paper

Multi-wavelength observations of SDSS J105621.45+313822.1, a broad-line, low-metallicity AGN

arXiv:2004.11295 · doi:10.3847/1538-4357/ab8b64

Abstract

In contrast to massive galaxies with Solar or super-Solar gas phase metallicities, very few Active Galactic Nuclei (AGN) are found in low-metallicity dwarf galaxies. Such a population could provide insight into the origins of supermassive black holes. Here we report near-infrared spectroscopic and X-ray observations of SDSS J105621.45+313822.1, a low-mass, low-metallicity galaxy with optical narrow line ratios consistent with star forming galaxies but a broad H line and mid-infrared colors consistent with an AGN. We detect the [Si VI] 1.96m coronal line and a broad Pa line with a FWHM of ~km~s. Together with the optical broad lines and coronal lines seen in the SDSS spectrum, we confirm the presence of a highly accreting black hole with mass ~M, with a bolometric luminosity of ~erg~s based on the coronal line luminosity, implying a highly accreting AGN. Chandra observations reveal a weak nuclear point source with ~erg~s, orders of magnitude lower than that predicted by the mid-infrared luminosity, suggesting that the AGN is highly obscured despite showing broad lines in the optical spectrum. The low X-ray luminosity and optical narrow line ratios of J1056+3138 highlight the limitations of commonly employed diagnostics in the hunt for AGNs in the low metallicity low mass regime.

13 pages, 6 figures, accepted to ApJ

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