간행물
천문학논총 KCI 등재 Publications of the Korean Astronomical Society
- 발행기관 한국천문학회
- 자료유형 학술지
- 간기 연3회
- ISSN 1225-1534 (Print)2287-6936 (Online)
- 수록기간 1984 ~ 2023
- 주제분류 자연과학 > 천문학 자연과학 분류의 다른 간행물
- 십진분류KDC 440DDC 520
권호리스트/논문검색
Volume 32 Issue 1 (2017년 3월) 77건
21.
2017.03
구독 인증기관 무료, 개인회원 유료
The existence of polycyclic aromatic hydrocarbons (PAHs) astronomically is well accepted, but the speci c molecular forms observed remain uncertain. To better understand the molecular structures which may be present along a given sightline, the 3.0 - 3.6 μm region is modelled with careful consideration given to the underlying sub-features arising from speci c structures within emitting molecules.
3,000원
22.
2017.03
구독 인증기관 무료, 개인회원 유료
Aaron C. Bell, Takashi Onaka, Yasuo Doi, Itsuki Sakon, Fumihiko Usui, Itsuki Sakon, Daisuke Ishihara, Hidehiro Kaneda, Martin Giard, Ronin Wu, Ryou Ohsawa, Tamami Mori-Ito, Mark Hammonds, Ho-Gyu Lee
Our understanding of dust emission, interaction, and evolution, is evolving. In recent years, electric dipole emission by spinning dust has been suggested to explain the anomalous microwave excess (AME), appearing between 10 and 90 Ghz. The observed frequencies suggest that spinning grains should be on the order of 10nm in size, hinting at polycyclic aromatic hydrocarbon molecules (PAHs). We present data from the AKARI/Infrared Camera (IRC) due to its high sensitivity to the PAH bands. By inspecting the IRC data for a few AME regions, we nd a preliminary indication that regions well- tted by a spinning- dust model have a higher 9 m than 18 m intensity vs. non-spinning-dust regions. Ongoing e orts to improve the analysis by using DustEM and including data from the AKARI Far Infrared Surveyor (FIS), IRAS, and Planck High Frequency Instrument (HFI) are described.
3,000원
23.
2017.03
구독 인증기관 무료, 개인회원 유료
Itsuki Sakon, Takashi Onaka, Fumihiko Usui, Sayaka Shimamoto, Ryou Ohsawa, Takehiko Wada, Hideo Matsuhara, Akira Arai
3,000원
24.
2017.03
구독 인증기관 무료, 개인회원 유료
Tamami I. Mori, Takashi Onaka, Itsuki Sakon, Ryou Ohsawa, Hidehiro Kaneda, Mitsuyoshi Yamagishi, Yoko Okada, Masahiro Tanaka, Takashi Shimonishi
We present results of AKARI/IRC near-infrared (NIR) slit-spectroscopy (2.5{5.0 m, R 100) of Galactic sources, focusing on ice absorption features. We investigate the abundance of H2O and CO2 ices and other ice species (CO and XCN ices) along lines of sight towards Galactic Hii regions, massive YSOs, and infrared di use sources. Even among those di erent kinds of astronomical objects, the abundance ratio of CO2 to H2O ices does not vary signi cantly, suggesting that the pathway to CO2 ice formation driven by UV irradiation is not e ective at least among the present targets.
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25.
2017.03
구독 인증기관 무료, 개인회원 유료
Sayaka Shimamoto, Itsuki Sakon, Takashi Onaka, Fumihiko Usui, Takafumi Ootsubo, Yasuo Doi, Ryou Ohsawa, Daisuke Ishihara
We detected bright mid- to far-infrared emission from the helium nova V445 Puppis in the AKARI all-sky survey data taken in 2006. Assuming an optically thin condition, we decomposed the spectral energy distribution (SED) of V445 Puppis in October 2006 by model tting and found that the SED can be explained by a combination of cold amorphous carbon (125 K and the mass of 4:5+6:6 2:7 X 10-4 M⊙) and warm amorphous carbon (250 K and the mass of 1:8+1:0 -0:5 X 10-5 M⊙). Assuming that the former is pre-existing dust formed in the past nova outbursts and the latter is newly formed dust in December 2000's nova wind, this result suggests that the amount of dust formed around V445 Puppis in a single outburst is larger than 10-5 M⊙, which is larger than those in any other classical novae ever reported.
