Planetary nebula luminosity function: Difference between revisions

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{{Short description|Astronomical function}}

'''Planetary Nebulanebula Luminosityluminosity Functionfunction''' ('''PNLF''') is a secondary<ref name="Ferrareseetal2000" /> [[standard candle|distance indicator]] used in [[astronomy]]. It makes use of the [[O III|[O&nbsp;III]]] λ5007 [[forbidden line]] found in all [[planetary nebula]] (PNe) which are members of the old stellar populations ([[Population II]]).<ref name="Ferrareseetal2000">{{harvnb|Ferrarese|Ford|Huchra|Kennicutt|2000}}</ref>

It workscan wellbe forused to determine distances to both [[spiral galaxy|spiral]] and [[elliptical galaxy|elliptical]] galaxies despite their completely different [[stellar populations]] and is part of the [[Extragalactic Distance Scale]].<ref name="=Schoenberneretal2007">{{harvnb|Schoenberner|Jacob|Steffen|Sandin|2007}}</ref>

== History and background ==

Starting with the time of [[Edwin Hubble]], the brightest stars have been employed as [[Extragalactic astronomy|extragalactic]] distance indicators. However, it was not until the early 1960s that planetary nebula (PNe) were recognized as being some of the “brightest stars” and consequently useful as extragalactic distance indicators. During the early stages of their evolution, a planetary nebula's luminosity is on par with their [[asymptotic giant branch]] (AGB) ancestors. Even though most of their continuum [[Emission (electromagnetic radiation)|emission]] emerges in the [[far-ultraviolet]], rather than the [[visible light|optical]] or [[near infrared]], their detectability is not hampered. In fact, since most of the [[central star|central star's]] [[flux]] is emitted at energies below 13.6 [[electron volt|eV]], the [[photoionization]] physics ensures that their energy is transformed into a series of optical, [[infrared]], and [[near-ultraviolet|near-UV]] [[emission line]]s. Fortuitously, approximately 10% of the flux emitted by a young PNe is in the one emission line of [[doubly-ionized oxygen]] at 5007 [[Ångström|Å]]. Therefore, for the purposes of [[cosmology]], a PNe may be thought of a cosmic machine that turns continuum emission into monochromatic [[flux]].

<ref name="Ciardullo2003">{{harvnb|Ciardullo|2003}}</ref>

It was not until late 1970s that the initial PNe derived distance estimates were computed. The first study of the PNLF was {{harvnb|Jacoby|1989}}. Ironically, the technique was first applied to galaxies outside our [[Local Group]] before being applied to it. The reason for this odd order of adoption is due to the fact that any one PNe is not a standard candle and that distance estimates to individual PNe within our own galaxy are very inaccurate, an error factor of 2<ref name="Ciardullo2003" /><ref name="Jacoby1989">{{harvnb|Jacoby|1989}}</ref> being normal. However, by way of sampling a large number of PNe, one may apply the PNLF to produce accurate distance estimates to galaxies. Because PNe are found in all galaxies, the PNLF is unique in that it may be utilized to estimate distances to all large galaxies within the [[Local Supercluster]] independent of their environment and [[Hubble type]].<ref name="Ciardullo2004">{{harvnb|Ciardullo|2004}}</ref>

== Procedure ==

ToThe distance estimate the distance to a galaxy using the PNLF onerequires mustdiscovery firstof locatesuch pointan sourcesobject withinin the target galaxy that areis 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 fluxesluminosity. 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 areThe two sources of thisextinction, are from within the [[MilkywayMilky Way]] and the 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, onlytype of extinction, occurs only in target galaxies which are either late type [[spiral galaxy|spiral]] or [[irregular galaxy|irregular]]. However, this extinction is difficult to measure. In the MilkywayMilky 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" />

