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Published July 10, 2007 | Published
Journal Article Open

Discovery of two spectroscopically peculiar, low-luminosity quasars at z ~ 4


We report the discovery of two low-luminosity quasars at z ~ 4, both of which show prominent N iv] λ1486 emission. This line is extremely rare in quasar spectra at any redshift; detecting it in two of a sample of 23 objects (i.e., ~9% of the sample) is intriguing and is likely due to the low-luminosity, high-redshift quasar sample we are studying. This is still a poorly explored regime, where contributions from associated, early starbursts may be significant. One interpretation of this line posits photoionization by very massive young stars. Seeing N iv] λ1486 emission in a high-redshift quasar may thus be understood in the context of coformation and early coevolution of galaxies and their supermassive black holes. Alternatively, we may be seeing a phenomenon related to the early evolution of quasar broad emission line regions. The nondetection (and possibly even broad absorption) of N v λ1240 line in the spectrum of one of these quasars may support that interpretation. These two objects may signal a new faint quasar population or an early AGN evolutionary stage at high redshifts.

Additional Information

© 2007 American Astronomical Society. Print publication: Issue 2 (2007 July 10); received 2007 April 30; accepted for publication 2007 May 24; published 2007 June 28. We thank the referee for helpful feedback. We are grateful to the staff of W. M. Keck observatory for their assistance during our observing runs. This work was supported in part by the NSF grant AST 04-07448, and by the Ajax foundation. The work of D. S. was carried out at Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

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