Day 1302

Thursday.  Friday.

1708.09813
Cosmological discordances II: Hubble constant, Planck and large-scale-structure data sets
Lin, Ishak

Examine systematically the (in)consistency between cosmological constraints as obtained from various current data sets of the expansion history, LSS, and CMB from Planck.  Run (dis)concordance tests within each set and across the sets using a recently introduced index of inconsistency (IOI) capable of dissecting inconsistencies between two or more data sets.  First, compare the constraints on H0 from 5 different methods and find that the IOI drops from 2.85 to 0.88 (on Jeffreys' scales) when the local H0 measurements is removed.  This seems to indicate that the local measurement is an outlier, thus favoring a systematics-based explanation.  Find a moderate inconsistency (IOI=2.61) between Planck temperature and polarization.  Find that current LSS data sets including WiggleZ, SDSS RSD, CFHTLenS, CMB lensing and SZ cluster count, are consistent one with another and when all combined.  However, find a persistent moderate inconsistency between Planck and individual or combined LSS probes.  For Planck TT+lowTEB versus individual LSS probes, the IOI spans the range 2.92--3.72 and increases to 3.44--4.20 when the polarization data is added in.  The joint LSS versus the combined Planck temperature and polarization has an IOI of 2.83 in the most conservative case.  But if Planck lowTEB is added to the joint LSS to constrain tau and break degeneracies, the inconsistency between Planck and joint LSS data increases to the high-end of the moderate range with IOI=4.81.  Whether due to systematic effects in the data or to the underlying model, these inconsistencies need to be resolved.  Finally, perform forecast calculations using LSST and find that the discordance between Planck and future LSS data, if it persists at present, can rise up to a high IOI of 17, thus falling in the very strong range of inconsistency.

Day 1301

Monday.  Tuesday.  Wednesday.

1708.08454
Large-Distance Lens Uncertainties and Time-Delay Measurements of $H_0$
Muñoz, Kamionkowski

Consider the uncertainties in the mass distribution in the outskirts of the lens.  Show that these can lead to errors in the inferred $H_0$ on the order of a percent and, once accounted for, would correct $H_0$ upward (thus increasing slightly the tension with the CMB).  Weak gravitational lensing and simulations may halve to reduce these uncertainties.

Day 1300

Wednesday.  Thursday.  Friday.

1708.07349
The concentration-mass relation of clusters of galaxies from the OmegaWINGS survey
Biviano, et al

The relation between a cosmological halo concentration and its mass (cMr) is a powerful tool to constraint cosmological models of halo formation and evolution.  On the scale of galaxy clusters the cMr has so far been determined mostly with X-ray and gravitational lensing data.  The use of independent techniques is helpful in assessing possible systematics.  Provide one of the few determinations of the cMr by the dynamical analysis of the projected-phase-space distribution of cluster members.  Based on the WINGS and OmegaWINGS data sets, use the Jeans analysis with the MAMPOSSt technique to determine masses and concentrations for 49 nearby clusters, each of which has ~60 spectroscopic members or more within the viral region, after removal of substructures.  The cMr is in statistical agreement with theoretical predictions based on LCDM cosmo sims.  The cMr is different from most previous observational determinations because of its flatter slope and lower normalization.  It is however in agreement with 2 recent cMr obtained using the lensing technique on the CLASH and LoCuSS cluster data sets.  In the future, will extend the analysis to galaxy systems of lower mass and at higher redshifts.


1708.07433
The impact of the temporal distribution of communicating civilizations on their detectability
Balbi

Use a statistical model to investigate the detectability (defined by the requirement that they are in causal contact with us) of communicating civilizations within a volume of the universe surrounding the location.  If the civilizations are located in the Galaxy, the detectability requirement imposes a strict constraint on their epoch of appearance and their communicating lifespan.  This, in turn, implies that the fraction of civilizations of which we can find any empirical evidence strongly depends on the specific features of their temporal distribution.  The approach shed light on aspects of the problem that can escape the standard treatment based on the Drake equation.  Therefore, it might provide the appropriate framework for future studies dealing with the evolutionary aspects of the search for extraterrestrial intelligence (SETI).


