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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。
