Day 1433

Friday.

1806.10614
The Wendelstein Weak Lensing (WWL) pathfinder: accurate weak lensing masses for Planck clusters
Rehmann, Gruen, Seitz, Bender, et al

Present results from WWL project, in which 3 intermediate redshift Planck clusters of galaxies were observed with the new 30'x30' wide field imager at the 2m Fraunhofer Telescope at Wendelstein Observatory.  Investigate the presence of biases in the shear catalogues and estimate their impact on the WL mass estimates.  The overall calibration uncertainty depends on the cluster redshift and is below 8.1-15% for z~0.27-0.77.  It will decrease with improvements on the background sample selection and the multiplicative shear bias calibration.  Present the first WL mass estimates for PSZ1 G109.88+28.94 and PSZ1 G139.61+24.20, two SZ-selected cluster candidates.  Based on Wendelstein colors and SDSS photometry, find that the redshift of PSZ1 G10988 has to be corrected to z~0.77.  Investigate the influence of LoS structures on the WL mass esimtates and find upper limits for 2 groups in each of the fields of PSZ1 G109 and PSZ1 G186.  Compare the results to SZ and dynamical mass estimates from the literature, and in the case of PSZ1 G186 to previous WL mass estimates.  Conclude that the pathfinder project demonstrates that WL cluster masses can be accurately measured with the 2m Fraunhofer Telescope.

Day 1432

Thursday.

1806.09530
Note on the Kaiser-Peacock paper regarding gravitational lensing effects
Ellis, Durrer

This paper revisits the controversy concerning whether gravitational lensing effects make a significant difference to estimation of distance to the CMB LSS in cosmology.  A recent paper by Kaiser and Peacock supports a previous paper by Weinberg stating that such affects average to zero because of energy conservation.  In this note, problems are pointed out in the Kaiser and Peacock analysis related to their choice of endpoint of integration, and to the 'wrinkly surface' argument.


1806.10537
A highly precise shape-noise-free shear bias estimator
Pujol, Kilbinger, Sure, Bobin

Present a new method to estimate shear measurement bias in image sims that significantly improves its precision with respect to the state-of-the art methods.  This method is based on measuring the shear response for individual images.  Generate sheared versions of the same image to measure how the shape measurement changes with the changes in the shear, so that one obtains a shear response for each original image, as well as its additive bias.  Using the exact same noise realizations for each sheared version allows obtaining an exact estimation of its shear response.  The estimated shear bias of a sample of galaxies comes from the measured averages of the shear response and individual additive bias.  The precision of this method supposes an improvement with respect to previous methods since the method is not affected by shape noise.  As a consequence, this method does not require shape noise cancellation for a precise estimation of shear bias.  The method can be easily applied to many applications such as shear measurement validation and calibration, reducing the number of necessary simulated images by a few orders of magnitude to achieve the same precision requirements.

Day 1431

Wednesday.


1806.09822
Morphological properties of galaxies in different Local Volume environments
Karachentsev, Kaisina, Makarov

Consider an all-sky sample of 1029 Local Volume (LV) galaxies situated within a distance of 11 Mpc.  Their majority have precise distances, estimates of H mass fraction and SFR drives from far-UV or H_alpha fluxes.  To describe an environment, attribute two dimensionless values: the density contrast created by the most significant neighbor and the local density contrast produced by all neighbors within a separation of 1Mpc.  The H mass fraction exhibits a weak effect of HI deficiency being the most pronounced for dwarf irregular galaxies.  The sSFR is more sensitive to the environment than the H mass fraction.  Almost all (99%) LV galaxies have their sSFR below -9.4 dex (1/yr).  Notice that irregular dwarfs as well as late-type bulgeless galaxies are capable to reproduce their stellar mass with the observed sSFR over the cosmic time.  Thus, the transformation of gas into stars in dIrs and spiral disks is rather sluggish unlike that in E, S0, dSph galaxies, whose SFH has been stormy and short.  Scatter of SFR(H_alpha)-to-SFR(FUV) ratio increases from Sc, Sd, Sm galaxies towards BCD, Im, Ir types that favors the idea of bursty SFs in low-mass galaxies.  However, the bursty activity is caused rather by internal processes than by an external tidal action.  A fraction of quenched E, S0, dSph galaxies increases from ~5% in the field up to ~50% in the densest regions.


