Day 1314

Friday.

1709.09721
Deep lensing with a twist: E and B modes in a field with multiple lenses
Bradshaw, Jee, Tyson

Explore aperture mass mapping of LSS using the E- and B-modes produced in the WL analysis of a field of galaxy clusters in Lynx.  Deep multi-color Suprime-cam and HST imaging data are jointly analyzed to produce estimates of the locations and shear of background galaxies, which are then used to infer the locations and masses of foreground over densities (E-modes) through the optimal filtering of axisymmetric tangential shears.  By approximating this foreground structure of E-monds as a superposition of NFW-like halos, model the observed ellpiticitiy of each source galaxy as a sum of shears induced by foreground mass structures.  Also make maps of the B-modes by similarly filtering the axisymmetric cross shear and show that these B-modes in fact contain information about the cluster masses and locations after identifying several expected sources of B-modes including edge effects, source clustering, and multiple lensing.  Verify this reconstruction method using N-body sim data and demonstrate how the observed B-modes naturally occur when background galaxies are sheared through a cosmic web of lenses.

Day 1313

Tuesday.  Wednesday.  Thursday.

1709.07881
The build up of the correlation between halo spin and the large scale structure
Wang, Kang

Both simulations and observations have confirmed that the spin of haloes/galaxies is correlated with the LSS with a mass dependence such that the spin of low-mass halos/galaxies tend to be parallel with the LSS, while that of massive halos/galaxies tend to be perpendicular with the LSS.  It is still unclear how this mass dependence is built up over time.  Use N-body sims to trace the evolution of the halo spin-LSS correlation and find that at early times the spin of all halo progenitors is parallel with the LSS.  As time goes on, mass collapsing around massive halo is more isotropic, especially the recent mass accretion along the slowest collapsing direction is significant and it brings the halo spin to be perpendicular with the LSS.  Adopting the fractional anisotropy (FA) parameter to describe the degree of anisotropy of the LSS, find that the spin-LSS correlation is a strong function of the environment such that a higher FA (more anisotropic environment) leads to an aligned signal, and a lower anisotropy leads to a misaligned signal.  The results show in general that the spin-LSS correlation is a combined consequence of mass flow and halo growth within the cosmic web.  The predicted environmental dependence between spin and large-scale structure can be further tested using galaxy surveys.


1709.08186
The effects of the WISE/GALEX photometry for the SED-Fitting with M31 star clusters and candidates
Fan, Wang

Conclude that the GALEX FUV/NUV bands are more crucial for the SED-fittting of ages and metallicities than the other bands [in UBVRIJHK], and high-quality UV data (with high photometry precision) are required.


1709.08437
How to confirm the existence of population III stars by observations of gravitational waves
Miyamoto, et al

Propose a method for confirmation of the existence of Pop III stars with massive BH binaries as GW15914 in gravitational wave (GW) observation.  When there are enough number of events, want to determine which model is closer to reality, with and without Pop III stars.  Need to prepare various "Pop I/II models" and various Pop I/II/III models" and investigate which model is consistent with the events.  To demonstrate the analysis, simulate detections of GW events for some examples of population synthesis models with and without Pop III stars.  Calculate the likelihood ratio with the realistic number of events and evaluate the probability of identifying the existence of Pop III stars.  In typical cases, the analysis can distinguish between Pop I/II model and Pip I/II/III model with 90% probability by 22 GW signals from BH-BH binary mergers.


1709.08647
Comparing galaxy formation in semi-analytic models and hydrodynamical simulations
Mitchell, et al

It is now possible for hydro sims to reproduce a representative galaxy population.  Accordingly, it is timely to assess critically some of the assumptions of traditional semi-analytic galaxy formation models.  Use the Eagle sims to assess assumptions built into the Galform SAM, focussing on those relating to baryon cycling, angular momentum ad feedback.  Show that the assumption in Galform that newly formed stars have the same specific angular momentum as the total disc leads to a significant overestimate of the total stellar specific angular momentum of disc galaxies.  In Eagle, stars form preferentially out of low specific angular momentum gas in the ISM due to the assumed gas density threshold for stars to form, leading to more realistic galaxy sizes.  Find that stellar mass assembly is similar between Galform and Eagle but that the evolution of gas properties is different, with various indications that the rate of baryon cycling in Eagle is slower than is assumed in Galform.  Finally, by matching individual galaxies between Eagle and Galform, find that an artificial dependence of AGN feedback and gas infall rates on halo mass doubling events in Galform drives most of the scatter in stellar mass between individual objects.  Put together the results suggest that the Galform SM can be significantly improved in light of recent advances.


