The recent structural evolution of the SMC

et al. 2009

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Aims. The star complexes (large scale star forming regions) of NGC 6822 were traced and mapped and their size distribution was compared with the size distribution of star complexes in the Magellanic Clouds (MCs). The spatial distributions of different age stellar populations were compared with each other. Methods. The star complexes of NGC 6822 were determined by using the isopleths, based on star counts, of the young stars of the galaxy, using a statistical cutoff limit in density. In order to map them and determine their geometric properties, an ellipse was fitted to each distinct region satisfying this minimum limit. The Kolmogorov-Smirnov statistical test was used to study possible patterns in their size distribution. Isopleths were also used to study the stellar populations of NGC 6822. Results. The star complexes of NGC 6822 were detected and a list of their positions and sizes was produced. Indications of hierarchical star formation, in terms of spatial distribution, time evolution and preferable sizes were found in NGC 6822 and the MCs. The spatial distribution of the various age stellar populations has indicated traces of an interaction in NGC 6822, dated before 350 ± 50 Myr.

Section: Hierarchical Star Formationsupporting

confidence: 92%

Star complexes and stellar populations in NGC 6822

Karampelas¹,

Dapergolas

et al. 2009

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“…They also explain that the presence of the Bar or a strong tidal disturbance confer extra streaming motion to a system and thus old and young populations can have distinct kinematics. The strong interactions of the SMC with the LMC and the MilkyWay that have probably contributed to the formation of the Bar (Maragoudaki et al 2001) could also have as a result the observed difference in the centres of the distributions of the stellar and the gas component as well as the small radial velocity gradient among SMC stars (Bekki & Chiba 2008), that contradicts the exponential profile of the stellar component. Stanimirovic et al (2004) suggest that according to SMC rotation curve, a dark matter halo is not needed to explain itt's dynamics.…”

Section: The Center Offsetmentioning

confidence: 99%

“…The AGB and RGB stars are characterised by a regular but double peaked structure, an offset from the HI distribution, and a mean age difference of the two maxima of their star count map. Maragoudaki et al (2001) studied the spatial distribution of the SMC stellar population according to their age, based on optical data. They have shown that the older stellar population shows a rather regular and smooth distribution, while the youngest stellar component (age less than 8 × 10 6 yr) appears mainly along the northeast-southwest direction, forming the Bar.…”

Section: Introductionmentioning

confidence: 99%

Structure of the SMC

Gonidakis¹,

Livanou²,

et al. 2009

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Aims. The spatial distribution of the SMC stellar component is investigated from 2MASS data. The morphology of the different age populations is presented. The center of the distribution is calculated and compared with previous estimations. The rotation of the stellar content and possible consequence of the presence of dark matter is discussed. Methods. The different stellar populations are identified through a CMD diagram of the 2MASS data. Isopleth contour maps are produced in each case, to reveal the spatial distribution. The derived density profiles are discussed. Results. The older stellar population follows an exponential profile at projected diameters of about 5 kpc (∼5 • ) for the major axis and ∼4 kpc for the minor axis, centred at RA: 0 h 51 min , Dec: −73 • 7 (J2000.0). The centre coordinates are found to be the same for all the different age population maps and are in good accordance with the kinematical centre of the SMC. However they are found to be considerably different to the coordinates of the centre of the gas distribution. The fact that the older population is found in an exponential disk suggests that the stellar content is rotating, a possible consequence of dark matter presence. The strong interactions between the MCs and the MilkyWay might explain the difference in the distributions of the stellar and gas components. The lack of an observed velocity element, which implies an absence of rotation and contradicts the consequences of an exponential profile of the stellar component, may also be a result of gravitational interactions.

“…3 to 25 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/554/A16 due to the recent interaction has been revealed in the morphological evolution of the LMC and SMC (Maragoudaki et al 1998(Maragoudaki et al , 2001.…”

Section: Introductionmentioning

confidence: 99%

Age – metallicity relation in the Magellanic Clouds clusters

Livanou

Dapergolas

et al. 2013

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Aims.We study small open star clusters, using Strömgren photometry to investigate a possible dependence between age and metallicity in the Magellanic Clouds (MCs). Our goals are to trace evidence of an age metallicity relation (AMR) and correlate it with the mutual interactions of the two MCs and to correlate the AMR with the spatial distribution of the clusters. In the Large Magellanic Cloud (LMC), the majority of the selected clusters are young (up to 1 Gyr), and we search for an AMR at this epoch, which has not been much studied. Methods. We report results for 15 LMC and 8 Small Magellanic Cloud (SMC) clusters, scattered all over the area of these galaxies, to cover a wide spatial distribution and metallicity range. The selected LMC clusters were observed with the 1.54 m Danish Telescope in Chile, using the Danish Faint Object Spectrograph and Camera (DFOSC) with a single 2k × 2k CCD. The SMC clusters were observed with the ESO 3.6 m Telescope, also in Chile, using the ESO Faint Object Spectrograph and Camera (EFOSC). The obtained frames were analysed with the conventional DAOPHOT and IRAF software. We used Strömgren filters in order to achieve reliable metallicities from photometry. Isochrone fitting was used to determine the ages and metallicities. Results. The AMR for the LMC displays a metallicity gradient, with higher metallicities for the younger ages. The AMR for LMC-SMC star clusters shows a possible jump in metallicity and a considerable increase at about 6 × 10 8 yr. It is possible that this is connected to the latest LMC-SMC interaction. The AMR for the LMC also displays a metallicity gradient with distance from the centre. The metallicities in SMC are lower, as expected for a metal-poor host galaxy.