The planetary nebula M2-9: Balmer line profiles of

the nuclear region

Silvia Torres-Peimbert1

Anabel Arrieta2

Leonid Georgiev1

1 Instituto de Astronomía, UNAM, México2 Universidad Iberoamericana, México

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

Observations

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

We attempt to fit the complex line profiles of the Balmer series of the central object of M2-9

This presentation

Direct image and spectroscopy

[S II] 6717 [S II] 6731 [N II] 5755 He I 5876

H [N II] 6584 H [O III] 5007

Complex line profile of H Extended wings can be explained by Raman scattering:

• Ly 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

Firstly, we derive the systemic velocity Long slit spectrum of H 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).

North

arc

sec

Inte

nsi

ty

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

H/H intensity ratios and optical depth

Inte

nsi

tyR

ela

tive inte

nsi

ty

uncertainty

Observed H/H = 33.6

Derredened H/H = 17.4, corrected for Av = 2.7 mag, and R = 5.0, by fitting the rest of the H lines

We derive H ~ 14

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-3 to r-5 (steep density gradient)• Inner radius at ~10 Rstar

• Outer radius at ~1000 Rstar

• Rstar ~ 1 Rsun

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)

R/Rstar

v/vinfinityRadiation driven wind

Slow velocity gradientwind

1

Fit to M2-9 Balmer profiles

H

H

H

observed computed

M2-9 is not the only object with double H & H profiles

Some examples of other young PNe and symbiotic stars

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)

Conclusions (2)

The proposed expanding wind model 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 H/H/H

It may correspond to a transient wind in PPNe and symbiotic stars