1,588 research outputs found
Contribution of Extragalactic Infrared Sources to CMB Foreground Anisotropy
We estimate the level of confusion to Cosmic Microwave Background anisotropy
measurements caused by extragalactic infrared sources. CMB anisotropy
observations at high resolution and high frequencies are especially sensitive
to this foreground. We use data from the COBE satellite to generate a Galactic
emission spectrum covering mm and sub-mm wavelengths. Using this spectrum as a
template, we predict the microwave emission of the 5319 brightest infrared
galaxies seen by IRAS. We simulate skymaps over the relevant range of
frequencies (30-900 GHz) and instrument resolutions (10'-10 degrees Full Width
Half Max). Analysis of the temperature anisotropy of these skymaps shows that a
reasonable observational window is available for CMB anisotropy measurements.Comment: 14 pages (LaTex source), 3 PostScript figures. Final version, to
appear in ApJLetters May 1. Expanded discussion of systematic error
An algorithm for operational flood mapping from Synthetic Aperture Radar (SAR) data using fuzzy logic
Abstract. An algorithm developed to map flooded areas from synthetic aperture radar imagery is presented in this paper. It is conceived to be inserted in the operational flood management system of the Italian Civil Protection and can be used in an almost automatic mode or in an interactive mode, depending on the user's needs. The approach is based on the fuzzy logic that is used to integrate theoretical knowledge about the radar return from inundated areas taken into account by means of three electromagnetic scattering models, with simple hydraulic considerations and contextual information. This integration aims at allowing a user to cope with situations, such as the presence of vegetation in the flooded area, in which inundation mapping from satellite radars represents a difficult task. The algorithm is designed to work with radar data at L, C, and X frequency bands and employs also ancillary data, such as a land cover map and a digital elevation model. The flood mapping procedure is tested on an inundation that occurred in Albania on January 2010 using COSMO-SkyMed very high resolution X-band SAR data
The Extraordinary Infrared Spectrum of NGC 1222 (Mkn 603)
The infrared spectra of starburst galaxies are dominated by the
low-excitation lines of [NeII] and [SIII], and the stellar populations deduced
from these spectra appear to lack stars larger than about 35 Msun. The only
exceptions to this result until now were low metallicity dwarf galaxies. We
report our analysis of the mid-infrared spectra obtained with IRS on Spitzer of
the starburst galaxy NGC 1222 (Mkn 603). NGC 1222 is a large spheroidal galaxy
with a starburst nucleus that is a compact radio and infrared source, and its
infrared emission is dominated by the [NeIII] line. This is the first starburst
of solar or near-solar metallicity, known to us, which is dominated by the
high-excitation lines and which is a likely host of high mass stars. We model
the emission with several different assumptions as to the spatial distibution
of the high- and low-excitation lines and find that the upper mass cutoff in
this galaxy is 40-100 Msun.Comment: accepted, Astronomical Journal. 29 pp, 4 figures. In replacement
version an acknowledgment to NRAO is adde
The variable stellar wind of Rigel probed at high spatial and spectral resolution
We present a spatially resolved, high-spectral resolution (R=12000) K-band
temporal monitoring of Rigel using AMBER at the VLTI. Rigel was observed in the
Bracket Gamma line and its nearby continuum in 2006-2007, and 2009-2010. These
unprecedented observations were complemented by contemporaneous optical
high-resolution spectroscopy. We analyse the near-IR spectra and visibilities
with the 1D non-LTE radiative-transfer code CMFGEN. The differential and
closure phase signal exhibit asymmetries that are interpreted as perturbations
of the wind. A systematic visibility decrease is observed across the Bracket
Gamma. During the 2006-2007 period the Bracket Gamma and likely the continuum
forming regions were larger than in the 2009-2010 epoch. Using CMFGEN, we infer
a mass-loss rate change of about 20% between the two epochs. We further find
time variations in the differential visibilities and phases. The 2006-2007
period is characterized by noticeable variations of the differential
visibilities in Doppler position and width and by weak variations in
differential and closure phase. The 2009-2010 period is much more quiet with
virtually no detectable variations in the dispersed visibilities but a strong
S-shape signal is observed in differential phase coinciding with a strong
ejection event discernible in the optical spectra. The differential phase
signal that is sometimes detected is reminiscent of the signal computed from
hydrodynamical models of corotating interaction regions. For some epochs the
temporal evolution of the signal suggests the rotation of the circumstellar
structures.Comment: Paper accepted in the A&A journa
Aeration strategies to improve nitrogen removal using deammonification process in EGSB reactor.
Anaerobic digestion technology for stabilization and organic matter removal from swine slurry is widely used and long known, but this method not degrades nitrogen compounds present in abundance in the digestate. So, deammonification is being studied as an alternative for post treatment. In this process, two groups of bacteria nitrifying bacteria (aerobic microorganisms) and anammox (anoxic microorganisms) have to cooperate to complete ammonia remove. In this process, the ammonia oxidation by partial nitrification (PN) generate substrate to anammox activity, so there must have PN control to prevent nitrite accumulation. This way making the dissolved oxygen (DO) supply an important key to control and stabilization process. The present study aimed to test the aeration effect on the nitrogen removal using deammonification process in an EGSB reactor. The results show the use of DO control to avoid nitrite accumulation in a deammonification single reactor is a good strategy to increase anammox activity
Dust reverberation-mapping of the Seyfert 1 galaxy WPVS48
Using robotic telescopes of the Universitatssternwarte Bochum near Cerro
Armazones in Chile, we monitored the z=0.0377 Seyfert 1 galaxy WPVS48 (2MASX
J09594263-3112581) in the optical (B and R) and near-infrared (NIR, J and Ks)
with a cadence of two days. The light curves show unprecedented variability
details. The NIR variation features of WPVS48 are consistent with the
corresponding optical variations, but the features appear sharper in the NIR
than in the optical, suggesting that the optical photons undergo multiple
scatterings. The J and Ks emission, tracing the hot (1600 K) dust echo, lags
the B and R variations by on average 64 +/- 4 days and 71 +/- 5 days,
respectively (restframe). WPVS48 lies on the known tau-M_V relationship.
