Achievements & Publications

First-principles study of the formation of glycine-producing radicals from common interstellar species

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Sato, Akimasa,   Kitazawa, Yuya,   Ochi, Toshiro,   Shoji, Mitsuo,   Komatsu, Yu,   Kayanuma, Megumi

Glycine, the simplest amino acid, has been intensively searched for in molecular clouds, and the comprehensive clarification of the formation path of interstellar glycine is now imperative. Among all the possible glycine formation pathways, we focused on the radical pathways revealed by Garrod (2013). In the present study, we have...

Multiple Paths of Deuterium Fractionation in Protoplanetary Disks

Image

Aikawa, Yuri,   Furuya, Kenji,   Hincelin, Ugo,   Herbst, Eric

We investigate deuterium chemistry coupled with the nuclear spin-state chemistry of H$_2$ and \\\H\\\$_3$$^+$ in protoplanetary disks. Multiple paths of deuterium fractionation are found; exchange reactions with D atoms, such as HCO$^+$ + D, are effective in addition to those with HD. In a disk model with grain sizes appropriate...

Systematic Identification of LAEs for Visible Exploration and Reionization Research Using Subaru HSC (SILVERRUSH). I. Program strategy and clustering properties of ̃2000 Ly\ensuremathα emitters at z = 6-7 over the 0.3-0.5 Gpc$^2$ survey area

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Ouchi, Masami,   Harikane, Yuichi,   Shibuya, Takatoshi,   Shimasaku, Kazuhiro,   Taniguchi, Yoshiaki,   Konno, Akira

We present the SILVERRUSH program strategy and clustering properties investigated with ̃2000 Ly\ensuremathα emitters (LAEs) at z = 5.7 and 6.6 found in the early data of the Hyper Suprime- Cam (HSC) Subaru Strategic Program survey exploiting the carefully designed narrow-band filters. We derive angular correlation functions with the unprecedentedly...

Ionized Gas Outflows in Infrared-bright Dust-obscured Galaxies Selected with WISE and SDSS

Image

Toba, Yoshiki,   Bae, Hyun-Jin,   Nagao, Tohru,   Woo, Jong-Hak,   Wang, Wei-Hao,   Wagner, Alexander Y.

We present the ionized gas properties of infrared (IR)-bright dust- obscured galaxies (DOGs) that show an extreme optical/IR color, \(i-[22])\$_\AB$\> 7.0, selected with the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). For 36 IR-bright DOGs that show [O III]\ensuremathłambda5007 emission in the SDSS spectra, we performed...

Multidimensional Vlasov-Poisson Simulations with High-order Monotonicity- and Positivity-preserving Schemes

Image

Tanaka, Satoshi,   Yoshikawa, Kohji,   Minoshima, Takashi,   Yoshida, Naoki

We develop new numerical schemes for Vlasov-Poisson equations with high- order accuracy. Our methods are based on a spatially monotonicity-preserving (MP) scheme and are modified suitably so that the positivity of the distribution function is also preserved. We adopt an efficient semi-Lagrangian time integration scheme that is more accurate and...

A theoretical study of the formation of glycine via hydantoin intermediate in outer space environment

Image

Kayanuma, Megumi,   Kidachi, Kaori,   Shoji, Mitsuo,   Komatsu, Yu,   Sato, Akimasa,   Shigeta, Yasuteru

As a possible formation mechanism of glycine in astrophysical environments, a reaction path via aminoacetonitrile and hydantoin (2,4-imidazolidinedione), which have been detected in an interstellar cloud and meteorites, respectively, were analyzed using the density functional theory. The formation of hydantoin from aminoacetonitrile via the Bücherer-Bergs reaction and the hydrolysis of...

ALMA Observations of the Protostar L1527 IRS: Probing Details of the Disk and the Envelope Structures

Image

Aso, Yusuke,   Ohashi, Nagayoshi,   Aikawa, Yuri,   Machida, Masahiro N.,   Saigo, Kazuya,   Saito, Masao

We have recently observed the Class 0/I protostar L1527 IRS using the Atacama Large Millimeter/submillimeter Array (ALMA) during its Cycle 1 in 220 GHz dust continuum and C$^18$O (J=2-1) line emissions with a ̃2 times higher angular resolution (̃ 0\textbac kslashbuildrel\\prime\prime\\textbac kslashover\.\ 5) and ̃4 times better sensitivity than our...