1708.07502
Fundamental physics from future weak-lensing calibrated Sunyaev-Zel'dovich galaxy cluster counts

Madhavacheril, Battaglia, Miyatake

Future high-resolution measurements of the CMB will produce catalogs of tens of thousands of galaxy clusters through the tSZ effect.  Forecast how well different configurations of a CMB Stage-4 experiment can constrain cosmological parameters, in particular the amplitude of structure as a function of redshift sigma8(z), the sum of neutrino masses Sigma m_nu, and the dark energy EoS w(z).  A key element of this effort is calibrating the tSZ scaling relation by measuring the lensing signal around clusters.  Examine how the mass calibration from future optical surveys like LSST compares with a purely internal calibration using lensing of the CMB itself.  Find that, due to its high-redshift leverage, internal calibration gives constraints on cosmo parameters comparable to the optical calibration, and can be used as a cross-check of systematics in the optical measurement.  Also show that in contrast to the constraints using the CMB lensing power spectrum, lensing-calibrated tSZ cluster counts can detect a minimal Sigma m_nu at  the 3-5 sigma level even when the DE EoS is freed up.

Day 1299

Tuesday.

1708.06181
Haloes at the ragged edge: the importance of the splash back radius
Snaith, et al

Explored the outskirts of DM haloes out to 2.5 times the viral radius using a large sample of haloes drawn from Illustris, along with a set of zoom simulations (MUGS).  Using these, make a systematic exploration of the shape profile beyond R_vir.  In the mean sphericity profile of Illustris haloes, identify a dip close to the viral radius, which is robust across a broad range of masses and infall rates.  The inner edge of this feature may be related to the viral radius and the outer edge with the splash back radius.  Due to the high halo-to-halo variation this result is visible only on average.  However, in 4 individual haloes in the MUGS sample, a decrease in the sphericity and a subsequent recovery is evident close to the splashback radius.  Find that this feature persists for several Gyr, growing with the halo.  This feature appears at the interface between the spherical halo density distribution and the filamentary structure in the environment.  The shape feature is strongest when there is a high rate of infall, implying that the effect is due to the mixing of accreting and virtualizing material.  The filamentary velocity field becomes rapidly mixed in the halo region inside the viral radius, with the area between this and the splash back radius serving as the transition region.  Also identify a long-lasting and smoothly evolving splash back region in the radial density gradient in many of the MUGS halos.

Day 1298

Monday.

1708.05643
DES Science Portal: I - computing photometric redshifts
Gschwend, et al

Present the DES Science Portal, an integrated web-based data interface designed to facilitate scientific analysis.  Demonstrate how the Portal can provide a reliable environment to access complete data sets, provide validation algorithms and metrics in the case of multiple methods and training configurations, and maintain the provenance between the different steps of a complex calculations, while ensuring reproducibility of the results.  Use the estimation of DES photometric redshifts (photo-z's) as an example.  A significant challenge facing photometric surveys for cosmological purposes, such as DES, is the need to produce reliable z estimates.  The choice between competing algorithms and configurations and the maintenance of an up-to-date spectroscopic database to build training sets, for example, are complex tasks when dealing with large amounts of data that are regularly updated and constantly growing. Show how the DES Science Portal can be used to train and validate several photo-z algorithms using the DES first year (Y1A1) data.  The photo-z's estimated in the Portal are used to feed the creation of catalogs for scientific workflows.  While the DES collaboration is still developing techniques to obtain precise photo-z's, having a structured framework like the one presented here is critical for the systematic vetting of DES algorithmic improvements and the consistent production of photo-z's in future DES releases.


1708.05642
DES Science Portal: II - Creating Science-Ready catalogs
Neto, et al

Present a novel approach for creating science-ready catalogs through a SW infrastructure developed for DES.  Integrate the data products release by the DES Data Management and additional products created by the DES collaboration in an environment known as DES Science Portal.  Each step involved in the creation of a science-ready catalog is recorded in a relational database and can be recovered at any time.  Describe how the DES Science Portal automates the creation and characterization of lightweight catalogs for DES Y1 Annual Release, and show its flexibility in creating multiple catalogs with different inputs and configurations.  Finally, discuss the advantages of this infrastructure for large surveys such as DES and LSST.  The capability of creating science-ready catalogs efficiently and with full control of the inputs and configurations used is an important asset for supporting science analysis using data from large astronomical surveys.

Day 1297

Monday.  Tuesday.  Wednesday.  Thursday.  Friday.

1708.04526
OzDES multifire spectroscopy for the Dark Energy Survey: Three year results and first data release
Childress, et al

Present results for the first 3 years of OzDES, a 6-yr program to obtain z for objects in DES SN fields using the 2dF fibre positioned and AAOmega spectrograph on the Anglo-Australian Telescope.  OzDES is a multi-object spectroscopic survey targeting multiple types of targets at multiple epochs over a multi-year baseline, and is one of the first multi-object spectroscopic surveys to dynamically include transients in to the large list soon after their discovery.  At the end of 3 years, OzDES has spectorsopically confirmed almost 100 SNe, and has measured z for 17k objects, including the z of 2,566 SN hosts.  Examine how the ability to measure z for targets of various types depends on S/N, magnitude, and exposure time, finding that the z success rate increases singifincatly at a S/N of 2 to 3 per 1-Angstrom bin.  Also find that the change in S/N with exposure time closely matches the Poisson limit for stacked exposures as long as 10 hrs.  Use these results to predict the z yield of the full OzDES survey, as well as the potential yields of future surveys on other facilities such as the 4mMOST, the Subaru PFS, and the Maunakea Spectroscopic Explorer.  This work marks the first OzDES data release, comprising 14,693 redshifts.  OzDES is on target to obtain over a yield of approximately 5,700 SN host-galaxy redshifts.


