32 research outputs found
Testing LSST dither strategies for Survey Uniformity and Large-Scale Structure Systematics
The Large Synoptic Survey Telescope (LSST) will survey the southern sky from 2022{2032 with unprecedented detail. Since the observing strategy can lead to artifacts in the data, we investigate the eects of telescope-pointing osets (called dithers) on the r-band coadded 5 depth yielded after the 10-year survey. We analyze this survey depth for several geometric patterns of dithers (e.g.,random, hexagonal lattice, spiral) with amplitude as large as the radius of the LSST eld-of-view, implemented on dierent timescales (per season, per night, per visit). Our results illustrate that per night and per visit dither assignments are more eective than per season. Also, we find that some dither geometries (e.g., hexagonal lattice) are particularly sensitive to the timescale on whichthe dithers are implemented, while others like random dithers perform well on all timescales. We then model the propagation of depth variations to articial uctuations in galaxy counts, which are a systematic for large-scale structure studies. We calculate the bias in galaxy counts caused by the observing strategy, accounting for photometric calibration uncertainties, dust extinction, and magnitude cuts; uncertainties in this bias limit our ability to account for structure induced by the observing strategy. We nd that after 10 years of the LSST survey, the best dither strategies lead to uncertainties in this bias smaller than the minimum statistical floor for a galaxy catalog as deep asr<27.5. A few of these strategies bring the uncertainties close to the statistical floor for r<25.7 after only one year of survey.Fil: Awan, Humna. Rutgers University; Estados UnidosFil: Gawiser, Eric. Rutgers University; Estados UnidosFil: Kurczynski, Peter. Rutgers University; Estados UnidosFil: Lynne Jones, R.. University of Washington; Estados UnidosFil: Zhan, Hu. Chinese Academy of Sciences; República de ChinaFil: Padilla, Nelson David. Pontificia Universidad Católica de Chile; ChileFil: Muñoz Arancibia, Alejandra M.. Pontificia Universidad Católica de Chile; ChileFil: Orsi, Alvaro. Centro de Estudios de Fisica del Cosmos de Aragon; EspañaFil: Cora, Sofia Alejandra. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; ArgentinaFil: Yoachim, Peter. University of Washington; Estados Unido
Unbiased Cosmological Parameter Estimation from Emission Line Surveys with Interlopers
The galaxy catalogs generated from low-resolution emission line surveys often
contain both foreground and background interlopers due to line
misidentification, which can bias the cosmological parameter estimation. In
this paper, we present a method for correcting the interloper bias by using the
joint-analysis of auto- and cross-power spectra of the main and the interloper
samples. In particular, we can measure the interloper fractions from the
cross-correlation between the interlopers and survey galaxies, because the true
cross-correlation must be negligibly small. The estimated interloper fractions,
in turn, remove the interloper bias in the cosmological parameter estimation.
For example, in the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX)
low-redshift () [O II] {\AA} emitters contaminate
high-redshift () Lyman- line emitters. We demonstrate that
the joint-analysis method yields a high signal-to-noise ratio measurement of
the interloper fractions while only marginally increasing the uncertainties in
the cosmological parameters relative to the case without interlopers. We also
show the same is true for the high-latitude spectroscopic survey of Wide-Field
Infrared Survey Telescope (WFIRST) mission where contamination occurs between
the Balmer- line emitters at lower redshifts () and Oxygen
([O III] {\AA}) line emitters at higher redshifts ().Comment: 36 pages, 26 figure
Testing LSST dither strategies for survey uniformity and large-scale structure systematics
The Large Synoptic Survey Telescope (LSST) will survey the southern sky from 2022-2032 with unprecedented detail. Since the observing strategy can lead to artifacts in the data, we investigate the effects of telescope-pointing offsets (called dithers) on the r-band coadded 5σ depth yielded after the 10-year survey. We analyze this survey depth for several geometric patterns of dithers (e.g., random, hexagonal lattice, spiral) with amplitudes as large as the radius of the LSST field of view, implemented on different timescales (per season, per night, per visit). Our results illustrate that per night and per visit dither assignments are more effective than per season assignments. Also, we find that some dither geometries (e.g., hexagonal lattice) are particularly sensitive to the timescale on which the dithers are implemented, while others like random dithers perform well on all timescales. We then model the propagation of depth variations to artificial fluctuations in galaxy counts, which are a systematic for LSS studies. We calculate the bias in galaxy counts caused by the observing strategy accounting for photometric calibration uncertainties, dust extinction, and magnitude cuts; uncertainties in this bias limit our ability to account for structure induced by the observing strategy. We find that after 10 years of the LSST survey, the best dither strategies lead to uncertainties in this bias that are smaller than the minimum statistical floor for a galaxy catalog as deep as r < 27.5. A few of these strategies bring the uncertainties close to the statistical floor for r < 25.7 after the first year of survey.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat
Testing LSST dither strategies for survey uniformity and large-scale structure systematics
