The Next Generation Atlas of Quasar Spectral Energy Distributions From Radio to X-Rays

Shang, Zhaohui; Brotherton, Michael S.; Wills, Beverley J.; Wills, D.; Cales, Sabrina; Dale, Daniel A.; Green, Richard F.; Runnoe, Jessie C.; Nemmen, R.; Gallagher, S. C.; Ganguly, R.; Hines, Dean C.; Kelly, Benjamin J.; Kriss, G. A.; Li, Jun; Tang, Baitian; Xie, Yanxia

doi:10.1088/0067-0049/196/1/2

Cited by 234 publications

(366 citation statements)

References 84 publications

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“…The SED derived from broadband photometry should be compared with a smoothed version of the composite spectrum, shown here in magenta for only the radioquiet quasars. The blue curve is the composite SED derived from SDSS and GALEX photometric data (Trammell et al 2007), and A83, page 6 of 33 it extends to shorter wavelengths than in Shang et al (2011). The green curve is the composite from SDSS and 2MASS photometry (Labita et al 2008), the red one is the NIR spectral template from Glikman et al (2006).…”

Section: Fitting the Photometric Datamentioning

confidence: 99%

Broad-band spectral energy distribution of 3000 Å break quasars from the Sloan Digital Sky Survey

Meusinger

Schalldach

Mirhosseini

et al. 2016

A&A

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Context. In past decades, huge surveys have confirmed the existence of populations of exotic and hitherto unknown quasar types. The discovery and investigation of these rare peculiar objects is important because they may represent links to special evolutionary stages and hold clues to the evolution of quasars and galaxies. Aims. The Sloan Digital Sky Survey (SDSS) discovered the unusual quasars J010540.75-003313.9 and J220445.27+003141.8 and a small number of similar objects. Their spectra are characterised by a break in the continuum around 3000 Å that neither shows the typical structure of broad absorption line (BAL) troughs nor is explained by typical intrinsic dust reddening. The main aim of the present paper was twofold. First, a new target-oriented search was performed in the spectra database of the SDSS to construct a sizable sample of such 3000 Å break quasars. Second, their broad-band spectral energy distribution (SED) was compared with SEDs of BAL quasars. Methods. We used the method of Kohonen self-organising maps for data mining in the SDSS spectra archive to search for more quasars with properties comparable to the prototypes J010540.75-003313.9 and J220445.27+003141.8. We constructed a sample of 3000 Å break quasars and comparison samples of quasars with similar properties, to some extent, but also showing indications for typical BAL features. Particular attention was payed to a possible contamination by rare stellar spectral types, in particular DQ white dwarfs. We construct ensemble-averaged broad-band SEDs based on archival data from SDSS, GALEX, 2MASS, UKIDSS, WISE, and other surveys. The SEDs were corrected for dust absorption at the systemic redshifts of the quasars by the comparison with the average SED of normal quasars. Results. We compiled a list of 23 quasars classified as 3000 Å break quasars with properties similar to 010540.75-003313.9 and J220445.27+003141.8. Their de-reddened arithmetic median composite SED is indistinguishable from that of the unusual BAL quasars. We conclude that 3000 Å break quasars are most likely extreme versions of BAL quasars. Assuming that the intrinsic SED of the continuum source is represented by the quasar composite SED, the 3000 Å break quasars tend to be intrinsically more luminous than ordinary quasars.

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Section: Fitting the Photometric Datamentioning

confidence: 99%

Broad-band spectral energy distribution of 3000 Å break quasars from the Sloan Digital Sky Survey

Meusinger

Schalldach

Mirhosseini

et al. 2016

A&A

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“…Since we are dealing with an IR selected sample, we consider the AGN spectral energy distribution (SED) reported by Shang et al (2011). These authors have compiled SED for 85 quasars using high-quality multi-wavelength data from radio to X-rays and they constructed the median SEDs for radio loud and radio quiet quasars.…”

