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 ~ 2024
- 주제분류 자연과학 > 천문학 자연과학 분류의 다른 간행물
- 십진분류KDC 440DDC 520
권호리스트/논문검색
Volume 27 Issue 4 (2012년 9월) 71건
21.
2012.09
구독 인증기관 무료, 개인회원 유료
PLANCK COLLABORATION, M. GIARD, O. BERNE, Y. DOI, D. ISHIHARA, CH. JOBLIN, I. KANEDA, D. MARSHALL, T. NAKAGAWA, R. OHSAWA, T. ONAKA, I. SAKON, H. SHIBAI, N. YSARD
We show how the rotation emission from isolated interstellar Polycyclic Aromatic Hydrocarbons (PAHs) can explain the so-called anomalous microwave emission (AME). AME has been discovered in the last decade as microwave interstellar emission (10 to 70 GHz) that is in excess compared to the classical emission processes: thermal dust, free-free and synchrotron. The PAHs are the interstellar planar nano-carbons responsible for the near infrared emission bands in the 3 to 15 micron range. Theoretical studies show that under the physical conditions of the interstellar medium (radiation and density) the PAHs adopt supra-thermal rotation velocities, and consequently they are responsible for emission in the microwave range. The first results from the PLANCK mission unexpectedly showed that the AME is not only emitted by specific galactic interstellar clouds, but it is present throughout the galactic plane, and is particularly strong in the cold molecular gas. The comparison of theory and observations shows that the measured emission is fully consistent with rotation emission from interstellar PAHs. We draw the main lines of our PLANCK-AKARI collaborative program which intends to progress on this question by direct comparison of the near infrared (AKARI) and microwave (PLANCK) emissions of the galactic plane.
4,000원
22.
2012.09
구독 인증기관 무료, 개인회원 유료
GLENN J. WHITE, YASUO DOI, SHINYA KOMUGI, MITSUNOBU KAWADA, SATOSHI TAKITA, KO ARIMATSU, NORIO IKEDA, DAISUKE KATO, YOSHIMI KITAMURA, TAKAO NAKAGAWA, TAKAFUMI OOTSUBO, TAKAHIRO MORISHIMA, MAKOTO HATTORI, MASAHIRO TANAKA, MIREYA ETXALUZE, HIROSHI SHIBAI
Following the first Public Release of the AKARI Point Source catalogues, we have worked on the production of a new far-infrared All-Sky Diffuse mapping product. In this paper we report first results from the All Sky diffuse maps that will shortly be released to the community, based on analysis of data from the Far Infrared Surveyor ( 65 μm − 160 μm ) instrument. These data are likely to have a strong impact on studies of extended structures, and the diffuse ISM.
4,000원
23.
2012.09
구독 인증기관 무료, 개인회원 유료
We present the results of the near-infrared (NIR) to mid-infrared (MIR) slit spectroscopic observations of the diffuse emission toward nine positions in the nearby irregular galaxy Large Magellanic Cloud (LMC) with the Infrared Camera (IRC) on board AKARI. The unique characteristic of AKARI/IRC provides a great opportunity to analyze variations in the unidentified infrared (UIR) bands based on continuous spectra from 2.5 to 13.4 μm of the same slit area. The observed variation of I3.3 / I11.3 suggests destruction of small-sized UIR band carriers, polycyclic aromatic hydrocarbons (PAHs) in harsh environments. This result demonstrates that the UIR 3.3 μm band provides us powerful information on the excitation conditions and/or the size distribution of PAHs, which is of importance for understanding the evolutionary process of hydrocarbon grains in the Universe. It also suggests a new diagnostic diagram of two band ratios, such as I3.3 / I11.3 versus I7.7 / I11.3 , for the interstellar radiation conditions. We discuss on the applicability of the diagnostic diagram to other astronomical objects, comparing the LMC results with those observed in other galaxies such as NGC 6946, NGC 1313, and M51.
3,000원
24.
2012.09
구독 인증기관 무료, 개인회원 유료
We have collected dozens of mid-infrared spectra showing UIR bands from diffuse Galactic emitting regions with the AKARI's Infrared Camera (IRC) onboard AKARI, as part of the ISMGN Mission Program. The datasets cover various directions in the inner Galactic Plane ( |l| < 70 deg), in the outer Galactic Plane ( |l| > 70 deg), and in the off-Plane ( |b| > 2 deg). The variations in the UIR band ratios are examined in terms of the radiation environments judged from the far-infrared ( 50 − 170 μm ) spectral energy distribution (SED) made with AKARI/FIS All Sky Survey data at each slit position where mid-IR spectra were obtained. We have found that the band ratios of 6.2 μm / 11.2 μm and 7.7 μm / 11.2 μm toward the inner Galaxy are systematically higher than those toward the outer Galaxy and off the Galactic plane. Likely causes of the variations in properties of UIR bands in diffuse emission on a Galactic scale are discussed in this paper.
