Physical Relation of Source I to IRc2 in the Orion KL Region

We present mid-infrared narrow-band images of the Orion BN/KL region, and N-band low-resolution spectra of IRc2 and the nearby radio source "I." The distributions of the silicate absorption strength and the color temperature have been revealed with a sub-arcsecond resolution. The detailed structure of the 7.8 micron/12.4 micron color temperature distribution was resolved in the vicinity of IRc2. A mid-infrared counterpart to source I has been detected as a large color temperature peak. The color temperature distribution shows an increasing gradient from IRc2 toward source I, and no dominant temperature peak is seen at IRc2. The spectral energy distribution of IRc2 could be fitted by a two-temperature component model, and the "warmer component" of the infrared emission from IRc2 could be reproduced by scattering of radiation from source I. IRc2 itself is not self-luminous, but is illuminated and heated by an embedded luminous young stellar object located at source I.Comment: 20 pages, 11 figures. Minor corrections had been done in the ver.2. Accepted for publication in PAS

Scattering polarization of 3-μ\mum water-ice feature by large icy grains

Water ice has a strong spectral feature at a wavelength of approximately $3~\mu$m, which plays a vital role in our understanding of the icy universe. In this study, we investigate the scattering polarization of this water-ice feature. The linear polarization degree of light scattered by $\mu$m-sized icy grains is known to be enhanced at the ice band; however, the dependence of this polarization enhancement on various grain properties is unclear. We find that the enhanced polarization at the ice band is sensitive to the presence of $\mu$m-sized grains as well as their ice abundance. We demonstrate that this enhancement is caused by the high absorbency of the water-ice feature, which attenuates internal scattering and renders the surface reflection dominant over internal scattering. Additionally, we compare our models with polarimetric observations of the low-mass protostar L1551 IRS 5. Our results show that scattering by a maximum grain radius of a few microns with a low water-ice abundance is consistent with observations. Thus, scattering polarization of the water-ice feature is a useful tool for characterizing ice properties in various astronomical environments.Comment: 19 pages, 17 figures, 1 table; Accepted for publication in Ap

Ionization of Polycyclic Aromatic Hydrocarbon Molecules around the Herbig Ae/Be environment

We present the results of mid-infrared N-band spectroscopy of the Herbig Ae/Be system MWC1080 using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on board the 8m Subaru Telescope. The MWC1080 has a geometry such that the diffuse nebulous structures surround the central Herbig B0 type star. We focus on the properties of polycyclic aromatic hydrocarbons (PAHs) and PAH-like species, which are thought to be the carriers of the unidentified infrared (UIR) bands in such environments. A series of UIR bands at 8.6, 11.0, 11.2, and 12.7um is detected throughout the system and we find a clear increase in the UIR 11.0um/11.2um ratio in the vicinity of the central star. Since the UIR 11.0um feature is attributed to a solo-CH out-of-plane wagging mode of cationic PAHs while the UIR 11.2um feature to a solo-CH out-of-plane bending mode of neutral PAHs, the large 11.0um/11.2um ratio directly indicates a promotion of the ionization of PAHs near the central star.Comment: accepted for publication in Advances in Geoscienc

Thermal-infrared adaptive optics imaging- and spectro-polarimetry with the infrared camera and spectrograph (IRCS) for the Subaru Telescope

A thermal-infrared polarimetric capability of the Infrared Camera and Spectrograph (IRCS) for the Subaru Telescope is described. A new half-wave retarder for the thermal-infrared band in 2–5 µm is introduced into the Waveplate Unit of the Nasmyth platform on the infrared side of the telescope to realize imaging- and low resolution spectro-polarimetry in that wavelength region. Through day-time calibrations using a wire-grid polarizer, the peak efficiency of the polarization is found to be 90-98% consistently in both imaging- and spectro- polarimetry in the thermal-infrared bands. In 2016 May and 2017 June, two engineering observing runs have been carried out to verify the on-sky performance

Crystalline Silicate Feature of the Vega-like star HD145263

We have observed the 8-13 $\mu$m spectrum (R$\sim$250) of the Vega-like star candidate HD145263 using Subaru/COMICS. The spectrum of HD145263 shows the broad trapezoidal silicate feature with the shoulders at 9.3 $\mu$m and 11.44 $\mu$m, indicating the presence of crystalline silicate grains. This detection implies that crystalline silicate may also be commonly present around Vega-like stars. The 11.44 $\mu$m feature is slightly shifted to a longer wavelength compared to the usual 11.2-3 $\mu$m crystalline forsterite feature detected toward Herbig Ae/Be stars and T Tauri stars. Although the peak shift due to the effects of the grain size can not be ruled out, we suggest that Fe-bearing crystalline olivine explains the observed peak wavelength fairly well. Fe-bearing silicates are commonly found in meteorites and most interplanetary dust particles, which originate from planetesimal-like asteroids. According to studies of meteorites, Fe-bearing silicate must have been formed in asteroidal planetesimals, supporting the scenario that dust grains around Vega-like stars are of planetesimal origin, if the observed 11.44 $\mu$m peak is due to Fe-bearing silicates.Comment: accepted for Publication in ApJ

Reduced serum level of leukocyte cell-derived chemotaxin 2 is associated with the presence of diabetic retinopathy

AbstractBackgroundVascular endothelial growth factor (VEGF) signaling is an important pathway in the development of diabetic retinopathy (DR). A recent report showed that leukocyte cell-derived chemotaxin 2 (LECT2) suppresses the VEGF signaling in endothelial cells. However, the clinical relevance of LECT2 in DR is unknown. This study aimed to investigate serum LECT2 levels and the presence of DR.MethodsThe study included 230 people with type 2 diabetes mellitus (DM), 95 with DR and 135 without DR. Serum LECT2 levels were measured using an enzyme-linked immunosorbent assay. Data were evaluated using Spearman's rank correlation, univariate and multivariate logistic regression.ResultsSerum LECT2 levels were significantly lower in participants with DM having DR than in those not having DR (35.6±14.9ng/ml vs. 44.5±17.6ng/ml, P<0.001). Spearman's rank correlation analysis revealed a significant association between serum LECT2 levels and the presence of DR (P<0.001). Multiple regression analysis revealed that serum LECT2 levels were independently related to DR (P<0.001).ConclusionsThese findings indicated that serum LECT2 level is negatively associated with the presence of DR and suggest that low circulating LECT2 level is a risk factor for DR