Complex organics in IRAS 4A revisited with ALMA and PdBI: Striking contrast between two neighbouring protostellar cores

Image

López-Sepulcre, A.,   Sakai, N.,   Neri, R.,   Imai, M.,   Oya, Y.,   Ceccarelli, C.

Context. Hot corinos are extremely rich in complex organic molecules (COMs). Accurate abundance measurements of COMs in such objects are crucial to constrain astrochemical models. In the particular case of close binary systems this can only be achieved through high angular resolution imaging. Aims: We aim to perform an interferometric...

The Formation and Physical Origin of Highly Ionized Cooling Gas

Image

Bordoloi, Rongmon,   Wagner, Alexander Y.,   Heckman, Timothy M.,   Norman, Colin A.

We present a simple model that explains the origin of warm, diffuse gas seen primarily as highly ionized absorption-line systems in the spectra of background sources. We predict the observed column densities of several highly ionized transitions such as O VI, O vii, Ne viii, N v, and Mg x,...

The nature of the progenitor of the M31 north-western stream: globular clusters as milestones of its orbit

Image

Kirihara, T.,   Miki, Y.,   Mori, M.

We examine the nature, possible orbits and physical properties of the progenitor of the north-western stellar stream (NWS) in the halo of the Andromeda galaxy (M31). The progenitor is assumed to be an accreting dwarf galaxy with globular clusters (GCs). It is, in general, difficult to determine the progenitor's orbit...

Universal Dark Halo Scaling Relation for the Dwarf Spheroidal Satellites

Image

Hayashi, Kohei,   Ishiyama, Tomoaki,   Ogiya, Go,   Chiba, Masashi,   Inoue, Shigeki,   Mori, Masao

Motivated by a recently found interesting property of the dark halo surface density within a radius, \r\$_\max $, giving the maximum circular velocity, \V\$_\max $, we investigate it for dark halos of the Milky Way\textquoterights and Andromeda\textquoterights dwarf satellites based on cosmological simulations. We select and analyze the simulated subhalos...

NH$_3$ (1$_0$-0$_0$) in the pre-stellar core L1544

Image

Caselli, P.,   Bizzocchi, L.,   Keto, E.,   Sipilä, O.,   Tafalla, M.,   Pagani, L.

Pre-stellar cores represent the initial conditions in the process of star and planet formation, therefore it is important to study their physical and chemical structure. Because of their volatility, nitrogen-bearing molecules are key to study the dense and cold gas present in pre-stellar cores. The NH$_3$ rotational transition detected with...

Image

First-principles study of the formation of glycine-producing radicals from common interstellar species

Sato, Akimasa,   Kitazawa, Yuya,   Ochi, Toshiro,   Shoji, Mitsuo,   Komatsu, Yu,   Kayanuma, Megumi

Glycine, the simplest amino acid, has been intensively searched for in molecular clouds, and the comprehensive clarification of the formation path of interstellar glycine is now imperative. Among all the possible glycine formation pathways, we focused on the radical pathways revealed by Garrod (2013). In the present study, we have...

March 2018  
Image

Multiple Paths of Deuterium Fractionation in Protoplanetary Disks

Aikawa, Yuri,   Furuya, Kenji,   Hincelin, Ugo,   Herbst, Eric

We investigate deuterium chemistry coupled with the nuclear spin-state chemistry of H$_2$ and \\\H\\\$_3$$^+$ in protoplanetary disks. Multiple paths of deuterium fractionation are found; exchange reactions with D atoms, such as HCO$^+$ + D, are effective in addition to those with HD. In a disk model with grain sizes appropriate...

March 2018   The Astrophysical Journal
Image

Systematic Identification of LAEs for Visible Exploration and Reionization Research Using Subaru HSC (SILVERRUSH). I. Program strategy and clustering properties of ̃2000 Ly\ensuremathα emitters at z = 6-7 over the 0.3-0.5 Gpc$^2$ survey area

Ouchi, Masami,   Harikane, Yuichi,   Shibuya, Takatoshi,   Shimasaku, Kazuhiro,   Taniguchi, Yoshiaki,   Konno, Akira

We present the SILVERRUSH program strategy and clustering properties investigated with ̃2000 Ly\ensuremathα emitters (LAEs) at z = 5.7 and 6.6 found in the early data of the Hyper Suprime- Cam (HSC) Subaru Strategic Program survey exploiting the carefully designed narrow-band filters. We derive angular correlation functions with the unprecedentedly...