1709.09371
Are redshift-space distortions actually a probe of growth of structure?
Kimura, et al

Present an impact of coupling between DM and a scalar field, which might be responsible for DE, son measurements of z-space distortions.  Point out that, in the presence of conformal and/or disformal coupling, linearized continuity and Euler equations for total matter fluid significantly deviate from the standard ones even in the sub-horizon scales.  In such a case, a peculiar velocity of total matter field is determined not only by a logarithmic time derivative of its density perturbation but also by density perturbations for both DM and baryon, leading to a large modification of the physical interpretation of observed data obtained by measurements of z-space distortions.  Reformulate galaxy 2-pt correlation function in the space based on the modified continuity and Eulier equations.  Conclude from the resultant formula that the true value of the linear growth rate of LSS cannot be necessarily constrained by single-z measurements of the z-space distortions, unless one observed the actual time-evolution of structure.

Day 1312

Monday.

1709.07003
Low metallicities and old ages for three ultra-diffuse galaxies in the Coma cluster
Gu, Conroy, et al

A large population of UDGs was recently discovered in the Coma cluster.  Present optical spectra of 3 such UDGs, DF7, DF44, and DF17, which have central surface brightnesses of mu_g~24.4-25.1 mag/arcsec^2.  The spectra were acquired as part of an ancillary program within the SDSS-IV MaNGA Survey.  Stacked 19 fibers in the central regions from larger integral field units (IFUs) per source.  With over 13.5 hours of on-source integration, achieved a mean S/N ratio in the optical 9.5A, 7.8A and 5.0A, respectively, for DF7, DF44, and DF17.  Stellar population models applied to these spectra enable measurements of recession velocities, ages and metallicities.  The recession velocities of each are 6599+40-39, 6402+41-39, and 8315±43 km/s, spectroscopically confirming that all of them reside in the Coma cluster.  The stellar populations of these 3 galaxies are old and metal-poor, with ages of 7.9+3.6-2.5 Gyr, 8.9+4.3-3.3 Gyr and 9.1+3.9-5.5 Gyr ,and iron abundances of [Fe/H]-1.0+0.3-0.4, -1.3±0.4 and -0.8±0.5, respectively.  Their stellar masses are 3-6e8 Msun.  The UDGs in the sample are as old or older than galaxies at similar stellar mass or velocity dispersion (only DF44 has an independently measured dispersion).  They all follow the well-established stellar mass-stellar metallicity relation, while DF44 lies below the velocity dispersion-metallicity relation.  These results, combined with the fact that UDGs are unusually large for their stellar mass, suggest that stellar mass plays a more important role in setting stellar population properties for these galaxies than either size or surface brightness.


1709.07457
Internal dark matter structure of the most massive galaxy clusters
Le Brun, Arnaud, Pratt, Teyssier

Investigate the evolution of the DM density profiles of the most massive galaxy clusters in the Universe.  Using a 'zoom-in' procedure on a large suite of cosmological simulations of total comoving volume of 3(Gpc/h)^3, study the 25 most massive clusters in 4 z slices from z~1 to the present.  The minimum mass is M_500>5.5e14 Msun at z=1.  Each system has more than 2 M particles within r_500.  Once scaled to the critical density at each redshift, the dark matter profiles within r_500 are strikingly similar from z~1 to the present day, exhibiting a low dispersion of 0.15 dex, and showing little evolution with redshift in the radial logarithmic slope and scatter.  They have the running power law shape typical of the NFW-type profiles, and their inner structure, resolved to 3.8 h^-1 comoving kpc at z=1, shows no signs of converging to an asymptotic slope.  The results suggest that this type of profile is already in place at z>1 in the highest-mass haloes in the Universe, and that it remains exeptionally robust to merging activity.


