Structures in surface-brightness profiles of LMC and SMC star clusters: evidence of mergers?

The LMC and SMC are rich in binary star clusters, and some mergers are expected. It is important to characterize single clusters, binary clusters and candidates to mergers. We selected a sample of star clusters in each Cloud with this aim. Surface photometry of 25 SMC and 22 LMC star clusters was carried with the ESO Danish 1.54 m telescope. 23 clusters were observed for the first time for these purposes. We fitted Elson, Fall and Freeman (1987, EFF) profiles to the data, deriving structural parameters, luminosities and masses. We also use isophotal maps to constrain candidates to cluster interactions.} {The structural parameters, luminosities and masses presented good agreement with those in the literature. Three binary clusters in the sample have a double profile. Four clusters (NGC 376, K 50, K 54 and NGC 1810) do not have companions and present as well important deviations from EFF profiles. The present sample contains blue and red Magellanic clusters. Extended EFF profiles were detected in some blue clusters. We find evidence that important deviations from the body of EFF profiles might be used as a tool to detect cluster mergers.Comment: 16 pages and 8 figures. Accepted by A&

Integrated spectral analysis of 18 concentrated star clusters in the Small Magellanic Cloud

We present in this study flux-calibrated integrated spectra in the range 3600-6800A for 18 concentrated SMC clusters. Cluster reddening values were estimated by interpolation between the extinction maps of Burstein & Heiles (1982, AJ, 87, 1165) and Schlegel et al. (1998, ApJ, 500, 525). The cluster parameters were derived from the template matching procedure by comparing the line strengths and continuum distribution of the cluster spectra with those of template cluster spectra with known parameters and from the equivalent width (EW) method. In this case, new calibrations were used together with diagnostic diagrams involving the sum of EWs of selected spectral lines. A very good agreement between ages derived from both methods was found. The final cluster ages obtained from the weighted average of values taken from the literature and the present measured ones range from 15 Mr (e.g. L51) to 7 Gyr (K3). Metal abundances have been derived for only 5 clusters from the present sample, while metallicity values directly averaged from published values for other 4 clusters have been adopted. Combining the present cluster sample with 19 additional SMC clusters whose ages and metal abundances were put onto a homogeneous scale, we analyse the age and metallicity distributions in order to explore the SMC star formation history and its spatial extent. By considering the distances of the clusters from the SMC centre instead of their projections onto the right ascension and declination axes, the present age-position relation suggests that the SMC inner disk could have been related to a cluster formation episode which reached the peak ~2.5 Gyr ago. Evidence for an age gradient in the inner SMC disk is also presented.Comment: 21 pages, 21 figures. Accepted for publication in A&

Richness, diversity, and factors influencing occupancy of mammal communities across human-modified landscapes in Colombia

As human-modified landscapes are increasing in the tropics, it becomes critical to understand how they affect mammal communities to reconcile conservation and development. We combined land cover information and camera-trapping data to explore the effects of agricultural expansion on mammals in the Magdalena river valley of Colombia. We estimated species diversity, evenness, and dominance across two agricultural landscapes, modified by cattle ranching and oil palm cultivation. We further assessed which variables influence species- and community-level occupancy using multi-species occupancy models. Results highlight that modified landscapes display lower species richness, diversity and evenness, and higher dominance than more pristine sites. Residual forest cover and distance to water had significant effect on community occupancy (positive and negative respectively). Forests were particularly important for pumas, ocelots, lowland pacas, Central American agoutis, and crab-eating raccoons while wetlands had a positive effect on jaguars, the apex predator in the region. The influence of anthropogenic pressure was not clearly evident, though pastures were not valuable habitats for any mammal species, as they had a negative, yet not significant, effect on species and community occupancy. In light of rapidly expanding agriculture across the tropics, our findings highlight species-specific responses to disturbance that can inform land use planning and conservation policies. We stress the conservation value of forest and wetland habitat to mammal occupancy in heterogeneous ecosystems. Moreover, our results demonstrate that oil palm and crop expansion should target existing pastures, which displayed limited conservation value for Neotropical mammals but occupy vast swathes of land across Latin America