We observed a sample of evolved stars in the Large and Small Magellanic Clouds (LMC and SMC) with the Infrared Spectrograph on the Spitzer Space Telescope. Comparing samples from the SMC, LMC, and the Galaxy reveals that the dust-production rate depends on metallicity for oxygen-rich stars, but carbon stars with similar pulsation properties produce similar quantities of dust, regardless of their initial metallicity. Other properties of the oxygen-rich stars also depend on metallicity. As the metallicity decreases, the fraction of naked (i.e. dust-free) stars increases, and among the naked stars, the strength of the 8 um absorption band from SiO decreases. Our sample includes several massive stars in the LMC with long pulsation periods which produce significant amounts of dust, probably because they are young and relatively metal rich. Little alumina dust is seen in circumstellar shells in the SMC and LMC, unlike in Galactic samples. Three oxygen-rich sources also show emission from magnesium-rich crystalline silicates. Many also show an emission feature at 14 um. The one S star in our sample shows a newly detected emission feature centered at 13.5 um. At lower metallicity, carbon stars with similar amounts of amorphous carbon in their shells have stronger absorption from molecular acetylene (C_2H_2) and weaker emission from SiC and MgS dust, as discovered in previous studies.
Using Spitzer archival data from the SAGE (Surveying the Agents of a Galaxy's Evolution) program, we derive the Cepheid period-luminosity (P-L) relation at 3.6, 4.5, 5.8 and 8.0 microns for Large Magellanic Cloud (LMC) Cepheids. These P-L relations can be used, for example, in future extragalactic distance scale studies carried out with the James Webb Space Telescope. We also derive Cepheid period-color (P-C) relations in these bands and find that the slopes of the P-C relations are relatively flat. We test the nonlinearity of these P-L relations with the F statistical test, and find that the …
We present a study of the mid-infrared properties and dust content of a sample of 27 HII ``blobs'', a rare class of compact HII regions in the Magellanic Clouds. A unique feature of this sample is that even though these HII regions are of high and low excitation they have nearly the same physical sizes ~1.5-3 pc. We base our analysis on archival 3-8 microns infrared imagery obtained with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope. We find that despite their youth, sub-solar metallicity and varied degrees of excitation, the mid-infrared colors of these regions are sim…
Formation of GMCs is one of the most crucial issues in galaxy evolution. I will compare CO and HI in the LMC in 3 dimensional space for the first time aiming at revealing the physical connection between GMCs and associated HI gas at a ~40 pc scale. The present major findings are 1) [total CO intensity] [total HI intensity]0.8 for the 110 GMCs, and 2) the HI intensity tends to increase with the evolution of GMCs. I argue that these findings are consistent with the growth of GMCs via HI accretion over a time scale of a few x 10 Myrs. I will also discuss the role of the background stellar gravity…
We present the first thermal-infrared spectra of an extra-galactic Young Stellar Object (YSO), IRAS05328-6827 in the HII region LHA 120-N148 in the Large Magellanic Cloud. The observed and modelled spectral energy distribution reveals a massive YSO, M=20 Msun, which is heavily-embedded and probably still accreting. The reduced dust content as a consequence of the lower metallicity of the LMC allows a unique view into this object, and together with a high C/O ratio may be responsible for the observed low abundance of water ice and relatively high abundances of methanol and CO2 ices.
