Infrared spectra and photometry of complete samples of PG and 2MASS
  quasars
  As a step toward a comprehensive overview of the infrared diagnostics of the
central engines and host galaxies of quasars at low redshift, we present
Spitzer Space Telescope spectroscopic (5-40 {\mu}m) and photometric (24, 70 and
160 {\mu}m) measurements of all Palomar-Green (PG) quasars at z < 0.5 and 2MASS
quasars at z < 0.3. We supplement these data with Herschel measurements at 160
{\mu}m. The sample is composed of 87 optically selected PG quasars and 52
near-IR selected 2MASS quasars. Here we present the data, measure the prominent
spectral features, and separate emission due to star formation from that
emitted by the dusty circumnuclear torus. We find that the mid-IR (5-30 {\mu}m)
spectral shape for the torus is largely independent of quasar IR luminosity
with scatter in the SED shape of ~ 0.2 dex. Except for the silicate features,
no large difference is observed between PG (unobscured - silicate emission) and
2MASS (obscured - silicate absorption) quasars. Only mild silicate features are
observed in both cases. When in emission, the peak wavelength of the silicate
feature tends to be longer than 9.7 {\mu}m, possibly indicating effects on
grain properties near the AGN. The IR color is shown to correlate with the
equivalent width of the aromatic features, indicating that the slope of the
quasar mid- to far-IR SED is to first order driven by the fraction of radiation
from star formation in the IR bands.
