Papers - Tanaka, Kunihiko

ALMA [CI] Image of the Circumnuclear Disk of the Milky Way: Inflowing Low-density Molecular Gas

Kunihiko Tanaka, Makoto Nagai, Kazuhisa Kamegai

The Astrophysical Journal (IOP science)   2026

Research paper (scientific journal), Joint Work, Lead author, Accepted

The LMT 2 millimeter receiver system (B4R). II. Science demonstration observations toward Orion-KL/OMC-1

Yonetsu T., Kawabe R., Yoshimura Y., Taniguchi K., Shimajiri Y., Rojas-García O.S., Gómez-Ruiz A.I., Sakai T., Tanaka K., Hatsukade B., Taniguchi A., Tamura Y., Takekoshi T., Oshima T., Kohno K., Hagimoto M., Hughes D.H., Schloerb F.P., Sánchez-Argüelles D., Souccar K., Narayanan G., Yun M.S., Gómez-Rivera V., Rodríguez-Montoya I., Colín-Beltrán E., Chávez Dagostino M., Zaragoza-Cardiel J., Fujita S., Maezawa H.

Publications of the Astronomical Society of Japan 77 ( 6 ) 1224 - 1258 2025.12

ISSN  00046264

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We present the results of mapping and single-point spectral scans toward Orion-KL/OMC-1 performed as science demonstrations of a 2mm superconductor–insulator–superconductor receiver, named the Band 4 Receiver (B4R), installed on the Large Millimeter Telescope (LMT), with a diameter of 50m. To prove the capabilities of mapping and spectral scans with the B4R on the LMT, commissioning observations were conducted employing the on-the-fly mapping technique toward Orion-KL/OMC-1, which covers a map size of 5′ × 5′. These mapping observations were performed with two frequency settings providing 10GHz in total (131.4–133.9 and 145.1–147.6GHz; 136.2–138.7 and 149.9–152.4GHz) with a frequency resolution of 76.293kHz. In this study, we conducted spectral line identification analysis for the hot core and compact ridge regions in the Orion-KL with a beam size of 11″–12″. We detected nearly 400 emission lines and identified two recombination lines and 29 molecular species, including isotopologues, deuterated molecules, and vibrational excited states, despite the short integration time. These results of line detection are consistent with those of previous studies. The 29 molecular species include nitrogen (N)-bearing complex organic molecules (COMs) and oxygen (O)-bearing COMs. To demonstrate the capability of the B4R in astrochemistry, we conducted detailed analyses of column densities, rotational temperatures, and relative abundances with respect to H<inf>2</inf> on two representative COMs, N-bearing C<inf>2</inf>H<inf>5</inf>CN and O-bearing CH<inf>3</inf>OCHO in the central 40″ × 40″ area of the map. The wide bandwidth of 10GHz enabled the use of 8 and 34 emission lines, respectively. The spatial differences in the physical and chemical properties between the above two molecules were derived at a spatial resolution of ∼12″. The B4R on the LMT was successfully demonstrated to be powerful for mapping and spectral scans and to have high potential for the study of interstellar chemistry.

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The LMT 2 Millimeter Receiver System (B4R). I. Overview and Results of Science Demonstration

Ryohei Kawabe, Takeshi Sakai, Kunihiko Tanaka, Akio Taniguchi, Bunyo Hatsukade, Yoichi Tamura, Yuki Yoshimura, Tatsuya Takekoshi, Tai Oshima, Masato Hagimoto, Teppei Yonetsu, Kotomi Taniguchi, Kotaro Kohno, Hiroyuki Maezawa, David H. Hughes, Peter F. Schloerb, Edgar Colín-Beltrán, Miguel Chávez Dagostino, Víctor Gómez-Rivera, Arturo I. Gómez-Ruiz, Gopal Narayanan, Iván Rodríguez-Montoya, David Sánchez-Argüelles, Yoshito Shimajiri, Kamal Souccar, Min S. Yun, Tom J. L. C. Bakx, Kevin C. Harrington, Shinji Fujita, Fumitaka Nakamura, O. S. Rojas-García, Alfredo A. Montaña Barbano, Javier Zaragoza-Cardiel

