113 research outputs found
Cosmological constraints from the convergence 1-point probability distribution
We examine the cosmological information available from the 1-point
probability distribution (PDF) of the weak-lensing convergence field, utilizing
fast L-PICOLA simulations and a Fisher analysis. We find competitive
constraints in the - plane from the convergence PDF with
pixels compared to the cosmic shear power spectrum with an
equivalent number of modes (). The convergence PDF also partially
breaks the degeneracy cosmic shear exhibits in that parameter space. A joint
analysis of the convergence PDF and shear 2-point function also reduces the
impact of shape measurement systematics, to which the PDF is less susceptible,
and improves the total figure of merit by a factor of , depending on the
level of systematics. Finally, we present a correction factor necessary for
calculating the unbiased Fisher information from finite differences using a
limited number of cosmological simulations.Comment: 10 pages, 5 figure
The Astropy Problem
The Astropy Project (http://astropy.org) is, in its own words, "a community
effort to develop a single core package for Astronomy in Python and foster
interoperability between Python astronomy packages." For five years this
project has been managed, written, and operated as a grassroots,
self-organized, almost entirely volunteer effort while the software is used by
the majority of the astronomical community. Despite this, the project has
always been and remains to this day effectively unfunded. Further, contributors
receive little or no formal recognition for creating and supporting what is now
critical software. This paper explores the problem in detail, outlines possible
solutions to correct this, and presents a few suggestions on how to address the
sustainability of general purpose astronomical software
Dust Reverberation Mapping in Distant Quasars from Optical and Mid-Infrared Imaging Surveys
The size of the dust torus in Active Galactic Nuclei (AGN) and their
high-luminosity counterparts, quasars, can be inferred from the time delay
between UV/optical accretion disk continuum variability and the response in the
mid-infrared (MIR) torus emission. This dust reverberation mapping (RM)
technique has been successfully applied to AGN and
quasars. Here we present first results of our dust RM program for distant
quasars covered in the SDSS Stripe 82 region combining -yr
ground-based optical light curves with 10-yr MIR light curves from the WISE
satellite. We measure a high-fidelity lag between W1-band (3.4 m) and
band for 587 quasars over (\left\sim 0.8)
and two orders of magnitude in quasar luminosity. They tightly follow
(intrinsic scatter dex in lag) the IR lag-luminosity relation
observed for AGN, revealing a remarkable size-luminosity relation for
the dust torus over more than four decades in AGN luminosity, with little
dependence on additional quasar properties such as Eddington ratio and
variability amplitude. This study motivates further investigations in the
utility of dust RM for cosmology, and strongly endorses a compelling science
case for the combined 10-yr Vera C. Rubin Observatory Legacy Survey of Space
and Time (optical) and 5-yr Nancy Grace Roman Space Telescope 2m light
curves in a deep survey for low-redshift AGN dust RM with much lower
luminosities and shorter, measurable IR lags. The compiled optical and MIR
light curves for 7,384 quasars in our parent sample are made public with this
work.Comment: Accepted for publication in Ap
A catalogue of structural and morphological measurements for DES Y1
We present a structural and morphological catalogue for 45 million objects selected from the first year data of the Dark Energy Survey (DES). Single Sersic fits and non-parametric ´ measurements are produced for g, r, and i filters. The parameters from the best-fitting Sersic ´ model (total magnitude, half-light radius, Sersic index, axis ratio, and position angle) are mea- ´ sured with GALFIT; the non-parametric coefficients (concentration, asymmetry, clumpiness, Gini, M20) are provided using the Zurich Estimator of Structural Types (ZEST+). To study the statistical uncertainties, we consider a sample of state-of-the-art image simulations with a realistic distribution in the input parameter space and then process and analyse them as we do with real data: this enables us to quantify the observational biases due to PSF blurring and magnitude effects and correct the measurements as a function of magnitude, galaxy size, Sersic ´ index (concentration for the analysis of the non-parametric measurements) and ellipticity. We present the largest structural catalogue to date: we find that accurate and complete measurements for all the structural parameters are typically obtained for galaxies with SEXTRACTOR MAG AUTO I ≤ 21. Indeed, the parameters in the filters i and r can be overall well recovered up to MAG AUTO ≤ 21.5, corresponding to a fitting completeness of ∼90 per cent below this threshold, for a total of 25 million galaxies. The combination of parametric and non-parametric structural measurements makes this catalogue an important instrument to explore and understand how galaxies form and evolve. The catalogue described in this paper will be publicly released alongside the DES collaboration Y1 cosmology data products at the following URL: https://des.ncsa.illinois.edu/releases
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