1710.03235
Weak lensing for precision cosmology
Mandelbaum
WL, the deflection of light by mass, is one of the best tools to constrain the growth of cosmic structure with time and reveal the nature of DE. Discuss the sources of systematic uncertainty in WL measurements and their theoretical interpretation, including the current understanding and other options for future improvement. These include long-standing concerns such as the estimation of coherent shears from galaxy images or redshift distributions of galaxies selected based on photometric z, along with systematic uncertainties that have received less attention to date because they are subdominant contributors to the error budget in current surveys. Also discuss methods for automated systematics detection using survey data of the 2020s. The goal of this review is to describe the current state of the field and what must be done so that if WL measurements lead toward surprising conclusions about key questions such as the nature of DE, those conclusion will be credible.
1710.03251
Halo mass and weak galaxy-galaxy lensing profiles in rescaled cosmological $N$-body simulations
Reneby, Hilbert, Angulo
Investigate 3D density and WL profiles of DM haloes predicted by a cosmology-rescaling algorithm for $N$-body simulations. Extend the rescaling method of Angulo+White (2010) and Angulo+Hilbert (2015) to improve its performance on intra-halo scales by using models for the concentration-mass-z relation based on excursion set theory. The method's accuracy is tested with numerical simulations carried out with different cosmological parameters. Find that predictions for median density profiles are more accurate than ~5%, for haloes with masses of 1e12.0 - 1e14.5 Msun/h for radii 0.05 < r/r_200 < 0.5, and for cosmologies with Omega_m in [0.15, 0.40] and sigma8 in [0.6, 1.0]. For larger radii, 0.5 < r/r200 < 5, the accuracy degrades to ~20% due to inaccurate modeling of the cosmological and z dependence of the splash back radius. For changes in cosmology allowed by current data, the residuals decrease to ~<2%, up to scales twice the viral radius. Illustrate the usefulness of the method by estimating the mean halo mass of a mock galaxy group sample. Find that the algorithm's accuracy is sufficient for current data. Improvements in the algorithm, particularly in the modeling of baryons, are likely required for interpreting future (DE task force stage IV) experiments.
1710.03747
Measuring the small-scale matter power spectrum with high-resolution CMB lensing
Nguyen, Sehgal, Madhavacheril
Present a method to measure the small-scale matter power spectrum using high-resolution measurements of the gravitational lensing of the CMB. To determine whether small-scale structure today is suppressed on scales below 10 kpc (corresponding to M<1e9 Msun), one needs to probe CMB-lensing modes out to ell~35,000, requiring a CMB experiment with about 20 arc second resolution or better. Show that a CMB survey covering 4,000 sq degs of sky, with an instrumental sensitivity of 0.5 uK-arcmin at 18 arc second resolution, could distinguish between cold DM and an alternative, such as 1keV warm DM or 1e-22 eV fuzzy DM with a bout 4-sigma significance. A survey of the same resolution with 0.1 uK-arcmin noise could distinguish between CDM and these alternatives at better than 20-sigma significance; such high-significance measurements may also allow one to distinguish between a suppression of power due to either baryonic effects or the particle nature of DM, since each impacts the shape of the lensing PS differently. CMB temperature maps yield higher S/N than polarization maps in this small-scale regime; thus, systematic effects, such as from extragalactic astrophysical foregrounds, need to be carefully considered. However, these systematic concerns can likely be mitigated with known techniques. Next-generation CMB lensing may thus provide a robust and powerful method of measuring the small-scale matter power spectrum.
1710.04301
The LAMOST Complete spectroscopic survey of pointing area (LaCoSSPAr) in the southern galactic cap I. The spectroscopic redshift catalog
Yang, et al
In the southern galactic cap (SGC), limiting magnitude of r=18.1 mag, in two 20 deg^2 fields. Focusing on completeness and the deficiencies of source selection methods and at the basic performance parameters of LAMOST telescope. In both fields, >95% of galaxies observed. Majority of remaining sky background residuals removed from the 1D spectrum. >10k spectra visually inspected, using combinations of emission/absorption features with sigma_z/(1+z) < 0.001. 1528 redshifts in field A and 1570 z in field B measured. Results show that it is possible to derive z from low SNR galaxies with the post-processing and visual inspection. The analysis also indicates that up to 1/4 of the input targets for a typical extra-galactic spectroscopic survey might be unreliable. The multi-wavelength data analysis shows that the majority of mid IR detected absorption (91.3%) and emission ling galaxies (93.3%) can be well separated by an empirical criterion of W2-W3=2.4. Meanwhile, a fainter sequence paralleled to the main population of galaxies has been witnessed both in Mr/W2-W3 and M*/W2-W3 diagrams, which could be the population of luminous dwarf galaxies but contaminated by the edge-on/highly inclined galaxies (~30%).
1710.04896
Improving catalog matching by supplementing astrometry with additional photometric information
Wilson, Naylor
Apply to IPHAS-Gaia matches (different dynamical ranges), and IPHAS and 2MASS (approximately equal astrometric precision). Important to include magnitude information in both cases. Discuss extending the method to multiple catalogue matches through an interactive matching process. The method allows for the selection of high-quality matches by providing an overall probability for each pairing, giving the flexibility to choose stars know to be good matches.
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