Obscuration in Extremely Luminous Quasars

Polletta, M.; Weedman, D. W.; Hönig, S. F.; Lonsdale, C. J.; Smith, H. E.; Houck, J. R.

doi:10.1086/524343

Cited by 134 publications

(251 citation statements)

References 111 publications

(272 reference statements)

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“…Our results are complementary to those derived from obscured quasars selected from hard X-ray surveys Szokoly et al 2004;Barger et al 2005;Markwardt et al 2005;Treister et al 2006;Beckmann et al 2006;Sazonov et al 2007) and mid-IR color selection (Lacy et al 2005;Stern et al 2005;Martínez-Sansigre et al 2006;Polletta et al 2008). For example, up to 20% of the hard X-ray-selected AGNs do 2374 REYES ET AL.…”

Section: Introductionsupporting

confidence: 78%

“…Polletta et al (2008) estimated the fraction of obscured quasars to be 60-65% at bolometric luminosities 10 46-47 erg s −1 (L [O iii] ∼ 10 9 L ), using a sample of type 2 quasars with Si absorption. Again, these values should be taken as lower limits because, e.g., the former sample excludes radioweak objects, while the latter excludes sources with featureless IR spectra (Sturm et al 2006).…”

Section: Type 2 Quasar Fractionmentioning

confidence: 99%

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Space Density of Optically Selected Type 2 Quasars

Reyes¹,

Zakamska²,

Strauss³

et al. 2008

The Astronomical Journal

271

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: Introductionsupporting

confidence: 78%

Section: Type 2 Quasar Fractionmentioning

confidence: 99%

Space Density of Optically Selected Type 2 Quasars

Reyes¹,

Zakamska²,

Strauss³

et al. 2008

The Astronomical Journal

271

167

View full text Add to dashboard Cite

show abstract

“…It is worth noting that all but one sources in our sample lie within the AGN region, and most of them show extreme red colors i.e. log(F 5.8 /F 3.6 ) > ∼ 0.4 and log(F 8.0 /F 4.5 ) > ∼ 0.4 similarly to the luminous obscured quasars at z = 1.3-3 in the Polletta et al (2008a) sample. The only source falling outside the box has the lowest spectroscopic redshift in the sample, i.e.…”

Section: Selection Criteriamentioning

confidence: 65%

“…It is worth noting that this is a conservative assumption since the typical value of z found for large samples of DOGs is ∼2 (e.g. Polletta et al 2008a;Dey et al 2008, and references therein).…”

Section: Redshiftsmentioning

confidence: 99%

Revealing X-ray obscured quasars in SWIRE sources with extreme mid-IR/optical flux ratios

Lanzuisi

Piconcelli²,

Fiore³

et al. 2009

A&A

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Recent works have suggested that selection criteria based on mid-IR properties, i.e. extreme colors and bright flux levels, can be used to reveal a population of dust-enshrouded, extremely-luminous quasars at z ∼ 1-2. However, the X-ray spectral properties of these intriguing objects still remain largely unexplored. We have performed an X-ray study of a large sample of bright mid-IR (F 24 μm > 1.3 mJy) galaxies showing an extreme MIR/Optical flux ratio (F 24 μm /F R > 2000) in order to confirm the presence of a luminous active nucleus in these very red objects. Sampling of a large area is required to pick up objects at the highest luminosities given their low surface density. Accordingly, we have applied our selection criteria to an area of ∼6 deg 2 covered by XMM-Newton/Chandra observations within the ∼50 deg 2 SWIRE survey, resulting in a final sample of 44 objects. The vast majority of the source redshifts, both spectroscopic and photometric, are in the range 0.7 < ∼ z < ∼ 2.5. The X-ray coverage of the sample is highly inhomogeneous (from snap-shot 5 ks Chandra observations to medium-deep XMM-Newton exposures of 70 ks) and, consequently, a sizable fraction of them (≈43%) remains undetected in the 0.5-10 keV band. Using spectral or hardness information we were able to estimate the value of the absorbing column density in 23 sources. 95% of them are consistent with being obscured by neutral gas with an intrinsic column density of N H ≥ 10 22 cm −2 . Remarkably, we also find that ∼55% of these sources can be classified as type 2 quasars on the basis of their absorption properties and X-ray luminosity. Moreover, most of the X-ray undetected sources show extreme mid-IR colors, consistent with being luminous AGN-powered objects, suggesting they might host heavily obscured (possibly Compton-thick) quasars in X-rays. This demonstrates that our selection criteria applied to a wide area survey is very efficient in finding a large number of type 2 quasars at z > ∼ 1. The existence of this class of very powerful, obscured quasars at high z could have important implications in the context of the formation and cosmological evolution of accreting supermassive black holes and their host galaxies.

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“…It is however unlikely that all our QSOs exhibit such low inclination (e.g. Polletta et al 2008, did not find any preferred inclination for luminous QSOs). At least this is not the case for QSO 6 with a measured inclination of ∼65 • .…”

Section: Resultsmentioning

confidence: 83%

Dust grain growth in the interstellar medium of 5 < z < 6.5 quasars

Michałowski

Murphy

Hjorth

et al. 2010

A&A

107

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Aims. We investigate whether stellar dust sources i.e. asymptotic giant branch (AGB) stars and supernovae (SNe) can account for dust detected in 5 < z < 6.5 quasars (QSOs). Methods. We calculate the required dust yields per AGB star and per SN using the dust masses of QSOs inferred from their millimeter emission and stellar masses approximated as the difference between the dynamical and the H 2 gas masses of these objects. Results. We find that AGB stars are not efficient enough to form dust in the majority of the z > 5 QSOs, whereas SNe may be able to account for dust in some QSOs. However, they require very high dust yields even for a top-heavy initial mass function.Conclusions. This suggests additional non-stellar dust formation mechanism e.g. significant dust grain growth in the interstellar medium of at least three out of nine z > 5 QSOs. SNe (but not AGB stars) may deliver enough heavy elements to fuel this growth.

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Obscuration in Extremely Luminous Quasars

Cited by 134 publications

References 111 publications

Space Density of Optically Selected Type 2 Quasars

Space Density of Optically Selected Type 2 Quasars

Revealing X-ray obscured quasars in SWIRE sources with extreme mid-IR/optical flux ratios

Dust grain growth in the interstellar medium of 5 < z < 6.5 quasars

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