2002/08/28 by F. Panessa, Francesca Panessa, L. Bassani +1 · 187 citations
Physics and Astronomy · #Absorption (acoustics) #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #Galaxy #Line (geometry) #Luminosity #Luminous infrared galaxy #Population #Torus #Type (biology) #astro-ph
paper · pdf · doi:10.1051/0004-6361:20021161
published in Astronomy and Astrophysics 394(2), 435-442 (EDP Sciences) · 9 pages, 5 figures. Accepted for publication in A&A
arxiv created 2002/08/28 · openalex publication_date 2002/10/15 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present a sample of 17 type 2 Seyfert galaxies which have an X-ray column density lower than 1022 cm-2. The Compton thin nature of these sources is strongly suggested by isotropic indicators. We estimate the fraction of these sources to be in the range of 10%–30% of the population of type 2 Seyfert galaxies. Furthermore, this fraction appears to increase progressively at lower luminosities. The simple formulation of the Unified Model for Seyfert galaxies is not applicable in such sources since the pc-scale molecular torus is not likely to be responsible for the low column density observed; instead the absorption observed is likely to originate at larger scales. According to this hypothesis, in these objects the broad line regions are covered by some dusty obscuring material. In particular, this could occur in objects with dust lanes, patches or HII regions. However, we cannot rule out that in the lowest luminosity sources the BLR is weak, absent or has faded away. This last scenario is consistent with the predictions of some recent theoretical models for low luminosity AGNs.