 2025.11

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We report on the results of the on-sky test and science demonstration conducted with the 2 mm receiver system, B4R, on the 50 m Large Millimeter Telescope (LMT), located at an altitude of 4600 m in Mexico. The B4R receiver was developed based on the dual-polarization sideband-separating mixer technology of the Atacama Large Millimeter/submillimeter Array, and is equipped with a fast Fourier transform digital spectrometer, XFFTS. The primary science objective is the spectroscopic redshift identification of high-redshift dusty star-forming galaxies, complementing the existing 3 mm Redshift Search Receiver by enabling the detection of multiple carbon monoxide lines. Additionally, the B4R receiver broadens the range of science cases possible with the LMT, including astrochemistry, as the 2 mm band encompasses unique molecular lines such as deuterated molecules and shock tracers. During on-site commissioning in 2018 and 2019, we successfully demonstrated on-the-fly mapping and position-switching observations toward the Orion Molecular Cloud 1 and bright high-redshift dusty star-forming galaxies, respectively. We confirmed that the installed B4R system largely met its basic performance specifications. Furthermore, we measured the LMT's aperture efficiencies across the entire B4R frequency range (130-160 GHz), finding them to be roughly consistent with expectations based on a surface accuracy of 100 $μ$m and the receiver optics design. These results with the B4R will enable the most sensitive single-dish spectroscopic observations at 2 mm using the LMT.

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Shock-induced HCNH+ abundance enhancement in the heart of the starburst galaxy NGC 253 unveiled by ALCHEMI

Y. Gong, C. Henkel, C. T. Bop, J. G. Mangum, E. Behrens, F. J. Du, S. B. Zhang, S. Martin, K. M. Menten, N. Harada, M. Bouvier, X. D. Tang, K. Tanaka, S. Viti, Y. T. Yan, W. Yang, R. Q. Mao, D. H. Quan

Astronomy and Astrophysics  2025

Joint Work, Accepted

Spatially-resolved spectro-photometric SED Modeling of NGC 253's Central Molecular Zone I. Studying the star formation in extragalactic giant molecular clouds

Humire, Pedro K. ; Dey, Subhrata ; Ronconi, Tommaso ; Sasse, Victor H. ; Cid Fernandes, Roberto ; Martín, Sergio ; Donevski, Darko search by orcid ; Małek, Katarzyna ; Fernández-Ontiveros, Juan A. ; Song, Yiqing ; Hamed, Mahmoud ; Mangum, Jeffrey G. ; Henkel, Christian ; Rivilla, Víctor M. ; Colzi, Laura ; Harada, N. ; Demarco, Ricardo ; Goyal, Arti ; Meier, David S. ; Panda, Swayamtrupta ; Krabbe, Ângela C. ; Yan, Yaoting ; Lopes, Amanda R. search by orcid ; Sakamoto, K. ; Muller, S. ; Tanaka, K. ; Yoshimura, Y. ; Nakanishi, K. ; Kanaan, Antonio ; Ribeiro, Tiago ; Schoenell, William ; Mendes de Oliveira, Claudia

Astronomy and Astrophysics  2025

Research paper (scientific journal), Joint Work, Accepted

Neural Network Constraints on the Cosmic-Ray Ionization Rate and Other Physical Conditions in NGC 253 with ALCHEMI Measurements of HCN and HNC

Neural Network Constraints on the Cosmic-Ray Ionization Rate and Other Physical Conditions in NGC 253 with ALCHEMI Measurements of HCN and HNC

977   38 2024.12

Research paper (scientific journal), Joint Work, Accepted

Bright-rimmed clouds in IC 1396: I. Dynamics

Okada Yoko, Kabanovic Slawa, Güsten Rolf, Ossenkopf-Okada Volker, Schneider Nicola, Simon Robert, Buchbender Christof, Higgins Ronan, Yanitski Craig, Röllig Markus, Stutzki Jürgen, Ishihara Daisuke, Tanaka Kunihiko, Chambers Edward, Honingh Netty, Justen Matthias, Riquelme Denise

