M.Otsuka's homepage

Background image:  imaginative picture of fullerene C60 molecules distributing into interstellar medium from a planetary nebula. 

credit: National Astronomical Observatory of JAPAN (国立天文台)

• Ph.D. Astronomy Dept., Tohoku University (2007)

• M.S. Astronomy Dept., Tohoku University (2001)

• B.S. Astronomy Dept., Tohoku University (1999)

• Project-specified Assistant Professor, Okayama Observatory, Kyoto University (2018/04-present)

• Ministry of Science and Technology (MoST, R.O.C.) Assistant Research Scholar (Assistant Professor ("助教" in Japan), 2015/08-2018/03)

• Visiting Scholar, Institute of Astronomy and Astrophysics, Academia Sinica (2015/04-2018/03)

• Support Astronomer, Subaru Telescope, NAOJ (2014/07-2015/03)

• Postdoctoral Research Fellow, Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA, 2011/06-2014/05) 

• Postdoctoral Research Fellow, Space Telescope Science Institute (STScI, 2008/06-2011/05)

• Research Assistant, Okayama Astrophysical Observatory, NAOJ (2004/06-2008/05)

• International Astronomical Union (2012-current)

• Astronomical Society of Japan (2001-current)

• 面分光研究会2019 －新面分光装置で花開く新しいサイエンス 世話人 (2019/10)

• Kyoto U. Seimei users meeting organizer (2019/08-current)

• Kyoto U. Seimei 3.8-m Telescope time allocation committee (for Kyoto U. observation time, 2019/02-current)

• すばる望遠鏡観測による惑星状星雲にまつわる国際研究ワークショプ チェア (2017/12)

• ASROC best poster award selection committee (2016/05)

• Canada France Hawaii Telescope (CFHT) (2012-2013) 

• Subaru Data Reduction Winter School 2016, NCU, Taiwan (w. seminar, 2016/12)

• Monthly Notices of the Royal Astronomical Society (MNRAS),  The Astrophysical Journal (ApJ), Publications of the Astronomical Society of Japan  reviewer

• Observing proposal referee for Okayama Astrophysical Observatory, NAOJ (2009-2010)

• Ms. Evaria Puspitaningrum (master course), IAA, Academia Sinica (2016/08-2017/08)

• Mr. Thomas Lai (research assistant), IAA, Academia Sinica (2013/07-2014/05)

• Mr. Ben Ling (summer student), IAA, Academia Sinica (2013/07-2013/08)

• Ms. Justice Bruursema (with Dr. M. Meixner), Johns Hopkins University (2013/05-2014/05)

• The 58th Fullerenes-Nanotubes-Graphene General Symposium (2020/03/15-17 at The University of Tokyo)

  • The 50th year anniversary for the theoretical prediction of the aromatic stability of fullerene C60 molecules by Prof. Eiji Ohsawa

    • My talk title: "Unveiling the origin of cosmic fullerenes through investigations into physical properties of fullerene-containing planetary nebulae"

• MoST Scholarship; Assistant Researcher Scholar (2015/08-2018/03)

• Academia Sinica Regular Postdoctoral Fellowship (2012/01-2014/05)

• 2023 JSPS Grants-in-Aid for International Fellowships for Research in Japan, "Understanding of Circumsteller Medium around Low-Intermediate mass stars via the observations of Planetary Nebula with Kyoto Semi 3.8-m/KOOLS-IFU (2023/11 - 2023/12, Prof. T. Ueta)

• 2023 National Astronomical Observatory of Japan, commission research fund, "Establishment of A Fully Data-Driven Method for Dust Extinction Correction and Proper Plasma Diagnostics", JPY 850,000 (2023/08-2024/03) 

• 2022 JSPS Grants-in-Aid for Scientific Research, “Investigation into the Stellar Mass-Loss Based on Spatially Highly-Resolved Multiwavelength 3-D Spectra of Galactic Planetary Nebulae”,  fund type C, 22K03675, JPY 3,510,000  (2022/04-2026/03)

• 2020 JSPS Grants-in-Aid for International Fellowships for Research in Japan, "Understanding of Circumsteller Medium around Low-Intermediate mass stars via the observations of Planetary Nebula with Kyoto Semi 3.8-m/KOOLS-IFU (2020/12 - 2021/08, Prof. T. Ueta) 

• 2019 JSPS Grants-in-Aid for Scientific Research, “Investigation into Stellar Mass Loss Based on Three-Dimensional MultipleWavelength Spectra of Galactic Planetary Nebulae”,  fund type C, JP19K03914, JPY 3,380,000  (2019/04-2023/03) 

• 2018 Japan Foundation for Promotion of Astronomy, for visit to NOAO/KPNO and Denver University, JPY 270,000 (2018/07)

• 2015 MoST research scholarship with MoST subsidies, “Unveiling the Missing Stellar Dust Mass Yield in the Cold: Rigorous Model Fitting of the Gas and Dust Components in Galactic Planetary Nebulae”, USD 128,279.26 (including salary, 2015/08-2018/03) 

• 2008 STScI Discretionary Research Funds, “A Search for Neutron Capture Elements in Galactic Halo Planetary Nebulae”, USD 3000.00 (2008/10)

During the last stages of stellar evolution, stars eject materials enriched with atoms, molecules, and dust grains into circumstellar shells, and eventually these materials are returned back to the interstellar medium of the host galaxies. An investigation on atomic/molecule gas and dust grains ejected from evolved stars increases our understanding of stellar evolution, and chemical evolution of galaxies, and ultimately provides useful information for the formation of the solar system and the origin of our life.

