Phosphorus-bearing molecules in massive dense cores

TL;DR

This study reports the detection of phosphorus nitride in various dense cores involved in star formation, revealing that P-bearing molecules can exist in cold, quiescent gas, challenging existing models of phosphorus chemistry in space.

Contribution

It provides new observational evidence of phosphorus nitride in cold, quiescent regions, expanding understanding of phosphorus chemistry in star-forming environments.

Findings

PN detected in cold, quiescent dense cores

Line widths smaller than 5 km/s indicating low turbulence

Column densities around 10^{11-12} cm^{-2}

Abstract

Phosphorus is a crucial element for the development of life, but so far P-bearing molecules have been detected only in a few astrophysical objects, hence its interstellar chemistry is almost totally unknown. Here we show new detections of phosphorus nitride in a sample of dense cores in different evolutionary stages of the intermediate- and high-mass star formation process: starless, with protostellar objects, and with ultracompact HII regions. All detected PN line widths are smaller than ~5 km/s , and they arise from regions associated with kinetic temperatures smaller than 100 K. Because the few previous detections reported in the literature are associated with warmer and more turbulent sources, the results of this work show that PN can arise from relatively quiescent and cold gas. This information is challenging for theoretical models that invoke either high desorption temperatures or grain sputtering from shocks to release phosphorus into the gas phase. Derived column densities are of the order of 10^{11-12} cm^{-2}, marginally lower than the values derived in the few high-mass star forming regions detected so far. New constraints on the column density upper limit of phosphorus monoxide, the fundamental unit of biologically relevant molecules, are also given.