Astronomy and Astrophysics 690 ( 45 )  2024.10

Research paper (scientific journal), Joint Work, Accepted

Molecular isotopologue measurements toward super star clusters and the relation to their ages in NGC253 with ALCHEMI

Butterworth, J. , Viti, S. , Van der Werf, P. P. , Mangum, J. G. , Martín, S. , Harada, N. , Emig, K. L. , Muller, S. , Sakamoto, K. , Yoshimura, Y. , Tanaka, K. , Herrero-Illana, R. , Colzi, L. , Rivilla, V. M. , Huang, K. Y. , Bouvier, M. , Behrens, E. , Henkel, C. , Yan, Y. T. , Meier, D. S. , Zhou, D.

Astronomy and Astrophysics (EDP Science)  686   31 2024.06

Research paper (scientific journal), Joint Work, Accepted

Physical Properties of the Southwest Outflow Streamer in the Starburst Galaxy NGC 253 with ALCHEMI

Bao, Min ; Harada, Nanase ; Kohno, Kotaro ; Yoshimura, Yuki ; Egusa, Fumi ; Nishimura, Yuri ; Tanaka, Kunihiko ; Nakanishi, Kouichiro ; Martín, Sergio ; Mangum, Jeffrey G. ; Sakamoto, Kazushi ; Muller, Sébastien ; Bouvier, Mathilde ; Colzi, Laura search by orcid ; Emig, Kimberly L. ; Meier, David S. ; Henkel, Christian ; Humire, Pedro ; Huang, Ko-Yun ; Rivilla, Víctor M. ; van der Werf, Paul ; Viti, Serena

Astronomy & Astrophysics (EDP Science)  687   43 2024.05

Research paper (scientific journal), Joint Work, Accepted

The ALCHEMI atlas: principal component analysis reveals starburst evolution in NGC 253

Harada, Nanase ; Meier, David S. ; Martín, Sergio ; Muller, Sebastien ; Sakamoto, Kazushi ; Saito, Toshiki ; Gorski, Mark D. ; Henkel, Christian ; Tanaka, Kunihiko ; Mangum, Jeffrey G. ; Aalto, Susanne ; Aladro, Rebeca ; Bouvier, Mathilde ; Colzi, Laura search by orcid ; Emig, Kimberly L. ; Herrero-Illana, Rubén ; Huang, Ko-Yun ; Kohno, Kotaro ; König, Sabine ; Nakanishi, Kouichiro ; Nishimura, Yuri ; Takano, Shuro ; Rivilla, Víctor M. ; Viti, Serena ; Watanabe, Yoshimasa ; van der Werf, Paul P. , Yoshimura, Yuki

The Astrophysical Journal Supplement Series (IOP publishing)  271   38 2024.04

Research paper (scientific journal), Joint Work, Accepted

Volume Density Structure of the NGC253 CMZ through ALCHEMI Excitation Analysis

Tanaka, Kunihiko ; Mangum, Jeffrey G. ; Viti, Serena ; Martin, Sergio ; Harada, Nanase ; Sakamoto, Kazushi ; Muller, Sebastien ; Yoshimura, Yuki ; Nakanishi, Kouichiro ; Herrero Illana, Ruben ; Emig, Kimberly L. ; Muhle, S. ; Kaneko, Hiroyuki ; Tosaki, Tomoka ; Behrens, Erica ; Rivilla, Victor M. ; Colzi, Laura ; Nishimura, Yuri ; Humire, P. K. ; Bouvier, Mathilde ; Huang, Ko-Yun ; Butterworth, Joshua ; Meier, David S. ; van der Werf, Paul P.