1709.07651
KiDS-450: Cosmological constraints from weak lensing peak statistics-I: inference from analytical prediction of high signal-to-noise ratio convergence peaks
Shan, Liu, et al

First of a series of papers constraining cosmo params with WL peak statistics using ~450 deg^2 of imaging data from KiDS-450.  Measure high S/N WL convergence peaks in the range 3<S/N<5, and employ theoretical models to derive expected values.  These models are validated using a suite of simulations.  Take into account 2 major systematics effects, the boost factor and the effect of baryons on the mass-concentration relation of DM haloes.  In addition, investigate the impacts of other potential astrophysical systematics including the projection effects of large scale structures, IA, as well as residual measurement of uncertainties in the shear and redshift calibration.  Assuming a flat LCDM model, find constraints for S8=sigma8(Omega_m/0.3)^0.5=0.746+0.046-0.107 according to the degeneracy direction of the cosmic shear analysis, and Sigma8=sigma8(Omega_m/0.3)^0.38=0.696+0.048-0.050 based on the derived degeneracy direction of the high S/N peak statistics.  The difference between the power index of S8 and in Sigma8 indicates that combining the two probes has the potential to break the degeneracy in sigma8 and Omega_m.  The results are consistent with the cosmic shear tomographic correlation analysis of the same dataset and ~2sigma lower than the Planck 2016 results.


1709.07678
KiDS-450: Cosmological constraints from weak lensing peak statistics - II: inference from shear peaks in N-body simulations
Martinet, Schneider, Hildebrandt, Shan, et al

Study the statistics of peaks in a WL reconstructed mass map of the first 450 sq. deg. of KiDS.  The map is computed with aperture masses directly applied to the shear field with an NFW-like compensated filter.  Compare the peak statistics in the observations with that of simulations for various cosmologies to constrain the cosmo parameter S8=sigma8(Omega_m/0.3)^0.5, which probes the (Omega_m, sigma8) plane perpendicularly to its main degeneracy.  Estimate S8=0.750±0.059, using peaks in the range 0<=S/N<=4, and accounting for various systematics, such as multiplicative shear bias, mean z bias, baryon feedback, IA, and shear-position coupling.  These constraints are ~25% tighter than the constraints from the high significance peaks alone (3<=S/N<=4) which typically trace single-massive haloes.  This demonstrates the gain of information from low-S/N peaks which correspond to the projection of several small-mass haloes along the LoS.  The results are in good agreement with the tomographic shear 2pt correlation function measurement in KiDS-450.  Combining shear peaks with non-tomographic measurements of the shear 2pt correlation functions yields an ~20% improvement in the uncertainty on S8 compared to the shear 2pt correlation functions alone, highlighting the great potential of peaks as a cosmological probe.


1709.07854
Relativistic asymmetries in the galaxy cross-correlation funciton
Guisarma et al

Study the asymmetry in the 2pt X-correlation function of 2 populations of galaxies focusing in particular on the relativistic effects that include the gravitational redshift.  Derive the cross-correlation function on small and large scales using 2 different approaches: GR and Newtonian perturbation theory.  Following recent work by Bonvin+, Gaztanaga+ and Croft, calculate the dipole and the shell estimator with the 2 procedures and compare results.  Find that while GR perturbation theory (GRPT) is able to make predictions of relativistic effects on very large, obviously linear scales (r>50 Mpc/h), the presence of non-linearities physically occurring on much smaller scales (down to those describing galactic potential wells) can strongly affect the asymmetry estimators. These can lead to cancellations of the relativistic terms, and sign changes in the estimators on scales up to r~50 Mpc/h.  On the other hand, with an appropriate NL gravitational potential, the results obtained using  Newtonian theory can successfully describe the asymmetry on smaller, NL scales (r<20Mpc/h) where gravitational redshift is the dominant term.  On large scales the asymmetry is much smaller in magnitude, and measurement is not within reach of current observations.  This is in agreement with the observational results obtained by Gaztanaga+ and the first detection of relativistic effects (on r<20Mpc/h scales) by Alam+.


1709.07855
Relativistic distortions in the large-scale clustering of SDSS-III BOSS CMASS galaxies
Alam, et al

GR effects have long been predicted to subtly influence the observed LSS of the universe. The current generation of galaxy redshift surveys have reached a size where detection of such effects is becoming feasible.  In this paper, report the first detection of the z asymmetry from the X-correlation function of 2 galaxy populations which is consistent with relativistic effects.  The dataset is taken from SDSS DR12 CMASS galaxy sample, and the asymmetry is detected at the 2.7sigma level by applying a shell-averaged estimator to the X-correlation function.  The measurement dominates at scales around 10 Mpc/h, larger than those over which the gravitational z profile has been recently measured in galaxy clusters, but smaller than scales for which linear perturbation theory is likely to be accurate.  The detection significance varies by 0.5 sigma with the details of the measurement and tests for systematic effects.  Also devised 2 null tests to check for various survey systematics and show that both results are consistent with the null hypothesis.  Measure the dipole moment of the X-correlation function, and from this the asymmetry is also detected, at the 2.8sigma level.  The amplitude and scale-dependence of the clustering asymmetries are approximately consistent with the expectations of GR and a biased galaxy population, within large uncertainties.  Explore theoretical predictions using numerical sims in a companion paper.

