Luciano Cerrigone1,2, Joseph L. Hora2, Grazia Umana1, Corrado Trigilio1

1 INAF, Catania Astrophysical Observatory, Italy2 Harvard-Smithsonian Center for Astrophysics, USA

Asymmetrical Planetary Nebulae IV, La Palma, June 17-22 2007

Radio and Infrared observations of Transition

Objects

Spectraltype

Luminosity

O B A F G K M

106 L

104 L

102 L

1 L

10-2 L

10-4 L

pre-Planetary Nebulae in the HR diagram

L. Cerrigone APN IV, La Palma June 17-22, 2007

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.

Radio continuum

Infrared

Ionized gas

Dust and molecular gas

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:

L. Cerrigone APN IV, La Palma June 17-22, 2007

Our project

•systematic differences between ionized and non ionized objects;

•relation between ionized gas and molecular gas or dust;

Very Large Array, array A

Frequency: 8.4 GHz

Resolution: 0.3’’

L. Cerrigone APN IV, La Palma June 17-22, 2007

VLA: High resolution radio maps

Spitzer: IRAC imaging

L. Cerrigone APN IV, La Palma June 17-22, 2007

~20’’

IRAC observations give us an upper limit on sizes: ~5’’

Extended structures have been detected in two targets

IRAS 18070-2346 IRAS 19590-12498.0 m 3.6 m

Spitzer: IRS spectra

L. Cerrigone APN IV, La Palma June 17-22, 2007

IRAS 22495+5134

[ArII][NeII]

PAH PAHSilicates

Silicates

Radio detectedtargets IRAS 20462+3416

[NeII]PAH

Silicates

PAH

Silicates

Spitzer: IRS spectra

L. Cerrigone APN IV, La Palma June 17-22, 2007

IRAS 20572+4919

IRAS 21289+5815

PAHSilicates

Silicates

Non radio detected targets

Target 6.2 [ArII] 7.7 8.5 10 [NeII] Radio

17364 x x

18379 x x x x

19306 x x x

21289 x x x

18062 x x x

19336 x x x x x x

19590 x x x x x x

20462 x x x x x x

22023 x x x x x x x

22495 x x x x x x

17203 x

19157 x

20572 x

17460 x x

17381 x x x x

17542 x x

18435 x

19200 x x x

01005 x x x x

06556 x x x x

6.2, 7.7, 8.5 m => PAH

10 m => silicates

[ArII] => 7.0 m; [NeII] => 12.8 m

Summary of spectral detections

L. Cerrigone APN IV, La Palma June 17-22, 2007

Silicates and radio

Silicates, PAH and radio

PAH, no radio

Silicates, PAH, no radio

Silicates, no radio

PAH and radio

IRAS 17423-1755

SEDs

L. Cerrigone APN IV, La Palma June 17-22, 2007

DUSTY parameters

Tstar= 20000 K

Chemistry: amorphous C

Tdust 1= 950 K; 1(0.55m)= 0.14

Tdust 2= 110 K; 2(0.55m)= 0.18

The combination of IR and radio (cm and mm) data provides us with a strong consraint on the sub-mm SED

IRAS 19590-1249

SEDs

L. Cerrigone APN IV, La Palma June 17-22, 2007

DUSTY parameters

Tstar= 24000 K

Chemistry: silicates

Tdust= 130 K

(0.55m)= 0.115

IRS spectrum overplotted in red

Mid-IR imaging

L. Cerrigone APN IV, La Palma June 17-22, 2007

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 m range (~0.5’’).The shown images are scaled to the same resolution.

MIRAC11.7 m

VLA3.6 cm

IRAS 22023+5249

Summary

L. Cerrigone APN IV, La Palma June 17-22, 2007

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.

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).