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Radiative transfer modelling for the NOMAD-UVIS instrument on the ExoMars Trace Gas Orbiter mission
The NOMAD (Nadir and Occultation for MArs Discovery) instrument is a 3-channel (2 IR, 1 UV/Vis) spectrometer due to fly on the 2016 ExoMars Trace Gas Orbiter mission. A radiative transfer model for Mars has been developed providing synthetic spectra to simulate observations of the UVIS channel in both solar occultation and nadir viewing geometries. This will allow for the characterization and mitigation of the influence of dust on retrievals of ozone abundance
Time-division SQUID multiplexers with reduced sensitivity to external magnetic fields
Time-division SQUID multiplexers are used in many applications that require
exquisite control of systematic error. One potential source of systematic error
is the pickup of external magnetic fields in the multiplexer. We present
measurements of the field sensitivity figure of merit, effective area, for both
the first stage and second stage SQUID amplifiers in three NIST SQUID
multiplexer designs. These designs include a new variety with improved
gradiometry that significantly reduces the effective area of both the first and
second stage SQUID amplifiers.Comment: 4 pages, 7 figures. Submitted for publication in the IEEE
Transactions on Applied Superconductivity, August 201
Near-infrared colors of minor planets recovered from VISTA - VHS survey (MOVIS)
The Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer
(WISE) provide information about the surface composition of about 100,000 minor
planets. The resulting visible colors and albedos enabled us to group them in
several major classes, which are a simplified view of the diversity shown by
the few existing spectra. We performed a serendipitous search in VISTA-VHS
observations using a pipeline developed to retrieve and process the data that
corresponds to solar system objects (SSo). The colors and the magnitudes of the
minor planets observed by the VISTA survey are compiled into three catalogs
that are available online: the detections catalog (MOVIS-D), the magnitudes
catalog (MOVIS-M), and the colors catalog (MOVIS-C). They were built using the
third data release of the survey (VISTA VHS-DR3). A total of 39,947 objects
were detected, including 52 NEAs, 325 Mars Crossers, 515 Hungaria asteroids,
38,428 main-belt asteroids, 146 Cybele asteroids, 147 Hilda asteroids, 270
Trojans, 13 comets, 12 Kuiper Belt objects and Neptune with its four
satellites. The colors found for asteroids with known spectral properties
reveal well-defined patterns corresponding to different mineralogies. The
distributions of MOVIS-C data in color-color plots shows clusters identified
with different taxonomic types. All the diagrams that use (Y-J) color separate
the spectral classes more effectively than the (J-H) and (H-Ks) plots used
until now: even for large color errors (<0.1), the plots (Y-J) vs (Y-Ks) and
(Y-J) vs (J-Ks) provide the separation between S-complex and C-complex. The end
members A, D, R, and V-types occupy well-defined regions.Comment: 19 pages, 16 figure
Strongly quadrature-dependent noise in superconducting micro-resonators measured at the vacuum-noise limit
We measure frequency- and dissipation-quadrature noise in superconducting
lithographed microwave resonators with sensitivity near the vacuum noise level
using a Josephson parametric amplifier. At an excitation power of 100~nW, these
resonators show significant frequency noise caused by two-level systems. No
excess dissipation-quadrature noise (above the vacuum noise) is observed to our
measurement sensitivity. These measurements demonstrate that the excess
dissipation-quadrature noise is negligible compared to vacuum fluctuations, at
typical readout powers used in micro-resonator applications. Our results have
important implications for resonant readout of various devices such as
detectors, qubits and nano-mechanical oscillators.Comment: 13 pages, 4 figure
Radio haloes in nearby galaxies modelled with 1D cosmic-ray transport using SPINNAKER
We present radio continuum maps of 12 nearby (), edge-on
(), late-type spiral galaxies mostly at and 5 GHz,
observed with the Australia Telescope Compact Array, Very Large Array,
Westerbork Synthesis Radio Telescope, Effelsberg 100-m and Parkes 64-m
telescopes. All galaxies show clear evidence of radio haloes, including the
first detection in the Magellanic-type galaxy NGC 55. In 11 galaxies, we find a
