The Distance to the Galactic Center Derived From Infrared Photometry of Bulge Red Clump Stars

On the basis of the near infrared observations of bulge red clump stars near the Galactic center, we have determined the galactocentric distance to be R_0 = 7.52 +- 0.10 (stat) +- 0.35 (sys) kpc. We observed the red clump stars at |l| < 1.0 deg and 0.7 deg < |b| < 1.0 deg with the IRSF 1.4 m telescope and the SIRIUS camera in the H and Ks bands. After extinction and population corrections, we obtained (m - M)_0 = 14.38 +- 0.03 (stat) +- 0.10 (sys). The statistical error is dominated by the uncertainty of the intrinsic local red clump stars' luminosity. The systematic error is estimated to be +- 0.10 including uncertainties in extinction and population correction, zero-point of photometry, and the fitting of the luminosity function of the red clump stars. Our result, R_0 = 7.52 kpc, is in excellent agreement with the distance determined geometrically with the star orbiting the massive black hole in the Galactic center. The recent result based on the spatial distribution of globular clusters is also consistent with our result. In addition, our study exhibits that the distance determination to the Galactic center with the red clump stars, even if the error of the population correction is taken into account, can achieve an uncertainty of about 5%, which is almost the same level as that in recent geometrical determinations.Comment: 14 pages, 4 figures, accepted by Ap

Interstellar Extinction Law in the J, H, and Ks Bands toward the Galactic Center

We have determined the ratios of total to selective extinction in the near-infrared bands (J, H, Ks) toward the Galactic center from the observations of the region |l| < 2.0deg and 0.5deg < |b| < 1.0deg with the IRSF telescope and the SIRIUS camera. Using the positions of red clump stars in color-magnitude diagrams as a tracer of the extinction and reddening, we determine the average of the ratios of total to selective extinction to be A(Ks)/E(H-Ks) = 1.44+-0.01, A(Ks)/E(J-Ks) = 0.494+-0.006, and A(H)/E(J-H) = 1.42+-0.02, which are significantly smaller than those obtained in previous studies. From these ratios, we estimate that A(J) : A(H) : A(Ks) = 1 : 0.573+-0.009 : 0.331+-0.004 and E(J-H)/E(H-Ks) = 1.72+-0.04, and we find that the power law A(lambda) \propto lambda^{-1.99+-0.02} is a good approximation over these wavelengths. Moreover, we find a small variation in A(Ks)/E(H-Ks) across our survey. This suggests that the infrared extinction law changes from one line of sight to another, and the so-called ``universality'' does not necessarily hold in the infrared wavelengths.Comment: 18 pages, 9 figures, Accepted for publication in the Ap

Near-IR imaging polarimetry toward a bright-rimmed cloud: Magnetic field in SFO 74

We have made near-infrared (JHKs) imaging polarimetry of a bright-rimmed cloud (SFO 74). The polarization vector maps clearly show that the magnetic field in the layer just behind the bright rim is running along the rim, quite different from its ambient magnetic field. The direction of the magnetic field just behind the tip rim is almost perpendicular to that of the incident UV radiation, and the magnetic field configuration appears to be symmetric as a whole with respect to the cloud symmetry axis. We estimated the column and number densities in the two regions (just inside and far inside the tip rim) and then derived the magnetic field strength, applying the Chandrasekhar-Fermi method. The estimated magnetic field strength just inside the tip rim, ~90 ?G, is stronger than that far inside, ~30 ?G. This suggests that the magnetic field strength just inside the tip rim is enhanced by the UV-radiation-induced shock. The shock increases the density within the top layer around the tip and thus increases the strength of the magnetic field. The magnetic pressure seems to be comparable to the turbulent one just inside the tip rim, implying a significant contribution of the magnetic field to the total internal pressure. The mass-to-flux ratio was estimated to be close to the critical value just inside the tip rim. We speculate that the flat-topped bright rim of SFO 74 could be formed by the magnetic field effect

Near-Infrared Imaging Polarimetry of the Serpens Cloud Core: Magnetic Field Structure, Outflows, and Inflows in A Cluster Forming Clump

We made deep NIR imaging polarimetry toward the Serpens cloud core. The polarization vector maps enable us to newly detect 24 small IR reflection nebulae with YSOs. Polarization measurements of NIR point sources indicate an hourglass-shaped magnetic field, of which symmetry axis is nearly perpendicular to the elongation of the C18O (J=1-0) or submillimeter continuum emission. The bright part of C18O (J=1-0), submillimeter continuum cores as well as many class 0/I objects are located just toward the constriction region of the hourglass-shaped magnetic field. Applying the CF method, the magnetic field strength was estimated to be ~100 muG, suggesting that the ambient region of the Serpens cloud core is moderately magnetically supercritical. These suggest that the Serpens cloud core first contracted along the magnetic field to be an elongated cloud, which is perpendicular to the magnetic field, and that then the central part contracted cross the magnetic field due to the high density in the central region of the cloud core, where star formation is actively continuing. Comparison of this magnetic field with the previous observations of molecular gas and large-scale outflows suggests a possibility that the cloud dynamics is controlled by the magnetic field, protostellar outflows and gravitational inflows. This appears to be in good agreement with the outflow-driven turbulence model and implies the importance of the magnetic field to continuous star formation in the center region of the cluster forming region.Comment: 36 pages, 11 figures, 2 tables, accepted for publication in the Astrophysical Journa

