In this paper we analyse the evolutionary status of three open clusters: NGC 1817, NGC 2141 and Berkeley 81. They are all of intermediate age, two are located in the Galactic anticentre direction ...while the third one is located in the Galactic Centre direction. All of them were observed with Large Binocular Camera at Large Binocular Telescope using the Bessel B, V and I filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram (CMD) method, i.e. the direct comparison of the observational CMDs with a library of synthetic CMDs generated with different evolutionary sets (Padova, FRANEC and FST). This analysis shows that NGC 1817 has subsolar metallicity, age between 0.8 and 1.2 Gyr, reddening E(B − V) in the range 0.21 and 0.34 and distance modulus (m − M)0 of about 10.9; NGC 2141 is older, with age in the range 1.25 and 1.9 Gyr, E(B − V) between 0.36 and 0.45, (m − M)0 between 11.95 and 12.21 and subsolar metallicity; Berkeley 81 has metallicity about solar, with age between 0.75 and 1.0 Gyr, has reddening E(B − V) ∼ 0.90 and distance modulus (m − M)0 ∼ 12.4. Exploiting the large field of view of the instrument we derive the structure parameters for NGC 2141 and Berkeley 81 by fitting a King profile to the estimated density profile. Combining this information with the synthetic CMD technique we estimate a lower limit for the cluster total mass for these two systems.
Following inoculation of the base of soft wheat seedlings with Fusarium culmorum, disease symptoms typical of crown rot developed at the stem base and extended up to the third node by plant maturity. ...Fungus was isolated from all tissues exhibiting symptoms but not from symptomless tissues. Histopathological analysis revealed that the fungus was present mainly in the parenchymatic cells of the stem base and colonized the tissues via apoplastic and symplastic pathways. Host response in advance of pathogen colonization was observed. At maturity, plants were divided into sections from the inoculated area to the head. Heads were also separated into grain, rachis and chaff components. Colonization by the fungus was assessed by isolation from surface‐sterilized segments and quantified by real‐time PCR. Disease symptoms and the fungus were detected up to the third node, while deoxynivalenol (DON) was present in all stem segments and heads. Within the head, the DON concentration was higher in the rachis than in the chaff and grain components. These results demonstrate that F. culmorum can extensively colonize stem tissues but not reach the head by the time of plant maturity. In contrast, DON was detected in tissues beyond those colonized by the fungus, translocating to the head where, although accumulating mainly in the rachis, significant quantities accumulated in the grain. These findings indicate that there is a potential threat of contamination of grain with DON where severe crown rot is present in a crop.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Contamination of wheat grain by beauvericin (BEA) and enniatins (ENs) is a global emerging mycotoxicological food problem. In this study, strains of Fusarium avenaceum (FA), Fusarium poae (FP), ...Fusarium equiseti and Fusarium sporotrichioides, all potential BEA and EN producers, isolated from 162 grain samples of durum and soft wheat harvested in 2009 and 2010 collected in an area of central Italy, were preliminarily screened for the presence of the esyn1 gene, encoding the multifunctional enzyme enniatin-synthetase for the detection of potential hexadepsipeptide-producing isolates. All positive isolates were tested for their ability to biosynthesize BEA and ENs in vitro. In addition, all wheat samples were investigated for the natural presence of BEA and ENs (ENA, ENA1, ENB, ENB1). All FA and FP strains resulted to be positive for the presence of the esyn1 gene. All FA strains showed the ability to biosynthesize ENs in vitro but not BEA. Conversely, all FP strains resulted to be BEA producers and some of them co-biosynthesized ENs. A remarkable presence of “emerging” mycotoxins was found in the grains, particularly ENs. Co-contamination by BEA and ENs also occurred. This study gives an important contribution to assess the risk posed by mycotoxigenic fungi and their mycotoxins in food.
•Esyn1 gene presence in Fusarium avenaceum and Fusarium poae indicates them as BEA and EN producers.•F. avenaceum strains showed the ability to biosynthesize ENs in vitro.•F. poae strains were able to produce BEA in vitro.•BEA and EN contaminations were detected in the analyzed wheat grain samples.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We used deep observations collected with Advanced Camera for Surveys (ACS) at Hubble Space Telescope (HST) to derive the fraction of binary systems in a sample of 13 low-density Galactic globular ...clusters. By analysing the colour distribution of main-sequence stars we derived the minimum fraction of binary systems required to reproduce the observed colour–magnitude diagram morphologies. We found that all the analysed globular clusters contain a minimum binary fraction larger than 6 per cent within the core radius. The estimated global fractions of binary systems range from 10 to 50 per cent depending on the cluster. A dependence of the relative fraction of binary systems on the cluster age has been detected, suggesting that the binary disruption process within the cluster core is active and can significantly reduce the binary content in time.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
We present an imaging survey that searches for the stellar counterparts of recently discovered ultra-compact high-velocity H I clouds (UCHVC). It has been proposed that these clouds are candidate ...mini-haloes in the Local Group and its surroundings within a distance range of 0.25-2.0 Mpc. Using the Large Binocular Telescope we obtained wide-field g- and r-band images of the twenty-five most promising and most compact clouds amongst the fifty-nine that have been identified. Sensitivity tests show that our survey would have detected any dwarf galaxy dominated by an old stellar population, with an integrated absolute magnitude of MsubV < or = - 8.0 and a half-light radius of rsubh < or = 300 pc that lies within 1.5 Mpc of us, thereby confirming that it is unlikely that the observed UCHVCs are associated with the stellar counterparts typical of known Local Group dwarf galaxies.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
