A Tale of Three Galaxies: Anomalous Dust Properties in IRAS F10398+1455, IRAS F21013-0739, and SDSS J0808+3948
Abstract
On a galactic scale, the 9.7 μm silicate emission is usually only seen in type 1 active galactic nuclei (AGNs). They usually also display a flat emission continuum at ~5-8 μm and the absence of polycyclic aromatic hydrocarbon (PAH) emission bands. In contrast, starburst galaxies, luminous infrared (IR) galaxies, and ultraluminous IR galaxies exhibit a red 5-8 μm emission continuum, strong 9.7 μm and 18 μm silicate absorption features, and strong PAH emission bands. Here, we report the detection of anomalous dust properties by the Spitzer/Infrared Spectrograph in three galaxies (IRAS F10398+1455, IRAS F21013-0739, and SDSS J0808+3948) which are characterized by the simultaneous detection of a red 5-8 μm emission continuum, the 9.7 and 18 μm silicate emission features, as well as strong PAH emission bands. These apparently contradictory dust IR emission properties are discussed in terms of iron-poor silicate composition, carbon dust deficit, small grain size, and low dust temperature in the young AGN phase of these three galaxies.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2014
- DOI:
- 10.1088/2041-8205/794/2/L19
- arXiv:
- arXiv:1407.0914
- Bibcode:
- 2014ApJ...794L..19X
- Keywords:
-
- dust;
- extinction;
- galaxies: active;
- galaxies: individual: IRAS F10398+1455 IRAS F21013–0739 SDSS J0808+3948;
- infrared: galaxies;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- accepted for publication in ApJL