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1. Abundances of LMC bar and disk stars
ID:
ivo://CDS.VizieR/J/A+A/560/A44
Title:
Abundances of LMC bar and disk stars
Short Name:
J/A+A/560/A44
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper compares the chemical evolution of the Large Magellanic Cloud (LMC) to that of the Milky Way (MW) and investigates the relation between the bar and the inner disc of the LMC in the context of the formation of the bar. We obtained high-resolution and mid signal-to-noise ratio spectra with FLAMES/GIRAFFE at ESO/VLT (Proposals 072.B-0293(B) and 078.B-0323(A), P.I. Vanessa Hill) and performed a detailed chemical analysis of 106 and 58 LMC field red giant stars (mostly older than 1Gyr), located in the bar and the disc of the LMC respectively. To validate our stellar parameter determinations and abundance measurement procedures, we performed thorough tests using the well-known mildly metal-poor Milky-Way thick disc giant Arcturus (HD 124897, alpha Boo). We measured elemental abundances for O, Mg, Si, Ca, Ti (alpha-elements), Na (light odd element), Sc, V, Cr, Co, Ni, Cu (iron-peak elements), Y, Zr, Ba, La and Eu (s- and r-elements). We used the automated tool DAOSPEC to measure the equivalent width (EW) and their associated error, and we used the grid of OSMARCS model atmospheres together with the spectrum synthesis code turbospectrum to convert the EW into abundances. Since our stars are giants, atmosphere models and radiative transfer were both in spherical geometry. We built the atmosphere model for a given set of stellar parameters by interpolation onto the OSMARCS grid with the interpolation routine written by T. Masseron.
2. Abundances of 59 red giants in LMC
ID:
ivo://CDS.VizieR/J/A+A/480/379
Title:
Abundances of 59 red giants in LMC
Short Name:
J/A+A/480/379
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used FLAMES (the Fibre Large Array Multi Element Spectrograph) at the VLT-UT2 telescope to obtain spectra of a large sample of red giant stars from the inner disk of the LMC, ~2kpc from the center of the galaxy. We investigate the chemical abundances of key elements to understand the star formation and evolution of the LMC disk: heavy and light [s-process/Fe] and [alpha/Fe] give constraints on the time scales of formation of the stellar population. Cu, Na, Sc, and the iron-peak elements are also studied aiming to better understand the build up of the elements of this population and the origin of these elements. We aim to provide a more complete picture of the LMC's evolution by compiling a large sample of field star abundances. LTE abundances were derived using line spectrum synthesis or equivalent width analysis. We used OSMARCS model atmospheres and an updated line list.
3. Abundance study of LMC post-AGB stars
ID:
ivo://CDS.VizieR/J/A+A/554/A106
Title:
Abundance study of LMC post-AGB stars
Short Name:
J/A+A/554/A106
Date:
21 Oct 2021
Publisher:
CDS
Description:
The photospheric abundances of evolved solar-type stars of different metallicities serve as probes into stellar evolution theory. Stellar photospheres of post-asymptotic giant branch (post-AGB) stars bear witness to the internal chemical enrichment processes, integrated over their entire stellar evolution. Here we study post-AGB stars in the Large Magellanic Cloud (LMC). With their known distances, these rare objects are ideal tracers of AGB nucleosynthesis and dredge-up phenomena.
4. Ae/Be stars of Magellanic Bridge in JHKs
ID:
ivo://CDS.VizieR/J/ApJ/658/358
Title:
Ae/Be stars of Magellanic Bridge in JHKs
Short Name:
J/ApJ/658/358
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have found Herbig Ae/Be star candidates in the western region of the Magellanic Bridge. Using the near-infrared camera SIRIUS and the 1.4m telescope IRSF, we surveyed ~3.0{deg}x1.3{deg} (24{deg}<~RA<~36{deg}, -75.0{deg}<~DE<~-73.7{deg}) in the J, H, and Ks bands. On the basis of colors and magnitudes, about 200 Herbig Ae/Be star candidates are selected. Considering the contaminations by miscellaneous sources, such as foreground stars and early-type dwarfs in the Magellanic Bridge, we estimate that about 80 (#40%) of the candidates are likely to be Herbig Ae/Be stars. We also found one concentration of the candidates at the young star cluster NGC 796, strongly suggesting the existence of pre-main-sequence (PMS) stars in the Magellanic Bridge. This is the first detection of PMS star candidates in the Magellanic Bridge, and if they are genuine PMS stars, this could be direct evidence of recent star formation. However, the estimate of the number of Herbig Ae/Be stars depends on the fraction of classical Be stars, and thus a more precise determination of the Be star fraction or observations to differentiate between the Herbig Ae/Be stars and classical Be stars are required.