Day 1311

Friday.

1709.07099
Emulating galaxy clustering and galaxy-galaxy lensing into the deeply nonlinear regime: methodology, information, and forecasts
Wibking, et al

The combination of GGL with galaxy clustering is one of the most promising routes to determining the amplitude of matter clustering at low z.  Show that extending clustering+GGL analyses from the linear regime down to ~0.5 Mpc/h scales increases their constraining power considerably, even after marginalizing over a flexible model of non-linear galaxy bias.  Using a grid of cosmological N-body sims, construct a Taylor-expansion emulator that predicts the galaxy autocorrelation xi_gg(r) and galaxy-matter cross-correlation xi_gm(r) as a function of sigma8, Omega_m, and halo occupation distribution parameters, which are allowed to vary with large scale environment to represent possible effects of galaxy assembly bias.  Present forecasts for a fiducial case that corresponds to BOSS LOWZ galaxy clustering and SDSS-depth weak lensing (effective source density ~0.3 arcmin^-2).  Using tangential shear and projected correlation function measurements over 0.5<=r_p<=30 Mpc/h yields a 1.8% constraint on the parameter combination of sigma8 Omega_m^0.58, a factor of two better than a constraint that excludes non-linear scales (r_p>2Mpc/h, 4Mpc/h for gamma_t, w_p).  Much of the improvement comes from the non-linear clustering information, which break degeneracies among HOD parameters that would otherwise degrade the inference of matter clustering from GGL.  Increasing the effective source density to 3 arcmin^-2 sharpens the constraint on sigma8 Omega_m^0.58 by a further factor of two.  With robust modeling into the non-linear regime, low redshift measurements of matter clustering at the 1% level with clustering+GGL alone are well within reach of current data sets such as those provided by the DES.

Day 1310

Wednesday.  Thursday. 

1709.06992
Report of the Kavli IAU Workshop on Global Coordination: future space-based ultraviolet-optical-infrared telescopes
Elmegreen, Dishoeck, Spergel, Davies

International efforts play a key role in driving all areas of astrophysics.  Strategic planning is essential to explore possible partnerships and joint projects that otherwise could not be afforded, and to maximize their scientific return.  For these reasons, the International Astronomical Uniton (IAU) established in 2016 the Working Group on Global Coordination of Ground and Space Astrophysics.  The WG held a Kavli IAU Workshop on in July 2017, bringing together scientific leaders from 17 countries to discuss compelling science drivers, technical requirements, political constraints, and opportunities for a future large-scale UV/optical/IR space mission.  This report summarizes the workshop and recommends that astronomers worldwide intensify their activities to explore the possibilities for science with such a mission, including consideration of instrumentation and technology definition and development, construction, launch, data analysis, and complementary science.  The workshop presentations are available at www.strw.leidenuniv.nl/KavliAU2017.

Day 1309

Tuesday.


1709.05830
The influence of host galaxies in type Ia supernova cosmology
Uddin, et al

Use a sample of 1338 spectroscopically confirmed and photometrically classified SNe Ia, sourced from the CSP, CfA, SDSS-II, and SNLS supernova samples, to examine the relationships between SNe Ia and the galaxies that host them.  The results provide confirmation with improved statistical significance that SNe Ia, after standardization, are on average more luminous in massive hosts (significance >5 sigma), and decline more rapidly in massive hosts (significance > 9 sigma) and in hosts with low specific star formation rates ( significance > 8 sigma).  Study the variation of these relationships with redshift and detect no evolution.  Split SNe Ia into pairs of subsets that are based on the properties of the hosts, and fit cosmological models to each subset.  Including both systematic and statistical uncertainties, do not find any significant shift in the best-fit cosmological parameters between the subsets.  Among different SN Ia subsets, find that SNe Ia in hosts with high specific star formation rates have the least intrinsic scatter (sigma_int=0.08±0.01) in luminosity after standardization.

Day 1308

Friday.  Monday.

