Our new survey for Wolf-Rayet stars in the Magellanic Clouds is only 15% complete but has already found 9 new Wolf-Rayet (WR) stars in the Large Magellanic Cloud (LMC). This suggests that the total WR population in the LMC may be underestimated by 10-40%. Eight of the nine are of the WN subtype, demonstrating that the “observed” WC to WN ratio is too large, and is biased towards WC stars. The ninth is another rare WO star, the second we have found in the LMC in the past two years. Five (and possibly six) of the 8 WNs are of a new class of WRs, which pose a significant challenge to our understanding. Naively we would classify these stars as “WN3+O3V,” but there are several reasons why such a pairing is unlikely, not the least of which is that the absolute visual magnitudes of these stars are faint, with MV ~ -2.3 to -3.1. We have performed a preliminary analysis with the atmospheric code CMFGEN, and we find that (despite the faint visual magnitudes) the bolometric luminosities of these stars are normal for early-type WNs. Our fitting suggests that these stars are evolved, with significantly enriched N and He. Their effective temperatures are also normal for early-type WNs. What is unusual about these stars is that they have a surprisingly small mass-loss rate compared to other early-type WNs. How these stars got to be the way they are (single star evolution? binary evolution?) remains an open question. For now, we are designating this class as WN3/O3, in analogy to the late-type WN “slash” stars.

We present a precise and accurate measurement of the distance to the Large Magellanic Cloud based on late-type eclipsing-binary systems. Our results provide curently the most accurate zero point for the extragalactic distance scale.

I use high resolution N-body/SPH simulations to model the new proper motion of the Large Magellanic Cloud (LMC) within the Milky Way (MW) halo and investigate the effects of gravitational and hydrodynamical forces on the formation of the Magellanic Stream (MS). Both the LMC and the MW are fully self consistent galaxy models embedded in extended cuspy ΛCDM dark matter halos. I find that ram-pressure from a low density ionized halo is sufficient to remove a large amount of gas from the LMC's disk forming a trailing Stream that extends more than 120 degrees from the Cloud. Tidal forces elongate the satellite's disk but do not affect its vertical structure. No stars become unbound showing that tidal stripping is almost effectless.

We have obtained metallicities from near-infrared calcium triplet spectroscopy for nearly a thousand red giants in 28 fields spanning a range of radial distances from the center of the bar to near the tidal radius. We have used these data to investigate the radius-metallicity and age-metallicity relations. A powerful application of these data is in conjunction with the analysis of deep HST color–magnitude diagrams (CMDs). Most of the power in determining a robust star-formation history from a CMD comes from the main-sequence turnoff and subgiant branches. The age-metallicity degeneracy that results is largely broken by the red giant branch color, but theoretical model RGB colors remain uncertain. By incorporating the observed metallicity distribution function into the modelling process, a star-formation history with massively increased precision and accuracy can be derived. We incorporate the observed metallicity distribution of the LMC bar into a maximum-likelihood analysis of the bar CMD, and present a new star formation history and age–metallicity relation for the bar. The bar is certainly younger than the disk as a whole, and the most reliable estimates of its age are in the 5–6 Gyr range, when the mean gas abundance of the LMC had already increased to [Fe/H] ≳ −0.6. There is no obvious metallicity gradient among the old stars in the LMC disk out to a distance of 8–10 kpc, but the bar is more metal-rich than the disk by ≈0.1–0.2 dex. This is likely to be the result of the bar's younger average age. In both disk and bar, 95% of the red giants are more metal-rich than [Fe/H] = −1.2.

Spitzer's sensitive mid-IR photometric surveys of the Magellanic Clouds provide a relatively extinction-free census of star formation activity, and sub-parsec resolution permits the study of individual massive protostars and small clusters. Using the SAGE survey of the LMC, we identify over 1000 massive YSO candidates by their MIR colors. Analysis of their spectral energy distributions (SEDs) constrains the stellar content and evolutionary state, beginning to realize for the first time the unique potential of the Clouds to study an entire galaxy's population of individual protostars. We probe the physics underlying the Schmidt-Kennicutt scaling law by analyzing how it begins to break down at 10–100 pc spatial scales. MIR spectroscopic surveys currently underway like SAGE-SPEC will enable us to couple the circumprotostellar dust distribution (the evolutionary state reflected in the SED) with the physical state of the gas, dust and ice.

