1. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 1 o The use of PNe precursors in the study of Diffuse Interstellar Bands The use of PNe precursors in the study of Diffuse Interstellar Bands ¹ ESA/ISO Data Centre. ESAC, Madrid, Spain ² E. Politécnica Superior de Alcoy, Spain Pedro García-Lario¹, Ramon Luna² & M.A. Satorre² In collaboration with: H. van Winckel, M. Reyniers (K.U. Leuven); O. Suárez (INTA/LAEFF); B. Foing, N. Boudin (ESA/ESTEC)

2. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 2 –Diffuse Interstellar Bands (DIBs) are bands of variable strength and width of still unknown origin which appear overimposed on the spectra of bright but heavily reddened stars –Discovered in the early 1900’s ! but still unknown origin (presumed interstellar because of their correlation with dust extinction) What are DIBs ? From P. Jenniskens Adapted from P. Jenniskens

3. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 3 –More than 300 catalogued (McCall et al. 2002) from UV to near- infrared wavelengths (3600 -10200 Å) –The most studied ones: 4430 Å, 5780, 5797 Å, 6284 Å –Many carriers proposed; none convincing –A major challenge for spectroscopists, astronomers, and physicists What do we know about DIBs ?

4. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 4 –Detection of substructures in the profiles of several DIBs indicates the molecular nature of some DIB carriers (e.g. 5797, 6379 and 6614 Å ) (Kerr et al. 1998) What are their carrier(s) ?

5. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 5 –Existence of `families’ of DIBs suggest not a unique carrier (Krelowski & Walker 1987) Families of DIBS: 1: 4430, 6180 2: 5780, 6196, 6203, 6269, 6284 3: 5797, 5850, 6376, (2200) What are their carrier(s) ?

6. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 6 –Interstellar origin supported by correlation with reddening found in galactic early-type stars, measured as E(B-V) (Herbig 1995) Prototypical star: HD 183143 What are their carrier(s) ? DBEW/E(B-V)FWHM 57800.442.2 57970.131.1 58500.0451.1 61960.0440.90 62841.14.5 63790.0671.1 66140.201.2 69930.101.6 72240.201.3

7. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 7 –They are ubiquitous; detected towards a wide variety of astronomical sources –Most promising hypothesis: large carbon-bearing molecules: Long carbon chains? (Douglas 1977) PAH cations? (Allamandola et al. 1998; Salama et al. 1999) Fullerenes? (Foing & Ehrenfreund 1997) What are their carrier(s) ?

8. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 8 –There are strong evidences that the relative strength of DIBs are correlated with the properties of the clouds in the line of sight –Environmental dependence of DIBs may reflect an interplay of ionization, recombination, dehydrogenation and destruction of chemically stable, carbonaceous species (Salama et al. 1996) –Investigations of DIBs in regions of different metallicity, chemical properties and UV radiation field may allow us to constrain the physico-chemical properties of the (different) DIB carriers. –Difficult to probe the ISM along a given line of sight; usually this is a combination of many different clouds with inhomogeneous properties and complex morphologies What else can we do?

9. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 9 –Are there also Diffuse Circumstellar Bands (DCBs) ? –First suggested by Le Bertre & Lequeux (1993) –Circumstellar shells around low- and intermediate-mass evolved stars are a ‘natural’ environment where DB carriers may form. –They are among the most important contributors of gas and dust to the ISM –Dense outflows of cool C-rich AGB stars are the best candidates –Observational problems because of the presence of strong molecular bands in their optical spectra; difficult to model stellar continuum; complex photospheres –Thus… No attempt yet made for a systematic search for DCBs –Ways around to address the problems needed (IRC +10º216) unsuccessful What about circumstellar DIBs?

10. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 10 –Diffuse Interstellar Bands (DIBs) are Search for DCBs in AGBs IRC +10º 216, Kendall 2002 12.4’ 2’

11. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 11 –Diffuse Bands (DBs) may potentially be detected also towards post-AGB stars –Post-AGB stars show a wide range of spectral types (from M to B) in their way to become PNe –High galactic latitude helps! –For many of them we know the chemical composition of the dust grains (ISO, mm/submm, radio) –Some results on individual post- AGB stars look promising (Zacs et al. 1999, 2001; García-Lario et al. 1999; Klochkova et al. 2000) A way around: post-AGB stars post-AGB

12. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 12 DBs in post-AGB stars (Zacs et al. 1999)

13. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 13 Not always so simple… Not the 5850 Å DB !

14. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 14 –9 of the strongest Diffuse Interstellar Bands (DIBs) were investigated in a sample of 33 post-AGB stars –Spectral types: B – G –A mixture of C-rich and O-rich stars (chemistry derived from ISO data in most cases; also from submm and/or radio observations) –Wide range of galactic latitudes and overall extinction –high-radial velocity stars were favoured (to help discrimination of ISM vs. CSE features) –Several runs using 5 telescopes at three different observatories ESO/La Silla (ESO 1.52m/FEROS + ESO NTT/EMM) ESO/Paranal (VLT/UVES) Roque de los Muchachos, La Palma (TNG/SARG + WHT/UES) –Spectral resolution  50,000; most of the observations so far analyzed were initially taken for other purposes A systematic search for DBs

15. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 15 A systematic search for DBs Recalculation of EW / E(B-V) dependence using a sample of 53 reddened stars of early spectral type (Thorburn et al. 2003) At 5780, 5797, 6196, 6284, 6379 and 6614 Å Original spectroscopic data R  38000

16. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 16 A systematic search for DBs Recalculation of EW/E(B-V) dependence using 4 reddened early type stars (Jenniskens et al. 2003) At 5850, 6196 and 7224 Å Original spectroscopic data: R  20000 EW = α· E(B-V) DBrEW/E(B-V) 57800.650.46 57970.700.19 58500.960.050 61960.790.053 62840.741.05 63790.590.093 66140.780.21 69930.950.12 72240.990.25 EW/E(B-V) 0.44 0.13 0.045 0.044 1.1 0.067 0.20 0.10 0.20 HD 183143

17. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 17 ISM vs. CS extinction Overall extinction = ISM contribution + CS contribution

18. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 18 A systematic search for DBs Old Observations available IRAS 04296+3429IRAS 12175-5338IRAS 17436+5003IRAS 20462+3416 IRAS 05113+1347IRAS 16594-4656IRAS 18025-3906IRAS 22023+5249 IRAS 05341+0852IRAS 17086-2403IRAS 18062+2410IRAS 22223+4327 IRAS 06530-0213IRAS 17097-3210HD 172324IRAS 22272+5435 IRAS 07134+1005IRAS 17150-3224IRAS 19114+0002IRAS 23304+6147 IRAS 08005-2356IRAS 17245-3951IRAS 19386+0155 IRAS 08143-4406IRAS 17395-0841IRAS 19500-1709 IRAS 08544-4431IRAS 17423-1755IRAS 20000+3239 September 2003 observations IRAS 01005+7910IRAS Z02229+6208IRAS F05251-1244IRAS 19200+3457 June 2004 observations (under analysis) IRAS 17023-1534IRAS 17364-1238IRAS 18379-1707IRAS 21153-6842 IRAS 17074-1845IRAS 17381-1616IRAS 18442-1144IRAS 21190+5140 IRAS 17195-2710IRAS 17542-0603IRAS 20572+4919IRAS 21546+4721

19. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 19 A systematic search for DBs t tt

20. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 20 The DB at 6284 Å IRAS 19500-1709 E(B-V) = 0.37 IRAS 22023+5249 E(B-V) = 0.52

21. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 21 No clear correlation between EW and E(B-V) in P-AGB stars Many stars show values well below the expectations Some DBs are not even detected in strongly reddened P-AGB stars DB strength vs. E(B-V)

22. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 22 In general, DCS PAGB stars show always the lower values Non-detections at high E(B-V) are only found in DCS PAGB stars Non-DCS PAGB stars show values which are in many cases consistent with the values expected for ISM DIBs DB strength vs. E(B-V)

23. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 23 The DB at 6284 Å

24. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 24 The DB at 5780 Å

25. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 25 The DB at 5797 Å

26. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 26 The DB at 6614 Å

27. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 27 The DB at 7224 Å

28. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 28 Analysis of radial velocities Na D 2 5896 Å

29. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 29 Analysis of radial velocities

30. Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 30 –The strength of 9 of the strongest DBs has been systematically searched and analysed in a sample of 33 PAGB stars. –They are found to be extremely weak as compared to the results obtained in other samples of reddened stars –The effect is more clearly observed in P-AGB stars dominated by circumstellar extinction –Our results suggest that DIBs are not formed (yet) in the circumstellar shells around PAGB stars –If connected with PAHs, as suggested in the literature, their carriers must form at a later stage as the result of their processing by the hard UV field in the ISM –Their identification as strongly ionized PAHs and/or radicals liberated from carbonaceous species as a consequence of photoevaporation of dust grains in the ISM would be consistent with our observations –Interesting to observe CSPNe with various dominant chemistries and a lot of internal extinction! Conclusions