Bibcode
Flores-Durán, S. N.; Peña, M.; Hernández-Martínez, L.; García-Rojas, J.; Ruiz, M. T.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 568, id.A82, 8 pp.
Fecha de publicación:
8
2014
Revista
Número de citas
5
Número de citas referidas
5
Descripción
Context. The kinematics of planetary nebulae in external galaxies and in
our own is a clue for understanding the behavior of the low- and
intermediate-mass stars and their relation with other components of the
galaxies. Aims: By measuring precise radial velocities of
planetary nebulae (which belong to the intermediate-age population), H
ii regions and A-type supergiant stars (which are members of the young
population) in NGC 6822, we aim to determine whether both types of
population share the kinematics of the disk of H i found in this galaxy.
Methods: Spectroscopic data for six planetary nebulae were
obtained with the high spectral-resolution spectrograph Magellan Inamori
Kyocera Echelle (MIKE) on the Magellan telescope at Las Campanas
Observatory. Data for another three PNe and one H ii region were
obtained from the SPM Catalog of Extragalactic Planetary Nebulae, which
employed the Manchester Echelle Spectrometer attached to the 2.1m
telescope at the Observatorio Astronómico Nacional,
México. An additional PN and one H ii region were observed with
this same telescope-spectrograph in 2013. Thus, in total we have
high-quality data for 10 of the 26 PNe detected in this galaxy. In the
wavelength calibrated spectra, the heliocentric radial velocities were
measured with a precision better than 5-6 km s-1. Data for
two additional H ii regions and two A-type supergiant stars were
collected from the literature. The heliocentric radial velocities of the
different objects were compared to the velocities of the H i disk at the
same position. Results: From the analysis of radial velocities we
found that H ii regions and A-type supergiants do share the kinematics
of the H i disk at the same position, as expected for these young
objects. In contrast, most planetary nebula velocities differ
significantly (more than 12 km s-1) from that of the H i at
the same position. The kinematics of planetary nebulae is different from
the young population kinematics and is more similar to the behavior
shown by carbon stars, which are intermediate-age members of the stellar
spheroid existing in this galaxy. Our results confirm that there are at
least two very different kinematical systems in NGC 6822.
Based on data obtained at Las Campanas Observatory, Carnegie
Institution, Chile.Based on data collected at the Observatorio
Astronómico Nacional, SPM. B.C., México.
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