| Summary: | Star formation, chemical evolution, and co-evolution with active galactic nuclei (AGN) are key to understanding galaxy formation and evolution. High-redshift dusty galaxies are excellent sites to investigate mass assembly and growth, star formation rates (both obscured and unobscured star formation), and chemical and physical conditions. This dissertation is based on two populations of high-redshift dusty galaxies, submillimeter galaxies and quasar 2175 Angstrom dust absorbers, which are selected by dust emission and dust absorption respectively. I studied the gravitationally lensed dusty, star-forming galaxies (DSFGs) at 2.8 < z < 5.7, which were first discovered by the South Pole Telescope (SPT) and further confirmed by ALMA. My work is focused on the stellar masses and star formation rates, and AGN contribution of these objects by means of multi-wavelength spectral energy distribution (SED) modeling. The data include HST, Spitzer, Herschel, APEX, and SPT. Compared to the star-forming main sequence, these DSFGs have specific SFRs that lie above the main sequence, suggesting that we are witnessing ongoing strong starburst events that may be driven by major mergers. SPT0346-52 at z = 5.7, the most extraordinary source in the SPT survey for which we obtained Chandra X-ray and ATCA radio data, was confirmed to have the highest star formation surface density of any known galaxy at high-z. I also tested the reliability of panchromatic SED fitting in preparation for JWST, using synthetic photometry generated from dust radiative transfer on hydrodynamical simulations. Quasar 2175 Angstrom dust absorbers are a new population of quasar absorption line systems, which are excellent probes of gas and dust properties, chemical evolution and physical conditions in the absorbing galaxies. This sample was selected from the SDSS and BOSS surveys and followed up with the Echelle Spectrograph and Imager on the Keck-II telescope, the Red & Blue Channel Spectrographs on the MMT, and the Ultraviolet and Visible Echelle Spectrograph on the VLT. I found a correlation between the presence of the 2175 Angstrom bump and other ingredients including high metallicity, high depletion level, overall low ionization state of gas, and neutral carbon and molecules.
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