Regions In Large Magellanic Cloud Research Articles

A likely runaway star cluster in the outer disc of the Large Magellanic Cloud

We present results from photometric and spectroscopic data obtained with SOAR and Gemini observatory facilities in the field of a recently discovered star cluster. The cluster, projected towards the Eastern side of the outer disc of the Large Magellanic Cloud (LMC), was originally placed nearly 10 kpc behind the LMC with an age and metallicity typical of the innermost LMC star cluster population. We assigned radial velocity (RV) memberships to stars observed spectroscopically, and derived the cluster age and distance from theoretical isochrone fitting to the cluster colour-magnitude diagram. The new object turned out to be a 0.9 Gyr old outer LMC disc cluster, which possibly reached the present position after being scattered from the innermost LMC regions where it might have been born. We arrived at this conclusion by examining the spatial distribution of LMC star clusters of similar age, by comparing the derived spectroscopic metallicity with that expected for an outside-in galaxy formation scenario, by considering the cluster internal dynamical stage as inferred from its derived structural parameters and by estimating the circular velocity of a disc that rotates with the corresponding star cluster radial velocity at the cluster's deprojected distance, which resulted to be nearly 60 per cent higher than that of most of the outer LMC disc clusters.

Minimum Spanning Tree cluster analysis of the LMC region above 10 GeV: detection of the SNRs N 49B and N 63A

We present the results of a cluster search in the gamma-ray sky images of the Large Magellanic Cloud region by means of the Minimum Spanning Tree algorithm at energies higher than 10 GeV, using 9 years of Fermi-LAT data. Several significant clusters were found, the majority of which associated with previously known gamma-ray sources. New significant clusters associated with the supernova remnants N 49B and N 63A are also found, and confirmed with a Maximum Likelihood analysis of the Fermi-LAT data.

Stellar density distribution along the minor axis of the Large Magellanic Cloud

We studied the spatial distribution of young and old stellar populations along the western half part of the minor axis of the Large Magellanic Cloud (LMC) using Washington MT1 photometry of selected fields, which span a deprojected distance range from the LMC bar centre out to ~ 31.6 kpc. We found that both stellar populations share a mean LMC limiting radius of 8.9+-0.4 kpc; old populations are three times more dense that young populations at that LMC limit. When comparing this result with recent values for the LMC extension due to north, the old populations resulted significantly more elongated than the young ones. Bearing in mind previous claims that the elongation of the outermost LMC regions may be due to the tidal effects of the Milky Way (MW), our findings suggest that such a tidal interaction should not have taken place recently. The existence of young populations in the outermost western regions also supports previous results about ram pressure stripping effects of the LMC gaseous disc due to the motion of the LMC in the MW halo.

Comparison of diffuse infrared and far-ultraviolet emission in the Large Magellanic Cloud: The data

Dust scattering is the main source of diffuse emission in the far-ultraviolet (FUV). For several locations in the Large Magellanic Cloud (LMC), Far Ultraviolet Spectroscopic Explorer (FUSE) satellite has observed diffuse radiation in the FUV with intensities ranging from 1000 to 3×105 photon units and diffuse fraction between 5% and 20% at 1100Å. Here, we compare the FUV diffuse emission with the mid-infrared (MIR) and far-infrared (FIR) diffuse emission observed by the Spitzer Space Telescope and the AKARI satellite for the same locations. The intensity ratios in the different MIR and FIR bands for each of the locations will enable us to determine the type of dust contributing to the diffuse emission as well as to derive a more accurate 3D distribution of stars and dust in the region, which in turn may be used to model the observed scattering in the FUV. In this work we present the infrared (IR) data for two different regions in LMC, namely N11 and 30 Doradus. We also present the FUV~IR correlation for different infrared bands.

