2003/02/14 by J. A. Stevens, M. J. Page, R. J. Ivison +4 · 1 citation
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #Galaxy #Infrared #Luminous infrared galaxy #Physics #Radio galaxy #Redshift #Star formation #Starlight #Stars #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.2003.06534.x
published as Mon.Not.Roy.Astron.Soc. 342 (2003) 249 · MNRAS, in press, 10 pages, 7 figures
arxiv created 2003/02/14 · openalex publication_date 2003/06/02 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report on the X-ray, optical, near-infrared, submillimetre and radio properties of five extremely red objects (EROs) selected at X-ray wavelengths by XMM-Newton in the Lockman Hole field. They all have enough counts in the X-ray band to allow spectral fitting: four are most probably obscured, Compton-thin active galactic nuclei (AGNs) with redshift-dependent absorbing column densities of 1022–1024 cm−2, whilst the fifth is best fitted by a thermal spectrum and is likely to be a massive elliptical galaxy in a deep gravitational potential. Their optical/near-infrared colours and sizes suggest that X-ray selected EROs comprise a mixture of dusty ‘starburst’ galaxies and non-dusty galaxies that are dominated by either starlight or light from an active nucleus. The colour diagnostics are supported by the submillimetre and radio data; the two AGNs with ‘starburst’ colours have submillimetre or radio flux densities that imply large star formation rates, whilst those with ‘elliptical’ colours do not. The one source detected in the submillimetre waveband has narrow emission lines at a redshift of 1.45. Although the bulk of its radio emission originates from processes other than star formation, it is most probably a radio-quiet ultraluminous infrared galaxy.