1709.04469
Hot dust in Panchromatic SED fitting: identification of AGN and improved galaxy properties
Leja, Johnson, Conroy, van Dokkum

Forward modeling of the full galaxy SED is a powerful technique, providing self-consistent constraints on stellar ages, star formation rates, dust properties, and metallicities.  However, the accuracy of these results is contingent on the accuracy of the model.  One significant source of uncertainty is the contribution of obscured AGN to the SED, as they are relatively common and can produce substantial id-IR (MIR) emission.  Here, include emission from dusty AGN tore in the Prospector SED-fitting framework, and fit the UV-IR broadband photometry of 129 nearby galaxies.  Find that 10% of the fitted galaxies host an AGN contribution at least 10% of the total observed MIR luminosity.  Demonstrate the necessity of this AGN component in the following ways.  First, we compare observed spectral features to spectral features predicted from the model fit to the photometry.  Find that the AGN component greatly improves predictions for observed H_alpha and H_beta luminosities, as well as MIR Akari and Spitzer/IRS spectra.  Second, show that inclusion of the AGN component changes stellar ages and SFRs by up to a factor of 10, and dust attenuations by up to a factor of 2.5.  Finally, show that the strength of the AGN component in the model correlates with independent AGN indicators, including X-ray fluxes, MIR color gradients, emission line ratios, and other published AGN diagnostics.  This evidence strongly implies that these galaxies truly host AGN, and that the full SED modeling approach is able to detect AGN down to contrasts of L_MIR,AGN / LMIR,tot ~ 0.1.  Notably, only 46% of the SED-detected AGN would be detected with a simple MIR color selection.  Based on these results, conclude that SED models which do not include AGN when fitting MIR data are vulnerable to substantial bias in their derived stellar populations parameters.


1709.04484
First results on the cluster galaxy population from the Subary Hyper Suprime-Cam survey. III. Brightest cluster galaxies, stellar mass distribution, and active galaxies
Lin, et al

The unprecedented depth and area surrey by the Subaru Strategic Program with the Hyper Suprime-Cam (HSC-SSP) have enabled construction of the largest distant cluster sample out to z~1 to date.  In this exploratory study of cluster galaxy evolution from z=1 to z=0.3, investigate the stellar mass assembly history of BCGs, and evolution of stellar mass and luminosity distributions ,stellar mass surface density profile, as well as the population of radio galaxies.  The analysis is the first high redshift application of the top N richest cluster selection, which is shown to allow tracing of the cluster evolution faithfully.  The stellar mass is derived from a machine-learning algorithm, which is shown to be unbiased and accurate with respect to the COSMOS data.  Find very mild stellar mass growth in BCGs, and no evidence for evolution in both the total stellar mass-cluster mass correlation and the shape of the stellar mass surface density profile.  Also present the first measurement of the radio luminosity distribution in clusters out to z~1.


1709.05024
A search for warm/hot gas filaments between pairs of SDSS luminous red galaxies
Tanimura, et al

Search the Planck data for a thermal SZ (tSZ) signal due to gas filaments between pairs of LRG's taken from SDSS DR12.  Identify ~260,000 LRG pairs in the DR12 catalog that lie within 6-10 Mpc/h of each other in tangential direction and within 6 Mpc/h in radial direction.  Stack pairs by rotating and scaling the angular positions of each LRG so they lie on a common reference frame, then subtract a circularly symmetric halo from each member of the pair to search for residual signal between the pair members.  Find a statistically significant (5.3 sigma) between LRG pairs in the stacked data with a magnitude Delta y=(1.31±0.25) e-8.  The uncertainty is estimated from two MC nu tests which also establish the reliability of the analysis.  Assuming a simple, isothermal, cylindrical filament model of electron over-density with a radial density profile proportional to r_c/r (as determined from simulations), where r is the perpendicular distance from the cylinder axis and r_c is the core radius of the density profile, constrain the product of over-density and filament temperature to be delta_c*(T_c/1e7K)*(r_c/0.5Mpc/h) = 2.7±0.5.  To best knowledge, this is the first detection of filamentary gas at over-densities typical of cosmological LSS.  Compare the results to the BAHAMAS suite of cosmological hydrodynamic simulations (McCarthy+2017) and find a slightly lower, but marginally consistent Comptonization excess, Delta y = (0.84±0.24)e-8.

Day 1307

Wednesday.

