Day 1075

Thursday.

Nature
Contribution of Antarctica to past and future sea-level rise
DeConto & Pollard

Polar temperatures over the last several miilon years have, at times, been slightly warmer than today, yet global mean sea level has been 6-9 meters higher as recently as the Last Interglacial (130,000 to 115,000 years ago) and possibly higher during the Pliocene epoch (about 3 Myrs ago).  In both cases the Antarctic ice sheet has been implicated as the primary contributor, hinting at its future vulnerability.  Here, use a model coupling ice sheet and climate dynamics -- including previously under appreciated processes linking atmospheric warming with hydrofracture of buttressing ice shelves and structural collapse of marine-terminating ice cliffs that is calibrated against Pliocene and Last Interglacial sea-level estimates and applied to future greenhouse gas emission scenarios.  Antarctica has the potential to contribute more than a meter of sea-level rise by 2100 and more than 15 meters by 2500, if emissions continue unabated.  In this case, atmospheric warming will soon become the dominant driver of ice loss, but prolonged ocean warming will delay its recovery for thousands of years.


1603.08923
Cosmological simulations of early blackhole formation: halo mergers, tidal disruption, and the conditions for direct collapse
Chon, Hirano, Hosokawa, Yoshida

Gravitational collapse of a massive primordial gas cloud is thought to be a promising path for the formation of SMBHs in the early universe.  Study conditions for the so-called direct collapse (DC) BH formation in a fully cosmological context.  Combine a semi-analytic model of early galaxy formation with halo merger trees constructed from DM N-body sims.  Locate a total of 68 possible DC sites in a volume of 20 Mpc/h on a side.  Then perform hydro sims for 42 selected halos to study in detail the evolution of the massive clouds within them.  Find only 2 successful cases where the gas clouds rapidly collapse to form stars.  In the other cases, gravitational collapse is prevented by the tidal force exerted by a nearby massive halo, which otherwise should serve as a radiation source necessary for DC.  Ram pressure stripping disturbs the cloud approaching the source.  In many cases, a DC halo and its nearby light source halo merge before the onset of cloud collapse.  Only when the DC halo is assembled through major mergers, the gas density increases rapidly to trigger gravitational instability.  Based on the cosmo sims, conclude that the event rate of DC is an order of magnitude smaller than reported in previous studies, although the absolute rate is still poorly constrained.  It is necessary to follow the dynamical evolution of a DC cloud and its nearby halo(s) in order to determine the critical radiation flux for DC.

Day 1074

Wednesday.

1603.08522
First identification of direct collapse black hole candidates in the early universe in CANDELS/GOODS-S
Pacucci, Ferrara, Grazian, Fiore, Giallongo

The first BH seeds, formed when the universe was younger than 500 Myr, are recognized to play an important role for the growth of early (z~7) SMBHs.  While progresses have been made in understanding their formation and growth, their observational signatures remain largely unexplored.  As a result, no detection of such sources has been confirmed so far.  Supported by numerical simulations, present a novel photometric method to identify BH seed candidates in deep multi-wavelength surveys.  Predict that these highly-obscured sources are characterized by a steep spectrum in the IR (1.6-4.5 um), i.e., by very red colors.  The method selects the only 2 objects with a robust x-ray detection found in the CANDELS/GOODS-S survey with a photometric redshift z>6.  Fitting their IR spectra only with a stellar component would require unrealistic SFRs (>2000 Msun/yr).  To date, the selected objects represent the most promising BH seed candidates, possibly formed via the direct collapse BH scenario, with predicted mass > 1e5 Msun.  While this result is based on the best photometric observations of high-z sources available to date, additional progress is expected from spectroscopic and deeper X-ray data.  Upcoming observatories, like the JWST, will greatly expand the scope of this work.


1603.08609
Covariance in the Thermal SZ-Weak lensing mass scaling relation of galaxy clusters
Shirasaki, Nagai, Lau

Investigate the origin of observed scatter in the tSZ-WL scaling relation, using mock maps of galaxy clusters extracted from cosmo hydro sims.  Show that the inferred intrinsic scatter from mock tSZ-WL analyses is considerably larger than the intrinsic scatter measured in simulations, and comparable to the scatter in the observed tSZ-WL relation.  Show that this enhanced scatter originates form the combination of the projection of correlated structures along the line of sight and the uncertainty in the cluster radius associated with WL mass estimates, causing the amplitude of the scatter to depend on the covariance between tSZ and WL signals.  Present a statistical model to recover the unbiased cluster scaling relation and cosmological parameter by taking into account the covariance in the tSZ-WL mass relation from multi-wavelength cluster surveys.


1603.08626
The composite spectrum of BOSS quasars selected for suites of the LYman-alpha forest
Harris, Jensen, Suzuki, et al

BOSS has collected more than 150,000 2.1<z<3.5 quasar spectra since 2009.  Using this unprecedented sample, create a composite spectrum in the rest-frame of 102,150 quasar spectra from 800A to 3300A at a S/N ratio close to 1000 per pixel (Delta nu of 69 km/s).  Included in this analysis is a correction to account for flux calibration residuals in the BOSS spectrophotometry.  Determine the spectral index as a function of z of the full sample, warp the composite spectrum to match the median spectral index, and compare the resulting spectrum to SDSS photometry used in target selection.  The quasar composite matches the color of the quasar population to within 0.02 magnitudes in g-r, 0.03 magnitudes in r-i, and 0.01 magnitudes in i-z over 2.2<z<2.6.  The composite spectrum deviates from the imaging photometry by 0.05 mag around z=2.7, likely due to differences in target selection as the quasar colors become similar to the stellar locus at this redshift.  Finally, characterize the line features in the high S/N composite and identity 9 faint lines not found in the previous composite spectrum from SDSS.

