Stellar Populations in a semi-analytic model I: Bulges of Milky Way-like galaxies

We study the stellar populations of bulges of MilkyWay-like (MW-like) galaxies with the aim of identifying the physical processes involved in the formation of the bulge of our Galaxy. We use the semi-analytic model of galaxy formation and evolution SAG adapted to this aim; these kind of models can trace the properties of galaxies and their components like stellar discs, bulges and haloes, but resolution limits prevent them from reaching the scale of stellar populations (SPs). Properties of groups of stars formed during single star formation events are stored and tracked in the model and results are compared with observations of stars in the galactic bulge. MW-like galaxies are selected using two different criteria. One of them considers intrinsic photo-metric properties and the second is focused on the cosmological context of the local group (LG) of galaxies. We compare our model results with spectroscopic and photometric stellar metallicity distributions. We find that 87 per cent of stars in bulges of MW-type galaxies in our model are accreted and formed in starbursts during disc instability events. Mergers contribute to 13 per cent of the mass budget of the bulge and are responsible for the low metallicity tail of the distribution. Abundance ratios of α elements with respect to iron, [α/Fe], are measured in SPs of model galaxies. The patterns found in the model for SPs with different origins help to explain the lack of a gradient of [α/Fe] ratios in observed stars along the minor axis of the bulge.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Implementation and use of green manures for weed suppression in sequential maize cropping

Correspondence should be addressed to Amílcar Servín Niz; [email protected] ground cover produced by green manures has a direct influence on weed suppression and, in addition, the biomass produced by these same plants influences crop growth. This study was carried out to compare the effect of green manure species on the incidence of weeds, in sequence, in order to evaluate the effects of the use of green manure cover on the productive characteristics of maize plants. A completely randomised experimental design was used, with 11 treatments and 4 replications. The treatments were cover crops Canavalia ensiformis (T1), Cajanus cajan (T2), Stizolobium pruriens (T3), Crotalaria juncea (T4), Phaseolus vulgaris (T5), Stizolobium trigre (T6), Stizolobium aterrimum (T7), Crotalaria retusa (T8), Crotalaria breviflora (T9), Dolichos lablab (T10), and conventional system (T11). Ninety days after sowing, the green manures were cut, and 30 days after the green manures were cut, the hybrid maize Crop Top 520 was sown. The variables evaluated in relation to the planting of green manures were the green and dry biomass of green manures, alongside the green biomass of weeds and suppression of weeds. Concerning maize plants, the variables evaluated were plant height at 60 DAS, stalk diameter at 60 DAS, number of grain rows per ear, number of grains per grain row, and yield. The averages were subsequently analyzed using Tukey’s test at 95% significance level. The use of green manure significantly reduces the green mass of weeds up to 90 days due to lack of access to light of the weeds, which reduces their appearance and growth. Stizolobium aterrimum showed the best results both as a dry mass producer and weed suppressor and also as a yield enhancer in maize crops.Consejo Nacional de Ciencia y TecnologíaPrograma Paraguayo para el Desarrollo de la Ciencia y Tecnología. Programa Nacional de Incentivo a los Investigadore

Stellar Populations in a semi-analytic model I: Bulges of Milky Way-like galaxies

We study the stellar populations of bulges of MilkyWay-like (MW-like) galaxies with the aim of identifying the physical processes involved in the formation of the bulge of our Galaxy. We use the semi-analytic model of galaxy formation and evolution SAG adapted to this aim; these kind of models can trace the properties of galaxies and their components like stellar discs, bulges and haloes, but resolution limits prevent them from reaching the scale of stellar populations (SPs). Properties of groups of stars formed during single star formation events are stored and tracked in the model and results are compared with observations of stars in the galactic bulge. MW-like galaxies are selected using two different criteria. One of them considers intrinsic photo-metric properties and the second is focused on the cosmological context of the local group (LG) of galaxies. We compare our model results with spectroscopic and photometric stellar metallicity distributions. We find that 87 per cent of stars in bulges of MW-type galaxies in our model are accreted and formed in starbursts during disc instability events. Mergers contribute to 13 per cent of the mass budget of the bulge and are responsible for the low metallicity tail of the distribution. Abundance ratios of α elements with respect to iron, [α/Fe], are measured in SPs of model galaxies. The patterns found in the model for SPs with different origins help to explain the lack of a gradient of [α/Fe] ratios in observed stars along the minor axis of the bulge.Fil: Gargiulo, Ignacio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Cora, Sofia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Vega Martínez, Cristian Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Gonzalez, Osmar Alcides. 8uk Astronomy Technology Centre; Reino UnidoFil: Zoccali, Manuela. The Milky Way Millennium Nucleus; ChileFil: González, R.. Departamento de Astronomia y Astrofisica; ChileFil: Ruiz, Andrés Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Padilla, Nelson David. Departamento de Astronomia y Astrofisica; Chil