1806.10003
An almanac of predicted micorlneing events for the 21st century
Bramich, Nielsen

Using Gaia DR2, present an almanac of 2,509 predicted microlensing events, caused by 2,130 unique lens stars, that will peak between 25 July 2026 and the end of the century.  This work extends and completes a thorough search for future microlensing events initiated by Bramich (2018) and Nielsen&Bramich (2018) using GDR2.  The almanac includes 161 lenses that will cause at least two microlensing events.  A few highlights are presented and discussed, including (i) an astrometric microlensing event with a peak amplitude of ~9.7 mas, (ii) an event that will probe the planetary system of a lens with 3 known planets, and (iii) an event (resolvable from space) where the lens will brighten by a detectable amount (~2 mmag) due to the appearance of the minor source image.


1806.10122
Testing general relativity in cosmology
Ishak

Review recent developments and results in testing GR at cosmological scales.  The subject has witnessed rapid growth during the last 2 decades with the aim of addressing the question of cosmic acceleration and the DE associated with it.  However, with the advent of precision cosmology, it has also become a well-motivated endeavor by itself to test gravitational physics at cosmic scales.  Overview cosmological probes of gravity, formalisms and parameterizations for testing deviations from GR at cosmological scales, selected MG theories, gravitational screening mechanisms, and computer codes developed for these tests.  Then provide summaries of recent cosmo constraints on MG parameters and selected MG models.  Supplement these cosmological constraints with a summary of implications from the recent binary neutron star merger event.  Next, summarize some results on MG parameter forecasts with and without astrophysical systematics that will dominate the uncertainties.  The review aims at providing an overall picture of at the subject and an entry point to students and researchers interested in joining the field.  It can also serve as a quick reference to recent results and constraints on testing gravity at cosmological scales.

Day 1430

Tuesday.

1806.08395
Observations of the missing baryons in the warm-hot intergalactic medium
Nicastro, et al

It has been known for decades that the observed number of baryons in the local universe falls about 30-40% short of the total number of baryons predicted by BBN, as inferred from density fluctuations of the CMB and seen during the first 2-3 billion years of hate universe in the so called Lyman-alpha Forest.   A theoretical solution to this paradox locates the missing baryons in the hot and tenuous filamentary gas between galaxies, known as the warm-hot IGM.  However, it is difficult to detect them there because the largest by far constituent of this gas - hydrogen - is mostly ionized and therefore almost invisible in far-UV spectra with typical S/N ratios.  Despite the large observational efforts, only a few marginal claims of detection have been made so far.  Report observations of two absorbers of highly ionized oxygen (OVII) in the high S/N ratio X-ray spectrum of a quasar at z>0.4.  These absorbers show no variability over a 2yr timescale and have no associated cold absorption, making the assumption that they originate from the quasar's intrinsic outflow or the host galaxy's ISM implausible.  The OVII systems lie in regions characterized by large (x4 compared to average) galaxy over-densities and their number (Down to the sensitivity threshold of the data), agrees well with numerical simulations predictions for the long-sought warm-hot IGM (WHIM).  Conclude that the missing baryons have been found.


