UNIFICATION OF LUMINOUS TYPE 1 QUASARS THROUGH C iv EMISSION

By Gordon Richards, N. Kruczek, S. Gallagher, P. Hall, Paul Hewett, Karen M. Leighly Rajesh P. Deo, Rachael M. Kratzer, Yue Shen Drexel University, U. W. Ontario, York University and 3 more. 2010

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Using a sample of ∼30,000 quasars from the 7th Data Release of the Sloan Digital Sky Survey, we explore the range of properties exhibited by high-ionization, broad emission lines, such as C iv λ1549. Specifically, we investigate the anti-correlation between continuum luminosity and emission-line equivalent width (the Baldwin Effect (BEff)) and the “blueshifting” of the high-ionization emission lines with respect to low-ionization emission lines. Employing improved redshift determinations from Hewett & Wild, the blueshift of the C iv emission line is found to be nearly ubiquitous, with a mean shift of ∼810 km s−1 for radio-quiet (RQ) quasars and ∼360 km s−1 for radio-loud (RL) quasars. The BEff is present in both RQ and RL samples. We consider these phenomena within the context of an accretion disk-wind model that is modulated by the nonlinear correlation between ultraviolet and X-ray continuum luminosity. Composite spectra are constructed as a function of C iv emission-line properties in an attempt to reveal empirical relationships between different line species and the continuum. Within a two-component disk+wind model of the broad emission-line region (BELR), where the wind filters the continuum seen by the disk component, we find that RL quasars are consistent with being dominated by the disk component, while broad absorption line quasars are consistent with being dominated by the wind component. Some RQ objects have emission-line features similar to RL quasars; they may simply have insufficient black hole (BH) spin to form radio jets. Our results suggest that there could be significant systematic errors in the determination of Lbol and BH mass that make it difficult to place these findings in a more physical context. However, it is possible to classify quasars in a paradigm where the diversity of BELR parameters is due to differences in an accretion disk wind between quasars (and over time); these differences are underlain primarily by the spectral energy distribution, which ultimately must be tied to BH mass and accretion rate.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

Evolution of broad-line emission from active galactic nuclei (2013, background): “Disk winds also provide satisfactory explanations for the trends exhibited by high-ionization, broad emission lines from 30,000 SDSS quasars (Richards et al. 2011) as well as the general properties of UV and X-ray absorption lines in both quasars and Seyfert galaxies (Schurch et al. 2009; Fukumura…”
BLACK HOLE MASS ESTIMATES AND EMISSION-LINE PROPERTIES OF A SAMPLE OF REDSHIFT z > 6.5 QUASARS (2013, background): “…lines are preferred to highionization lines (e.g., C iv) because the latter can present highvelocity offsets with respect to the source systemic redshift (Δv 1000 km s−1, corresponding to Δz ∼ 0.02 at z ∼ 6, see, e.g., Richards et al. 2002, 2011; Shang et al. 2007 and references therein).”
THE z = 5 QUASAR LUMINOSITY FUNCTION FROM SDSS STRIPE 82 (2012, background): “These distributions recover trends in the mean and scatter of the line parameters as a function of continuum luminosity, e.g., the Baldwin Effect (Baldwin 1977), and blueshifted lines (Gaskell 1982; Richards et al. 2011).”
A systematic search for changing-look quasars in SDSS (2015, background): “The lack of significant changes in the C iv and Mg ii lines may be due to the fact that C iv is affected by winds (Richards et al. 2011) and that Mg ii has a relatively weak responsivity (Goad et al. 1993; Cackett et al. 2015).”
The Giant Gemini GMOS survey of zem > 4.4 quasars – I. Measuring the mean free path across cosmic time (2014, background): “As almost all Shen–zem values are based on Si IV and C IV (Table 3), with the former being blended with O IV] and the latter showing a blueshift that increases with luminosity (Richards et al. 2011), we consider the GGG–zem values more reliable for our sample of very luminous quasars (Fig.”
THE LICK AGN MONITORING PROJECT 2011: SPECTROSCOPIC CAMPAIGN AND EMISSION-LINE LIGHT CURVES (2015, background): “This point has been emphasized by Richards et al. (2011) and Shen (2013) in the context of examining biases inherent in single-epoch masses derived from the CIV line.”
The clustering of intermediate-redshift quasars as measured by the Baryon Oscillation Spectroscopic Survey (2012, background): “C III] is often blended with Si III], Al III and Fe III complexes, C IV can be shifted from the systemic redshift by strong outflows, and Lyα is often affected by Lyα Forest absorption and is blended with NV (e.g., Vanden Berk et al. 2001; Richards et al. 2002b, 2011).”
Black Hole Growth to z = 2 - I: Improved Virial Methods for Measuring M_BH and L/L_Edd (2012, background): “Previous studies suggested that the large blue-shifts often observed in C IV indicate that the emission originates from non-virializedgas motion (e.g., BL05, Richards et al. 2011).”
What drives the growth of black holes (2011, background): “In the spectra of high-z quasars from SDSS, the peak of the broad C iv emission is typically blueshifted, indicating outflows with ∼1000 km s−1 (e.g., Richards et al., 2002, 2011).”
A CATALOG OF QUASAR PROPERTIES FROM SLOAN DIGITAL SKY SURVEY DATA RELEASE 7 (2010, background): “Richards et al. (2011) further developed a unified picture in which the CIV line has both a non-virial wind component and a traditional virial component, and it is plausible thatt e BH mass scaling relation based on CIV is only relevant for objects dominated by the virial component.”
Measuring the Masses of Supermassive Black Holes (2014, background): “Richards et al. (2011) note, for example, the absence in the reverberation sample of quasars with blueshifted C iv emission.”
Erratum: Updating quasar bolometric luminosity corrections (2012, background): “It has been suggested that the intrinsic SED contin- c© 2011 RAS, MNRAS 000, 1–18 uum may be different from what we view (e.g., Korista et al. 1997; Lawrence 2011) and some tentative evidence may exist to support this (e.g., Richards et al. 2011; Kruczek et al. 2011).”
Physical Properties of 15 Quasars at z ≳ 6.5 (2017, background): “For comparison, we select a subsample of objects at low redshift, partially following Richards et al. (2011): we consider quasars in the redshift range 1.52 < z < 2.2 (where both the C IV and Mg II emission lines are covered), with significant detection of the broad C IV emission line (FWHMC IV >…”
THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: TECHNICAL OVERVIEW (2014, methodology): “The right panel of Figure 1 presents a similar bias of the current RM sample, in terms of C iv properties (e.g., Richards et al. 2011).”