432 research outputs found
A high signal to noise ratio map of the Sunyaev-Zel'dovich increment at 1.1 mm wavelength in Abell 1835
We present an analysis of an 8 arcminute diameter map of the area around the
galaxy cluster Abell 1835 from jiggle map observations at a wavelength of 1.1
mm using the Bolometric Camera (Bolocam) mounted on the Caltech Submillimeter
Observatory (CSO). The data is well described by a model including an extended
Sunyaev-Zel'dovich (SZ) signal from the cluster gas plus emission from two
bright background submm galaxies magnified by the gravitational lensing of the
cluster. The best-fit values for the central Compton value for the cluster and
the fluxes of the two main point sources in the field: SMM J140104+0252, and
SMM J14009+0252 are found to be ,
6.5 mJy and 11.3 mJy, where the first error
represents the statistical measurement error and the second error represents
the estimated systematic error in the result. This measurement assumes the
presence of dust emission from the cluster's central cD galaxy of
mJy, based on higher frequency observations of Abell 1835. The cluster image
represents one of the highest-significance SZ detections of a cluster in the
positive region of the thermal SZ spectrum to date. The inferred central
intensity is compared to other SZ measurements of Abell 1835 and this
collection of results is used to obtain values for and the cluster peculiar velocity km/s.Comment: 9 pages, 5 figure
The Game of Pure Strategy is solved!
We solve the classical "Game of Pure Strategy" using linear programming. We
notice an intricate even-odd behavior in the results of our computations, that
seems to encourage odd or maximal bids
Characterisation of Herschel-SPIRE flight model optical performances
The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on ESA's Herschel Space Observatory. This long wavelength instrument covers 200 to 670μm with a three band photometric camera and a two band imaging Fourier Transform Spectrometer (IFTS). Following first results reported in a previous paper, we discuss the in-band optical performances of the flight model as measured extensively during several dedicated test campaigns. Complementary to the experimentally probed spectral characteristics of the instrument detailed in an accompanying paper (see L.D. Spencer et al., in these proceedings), attention is focused here on a set of standard but key tests aimed at measuring the spatial response of the Photometer and Spectrometer end-to-end optical chain, including detector. Effects of defocus as well as source size extent, in-band wavelength, and polarization are also investigated over respective Photometer and Spectrometer field-of-views. Comparison with optical modelling, based on instrument design knowledge and some of the internal component measured characteristics, is performed. Beyond the specific characterisation of each effect, this allows estimating in each band where optical behaviour and detector behaviour respectively dominates and also reconstructing some of the contributors to the instrument throughput. Based on this analysis, retrieved optical performances are finally assessed against the related science-driven instrument requirements
Bolocam Survey for 1.1 mm Dust Continuum Emission in the c2d Legacy Clouds. II. Ophiuchus
We present a large-scale millimeter continuum map of the Ophiuchus molecular
cloud. Nearly 11 square degrees, including all of the area in the cloud with
visual extinction more than 3 magnitudes, was mapped at 1.1 mm with Bolocam on
the Caltech Submillimeter Observatory (CSO). By design, the map also covers the
region mapped in the infrared with the Spitzer Space Telescope. We detect 44
definite sources, and a few likely sources are also seen along a filament in
the eastern streamer. The map indicates that dense cores in Ophiuchus are very
clustered and often found in filaments within the cloud. Most sources are
round, as measured at the half power point, but elongated when measured at
lower contour levels, suggesting spherical sources lying within filaments. The
masses, for an assumed dust temperature of 10 K, range from 0.24 to 3.9 solar
masses, with a mean value of 0.96 solar masses. The total mass in distinct
cores is 42 solar masses, 0.5 to 2% of the total cloud mass, and the total mass
above 4 sigma is about 80 solar masses. The mean densities in the cores are
quite high, with an average of 1.6 x 10^6 per cc, suggesting short free-fall
times. The core mass distribution can be fitted with a power law with slope of
2.1 plus or minus 0.3 for M>0.5 solar masses, similar to that found in other
regions, but slightly shallower than that of some determinations of the local
IMF. In agreement with previous studies, our survey shows that dense cores
account for a very small fraction of the cloud volume and total mass. They are
nearly all confined to regions with visual extinction at least 9 mag, a lower
threshold than found previously.Comment: 47 pages, 16 figures, accepted for Ap
POLOCAM: a millimeter wavelength cryogenic polarimeter prototype for MUSIC-POL
As a proof-of-concept, we have constructed and tested a cryogenic polarimeter in the laboratory as a prototype for the MUSIC instrument (Multiwavelength Sub/millimeter Kinetic Inductance Camera). The POLOCAM instrument consists of a rotating cryogenic polarization modulator (sapphire half-waveplate) and polarization analyzer (lithographed copper polarizers deposited on a thin film) placed into the optical path at the Lyot stop (4K cold pupil stop) in a cryogenic dewar. We present an overview of the project, design and performance results of the POLOCAM instrument (including polarization efficiencies and instrumental polarization), as well as future application to the MUSIC-POL instrument
