Home > Solar and Space Plasma (SSP) Seminar | 科学研究部コロキウム > 2019.07.28-08.04


7月31日(水)13:30 ~15:00   科学研究部コロキウム       開発棟3号館3階会議室  
Jul 31 Wed        Colloquium of Division of Science  Conference room, Instrument Development Bldg. 3 3F

8月2日(金) 13:30~15:00   太陽天体プラズマセミナー     院生セミナー室  
Aug 2 Fri       Solar and Space Plasma Seminar     Student Seminar Room, Subaru Bldg.






7月31日(水曜日)13時30分 ー 15時


Bunyo Hatsukade

Institute of Astronomy, Univ. of Tokyo

Radio Exploration of the Host Galaxies of Massive Star Explosions

I present the results of radio observations of the host galaxies of long -duration gamma-ray bursts (GRBs) and superluminous supernovae (SLSNe).
GRBs are associated with the explosion of massive stars. Because GRBs are bright enough to be observable in the cosmological distances, they are expected to be a new tool to probe the cosmic star-formation history.
However, it is still a subject of debate whether they occur in normal star-forming environments or not. Observations of molecular gas, the fuel of star formation, are essential to understand the properties of host galaxies. We conducted ALMA CO observations toward GRB hosts at 0.1 < z < 2.5 and obtained the largest sample of GRB hosts with molecular gas information. We find no systematic offset for the GRB hosts from the scaling relation of normal star-forming galaxies in terms of gas consumption timescale or gas fraction, suggesting that GRBs occur in normal star-forming environments.
We are also working on radio continuum observations of SLSN hosts to constrain the obscured star formation. SLSNe are extremely luminous explosions, with peak magnitudes 10?100 times brighter than typical Type Ia and core-collapse SNe. The physical nature of SLSNe is still a matter of debate, and it is important to study the properties of their host galaxies. Our initial study found that four (out of eight) hosts at
0.01 < z < 0.3 have an excess in radio-derived SFRs compared to optically-derived SFRs, suggesting the existence of obscured star formation, which cannot be traced by optical studies. This suggests a higher fraction of starburst galaxies in SLSN hosts than estimated in previous studies. I also present ongoing projects and radio constraints on a pulsar-driven SLSN model.

-名前:Akimasa Kataoka


Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic
Date and time
2 August (Fri), 13:30-15:00
Student Seminar Room, Subaru Bldg.
David Orozco suarez
Instituto de Astrofisica de Andalucia
Non-LTE polarimetric inversions: An art form

Fast, robust and user friendly polarimetric inversion codes are usually programmed under the assumption of local thermodynamic equilibrium (LTE).
This is so because LTE allows a fast calculation of the spectral line radiative transfer and consequently inversion methods are fast and easily implemented in modern computers. However, LTE applies only in the photosphere. Most chromospheric spectral lines are not in LTE and require solving the statistical equilibrium equations and far more complicated transfer. This has consequences in both, the simplicity of the codes as well as their performance. NLTE inversion codes exist but they are slow and require a good knowledge on NLTE transfer line formation from the user point of view. In this presentation I will explain how to overcome these difficulties and present the new code, DeSIRer (Departure Coefficients Inversor Code), which can invert NLTE lines at a second per pixel time frames. Based on SIR (Stokes Inversion based on Response Functions; Ruiz Cobo & del Toro Iniesta 1992) and RH (Uitenbroek 2001) codes, I will show a brief overview of the code, its performance, limitations, and more importantly, how one can speed up NLTE computations and analyze big maps in reasonable times.

-Name:Masahito Kubo

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