Extragalactic PNe: methods of discovery using infrared photometry

1. Extragalactic PNe: methods of discovery using infrared photometry Pedro García-Lario, Amelia Bayo & Carlos Alfageme ESA/ISO Data Centre, VILSPA Madrid, Spain

2. Outline 1. A bit of history 2. The IRAS revolution 3. The ISO’s view 4. PNe in the near-infrared 5. PNe as seen by MSX and 2MASS 6. Extrapolation to other galaxies 7. The future 8. Conclusions

3. A bit of history • PNe are known to be strong infrared emitters since the 1960’s -First detection of an infrared excess at 10 microns in NGC 7027 (Gillet et al. 1967) - IRC Catalogue @ 2.2 microns (first all-sky survey) shows infrared excess in red Miras, some of them invisible in the optical! (Neugebauer & Leighton 1969) - Detection of double-peaked OH maser emission at 1612 MHz in optically invisible Miras (‘OH/IR stars), identified as precursors of planetary nebulae (Wilson & Barrett 1968) - AFGL catalogue (all-sky survey at 4.2, 11.0, 19.8, and 27.4 microns) (Price & Walker 1976) - Ground-based mid-infrared (8-20 microns) observations of planetary nebulae (Cohen & Barlow 1974, 1980) - Airborne stratospheric observatories like KAO (several flights since 1976 observing in the range 37-110 microns) (Moseley 1980)

4. The IRAS revolution • All-sky survey in four broad photometric bands centred at 12, 25, 60 and 100 microns, launched in 1983 (250,000 sources in the IRAS Point Source Catalogue) -F > 0.5 Jy at 12, 25 and 60 microns; - F > 1.5 Jy at 100 microns; - poor spatial resolution; confusion close to the GC • Additional spectra (LRS) in the range 7.7-13.4 + 11.0-22.6 microns of the strongest sources (5425 sources automatically extracted) - F>10 Jy at 12 microns; • 90% completeness for F> 28 Jy at 12 microns • R ~ 20-60

5. The IRAS revolution Region V is mostly populated by PNe (Van der Veen & Habing 1989)

6. The IRAS revolution • AGB stars follow a well-defined sequence in the IRAS [12]-[25] vs. [25]-[60] colour-colour diagram in their way to become planetary nebulae(van der Veen & Habing 1989) • Strong differences as a function of the dominant chemistry in the circumstellar shell (carbon-rich vs. oxygen-rich) • Planetary nebulae show characteristic infrared colours, corresponding to dust temperatures of 100-150 K(Pottasch et al. 1988) • First systematic searches for new planetary nebulae based on IRAS photometry(Preite-Martinez 1988; Garcia-Lario 1992)

7. The IRAS revolution Pottasch et al. (1988)

8. The IRAS revolution • The GLMP Catalogue of IRAS sources with colours like Planetary Nebulae(Garcia-Lario et al. 1997) • Selection criteria: • FQUAL  3 at 25 and 60 microns; FQUAL  2 at 12 microns • F (12) / F (25)  0.50 • F (25) / F (60)  0.35 • If FQUAL (100 microns)  2 ; F (60) / F (100)  0.60 • 1084 sources; 47% previously identified in the literature • 50% were PNe • 27% were OH/IR stars or post-AGB stars • A small contamination from YSO’s, Ultra-compact HII regions, Vega-like stars and Seyfert galaxies (in total less than 24%)

9. The IRAS revolution Distribution of identified sources in the GLMP catalogue Garcia-Lario et al. (1997)

10. The IRAS revolution Distribution of newly classified sources in the GLMP catalogue Mainly precursors! Garcia-Lario et al. (1997)

11. The IRAS revolution • IRAS colours are a very efficient way to search for planetary nebulae candidates but…. • Strong bias towards young planetary nebulae and precursors • Open questions: • How to distinguish planetary nebulae from their precursors? • Can JHK near-infrared photometry help? • Can these or similar criteria be applicable to other infrared surveys?

12. The ISO’s view C-rich O-rich • SWS + LWS (2-200 microns) • Relative contribution of: Dust thermal emission Nebular emission lines Solid state features • Two well-defined evolutionary sequences as a function of the dominant chemistry in the shell

13. The ISO’s view C-rich PN (young)

14. The ISO’s view O-rich PN (old)

15. PNe in the near-infrared Many PNe show a characteristic excess in the J-band ! J-H > 0.2 H-K >0.4 Useful to search for intermediate excitation PNe Garcia-Lario et al. (1997)

16. PNe as seen by MSX • Mid-Course Space Experiment (MSX), launched in 1999 • Galactic plane (|b|  6 degrees) survey at 4 main photometric bands centred at 8, 11, 14 and 21 microns (A,C,D and E bands) -Similar sensitivity to IRAS 12 and 25 micron bands - better spatial resolution; less confusion - good to detect GC PNe? • Plus a few high galactic latitude areas including the LMC, the SMC and a few nearby galaxies of the Local Group • MSX Point Source Catalogue v6 contains more than 400,000 sources (how many of them new PNe?) • Can we use a similar approach to the one used for IRAS in order to search for new PN candidates?

