49,692 research outputs found
Scientific Objectives for UV/Visible Astrophysics Investigations: A Summary of Responses by the Community (2012)
Following several recommendations presented by the Astrophysics Decadal
Survey 2010 centered around the need to define "a future ultraviolet-optical
space capability," on 2012 May 25, NASA issued a Request for Information (RFI)
seeking persuasive ultraviolet (UV) and visible wavelength astrophysics science
investigations. The goal was to develop a cohesive and compelling set of
science objectives that motivate and support the development of the next
generation of ultraviolet/visible space astrophysics missions. Responses were
due on 10 August 2012 when 34 submissions were received addressing a number of
potential science drivers. A UV/visible Mission RFI Workshop was held on 2012
September 20 where each of these submissions was summarized and discussed in
the context of each other. We present a scientific analysis of these
submissions and presentations and the pursuant measurement capability needs,
which could influence ultraviolet/visible technology development plans for the
rest of this decade. We also describe the process and requirements leading to
the inception of this community RFI, subsequent workshop and the expected
evolution of these ideas and concepts for the remainder of this decade.Comment: 22 pages, 1 figure, 3 table
REMOTE SENSING OF FOLIAR NITROGEN IN CULTIVATED GRASSLANDS OF HUMAN DOMINATED LANDSCAPES
Foliar nitrogen (N) concentration of plant canopies plays a central role in a number of important ecosystem processes and continues to be an active subject in the field of remote sensing. Previous efforts to estimate foliar N at the landscape scale have primarily focused on intact forests and grasslands using aircraft imaging spectrometry and various techniques of statistical calibration and modeling. The present study was designed to extend this work by examining the potential to estimate the foliar N concentration of residential, agricultural and other cultivated grassland areas within a suburbanizing watershed. In conjunction with ground-based vegetation sampling, we developed Partial Least Squares (PLS) models for predicting mass-based foliar N across management types using input from airborne and field based imaging spectrometers. Results yielded strong predictive relationships for both ground- and aircraft-based sensors across sites that included turf grass, grazed pasture, hayfields and fallow fields. We also report on relationships between imaging spectrometer data and other important variables such as canopy height, biomass, and water content, results from which show strong promise for detection with high quality imaging spectrometry data and suggest that cultivated grassland offer opportunity for empirical study of canopy light dynamics. Finally, we discuss the potential for application of our results, and potential challenges, with data from the planned HyspIRI satellite, which will provide global coverage of data useful for vegetation N estimation
The ATESP 5 GHz radio survey. II. Physical properties of the faint radio population
One of the most debated issues about sub-mJy radio sources, which are
responsible for the steepening of the 1.4 GHz source counts, is the origin of
their radio emission. Particularly interesting is the possibility of combining
radio spectral index information with other observational properties to assess
whether the sources are triggered by star formation or nuclear activity. The
aim of this work is to study the optical and near infrared properties of a
complete sample of 131 radio sources with S>0.4 mJy, observed at both 1.4 and 5
GHz as part of the ATESP radio survey. We use deep multi-colour (UBVRIJK)
images, mostly taken in the framework of the ESO Deep Public Survey, to
optically identify and derive photometric redshifts for the ATESP radio
sources. Deep optical coverage and extensive colour information are available
for 3/4 of the region covered by the radio sample. Typical depths of the images
are U~25, B~26, V~25.4, R~25.5, I~24.3, 19.5<K_s<20.2, J<22.2. Optical/near
infrared counterparts are found for ~78% (66/85) of the radio sources in the
region covered by the deep multi-colour imaging, and for 56 of these reliable
estimates of the redshift and type are derived. We find that many of the
sources with flat radio spectra are characterised by high radio-to-optical
ratios (R>1000), typical of classical powerful radio galaxies and quasars.
Flat-spectrum sources with low R values are preferentially identified with
early type galaxies, where the radio emission is most probably triggered by
low-luminosity active galactic nuclei. Considering both early type galaxies and
quasars as sources with an active nucleus, such sources largely dominate our
sample (78%). Flat-spectrum sources associated with early type galaxies are
quite compact (d<10-30 kpc), suggesting core-dominated radio emission.Comment: 15 pages, 13 figures, accepted for pubblication in A&
The Keck Cosmic Web Imager
We are designing the Keck Cosmic Web Imager (KCWI) as a new facility instrument for the Keck II telescope at the W. M. Keck Observatory (WMKO). KCWI is based on the Cosmic Web Imager (CWI), an instrument that has recently had first light at the Hale Telescope. KCWI is a wide-field integral-field spectrograph (IFS) optimized for precision sky limited spectroscopy of low surface brightness phenomena. KCWI will feature high throughput, and flexibility in field of view (FOV), spatial sampling, bandpass, and spectral resolution. KCWI will provide full wavelength coverage (0.35 to 1.05 ÎĽm) using optimized blue and red channels. KCWI will provide a unique and complementary capability at WMKO (optical band integral field spectroscopy) that is directly connected to one of the Observatory's strategic goals (faint object, high precision spectroscopy), at a modest cost and on a competitive time scale, made possible by its simple concept and the prior demonstration of CWI
The value of remote sensing techniques in supporting effective extrapolation across multiple marine spatial scales
