An imaging and spectroscopic study of the planetary nebulae in NGC 5128 (Centaurus A)
1 European Southern Observatory, Karl-Schwarzschild Strasse 2, 85748 Garching, Germany
e-mail: email@example.com; firstname.lastname@example.org
2 Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching, Germany
3 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHJ, UK
Received: 30 May 2014
Accepted: 8 September 2014
Context. Planetary nebulae (PNe) are excellent tracers of the common low mass stars through their strong and narrow emission lines. The velocities of large numbers of PNe are excellent tracers of galaxy kinematics. NGC 5128, the nearest large early-type galaxy, offers the possibility to gather a large sample.
Aims. Imaging and spectroscopic observations of PNe in NGC 5128 were obtained to find and measure their velocities. Combined with literature data, a large sample of high quality kinematic probes is assembled for dynamical studies.
Methods. NTT imaging was obtained in 15 fields in NGC 5128 across 1° with EMMI and [O III] and off-band filters. Newly detected sources, combined with literature PN, were used as input for FLAMES multi-fibre spectroscopy in MEDUSA mode. Spectra of the 4600–5100 Å region were analysed and velocities measured based on [O III]4959, 5007 Å and often Hβ.
Results. The chief results are catalogues of 1118 PN candidates and 1267 spectroscopically confirmed PNe in NGC 5128. The catalogue of PN candidates contains 1060 PNe discovered with NTT EMMI imaging and 58 from literature surveys. The spectroscopic PN catalogue has FLAMES radial velocity and emission line measurements for 1135 PNe, of which 486 are new. Another 132 PN radial velocities are available from the literature. For 629 PNe observed with FLAMES, Hβ was measured in addition to [O III]. Nine targets show double-lined or more complex profiles, and their possible origin is discussed. FLAMES spectra of 48 globular clusters were also targetted: 11 had emission lines detected (two with multiple components), but only 3 are PNe likely to belong to the host globular.
Conclusions. The total of 1267 confirmed PNe in NGC 5128 with radial velocity measurements (1135 with small velocity errors) is the largest collection of individual kinematic probes in an early-type galaxy. This PN dataset, as well as the catalogue of PN candidates, are valuable resources for detailed investigation of NGC 5128.
Key words: galaxies: kinematics and dynamics / planetary nebulae: general / galaxies: elliptical and lenticular, cD
Based on observations collected at the ESO La Silla-Paranal Observatory within observing programmes 060.A-9140 (FLAMES Science Verification) and 073.B-0434.
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