1,091 research outputs found
Snowmelt-triggered debris flows in seasonal snowpacks
Snowmelt-triggered debris flows commonly occur in mountains. On 14 June 2019, a debris flow occurred on a steep, east-facing slope composed of unconsolidated glacial and periglacial sediments in Yosemite National Park. Originating as a shallow landslide, ~1,300m3 of ripe snow was instantaneously entrained into the debris flow carrying boulders, trees, and soil downslope. The forested area at the toe of the slope strained out debris leaving a muddy slurry to issue across Highway 120 during dewatering. We document this mass movement and assesses its initiation using local snowpack and meteorological data as well as a regional atmospheric reanalysis to examine synoptic conditions. A multiday warming trend and ripening of the snowpack occurred prior to the event as a 500 hPa ridge amplified over western North America leading to record warm 700 hPa temperatures. Anomalous temperatures and cloud cover prevented refreezing of the snowpack and accelerated its ripening with meltwater contributing to soil saturation. Similar conditions occurred during the catastrophic 1983 Slide Mountain debris flow, also hypothesized to be snowmelt initiated. With projected increases in heat waves, our findings can support natural hazard early warning systems in snow-dominated environments
Data Reduction Pipeline for the CHARIS Integral-Field Spectrograph I: Detector Readout Calibration and Data Cube Extraction
We present the data reduction pipeline for CHARIS, a high-contrast
integral-field spectrograph for the Subaru Telescope. The pipeline constructs a
ramp from the raw reads using the measured nonlinear pixel response, and
reconstructs the data cube using one of three extraction algorithms: aperture
photometry, optimal extraction, or fitting. We measure and apply both
a detector flatfield and a lenslet flatfield and reconstruct the wavelength-
and position-dependent lenslet point-spread function (PSF) from images taken
with a tunable laser. We use these measured PSFs to implement a -based
extraction of the data cube, with typical residuals of ~5% due to imperfect
models of the undersampled lenslet PSFs. The full two-dimensional residual of
the extraction allows us to model and remove correlated read noise,
dramatically improving CHARIS' performance. The extraction produces a
data cube that has been deconvolved with the line-spread function, and never
performs any interpolations of either the data or the individual lenslet
spectra. The extracted data cube also includes uncertainties for each spatial
and spectral measurement. CHARIS' software is parallelized, written in Python
and Cython, and freely available on github with a separate documentation page.
Astrometric and spectrophotometric calibrations of the data cubes and PSF
subtraction will be treated in a forthcoming paper.Comment: 18 pages, 15 figures, 3 tables, replaced with JATIS accepted version
(emulateapj formatted here). Software at
https://github.com/PrincetonUniversity/charis-dep and documentation at
http://princetonuniversity.github.io/charis-de
Simulating the WFIRST coronagraph Integral Field Spectrograph
A primary goal of direct imaging techniques is to spectrally characterize the
atmospheres of planets around other stars at extremely high contrast levels. To
achieve this goal, coronagraphic instruments have favored integral field
spectrographs (IFS) as the science cameras to disperse the entire search area
at once and obtain spectra at each location, since the planet position is not
known a priori. These spectrographs are useful against confusion from speckles
and background objects, and can also help in the speckle subtraction and
wavefront control stages of the coronagraphic observation. We present a
software package, the Coronagraph and Rapid Imaging Spectrograph in Python
(crispy) to simulate the IFS of the WFIRST Coronagraph Instrument (CGI). The
software propagates input science cubes using spatially and spectrally resolved
coronagraphic focal plane cubes, transforms them into IFS detector maps and
ultimately reconstructs the spatio-spectral input scene as a 3D datacube.
