2018ApJ...859L..22E

A giant star-forming region in a metal-poor dwarf galaxy has been observed in optical lines with the 10 m Gran Telescopio Canarias (GTC) and in the emission line of CO(1-0) with the Northern Extended Millimeter Array (NOEMA) mm-wave interferometer. The metallicity was determined to be 12+log(O/H)=7.83±0.09, from which we estimate a conversion factor of α_CO ∼ 100 M_☉ pc^–2(K km s^–1)^–1 and a molecular cloud mass of ∼2.9 x 10⁷ M_☉. This is an enormous concentration of molecular mass at one end of a small galaxy, suggesting a recent accretion. The molecular cloud properties seem normal: the surface density, 120 M_☉ pc^–2, is comparable to that of a standard giant molecular cloud; the cloud's virial ratio of ∼1.8 is in the star formation range; and the gas consumption time, 0.5 Gyr, at the present star formation rate is typical for molecular regions. The low metallicity implies that the cloud has an average visual extinction of only 0.8 mag, which is close to the threshold for molecule formation. With such an extinction threshold, molecular clouds in metal-poor regions should have high surface densities and high internal pressures. If high pressure is associated with the formation of massive clusters, then metal-poor galaxies such as dwarfs in the early universe could have been the hosts of metal-poor globular clusters.