We have produced an atlas of Spitzer Infrared Spectrograph (IRS) spectra of mass-losing, evolved stars in the Large Magellanic Cloud. These stars were selected to have high mass-loss rates and so contribute significantly to the return of processed materials to the ISM. Our high-quality spectra enable the determination of the chemistry of the circumstellar envelope from the mid-IR spectral features and continuum. We have classified the spectral types of the stars and show that the spectral types separate clearly in infrared color-color diagrams constructed from 2MASS data and synthetic IRAC/MIP…
Planetary nebulae (PNe) in the Magellanic Clouds (LMC, SMC) offer a unique opportunity to study both the population and evolution of low- and intermediate-mass stars in an environment which is free of the distance scale bias that hinder Galactic PN studies. The emission shown by PNe in the 5-40 $μ$m range is characterized by the presence of a combination of solid state features (from the dust grains) and nebular emission lines over-imposed on a strong dust continuum. We acquired low resolution IRS spectroscopy of a selected sample of LMC and SMC PNe whose morphology, size, central star brightn…
We present Spitzer/IRAC photometry on the star-forming HII region N 90, related to the young stellar association NGC 602 in the Small Magellanic Cloud. Our photometry revealed bright mid-infrared sources, which we classify with the use of a scheme based on templates and models of red sources in the Milky Way, and criteria recently developed from the Spitzer Survey of the SMC for the selection of candidate Young Stellar Objects (YSOs). We detected 57 sources in all four IRAC channels in a 6.2' x 4.8' field-of-view centered on N 90; 22 of these sources are classified as candidate YSOs. We compar…
We observed 36 evolved stars in the Small Magellanic Cloud (SMC) using the low-resolution mode of the Infrared Spectrograph (IRS) on the Spitzer Space Telescope. Two of these stars, MSX SMC 014 and 155, have nearly featureless spectral energy distributions over the IRS wavelength range (5.2-35 um) and F_nu peaking at ~8-9 um. The data can be fit by sets of amorphous carbon shells or by single 600-700 K blackbodies. The most similar spectra found in extant spectral databases are of R CrB, although the spectral structure seen in R CrB and similar stars is much weaker or absent in the SMC sources…
We present Spitzer Space telescope spectroscopic observations of 14 carbon-rich AGB stars in the Small Magellanic Cloud. SiC dust is seen in most of the carbon-rich stars but it is weak compared to LMC stars. The SiC feature is strong only for stars with significant dust excess, opposite to what is observed for Galactic stars. We argue that in the SMC, SiC forms at lower temperature than graphite dust, whereas the reverse situation occurs in the Galaxy where SiC condenses at higher temperatures and forms first. Dust input into the interstellar medium by AGB stars consists mostly of carbonaceou…
We present IRAC and MIPS images and photometry of a sample of previously known planetary nebulae (PNe) from the SAGE survey of the Large Magellanic Cloud (LMC) performed with the Spitzer Space Telescope. Of the 233 known PNe in the survey field, 185 objects were detected in at least two of the IRAC bands, and 161 detected in the MIPS 24 micron images. Color-color and color-magnitude diagrams are presented using several combinations of IRAC, MIPS, and 2MASS magnitudes. The location of an individual PN in the color-color diagrams is seen to depend on the relative contributions of the spectral co…
We present 5 - 40 micron spectroscopy of 41 planetary nebulae (PNe) in the Magellanic Clouds, observed with the Infrared Spectrograph on board the Spitzer Space Telescope. The spectra show the presence of a combination of nebular emission lines and solid-state features from dust, superimposed on the thermal IR continuum. By analyzing the 25 LMC and 16 SMC PNe in our sample we found that the IR spectra of 14 LMC and 4 SMC PNe are dominated by nebular emission lines, while the other spectra show solid-state features. We observed that the solid-state features are compatible with carbon-rich dust …
