Are X-Ray Detected Active Galactic Nuclei in Dwarf Galaxies Gamma-Ray Bright?
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| Format: | Preprint |
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2025
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| _version_ | 1866911174112575488 |
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| author | Crnogorčević, Milena Linden, Tim Peter, Annika H. G. |
| author_facet | Crnogorčević, Milena Linden, Tim Peter, Annika H. G. |
| contents | The $γ$-ray emission from active galactic nuclei (AGN), including both beamed blazars and misaligned-AGN, dominates the extragalactic $γ$-ray point-source population count and flux. While multi-wavelength studies have detected an increasing number of AGN within dwarf galaxies in the local Universe, $γ$-ray emission has so far only been associated with systems hosting supermassive black holes (SMBHs). Dwarf-galaxy AGN are of particular interest because their central black holes fall in the intermediate-mass black hole (IMBH) regime, offering insight into the early evolution of SMBHs. Using 15~years of \textit{Fermi}-LAT data, we present the first search for $γ$-ray emission from dwarf-galaxy AGN. In the sample of 74 X-ray-selected dwarf-galaxy AGN, we find no sources that exceed the \textit{Fermi}-LAT detection threshold. However, a joint-likelihood analysis reveals a modest, trials-corrected population-level excess ($\sim2σ$) above blank-field expectations at very soft photon indices $Γ\gtrsim 3.8$ above 500~MeV. This hint is most pronounced when source contributions are weighed by $M^α_{{\rm IMBH},i}/d_i^2$, with $α\simeq1$--$1.5$, suggesting -- but not confirming -- that $γ$-ray emission could scale with the central black hole mass or a property correlated with it (e.g., accretion rate), but with a markedly softer spectrum than in SMBH-hosted AGN. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_18239 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Are X-Ray Detected Active Galactic Nuclei in Dwarf Galaxies Gamma-Ray Bright? Crnogorčević, Milena Linden, Tim Peter, Annika H. G. High Energy Astrophysical Phenomena Astrophysics of Galaxies The $γ$-ray emission from active galactic nuclei (AGN), including both beamed blazars and misaligned-AGN, dominates the extragalactic $γ$-ray point-source population count and flux. While multi-wavelength studies have detected an increasing number of AGN within dwarf galaxies in the local Universe, $γ$-ray emission has so far only been associated with systems hosting supermassive black holes (SMBHs). Dwarf-galaxy AGN are of particular interest because their central black holes fall in the intermediate-mass black hole (IMBH) regime, offering insight into the early evolution of SMBHs. Using 15~years of \textit{Fermi}-LAT data, we present the first search for $γ$-ray emission from dwarf-galaxy AGN. In the sample of 74 X-ray-selected dwarf-galaxy AGN, we find no sources that exceed the \textit{Fermi}-LAT detection threshold. However, a joint-likelihood analysis reveals a modest, trials-corrected population-level excess ($\sim2σ$) above blank-field expectations at very soft photon indices $Γ\gtrsim 3.8$ above 500~MeV. This hint is most pronounced when source contributions are weighed by $M^α_{{\rm IMBH},i}/d_i^2$, with $α\simeq1$--$1.5$, suggesting -- but not confirming -- that $γ$-ray emission could scale with the central black hole mass or a property correlated with it (e.g., accretion rate), but with a markedly softer spectrum than in SMBH-hosted AGN. |
| title | Are X-Ray Detected Active Galactic Nuclei in Dwarf Galaxies Gamma-Ray Bright? |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2509.18239 |