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26.
2017.03
구독 인증기관 무료, 개인회원 유료
L. Viktor Toth, Yasuo Doi, Sarolta Zahorecz, Marton Agas, Lajos G. Balazs, Adrienn Forro, Istvan I. Racz
A signi cant number of the parameters of a gamma-ray burst (GRB) and its host galaxy are calculated from the afterglow. There are various methods obtaining extinction values for the necessary correction for galactic foreground. These are: galaxy counts, from HI 21 cm surveys, from spectroscopic measurements and colors of nearby Galactic stars, or using extinction maps calculated from infrared surveys towards the GRB. We demonstrate that AKARI Far-Infrared Surveyor sky surface brightness maps are useful uncovering the ne structure of the galactic foreground of GRBs. Galactic cirrus structures of a number of GRBs are calculated with a 2 arcminute resolution, and the results are compared to that of other methods.
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27.
2017.03
구독 인증기관 무료, 개인회원 유료
We show Akari data, Herschel data and data from the SCUBA2 camera on JCMT, of molecular clouds. We focus on pre-stellar cores within the clouds. We present Akari data of the L1147-1157 ring in Cepheus and show how the data indicate that the cores are being externally heated. We present SCUBA2 and Herschel data of the Ophiuchus region and show how the environment is also a ecting core evolution in this region. We discuss the e ects of the magnetic eld in the Lupus I region, and how this lends support to a model for the formation and evolution of cores in lamentary molecular clouds.
4,000원
28.
2017.03
구독 인증기관 무료, 개인회원 유료
We present our AKARI study of massive star forming regions where a large-scale cloud-cloud collision possibly contributes to massive star formation. Our targets are Spitzer bubbles, which consist of two types of bubbles, closed and broken ones; the latter is a candidate of the objects created by cloud-cloud collisions. We performed mid- and far-infrared surface photometry toward Spitzer bubbles to obtain the relationship between the total infrared luminosity, LIR, and the bubble radius, R. As a result, we nd that LIR is roughly proportional to R where = 2:10:4. Broken bubbles tend to have larger radii than closed bubbles for the same LIR.
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29.
2017.03
구독 인증기관 무료, 개인회원 유료
We have observed 60 Weak-line T Tauri stars (WTTSs) toward the Chamaeleon star forming region using the AKARI Far-Infrared Surveyor (FIS) All-Sky maps. We could not detect any signi cant emission from each source even at the most sensitive WIDE-S band. Then, we have performed stacking analysis of these WTTSs using the WIDE-S band images to improve the sensitivity. However, we could not detect any signi cant emission in the resultant image with a noise level of 0.05 MJy sr-1, or 3 mJy for a point source. The three-sigma upper limit of 9 mJy leads to the disk dust mass of 0.01 M⊕. This result suggests that the disks around Chamaeleon WTTSs are already evolved to debris disks.
3,000원
30.
2017.03
구독 인증기관 무료, 개인회원 유료
We present the latest results from the Mission Program NIRLT (PI: I.Yamamura), the near-infrared spectroscopy of brown dwarfs using the AKARI/IRC grism mode with the spectral resolution of ~ 120. The near-infrared spectra in the wavelength range between 2.5 and 5.0 μm are especially important to study the brown dwarf atmospheres because of the presence of major molecular bands, including CH4 at 3.3 μm, CO2 at 4.2 μm, CO at 4.6 μm, and H2O around 2.7 μm. We observed 27 sources, and obtained 16 good spectra. Our model fitting reveals deviations between theoretical model and observed spectra in this wavelength range, which may be attributed to the physical condition of the upper atmosphere. The deviations indicate additional heating, which we hypothesize to be due to chromospheric activity. We test this effect by modifying the brown dwarf atmosphere model to artificially increase the temperature of the upper atmosphere, and compare the revised model with observed spectra of early- to mid-L type objects with Hα emission. We find that the chemical structure of the atmosphere changes dramatically, and the heating model spectra of early-type brown dwarfs can be considerably improved to match the observed spectra. Our result suggests that chromospheric activity is essential to understand early-type brown dwarf atmospheres.
3,000원
31.
