Discovery of a single faint AGN in a large sample of z>5 Lyman break galaxies

Simple item page
dc.creatorDouglas, Laura S.
dc.creatorBremer, Malcolm N.
dc.creatorStanway, Elizabeth R.
dc.creatorLehnert, Matthew D.
dc.date2007-01-25
dc.date.accessioned2026-07-07T10:21:36Z
dc.date.available2026-07-07T10:21:36Z
dc.descriptionAs part of a large spectroscopic survey of z>5 Lyman break galaxies (LBGs), we have identified a single source which is clearly hosting an AGN. Out of a sample of more than fifty spectroscopically-confirmed R-band dropout galaxies at z~5 and above, only J104048.6-115550.2 at z=5.44 shows evidence for a high ionisation-potential emission-line indicating the presence of a hard ionising continuum from an AGN. Like most objects in our sample the rest-frame-UV spectrum shows the UV continuum breaking across a Ly_alpha line. Uniquely within this sample of LBGs, emission from NV is also detected, a clear signature of AGN photo-ionisation. The object is spatially resolved in HST imaging. This, and the comparatively high Ly_alpha/NV flux ratio indicates that the majority of the Ly_alpha (and the UV continuum longward of it) originates from stellar photo-ionisation, a product of the ongoing starburst in the Lyman break galaxy. Even without the AGN emission, this object would have been photometrically-selected and spectroscopically-confirmed as a Lyman break in our survey. The measured optical flux (I(AB)=26.1) is therefore an upper limit to that from the AGN and is of order 100 times fainter than the majority of known quasars at these redshifts. The detection of a single object in our survey volume is consistent with the best current models of high redshift AGN luminosity function, providing a substantial fraction of such AGN are found within luminous starbursting galaxies. We discuss the cosmological implications of this discovery.
dc.description7 pages, 3 figures, MNRAS in press
dc.identifierhttps://arxiv.org/abs/astro-ph/0701724
dc.identifierhttp://arxiv.org/abs/astro-ph/0701724
dc.identifierMon.Not.Roy.Astron.Soc.376:1393-1398,2007
dc.identifierdoi:10.1111/j.1365-2966.2007.11546.x
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/175231
dc.subjectAstrophysics
dc.titleDiscovery of a single faint AGN in a large sample of z>5 Lyman break galaxies
dc.typetext

Files

Collections

arXiv