thin and a thick disc that can be better fitted by exponential rather than
Gaussian functions. We fit our SPINNAKER (SPectral INdex Numerical Analysis of
K(c)osmic-ray Electron Radio-emission) 1D cosmic-ray transport models to the
vertical model profiles of the non-thermal intensity and to the non-thermal
radio spectral index in the halo. We simultaneously fit for the advection speed
(or diffusion coefficient) and magnetic field scale height. In the thick disc,
the magnetic field scale heights range from 2 to 8 kpc with an average across
the sample of ; they show no correlation with either
star-formation rate (SFR), SFR surface density () or rotation
speed (). The advection speeds range from 100 to and display correlations of and
; they agree remarkably well with the
escape velocities (), which can be explained by
cosmic-ray driven winds. Radio haloes show the presence of disc winds in
galaxies with
that extend over several kpc and are driven by processes related to the
distributed star formation in the disc.Comment: 39 pages, 20 colour figures, 10 tables. Accepted by MNRA
ROSAT HRI X-ray Observations of the Open Globular Cluster NGC 288
A ROSAT HRI X-ray image was obtained of the open globular cluster NGC 288,
which is located near the South Galactic Pole. This is the first deep X-ray
image of this system. We detect a Low Luminosity Globular Cluster X-ray source
(LLGCX) RXJ005245.0-263449 with an X-ray luminosity of (5.5+-1.4)x10^32 ergs/s
(0.1-2.0 keV), which is located very close to the cluster center. There is
evidence for X-ray variability on a time scale of <~ 1 day. The presence of
this LLGCX in such an open cluster suggests that dense stellar systems with
high interaction rates are not needed to form LLGCXs. We also searched for
diffuse X-ray emission from NGC 288. Upper limits on the X-ray luminosities are
L_X^h < 9.5x10^32 ergs/s (0.52-2.02 keV) and L_X^s < 9.3x10^32 ergs/s
(0.11-0.41 keV). These imply upper limits to the diffuse X-ray to optical light
ratios in NGC 288 which are lower than the values observed for X-ray faint
early-type galaxies. This indicates that the soft X-ray emission in these
galaxies is due either to a component which is not present in globular clusters
(e.g., interstellar gas, or a stellar component which is not found in low
metallicity Population II systems), or to a relatively small number of bright
Low Mass X-ray Binaries (LMXBs).Comment: The Astrophysical Journal in press. Minor revisions to improve
presentation. 6 pages with 3 embedded Postscript figures in emulateapj.st
Carbon and nitrogen abundances of individual stars in the Sculptor dwarf spheroidal galaxy
We present [C/Fe] and [N/Fe] abundance ratios and CH({\lambda}4300) and
S({\lambda}3883) index measurements for 94 red giant branch (RGB) stars in the
Sculptor dwarf spheroidal galaxy from VLT/VIMOS MOS observations at a resolving
power R= 1150 at 4020 {\AA}. This is the first time that [N/Fe] abundances are
derived for a large number of stars in a dwarf spheroidal. We found a trend for
the [C/Fe] abundance to decrease with increasing luminosity on the RGB across
the whole metallicity range, a phenomenon observed in both field and globular
cluster giants, which can be interpreted in the framework of evolutionary
mixing of partially processed CNO material. Both our measurements of [C/Fe] and
[N/Fe] are in good agreement with the theoretical predictions for stars at
similar luminosity and metallicity. We detected a dispersion in the carbon
abundance at a given [Fe/H], which cannot be ascribed to measurement
uncertainties alone. We interpret this observational evidence as the result of
the contribution of different nucleosynthesis sources over time to a not
well-mixed interstellar medium. We report the discovery of two new
carbon-enhanced, metal-poor stars. These are likely the result of pollution
from material enriched by asymptotic giant branch stars, as indicated by our
estimates of [Ba/Fe]> +1. We also attempted a search for dissolved globular
clusters in the field of the galaxy by looking for the distinctive C-N pattern
of second population globular clusters stars in a previously detected, very
metal-poor, chemodynamical substructure. We do not detect chemical anomalies
among this group of stars. However, small number statistics and limited spatial
coverage do not allow us to exclude the hypotheses that this substructure forms
part of a tidally shredded globular cluster.Comment: 18 pages, 14 figures, 3 tables. Accepted to A&
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