High-sensitivity mapping of ammonia emission in the trumpler 14/car 1 photodissociation region

The photodissociation region in the immediate vicinity of the Trumpler 14 star cluster represents the nearest source (2.3 kpc) to study the physical parameters of a photodissociation region due to feedback from a large population of O-type stars. It resides in the Carina Nebula, a region rich in high-mass stars. We present the first detection and maps of the ammonia inversion emission of the first three metastable lines, (J, K) = (1,1), (2,2) and (3,3), in the Carina I dark cloud. These observations, made with the Tidbinbilla 70m radio telescope, are the initial results of a programme to implement full mapping capability. We also present velocity maps together with the optical depth and rotational (R₂₁) temperatures. The derived linewidths and rotational temperatures support evidence for an ionization front associated with the Carina I-E and Carina I-W substructures. Detection of the (3,3) metastable line suggests significantly higher kinetic temperatures in the molecular clumps than those derived with CO studies, implying that the CO emission is saturated despite photodissociation. The kinematics of the Carina I-E and Carina I-W ammonia substructures are consistent with studies of radio recombination and molecular lines. The prevailing morphological paradigm for Car I is considered, particularly by comparing the molecular structure traced by the ammonia emission to stellar infrared and radio sources in the region.