Day 1073

Tuesday.

1603.08431
Cosmic shear measurement with maximum likelihood and maximum a posteriori inference
Hall, Taylor

Investigate the problem of noise bias in maximum likelihood and maximum a posteriori estimators for cosmic shear.  Derive the leading and next-to-leading order biases and compute them in the context of galaxy ellipticity measurements, extending previous work on maximum likelihood inference for WL.  Show that a large part of the bias on these point estimators can be removed using information already contained in the likelihood when a galaxy model is specified, without the need for external calibration.  Test the bias-corrected estimators on simulated galaxy images similar to those expected from planned space-based WL surveys, with very promising results.  Find that the introduction of an intrinsic shape prior mitigates noise bias, such that the maximum a posteriori estimate can be made less biased than the maximum likelihood estimate.  Second-order terms offer a check on the convergence of the estimators, but are largely sub-dominant.  Show how biases propagate to shear estimates, demonstrating in the simple setup that shear biases can be reduced by orders of magnitude and potentially to within the requirements of planned space-based surveys.  Find that second-order terms can exhibit significant cancellations at low signal-to-noise when Gaussian noise is assumed, which has implications for inferring the performance of shear-measurement algorithms from simplified simulations.  Discuss the viability of the point estimators as tools for lensing inference, arguing that they allow for the robust measurement of ellipticity and shear.

Day 1072

Monday.

1603.07734
The rotation of the hot gas around the Milky Way
Hodges-Klick, Miller, Bregman

The hot gaseous halos of galaxies likely contain a large amount of mass and are an integral part of galaxy formation and evolution.  The MW has a 2e6 K halo that is detected in emission and by absorption in the OVII resonance line against bright background AGNs, and for which the best current model is an extended spherical distribution.  Using XMM-Newton RGS data, measure the Doppler shifts of the OVII absorption-line centroids toward an ensemble of AGNs. These Doppler shifts constrain the dynamics of the hot halo, ruling out a stationary halo at about 3 sigma and a corotating halo at 2 sigma, and leading to a best-fit rotational velocity of 183±41 km/s for an extended halo model.  These results suggest that the hot gas rotates and that it contains an amount of angular momentum comparable to that in the stellar disk.  Examine the possibility of a model with a kinematically distinct disk and spherical halo.  To be consistent with the emission-line X-ray data the disk must contribute less than 10% of the column density, implying that the Doppler shifts probe motion in the extended hot halo.


1603.07818
A pseudo-spectrum analysis of galaxy-galaxy lensing
Hikage, Oguri

Present the application of the pseudo-spectrum method to gg lensing.  Derive explicit expressions for the pseudo-spectrum analysis of the galaxy-shear cross spectrum, which is the Fourier space counterpart of the stacked gg lensing profile.  The pseudo-spectrum method corrects observational issues such as the survey geometry, masks of bright stars and their spikes, and inhomogeneous noise, which distort the spectrum and also mix the E-mode and the B-mode signals.  Using ray-tracing simulations in N-body sims including realistic masks, confirm that the pseudo-spectrum method successfully recovers the input galaxy-shear cross spectrum.  Also investigate the covariance of the galaxy-shear cross spectrum using the ray-tracing sims to show that there is an excess covariance relative to the Gaussian covariance at small scales where the shot noise is dominated in the Gaussian approximation.  Find that the excess of the covariance is consistent with the expectation from the halo sample variance (HSV), which originates from the matter fluctuations as scales larger than the survey area.  Apply the pseudo-spectrum method to the observational data of CFHTLenS shear catalogue and BOSS CMASS and LOWZ galaxies.  The galaxy-shear cross spectra are significantly detected at the level of 7-10 sigma using the analytic covariance with the HSV contribution included.  Also confirm that the observed spectra are consistent with the halo model predictions with the halo occupation distribution parameters estimated from previous work.  This work demonstrate the viability of gg lensing analysis in Fourier space.

Day 1071

Friday.

1603.07422
Extended stellar components of galaxies & the nature of dark matter
Power, Robotham

Deep observations of galaxies reveal faint extended stellar components (ESCs) of streams, shells, and halos.  These are a natural prediction of hierarchical galaxy formation, as accreted satellite galaxies are tidally disrupted by their host.  Investigate whether or not global properties of the ESC could be used to test of DM, reasoning that they should be sensitive to the abundance of low-mass satellites, and therefore the underlying DM model.  Using cosmo simulations of galaxy formation in the favored CDM and WDM models (m_WDM=0.5,1,2 keV/c^2), which suppress the abundance of low-mass satellites, find that the kinematics and orbital structure of the ESC is consistent across models.  However, find striking differences in its spatial structure, as anticipated -- a factor of ~10 drop in spherically averaged mass density between ~10% and ~75% of the viral radius in the more extreme WDM runs (m_WDM=0.5, 1keV/c^2) relative to the CDM run.  These differences are consistent with the mass assembly histories of the different components, and are present across redshifts.  However, even the least discrepant of the WDM models is incompatible with current observational limits on m_WDM.  Importantly, the differences observed when varying the underlying DM are comparable to the galaxy-to-galaxy variation expected within a fixed DM model.  This suggests that it will be challenging to place limits on DM using only the unresolved spatial structure of the ESC.


