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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
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
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 |
| 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 | |
| 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 | 2019/10/31(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 |
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 |