The VMC survey – XVI. Spatial variation of the cluster formation activity in the innermost regions of the Large Magellanic Cloud

We present results based on YJKs photometry of star clusters in the Large Magellanic Cloud (LMC), distributed throughout the central part of the galaxy's bar and the 30 Doradus region. We analysed the field-star-decontaminated colour–magnitude diagrams of 313 clusters to estimate their reddening values and ages. The clusters are affected by a mean reddening of E(B − V) ∈ [0.2, 0.3] mag, where the average internal LMC reddening amounts to ∼0.1–0.2 mag. The region covering 30 Doradus includes clusters with reddening values in excess of E(B − V) = 0.4 mag. Our cluster sample spans the age range 7.0 ≤ log (t yr−1) < 9.0, represents an increase of 30 per cent in terms of the number of clusters with robust age estimates and comprises a statistically complete sample in the LMC regions of interest here. The resulting cluster frequencies suggest that the outermost regions of the LMC bar first experienced enhanced cluster formation – log (t yr−1) ∈ [8.5, 9.0] – before the activity proceeded, although in a patchy manner, to the innermost regions, for log (t yr−1) < 7.7. Cluster frequencies in the 30 Doradus region show that the area is dominated by very recent cluster formation. The derived star formation frequencies suggest that the cluster and field-star populations do not seem to have fully evolved as fully coupled systems during the last ∼100 Myr.

The star cluster frequency throughout the Large Magellanic Cloud

We address the issue about the variation of the star cluster frequency (CF) in the Large Magellanic Cloud (LMC) in terms of the cluster spatial distribution. We adopted the LMC regions traced by Harris & Zaritsky (2009) and used an updated version of the cluster database compiled by Baumgardt et al. (2013). The CFs were produced by taking into account an appropriate selection of age bins. Since the uncertainty in a cluster's age can be large compared to the size of the age bins, we account for the fact that a cluster could actually reside in one of a few adjacent age bins. We confirm that there exist some variations of the LMC CFs in terms of their spatial distributions, although some caveats should be pointed out. 30 Doradus resulted to be the region with the highest relative frequency of youngest clusters, while the log($t$) = 9-9.5 (1-3 Gyr) age range is featured by cluster formation at a higher rate in the inner regions than in the outer ones. We compared the observed CFs to theoretical CFs, which are based on the star formation histories of the field stars in each region of the LMC, and found the former predicting more or fewer clusters than observed depending on the field and age range considered.

Structure of the Large Magellanic Cloud from near infrared magnitudes of red clump stars

The structural parameters, like the inclination, i and the position angle of the line of nodes (PA_lon) of the disk of the Large Magellanic Cloud (LMC) are estimated using the JH photometric data of red clump stars from the Infrared Survey Facility - Magellanic Cloud Point Source Catalog (IRSF-MCPSC). The observed LMC region is divided into several sub-regions and stars in each region are cross identified with the optically identified red clump stars to obtain the near infrared magnitudes. The peak values of H magnitude and (J-H) colour of the observed red clump distribution are obtained by fitting a profile to the distributions and also by taking the average value of magnitude and colour of the red clump stars in the bin with largest number. Then the dereddened peak H0 magnitude of the red clump stars in each sub-region is obtained. The RA, Dec and relative distance from the center of each sub-region are converted into x, y & z Cartesian coordinates. A weighted least square plane fitting method is applied to this x,y,z data to estimate the structural parameters of the LMC disk. A reddening map based on (J-H) colour of the RC stars is presented. When the peaks of the red clump distribution were identified by averaging, an inclination of 25.7 +/- 1.6 and PA_lon = 141.5 +/- 4.5 were obtained. We estimate a distance modulus of 18.47 +/- 0.1 mag to the LMC. Extra-planar features which are in front as well as behind the fitted plane are identified which match with the optically identified extra-planar features. The bar of the LMC is found to be part of the disk within 500 pc. The estimates of the structural parameters are found to be independent of the photometric bands used for the analysis. We find that the inner disk, within 3.0, is less inclined and has larger value of PA_lon when compared to the outer disk.

