22,760 research outputs found
Wavelength Dependent PSFs and their impact on Weak Lensing Measurements
We measure and model the wavelength dependence of the PSF in the Hyper
Suprime-Cam (HSC) Subaru Strategic Program (SSP) survey. We find that PSF
chromaticity is present in that redder stars appear smaller than bluer stars in
the and -bands at the 1-2 per cent level and in the and
-bands at the 0.1-0.2 per cent level. From the color dependence of the PSF,
we fit a model between the monochromatic PSF trace radius, , and wavelength
of the form . We find values of between -0.2
and -0.5, depending on the epoch and filter. This is consistent with the
expectations of a turbulent atmosphere with an outer scale length of m, indicating that the atmosphere is dominating the chromaticity. We
find evidence in the best seeing data that the optical system and detector also
contribute some wavelength dependence. Meyers and Burchat (2015) showed that
must be measured to an accuracy of not to dominate the
systematic error budget of the Large Synoptic Survey Telescope (LSST) weak
lensing (WL) survey. Using simple image simulations, we find that can be
inferred with this accuracy in the and -bands for all positions in the
LSST field of view, assuming a stellar density of 1 star arcmin and that
the optical PSF can be accurately modeled. Therefore, it is possible to correct
for most, if not all, of the bias that the wavelength-dependent PSF will
introduce into an LSST-like WL survey.Comment: 14 pages, 10 figures. Submitted to MNRAS. Comments welcom
Weak Lensing Determination of the Mass in Galaxy Halos
We detect the weak gravitational lensing distortion of 450,000 background
galaxies (20<R<23) by 790 foreground galaxies (R<18) selected from the Las
Campanas Redshift Survey (LCRS). This is the first detection of weak lensing by
field galaxies of known redshift, and as such permits us to reconstruct the
shear profile of the typical field galaxy halo in absolute physical units
(modulo H_0), and to investigate the dependence of halo mass upon galaxy
luminosity. This is also the first galaxy-galaxy lensing study for which the
calibration errors are negligible. Within a projected radius of 200 \hkpc, the
shear profile is consistent with an isothermal profile with circular velocity
164+-20 km/s for an L* galaxy, consistent with typical disk rotation at this
luminosity. This halo mass normalization, combined with the halo profile
derived by Fischer et al (2000) from lensing analysis SDSS data, places a lower
limit of (2.7+-0.6) x 10^{12}h^{-1} solar masses on the mass of an L* galaxy
halo, in good agreement with satellite galaxy studies. Given the known
luminosity function of LCRS galaxies, and the assumption that for galaxies, we determine that the mass within 260\hkpc of normal
galaxies contributes to the density of the Universe (for
) or for . These lensing data suggest
that (95% CL), only marginally in agreement with the usual
Faber-Jackson or Tully-Fisher scaling. This is the most
complete direct inventory of the matter content of the Universe to date.Comment: 18 pages, incl. 3 figures. Submitted to ApJ 6/7/00, still no response
from the referee after four months
Comparative Patterns Of Growth And Development In Cricetine Rodents And The Evolution Of Ontogeny
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137498/1/evo05721.pd
Clustered bottlenecks in mRNA translation and protein synthesis
We construct an algorithm that generates large, band-diagonal transition
matrices for a totally asymmetric exclusion process (TASEP) with local hopping
rate inhomogeneities. The matrices are diagonalized numerically to find
steady-state currents of TASEPs with local variations in hopping rate. The
results are then used to investigate clustering of slow codons along mRNA.
Ribosome density profiles near neighboring clusters of slow codons interact,
enhancing suppression of ribosome throughput when such bottlenecks are closely
spaced. Increasing the slow codon cluster size, beyond , does not
significantly reduce ribosome current. Our results are verified by extensive
Monte-Carlo simulations and provide a biologically-motivated explanation for
the experimentally-observed clustering of low-usage codons
More than a cognitive experience: unfamiliarity, invalidation, and emotion in organizational learning
Literature on organizational learning (OL) lacks an integrative framework that captures the emotions involved as OL proceeds. Drawing on personal construct theory, we suggest that organizations learn where their members reconstrue meaning around questions of strategic significance for the organization. In this 5-year study of an electronics company, we explore the way in which emotions change as members perceive progress or a lack of progress around strategic themes. Our framework also takes into account whether OL involves experiences that are familiar or unfamiliar and the implications for emotions. We detected similar patterns of emotion arising over time for three different themes in our data, thereby adding to OL perspectives that are predominantly cognitive in orientation
Testing the Hubble Law with the IRAS 1.2 Jy Redshift Survey
We test and reject the claim of Segal et al. (1993) that the correlation of
redshifts and flux densities in a complete sample of IRAS galaxies favors a
quadratic redshift-distance relation over the linear Hubble law. This is done,
in effect, by treating the entire galaxy luminosity function as derived from
the 60 micron 1.2 Jy IRAS redshift survey of Fisher et al. (1995) as a distance
indicator; equivalently, we compare the flux density distribution of galaxies
as a function of redshift with predictions under different redshift-distance
cosmologies, under the assumption of a universal luminosity function. This
method does not assume a uniform distribution of galaxies in space. We find
that this test has rather weak discriminatory power, as argued by Petrosian
(1993), and the differences between models are not as stark as one might expect
a priori. Even so, we find that the Hubble law is indeed more strongly
supported by the analysis than is the quadratic redshift-distance relation. We
identify a bias in the the Segal et al. determination of the luminosity
function, which could lead one to mistakenly favor the quadratic
redshift-distance law. We also present several complementary analyses of the
density field of the sample; the galaxy density field is found to be close to
homogeneous on large scales if the Hubble law is assumed, while this is not the
case with the quadratic redshift-distance relation.Comment: 27 pages Latex (w/figures), ApJ, in press. Uses AAS macros,
postscript also available at
http://www.astro.princeton.edu/~library/preprints/pop682.ps.g
Participatory Militias: An Analysis of an Armed Movement's Online Audience
Armed groups of civilians known as "self-defense forces" have ousted the
powerful Knights Templar drug cartel from several towns in Michoacan. This
militia uprising has unfolded on social media, particularly in the "VXM"
("Valor por Michoacan," Spanish for "Courage for Michoacan") Facebook page,
gathering more than 170,000 fans. Previous work on the Drug War has documented
the use of social media for real-time reports of violent clashes. However, VXM
goes one step further by taking on a pro-militia propagandist role, engaging in
two-way communication with its audience. This paper presents a descriptive
analysis of VXM and its audience. We examined nine months of posts, from VXM's
inception until May 2014, totaling 6,000 posts by VXM administrators and more
than 108,000 comments from its audience. We describe the main conversation
themes, post frequency and relationships with offline events and public
figures. We also characterize the behavior of VXM's most active audience
members. Our work illustrates VXM's online mobilization strategies, and how its
audience takes part in defining the narrative of this armed conflict. We
conclude by discussing possible applications of our findings for the design of
future communication technologies.Comment: Participatory Militias: An Analysis of an Armed Movement's Online
Audience. Saiph Savage, Andres Monroy-Hernandez. CSCW: ACM Conference on
Computer-Supported Cooperative Work 201
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