The origin of the Galactic center diffuse X-ray emission (GCDX) is still under intense investigation. In particular, the interpretation of the hot (kT ≈ 7 keV) component of the GCDX, characterised by the strong Fe 6.7 keV line emission, has been contentious. If the hot component originates from a truly diffuse interstellar plasma, not a collection of unresolved point sources, such plasma cannot be gravitationally bound, and its regeneration would require a huge amount of energy. Here we show that the spatial distribution of the GCDX does not correlate with the number density distribution of an old stellar population traced by near-infrared light, strongly suggesting a significant contribution of the diffuse interstellar plasma. Contributions of the old stellar population to the GCDX are implied to be ∼ 50 % and ∼ 20 % in the Nuclear stellar disk and Nuclear star cluster, respectively. For the Nuclear stellar disk, a scale height of 0. • 32 ± 0. • 02 is obtained for the first time from the stellar number density profiles. We also show the results of the extended near-infrared polarimetric observations in the central 3 • × 2 • region of our Galaxy, and confirm that the GCDX region is permeated by a large scale, toroidal magnetic field as previously claimed. Together with observed magnetic field strengths close to energy equipartition, the hot plasma could be magnetically confined, reducing the amount of energy required to sustain it.

X-ray and near-infrared ( $J$ – $H$ – $K_{\rm s}$ ) observations of the galactic black-hole binary GX 339 $-$ 4 in the low/hard state were performed with Suzaku and IRSF in 2009 March. The spectrum in the 0.5–300 keV band is dominated by thermal Comptonization of multicolor disk photons, with a small contribution from a direct disk component, indicating that the inner disk is almost fully covered by hot corona with an electron temperature of $\approx$ 175 keV. The Comptonizing corona has at least two optical depths, $\tau$$\approx$ 1, 0.4. Analysis of the iron-K line profile yields an inner-disk radius of (13.3 $^{+6.4}_{-6.0}$ ) $\ R_{\rm g}$ ( $\ R_{\rm g}$ represents the gravitational radius $GM/c^2$ ), with the best-fit inclination angle of $\approx$ 50 $^\circ$ . This radius is consistent with that estimated from the continuum fit by assuming the conservation of photon numbers in Comptonization. Our results suggest that the standard disk of GX 339 $-$ 4 is likely truncated before reaching the innermost stable circular orbit (for a non-rotating black hole) in the low/hard states at $\sim\ $ 1% of the Eddington luminosity. The one-day averaged near-infrared light curves are found to be correlated with hard X-ray flux with $F_{\rm Ks}$$\propto$$F_{\rm X}^{0.45}$ . The flatter near-infrared $\nu F_{\nu}$ spectrum than the radio one suggests that the optically thin synchrotron radiation from the compact jets dominates the near-infrared flux. Based on a simple analysis, we estimate the magnetic field and size of the jet base to be 5 $\times$ 10 $^{4}\ $ G and 6 $\times$ 10 $^{8}\ $ cm, respectively. The synchrotron self Compton component is estimated to be approximately 0.4% of the total X-ray flux.

We present a large-scale view of the magnetic field in the central 2 • ×2 • region of our Galaxy. The polarization of point sources has been measured in the J, H, and K S bands using the near-infrared polarimetric camera SIRPOL on the 1.4 m telescope IRSF. Comparing the Stokes parameters between high extinction stars and relatively low extinction ones, we obtain polarization originating from magnetically aligned dust grains in the central few-hundred pc of our Galaxy. We find that near the Galactic plane, the magnetic field is almost parallel to the Galactic plane (i.e., toroidal configuration) but at high Galactic latitudes (| b |> 0. • 4), the field is nearly perpendicular to the plane (i.e., poloidal configuration). This is the first detection of a smooth transition of the large-scale magnetic field configuration in this region.

