Table 2.
PN NGC 2818 and NGC 2818A OC physical properties.
| Parameter | PN NGC 2818 | Cluster NGC 2818A |
|---|---|---|
| RA (J2000) | 09:16:01.70 | 09:16:10.90 |
| Dec (J2000) | −36:37:38.75 | −36:38:02.00 |
| Apparent size (arcsec2) | 140 × 55 (1) | 450 (diameter) |
| Physical size (pc) | 2.24(±0.02) × 0.88(±0.01) | 3.6 ± 0.4 (radius) |
| Morphology | Bipolar | Open Cluster |
| Radial Velocity (km s−1) | 23.7, σ = 5.5 | 22.0 ± 1.3 |
| Distance (kpc) | 3.0 ± 0.8 (2) | 3.30 ± 0.03 |
| Reddening E(B − V) | 0.17 ± 0.08 (3) | 0.18 ± 0.02 (4) |
| Polar expansion velocity (km s−1) | 91, σ = 12 | |
| Equatorial expansion velocity (km s−1) | 42, σ = 6 | |
| Chemistry | Type I | [Fe/H] = −0.024 ± 0.015 (5) |
| Age | 11 ± 2 kyr | 955 ± 117 Myr |
| Cluster Turn-off Mass (M⊙) | 1.88 | |
| Nebular ionised mass (M⊙) | > 0.47 (6) | |
| Nebular electron temperature Te[NII] (K) | 11 500 ± 800 (7) | |
| Nebular electron density Ne (cm−3) | < 100 (8) | |
| Nebular absolute flux log(Hβ) (mW/m2) | −11.28 (9) | |
| CSPN Teff (kK) | 130 ± 12 (10) | |
| CSPN Zanstra T(HI) (kK) | 128 ± 39 | |
| CSPN Zanstra T(HeII) (kK) | 155 ± 47 | |
| Estimated CSPN Luminosity log L/L⊙ | 2.46 ± 0.14 (11) | |
| Proper motion pmRA (mas/yr) | −3.71 ± 0.19 | −4.421 ± 0.003 (12) |
| Proper motion pmDec (mas/yr) | 4.94 ± 0.18 | 4.548 ± 0.003 (12) |
| CSPN V magnitude | 19.04 ± 0.10 | |
| CSPN absolute magnitude MV | 5.9 ± 0.3 (13) | |
| CSPN initial mass (M⊙) | 2.33 ± 0.10 | |
| CSPN final mass (M⊙) | 0.58 ± 0.01 |
Notes. (1) The mean from Hα and [N II]λ6584 Å imaging from Derlopa et al. (2024). (2) Refers to the statistical PN distance from Frew et al. (2016). (3) As obtained from Frew et al. (2016). (4) Using the Cardelli et al. (1989) extinction law with Rv = 3.1. (5) metallicity Z = 0.0144 ± 0.0005 for Z⊙ = 0.0152. (6) Estimated following Corradi et al. (2015). (7) From Dufour (1984). (8) Average electron density derived from the observed [S II]λ6731/6716 Å ratio from all pointings assuming Te = 11 500 K. (9) As obtained from Bucciarelli & Stanghellini (2023). (10) Estimated from the Miller Bertolami (2016) evolutionary tracks for Z = 0.01. (11) For Teff = 130 kK. (12) From Gaia DR3 average of cluster members with membership probability > 0.9 from van Groeningen et al. (2023). (13) As derived for the adopted cluster distance and nebular reddening.
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