1708.04892
Accurate modeling of galaxy clustering on small scales: testing the standard $\Lambda\mathrm{CDM}$ + halo model
Snha, et al

Interpreting the small-scale clustering of galaxies with halo models can elucidate the connection between galaxies and DM halos. Unfortunately, the modeling is typically not sufficiently accurate for ruling out models in a statistical sense.  It is thus difficult to use the information encoded in small scales to test cosmological models or probe subtle features of the galaxy-halo connection.  Attempt to push halo modeling into the "accurate" regime with a fully numerical mock-based methodology and careful treatment of statistical and systematic errors.  An advantage of this approach is that it can easily incorporate clustering statistic beyond the traditional 2pt statistics.  Use this modeling methodology to test the standard LCDM + halo model against the clustering of SDSS DR7 galaxies.  Specifically, use the projected correlation function, group multiplicity function and galaxy number density as constraints.  Find that while the model provides a good match to each statistic separately, it struggles to fit them jointly.  Adding group statistics leads to a more stringent test of the model and significantly tighter constraints on model parameters.  Explore the impact of varying the adopted halo definition and cosmological model and find that changing the cosmology makes a significant difference.  The most successful model tried (Planck cosmology with Mir halos) matches the clustering of low luminosity galaxies, but exhibits a 2.3 sigma tension with the clustering of luminous galaxies, thus providing evidence that the "standard" halo model needs to be extended.  This work represents the most accurate modeling of small-scale clustering to date and opens the door to adding interesting freedom to the halo model and including additional clustering statistics as constraints.


1708.05177
PyCosmo: an integrated cosmological Boltzmann solver
Refregier, Camper, Amara, Heisenberg

As wide-field surveys yield ever more precise measurements, cosmology has entered a phase of high precision requiring highly accurate and fast theoretical predictions.  At the heart of most cosmo model predictions is a numerical solution of the EInstein-Boltzmann equations governing the evolution of linear perturbations in the Universe.  Present PyCosmo, a new Python based framework to solve this set of equations using a special purpose solver based on symbolic manipulations, automatic generation of C++ code and sparsity optimization.  The code uses a consistency relation of the field equations to adapt the time steps and does not rely on physical approximations for speed-up.  After reviewing the system of first-order linear homogeneous differential equations to be solved, describe the numerical scheme implemented in PyCosmo.  Then compare the predictions and performance of the code for the computation of the transfer functions of cosmological perturbations and compare it to existing cosmological Boltzmann codes.  Find that it achieves comparable execution times for comparable accuracies.  While PyCosmo does not yet have all the features of other codes, the approach is complementary to existing cosmo Boltzmann solvers and can be used as an independent test of their numerical solutions.  The symbolic representation of the Einstein-Boltzmann equation system in PyCosmo provides a convenient interface for implementing extended cosmological models.  Also discuss how the PyCosmo framework can also be used as a general framework to compute cosmological quantities as well as observables for both interactive and high-performance batch jobs applications.  Information about the PyCosmo package and future code releases are available at www.cosmology.ethz.ch/research/software-lab.html.

Day 1296

Wednesday, Thursday.  Friday.

1708.02981
Tidal locking of habitable exoplanets
Barnes

Potentially habitable planets can orbit close enough to their host star that the differential gravity across their diameters can fix the rotation rate at a specific frequency, a process called tidal locking.  Tidally locked planets on a circular orbits will rotate synchronously but those on eccentric orbits will either librate or rotate super-synchronously.  Calculate how habitable planets evolve under 2 commonly-used models and find, for example, that one model predicts that the Earths' rotation rate would have synchronized after 4.5 Gyr if its initial rotation period was 3 days, it had no satellites, and it always maintained the modern Earth's tidal properties.  Lower mass stellar hosts will induce stronger tidal effects on potentially habitable planets, and tidal locking is possible for most planets in the habitable zones of GKM dwarf stars.  For fast rotating planets, both models predict eccentricity growth and that circularization can only occur once the rotational frequency is similar to the orbital frequency.  The orbits of potentially habitable planets of very late M dwarfs (<0.15 Msun) are very likely to be circularized within 1 Gyr and hence those planets will be synchronous rotators.  Proxima b is almost assuredly tidally locked, but its orbit may not have circularized yet, so the planet could be rotating super-synchronously today.  The evolution of the isolated and potentially habitable Kepler planet candidates is computed and about half could be tidally locked.  Finally, projected TESS planets are simulated over a wide range of assumptions, and the vast majority of all cases are found to tidally lock within 1 Gyr.  These results suggest that the process of tidal locking is a major factor in the evolution of most of the potentially habitable exoplanets to be discovered in the near future.


