Interstellar C_2 in the Perseus molecular complex: excitation temperature and density of a molecular cloud with anomalous microwave emission

Abstract

Interstellar absorption lines up to J"=10 in the (2,0) band and up to J"=6 in the (3,0) band of the C${}_2$ $A^1{\Pi }_u$ - $X^1{\Sigma }_g^{+}$ system are detected toward star Cernis 52 (BD+31${}^o$ 640) in the Perseus molecular complex. The star lies in a redenned line of sight where various experiments have detected anomalous microwave emission spatially correlated with dust thermal emission. The inferred total C${}_2$ column density of N(C${}_2$) = (10.5$\pm$ 0.2) x 10${}^{13}$ cm${}^{-2}$ is well correlated with that of CH as expected from theoretical models and is among the highest reported on translucent clouds with similar extinction. The observed rotational C${}_2$ lines constrain the gas-kinetic temperature T and the density n=n(H)+n(H${}_2$) of the intervening cloud to T = 40$\pm$10 K and n = 250 $\pm$ 50 cm${}^{-3}$, respectively. This is the first determination of gas-kinetic temperature and particle density of a cloud with known anomalous microwave emission.

7, 3, aceppted MNRAS

References in corpus (3)

• Abundances and Behavior of 12CO, 13CO, and C2 in Translucent Sight Lines
• A search for interstellar anthracene toward the Perseus anomalous microwave emission region
• Abundances and rotational temperatures of the C2 interstellar molecule towards six reddened early-type stars

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