Herbig Ae/Be Stars in the Magellanic Bridge

We have found Herbig Ae/Be star candidates in the western region of the Magellanic Bridge. Using the near infrared camera SIRIUS and the 1.4 m telescope IRSF, we surveyed about 3.0 deg x 1.3 deg (24 deg < RA < 36 deg, -75 deg < Dec. < -73.7 deg) in the J, H, and Ks bands. On the basis of colors and magnitudes, about 200 Herbig Ae/Be star candidates are selected. Considering the contaminations by miscellaneous sources such as foreground stars and early-type dwarfs in the Magellanic Bridge, we estimate that about 80 (about 40%) of the candidates are likely to be Herbig Ae/Be stars. We also found one concentration of the candidates at the young star cluster NGC 796, strongly suggesting the existence of pre-main-sequence (PMS) stars in the Magellanic Bridge. This is the first detection of PMS star candidates in the Magellanic Bridge, and if they are genuine PMS stars, this could be direct evidence of recent star formation. However, the estimate of the number of Herbig Ae/Be stars depends on the fraction of classical Be stars, and thus a more precise determination of the Be star fraction or observations to differentiate between the Herbig Ae/Be stars and classical Be stars are required.Comment: 22 pages, 6 figures. Accepted for publication in Ap

A comparative method for evaluating ecosystem services from the viewpoint of public works

Nature-based solutions (NbS), such as the implementation of environmental conservation and restoration as public works projects, require accurate and cost-effective assessments of the values related to the projects. The values should represent collective ecosystem services, individual services such as food provision and water purification, and other intangible services. To comprehensively assess such services, we proposed a novel method, which we call the comparative evaluation method. Our method is able to assess the value of each service category of an NbS project from a single questionnaire survey. Survey participants are asked to compare values of multiple services having anchoring prices. Our method determines the permissible economic value of environmental public works (PEP) in response to the quantity of service. The questionnaire results used for analysis are limited to those from respondents who made their PEP evaluation on the basis of their consideration of the appropriate expenditure of taxes. In addition, the method controls for the effect of the satisfaction that a person experiences from doing good deeds to reduce an overestimation of the values of services. Moreover, PEPs are not influenced by the respondent's annual income, age, sex, or educational background, and are based on personal values. Applying this new method, we surveyed residents of the watersheds of Tokyo Bay and Osaka Bay and evaluated nine ecosystem services. Overall, our new method is shown to be an effective method for evaluating the ecosystem services of NbS projects from the viewpoint of public works

Green port structures and their ecosystem services in highly urbanized Japanese bays

Green port structures (i.e. green infrastructure in ports and harbors) featuring habitats for marine organisms have been promoted in Japan as part of a comprehensive policy to reduce the environmental impact of ports and carry out habitat conservation, restoration, and creation. In this study, we evaluated the ecosystem services provided by green port structures in two highly urbanized bays (Tokyo Bay and Osaka Bay) in Japan. Our results show that the provision of some ecosystem services can be limited by circumstances particular to ports and other areas with restricted access. In the case of green port structures that have strong usage restrictions, for example, cultural services can only be provided if relevant authorities are prepared to conduct public events while ensuring participant safety. On the other hand, green port structures with weak usage restrictions are often equipped with incidental facilities such as parking lots and restrooms; these facilities can enhance the provision of cultural services (e.g. recreation and environmental education). Green port structures in highly urbanized bays often have usage restrictions, but their proximity to large populations means that they can potentially provide numerous ecosystem services. However, our study shows that appropriate management goals, such as protecting species and ensuring healthy habitats, are needed to maintain the value of these services in highly urbanized and eutrophic bays

A Distinct Structure Inside the Galactic Bar

We present the result of a near-infrared (J H Ks) survey along the Galactic plane, -10.5deg < l < +10.5deg and b=+1.0deg, with the IRSF 1.4m telescope and the SIRIUS camera. Ks vs. H-Ks color-magnitude diagrams reveal a well-defined population of red clump (RC) stars whose apparent magnitude peak changes continuously along the Galactic plane, from Ks=13.4 at l=-10deg to Ks=12.2 at l=+10deg after dereddening. This variation can be explained by the bar-like structure found in previous studies, but we find an additional inner structure at |l| < 4deg, where the longitude - apparent magnitude relation is distinct from the outer bar, and the apparent magnitude peak changes by only 0.1 mag over the central 8deg. The exact nature of this inner structure is as yet uncertain.Comment: 8 pages, 4 figures. accepted by ApJ