Giant Molecular Outflows Powered by Protostars in L1448

We present sensitive, large-scale maps of the CO J=1-0 emission of the L1448 dark cloud. These maps were acquired using the On-The-Fly capability of the NRAO 12-meter telescope. CO outflow activity is seen in L1448 on parsec-scales for the first time. Careful comparison of the spatial and velocity distribution of our high-velocity CO maps with previously published optical and near-infrared images and spectra has led to the identification of six distinct CO outflows. We show the direct link between the heretofore unknown, giant, highly-collimated, protostellar molecular outflows and their previously discovered, distant optical manifestations. The outflows traced by our CO mapping generally reach the projected cloud boundaries. Integrated intensity maps over narrow velocity intervals indicate there is significant overlap of blue- and red-shifted gas, suggesting the outflows are highly inclined with respect to the line-of-sight, although the individual outflow position angles are significantly different. The velocity channel maps also show that the outflows dominate the CO line cores as well as the high-velocity wings. The magnitude of the combined flow momenta, as well as the combined kinetic energy of the flows, are sufficient to disperse the 50 solar mass NH3 cores in which the protostars are currently forming, although some question remains as to the exact processes involved in redirecting the directionality of the outflow momenta to effect the complete dispersal of the parent cloud.Comment: 11 pages, 9 figures, to be published in the Astronomical Journa

Models for Multiband IR Surveys

Empirical 'backward' galaxy evolution models for IR-bright galaxies are constrained using multiband IR surveys. A new Monte-Carlo algorithm is developed for this task. It exploits a large library of realistic Spectral Energy Distributions (SEDs) of 837 local IR galaxies (IRAS 25$\mu m$ selected) from the UV (1000{\AA}) to the radio (20cm), including ISO-measured 3--13$\mu m$ unidentified broad features (UIBs). The basic assumption is that the local correlation between SEDs and Mid-Infrared (MIR) luminosities can be applied to earlier epochs of the Universe. Three populations of IR sources are considered in the evolution models. These include (1) starburst galaxies, (2) normal late-type galaxies, and (3) galaxies with AGN. A set of models so constructed are compared with data from the literature. Predictions for number counts, confusion limits, redshift distributions, and color-color diagrams are made for multiband surveys using the upcoming SIRTF satellite.Comment: 40 pages latex. 32 GIF figures. New Version (July 8, 2001) to be accepted by ApJ. High quality figures (included in a PS file of the paper) can be found in http://spider.ipac.caltech.edu/staff/cxu/papers/paper_model_3.ps.g