However, the observed lag is about three times shorter than expected from the
dust sublimation radius r_sub inferred from the optical-UV luminosity, and
explanations for this common discrepancy are searched for. The sharp NIR echos
argue for a face-on torus geometry and allow us to put forward two potential
scenarios: 1) as previously proposed, in the equatorial plane of the accretion
disk the inner region of the torus is flattened and may come closer to the
accretion disk. 2) The dust torus with inner radius r_sub is geometrically and
optically thick, so that the observer only sees the facing rim of the torus
wall, which lies closer to the observer than the torus equatorial plane and
therefore leads to an observed foreshortened lag. Both scenarios are able to
explain the factor three discrepancy between tau and r_sub. Longer-wavelength
dust reverberation data might enable one to distinguish between the scenarios.Comment: 4 pages, 6 figures, Published in Astronomy and Astrophysic
Integrating physical and topographic information into a fuzzy scheme to map flooded area by SAR
A flood mapping procedure based on a fuzzy sets theory has been developed.
The method is based on the integration of Synthetic Aperture Radar (SAR) measurements
with additional data on the inundated area, such as a land cover map and a digital elevation
model (DEM). The information on land cover has allowed us to account for both specular
reflection, typical of open water, and double bounce backscattering, typical of forested and
urban areas. DEM has been exploited to include simple hydraulic considerations on the
dependence of inundation probability on surface characteristics. Contextual information
has been taken into account too. The proposed algorithm has been tested on a flood
occurred in Italy on November 1994. A pair of ERS-1 images, collected before and after
(three days later) the flood, has been used. The results have been compared with the data
provided by a ground survey carried out when the flood reached its maximum extension.
Despite the temporal mismatch between the survey and the post-inundation SAR image,
the comparison has yielded encouraging results, with the 87% of the pixels correctly
classified as inundated
Time-stepping approach for solving upper-bound problems: Application to two-dimensional Rayleigh-Benard convection
An alternative computational procedure for numerically solving a class of variational problems arising from rigorous upper-bound analysis of forced-dissipative infinite-dimensional nonlinear dynamical systems, including the Navier-Stokes and Oberbeck-Boussinesq equations, is analyzed and applied to Rayleigh-Benard convection. A proof that the only steady state to which this numerical algorithm can converge is the required global optimal of the relevant variational problem is given for three canonical flow configurations. In contrast with most other numerical schemes for computing the optimal bounds on transported quantities (e.g., heat or momentum) within the "background field" variational framework, which employ variants of Newton's method and hence require very accurate initial iterates, the new computational method is easy to implement and, crucially, does not require numerical continuation. The algorithm is used to determine the optimal background-method bound on the heat transport enhancement factor, i.e., the Nusselt number (Nu), as a function of the Rayleigh number (Ra), Prandtl number (Pr), and domain aspect ratio L in two-dimensional Rayleigh-Benard convection between stress-free isothermal boundaries (Rayleigh's original 1916 model of convection). The result of the computation is significant because analyses, laboratory experiments, and numerical simulations have suggested a range of exponents alpha and beta in the presumed Nu similar to (PrRa beta)-Ra-alpha scaling relation. The computations clearly show that for Ra <= 10(10) at fixed L = 2 root 2, Nu <= 0.106Pr(0)Ra(5/12), which indicates that molecular transport cannot generally be neglected in the "ultimate" high-Ra regime.NSF DMS-0928098 DMS-1515161 DMS-0927587 PHY-1205219Simons FoundationNSFONRInstitute for Computational Engineering and Sciences (ICES
A multiwavelength study of young massive star forming regions: II. The dust environment
We present observations of 1.2-mm dust continuum emission, made with the
Swedish ESO Submillimeter Telescope, towards eighteen luminous IRAS point
sources, all with colors typical of compact HII regions and associated with
CS(2-1) emission, thought to be representative of young massive star forming
regions. Emission was detected toward all the IRAS objects. We find that the
1.2-mm sources associated with them have distinct physical parameters, namely
sizes of 0.4 pc, dust temperatures of 30 K, masses of 2x10^3 Msun, column
densities of 3x10^23 cm^-2, and densities of 4x10^5 cm^-3. We refer to these
dust structures as massive and dense cores. Most of the 1.2-mm sources show
single-peaked structures, several of which exhibit a bright compact peak
surrounded by a weaker extended envelope. The observed radial intensity
profiles of sources with this type of morphology are well fitted with power-law
intensity profiles with power-law indices in the range 1.0-1.7. This result
indicates that massive and dense cores are centrally condensed, having radial
density profiles with power-law indices in the range 1.5-2.2. We also find that
the UC HII regions detected with ATCA towards the IRAS sources investigated
here (Paper I) are usually projected at the peak position of the 1.2-mm dust
continuum emission, suggesting that massive stars are formed at the center of
the centrally condensed massive and dense cores.Comment: 6 figures, accepted by Ap
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