1708.03002
Relativistic astronomy
Zhang, Li

The Breakthrough Initiatives are a program of scientific and technological exploration, probing some big questions of life in the universe.  Among them is the "Breakthrough Starshot" program, which aims at proving the concept of developing unmanned space flight (probe) at a good fraction of the speed of light, c.  Such a probe is designated to reach nearby stellar systems such as Alpha Centauri within decades, allowing humankind to explore extra-solar systems for the first time.  The first prototype "Sprites" of 3.5cm x 3.5 cm chips weighing just 4 grams each, which are the precursors to eventual "starChip" probes, have been recently launched to a low-earth orbit.  Point out that due to the relativistic effects, trans-relativistic cameras serve as natural lenses and spectrographs while traveling in space, allowing humankind to study the astrophysical objects in a unique manner and to conduct precise tests on special relativity.  Launching trans-relativistic cameras would mark the beginning of "relativistic astronomy".

Day 1295

Monday.  Tuesday.

1708.01441
Weak lensing deflection of three-point correlation functions
Pyne, Joachimi, Peiris

WL alters the apparent separations between observed sources, potentially affecting clustering statistics.  Derive a general expression for the lensing deflection which is valid for any 3-pt statistic, and investigate its effect on the 3pt clustering correlation function.  Find that deflection of the clustering correction function is greatest at around z=2.  It is most prominent in regions where the correlation function varies rapidly, in particular at the baryon acoustic oscillation scale where it smooths out the peaks and troughs, reducing the peak-to-trough difference by about 0.1 percent at z=1 and around 2.3 percent at z=10.  The modification due to lensing defection is typically at the per cent level of the expected errors in a euclid-like survey and therefore undetectable.


1708.01530
Dark Energy Survey Year 1 Results: cosmological constraints from galaxy clustering and weak lensing
DES Collaboration

Present cosmological results from a combined analysis of galaxy clustering and WL, using 1321 deg^2 of griz imaging data from DES Y1.  Combine three 2pt functions: (i) the cosmic shear correlation function of 16 million source galaxies in 4 redshift bins, (ii) the galaxy angular autocorrelation function of 650,000 LRGs in 5 z bins, and (iii) the galaxy-shear cross-correlation of luminous red galaxy positions and source galaxy shears.  To demonstrate the robustness of these results, use independent pairs of galaxy shape, photometric z estimation and validation, and likelihood analysis pipelines.  To prevent confirmation bias, the bulk of the analysis was carried out while blind to the true results; describe an extensive suite of systematics checks performed and passed during this blinded phase.  The data are modeled in flat LCDM and wCDM cosmologies, marginalizing over 20 nuisance parameters, varying 6 (for LCDM) or 7 (for wCDM) cosmological parameters including the neutrino mass density and including the 457x457 element analytic covariance matrix.  Find consistent cosmological results from these 3 two-point functions, and from their combination obtain S8=sigma8(Omega_m/0.3)^0.5=0.783±0.02 and Omega_m=0.264+0.03-0.02 for LCDM. For wCDM, find S8=0.794±0.02 and Omega_m=0.279+0.04-0.02, and w=-0.80±0.2 at 68% CL.  The precision of these DES Y1 results rivals that from the Planck CMB measurements, allowing a comparison of structure in the very early and late Universe on equal terms.  Although the DES Y1 best-fit values for S8 and Omega_m are lower than the central values from Planck for both LCDM and wCDM, the Bayes factor indicates that the DES Y1 and Planck data sets are consistent with each other in the context of LCDM.  Combining DES Y1 with Planck, BAO measurements from SDSS, 6dF, and BOSS, and SNe Ia from the JLA dataset, derive very tight constraints on cosmological parameters: S8=0.799±0.01 and Omega_m = 0.301±0.008 in LCDM, and w=-1.00±0.05 in wCDM.  Upcoming DES analyses will provide more stringent test of the LCDM model and extensions such as time-varying equation of state of DE or modified gravity.


