Broad-line region physical conditions along the quasar eigenvector 1 sequence

Abstract

We compare broad emission‐line profiles and estimate line ratios for all major emission lines between Lyα and Hβ in a sample of six quasars. The sources were chosen with two criteria in mind: the existence of high‐quality optical and ultraviolet spectra and the possibility of sampling the spectroscopic diversity in the 4D eigenvector 1 (4DE1) context. In the latter sense, each source occupies a region (bin) in the full width at half‐maximum (FWHM)(Hβ) versus Fe iiopt strength plane that is significantly different from the others. High signal‐to‐noise ratio Hβ emission‐line profiles are used as templates for modelling the other lines (Lyα, C ivλ1549, He iiλ1640, Al iiiλ1860, Si iii]λ1892 and Mg iiλ2800). We can adequately model all broad lines assuming the existence of three components distinguished by blueshifted, unshifted and redshifted centroids [indicated as a blue component (BLUE), broad component (BC) and very broad component (VBC), respectively]. BC (electron density ne∼ 1012 cm−3, ionization parameter U∼ 10−2 and column density Nc≳ 1023 cm−2) is present in almost all type‐1 quasars and therefore corresponds most closely to the classical broad‐line emitting region (the reverberating component). The bulk of Mg iiλ2800 and Fe ii emission also arises in this region. The BLUE emission (log ne∼ 10, log U∼−1 and log Nc < 23) arises in less optically thick gas; it is often thought to arise in an accretion disc wind. The least understood component involves the VBC (high ionization and large column density), which is found in no more than half (but almost all radio‐loud) type‐1 quasars and luminous Seyfert nuclei. It is perhaps the most distinguishing characteristic of quasars with FWHM (Hβ) ≳ 4000 km s−1 that belong to the so‐called population B of our 4DE1 space. Population A quasars [FWHM (Hβ) ≲ 4000 km s−1] are dominated by BC emission in Hβ and BLUE component emission in C ivλ1549 and other high ionization lines. 4DE1 appears to be the most useful current context for revealing and unifying spectral diversity in type‐1 quasars.

Is MgIIλ2800 a reliable virial broadening estimator for quasars?

“…Separating the sample into spectral types will allow us to avoid the danger of mixing sources together that show very different spectral line profile properties. Insofar as Hβ and Feii measures reflect physical conditions in the BLR, the bins isolate sources with similar values of density, ionization parameter, and L/L Edd (see e.g., Marziani et al 2001Marziani et al , 2010. Binning allows us to also take the complexity of line profiles into account, and to separate, at least in a heuristic way, major flux contributions that are due to gas that is not likely to be virialized (i.e., the redshifted very broad component of Hβ in Pop.…”

“…Interpreting of quasar spectra in the context of a 4D parameter space stemming from eigenvector studies reveals a wide diversity of line profile properties (Sulentic et al 2000a(Sulentic et al , 2007Marziani et al 2003bMarziani et al , 2010 that are most likely driven by L/L Edd , with M BH and source orientation also playing important roles (Boroson & Green 1992;Marziani et al 2001;Yip et al 2004). The 4DE1 (4D eigenvector 1) formalism owes its Now at Instituto de Astronomía, UNAM, Ensenada Campus, Baja California, México. inception to a principal component analysis study of systematic trends in quasar spectra (Boroson & Green 1992) from the the Palomar-Green (PG) survey.…”

Gravitational lens system SDSS J1339+1310: microlensing factory and time delay

“…From a multi-component decomposition of the carbon line profiles (e.g. Wills et al 1985;Kuraszkiewicz et al 2002;Marziani et al 2010;Sluse et al 2011), we derived two narrow-line flux ratios B/A, which were then used to achieve a reliable macrolens-extinction solution for a standard (linear) extinction law in G. This solution allowed us to remove macrolens and extinction contributions in our quasar spectra. We note that the narrow components of the carbon lines are related to line emitting gas with typical velocities of ∼ 700 (C iii]) and 1300 (C iv) km s −1 , which belong to the inner NLER (e.g.…”

“…A multi-component decomposition of line profiles has been used in many previous works with different aims (e.g. Wills et al 1985;Kuraszkiewicz et al 2002;Dietrich et al 2003;Sluse et al 2007;Marziani et al 2010), and recently, Sluse et al (2011) identified and studied different components of the C iii] and C iv lines in spectra of the gravitationally lensed quasar Q2237+0305.…”

Deep optical imaging and spectroscopy of the lens system SDSS J1339+1310

“…2.2, and each of these three emissions is most likely generated in spatially different regions (e.g., Marziani et al 2010;Sluse et al 2011;Motta et al 2012). According to Motta et al (2012), the broad wings of a given emission line could be produced in a compact region, whereas its core is probably dominated by photons arising from the NLR and the outer parts of the BLR.…”