My research goal is to investigate atomic and molecular gas and dust grains in evolved stars and galaxies, and understand both evolution of stars and galaxies. For that purpose, I have been with enthusiasm to study elemental abundances, dust, and molecules based on observational data obtained from 8-m class telescopes such as Subaru and infrared space telescopes such as Spitzer and Herschel. I have contributed to my research committee. 

Below, I introduce my highlights on fullerene C60 in Galactic planetary nebulae (my discovery of C60 in a planetary nebula, see my story)  and discovery of significant cold dust mass in the supernova SN1987A in the Large Magellanic Cloud.

keywords: Interstellar and circumstellar medium (atomic gas, molecular gas, dust grains), Stellar evolution, late stars (e.g., asymptotic giant branch stars, planetary nebulae, supernovae and their remnants), Elemental abundances, Diffuse interstellar bands (DIBs), Galaxy chemical evolution

Since their laboratory discoveries in 1985, particularly C60 have drawn considerable interest from astrochemists looking for them in circumstellar/interstellar conditions. Fullerenes are extremely stable and easily form in laboratories on the earth, so it had been thought that they should exist in interstellar space. However, the first confirmed detection of cosmic fullerenes was only recently reported in the C-rich planetary nebula (PN) Tc1 with mid-infrared (mid-IR) Spitzer Space Telescope. Figure 1 left shows the C60 emission lines in the PN M1-11 (Otsuka et al. 2013, ApJ, 764, 77O). So far, C60 has been found in about 20-30 objects in the Milky Way and the Magellanic Clouds. However, it is still unclear what kind of environment is required to form fullerenes and how fullerenes are excited in the circumstellar/interstellar space.

To answer these fundamental and important questions, we newly found out 6 fullerene-containing PNe out of ALL Spitzer spectra of  over 300 Galactic PNe, and we investigated elemental abundances, dust grains/molecules, and the central stars (Otsuka, M. et al. 2014, MNRAS, 437, 2577O). Our interesting findings are (1) the chemical abundances of C60-containing PNe can be explained by asymptotic giant branch (AGB) star nucleosynthesis models for initially 1.5-2.5 solar mass stars with 1/5 solar metallicity, and the progenitors are an older population, (2) most of C60-containing PNe are outside the solar circle, consistent with low metallicity value (Figure 1 right).

After the infrared space telescope James Webb Space Telescope (JWST) are launched, I will do spectroscopic survey with JWST/MIRI (mid-IR instrument)/NIRSpec (0.6-5 μm spectrograph) and investigate C+60  (i.e., ionized fullerene C60) and C60 bands (i.e., neutral C60).

In order to understand both stellar and galaxy evolution, we have to understand supernovae (SNe) as well. SNe influence atomic gas, dust, and molecules in interstellar matter, and they control the star formation rate. SN blast wave destroys interstellar matter. SNe play a critical role in material recycling in galaxies.

I have an interest in the origin of significant dust detected in high-z galaxies. At the present epoch in the Galaxy, both asymptotic giant branch (AGB) stars and core-collapsed SNe (CCSNe) are thought to be the important dust producers. In early galaxies, AGB stars are not likely to contribute significantly to dust production because such low-mass stars proceed too slowly toward the AGB to produce dust within 1 Gyr. However, massive stars can evolve into CCSNe in timespans under 20 Myr. Theoretical models predict that a CCSN evolved from a 20 solar mass star has to make at least ∼0.1-1 solar mass of dust in order to be a viable source for the dust found in high-z galaxies. However, there was a large discrepancy between the model predicted SN dust mass (~0.1 solar mass) and the estimated SN dust mass using mid-IR data (~1/10000 times solar mass).

From these reasons, therefore, since 2008 when I was a postdoc fellow  at the Space Telescope Science Institute, I have studied dust formation in SNe. By our Herschel far-IR observation, we resolved this discrepancy by our novel discovery of significant cold dust mass in the famous SN, SN1987A in the Large Magellanic Cloud (∼0.4-0.7 solar mass, Figure 2, Matsuura, Dwek, Meixner, Otsuka et al. 2011, Science, 333, 1258M). This result is strong evidence that CCSNe are significant dust producers in galaxies.

I still continue studying SN dust formation using mid-R instruments attached to ground-based telescope (i.e., Subaru/COMICS and VLT/VISIR). I am an active member of the JWST SN research consortium.

Chemical evolution of galaxies is the direct consequence of material cycling between stellar mass-loss and ISM. However, it is not well understood “when, in which directions, how much mass containing what types of atomic/molecular gas and dust did stars eject into ISM”. To answer this vital question is very important to understand both stellar and galaxy evolutions. Therefore, using multiwavelength 3-D spectroscopic data of Galactic PNe, I am recently studying (1) spatial distributions of elemental abundances and gas/dust masses and (2) PN shaping process. 

This study is supported by the 3.8-m Seimei Telescope/KOOLS-IFU and so on. Below, I introduce the recent results of the planetary nebula IC2165 using KOOLS-IFU (Otsuka, 2022, MNRAS, 511, 4774-4800).

103 papers, including 63 refeereed papers are publications of the following major journals; Science, Nature Astronomy, MNRAS, ApJ, ApJL, ApJS, AJ, A&A, PASP, and PASJ. Amongst them, 20 papers have been published as the 1st author (as of 2025/02). My h-index is 24 (12 as the first author). 

Dr. Francisca Kemper (ESO, ASIAA)

Research Fellow, former supervisor, collaborator

Dr. You-Hua Chu (ASIAA)

Distinguished Research Fellow, former director of ASIAA,  collaborator

 Dr. Margaret Meixner

NASA SOFIA director, former supervisor, collaborator

Prof. Toshiya Ueta

U. of Denver, Associate professor, Collaborator

Prof. Hideyuki Izumiura

NAOJ, PhD supervisor, formar supervisor