ALMA 12CO (J = 1–0) imaging of the nearby galaxy M 83: Variations in the efficiency of star formation in giant molecular clouds

PASJ: Publications of the Astronomical Society of Japan

Kawabe, Ryohei¹  Miura, Rie²  Tosaki, Tomoka³  Kuno, Nario⁴  Egusa, Fumi⁵  Hirota, Akihiko⁶  Muraoka, Kazuyuki⁶  Baba, Junichi⁶  Nakanishi, Hiroyuki⁷ 

[1] Department of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Japan;Division of Physics, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan;Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan;Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210, Japan;Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago 763-0355, Chile;National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan;Tomonaga Center for the History of the Universe, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan

关键词: galaxies: individual;    galaxies: ISM;    galaxies: star formation;    ISM: molecules;   

DOI  :  10.1093/pasj/psy071

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

We present results of the 12CO (1–0) mosaic observations of the nearby barred-spiral galaxy M 83 obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). The total flux is recovered by combining the ALMA data with single-dish data obtained using the Nobeyama 45 m telescope. The combined map covers a ∼13 kpc2 field that includes the galactic center, eastern bar, and spiral arm with a resolution of 2|${^{\prime\prime}_{.}}$|03 × 1|${^{\prime\prime}_{.}}$|15 (∼45 pc × ∼25 pc). With a resolution comparable to typical sizes of giant molecular clouds (GMCs), the CO distribution in the bar and arm is resolved into many clumpy peaks that form ridge-like structures. Remarkably, in the eastern arm, the CO peaks form two arc-shaped ridges that run along the arm and exhibit a distinct difference in the activity of star formation: the one on the leading side has numerous H ii regions associated with it, whereas the other one on the trailing side has only a few. To see whether GMCs form stars with uniform star formation efficiency (SFE) per free-fall time (SFEff), GMCs are identified from the data cube and then cross-matched with the catalog of |${H}\,\, \small {II}$| regions to estimate the star formation rate for each of them. 179 GMCs with a median mass of 1.6 × 106 M⊙ are identified. The mass-weighted average SFEff of the GMCs is ∼9.4 × 10−3, which is in agreement with models of turbulence regulated star formation. Meanwhile, we find that SFEff is not universal within the mapped region. In particular, one of the arm ridges shows a high SFEff with a mass-weighted value of ∼2.7 × 10−2, which is higher by more than a factor of 5 compared to the inter-arm regions. This large regional variation in SFEff favors the recent interpretation that GMCs do not form stars at a constant rate within their lifetime.

【 授权许可】

CC BY