140,779 research outputs found
Dark Energy Survey Year 1 Results: Cross-Correlation Redshifts in the DES -- Calibration of the Weak Lensing Source Redshift Distributions
We present the calibration of the Dark Energy Survey Year 1 (DES Y1) weak lensing source galaxy redshift distributions from clustering measurements. By cross-correlating the positions of source galaxies with luminous red galaxies selected by the redMaGiC algorithm we measure the redshift distributions of the source galaxies as placed into different tomographic bins. These measurements constrain any such shifts to an accuracy of ∼0.02 and can be computed even when the clustering measurements do not span the full redshift range. The highest-redshift source bin is not constrained by the clustering measurements because of the minimal redshift overlap with the redMaGiC galaxies. We compare our constraints with those obtained from COSMOS 30-band photometry and find that our two very different methods produce consistent constraints
Exhaustive and Efficient Constraint Propagation: A Semi-Supervised Learning Perspective and Its Applications
This paper presents a novel pairwise constraint propagation approach by
decomposing the challenging constraint propagation problem into a set of
independent semi-supervised learning subproblems which can be solved in
quadratic time using label propagation based on k-nearest neighbor graphs.
Considering that this time cost is proportional to the number of all possible
pairwise constraints, our approach actually provides an efficient solution for
exhaustively propagating pairwise constraints throughout the entire dataset.
The resulting exhaustive set of propagated pairwise constraints are further
used to adjust the similarity matrix for constrained spectral clustering. Other
than the traditional constraint propagation on single-source data, our approach
is also extended to more challenging constraint propagation on multi-source
data where each pairwise constraint is defined over a pair of data points from
different sources. This multi-source constraint propagation has an important
application to cross-modal multimedia retrieval. Extensive results have shown
the superior performance of our approach.Comment: The short version of this paper appears as oral paper in ECCV 201
Halo Occupation Distribution Modeling of Green Valley Galaxies
We present a clustering analysis of near ultraviolet (NUV) - optical color
selected luminosity bin samples of green valley galaxies. These galaxy samples
are constructed by matching the Sloan Digital Sky Survey Data Release 7 with
the latest Galaxy Evolution Explorer source catalog which provides NUV
photometry. We present cross-correlation function measurements and determine
the halo occupation distribution of these transitional galaxies using a new
multiple tracer analysis technique.
We extend the halo-occupation formalism to model the cross-correlation
function between a galaxy sample of interest and multiple tracer populations
simultaneously. This method can be applied to commonly used luminosity
threshold samples as well as to color and luminosity bin selected galaxy
samples, and improves the accuracy of clustering analyses for sparse galaxy
populations.
We confirm the previously observed trend that red galaxies reside in more
massive halos and are more likely to be satellite galaxies than average
galaxies of similar luminosity. While the change in central galaxy host mass as
a function of color is only weakly constrained, the satellite fraction and
characteristic halo masses of green satellite galaxies are found to be
intermediate between those of blue and red satellite galaxies.Comment: matches MNRAS accepted version; minor revisions, results unchange
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