D. Haasler, V. M. Rivilla, S. Martín, J. Holdship, S. Viti, N. Harada, J. Mangum, K. Sakamoto, S. Muller, K. Tanaka, Y. Yoshimura, K. Nakanishi, L. Colzi, L. Hunt, K. L. Emig, R. Aladro, P. Humire, C. Henkel, and P. van der Werf
reported on the
First Extragalactic Detection of a Phosphorus-bearing Molecule with ALCHEMI: Phosphorus Nitride (PN)
Astron. Astrophys. 659, (2022) Art. No. A158.

The J = 2 – 1 and J = 3 – 2 transitions of PN near 93.980 and 140.968 GHz, respectively, were observed with ALMA in the course of a very extensive molecular line survey (84.2 to 373.2 GHz) of the central molecular zone (CMZ) of the near-by star-burst galaxy NGC 253. Both transitions were detected toward the source GMC 6 with good and fairly good signal-to-noise ratios (S/N), respectively. The J = 2 – 1 transition was also detected with reasonable S/N toward the source GMC 4. The two transitions detected toward GMC 6 constrain the excitation temperature to 4.4 ± 1.3 K.

Other phosphorus-bearing molecules were searched for, but not detected. The PO/PN ratio was found to be < 1.3 for GMC 6, still compatible with PO/PN > 1 in Galactic sources. The PH₃/PN ratio was found to be < 2.7 toward the same position.

Contributor(s): H. S. P. Müller; 04, 2022