We report the results of the submillimeter observations with the ASTE 10 m telescope toward the giant molecular clouds (GMCs) in the Magellanic Clouds to reveal the physical properties of dense molecular gas, the principle sites of star and cluster formation. Six GMCs in the Large Magellanic Cloud have been mapped in the 12CO(J = 3 − 2) transition and 32 clumps are identified in these GMCs at a resolution of 5 pc. These data are combined with 12CO(J = 1 − 0) and 13CO(J = 1 − 0) results and compared with LVG calculations to derive the density and temperature of clumps. The derived density and temperature are distributed in wide ranges. We have made small mapping observations in the 13CO(J = 3 − 2) transition toward 9 representative peak positions of clumps to determine the density and temperature of clumps. These physical properties are constrained well and there are differences in density and temperature among clumps. We suggest that these differences of clump properties represent an evolutionary sequence of GMCs in terms of density increase leading to star formation.

We present the first results of the AKARI Infrared Camera near-infrared spectroscopic survey of the Large Magellanic Cloud (LMC). The circumstellar material of young stellar objects (YSOs) are affected by galactic environments such as a metallicity or radiation field. Ices control the chemical balance of circumstellar environments of embedded YSOs. We detected absorption features of the H2O ice 3.05 μm and the CO2 ice 4.27 μm stretching mode toward seven massive YSOs in the LMC. This is the first detection of the 4.27 μm CO2 ice feature toward extragalactic YSOs. The present samples are for the first time spectroscopically confirmed to be YSOs. We used a curve-of-growth method to evaluate the column densities of the ices and derived the CO2/H2O ratio to be 0.45±0.17. This is clearly higher than that seen in Galactic massive YSOs (0.17±0.03). We suggest that the strong ultraviolet radiation field and/or the high dust temperature in the LMC may be responsible for the observed high CO2 ice abundance.

The LMC clusters with similar ages to the Milky Way open clusters are in general more metal-poor and more populous than the latter, being located close enough to allow their stellar content to be well resolved. Therefore, they are unique templates of simple stellar population (SSP), being crucial to calibrate models describing the integral light as well as to test the stellar evolution theory. With this in mind we analyzed HST/WFPC2 (V, B − V) colour-magnitude diagrams (CMDs) of 15 populous LMC clusters with ages between ~0.3 Gyr and ~4 Gyr using different stellar evolutionary models. Following the approach described by Kerber, Santiago & Brocato (2007), we determined accurate and self-consistent physical parameters (age, metallicity, distance modulus and reddening) for each cluster by comparing the observed CMDs with synthetic ones generated using isochrones from the PEL and BaSTI libraries. These determinations were made by means of simultaneous statistical comparison of the main-sequence fiducial line and the red clump position, offering objective and robust criteria to select the best models. We compared these results with the ones obtained by Kerber, Santiago & Brocato (2007) using the Padova isochrones. This revealed that there are significant trends in the physical parameters due to the choice of stellar evolutionary model and treatment of convective core overshooting. In general, models that incorporate overshooting presented more reliable results than those that do not. Furthermore, the Padova models fitted better the data than the PEL and BaSTI models. Comparisons with the results found in the literature demonstrated that our derived metallicities are in good agreement with the ones from the spectroscopy of red giants. We also confirmed that, independent of the adopted stellar evolutionary library, the recovered 3D distribution for these clusters is consistent with a thick disk roughly aligned with the LMC disk as defined by field stars. Finally, we also provide new estimates of distance modulus to the LMC center, that are marginally consistent with the canonical value of 18.50 mag.

