The BLAST Survey of the Vela Molecular Cloud: Dynamical Properties of the Dense Cores in Vela-D

The Vela-D region, according to the nomenclature given by Murphy & May (1991), of the star forming complex known as the Vela Molecular Ridge (VMR), has been recently analyzed in details by Olmi et al. (2009), who studied the physical properties of 141 pre- and proto-stellar cold dust cores, detected by the ``Balloon-borne Large-Aperture Submillimeter Telescope'' (BLAST) during a much larger (55 sq. degree) Galactic Plane survey encompassing the whole VMR. This survey's primary goal was to identify the coldest, dense dust cores possibly associated with the earliest phases of star formation. In this work, the dynamical state of the Vela-D cores is analyzed. Comparison to dynamical masses of a sub-sample of the Vela-D cores estimated from the 13CO survey of Elia et al. (2007), is complicated by the fact that the 13CO linewidths are likely to trace the lower density intercore material, in addition to the dense gas associated with the compact cores observed by BLAST. In fact, the total internal pressure of these cores, if estimated using the 13CO linewidths, appears to be higher than the cloud ambient pressure. If this were the case, then self-gravity and surface pressure would be insufficient to bind these cores and an additional source of external confinement (e.g., magnetic field pressure) would be required. However, if one attempts to scale down the 13CO linewidths, according to the observations of high-density tracers in a small sample of sources, then most proto-stellar cores would result effectively gravitationally bound.Comment: This paper has 12 pages and 6 figures. Accepted for publication by the Astrophysical Journal on July 19, 201

Lake Afrera, a structural depression in the Northern Afar Rift (Red Sea)

The boundary between the African and Arabian plates in the Southern Red Sea region is displaced inland in the northern Afar rift, where it is marked by the Red Sea-parallel Erta Ale, Alaita, and Tat Ali volcanic ridges. The Erta Ale is offset by about 20 and 40 km from the two en echelon ridges to the south. The offset area is highly seismic and marked by a depression filled by lake Afrera, a saline body of water fed by hydrothermal springs. Acoustic bathymetric profiles show ≈80 m deep canyons parallel to the NNW shore of the lake, part of a system of extensional normal faults striking parallel to the Red Sea. This system is intersected by oblique structures, some with strike-slip earthquakes, in what might evolve into a transform boundary. Given that the lake’s surface lies today about 112 m below sea level, the depressed (minus ≈190 m below sea level) lake’s bottom area may be considered the equivalent of the “nodal deep” in slow-slip oceanic transforms. The chemistry of the lake is compatible with the water having originated from hydrothermal liquids that had reacted with evaporites and basalts, rather than residual from evaporation of sea water. Bottom sediments include calcitic grains, halite and gypsum, as well as ostracod and diatom tests. The lake’s level appears to have dropped by over 10 m during the last ≈50 years, continuing a drying up trend of the last few thousand years, after a “wet” stage 9,800 and 7,800 years before present when according to Gasse (1973) Lake Afrera covered an area several times larger than at present. This “wet” stage corresponds to an early Holocene warm-humid climate that prevailed in Saharan and Sub Saharan Africa. Lake Abhé, located roughly 250 km south of Afrera, shows similar climate-driven oscillations of its level

Effect of dietary fat level on carcass traits and flesh quality of European Sea Bass (Dicentrarchus labrax) from mariculture

The study aimed at evaluating the effect of the reduction of dietary fat on juvenile European sea bass nutritional value and quality traits. Fish were reared in floating cages (Trieste Gulf, Italy) from July (11) to October (10). Two isoproteic diets were compared: LF (low fat, EE = 19.4%) vs. HF (high fat, EE = 24.6%). No significantly different growth performance was observed. LF diet-fed fish were characterized by the reduction of celomatic fat (not edible fraction) and by the increase in dressing percentage. The tested dietary fat level also affected both fillet and epiaxial white muscle proximate composition, resulting in a significantly lower fillet lipid concentration in LF diet-fed fish. Dietary treatment influenced cooked fillet colour and texture probably as a consequence of the different intramuscular fat deposition. Fillet from HF-fed fish, in fact, presented higher lightness (L*) value and lower instrumental strengthness