17. Galactic PNe as seen by MSX 32,409 sources with good quality MSX photometry in A,C and D bands 90% of them with no Identification in SIMBAD

18. Galactic PNe as seen by MSX Only 10% (3,278 sources) of them were well identified in SIMBAD 155 sources identified as PNe or Post-AGB stars (~4.7% of the identified sources)

19. Galactic PNe as seen by MSX PNe and Post-AGB stars strongly concentrated in region defined by: [A] - [C]  0.7 [C] – [D]  0.7 Populated by 1,372 sources 400 sources well identified (~40% PNe or Post-AGB stars) 972 sources not identified Strong contamination by YSO’s

20. Galactic PNe as seen by MSX • s 15,068 sources with good quality MSX photometry in A,C,D and E bands Normal stars are eliminated by considering only good quality detections in the E` band

21. Galactic PNe as seen by MSX Again, stronger concentration of PNe and Post-AGB stars in region defined by: [A] - [C]  0.7 [C] – [D]  0.7 Populated by 1,042 sources But still not enough; only ~40% of PNe and Post-AGB stars among the 312 well identified sources in this group. Strong contamination by YSO’s • s

22. Galactic PNe as seen by MSX An additional selection criterium to avoid YSO’s: |b|  2 degrees  9,884 sources well detected in A,C and D bands  1,304 sources well identified 922 (71%) AGB stars 284 (22%) Stars 67 (5%) PN/PAGB 26 (2%) YSO’s 5 (<1%) Galaxies

23. Galactic PNe as seen by MSX Adding the selection criteria: [A]-[C]  0.7 [C]-[D]  0.7  Only 67 sources well identified 16 AGB stars 1 Star • PN/PAGB (~69%) 3 YSO’s 2 Galaxies Large majority of PNe!

24. Galactic PNe as seen by MSX An additional selection criterium to avoid YSO’s: |b|  2 degrees  4,305 sources well detected in A,C,D and E bands  764 sources well identified 616 (80%) AGB stars 61 (8%) Stars 61 (8%) PN/PAGB 21 (<3%) YSO’s 5 (~1%) Galaxies

25. Galactic PNe as seen by MSX Adding the selection criteria: [A]-[C]  0.7 [C]-[D]  0.7  Only 66 sources well identified 15 AGB stars 1 Star • PN/PAGB (~69%) 3 YSO’s 2 Galaxies Large majority of PNe!

26. Galactic PNe as seen by MSX We can do the same with other MSX colour-colour diagrams Using the [A] – [C] vs. [D] – [E] diagram we obtain very similar results

27. Galactic PNe as seen by MSX Again, PN/Post-AGB stars are strongly concentrated in a well defined region of the diagram Can a similar analysis be done on extragalactic sources detected by MSX?

28. Extragalatic PNe as seen by MSX Some good candidates found in the LMC Some are well known LMC Pne Others will need follow-up observations

29. Extragalactic PNe as seen by MSX Only a few in the SMC

30. Extragalactic PNe as seen by MSX • su Number of sources need to be substantially increased Use of not so good quality observations?

31. Extragalactic PNe as seen by MSX Use of other MSX colour-colour diagrams give very similar results, as for the galactic PNe

32. Extragalactic PNe as seen by MSX

33. Extragalactic PNe as seen by MSX

34. ..and what about 2MASS? - All-sky ground-based near-infrared survey (JHK photometry for ~470 million entries in the Point Source Catalogue) - Selection criteria: • J < 14.0 mag • Good quality (AAA) in all three bands • J – H < 0.2 • H – K > 0.4 • No confusion flags (to avoid binary systems formed by cool+hot star) • Only 535 2MASS sources satisfy the above criteria • 73 of them were also detected by MSX and 26 have the right colours expected for a PN ! Some of them are well known PNe. Follow-up observations needed for the rest • Extend this search to fainter sources and to the Magellanic Clouds

35. The (near) future • ASTRO-F survey (launch in August 2005) • All-sky survey at 50-110 microns (several narrow and broad bands in this wavelength range) as main goal (sensitivity ~0.1 Jy) • Possibly complemented with a mid-IR all-sky survey at 9 and 19 microns (sensitivity of 40 mJy and 80 mJy, respectively) still under study • Deeper observations of some high galactic latitude regions, including the Magellanic Clouds • Dedicated observations using specific filters with: • VISIR@VLT • Spitzer Space Telescope • In a more distant future… • JWST, Spica, …

36. Conclusions • Infrared colour-colour diagrams are a powerful tool to search for PNe and their immediate precursors in the Galaxy • Better sensitivity and higher spatial resolution will soon allow the application of similar colour criteria to search for planetary nebulae in nearby galaxies • Multi-wavelength observations covering the whole infrared spectral range are desirable. In some cases, follow-up observations in other spectral ranges will still be necessary to confirm candidate sources.