Planetary nebula luminosity function: Difference between revisions

Revision as of 16:48, 23 February 2015

Revision as of 17:17, 14 August 2015

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== Procedure ==

To estimate the distance to a galaxy using the PNLF one must first locate point sources within the galaxy that are visible at λ5007 but not when the entire spectrum is considered. These points are candidate PNe, however, there are three other types of objects that would also exhibit such an emission line that must be filtered out: [[HII region|HII&nbsp;regions]], [[supernova remnant]]s, and [[Lyα galaxy|Lyα galaxies]]. After the PNe are determined, to estimate a distance one must measure their monochromatic <nowiki>[O&nbsp;III]</nowiki> λ5007 fluxes. WithWhat thisremains one then hasis a statistical sample of

PNe. One then fits theThe observed luminosity function is then fitted to some standard law.<ref name="Ciardullo2004">{{harvnb|Ciardullo|2004}}</ref>

Finally, one must estimate the foreground [[interstellar extinction]]. There are two sources of this, from within the [[Milky Way]] and internal extinction of the target galaxy. The first is well known and can be taken from sources such as reddening maps computed from [[H I region|H&nbsp;I]] measurements and galaxy counts or from [[IRAS]] and [[Diffuse InfraRed Background Experiment|DIRBE]] satellite experiments. The later, only occurs in target galaxies which are either late type [[spiral galaxy|spiral]] or [[irregular galaxy|irregular]]. However, this extinction is difficult to measure. In the Milky Way, the scale height of PNe is much bigger than that of the dust. Observational data and models support that this holds true for other galaxies, that the bright edge of the PNLF is primarily due to PNe in front of the dust layer. The data and models support a less than 0.05 [[apparent magnitude|magnitude]] internal extinction of a galaxy's PNe.<ref name="Ciardullo2004" />