We use Spitzer Space Telescope observations from the Spitzer Survey of the Small Magellanic Cloud (S3MC) to study the young stellar content of N66, the largest and brightest HII region in the SMC. In addition to large numbers of normal stars, we detect a significant population of bright, red infrared sources that we identify as likely to be young stellar objects (YSOs). We use spectral energy distribution (SED) fits to classify objects as ordinary (main sequence or red giant) stars, asymptotic giant branch stars, background galaxies, and YSOs. This represents the first large-scale attempt at b…
Color-magnitude diagrams (CMDs) are presented for the Spitzer SAGE (Surveying the Agents of a Galaxy's Evolution) survey of the Large Magellanic Cloud (LMC). IRAC and MIPS 24 um epoch one data are presented. These data represent the deepest, widest mid-infrared CMDs of their kind ever produced in the LMC. Combined with the 2MASS survey, the diagrams are used to delineate the evolved stellar populations in the Large Magellanic Cloud as well as Galactic foreground and extragalactic background populations. Some 32000 evolved stars brighter than the tip of the red giant branch are identified. Of t…
We have observed an evolved star with a rare combination of spectral features, MSX SMC 029, in the Small Magellanic Cloud (SMC) using the low-resolution modules of the Infrared Spectrograph on the Spitzer Space Telescope. A cool dust continuum dominates the spectrum of MSX SMC 029. The spectrum also shows both emission from polycyclic aromatic hydrocarbons (PAHs) and absorption at 13.7 micron from C2H2, a juxtaposition seen in only two other sources, AFGL 2688 and IRAS 13416-6243, both post-asymptotic giant branch (AGB) objects. As in these sources, the PAH spectrum has the unusual trait that …
We present an atlas of Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of highly luminous, compact mid-infrared sources in the Large Magellanic Cloud. Sources were selected on the basis of infrared colors and 8 micron (MSX) fluxes indicative of highly evolved, intermediate- to high-mass stars with current or recent mass loss at large rates. We determine the chemistry of the circumstellar envelope from the mid-IR continuum and spectral features and classify the spectral types of the stars. In the sample of 60 sources, we find 21 Red Supergiants (RSGs), 16 C-rich Asymptotic Giant Bra…
We investigate the molecular bands in carbon-rich AGB stars in the Large Magellanic Cloud (LMC), using the InfraRed Spectrograph (IRS) on board the Spitzer Space Telescope (SST) over the 5--38 micron range. All 26 low-resolution spectra show acetylene (C2H2) bands at 7 and 14 micron. The hydrogen cyanide (HCN) bands at these wavelengths are very weak or absent. This is consistent with low nitrogen abundances in the LMC. The observed 14 micron C2H2 band is reasonably reproduced by an excitation temperature of 500 K. There is no clear dilution of the 14 micron band by circumstellar dust emission…
Using Spitzer IRAC and MIPS observations of the Large Magellanic Cloud, we have identified 13 objects that have extremely red mid-IR colors. Follow-up Spitzer IRS observations of seven of these sources reveal varying amounts of SiC and C2H2 absorption as well as the presence of a broad MgS feature in at least two cases, indicating that these are extreme carbon stars. Preliminary estimates find these objects have luminosities of 4-11x10^3 Lsol and preliminary model fitting gives mass-loss rates between 4x10^-5 and 2x10^-4 Msol/yr, higher than any known carbon-rich AGB star in the LMC. These spe…
We present the initial results from the Spitzer Survey of the Small Magellanic Cloud (S3MC), which imaged the star-forming body of the Small Magellanic Cloud (SMC) in all seven MIPS and IRAC wavebands. We find that the F_8/F_24 ratio (an estimate of PAH abundance) has large spatial variations and takes a wide range of values that are unrelated to metallicity but anticorrelated with 24 um brightness and F_24/F_70 ratio. This suggests that photodestruction is primarily responsible for the low abundance of PAHs observed in star-forming low-metallicity galaxies. We use the S3MC images to compile a…
We present a Spitzer Space Telescope spectroscopic survey of mass-losing carbon stars (and one oxygen-rich star) in the Large Magellanic Cloud. The spectra cover the wavelength range 5--38 micron. They show varying combinations of dust continuum, dust emission features (SiC, MgS) and molecular absorption bands (C2H2, HCN). A set of four narrow bands, dubbed the Manchester system, is used to define the infrared continuum for dusty carbon stars. The relations between the continuum colours and the strength of the dust and molecular features are studied, and are compared to Galactic stars of simil…
