What Types of Jets Does Nature Make? A New Population of Radio Quasars

Abstract

We use statistical results from a large sample of about 500 blazars, based on two surveys, the Deep X-ray Radio Blazar Survey (DXRBS), nearly complete, and the RASS-Green Bank survey (RGB), to provide new constraints on the spectral energy distribution of blazars, particularly flat-spectrum radio quasars (FSRQ). This reassessment is prompted by the discovery of a population of FSRQ with spectral energy distribution similar to that of high-energy peaked BL Lacs. The fraction of these sources is sample dependent, being ∼ 10% in DXRBS and ∼ 30% in RGB (and reaching ∼ 80% for the Einstein Medium Sensitivity Survey). We show that these "X-ray strong" radio quasars, which had gone undetected or unnoticed in previous surveys, indeed are the strong-lined counterparts of high-energy peaked BL Lacs and have synchrotron peak frequencies, ν peak , much higher than "classical" FSRQ, typically in the UV band for DXRBS. Some of these objects may be 100 GeV -TeV emitters, as are several known BL Lacs with similar broadband spectra. Our large, deep, and homogeneous DXRBS sample does not show anti-correlations between ν peak and radio, broad line region, or jet power, as expected in the so-called "blazar sequence" scenario. However, the fact that FSRQ do not reach X-ray-to-radio flux ratios and ν peak values as extreme as BL Lacs and the elusiveness of high ν peak -high-power blazars suggest that there might be an intrinsic, physical limit to the synchrotron peak frequency that can be reached by strong-lined, powerful blazars. Our findings have important implications for the study of jet formation and physics and its relationship to other properties of active galactic nuclei.

Looking below the floor: constraints on the AGN radio luminosity functions at low power

“…Furthermore, the brightest of these objects has a radio luminosity of 1.3 × 10 24 W Hz −1 . We estimated the corresponding non thermal contribution to the optical (r band) magnitude for similarly bright objects by assuming, conservatively, a radioto-optical spectral index of 0.5, typical of high energy peaked BL Lacs (Padovani et al 2003). We obtain r = 17.5 at z = 0.05 (and r =19.0 at z = 0.1), ∼ 1-4 magnitudes fainter than LRP AGN hosts.…”

From the ‘blazar sequence' to unification of blazars and radio galaxies

“…Various lines of evidence support the blazar sequence (Georganopoulos et al 2001;Cavaliere & D'Elia 2002;Maraschi & Tavecchio 2003;Xie et al 2007;Maraschi et al 2008;Ghisellini et al 2009Ghisellini et al , 2010Abdo et al 2010a;Chen & Bai 2011;Sambruna et al 2010;Finke et al 2013;Chen 2014). But many contrary opinions have been presented (Giommi, Menna & Padovani 1999;Caccianiga & Marcha 2004;Padovani et al 2003;Anton & Browne 2005;Nieppola et al 2006Nieppola et al , 2008Padovani 2007;Giommi et al 2012). The authors mainly focus on sample selection effect and beaming effect.…”

The Deep X‐Ray Radio Blazar Survey. III. Radio Number Counts, Evolutionary Properties, and Luminosity Function of Blazars

“…Deeper, sizable blazar samples, have started to be assembled in the past few years by us (Perlman et al [1998]; Landt et al [2001], hereafter Papers I and II, respectively; see also Padovani et al [2003]) and others (RGB: Laurent-Muehleisen et al [1999]; REX: Caccianiga et al [2002]; HRX: Beckmann et al [2003]; CLASS: Caccianiga & Marchã [2004]; and sedentary: Giommi et al [2005]; see also for a review). Some of these samples take advantage of the fact that blazars are relatively strong radio and X-ray sources and therefore use a double radio/ X-rayYselection method.…”