A systematic study of the long-term mid-infrared color variations of Seyfert 1 galaxies

@misc{wu2026systematic,
  title = {{A systematic study of the long-term mid-infrared color variations of Seyfert 1 galaxies}},
  author = {Jiahua Wu and Liming Dou and Zhining Chen and Fupeng Zhang and Luis C. Ho and Yanli Ai and Tinggui Wang and Xinwen Shu and Ning Jiang and Junfeng Wang},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.12390},
  eprint = {2609.12390},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.12390},
}

TY  - UNPB
TI  - A systematic study of the long-term mid-infrared color variations of Seyfert 1 galaxies
AU  - Jiahua Wu
AU  - Liming Dou
AU  - Zhining Chen
AU  - Fupeng Zhang
AU  - Luis C. Ho
AU  - Yanli Ai
AU  - Tinggui Wang
AU  - Xinwen Shu
AU  - Ning Jiang
AU  - Junfeng Wang
PY  - 2026
DA  - 2026/09/11
PB  - arXiv
DO  - 10.48550/arxiv.2609.12390
UR  - https://arxiv.org/abs/2609.12390
AB  - We present a comparative analysis of long-term mid-infrared (MIR) color variations (MCVs) for 1,977 narrow-line Seyfert 1 (NLSy1) and 4,113 broad-line Seyfert 1 (BLSy1) galaxies at z < 0.3. Using 14 years of WISE and NEOWISE data, we quantify the correlation between W1−W2 color and W1 magnitude. We categorize sources into bluer-when-brighter (BWB), redder-when-brighter (RWB), and weak/no MCV populations. Our results show that the MCV properties of BLSy1s are consistent with those of NLSy1s. This suggests that host-contaminated dust reprocessing is a universal mechanism across Seyfert 1s. Bolometric luminosity (Lbol) is the primary driver of MCV behavior. However, at fixed Lbol, the fraction of RWB sources decreases with increasing Eddington ratio (REdd). This reveals a secondary dependence on the accretion state. Ensemble structure function analysis further shows that higher-REdd sources exhibit flatter structure functions at a given Lbol, indicating smaller dust torus radii. These findings suggest that the central engine's radiation and accretion state shape the circumnuclear dust geometry. Radio-loud sources follow the same trends as radio-quiet counterparts, implying that jet emission does not significantly impact long-term MIR variability. Finally, modified blackbody modeling indicates that grains with sizes a ≳ 0.1 μm are responsible for the observed MCVs. Our results establish a unified framework for MCVs in Seyfert~1s, where the Eddington ratio modulates both variability patterns and the physical scale of the dust torus. Furthermore, given the similarity between the MCV distributions of CLAGNs and RWB sources, we estimate that ≲ 6% of Seyfert~1s may be CLAGN candidates, offering a potential MIR-based pre-selection.
ER  -