We describe an ongoing, large-scale, photometric and spectroscopic survey of the Large Magellanic Cloud (LMC) periphery. This survey uses Washington M, T2 + DDO51 photometry to identify distant LMC red giant branch (RGB) star candidates; multi-object spectroscopy is used to confirm the stellar surface gravities of these RGB stars and their association with the LMC (e.g., through radial velocities). The survey now encompasses hundreds of fields ranging from the LMC center with full azimuthal coverage around the LMC and out to 23° from the LMC center. We have confirmed the existence of RGB stars with (the unusual) Magellanic velocities out to the radial limit of this survey coverage. From data in a subsample of these fields, we show that this extended population of stars makes up a diffuse structure enveloping the LMC with a two-dimensional distribution resembling a classical halo with a shallow de Vaucouleurs profile and a broad metallicity spread around a typical mean value of [Fe/H] ~ −1.0.

LMC clusters offer an outstanding opportunity to investigate the late stages of stellar evolution of stars in the mass range between 1.5 and 2 M⊙. In this presentation we will focus on our results on mixing events during the evolution along the Asymptotic Giant Branch (AGB). Surface abundances have been determined for a number of cluster AGB stars from high resolution near infrared spectra. We show for the first time the evolution of C/O and 12C/13C ratios along a cluster AGB. The change of both quantities due to dredge up events is compared with model predictions. Our results indicate the late occurrence of a moderate extra-mixing in some cases.

Based on the quantitative analysis of a set of wide-field color—magnitude diagrams reaching the old main sequence-turnoffs, we present new LMC star-formation histories, and their variation with galactocentric distance. Some coherent features are found, together with systematic variations of the star-formation history among the three fields analyzed. We find two main episodes of star formation in all three fields, from 1 to 4 and 7 to 13 Gyr ago, with relatively low star formation around ≃ 4–7 Gyr ago. The youngest age in each field gradually increases with galactocentric radius; in the innermost field, LMC 0514–6503, an additional star formation event younger than 1 Gyr is detected, with star formation declining, however, in the last ≃ 200 Myr. The population is found to be older on average toward the outer part of the galaxy, although star formation in all fields seems to have started around 13 Gyr ago.

We present the first results of a long-term project based on the analysis of high-resolution optical spectra for a sample of Large Magellanic Cloud globular clusters. The final aim is to build a new, reliable metallicity scale for this cluster system and shed some light on the role played by the different chemical contributors (AGB, SN II and SN Ia), in order to understand the chemical enrichment history of the Large Magellanic Cloud. The analysis of 6 young and intermediate-age clusters and 11 field stars, observed with the UVES@FLAMES spectrograph, provides crucial information about the chemical composition of the dominant stellar population of the LMC. All these stars are metal-rich ([Fe/H]~ −0.4 dex), with solar-scaled [α/Fe] ratios, that point toward an enrichment from SN Ia. Moreover, we observed a general depletion for the [Al/Fe] ratio (indication of a chemical enrichment by metal-poor SN II) and a strong enhancement of the [Ba/Y] ratio (likely due to the enrichment by metal-poor AGB stars).

We have analysed spectra obtained with the Gemini Multi Object Spectrograph (GMOS) for more than 50 stars in the ionising cluster of 30 Doradus during a seven epochs observing campaign at Gemini South. We derive a binary candidate rate of about 50%, which is however consistent with an intrinsic 100% binary rate among massive stars. After decontaminating the sample from the stars that show binary orbital motions, we were able to calculate the “true” cluster velocity dispersion and found it to be about 8 km s−1. This value implies a virial mass of about 4.5 × 105 M⊙ which is consistent with previous photometric mass determinations therefore suggesting that NGC 2070 is a firm candidate for a future globular cluster.

The recent discovery of multiple stellar populations in massive Galactic globular clusters poses a serious challenge for models of star cluster formation and evolution. A new angle on this problem is being provided by rich intermediate-age clusters in the Magellanic Clouds. In this contribution we describe the discovery of three such LMC clusters with peculiar main-sequence turn-off morphologies. The simplest interpretation of our observations is that each of these three clusters is comprised of two or more stellar populations spanning an age interval of ~300 Myr. Surprisingly, such features may not be unusual in this type of cluster.

