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ABSTRACT The latest generation of Galactic Plane surveys is enhancing our ability to study the effects of galactic environment upon the process of star formation. We present the first data from CO Heterodyne Inner Milky Way Plane Survey 2 (CHIMPS2). CHIMPS2 is a survey that will observe the Inner Galaxy, the Central Molecular Zone (CMZ), and a section of the Outer Galaxy in 12CO, 13CO, and C18O $$(J = 3\rightarrow 2)$$ emission with the Heterodyne Array Receiver Program on the James Clerk Maxwell Telescope (JCMT). The first CHIMPS2 data presented here are a first look towards the CMZ in 12CO J = 3 → 2 and cover $${-}3^{\circ }\, \le \, \ell \, \le \, 5^{\circ }$$ and $$\mid {b} \mid \, \le \, 0{_{.}^{\circ}} 5$$ with angular resolution of 15 arcsec, velocity resolution of 1 km s−1, and rms $$\Delta \, T_A ^\ast =$$ 0.58 K at these resolutions. Such high-resolution observations of the CMZ will be a valuable data set for future studies, whilst complementing the existing Galactic Plane surveys, such as SEDIGISM, the $${Herschel}$$ infrared Galactic Plane Survey, and ATLASGAL. In this paper, we discuss the survey plan, the current observations and data, as well as presenting position–position maps of the region. The position–velocity maps detect foreground spiral arms in both absorption and emission.
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The Galactic Center arms inferred from the ALMA CMZ Exploration Survey (ACES)
Abstract Analyzing longitude–velocity diagrams (LVDs) in the CS (J = 2–1) and H$$^{13}$$CN (J = 1–0) molecular lines from the internal release data of the ALMA Central Molecular Zone (CMZ) Exploration Survey and in the $$^{13}$$CO (J = 1–0) line from the Nobeyama Galactic Center (GC) survey, we identify six GC arms as prominent straight LV ridges. In addition to the currently known Arms I to IV, we identify a new inner arm, Arm V, and further highlight the circumnuclear disk (CND) as Arm VI. Integrated intensity maps of the arms on the sky suggest that most of the arms compose ring-like structures inclined from the Galactic plane. We determine the radii (curvatures) of the arms using the velocity-gradient ($dv/dl$) method, assuming that the arms are rotating in circular orbits at a constant velocity of $$\sim$$150 km s$$^{-1}$$. We show that Arms I and II compose the main ring structure of the CMZ with radii $$\sim$$100–120 pc; Arm III is a dense arm 42 pc from the GC; Arm IV is a clear and narrow arm 20 pc from the GC; and Arm V is a faint, long arm of 8.2 pc radius. We show that the CND comprises the sixth arm, Arm VI, of radius $$\sim$$2.3 pc associated with bifurcated spiral fins. We also discuss the association of the 20 and 50 km s$$^{-1}$$ clouds with these arms. The radii of the arms fall on an empirical relation $$R\sim 630 (2/5)^N$$ for $N=1$ (Arm I) to 6 (VI), suggesting discrete rings or a logarithmic spiral with pitch angle $${\sim }22^{\circ }$$. The vertical full extent of the arm increases with radius and is represented by $$z\sim 0.7 (R/1 {\rm \ pc} )^{0.7}$$ pc. The tilt angle of the arms from the Galactic plane, or the warping, increases rapidly toward the GC.
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- PAR ID:
- 10686851
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Publications of the Astronomical Society of Japan
- Date Published:
- Journal Name:
- Publications of the Astronomical Society of Japan
- ISSN:
- 0004-6264
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1093/pasj/psaf034