2017.03
구독 인증기관 무료, 개인회원 유료
Hidehiro Kaneda, Takuma Kokusho, Rika Yamada, Daisuke Ishihara, Shinki Oyabu, Toru Kondo, Mitsuyoshi Yamagishi, Akiko Yasuda, Takashi Onaka, Toyoaki Suzuki
We have performed systematic studies of the properties of dust in various environments of nearby galaxies with AKARI. The unique capabilities of AKARI, such as near-infrared (near-IR) spectroscopy combined with all-sky coverage in the mid- and far-IR, enable us to study processing of dust, particularly carbonaceous grains includings polycyclic aromatic hydrocarbons (PAHs), for unbiased samples of nearby galaxies. In this paper, we first review our recent results on individual galaxies, highlighting the uniqueness of AKARI data for studies of nearby galaxies. Then we present results of our systematic studies on nearby starburst and early-type galaxies. From the former study based on the near-IR spectroscopy and mid-IR all-sky survey data, we find that the properties of PAHs change systematically from IR galaxies to ultra- luminous IR galaxies, depending on the IR luminosity of a galaxy or galaxy population. From the latter study based on the mid- and far-IR all-sky survey data, we find that there is a global correlation between the amounts of dust and old stars in early-type galaxies, giving an observational constraint on the origin of the dust.
4,000원
32.
2017.03
구독 인증기관 무료, 개인회원 유료
Mitsuyoshi Yamagishi, Hidehiro Kaneda, Shinki Oyabu, Daisuke Ishihara, Takashi Onaka, Takashi Shimonishi, Toyoaki Suzuki
We study CO2/H2O ice abundance ratios in nearby galaxies using AKARI near-infrared slit spec- troscopy. Past studies of the ices intensively examined CO2/H2O ratios mainly in our Galaxy, and found that there were considerable variations in the CO2/H2O ratios from object to object. The cause of the variations is, however, still under debate. As a result of the analysis of our sample that includes 1031 regions in 158 galaxies, the CO2/H2O ratios are in a range of 0.05-0.30. In the dataset, we nd that the CO2/H2O ratios positively correlate with the Brα/PAH 3.3 μm ratios which re ect the massive star formation activity. Furthermore, we find that the CO2/H2O ratios positively correlate with the specific star formation rates of the galaxies where the ices are detected, that re ect the evolutionary stage of a galaxy. These results suggest that the CO2/H2O ratios are enhanced in active star-forming regions and young galaxies.
4,000원
33.
2017.03
구독 인증기관 무료, 개인회원 유료
Since the launch of the Herschel Space Observatory, our understanding about the photo-dissociation regions (PDR) has taken a step forward. In the bandwidth of the Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) on board Herschel, ten CO rotational transitions, including J = 4-3 to J = 13-12, and three fine structure lines, including [Ci] 609, [Ci] 370, and [Nii] 205 μm, are covered. I present our findings from the FTS observations at the nuclear region of M83, based on the spatially resolved physical parameters derived from the CO spectral line energy distribution (SLED) map and the comparisons with the dust properties and star-formation tracers. This article discusses (1) the potential of using [Nii] 205 and [Ci] 370 μm as star-formation tracers; (2) the excitation mechanisms of warm CO in the nuclear region of M83.
3,000원
34.
2017.03
구독 인증기관 무료, 개인회원 유료
Early-type galaxies (ETGs) are generally dominated by old low-mass stars, which are not very productive of dust, and hot interstellar plasmas, which are very destructive of dust. Thus ETGs provide harsh environments for survival of dust. It has been found that some ETGs contain a large amount of dust, and yet its supply mechanism is not understood well. We present the result of a systematic study of dust in ETGs with the AKARI mid- and far-infrared all-sky surveys. From the AKARI result and the Ks band data obtained by ground-based telescopes, we nd that there is a global correlation between the dust mass and stellar luminosity. We also compare the AKARI all-sky survey result with the CO data to discuss origins of dust in ETGs.
3,000원
35.
