Letter to the Editor

Interferometric observations of FeO towards Sagittarius B2

¹ INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
² Nobeyama Radio Observatory, National Astronomical Observatory of Japan, Minamimaki, Minamisaku, Nagano 384-1305, Japan
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁴ Observatorio Astronómico Nacional, Apartado 1143, 28800 Alcalá de Henares, Madrid, Spain

Corresponding author: R. S. Furuya, rsf@astro.caltech.edu

Received: 12 June 2003
Accepted: 26 August 2003

Abstract

We have used the Nobeyama Millimeter Array (NMA) to carry out aperture synthesis observations of the ground state rotational transition of FeO molecule at 153.135273 GHz towards the galactic center Hii region Sagittarius B2 Main (Sgr B2 M). We confirm the detection of this line in absorption with the IRAM 30-m telescope by Walmsley et al. (2002). Due to the higher angular resolution () of our NMA observations, we were able to show that the absorption has a broader line width and a deeper apparent optical depth toward the central area around the ultra-compact (UC) Hii regions. This suggests a higher column density of FeO towards the UCHii regions associated with Sgr B2 M than along adjacent lines of sight sampled with the IRAM 30-m telescope. Our results will be a crucial step toward understanding not only the chemistry of iron-bearing species in the interstellar medium, but also the degree of depletion of heavy elements.