OVERTURNING THE CASE FOR GRAVITATIONAL POWERING IN THE PROTOTYPICAL COOLING LYα NEBULA
- Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark)
- Department of Astronomy, Yale University, New Haven, CT 06511 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- European Southern Observatory, Karl-Schwarzschildstrasse 2, D-85748 Garching bei München (Germany)
The Nilsson et al. Lyα nebula has often been cited as the most plausible example of an Lyα nebula powered by gravitational cooling. In this paper, we bring together new data from the Hubble Space Telescope and the Herschel Space Observatory as well as comparisons to recent theoretical simulations in order to revisit the questions of the local environment and most likely power source for the Lyα nebula. In contrast to previous results, we find that this Lyα nebula is associated with six nearby galaxies and an obscured AGN that is offset by ∼4″ ≈ 30 kpc from the Lyα peak. The local region is overdense relative to the field, by a factor of ∼10, and at low surface brightness levels the Lyα emission appears to encircle the position of the obscured AGN, highly suggestive of a physical association. At the same time, we confirm that there is no compact continuum source located within ∼2–3″ ≈ 15–23 kpc of the Lyα peak. Since the latest cold accretion simulations predict that the brightest Lyα emission will be coincident with a central growing galaxy, we conclude that this is actually a strong argument against, rather than for, the idea that the nebula is gravitationally powered. While we may be seeing gas within cosmic filaments, this gas is primarily being lit up, not by gravitational energy, but due to illumination from a nearby buried AGN.
- OSTI ID:
- 22522018
- Journal Information:
- Astrophysical Journal, Vol. 802, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
A giant Lyα nebula in the core of an x-ray cluster at z = 1.99: implications for early energy injection
The properties of Lyα nebulae: gas kinematics from nonresonant lines