We present new far infrared maps of the Small Magellanic Cloud (SMC) at 24, 70, and 160 microns obtained as part of the Spitzer Survey of the Small Magellanic Cloud (S3MC,Bolatto et al. 2006). These maps cover most of the active star formation in the SMC Bar and the more quiescent Wing. We combine our maps with literature data to derive the dust surface density across the SMC. We find a total dust mass of Mdust = 3 10^5 Msun, implying a dust-to-hydrogen ratio over the region studied of log D/H = -2.86, or 1-to-700, which includes H_2. Assuming the dust to trace the total gas column, we derive …
We discuss the young population of stars and clusters in the Magellanic Clouds. We present the discovery of pre-main sequence candidates in the nebula N~11 in the Large Magellanic Clouds using HST ACS photometry. The comparison of the Colour-Magnitude diagram with pre-main sequence tracks and the presence of Spitzer objects YSO I and II suggest that the star formation has been active for a long period in the region, from a few $10^5$ yrs to several Myr ago
In this review we address the progress that has been made toward the understanding the population of Magellanic Cloud planetary nebulae since the last Magellanic Cloud Symposium. Planetary nebulae in the Clouds are not only important as key probes of stellar and ISM evolution in these galaxies, but also reflect the evolution of AGB stars and beyond in low-metallicity environments. We present the recent surveys results, including the wide fields ground-based search for PNe, the {\it HST} study of the resolves ejecta and their central stars, and the {\it Spitzer} analysis of the gas contents of …
We are performing a uniform and unbiased, ~7x7 degrees imaging survey of the Large Magellanic Cloud (LMC), using the IRAC and MIPS instruments on board the Spitzer Space Telescope in order to survey the agents of a galaxy's evolution (SAGE), the interstellar medium (ISM) and stars in the LMC. The detection of diffuse ISM with column densities >1.2x10^21 H cm^-2 permits detailed studies of dust processes in the ISM. SAGE's point source sensitivity enables a complete census of newly formed stars with masses >3 solar masses that will determine the current star formation rate in the LMC. SAGE's de…
We combine Spitzer and ground-based observations to measure the microlens parallax of OGLE-2005-SMC-001, the first such space-based determination since S. Refsdal proposed the idea in 1966. The parallax measurement yields a projected velocity \tilde v ~ 230 km/s, the typical value expected for halo lenses, but an order of magnitude smaller than would be expected for lenses lying in the Small Magellanic Cloud (SMC) itself. The lens is a weak (i.e., non-caustic-crossing) binary, which complicates the analysis considerably but ultimately contributes additional constraints. Using a test proposed b…
To ascertain the nature of the brightest compact mid-infrared sources in the Large Magellanic Cloud (LMC), we have applied an updated version of the Buchanan et al. (2006) 2MASS-MSX color classification system, which is based on the results of Spitzer Space Telescope spectroscopy, to a mid-infrared (8 micron) flux-limited sample of 250 LMC objects for which 2MASS and MSX photometry is available. The resulting 2MASS-MSX ("JHK8") color-based classifications of these sources, which constitute the most mid-IR-luminous objects in the LMC, were augmented, cross-checked, and corrected where necessary…
The Tail region of the Small Magellanic Cloud (SMC) was imaged using the MIPS instrument on the Spitzer Space Telescope as part of the SAGE-SMC Spitzer Legacy. Diffuse infrared emission from dust was detected in all the MIPS bands. The Tail gas-to-dust ratio was measured to be 1200 +/- 350 using the MIPS observations combined with existing IRAS and HI observations. This gas-to-dust ratio is higher than the expected 500-800 from the known Tail metallicity indicating possible destruction of dust grains. Two cluster regions in the Tail were resolved into multiple sources in the MIPS observations …
We have imaged the entire Small Magellanic Cloud (SMC), one of the two nearest star-forming dwarf galaxies, in all seven IRAC and MIPS bands. The low mass and low metallicity (1/6 solar) of the SMC make it the best local analog for primitive galaxies at high redshift. By studying the properties of dust and star formation in the SMC at high resolution, we can gain understanding of similar distant galaxies that can only be observed in much less detail. In this contribution, we present a preliminary analysis of the properties of point sources detected in the Spitzer Survey of the Small Magellanic…
