ACA CO(J = 2–1) Mapping of the Nearest Spiral Galaxy M33. I. Initial Results and Identification of Molecular Clouds

Muraoka, Kazuyuki; ,; Konishi, Ayu; Tokuda, Kazuki; Kondo, Hiroshi; Miura, Rie E.; Tosaki, Tomoka; Onodera, Sachiko; Kuno, Nario; Kobayashi, Masato I. N.; Tsuge, Kisetsu; Sano, Hidetoshi; Kitano, Naoya; Fujita, Shinji; Nishimura, Atsushi; Onishi, Toshikazu; Saigo, Kazuya; Yamada, Rin I.; Demachi, Fumika; Tachihara, Kengo; Fukui, Yasuo; Kawamura, Akiko

doi:10.3847/1538-4357/ace4bd

Cited by 3 publications

(1 citation statement)

References 78 publications

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“…Data were reduced using CASA (CASA Team et al 2022) version 6.4.4-31. Standard calibrations provided by the ALMA observatory were applied to each measurement set in a total of 1501 pointings composed of 12 fields with the 7 m array and 9 with the TP array, and then we concatenated all of the visibility files and imaged them together. The imaging strategy is the same as for the previously reported ACA large-scale surveys (Tokuda et al 2021;Muraoka et al 2023). We used the tclean task with the multi-scale deconvolver (Kepley et al 2020) to recover the extended emission.…”

Section: Data Reductionmentioning

confidence: 99%

Internal 1000 au Scale Structures of the R CrA Cluster-forming Cloud. I. Filamentary Structures

Tachihara,

Fukaya,

Tokuda

et al. 2024

ApJ

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We report Atacama Large Millimeter/submillimeter Array/Atacama Compact Array observations of a high-density region of the Corona Australis cloud forming a young star cluster, and the results of resolving internal structures. In addition to embedded Class 0/I protostars in the continuum, a number of complex dense filamentary structures are detected in the C18O and SO lines by the 7 m array. These are substructures of the molecular clump that are detected by the total power array as extended emission. We identify 101 and 37 filamentary structures with widths of a few thousand astronomical units in C18O and SO, respectively, which are called feathers. The typical column density of the feathers in C18O is about 1022 cm−2, and the volume density and line mass are ∼105 cm−3 and a few M ☉ pc−1, respectively. This line mass is significantly smaller than the critical line mass expected for cold and dense gas. These structures have complex velocity fields, indicating a turbulent interior. The number of feathers associated with Class 0/I protostars is only ∼10, indicating that most of them do not form stars but rather are transient structures. The formation of feathers can be interpreted as a result of colliding gas flow because the morphology is well reproduced by MHD simulations, and this is supported by the presence of H i shells in the vicinity. The colliding gas flows may accumulate gas and form filaments and feathers, and trigger the active star formation of the R CrA cluster.

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Section: Data Reductionmentioning

confidence: 99%

Internal 1000 au Scale Structures of the R CrA Cluster-forming Cloud. I. Filamentary Structures

Tachihara,

Fukaya,

Tokuda

et al. 2024

ApJ

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Sub-kpc scale gas density histogram of the galactic molecular gas: a new statistical method to characterize galactic-scale gas structures

Matsusaka,

Handa,

Fujimoto

et al. 2024

Monthly Notices of the Royal Astronomical Society

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To understand physical properties of the interstellar medium (ISM) on various scales, we investigate it at parsec resolution on the kiloparsec scale. Here, we report on the sub-kpc scale Gas Density Histogram (GDH) of the Milky Way. The GDH is a density probability distribution function (PDF) of the gas volume density. Using this method, we are free from an identification of individual molecular clouds and their spatial structures. We use survey data of 12CO and 13CO (J=1–0) emission in the Galactic plane (l = 10○–50○) obtained as a part of the FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45m telescope (FUGIN). We make a GDH for every channel map of 2○ × 2○ area including the blank sky component, and without setting cloud boundaries. This is a different approach from previous works for molecular clouds. The GDH fits well to a single or double log-normal distribution, which we name the low-density log-normal (L-LN) and high-density log-normal (H-LN) components, respectively. The multi-log-normal components suggest that the L-LN and H-LN components originate from two different stages of structure formation in the ISM. Moreover, we find that both the volume ratios of H-LN components to total (fH) and the width of the L-LN along the gas density axis (σL) show coherent structure in the Galactic-plane longitude-velocity diagram. It is possible that these GDH parameters are related to strong galactic shocks and other weak shocks in the Milky Way.

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ACA CO(J = 2–1) mapping of the nearest spiral galaxy M 33. II. Exploring the evolution of giant molecular clouds

Konishi,

Muraoka,

Tokuda

et al. 2024

Publications of the Astronomical Society of Japan

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The evolution of giant molecular clouds (GMCs), the main sites of high-mass star formation, is an essential process to unravel the galaxy evolution. Using a GMC catalogue of M 33 from the ALMA-ACA (Atacama Large Millimeter/submillimeter Array–Atacama Compact Array) survey, we classified 848 GMCs into three types based on the association with H ii regions and their H$\alpha$ luminosities $L\, (\rm{H}\alpha )$: Type I is associated with no H ii regions; Type II with H ii regions of $L\, (\rm{H}\alpha )$ $\lt 10^{37.5}$ erg s$^{-1}$; and Type III with H ii regions of $L\, (\rm{H}\alpha )$ $\geqq$ $10^{37.5}$ erg s$^{-1}$. These criteria yield 224 Type I GMCs, 473 Type II GMCs, and 151 Type III GMCs. GMCs show changes in their physical properties according to the types; mass, radius, velocity dispersion, and $^{13}$CO detection rate of GMCs systematically increase from Type I to Type III, and additionally, Type III GMCs are closest to virial equilibrium. Type III GMCs show the highest spatial correlation with clusters younger than $10\:$Myr, Type II GMCs moderate correlation, and Type I GMCs are almost uncorrelated. We interpret that these types indicate an evolutionary sequence from Type I to Type II, and then to Type III with timescales of 4 Myr, 13 Myr, and 5 Myr, respectively, indicating a GMC lifetime of 22 Myr by assuming that a Type II GMC has the same timescale as the Large Magellanic Cloud. The evolved GMCs are concentrated on the spiral arms, while the younger GMCs are apart from the arm, both to the leading and trailing sides. This indicates that GMCs collide with each other via the spiral potential, leading to the compression of GMCs and the triggering of high-mass star formation, which may support the dynamic spiral model. Overall, we suggest that the GMC evolution concept helps illuminate the galaxy evolution, including the spiral arm formation.

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ACA CO(J = 2–1) Mapping of the Nearest Spiral Galaxy M33. I. Initial Results and Identification of Molecular Clouds

Cited by 3 publications

References 78 publications

Internal 1000 au Scale Structures of the R CrA Cluster-forming Cloud. I. Filamentary Structures

Internal 1000 au Scale Structures of the R CrA Cluster-forming Cloud. I. Filamentary Structures

Sub-kpc scale gas density histogram of the galactic molecular gas: a new statistical method to characterize galactic-scale gas structures

ACA CO(J = 2–1) mapping of the nearest spiral galaxy M 33. II. Exploring the evolution of giant molecular clouds

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