3,000원
25.
2012.09
구독 인증기관·개인회원 무료
Among the AKARI all-sky survey data, the 9 μm diffuse map is crucial to study the polycyclic aromatic hydrocarbon (PAH) emission features on large spatial scales, while the 18 μm map is useful to trace hot dust emission. To utilize these advantages, we have improved the AKARI mid-infrared (MIR) all-sky survey diffuse maps. For example, we have established special methods to remove the effects of the ionizing radiation in the South Atlantic Anomaly (SAA) and of the scattered light from the moon. Using improved diffuse map data, we study the properties of PAHs and dust in the Galactic center region associated with high-energy phenomena.
26.
2012.09
구독 인증기관·개인회원 무료
A. TAKAHASHI, A. YASUDA, H. KANEDA, M. KAWADA, Y. KIRIYAMA, A. MOURI, T. MORI, Y. OKADA, H. TAKAHASHI
We present the results of far-infrared spectroscopic observations of the Large Magellanic Cloud (LMC) with FIS-FTS. We covered a large area across the LMC, including 30 Doradus (30 Dor) and N44 star-forming regions, by 191 pointings in total. As a result, we detect the [OIII] and [CII] line emission as well as far-infrared dust continuum emission throughout the LMC. We find that the [OIII] emission is widely distributed around 30 Dor. The observed size of the distribution is too large to be explained by massive stars in 30 Dor, which are assumed to be enshrouded by clouds with the constant gas density estimated from the [OIII] line intensities. Therefore the surrounding structure is likely to be highly clumpy. We also find a global correlation between the [OIII] and the far-infrared continuum emission, suggesting that the gas and dust are well mixed in the highly-ionized region where the dust survives in clumpy dense clouds shielded from energetic photons. Furthermore we find that the ratios of [CII]/CO are as high as 110,000 in 30 Dor, and 45,000 even on average, while they are typically 6,000 for star-forming regions in our Galaxy. The unusually high [CII]/CO is also consistent with the picture of clumpy small dense clouds.
27.
2012.09
구독 인증기관·개인회원 무료
We present the results of far-infrared spectral mapping of the Galactic center region with FIS-FTS, which covered the two massive star-forming clusters, Arches and Quintuplet. We find that two dust components with temperatures of about 20 K and 50 K are required to fit the overall continuum spectra. The warm dust emission is spatially correlated with the [OIII] 88 μm emission and both are likely to be associated with the two clusters, while the cool dust emission is more widely distributed without any clear spatial correlation with the clusters. We find differences in the properties of the ISM around the two clusters, suggesting that the star-forming activity of the Arches cluster is at an earlier stage than that of the Quintuplet cluster.
28.
2012.09
구독 인증기관·개인회원 무료
Understanding the birth and evolution of galaxies, and the history of star formation in them, is one of the most important problems in astronomy. Using the data from the AKARI IRC survey of the Large Magellanic Cloud at 3.2, 7, 11, 15, and 24 μm , we have constructed a multi-wavelength catalog containing data from the cross-correlation with a number of other databases at different wavelengths. We present the first approach with a Support Vector Machine (SVM)-based method to separate different classes of stars in LMC in the color-color and color-magnitude diagrams.
29.
2012.09
구독 인증기관 무료, 개인회원 유료
Supernovae (SN) and supernova remnants (SNRs) play a major role in the life-cycle of interstellar dusts. Fast shock waves generated by SN explosions sweep out the interstellar space destroying dust grains and modifying their physical and chemical properties. The dense, cooling SN ejecta, on the other hand, provide an environment for dusts to condense. Recent space-infrared telescopes have revealed the hidden universe related to these fascinating microscopic processes. In this paper, I introduce the results on stardusts in young core-collapse supernova remnants obtained by AKARI. The AKARI results show diverse infrared characteristics of stardusts associated with SNRs, implying diverse physical/chemical stellar structures and circumstellar environments at the time of explosion.
4,000원
30.
2012.09
구독 인증기관 무료, 개인회원 유료
We present preliminary results of supernova remnants (SNRs) in the Large Magellanic Cloud (LMC) seen by AKARI as well as Spitzer. By examining the AKARI LMC survey and the Spitzer data, we have searched for IR counterparts to 45 known SNRs in the LMC and could identify 28 SNRs with associated IR emission. 13 SNRs among them are newly detected in IR bands. For the entire IR SNRs, we make a catalog containing general information and the AKARI and/or Spitzer fluxes. Using the catalog, their IR colors and the possible correlation of the IR fluxes with the X-ray fluxes are examined. For some interesting SNRs, we have performed NIR spectroscopy with AKARI. An aromatic feature at 3.3 μm can be identified in LMC SNR N49. We investigate the characteristics of the IR features and discuss the PAH mission mechanism in SNRs.
