AlO and 29SiO distributions around W Hya showed that AlO efficiently forms dust and contributes to the wind acceleration.

Luminous infrared galaxies (LIRGs) are enshrouded by a large amount of dust, produced by their active star formation, and it is difficult to measure their activity in the optical wavelength. We have carried out Paα narrow-band imaging observations of 38 nearby star-forming galaxies including 33 LIRGs listed in IRAS RBGS catalog with the Atacama Near InfraRed camera (ANIR) on the University of Tokyo Atacama Observatory (TAO) 1.0 m telescope (miniTAO). Star formation rates (SFRs) estimated from the Paα fluxes, corrected for dust extinction using the Balmer Decrement Method (typically A V ∼ 4.3 mag), show a good correlation with those from the bolometric infrared luminosity of IRAS data within a scatter of 0.27 dex. This suggests that the correction of dust extinction for Paα flux is sufficient in our sample. We measure the physical sizes and the surface density of infrared luminosities (Σ L(IR) ) and SFR (Σ SFR ) of star-forming region for individual galaxies, and find that most of the galaxies follow a sequence of local ultra luminous or luminous infrared galaxies (U/LIRGs) on the L(IR)-Σ L(IR) and SFR-Σ SFR plane. We confirm that a transition of the sequence from normal galaxies to U/LIRGs is seen at L(IR) = 8 × 10 10 L ⊙ . Also, we find that there is a large scatter in physical size, different from those of normal galaxies or ULIRGs. Considering the fact that most of U/LIRGs are merging or interacting galaxies, this scatter may be caused by strong external factors or differences of their merging stage.

ANIR (Atacama Near InfraRed camera) is a near infrared camera for the University of Tokyo Atacama 1m telescope, installed at the summit of Co. Chajnantor (5,640 m altitude) in northern Chile. The high altitude and extremely low water vapor (PWV = 0.5 mm) of the site enable us to perform observation of hydrogen Paα emission line at 1.8751 µm. Since its first light observation in June 2009, we have been carrying out a Paα narrow-band imaging survey of nearby luminous infrared galaxies (LIRGs), and have obtained Paα for 38 nearby LIRGs listed in AKARI/FIS-PSC at the velocity of recession between 2,800 km/s and 8,100 km/s. LIRGs are affected by a large amount of dust extinction (A V ∼ 3 mag), produced by their active star formation activities. Because Paα is the strongest hydrogen recombination line in the infrared wavelength ranges, it is a good and direct tracer of dust-enshrouded star forming regions, and enables us to probe the star formation activities in LIRGs. We find that LIRGs have two star-forming modes. The origin of the two modes probably come from differences between merging stage and/or star-forming process.

The disk around AB Aur was imaged and resolved at 24.6 µm using the Cooled Mid-Infrared Camera and Spectrometer on the 8.2m Subaru Telescope. The gaussian full-width at half-maximum of the source size is estimated to be 90 ± 6 AU, indicating that the disk extends further out at 24.6 µm than at shorter wavelengths. In order to interpret the extended 24.6 µm image, we consider a disk with a reduced surface density within a boundary radius R c , which is motivated by radio observations that suggest a reduced inner region within about 100 AU from the star. Introducing the surface density reduction factor f c for the inner disk, we determine that the best match with the observed radial intensity profile at 24.6 µm is achieved with R c =88 AU and f c =0.01. We suggest that the extended 1 Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

We imaged circumstellar disks around 22 Herbig Ae/Be stars at 25 µm using Subaru/COMICS and Gemini/T-ReCS. Our sample consists of equal numbers of objects belonging to the two categories defined by Meeus et al. (2001); 11 group I (flaring disk) and II (flat disk) sources. We find that group I sources tend to show more extended emission than group II sources. Previous studies have shown that the continuous disk is hard to be resolved with 8 meter class telescopes in Q-band due to the strong emission from the unresolved innermost region of the disk. It indicates that the resolved Q-band sources require a hole or gap in the disk material distribution to suppress the contribution from the innermost region of the disk. As many group I sources are resolved at 25 µm, we suggest that many, not all, group I Herbig Ae/Be disks have a hole or gap and are (pre-)transitional disks. On the other hand, the unresolved nature of many group II sources at 25 µm supports that group II disks have continuous flat disk geometry. It has been inferred that group I disks may evolve into group II through settling of dust grains to the mid-plane of the proto-planetary disk. However, considering growing evidence for the presence of a hole or gaps in the disk of group I sources, such an evolutionary scenario is unlikely. The difference between groups I and II may reflect different evolutionary pathways of protoplanetary disks.

