Day 580

Sunday.  Monday.
1401.3745
The VIMOS public extragalactic redshift survey (VIPERS).  Never mind the gaps: comparing techniques to restore homogeneous sky coverage
Cucciati, .. Iovino, … Peacock, … et al

In galaxy redshift surveys: non-uniform sampling, gaps in sky coverage common: these effects can degrade galaxy counts-in-cells and density estimates.  Carry out a comparison of methods that aim to fill the gaps to correct for the systematic effects.  VIPERS is a flux-limited (i<22.5) survey, on-pass observations with VIMOS, with gaps covering 25% of the surveyed area and a mean sampling rate of 35%.  Compare 1) two algorithms based on photo-z that assign z to galaxies based on the spectroscopic redshifts of the nearest neighbors, 2) two Bayesian methods, the Wiener filter and the Poisson-Lognormal filter.  Using galaxy mock catalogues, quantify the accuracy of the counts-in-cells measurements on scales of R=5 and 8 Mpc/h after applying each of these methods.  Also study how they perform to account for spectroscopic z error and inhomogeneous and sparse sampling rate.  Find that in VIPERS the error in counts-in-cells measurements on R<10 Mpc/h scales are dominated by the sparseness of the sample.  All methods under predict by 20-35% the counts at high densities.  This systematic bias is of the same order as random errors.  No method outperforms the others.  Random and systematic errors decrease for larger cells.  Show that it is possible to separate the lowest and highest densities on scales of 5 Mpc/h at 0.5<z<1.1, over a large volume such as in VIPERS; vital for the characterization of cosmic variance and rare populations (e.g., brightest galaxies) in environmental studies at these redshifts.

1401.3749
Stellar haloes outshine disc truncations in low-inclined spirals
Martín-Navarro, et al

The absence of stellar disc truncations in low-inclined spiral galaxies has been a matter of depute in the last decade.  Disc truncations are often observed in highly inclined galaxies but no obvious detection of this feature has so far been made in face-on spirals.  Show using a simple exp disc plus stellar halo model based on current observational constraints, that truncations in face-on projections occur at surface brightness levels comparable to the brightness of stellar haloes at the same radial distance.  In this sense, stellar haloes outshine the galaxy disc at the expected position of the truncations, forcing their studies only in highly inclined (edge-on) orientations.

1401.3919
Mapping the large scale structure around a z=1.46 galaxy cluster in 3-D using two adjacent narrow-band filters
Hayashi et al

Novel method to estimate accurate redshifts of SF galaxies by measuring the flux ratio of the same emission line observed through two adjacent narrow-band filters.  Apply this method to NB912 and data taken with Suprime-Cam on cluster XMMXCS J2215.9-1738, at z=1.46 and its surrounding structures.  Obtain redshifts for 170 [OII] emission line galaxies at z~1.46 among which 41 galaxies are spectroscopically confirmed, showing accuracy of sigma(delta z)/(1+z_spec)=0.002.  Reveals filamentary structures that penetrate towards the center of the galaxy cluster and intersect with other structures, consistent with the picture of hierarchical cluster formation.  Also find that the projected celestial distribution does not precisely trace the real distribution of galaxies, indicating the importance of the 3d view of structures to properly identify and quantify galaxy environments.  Investigate the environment dependence of galaxy properties with local density, confirming that the median color of galaxies becomes redder in higher density region while the SFR of SF galaxies does not depend strongly on local environment in this structure.  This implies that the SF activity in galaxies in truncated on a relatively short time scale in the cluster center.