The planetary nebula M2-9: Balmer line profiles of the nuclear region

1. The planetary nebula M2-9: Balmer line profiles of the nuclear region Silvia Torres-Peimbert1 Anabel Arrieta2 Leonid Georgiev1 1 Instituto de Astronomía, UNAM, México 2 Universidad Iberoamericana, México

2. M2-9, a young PN • Extreme bipolarity • Weak emission point symmetric at 60" from the nucleus • The inclination angle relative to the plane of the sky is of 15° and is located at a distance of 650 pc (Schwarz et al. 1997) • The condensations have shown motions parallel to the equatorial plane of 1“ in 10 years

3. This presentation Observations We attempt to fit the complex line profiles of the Balmer series of the central object of M2-9 • 2.1-m telescope San Pedro Mártir, BC f/7.5 • Echelle spectrograph R=5,000 to 18,000 for 3600-6800 Å • 1024x1024 pixels • Spatial resolution 0.99´´/pix • Spectral resolution less than 10.6 km/s

4. Direct image and spectroscopy Ha [N II] 6584 Hb [O III] 5007 [S II] 6717 [S II] 6731 [N II] 5755 He I 5876

5. Complex line profile of Ha • Extended wings can be explained by Raman scattering: • Lyb photons converted to optical photons • Requires column density of the scattering region of NHI ~ 1020 cm-2 • (Arrieta et al. 2003) • 6545A line is Raman scattered 1025A He II line (Lee, Kang & Byun 2001) • Our purpose is to explain the double profile of the core of the line

6. North arcsec Intensity Firstly, we derive the systemic velocity Long slit spectrum of Ha profile. To determine the systemic velocity it has been assumed that knots N3 and S3 are moving at V % R. A systemic velocity of 40 km/s is derived which corresponds to +61 km/s heliocentric velocity. Heliocentric velocity of +69.2 km/s (Smith et al. 2005).

7. Balmer and Paschen line profiles 3 - 2 4 - 2 5 - 2 6 - 2 7 - 2 9 – 3 11 - 3 12 - 3 14 - 3 15 - 3 • The observed profiles are: • asymmetric • there is a decrease in the blue/red velocity difference for the higher series lines

8. Intensity uncertainty Relative intensity Ha/Hintensity ratios and optical depth Observed Ha/H = 33.6 Derredened Ha/H = 17.4, corrected for Av = 2.7 mag, and R = 5.0, by fitting the rest of the H lines We derive tHa ~ 14

9. We propose a toy model to fit the profile of the core of the Balmer lines, • We derive line profiles by assuming simple geometry, density and velocity laws • We obtain the source function from Sobolev´s approximation and solve 3D radiative transfer (Georgiev & Koenigsberger 2004) • For a disk viewed in profile • v % r (expanding wind) • r % r-3 to r-5 (steep density gradient) • Inner radius at ~10 Rstar • Outer radius at ~1000 Rstar • Rstar ~ 1 Rsun

10. v/vinfinity Radiation driven wind Slow velocity gradient wind R/Rstar 1 Sample of model profiles(for the core of the lines) The critical condition is a slow velocity gradient wind, not a classical radiation driven wind The profile is not sensitive to the shape of the disk (it could also be spherically symmetric)

11. Ha Hb Hg Fit to M2-9 Balmer profiles observed computed

12. M2-9 is not the only object with double Ha & Hb profiles Some examples of other young PNe and symbiotic stars

13. Conclusions (1) • Preliminary radiative transfer models have been computed to explain the hydrogen line profiles in M2-9. They require: • disk surrounding the central star from 1012 – 1015 cm • steep density law • rather flat velocity gradient (not classical radiatively accelerated wind)

14. Conclusions (2) • The proposedexpanding windmodel is compatible with: • the asymmetry of the profiles • the difference between the profiles of the Balmer series • the blue/red velocity difference between components • the optical depth of Ha/Hb/Hg • It may correspond to a transient wind in PPNe and symbiotic stars