On the origin of mid-infrared colors in $γ$-ray blazars
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arXiv
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| Autori principali: | , , |
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| _version_ | 1866909533451845632 |
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| author | de Menezes, Raniere D'Abrusco, Raffaele Massaro, Francesco |
| author_facet | de Menezes, Raniere D'Abrusco, Raffaele Massaro, Francesco |
| contents | Context. The combination between non-thermal and thermal emission in $γ$-ray blazars pushes them to a specific region of the mid-infrared three-dimensional color diagram, the so-called blazar locus, built based on observations performed with the Wide-field Infrared Survey Explorer. The selection of blazar candidates based on these mid-infrared colors has been extensively used in the past decade in the hunt for the counterparts of unassociated $γ$-ray sources observed with the Fermi Large Area Telescope and in the search for new blazars in optical spectroscopic campaigns.
Aims. In this work, we provide a theoretical description of the origin of the blazar locus and show how we can reasonably reproduce it with a model consisting of only three spectral components: a log-parabola accounting for the non-thermal emission, and an elliptical host and dust torus accounting for the thermal emission.
Methods. We simulate spectral energy distributions for blazars, starting with a pure log-parabola model and then increasing its complexity by adding a template elliptical galaxy and dust torus. From these simulations, we compute the mid-infrared magnitudes and corresponding colors to create our own version of the blazar locus.
Results. Our modeling allows for the selection of spectral parameters that better characterize the mid-infrared emission of $γ$-ray blazars, such as the log-parabola curvature ($β< 0.04$ for 50\% of our sample) and an average spectral peak around $E_p \approx 1.5 \times 10^{-13}$ erg. We also find that the log-parabola is the main spectral component behind the observed mid-infrared blazar colors, although additional components such as a host galaxy and a dust torus are crucial to obtain a precise reconstruction of the blazar locus. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_03466 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | On the origin of mid-infrared colors in $γ$-ray blazars de Menezes, Raniere D'Abrusco, Raffaele Massaro, Francesco High Energy Astrophysical Phenomena Context. The combination between non-thermal and thermal emission in $γ$-ray blazars pushes them to a specific region of the mid-infrared three-dimensional color diagram, the so-called blazar locus, built based on observations performed with the Wide-field Infrared Survey Explorer. The selection of blazar candidates based on these mid-infrared colors has been extensively used in the past decade in the hunt for the counterparts of unassociated $γ$-ray sources observed with the Fermi Large Area Telescope and in the search for new blazars in optical spectroscopic campaigns. Aims. In this work, we provide a theoretical description of the origin of the blazar locus and show how we can reasonably reproduce it with a model consisting of only three spectral components: a log-parabola accounting for the non-thermal emission, and an elliptical host and dust torus accounting for the thermal emission. Methods. We simulate spectral energy distributions for blazars, starting with a pure log-parabola model and then increasing its complexity by adding a template elliptical galaxy and dust torus. From these simulations, we compute the mid-infrared magnitudes and corresponding colors to create our own version of the blazar locus. Results. Our modeling allows for the selection of spectral parameters that better characterize the mid-infrared emission of $γ$-ray blazars, such as the log-parabola curvature ($β< 0.04$ for 50\% of our sample) and an average spectral peak around $E_p \approx 1.5 \times 10^{-13}$ erg. We also find that the log-parabola is the main spectral component behind the observed mid-infrared blazar colors, although additional components such as a host galaxy and a dust torus are crucial to obtain a precise reconstruction of the blazar locus. |
| title | On the origin of mid-infrared colors in $γ$-ray blazars |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2502.03466 |