First extragalactic detection of a phosphorus-bearing molecule with ALCHEMI: Phosphorus nitride (PN)
Artikel i vetenskaplig tidskrift, 2022

Context. Phosphorus (P) is a crucial element for life given its central role in several biomolecules. P-bearing molecules have been discovered in different regions of the Milky Way, but not yet towards an extragalactic environment.
Aims. We searched for P-bearing molecules outside the Milky Way towards the nearby starburst Galaxy NGC 253.
Methods. Using observations from the ALMA Comprehensive High-resolution Extragalactic Molecular Inventory (ALCHEMI) project, we used the MAdrid Data CUBe Analysis package to model the emission of P-bearing molecules assuming local thermodynamic equilibrium (LTE) conditions. We also performed a non-LTE analysis using SpectralRadex.
Results. We report the detection of a P-bearing molecule, phosphorus nitride (PN), for the first time in an extragalactic environment, towards two giant molecular clouds (GMCs) of NGC 253. The LTE analysis yields total PN beam-averaged column densities N = (1.20 +/- 0.09) x 10(13) cm(-2) and N = (6.5 +/- 1.6) x 10(12) cm(-2), which translate into abundances with respect to H-2 of chi = (8.0 +/- 1.0) x 10(-12) and chi = (4.4 +/- 1.2) x 10(-12). We derived a low excitation temperature of T-ex = (4.4 +/- 1.3) K towards the GMC with the brightest PN emission, which indicates that PN is sub-thermally excited. The non-LTE analysis results in column densities consistent with the LTE values. We also searched for other P-bearing molecules (PO, PH3, CP, and CCP), and upper limits were derived. The derived PO/PN ratios are < 1.3 and < 1.7. The abundance ratio between PN and the shock-tracer SiO derived towards NGC 253 follows the same trend previously found towards Galactic sources. Conclusions. Comparison of the observations with chemical models indicates that the derived molecular abundances of PN in NGC 253 can be explained by shock-driven chemistry followed by cosmic-ray-driven photochemistry.

individual

galaxies

ISM

clouds

abundances

ISM

astrochemistry

NGC 253

molecules

ISM

Författare

D. Haasler

Universidad Rey Juan Carlos

Centro de Astrobiología (INTA-CSIC)

V. M. Rivilla

Istituto nazionale di astrofisica (INAF)

Centro de Astrobiología (INTA-CSIC)

S. Martin

Atacama Large Millimeter-submillimeter Array (ALMA)

European Southern Observatory Santiago

J. Holdship

University College London (UCL)

Universiteit Leiden

S. Viti

University College London (UCL)

Universiteit Leiden

N. Harada

The Graduate University for Advanced Studies (SOKENDAI)

National Astronomical Observatory of Japan

Academia Sinica

J. Mangum

National Radio Astronomy Observatory

K. Sakamoto

Academia Sinica

Sebastien Muller

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium, Observationssupport

K. Tanaka

Keio University

Y. Yoshimura

University of Tokyo

K. Nakanishi

National Astronomical Observatory of Japan

The Graduate University for Advanced Studies (SOKENDAI)

L. Colzi

Istituto nazionale di astrofisica (INAF)

Centro de Astrobiología (INTA-CSIC)

L. Hunt

Istituto nazionale di astrofisica (INAF)

K. L. Emig

National Radio Astronomy Observatory

R. Aladro

Max-Planck-Gesellschaft

P. Humire

Max-Planck-Gesellschaft

C. Henkel

King Abdulaziz University

Max-Planck-Gesellschaft

Chinese Academy of Sciences

P. van der Werf

Universiteit Leiden

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 659 A158

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1051/0004-6361/202142032

Mer information

Senast uppdaterat

2022-04-07