Archival Legacy Investigations of Circumstellar Environments: Overview and First Results
We are currently conducting a comprehensive and consistent re-processing of
archival HST-NICMOS coronagraphic surveys using advanced PSF subtraction
methods, entitled the Archival Legacy Investigations of Circumstellar
Environments program (ALICE, HST/AR 12652). This virtual campaign of about 400
targets has already produced numerous new detections of previously unidentified
point sources and circumstellar structures. We present five newly spatially
resolved debris disks revealed in scattered light by our analysis of the
archival data. These images provide new views of material around young
solar-type stars at ages corresponding to the period of terrestrial planet
formation in our solar system. We have also detected several new candidate
substellar companions, for which there are ongoing followup campaigns (HST/WFC3
and VLT/SINFONI in ADI mode). Since the methods developed as part of ALICE are
directly applicable to future missions (JWST, AFTA coronagraph) we emphasize
the importance of devising optimal PSF subtraction methods for upcoming
coronagraphic imaging missions. We describe efforts in defining direct imaging
high-level science products (HLSP) standards that can be applicable to other
coronagraphic campaigns, including ground-based (e.g., Gemini Planet Imager),
and future space instruments (e.g., JWST). ALICE will deliver a first release
of HLSPs to the community through the MAST archive at STScI in 2014.Comment: Proceedings of the SPIE, 9143-199. 17 pages, 11 figure
Five Debris Disks Newly Revealed in Scattered Light from the HST NICMOS Archive
We have spatially resolved five debris disks (HD 30447, HD 35841, HD 141943,
HD 191089, and HD 202917) for the first time in near-infrared scattered light
by reanalyzing archival Hubble Space Telescope (HST)/NICMOS coronagraphic
images obtained between 1999 and 2006. One of these disks (HD 202917) was
previously resolved at visible wavelengths using HST/Advanced Camera for
Surveys. To obtain these new disk images, we performed advanced point-spread
function subtraction based on the Karhunen-Loeve Image Projection (KLIP)
algorithm on recently reprocessed NICMOS data with improved detector artifact
removal (Legacy Archive PSF Library And Circumstellar Environments Legacy
program). Three of the disks (HD 30447, HD 35841, and HD 141943) appear
edge-on, while the other two (HD 191089 and HD 202917) appear inclined. The
inclined disks have been sculpted into rings; in particular, the disk around HD
202917 exhibits strong asymmetries. All five host stars are young (8-40 Myr),
nearby (40-100 pc) F and G stars, and one (HD 141943) is a close analog to the
young sun during the epoch of terrestrial planet formation. Our discoveries
increase the number of debris disks resolved in scattered light from 19 to 23
(a 21% increase). Given their youth, proximity, and brightness (V = 7.2 to
8.5), these targets are excellent candidates for follow-up investigations of
planet formation at visible wavelengths using the HST/STIS coronagraph, at
near-infrared wavelengths with the Gemini Planet Imager (GPI) and Very Large
Telescope (VLT)/SPHERE, and at thermal infrared wavelengths with the James Webb
Space Telescope NIRCam and MIRI coronagraphs.Comment: 6 pages, 1 figure, 1 tabl
Experimental evidence for melt partitioning between olivine and orthopyroxene in partially molten harzburgite
Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 121 (2016): 5776–5793, doi:10.1002/2016JB013122.Observations of dunite channels in ophiolites and uranium series disequilibria in mid-ocean ridge basalt suggest that melt transport in the upper mantle beneath mid-ocean ridges is strongly channelized. We present experimental evidence that spatial variations in mineralogy can also focus melt on the grain scale. This lithologic melt partitioning, which results from differences in the interfacial energies associated with olivine-melt and orthopyroxene-melt boundaries, may complement other melt focusing mechanisms in the upper mantle such as mechanical shear and pyroxene dissolution. We document here lithologic melt partitioning in olivine-/orthopyroxene-basaltic melt samples containing nominal olivine to orthopyroxene ratio of 3 to 2 and melt fractions of 0.02 to 0.20. Experimental samples were imaged using synchrotron-based X-ray microcomputed tomography at a resolution of 700 nm per voxel. By analyzing the local melt fraction distributions associated with olivine and orthopyroxene grains in each sample, we found that the melt partitioning coefficient, i.e., the ratio of melt fraction around olivine to that around orthopyroxene grains, varies between 1.1 and 1.6. The permeability and electrical conductivity of our digital samples were estimated using numerical models and compared to those of samples containing only olivine and basaltic melt. Our results suggest that lithologic melt partitioning and preferential localization of melt around olivine grains might play a role in melt focusing, potentially enhancing average melt ascent velocities.National Science Foundation Grant Numbers: 1250338, 1551300;
Basic Energy Sciences Grant Number: DEFG0207ER15916;
Advanced Photon Source Grant Number: DE-AC02-06CH113572017-02-2
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