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We present observations in eight wavebands from 1.25-24 microns of four densecores: L204C-2, L1152, L1155C-2, and L1228. Our goals are to study the YSOpopulation of these cores and to measure the mid-infrared extinction law. Withour combined near-infrared and Spitzer photometry, we classify each source inthe cores as, among other things, background stars, galaxies, or embedded youngstellar objects (YSOs). L1152 contains three YSOs and L1228 has seven, butneither L204C-2 nor L1155C-2 appear to contain any YSOs. We estimate an upperlimit of 7x10^-5 to 5x10^-4 solar luminosities for any undiscovered YSOs in ourcores. We also compute the line-of-sight extinction law towards each backgroundstar. These measurements are averaged spatially, to create chi-squared maps ofthe changes in the mid-infrared extinction law throughout our cores, and alsoin different ranges of extinction. From the chi-squared maps we identify twosmall regions in L1152 and L1228 where the outflows in those cores appear to bedestroying the larger dust grains, thus altering the extinction law in thoseregions. On average, however, our extinction law is relatively flat from 3.6 to24 microns for all ranges of extinction and in all four cores. From 3.6 to 8microns this law is consistent with a dust model that includes larger dustgrains than the diffuse interstellar medium, which suggests grain growth hasoccurred in our cores. At 24 microns, our extinction law is 2-4 times higherthan predicted by dust models. However, it is similar to other empiricalmeasurements.

Deep JHKs and Spitzer Imaging of Four Isolated Molecular Cloud Cores