5. AGAPEROS: variable stars in the LMC Bar
ID:
ivo://CDS.VizieR/J/A+AS/145/11
Title:
AGAPEROS: variable stars in the LMC Bar
Short Name:
J/A+AS/145/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
The 91-92 EROS-1 data set has been used to select Long Timescale and Long Period Variables (LT&LPV). We choose to perform a selection of variable objects as comprehensive as possible, independent of periodicity and of their position on the colour magnitude diagram, and produce a catalogue of 632 variable objects. Table 2 provides the parameters of the variable objects detected in this paper. They are sorted in order of increasing right ascension. The columns contains the name of the variable including the RA,DEC (J2000.0) coordinates, the number of the chip and (x,y) position, the blending flags (PhiC/Phi0)_B_, (PhiC/Phi0)_R_ in both colours, the B_EROS_ and R_EROS_ magnitude, the number of star N_star_B, N_star_R found in the superpixel, the magnitude B_EROS_DAO and R_EROS_DAO estimated with DAOPHOT, and when available the cross-identifications with previous catalogue.
6. Age and metallicity relation in MC clusters
ID:
ivo://CDS.VizieR/J/A+A/554/A16
Title:
Age and metallicity relation in MC clusters
Short Name:
J/A+A/554/A16
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study small open star clusters, using Stroemgren 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 1Gyr), and we search for an AMR at this epoch, which has not been much studied. 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 1.54m Danish Telescope in Chile, using the Danish Faint Object Spectrograph and Camera (DFOSC) with a single 2kx2k CCD. The SMC clusters were observed with the ESO 3.6m 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 Stroemgren filters in order to achieve reliable metallicities from photometry. Isochrone fitting was used to determine the ages and metallicities. 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 6x10^8^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.
7. Age estimates of SMC clusters
ID:
ivo://CDS.VizieR/J/MNRAS/478/784
Title:
Age estimates of SMC clusters
Short Name:
J/MNRAS/478/784
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Small Magellanic Cloud (SMC) has recently been found to harbour an increase of more than 200 per cent in its known cluster population. Here, we provide solid evidence that this unprecedented number of clusters could be greatly overestimated. On the one hand, the fully automatic procedure used to identify such an enormous cluster candidate sample did not recover ~50 per cent, on average, of the known relatively bright clusters located in the SMC main body. On the other hand, the number of new cluster candidates per time unit as a function of time is noticeably different from the intrinsic SMC cluster frequency (CF), which should not be the case if these new detections were genuine physical systems. We found additionally that the SMC CF varies spatially, in such a way that it resembles an outside-in process coupled with the effects of a relatively recent interaction with the Large Magellanic Cloud. By assuming that clusters and field stars share the same formation history, we showed for the first time that the cluster dissolution rate also depends on position in the galaxy. The cluster dissolution becomes higher as the concentration of galaxy mass increases or if external tidal forces are present.
