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Abstract: I will review our series of successful programs to dissect the interstellar medium of distant, star-forming galaxies with the Atacama Large Millimeter Array (ALMA). In particular, I will discuss surveys of the set of HI-selected galaxies known as the damped Lya systems (DLAs). We resolve, in part, a decades old struggle to identify the galactic counterparts of these DLAs and thereby place them firmly in the modern picture of galaxy formation. I will also highlight high spectral and spatial resolution observations of the Wolfe Disk, a z~4 galaxy with a Milky Way-like rotation curve.
Abstract: Short and intense transients like gamma-ray bursts (GRBs), and fast radio bursts (FRBs) provide us with irreplaceable laboratories of physics and unique probes of the evolution of the universe. However, observationally obtaining a direct evidence that clarifies the nature of those transients is often difficult due to their short timescale and large distance toward them. In this talk, I will discuss how the origin of GRBs has been unveiled via observationally available clues, and what can we learn about FRBs from the limited information currently available.
Language: English
Abstract: Active Galactic Nucleus (AGN) feedback is widely invoked in galaxy evolutionary models, while evidence of such AGN feedback in action is now observed in the form of galactic outflows. However, the physical mechanism driving AGN feedback remains ill-understood, and whether galactic outflows are powered by jets, winds, or radiation, is still a source of much debate. We consider AGN feedback driven by radiation pressure on dust. We show that such radiative feedback is capable of accounting for the observed dynamics and energetics of galactic outflows, provided that radiation trapping is properly taken into account.
Feedback from the central black hole is usually invoked to quench star formation in galaxies (the standard negative feedback paradigm). We consider the alternative possibility of triggering star formation in the host galaxy, within the feedback-driven outflows (a form of positive feedback). Such "AGN feedback-driven star formation" may contribute to the size and morphological evolution of galaxies over cosmic time. Recently, there has been growing observational evidence for such star formation occurring inside galactic outflows. I will discuss the multiple roles of AGN feedback in galaxy evolution, and how radiative feedback may ultimately shape the co-evolutionary path.
Abstract: 近年の観測機器の目覚ましい発展により、数多くの遠方銀河が検出された。それにより、塵に覆われた爆発的星形成銀河（サブミリ波銀河）、ライマンアルファ輝線を強く放射する銀河（ライマンアルファエミッター）、超巨大ブラックホールを持つ銀河など、宇宙年齢わずか１０億年未満に銀河の多様性がすでに生まれている事が明らかとなった。そして、現在すばるHSC銀河サーベイによって、原始銀河団の候補が多数見つかってきている。初代銀河形成からわずか１０億年の間に、このような銀河の多様性を引き起こしたメカニズムは何だったのか？ そして、原始銀河団のような超高密度領域で銀河進化はどのように進んだのか？ これらを明らかにするため、我々は近年大規模な宇宙論的流体シミュレーションを進めている。結果として、初期宇宙の銀河は超新星爆発のフィードバックにより、星形成が間欠的になること、それにともなって輻射特性も大きく変化する事が分かった。フィードバックによるガスアウトフローとともに、紫外線連続波やライマンアルファ光子は効率良く脱出し、銀河はライマンアルファエミッター・ブロッブとなる。また、原始銀河団領域では、サブミリ波銀河がフィラメント構造にそって複数形成されることが分かった。本講演では、これらのシミュレーション結果について紹介するとともに、銀河とブラックホールの共進化についても議論する。
Abstract: 太陽系にはさまざまな形態の水が広く存在しているが、特に小惑星には、含水鉱物として水が保持されていると考えられている。この含水鉱物は液体の水と無水鉱物が反応して生成されるが、水氷の昇華温度以上でも比較的安定であるため、水の存在を示す重要なトレーサーである。含水鉱物は近赤外線の波長2.7 µm付近に吸収フィーチャーを持つことが知られているが、この波長域は地球大気の吸収のために、地上望遠鏡では観測できていなかった。我々は赤外線天文衛星「あかり」を用いて、地球大気に影響されることなく小惑星の近赤外線分光観測を行い、小惑星66天体のスペクトルを得ることに成功した。その結果、多くのC型小惑星には含水鉱物に起因する顕著な吸収が見られること、一方ほとんどのS型小惑星にはそのような吸収が見られないことがわかった。本講演では、「あかり」による小惑星の近赤外線分光観測の概要とその結果から考えられる小惑星の形成進化過程について紹介し、さらにTAO/MIMIZUKUを用いた世界初の小惑星母天体の内部構造探査計画について議論する。
Abstract: The Juno spacecraft was launched in August of 2011 and was placed into orbit around Jupiter in July of 2016. It is the first solar-powered spacecraft in the outer solar system and the first to be placed into polar orbits. Its primary goals are (1) to determine the O/H ratio from the abundance of water in the atmosphere to discriminate between alternatives for its origin, (2) to understand Jupiter's interior structure and dynamical properties by mapping its gravitational and magnetic fields, (3) to map variations in atmospheric composition, cloud opacity and dynamics to depths of over 100 atmospheres of pressure at all latitudes, and (4) to characterize the 3-dimensional structure of Jupiter's polar magnetosphere and its auroras. Juno is also the first mission to include a public-outreach camera on its instrument payload, which has been providing stunning images of Jupiter at nearly unprecedented spatial resolutions. This talk will survey those results and identify ways in which the general public, as well as space scientists, can become involved in this mission directly.
Abstract: We present cross correlations of the SMARTS optical/infrared and Fermi-LAT gamma-ray light curves for 8 bright blazars that have been monitored with 1 day time bin over the past decade. For the temporal correlation analysis of unevenly sampled variability data, we use the Discrete Correlation Function (DCF), creating an empirical bootstrapping method to assess the significance of the DCF amplitude for each blazar. Our results are perhaps surprising. Early on in the Fermi mission, the brightest gamma-ray blazar 3C 454.3 showed zero lag between optical/infrared and gamma-ray fluxes as reported by Bonning et al. (2012), which was consistent with the leptonic model that optical/infrared photons are produced by synchrotron radiation of relativistic electrons and gamma rays are produced by inverse Compton scattering of ambient photons by the synchrotron-emitting electrons. However, among the 8 blazars, only one blazar ― 3C 454.3 ― shows a significant peak at zero lag, and the other 7 blazars show no significant peak at zero lag. Some blazars show broad peaks at tens of days of lags at or just below 3 sigma significance. In addition, for a given blazar, strong changes of the DCFs from one epoch to the next are shown by the analyses of time periods of one or two year. These results make it complicated to understand blazar emission mechanisms. Possible physical explanations are discussed.
Language: Japanese