Simulated IFS cubes can be used to test data extraction techniques, refine
sensitivity analyses and carry out design trade studies of the flight CGI-IFS
instrument. crispy is a publicly available Python package and can be adapted to
other IFS designs.Comment: 15 page
Conceptual Design of the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) for the Subaru Telescope
Recent developments in high-contrast imaging techniques now make possible
both imaging and spectroscopy of planets around nearby stars. We present the
conceptual design of the Coronagraphic High Angular Resolution Imaging
Spectrograph (CHARIS), a lenslet-based, cryogenic integral field spectrograph
(IFS) for imaging exoplanets on the Subaru telescope. The IFS will provide
spectral information for 140x140 spatial elements over a 1.75 arcsecs x 1.75
arcsecs field of view (FOV). CHARIS will operate in the near infrared (lambda =
0.9 - 2.5 microns) and provide a spectral resolution of R = 14, 33, and 65 in
three separate observing modes. Taking advantage of the adaptive optics systems
and advanced coronagraphs (AO188 and SCExAO) on the Subaru telescope, CHARIS
will provide sufficient contrast to obtain spectra of young self-luminous
Jupiter-mass exoplanets. CHARIS is in the early design phases and is projected
to have first light by the end of 2015. We report here on the current
conceptual design of CHARIS and the design challenges
The Optical Design of CHARIS: An Exoplanet IFS for the Subaru Telescope
High-contrast imaging techniques now make possible both imaging and
spectroscopy of planets around nearby stars. We present the optical design for
the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), a
lenslet-based, cryogenic integral field spectrograph (IFS) for imaging
exoplanets on the Subaru telescope. The IFS will provide spectral information
for 138x138 spatial elements over a 2.07 arcsec x 2.07 arcsec field of view
(FOV). CHARIS will operate in the near infrared (lambda = 1.15 - 2.5 microns)
and will feature two spectral resolution modes of R = 18 (low-res mode) and R =
73 (high-res mode). Taking advantage of the Subaru telescope adaptive optics
systems and coronagraphs (AO188 and SCExAO), CHARIS will provide sufficient
contrast to obtain spectra of young self-luminous Jupiter-mass exoplanets.
CHARIS will undergo CDR in October 2013 and is projected to have first light by
the end of 2015. We report here on the current optical design of CHARIS and its
unique innovations.Comment: 15 page
CHARIS Science: Performance Simulations for the Subaru Telescope's Third-Generation of Exoplanet Imaging Instrumentation
We describe the expected scientific capabilities of CHARIS, a high-contrast
integral-field spectrograph (IFS) currently under construction for the Subaru
telescope. CHARIS is part of a new generation of instruments, enabled by
extreme adaptive optics (AO) systems (including SCExAO at Subaru), that promise
greatly improved contrasts at small angular separation thanks to their ability
to use spectral information to distinguish planets from quasistatic speckles in
the stellar point-spread function (PSF). CHARIS is similar in concept to GPI
and SPHERE, on Gemini South and the Very Large Telescope, respectively, but
will be unique in its ability to simultaneously cover the entire near-infrared
, , and bands with a low-resolution mode. This extraordinarily broad
wavelength coverage will enable spectral differential imaging down to angular
separations of a few , corresponding to 0.\!\!''1. SCExAO
will also offer contrast approaching at similar separations,
0.\!\!''1--0.\!\!''2. The discovery yield of a CHARIS survey will
depend on the exoplanet distribution function at around 10 AU. If the
distribution of planets discovered by radial velocity surveys extends unchanged
to 20 AU, observations of 200 mostly young, nearby stars targeted
by existing high-contrast instruments might find 1--3 planets. Carefully
optimizing the target sample could improve this yield by a factor of a few,
while an upturn in frequency at a few AU could also increase the number of
detections. CHARIS, with a higher spectral resolution mode of , will
also be among the best instruments to characterize planets and brown dwarfs
like HR 8799 cde and And b.Comment: 13 pages, 7 figures, proceedings from SPIE Montrea
Alphaflexivirus genomes in stony coral tissue loss disease-affected, disease-exposed, and disease-unexposed coral colonies in the U.S. Virgin Islands
© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Veglia, A., Beavers, K., Van Buren, E., Meiling, S., Muller, E., Smith, T., Holstein, D., Apprill, A., Brandt, M., Mydlarz, L., & Correa, A. Alphaflexivirus genomes in stony coral tissue loss disease-affected, disease-exposed, and disease-unexposed coral colonies in the U.S. Virgin Islands. Microbiology Resource Announcements, 11(2), (2022): e01199–e01121, https://doi.org/10.1128/mra.01199-21.Stony coral tissue loss disease (SCTLD) is decimating Caribbean corals. Here, through the metatranscriptomic assembly and annotation of two alphaflexivirus-like strains, we provide genomic evidence of filamentous viruses in SCTLD-affected, -exposed, and -unexposed coral colonies. These data will assist in clarifying the roles of viruses in SCTLD.This work was supported by the National Science Foundation (Biological Oceanography) award numbers 1928753 to M.E.B. and T.B.S., 1928609 to A.M.S.C., 1928817 to E.M.M., 19228771 to L.D.M., 1927277 to D.M.H., and 1928761 to A.A., as well as by VI EPSCoR (NSF numbers 0814417 and 1946412)
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