The Planetary Nebulae Population in the Nuclear Regions of M31: the SAURON view

Abstract

Following a first study of the central regions of M32 that illustrated the power of integral-field spectroscopy (IFS) in detecting and measuring the [O III]λ5007 emission of PNe against a strong stellar background, we turn to the very nuclear PN population of M31, within 80 pc of its centre. We show that PNe can also be found in the presence of emission from diffuse gas and further illustrate the excellent sensitivity of IFS in detecting extragalactic PNe through a comparison with narrowband images obtained with the Hubble Space Telescope. We find the nuclear PNe population of M31 is only marginally consistent with the generally adopted form of the PNe luminosity function (PNLF). In particular, this is due to a lack of PNe with absolute magnitude M5007 brighter than -3, which would only result from a rather unfortunate draw from such a model PNLF. We suggest that the observed lack of bright PNe in the nuclear regions of M31 is due to a horizontal-branch population that is more tilted toward less massive and hotter He-burning stars, so that its progeny consists mostly of UV-bright stars that fail to climb back up the asymptotic giant branch (AGB) and only of few, if any, bright PNe powered by central post-AGB stars. These results are also consistent with recent reports on a dearth of bright post-AGB stars towards the nucleus of M31, and lend further support to the idea that the metallicity of a stellar population has an impact on the way the horizontal branch is populated and to the loose anticorrelation between the strength of the UV-upturn and the specific number of PNe that is observed in early-type galaxies. Finally, our investigation also serves to stress the importance of considering the same spatial scales when comparing the PNe population of galaxies with the properties of their stellar populations.

11 pages, 10 figures, accepted for publication on Monthly Notices of the Royal Astronomical Society

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Cited by in corpus (12)

• The Fornax3D project: overall goals, galaxy sample, MUSE data analysis and initial results
• The WAGGS project - I. The WiFeS Atlas of Galactic Globular cluster Spectra
• The Star Formation History in the M31 Bulge
• Fornax 3D project: automated detection of planetary nebulae in the centres of early-type galaxies and first results
• A Search for Planetary Nebulae With the SDSS: the outer regions of M31
• The Fornax 3D project: PNe populations and stellar metallicity in edge-on galaxies
• Planetary Nebulae and How to Find Them: Color Identification in Big Broadband Surveys
• Planetary Nebulae in the Circumnuclear Region of M31: A Spectroscopic Sample
• The Planetary Nebulae Populations in the Local Group
• M31 nucleus: molecular and ionised gas content upper limits
• The survey of Planetary Nebulae in Andromeda (M31): I. Imaging the disk and halo with MegaCam@CFHT
• The Fornax3D project: Planetary nebulae catalogue and independent distance measurements to Fornax cluster galaxies