Mid-Infrared Selected Quasars I: Virial Black Hole Mass and Eddington
  Ratios
  We provide a catalog of 391 mid-infrared-selected (MIR, 24$\mu$m)
broad-emission-line (BEL, type 1) quasars in the 22 deg$^2$ SWIRE Lockman Hole
field. This quasar sample is selected in the MIR from Spitzer MIPS with $S_{\rm
24} > 400\mu$Jy, jointly with an optical magnitude limit of r (AB) $<$ 22.5 for
broad line identification. The catalog is based on MMT and SDSS spectroscopy to
select BEL quasars, extends the SDSS coverage to fainter magnitudes and lower
redshifts, and recovers a more complete quasar population. The MIR-selected
quasar sample peaks at $z\sim$1.4, and recovers a significant and constant
(20\%) fraction of extended objects with SDSS photometry across magnitudes,
which was not included in the SDSS quasar survey dominated by point sources.
This sample also recovers a significant population of $z < 3$ quasars at $i >
19.1$. We then investigate the continuum luminosity and line profiles of these
MIR quasars, and estimate their virial black hole masses and the Eddington
ratios. The SMBH mass shows evidence of downsizing, though the Eddington ratios
remain constant at $1 < z < 4$. Compared to point sources in the same redshift
range, extended sources at $z < 1$ show systematically lower Eddington ratios.
The catalog and spectra are publicly available online.