3,000원
31.
2012.09
구독 인증기관·개인회원 무료
We carry out a systematic study of Galactic supernova remnants (SNRs) using the AKARI Far Infrared Surveyor (FIS) survey data. The AKARI Infrared Astronomical Satellite observed the whole sky using the four FIS bands covering 50 to 180 microns with ~1 arcmin resolution. The all-sky coverage with high-spatial resolution provides an unprecedented opportunity to study diffuse, extended far-infrared (FIR) sources such as SNRs. We have searched for FIR counterparts to all 274 known Galactic SNRs, and investigate their FIR properties of identified SNRs. We report preliminary results of the study.
32.
2012.09
구독 인증기관 무료, 개인회원 유료
We have performed a systematic study of interstellar dust grains in various environments of galaxies. AKARI has revealed the detailed properties of dust grains not only in star-forming regions but also in regions not relevant to star formation, some of which are found not to follow our old empirical knowledge. Because of its unique capabilities, AKARI has provided new knowledge on the processing of large grains and polycyclic aromatic hydrocarbons (PAHs). For example, we detect PAHs from elliptical galaxies, which show unusual spectral features and spatial distributions, demonstrating importance of material processing in the interstellar space. We find that copious amounts of large grains and PAHs are flowing out of starburst galaxies by galactic superwinds, which are being shattered and destroyed in galactic haloes. We discover evidence for graphitization of carbonaceous grains near the center of our Galaxy, providing a clue to understanding the activity of the Galactic center. We review the results obtained from our AKARI program, focusing on the processing of carbonaceous grains in various environments of galaxies.
4,000원
33.
2012.09
구독 인증기관 무료, 개인회원 유료
Nearby spiral galaxies M101 and M81 are considered to have undergone a galaxy-galaxy interaction. M101 has experienced HI gas infall due to the interaction. With AKARI far-infrared (IR) photometric observations, we found regions with enhanced star forming activity, which are spatially close to regions affected by the interaction. In addition, the relation between the star formation rate (SFR) and the gas content for such regions shows a significant difference from typical spiral arm regions. We discuss possible explanations for star formation processes on a kiloparsec scale and the association with interaction-triggered star formation. We also observed the compact group of galaxies Stephan's Quintet (SQ) with the AKARI Far-infrared Surveyor (FIS). The SQ shows diffuse intergalactic medium (IGM) due to multiple collisions between the member galaxies and the IGM. The intruder galaxy NGC 7318b is currently colliding with the IGM and causes a large-scale shock. The 160 micron image clearly shows the structure along the shock ridge as seen in warm molecular hydrogen line emission and X-ray emission. The far-IR emission from the shocked region comes from the luminous [CII] 158 μm line and cold dust (~ 20 K) that coexist with molecular hydrogen gas. Survival of dust grains is indispensable to form molecular hydrogen gas within the collision age (~ 5 Myr). At the stage of the dusty IGM environment, [CII] and H2 lines rather than X-ray emission are powerful cooling channels to release the collision energy.
4,000원
34.
2012.09
구독 인증기관 무료, 개인회원 유료
The absorption features due to interstellar ices, especially H2O and CO2 ices, provide us with crucial information on present and past interstellar environments, and thus the evolutionary histories of galaxies. Before AKARI, however, few detections of ices were reported for nearby galaxies. The AKARI's unique capability of near-infrared spectroscopy with high sensitivity enables us to systematically study ices in nearby galaxies. Thus we have explored many near-infrared spectra ( 2.5−5μm ) of the 211 pointed observations, searching for the absorption features of ices. As a result, out of 122 nearby galaxies, we have significantly detected H2O ice from 36 galaxies and CO2 ice from 9 galaxies. It is notable that the ices are detected not only in late-type galaxies but also in early-type galaxies. We find that CO2 ice is more compactly distributed near the galactic center than H2O ice. Finally, we suggest that the gas density of a molecular cloud and UV radiation may be important factors to determine the abundance of ices.
3,000원
35.
2012.09
구독 인증기관 무료, 개인회원 유료
We present the IRC images of M51, a pair of interacting galaxies. Given the high angular resolution (7.4") and the wide field of view (~ 10') covering almost the entire M51 system, we investigate dust properties and their connection to the spiral arm structure. We have applied image-filtering processes including the wavelet analysis to the N3 image, which traces the total stellar mass best among the IRC bands. From this filtered image, the center, arm, and interarm regions are defined. A color, or flux ratio among the MIR bands, has been measured at each pixel (3.7" in size). We find a wide variety of S7/S11 with a difference between arm and interarm regions. We also find that at some positions S11 seems to be higher than predicted by MW dust models. Estimated contributions from the stellar continuum and gas emission lines to the band are not enough to explain this discrepancy. From these results, we deduce that the PAH ionization condition and its fraction to the total dust mass in M51 are different from those in MW.
