1706.00427
Source selection for cluster weak lensing measurements in the Hyper Suprime-Cam survey
Medezinski, et al
Present optimal source galaxy selection schemes for measuring unbiased cluster WL mass profiles from HSC-SSP. The ongoing HSC-SSP survey will uncover thousands of galaxy clusters to z<~1.5. In deriving cluster masses via WL, a critical source of systematics is contamination and dilution of the lensing signal by cluster and FG galaxies. Using the first-year CAMIRA catalog of ~900 clusters with richness larger than 20 found in ~140 deg^2 of HSC-SSP data, devise and compare several source selection methods, including selection in color-color space (CC-cut), and selection of robust photometric redshifts by applying constraints on their cumulative probability distribution function (PDF; P-cut). Examine the dependence of the contamination on the chosen limits adopted for each method. Using the proper limits, these methods give dilution-free mass profiles in agreement with one another. Find that not adopting either the CC-cut or P-cut methods results in a underestimation of the total cluster mass (13±4%) and the concentration of the profile (24±11%). The robust methods yield a ~60sigma detection of the stacked CAMIRA surface mass density profile, with a mean mass of M_200c=1.67±0.05 e14 Msun/h.
1706.00434
Planck Sunyaev-Zel'dovich cluster mass calibration using Hyper Suprime-Cam weak lensing
Medezinski, et al
Using ~140 deg&2 HSC survey data, stack the WL signal around 5 Planck clusters found within the footprint. This yields a 15 sigma detection of the mean Planck cluster mass density profile. The 5 Planck clusters span a relatively wide mass range, M_WL,500c=2-25e14 Msun with a mean mass of M_WL,500c=4.1±0.5e14 Msun. The mean ratio of the SZ mass to the WL mass is M_SZ/M_WL=1-b=0.8±0.1. This mass bias is consistent with previous WL mass calibrations of Planck clusters within the errors. Discuss the implications of the findings for the calibration of SZ cluster counts and the much discussed tension between Planck SZ cluster counts and Planck LCDM cosmology.
1706.00566
Deep optical imaging of the COSMOS field with Hyper Suprime-Cam using data from the Subaru Strategic Program and the University of Hawaii
Tanaka, et al
Present the deepest optical images of the COSMOS field based on a joint dataset taken with HSC by the HSC-SSP team and UH. The COSMOS field is one of the key extragalactic fields with a wealth of deep, multi-wavelength data. However, the current optical data are not sufficiently deep to match with, e.g., the UltraVista data in the NIR. The SSP team and UH have jointed forces to produce very deep optical images of the COSMOS field by combining data from both teams. The coadd images reach depths of g=27.8, r-27.7, i-27.6, z-26.8, and y-26.2 mag at 5 sigma for point sources based on flux uncertainties quoted by the pipeline and they cover essentially the entire COSMOS 2 sq deg field. The seeing is between 0.6 and 0.9 arcsec on the coadds. Perform several quality checks and confirm tat the data are of science quality; ~2% photometry and 30 has astrometry. This accuracy is identical to the Public DR1 from HSC-SSP. Make the joint dataset including fully calibrated catalogs of detected objects available to the community at https://hsc-release.mtk.nao.ac.jp/.
1706.01542
Forward globara photometric calibration of the Dark Energy Survey
Burke, Rykoff, ... Bernstein, ... et al
Many scientific goals for the DES require calibration of optical/NIR broadband b=grizY photometry that is stable in time and uniform over the celestial sky to one percent or better. It is also necessary to limit to similar accuracy systematic uncertainty in the calibrated broadband magnitudes due to uncertainty in the spectrum of the source. Here present a "Forward Global Calibration Method (FGCM)" for photometric calibration of the DES, and present results of its application to the first 3 years of the survey (Y3A1). The FGCM combines data taken with auxiliary instrumentation at the observatory with data from the broad-band survey imaging itself and models of the instrument and atmosphere to estimate the spatial- and time-dependence of the passbands of individual DES survey exposures. "Standard" passbands are chosen that are typical of the passbands encountered during the survey. The passband of any individual observation is combined with an estimate of the source spectral space to yield a magnitude M_b^std in the standard system. This "chromatic correction" to the standard system is necessary to achieve sub-percent calibrations. The FGCM achieves reproducible and stable photometric calibration of standard magnitudes M_b^std of stellar sources over the multi-year Y3A1 data sample with residual random calibration errors of sigma=5-6 mmag per exposure. The accuracy of the calibration is uniform across the 5000 deg^2 DES footprint to within sigma=7 mmag. The systematic uncertainties of magnitudes in the standard system due to the spectra of sources are less than 5 mmag for main sequence stars with 0.5<g-i<3.0.