1708.01531
Dark Energy Survey Year 1 results: photometric data set for cosmology
Drlica-Wagner, et al

DES internal Y1A1 GOLD cosmology dataset, from multiple epochs of DES imaging, consisting of calibrated photometric zeropointes, object catalogs, and ancillary data products (maps of survey depth and observing conditions, star-galaxy classification, and photo-z estimates) that are necessary for accuracy cosmo analyses.  Consists of ~137 million objects over ~1800 deg^2 in DES grizY filters.  10 sigma limiting mag for galaxies is g=23.4, r=23.2, i=22.5, z=21.8, and Y=20.1.  Photometric calibration by stellar-locus regression, with absolute calibration accuracy better than 2% over the survey area.  Enables measurements of cosmic acceleration at z<~1.


1708.01532
Dark Energy Survey Year 1 results: Redshift distributions of the weak lensing source galaxies
Hoyle, Gruen, Bernstein, et al

Describe the derivation and validation of z distribution estimates and their uncertainties for the galaxies used as WL sources in DES Y1 cosmo analyses.  BPZ code is used to assign galaxies to 4 z bins between z=0.2 and 1.3, and to produce initial estimates of the lensing-weighted z distributions n_PZ^i(z) for bin i.  Accurate determination of cosmo parameters depends critically on knowledge of n^i but is insensitive to bin assignments or z errors for individual galaxies.  The cosmological analyses allow for shifts n^i(z)=n^i_PZ(z-Delta z^i) to correct the mean redshift of n^i(z) for biases in n^i_PZ.  The Delta z^i are constrained by comparison of independently estimated 30-band photo-z of galaxies in the COSMOS field to BPZ estimates made from the DES griz fluxes, for a sample matched in fluxes, pre-seeing size, and lensing weight to the DES WL sources.  In companion papers, the Delta z^i are further constrained by the angular clustering of the source galaxies around red galaxies with secure photo-z at 0.15<z<0.9.  This paper details the BPZ and COSMOS procedures, and demonstrates that the cosmological inference is insensitive to details of the n^i(z) beyond the choice of Delta z^i.  The clustering and COSMOS validation methods produce consistent estimates of Delta z^i, with combined uncertainties of sigma_Delta z^i=0.015, 0.013, 0.011, and 0.022 in the 4 bins.  Marginalize over these in all analyses to follow, which does not diminish the constraining power significantly.  Repeating the photo-z procedure using the Directional Neighborhood Fitting (DNF) algorithm instead of BPZ, or using the n^i(z) directly estimated from COSMOS, yields no discernible difference in cosmological inferences.


1708.01533
Dark Energy Survey Year 1 results: Weak lensing shape catalogues
Zuntz, Sheldon, et al

Two galaxy shape catalogs from DES Y1, covering 1500 deg^2 with median z~0.59.  Over 2 main fields: stripe 82 and an area overlapping the SPT survey region.  Two independent shear measurement pipelines: METACALBRATION and IM3SHAPE.  METACALIBRATION uses a Gaussian model with an internal calibration scheme and applied to riz-bands, yielding 24.8M objects.  IM3SHAPE uses maximum-likelihood bulge/disc model calibrated using sims, and applied to r-band data, yielding 21.9M objects.  Both catalogues pass a suite of null tests that demonstrate their fitness for use in WL science.  Estimate the 1 sigma uncertainties in multiplicative shear calibration to be 0.013 and 0.025 for the METACALIBRATION and IM3SHAPE catalogues, respectively.


1708.01534
Dark Energy Survey Year 1 results: The impact of galaxy neighbors on weak lensing cosmology with im3shape
Samuroff, Bridle, Zuntz, et al

Use a suite of simulated images based on DES Y1 to explore the impact of galaxy neighbors on shape measurement and shear cosmology.  The hoopoe image sims include realistic blending, galaxy positions, and spatial variations in depth and PSF properties.  Using the im3shape maximum-likelihood shape measurement code, identify 4 mechanisms by which neighbors can have a non-negligible influence on shear estimation.  These effects, if ignored, would contribute a net multiplicative bias of m~0.03-0.09 in the DES Y1 im3shape catalogue, though the precise impact will be dependent on both the measurement code and the selection cuts applied.  This can be reduced to percentage level or less by removing objects with close neighbors, at a cost to the effective number density of galaxies n_eff of 30%.  Use the cosmological inference pipeline of DES Y1 to explore the cosmo implications of neighbor bias and show that omitting blending from the calibration simulation for DES Y1 would bias the inferred clustering amplitude S8=sigma8(Omega_m/0.3)^0.5 by 2 sigma towards low values.  Use the hoopoe sims to test the effect of neighbor-induced spatial correlations in the multiplicative bias.  Find the impact on the recovered S8 of ignoring such correlations to be subdominant to statistical error at the current level of precision.


