Stellar magnetic activity is important for formulating the evolution of the star. To represent the stellar magnetic activity, the S index is defined using the Ca II H+K flux measure from the Mount Wilson Observatory. MgII lines are generated in a manner similar to the formation of Ca II lines, which are more sensitive to weak chromospheric activity. MgII flux data are available from the International Ultraviolet Explorer (IUE). Thus, the main purpose of this study was to analyze the magnetic activity of stars. We used 343 high-resolution IUE spectra of 14 main-sequence G stars to obtain the MgII continuum surface flux and MgII line-core flux around 2,800 ˚A. We calculated S index using the IUE spectra and compared it with the conventional Mount Wilson S index. We found a color (B − V ) dependent association between the S index and the MgII emission line-core flux. Furthermore, we attempted to obtain the magnetic activity cycles of these stars based on the new S index. Unfortunately, this was not successful because the IUE observation interval of approximately 17 years is too short to estimate the magnetic activity cycles of G-type stars, whose cycles may be longer than the 11 year mean activity cycle of the sun.

In order to reveal physical conditions of molecular gas in active galaxies (active galaxies mean both starbursts and AGNs in this paper), we carried out systematic observations (R = 19 ~ 120) of CO funda- mental band at 4.7 m in absorption with AKARI. We also made follow-up CO absorption observations at higher spectral resolution (R = 5000 ~ 1000) with Subaru. Recently, Herschel made extensive ob- servations of highly-excited CO lines in emission in the far-infrared. The two data sets (absorption and emission) sometimes provide us with apparently inconsistent results. One case is starburst galaxies: Sub- aru observations showed low temperature of molecular gas toward the starburst NGC 253, while Herschel detected highly excited CO lines in the starburst. This suggests that warm molecular clouds are more deeply embedded than newly formed star clusters. The other case is obscured AGNs; Herschel detected highly excited CO lines in emission in nearby AGNs, while AKARI and Subaru observations showed CO absorption only in some of the obscured AGNs. This could re ect the dierence of nature of molecular tori in these AGNs. We propose the combination of the absorption and emission observations as an eective tool to reveal geometry of warm molecular clouds in active galaxies.

[Fe II] emission lines are prominent in the infrared (IR) and important as diagnostic tools for radiative atomic shocks. We investigate the emission characteristics of [Fe II] lines using a shock code developed by Raymond (1979) with updated atomic parameters. We rst review general characteristics of the IR [Fe II] emission lines from shocked gas, and derive their uxes as a function of shock speed and ambient density. We have compiled available IR [Fe II] line observations of interstellar shocks and compare them to the ratios predicted from our model. The sample includes both young and old supernova remnants in the Galaxy and the Large Magellanic Cloud and several Herbig-Haro objects. We nd that the observed ratios of the IR [Fe II] lines generally fall on our grid of shock models, but the ratios of some mid- IR lines, e.g., [Fe II] 35.35 m=[Fe II] 25.99 m, [Fe II] 5.340 m=[Fe II] 25.99 m, and [Fe II] 5.340 m=[Fe II] 17.94 m, are signicantly oset from our model grid. We discuss possible explanations and conclude that while uncertainties in the shock modeling and the observations certainly exist, the uncertainty in atomic rates appears to be the major source of discrepancy.

The aim of this research is to reveal the spatial distribution of the star formation activity of nearby galaxies by comparing CO molecular emission lines with the large area observation in far-infrared (FIR) lines. We report the imaging observations of NGC 253 by FIR forbidden lines via FIS-FTS and CO molecular lines from low to high excitation levels with ASTE, which are good tracers of star forming regions or photo-dissociation regions, especially spiral galaxies, in order to derive the information of the physical conditions of the ambient interstellar radiation fields. The combination of spatially resolved FIR and sub-mm data leads to the star formation efficiency within galaxy. The ratio between the FIR luminosity and molecular gas mass, LFIR/MH2 , is expected to be proportional to the number of stars formed in the galaxy per unit molecular gas mass and time. Moreover the FIR line ux shows current star formation activity directly. Furthermore these can be systematic and statistical data for star formation history and evolution of spiral galaxies.

We are often faced with the task of having to estimate the amplitude of a source signal in the presence of a background. In the simplest case, the background can be taken as being flat, and of unknown magnitude B, and the source signal of interest assumed to be the amplitude A of a peak of known shape and position. We present a robust method to find the most probable values of A and B by applying the one-dimensional Newton-Raphson method. In the derivation of the formula, we adopted the Bayesian statistics and assmumed Poisson distribution so that the results could be applied to the analysis of very weak signals, as observed in FIMS (Far-ultraviolet IMaging Spectrogaph).

In Lee, Kang & Byun (2001) the discovery of Raman scattered 6545 A feature was reported in symbiotic stars and the planetary nebula M2-9. The broad emission feature around 6545 A is formed as a result of Raman scattering of He II n = 6 → n = 2 photons by atomic hydrogen. In this paper, we introduce a method to compute the equivalent width of He II ⋋ 1025 line and present an optical spectrum of the symbiotic star RR Telescopii as an example for a detailed illustration. In this spectrum, we pay attention to the broad Hα wings and the Raman scattered He II 6545 feature. The broad Ha wings are also proposed to be formed through Raman scattering of continuum around Lyβ by Lee (2000), and therefore we propose that the equivalent width of the He II ⋋ 1025 emission line is obtained by a simple comparison of the strengths of the 6545 feature and the broad Hα wings. We prepare a template Hα wing profile from continuum radiation around Lyβ with the neutral scattering region that is supposed to be responsible for the formation of Raman scattered He II 6545 feature. Isolation of the 6545 feature that is blended with [N II] ⋋ 6548 is made by using the fact that [N II] ⋋ 6584 is always 3 times stronger than [N II] ⋋ 6548. We also fit the 6545 feature by a Gaussian which has a width 6.4 times that of the He II ⋋ 6527 line. A direct comparison of these two features for RR Tel yields the equivalent width EW Hel025 = 2.3 Å of He II ⋋ 1025 line. Even though this far UV emission line is not directly observable due to heavy interstellar extinction, nearby He II lines such as He II ⋋ 1085 line may be observed using far UV space instruments, which will verify this calculation and hence the origins of various features occurring in spectra around Hα.