Our discovery and analysis of 452 new planetary nebulae (PNe) in the Large Magellanic Cloud (LMC) has tripled the number of known LMC PNe, providing a powerful new resource for probing the kinematics of the LMC as well as contributing fresh insight into the PN luminosity function (PNLF) which we now extend to over 10 magnitudes in [O iii] and Hα. These discoveries have resulted from a new, deep (R ≡ 22), high resolution Hα map of the central 25 deg2 of the LMC, achieved by a process of multi-exposure median co-addition of a dozen 2-hour exposures. The resulting map is at least 1 magnitude deeper than the best wide-field narrow-band LMC images currently available and has proven a major resource for the discovery of emission objects of all kinds. As a result, the near complete sample of the PN population in the central 25 deg2 of the LMC has permitted truly meaningful quantitative determinations of the PNLF, distribution, abundances and kinematics. We briefly describe the importance of these PN discoveries, the additional spectroscopic confirmation of >2,000 compact emission sources, flux calibration, the newly derived electron temperatures and electron densities.

The detected variety in chemistry and circumstellar shell morphology of the limited sample of Galactic post-AGB stars is so large, that there is no consensus yet on how individual objects are linked by evolutionary channels. The evaluation is complicated by the fact that the distances and hence luminosities of these objects are poorly known. In this contribution we report on our project to overcome this problem by focusing on a significant sample of post-AGB stars with known distances: those in the LMC. Via cross-correlation of the infrared SAGE-SPITZER catalogue with optical catalogues we selected a sample of 322 LMC post-AGB candidates based on their position in the various colour-colour diagrams. We determined the fundamental properties of 82 of them, using low resolution optical spectra that we obtained at Siding Spring and SAAO. We selected a subsample to be studied at high spectral resolution in order to obtain accurate abundances of a wide range of species. This will allow us to connect the theoretical predictions with the obtained surface chemistry at a given luminosity and metallicity. By this, we want to constrain important structure parameters of the evolutionary models. Preliminary results of the selection process are presented.

The recycling of matter between the interstellar medium (ISM) and stars are key evolutionary drivers of a galaxy's baryonic matter. The Spitzer wavelengths provide a sensitive probe of circumstellar and interstellar dust and hence, allow us to study the physical processes of the ISM, the formation of new stars and the injection of mass by evolved stars and their relationships on the galaxy-wide scale of the LMC. Due to its proximity, favorable viewing angle, multi-wavelength information, and measured tidal interactions with the Small Magellanic Cloud (SMC), the LMC is uniquely suited for surveying the agents of a galaxy's evolution (SAGE), the ISM and stars. The SAGE-LMC project is measuring these key transition points in the life cycle of baryonic matter in the LMC. Here we present a connective view of the preliminary quantities estimated from SAGE-LMC for the total mass of the ISM, the galaxy wide star formation rate and the current stellar mass loss return. For context, we compare these numbers to the LMC's stellar mass.

We observed an area of 10 deg2 of the Large Magellanic Cloud using the Infrared Camera on board AKARI. The observations were carried out using five imaging filters (3, 7, 11, 15, and 24 μm) and a dispersion prism (2 − 5 μm, λ/Δλ ~ 20) equipped in the IRC. The 11 and 15 μm data, which are unique to AKARI IRC, allow us to construct color-magnitude diagrams that are useful to identify stars with circumstellar dust. We found a new sequence in the color-magnitude diagram, which is attributed to red giants with luminosity fainter than that of the tip of the first red giant branch. We suggest that this sequence is likely to be related to the broad emission feature of aluminium oxide at 11.5 μm.

In the study of stars, the high energy domain occupies a place of choice, since it is the only one able to directly probe the most violent phenomena: indeed, young pre-main sequence objects, hot massive stars, or X-ray binaries are best revealed in X-rays. However, previously available X-ray observatories often provided only crude information on individual objects in the Magellanic Clouds. The advent of the highly efficient X-ray facilities XMM-Newton and Chandra has now dramatically increased the sensitivity and the spatial resolution available to X-ray astronomers, thus enabling a fairly easy determination of the properties of individual sources in the LMC.