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第177回: 2011/05/19(木) 15:30-16:30 田村 陽一 氏 (東京大学・天文学教育研究センター) 「ASTE搭載用超伝導転移端センサ型ボロメータカメラとALMA初期科学運用」 "The new TES bolometer camera for ASTE and the ALMA early science operation" 東京大学天文センター・国立天文台・北海道大学は、チリ・アタカマ砂漠に設置された ASTE望遠鏡への搭載を目的とした超伝導転移端センサ型ボロメータカメラ開発を、 2009年より推進している。本カメラは本年7月にASTE望遠鏡に搭載され、1100、850ミクロン （将来的には450ミクロンも）における地上天文観測を開始する予定だ。 その観測対象は、遠方銀河・銀河団、ガンマ線バースト、マゼラン雲、原始惑星系円盤と 多岐にわたる。本講演の前半では、ASTE観測所の現状、本サブミリ波カメラプロジェクトの サイエンスケース、および進捗を紹介する。 本講演の後半では、いよいよ開始されるALMAの初期科学運用に触れたい。 3月末に観測提案公募の情報が、のべ100ページに迫る複数の文書とともに公表された。 この公募の独特な点は、世界各国の電波天文学者の注目の高さもさることながら、 観測提案者・提案内容に課せられた条件の多さにあると言える。ひとりのユーザの視点から、 初期運用フェイズのALMAの性能・観測公募の内容を読み解きたい。
第178回: 2011/06/16(木) 15:30-16:30 Michael Richmond 氏 (Rochester Institute of Technology) "Looking for eclipsing RR Lyr stars in the MACHO database" The MACHO Project collected photometry of many RR Lyrae stars from its observations of the Milky Way's bulge. We examined the lightcurves of 3256 stars identified as RRab Lyr variables by Kund et al. 2008, subtracting an empirical model of the pulsation lightcurve and searching for periodic variation in the residuals. There are no systems which show the brief dips in light characteristic of detached eclipsing binary systems. We discuss the results for objects which show the largest residual periodic modulation, most of which are probably due to aliases of the fundamental period. (See http://arxiv.org/abs/1106.0697.)
第179回: 2011/06/30(木) 15:30-16:30 田中 賢幸 氏 (東京大学・IPMU) "A new method to identify AGNs and the nature of low-luminosity AGNs" We develop a new method to identify AGNs using optical spectra of galaxies. The newly developed method is fairly sensitive to low-luminosity AGNs and also it allows us to cleanly subtract emission line fluxes due to star formation and extract pure AGN emission, which is crucial to characterize AGN activities. We study the nature of the identified low-luminosity AGNs with black hole masses, accretion rates and host galaxy properties. Our findings include (1) AGNs reside in massive galaxies (>1010 M_sun), (2) accretion rates increase with increasing host galaxy star formation rates, and (3) black hole growth rates increase with increasing host galaxy growth rates. We discuss implications of these findings for the BH-galaxy co-evolution.
第180回: 2011/07/07(木) 15:30-16:30 橋本 哲也 氏 (国立天文台) "A hint of AGN feedback: Shock heating of ISM induced by a jet in NGC 1068" We present J-band long-slit spectroscopic observation of NGC 1068 classified as a Seyfert 2 galaxy. J-band observations with OAO/ISLE provide clear detection of spatially extended [Fe II]1.257um and [P II]1.188um lines. We found that [Fe II]1.257um/[P II]1.188um increases with distance from a central continuum peak. Observed line ratios around the nucleus (continuum peak) are consistent with a typical value expected from photoionization models, while the ratios at 3 arcsec - 4 arcsec (210-280 pc) east and west of the nucleus are slightly higher than this. In the off nucleus region of NGC 1068 we also found a possible association between [Fe II]1.257um/[P II]1.188um and the radio continuum. This suggests a mild contribution of shock ionization induced by a radio jet outside nucleus while photoionization by the central energy source is dominant near the nucleus. This result is a hint to investigate the on going site where the AGN activity inputs its energy to surrounding interstellar medium (ISM) through a shock heating induced by a jet. This kind of energy input into ISM may be the key to reveal a recently emerged serious problem that theoretical simulations predict too many massive galaxies due to long-duration star formations in contrast to early-time quenching of star formation in observed massive galaxies, and may be also closely correlated with the co-evolution of super massive black hole and its host galaxy. We also present preliminary result of J-band integral field unit spectroscopy (NIFS+AO) of narrow line region in NGC 1275.
第181回 2011/07/21(木) 15:30~16:30 柏川 伸成 氏 (国立天文台) 「AKB48 vs. NMB48 vs. SKE48, そして LAE45vs.LAE54」 "Completing the Census of Lyα Emitters at the Reionization Epoch" We carried out extended spectroscopic confirmations of Lyα emitters (LAEs) at z = 6.5 and 5.7 in the Subaru Deep Field. Now, the total number of spectroscopically confirmed LAEs is 45 and 54 at z = 6.5 and 5.7, respectively, and at least 81% (70%) of our photometric candidates at z = 6.5 (5.7) have been spectroscopically identified as real LAEs. We made careful measurements of the Lyα luminosity, both photometrically and spectroscopically, to accurately determine the Lyα and rest-UV luminosity functions (LFs). The substantially improved evaluation of the Lyα LF at z = 6.5 shows an apparent deficit from z = 5.7 at least at the bright end, and a possible decline even at the faint end, though small uncertainties remain. The rest-UV LFs at z = 6.5 and 5.7 are in good agreement, at least at the bright end, in clear contrast to the differences seen in the Lyα LF. These results imply an increase in the neutral fraction of the intergalactic medium from z = 5.7 to 6.5. The rest-frame equivalent width (EW_0 ) distribution at z = 6.5 seems to be systematically smaller than z = 5.7, and it shows an extended tail toward larger EW_0 . The bright end of the rest-UV LF can be reproduced from the observed Lyα LF and a reasonable EW_0 -UV luminosity relation. Integrating this rest-UV LF provides the first measurement of the contribution of LAEs to the photon budget required for reionization. The derived UV LF suggests that the fractional contribution of LAEs to the photon budget among Lyman break galaxies significantly increases toward faint magnitudes. Low-luminosity LAEs could dominate the ionizing photon budget, though this inference depends strongly on the uncertain faint-end slope of the Lyα LF.