1709.03992
HST Grism observations of a gravitationally lensed redshift 10 galaxy
Hoag, et al

Present deep spectroscopic observations of a Lyman-break galaxy candidate (MACS1149-JD) at z~10 with HST WFC3/IR prisms.  The grism observations were taken at 4 distinct position angles, totally 34 orbits with the G141 grism, although only 19 of the orbits are relatively uncontaminated along the trace of MACS1149-JD.  Fit a 3 parameter (z, F160W mag, and rest-frame Lyman-alpha equivalent width) Lyman-break galaxy template to the 3 least contaminated grism position angles using a MCMC approach.  he grism data alone are best fit with z = 9.53+0.39-0.60 (68% CL), in good agreement with the photometric estimate of z= 0.51+0.06-0.12.  The analysis rules out Lyman-alpha emission from MACS1149-JD above a 3 sigma rest-frame equivalent width of 21A, consistent with a highly neutral IGM.  Explore a scenario where the red Spitzer IRAC 3.6-4.5 color of the galaxy previously pointed out in the literature is due to strong rest-frame optical emission lines rather than a 4000 A break.  Find that this can provide an explanation for the observed IRAC photometry, but only with a probability of 0.05.  Instead, the grism data add credence to the scenario that the red IRAC color is best explained by a 4000 A break, characteristic of a relatively evolved stellar populations.  In this interpretation, the photometry indicates that a 340+29-35 Myr stellar population is already present in this galaxy only ~500 Myr after the Big Bang.


1709.04205
Photometric redshifts for the Kilo-Degree Survey.  Machine-learning analysis with artificial neural networks
Bilicki, et al

Present a machine-learning photometric redshift analysis of KiDS DR3 using 2 neural network based techniques: ANNz2 and MLPQNA.  Despite limited coverage of spectroscopic training sets, these ML codes provide photo-zs of quality comparable to, if not better than, those from the BPZ code, at least up to a-hot<0.9 and r<23.5.  At the bright end of r<20, where very complete spectroscopic data overlapping with KiDS are available, the performance of the ML photo-zs clearly surpasses that of BPZ, currently the primary photo-z method for KiDS.  Using the GAMA spectroscopic survey as calibration, further study how photo-zs improve for bright sources when photometric parameters additional to magnitudes are included in the photo-z derivation, as well as when VIKING and WISE infrared bands are added.  While the fiducial four-band ugri setup gives a photo-z bias delta z=-2e-4 and scatter sigma_z<0.022 at mean z=0.23, combining magnitudes, colors and galaxy sizes reduces the scatter by ~7% and the bias by an order of magnitude.  Once the ugri and IR magnitudes are joined into 12-band photometry spanning up to 12 mu, the scatter decreases by more than 10% for the fiducial case.  Finally, using the 12 bands together with optical colors and linear sizes gives delta z < 4e-5 and sigma_z<0.019.  This paper also serves as a reference for 2 public photo-z catalogues accompanying KiDS DR3, both obtained using the ANNz2 code.  The first one, of general purpose, includes all the 39 million KiDS sources with 4-band ugri measurements in DR3.  The second dataset, optimized for low-z studies such as galaxy-galaxy lensing, is limited to r<20, and provides photo-zs of much better quality than in the full-depth case thanks to incorporating optical magnitudes, colors, and sizes in the GAMA-calirated photo-z derivation.


1709.04444
Imitating intrinsic alignments: a bias to the CMB lensing-galaxy shape cross-correlation power spectrum induced by the large-scale structure bispectrum
Merkel, Schaefer

Cross-correlating the lensing signals of galaxies and CMB fluctuations is expected to provide valuable cosmological information.  In particular it may help tighten constraints on parameters describing the properties of intrinsically aligned galaxies at high z.  To access the information conveyed by the cross-correlation signal its accurate theoretical description is required.  Compute the bias to CMB lensing-galaxy shape cross-correlation measurements induced by nonlinear structure growth.  Using tree-level perturbation theory for the large-scale structure bispectrum find that the bias is negative on most angular scales, therefore mimicking the signal of IA.  Combining Euclid-like galaxy lensing data with CMB experiment comparable to the Planck satellite mission the bias becomes significant only on smallest scales (ell>~2500).  For improved CMB observations, however, the corrections amount to 10-15% of the CMB lensing-IA signal over a wide multipole range (10 <~ ell <~ 2000).  Accordingly the power spectrum bias, if uncorrected, translates to 2 sigma and 3 sigma errors in the determination of the IA amplitude in case of CMB stage III and stage IV experiments, respectively.

Day 1306

Tuesday.  Wednesday.