The Astrophysical Journal (IOP publishing)  916   18 2024.01

Research paper (scientific journal), Joint Work, Lead author, Corresponding author, Accepted

FINER: Far-Infrared Nebular Emission Receiver for the Large Millimeter Telescope

Tamura, Yoichi ; Sakai, Takeshi ; Kawabe, Ryohei ; Kojima, Takafumi ; Taniguchi, Akio ; Takekoshi, Tatsuya ; Kang, Haoran ; Shan, Wenlei ; Hagimoto, Masato ; Okauchi, Norika ; Tetsuka, Airi ; Inoue, Akio K. ; Kohno, Kotaro ; Tanaka, Kunihiko ; Bakx, Tom J. L. C. ; Fudamoto, Yoshinobu ; Fujita, Kazuyuki ; Harikane, Yuichi ; Hashimoto, Takuya ; Hatsukade, Bunyo ; Hughes, David H. ; Iino, Takahiro ; Kimura, Yuki ; Maezawa, Hiroyuki ; Matsuda, Yuichi ; Mawatari, Ken ; Nakajima, Taku ; Nakatsubo, Shunichi ; Oshima, Tai ; Sagawa, Hideo ; Schloerb, F. Peter ; Takahashi, Shigeru ; Taniguchi, Kotomi ; Tsujita, Akiyoshi ; Umehata, Hideki ; Yonetsu, Teppei ; Yun, Min S.

Proceedings paper presented in SPIE Astronomical Telescope and Instrumentation 2024 13102 2024

ISSN  0277786X

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Unveiling the emergence and prevalence of massive/bright galaxies during the epoch of reionization and beyond, within the first 600 million years of the Universe, stands as a pivotal pursuit in astronomy. Remarkable progress has been made by JWST in identifying an immense population of bright galaxies, which hints at exceptionally efficient galaxy assembly processes. However, the underlying physical mechanisms propelling their rapid growth remain unclear. With this in mind, millimeter and submillimeter-wave spectroscopic observations of redshifted far-infrared spectral lines, particularly the [O iii] 88 µm and [C ii] 158 µm lines, offers a crucial pathway to address this fundamental query. To this end, we develop a dual-polarization sideband-separating superconductor-insulator-superconductor (SIS) mixer receiver, FINER, for the Large Millimeter Telescope (LMT) situated in Mexico. Harnessing advancements from ALMA's wideband sensitivity upgrade (WSU) technology, FINER covers radio frequencies spanning 120-360 GHz, delivering an instantaneous intermediate frequency (IF) of 3-21 GHz per sideband per polarization, which is followed by a set of 10.24 GHz-wide digital spectrometers. At 40% of ALMA's light-collecting area, the LMT's similar atmospheric transmittance and FINER's 5 times wider bandwidth compared to ALMA culminate in an unparalleled spectral scanning capability in the northern hemisphere, paving the way for finer spectral-resolution detection of distant galaxies.

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A 10.24-GHz-wide digital spectrometer array system for LMT-FINER: system design and laboratory performance verification

Hagimoto, Masato ; Taniguchi, Akio ; Tamura, Yoichi ; Okauchi, Norika ; Kawamoto, Hiroaki ; Nakajima, Taku ; Hikosaka, Takumi ; Harada, Kenichi ; Taniguchi, Toru ; Kamazaki, Takeshi ; Sakai, Takeshi ; Tanaka, Kunihiko ; Kawabe, Ryohei

Proceedings paper presented in SPIE Astronomical Telescope and Instrumentation 2024 13102 2024

ISSN  0277786X

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For efficient spectroscopic redshift identification of early galaxies in the northern hemisphere, we aim to combine the Large Millimeter Telescope (LMT) with a wide-band heterodyne receiver, FINER, which will cover radio frequencies of 120-360 GHz and offer a 3-21 GHz intermediate frequency (IF) per sideband and polarization. To take full advantage of such wide IFs, we present a novel 10.24-GHz-wide digital spectrometer, DRS4 (Elecs Industry Co., Ltd.). It incorporates 20.48 Gsps samplers with an FPGA-based digital signal processing module. To mitigate the noise contamination from the image sideband, it is equipped with a digital sideband separation function to improve the sideband rejection up to 25 dB. Laboratory performance evaluations show that it exhibits an Allan time of at least ∼ 100 s and a total power dynamic range of at least 7 dB. These results demonstrate its capability of instantaneously wide-band spectroscopy toward high-redshift galaxies with position-switching observations.

