1,397 research outputs found
Linear Redshift Distortions and Power in the PSCz Survey
We present a state-of-the-art linear redshift distortion analysis of the
recently published IRAS Point Source Catalog Redshift Survey (PSCz). The
procedure involves linear compression into 4096 Karhunen-Loeve modes culled
from a potential pool of about 3 x 10^5 modes, followed by quadratic
compression into three separate power spectra, the galaxy-galaxy,
galaxy-velocity, and velocity-velocity power spectra. Least squares fitting to
the decorrelated power spectra yields a linear redshift distortion parameter
beta = Omega_m^0.6/b = 0.41(+0.13,-0.12).Comment: Minor changes to agree with accepted version. Slight changes to power
spectrum, including one more point added at large scales, from binning points
formerly discarded as too noisy. 5 pages, including 4 embedded PostScript
figures. Accepted for publication in MNRAS Letters (pink pages). Power
spectrum data available at http://casa.colorado.edu/~ajsh/pscz
Watch and Learn: Semi-Supervised Learning of Object Detectors from Videos
We present a semi-supervised approach that localizes multiple unknown object
instances in long videos. We start with a handful of labeled boxes and
iteratively learn and label hundreds of thousands of object instances. We
propose criteria for reliable object detection and tracking for constraining
the semi-supervised learning process and minimizing semantic drift. Our
approach does not assume exhaustive labeling of each object instance in any
single frame, or any explicit annotation of negative data. Working in such a
generic setting allow us to tackle multiple object instances in video, many of
which are static. In contrast, existing approaches either do not consider
multiple object instances per video, or rely heavily on the motion of the
objects present. The experiments demonstrate the effectiveness of our approach
by evaluating the automatically labeled data on a variety of metrics like
quality, coverage (recall), diversity, and relevance to training an object
detector.Comment: To appear in CVPR 201
The power spectrum of galaxies in the 2dF 100k redshift survey
We compute the real-space power spectrum and the redshift-space distortions
of galaxies in the 2dF 100k galaxy redshift survey using pseudo-Karhunen-Loeve
eigenmodes and the stochastic bias formalism. Our results agree well with those
published by the 2dFGRS team, and have the added advantage of producing
easy-to-interpret uncorrelated minimum-variance measurements of the
galaxy-galaxy, galaxy-velocity and velocity-velocity power spectra in 27
k-bands, with narrow and well-behaved window functions in the range 0.01h/Mpc <
k < 0.8h/Mpc. We find no significant detection of baryonic wiggles, although
our results are consistent with a standard flat Omega_Lambda=0.7
``concordance'' model and previous tantalizing hints of baryonic oscillations.
We measure the galaxy-matter correlation coefficient r > 0.4 and the
redshift-distortion parameter beta=0.49+/-0.16 for r=1 (beta=0.47+/- 0.16
without finger-of-god compression). Since this is an apparent-magnitude limited
sample, luminosity-dependent bias may cause a slight red-tilt in the power
spectum. A battery of systematic error tests indicate that the survey is not
only impressive in size, but also unusually clean, free of systematic errors at
the level to which our tests are sensitive. Our measurements and window
functions are available at http://www.hep.upenn.edu/~max/2df.html together with
the survey mask, radial selection function and uniform subsample of the survey
that we have constructed.Comment: Replaced to match accepted MNRAS version, with new radial/angular
systematics plot and sigma8 typo corrected. High-res figures, power spectra,
windows and our uniform galaxy subsample with mask at
http://www.hep.upenn.edu/~max/2df.html or from [email protected]. 26
journal pages, 28 fig
Exploiting the full potential of photometric quasar surveys: Optimal power spectra through blind mitigation of systematics
We present optimal measurements of the angular power spectrum of the XDQSOz
catalogue of photometric quasars from the Sloan Digital Sky Survey. These
measurements rely on a quadratic maximum likelihood estimator that
simultaneously measures the auto- and cross-power spectra of four redshift
samples, and provides minimum-variance, unbiased estimates even at the largest
angular scales. Since photometric quasars are known to be strongly affected by
systematics such as spatially-varying depth and stellar contamination, we
introduce a new framework of extended mode projection to robustly mitigate the
impact of systematics on the power spectrum measurements. This technique
involves constructing template maps of potential systematics, decorrelating
them on the sky, and projecting out modes which are significantly correlated
with the data. Our method is able to simultaneously process several thousands
of nonlinearly-correlated systematics, and mode projection is performed in a
blind fashion. Using our final power spectrum measurements, we find a good
agreement with theoretical predictions, and no evidence for further
contamination by systematics. Extended mode projection not only obviates the
need for aggressive sky and quality cuts, but also provides control over the
level of systematics in the measurements, enabling the search for small signals
of new physics while avoiding confirmation bias.Comment: 13 pages, 8 figures. v2: version accepted by MNRAS. v3: systematics
templates publicly available on www.earlyuniverse.org/code, no change to
pape
Running bumps from stealth bosons
For the "stealth bosons" , light boosted particles with a decay into four quarks and reconstructed as a single fat jet,
the groomed jet mass has a strong correlation with groomed jet substructure
variables. Consequently, the jet mass distribution is strongly affected by the
jet substructure selection cuts when applied on the groomed jet. We illustrate
this fact by recasting a CMS search for low-mass dijet resonances and show a
few representative examples. The mass distributions exhibit narrow and wide
bumps at several locations in the 100 - 300 GeV range, between the masses of
the daughter particles and the parent particle , depending on the jet
substructure selection. This striking observation introduces several caveats
when interpreting and comparing experimental results, for the case of
non-standard signatures. The possibility that a single boosted particle
decaying hadronically produces multiple bumps, at quite different jet masses,
and depending on the event selection, brings the game of anomaly chasing to the
next level.Comment: LaTeX 21 pages. Added one appendix and some plots. Journal versio
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