8. Ages and masses for 920 LMC clusters
ID:
ivo://CDS.VizieR/J/ApJ/751/122
Title:
Ages and masses for 920 LMC clusters
Short Name:
J/ApJ/751/122
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new age and mass estimates for 920 stellar clusters in the Large Magellanic Cloud (LMC) based on previously published broadband photometry and the stellar cluster analysis package, MASSCLEANage. Expressed in the generic fitting formula, d^2^N/dMdt{prop.to}M^{alpha}^t^{beta}^, the distribution of observed clusters is described by {alpha}=-1.5 to -1.6 and {beta}=-2.1 to -2.2. For 288 of these clusters, ages have recently been determined based on stellar photometric color-magnitude diagrams, allowing us to gauge the confidence of our ages. The results look very promising, opening up the possibility that this sample of 920 clusters, with reliable and consistent age, mass, and photometric measures, might be used to constrain important characteristics about the stellar cluster population in the LMC. We also investigate a traditional age determination method that uses a {chi}^2^ minimization routine to fit observed cluster colors to standard infinite-mass limit simple stellar population models. This reveals serious defects in the derived cluster age distribution using this method. The traditional {chi}^2^ minimization method, due to the variation of U, B, V, R colors, will always produce an overdensity of younger and older clusters, with an underdensity of clusters in the log(age/yr)=[7.0,7.5] range. Finally, we present a unique simulation aimed at illustrating and constraining the fading limit in observed cluster distributions that includes the complex effects of stochastic variations in the observed properties of stellar clusters.
9. Ages and masses of LMC clusters
ID:
ivo://CDS.VizieR/J/MNRAS/436/136
Title:
Ages and masses of LMC clusters
Short Name:
J/MNRAS/436/136
Date:
21 Oct 2021
Publisher:
CDS
Description:
Whether or not the rich star cluster population in the Large Magellanic Cloud (LMC) is affected by significant disruption during the first few x10^8^yr of its evolution is an open question and the subject of significant current debate. Here, we revisit the problem, adopting a homogeneous data set of broad-band imaging observations. We base our analysis mainly on two sets of self-consistently determined LMC cluster ages and masses, one using standard modelling and one which takes into account the effects of stochasticity in the clusters' stellar mass functions. On their own, the results based on any of the three complementary analysis approaches applied here are merely indicative of the physical conditions governing the cluster population. However, the combination of our results from all three different diagnostics leaves little room for any conclusion other than that the optically selected LMC star cluster population exhibits no compelling evidence of significant disruption - for clusters with masses, M_cl_, of log(M_cl_/M_{sun}_)>~3.0-3.5 - between the age ranges of [3-10 and 30-100]Myr, either 'infant mortality' or otherwise. In fact, there is no evidence of any destruction beyond that expected from simple models just including stellar dynamics and stellar evolution for ages up to 1Gyr. It seems, therefore, that the difference in environmental conditions in the Magellanic Clouds on the one hand and significantly more massive galaxies on the other may be the key to understanding the apparent variations in cluster disruption behaviour at early times.
10. Ages & luminosities of young SMC/LMC star clusters
ID:
ivo://CDS.VizieR/J/A+A/517/A50
Title:
Ages & luminosities of young SMC/LMC star clusters
Short Name:
J/A+A/517/A50
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we discuss the age and spatial distribution of young (age<1Gyr) SMC and LMC clusters using data from the Magellanic Cloud Photometric Surveys. Luminosities are calculated for all age-dated clusters. Ages of 324 and 1193 populous star clusters in the Small and the Large Magellanic Cloud have been determined fitting Padova and Geneva isochrone models to their resolved color-magnitude diagrams. The clusters cover an age range between 10Myr and 1Gyr in each galaxy. For the SMC a constant distance modulus of (m-M)_0_=18.90 and a metallicity of Z=0.004 were adopted. For the LMC, we used a constant distance modulus of (m-M)_0_=18.50 and a metallicity of Z=0.008. For both galaxies, we used a variable color excess to derive the cluster ages. We find two periods of enhanced cluster formation in both galaxies at 160Myr and 630Myr (SMC) and at 125Myr and 800Myr (LMC). We present the spatially resolved recent star formation history of both Clouds based on young star clusters. The first peak may have been triggered by a close encounter between the SMC and the LMC. In both galaxies the youngest clusters reside in the supergiant shells, giant shells, the inter-shell regions, and toward regions with a high H\alpha content, suggesting that their formation is related to expansion and shell-shell interaction. Most of the clusters are older than the dynamical age of the supergiant shells. No evidence for cluster dissolution was found. Computed V band luminosities show a trend for fainter magnitudes with increasing age as well as a trend for brighter magnitudes with increasing apparent cluster radii.

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