1806.09477
Comparing approximate methods for mock catalogues and covariance matrices I: correlation function
Lippich, et al

This paper is the first in a set that analyses the covariance matrices of clustering statistics obtained from several approximate methods for gravitational structure formation.  Focus here on the covariance matrices of anisotropic 2pt correlation function measurements.  The comparison includes 7 approximate methods, which can be divided into 3 categories: predictive methods that follow the evolution of the linear density field deterministically (ICE-COLA, Peak Patch, and Pinocchio), methods that require a calibration with N-body sims (Patchy and Halogen), and simpler recipes based on assumptions regarding the shape of the probability distribution function (PDF) of density fluctuations (log-normal and Gaussian density fields).  Analyse the impact of using covariance estimates obtained from these approximate methods on cosmological analyses of galaxy clustering measurements, using as a reference the covariances inferred from a set of full N-body sims.  Find that all approximate methods can accurately recover the mean parameter values inferred using the N-body covariances.  The obtained parameter uncertainties typically agree with the corresponding N-body results within 5% for the lower mass threshold, and 10% for the higher mass threshold.  Furthermore, find that the constraints for some methods can differ by up to 20% depending on whether the halo samples used to define the covariance matrices are defined by matching the mass, number density, or clustering amplitude of the parent N-body samples.  The results of the configuration-space analysis indicate that most approximate methods provide similar results, with no single method clearly outperforming the others.


1806.09497
Comparing approximate methods for mock catalogues and covariance matrices II: power spectrum multipoles
Blot, et al

[...] The variance of the multipoles is typically reproduced within 10%; overall, find that covariances built from ICE-COLA, Pinocchio, PeakPatch, Patchy and the Gaussian approximation yield errors on model parameters with 5% of those from the N-body based covariance, while for Halogen and lognormal this agreement degrades to ~10%.


1806.09499
Comparing approximate methods for mock catalogues and covariance matrices III: Bispectrum
Colavincenzo, et al

Employ a large set of 300 realizations of the same cosmology for each method, run with matching initial conditions in order to reduce the contribution of cosmic variance to the comparison.  In addition, compare how the error on cosmological parameters such as linear and nonlinear bias parameters depends on the approximate method used for the determination of the bispectrum variance.  As general result, most methods provide errors within 10% of the errors estimated from N-body simulations.  Exceptions are those methods requiring calibration of the clustering amplitude but restrict this to 2pt statistics.  Finally, test how the results are affected by being limited to a few hundreds measurements from N-body sims, and therefore to the bispectrum variance, by comparing with a larger set of several thousands realizations performed with one approximate method.

Day 1429

Monday.

1806.08371
Novel constraints on non-cold (non-thermal) Dark Matter from Lyman-$\alpha$ forest data
Murgia, Iršic, Viel

Present an efficient method for constraining both thermal and non-thermal DM scenarios with the Ly-a forest, based on a simple and flexible parameterization capable to reproduce the small scale clustering signal of a large set of non-cold (nCDM) models.  By using a large suite of hydro sims, determine constraints on both astrophysical, cosmological and nCDM parameters by performing a full MCMC analysis.  Obtain a marginalized upper limit on the largest possible scale at which a power suppression induced by nearly any nCDM scenario can occur, i.e. alpha<0.03 Mpc/h (2sigma CL).  Explicitly describe how to test several of the most viable nCDM scenarios without the need to run any specific numerical simulations, due to the novel parameterization proposed, and due to a new scheme that interpolates between the cosmo models explored.  The shape of the linear matter power spectrum for standard thermal warm DM models appear to be in mild tension (~2 sigma CL) with the data, compared to non-thermal scenarios.  This is the first sturdy that allows to probe the linear small scale shape of the DM power spectrum for a large set of nCDM models.

Day 1428

Friday.