1706.01916
Understanding 'galaxy groups' as a unique structure in the universe
Paul, John, Gupta, Kumar
'Galaxy groups' have hardly been realized as a separate class of objects with specific characteristics in the structural hierarchy The presumption that the self-similarity of DM structures is a valid prescription for the baryonic universe at all scales has rendered smaller structures undetectable by current observational facilities, leading to lesser dedicated studies on them. Some recent reports that indicate a deviation from Lx-T scaling in groups compared to clusters have motivated the study of their physical properties in depth. In this article, report the extensive study on physical properties of groups in comparison to the clusters through cosmological hydrodynamic plus N-body sims using ENZO 2.2 code. As additional physics, radiative cooling, heating due to SNe and star motions, SF and stellar feedback has been implemented. Produce a mock sample of 362 objects with mass ranging from 5e12 Msun to 2.5e15 Msun. Strikingly, found that objects with mass below ~8e13 Msun do not follow any of the cluster self-similar laws in hydrostatistics, not even in thermal and non-thermal energies. Two distinct scaling laws are observed to be followed with breaks at ~8e13 Msun for mass, ~1 keV for temperature and ~1 Mpc for radius. This places groups as a distinct entity in the hierarchical structures, well demarcated from clusters. This study reveals that groups are mostly far away from virtualization, suggesting the need for formulating new models for deciphering their physical parameters. They are also shown to have high turbulence and more non-thermal energy stored, indicating better visibility in the non-thermal regimes.
1706.02018
On the age of the TRAPPIST-1 system
Burgasser, Mamajek
Given the TRAPPIST-1 system importance for testing planet formation and evolution theories, and for assessing the prospects for habitability among Earth-size exoplanets orbiting the most common type of star in the Galaxy, present a comprehensive assessment of the age of this system. Collate empirical age constraints based on the color-absolute magnitude diagram, average density, Li absorption, surface gravity features, metallicity, kinematics, rotation, and magnetic activity; and conclude that TRAPPIST-1 is a transitional thin/thick disk star with an age of 7.6±2.2 Ghr. The star's color-magnitude position is consistent with it being slightly metal-rich ([Fe/H]~ +0.06), in line with its previously reported NIR spectroscopic metallicity; and it has a radius (R=0.121±0.003 Rsun) that is larger by 8-14% compared to solar-metallicity evolutionary models. Discuss some implications of the old age of this system with regard to the stability and habitability of its planets.
1706.02362
Extending the modeling of the anisotropic galaxy power spectrum to k=0.4 h/Mpc
Hand, Seljak, Beutler, Vlah
Present a new model for the z-space power spectrum of galaxies and demonstrate its accuracy in modeling the monopole, quadrupole, and hexadecapole of the galaxy density field down to scales of k=0.4 h/Mpc. The model describes the clustering of galaxies in the context of a halo model and the clustering of the underlying haloes in redshift space using a combination of Eulerian perturbation theory and N-body sims. The modeling of z-space distortions is done using the so-called distribution function approach. The final model has 13 free parameters, and each parameter is physically motivated rather than a nuisance parameter, which allows the use of well-motivated priors. Account for the FoG effect from centrals and both isolated and non-isolated satellites rather than using a single velocity dispersion to describe the combined effect. Test and validate the accuracy of the model on several sets of high-fidelity N-body sims, as well as realistic mock catalogs designed to simulate the BOSS DR12 CMASS data set. The suite of sims covers a range of cosmologies and galaxy bias models, providing a rigorous test of the level of theoretical systematics present in the model. The level of bias in the recovered values of f-sigma_8 is found to be small. When including scales to k=0.4 h/Mpc, find 15-30% gains in the statistical precision of f-sigma_8 relative to k=0.2 h/Mpc and a roughly 10-15% improvement for the perpendicular Alcock-Paczynski parameter alpha_perp. Using the BOSS DR12 CMASS mocks as a benchmark for comparison, estimate an uncertainty on f-sigma_8 that is ~10-20% larger than other similar Fourier-space RSD models in the literature that use k<0.2h/Mpc, suggesting that these models likely have a too-limited paramterization.
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