12,634 research outputs found
OmegaWINGS: OmegaCAM@VST observations of WINGS galaxy clusters
The Wide-field Nearby Galaxy-cluster Survey (WINGS) is a wide-field
multi-wavelength survey of X-ray selected clusters at z =0.04-0.07. The
original 34'x34' WINGS field-of- view has now been extended to cover a 1 sq.deg
field with both photometry and spectroscopy. In this paper we present the
Johnson B and V-band OmegaCAM/VST observations of 46 WINGS clusters, together
with the data reduction, data quality and Sextractor photometric catalogs.
With a median seeing of 1arcs in both bands, our 25-minutes exposures in each
band typically reach the 50% completeness level at V=23.1 mag. The quality of
the astrometric and photometric accuracy has been verified by comparison with
the 2MASS as well as with SDSS astrometry, and SDSS and previous WINGS imaging.
Star/galaxy separation and sky-subtraction procedure have been tested comparing
with previous WINGS data.
The Sextractor photometric catalogues are publicly available at the CDS, and
will be included in the next release of the WINGS database on the VO together
with the OmegaCAM reduced images. These data form the basis for a large ongoing
spectroscopic campaign with AAOmega/AAT and is being employed for a variety of
studies. [abridged]Comment: submitted to A&
High-resolution polarimetry of Parsamian 21: revealing the structure of an edge-on FU Ori disc
We present the first high spatial resolution near-infrared direct and
polarimetric observations of Parsamian 21, obtained with the VLT/NACO
instrument. We complemented these measurements with archival infrared
observations, such as HST/WFPC2 imaging, HST/NICMOS polarimetry, Spitzer IRAC
and MIPS photometry, Spitzer IRS spectroscopy as well as ISO photometry. Our
main conclusions are the following: (1) we argue that Parsamian 21 is probably
an FU Orionis-type object; (2) Parsamian 21 is not associated with any rich
cluster of young stars; (3) our measurements reveal a circumstellar envelope, a
polar cavity and an edge-on disc; the disc seems to be geometrically flat and
extends from approximately 48 to 360 AU from the star; (4) the SED can be
reproduced with a simple model of a circumstellar disc and an envelope; (5)
within the framework of an evolutionary sequence of FUors proposed by Green et
al. (2006) and Quanz et al. (2007), Parsamian 21 can be classified as an
intermediate-aged object.Comment: Accepted for publication in the MNRAS. 16 pages, 18 figures and 5
table
Current methods for characterising mixing and flow in microchannels
This article reviews existing methods for the characterisation of mixing and flow in microchannels, micromixers and microreactors. In particular, it analyses the current experimental techniques and methods available for characterising mixing and the associated phenomena in single and multiphase flow. The review shows that the majority of the experimental techniques used for characterising mixing and two-phase flow in microchannels employ optical methods, which require optical access to the flow, or off-line measurements. Indeed visual measurements are very important for the fundamental understanding of the physics of these flows and the rapid advances in optical measurement techniques, like confocal scanning laser microscopy and high resolution stereo micro particle image velocimetry, are now making full field data retrieval possible. However, integration of microchannel devices in industrial processes will require on-line measurements for process control that do not necessarily rely on optical techniques. Developments are being made in the areas of non-intrusive sensors, magnetic resonance techniques, ultrasonic spectroscopy and on-line flow through measurement cells. The advances made in these areas will certainly be of increasing interest in the future as microchannels are more frequently employed in continuous flow equipment for industrial applications
Studying the galactic outflow in NGC 1569
We present deep WIYN H-alpha imaging of the dwarf irregular starburst galaxy
NGC 1569, together with WIYN SparsePak spatially-resolved optical spectroscopy
of the galactic outflow. This leads on from our previous detailed analyses of
the state of the ISM in the central regions of this galaxy. Our deep imaging
reveals previously undetected ionized filaments in the outer halo. Through
combining these results with our spectroscopy we have been able to re-define
the spatial extent of the previously catalogued superbubbles, and derive
estimates for their expansion velocities, which we find to be in the range
50-100 km/s. The implied dynamical ages of <25 Myr are consistent with the
recent star- and cluster-formation histories of the galaxy. Detailed
decomposition of the multi-component H-alpha line has shown that within a
distinct region ~700x500 pc in size, roughly centred on the bright super star
cluster A, the profile is composed of a bright, narrow (FWHM <= 70 km/s)
feature with an underlying, broad component (FWHM ~ 150 km/s). Applying the
conclusions found in our previous work regarding the mechanism through which
the broad component is produced, we associate the faint, broad emission with
the interaction of the hot, fast-flowing winds from the young star clusters
with cool clumps of ISM material. This interaction generates turbulent mixing
layers on the surface of the clouds and the evaporation and/or ablation of
material into the outflow. Under this interpretation, the extent of the broad
component region may indicate an important transition point in the outflow,
where ordered expansion begins to dominate over turbulent motion. In this
context, we present a multi-wavelength discussion of the evolutionary state of
the outflow.Comment: 17 pages, 12 figures, 2 tables, accepted for publication in MNRA
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
SusOrganic - Development of quality standards and optimised processing methods for organic produce - Final report