1603.07519
Angular distribution of cosmological parameters as a probe of inhomogeneities: a kinematic parameterisation
Carvalho, Basilakos

Use a kinematic parameterization of the luminosity distance to measure the angular distribution of the sky of time derivatives of the scale factor, in particular the Hubble parameter H_0, the deceleration parameter q_0 and the jerk parameter j_0.  Apply the method introduced in Carvalho & Marques (2015) to complement probing the inhomogeneity of the LSS by means of the inhomogeneity in the cosmic expansion.  This parameteristion is independent of the cosmo equation of state, which renders it adequate to test interpretations of the cosmic acceleration alternative to the cosmo constant.  Also measure the anisotropy of the parameters by computing the PS of the corresponding parameters' maps up to ell=3.  Finally for an analytical toy model of an inhomogeneous ensemble of homogeneous pixels, derive the back reaction term in j_0 use to the fluctuations of {H+0,q+0} and measure it to be of order 0.01 the corresponding average over the pixels in the absence of back reaction.  The back reaction effect on q_0 remains below the detection threshold, in agreement with that computed using a LCDM parameterization of the luminosity distance.  Although the back reaction effect on j_0 is about 10x that on q_0, it is also below the detection threshold.  Hence back reaction remains unobservable both in q_0 and in j_0.


1603.07722
RCSLenS: The Red Cluster Sequence Lensing Survey
Hildebrandt, et al

Present RCSLenS, and application of the methods developed for CFHTLenS to the ~785 deg^2, multi-band imaging data of RCS2.  This project represents the largest public, sub-acrsecond seeing, multi-band survey to date that is suited for WL measurements.  With a careful assessment of systematic errors in shape measurements and photometric redshifts, extend the use of this data set to allow cross-correlation analysis between WL observables and other data sets.  Describe the imaging data, the data reduction, masking ,multicolor photometry, photo-z, shape measurements, tests for systematic errors, and a blinding scheme to allow for more objective measurements.  In total, analyze 761 pointings with r-band coverage, which constitutes the lensing sample.  Residual large-scale B-mode systematics prevent the use of this shear catalog for cosmic shear science.  The effective number density of lensing sources over an unmasked area of 751.7 deg^2 and down to a magnitude limit of r~24.5 is 8.1 galaxies per arcmin^2 (weighted: 5.5 arcmin^-2) distributed over 14 patches on the sky.  Photometric redshifts based on 4-band griz data are available for 513 pointings covering an unmasked area of 383.5 deg^2.  Present WL mass reconstructions of some example clusters as well as the full survey representing the largest areas that have been mapped in this way.  All the data products are publicly available through CADC at www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/community/rcslens/query.html in a format very similar to the CFHTLenS data release.


1603.07723
CFHTLenS and RCSLenS Cross-correlation with Planck Lensing detecting in Fourier and configuration space
Harnois-Déraps, et al

Measure the cross-correlation signature between the Planck CMB lensing map and the WL observations from both the RCSLenS and CFHTLenS.  In addition to a Fourier analysis, include the first configuration-space detection, based on the estimators <k_CMB k_gal> and <k_CMB gamma_t>.  Combining 747.2 deg^2 from both surveys, find a detection significance that exceeds 4.2 sigma in both Fourier- and configuration-space analyses.  Scaling the predictions by a free parameter A, obtain A^Planck_CFHT=0.68±0.31 and A^Planck_RCS=1.31±0.33.  In preparation for the next generation of measurements similar to these, quantify the impact of different analysis choices on these results.  First, since none of these estimators probes the exact same dynamical range, improve the detection by combining them.  Second, carry out a detailed investigation on the effect of apodization, zero-padding and mask multiplication, validated on a suite of high-resolution simulations, and find that the latter produces the largest systematic bias in the cosmo interpretation.  Finally, show that residual contamination from intrinsic alignment and the effect of photo-z error are both largely degenerate with the characteristic signal from massive neutrinos, however the signature of baryon feedback might be easier to distinguish.  The RCSLenS lensing data are now publicly available.

Day 1070

Thursday.

1603.06953

Weak lensing measurement of the mass--richness relation of SDSS redMaPPer Clusters

Simet, et al

Perform a measurement of the mass-richness relation of the redMaPPer galaxy cluster catalogue using WL data from SDSS.  Characterize a broad range of systematic uncertainties, including shear calibration errors, photo-z biases, dilution by member galaxies, source obscuration, magnification bias, incorrect assumptions about cluster mass profiles, cluster centering, halo triaxiality, and projection effects.  Also compare measurements of the lensing signal from two independently-produced shear and photo-z catalogues to characterize systematic error in the lensing signal itself.  Using a sample of 5,570 clusters from 0.1<=z<=0.33, the normalization of the power-law mass vs lambda relation is log10[M200m/(Msun/h)] = 14.344±0.021 (stat) ± 0.023 (sys) at a richness lambda=40, a 7% calibration uncertainty, with a power-law index of 1.33±0.09 (1sigma).  The detailed systematics characterization in this work renders it the definitive WL mass calibration for SDSS redMaPPer clusters at this time.

1603.06955

Cosmic web type dependence of halo clustering

Fisher, Faltenbecher

Use the Millennium sim to show that halo clustering varies significantly with cosmic web type.  Haloes are classified as node, filament, sheet and void halos based on the eigenvalue decomposition of the velocity shear tensor.  This classification allows examination of the clustering of halos as a function of web type in different mass ranges.  Find that node haloes show positive bias for all mass ranges probed, even from 1e11 and 1e12 Msun/h mass bins where the clustering of the entire halo sample is anti-biased.  In all mass bins filament halos show negligible bias, whereas void and sheet halos are anti-biased.  The zero-crossing of the void and sheet correlation functions occur at much smaller scales Mpc/h when compared to the same correlation functions for the entire halo sample.  The realists suggest that the mass dependence of halo clustering is rooted in the composition of web types in the mass bin.  The substantial fraction of node type halos for halo masses 2e13 Msun/h leads to positive bias.  Filament type halos prevail at intermediate masses, 1e12-13 Msun/h, resulting in unbiased clustering.  The large contribution of sheet type halos at low halo masses 1e12 Msun/h generates anti-biasing.

