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Abstract: I will present my recent papers on (i) the luminosity-duration relation of fast radio bursts (FRBs), (ii) ALMA observations of Gamma-Ray Burst (GRB) host galaxies, and (iii) a blue cluster in the local Universe. Brief summaries of each paper are as follows.
(i) Luminosity-duration relation of fast radio bursts We discovered an empirical correlation between luminosity and duration of FRBs. We propose a new distance measure using the relation of FRBs, which can reach more distant Universe than type Ia supernovae in quantity. This method can potentially reveal the time variability of the dark energy, which is one of the central foci of observational cosmology.
(ii) SFRs of two GRB host galaxies at z~2 and a [CII] deficit observed with ALMA We discovered a new parameter to characterize GRB host galaxies, [CII] deficit, by overcoming a serious dust-extinction problem of GRB host galaxies. Possible parameters controlling the deficit include the metallicity, initial mass function, and gas density.
(iii) A young galaxy cluster in the old Universe We discovered a 'blue cluster', that is a local galaxy cluster with an unprecedentedly high fraction of blue star-forming galaxies yet hosted by a massive dark matter halo. The blue cluster challenges the current standard understanding of galaxy formation under the Lambda CDM Universe.
Language: English
Abstract: Cool-core clusters of galaxies were originally predicted to form massive (~10^2 - 10^3 Msun/yr) cooling flows as the intracluster medium (ICM) radiatively dissipates thermal energy and descends the gravitational potential well of the cluster. However, mechanical mode feedback from the active galactic nuclei (AGN) of the brightest cluster galaxies (BCGs) in cool-core clusters has sufficient energy to offset cooling in the core, and suppresses cooling flows. Residual ICM condensation gives rise to spectacular starbursts in the normally "red-and-dead" BCG and cold molecular gas reservoirs that can be several 10^10 Msun, and observations of condensed material provides important clues for how feedback moderates cooling in galaxy clusters. In this talk, I will focus on our observations of star formation and condensed material in the CLASH (Cluster Lensing And Supernova survey with Hubble) sample of galaxy clusters, with particular focus on our recent study of dust and molecular gas in the BCG of MACS 1931.8-2635 conducted with ALMA. MACS 1931 hosts one of the most extreme BCG starbursts known in a cool-core cluster, with a star formation rate of ~250 Msun/yr, and multiphase gas filaments extending ~30 kpc from the center of the BCG. Our observations in MACS 1931 reveal a massive (~2 x 10^10 Msun) molecular gas reservoir that is highly excited (R_31 = 0.93 +/- 0.16), suggesting that gas excitation is being partially driven by non-photodissociation region- related processes, while continuum observations of dust allow us to constrain the temperature of several dust clumps to <10 K, which is too cold to be directly interacting with the surrounding ~4.8 keV intracluster medium (ICM). Excitingly, our findings imply a scenario where BCG dust, which is not predicted to survive on longer than Myr timescales in hot ICM environments, can be shielded from ICM sputtering. I conclude by discussing how observations like our observation of MACS 1931 constrain the formation and evolution of dust and gas in the extreme feedback-regulated environments of cool-core clusters.