The searching for StEllar Counterparts of COmpact high velocity clouds (SECCO) survey is devoted to the search for stellar counterparts within ultra compact high velocity clouds that are candidate ...low-mass, low-luminosity galaxies. We present the results of a set of simulations aimed at the quantitative estimate of the sensitivity of the survey as a function of the total luminosity, size, and distance of the stellar systems we are looking for. For all of our synthetic galaxies we assumed an exponential surface brightness profile and an old and metal-poor population. The synthetic galaxies are simulated both on the images and on the photometric catalogues, taking all the observational effects into account. In the fields where the available observational material is of top quality (=36% of the SECCO fields), we detect synthetic galaxies as > or =5sigma over-densities of resolved stars down to muV, h= 30.0 mag/arcsec super(2), for D< or = 1.5 Mpc, and down to muV, h= 29.5 mag/arcsec super(2), for D< or = 2.5 Mpc. In the field with the worst observational material of the whole survey, we detect synthetic galaxies with muV, h< or = 28.8 mag/arcsec super(2) out to D< or = 1.0 Mpc, and those with muV, h< or = 27.5 mag/arcsec super(2) out to D< or = 2.5 Mpc. Dwarf galaxies with MV= -10.0, with sizes in the range spanned by known dwarfs, are detected by visual inspection of the images up to D= 5 Mpc independent of the image quality. In the best quality images, dwarfs are partially resolved into stars up to D= 3.0 Mpc and completely unresolved at D= 5 Mpc. As an independent test of the sensitivity of our images to low surface brightness galaxies, we report on the detection of several dwarf spheroidal galaxies probably located in the Virgo cluster with MV< or = -8.0 and muV, h< or = 26.8 mag/arcsec super(2). The nature of the previously discovered SECCO 1 stellar system, also likely located in the Virgo cluster, is rediscussed in comparison with these dwarfs. While specific for the SECCO survey, our study may also provide general guidelines for the detection of faint stellar systems with 8 m class telescopes.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
We present a detailed study of the stellar and H I structure of the dwarf irregular galaxies Sextans A and Sextans B, members of the NGC 3109 association. We use newly obtained deep and wide-field g ...and r photometry to extend the surface brightness (SB) profiles of the two galaxies down to mu sub nu=31.0 mag/arcsecsup 2. We find that both galaxies are significantly more extended than previously traced with surface photometry, out to ~4 kpc from their centres along their major axes. Older stars are found to have more extended distribution than younger populations. We discuss these, as well as other evidence of tidal disturbance, in the framework of a past passage of the NGC 3109 association close to the Milky Way, which has been hypothesised by several authors and is also supported by the recently discovered filamentary configuration of the association itself.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
We present a detailed investigation of the radial distribution of blue straggler star (BSS) and binary populations in the Galactic globular cluster NGC 5466, over the entire extension of the system. ...We used a combination of data acquired with the Advanced Camera for Survey on board the Hubble Space Telescope, the LBC-blue mounted on the Large Binocular Telescope, and MEGACAM on the Canada-France-Hawaii Telescope. BSSs show a bimodal distribution with a mild central peak and a quite internal minimum. This feature is interpreted in terms of a relatively young dynamical age in the framework of the "dynamical clock" concept proposed by Ferraro et al. The estimated fraction of binaries is ~6%-7% in the central region (r < 90") and slightly lower (~5.5%) in the outskirts, at r > 200". Quite interestingly, the comparison with the results of Milone et al. suggests that binary systems may also display a bimodal radial distribution, with the position of the minimum consistent with that of BSSs. If confirmed, this feature would give additional support to the scenario where the radial distribution of objects more massive than the average cluster stars is primarily shaped by the effect of dynamical friction. Moreover, this would also be consistent with the idea that the unperturbed evolution of primordial binaries could be the dominant BSS formation process in low-density environments.
We study the binary fraction of the globular cluster M10 (NGC 6254) as a function of the radius from the cluster core to the outskirts, by means of a quantitative analysis of the color distribution ...of stars relative to the fiducial main sequence. By taking advantage of two data sets, acquired with the Advanced Camera for Survey and the Wide Field Planetary Camera 2 on board the Hubble Space Telescope, we have studied both the core and the external regions of the cluster. The binary fraction is found to decrease from ~14% within the core, to ~1.5% in a region between 1 and 2 half-mass radii from the cluster center. Such a trend and the derived values are in agreement with previous results obtained in clusters of comparable total magnitude. The estimated binary fraction is sufficient to account for the suppression of mass segregation observed in M10, without any need to invoke the presence of an intermediate-mass black hole in its center.
Context. We present a study of the mass accretion rates of pre-main sequence (PMS) stars in the cluster Trumpler 14 (Tr 14) in the Carina Nebula. Using optical multiband photometry we were able to ...identify 356 PMS stars showing Hα excess emission with equivalent width EW(Hα) > 20 Å. We interpret this observational feature as an indication that these objects are still actively accreting gas from their circumstellar medium. From a comparison of the HR diagram with PMS evolutionary models we derive ages and masses of the PMS stars. We find that most of the PMS objects are younger than 10 Myr with a median age of ~3 Myr. Surprisingly, we also find that ~20% of the mass accreting objects are older than 10 Myr. For each PMS star in Trumpler 14 we determine the mass accretion rate (Ṁacc) and discuss its dependence on mass and age. We finally combine the optical photometry with near-IR observations to build the spectral energy distribution (SED) for each PMS star in Tr 14. The analysis of the SEDs suggests the presence of transitional discs in which a large amount of gas is still present and sustains accretion onto the PMS object at ages older than 10 Myr. Our results, discussed in light of recent recent discoveries with Herschel of transitional discs containing a massive gas component around the relatively old PMS stars TW Hydrae, 49 Ceti, and HD 95086, support a new scenario n which old and evolved debris discs still host a significant amount of gas. Aims. Methods. Results.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
PDF
