The Extreme Red Excess in Blazar Ultraviolet Broad Emission Lines

Abstract

We present a study of quasars with very redward asymmetric (RA) ultraviolet (UV) broad emission lines (BELs). An excess of redshifted emission has been previously shown to occur in the BELs of radio-loud quasars and is most extreme in certain blazars. Paradoxically, blazars are objects that are characterized by a highly relativistic blueshifted outflow toward Earth. We show that the red emitting gas resides in a very broad component (VBC) that is typical of Population B quasars that are defined by a wide Hβ BEL profile. Empirically, we find that RA BEL blazars have both low Eddington rates (1%) and an inordinately large (order unity) ratio of long-term timeaveraged jet power to accretion luminosity. The latter circumstance has been previously shown to be associated with a depressed extreme UV ionizing continuum. Both properties conspire to produce a low flux of ionizing photons, two orders of magnitude less than typical Population B quasars. We use CLOUDY models to demonstrate that a weak ionizing flux is required for gas near the central black hole to be optimally ionized to radiate BELs with high efficiency (most quasars overionize nearby gas, resulting in low radiative efficiency). The large gravitational redshift and transverse Doppler shift result in a VBC that is redshifted by ∼2000-5000 km s −1 with a correspondingly large line width. The RA BELs result from an enhanced efficiency (relative to typical Population B quasars) to produce a luminous, redshifted VBC near the central black hole.

Optical Singly-Ionized Iron Emission in Radio-Quiet and Relativistically Jetted Active Galactic Nuclei

“…Conversely, Population B sources have a lower Eddington ratio, and their line asymmetries are predominantly towards the red [19,20]. The origin of the asymmetry is a topic of current debate: partial obscuration and infall [21], and gravitational redshift [22][23][24][25][26], are two processes that have been proposed.…”

Past, Present, and Future of the Scaling Relations of Galaxies and Active Galactic Nuclei

“…Reverberation mapping studies of lines from different ionic species have provided evidence of "ionization stratification" and velocity-resolved reverberation mapping of sources with asymmetric Hβ basically confirms the scenario of a Keplerian velocity field (Du et al, 2018b;Brotherton et al, 2020). The red-ward asymmetry has been interpreted as due to gravitational and transverse redshift (Bon et al, 2015;Punsly et al, 2020) or by gas clouds infalling toward the central black hole (Wang et al, 2017). At the extreme end of Pop.…”

“…Only in a few special cases this feat has been possible. In such cases the viewing angle is constrained by data unrelated to the spectra, such as the radio morphology or the jet beaming (Wills and Browne, 1986;Decarli et al, 2011;Punsly et al, 2020). The dependence on orientation can be overcome by spectropolarimetric measurements: if the emission line light is scattered by an equatorial scatterer, then the width of the polarized line flux should be related to the velocity field as measured by an observer in the equatorial plane of the accretion disk, i.e., as if the viewing angle were θ 90 from the disk axis, de facto removing the orientation effect.…”

The Main Sequence of quasars: the taming of the extremes

“…The emission line profiles of radio-loud quasars are often characterized by extreme redward asymmetries in the line profiles (Marziani, Sulentic, Dultzin-Hacyan, Calvani, & Moles, 1996;Punsly, 2010). A recent survey of blazar spectra (Punsly, Marziani, Berton, & Kharb, 2020) show consistency with a large contribution from the inner region of an accretion disk to the line profiles, with disk inner radius ̃ BLR ≲ 100 g . In this case, the model profiles constrain the disk viewing angle to be ≲ 5 degrees.…”