Day 1069

Monday.  Tuesday.  Wednesday.

1603.05653

The origin of the $\alpha$-enhancement of massive galaxies

Segers, Schaye, Bower, Crain, Schaller, Theuns

Study the origin of the stellar alpha-element-to-iron abundance ratio, [alpha/Fe]*, of present-day central galaxies, using cosmological, hydrodynamical simulations from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) project.  For galaxies with stellar masses of M* > 1e10.5 Msun, [alpha/Fe]* increases with increasing galaxy stellar mass and age.  These trends are in good agreement with observations of early-type galaxies, and are consistent with a `downsizing' galaxy formation scenario: more massive galaxies have formed the bulk of their stars earlier and more rapidly, hence from an ISM that was mostly alpha-enriched by massive stars.  In the absence of feedback from AGN, however, [alpha/Fe]* in M*>1e10.5 Msun galaxies is roughly constant with stellar mass and decreases with mean stellar age, extending the trends found for lower-mass galaxies in both simulations with and without AGN.  Conclude that AGN feedback can account for the alpha-enhancement of massive galaxies, as it suppresses their star formation, quenching more massive galaxies at earlier times, thereby preventing the Fe from longer-lived intermediate-mass stars (SNIa) from being incorporated into younger stars.

1603.05690

Selecting background galaxies in weak-lensing analysis of galaxy clusters

Formicola, Radovich, Mereghetti, Mazzotta, Grado, Giocoli

Present a new method to select the faint, BG galaxies used to derive the mass of galaxy clusters by WL.  The method is based on the simultaneous analysis of the shear signal, that should be consistent with zero for the FG, unlensed galaxies, and of the colors of the galaxies: photometric data from the COSMic evOlution Survey are used to train the color selection.  In order to validate this methodology, test it against a set of state-of-the-art image sims of mock galaxy clusters in different z [0.23-0.45] and mass [0.5-1.55e15 Msun] ranges, mimicking medium-deep multicolor imaging observations (e.g. SUBARU, LBT).  The performance of the method in terms of contamination by unlensed sources is comparable to a selection based on photo-z, which however requires a good spectral coverage and its thus much more observationally demanding.  The application of the method to simulations gives an average ratio between estimated and true asses of ~0.98±0.09.  As a further test, finally apply the method to real data, and compare the results with other WL mass estimates in the literature: for this purpose, choose the cluster A2219 (z=0.228), for which multi-band (BVRi) data are publicly available.

1603.05790

Galaxy-galaxy lensing in the DES science verification data

Clampitt, et al

Present gg lensing results from 139 sq. deg. of DES SV data.  The lens sample consists of red galaxies, known as redMaGiC, which are specifically selected to have low photo-z error and outlier rate.  The lensing measurement has a total S/N of 29, including all lenses over a wide redshift range 0.2<z<0.8.   Dividing the lenses into 3 redshift bins, find no evidence for evolution in the halo mass with redshift.  Obtain consistent results for the lensing measurement with 2 independent shear pipelines, ngmix and im3shape.  Perform a number of null tests on the shear and photometric z catalogs and quantify resulting systematic errors.  Covariances from jackknife subsamples of the data are validated with a suite of 50 mock surveys.  The results and systematics checks in this work provide a critical input for future cosmo and galaxy evolution studies with the DES data and redMaGiC galaxy samples.  Fit a HOD model, and demonstrate that the data constrains the mean halo mass of the lens galaxies, despite strong degeneracies between individual HOD parameters.

1603.05833

MUSE observations of the lensing cluster Abell 1689

Bina, et al

Present the results obtained with MUSE on the core of A1689.  Integral-field observations with MUSE provide a unique view of the central region, allowing a complete census on both cluster galaxies and lensed BG sources, identified based on their spectral features without preselection.  Investigate the multiple-image configuration for all known sources in the field.  Previous to the survey, 28 different lensed galaxies displaying 46 multiple images were known in the MUSE field of view, most of them based on photo-z and lensing considerations.  Among them, spectroscopically confirm 12 images based on emission lines, corresponding to 7 different lensed galaxies between z=0.95 and 5.0.  In addition, 14 new galaxies have been spectroscopically identified in this area, with redshifts ranging between 0.8 and 6.2.  All background sources within the MUSE field of view correspond to multiple-imaged systems lensed by A1689. 17 sources in total are found at z>3 based on their Ly-a emission, with Ly-a luminosities ranging between 40.5<log(Lya)<42.5 after correction for magnification.  This sample is particularly sensitive to the slope of the LF toward the faintest-end.  The density of sources obtained in this survey is consistent with a steep value of alpha<-1.5, although this result still needs further investigation. These results illustrate the efficiency of MUSE in the characterization of lensing clusters on one hand, and the study of faint and distant populations of galaxies on the other hand.  In particular, the current survey of lensing clusters should provide a unique census of sources responsible for the reionization in a representative volume at z~4-7.

