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Submillimeter Array Observations of Extended CO (J = 2 ‑ 1) Emission in the Interacting Galaxy NGC 3627

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Abstract

  • We present moderate (∼5″) and high angular resolution (∼1″) observations of 12CO (J = 2 ‑ 1) emission toward the nearby interacting galaxy NGC 3627 taken with the Submillimeter Array (SMA). These SMA mosaic maps of NGC 3627 reveal a prominent nuclear peak, inter-arm regions, and diffuse, extended emission in the spiral arms. A velocity gradient of ∼400–450 km s‑1 is seen across the entire galaxy with velocity dispersions ranging from ≲80 km s‑1 toward the nuclear region to ≲15 km s‑1 in the spiral arms. We also detect unresolved 13CO (J = 2 ‑ 1) line emission toward the nuclear region, southern bar end, and in a relatively isolated clump in the southern portion of the galaxy, while no C18O(J = 2 ‑ 1) line emission is detected at a 3σ rms noise level of 42 mJy beam‑1 per 20 km s‑1 channel. Using RADEX modeling with a large velocity gradient approximation, we derive kinetic temperatures ranging from ∼5 to 10 K (in the spiral arms) to ∼25 K (at the center) and H2 number densities from ∼400 to 1000 cm‑3 (in the spiral arms) to ∼12,500 cm‑3 (at the center). From this density modeling, we find a total H2 mass of 9.6 × 109 M , which is ∼50% higher than previous estimates made using a constant H2–CO conversion factor, but is largely dependent on the assumed vertical distribution of the CO gas. With the exception of the nuclear region, we also identify a tentative correlation between star formation efficiency and kinetic temperature. We derive a galactic rotation curve, finding a peak velocity of ∼207 km s‑1 and estimate a total dynamical mass of 4.94 ± 0.70 × 1010 M at a galactocentric radius of ∼6.2 kpc (121″).

Publication Date

  • 2018

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