1,641 research outputs found
Density mapping with weak lensing and phase information
The available probes of the large scale structure in the Universe have
distinct properties: galaxies are a high resolution but biased tracer of mass,
while weak lensing avoids such biases but, due to low signal-to-noise ratio,
has poor resolution. We investigate reconstructing the projected density field
using the complementarity of weak lensing and galaxy positions. We propose a
maximum-probability reconstruction of the 2D lensing convergence with a
likelihood term for shear data and a prior on the Fourier phases constructed
from the galaxy positions. By considering only the phases of the galaxy field,
we evade the unknown value of the bias and allow it to be calibrated by lensing
on a mode-by-mode basis. By applying this method to a realistic simulated
galaxy shear catalogue, we find that a weak prior on phases provides a good
quality reconstruction down to scales beyond l=1000, far into the noise domain
of the lensing signal alone.Comment: 11 pages, 9 figures, published in MNRA
AGAPE, an experiment to detect MACHO's in the direction of the Andromeda galaxy
The status of the Agape experiment to detect Machos in the direction of the
andromeda galaxy is presented.Comment: 4 pages, 1 figure in a separate compressed, tarred, uuencoded uufile.
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Микрохирургическая техника комбинированной трансплантации поджелудочной железы и почки в экспериментальной модели
ПОДЖЕЛУДОЧНАЯ ЖЕЛЕЗА /хирПОЧКИ /хирТРАНСПЛАНТАЦИЯаллографтхирургические техник
Микрохирургическая техника комбинированной трансплантации поджелудочной железы и почки в экспериментальной модели
ПОДЖЕЛУДОЧНАЯ ЖЕЛЕЗА /хирПОЧКИ /хирТРАНСПЛАНТАЦИЯаллографтхирургические техник
Difference Image Analysis of Galactic Microlensing I. Data Analysis
This is a preliminary report on the application of Difference Image Analysis
(DIA) to galactic bulge images. The aim of this analysis is to increase the
sensitivity to the detection of gravitational microlensing. We discuss how the
DIA technique simplifies the process of discovering microlensing events by
detecting only objects which have variable flux. We illustrate how the DIA
technique is not limited to detection of so called ``pixel lensing'' events,
but can also be used to improve photometry for classical microlensing events by
removing the effects of blending. We will present a method whereby DIA can be
used to reveal the true unblended colours, positions and light curves of
microlensing events. We discuss the need for a technique to obtain the accurate
microlensing time scales from blended sources, and present a possible solution
to this problem using the existing HST colour magnitude diagrams of the
galactic bulge and LMC. The use of such a solution with both classical and
pixel microlensing searches is discussed. We show that one of the major causes
of systematic noise in DIA is differential refraction. A technique for removing
this systematic by effectively registering images to a common airmass is
presented. Improvements to commonly used image differencing techniques are
discussed.Comment: 18 pages, 8 figures, uses AAS LaTEX 4.0, To appear in Astrophysical
Journa
Evidence for Ubiquitous, High-EW Nebular Emission in z~7 Galaxies: Towards a Clean Measurement of the Specific Star Formation Rate using a Sample of Bright, Magnified Galaxies
Growing observational evidence now indicates that nebular line emission has a
significant impact on the rest-frame optical fluxes of z~5-7 galaxies observed
with Spitzer. This line emission makes z~5-7 galaxies appear more massive, with
lower specific star formation rates. However, corrections for this line
emission have been very difficult to perform reliably due to huge uncertainties
on the overall strength of such emission at z>~5.5. Here, we present the most
direct observational evidence yet for ubiquitous high-EW [OIII]+Hbeta line
emission in Lyman-break galaxies at z~7, while also presenting a strategy for
an improved measurement of the sSFR at z~7. We accomplish this through the
selection of bright galaxies in the narrow redshift window z~6.6-7.0 where the
IRAC 4.5 micron flux provides a clean measurement of the stellar continuum
light. Observed 4.5 micron fluxes in this window contrast with the 3.6 micron
fluxes which are contaminated by the prominent [OIII]+Hbeta lines. To ensure a
high S/N for our IRAC flux measurements, we consider only the brightest
(H_{160}<26 mag) magnified galaxies we have identified in CLASH and other
programs targeting galaxy clusters. Remarkably, the mean rest-frame optical
color for our bright seven-source sample is very blue, [3.6]-[4.5]=-0.9+/-0.3.
Such blue colors cannot be explained by the stellar continuum light and require
that the rest-frame EW of [OIII]+Hbeta be greater than 637 Angstroms for the
average source. The bluest four sources from our seven-source sample require an
even more extreme EW of 1582 Angstroms. Our derived lower limit for the mean
[OIII]+Hbeta EW could underestimate the true EW by ~2x based on a simple
modeling of the redshift distribution of our sources. We can also set a robust
lower limit of >~4 Gyr^-1 on the specific star formation rates based on the
mean SED for our seven-source sample. (abridged)Comment: 9 pages, 6 figures, 1 table, submitted to the Astrophysical Journa
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