1708.01535
Dark Energy Survey Year 1 results: Curved-Sky weak lensing mass map
Chang, Pujol, et al

Construct the largest curved-sky galaxy WL mass map to date from DES Y1 data.  The map, about 10x larger than previous work, is constructed over a contiguous ~1500 deg^2, covering a comoving volume of ~10 Gpc^3.  The effects of masking, sampling and noise are tested using simulations.  Generate WL maps from 2 DES Y1 shear catalogs, Metacalibration and Im3shape, with sources at 0.2<z<1.3, and in each of 4 bins in this range.  In the highest S/N map, the ratio between the mean S/N in the E-mode and the B-mode map is ~1.5(~2) when smoothed with a Gaussian filter of sigma_G=30(80) arc minutes.  The second and third moments of the convergence kappa in the maps are in agreement with sims.  Also find no significant correlation of kappa with maps of potential systematic contaminants.  Finally, demonstrate 2 applications of the mass maps: (1) cross-correlation with different foreground tracers of mass and (2) exploration of the largest peaks and voids in the maps.


1708.01536
Dark Energy Survey Year 1 results: Galaxy clustering for combined probes
Elvin-Poole, Crocce, Ross, et al

Measure the clustering of DES Y1 galaxies that are intended to be combined with WL samples in order to produce cosmo constraints from the joint analysis of LSS and lensing correlations.  2pt correlation functions are measured for a sample of 6.6e5 LRGs selected using the redMaGiC algorithm over an area of 1321 square degrees, in the range 0.15<z<0.9, split into 5 tomographic z bins.  The sample has a mean redshift uncertainty of sigma_z/(1+z)=0.017.  Quantify and correct spurious correlations induced by spatially variable survey properties, testing their impact on the clustering measurements and covariance.  Demonstrate the sample's robustness by testing for stellar contamination, for potential biases that could arise for the systematic correction, and for the consistency between the 2pt auto- and cross-correlation functions.  Show that the corrections applied have a significant impact on the resultant measurement of cosmo params, but that the results are robust against arbitrary choices in the correction method.  Find the linear galaxy bias in each z bin in a fiducial cosmology to be b(z=0.24) =1.50±0.08, b(z=0.38)=1.61±0.05, b(z=0.53)=1.60±0.04 for galaxies with luminosities L/L* > 0.5, b(z=0.68)=1.93±0.05 for L/L*>1 and b(z=0.83)=1.99±0.07 for L/L*>1.5, broadly consistent with expectations for the z and L dependence of the bias of red galaxies.  Show these measurements to be consistent with the linear bias obtained from tangential shear measurements.


1708.01537
Dark Energy Survey Year 1 results: Galaxy-galaxy lensing
Prat, et al

Present gg lensing measurements from 1321 deg^2 of DES Y1 data.  The lens sample consists of a selection of 660,000 red galaxies with high-precision photo-z, known as redMaGiC, split into 5 tomographic bins in the range 0.15<z<0.9.  Use 2 different source samples, obtained from Metacalibration (26M galaxies) and Im3shape (18M galaxies) shear estimation codes, which are split into 4 photo-z bins in the range 0.2<z<1.3.  Perform extensive testing of potential systematic effects that can bias the gg lensing signal, including those from shear estimation, photo-z, and observational properties.  Covariance are obtained from jackknife subsamples of the data and validated with a suite of log-normal simulations.  Use the shear-ratio geometric test to obtain independent constraints on the mean of the source z distributions, providing validation of these obtained form other photo-z studies with the same data.  Find consistency between the galaxy bias estimates obtained from the gg lensing measurements and from galaxy clustering, therefore showing the galaxy-matter cross-correlation coefficient r to be consistent with one, measured over the scales used for the cosmo analysis.  The results in this work present one of the 3 2pt correlation functions, along with galaxy clustering and cosmic shear, used in the DES cosmo analysis of Y1 data, and hence the methodology and the systematics tests presented here provide a critical input for that study as well as for future cosmo analyses in DES and other photometric galaxy surveys.


