A Spectroscopic Survey of WISE-selected Obscured Quasars with the Southern African Large Telescope

Abstract

We present the results of an optical spectroscopic survey of a sample of 40 candidate obscured quasars identified on the basis of their mid-infrared emission detected by the Wide-Field Infrared Survey Explorer (WISE). Optical spectra for this survey were obtained using the Robert Stobie Spectrograph (RSS) on the Southern African Large Telescope (SALT). Our sample was selected with WISE colors characteristic of AGNs, as well as red optical to mid-IR colors indicating that the optical/UV AGN continuum is obscured by dust. We obtain secure redshifts for the majority of the objects that comprise our sample (35/40), and find that sources that are bright in the WISE W4 (22$\mu$m) band are typically at moderate redshift (<z> = 0.35$)whilesourcesfainterinW4areathigherredshifts(<z>=0.73$). The majority of the sources have narrow emission lines, with optical colors and emission line ratios of our WISE-selected sources that are consistent with the locus of AGN on the rest-frame $g-z$ color vs. [NeIII]$\lambda$3869 / [OII]$\lambda \lambda$3726+3729 line ratio diagnostic diagram. We also use empirical AGN and galaxy templates to model the spectral energy distributions (SEDs) for the objects in our sample, and find that while there is significant variation in the observed SEDs for these objects, the majority require a strong AGN component. Finally, we use the results from our analysis of the optical spectra and the SEDs to compare our selection criteria to alternate criteria presented in the literature. These results verify the efficacy of selecting luminous obscured AGNs based on their WISE colors.

21 pages, 13 figures, 3 tables, Accepted for publication in ApJ

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Cited by in corpus (17)

• The MIXR sample: AGN activity versus star formation across the cross-correlation of WISE, 3XMM, and FIRST/NVSS
• The Complete Infrared View of Active Galactic Nuclei from the 70-month Swift/BAT Catalog
• Mid-Infrared Colors of Dwarf Galaxies: Young Starbursts Mimicking Active Galactic Nuclei
• AGN Selection and Demographics in GOODS-S/HUDF from X-ray to Radio
• NuSTAR observations of WISE J1036+0449, a Galaxy at z$\sim 1$ obscured by hot dust
• A Connection between Obscuration and Star Formation in Luminous Quasars
• Composite Spectral Energy Distributions and Infrared-Optical Colors of Type 1 and Type 2 Quasars
• Infrared Spectral Energy Distribution and Variability of Active Galactic Nuclei: Clues to the Structure of Circumnuclear Material
• An obscured AGN population hidden in the VIPERS galaxies: identification through spectral energy distribution decomposition
• A New Infrared Criterion for Selecting Active Galactic Nuclei to Lower Luminosities
• A Large Population of Luminous Active Galactic Nuclei Lacking X-ray Detections: Evidence for Heavy Obscuration?
• Galaxy and Mass Assembly (GAMA): A $\text{WISE}$ study of the activity of emission-line systems in G23
• Forward modeling the multiwavelength properties of Active Galactic Nuclei: application to X-ray and WISE mid-infrared samples
• Characterizing the WISE-selected Heavily Obscured Quasar Population with Optical Spectroscopy from the Southern African Large Telescope
• A unifying evolutionary framework for infrared-selected obscured and unobscured quasar host haloes
• A population of Optically Quiescent Quasars from WISE and SDSS
• A Peculiar Type~II QSO Identified via Broad-band Detection of Extreme Nebular Line Emission