1603.05981

Galaxy populations in the 26 most massive Galaxy Clusters in the South Pole Telescope SZE survey

Zenteno, Mohr, et al

Present a study of the optical properties of the 26 most massive galaxy clusters selected within the SPT-SZ 2500 deg2 survey.  This SZ effect selected sample spans 0.10<z<1.13.  Measure the galaxy radial profile, the LF, and the halo occupation number (HON) using optical data with a typical depth of m*+2.  The stacked radial profiles are consistent with a NFW profile with a concentration of 2.84+0.40-0.37 for the red sequence and 2.36+0.38-0.35 for the total population.  Stacking the data in multiple redshift bins shows a hint of redshift evolution in the concentration when both the total population is used, and when only RS galaxies are used (at 2.1 sigma and 2.8 sigma, respectively).  The stacked LF shows a faint end slope alpha=-1.06+0.04-0.03 for the total and alpha=0.80+0.04-0.03 for the RS population.  The redshift evolution of m* is found to be consistent with a passively evolving Composite Stellar Population (CSP) model.  By adopting the CSP model predictions, explore the redshift evolution of the Schechter parameters alpha and phi*.  Find alpha for the total population to be consistent with no evolution (0.3 sigma), while evidence of evolution for the red galaxies is mildly significant (1.1-2.1 sigma).  The data show that the density phi*/E^2(z) decreases with redshift, in tension with the self-similar expectation at a 2.4 sigma level for the total population.  The measured HON-mass relation has a lower normalization than previous studies at low z.  Finally, the data support HON redshift evolution at a 2.1 sigma level, with clusters at higher z containing fewer galaxies per unit mass to m*+3 than their low-z counterparts.

1603.06773

A new model to predict weak-lensing peak counts III.  Filtering technique comparisons

Lin, Kilbinger, Pires

3rd in a series of papers that develop a new and flexible model to predict WL peak counts, which have been shown to be very valuable non-Gaussian probe of cosmology.  In this paper, compare the cosmo information extracted from WL peak counts using different filtering techniques of the galaxy shear data, including linear filtering with a Gaussian and 2 compensated filters (the starlet wavelet and the aperture mass), and the nonlinear filtering method MRLens.  Present improvements to the model that count for realistic survey conditions, which are masks, shear-to-convergence transformations, and non-constant noise.  Create simulated peak counts from the stochastic model, from which the constraints on the matter density Omega_m, the PS normalization sigma8, and the DE parameter W_0 are obtained.  Use 2 methods for parameter inference, a coulee likelihood, and approximate Bayesian computation (ABC).  Measure the contour width in the Omega_m sigma8 degeneracy direction and the figure of merit to compare constraints from different filtering techniques.  Find that starlet filtering outperforms the Gaussian kernel, and that including peak counts from different scales helps to lift parameter degeneracies.  Peak counts from different smoothing scales with a compensated filter show very little cross-correlation, and adding information from different scales can therefore strongly enhance the available information.  Measuring peak counts separately from different scales yields tighter constraints than using a combined peak histogram from a single map that includes multi scale information.  The results suggest that a compensated filter function with counts included separately from different smoothing scales yields the tightest constraints on cosmo parameters from WL peaks.

Day 1068

Friday.


1603.05249
On the feasibility of characterizing free-floating planets with current and future space-based microlensing surveys
Henderson, Shvartzvald

Simultaneous space- and ground-based microlensing surveys, such as K2's Campaign 9 (K2C9) and WFIRST, facilitate measuring the masses and distances of free-floating planet (FFP) candidates.  FFPs are identified as single-lens events with a short timescale, of order 1 day.  Measuring the mass of the lensing object requires determining the finite size of the source star rho, as well as the microns parallax pi_E.  A planet that is bound to but widely separated from a host star can produce a light curve similar to that of an FFP.  This tension can be resolved with high-resolution imaging of the microlensing target to search for the lens flux F_l from a possible host star.  Here, investigate the accessible parameter space for each of these components --- pi_E, rho and F_l -- considering different satellites for a range of FFP masses, Galactic distances, and source star properties.  Find that at the beginning of K2C9, when its projected separation from the Earth (as viewed from the center of its survey field) is <~0.2 AU, it will be able to measure pi_E for Jupiter-mass FFP candidates at distances lager than ~2 kpc and to Earth-mass lenses at ~8 kpc.  At the end of its campaign, when D_perp=0.81 AU, it is sensitive to planetary-mass lenses for distances >~3.5 kpc, and even then only to those with mass >~ M_Jup.   From lens flux constraints, find that it will be possible to exclude all stellar-mass host stars (down to the deuterium-burning limit) for events within ~2kpc.  Together these indicate that the ability to characterize FFPs detected during K2C9 is optimized for events occurring toward the beginning of the campaign.   WFIRST, on the other hand, will be able to detect and characterize FFPs with masses at least as low as super-Earths throughout the Galaxy during its entire microlensing survey.


1603.05253
Cosmological $N$-body simulations with suppressed variance
Angulo, Pontzen

Present and test a method that dramatically reduces variance arising from the sparse sampling of wave modes in cosmo sims.  The method uses two sims which are fixed (the initial Fourier mode amplitudes are fixed to the ensemble average PS) and paired (with initial modes exactly out of phase).  Measure the PS, monopole and quadrupole z-space correlation functions, halo mass function and reduced bispectrum at z=1.  By these measures, predictions from a fixed pair can be as precise on non-linear scales as an average over 50 traditional simulations.  The fixing procedure introduces a non-Gaussian correction to the initial conditions; give an analytic argument showing why the simulations are still able to predict the mean properties of the Gaussian ensemble. Anticipate that the method will drive down the computational time requirements for accurate large-scale explorations of galaxy bias and clustering statistics, enabling more precise comparisons with theoretical models, and facilitating the use of numerical simulations in cosmo data interpretation.