The SusOrganic project aimed to develop improved drying and cooling/freezing processes for organic products in terms of sustainability and objective product quality criteria. Initially, the consortium focused on a predefined set products to investigate (fish, meat, fruits and vegetables). Contacting participants in the fruit and vegetable sector showed that there is only little perceived need for making changes for the improvement of the processes. At the same time, it became clear that hops and herb producers (drying) face several challenges in terms of product quality and cost of drying processes. Therefore, the range of products was extended to these products. The results of a consumer survey conducted as part the project showed clearly that consumers trust in the organic label, but also tend to mix up the term organic with regional or fair trade. Further, the primary production on farm and not the processing is explicitly included in the consumers’ evaluation of sustainability. Appearance of organic products was found to be one of the least important quality criteria or attributes regarding buying decisions. However, there are indications that an imperfect appearance could be a quality attribute for consumers, as the product then is perceived to be processed without artificial additives. Regarding drying operations, small scale producers in the organic sector often work with old and/or modified techniques and technologies, which often leads to an inefficient drying processes due to high energy consumptions and decreased product quality. Inappropriate air volume flow and distribution often cause inefficient removal of the moisture from the product and heterogeneous drying throughout the bulk. Guidelines for improvement of the physical setup of existing driers as well as designs for new drying operations, including novel drying strategies were developed. Besides chilling and freezing, the innovative idea of superchilling was included into the project.The superchilled cold chain is only a few degrees colder than the refrigeration chain but has a significant impact on the preservation characteristic due to shock frosting of the outer layer of the product and the further distribution of very small ice crystals throughout the product during storage. Superchilling of organically grown salmon eliminated the demand of ice for transport, resulting in both, a reduction of energy costs and a better value chain performance in terms of carbon foot printing. This is mainly due to the significantly reduced transport volume and weight without the presence of ice. The product quality is not different but the shelf life is extended compared to chilled fish. This means that the high quality of organic salmon can be maintained over a longer time period, which can be helpful,e.g. to reach far distant markets. The same trend was found for superchilled organic meat products such as pork and chicken. The consortium also developed innovative noninvasive measurement and control systems and improved drying strategies and systems for fruits, vegetables, herbs, hops and meat. Those systems are based on changes occurring inside the product and therefore require observation strategies of the product during the drying process. Through auditing campaigns as well as pilot scale drying tests it has been possible to develop optimisation strategies for both herb and hops commodities, which can help reduce microbial spoilage and retain higher levels of volatile product components whilst reducing the energy demands. These results can be applied with modifications to the other commodities under investigation. The environmental and cost performance of superchilling of salmon and drying of meat, fruit and vegetables were also investigated and the findings indicated that both superchilling and drying could improve sustainability of organic food value chains especially in case of far distant markets. An additional outcome of the project, beyond the original scope was the development of a noninvasive, visual sensor based detection system for authenticity checks of meat products in terms of fresh and prefrozen meats
Stellar populations -- the next ten years
The study of stellar populations is a discipline that is highly dependent on
both imaging and spectroscopy. I discuss techniques in different regimes of
resolving power: broadband imaging (R~4), intermediate band imaging (R~16, 64),
narrowband spectral imaging (R~256, 1024, 4096). In recent years, we have seen
major advances in broadband all-sky surveys that are set to continue across
optical and IR bands, with the added benefit of the time domain, higher
sensitivity, and improved photometric accuracy. Tunable filters and integral
field spectrographs are poised to make further inroads into intermediate and
narrowband imaging studies of stellar populations. Further advances will come
from AO-assisted imaging and imaging spectroscopy, although photometric
accuracy will be challenging. Integral field spectroscopy will continue to have
a major impact on future stellar population studies, extending into the near
infrared once the OH suppression problem is finally resolved. A sky rendered
dark will allow a host of new ideas to be explored, and old ideas to be
revisited.Comment: Invited review, IAUS 241, "Stellar Populations as Building Blocks of
Galaxies," eds. Vazdekis, Peletier. 12 pages, 1 table. (The sideways table
should print ok; there are 10 columns.
IP Pegasi in outburst: Echelle spectroscopy & Modulation Doppler Tomography
We analyse a unique set of time-resolved echelle spectra of the dwarf nova IP
Peg, obtained at ESO's NTT with EMMI. The dataset covers the wavelength range
of 4000-7500A and shows Balmer, HeI, HeII and heavier elements in emission. IP
Peg was observed one day after the peak of an outburst. The trailed spectra,
spectrograms and Doppler maps show characteristics typical of IP Pegasi during
the early stages of its outburst. The high-ionisation line of HeII 4686A is the
most centrally located line and has the greatest radial extension compared to
the HeI lines. The Balmer lines extend from close to the white dwarf up to
approximately 0.45 times R_L, with the outer radius gradually increasing when
moving from H delta to H alpha. The application, for the first time, of the
modulation Doppler tomography technique, maps any harmonically varying
components present in the system configuration. We find, as expected, that part
of the strong secondary star emission in Balmer and HeI lines is modulated
predominantly with the cosine term, consistent with the emission originating
from the irradiated front side of the mass-donor star, facing the accreting
white dwarf. For the Balmer lines the level of the modulation, compared to the
average emission, decreases when moving to higher series. Emission from the
extended accretion disk appears to be only weakly modulated, with amplitudes of
at most a few percent of the non-varying disk emission. We find no evidence of
modulated emission in the spiral arms, which if present, is relatively weak at
that our signal-to-noise ratio was good enough to put a lower detection limit
of any modulated emission at 5--6%. Only in one arm of the HeII 4686A line, is
there a possibility of modulated emission, but again, we cannot be sure this is
not caused by blending with the nearby Bowen complex of lines.Comment: 20 pages, 8 figures, submitted to Journal of Astronomical Dat
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