Extragalactic point source detection in Wilkinson Microwave Anisotropy Probe 7-year data at 61 and 94 GHz

The detection of point sources in cosmic microwave background maps is usually based on a single-frequency approach, whereby maps at each frequency are filtered separately and the spectral information on the sources is derived combining the results at the different frequencies. In contrast, in the case of multifrequency detection methods, source detection and spectral information are tightly interconnected in order to increase the source detection efficiency. In this work we apply the matched multifilter method to the detection of point sources in the Wilkinson Microwave Anisotropy Probe (WMAP) 7-year data at 61 and 94 GHz. This linear filtering technique takes into account the spatial and the cross-power spectrum information at the same time using the spectral behaviour of the sources without making any a priori assumption about it. We follow a two-step approach. First, we do a blind detection of the sources over the whole sky. Secondly, we do a refined local analysis at their positions to improve the signal-to-noise ratio of the detections. At 94 GHz we detect 129 5σ objects at |b| > 5 ◦ (excluding the Large Magellanic Cloud region); 119 of them are reliable extragalactic sources and 104 of these 119 lie outside the WMAP Point Source Catalogue mask. Nine of the total 129 detections are known Galactic sources or lie in regions of intense Galactic emission and one additional (weak) high Galactic latitude source has no counterpart in low-frequency radio catalogues. Our results constitute a substantial improvement over the New Extragalactic WMAP Point Source (NEWPS) 3-year catalogue.

Common Correlations between 60, 100, and 140$\, {\mu \mathrm {m}}$ Intensities in the Galactic Plane and Magellanic Clouds

Abstract We investigated the far-infrared SED of the Galaxy and the Magellanic Clouds by using the COBE (COsmic Background Explorer)/DIRBE (Diffuse InfraRed Background Experiment) ZSMA (Zodi-Subtracted Mission Average) maps at wavelengths of 60$\, {\mu \mathrm {m}}$, 100$\, {\mu \mathrm {m}}$, and 140$\, {\mu \mathrm {m}}$. We analyzed three regions: the galactic plane region with the galactic latitude $\vert b\vert &amp;lt; 5^{\circ}$, the Large Magellanic Cloud region, and the Small Magellanic Cloud region. Because the dust optical depth is much smaller in the far-infrared than in the visible, we could observe cumulative far-infrared radiation from regions with various interstellar radiation field in the line of sight. As a consequence of considering such an effect, we found a common far-infrared color correlation between the 140–100$\, {\mu \mathrm {m}}$ and 100–60$\, {\mu \mathrm {m}}$ intensity ratios in all three galaxies. Although this color correlation cannot be explained by any existing model, it fits very well the far-infrared color of nearby star-forming galaxies.

A New Giant Branch Clump Structure in the Large Magellanic Cloud

We present Washington C and T1 CCD photometry of 21 fields located in the northern part of the Large Magellanic Cloud (LMC), and spread over a region of more than 2.5 deg2 approximately 6° from the bar. The surveyed areas were chosen on the basis of their proximity to SL 388 and SL 509, whose fields showed the presence of a secondary giant clump, observationally detected by Bica et al. We also observed NGC 2209, located ~14° away from SL 509. From the collected data, we found that most of the observed field CMDs do not show a separate secondary clump, but rather reveal a continuous vertical structure (VS), which is clearly seen for the first time. The VS also appears in the field of NGC 2209. Its position and size are nearly the same throughout the surveyed regions: it lies below the red giant clump (RGC) and extends from the bottom of the RGC to ~0.45 mag fainter, spanning the bluest color range of the RGC. In two fields in addition to the NGC 2209 field the RGC is slightly tilted, following approximately the reddening vector, while the VS maintains its verticality. We found that the number of stars in the VS box defined by Δ(C - T1) = 1.45–1.55 mag and ΔT1 = 18.75–19.15 mag has a strong spatial variation, reaching the highest VS star density just northeast of SL 509. Moreover, the more numerous the VS stars in a field, the larger the number of LMC giants in the same zone. We also found that, in addition to SL 509, two relatively massive star clusters, SL 515 and NGC 2209, separated by more than 10° from each other, develop giant clumps with a considerable number of VS stars. This result demonstrates that VS stars belong to the LMC and are most likely the result of some kind of evolutionary process in the LMC, particularly in those LMC regions with a noticeable large giant population. Our results are successfully predicted by the models of Girardi in the sense that a large proportion of 1–2 Gyr old stars mixed with older stars and with metallicities higher than [Fe/H] -0.7 should result in a fainter and bluer secondary clump near the mass at which degenerate core He burning takes place. However, our results apparently suggest that in order to trigger the formation of VS stars, there should be other conditions in addition to the appropriate age, metallicity, and the necessary red giant star density. Indeed, stars satisfying the requisites mentioned above are commonly found throughout the LMC, but the VS phenomenon is only clearly seen in some isolated regions. Finally, the fact that clump stars have an intrinsic luminosity dispersion further constrains the use of the clump magnitude as a reliable distance indicator.