WITHDRAWN: Experimental evidence of the wind-induced bias of precipitation gauges using Particle Image Velocimetry and particle tracking in the wind tunnel

n/

Comparative Proteomic Profiling of Divergent Phenotypes for Water Holding Capacity across the Post Mortem Ageing Period in Porcine Muscle Exudate

peer-reviewedTwo dimensional Difference Gel Electrophoresis (2-D DIGE) and mass spectrometry were applied to investigate the changes in metabolic proteins that occur over a seven day (day 1, 3 and 7) post mortem ageing period in porcine centrifugal exudate from divergent meat quality phenotypes. The objectives of the research were to enhance our understanding of the phenotype (water holding capacity) and search for biomarkers of this economically significant pork quality attribute. Major changes in protein abundance across nine phenotype-by-time conditions were observed. Proteomic patterns were dominated by post mortem ageing timepoint. Using a machine learning algorithm (l1-regularized logistic regression), a model was derived with the ability to discriminate between high drip and low drip phenotypes using a subset of 25 proteins with an accuracy of 63%. Models discriminating between divergent phenotypes with accuracy of 72% and 73% were also derived comparing respectively, high drip plus intermediate phenotype (considered as one phenotype) versus low drip and comparing low drip plus intermediate phenotype (considered as one phenotype) versus high drip. In all comparisons, the general classes of discriminatory proteins identified include metabolic enzymes, stress response, transport and structural proteins. In this research we have enhanced our understanding of the protein related processes underpinning this phenotype and provided strong data to work toward development of protein biomarkers for water holding capacity.This research was funded through the Irish National Development Plan through the Food Institutional Research Measure of the Department of Food Agriculture and the Marine, Project 06RDNUIG470

Spitzer-IRAC survey of molecular jets in Vela-D

We present a survey of H2 jets from young protostars in the Vela-D molecular cloud (VMR-D), based on Spitzer -IRAC data between 3.6 and 8.0 micron. Our search has led to the identification of 15 jets and about 70 well aligned knots within 1.2 squared degree. We compare the IRAC maps with observations of the H2 1-0 S(1) line at 2.12 micron, with a Spitzer-MIPS map at 24 and 70 micron, and with a map of the dust continuum emission at 1.2 mm. We find a association between molecular jets and dust peaks. The jet candidate exciting sources have been searched for in the published catalog of the Young Stellar Objects of VMR-D. We selected all the sources of Class II or earlier which are located close to the jet center and aligned with it.The association between jet and exciting source was validated by estimating the differential extinction between the jet opposite lobes. We are able to find a best-candidate exciting source in all but two jets. Four exciting sources are not (or very barely) observed at wavelengths shorter than 24 micron, suggesting they are very young protostars. Three of them are also associated with the most compact jets. The exciting source Spectral Energy Distributions have been modeled by means of the photometric data between 1.2 micron and 1.2 mm. From SEDs fits we derive the main source parameters, which indicate that most of them are low-mass protostars. A significant correlation is found between the projected jet length and the [24] - [70] color, which is consistent with an evolutionary scenario according to which shorter jets are associated with younger sources. A rough correlation is found between IRAC line cooling and exciting source bolometric luminosity, in agreement with the previous literature. The emerging trend suggests that mass loss and mass accretion are tightly related phenomena and that both decrease with time.Comment: Accepted by The Astrophysical Journa

