skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Modeling Blazar Broadband Emission with a Convolutional Neural Network. I. Synchrotron Self-Compton Model
Abstract Modeling the multiwavelength spectral energy distributions (SEDs) of blazars provides key insights into the underlying physical processes responsible for the emission. While SED modeling with self-consistent models is computationally demanding, it is essential for a comprehensive understanding of these astrophysical objects. We introduce a novel, efficient method for modeling the SEDs of blazars by the mean of a convolutional neural network (CNN). In this paper, we trained the CNN on a leptonic model that incorporates synchrotron and inverse Compton emissions, as well as self-consistent electron cooling and pair creation–annihilation processes. The CNN is capable of reproducing the radiative signatures of blazars with high accuracy. This approach significantly reduces the computational time, thereby enabling real-time fitting to multiwavelength data sets. As a demonstration, we used the trained CNN withMultiNestto fit the broadband SEDs of Mrk 421 and 1ES 1959+650, successfully obtaining their parameter posterior distributions. This novel framework for fitting the SEDs of blazars will be further extended to incorporate more sophisticated models based on external Compton and hadronic scenarios, allowing for multimessenger constraints in the analysis. The models will be made publicly available via a web interface at the Markarian Multiwavelength Data Center to facilitate self-consistent modeling of multimessenger data from blazar observations.  more » « less
Award ID(s):
2011759
PAR ID:
10548232
Author(s) / Creator(s):
; ; ; ; ; ; ;
Publisher / Repository:
American Astronomical Society
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
963
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
71
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, The Astrophysical Journal)
    Abstract Multiwavelength observations are now the norm for studying blazars’ various states of activity, classifying them, and determining the possible underlying physical processes driving their emission. Broadband emission models became unavoidable tools for testing emission scenarios and setting the values of physical quantities such as the magnetic field strength, Doppler factor, or shape of the particle distribution of the emission zone(s). We announce here the first public release of a new tool,Bjet_MCMC, that can automatically fit the broadband spectral energy distributions (SEDs) of blazars. The complete code is available on GitHub and allows for testing leptonic synchrotron self-Compton models with or without external inverse-Compton processes from the thermal environment of supermassive black holes (accretion disk and broad-line region). The code is designed to be user-friendly and computationally efficient. It contains a core written in C++ and a fully parallelized SED fitting method. The original multi-SSC zone model ofBjetis also available on GitHub but is not included in the Markov Chain Monte Carlo fitting process at the moment. We present the features, performance, and results ofBjet_MCMC, as well as user advice. 
    more » « less
  2. ; ; ; ; (, Monthly Notices of the Royal Astronomical Society)
    ABSTRACT Gamma-ray observations have revealed strong variability in blazar luminosities in the gamma-ray band over time-scales as short as minutes. We show, for the first time, that the correlation of the spectrum with intensity is consistent with the behaviour of the luminosity variation of blazar spectral energy distributions (SEDs) along a blazar sequence for low synchrotron peak blazars. We show that the observational signatures of variability with flux are consistent with wakefield acceleration of electrons initiated by instabilities in the blazar accretion disc. This mechanism reproduces the observed time variations as short as 100 s. The wakefield mechanism also predicts a reduction of the electron spectral index with increased gamma-ray luminosity, which could be detected in higher energy observations well above the inverse Compton peak. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, The Astrophysical Journal)
    Abstract The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory surveys the very high-energy sky in the 300 GeV to >100 TeV energy range. HAWC has detected two blazars above 11 σ , Markarian 421 (Mrk 421) and Markarian 501 (Mrk 501). The observations are comprised of data taken in the period between 2015 June and 2018 July, resulting in ∼1038 days of exposure. In this work, we report the time-averaged spectral analyses for both sources, above 0.5 TeV. Taking into account the flux attenuation due to the extragalactic background light, the intrinsic spectrum of Mrk 421 is described by a power law with an exponential energy cutoff with index α = 2.26 ± 0.12 stat − 0.2 + 0.17 sys and energy cutoff E c = 5.1 ± 1.6 stat − 2.5 + 1.4 sys TeV, while the intrinsic spectrum of Mrk 501 is better described by a simple power law with index α = 2.61 ± 0.11 stat − 0.07 + 0.01 sys . The maximum energies at which the Mrk 421 and Mrk 501 signals are detected are 9 and 12 TeV, respectively. This makes these some of the highest energy detections to date for spectra averaged over years-long timescales. Since the observation of gamma radiation from blazars provides information about the physical processes that take place in their relativistic jets, it is important to study the broadband spectral energy distributions (SEDs) of these objects. For this purpose, contemporaneous data in the gamma-ray band to the X-ray range, and literature data in the radio to UV range, were used to build time-averaged SEDs that were modeled within a synchrotron-self Compton leptonic scenario. 
    more » « less
  4. ; ; (, Monthly Notices of the Royal Astronomical Society)
    ABSTRACT Jetted active galactic nuclei (AGNs) are the principal extragalactic γ-ray sources. Fermi-detected high-redshift (z > 3) blazars are jetted AGNs thought to be powered by massive, rapidly spinning supermassive black holes (SMBHs) in the early universe (<2 Gyr). They provide a laboratory to study early black hole (BH) growth and super-Eddington accretion – possibly responsible for the more rapid formation of jetted BHs. However, previous virial BH masses of z > 3 blazars were based on C iv λ1549 in the observed optical, but C iv λ1549 is known to be biased by strong outflows. We present new Gemini/GNIRS near-infrared spectroscopy for a sample of nine z > 3 Fermi γ-ray blazars with available multiwavelength observations that maximally sample the spectral energy distributions (SEDs). We estimate virial BH masses based on the better calibrated broad H β and/or Mg ii λ2800. We compare the new virial BH masses against independent mass estimates from SED modelling. Our work represents the first step in campaigning for more robust virial BH masses and Eddington ratios for high-redshift Fermi blazars. Our new results confirm that high-redshift Fermi blazars indeed host overly massive SMBHs as suggested by previous work, which may pose a theoretical challenge for models of the rapid early growth of jetted SMBHs. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al (, The Astrophysical Journal Supplement Series)
    Abstract W-CDF-S, ELAIS-S1, and XMM-LSS will be three Deep-Drilling Fields (DDFs) of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), but their extensive multiwavelength data have not been fully utilized as done in the COSMOS field, another LSST DDF. To prepare for future science, we fit source spectral energy distributions (SEDs) from X-ray to far-infrared in these three fields mainly to derive galaxy stellar masses and star formation rates. We use CIGALE v2022.0, a code that has been regularly developed and evaluated, for the SED fitting. Our catalog includes 0.8 million sources covering 4.9 deg 2 in W-CDF-S, 0.8 million sources covering 3.4 deg 2 in ELAIS-S1, and 1.2 million sources covering 4.9 deg 2 in XMM-LSS. Besides fitting normal galaxies, we also select candidates that may host active galactic nuclei (AGNs) or are experiencing recent star formation variations and use models specifically designed for these sources to fit their SEDs; this increases the utility of our catalog for various projects in the future. We calibrate our measurements by comparison with those in well-studied smaller regions and briefly discuss the implications of our results. We also perform detailed tests of the completeness and purity of SED-selected AGNs. Our data can be retrieved from a public website. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email