1709.03491

The Breakthrough Listen Search for Intelligent Life: 1.1-1.9 GHz observations of 692 nearby stars

Enriquez, et al

Report on a search for engineered signals from a sample of 692 nearby stars using the Green Bank Telescope (GBT), undertaken as part of the Breakthrough Listen Initiative search for extraterrestrial intelligence.  Observations were made over 1.1-1.9 GHz (L-band), with 3 sets of 5 minute observations of the 692 primary targets, interspersed with 5-minute observations of secondary targets.  By comparing the "on" and "off" observations, able to identify terrestrial interference and place limits on the presence of engineered signals from putative extraterrestrial civilizations inhabiting the environs of the target stars.  During the analysis, 11 events passed the thresholding algorithm, but detailed analysis of their properties indicates they are consistent with known examples of anthropogenic radio frequency interference.  Conclude that at the time of the observations none of the observed systems host high-duty-cycle radio transmitters emitting between 1.1 to 1.9 GHz with an EIRP of ~1e13W, which is readily achievable by our own civilization.  The results suggest that fewer than ~0.1% of the stellar systems within 50pc possess the type of transmitters searched in this survey.

1709.03499

Stochastic order redshift technique (SORT): a simple, efficient and robust method to improve cosmological redshift measurements

Tejos, Rodrigez-Puebla, Primack

The method is based on the presence of a reference sample for which a precise redshift number distribution (dN/dz) can be obtained for different pencil-beam-like sub-volumes within the original survey.  For each sub-volume impose: (i) that the redshift number distribution of the uncertain redshift measurements matches the reference dN/dz corrected by their selection functions; and (ii) the rank order in redshift of the original ensemble of uncertain measurements is preserved.  The latter step is motivated by the fact that random variables drawn from Gaussian probability density functions (PDFs) of different means and arbitrarily large standard deviations satisfy stochastic ordering.  Then repeat this simple algorithm for multiple arbitrary pencil-beam-like overlapping sub-volumes; in this manner, each uncertain measurement has multiple (non-independent) "recovered" redshifts which can be used to estimate a new redshift PDF.  Refer to this method as SORT.  Used a state-of-the-art N-body simulation to test the performance of SORT under simple assumptions and found that it can improve the quality of cosmological redshifts in an efficient and robust manner.  Particularly, SORT redshifts are able to recover the distinctive features of the 'cosmic web' and can provide unbiased measurement of the 2pt correlation function on scales > 4 Mpc/h.  Given its simplicity, envision that a method like SORT can be incorporated into more sophisticated algorithms aimed to exploit the full potential of large extragalactic photometric surveys.


1709.03542
The last 6 Gyr of dark matter assembly in massive galaxies from the Kilo Degree Survey
Tortora, et al

Study the DM assembly in the central regions of massive early-type galaxies up to z~0.65.  Use a sample of ~3800 massive log(M*/Msun)>11.2 galaxies with photometry and structural parameters from 156 sq deg of KiDS, and spectroscopic redshifts and velocity dispersions from SDSS.  Obtain central total-to-stellar mass ratios, Mdyn/M*, and DM fractions, by determining dynamical masses, Mdyn from Jeans modeling of SDSS aperture velocity dispersion and stellar masses, M*, from KiDS galaxy colors.  First show how the central DM fraction correlates with structural parameters, mass and density proxies, and demonstrate that most of the local correlations are still observed up to z~0.65; at fixed M*, local galaxies have larger DM fraction, on average, than their counterparts at larger redshift.  Also interpret these trends with a non universal IMF, finding a strong evolution with z, which contrast independent observations and is at odds with the effect of galaxy mergers.  For a fixed IMF, the galaxy assembly can be explained, realistically, by mass and size accretion, which can be physically achieved by a series of minor mergers.  Reproduce both the Re-M* and Mdyn/M* - M* evolution with stellar and dark mass changing at different rate.  This results suggests that the main progenitor galaxy is merging with less massive systems, characterized by a smaller Mdyn/M*, consistently with results from halo abundance matching.