The reporting of ecological phenomena and environmental status routinely required point observations, collected with traditional sampling approaches to be extrapolated to larger reporting scales. This process encompasses difficulties that can quickly entrain significant errors. Remote sensing techniques offer insights and exceptional spatial coverage for observing the marine environment. This review provides guidance on (i) the structures and discontinuities inherent within the extrapolative process, (ii) how to extrapolate effectively across multiple spatial scales, and (iii) remote sensing techniques and data sets that can facilitate this process. This evaluation illustrates that remote sensing techniques are a critical component in extrapolation and likely to underpin the production of high-quality assessments of ecological phenomena and the regional reporting of environmental status. Ultimately, is it hoped that this guidance will aid the production of robust and consistent extrapolations that also make full use of the techniques and data sets that expedite this process
Titan Science with the James Webb Space Telescope (JWST)
The James Webb Space Telescope (JWST), scheduled for launch in 2018, is the
successor to the Hubble Space Telescope (HST) but with a significantly larger
aperture (6.5 m) and advanced instrumentation focusing on infrared science
(0.6-28.0 m ). In this paper we examine the potential for scientific
investigation of Titan using JWST, primarily with three of the four
instruments: NIRSpec, NIRCam and MIRI, noting that science with NIRISS will be
complementary. Five core scientific themes are identified: (i) surface (ii)
tropospheric clouds (iii) tropospheric gases (iv) stratospheric composition and
(v) stratospheric hazes. We discuss each theme in depth, including the
scientific purpose, capabilities and limitations of the instrument suite, and
suggested observing schemes. We pay particular attention to saturation, which
is a problem for all three instruments, but may be alleviated for NIRCam
through use of selecting small sub-arrays of the detectors - sufficient to
encompass Titan, but with significantly faster read-out times. We find that
JWST has very significant potential for advancing Titan science, with a
spectral resolution exceeding the Cassini instrument suite at near-infrared
wavelengths, and a spatial resolution exceeding HST at the same wavelengths. In
particular, JWST will be valuable for time-domain monitoring of Titan, given a
five to ten year expected lifetime for the observatory, for example monitoring
the seasonal appearance of clouds. JWST observations in the post-Cassini period
will complement those of other large facilities such as HST, ALMA, SOFIA and
next-generation ground-based telescopes (TMT, GMT, EELT).Comment: 50 pages, including 22 figures and 2 table
The Study of Nebular Emission on Nearby Spiral Galaxies in the IFU Era
A new generation of wide-field emission-line surveys based on integral field
units (IFU) is allowing us to obtain spatially resolved information of the
gas-phase emission in nearby late-type galaxies, based on large samples of HII
regions and full two-dimensional coverage.These observations are allowing us to
discover and characterise abundance differentials between galactic
substructures and new scaling relations with global physical properties. Here I
review some highlights of our current studies employing this technique: (1) the
case study of NGC 628, the largest galaxy ever sampled with an IFU; (2) a
statistical approach to the abundance gradients of spiral galaxies, which
indicates a universal radial gradient for oxygen abundance; and (3) the
discovery of a new scaling relation of HII regions in spiral galaxies, the
local mass-metallicity relation of star-forming galaxies. The observational
properties and constrains found in local galaxies using this new technique will
allow us to interpret the gas-phase abundance of analogue high-z systems.Comment: Review article to appear in: "Metals in 3D: A Cosmic View from
Integral Field Spectroscopy", Advances in Astronomy, Hindawi Publishing
Corporatio
The VIMOS VLT Deep Survey final data release: a spectroscopic sample of 35016 galaxies and AGN out to z~6.7 selected with 17.5<=i_{AB}<=24.7
We describe the completed VIMOS VLT Deep Survey, and the final data release
of 35016 galaxies and type-I AGN with measured spectroscopic redshifts up to
redshift z~6.7, in areas 0.142 to 8.7 square degrees, and volumes from 0.5x10^6
to 2x10^7h^-3Mpc^3. We have selected samples of galaxies based solely on their
i-band magnitude reaching i_{AB}=24.75. Spectra have been obtained with VIMOS
on the ESO-VLT, integrating 0.75h, 4.5h and 18h for the Wide, Deep, and
Ultra-Deep nested surveys. A total of 1263 galaxies have been re-observed
independently within the VVDS, and from the VIPERS and MASSIV surveys. They are
used to establish the redshift measurements reliability, to assess
completeness, and to provide a weighting scheme taking into account the survey
selection function. We describe the main properties of the VVDS samples, and
the VVDS is compared to other spectroscopic surveys. In total we have obtained
spectroscopic redshifts for 34594 galaxies, 422 type-I AGN, and 12430 Galactic
stars. The survey has enabled to identify galaxies up to very high redshifts
with 4669 redshifts in 1<=z_{spec}<=2, 561 in 2<=z_{spec}<=3 and 468 with
z_{spec}>3, and specific populations like LAE have been identified out to
z=6.62. We show that the VVDS occupies a unique place in the parameter space
defined by area, depth, redshift coverage, and number of spectra. The VVDS
provides a comprehensive survey of the distant universe, covering all epochs
since z, or more than 12 Gyr of cosmic time, with a uniform selection, the
largest such sample to date. A wealth of science results derived from the VVDS
have shed new light on the evolution of galaxies and AGN, and their
distribution in space, over this large cosmic time. A final public release of
the complete VVDS spectroscopic redshift sample is available at
http://cesam.lam.fr/vvds.Comment: Submitted 30 June 2013, Accepted 22 August 2013. Updated with
published versio
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