To show the importance of high-spatial resolution observations of HII regions when compared with observations obtained with larger apertures such as ISO, we present mid-infrared spectra of two Magellanic Cloud HII regions, N88A and N160A. We obtained mid-infrared (8-13 um), long-slit spectra with TIMMI2 on the ESO 3.6m telescope. These are combined with archival spectra obtained with the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope, and are compared with the low-spatial resolution ISO-SWS data. An inventory of the spectra in terms of atomic fine-structure lines and molecular…
We have used the instruments on the Spitzer Space Telescope to study the Large Magellanic Cloud supernova remnants (SNRs) N11L, N44, N49, N206, N63A, and N157B. The two large SNRs N44 and N206 were not detected in any IRAC or MIPS wavebands; the remainder were detected at one or more wavelengths. In particular, the SNRs N49 and N63A each had features that were evident in all available IRAC and MIPS bands. Each of these two also displayed faint limb emission in the MIPS 24 micron band only. IRS spectra obtained for the N49 SNR showed a number of prominent lines, with little continuum contributi…
We present infrared observations of the young, oxygen-rich supernova remnant 1E 0102.2-7219 (E0102) in the Small Magellanic Cloud, obtained with the Spitzer Space Telescope. The remnant is detected at 24 um but not at 8 or 70 um and has a filled morphology with two prominent filaments. We find evidence for the existence of up to 8x10^-4 Msolar of hot dust (T~120 K) associated with the remnant. Most of the hot dust is located in the central region of E0102 which appears significantly enhanced in infrared and radio continuum emission relative to the X--ray emission. Even if all of the hot dust w…
We present a novel classification scheme for stars evolving in the transition phase between the Asymptotic Giant Branch (AGB) to the Planetary Nebula (PN) stage based on the results obtained with ISO-SWS. With the better sensitivity and higher spatial resolution of Spitzer this analysis can now be extended to a larger number of sources located in the Galactic Bulge, in the Magellanic Clouds and in other Galaxies of the Local Group, offering an excellent opportunity to study the validity of the proposed scheme in environments which are free of the distance scale bias that hinder the observation…
We present a systematic survey for ultracompact HII (UCHII) regions in the Magellanic Clouds. Understanding the physics of massive star formation (MSF) is a critical astrophysical problem. The study of MSF began in our galaxy with surveys of UCHII regions, but before now this has not been done for other galaxies. We selected candidates based on their Infrared Astronomical Satellite (IRAS) colors and imaged them at 3 and 6 cm with the Australia Telescope Compact Array (ATCA). Nearly all of the observed regions contain compact radio sources consistent with thermal emission. Many of the sources a…
We present new optical spectroscopic and archival Spitzer IRAC photometric observations of a B-type star in the SMC cluster NGC 346, NGC 346:KWBBe 200. We detect numerous Fe II, [O I], and [Fe II] lines, as well as strong P-Cygni profile H I emission lines in its optical spectrum. The star's near-IR color and optical to IR SED clearly indicate the presence of an infrared excess, consistent with the presence of gas and warm, T ~800 K, circumstellar dust. Based on a crude estimate of the star's luminosity and the observed spectroscopic line profile morphologies, we find that the star is likely t…
Because Spitzer is an Earth-trailing orbit, losing about 0.1 AU/yr, it is excellently located to perform microlens parallax observations toward the Magellanic Clouds (LMC/SMC) and the Galactic bulge. These yield the so-called ``projected velocity'' of the lens, which can distinguish statistically among different populations. A few such measurements toward the LMC/SMC would reveal the nature of the lenses being detected in this direction (dark halo objects, or ordinary LMC/SMC stars). Cool Spitzer has already made one such measurement of a (rare) bright red-clump source, but warm (presumably le…
