A high signal-to-noise ratio composite quasar spectrum

Francis, Paul; Hewett, Paul C.; Foltz, C. B.; Chaffee, Frederic H.; Weymann, R. J.; Morris, Simon L.

doi:10.1086/170066

Cited by 612 publications

(784 citation statements)

References 8 publications

Supporting

Mentioning

745

Contrasting

Unclassified

Order By: Relevance

“…Numerous composite spectra exist, constructed by averaging over a vastly different number of QSOs (e.g. Francis et al 1991;Brotherton et al 2001;Vanden Berk et al 2001;Telfer et al 2002;Shull et al 2012;Stevans et al 2014;Harris et al 2016). However, by construction, these composite spectra only describe the average properties of QSOs, not the intrinsic variations of individual QSOs.…”

Section: E-mail: Bradleygreig@snsit (Bg)mentioning

confidence: 99%

Lyα emission-line reconstruction for high-zQSOs

Greig

Mesinger

McGreer

et al. 2016

Mon. Not. R. Astron. Soc.

View full text Add to dashboard Cite

We introduce an intrinsic Lyα emission line profile reconstruction method for high-z quasars (QSOs). This approach utilises a covariance matrix of emission line properties obtained from a large, moderate-z (2 ≤ z ≤ 2.5), high signal to noise (S/N> 15) sample of BOSS QSOs. For each QSO, we complete a Monte Carlo Markov Chain fitting of the continuum and emission line properties and perform a visual quality assessment to construct a large database of robustly fit spectra. With this dataset, we construct a covariance matrix to describe the correlations between the high ionisation emission lines Lyα, C IV, Si IV +O IV] and C III], and find it to be well approximated by an N -dimensional Gaussian distribution. This covariance matrix characterises the correlations between the line width, peak height and velocity offset from systemic while also allowing for the existence of broad and narrow line components for Lyα and C IV. We illustrate how this covariance matrix allows us to statistically characterise the intrinsic Lyα line solely from the observed spectrum redward of 1275Å. This procedure can be used to reconstruct the intrinsic Lyα line emission profile in cases where Lyα may otherwise be obscured. Applying this reconstruction method to our sample of QSOs, we recovered the Lyα line flux to within 15 per cent of the measured flux at 1205Å (1220Å) ∼ 85 (90) per cent of the time.

show abstract

Section: E-mail: Bradleygreig@snsit (Bg)mentioning

confidence: 99%

Lyα emission-line reconstruction for high-zQSOs

Greig

Mesinger

McGreer

et al. 2016

Mon. Not. R. Astron. Soc.

View full text Add to dashboard Cite

show abstract

“…The uncertainty in Pjet was dominated by the scatter in the correlation of Cavagnolo et al (2010) and corresponded to 0.7 dex. The uncertainties on broad line luminosity were based on the standard deviation of Mg II/Lyα, Hβ/Lyα and C IV/Lyα in the composite quasar spectrum of Francis et al (1991) (Wang et al 2004). We assumed that the uncertainties on broad line luminosity were to be 0.5 dex for all sources.…”

Section: The Samplesmentioning

confidence: 99%

Basic properties of Fermi blazars and the ‘blazar sequence’

Xiong

Zhang

Bai

et al. 2015

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

By statistically analyzing a large sample which includes blazars of Fermi detection (FBs) and non-Fermi detection (NFBs), we find that there are significant differences between FBs and NFBs for redshift, black hole mass, jet kinetic power from "cavity" power, broad-line luminosity, and ratio of core luminosity to absolute V-band magnitude (R v ), but not for ratio of radio core to extended flux (R c ) and Eddington ratio. Compared with NFBs, FBs have larger mean jet power, R c and R v while smaller mean redshift, black hole mass, broad-line luminosity. These results support that the beaming effect is main reason for differences between FBs and NFBs, and that FBs are likely to have a more powerful jet. For both Fermi and non-Fermi blazars, there are significant correlations between jet power and the accretion rate (traced by the broad-emission-lines luminosity), between jet power and black hole mass; for Fermi blazars, the black hole mass does not have significant influence on jet power while for non-Fermi blazars, both accretion rate and black hole mass have contributions to the jet power. Our results support the "blazar sequence" and show that synchrotron peak frequency (ν peak ) is associated with accretion rate but not with black hole mass.

show abstract

“…ii) We use the line ratios reported by Francis et al (1991) (see their Table 1 for a complete list), mainly because of the large statistic and the range of lines included ⋆ . They refer to an optical sample, mostly consisting of radio quiet sources, but no major differences in the broad line fluxes between radio quiet and radio loud objects has been clearly determined (e.g.…”

Section: Broad Line Luminositymentioning

confidence: 99%

“…iii) We then consider the sum of the line luminosities of all the lines reported by Francis et al (1991) with respect to the Lyα, to which we assign a reference value of 100 (hereafter the asterisk refers to luminosities in the same units). To this, we also add the contribution from L * Hα (which is not included in the list of Francis et al), with a value of 77 (from Gaskell et al 1981).…”

Section: Broad Line Luminositymentioning

confidence: 99%

Jets and accretion processes in active galactic nuclei: further clues

Celotti¹,

Padovani²,

Ghisellini³

1997

Monthly Notices of the Royal Astronomical Society

268

290

View full text Add to dashboard Cite

We present evidence in favour of a link between the luminosity radiatively dissipated in the central engine of radio-loud Active Galactic Nuclei and the kinetic power in their jets. This piece of evidence is based on the relation we find between the luminosity in broad emission lines and the kinetic power in pc-scale radio jets, for a sample of radio-loud quasars for which suitable data are available in the literature. We find that the ionizing luminosity and the kinetic one are of the same order of magnitude, suggesting that the processes responsible for them are somehow related. A strong magnetic field in equipartition with the radiation field could be responsible for regulating both processes. BL Lac objects seem to follow a similar behaviour, but with comparatively fainter broad line emission.

show abstract

A high signal-to-noise ratio composite quasar spectrum

Cited by 612 publications

References 8 publications

Lyα emission-line reconstruction for high-zQSOs

Lyα emission-line reconstruction for high-zQSOs

Basic properties of Fermi blazars and the ‘blazar sequence’

Jets and accretion processes in active galactic nuclei: further clues

Contact Info

Product

Resources

About