A population of Optically Quiescent Quasars from WISE and SDSS

0582370 - ASÚ 2025 RIV US eng J - Journal Article
Greenwell, C. - Gandhi, P. - Stern, D. - Lansbury, G. B. - Mainieri, V. - Boorman, Peter G. - Toba, Y.
A population of Optically Quiescent Quasars from WISE and SDSS.
Monthly Notices of the Royal Astronomical Society. Roč. 527, č. 4 (2023), s. 12065-12090. ISSN 0035-8711. E-ISSN 1365-2966
R&D Projects: GA ČR(CZ) GA22-22643S
Institutional support: RVO:67985815
Keywords : active galactic nuclei * dust-obscured galaxies * digital sky survey
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 4.8, year: 2022
Method of publishing: Open access

The growth of active galactic nuclei (AGNs) occurs under some form of obscuration in a large fraction of the population. The difficulty in constraining this population leads to high uncertainties in cosmic X-ray background and galaxy evolution models. Using an SDSS-WISE cross-match, we target infrared luminous AGN (W1 W2 > 0.8, and monochromatic rest-frame luminosity above lambda L-lambda(12 mu m) approximate to 3 x 10(44) erg s(-1)), but with passive galaxy-like optical spectra (Optically Quiescent Quasars, OQQs). We find 47 objects that show no significant [O III]lambda 5007 emission, a typically strong AGN optical emission line. As a comparison sample, we examine SDSS-selected Type 2 quasars (QSO2s), which show a significant [O III]lambda 5007 line by definition. We find a 1:16 ratio of OQQs compared to QSO2s, suggesting that the OQQ duty cycle is likely much shorter than that of QSO2s (though selection biases are not fully quantified). We consider observed properties in comparison with other galaxy types, and examine them for consistency with theories on their intrinsic nature: chiefly (a) a high covering factor for surrounding obscuring matter, preventing the detection of high-ionisation emission lines 'cocooned AGN', or (b) ionized gas being absent on the kpc scales of the Narrow Line Region (NLR), perhaps due to a 'switching on' or 'young' AGN. OQQs do not obviously fit the standard paradigm for merger-driven AGN and host galaxy evolution, implying we may be missing part of the flow of AGN evolution.



Permanent Link: https://hdl.handle.net/11104/0353273