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An ALCHEMI inspection of sulphur-bearing species towards the central molecular zone of NGC 253

Bouvier, M. ; Viti, S. ; Behrens, E. ; Butterworth, J. ; Huang, K. -Y. ; Mangum, J. G. ; Harada, N. ; Martín, S. ; Rivilla, V. M. ; Muller, S. ; Sakamoto, K. ; Yoshimura, Y. ; Tanaka, K. ; Nakanishi, K. ; Herrero-Illana, R. ; Colzi, L. ; Gorski, M. D. ; Henkel, C. ; Humire, P. K. ; Meier, D. S. ; van der Werf, P. P. ; Yan, Y. T.

Astronomy & Astrophysics (EDP Science)   2024

Research paper (scientific journal), Joint Work, Accepted

Distributions of the Density and Kinetic Temperature of the Molecular Gas in the Central Region of NGC 613 Using Hierarchical Bayesian Inference

Kaneko, Hiroyuki; Tosaki, Tomoka; Tanaka, Kunihiko ; Miyamoto, Yusuke

The Astrophysical Journal (IOP publishing)  953   139 2023.08

Research paper (scientific journal), Joint Work, Accepted

Reconstructing the shock history in the CMZ of NGC 253 with ALCHEMI

Huang, K. -Y. ; Viti, S. ; Holdship, J. ; Mangum, J. G. ; Martín, S. ; Harada, N. ; Muller, S. ; Sakamoto, K. ; Tanaka, K. ; Yoshimura, Y. ; Herrero-Illana, R. ; Meier, D. S. ; Behrens, E. ; van der Werf, P. P. ; Henkel, C. ; García-Burillo, S. ; Rivilla, V. M. ; Emig, K. L. ; Colzi, L. search by orcid ; Humire, P. K. ; ...

 2023.03

Research paper (scientific journal), Joint Work, Accepted

Tracing Interstellar Heating: An ALCHEMI Measurement of the HCN Isomers in NGC 253

Behrens, Erica ; Mangum, Jeffrey G. ; Holdship, Jonathan ; Viti, Serena ; Harada, Nanase ; Martin, Sergio ; Sakamoto, Kazushi ; Muller, Sebastien ; Tanaka, Kunihiko ; Nakanishi, Kouichiro ; Herrero-Illana, Ruben ; Yoshimura, Yuki ; Aladro, Rebeca ; Colzi, Laura ; Emig, Kimberly L. ; Henkel, Christian ; Huang, Ko-Yun ; Humire, P. K. ; Meier, David S. ; Rivilla, Victor M. Abstract

939   119 2022.11

Research paper (scientific journal), Accepted

ALCHEMI finds a "shocking" carbon footprint in the starburst galaxy NGC~253

Harada, Nanase ; Martin, Sergio ; Mangum, Jeff ; Sakamoto, Kazushi ; Muller, Sebastian ; Rivilla, Victor ; Henkel, Christian ; Meier, David ; Colzi, Laura ; Yamagishi, Mitsuyoshi ; Tanaka, Kunihiko ; Nakanishi, Kouichiro ; Herrero-Illana, Ruben ; Yoshimura, Yuki ; Humire, Pedro ; Aladro, Rebeca ; van der Werf, Paul ; Emig, Kim

938   80 2022.10

Research paper (scientific journal), Joint Work, Accepted

Methanol masers in NGC 253 with ALCHEMI

Humire, P. K. ; Henkel, C. ; Hernández-Gómez, A. ; Martín, S. ; Mangum, J. ; Harada, N. ; Muller, S. ; Sakamoto, K. ; Tanaka, K. ; Yoshimura, Y. ; Nakanishi, K. ; Mühle, S. ; Herrero-Illana, R. ; Meier, D. S. ; Caux, E. ; Aladro, R. ; Mauersberger, R. ; Viti, S. ; Colzi, L. ; Rivilla, V. M. ;