It has been commonly conjectured that all massive >10 Msun stars are born in OB associations or clusters. Many O and B stars in the Galaxy or the Magellanic Clouds appear to exist in isolation, however. While some of these field OB stars have been ejected from their birthplaces, some are too far away from massive star forming regions to be runaways. Can massive stars form in isolation? The Spitzer survey of the Large Magellanic Cloud (aka SAGE) provides a unique opportunity for us to investigate and characterize the formation sites of massive stars for an entire galaxy. We have identified all …
The chemical abundances of neon and sulfur for 25 planetary nebulae (PNe) in the Magellanic Clouds are presented. These abundances have been derived using mainly infrared data from the Spitzer Space Telescope. The implications for the chemical evolution of these elements are discussed. A comparison with similarly obtained abundances of Galactic PNe and HII regions and Magellanic Clouds HII regions is also given. The average neon abundances are 6.0x10(-5) and 2.7x10(-5) for the PNe in the Large and Small Magellanic Clouds respectively. These are ~1/3 and 1/6 of the average abundances of Galacti…
We compare the CO 2-1 observations against previously taken CO 4-3 observations and analyze the spatial distribution of young stellar objects (YSO's) within the cloud using the Spitzer IRAC observations of the 30 Doradus complex. Both peaks of CO 2-1 and 4-3 emitting clouds coincide with the densest region of the filaments where multiple shells are colliding. We find that the YSO's are clustered in the southern ridge of the warm and dense molecular gas clouds traced by CO J=4-3, indicating a filamentary structure of star formation throughout the 30 Doradus. We also find that some of Class I YS…
Large-scale star formation in disk galaxies is hypothesized to be driven by global gravitational instability. The observed gas surface density is commonly used to compute the strength of gravitational instability, but according to this criterion star formation often appears to occur in gravitationally stable regions. One possible reason is that the stellar contribution to the instability has been neglected. We have examined the gravitational instability of the Large Magellanic Cloud (LMC) considering the gas alone, and considering the combination of collisional gas and collisionless stars. We …
We present initial results and source lists of variable sources in the Large Magellanic Cloud (LMC) for which we detect thermal infrared variability from the SAGE (Surveying the Agents of a Galaxy's Evolution) survey, which had 2 epochs of photometry separated by three months. The SAGE survey mapped a 7 degree by 7 degree region of the LMC using the IRAC and the MIPS instruments on board Spitzer. Variable sources are identified using a combination of the IRAC 3.6, 4.5, 5.8, 8.0 \micron bands and the MIPS 24 \micron bands. An error-weighted flux difference between the two epochs is used to asse…
We present mid-infrared spectral mapping observations of the core-collapse supernova remnant 1E 0102.2-7219 in the Small Magellanic Cloud using the InfraRed Spectrograph (IRS) on the Spitzer Space Telescope. The remnant shows emission from fine structure transitions of neon and oxygen as well as continuum emission from dust. Comparison of the mid-IR dust emission with observations at x-ray, radio and optical wavelengths shows that the dust is associated with the supernova ejecta and is thus newly formed in the remnant. The spectrum of the newly formed dust is well reproduced by a model that in…
NGC 602 is a young stellar cluster located in a peripheral region of the Small Magellanic Cloud known as the wing. Far from the main body of the galaxy and abutting the Magellanic Bridge, the SMC's wing is characterized by low gas and stellar content. With deep optical imaging from the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST), we have discovered an extensive pre-Main Sequence (PMS) population, with stellar masses in the range 0.6-3 Solar masses. These low mass PMS stars formed coevally with the central cluster about 4 Myr ago. Spitzer Space Telescope (Spitzer) …
We present new stellar population models that include the contribution of the Thermally Pulsing Asymptotic Giant Branch (TP-AGB) phase also in the synthetic spectral energy distribution (SED). The TP-AGB phase is essential for a correct modeling of intermediate-age (0.2 < t/Gyr < 1-2) stellar populations, because it provides ~40% of the bolometric contribution, and up to ~80% of that in the K-band. These models are obtained by coupling the energetic of the TP-AGB phase as calibrated with data of Magellanic Clouds star clusters (Maraston 1998), with empirical spectra of TP-AGB stars (Lancon & M…
