Capitalizing on the all-sky coverage of WISE and the 35% and 50% sky coverage from Sloan Digital Sky Survey and Pan-STARRS, respectively, we explore the efficacy of mR (optical) - (mid-infrared), hereafter , as a color diagnostic to identify obscured supermassive black hole accretion in wide-area X-ray surveys. We use the ∼16.5 deg2 Stripe 82 X-ray survey data as a test bed to compare with R - K, an oft-used obscured active galactic nucleus (AGN) selection criterion, and examine where different classes of objects lie in this parameter space. Most stars follow a well-defined path in R - K versus space. We demonstrate that optically normal galaxies hosting X-ray AGNs at redshifts can be recovered with an color cut, while they typically are not selected as AGNs based on their colors. Additionally, different observed X-ray luminosity bins favor different regions in parameter space: moderate-luminosity AGNs (1043 erg erg s-1) tend to have red colors, while the highest-luminosity AGNs ( erg s-1) have bluer colors; higher spectroscopic completeness of the Stripe 82X sample is needed to determine whether this is a selection effect or an intrinsic property. Finally, we parameterize X-ray obscuration of Stripe 82X AGNs by calculating their hardness ratios (HRs) and find no clear trends between HR and optical reddening. Our results will help inform best-effort practices in following up obscured AGN candidates in current and future wide-area, shallow X-ray surveys, including the all-sky eROSITA mission.
ON R - W1 AS A DIAGNOSTIC to DISCOVER OBSCURED ACTIVE GALACTIC NUCLEI in WIDE-AREA X-RAY SURVEYS / Lamassa, Stephanie M.; Civano, Francesca; Brusa, Marcella; Stern, Daniel; Glikman, Eilat; Gallagher, Sarah; Urry, C. Meg; Cales, Sabrina; Cappelluti, Nico; Cardamone, Carolin; Comastri, Andrea; Farrah, Duncan; Greene, Jenny E.; Komossa, S.; Merloni, Andrea; Mroczkowski, Tony; Natarajan, Priyamvada; Richards, Gordon; Salvato, Mara; Schawinski, Kevin; Treister, Ezequiel. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - ELETTRONICO. - 818:1(2016), pp. 88.88-88.88. [10.3847/0004-637X/818/1/88]
ON R - W1 AS A DIAGNOSTIC to DISCOVER OBSCURED ACTIVE GALACTIC NUCLEI in WIDE-AREA X-RAY SURVEYS
BRUSA, MARCELLA;
2016
Abstract
Capitalizing on the all-sky coverage of WISE and the 35% and 50% sky coverage from Sloan Digital Sky Survey and Pan-STARRS, respectively, we explore the efficacy of mR (optical) - (mid-infrared), hereafter , as a color diagnostic to identify obscured supermassive black hole accretion in wide-area X-ray surveys. We use the ∼16.5 deg2 Stripe 82 X-ray survey data as a test bed to compare with R - K, an oft-used obscured active galactic nucleus (AGN) selection criterion, and examine where different classes of objects lie in this parameter space. Most stars follow a well-defined path in R - K versus space. We demonstrate that optically normal galaxies hosting X-ray AGNs at redshifts can be recovered with an color cut, while they typically are not selected as AGNs based on their colors. Additionally, different observed X-ray luminosity bins favor different regions in parameter space: moderate-luminosity AGNs (1043 erg erg s-1) tend to have red colors, while the highest-luminosity AGNs ( erg s-1) have bluer colors; higher spectroscopic completeness of the Stripe 82X sample is needed to determine whether this is a selection effect or an intrinsic property. Finally, we parameterize X-ray obscuration of Stripe 82X AGNs by calculating their hardness ratios (HRs) and find no clear trends between HR and optical reddening. Our results will help inform best-effort practices in following up obscured AGN candidates in current and future wide-area, shallow X-ray surveys, including the all-sky eROSITA mission.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.