1603.05275
Local analogs for high-redshift galaxies: resembling the physical conditions of the interstellar medium in high-redshift galaxies
Bian, et al

The sample of local analogs for high-z galaxies in SDSS, selected based on their positions in the [OIII]/Hbeta versus [NII]/Halpha nebular emission-line diagram, resemble the physical conditions of the ISM to those in high-z galaxies.  Physical properties such as sSFRs, flat UV continuum and compact galaxy sizes are found to also be similar.  In particular, the ionization parameters and electron densities in these analogs are comparable to those in z~2-3 galaxies, but higher than those in normal SDSS galaxies by ~0.6 dex and ~0.9 dex, respectively.  The mass-metallicity relation (MZR) in these local analogs shows -0.2 dex offset from that in SDSS SF galaxies at the low mass end, which is consistent with the MZR of the z~2-3 galaxies.  Compare the local analogs in this study with those in other studies, including Lyman break analogs (LBA) and green pea (GP) galaxies.  The analogs in this study share a similar SF surface density with LBAs, but the ionization parameters and electron densities in the analogs are higher than those in LBAs by factors of 1.5 and 3, respectively.  The analogs in this study have comparable ionization parameter and electron density to the GP galaxies, but the method can select galaxies in a wider z range.  Find the high sSFR and SFR surface density can increase the electron density and ionization parameters, but still cannot fully explain the difference in ISM condition between nearby galaxies and the local analogs/high-z galaxies.

Day 1067

Thursday.


Nature
Acceleration of petaelectronvolt protons in the Galactic Centre
HESS collaboration

Galactic CRs reach energies of at least a few PeV (~1e15 eV).  This implies that the Galaxy contains PeV accelerators ('PeVatrons'), but all proposed models of Galactic CR accelerators encounter difficulties at exactly these energies.  Dozens of Galactic accelerators capable of accelerating particles to energies of tens of TeVs (of the order of 1e13 eV) were inferred from recent gamma-ray observations.  However, none of the currently known accelerators -- not even the handful of shell-type SN remnants commonly believed to supply most Galactic CRs -- has shown the characteristic tracers of PeV parties, namely, power-law spectra of gamma-rays extending without a cut-off or a spectral break to tens of TeVs.  Here, report deep gamma-ray observations with arc minute angular resolution of the region surrounding the Galactic Centre, which show the expected tracer of the presence of PeV protons within the central 10 pcs of the Galaxy.  Propose that the SMBH Sgr A* is linked to this PeVatron.  Sagittarius A* went through active phases in the past, as demonstrated by X-ray outbursts and an outflow from the Galactic Centre.  Although its current rate of particle acceleration is not sufficient to provide a substantial contribution to Galactic CRs, Sgr A* could have plausibly been more active over the last 1e6-7 years, and therefore should be considered as a viable alternative to SN remnants as a source of PeV Galactic CRs.


1603.04855
Organized chaos: scatter in the relation between stellar mass and halo mass in small galaxies
Garrison-Kimmel, Bullock, Moylan-Kolchin, Bardwell

Use LG galaxy counts together with the ELVIS N-body sims to jointly constrain the scatter and slope in the stellar mass vs halo mass relation at low masses, M*~1e5-8 Msun.  Assuming log-normal scatter about a median relation of the form M*~M_halo^alpha, the preferred log-slope steepens from alpha~1.8 in the limit of zero scatter to alpha~2.6 in the case of 2 dex off scatter in M* at fixed halo mass.  Provide fitting functions for the best-fit relations as a function of scatter, including cases where the relation becomes increasingly stochastic with decreasing mass.  Show that if the scatter at fixed halo mass is large enough  (>~1 dex) and if the median relation is steep enough (alpha>~2), then the "too-big-to-fail" problem seen in the LG can be self-consistently eliminated in about ~5-10% of realizations.  This scenario requires that the most massive sub halos host unobservable ultra-faint dwarfs fairly often; discuss potentially observable signatures of these systems.  Compare the derived constraints to recent high-resolution simulations of dwarf galaxy formation in the literature.  Through sim-to-sim scatter in M* at fixed M_halo is large among separate authors (~2 dex), individual codes produce relations with much less scatter and usually give relations that would over-produce local galaxy counts.


1603.05040
Cosmology constraints from shear peak statistics in Dark Energy Survey Science Verification data
Kacprzak, Kirk, .. et al

Shear peak statistics has gained a log of attention recently as a practical alternative to the 2pt statistics for containing cosmological parameters.  Perform a shear peak statistics analysis of the DES SV data, using WL measurements from a 139 deg2 field.  Measure the abundance of peaks identified in aperture mass maps, as a function of their S/N ratio, in the S/N ranges 0<S/N<4.  To predict the peak counts as a function of cosmo parameters, use a suite of N-body sims spanning 158 models with varying Omega_m and sigma_8, fixing w=-1, Omega_b=0.04, h=0.7 and n_s=1, to which the DES SV mask and z distribution is applied.  In the fiducial analysis, measure sigma_8(Omega_m/0.3)^0.6=0.77±0.07, after marginalizing over the shear multpicative bias and the error on the mean redshift of the galaxy sample.  Introduce models of IAs, blending, and source contamination by cluster members.  These models indicate that peaks with S/N>4 would require significant corrections, which is why the are not included in the analysis.  Compare the results to the cosmo constraints from the 2pt analysis on the SV field and find them to be in good agreement in both the central value and its uncertainty.  Discuss prospects for future peak statistics analysis with upcoming DES data.


1603.05184
Redshift-space distortions around voids
Cai, Taylor, Peacock, Padilla

Derive estimators for the linear growth rate of density fluctuations using the cross-correlation function of voids and haloes in z-space, both directly and in Fourier form.  In linear theory, this cross-correlation contains only monopole and quadrupole terms.  At scales grater than the void radius, linear theory is a good match to voids traced out by haloes in N-body simulations; small-scale random velocities are unimportant at these radii, only tending to cause small and often negligible elongation of the redshift-space cross-correlation function near its origin.  By extracting the monopole and quadrupole from the cross-correlation function, measure the linear growth rate without prior knowledge of the void profile or velocity dispersion.  Recover the linear growth parameter beta to 9% precision from an effective volume of 3(Gpc/h)^3 using voids with radius greater than 25 Mpc/h.  Smaller voids are predominantly sub-voids, which may be more sensitive to the random velocity dispersion; they introduce noise and do not help to improve the measurement.  Adding velocity dispersion as a free parameter allows use of information at radii as small as half of the void radius.  The precision on beta is reduced to approximately 5%.  Contrary to the simple z-space distortion patter in over densities, voids show diverse shapes in z-space, and can appear either enlarged or flattened along the LoS.  This can be explained by the competing amplitudes of the local entity contrast, plus the radial velocity profile and its gradient, with the latter two factors being determined by the cumulative density profile of voids.  The distortion pattern is therefore determined solely by the void profile and is different for void-in-cloud and void-in-void.  This diversity of z-space void morphology complicates measurements of the Alcock-Paczynski effect using voids.

