, and 1.35 Msun CO Was accreting He-rich matter with several mass-accretion rates ranging from 1e-7 Msun/yr to 7.5e-7 Msun/yr.  For the 1.35 Msun WD with the accretion rate of 1.6e-7 Msun/yr, the surface layer developed as He burning ash and consisted of 40% 24Mg, 33%12C, 23% 28Si, and a few percent of 20Ne by weight.  For a higher mass accretion rate of 7.5e-7 Msun/yr, the surface layer consisted of 58%12C, 31%24Mg, and 0.43% 28Si.  For the 1.2 Msun WDs, Si is produced only for lower mass accretion rates (2% for 1.6e-7 Msun/yr).  No substantial Si (<0.07%) is produced on the 1.0 Msun WD independently of the mass-accretion rate.  If the Si-rich surface layer is the origin of Si II HVFs, its characteristics are consistent with that of mass increasing WDs.  Also discuss possible Ca production on very massive Was (>~1.38 Msun).


1807.04194
Aerogel scattering filters for cosmic microwave background observations
Essinger-Hileman, Bennett, et al

Present the design and performance of broadband and tunable IR-blocking filters for millimeter and sub-millimeter astronomy composed of small scattering particles embedded in a aerogel substrate.  The ultra-low-density (<100 mg/cm^3) aerogel substrate provides an index of refraction as low as 1.05, removing the need for anti-reflection coatings and allowing for broad band operation from DC to above 1THz.  The size distribution of the scattering particles can be tuned to provide a variable cutoff frequency.  Aerogel filters with embedded high-resistivity Si powder are being produced at 40cm diameter to enable large-aperture cryogenic receivers for CMB polarimeters, which require large arrays of sub-Kelvin detectors in their search for the signature of an inflationary gravitational-wave background.


1807.04215
GridSPT: Grid-based calculation for perturbation theory of large-scale structure
Taruya, Nishimichi, Jeong

PT (perturbation theory) calculation of large-scale structure has been used to interpret the observed NL statistics of large-scale structure at the quasi-linear regime.  In particular, the so-called standard perturbation theory (SPT) provides a basis for the analytical computation of the higher-order quantities of large-scale structure.  Here, present a novel, grid-based algorithm for the SPT calculation, hence named GridSPT, to generate the higher-order density and velocity fields from a given linear power spectrum.  Taking advantage of the Fast Fourier Transform, the GridSPT quickly generates the NL density fields at each order, from where the statistical quantities such as NL PS and bispectrum are calculated.  Comparing the density yields (to fifth order) from GridSPT with those from the full N-body simulations in the configuration space, find that GridSPT accurately reproduces the N-body result on large scales.  The agreement worsens with smaller smoothing radius, particularly for the under-dense regions where it is found that 2LPT (second-order Lagrangian perturbation theory) algorithm performs well.


1807.04266
Accurate cosmic shear errors: do we need ensembles of simulations?
Barreira, Krause, Schmidt

Accurate inference of cosmology from WL shear requires an accurate shear PS covariance matrix.  Here, investigate the accuracy requirement and quantify the relative importance of the Gaussian (G), SSC and connected non-Gaussian (cNG) contributions to the covariance.  Specifically, forecast cosmological parameter constraints for future wide-field surveys and study how different covariance matrix components affect parameter bounds.  The main results is that the cNG term represents only a small and potentially negligible contribution to statistical parameter errors: the errors obtained using the G+SSC subset are within <~5% of those obtained with the full G+SSC+cNG matrix for a Euclid-like survey.  This result also holds for the shear correlation function, variations in survey specifications and for different analytical prescriptions of the cNG term.  The cNG term is that which is often tackled using numerical expensive ensembles of survey realizations.  The results suggest however that the accuracy of analytical or approximate numerical methods to compute the cNG term is likely to be sufficient for cosmic shear inference from the next generation of surveys.

Day 1437

Tuesday.

1806.02845
Gaia GraL III - Gaia DR2 Graviational Lens Systems: A systematic blind search for new lensed systems
Delchambre, et al

Context: Strong GL represents an invaluable tool for answering some of the most important questions from cosmology.  It however strongly depends on the availability of a statistically significant number of lenses, coming along with sufficient constraints to model each system in a realistic way.  Still, the number of currently known quadruply-imaged systems remains very limited, mostly because of their scarcity and to inherent difficulties in identifying them amongst extremely large catalogues along with a sufficiently low misclassification rate.  Aims: In this work, aim to provide a reliable list of gravitational lens candidates coming from a blind search analysis performed over the entire Gaia DR2.  Also aim to show that the sole astrometric and photometric informations coming from the Gaia satellite yield sufficient insights for supervised learning methods to automatically identify strong gravitational lens candidates with an efficiency that is comparable to methods based on image processing.  Results: Report the discovery of 15 new quadruply-imaged lens candidates with angular separations less than 6" and assess the performances of the approach by recovering 11 out of the 12 known quadruply-imaged systems having all their components detected in Gaia DR2 with a misclassification rate of fortuitous clusters of stars as lens systems that is below 1%.  Similarly, the identification capability of the method regarding quadruply-imaged systems where 3 images are detected in Gaia DR2 is assessed by recovering 9 out of the 12 known quadruply-imaged systems having one of their constituting images being discarded.  The associated misclassification rate caring then between 5.83% and 20%, depending on the image that was removed.