1806.07893
UniverseMachine: the correlation between galaxy growth and dark matter halo assembly from z=0-10
Behroozi, Wechsler, Hearin, Conroy

Present a method to flexibly and self-consistently determine individual galaxies' SFRs from their host haloes' potential well depths, assembly histories, and redshifts.  The method is constraint by galaxies' observed stellar mass functions, SFRs (specific and cosmic), quenched fractions, UV luminosity functions, UV-stellar mass relations, autocorrelation functions (including quenched and SF subsamples), and quenching dependence on environment; each observable is reproduced over the full z range available, up to 0<z<10.  Key findings include: galaxy assembly correlates strongly with halo assembly; quenching at z>1 correlates strongly with halo mass; quenched fractions at fixed halo mass decrease with increasing redshift; massive quenched galaxies reside in higher-mass haloes than star-forming galaxies at fixed galaxy mass; SF and quenched galaxies' SFHs at fixed mass differ most at z<0.5; satellites have large scatter in quenching timescales after infall, and have modestly higher quenched fractions than central galaxies; Planck cosmologies result in up to 0.3 dex lower stellar mass-halo mass ratios at early times; and nonetheless, stellar mass-halo mass ratios rise at z>5.  Also presented are revised stellar mass-halo mass relations for all, quenched, SFing, central and satellite galaxies; the dependence of SFHs on halo mass, stellar mass, and galaxy sSFR; quenched fractions and WL surface densities.  The public data release includes the massively parallel (>1e5 cores) implementation (the UniverseMachine), the newly complied and remeasured observational data, derived galaxy formation constrains, and mock catalogs including light cones.


1806.08120
Galaxy-galaxy lensing in the outskirts of CLASH clusters: constraints on local shear and testing mass-luminosity scaling relation
Desprez, et al

Present a selection of 24 candidate GGL identified from Hubble images in the outskirts of the massive galaxy clusters from the CLASH survey.  These GGLs provide insights into the mass distributions at larger scales than the strong lensing region in the cluster cores.  Built parametric mass models for three of these GGLs showing simple lensing configurations, in order to assess the properties of their lens and its environment.  Show that the local shear estimated from the GGLs traces the gravitational potential of the clusters at 1-2 arcmin radial distance, allowing us to derive their velocity dispersion.  Also find a good agreement between the strength of the shear measured at the GGL positions through strong-lensing modeling and the value derived independently from a WL analysis of the background sources.  Overall, show the advantages of using single GGL events in the outskirts of clusters to robustly constrain the local shear, even when only photometric z estimates are known for the source.  Argue that the mass-luminosity scaling relation of cluster members can be tested by moving the GGLs found around them, and show that the mass parameters can vary up to ~30% between the cluster and GGL models assuming this scaling relation.

Day 1427

Wednesday.  Thursday.

1806.07430
Direct measurement of the intra-pixel response function of Kepler Space TElescope's CCDs
Vorobiev, et al

Space missions designed for high precision photometric monitoring of stars often under-sample the point-spread function, with much of the light landing within a single pixel. Missions like MOST, Kepler, BRITE, and TESS, do this to avoid uncertainties due to pixel-to-pixel response non uniformity.  This approach has worked remarkable well.  However, individual pixels also exhibit response non uniformity.  Typically, pixels are most sensitive near their centers and less sensitive near the edges, with a difference in response of as much as 50%.  The exact shape of this fall-off, and its dependence on the wavelength of light, is the intra-pixel response function (IPRF).  A direct measurement of the IPRF can be used to improve the photometric uncertainties, leading to improved photometry and astrometry of under-sampled systems.  Using the spot-scan technique, measure the IPRF of a flight spare e2v CCD90 imaging sensor, which is used in the Kepler focal plane.  The spot scanner generates spots with a FWHM of <~5 um across the range of 400-900 nm.  Find that Kepler's CCD shows similar IPRF behavior to other back-illuminated devices, with a decrease in responsively near th e edges of a pixel by ~50%.  The IPRF also depends on wavelength, exhibiting a large amount of diffusion at shorter wavelengths and becoming much more defined by the gate structure in the near-IR.  This method can also be used to measure the IPRF of the CCDs used for TESS, which borrows much from the Kepler mission.


