Kyushu University · Physics and Astronomy
Professor Kazuki Tokuda's research lab specializes in high-resolution millimeter and submillimeter observations of dense molecular clouds and star-forming regions across diverse galactic environments, from the Milky Way to nearby galaxies such as the Small and Large Magellanic Clouds. The lab focuses on understanding the initial conditions of star and brown dwarf formation, particularly through detailed studies of prestellar and protostellar cores, filamentary structures, and the role of molecular tracers like CO and dust continuum in low-metallicity and high-mass environments. Using ALMA and other state-of-the-art facilities, the lab investigates the physical and chemical properties of dense gas, protostellar disks, and clumps to unravel the mechanisms governing the formation of stars and stellar clusters.
Figures are computed from collected data and may differ slightly.
Abstract We have performed survey-type observations in 1 mm continuum and molecular lines toward dense cores (32 prestellar + 7 protostellar) with an average density of ≳10 5 cm −3 in the Taurus molecular clouds using the Atacama Large Millimeter/submillimeter Array–Atacama Compact Array (ALMA-ACA) stand-alone mode with an angular resolution of 6.″5 (∼900 au). The primary purpose of this study is to investigate the innermost part of dense cores with view to understanding the initial condition of
Abstract We report molecular line and continuum observations toward one of the most massive giant molecular clouds (GMCs), GMC-16, in M33 using ALMA with an angular resolution of 0.″44 × 0.″27 (∼2 pc × 1 pc). We have found that the GMC is composed of several filamentary structures in 12 CO and 13 CO( J = 2–1). The typical length, width, and total mass are ∼50–70 pc, ∼5–6 pc, and ∼10 5 M ⊙ , respectively, which are consistent with those of giant molecular filaments (GMFs) as seen in the Galactic
Abstract We have analyzed the data from a large-scale CO survey toward the northern region of the Small Magellanic Cloud (SMC) obtained with the Atacama Compact Array (ACA) stand-alone mode of ALMA. The primary aim of this study is to comprehensively understand the behavior of CO as an H 2 tracer in a low-metallicity environment ( Z ∼ 0.2 Z ⊙ ). The total number of mosaic fields is ∼8000, which results in a field coverage of 0.26 deg 2 (∼2.9 ×10 5 pc 2 ), corresponding to ∼10% of the area of the
Abstract Massive dense clumps in the Large Magellanic Cloud can be an important laboratory to explore the formation of populous clusters. We report multiscale ALMA observations of the N159W-North clump, which is the most CO-intense region in the galaxy. High-resolution CO isotope and 1.3 mm continuum observations with an angular resolution of ∼0.″25 (∼0.07 pc) revealed more than five protostellar sources with CO outflows within the main ridge clump. One of the thermal continuum sources, MMS-2, s
Abstract The formation scenario of brown dwarfs is still unclear because observational studies to investigate its initial condition are quite limited. Our systematic survey of nearby low-mass star-forming regions using the Atacama Compact Array (aka the Morita array) and the IRAM 30-m telescope in 1.2 mm continuum has identified a centrally concentrated starless condensation with a central H2 volume density of ∼106 cm−3, MC5-N, connected to a narrow (width ∼0.03 pc) filamentary cloud in the Taur
Abstract Recent millimeter/submillimeter facilities have revealed the physical properties of filamentary molecular clouds in relation to high-mass star formation. A uniform survey of the nearest, face-on star-forming galaxy, the Large Magellanic Cloud (LMC), complements the Galactic knowledge. We present ALMA survey data with a spatial resolution of ∼0.1 pc in the 0.87 mm continuum and HCO + (4–3) emission toward 30 protostellar objects with luminosities of 10 4 –10 5.5 L ⊙ in the LMC. The spati
Abstract The nature of molecular clouds and their statistical behavior in subsolar metallicity environments are not fully explored yet. We analyzed data from an unbiased CO ( J = 2–1) survey at the spatial resolution of ∼2 pc in the northern region of the Small Magellanic Cloud with the Atacama Compact Array to characterize the CO cloud properties. A cloud-decomposition analysis identified 426 spatially/velocity-independent CO clouds and their substructures. Based on the cross-matching with know
Abstract Protostellar outflows are one of the most outstanding features of star formation. Observational studies over the last several decades have successfully demonstrated that outflows are ubiquitously associated with low- and high-mass protostars in solar-metallicity Galactic conditions. However, the environmental dependence of protostellar outflow properties is still poorly understood, particularly in the low-metallicity regime. Here we report the first detection of a molecular outflow in t
Abstract Transferring a significant fraction of the magnetic flux from a dense cloud core is essential in the star formation process. A ringlike structure produced by magnetic flux loss has been predicted theoretically, but no observational identification has been presented. We have performed ALMA observations of the Class I protostar IRS 2 in the Corona Australis star-forming region and resolved a distinctive gas ring in the C 18 O ( J = 2–1) line emission. The center of this gas ring is ∼5000
Abstract We present 12 CO ( J = 2–1), 13 CO ( J = 2–1), and C 18 O ( J = 2–1) observations toward GMC-8, one of the most massive giant molecular clouds (GMCs) in M33 using ALMA with an angular resolution of 0.″44 × 0.″27 (∼2 pc × 1 pc). The earlier studies revealed that its high-mass star formation is inactive in spite of a sufficient molecular reservoir with a total mass of ∼10 6 M ⊙ . The high-angular resolution data enable us to resolve this peculiar source down to a molecular clump scale. On
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