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ANGULAR EXPANSION IN PLANETARY NEBULAE FROM RADIO INTERFEROMETRIC DATA

ANGULAR EXPANSION IN PLANETARY NEBULAE FROM RADIO INTERFEROMETRIC DATA. Yolanda Gómez. Centro de Radioastronomía y Astrofísica, UNAM México. Colaborators. Lizette Guzmán (CRyA, UNAM, México) Luis F. Rodríguez (CRyA, UNAM, México). Angular expansion technique.

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ANGULAR EXPANSION IN PLANETARY NEBULAE FROM RADIO INTERFEROMETRIC DATA

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  1. ANGULAR EXPANSION IN PLANETARY NEBULAE FROM RADIO INTERFEROMETRIC DATA Yolanda Gómez Centro de Radioastronomía y Astrofísica, UNAM México

  2. Colaborators • Lizette Guzmán (CRyA, UNAM, México) • Luis F. Rodríguez (CRyA, UNAM, México) Asymmetrical Planetary Nebulae IV, La Palma, España

  3. Angular expansion technique • A geometrical method in which we substract two images, taken over a period of a few years, to estimate the angular expansion rate of the nebula, • First applied by Masson (1986) to radio interferometric data to estimate distances to PNe. v D=v/ D Asymmetrical Planetary Nebulae IV, La Palma, España

  4. Some examples (Masson 1986; 1989) NGC 7027 • This technique has been applied with success to several PNe: e.g. NGC6302(Gómez et al. 1993) , NGC6572(Hajian et al. 1995) , Vy 2-2(Christianto & Seaquist 1998). • For PNe with distances > 1 kpc the expected angular expansion rate is < 2 mas/yr. Asymmetrical Planetary Nebulae IV, La Palma, España

  5. Planetary Nebula M 2-43 (Guzmán, Gómez & Rodríguez 2006) 1999.72+1995.65 This is the largest distance for a PN measured, up to now, with the angular expansion technique. 1999.72–1995.65 VLA 3.6 cm See poster by Guzmán et al. Asymmetrical Planetary Nebulae IV, La Palma, España

  6. Other application for the angular expansion technique Asymmetrical Planetary Nebulae IV, La Palma, España

  7. The “Saturn Nebula” NGC 7009 • The ansae (handles) are present in PNe with bipolar, rotating, episodic jets ( BRETS; e.g. López et al. 1995) and fast, low ionization emission regions (FLIERS; Balick et al. 1993). • In NGC 7009 the ansae are moving at about 100 km/s in the plane of the sky, relative to the nucleus (Reay & Atheton 1985; Balick et al. 1987). • The ansae are possibly the termination points of the jets (Balick et al. 1987; López et al. 2000; Steffen et al. 2001). ansae HST Red [NII]; green [OIII]; blue [He II] Asymmetrical Planetary Nebulae IV, La Palma, España

  8. Proper motions of ansae Optical • Few measurements of proper motions of ansae: KjPn 8 (Meaburn 1997), Hen 2-90 (Sahai et al. 2002), NGC7009 (Fernández et al. 2004). • NGC 7009: From photographic plates a PM of 16 3 mas/yr (Liller 1965) From HST images a PM for the eastern ansa of 28 8 mas/yr (Fernández et al. 2004) is derived. NGC 7009 HST images of the east ansa (Fernández, Monteiro & Schwarz 2004) Asymmetrical Planetary Nebulae IV, La Palma, España

  9. Applying the angular expansion technique to NGC 7009 to measure proper motions of the ansae at radio. • Archive VLA data for NGC 7009 at 3.6 cm in two epochs: 1989.24 and 1997.33 VLA Observations VLA 3.6 cm NGC 7009 Asymmetrical Planetary Nebulae IV, La Palma, España

  10. Ansae proper motions 23 +/- 6 mas/yr Eastern 34 +/- 10 mas/yr (Rodríguez & Gómez 2007, RevMexAA, 43, 173) Western Asymmetrical Planetary Nebulae IV, La Palma, España

  11. Derived parameters for the ansae NGC 7009 • Assuming D= 860 +/- 340 pc, the velocities of the ansae in the plane of the sky are: EAST ansa 100 +/- 50 km/s WEST ansa 140 +/- 70 km/s • If the ansae are moving ballistically the estimated age is: ~300 years if they originated from the main body ~850 years if they originated from the central star. Asymmetrical Planetary Nebulae IV, La Palma, España

  12. Upper limit to the expansion • The flux density of the main body remains constant. • The flux density of the jets decreased in 30%. With an electron density 1000 – 4000 cm-3(Bohigas et al. 1994; Goncalves et al. 2003) the recombination timescales are between 30 to 120 yrs. D 700 pc Lower limit consistent with the average of 14 available values (Acker et al. 1992; Fernández et al. 2004), 860 +/- 340 pc. Difference image Asymmetrical Planetary Nebulae IV, La Palma, España

  13. Conclusions • Interferometric data taken with a few years of separation can reveal the angular expansion of the nebula and it is possible to estimate its distance (e.g. M 2-43; Guzmán et al. 2006). • This is the first time that proper motions of ansae in PNe are determined with radio observations (NGC 7009; Rodríguez & Gómez 2007). Asymmetrical Planetary Nebulae IV, La Palma, España

  14. Thank you Asymmetrical Planetary Nebulae IV, La Palma, España

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