Radio and Infrared observations of Transition Objects

1. Radio and Infrared observations of Transition Objects Luciano Cerrigone1,2, Joseph L. Hora2, Grazia Umana1, Corrado Trigilio1 1 INAF, Catania Astrophysical Observatory, Italy 2 Harvard-Smithsonian Center for Astrophysics, USA Asymmetrical Planetary Nebulae IV, La Palma, June 17-22 2007

2. pre-Planetary Nebulae in the HR diagram Proto-PN spectra range from G to A types. The evolution continues towards hotter temperatures, then pre-PN are found as B spectral type sources. We selected a sample of post-AGB objects, then having far-infrared excess, optically classified as B stars. Luminosity 106 L 104 L 102 L 1 L 10-2 L 10-4 L Spectral type O B A F G K M APN IV, La Palma L. Cerrigone June 17-22, 2007

3. Our project Goal:contributing to explain the origin of non-spherical symmetry in PN and in general to understand the post-AGB to PN transition Method:inspecting envelope properties in a sample of transition objects and in particular: • systematic differences between ionized and non ionized objects; • relation between ionized gas and molecular gas or dust; Ionized gas Dust and molecular gas Radio continuum Infrared L. Cerrigone June 17-22, 2007 APN IV, La Palma

4. VLA: High resolution radio maps Very Large Array, array A Frequency: 8.4 GHz Resolution: 0.3’’ L. Cerrigone June 17-22, 2007 APN IV, La Palma

5. Spitzer: IRAC imaging IRAC observations give us an upper limit on sizes: ~5’’ Extended structures have been detected in two targets IRAS 18070-2346 8.0 mm IRAS 19590-1249 3.6 mm ~20’’ L. Cerrigone June 17-22, 2007 APN IV, La Palma

6. Spitzer: IRS spectra IRAS 22495+5134 Silicates [NeII] [ArII] PAH PAH Silicates Radio detected targets IRAS 20462+3416 Silicates PAH [NeII] PAH Silicates L. Cerrigone June 17-22, 2007 APN IV, La Palma

7. Spitzer: IRS spectra IRAS 20572+4919 Silicates Non radio detected targets IRAS 21289+5815 Silicates PAH L. Cerrigone June 17-22, 2007 APN IV, La Palma

8. Summary of spectral detections Silicates, PAH, no radio Silicates, PAH and radio Silicates, no radio Silicates and radio PAH, no radio PAH and radio 6.2, 7.7, 8.5 mm => PAH 10 mm => silicates [ArII] => 7.0 mm; [NeII] => 12.8 mm L. Cerrigone June 17-22, 2007 APN IV, La Palma

9. SEDs IRAS 17423-1755 DUSTY parameters Tstar= 20000 K Chemistry: amorphous C Tdust 1= 950 K; t1(0.55mm)= 0.14 Tdust 2= 110 K; t2(0.55mm)= 0.18 The combination of IR and radio (cm and mm) data provides us with a strong consraint on the sub-mm SED L. Cerrigone June 17-22, 2007 APN IV, La Palma

10. SEDs IRAS 19590-1249 DUSTY parameters Tstar= 24000 K Chemistry: silicates Tdust= 130 K t(0.55mm)= 0.115 IRS spectrum overplotted in red L. Cerrigone June 17-22, 2007 APN IV, La Palma

11. Mid-IR imaging We have performed mid-IR observations with MIRAC at the MMT Observatory. The Natural Star Adaptive Optics system allows nearly diffraction limited resolution in the 4 to 13 mm range (~0.5’’). The shown images are scaled to the same resolution. IRAS 22023+5249 MIRAC 11.7 mm VLA 3.6 cm L. Cerrigone June 17-22, 2007 APN IV, La Palma

12. Summary We are characterizing a sample of Transition Objects selected on the basis of their Far-Infrared and Optical properties (B spectral type with IR excess). • Radio and Infrared observations will allow us to: • build SEDs and detect the presence of different dust components; • inspect the chemistry of the sample and check for an evolutionary path within this phase. L. Cerrigone June 17-22, 2007 APN IV, La Palma