Candidate Type II Quasars from the Sloan Digital Sky Survey. I. Selection and Optical Properties of a Sample at 0.3&lt;<i>Z</i>&lt;0.83

Zakamska, Nadia L.; Strauss, Michael A.; Krolik, Julian H.; Collinge, Matthew J.; Hall, Patrick B.; Hao, Lei; Heckman, Timothy M.; Ivezić, Željko; Richards, Gordon T.; Schlegel, David J.; Schneider, Donald P.; Strateva, Iskra; Berk, D. E. vanden; Anderson, Scott F.; Brinkmann, J.

doi:10.1086/378610

Cited by 344 publications

(430 citation statements)

References 88 publications

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“…We consider the [NeV]3346,3426 emission lines to be unambiguous signs of an underlying AGN continuum (Groves et al 2004;Nagao et al 2006), so if either one of these lines is detected (if a single line is detected, it is usually [NeV]3426), the object is considered an AGN. If neither of the [NeV] lines is detected, we use the criterion FWHM([O iii]5007) > 400 km s −1 as a sign of AGN activity (Zakamska et al 2003;Hao et al 2005a). Since the [NeV] lines are weak, our selection is more robust at high luminosities, where these lines are more likely to be detected.…”

Section: Spectroscopic Selection Of Type 2 Quasarsmentioning

confidence: 99%

Space Density of Optically Selected Type 2 Quasars

Reyes¹,

Zakamska²,

Strauss³

et al. 2008

The Astronomical Journal

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275

167

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Type 2 quasars are luminous active galactic nuclei whose central regions are obscured by large amounts of gas and dust. In this paper, we present a catalog of type 2 quasars from the Sloan Digital Sky Survey, selected based on their optical emission lines. The catalog contains 887 objects with redshifts z < 0.83; this is 6 times larger than the previous version and is by far the largest sample of type 2 quasars in the literature. We derive the [O iii]5007 luminosity function (LF) for 10 8.3 L < L [O iii] < 10 10 L (corresponding to intrinsic luminosities up to M[2500 Å] −28 mag or bolometric luminosities up to 4 × 10 47 erg s −1 ). This LF provides robust lower limits to the actual space density of obscured quasars due to our selection criteria, the details of the spectroscopic target selection, and other effects. We derive the equivalent LF for the complete sample of type 1 (unobscured) quasars and determine the ratio of type 2 to type 1 quasar number densities. Our data constrain this ratio to be at least ∼ 1.5:1 for 10 8.3 L < L [O iii] < 10 9.5 L at z < 0.3, and at least ∼ 1.2:1 for L [O iii] ∼ 10 10 L at 0.3 < z < 0.83. Type 2 quasars are at least as abundant as type 1 quasars in the relatively nearby universe (z 0.8) for the highest luminosities.

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Section: Spectroscopic Selection Of Type 2 Quasarsmentioning

confidence: 99%

Space Density of Optically Selected Type 2 Quasars

Reyes¹,

Zakamska²,

Strauss³

et al. 2008

The Astronomical Journal

Self Cite

275

167

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“…As Hα is redshifted out of the optical bandpass at z 0.5 > , alternative obscured AGN selection methods using observed optical spectra have been developed to capitalize on the existing rich data sets from wide-area optical surveys, including: Gilli et al 2010;Mignoli et al 2013) 20 ; 5. a combination of narrow emission lines withFWHMva-lues <2000 km s −1 , ratios of narrow emission lines suggesting AGNs rather than star formation ionization, and a high [O III] luminosity, which is applicable between z 0.3 0.83 < < (Zakamska et al 2003;Reyes et al 2008); 6. strong C IV and Lyα emission with FWHM <2000 km s −1 and weak rest-frame ultraviolet continuum values, which identifies AGNs between z 2 4.3 < < (Alexandroff et al 2013; see also Steidel et al 2002;Hainline et al 2011).…”

Section: Identifying Type 2 Agnsmentioning

confidence: 99%

On R − W1 as a Diagnostic to Discover Obscured Active Galactic Nuclei in Wide-Area X-Ray Surveys

LaMassa

Civano

Brusa

et al. 2016

ApJ

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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-, as a color diagnostic to identify obscured supermassive black hole accretion in wide-area X-ray surveys. We use the ∼16.5 deg 2 Stripe 82 X-ray survey data as a testbed to compare R W1 -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 R W1space. We demonstrate that optically normal galaxies hosting X-ray AGNs at redshifts z 0.5 1 < < can be recovered with an R W1 4 -> colorcut, while they typically are not selected as AGNs based on their W W 1 2 -colors. Additionally, different observed X-ray luminosity bins favor different regions in R W1 -parameter space: moderate-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.

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“…The only other sample that spans a comparable redshift range is selected in a very similar way from the Sloan Digital Sky Survey (SDSS) Data Release 1 (DR1) by Zakamska et al (2003). Their sample consists of 291 type-2 AGN at 0.3 < z < 0.83 (the redshift range chosen to ensure that the [O iii]λ5007 Å line is present in all spectra).…”

Section: Comparison With Other Optical Surveysmentioning

confidence: 99%

“…3, are: 1) the lines are relatively strong; 2) the line ratios are relatively insensitive to reddening corrections because of their close separation; and 3) at least at low redshift (z 0.5) the lines are accessible using ground-based optical telescopes. Several samples have been selected in the past using the BPT diagrams and the method select AGN reliably with high completeness (Dessauges-Zavadsky et al 2000;Zakamska et al 2003;Hao et al 2005b).…”

Section: Introductionmentioning

confidence: 99%

The [O iii] emission line luminosity function of optically selected type-2 AGN from zCOSMOS$^{\rm,}$

Bongiorno

Mignoli

Zamorani

et al. 2010

A&A

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Aims. We present a catalog of 213 type-2 AGN selected from the zCOSMOS survey. The selected sample covers a wide redshift range (0.15 < z < 0.92) and is deeper than any other previous study, encompassing the luminosity range 10 5.5 L < L [OIII] < 10 9.1 L . We explore the intrinsic properties of these AGN and the relation to their X-ray emission (derived from the XMM-COSMOS observations). We study their evolution Results. Combining our sample with one drawn from SDSS, we found that the best description of the evolution of type-2 AGN is a luminositydependent density evolution model. Moreover, using the type-1 AGN LF we were able to constrain the fraction of type-2 AGN to the total (type-1 + type-2) AGN population. We found that the type-2 fraction decreases with luminosity, in agreement with the most recent results, and shows signs of a slight increase with redshift. However, the trend with luminosity is visible only after combining the SDSS+zCOSMOS samples. From the COSMOS data points alone, the type-2 fraction seems to be quite constant with luminosity.

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Candidate Type II Quasars from the Sloan Digital Sky Survey. I. Selection and Optical Properties of a Sample at 0.3<Z<0.83

Cited by 344 publications

References 88 publications

Space Density of Optically Selected Type 2 Quasars

Space Density of Optically Selected Type 2 Quasars

On R − W1 as a Diagnostic to Discover Obscured Active Galactic Nuclei in Wide-Area X-Ray Surveys

The [O iii] emission line luminosity function of optically selected type-2 AGN from zCOSMOS$^{\rm,}$

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