Agroforestry at all latitudes ? Unexpected results about best designs to allow more light to the crops at various latitudes

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CO observations of southern mergers

There are good reasons to believe that the formation of some elliptical galaxies result from the merging of two disk galaxies, as Toomre and Toomre first suggested (1972, Ap. J. 178, 623). Such a process strongly enhances the star-formation activity of the system, thus consuming its molecular gas. This might account for the low cold-gas content of elliptical galaxies compared to that of spirals. Researchers present here CO(1-0) and CO(2-1) observations of a sequence of three objects, NGC 1614, NGC 3256, and NGC 7252, that present characteristic features of merger remnants: single body and extended tidal tails. NGC 3256 and 7252 even exhibit the r(exp 1/4) radial light distribution that is the signature of elliptical galaxies, which indicates that their stellar bodies are in late stages of relaxation. Both NGC 1614 and NGC 3256 undergo extended bursts of star formation revealed by their large far-infrared luminosities, and by the presence in the near-infrared spectrum of the 3.28 microns feature (Morwood: 1986, A. A. 166, 4) attributed to polycyclic aromatic hydrocarbons. On the other hand, NGC 7252 has a milder activity of star formation, as suggested by a lower infrared luminosity, and thus seems to have gone past the starburst phase. The CO data were collected with the Swedish-ESO 15 m Submillimeter Telescope (SEST) (beamsize = 43 seconds at 115 GHz, 23 seconds at 230 GHz). For NGC 7252, researchers have only observed the central position in CO-12(1-0). The spectrum is displayed together with an HI spectrum obtained with the Nancay radiotelescope. Researchers mapped NGC 1614 and NGC 3256 in CO-12(1-0) and CO-12(2-1), and also observed the nucleus of NGC 3256 in CO-13(1-0). The various CO spectra obtained towards the nuclei of both galaxies are presented. Characteristics of the galaxies are gathered, with luminosities and masses in solar units and temperatures in Kelvins

Simulations of shell galaxies with GADGET-2: Multi-generation shell systems

As the missing complement to existing studies of shell galaxies, we carried out a set of self-consistent N-body simulations of a minor merger forming a stellar shell system within a giant elliptical galaxy. We discuss the effect of a phenomenon possibly associated with the galaxy merger simulations --- a presence of multiple generations of shells.Comment: 2 pages, 1 figure, to appear in the Proceedings of JENAM 2010, Symposium 2: "Environment and the formation of galaxies: 30 years later

Two tails in NGC 3656, and the major merger origin of shell and minor axis dust lane ellipticals

I report on the discovery of two faint (~ 26.8 Rmag/arcsec^2) tidal tails around the shell elliptical NGC 3656 (Arp 155). This galaxy had previously been interpreted as a case of accretion, or minor merger. The two tidal tails are inconsistent with a minor merger, and point instead to a disk-disk major merger origin. NGC 3656 extends Toomre's merger sequence toward normal elliptical galaxies, and hints at a major merger origin for shells and minor-axis dust lanes. A dwarf galaxy lies at the tip of one of the tidal tails. A prominent shell, which shows sharp azymuthal color discontinuities, belongs to a rotating dynamical component of young stars which includes the inner dust lane.Comment: 9 pages, 2 plates, 1 figure, uses aaspp.sty, accepted for publication in The Astrophysical Journal Letters. Files also available by anonymous ftp at ftp.iac.es, directory ./pub/balcell

High intensity X/ γ photon beams for nuclear physics and photonics

In this manuscript we review the challenges of Compton back-scattering sources in advancing photon beam performances in the1−20MeVenergy range, underlining the design criteria bringing tomaximum spectral luminosity and briefly describing the main achieve-ments in conceiving and developing new devices (multi-bunch RF cav-ities and Laser recirculators) for the case of ELI-NP Gamma BeamSystem (ELI-NP-GBS)

Evidence for Three Subpopulations of Globular Clusters in the Early-Type Post-Starburst Shell Galaxy AM 0139-655

We present deep HST ACS images of the post-starburt shell galaxy AM 0139-655. We find evidence for the presence of three distinct globular cluster subpopulations associated with this galaxy: a centrally concentrated young population (~ 0.4 Gyr), an intermediate age population (~ 1 Gyr) and an old, metal-poor population similar to that seen around normal galaxies. The g-I color distribution of the clusters is bimodal with peaks at 0.85 and 1.35. The redder peak at g-I=1.35 is consistent with the predicted color for an old metal-poor population. The clusters associated with the peak at g-I=0.85 are centrally concentrated and interpreted as a younger and more metal-rich population. We suggest that these clusters have an age of ~ 0.4 Gyr and solar metallicity based on a comparison with population synthesis models. The luminosity function of these "blue" clusters is well represented by a power law. Interestingly, the brightest shell associated with the galaxy harbors some of the youngest clusters observed. This seems to indicate that the same merger event was responsible for the formation of both the shells and the young clusters. The red part of the color distribution contains several very bright clusters, which are not expected for an old, metal-poor population. Furthermore, the luminosity function of the "red" GCs cannot be fit well by either a single gaussian or a single power law. A composite (gaussian + power law) fit to the LF of the red clusters yields both a low rms and very plausible properties for an old population plus an intermediate-age population of GCs. Hence, we suggest that the red clusters in AM 0139-655 consist of two distinct GC subpopulations, one being an old, metal-poor population as seen in normal galaxies and one having formed during a recent dissipative galaxy merger.Comment: 35 pages, 12 figures, accepted for publication in A

Are Red Tidal Features Unequivocal Signatures of Major Dry Mergers?

We use a cosmological numerical simulation to study the tidal features produced by a minor merger with an elliptical galaxy. We find that the simulated tidal features are quantitatively similar to the red tidal features, i.e., dry tidal features, recently found in deep images of elliptical galaxies at intermediate redshifts. The minor merger in our simulation does not trigger star formation due to active galactic nuclei heating. Therefore, both the tidal features and the host galaxy are red, i.e. a dry minor merger. The stellar mass of the infalling satellite galaxy is about 10^10 Msun, and the tidal debris reach the surface brightness of mu_R~27 mag arcsec^-2. Thus, we conclude that tidal debris from minor mergers can explain the observed dry tidal features in ellipticals at intermediate redshifts, although other mechanisms (such as major dry mergers) may also be important.Comment: 7 pages, 7 figures, accepted for publication in Ap

Farmer perception of benefits, constraints and opportunities for silvoarable systems: preliminary insights from Bedfordshire, England

Silvoarable agroforestry integrates the use of trees and arable crops on the same area of land, and such systems can be supported by national governments under the European Union’s (EU) Rural Development Regulations (2014–2020). In order to improve the understanding of farmers’ perceptions of such systems, detailed face-to-face interviews were completed with 15 farmers in Bedfordshire, England. Most of these farmers thought that silvoarable systems would not be profitable on their farms and that benefits would tend to be environmental or social rather than economic. Most farmers also thought that management and use of machinery would become more difficult. They felt that the tree component could potentially disrupt field operations and drainage and expressed concerns over the uncertain and long-term nature of timber revenue and the effect of intercrop yield reductions on crop revenue. Even so, 20% of the farmers stated they would use silvoarable systems if convinced that they were more profitable than conventional arable farming. A further 20% said they would farm the intercrop area belonging to someone else, if the rent was reduced to compensate for crop yield reductions. These results suggest that for most arable farmers, an economic advantage over current practice needs to exist before silvoarable systems are likely to be adopted. However, a minority might rent the crop component of a silvoarable system from another party or implement a full system for perceived environmental or social benefits