We present the first mid-infrared spectra of SMP LMC 11 in the Large Magellanic Cloud. While this object resembles a planetary nebula in the optical, its infrared properties are more similar to an object in transition from the asymptotic giant branch to the planetary nebula phase. A warm dust continuum dominates the infrared spectrum. The peak emission corresponds to a mean dust temperature of 330 K. The spectrum shows overlapping molecular absorption bands from 12 to 17 um corresponding to acetylene and polyacetylenic chains and benzene. This is the first detection of C4H2, C6H2, C6H6 and oth…
We present first results from an extensive survey of Magellanic Clouds supernova remnants (SNRs) with the Spitzer Space Telescope. We describe IRAC and MIPS imaging observations at 3.6, 4.5, 5.8, 8, 24, and 70 microns of four Balmer-dominated Type Ia SNRs in the Large Magellanic Cloud (LMC): DEM L71 (0505-67.9), 0509--67.5, 0519--69.0, and 0548-70.4. None was detected in the four short-wavelength IRAC bands, but all four were clearly imaged at 24 microns, and two at 70 microns. A comparison of these images to Chandra broadband X-ray images shows a clear association with the blast wave, and not…
We have observed a sample of 36 objects in the Small Magellanic Cloud (SMC) with the Infrared Spectrometer on the Spitzer Space Telescope. Nineteen of these sources are carbon stars. An examination of the near- and mid-infrared photometry shows that the carbon-rich and oxygen-rich dust sources follow two easily separated sequences. A comparison of the spectra of the 19 carbon stars in the SMC to spectra from the Infrared Space Observatory (ISO) of carbon stars in the Galaxy reveals significant differences. The absorption bands at 7.5 um and 13.7 um due to C2H2 are stronger in the SMC sample, a…
We report observations with the MIPS instrument aboard the {\it Spitzer Space Telescope} (SST) of four supernova remnants (SNRs) believed to be the result of core-collapse SNe: N132D (0525-69.6), N49B (0525-66.0), N23 (0506-68.0), and 0453-68.5. All four of these SNRs were detected in whole at 24 $μ$m and in part at 70 $μ$m. Comparisons with {\it Chandra} broadband X-ray images show an association of infrared (IR) emission with the blast wave. We attribute the observed IR emission to dust that has been collisionally heated by electrons and ions in the hot, X-ray emitting plasma, with grain siz…
We investigate the conditions of star formation in the Large Magellanic Cloud. We have conducted a survey for water maser emission arising from massive young stellar objects in the 30 Doradus region (N 157) and several other H II regions in the Large Magellanic Cloud (N 105A, N 113 and N 160A). We have identified a new maser source in 30 Dor at the systemic velocity of the LMC. We have obtained 3-4 micron spectra, with the ESO Very Large Telescope, of two candidate young stellar objects. N 105A IRS1 shows H recombination line emission and its Spectral Energy Distribution (SED) and mid-infrared…
We present N-band spectro-interferometric observations of the red supergiant WOH G64 in the Large Magellanic Cloud (LMC) using MIDI at the Very Large Telescope Interferometer (VLTI). The location of WOH G64 on the H-R diagram based on the previously estimated luminosities is in serious disagreement with the current stellar evolution theory. The dust envelope around WOH G64 has been spatially resolved with a baseline of ~60 m--the first MIDI observations to resolve an individual stellar source in an extragalactic system. The observed N-band visibilities show a slight decrease from 8 to 10 micro…
We present the near- to mid-infared study of supernova remnants (SNRs) using the AKARI IRC Survey of the Large Magellanic Cloud (LMC). The LMC survey observed about a 10 square degree area of the LMC in five bands centered at 3, 7, 11, 15, and 24 \micron using the Infrared Camera (IRC) aboard AKARI. The number of SNRs in the survey area is 21, which is about a half of the known LMC SNRs. We systematically examined the AKARI images and identified eight SNRs with distinguishable infrared emission. All of them were detected at $\gtrsim 10$ \micron and some at 3 and 7 \micron, too. We present thei…