1709.03599
Lens covariance effects on likelihood analyses of CMB power spectra
Motloch, Hu

Non-Gaussian correlations induced in CMB PS by gravitational lensing must be included n likelihood analyses for future CMB experiments.  Present a simple but accurate likelihood model which includes these correlations and use it for MCMC parameter estimation from simulated lensed CMB maps in the context of LCDM and extensions which include the sum of neutrino masses or the DE EoS w. If lensing-induced covariance is not taken into account for a CMB-S4 type experiment, the errors for one combination of parameters in each case would be underestimated by more than a factor of two and lower limits on w could be misestimated substantially.  The frequency of falsely ruling out the true model or finding tension with other data sets would also substantially increase.  The analysis also enables a separation of lens and unlicensed information from CMB PS, which provides for consistency tests of the model and, if combined with other such measurements, a nearly lens-sample-variance free test for systematics and new physics in the unlensed spectrum . This parameterization also leads to a simple effective likelihood that can be used to assist model building in case consistency tests of LCDM fail.

Day 1305

Thursday.  Friday.  Monday.

1709.02543
The first detection of the imprint of filaments on CMB lensing
He, Alam, Ferraro, Chen, Ho

Galaxy redshift surveys, such as 2dF, SDSS, 6df, GAMA and VIPERS, have shown that the spatial distribution of matter formed a hierarchical structure consisting of clusters, filaments, sheets and voids.  This hierarchical structure is known as the cosmic web.  The majority of galaxy survey analyses measure the 2pt correlation, but ignoring the information beyond a small number of summary statistics.  Since the matter density field becomes highly non-Gaussian as structures evolve, expect other statistical descriptions of the field to provide with additional information.  One way to study the non-Gaussianity is to study filaments, which evolve non-linearly from the initial density fluctuation.  Several previous works have studied the gravitational lensing of filaments to detect filaments and learn their mass profile.  In this study, provide the first detection of CMB lensed by filaments and measure how filaments trace the matter distribution on large scales.  More specifically, assume that, on large scales, filaments trace matter with a constant filament bias, defined as the ratio between the filament overdensity and the mass overdensity.  Propose a phenomenological model for the cross power spectrum between filaments and the CMB lensing convergence field.  By fitting the model to the data, measure filament bias.

Day 1304

Wednesday.

1709.01278
Implications for the missing low-mass galaxies (satellites) problem from cosmic shear
Jimenez, Verde, Kitching

The number of observed dwarf galaxies, with DM mass <~1e11 Msun in the MW or the Andromeda galaxy does not agree with predictions from the successful LCDM paradigm. To alleviate this problem there has been a conjecture that there may be suppression of DM clustering on very small scales.  However, the abundance of DM haloes outside the immediate neighborhood (The Local Group) does seem to agree with the expected abundance from the LCDM paradigm.  Here, make the link between these problems and observations of WL cosmic shear, pointing out that cosmic shear can make significant statements about missing satellites problem in a statistical way.  As an example and pedagogical application, use the recently measured small-scale matter PS from a spherical-Bessel analysis of current cosmic shear data that constrains the suppression of power on small-scales and thus indirectly estimates, on average, the abundance of DM haloes.  In this example application find, on average, in a local region of ~Gpc^3 there is no significant small-scale power suppression implying that suppression of small-scale power is not a viable solution to the 'missing satellites problem' or, alternatively, that there is no 'missing satellite problem' for DM masses >5e9 Msun.  Further analysis of current and future WL surveys will provide details on the power spectrum at scales much smaller than k>10 h/Mpc corresponding roughly to masses M<1e9 Msun.

Day 1303

Monday.  Tuesday.

1709.00992
Dark Energy Survey Year 1 Results: Cross-Correlation Redshifts - Methods and systematics characterization
Gatti, et al

Use numerical simulations to characterize the performance of a clustering-based method to calibrate photo-z biases.  In particular, X-correlate WL source galaxies from DES Y1 sample with redMaGiC galaxies (luminous red galaxies with secure photo-z) to estimate the z distribution of the former sample.  The recovered redshift distributions are used to calibrate the photo-z bias of standard photo-z methods applied to the same source galaxy sample.  Apply the method to 3 photo-z codes run in the simulated data: BPZ, Directional Neighborhood Fitting (DNF), and Random Forest-based photo-z (RF).  Characterize the systematic uncertainties of the calibration procedure, and find that these systematic uncertainties dominate the error budget.  The dominant systematics are due to the assumption of involving bias and clustering across each z bin, ad to differences between the shapes of the z distributions derived by clustering vs photo-z's.  The systematic uncertainty in the mean redshift bias of the source galaxy sample is Delta z <~ 0.02, though the precise value depends on the z bin under consideration.  Discuss possible ways to mitigate the impact of the dominant systematics in future analysis.