The Detection of Silicate Emission from Quasars at 10 and 18 Microns
نویسندگان
چکیده
We report the spectroscopic detection of silicate emission at 10 and 18μm in five PG quasars, the first detection of these two features in galaxies outside the Local Group. This finding is consistent with the unification model for Active Galactic Nuclei (AGNs), which predicts that an AGN torus seen pole-on should show a silicate emission feature in the mid-infrared. The strengths of the detected silicate emission features range from 0.12 to 1.25 times the continuum at 10μm and from 0.20 to 0.79 times the continuum at 18μm. The silicate grain temperatures inferred from the ratio of 18-to-10μm silicate features under the assumption of optically thin emission range from 140 to 220 K. Subject headings: galaxies: active — quasars: emission lines — galaxies: ISM — infrared: galaxies
منابع مشابه
The Distribution of Silicate Strength in Spitzer Spectra of Agns and Ulirgs
A sample of 196 AGNs and ULIRGs observed by the Infrared Spectrograph (IRS) on Spitzer is analyzed to study the distribution of the strength of the 9.7μm silicate feature. Average spectra are derived for quasars, Seyfert 1 and Seyfert 2 AGNs, and ULIRGs. We find that quasars are characterized by silicate features in emission and Seyfert 1s equally by emission or weak absorption. Seyfert 2s are ...
متن کاملDiscovery of 10 μ m silicate emission in quasars . Evidence of the AGN unification scheme
Discovery of 10 µm silicate emission in quasars. Evidence of the AGN unification scheme. Abstract. According to the unified scheme, AGN are surrounded by a dust-torus, and the observed diversity of AGN properties results from the different orientations relative to our line of sight. The strong resonance of silicate dust at 10 µm is therefore, as expected, seen in absorption towards many type-2 ...
متن کاملDiscovery of a very Lyman-α-luminous quasar at z = 6.62
Distant luminous quasars provide important information on the growth of the first supermassive black holes, their host galaxies and the epoch of reionization. The identification of quasars is usually performed through detection of their Lyman-α line redshifted to 0.9 microns at z > 6.5. Here, we report the discovery of a very Lyman-α luminous quasar, PSO J006.1240 + 39.2219 at redshift z = 6.61...
متن کاملEstimating the continuum of quasars using the articial neural networks
A lot of absorption lines are in the bluewards of Lyα emission line of quasar which is well-known as Lyαforest. Most of absorption lines in this forest belong to the Lyα absorption of the neutral hydrogen in the inter-galactic medium (IGM). For high redshift quasars and in the continuum with low and medium resolution, there are no many regions without absorption, so that, the quasar continuum i...
متن کاملFIRST REPORT ON PLATINUM-GROUP MINERALS IN CHROMITITES J%OM NORTHWESTERN NEYRIZ OPHIOLITE, IRAN
Electron-probe microanalyses and scanning electron microscopy of chrornitites from some ultramafic members of Neyriz ophiolite indicate that sulifides of platinum- group minerals (PGMs) occur as solid inclusions in chromite grains. Laurite with the general formula of (Ru ,Os ,lr ) S , and erlichmanite are the main identified sulfide phases. The PGMs occur as 4 to 20 microns euhedral to rect...
متن کامل