1708.01538
Dark Energy Survey Year 1 results: Cosmological constraints from cosmic shear
Troxel, MacCrann, Zuntz, Eifler, Krause, Dodelson, Gruen, Blazek, et al

Use 26M galaxies from DES Y1 shape catalogs over 1321 deg^2 of the sky to produce the most significant measurement of cosmic shear in a galaxy survey to date.  Constrain cosmological parameters in both the flat LCDM and wCDM models, while also varying the neutrino mass density.  These results are shown to be robust using 2 independent shape catalogs, 2 independent photo-z calibration methods, and 2 independent analysis pipelines in a blind analysis.  Find a 3% fractional uncertainty on sigma8(Omega_m/0.3)^0.5 = 0.789±0.025 at 68% CL, which is a factor of 3 improvement over the fractional constraining power of the DES SV results and a factor 1.5 tighter than the previous state-of-the-art cosmic shear results.  In wCDM, find a 5% fractional uncertainty on sigma8(Omega_m/0.3)^0.5 = 0.789±0.037 and a DE EoS w=-0.82+0.26-0.48.  Find results that are consistent with previous cosmic shear constraints in sigma8-Omega_m, nevertheless see no evidence for disagreement of WL data with data from the CMB.  Finally, find no evidence preferring a wCDM model allowing w!=-1.  Expect further significant improvements with subsequent years of DES data, which will more than 3x the sky coverage of the shape catalogs and double the effective integrated exposure time per galaxy.

1708.01617

Large Synoptic Survey Telescope Galaxies Science Roadmap

Robertson, et al

LSST will enable revolutionary studies of galaxies, DM and BHs over cosmic time.  The LSST Galaxies Science Collaboration has identified a host of preparatory research cases required to leverage fully the LSST dataset for extragalactic science beyond the study of DE.  This Galaxies Science Roadmap provides a brief introduction to critical extragalactic science to be conducted ahead of LSST operations, and a detailed list of preparatory science tasks including the motivation, activities, and deliverables associated with each.  The Galaxies Science Roadmap will serve as a guiding document for researchers interested in conducting extragalactic science in anticipation of the forthcoming LSST era.

Day 1294

Thursday.  Friday.

1708.00447
Discovery of a Proto-cluster Associated with a Ly-$\alpha$ Blob Pair at z=2.3
Bădescu, yang, Bertoldi, Zabludoff, Karim, Magnelli

Bright Ly-alpha blobs (LABs) --- extended nebulae with sizes of ~100 kpc and Ly-alpha luminosities of ~1e44 erg/s --- often reside in over densities of compact Ly-alpha emitters (LAEs) that may be galaxy protoclusters.  The number density, variance, and internal kinematics of LABs suggest that they themselves trace group-like halos.  Test this hierarchical picture, presenting deep, wide-field Ly-alpha narrowband imaging of a 1 deg x 0.5 deg region around a LAB pair at z=2.3 discovered previously by a blind survey.  Find 183 Ly-alpha emitters, including the original LAB pair and 3 new LABs with Ly-alpha luminosities of (0.9--1.3)e43 erg/s and isophotal areas of 16-24 arcsec^2.  Using the LAEs as tracers and a new kernel density estimation method, discover a large-scale overdensity (Boötes J1430+3522) with a surface density contrast of delta_Sigma=2.7, a volume density contrast of delta~10.4, and a projected diameter of ~20 comoving Mpc.  Comparing with cosmological simulations, conclude that this LAE overdensity will evolve into a present-day Coma-like cluster with log (M/Msun)~15.1±0.2.  In this and 3 other wide-field LAE surveys reanalyzed here, the extents and peak amplitudes of the largest LAE over densities are similar, not increasing with survey size, implying that they were indeed the largest structures then and do evolve into rich clusters today.  Intriguingly, LABs favor the outskirts of the densest LAE concentrations, i.e., intermediate LAE over densities of delta_Sigma=1-2.  Speculate that these LABs mark infalling proto-gorups being accreted by the more massive protocluster.


1708.00866
Galaxy Zoo: major galaxy mergers are not a significant quenching pathway
Weigel, et al

Use stellar mass functions to study the properties and the significance of quenching through major galaxy mergers.  In addition to SDSS DR7 and Galaxy Zoo 1 data, use samples of visually selected major galaxy mergers and post merger galaxies.  Determine the stellar mass functions of the stages that major merger quenched galaxies are expected to pass through on their way from the blue cloud to the red sequence: 1: major mergers, 2: post merger, 3: blue early type, 4: green early type and 5: red early type.  Based on the similar mass function shapes, conclude that major mergers are likely to form an evolutionary sequence from star formation to quiescence via quenching.  Relative to all blue galaxies, the major mergers fraction increases as a function of stellar mass.  Major merger quenching is inconsistent with the mass and environment quenching model.  At z~0 major merger quenched galaxies are unlikely to constitute the majority of galaxies that transition the green valley.  Furthermore, between z~0-0.5 major merger quenched galaxies account for 1-5% of all quenched galaxies at a given stellar mass.  Major galaxy mergers are therefore not a significant quenching pathway, neither at z~0 nor within the last 5 Gyr.  The majority of red galaxies must have been quenched through an alternative quenching mechanism which causes a slow blue to red evolution.


