Dense Clumps in Giant Molecular Clouds in the Large Magellanic Cloud: Density and Temperature Derived from 13^{13}CO(J=3−2J=3-2) Observations

In order to precisely determine temperature and density of molecular gas in the Large Magellanic Cloud, we made observations of optically thin $^{13}$CO($J=3-2$) transition by using the ASTE 10m telescope toward 9 peaks where $^{12}$CO($J=3-2$) clumps were previously detected with the same telescope. The molecular clumps include those in giant molecular cloud (GMC) Types I (with no signs of massive star formation), II (with HII regions only), and III (with HII regions and young star clusters). We detected $^{13}$CO($J=3-2$) emission toward all the peaks and found that their intensities are 3 -- 12 times lower than those of $^{12}$CO($J=3-2$). We determined the intensity ratios of $^{12}$CO($J=3-2$) to $^{13}$CO($J=3-2$), $R^{12/13}_{3-2}$, and $^{13}$CO($J=3-2$) to $^{13}$CO($J=1-0$), $R^{13}_{3-2/1-0}$, at 45\arcsec resolution. These ratios were used for radiative transfer calculations in order to estimate temperature and density of the clumps. The parameters of these clumps range kinetic temperature $T\mathrm{_{kin}}$ = 15 -- 200 K, and molecular hydrogen gas density $n(\mathrm{H_2})$ = 8$\times 10^2$ -- 7$\times 10^3$ cm$^{-3}$. We confirmed that the higher density clumps show higher kinetic temperature and that the lower density clumps lower kinetic temperature at a better accuracy than in the previous work. The kinetic temperature and density increase generally from a Type I GMC to a Type III GMC. We interpret that this difference reflects an evolutionary trend of star formation in molecular clumps. The $R^{13}_{3-2/1-0}$ and kinetic temperature of the clumps are well correlated with H$\alpha$ flux, suggesting that the heating of molecular gas $n(\mathrm{H_2})$ = $10^3$ -- $10^4$ cm$^{-3}$ can be explained by stellar FUV photons.Comment: 39 pages, 7 figures, 4 tables. Accepted for publication in The Astronomical Journa

ASTE CO(3-2) Mapping toward the Whole Optical Disk of M 83: Properties of Inter-arm GMAs

We present a new on-the-fly (OTF) mapping of CO(J=3-2) line emission with the Atacama Submillimeter Telescope Experiment (ASTE) toward the 8' x 8' (or 10.5 x 10.5 kpc at the distance of 4.5 Mpc) region of the nearby barred spiral galaxy M 83 at an effective resolution of 25''. Due to its very high sensitivity, our CO(J=3-2) map can depict not only spiral arm structures but also spur-like substructures extended in inter-arm regions. This spur-like substructures in CO(J=3-2) emission are well coincident with the distribution of massive star forming regions traced by Halpha luminosity and Spitzer/IRAC 8 um emission. We have identified 54 CO(J=3-2) clumps as Giant Molecular-cloud Associations (GMAs) employing the CLUMPFIND algorithm, and have obtained their sizes, velocity dispersions, virial masses, and CO luminosity masses. We found that the virial parameter alpha, which is defined as the ratio of the virial mass to the CO luminosity mass, is almost unity for GMAs in spiral arms, whereas there exist some GMAs whose alpha are 3 -- 10 in the inter-arm region. We found that GMAs with higher $\alpha$ tend not to be associated with massive star forming regions, while other virialized GMAs are. Since alpha mainly depends on velocity dispersion of the GMA, we suppose the onset of star formation in these unvirialized GMAs with higher alpha are suppressed by an increase in internal velocity dispersions of Giant Molecular Clouds within these GMAs due to shear motion.Comment: 42 pages, 16 figures, ApJ in press, version with high resolution figures is available via http://www.nro.nao.ac.jp/~kmuraoka/m83paper/m83aste-otf.pd

Dense Molecular Clumps associated with the LMC Supergiant Shells LMC 4 \& LMC 5

We investigate the effects of Supergiant Shells (SGSs) and their interaction on dense molecular clumps by observing the Large Magellanic Cloud (LMC) star forming regions N48 and N49, which are located between two SGSs, LMC 4 and LMC 5. $^{12}$CO ($J$=3-2, 1-0) and $^{13}$CO ($J$=1-0) observations with the ASTE and Mopra telescopes have been carried out towards these regions. A clumpy distribution of dense molecular clumps is revealed with 7 pc spatial resolution. Large velocity gradient analysis shows that the molecular hydrogen densities ($n({\rm H}_2)$) of the clumps are distributed from low to high density ($10^3$-$10^5$ cm$^{-3}$) and their kinetic temperatures ($T_{\rm kin}$) are typically high (greater than $50$ K). These clumps seem to be in the early stages of star formation, as also indicated from the distribution of H$\alpha$, young stellar object candidates, and IR emission. We found that the N48 region is located in the high column density HI envelope at the interface of the two SGSs and the star formation is relatively evolved, whereas the N49 region is associated with LMC 5 alone and the star formation is quiet. The clumps in the N48 region typically show high $n({\rm H}_2)$ and $T_{\rm kin}$, which are as dense and warm as the clumps in LMC massive cluster-forming areas (30 Dor, N159). These results suggest that the large-scale structure of the SGSs, especially the interaction of two SGSs, works efficiently on the formation of dense molecular clumps and stars.Comment: 26 pages, 7 tables, 16 figure

The Ganymede Laser Altimeter (GALA) for the Jupiter Icy Moons Explorer (JUICE): Mission, science, and instrumentation of its receiver modules

The Jupiter Icy Moons Explorer (JUICE) is a science mission led by the European Space Agency, being developed for launch in 2023. The Ganymede Laser Altimeter (GALA) is an instrument onboard JUICE, whose main scientific goals are to understand ice tectonics based on topographic data, the subsurface structure by measuring tidal response, and small-scale roughness and albedo of the surface. In addition, from the perspective of astrobiology, it is imperative to study the subsurface ocean scientifically. The development of GALA has proceeded through an international collaboration between Germany (the lead), Japan, Switzerland, and Spain. Within this framework, the Japanese team (GALA-J) is responsible for developing three receiver modules: the Backend Optics (BEO), the Focal Plane Assembly (FPA), and the Analog Electronics Module (AEM). Like the German team, GALA-J also developed software to simulate the performance of the entire GALA system (performance model). In July 2020, the Proto-Flight Models of BEO, FPA, and AEM were delivered from Japan to Germany. This paper presents an overview of JUICE/GALA and its scientific objectives and describes the instrumentation, mainly focusing on Japan’s contribution

The ASTRO-H X-ray Observatory

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-throughput spectrometer sensitive over 0.3-2 keV with high spectral resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes.Comment: 22 pages, 17 figures, Proceedings of the SPIE Astronomical Instrumentation "Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray