Extended CO emission in the field of the light echo of V838 Mon

TL;DR

This study investigates the origin of CO emission around V838 Mon, revealing that the emission is extended, complex, and likely from interstellar clouds associated with the light echo.

Contribution

First detailed mapping of CO emission in the light echo region of V838 Mon, linking molecular gas to the interstellar dust responsible for the echo.

Findings

CO emission is extended and complex.

Emission likely originates from diffuse interstellar clouds.

CO-bearing gas is collocated with echoing dust.

Abstract

V838 Mon erupted at the beginning of 2002 becoming an extremely luminous star with L=10^6 L_sun. The outburst was followed by the spectacular light echo that revealed that the star is immersed in a diffuse and dusty medium, plausibly interstellar in nature. Low angular resolution observations in the lowest CO rotational transitions revealed a molecular emission from the direction of V838 Mon. The origin of this CO emission has not been established. In this paper we investigate the idea that the molecular emission originates in the material responsible for the optical light echo. We report on observations of 13 positions within the light echo in the two lowest rotational transitions of CO using the IRAM 30 m telescope. Emission in CO J=1-0 and J=2-1 was detected in three positions. In three other positions only weak J=1-0 lines were found. We conclude that the molecular emission from the direction of V838 Mon is extended and has a complex distribution. We identify the emission as arising from diffuse interstellar clouds and suggest that the CO-bearing gas and the echoing dust are collocated in the same interstellar cloud.