1708.01235
Simulations for 21 cm radiation lensing at EoR redshifts
Romeo, Metcalf, Pourtsidou

Introduce sims aimed at assessing how well WL of 21cm radiation from EoR (z~8) can be measured by an SKA-like radio telescope.  A simulation pipeline has been implemented to study the performance of lensing reconstruction techniques.  Show how well the lensing signal can be reconstructed using the 3-d quadratic lensing estimator in Fourier space assuming different survey strategies.  The numerical code introduced in this work is capable of dealing with issues that can not be treated analytically such as the discreteness of visibility measurements and the inclusion of a realistic model for the antennae distribution.  This paves the way for future numerical studies implementing more realistic reionization models, foreground subtraction schemes, and testing the performance of lensing estimators that take into account the non-Gaussian distribution of HI after reionization.  If multiple frequency channels covering z~7-11.6 are combined, Phase 1 of SKA-Low should be able to obtain good quality images of the lensing potential with a total resolution of ~1.6 arcmin.  The SKA-Low phase 2 should be capable of providing images with high-fidelity even using data from z~7.7-8.3.  Perform test aimed at evaluating the numerical implementation of the mapping reconstruction.  Also discuss the possibility of measuring an accurate lensing power spectrum.  Combining data from z~7-11.6 using the SKA2-Low telescope model, find constraints comparable to sample variance in the range L<1000, even for survey areas as small as 25 deg^2.

Day 1293

Wednesday. 

1708.00003
Precise time delays from chromatically micro lensed Type Ia supernovae
Goldstein, Nugent, Kasen, Collett

Perform detailed population, microlensing, radiation transport, and light-curve simulations to quantify (a) the effect of microlensing on the strongly lensed Type Ia supernova (LSN Ia) yield of the LSST and (b) the effect of microlenising on the precision and accuracy of time delays that can be extracted from LSST LSNe Ia.  Microlensing has a negligible effect on the LSST LSN Ia yield, but it can be increased by a factor of ~2 to 930 systems (comparable to the expected yield of l lensed quasars) using a novel photometric identification technique based on spectral template fitting.  Crucially, the microlensing of LSNe Ia is achromatic until 3 rest-frame weeks after the explosion, making features in the early-time color curves precise time delay indicators.  By fitting simulated flux and color observations of microlensed LSNe Ia with their underlying, unlensed spectral templates, forecast the distribution of absolute time delay error due to mcirolensing for LSST, which is unbiased at the sub-percent level and peaked at 1% for color curve observations in the achromatic phase, while for light curve observations it is comparable to mass modeling uncertainties (4%).  About 70% of LSST LSN Ia images should be discovered during the achromatic phase, indicating the microlensing time delay uncertainties can be minimized if prompt multicolor follow-up observations are obtained.  Accounting for microlensing, the 1-2 day time delay on the recently discovered LSN Ia iPTF16geu can be measured to 40% precision, limiting is cosmological utility.  The relatively low precision of this time delay is due to (a) its remarkably short duration and (b) the fact that follow-up observations began long after peak brightness, during a period of significant chromatic uncertainty..


1708.00022
In the crosshair: astrometric exoplanet detection with WFIRST's diffraction spikes
Melchior, Spergel, Lanz

WFIRST will conduct a corona graphic program of characterizing the atmospheres of planets around bright nearly stars.  When observed with the WFIRST WFC, these stars will saturate the detector and produce very strong diffraction spikes.  In this paper, forecast the astrometric precision that WFIRST can achieve by centering on the diffraction spikes of highly saturated stars.  This measurement principle is strongly facilitated by the WFIRST H4RG detectors, which confine excess charges within the potential well of saturated pixels.  By adopting a simplified analytical model of the diffraction spike caused by a single support strut obscuring the telescope aperture, integrated over the WFIRST pixel size, predict the performance of this approach with the Fisher-matrix formalism.  Discuss the validity of the model and find that 10 mas astrometric precision is achievable with a single 100s exposure of a R=6 or a J=5 star.  Discuss observational limitations from the optical distortion correction and pixel-level artifacts, which need to be calibrated at the level of 10-20 mas so as to not dominate the error budget.  To suppress those systematics, suggest a series of short exposures, dithered by at least several hundred pixels, to reach an effective per-visit astrometric precision of better than 10 mas.  If this can be achieved, a dedicated WFIRST GO program will be able to detect Earth-mass exoplanets with orbital periods of 1 yr around stars within a few pc as well as Neptune-like planets with shorter periods or around more massive or distant stars.  Such a program will also enable mass  measurements of many anticipated direct-imaging exoplanet targets of the WFIRST coronagraph and a "star shade" occulter.