Half of the Seyfert-2 galaxies escaped detection of broad lines in their polarised spectra observed so far. Some authors have suspected that these non-HBLRs contain real Sy2 nuclei without intrinsic broad line region hidden behind a dust torus. If this were true, then their nuclear structure would fundamentally differ from that of Sy2s with polarised broad lines: in particular, they would not be explained by orientation-based AGN unification. Further arguments for two physically different Sy2 populations have been derived from the warm and cool IRAS F25/F60 ratios. These ratios, however, refer to the entire host galaxies and are unsuitable to conclusively establish the absence of a nuclear dust torus. Instead, a study of the Seyfert-2 dichotomy should be performed on the basis of nuclear properties only. Here we present the first comparison between [OIII] 5007A and mid-infrared imaging at matching spatial resolution. Exploring the Seyfert-2 dichotomy we find that the distributions of nuclear mid-infrared/[OIII] luminosity ratios are indistinguishable for Sy1s and Sy2s with and without detected polarised broad lines and irrespective of having warm or cool IRAS F25/F60 ratios. We find no evidence for the existence of a population of real Sy2s with a deficit of nuclear dust emission. Our results suggest 1) that all Seyfert nuclei possess the same physical structure including the putative dust torus and 2) that the cool IRAS colours are caused by a low contrast of AGN to host galaxy. Then the Seyfert-2 dichotomy is explained in part by unification of non-HBLRs with narrow-line Sy1s and to a larger rate by observational biases caused by a low AGN/host contrast and/or an unfavourable scattering geometry.
Estimation of the dust mass-loss rates from AGB stars in the Fornax and Sagittarius dwarf Spheroidal galaxies
为了研究金属丰度对AGB星质量损失的影响，我们在VLT用VISIR的10微米照相机对人马座和天炉座矮椭球星系（[Fe/H]=-1.1和-1.3）中的AGB星进行了中红外光度测量。这些观测与以前的近红外光度测量相结合，使我们能够估计这些星系的质量损失率。我们在这里表明，所观察到的AGB显示灰尘驱动的质量损失。尘埃的质量损失率被发现的范围内0.2 $\times10^{-10}-1.3\times10^{-8}$ M $_{\odot}$年$^{-1}$观测到的AGB星在SgrD和周围5 $\times10^{-11}$ M $_{\odot}$年$^{-1}$观测到的恒星在天炉座。
The enigma of GCIRS 3 - Constraining the properties of the mid-infrared reference star of the central parsec of the Milky Way with optical long baseline interferometry