1806.07752
The halo masses of galaxies to $z\sim 3$: a hybrid observational and theoretical approach
Conselice, et al

Use a hybrid observational/theoretical approach to study the relation between galaxy kinematics and the derived stellar and halo masses of galaxies up to z=3 as a function of M*, z and morphology.  The observational sample consists of a concatenation of 1125 galaxies with kinematic measurements at 0.4<z<3 from long-slit and integral-field studies.  Investigate several ways to measure halo masses from observations based on results from SAMs, showing that galaxy halo masses can be retrieved with a scatter of ~0.4 dex by using only stellar masses.  Discover a third parameter, relating to the time of the formation of the halo, which reduces the scatter in the relation between the stellar and halo masses, such that systems forming earlier have a higher stellar mass to halo mass ratio, which is also found observationally.  Find that this scatter correlates with morphology, such that early-type, or older stellar systems, have higher M*/Mhalo ratios.  Furthermore show using this approach and through WL and abundance matching, that the ratio of stellar to halo mass does not significantly evolve with redshift at 1<z<3.  This is evidence for the regulated hierarchical assembly of galaxies such that the ratio of stellar to DM mass remains approximately constant since z=2.  Use these results to show that the DM accretion rate evolves from dM_halo/dt ~ 4000 Msun/yr at z~2.5, to a few 100 Msun/yr by z~0.5.

Day 1426

Tuesday.

1806.06781
Model independent $H(z)$ reconstruction using the cosmic inverse distance ladder
Lemos, Lee, Efstathiou, Gratton

Recent distance ladder determinations of the Hubble constant H0 disagree at about the 3.5 sigma level with the value determined from Planck measurements of the CMB assuming LCDM cosmology.  This discrepancy has prompted speculation that new physics might be required beyond that assumed in the LCDM model.  In this paper, apply the inverse distance ladder to fiat a parametric form of H(z) to BAO and SN Ia data together with priors on the sound horizon at the end of the radiation drag epoch, r_d.  Apply priors on the r_d, based on inferences from either Planck or WMAP, and demonstrate that these values are consistent with CMB-independent determinations of r_d derived from measurements of the primordial deuterium abundance, BAO and SNe data assuming the LCDM cosmology.  The H(z) constraints that were derived are independent of detailed physics within the dark sector at low z, relying only on the validity of the FRW metric of GR.  For each assumed prior on r_d, find consistency with the inferred value of H0 and the Planck LCDM value and corresponding tension with the distance ladder estimate.

Day 1425

Monday.

1806.05676
The Clusters Hiding in Plain Sight (CHiPS) survey: a first discovery of a massive nearby cluster around PKS1353-341
Somboonpanyakul, et al

Introduce the first result of the CHiPS survey, which aims to discover new, nearby, and massive galaxy clusters that were incorrectly identified as isolated point sources in the ROSAT All-Sky Survey.  Present a Chandra X-ray observation of the first newly discovered low-redshift (z=0.223) galaxy cluster with a central X-ray bright point source, PKS1353-341.  After removing the point source contribution to the cluster core, determine various properties of the cluster.  The presence of a relaxed X-ray morphology, a central temperature drop, and a central cooling time around 400 Myr point to it being a strong cool-core cluster.  The central galaxy appears to be forming stars at the rate of 6.2±3.6 Msun/yr, corresponding to ~1% of the classical cooling prediction.  The SMBH in the central galaxy appear to be accreting at ~0.1% of the Eddington rate with the total power output of ~5e45 ergs/s, split nearly equally between radiative and mechanical power.  Comparing the cluster's bulk properties with those of other known clusters (e.g., M500=6.9(+4.3)(-2.6)e14 Msun, and L_X=7e44 erg/s), show that this cluster is sufficiently luminous that it would have been identified as a cluster in the ROSAT All Sky-Survey data, if it did not have such a bright central point source.  This discovery demonstrate the potential of the CHiPS survey to find massive nearby clusters with extreme central properties that may have been missed or misidentified by previous surveys.


