Using six-dimensional phase-space information from the Fourth Data release of the RAdial Velocity Experiment (RAVE) over the range of Galactic longitude 240• < l < 360• and V LSR < −239 km s −1 , we computed orbits for 329 RAVE stars that were originally selected as chemically and kinematically related to ω Centauri. The orbits were integrated in a Milky-Way-like axisymmetric Galactic potential, ignoring the effects of the dynamical evolution of ω Centauri due to the tidal effects of the Galaxy disk on the cluster along time. We also ignored secular changes in the Milky Way potential over time. In a Monte Carlo scheme, and under the assumption that the stars may have been ejected with velocities greater than the escape velocity (V rel > V esc,0 ) from the cluster, we identified 15 stars as having close encounters with ω Centauri: (i) 8 stars with relative velocities V rel < 200 km s −1 may have been ejected ∼200 Myr ago from ω Centauri; (ii) another group of 7 stars were identified with high relative velocity V rel > 200 km s −1 during close encounters, and it seems unlikely that they were ejected from ω Centauri. We also confirm the link between J131340.4-484714 as a potential member of ω Centauri, and probably ejected ∼2.0 Myr ago, with a relative velocity V rel ∼ 80 km s −1 .

We present and discuss results from chemical evolution models for M33. For our models we adopt a galactic formation with an inside-out scenario. The models are built to reproduce three observational constraints of the M33 disk: the radial distributions of the total baryonic mass, the gas mass, and the O/H abundance. From observations, we find that the total baryonic mass profile in M33 has a double exponential behavior, decreasing exponentially for r ≤ 6 kpc, and increasing lightly for r > 6 kpc due to the increase of the gas mass surface density. To adopt a concordant set of stellar and H II regions O/H values, we had to correct the latter for the effect of temperature variations and O dust depletion. Our best model shows a good agreement with the observed radial and Z. According to our model, the star formation efficiency is constant in time and space for r ≤ 6 kpc, but the SFR efficiency decreases with time and galactocentric distance for r > 6 kpc. The reduction of the SFR efficiency occurs earlier at higher r. While the galaxy follows the inside-out formation scenario for all r, the stars follow the inside-out scenario only up to r = 6 kpc, but for r > 6 kpc the stars follow an outside-in formation. The stellar formation histories inferred for each r imply that the average age of the stars for r > 6 increases with r.In the present work, the chemical evolution models were built to reproduce three main observational constraints of the M33 disk: the radial distributions of the total baryonic mass, the gas mass, and the oxygen abundance, which are shown in Figures 1 and 2. The chemical evolution models were tested with other observational constraints of the M33 disk, such as the radial distributions of: the star formation rate, the stellar mass, the chemical abundances of nine elements and the metallicity, which are shown in Figures 3, 4, and 5. Moreover, the models were built to reproduce the average abundance of iron in the M33 halo, considering the value ‹[Fe/H]› = -1.24, estimated for halo stars by Brooks et al. (2004). In this section, we describe the observations used to constrain the models as a function of the galactocentric distance, r, hereafter in kpc units. Radial distribution of the gas mass surface density, Mgas (r)Mgas (r) represents the atomic and molecular gas that contains all the chemical elements in the disk of M33: X, Y, and Z ; i.e. Mgas (r) = MX (r) + MY (r) + MZ (r). In Figure 1 we show the Mgas (r), as filled black circles, which includes the atomic and molecular components of X, Y , and Z.To obtain MX (r) we use the updated surface density of hydrogen azimuthally averaged and corrected by the inclination angle by Gratier et al. (2010) from 0.5 to 8.5 kpc.We added atomic and molecular hydrogen, the sum of both components shows an increase at r > 6 kpc, consequently MX (r) presents a double exponential profile (see Figure 8 by Gratier et al. 2010, and Figure 4 by Verley et al. 2009). In this context, Corbelli & Schneider (1997) observed the distribution of HI in the M33 disc, and found t...

We present results from models of galactic winds driven by energy injected from nuclear (at the galactic center) and non-nuclear starbursts. The total energy of the starburst is provided by very massive young stellar clusters,which can push the galactic interstellar medium and produce an important outflow. Such outflow can be a well, or partially mixed wind, or a highly metallic wind. We have performed adiabatic 3D N-Body/Smooth Particle Hydrodynamics simulations of galactic winds using the gadget-2 code. The numerical models cover a wide range of parameters, varying the galaxy concentration index, gas fraction of the galactic disk, and radial distance of the starburst. We show that an off-center starburst in dwarf galaxies is the most effective mechanism to produce a significant loss of metals (material from the starburst itself). At the same time a non-nuclear starburst produce a high efficiency of metal loss, in spite of having a moderate to low mass loss rate.