2017.03
구독 인증기관 무료, 개인회원 유료
Shinki Oyabu, Hidehiro Kaneda, Masaya Izuhara, Keisuke Tomita, Daisuke Ishihara, Kimiaki Kawara, Yoshiki Matsuoka
The dusty torus of Active Galactic Nuclei (AGNs) is one of the important components for the unification theory of AGNs. The geometry and properties of the dusty torus are key factors in understanding the nature of AGNs as well as the formation and evolution of AGNs. However, they are still under discussion. Infrared observation is useful for understanding the dusty torus as thermal emission from hot dust with the dust sublimation temperature (~ 1500 K) has been observed in the infrared. We have analyzed infrared spectroscopic data of low-redshift and high-redshift quasars, which are luminous AGNs. For the low-redshift quasars, we constructed the spectral energy distributions (SEDs) with AKARI near-infrared and Spitzer mid-infrared spectra and decomposed the SEDs into a power-law component from the nuclei, silicate features, and blackbody components with different temperatures from the dusty torus. From the decomposition, the temperature of the innermost dusty torus shows the range between 900-2000 K. For the high-redshift quasars, AKARI traced rest-frame optical and near-infrared spectra of AGNs. Combining with WISE data, we have found that the temperature of the innermost dusty torus in high redshift quasars is lower than that in typical quasars. The hydrogen Hα emission line from the braod emission line region in the quasars also shows narrow full width at half maximum of 3000-4000 km s-1. These results indicate that the dusty torus and the broad emission line region are more extended than those of typical quasars.
4,000원
36.
2017.03
구독 인증기관 무료, 개인회원 유료
Myungshin Im, Hyunsung Jun, Dohyeong Kim, Hyung Mok Lee, Youichi Ohyama, Ji Hoon Kim, Takao Nakagawa, QSONG Team
Utilizing a unique capability of AKARI that allows deep spectroscopy at 2.5 - 5.0 μm, we performed a spectroscopy study of more than 200 quasars through one of the AKARI mission programs, QSONG (Quasar Spectroscopic Observation with NIR Grism). QSONG targeted 155 high redshift (3:3 < z < 6:42) quasars and 90 low redshift active galactic nuclei (0:002 < z < 0:48). In order to provide black hole mass estimates based on the rest-frame optical spectra, the high redshift part of QSONG is designed to detect the Hα line and the rest-frame optical spectra of quasars at z > 3:3. The low redshift part of QSONG is geared to uncover the rest-frame 2.5 - 5.0 μm spectral features of active galactic nuclei to gain useful information such as the dust-extinction-free black hole mass estimators based on the Brackett lines and the temperatures of the hot dust torus. We outline the program strategy, and present some of the scientific highlights from QSONG, including the detection of the Hα line from a quasar at z > 4:5 which indicates a rigorous growth of black holes in the early universe, and the Brβ-based black hole mass estimators and the hot dust temperatures (~ 1100 K) of low redshift AGNs.
4,000원
37.
2017.03
구독 인증기관 무료, 개인회원 유료
4,000원
38.
2017.03
구독 인증기관 무료, 개인회원 유료
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 di erence of nature of molecular tori in these AGNs. We propose the combination of the absorption and emission observations as an e ective tool to reveal geometry of warm molecular clouds in active galaxies.
3,000원
39.
2017.03
구독 인증기관 무료, 개인회원 유료
AKARI and the subsequent Herschel Space Observatory have yielded tremendous advancement in our knowledge of the infrared-submillimeter properties of active galaxies and active galactic nuclei, AGN. This short review describes some highlights. Active galaxies are found to do what they are supposed to do: build up their stellar bodies while building up their central black holes.
4,000원
40.
2017.03
구독 인증기관 무료, 개인회원 유료
Naoki Isobe, Takao Nakagawa, Kenichi Yano, Shunsuke Baba, Shinki Oyabu, Yoshiki Toba, Yoshihiro Ueda, Taiki Kawamuro
Combining the AKARI Point Source Catalog and the 37-month Monitor of All-sky X-ray Image (MAXI) catalog, the infrared and X-ray properties of nearby active galactic nuclei were investigated. The 37-month MAXI catalog tabulates 100 nearby Seyfert galaxies, 73 of which are categorized into Seyfert I galaxies. Among these Seyfert galaxies, 69 ones were found to have an AKARI infrared counterpart. For the Seyfert I galaxies in this sample, a well-known correlation was found between the infrared and X-ray luminosities. However, the observed X-ray luminosity of the Seyfert II galaxies tends to be lower for the infrared luminosity than the Seyfert I galaxies. This suggests that the X-ray absorption is significant in the Seyfert II galaxies. The Seyfert II galaxies seem to have a bimodal distribution of the IR color between 18 μm and 90 μm. Especially, a large fraction of the Seyfert II galaxies exhibits a redder IR color than the Seyfert I galaxies. A possible origin of the redder IR color is brie y discussed, in relation to the star formation activity in the host galaxy, and to the X-ray absorption.
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