Modeling the Anomalous Microwave Emission with Spinning Nanoparticles:
  No PAHs Required
  In light of recent observational results indicating an apparent lack of
correlation between the Anomalous Microwave Emission (AME) and mid-infrared
emission from polycyclic aromatic hydrocarbons (PAHs), we assess whether
rotational emission from spinning silicate and/or iron nanoparticles could
account for the observed AME without violating observational constraints on
interstellar abundances, ultraviolet extinction, and infrared emission. By
modifying the SpDust code to compute the rotational emission from these grains,
we find that nanosilicate grains could account for the entirety of the observed
AME, whereas iron grains could be responsible for only a fraction, even for
extreme assumptions on the amount of interstellar iron concentrated in
ultrasmall iron nanoparticles. Given the added complexity of contributions from
multiple grain populations to the total spinning dust emission, as well as
existing uncertainties due to the poorly-constrained grain size, charge, and
dipole moment distributions, we discuss generic, carrier-independent
predictions of spinning dust theory and observational tests that could help
identify the AME carrier(s).
