Discovery of a Radio-loud Narrow-line Seyfert 1 Galaxy at Z = 0.9 Reddened with a Strong 2175 Å Bump

We present a broadband spectrophotometric analysis of an unusual quasar, SDSS J160558.86+474300.1, at z = 0.9, found in a systematic search for reddened radio-loud narrow-line Seyfert 1 galaxies (NLS1s). J1605+4743 qualifies for the conventional definition of an NLS1 in its permitted emission line widths and H beta/[O iii] flux ratio. It also shows strong Fe ii emissions. J1605+4743 has a steep radio spectrum. With a radio loudness of similar to 150 (70) before (after) reddening correction, it is among the most radio-loud NLS1s discovered. In addition, the blueshifted emission lines are also found to be weak, suggesting that it can be an exotic "wind-dominated" Seyfert similar to weak-line quasars, especially the ones with strong reddening. As an extreme hybrid central engine, its environment and host galaxy become rather intriguing. We discover in it a proximate 2175 angstrom absorber with a bump strength similar to the average value of 2175 angstrom absorbers in the Milky Way, which we suspect can be intrinsic to the quasar. In addition, the quasar seems to have enhanced instead of suppressed star formation at a rate of greater than or similar to 94 M (circle dot) yr(-1). The combination of these unusual properties, i.e., the unique extinction, strong Fe ii and [O ii] lines, weak [O iii], Mg ii, and Balmer lines, and large radio loudness, might hold important clues to accretion physics, the formation/destruction of dust grains in the environment of active galactic nuclei, and possibly also the coevolution of supermassive black holes and their host galaxies in general.