1806.05685
Compact groups analysis using weak gravitational lensing II: CFHT Stripe 82 data
Chalela, et al

In this work, present a lensing study of CGs using data obtained from the high quality CFHT Stripe 82 Survey.  Using stacking techniques, obtain the average density contrast profile.  Analyise the lensing signal dependence on the groups surface brightness and morphological content, for CGs in the z range z=0.2-0.4.  Obtain a larger lensing signal for CGs with higher surface brightness, probably due to their lower contamination by interlopers.  Also, find a strong dependence of the lensing signal on the group concentration parameter, with the most concentrated quintile showing a significant lensing signal, consistent with an isothermal sphere with sigma_V=336 ± 28 km/s and a NFW profile with R_200=0.60±0.05 Mpc/h_70.  Also compare lensing results with dynamical estimates finding a good agreement with lensing determinations for CGs with higher surface brightness and higher concentration indexes.  On the other hand, CGs that are more contaminated by interlopers show larger dynamical dispersions, since interlopers bias dynamical estimate to larger values, although the lensing signal is weakened.


1806.05697
Electromagnetic emission from supermassive binary black holes approaching merger
d'Ascoli, et al

Present a fully relativistic prediction fo the EM emission from the surrounding gas for a SMBH system approaching merger.  Using a rays-racing code to post-process data from a general relativistic 3d MHD sim, generate images and spectra, and analyze the viewing angle dependence of the light emitted.  When the accretion rate is relatively high, the circumbinary disk accretion stream, and mini-disks combine to emit light in the UV/EUV bands.  Posit a thermal Compton hard X-ray spectrum for coronal emission; at high accretion rates, it is almost entirely produced in the mini-disks, but at lower accretion rates it is the primary radiation mechanism in the mini-disks and accretion streams as well.  Due to relativistic beaming and gravitational lensing, the angular distribution of the power radiated is strongly anisotropic, especially near the equatorial plane.


1806.05870
BAM: Bias assignment method to generate mock catalogs
Balaguera-Antolínez, Kitaura, et al

Present BAM: a novel Bias Assignment Method envisaged to generate mock catalogs by linking the continuous cosmic dark matter field to a discrete population of tracers, such as DM haloes or galaxies.  Using a reference high resolution cosmo N-body sim to extract a bias scheme, can generate halo catalogues starting from a much coarser density fields calculated from downsampled initial conditions using efficient structure formation solvers.  Characterize the halo-bias relation as a function of a number of properties (e.g. local density, cosmic web type) to the DM density field defined on a mesh of a 3 Mpc/h cell side resolution, derived from the fast structure formation solvers.  In this way, the bias description automatically includes stochastic, deterministic, local and non-local component directly extracted from full N-body sims.  Sample the halo density field according to the observed halo bias, such that the 2pt statistics of the mock halo catalog follows the same statistics as the reference.  By construction, the approach reaches percentage accuracy, 1%, in the majority of the k-range up to the Nyquist frequency without systematic deviations for the power spectra (about k~1 h/Mpc) using either particle mesh or Lagrangian perturbation theory biased solvers.  When using phase-space mapping to compensate the low resolution of the approximate gravity solvers, the method is able to reproduce the bispectra of the reference within 10% precision studying configurations tracing the quasi-nonlinear regime.  Therefore BAM promises to become a standard technique to produce mock halo and galaxy catalogs for future galaxy surveys and cosmological studies being highly accurate, efficient and parameter free.