Section: Comparison With Other Samplesmentioning

confidence: 99%

A new technique to efficiently select Compton-thick AGN

Severgnini

Caccianiga

Ceca

2012

A&A

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Aims. We present a new efficient diagnostic method, based on mid-infrared and X-ray data, to select local (z < 0.1) Compton-thick AGN with the aim of estimating their surface and space density. Methods. We define a region in the X-ray-to-mid-IR [F(2−12 keV)/F 25 ν 25 ] vs. X-ray color (HR) plane associated to Compton-thick AGN, i.e. [F(2−12 keV)/F 25 ν 25 ] < 0.02 and HR > −0.2. On the basis of this selection method we build up a sample of 43 Comptonthick AGN candidates using data from IRAS Point Source and 2XMM-Newton catalogues. In order to test the efficiency of the proposed method in selecting Compton-thick AGN we use the results of the X-ray spectral analysis performed on all the sources of our sample (presented in a parallel work). After taking into account the different selection effects, we have estimated the number of Compton-thick in the local Universe and their density down to the IRAS flux limit of F 25 = 0.5 Jy. Results. We find that the diagnostic plot proposed here is an efficient method to select Compton-thick AGN in the nearby Universe since ∼84% of the sources populating the proposed Compton-thick region are actually Compton-thick AGN. Twenty percent are newly-discovered Compton-thick AGN. We then estimate the surface density of Compton-thick AGN down to the IRAS PSC catalogue flux limit (F 25 = 0.5 Jy) that turns out to be ρ CT ∼ 3 × 10 −3 src deg −2 . After estimating an equivalent IR-to-hard-X-ray limiting flux, we compare our result with those found with Swift-BAT. We find that the surface density derived here is a factor 4 above the density computed in the hard X-ray surveys. This difference is ascribed, at least in part, to a significant contribution (∼60−90%) of the star-forming activity to the total 25 μm emission for the sources in our sample. By considering only the 25 μm AGN emission, we estimate a surface density of Compton-thick AGN which is consistent with the results found by hard X-ray surveys. Finally, we estimated the co-moving space density of Compton-thick AGN with intrinsic L X > 10 43 erg s −1 (0.004 < z < 0.06): Φ C−thick ∼ (3.5 +4.5 −0.5 ) × 10 −6 Mpc −3 . The prediction for Compton-thick AGN based on the synthesis model of X-ray background in Gilli et al. (2007) is consistent with this value.

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“…The spectral energy distribution (SED) of active galactic nuclei (AGN) shows a prominent bump, the so-called "Big Blue Bump" (BBB), which appears to peak in the UV and decline at higher energies (Sanders et al 1989;Elvis et al 1994). However, the intrinsic position and possible luminosity dependence of the BBB has not been properly estimated due to the lack of UV observations corrected for the intergalactic medium (IGM) absorption by neutral hydrogen along the line of sight (Richards et al 2006a;Trammell et al 2007;Shang et al 2011;Elvis et al 2012).…”

Section: Introductionmentioning

confidence: 99%

The first ultraviolet quasar-stacked spectrum at z ≃ 2.4 from WFC3

Lusso

Worseck

Hennawi

et al. 2015

Monthly Notices of the Royal Astronomical Society

273

355

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The ionising continuum from active galactic nuclei (AGN) is fundamental for interpreting their broad emission lines and understanding their impact on the surrounding gas. Furthermore, it provides hints on how matter accretes onto supermassive black holes. Using HST's Wide Field Camera 3 we have constructed the first stacked ultraviolet (rest-frame wavelengths 600-2500Å) spectrum of 53 luminous quasars at z 2.4, with a state-of-the-art correction for the intervening Lyman forest and Lyman continuum absorption. The continuum slope (f ν ∝ ν αν ) of the full sample shows a break at ∼912Å with spectral index α ν = −0.61 ± 0.01 at λ > 912Å and a softening at shorter wavelengths (α ν = −1.70 ± 0.61 at λ 912Å). Our analysis proves that a proper intergalactic medium absorption correction is required to establish the intrinsic continuum emission of quasars. We interpret our average ultraviolet spectrum in the context of photoionisation, accretion disk models, and quasar contribution to the ultraviolet background. We find that observed broad line ratios are consistent with those predicted assuming an ionising slope of α ion =−2.0, similar to the observed ionising spectrum in the same wavelength range. The continuum break and softening are consistent with accretion disk plus X-ray corona models when black hole spin is taken into account. Our spectral energy distribution yields a 30% increase to previous estimates of the specific quasar emissivity, such that quasars may contribute significantly to the total specific Lyman limit emissivity estimated from the Lyα forest at z < 3.2.

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The Next Generation Atlas of Quasar Spectral Energy Distributions From Radio to X-Rays

Cited by 234 publications

References 84 publications

Broad-band spectral energy distribution of 3000 Å break quasars from the Sloan Digital Sky Survey

Broad-band spectral energy distribution of 3000 Å break quasars from the Sloan Digital Sky Survey

A new technique to efficiently select Compton-thick AGN

The first ultraviolet quasar-stacked spectrum at z ≃ 2.4 from WFC3

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