要旨： 星間空間に多大な影響を及ぼし銀河進化を規定する大質量星の形成条件を探るためにはその主たる前駆体である巨大分子雲の理解が重要となる。これまでは分子雲を空間分解した観測は単一電波望遠鏡による銀河系内の分子雲のみに限定されてきたが、ALMAの登場により星形成の直接母体となる分子雲コア/クランプ(数pc~0.1pc)を空間分解可能な観測は系外銀河(大小マゼラン雲やM33)の分子雲に拡大されつつある。これらの観測は、視線方向上の重なりを考慮する必要がほとんどないことに加えて、金属量による違いや銀河スケールの構造/現象による星形成への影響を調べる上でも重要であり、宇宙進化史における星形成の一般的な理解に向けてさらなる飛躍をもたらすと期待される。
本講演では主に、ALMAによる0.”2(～0.07 pc)の高分解能観測によって得られた大マゼラン雲N159領域の結果について紹介する。EとW領域にて、~0.1 pc 幅のフィラメント状分子雲と大質量原始星からのアウトフロー、わし座で見られる”創造の柱”構造などを系外銀河の分子雲で初めて同定した。この2つの領域は互いに 50 pc以上離れているにも関わらず、非常に似た性質/進化段階を示すことから、銀河規模の大局的なガスフローが同時多発的なフィラメント状分子雲/大質量星形成に重要な役割を果たしたと考えられる。
この他マゼラン雲やM33に対するALMAを用いた観測の進行状況を簡単に紹介し、今後の展望について議論する。
Language: Japanese
東京大学・天文学教育研究センターでは2003年4月から, 院生コロキウムに引き続き, 談話会を開いています. 第一線で活躍されている研究者の方々を講師にお招きし, 最先端の研究成果をお話しいただきます. 講師の方には, 大学院生の参加者のことも考慮し, レビュー的な側面も含めた上で, ご自身の研究紹介をお願いしています.
| 13:30-14:30 | 院生コロキウム | 講義室 |
| 15:30-16:30 | 談話会 | 講義室 |
| 16:30- | お茶の時間 | 講義室横のお茶部屋~講師の方を交えて~ |
please replace _at_ to @
| # | Date | Speaker | Title | Chair |
| 352 | 2019/10/24(Thu) 15:30 - 16:30 | 橋本哲也 Tetsuya Hashimoto (台湾国立清華大学) | Recent three discoveries from NTHU cosmology group | YN |
| 353 | 2019/10/28(Mon) 13:00 - 14:-0 | Kevin Fogarty (Caltech) | Cooling and Condensation in Cool-Core Galaxy Clusters: the Case of MACS 1931.8-2635 | KK |
| 354 | 2019/10/31(Thu) 15:30 - 16:30 | 徳田一起 Kazuki Tokuda (Osaka Prefecture University) | ALMAによる大小マゼラン雲とM33の巨大分子雲観測 ALMA observations of GMCs in the Large/Small Magellanic Clouds and M33 | KK |
| 355 | 2019/11/07(Thu) 15:30 - 16:30 | 高倉理 Satoru Takakura (IPMU/U.Tokyo) | (TBA) | KK |
| 356 | 2019/12/05(Thu) 15:30 - 16:30 | 鮫島寛明 Hiroaki Sameshima (IoA/U.Tokyo) | (TBA) | KK |
詳細はこちら: 平成31(2019)年度談話会
| # | Date | Speaker | Title | Chair |
| 345 | 2019/04/01(Mon) 15:30 - 16:30 | J. Xavier Prochaska (UCO/Lick Observatory) | The Wolfe Disk: ALMA Discoveries of Distant, HI-selected Galaxies | KK |
| 346 | 2019/06/27(Thu) 15:30 - 16:30 | Yuu NIINO (IoA/Univ. of Tokyo) | The origin of short and intense explosions in the universe | KK |
| 347 | 2019/07/02(Tue) 16:00 - 17:00 | Wakiko ISHIBASHI (University of Zurich) | How AGN radiative feedback may shape black hole-galaxy co-evolution | KK |
| 348 | 2019/07/04(Thu) 15:30 - 16:30 | Hidenobu YAJIMA (Univ. of Tsukuba) | Cosmological simulations of galaxy formation at the epoch of reionization | KK |
| 349 | 2019/07/11(Thu) 15:30 - 16:30 | Fumihiko USUI (Kobe University) | 近赤外線分光観測による小惑星の含水鉱物探査 | RO |
| 350 | 2019/08/26(Mon.) 15:30 - 16:30 | Glenn Orton (NASA/JPL) | The Exploration of Jupiter by the Juno Mission | RO |
| 351 | 2019/10/2(Wed) 13:15 - 14:15 | 吉田健二 Kenji Yoshida (芝浦工業大学) | Correlations between Optical/Infrared and Gamma-ray Variability in Bright Well-Monitored Blazars 2008-2017 | YN |