January 2018   Publications of the Astronomical Society of Japan
Image

Ionized Gas Outflows in Infrared-bright Dust-obscured Galaxies Selected with WISE and SDSS

Toba, Yoshiki,   Bae, Hyun-Jin,   Nagao, Tohru,   Woo, Jong-Hak,   Wang, Wei-Hao,   Wagner, Alexander Y.

We present the ionized gas properties of infrared (IR)-bright dust- obscured galaxies (DOGs) that show an extreme optical/IR color, \(i-[22])\$_\AB$\> 7.0, selected with the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). For 36 IR-bright DOGs that show [O III]\ensuremathłambda5007 emission in the SDSS spectra, we performed...

December 2017   The Astrophysical Journal
Image

Multidimensional Vlasov-Poisson Simulations with High-order Monotonicity- and Positivity-preserving Schemes

Tanaka, Satoshi,   Yoshikawa, Kohji,   Minoshima, Takashi,   Yoshida, Naoki

We develop new numerical schemes for Vlasov-Poisson equations with high- order accuracy. Our methods are based on a spatially monotonicity-preserving (MP) scheme and are modified suitably so that the positivity of the distribution function is also preserved. We adopt an efficient semi-Lagrangian time integration scheme that is more accurate and...

November 2017   The Astrophysical Journal
Image

A theoretical study of the formation of glycine via hydantoin intermediate in outer space environment

Kayanuma, Megumi,   Kidachi, Kaori,   Shoji, Mitsuo,   Komatsu, Yu,   Sato, Akimasa,   Shigeta, Yasuteru

As a possible formation mechanism of glycine in astrophysical environments, a reaction path via aminoacetonitrile and hydantoin (2,4-imidazolidinedione), which have been detected in an interstellar cloud and meteorites, respectively, were analyzed using the density functional theory. The formation of hydantoin from aminoacetonitrile via the Bücherer-Bergs reaction and the hydrolysis of...

November 2017  
Image

ALMA Observations of the Protostar L1527 IRS: Probing Details of the Disk and the Envelope Structures

Aso, Yusuke,   Ohashi, Nagayoshi,   Aikawa, Yuri,   Machida, Masahiro N.,   Saigo, Kazuya,   Saito, Masao

We have recently observed the Class 0/I protostar L1527 IRS using the Atacama Large Millimeter/submillimeter Array (ALMA) during its Cycle 1 in 220 GHz dust continuum and C$^18$O (J=2-1) line emissions with a ̃2 times higher angular resolution (̃ 0\textbac kslashbuildrel\\prime\prime\\textbac kslashover\.\ 5) and ̃4 times better sensitivity than our...

November 2017   The Astrophysical Journal
Image

Complex organics in IRAS 4A revisited with ALMA and PdBI: Striking contrast between two neighbouring protostellar cores

López-Sepulcre, A.,   Sakai, N.,   Neri, R.,   Imai, M.,   Oya, Y.,   Ceccarelli, C.

Context. Hot corinos are extremely rich in complex organic molecules (COMs). Accurate abundance measurements of COMs in such objects are crucial to constrain astrochemical models. In the particular case of close binary systems this can only be achieved through high angular resolution imaging. Aims: We aim to perform an interferometric...

October 2017  
Image

The Formation and Physical Origin of Highly Ionized Cooling Gas

Bordoloi, Rongmon,   Wagner, Alexander Y.,   Heckman, Timothy M.,   Norman, Colin A.

We present a simple model that explains the origin of warm, diffuse gas seen primarily as highly ionized absorption-line systems in the spectra of background sources. We predict the observed column densities of several highly ionized transitions such as O VI, O vii, Ne viii, N v, and Mg x,...

October 2017   The Astrophysical Journal
Image

The nature of the progenitor of the M31 north-western stream: globular clusters as milestones of its orbit

Kirihara, T.,   Miki, Y.,   Mori, M.

We examine the nature, possible orbits and physical properties of the progenitor of the north-western stellar stream (NWS) in the halo of the Andromeda galaxy (M31). The progenitor is assumed to be an accreting dwarf galaxy with globular clusters (GCs). It is, in general, difficult to determine the progenitor's orbit...

