Infrared Luminosities and Aromatic Features in the 24um Flux Limited Sample of 5MUSES

We study a 24,$mu$m selected sample of 330 galaxies observed with the Infrared Spectrograph for the 5,mJy Unbiased Spitzer Extragalactic Survey. We estimate accurate total infrared luminosities by combining mid-IR spectroscopy and mid-to-far infrared photometry, and by utilizing new empirical spectral templates from {em Spitzer} data. The infrared luminosities of this sample range mostly from 10$^9$L$_odot$ to $10^{13.5}$L$_odot$, with 83% in the range 10$^{10}$L$_odot$$<$L$_{rm IR}$$<10^{12}$L$_odot$. The redshifts range from 0.008 to 4.27, with a median of 0.144. The equivalent widths of the 6.2,$mu$m aromatic feature have a bimodal distribution. We use the 6.2,$mu$m PAH EW to classify our objects as SB-dominated (44%), SB-AGN composite (22%), and AGN-dominated (34%). The high EW objects (SB-dominated) tend to have steeper mid-IR to far-IR spectral slopes and lower L$_{rm IR}$ and redshifts. The low EW objects (AGN-dominated) tend to have less steep spectral slopes and higher L$_{rm IR}$ and redshifts. This dichotomy leads to a gross correlation between EW and slope, which does not hold within either group. AGN dominated sources tend to have lower log(L$_{rm PAH 7.7mu m}$/L$_{rm PAH 11.3mu m}$) ratios than star-forming galaxies, possibly due to preferential destruction of the smaller aromatics by the AGN. The log(L$_{rm PAH 7.7mu m}$/L$_{rm PAH 11.3mu m}$) ratios for star-forming galaxies are lower in our sample than the ratios measured from the nuclear spectra of nearby normal galaxies, most probably indicating a difference in the ionization state or grain size distribution between the nuclear regions and the entire galaxy. Finally, we provide a calibration relating the monochromatic 5.8, 8, 14 and 24um continuum or Aromatic Feature luminosity to L$_{rm IR}$ for different types of objects.