HII regions are the birth places of stars, and as such they provide the best measure of current star formation rates (SFRs) in galaxies. The close proximity of the Magellanic Clouds allows us to probe the nature of these star forming regions at small
spatial scales. We aim to determine the monochromatic IR band that most accurately traces the bolometric IR flux (TIR), which can then be used to estimate an obscured SFR. We present the spatial analysis, via aperture/annulus photometry, of 16 LMC and 16 SMC HII region complexes using the Spitzer IRAC and MIPS bands. UV rocket data and SHASSA H-alpha data are also included. We find that nearly all of the LMC and SMC HII region SEDs peak around 70um, from ~10 to ~400 pc from the central sources. As a result, the sizes of HII regions as probed by 70um is approximately equal to the sizes as probed by TIR (about 70 pc in radius); the radial profile of the 70um flux, normalized by TIR, is constant at all radii (70um ~ 0.45 TIR); the 1-sigma standard deviation of the 70um fluxes, normalized by TIR, is a lower fraction of the mean (0.05 to 0.12 out to ~220 pc) than the normalized 8, 24, and 160um normalized fluxes (0.12 to 0.52); and these results are invariant between the LMC and SMC. From these results, we argue that 70um is the most suitable IR band to use as a monochromatic obscured star formation indicator because it most accurately reproduces the TIR of HII regions in the LMC and SMC and over large spatial scales. We also explore the general trends of the 8, 24, 70, and 160um bands in the LMC and SMC HII region SEDs, radial surface brightness profiles, sizes, and normalized (by TIR) radial flux profiles. We derive an obscured SFR equation that is modified from the literature to use 70um luminosity, SFR(Mo/yr) = 9.7(0.7)x10^{-44} L(70)(ergs/s), which is applicable from 10 to 300 pc distance from the center of an HII region.
Are the organic molecules crucial for life on Earth abundant in early-epoch galaxies? To address this, we searched for organic molecules in extragalactic sources via their absorption features, known as diffuse interstellar bands (DIBs). There is stro
ng evidence that DIBs are associated with polycyclic aromatic hydrocarbons (PAHs) and carbon chains. Galaxies with a preponderance of DIBs may be the most likely places in which to expect life. We use the method of quasar absorption lines to probe intervening early-epoch galaxies for the DIBs. We present the equivalent width measurements of DIBs in one neutral hydrogen (HI) abundant galaxy and limits for five DIB bands in six other HI-rich galaxies (damped Lyman-alpha systems--DLAs). Our results reveal that HI-rich galaxies are dust poor and have significantly lower reddening than known DIB-rich Milky Way environments. We find that DIBs in HI-rich galaxies do not show the same correlation with hydrogen abundance as observed in the Milky Way; the extragalactic DIBs are underabundant by as much as 10 times. The lower limit gas-to-dust ratios of four of the HI-rich early epoch galaxies are much higher than the gas-to-dust ratios found in the Milky Way. Our results suggest that the organic molecules responsible for the DIBs are underabundant in HI-rich early epoch galaxies relative to the Milky Way.
