We present Chandra snapshot observations for a sample of seven sources selected from the Arecibo OH megamaser (OHM) survey at z ≈ 0.13-0.22 and with far-infrared (FIR) luminosities in excess of 1011 L ⊙. In contrast with the known H2O megamasers, which are mostly associated with powerful active galactic nuclei (AGN), the situation is far less clear for OHMs, which have been poorly studied in the X-ray band thus far. All of the observed sources are X-ray weak, with only one OHM, IRAS FSC 03521+0028 (z = 0.15), being detected by Chandra (with five counts). The results from this pilot programme indicate that the X-ray emission, with luminosities of less than ≈1042 erg s-1, is consistent with that from star formation (as also suggested in some cases by the optical spectra) and low-luminosity active galactic nuclei (LLAGN) emission. If an AGN is present, its contribution to the broad-band emission of OHM galaxies is likely modest. Under reasonable assumptions about the intrinsic X-ray spectral shape, the observed count distribution from stacking analysis suggests absorption of ≈1022cm-2.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science