Day 1066

Wednesday.


1603.04441
Revealing the z~2.5 cosmic web with 3d Lyman-Alpha forest tomography: a deformation tensor approach
Lee, White

Studies of cosmological objects should take into account their positions within the cosmic web of LSS.  Unfortunately, the cosmic web has only been extensively mapped at low-redshifts (z<1), using galaxy redshifts as tracers of the underlying density field.  At z>1, the required galaxy densities are inaccessible for the foreseeable future, but 3d reconstructions of alpha forest absorption in closely-separated background QSOs and SF galaxies already offer a detailed window in to z~2-3 large-scale structure.  Quantify the utility of such maps for studying the cosmic web by using realistic z-2.5 Lya forest simulations matched to observational properties of upcoming surveys.  A deformation tensor-based analysis is used to classify voids, sheets, filaments and nodes in the flux, which is compared to those determined from the underlying DM field.  Find an extremely good correspondence, with 70% of the volume in the flux maps correctly classified relative to the DM web, and 99% classified to within 1 eigenvalue.  This compares favorably to the performance of galaxy-based classifiers with even the highest galaxy densities at low-redshift.  Find that narrow survey geometries can degrade the cosmic web recovery unless the survey is >60 Mpc/h or >1 deg on the sky.  Also examine halo abundances as a function of the cosmic web, and find a clear dependence as a function of flux overdensity, but little expect dependence on the cosmic web.  These methods will provide a new window on cosmo environments of galaxies at this special time in galaxy formation, "high noon", and on overall properties of cosmological structures at this epoch.


1603.04536
Oxygen isotopic evidence for vigorous mixing during the Moon-forming Giant Impact
Young, et al

Earth and Moon are shown to be composed of O isotope reservoirs that are indistinguishable, with a difference in Detla ^17O of -1±5ppm (2se).  Based on these data and the new planet formation simulations that include a realistic model for O isotopic reservoirs, the results favor vigorous mixing during the giant impact and therefore a high-energy high- angular-momentum impact.  The results indicate that the late veneer impactors had an average Delta ^17O within approximately 1 per mil of the terrestrial value, suggesting that these impactors were water rich.


1603.04696
Weak lensing study of 16 DAFT/FADA clusters: substructures and filaments
Martinet et al

While the current cosmological model places galaxy clusters at the nodes of a filament network, we still struggle to detect these filaments at high redshifts.  Perform a WL study for a sample of 16 massive, medium-high redshift (0.4<<0.9) galaxy clusters from the DAFT/FADA survey, that are imaged in at least 3 optical bands with Subaru/Suprime-Cam or CFHT/MegaCam.  Estimate the cluster masses using a NFW fit to the shear profile measured in a KSB-like method, adding the contribution to the calibraiton of the observable-mass relation required for cluster abundance cosmo studies.  Compute convergence maps and select structures within, securing their detection with noise re-sampling techniques.  Taking advantage of the large field of view of the data, study cluster environment, adding information from galaxy density maps at the cluster redshift and from X-ray images when available. Find that clusters show a large variety of WL maps at large scales and that they may all be embedded in filamentary structures at Mpc scale.  Classify them in 3 categories according to the smoothness of their WL contours and to the amount of substructures: relaxed (~7%), past mergers (~21.5%), recent or present mergers (~71.5%).  The fraction of clusters undergoing merging events observationally supports the hierarchical scenario of cluster growth, and implies that massive clusters are strongly evolving at the studied redshifts.  Finally, report the detection of unusually elongated structures in CLJ0152, MACSJ0454, MACSJ0717, A851, BMW1226, MACSJ1621, and MS1621.


1603.04698
Roulettes: a weak lensing formalism for strong lensing - I. Overview
Clarkson

Present a new perspective on gravitational lensing.  Describe a new extension of the WL formalism capable of describing strongly lensed images.  By integrating the non-linear geodesic deviation equation, the amplification matrix of WL is generalized to a sum over independent amplification tensors of increasing rank.  Show how an image distorted by a generic lens may be constructed as a sum over 'roulettes', which have the natural curves associated with the independent spin modes of the amplification tensors.  Highly distorted images can be constructed even for large sources observed near or within the Einstein radius of a lens where the shear and convergence are large.  The amplitude of each roulette is formed from a sum over appropriate derivatives of the lensing potential.  Consequently, measuring these individual roulette is formed from a sum over appropriate derivatives of the lensing potential.  Consequently, measuring these individual roulettes for images around a lens gives a new way to reconstruct a strong lens mass distribution without requiring a lens model.  This formalism generalists the convergence, shear and flexion of WL to arbitrary order, and provides a unified bridge between the strong and weak lensing regimes.  This overview paper is accompanied by a much more detailed Paper II.


1603.04784
Radio weak lensing shear measurement in the visibility domain - I. Methodology
Rivi, Miller, Makhathini, Abdalla

Present an adaptation to radio data of "lensfit".  Simulations show additive and multiplicative bias values that are comparable to SKA1 requirements for SNR>18 and SNR>30.  The multiplicative bias for SNR>10 is comparable to that found in ground-based optical surveys such as CFHTLenS, and it is anticipated that similar shear measurement calibration strategies for those red for optical surveys may be used to good effect in the analysis of SKA radio interferometer data.