A ROSAT PSPC catalogue of X-ray sources in the LMC region

We analyzed more than 200 ROSAT PSPC observations in a 10 by 10 degree field centered on the Large Magellanic Cloud (LMC) and performed between 1990 and 1994 to derive a catalogue of X-ray sources. The list contains 758 sources with their X-ray properties. From cross-correlations of the PSPC catalogue with the SIMBAD data base and literature searches we give likely identifications for 144 X-ray sources based on positional coincidence, but taking into account X-ray properties like hardness ratios and source extent. 46 known sources are associated with supernova remnants (SNRs) and candidates in the LMC, most of them already detected by previous X-ray missions. Including the new candidates from Haberl & Pietsch (1999) based on variability studies of the sources in our PSPC catalogue, the number of X-ray binaries in the LMC increased to 17 and that of the supersoft sources (SSSs) to 9. The remaining ~50% of the identified sources comprise mainly foreground stars (up to 57) and background extragalactic objects (up to 15). The often distinguished X-ray properties of the different source types were used for a first classification of new, unknown X-ray sources. Eight new PSPC sources are classified as SNRs from their hardness ratios and one promising new SNR candidate with extended X-ray emission is found further north than all known SNRs. Three soft X-ray sources have hardness ratios compatible to those of the known SSSs. A selection on hardness ratios and X-ray to optical flux ratio further suggests 27 foreground stars and 3 AGN.

Ultraviolet Imaging Telescope Observations of OB Stars in the N 11 Region of the Large Magellanic Cloud

We present an analysis of far-ultraviolet (FUV; 1300-1800 A) and optical (U, B, and V) data of the stellar and nebular content of the OB associations LH 9, 10, and 13 in the Large Magellanic Cloud region N 11. The FUV images from the Ultraviolet Imaging Telescope strongly select the hot O and B stars; over 1900 stars were detected in the FUV to a limiting magnitude of m152 = 17 mag. The resulting FUV photometry combined with optical ground-based data indicate there are approximately 88 confirmed or candidate O stars in the LH 9, 10, and 13 fields alone (in an area of ~41 arcmin2) and possibly as many as 170-240 O-type stars within the entire 40' diameter field of view.

Charting cool carbon stars in the Large Magellanic Cloud

We describe the preparation of charts and positions for 1035 cool red giant carbon stars discovered by the authors in the Large Magellanic Cloud (LMC). Not considered here are Small Magellanic Cloud (SMC) carbon stars, nor the M-type giants found in the LMC and SMC (Blanco et al. 1980, Blanco &amp; McCarthy 1983). Charts of the C stars discovered are available in three formats: (a) 12 charts contain 186 C stars discovered in three central LMC regions (Blanco et al. 1980); (b) charts of C and late M stars in 52 LMC regions; these charts will not be published but are available from the authors (Blanco &amp; McCarthy 1983, discussion); and (c) charts for 849 individual C stars in 49 regions of LMC (Blanco &amp; McCarthy 1990).