The Large Synoptic Survey Telescope (LSST) will survey the southern sky from 2022-2032 with unprecedented detail. Since the observing strategy can lead to artifacts in the data, we investigate the effects of telescope-pointing offsets (called dithers) on the r-band coadded 5σ depth yielded after the 10-year survey. We analyze this survey depth for several geometric patterns of dithers (e.g., random, hexagonal lattice, spiral) with amplitudes as large as the radius of the LSST field of view, implemented on different timescales (per season, per night, per visit). Our results illustrate that per night and per visit dither assignments are more effective than per season assignments. Also, we find that some dither geometries (e.g., hexagonal lattice) are particularly sensitive to the timescale on which the dithers are implemented, while others like random dithers perform well on all timescales. We then model the propagation of depth variations to artificial fluctuations in galaxy counts, which are a systematic for LSS studies. We calculate the bias in galaxy counts caused by the observing strategy accounting for photometric calibration uncertainties, dust extinction, and magnitude cuts; uncertainties in this bias limit our ability to account for structure induced by the observing strategy. We find that after 10 years of the LSST survey, the best dither strategies lead to uncertainties in this bias that are smaller than the minimum statistical floor for a galaxy catalog as deep as r < 27.5. A few of these strategies bring the uncertainties close to the statistical floor for r < 25.7 after the first year of survey.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat
Tomographic galaxy clustering with the Subaru Hyper Suprime-Cam first year public data release
We analyze the clustering of galaxies in the first public data release of the
HSC Subaru Strategic Program. Despite the relatively small footprints of the
observed fields, the data are an excellent proxy for the deep photometric
datasets that will be acquired by LSST, and are therefore an ideal test bed for
the analysis methods being implemented by the LSST DESC. We select a magnitude
limited sample with and analyze it in four redshift bins covering
. We carry out a Fourier-space analysis of the
two-point clustering of this sample, including all auto- and
cross-correlations. We demonstrate the use of map-level deprojection methods to
account for fluctuations in the galaxy number density caused by observational
systematics. Through an HOD analysis, we place constraints on the
characteristic halo masses of this sample, finding a good fit up to scales
, including both auto- and cross-correlations.
Our results show monotonically decreasing average halo masses, which can be
interpreted in terms of the drop-out of red galaxies at high redshifts for a
flux-limited sample. In terms of photometric redshift systematics, we show that
additional care is needed in order to marginalize over uncertainties in the
redshift distribution in galaxy clustering, and that these uncertainties can be
constrained by including cross-correlations. We are able to make a
detection of lensing magnification in the HSC data. Our results
are stable to variations in and and we find constraints
that agree well with measurements from Planck and low-redshift probes. Finally,
we use our pipeline to study the clustering of galaxies as a function of
limiting flux, and provide a simple fitting function for the linear galaxy bias
for magnitude limited samples as a function of limiting magnitude and redshift.
[abridged]Comment: 65 pages, 30 figures, 5 tables, to be submitted to JCA
The LSST Dark Energy Science Collaboration (DESC) Science Requirements Document
The Large Synoptic Survey Telescope (LSST) Dark Energy Science Collaboration
(DESC) will use five cosmological probes: galaxy clusters, large scale
structure, supernovae, strong lensing, and weak lensing. This Science
Requirements Document (SRD) quantifies the expected dark energy constraining
power of these probes individually and together, with conservative assumptions
about analysis methodology and follow-up observational resources based on our
current understanding and the expected evolution within the field in the coming
years. We then define requirements on analysis pipelines that will enable us to
achieve our goal of carrying out a dark energy analysis consistent with the
Dark Energy Task Force definition of a Stage IV dark energy experiment. This is
achieved through a forecasting process that incorporates the flowdown to
detailed requirements on multiple sources of systematic uncertainty. Future
versions of this document will include evolution in our software capabilities
and analysis plans along with updates to the LSST survey strategy.Comment: 32 pages + 60 pages of appendices. This is v1 of the DESC SRD, an
internal collaboration document that is being made public and is not planned
for submission to a journal. Data products for reproducing key plots are
available at the LSST DESC Zenodo community,
https://zenodo.org/communities/lsst-desc; see "Executive Summary and User
Guide" for instructions on how to use and cite those product
Unbiased Cosmological Parameter Estimation from Emission-Line Surveys with Interlopers
The galaxy catalogs generated from low-resolution emission-line surveys often contain both foreground and background interlopers due to line misidentification, which can bias the cosmological parameter estimation. In this paper, we present a method for correcting the interloper bias by using the joint analysis of auto- and cross-power spectra of the main and the interloper samples. In particular, we can measure the interloper fractions from the cross-correlation between the interlopers and survey galaxies, because the true cross-correlation must be negligibly small. The estimated interloper fractions, in turn, remove the interloper bias in the cosmological parameter estimation. For example, in the Hobby-Eberly Telescope Dark Energy Experiment low-redshift (z \u3c 0.5) [O ii] λ3727A emitters contaminate high-redshift (1.9 \u3c z \u3c 3.5) Lyα line emitters. We demonstrate that the joint-analysis method yields a high signal-to-noise ratio measurement of the interloper fractions while only marginally increasing the uncertainties in the cosmological parameters relative to the case without interlopers. We also show that the same is true for the high-latitude spectroscopic survey of the Wide-field Infrared Survey Telescope mission where contamination occurs between the Balmer-α line emitters at lower redshifts (1.1 \u3c z \u3c 1.9) and oxygen ([O III] λ5007A) line emitters at higher redshifts (1.7 \u3c z \u3c 2.8)