The Spitzer-IRAC Point Source Catalog of the Vela-D Cloud

This paper presents the observations of the Cloud D in the Vela Molecular Ridge, obtained with the IRAC camera onboard the Spitzer Space Telescope at the wavelengths \lambda = 3.6, 4.5, 5.8, 8.0 {\mu}m. A photometric catalog of point sources, covering a field of approximately 1.2 square degrees, has been extracted and complemented with additional available observational data in the millimeter region. Previous observations of the same region, obtained with the Spitzer MIPS camera in the photometric bands at 24 {\mu}m and 70 {\mu}m, have also been reconsidered to allow an estimate of the spectral slope of the sources in a wider spectral range. A total of 170,299 point sources, detected at the 5-sigma sensitivity level in at least one of the IRAC bands, have been reported in the catalog. There were 8796 sources for which good quality photometry was obtained in all four IRAC bands. For this sample, a preliminary characterization of the young stellar population based on the determination of spectral slope is discussed; combining this with diagnostics in the color-magnitude and color-color diagrams, the relative population of young stellar objects in the different evolutionary classes has been estimated and a total of 637 candidate YSOs have been selected. The main differences in their relative abundances have been highlighted and a brief account for their spatial distribution is given. The star formation rate has been also estimated and compared with the values derived for other star forming regions. Finally, an analysis of the spatial distribution of the sources by means of the two-point correlation function shows that the younger population, constituted by the Class I and flat-spectrum sources, is significantly more clustered than the Class II and III sources.Comment: Accepted by Ap

Near- and Far-Infrared Counterparts of Millimeter Dust Cores in the Vela Molecular Ridge Cloud D

The aim of this paper is to identify the young protostellar counterparts associated to dust millimeter cores of the Vela Molecular Ridge Cloud D through new IR observations (H_2 narrow-band at 2.12 micron and N broad band at 10.4 micron) along with an investigation performed on the existing IR catalogues. The association of mm continuum emission with infrared sources from catalogues (IRAS, MSX, 2MASS), JHK data from the literature and new observations, has been established according to spatial coincidence, infrared colours and spectral energy distributions. Only 7 out of 29 resolved mm cores (and 16 out of the 26 unresolved ones) do not exhibit signposts of star formation activity. The other ones are clearly associated with: far-IR sources, H_2 jets or near-IR objects showing a high intrinsic colour excess. The distribution of the spectral indices pertaining to the associated sources is peaked at values typical of Class I objects, while three objects are signalled as candidates Class 0 sources. We remark the high detection rate (30%) of H_2 jets driven by sources located inside the mm-cores. They appear not driven by the most luminous objects in the field, but rather by less luminous objects in young clusters, testifying the co-existence of both low- and intermediate-mass star formation. The presented results reliably describe the young population of VMR-D. However, the statistical evaluation of activity vs inactivity of the investigated cores, even in good agreement with results found for other star forming regions, seems to reflect the limiting sensitivity of the available facilities rather than any property intrinsic to the mm-condensations.Comment: 38 pages. To be published to Astronomy & Astrophysic

Pre-Main Sequence variables in the VMR-D : identification of T Tauri-like accreting protostars through Spitzer-IRAC variability

We present a study of the infrared variability of young stellar objects by means of two Spitzer-IRAC images of the Vela Molecular Cloud D (VMR-D) obtained in observations separated in time by about six months. By using the same space-born IR instrumentation, this study eliminates all the unwanted effects usually unavoidable when comparing catalogs obtained from different instruments. The VMR-D map covers about 1.5 square deg. of a site where star formation is actively ongoing. We are interested in accreting pre-main sequence variables whose luminosity variations are due to intermittent events of disk accretion (i.e. active T Tauri stars and EXor type objects). The variable objects have been selected from a catalog of more than 170,000 sources detected at a S/N ratio > 5. We searched the sample of variables for ones whose photometric properties are close to those of known EXor's. These latter are monitored in a more systematic way than T Tauri stars and the mechanisms that regulate the observed phenomenology are exactly the same. Hence the modalities of the EXor behavior is adopted as driving criterium for selecting variables in general. We selected 19 bona fide candidates that constitute a well-defined sample of new variable targets for further investigation. Out of these, 10 sources present a Spitzer MIPS 24 micron counterpart, and have been classified as 3 Class I, 5 flat spectrum and 2 Class II objects, while the other 9 sources have spectral energy distribution compatible with phases older than Class I. This is consistent with what is known about the small sample of known EXor's, and suggests that the accretion flaring or EXor stage might come as a Class I/II transition. We present also new prescriptions that can be useful in future searches for accretion variables in large IR databases.Comment: 35 pages, 12 figures To appear in Ap