Nonvariable OH/IR stars are thought to have just left the asymptotic giant branch (AGB) phase. In this conventional picture, they must still show strong circumstellar extinction caused by the dust ejected during the AGB phase, and the extinction is expected to decrease over time because of the dispersal of the circumstellar dust after the cessation of stellar mass loss. The reduction of extinction makes the stars become apparently brighter and bluer with time, especially in the near-infrared (NIR) range. We look for such long-term brightening of nonvariable OH/IR stars by using 2MASS, UKIDSS, and OAOWFC survey data. As such, we obtain multiepoch NIR data taken over a 20 yr period (1997–2017) for 6 of 16 nonvariable OH/IR stars, and all 6 objects are found to be brightening. The K-band brightening rate of five objects ranges from 0.010 to 0.130 mag yr−1, which is reasonably explained with the conventional picture. However, one OH/IR star, OH 31.0−0.2, shows a rapid brightening, which cannot be explained only by the dispersal of the dust shell. Multicolor (J-, H-, and K-band) data are obtained for three objects, OH 25.1−0.3, OH 53.6−0.2, and OH 77.9+0.2. Surprisingly, none of them appears to have become bluer, and OH 53.6−0.2 is found to have reddened at a rate of 0.013 mag yr−1 in (J – K). Our findings suggest other mechanisms such as rapid changes in stellar properties (temperature or luminosity) or a generation of a new batch of dust grains.

High-temperature molecular gas containing metallic elements is potentially a good probe to trace the kinematics/dynamics of circumstellar disks, and its presence in circumstellar disks around young stellar objects (YSOs) may also give some insights into formation processes of high-temperature meteoritic components formed in the Sun’s protoplanetary disk. The Orion Kleimann–Low (KL) region is the most famous and nearest massive star formation site, and has been extensively studied since the 1970s. The KL region harbors a candidate high-mass YSO, Source I, which has a hot circumstellar rotating gas disk emanating a magnetocentrifugal wind of SiO. In this study, we report spatially resolved distributions of aluminum monoxide (AlO) emission lines at 497 and 650 GHz in the rotating outflow of Orion Source I based on subarcsecond observations obtained by the Atacama Large Millimeter/Submillimeter Array for the first time in star-forming regions. These AlO emissions are detected only at the base of the outflow as the high excitation line of H2O in spite of their low excitation temperatures. The limited distribution of AlO to the launching point of the outflow indicates that AlO is not in the gas phase in the outer part of the outflow lobes away from the disk surface, which could be attributed to recondensation of AlO as dust due to its refractory nature.

The near-Earth asteroid 308635 (2005 YU 55 ) is a potentially hazardous asteroid which was discovered in 2005 and passed Earth on Nov. 8, 2011 at 0.85 lunar distances. This was the closest known approach by an asteroid of several hundred metres in diameter since 1976 when an object of similar size passed at 0.5 lunar distances. We observed 2005 YU 55 from the ground with a recently developed mid-IR camera (miniTAO/MAX38) in N and Q bands and with the Submillimeter Array (SMA) at 1.3 mm. In addition, we obtained space observations with Herschel/PACS at 70, 100, and 160 μm. Our thermal measurements cover a wide range of wavelengths from 8.9 μm to 1.3 mm and were taken after opposition at phase angles between -97 • and -18 • . We performed a radiometric analysis via a thermophysical model and combined our derived properties with results from radar, adaptive optics, lightcurve observations, speckle, and auxiliary thermal data. We find that 308635 (2005 YU 55 ) has an almost spherical shape with an effective diameter of 300 to 312 m and a geometric albedo p V of 0.055 to 0.075. Its spin axis is oriented towards celestial directions (λ ecl , β ecl ) = (60 • ± 30 • , -60 • ± 15 • ), which means it has a retrograde sense of rotation. The analysis of all available data combined revealed a discrepancy with the radar-derived size. Our radiometric analysis of the thermal data together with the problem to find a unique rotation period might be connected to a non-principal axis rotation. A low to intermediate level of surface roughness (rms mean slope in the range 0.1-0.3) is required to explain the available thermal measurements. We found a thermal inertia in the range 350−800 Jm −2 s −0.5 K −1 , very similar to the rubble-pile asteroid 25 143 Itokawa and indicating a surface with a mixture of low conductivity fine regolith with larger rocks and boulders of high thermal inertia.