Extragalactic planetary nebulae in the central regions of galaxies
Magda Arnabold & Johanna Hartke (Oxford)
With this project, by searching for ``the needle in the haystack”, we are after the green light emitted by the nebulae of dying stars at the centers of galaxies. We will learn about these stars’ mass loss and how they contribute to the dust and metals in the heart of galaxies.
Planetary nebulae (PNe) are the last phase of the stellar evolution of intermediate to low mass stars. Because of their bright envelope that shine of an aquamarine hue, they become important tracers of motions and chemistry in galaxies. Because of their bright envelope, they are the only single stars (a part from Supernovae!) that can be individually detected and whose line-of-sight velocities can be measured at distances of several tens of Megaparsecs. Their bright [OIII] emission at 5007 AA and the absence of a continuum makes it easy to identify PNe with photometry surveys. However, these surveys are blind to the PN populations in the very centre of galaxies as the light from the galaxy itself outshines them. The advance of integral-field spectroscopy can overcome this limitation as the spectra in the bright central region can be decomposed into their respective stellar and nebular contribution.
In order to better understand the link between the PN population properties and those of their host stellar population, it is important to study the centres of nearby early-type galaxies. With data from the integral-field spectrograph MUSE, one is able to both investigate the properties and kinematics of the host stellar population as well as identify and characterise individual planetary nebulae.
This project is based on selected data sets from the ESO Science Portal. Such data have already been reduced and calibrated, hence it is possible to go into the analysis phase after checking the integrity of the data cubes. With each MUSE data cube, one is able to analyse about 90,000 spectra per pointing. The first task will be to familiarise with the cube data and to visualise it in different wavelength ranges. We will then characterise the stellar population of the early-type galaxy by fitting synthetic spectra as a function of radius. This will enable us to create two-dimensional maps of the abundances and kinematics and to identify any trends with radius. The next step will be to identify emission-line objects such as planetary nebulae and to link their population properties such as the density distribution and luminosity function to the general stellar population properties , including those linked to of the post Asymptotic Giant Branch phase, derived previously.
#spectroscopy #MUSE #VLT #optical #dyingstars #planetarynebulae #python #oxygen #dust