We present a near- to mid-infrared point source catalog of 5 photometric bands at 3.2, 7, 11, 15 and 24 um for a 10 deg2 area of the Large Magellanic Cloud (LMC) obtained with the Infrared Camera (IRC) onboard the AKARI satellite. To cover the survey
area the observations were carried out at 3 separate seasons from 2006 May to June, 2006 October to December, and 2007 March to July. The 10-sigma limiting magnitudes of the present survey are 17.9, 13.8, 12.4, 9.9, and 8.6 mag at 3.2, 7, 11, 15 and 24 um, respectively. The photometric accuracy is estimated to be about 0.1 mag at 3.2 um and 0.06--0.07 mag in the other bands. The position accuracy is 0.3 at 3.2, 7 and 11um and 1.0 at 15 and 24 um. The sensitivities at 3.2, 7, and 24 um are roughly comparable to those of the Spitzer SAGE LMC point source catalog, while the AKARI catalog provides the data at 11 and 15 um, covering the mid-infrared spectral range contiguously. Two types of catalog are provided: a Catalog and an Archive. The Archive contains all the detected sources, while the Catalog only includes the sources that have a counterpart in the Spitzer SAGE point source catalog. The Archive contains about 650,000, 140,000, 97,000, 43,000, and 52,000 sources at 3.2, 7, 11, 15, and 24 um, respectively. Based on the catalog, we discuss the luminosity functions at each band, the color-color diagram, and the color-magnitude diagram using the 3.2, 7, and 11 um band data. Stars without circumstellar envelopes, dusty C-rich and O-rich stars, young stellar objects, and background galaxies are located at distinct regions in the diagrams, suggesting that the present catalog is useful for the classification of objects towards the LMC.
The aim of this study is to understand the chemical conditions of ices around embedded young stellar objects (YSOs) in the metal-poor Large Magellanic Cloud (LMC). We performed near-infrared (2.5-5 micron) spectroscopic observations toward 12 massive
embedded YSOs and their candidates in the LMC using the Infrared Camera (IRC) onboard AKARI. We estimated the column densities of the H2O, CO2, and CO ices based on their 3.05, 4.27, and 4.67 micron absorption features, and we investigated the correlation between ice abundances and physical properties of YSOs.The ice absorption features of H2O, CO2, 13CO2, CO, CH3OH, and possibly XCN are detected in the spectra. In addition, hydrogen recombination lines and PAH emission bands are detected toward the majority of the targets. The derived typical CO2/H2O ice ratio of our samples (~0.36 +- 0.09) is greater than that of Galactic massive YSOs (~0.17 +- 0.03), while the CO/H2O ice ratio is comparable. It is shown that the CO2 ice abundance does not correlate with the observed characteristics of YSOs; the strength of hydrogen recombination line and the total luminosity. Likewise, clear no correlation is seen between the CO ice abundance and YSO characteristics, but it is suggested that the CO ice abundance of luminous samples is significantly lower than in other samples.The systematic difference in the CO2 ice abundance around the LMCs massive YSOs, which was suggested by previous studies, is confirmed with the new near-infrared data. We suggest that the strong ultraviolet radiation field and/or the high dust temperature in the LMC are responsible for the observed high abundance of the CO2 ice. It is suggested that the internal stellar radiation does not play an important role in the evolution of the CO2 ice around a massive YSO, while more volatile molecules like CO are susceptible to the effect of the stellar radiation.
We present the first results of AKARI Infrared Camera near-infrared spec- troscopic survey of the Large Magellanic Cloud (LMC). We detected absorption features of the H2O ice 3.05 um and the CO2 ice 4.27 um stretching mode toward seven massive young
stellar objects (YSOs). These 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 pm 0.17. This is clearly higher than that seen in Galactic massive YSOs (0.17 pm 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.
We observed an area of 10 deg^2 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 micron) and a dispersion prism (2 -- 5 micron, $lambda / Deltal
ambda$ $sim$ 20) equipped in the IRC. This paper describes the outline of our survey project and presents some initial results using the imaging data that detected over 5.9x10^5 near-infrared and 6.4x10^4 mid-infrared point sources. The 10 $sigma$ detection limits of our survey are about 16.5, 14.0, 12.3, 10.8, and 9.2 in Vega-magnitude at 3, 7, 11, 15, and 24 micron, respectively. The 11 and 15 micron 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 micron. The 11 and 15 micron data also indicate that the ([11] - [15]) micron color of both oxygen-rich and carbon-rich red giants once becomes blue and then turns red again in the course of their evolution, probably due to the change in the flux ratio of the silicate or silicon carbide emission feature at 10 or 11.3 micron to the 15 micron flux.