Seed retention time (SRT), the time interval between seed ingestion and defaecation, is a critical parameter that determines the spatial pattern of seed dispersal created by an animal, and is therefore, an essential component of trait‐based modelling of seed dispersal functions. However, no simple predictive model of SRT for any given animal exists. We explored the linkage between animal traits and SRT. We collected previously published data on mean SRT for 112 species of birds, mammals, reptiles and fishes and investigated the general allometric scaling of mean SRT with body mass for each taxon. Moreover, we analysed the effects of food habit and digestive strategy on mean SRT for birds and mammals. In general, mean SRT increased with body mass in all four taxa, whereas the pattern of allometric scaling varied greatly among the taxa. Birds had a smaller intercept and larger slope than those of mammals, whereas reptiles had a much larger intercept and smaller slope than those of either birds or mammals. For birds, food habit was also detected as an important factor affecting SRT. We applied the allometric scaling that was obtained for birds to estimate mean SRT of extinct Mesozoic dinosaurs (Theropoda) – few of which are assumed to have acted as seed dispersers. SRT for large carnivorous theropods was estimated to be 4–5 days, when considering only body mass. The present study provides allometric scaling parameters of mean SRT for a variety of seed‐dispersing animals, and highlights large variations in scaling among taxa. The allometric scaling obtained could be a critical component of further trait‐based modelling of seed dispersal functions. Further, the potential and limitations of the scaling of animal SRT with body mass and a future pathway to the development of trait‐based modelling are discussed.

We report the results from X-ray studies of the newly discovered black hole candidate MAXI J1305-704 based on Suzaku and Swift observations in the low/hard and high/soft states, respectively. The long Suzaku observation shows two types of clear absorption dips, both of which recur on a dip interval of 9.74 ± 0.04 hours, which we identify with the orbital period. There is also partially ionized absorption in the non-dip (persistent) emission in both the high/soft state and, very unusually, the low/hard state. However, this absorption (in both states) has substantially lower ionization than that seen in other high inclination systems, where the material forms a homogeneous disk wind. Here instead the absorption is most probably associated with clumpy, compact structures associated with the dipping material, which we see uniquely in this source likely because we view it at a very large inclination angle. A large inclination angle is also favored, together with a low black hole mass, to explain the high disk temperature seen in the fairly low luminosity high/soft state, as Doppler boosting enhances the disk temperature at high inclination. The disk radius inferred from these data is significantly smaller than that of the soft component seen in the low/hard state, supporting models where the disk is truncated at low luminosities. We find, however, that the lack of variability power on time scales of ∼ 50 sec in the Suzaku low/hard state data is difficult to explain, even with a low mass black hole.

Context. Nuclear star clusters (NSCs) at the dynamical center of galaxies appear to have a complex star formation history. This suggests repeated star formation, even in the influence of the strong tidal field from supermassive black holes. Although the central region of our Galaxy is an ideal target for studies of the star formation history in the NSCs, most studies in the past have concentrated on a projected distance of R Sgr A * ∼ 0.5 pc from the supermassive black hole Sgr A*. Aims. In our previous study, we detected 31 so far unknown early-type star candidates throughout the Galactic NSC (at R Sgr A * = 0.5-3 pc). They were found via near-infrared (NIR) imaging observations with narrow-band filters which are sensitive to CO absorption lines at ∼2.3 μm, a prominent feature for old, late-type stars. The aim of this study is to confirm the spectral type for the early-type star candidates. Methods. We have carried out NIR spectroscopic observations of the early-type star candidates using Subaru/IRCS/AO188 and the laser guide star system. K-band spectra for 20 out of the 31 candidates and reference late-type stars were obtained. By determining an equivalent width, EW(CO), of the 12 CO absorption feature at ≈2.294 μm, we have derived an effective temperature and a bolometric magnitude for each candidate and late-type star, and then constructed an HR diagram. Results. No young (∼Myr) massive stars are included in the 20 candidates we observed; however, 13 candidates are most likely intermediate-age giants (50-500 Myr). Two other sources have ages of ∼1 Gyr and the remaining five sources are old (>1 Gyr), late-type giants. Conclusions. Although none of the early-type star candidates from our previous narrow-band imaging observations can be confirmed as a young star, we find that the photometric technique can distinguish old, late-type giants from young and intermediate-age populations. From the 20 spectroscopically observed candidates, 65% of them are confirmed as being younger than 500 Myr. The intermediate-age stars could be as yet unknown members of a population formed in a starburst ∼100 Myr ago. Finding no young (∼a few Myr) stars at R Sgr A * = 0.5-3 pc favors the in situ formation scenario for the presence of the young stars at R Sgr A * < 0.5 pc, although we do not completely exclude the possible existence of unknown young, massive stars in the region from our observations. Furthermore, the different spatial distributions of the young and the intermediate-age stars imply that the Galactic NSC is an aggregate of stars that were born in different places and under a variety of physical conditions.

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