August 2017   Monthly Notices of the Royal Astronomical Society
Image

Universal Dark Halo Scaling Relation for the Dwarf Spheroidal Satellites

Hayashi, Kohei,   Ishiyama, Tomoaki,   Ogiya, Go,   Chiba, Masashi,   Inoue, Shigeki,   Mori, Masao

Motivated by a recently found interesting property of the dark halo surface density within a radius, \r\$_\max $, giving the maximum circular velocity, \V\$_\max $, we investigate it for dark halos of the Milky Way\textquoterights and Andromeda\textquoterights dwarf satellites based on cosmological simulations. We select and analyze the simulated subhalos...

July 2017   The Astrophysical Journal
Image

NH$_3$ (1$_0$-0$_0$) in the pre-stellar core L1544

Caselli, P.,   Bizzocchi, L.,   Keto, E.,   Sipilä, O.,   Tafalla, M.,   Pagani, L.

Pre-stellar cores represent the initial conditions in the process of star and planet formation, therefore it is important to study their physical and chemical structure. Because of their volatility, nitrogen-bearing molecules are key to study the dense and cold gas present in pre-stellar cores. The NH$_3$ rotational transition detected with...

July 2017  

First-principles study of the formation of glycine-producing radicals from common interstellar species

Sato, Akimasa,   Kitazawa, Yuya,   Ochi, Toshiro,   Shoji, Mitsuo,   Komatsu, Yu,   Kayanuma, Megumi
March 2018  

Multiple Paths of Deuterium Fractionation in Protoplanetary Disks

Aikawa, Yuri,   Furuya, Kenji,   Hincelin, Ugo,   Herbst, Eric
March 2018   The Astrophysical Journal

Systematic Identification of LAEs for Visible Exploration and Reionization Research Using Subaru HSC (SILVERRUSH). I. Program strategy and clustering properties of ̃2000 Ly\ensuremathα emitters at z = 6-7 over the 0.3-0.5 Gpc$^2$ survey area

Ouchi, Masami,   Harikane, Yuichi,   Shibuya, Takatoshi,   Shimasaku, Kazuhiro,   Taniguchi, Yoshiaki,   Konno, Akira
January 2018   Publications of the Astronomical Society of Japan

Ionized Gas Outflows in Infrared-bright Dust-obscured Galaxies Selected with WISE and SDSS

Toba, Yoshiki,   Bae, Hyun-Jin,   Nagao, Tohru,   Woo, Jong-Hak,   Wang, Wei-Hao,   Wagner, Alexander Y.
December 2017   The Astrophysical Journal

Multidimensional Vlasov-Poisson Simulations with High-order Monotonicity- and Positivity-preserving Schemes

Tanaka, Satoshi,   Yoshikawa, Kohji,   Minoshima, Takashi,   Yoshida, Naoki
November 2017   The Astrophysical Journal

A theoretical study of the formation of glycine via hydantoin intermediate in outer space environment

Kayanuma, Megumi,   Kidachi, Kaori,   Shoji, Mitsuo,   Komatsu, Yu,   Sato, Akimasa,   Shigeta, Yasuteru
November 2017  

ALMA Observations of the Protostar L1527 IRS: Probing Details of the Disk and the Envelope Structures

Aso, Yusuke,   Ohashi, Nagayoshi,   Aikawa, Yuri,   Machida, Masahiro N.,   Saigo, Kazuya,   Saito, Masao
November 2017   The Astrophysical Journal

Complex organics in IRAS 4A revisited with ALMA and PdBI: Striking contrast between two neighbouring protostellar cores

López-Sepulcre, A.,   Sakai, N.,   Neri, R.,   Imai, M.,   Oya, Y.,   Ceccarelli, C.
October 2017  

The Formation and Physical Origin of Highly Ionized Cooling Gas

Bordoloi, Rongmon,   Wagner, Alexander Y.,   Heckman, Timothy M.,   Norman, Colin A.
October 2017   The Astrophysical Journal

The nature of the progenitor of the M31 north-western stream: globular clusters as milestones of its orbit

Kirihara, T.,   Miki, Y.,   Mori, M.
August 2017   Monthly Notices of the Royal Astronomical Society

Universal Dark Halo Scaling Relation for the Dwarf Spheroidal Satellites

Hayashi, Kohei,   Ishiyama, Tomoaki,   Ogiya, Go,   Chiba, Masashi,   Inoue, Shigeki,   Mori, Masao
July 2017   The Astrophysical Journal

NH$_3$ (1$_0$-0$_0$) in the pre-stellar core L1544

Caselli, P.,   Bizzocchi, L.,   Keto, E.,   Sipilä, O.,   Tafalla, M.,   Pagani, L.
July 2017