Day 1065

Tuesday.


1603.03773
Microlensing by Kuiper, Oort, and Free-floating planets
Gould

Microlensing is generally thought to probe planetary systems only out to a few Einstein radii.  Microlensing events generated by bound planets beyond about 10 Einstein radii generally do not yield any trace of their hosts, and so would be classified as free floating planets (FFPs).  Show that it is already possible, using AO, to constrain the presence of potential hosts to FFP candidates at separations comparable to the Oort Cloud.  With next-generation telescopes, planets at Kuiper-Belt separations can be probed.  Next generation telescopes will also permit routine vetting for all FFP candidates, simply by obtaining second epochs 4-8 years after the event.  At present, the search for such hosts is restricted to within the "confusion limit" of theta_confus~250 mas, but future WFIRST observations will allow one to probe beyond this confusion limit as well.


1603.04152
Alignments of dark matter haloes with large-scale tidal fields: mass and redshift dependence
Chen, Wang, Mo, Shi

LS tidal field estimated directly from the distribution of DM haloes is used to investigate how halo shapes and spin vectors are aligned with the cosmic web.  The major, intermediate and minor axes of haloes are aligned with the corresponding tidal axes, and halo spin axes tend to be parallel with the intermediate axes and perpendicular to the major axes of tidal field.  The strengths of these alignments generally increase with halo mass and redshift, but the dependencies are only through the peak height nu.  The scaling relations of the alignment strengths with the value of nu indicate that the alignment strengths remain roughly constant when the structures within which the haloes reside are still in quasi-linear regime, but decreases as nonlinear evolution becomes more important.  Also calculate the alignments in projection so that the results can be compared directly with observations.  Finally, investigate the alignments of tidal tensors on large scales, and use the results to understand alignments of halo pairs separated at various distances.  The results suggest coherent structure of the tidal field is the underlying  reason for the alignments of haloes and galaxies seen in numerical simulations and in observations.


1603.04226
Generalized shear-ratio tests: a new relation between cosmological distances, and a diagnostic for a redshift-dependent multiplicative bias in shear measurements
Schneider

Derive a new relation between cosmological distances, valid in any (statistically) isotropic space-time and independent of cosmological parameters or even the validity of the field equation of GR.  In particular, this relation yields an equation between those distance ratios which are the geometrical factors determining the strength of the gravitational lensing effect of mass concentrations.  Considering a combination of WL shear ratios, based on lenses at two different redshifts, and sources at 3 different redshifts, derive a relation between shear-ratio tests which must be identically satisfied.  A redshift-dependent multiplicative bias in shear estimates will violate this relation, and thus can be probed by this generalized shear-ratio test. Combining the lensing effect for lenses at 3 different redshifts and 3 different source redshifts, a relation between shear ratios is derived which must be valid independent of a multiplicative bias.  Propose these generalized shear-ratio tests are a diagnostic for the presence of systematics in upcoming WL surveys.

Day 1064

Friday.  Monday.


1603.03494
The spatial distribution of ultra diffuse galaxies within large scale structures
Roman, Trujillo

SDSS Stripe82, 8x8 Mpc^2 around Abell 168 (z=0.045) -- check distribution of UDGs around it.  Find that UDGs are located within the large scale structures that comprise the A168 overdensity.  Approximately 42% of the UDGs analysed inhabit the cluster region, ~7±3% in the core and ~35±7% in the outskirts whereas the remaining UDGs are found outside the main overdensity: ~19±5% in groups and ~40% in filaments.  UDGs structural properties gradually change form the lowest to the densest regions with a decrease of their stellar mass by a factor of ~1.5, an increase of their Sersic index n by a factor of ~1.25 and a decrease in their tis ratio (b/a) by a factor of ~1.13.  This transformation supports the idea that UDGs probably form outside clusters and are later on accreted towards the cluster's central regions, where they are finally destroyed by disruption.  Finally, the spatial distribution of the UDGs is very similar to the one found for dwarf galaxies but significantly different for the distribution of galaxies like the MW, suggesting that UDGs could be bona fide dwarfs and not failed L* galaxies.


1603.03709
AKARI far-infrared maps of the zodiacal dust bands
Ootsubo, et al

Zodiacal emission is thermal emission from interplanetary dust.  Its contribution of the sky brightness is non-negligible in the region near the ecliptic plane, even in the far-IR wavelength regime.  Analyze zodiacal emission observed by the AKARI FIR all-sky survey, which covers 97% of the entire sky at arcminute-scale resolution in 4 photometric bands, with central wavelengths of 65, 90, 140, and 160 um.  AKARI detected small-scale structures in the zodiacal dust cloud, including the asteroidal dust bands and the circumsolar ring, at FIR wavelengths.  Although the smooth component of the zodiacal emission structure in the FIR sky can be reproduced well by models based on existing FIR observations, previous zodiacal emission models have discrepancies in the small-scale structures compared with observations.  Investigate the geometry of the small-scale dust-band structures in the AKARI FIR all-sky maps and construct template maps of the asteroidal dust bands and the circumsolar ring components based on the AKARI FIR maps.  In the maps, ±1.4deg, ±2.1 deg and ±10 deg asteroidal dust-band structures are detected in the 65um and 90um bands.  A possible ±17deg band may also have been detected.  No evident dust-band structures are identified in either the 140um or the 160um bands.  By subtracting the dust-band templates constructed in this paper, can achieve a similar level of flux calibration of the AKARI FIR all-sky maps in the |beta|<40 deg region to that in the region for |beta|>40 deg.