1806.05995
Learning from deep learning: better cosmological parameter inference from weak lensing maps
Ribli, et al

WL: Due to NL on small scales, the traditional analysis with 2pt statistics does not fully capture all the underlying information.  Multiple inference method were prosed to extract more details based on higher order statistics, peak statistics, Minkowski functions and recently convolutional neural networks (CNN).  Present an improved CNN that gives significantly better estimates of Omega_m and sigma8 cosmological parameters from simulated convergence maps than the state of the art method and also is free of systematic bias.  Going beyond "black box" style predictions, the investigation of the features learned by a high performing CNN revealed interesting insights.  Without direct human assistance, only from the training data, the CNN discovered 2 familiar convolutional operators: the discrete Laplace operator and a Roberts cross kernel, which both characterize the steepness of the peaks.  Using this insight, constructed a new, easy-to-understand, and robust peak counting algorithm which uses these operators, instead of the heights of the peaks.  The new scheme significantly reduced prediction errors, and turned out to be even more accurate than the neural network.

Day 1424

Thursday.  Friday.  Monday.  Tuesday.  Wednesday.  Thursday.  Friday.

1806.02841
Calibrating long period variables as standard candles with machine learning
Rau, Koposov, Trac, Mandelbaum

Variable stars with well-calibrated period-luminosity relationships provide accurate distance measurements to nearby galaxies and are therefore a vital tool for cosmology and astrophysics.  While these measurements typically rely on samples of Cepheid and RR-Lyrae stars, abundant populations of luminous variable stars with longer periods of 10-1000 days remain largely unused.  Apply machine learning to derive a mapping between light curve features of these variable stars and their magnitude to extend the traditional period-luminosity (PL) relation commonly used for Cepheid samples.  Using photometric data for long period variable stars in the LMC, demonstrate that the predictions produce residual errors comparable to those obtained on the corresponding Cepheid population.  Show that the model generalizes well to other samples by performing a blind test on photometric data from the SMC.  The predictions on the SMC again show small residual errors and biases, comparable to results that employ PL relations fitted on Cepheid samples.  The residual biases are complementary between the long period variable and Cepheid fits, which provides exciting prospects to better control sources of systematic error in cosmo distance measurements.  Finally show that the proposed methodology can be used to optimize samples of variable stars as standard candles independent of any prior variable star classification.


1806.03356
A family-based method of quantifying NEOWISE diameter errors
Masiero, Mainzer, Wright

Quantifying the accuracy with which physical properties of asteroids can be determined from thermal modeling is critical to measuring the impact of IR data on the understanding of asteroids.  Previous work (Mainzer+ 2011) has used independently-derived diameters (from asteroid radar, occultation, and spacecraft visits) to test the accuracy of the NEOWISE diameter determinations.  Here, present a new and different method for bounding the actual NEOWISE diameter errors in the Main Belt based on the knowledge of the albedos of asteroid families.  Show the 1 sigma relative diameter error for the Main Belt population must be less than 17.5% for the vast majority of objects.  For a typical uncertainty on H magnitude of 0.2 mag, the relative error on diameter for the population would be ~10%.


1806.03681
CAMELOT: Cubesats Appiled for MEasuring and LOcalising Transients - mission overview
Werner, et al

Propose a fleet of nano satellites to perform an all-sky monitoring and timing based localization of gamma-ray transients.  The fleet of at least nine 3U cubesats shall be equipped with large and thin CsI (Tl) scintillator based soft gamma-ray detectors read out by multi-pixel photon counters.  For bright short gamma-ray bursts (GRBs), by cross-correlating their light curves, the fleet shall be able to determine the time difference of the arriving GRB signal between the satellites and thus determine the source position with an accuracy of ~10'.  This requirement demands precise time synchronization and accurate time stamping of the detected gamma-ray photons, which will be achieved by using on-board GPS receivers.  Rapid follow up observations at other wavelengths require the capability for fast, nearly simultaneous downlink of data using a global inter satellite communication network.  In terms of all-sky coverage, the proposed fleet will outperform all GRB monitoring missions.


