We present moderate ( { \sim } 5 ^ { \prime \prime } ) and high angular resolution ( { \sim } 1 ^ { \prime \prime } ) observations of ^ { 12 } CO ( J = 2 - 1 ) emission toward 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 { \sim } 400 – 450 km s ^ { -1 } is seen across the entire galaxy with velocity dispersions ranging from \lesssim 80 km s ^ { -1 } toward the nuclear region to \lesssim 15 km s ^ { -1 } in the spiral arms .
We also detect unresolved ^ { 13 } CO ( 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 C ^ { 18 } O ( J = 2 - 1 ) line emission is detected at a 3 \sigma 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 { \sim } 5 – 10 K ( in the spiral arms ) to { \sim } 25 K ( at the center ) and H _ { 2 } number densities from { \sim } 400–1000 cm ^ { -3 } ( in the spiral arms ) to { \sim } 12500 cm ^ { -3 } ( at the center ) .
From this density modeling , we find a total H _ { 2 } mass of 9.6 \times 10 ^ { 9 } ~ { } M _ { \odot } , which is { \sim } 50 \% higher than previous estimates made using a constant H _ { 2 } –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 { \sim } 207 km s ^ { -1 } and estimate a total dynamical mass of 4.94 \pm 0.70 \times 10 ^ { 10 } M _ { \odot } at a galactocentric radius of { \sim } 6.2 kpc ( 121 ^ { \prime \prime } ) .