== Physics behind process ==

The PNLF method is unbiased by [[metallicity]]. This is because [[oxygen]] is a primary nebular coolant,; any drop in its concentration raises the plasma’splasma's electron temperature and raises the amount of [[collisional excitation]]s per ion. This compensates for having a smaller number of emitting ions in the PNe resulting in little change in the λ5007 emissions . Consequently, a reduction in oxygen density only lowers the emergent <nowiki>[O&nbsp;III]</nowiki> λ5007 emission line fluxintensity by approximately the square root of the difference in abundance. At the same time, the PNe’sPNe's core responds to metallicity the opposite way. In the case where the metallicity of the progenitor star is smaller, then the PNe’sPNe's [[central star]] will be a bit more massive and its emergentilluminating ultraviolet flux will be a bit largergreater. This added energy almost precisely accounts for the decreased emissions of the PNe. Consequently, the total <nowiki>[O&nbsp;III]</nowiki> λ5007 fluxluminosity that is produced by a PNe is practically

uncorrelated to metallicity. This beneficial negation is in agreement with more precise models of PNe evolution. Only in extremely metal-poor PNe does the brightness of the PNLF cutoff dim by more than a small percentage.<ref name="Ciardullo2004" />

The relative independence of the PNLF cutoff with respect to population age is harder to understand. The [O&nbsp;III] 5007λ5007 flux of a PNe directly correlates to the brightness of its central star. Further, the brightness of its central star directly correlates to its mass. In a PNe,and the central star's mass directly varies in relation to its progenitor's mass. However, by observation, it is demonstrated that reduced brightness does not happen.<ref name="Ciardullo2004" />

== Notes ==

{{Reflist}}

<div class="references-small"><references/>

</div>

== References ==

{{refbegin}}

<div class="references-small">

* {{citation

| last1 = Ciardullo

| first1 = Robin

| title = Distances from Planetary Nebulae

| journal = eprint arXiv:astro-ph/0301279

<!-- Invited review at the International Workshop on "Stellar Candles for the Extragalactic Distance Scale", held in Concepcion, Chile -->

| year = 2003

| date = January 2003

| urlarxiv = http://adsabs.harvard.edu/absastro-ph/0301279 |bibcode = 2003astro.ph..1279C }}

}}

* {{citation

| last1 = Ciardullo

| first1 = Robin

| title = The Planetary Nebula Luminosity Function

| journal = eprint arXiv:astro-ph/0407290

| year = 2004

| date = July 2004

| urlarxiv = http://adsabs.harvard.edu/absastro-ph/0407290 |bibcode = 2004astro.ph..7290C }}

}}

* {{citation

| last1 = Ferrarese

Line 53 ⟶ 43:

| first3 = John

| last4 = Kennicutt

| first4 = Robert C., Jr.

| last5 = Mould

| first5 = Jeremy R.

Line 82 ⟶ 72:

| title = A Database of Cepheid Distance Moduli and Tip of the Red Giant Branch, Globular Cluster Luminosity Function, Planetary Nebula Luminosity Function, and Surface Brightness Fluctuation Data Useful for Distance Determinations

| journal = The Astrophysical Journal Supplement Series

| yeardate = 2000

| volume = 128

| issue = 2

| pages = 431-459431–459

| urlbibcode = http://adsabs.harvard.edu/abs/2000ApJS..128..431F

| doi = 10.1086/313391

}}

|arxiv = astro-ph/9910501 | display-authors = 8

}}

* {{citation

| last1= Jacoby

| first1 = George H.

| title = Planetary nebulae as standard candles. I - Evolutionary models

| journal = Astrophysical Journal, Part 1 (ISSN 0004-637X)

| yeardate = April 1, 1989

| date = [[April 1]] [[1989]]

| volume = 339

| issue =

| pages = 39-5239–52

| urlbibcode = http://adsabs.harvard.edu/abs/1989ApJ...339...39J

| doi= 10.1086/167274

}}

* {{citation

Line 109 ⟶ 101:

| last4 = Sandin

| first4 = C.

| title = The evolution of planetary nebulae IV. On the physics of the luminosity function

| journal = eprintAstronomy arXiv:0708.4292& Astrophysics

| year = 2007

| date = August 2007

| volume =473

| issue = 2

| pages =467–484

| bibcode = 2007A&A...473..467S

| url = http://adsabs.harvard.edu/abs/2007arXiv0708.4292S

| doi= 10.1051/0004-6361:20077437

}}

| arxiv=0708.4292

</div>

| s2cid = 56363650

}}

{{refend}}

[[Category:Large-scale structure of the cosmos]]

[[Category:Planetary nebulae]]

[[Category:CosmologyPhysical cosmology]]

[[Category:Standard candles]]