The pre-ZAMS nature of Mol160/IRAS23385+6053 confirmed by Spitzer

Determining the timeline for the formation of massive YSOs requires the identification and characterisation of all the phases that a massive forming YSO undergoes. It is of particular interest to verify the observability of the phase in which the object is rapidly accreting while not yet igniting the fusion of hydrogen that marks the arrival on the ZAMS. One of the candidate prototypical objects for this phase is Mol160/IRAS23385+6053, which previous studies suggest it could be in a pre-Hot Core stage. We further investigate this issue by means of Spitzer imaging and spectroscopy in the 5-70 micron range. The dense core of Mol160/IRAS23385+6053, which up to now had only been detected at submm and mm wavelenghts has been revealed for the first time at 24 and 70 micron by Spitzer. The complete 24 micron -3.4 mm continuum cannot be fitted with a standard model of a Zero-Age Main-Sequence (ZAMS) star embedded in an envelope. A simple greybody fit yields a mass of 220 solar masses. The luminosity is slightly in excess of 3000 solar luminosities, which is a factor of 5 less than previous estimates when only IRAS fluxes were available between 20 and 100 micron. The source is under-luminous by the same factor with respect to UCHII regions or Hot-Cores of similar circumstellar mass, and simple models show that this is compatible with an earlier evolutionary stage. Spectroscopy between 5 and 40 microns revelas typical PDR/PIR conditions, where the required UV illumination may be provided by other sources revealed at 24 microns in the same region, and which can be plausibly modeled as moderately embedded intermediate-mass ZAMS stars. Our results strengthen the suggestion that the central core in Mol160/IRAS23385+6053 is a massive YSO actively accreting from its circumstellar envelope and which did not yet begin hydrogen fusion.Comment: Accepted by A&

IRAS 23385+6053: a candidate protostellar massive object

We present the results of a multi-line and continuum study towards the source IRAS 23385+6053,performed with the IRAM-30m telescope, the Plateau de Bure Interferometer, the Very Large Array Interferometer and the James Clerk Maxwell Telescope. The new results confirm our earlier findings, namely that IRAS 23385+6053 is a good candidate high-mass protostellar object, precursor of an ultracompact H$_{II}$ region. The source is roughly composed of two regions: a molecular core $\sim0.03\div0.04$ pc in size, with a temperature of $\sim40$ K and an H$_{2}$ volume density of the order of 10$^{7}$ cm$^{-3}$, and an extended halo of diameter $\leq$0.4 pc, with an average kinetic temperature of $\sim 15$ K and H$_{2}$ volume density of the order of 10$^{5}$ cm$^{-3}$. The core temperature is much smaller than what is typically found in molecular cores of the same diameter surrounding massive ZAMS stars. We deduce that the core luminosity is between 150 and $1.6\times10^{4}L_{\odot}$, and we believe that the upper limit is near the ``true'' source luminosity. Moreover, by comparing the H$_{2}$ volume density obtained at different radii from the IRAS source, we find that the halo has a density profile of the type $n_{\rm H_{2}}\propto r^{-2.3}$. This suggests that the source is gravitationally unstable. Finally, we demonstrate that the temperature at the core surface is consistent with a core luminosity of $10^3 L_{\odot}$ and conclude that we might be observing a protostar still accreting material from its parental cloud, whose mass at present is $\sim 6 M_{\odot}$.Comment: 18 pages, 20 figure

Search for massive protostellar candidates in the southern hemisphere: I. Association with dense gas

(Abridged) We have observed CS and C17O lines, and 1.2 mm cont. emission towards a sample of 130 high-mass protostellar candidates with DEC<-30 deg. This is the first step of the southern extension of a project started more than a decade ago aimed at the identification of massive protostellar candidates. We selected from the IRAS PSC 429 sources which potentially are compact molecular clouds. The sample is divided into two groups: the 298 sources with [25-12]>0.57 and [60-12]>1.30 we call 'High' sources, the remaining 131 we call 'Low' sources. In this paper, we check the association with dense gas and dust in 130 'Low' sources. We find a detection rate of ca. 85% in CS, demonstrating a tight association with dense molecular clumps. Among the sources detected in CS, ca. 76% have also been detected in C17O and ca. 93% in the 1.2 mm cont. Mm-cont. maps show the presence of clumps with diameters 0.2-2 pc and masses from a few Msun to 10^5 Msun; H2 volume densities lie between ca. 10^{4.5} and 10^{5.5} cm^{-3}. The L(bol) are 10^3-10^6 Lsun, consistent with embedded high-mass objects. Based on our results and those found in the literature for other samples, we conclude that our sources are massive objects probably in a stage prior to the formation of an HII region. We propose a scenario in which 'High' and 'Low' sources are both made of a massive clump hosting a high-mass protostellar candidate and a nearby stellar cluster. The difference might be due to the fact that the IRAS 12mu flux, the best discriminant between the two groups, is dominated by the emission from the cluster in 'Lows' and from the massive protostellar object in 'Highs'.Comment: Accepted for publication in Astron. & Astroph.; 34 pages (incl. 14 figures and 8 tables

