Molecular outflows in local galaxies: Method comparison and a role of
  intermittent AGN driving
  We report new detections and limits from a NOEMA and ALMA CO(1-0) search for
molecular outflows in 13 local galaxies with high FIR surface brightness, and
combine with results from the literature. CO line ratios and outflow structure
provide some constraints on the conversion from observables to quantities such
as molecular mass outflow rates. Ratios between outflow emission in higher J CO
transitions and in CO(1-0) typically are consistent with excitation Ri1<~1. For
IRAS 13120-5453, however, R31=2.10 indicates optically thin CO in the outflow.
Like much of the outflow literature, we use alpha(CO) = 0.8, and we present
arguments for using C=1 in deriving molecular mass outflow rates Mdot =
C*M*v/R. We compare the two main methods for molecular outflow detection: CO mm
interferometry and Herschel OH spectroscopy. For 26 sources studied with both
methods, we find 80% agreement in detecting vout>~150km/s outflows, and
non-matches can be plausibly ascribed to outflow geometry and SNR. For 12
bright ULIRGs with detailed OH-based outflow modeling, CO outflows are detected
in all but one. Outflow masses, velocities, and sizes for these 11 sources
agree well between the two methods, and modest remaining differences may relate
to the different but overlapping regions sampled by CO emission and OH
absorption. Outflow properties correlate better with AGN luminosity and with
bolometric luminosity than with FIR surface brightness. The most massive
outflows are found for systems with current AGN activity, but significant
outflows in non-AGN systems must relate to star formation or to AGN activity in
the recent past. We report scaling relations for the increase of outflow mass,
rate, momentum rate, and kinetic power with bolometric luminosity. Short
~10^6yr flow times and some sources with resolved multiple outflow episodes
support a role of intermittent driving, likely by AGN. (abridged)
