The Rest-Frame Extreme-Ultraviolet Spectral Properties of Quasi-stellar Objects

By R. Telfer, Wei Zheng, G. Kriss, A. Davidsen. 2001

488 citations recorded by the source corpus.

We use a sample of 332 Hubble Space Telescope spectra of 184 quasi-stellar objects (QSOs) with z > 0.33 to study the typical ultraviolet spectral properties of QSOs, with emphasis on the ionizing continuum. Our sample is nearly twice as large as that from previous work by W. Zheng and colleagues and provides much better spectral coverage in the extreme-ultraviolet (EUV). The overall composite continuum can be described by a power law with index αEUV = -1.76 ± 0.12 (fν ∝ να) between 500 and 1200 Å. The corresponding results for subsamples of radio-quiet and radio-loud QSOs are αEUV = -1.57 ± 0.17 and αEUV = -1.96 ± 0.12, respectively. We also derive αEUV for as many individual objects in our sample as possible, totaling 39 radio-quiet and 40 radio-loud QSOs. The typical individually measured values of αEUV are in good agreement with the composites. We find no evidence for evolution of αEUV with redshift for either radio-loud or radio-quiet QSOs. However, we do find marginal evidence for a trend toward harder EUV spectra with increasing luminosity for radio-loud objects. An extrapolation of our radio-quiet QSO spectrum is consistent with existing X-ray data, suggesting that the ionizing continuum may be represented by a single power law. The resulting spectrum is roughly in agreement with models of the intergalactic medium photoionized by the integrated radiation from QSOs.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/4af88f2219d8cdc202f6b251e76fee483bad724c

