The Evolution of Swift/BAT blazars and the origin of the MeV background (0905.0472v1)

Abstract: We use 3 years of data from the Swift/BAT survey to select a complete sample of X-ray blazars above 15 keV. This sample comprises 26 Flat-Spectrum Radio Quasars (FSRQs) and 12 BL Lac objects detected over a redshift range of 0.03<z<4.0. We use this sample to determine, for the first time in the 15--55 keV band, the evolution of blazars. We find that, contrary to the Seyfert-like AGNs detected by BAT, the population of blazars shows strong positive evolution. This evolution is comparable to the evolution of luminous optical QSOs and luminous X-ray selected AGNs. We also find evidence for an epoch-dependence of the evolution as determined previously for radio-quiet AGNs. We interpret both these findings as a strong link between accretion and jet activity. In our sample, the FSRQs evolve strongly, while our best-fit shows that BL Lacs might not evolve at all. The blazar population accounts for 10-20 % (depending on the evolution of the BL Lacs) of the Cosmic X-ray background (CXB) in the 15--55 keV band. We find that FSRQs can explain the entire CXB emission for energies above 500 keV solving the mystery of the generation of the MeV background. The evolution of luminous FSRQs shows a peak in redshift ($z_c$=4.3$\pm0.5$) which is larger than the one observed in QSOs and X-ray selected AGNs. We argue that FSRQs can be used as tracers of massive elliptical galaxies in the early Universe.

Overview of the Evolution of {\em Swift}/BAT Blazars

The paper, "The Evolution of {\em Swift}/BAT blazars and the origin of the MeV background" by Ajello et al., provides a detailed analysis of blazars based on data from the {\em Swift}/BAT survey. This work presents significant findings on the evolution of blazars and their contribution to the cosmic X-ray background (CXB), particularly focusing on the MeV region.

Key Findings

The blazar sample, collected over three years using the {\em Swift}/BAT survey targeting X-ray emissions above 15 keV, consists of 26 Flat-Spectrum Radio Quasars (FSRQs) and 12 BL Lac objects. Ajello et al. distinguish the evolutionary patterns in the 15-55 keV band, highlighting a strong positive evolution for blazars. FSRQs, specifically, show robust evolutionary trends, whereas BL Lac objects exhibit more subdued changes, potentially not evolving at all.

Numerical Insights

FSRQs are identified as significant contributors to the CXB at energies above 500 keV, suggesting they might account for the entire MeV background. The research quantifies that blazars comprise approximately 10-20% of the CXB within the 15-55 keV range. Furthermore, it specifies a peak in redshift for luminous FSRQs ($z_c = 4.3 \pm 0.5$), which exceeds that observed in QSOs and X-ray-selected AGNs, thus proposing that FSRQs are markers for massive elliptical galaxies in the early universe.

Theoretical and Practical Implications

The correlation between accretion and jet activity in blazars remains a pivotal discovery. It points to profound connections within the mechanisms underpinning the energetic phenomena in the early universe, especially concerning galaxy evolution and black hole formation processes.

The implications extend into astrophysical applications, such as enhancing the understanding of galaxy formation timelines and energy distribution in cosmic structures. The confirmation of FSRQs as MeV blazars plays a critical role in explaining the unresolved high-energy CXB emission, reducing the ambiguity surrounding the MeV background mystery.

Speculations on Future AI Developments

The methodologies applied in this paper can guide future AI developments in data analysis for large astrophysical datasets. Enhancing pattern recognition capabilities and refining machine learning algorithms will facilitate deeper insights into cosmic phenomena and improve analytical efficiency.

Conclusion

In conclusion, Ajello et al.'s research advances the characterization of blazar evolution and their significant contribution to the high-energy cosmic background. The detailed quantification of FSRQs offers pathways for future exploration into galaxy and black hole evolution in the high-redshift universe. The paper affirms the necessity of continued investigation with increasingly sophisticated AI models for processing and interpreting extensive astronomical datasets.