Lineless Quasars at High-Redshift: BL Lacs or A New Class of Unbeamed Quasars?

Details Lineless Quasars at High-Redshift: BL Lacs or A New Class of Unbeamed Quasars? Lineless Quasars at High-Redshift: BL Lacs or A New Class of Unbeamed Quasars?

Sep 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004sptz.prop.3221f&link_type=abstract

Spitzer Proposal ID #3221

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Scientific paper

The Sloan Digital Sky Survey (SDSS) has recently discovered a class of high-redshift quasars with no or extremely weak optical emission lines. Their redshifts are determined by the presence of strong Lyman break and Lyman Limit Systems. Their nature remains unknown: they could be analogs of BL Lac objects at high redshift, a new type of unbeamed quasar whose broad emission-line region is very weak or absent, or a combination of both. The proto-type object, SDSS J1532-0039 (z=4.6), lacks other signatures of a typical BL Lac object: it has no detectable radio or X-ray emission and is not strongly polarized or variable in the optical. Other objects in the sample show a variety of radio and X-ray properties. We propose to obtain Spitzer IRAC and MIPS 24 micron photometry of four lineless quasars at z = 4 - 4.6, two of which are radio/X-ray quiet, and the other two are radio/X-ray loud. The Spitzer photometry will probe the spectral region where there is a dramatic contrast between beamed synchrotron emission in BL Lac objects and thermal dust emission in unbeamed quasars: we expect a factor of 5 difference in Spitzer fluxes between the two cases. It will reveal the nature of the IR emission mechanism, and unambiguously determine whether these lineless quasars are beamed sources similar to BL Lac objects, or a new type of unbeamed quasar.

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