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Citations in the corpus

Fueling Low-Level AGN Activity through Stochastic Accretion of Cold Gas (2006, methodology): “…(2004), based on optical through hard X-ray observations (e.g., Elvis et al. 1994; George et al. 1998; Vanden Berk et al. 2001; Perola et al. 2002; Telfer et al. 2002; Ueda et al. 2003; Vignali et al. 2003), with an Xray reflection component generated by the PEXRAV model (Magdziarz & Zdziarski…”
Evolution of the Intergalactic Opacity: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity (2008, unknown): “To convert to an emissivity at the Lyman limit, we assume that quasars have a spectral index α = 0.3 at 2500-4400 Å, 0.8 at 1050-2500 Å (Madau et al. 1999), and 1.6 from 1050 Å to 228 Å (Telfer et al. 2002).”
New Measurements of the Ionizing Ultraviolet Background over 2 < z < 5 and Implications for Hydrogen Reionization (2013, methodology): “For AGN, a value of α = 1.6 (Telfer et al. 2002) is commonly used, whereas for galaxies the adopted values of α range between 1 and 3 (e.g., Bolton & Haehnelt 2007; Ouchi et al. 2009; Kuhlen & Faucher-Giguère 2012).”
Black Hole Masses and Enrichment of z ~ 6 SDSS Quasars (2007, unknown): “However, as noted by White et al. (2003), who have used the quasar templates by Telfer et al. (2002), the ionization rates by Elvis et al. may be too low by a factor of five.”
New Constraints on the Lyman Continuum Escape Fraction at z ~ 1.3 (2007, background): “For the most luminous, unobscured AGN (QSOs), the majority of the Lyman continuum escapes into the IGM (Telfer et al. 2002).”
A Population of Faint Extended Line Emitters and the Host Galaxies of Optically Thick QSO Absorption Systems (2007, methodology): “According to the study by Scott et al. (2004), the power-law index for a QSO with log kL(1050 8) 9:8 ; 1045 erg s 1, where L( ) ¼ L( 0) = 0ð Þ ð18Þ is (statistically) consistent with 1:5 (in good agreement with 1:57 for the radio-quiet sample from Telfer et al. 2002).”
An Observational Determination of the Bolometric Quasar Luminosity Function (2006, methodology): “…for any dependence of bolometric corrections on redshift, in agreement with a number of direct measurements of quasar SEDs (e.g., Elvis et al. 1994; Vanden Berk et al. 2001; Telfer et al. 2002; Vignali et al. 2003; Fan et al. 2003; Steffen et al. 2006; Richards et al. 2006c; Shemmer et al. 2006).”
The Giant Gemini GMOS survey of zem > 4.4 quasars – I. Measuring the mean free path across cosmic time (2014, methodology): “This accounts for uncertainty in evaluating f obs912 from the stacked spectrum; (ii) a power-law tilt δαT applied to the assumed Telfer et al. (2002) SED, normalized at 1450 Å f SEDλ = f Telferλ f Telfer1450 ( λ 1450 Å )δαT ; (3) (iii) an exponent γ τ which determines the redshift evolution of the…”
Piecing together the X-ray background : bolometric corrections for active galactic nuclei (2007, methodology): “Without a record of the objects in the Telfer et al. (2002) sample along with mass estimates (to constrain the shape of the disk model in the UV), it is difficult to make any predictions as to hw the bolometric corrections might vary between these two samples.”
GeV gamma-ray attenuation and the high-redshift UV background (2009, methodology): “In the extreme-UV, we have adopted the hard spectrum suggested by Telfer et al. (2002), from observations with the Faint Object Spectrograph on HST of quasars at a wide variety of non-local redshifts (z > 0.33).”
THE NEXT GENERATION ATLAS OF QUASAR SPECTRAL ENERGY DISTRIBUTIONS FROM RADIO TO X-RAYS (2011, background): “Figure 9 shows the comparison between our SEDs from Far-UV to Mid-IR and other quasar composite spectra, including the HST ultraviolet composites (Telfer et al. 2002), the composite from Sloan Digital Sky Survey (SDSS, Vanden Berk et al. 2001), and a Near-IR composite of 27 SDSS quasars (Glikman et…”
Faint AGNs at z > 4 in the CANDELS GOODS-S field: looking for contributors to the reionization of the Universe (2015, methodology): “The shape of the AGN SED from λ = 1450 Å to λ = 912 Å has been represented by a double power law with slopes adopted after Schirber & Bullock (2003), Telfer et al. (2002) and Vanden Berk et al. (2001).”
Detection of extended He II reionization in the temperature evolution of the intergalactic medium (2010, unknown): “For an ionizing spectrum Jν ∝ ν−α, this will produce 〈E〉thin = 54.4 (α + 2)−1 eV, which for a quasar-like spectrum (α = 1.5; Telfer et al. 2002) gives ∆Tthin ≈ 4 000K.”
THE BARYON CENSUS IN A MULTIPHASE INTERGALACTIC MEDIUM: 30% OF THE BARYONS MAY STILL BE MISSING (2011, unknown): “Here, 〈αs〉 ≈ 1.6 − 1.8 is the mean QSO spectral index between 1.0–1.5 ryd (Telfer et al. 2002; Shull et al. 2012b).”
A Near-Infrared Spectral Template for Quasars (2005, methodology): “Telfer et al. (2002) order their spectra beginning with objects that contribute to the best-sampled part of their wavelength coverage.”
THE z = 5 QUASAR LUMINOSITY FUNCTION FROM SDSS STRIPE 82 (2012, methodology): “The blue slope is drawn from a normal distribution with µ(α) = −1.7 and σ(α) = 0.3 (Telfer et al. 2002)20; the distribution for the red slope is µ(α) = −0.5 and σ(α) = 0.3.”
Evolution of the AGN UV luminosity function from redshift 7.5 (2018, background): “While the Lusso et al. (2015) spectrum is for luminous (M1450 ' −27.2) quasars, UV composite spectra including fainter quasars (Telfer et al. 2002; Shull et al. 2012b; Stevans et al. 2014) give similar values, such that our bandpass corrections remain applicable at M1450 <∼ − 24.”