Astronomy and Astrophysics (Astronomy and Astrophysics)  663   33 2022.07

Research paper (scientific journal), Accepted,  ISSN  00046361

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Context. Methanol masers of Class I (collisionally pumped) and Class II (radiatively pumped) have been studied in great detail in our Galaxy in a variety of astrophysical environments such as shocks and star-forming regions and are they are helpful to analyze the properties of the dense interstellar medium. However, the study of methanol masers in external galaxies is still in its infancy. Aims. Our main goal is to search for methanol masers in the central molecular zone (CMZ; inner 500 pc) of the nearby starburst galaxy NGC253. Methods. Covering a frequency range between 84 and 373 GHz (λ = 3.6-0.8 mm) at high angular (1."6 ∼ 27 pc) and spectral (∼8-9 km s-1) resolution with ALCHEMI (ALMA Comprehensive High-resolution Extragalactic Molecular Inventory), we have probed dierent regions across the CMZ of NGC253. In order to look for methanol maser candidates, we employed the rotation diagram method and a set of radiative transfer models. Results.We detect for the first time masers above 84 GHz in NGC253, covering an ample portion of the J-1 (J-1)0-E line series (at 84, 132, 229, and 278 GHz) and the J0 (J-1)1 A series (at 95, 146, and 198 GHz). This confirms the presence of the Class I maser line at 84 GHz, which was already reported, but now being detected in more than one location. For the J-1 (J-1)0-E line series, we observe a lack of Class I maser candidates in the central star-forming disk. Conclusions. The physical conditions for maser excitation in the J-1 (J-1)0-E line series can be weak shocks and cloud-cloud collisions as suggested by shock tracers (SiO and HNCO) in bi-symmetric shock regions located in the outskirts of the CMZ. On the other hand, the presence of photodissociation regions due to a high star-formation rate would be needed to explain the lack of Class I masers in the very central regions.

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Energizing Star Formation: The Cosmic-Ray Ionization Rate in NGC 253 Derived from ALCHEMI Measurements of H<inf>3</inf>O⁺and SO

Holdship J., Mangum J.G., Viti S., Behrens E., Harada N., Martín S., Sakamoto K., Muller S., Tanaka K., Nakanishi K., Herrero-Illana R., Yoshimura Y., Aladro R., Colzi L., Emig K.L., Henkel C., Nishimura Y., Rivilla V.M., Van Der Werf P.P.

Astrophysical Journal (Astrophysical Journal)  931 ( 2 )  2022.06

Research paper (scientific journal), Accepted,  ISSN  0004637X

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The cosmic-ray ionization rate (CRIR) is a key parameter in understanding the physical and chemical processes in the interstellar medium. Cosmic rays are a significant source of energy in star formation regions, impacting the physical and chemical processes that drive the formation of stars. Previous studies of the circum-molecular zone of the starburst galaxy NGC 253 have found evidence for a high CRIR value: 103-106 times the average CRIR within the Milky Way. This is a broad constraint, and one goal of this study is to determine this value with much higher precision. We exploit ALMA observations toward the central molecular zone of NGC 253 to measure the CRIR. We first demonstrate that the abundance ratio of H3O+ and SO is strongly sensitive to the CRIR. We then combine chemical and radiative transfer models with nested sampling to infer the gas properties and CRIR of several star-forming regions in NGC 253 from emission from their transitions. We find that each of the four regions modeled has a CRIR in the range (1-80) × 10-14 s-1 and that this result adequately fits the abundances of other species that are believed to be sensitive to cosmic rays, including C2H, HCO+, HOC+, and CO. From shock and photon-dominated/X-ray dominated region models, we further find that neither UV-/X-ray-driven nor shock-dominated chemistry is a viable single alternative as none of these processes can adequately fit the abundances of all of these species.

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