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Distances to PNe using angular expansion parallax

Distances to PNe using angular expansion parallax. Lizette Guzman-Ramirez (JBCA, University of Manchester) Yolanda Gomez and Laurent Loinard (CRyA, UNAM, Mexico) 41st YERAC University of Manchester/Jodrell Bank Observatory, 18-20 July 2011. Why distances are important?.

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Distances to PNe using angular expansion parallax

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  1. Distances to PNe using angular expansion parallax Lizette Guzman-Ramirez (JBCA, University of Manchester) Yolanda Gomez and Laurent Loinard (CRyA, UNAM, Mexico) 41st YERAC University of Manchester/Jodrell Bank Observatory, 18-20 July 2011

  2. Why distances are important? • Essential parameter for studying the stellar and nebular parameters as well as the evolution of the central star. • While the total number of PNe in the Milky Way has been estimated to be somewhere between 5000 and 25,000, less than 50 have distances with reasonable accuracy. • Used to measure the rotational curve in other galaxies, dark matter halos and using the PNLF estimate the distance to this galaxies.

  3. PNe • M2-43 [WC8] • Distance estimations 1.4 kpc (Cahn et al. 1992) to 4.45 kpc (Van de Steen et al. 1994b) • IC 418 • Distances estimations 0.36 kpc (Acker et al. 1978) to 5.74 kpc (Phillips et al. 1984) • NGC 6881 • Distance estimations 1.5 kpc (Cahn et al. 1984) to 6.4 kpc (Zhang et al. 1995)

  4. Angular Expansion in Radio • Masson (1986), was the first person to use this technique. • Observed NGC 7027 in two epochs with a 2.8 years gap. • Because you are trying to observe very small changes in the nebula, this technique requires very high resolution data. • Interferometry is the way to go.

  5. M2-43 • VLA-A, 1995.65 & 1999.72 • At 8Ghz (3.6 cm) • Angular resolution of 0.3” • t=4.07 yr Model

  6. IC 418 • VLA-B, 1986.49 & 2007.85 • At 5GHz (6 cm) • Angular resolution of 3” • t=21.36 yr

  7. NGC 6881 • VLA-A, 1984.99 & 1994.24 • At 4.8GHz (6 cm) • Angular resolution of 0.8” • t=9.25 yr

  8. Angular Expansion d/dt = /t, where  is the size of the nebula (“) and t is the difference between the two epochs. • M2-43 d/dt = 0.61 +/- 0.09 mas/yr. • IC418 d/dt = 5.80 +/- 1.50 mas/yr. • NGC 6881 d/dt = 2.10 +/- 0.70 mas/yr. D = 211(vexp / d/dt ), • M2-43 D = 6.9 +/- 1.5 kpc. • IC 418 D = 1.3 +/- 0.4 kpc. • NGC 6881 D = 1.6 +/- 0.5 kpc.

  9. Important Parameters NGC 6881 • Ionised Mass Mion = 0.002 M • Electronic Density ne = 5 x 104 cm-3 • Emission Measure EM = 28 x 106 cm-6pc • Kinematic Age T = 350 yr M2-43 • Ionised Mass Mion = 0.03 M • Electronic Density ne = 1.1 x 105 cm-3 • Emission Measure EM = 4 x 108 cm-6pc • Kinematic Age T = 500 yr IC 418 • Ionised Mass Mion = 8.7 M • Electronic Density ne = 6.2 x 103 cm-3 • Emission Measure EM = 5 x 106 cm-6pc • Kinematic Age T = 1200 yr

  10. Conclusions and Future Work • Distances are important! • Angular expansion technique give us reliable distances with a good accuracy. • Proposal for eMerlin for a few more objects that have already been observed so we only need a second epoch.

  11. Thank you!

  12. Radial velocity • M2-43, radial velocity of 111 +/- 40 km/s (Schneider et al., 1983), • Galactic model from Brand & Blitz (1993).

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