Implications for the blazar sequence and inverse Compton models from Fermi bright blazars.
CHEN L. and BAI J.M.
Abstract (from CDS):
In this paper, we use the quasi-simultaneous spectra of Fermi bright blazars and Fermi-detected narrow-line Seyfert 1 (NLS1) to study the blazar sequence and inverse Compton models. (1) The synchrotron peak luminosities (Ls) significantly correlate inversely with the synchrotron peak frequencies (νs), Ls∝ν–0.44±0.11s, which is consistent with the blazar sequence. In addition to the correlation, there are some blazars showing low νs and low Ls. To study the relation between these low-νs-low-Ls blazars and the blazar sequence, we present correlations of the parameter Lsν1/4s with the ratio of Compton to synchrotron peak frequencies (rCs≡ νC/νs) and with the ratio of Compton to synchrotron luminosities (CD ≡ LC/Ls ). The results indicate that both correlations are significant with a Pearson's probability for a null correlation of p = 0.0218 and p = 0.0286, respectively. This does not support the idea that the low-νs-low-Ls blazars are sources with less beaming. Another possibility, as suggested by Ghisellini & Tavecchio, is that these blazars have relatively lower black hole masses. To test this, we collect the black hole masses of 30 blazars from archives and find that the black hole mass correlates with the parameter Lsν0.44s(p = 0.0344). Therefore, the black hole masses of low-νs-low-Ls blazars are statistically small. The NLS1s are thought to have lower black hole masses. We find that the four NLS1s detected by Fermi have low ν_ s_ and low Ls. This supports the above result. (2) The ratio rCscorrelates with CD significantly (p = 0.00375). The external Compton model can naturally explain this correlation, while the synchrotron self-Compton model cannot. This agrees with the findings of many authors that the EC process dominates the gamma-ray emission of flat spectrum radio quasars.
BL Lacertae objects: general - galaxies: jets - quasars: general - radiation mechanisms: non-thermal