3,000원
36.
2012.09
구독 인증기관·개인회원 무료
With AKARI, we carried out near-infrared spectroscopy of the nearby barred spiral galaxy, NGC 1097, categorized as Seyfert 1 with a circumnuclear starburst ring. Our observations mapped the galactic center region. As a result, we obtain the spatial distributions of the polycyclic aromatic hydrocarbon 3.3μm and the aliphatic hydrocarbon 3.4−3.6 μm emission. The former is detected from all the observed regions and the latter is enhanced near the bar connecting the ring with the nucleus. In addition, we detect absorption features due to H2O ice and CO/SiO at the ring and the galactic center, while we detect the hydrogen recombination line Brα only from the ring. Hence the observed spectra change dramatically within the central 1 kpc region.
37.
2012.09
구독 인증기관·개인회원 무료
R. OHSAWA, T. ONAKA, I. SAKON, T. I. MORI, I. YAMAMURA, M. MATSUURA, H. KANEDA, J. BERNARD-SALAS, O. BERNE, C. JOBLIN
Polycyclic aromatic hydrocarbons (PAHs) in Galactic planetary nebulae (PNe) are investigated by means of the unidentified infrared (UIR) bands. Continuous near- to mid-infrared spectra of PNe are obtained with the AKARI/IRC and the Spitzer/IRS. All 19 PNe in the present study show prominent dust emissions and we investigate the variation in the intensity ratios among the UIR bands. The ionization fraction and the size distribution of PAHs in PNe are derived using the UIR band ratios. We find that the ionization fraction of PAHs in PNe is around 0.0-0.6 and that small PAHs are scarce. The present result indicates a systematic trend of the 3.4 μm aliphatic feature to become weak as the PAH ionization fraction increases.
38.
2012.09
구독 인증기관·개인회원 무료
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.
39.
2012.09
구독 인증기관·개인회원 무료
PROPERTIES OF DUST IN EARLY-TYPE GALAXIES BASED ON THE ALL-SKY-SURVEY DATA AND NEAR-INFRARED SPECTRA
We present the properties of dust and the near-infrared spectral features in nearby early-type galaxies. The properties of dust are obtained from the AKARI far-infrared all-sky survey diffuse map. The AKARI/IRC is used for the near-infrared spectra. We improve spectral data with the new dark subtraction method on the basis of the knowledge acquired in our laboratory experiments of the engineering-model detector for the IRC. We have succeeded in fitting the continuum by a power-law function and detecting CO and SiO absorption features in early-type galaxy spectra. Comparing the properties of dust and near-infrared spectral features, we find that the power-law slope depends on dust temperature, but not on the dust mass, which suggests that low-luminosity AGNs may contribute to the changes in the power-law slope and dust temperature.
40.
2012.09
구독 인증기관 무료, 개인회원 유료
S. OYABU, D. ISHIHARA, R. YAMADA, H. KANEDA, M. YAMAGISHI, Y. TOBA, H. MATSUHARA, T. NAKAGAWA, M. MALKAN, M SHIRAHATA
Many observations have found evidence of the presence of a large number of heavily obscured Active Galactic Nuclei (AGNs). However, the nature of this population is only poorly understood because heavy obscuration by dust prevents one from finding them at optical wavelengths. Mid-infrared AGN searches can overcome this obstacle by penetrating through dust and by detecting direct emission from the dust torus. Thus, we can identify most of the AGN population, including type-2 and buried AGNs. Using the AKARI mid-infrared all-sky survey, we performed an AGN search in the nearby universe. Utilizing the 2MASS photometry, we selected mid-infrared-excess sources and carried out near-infrared spectroscopic observations in the AKARI Phase 3. During these follow-up observations, we have found three galaxies that show strong near-infrared red continuum from hot dust with a temperature of about 500 K, but do not show any AGN features in other wavelengths. The most suitable explanation of near-infrared continuum is the presence of central AGNs. Therefore, we conclude that they are AGNs obscured by dust. We performed X-ray observations of the two galaxies with SUZAKU. No detections in the 0.4-10 keV suggest that the column density may be much higher than NH=1023.5cm−2 . Comparing the masses of the host galaxies with those of the SDSS AGNs, we find that the host galaxies of the dusty AGNs discovered with AKARI are less massive populations than those of optically selected AGNs.
4,000원