1806.04150
The distance to the galaxy coma P
Anand, et al

If the extremely low surface brightness galaxy Coma P lies at 5.5±0.3 Mpc as recently proposed, then it would have an extraordinarily deviant peculiar velocity of ~900 km/s at a location where differential velocities between galaxies are low.  Access images from the HST archives used to derive the literature distance from the magnitude of the tip of the red giant branch.  This paper's analysis gives the distance to be 10.9±1.0 Mpc.  At this location the galaxy lies within the infall region of the Virgo Cluster, such that its still considerable peculiar velocity of ~500 km/s is consistent with an established model.  Coma P has an unusually pronounced asymptotic giant branch relative to its red giant branch.  The dominant stellar population is just a few Gyr old.


1806.04292
A new measure of tension between experiments
Adhikari, Huterer

Tensions between cosmo measurements by different surveys or probes have always been important --- and are presently much discussed --- as they may lead to evidence of new physics.  Several tests have been devised to probe the consistency of datasets given a cosmological model, but they often have undesired features such as dependence on the Bayesian priors given to parameters, or burdensome requirements such as that of near-Gaussian posterior distributions.  Propose a new quantity, defined in a similar way as the Bayesian evidence ratio and therefore calibrated on the familiar Jeffreys scale, in which these undesired properties are absent.  Test the quantity on simple models with Gaussian and non-Gaussian likelihoods.  Then apply it to data from the Planck satellite:  Investigate the consistency of the TT and EE angular power spectrum measurements, as well as the mutual consistency of small- and large-angle portion of each measurement, finding mild (~2-3 sigma) discrepancies in agreement with previous work.


1806.04649
Concordance and Discordance in Cosmology
Raveri, Hu

The success of present and future cosmological studies is tied to the ability to detect discrepancies in complex data sets within the framework of a cosmological model. Tensions caused by the presence of unknown systematic effects need to be isolated and corrected to increase the overall accuracy of parameter constraints, while discrepancies due to new physical phenomena need to be promptly identified.  Develop a full set of estimators of internal and mutual agreement and disagreement, whose strengths complement each other.  These allow to take into account the effect of prior information and compute the statistical significance of both tensions and confirmatory biases.  Apply them to a wide range of state of the art cosmo probes and show that these estimators can be easily used, regardless of model and data complexity.  Derive a series of results that show that discrepancies indeed arise within the standard LCDM model.  Several of them exceed the probability threshold of 95% and deserve a dedicated effort to understand their origin.


1806.04668
The Universe at extreme magnification
Diego

Extreme magnifications of distant objects by factors of several thousand have recently become a reality.  Small very luminous compact objects, such as SNe, giant stars at z=1-2, Pop III stars at z>7 and even gravitational waves from merging binary black holes near caustics of gravitational lenses can be magnified to many thousands or even tens of thousands thanks to their small size.  Explore the probability of such extreme magnifications in a cosmological context including also the effect of micro lenses near critical curves.  Show how a natural limit to the maximum magnification appears due to the presence of micro lenses near critical curves.  Use a combination of state of the art halo mass functions, high-resolution analytical models for the density profiles and inverse ray tracing to estimate the probability of magnification near caustics.  Estimate the rate of highly-magnified events in the case of SNe, GW and very luminous stars including Pop III stars.  The findings reveal that future observations will increase the number of events at extreme magnifications opening the door not only to study individual sources at cosmic distances but also to constrain compact dark matter candidates.


1806.05189
A dynamical origin for planets in triple star systems
Fragile, Loeb, Ginsburg

Recent radial velocity and transit data discovered ~100 planets in binary or triple stellar systems out of the entire population of a few thousand known planets.  Stellar companions are expected to strongly influence both the formation and the dynamical evolution of planets in multiple star systems.  Explore the possibility that planets in triples are formed as a consequence of the dynamical interactions of binaries in star clusters.  Simulations show that the probability of forming triple star systems with a planet is in the range 0.5-3%, potentially accounting for most of the observed population.  The recently launched TESS satellite is expected to find a larger sample of planets in triple systems.