Effects of Chia Seed Supplementation on Biochemical Markers of Cardiometabolic Diseases in Spontaneously Hypertensive Rats

Some studies suggested a positive effect against cardiometabolic diseases of supplementation of alpha-linolenic acid (ALA, C18:3 n-3) rich foods in pathological subjects, even if the total literature is controversial. In order to clarify ALA-rich chia seed action in hypertensive model with the overt pathology and without drug interference, in the present study the biochemical markers of cardiometabolic diseases (endothelin-1, ET-1; nitric oxide, NO; and bradykinin, BK) in Spontaneously Hypertensive Rats (SHRs) were analysed after 5% chia seed dietary supplementation for five weeks, and compared with the staple raw material wheat and corn. At the end of the experimental period, also plasma antioxidant capacity and inflammatory condition were evaluated. Our results showed that the chia seed group was more oxidized. On the other hand, ET-1 significantly decreased in chia seed group, and there was no difference between groups for NO, BK, and the inflammatory C-reactive protein (CRP). In conclusion, some positive effects of chia seed consumption on cardiometabolic markers in SHRs were observed, despite this the association of chia seeds with antioxidants is suggested to avoid plasma oxidation increase

C3N4 for CO2 photoreduction: catalyst performance and stability in batch and continuous reactor

In this study, various C3N4 samples were prepared and characterized. CO2 photoreduction was carried out by using C3N4 as powder and coated on glass support in a batch reactor or embedded in a Nafion membrane in a continuous reacto

Connecting scaling with short-range correlations

We reexamine several issues related to the physics of scaling in electron scattering from nuclei. A basic model is presented in which an assumed form for the momentum distribution having both long- and short-range contributions is incorporated in the single-particle Green function. From this one can obtain saturation of nuclear matter for an NN interaction with medium-range attraction and short-range repulsion, and can obtain the density-density polarization propagator and hence the electromagnetic response and scaling function. For the latter, the shape of the scaling function and how it approaches scaling as a function of momentum transfer are both explored.Comment: 24 pages, 15 figures. A reference has been corrected and update

Two massive star-forming regions at early evolutionary stages

We report sensitive ATCA radio-continuum observations toward IRAS 15596-5301 and 16272-4837, two luminous objects (> 2x10^4 Lsun) thought to represent massive star-forming regions in early stages of evolution (due to previously undetected radio emission at the 1-sigma level of 2 mJy per beam). Also reported are 1.2-millimeter continuum and a series of molecular-line observations made with the SEST telescope. For IRAS 15596-5301, the observations reveal the presence of three distinct compact radio-continuum sources associated with a dense molecular core. We suggest that this core contains a cluster of B stars which are exciting compact HII regions that are in pressure equilibrium with the dense molecular surroundings. No radio continuum emission was detected from IRAS 16272-4837 (3-sigma limit of 0.2 mJy). However, a dense molecular core has been detected. The high luminosity and lack of radio emission from this massive core suggests that it hosts an embedded young massive protostar that is still undergoing an intense accretion phase. This scenario is supported by the observed characteristics of the line profiles and the presence of a bipolar outflow detected from observations of the SiO emission. We suggest that IRAS 16272-4837 is a bona fide massive star- forming region in a very early evolutionary stage, being the precursor of an ultra compact HII region.Comment: 25 pages, 9 figures, accepted for publication in The Astrophysical Journa

Virtual Photon Contribution to Frictional Drag in double-layer Devices

The first order contribution to frictional drag in bi-layered fermion gas is examined. We discuss the relevance of single photon exchange in the evaluation of transresistance, which is usually explained by second order effects such as Coulomb and phonon drag. Since the effective e.m. interaction is unscreened, in the d.c. limit we obtain a finite (and large) contribution to transconductivity.Comment: 13 pages, 1 figur