200 research outputs found
OzDES Reverberation Mapping Program: H lags from the 6-year survey
Reverberation mapping measurements have been used to constrain the
relationship between the size of the broad-line region and luminosity of active
galactic nuclei (AGN). This relation is used to estimate single-epoch
virial black hole masses, and has been proposed for use to standardise AGN to
determine cosmological distances. We present reverberation measurements made
with H from the six-year Australian Dark Energy Survey (OzDES)
Reverberation Mapping Program. We successfully recover reverberation lags for
eight AGN at , probing higher redshifts than the bulk of H
measurements made to date. Our fit to the relation has a slope of
and an intrinsic scatter of dex. The
results from our multi-object spectroscopic survey are consistent with previous
measurements made by dedicated source-by-source campaigns, and with the
observed dependence on accretion rate. Future surveys, including LSST, TiDES
and SDSS-V, which will be revisiting some of our observed fields, will be able
to build on the results of our first-generation multi-object reverberation
mapping survey.Comment: Submitted to MNRA
Beyond the 3rd moment: A practical study of using lensing convergence CDFs for cosmology with DES Y3
Widefield surveys of the sky probe many clustered scalar fields -- such as
galaxy counts, lensing potential, gas pressure, etc. -- that are sensitive to
different cosmological and astrophysical processes. Our ability to constrain
such processes from these fields depends crucially on the statistics chosen to
summarize the field. In this work, we explore the cumulative distribution
function (CDF) at multiple scales as a summary of the galaxy lensing
convergence field. Using a suite of N-body lightcone simulations, we show the
CDFs' constraining power is modestly better than that of the 2nd and 3rd
moments of the field, as they approximately capture the information from all
moments of the field in a concise data vector. We then study the practical
aspects of applying the CDFs to observational data, using the first three years
of the Dark Energy Survey (DES Y3) data as an example, and compute the impact
of different systematics on the CDFs. The contributions from the point spread
function are 2-3 orders of magnitude below the cosmological signal, while those
from reduced shear approximation contribute to the signal.
Source clustering effects and baryon imprints contribute . Enforcing
scale cuts to limit systematics-driven biases in parameter constraints degrades
these constraints a noticeable amount, and this degradation is similar for the
CDFs and the moments. We also detect correlations between the observed
convergence field and the shape noise field at . We find that the
non-Gaussian correlations in the noise field must be modeled accurately to use
the CDFs, or other statistics sensitive to all moments, as a rigorous cosmology
tool.Comment: 21 pages, 12 figure
A measurement of the mean central optical depth of galaxy clusters via the pairwise kinematic Sunyaev-Zel'dovich effect with SPT-3G and DES
We infer the mean optical depth of a sample of optically-selected galaxy
clusters from the Dark Energy Survey (DES) via the pairwise kinematic
Sunyaev-Zel'dovich (kSZ) effect. The pairwise kSZ signal between pairs of
clusters drawn from the DES Year-3 cluster catalog is detected at
in cosmic microwave background (CMB) temperature maps from two years of
observations with the SPT-3G camera on the South Pole Telescope. After cuts,
there are 24,580 clusters in the deg of the southern sky
observed by both experiments. We infer the mean optical depth of the cluster
sample with two techniques. The optical depth inferred from the pairwise kSZ
signal is , while that inferred
from the thermal SZ signal is . The two measures agree at . We
perform a suite of systematic checks to test the robustness of the analysis
Mapping Variations of Redshift Distributions with Probability Integral Transforms
We present a method for mapping variations between probability distribution
functions and apply this method within the context of measuring galaxy redshift
distributions from imaging survey data. This method, which we name PITPZ for
the probability integral transformations it relies on, uses a difference in
curves between distribution functions in an ensemble as a transformation to
apply to another distribution function, thus transferring the variation in the
ensemble to the latter distribution function. This procedure is broadly
applicable to the problem of uncertainty propagation. In the context of
redshift distributions, for example, the uncertainty contribution due to
certain effects can be studied effectively only in simulations, thus
necessitating a transfer of variation measured in simulations to the redshift
distributions measured from data. We illustrate the use of PITPZ by using the
method to propagate photometric calibration uncertainty to redshift
distributions of the Dark Energy Survey Year 3 weak lensing source galaxies.
For this test case, we find that PITPZ yields a lensing amplitude uncertainty
estimate due to photometric calibration error within 1 per cent of the truth,
compared to as much as a 30 per cent underestimate when using traditional
methods
Dark Energy Survey Year 3 Results: Redshift Calibration of the MagLim Lens Sample from the combination of SOMPZ and clustering and its impact on Cosmology
We present an alternative calibration of the MagLim lens sample redshift
distributions from the Dark Energy Survey (DES) first three years of data (Y3).
The new calibration is based on a combination of a Self-Organising Maps based
scheme and clustering redshifts to estimate redshift distributions and inherent
uncertainties, which is expected to be more accurate than the original DES Y3
redshift calibration of the lens sample. We describe in detail the methodology,
we validate it on simulations and discuss the main effects dominating our error
budget. The new calibration is in fair agreement with the fiducial DES Y3
redshift distributions calibration, with only mild differences () in
the means and widths of the distributions. We study the impact of this new
calibration on cosmological constraints, analysing DES Y3 galaxy clustering and
galaxy-galaxy lensing measurements, assuming a CDM cosmology. We
obtain , and , which implies a shift in the
plane compared to the fiducial DES Y3 results, highlighting the importance of
the redshift calibration of the lens sample in multi-probe cosmological
analyses
Dark Energy Survey Year 3 results: Magnification modeling and impact on cosmological constraints from galaxy clustering and galaxy-galaxy lensing
We study the effect of magnification in the Dark Energy Survey Year 3
analysis of galaxy clustering and galaxy-galaxy lensing, using two different
lens samples: a sample of Luminous red galaxies, redMaGiC, and a sample with a
redshift-dependent magnitude limit, MagLim. We account for the effect of
magnification on both the flux and size selection of galaxies, accounting for
systematic effects using the Balrog image simulations. We estimate the impact
of magnification on the galaxy clustering and galaxy-galaxy lensing cosmology
analysis, finding it to be a significant systematic for the MagLim sample. We
show cosmological constraints from the galaxy clustering auto-correlation and
galaxy-galaxy lensing signal with different magnifications priors, finding
broad consistency in cosmological parameters in CDM and CDM.
However, when magnification bias amplitude is allowed to be free, we find the
two-point correlations functions prefer a different amplitude to the fiducial
input derived from the image simulations. We validate the magnification
analysis by comparing the cross-clustering between lens bins with the
prediction from the baseline analysis, which uses only the auto-correlation of
the lens bins, indicating systematics other than magnification may be the cause
of the discrepancy. We show adding the cross-clustering between lens redshift
bins to the fit significantly improves the constraints on lens magnification
parameters and allows uninformative priors to be used on magnification
coefficients, without any loss of constraining power or prior volume concerns.Comment: 21 pages, 13 figures, See this
https://www.darkenergysurvey.org/des-year-3-cosmology-results-papers/ URL for
the full DES Y3 cosmology releas
Non-local contribution from small scales in galaxy-galaxy lensing: Comparison of mitigation schemes
Recent cosmological analyses with large-scale structure and weak lensing
measurements, usually referred to as 32pt, had to discard a lot of
signal-to-noise from small scales due to our inability to precisely model
non-linearities and baryonic effects. Galaxy-galaxy lensing, or the
position-shear correlation between lens and source galaxies, is one of the
three two-point correlation functions that are included in such analyses,
usually estimated with the mean tangential shear. However, tangential shear
measurements at a given angular scale or physical scale carry
information from all scales below that, forcing the scale cuts applied in real
data to be significantly larger than the scale at which theoretical
uncertainties become problematic. Recently there have been a few independent
efforts that aim to mitigate the non-locality of the galaxy-galaxy lensing
signal. Here we perform a comparison of the different methods, including the Y
transformation described in Park et al. (2021), the point-mass marginalization
methodology presented in MacCrann et al. (2020) and the Annular Differential
Surface Density statistic described in Baldauf et al. (2010). We do the
comparison at the cosmological constraints level in a noiseless simulated
combined galaxy clustering and galaxy-galaxy lensing analysis. We find that all
the estimators perform equivalently using a Rubin Observatory Legacy Survey of
Space and Time (LSST) Year 1 like setup. This is because all the estimators
project out the mode responsible for the non-local nature of the galaxy-galaxy
lensing measurements, which we have identified as . We finally apply all
the estimators to DES Y3 data and confirm that they all give consistent
results.Comment: 9+3 pages, 3+3 figures. To be submitted to MNRA
Measurement of the mean central optical depth of galaxy clusters via the pairwise kinematic Sunyaev-Zel'dovich effect with SPT-3G and des
We infer the mean optical depth of a sample of optically selected galaxy clusters from the Dark Energy Survey via the pairwise kinematic Sunyaev-Zel'dovich (KSZ) effect. The pairwise KSZ signal between pairs of clusters drawn from the Dark Energy Survey Year-3 cluster catalog is detected at 4.1σ in cosmic microwave background temperature maps from two years of observations with the SPT-3G camera on the South Pole Telescope. After cuts, there are 24,580 clusters in the ∼1,400 deg2 of the southern sky observed by both experiments. We infer the mean optical depth of the cluster sample with two techniques. The optical depth inferred from the pairwise KSZ signal is τ¯e=(2.97±0.73)×10-3, while that inferred from the thermal SZ signal is τ¯e=(2.51±0.55stat±0.15syst)×10-3. The two measures agree at 0.6σ. We perform a suite of systematic checks to test the robustness of the analysis
The MADPSZ catalogue of Planck clusters over the DES region: extending to lower mass and higher redshift
We present the first systematic follow-up of Planck Sunyaev-Zeldovich effect
(SZE) selected candidates down to signal-to-noise (S/N) of 3 over the 5000
deg covered by the Dark Energy Survey. Using the MCMF cluster confirmation
algorithm, we identify optical counterparts, determine photometric redshifts
and richnesses and assign a parameter, , that reflects the
probability that each SZE-optical pairing represents a real cluster rather than
a random superposition of physically unassociated systems. The new MADPSZ
cluster catalogue consists of 1092 MCMF confirmed clusters and has a purity of
85%. We present the properties of subsamples of the MADPSZ catalogue that have
purities ranging from 90% to 97.5%, depending on the adopted
threshold. halo mass estimates, redshifts, richnesses, and optical
centers are presented for all MADPSZ clusters. The MADPSZ catalogue adds 828
previously unknown Planck identified clusters over the DES footprint and
provides redshifts for an additional 50 previously published Planck selected
clusters with S/N>4.5. Using the subsample with spectroscopic redshifts, we
demonstrate excellent cluster photo- performance with an RMS scatter in
of 0.47%. Our MCMF based analysis allows us to infer the
contamination fraction of the initial S/N>3 Planck selected candidate list,
which is 50%. We present a method of estimating the completeness of the MADPSZ
cluster sample and selected subsamples. In comparison to the
previously published Planck cluster catalogues. this new S/N 3 MCMF
confirmed cluster catalogue populates the lower mass regime at all redshifts
and includes clusters up to z1.3.Comment: 20 pages, 5 Appendices, 17 figures, submitted to MNRA
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