A Left and Right Truncated Schechter Luminosity Function for Quasars

The luminosity function for quasars (QSOs) is usually fitted by a Schechter function. The dependence of the number of quasars on the redshift, both in the low and high luminosity regions, requires the inclusion of a lower and upper boundary in the Schechter function. The normalization of the truncat...

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Main Author: Lorenzo Zaninetti
Format: Article
Language:English
Published: MDPI AG 2017-05-01
Series:Galaxies
Subjects:
Online Access:http://www.mdpi.com/2075-4434/5/2/25
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spelling doaj-ad465d6ede68497fad07f02252bb9c402020-11-24T21:56:56ZengMDPI AGGalaxies2075-44342017-05-01522510.3390/galaxies5020025galaxies5020025A Left and Right Truncated Schechter Luminosity Function for QuasarsLorenzo Zaninetti0Physics Department, via P.Giuria 1, I-10125 Turin, ItalyThe luminosity function for quasars (QSOs) is usually fitted by a Schechter function. The dependence of the number of quasars on the redshift, both in the low and high luminosity regions, requires the inclusion of a lower and upper boundary in the Schechter function. The normalization of the truncated Schechter function is forced to be the same as that for the Schechter function, and an analytical form for the average value is derived. Three astrophysical applications for QSOs are provided: deduction of the parameters at low redshifts, behavior of the average absolute magnitude at high redshifts, and the location (in redshift) of the photometric maximum as a function of the selected apparent magnitude. The truncated Schechter function with the double power law and an improved Schechter function are compared as luminosity functions for QSOs. The chosen cosmological framework is that of the flat cosmology, for which we provided the luminosity distance, the inverse relation for the luminosity distance, and the distance modulus.http://www.mdpi.com/2075-4434/5/2/25quasarsactive or peculiar galaxiesobjectssystems cosmology
collection DOAJ
language English
format Article
sources DOAJ
author Lorenzo Zaninetti
spellingShingle Lorenzo Zaninetti
A Left and Right Truncated Schechter Luminosity Function for Quasars
Galaxies
quasars
active or peculiar galaxies
objects
systems cosmology
author_facet Lorenzo Zaninetti
author_sort Lorenzo Zaninetti
title A Left and Right Truncated Schechter Luminosity Function for Quasars
title_short A Left and Right Truncated Schechter Luminosity Function for Quasars
title_full A Left and Right Truncated Schechter Luminosity Function for Quasars
title_fullStr A Left and Right Truncated Schechter Luminosity Function for Quasars
title_full_unstemmed A Left and Right Truncated Schechter Luminosity Function for Quasars
title_sort left and right truncated schechter luminosity function for quasars
publisher MDPI AG
series Galaxies
issn 2075-4434
publishDate 2017-05-01
description The luminosity function for quasars (QSOs) is usually fitted by a Schechter function. The dependence of the number of quasars on the redshift, both in the low and high luminosity regions, requires the inclusion of a lower and upper boundary in the Schechter function. The normalization of the truncated Schechter function is forced to be the same as that for the Schechter function, and an analytical form for the average value is derived. Three astrophysical applications for QSOs are provided: deduction of the parameters at low redshifts, behavior of the average absolute magnitude at high redshifts, and the location (in redshift) of the photometric maximum as a function of the selected apparent magnitude. The truncated Schechter function with the double power law and an improved Schechter function are compared as luminosity functions for QSOs. The chosen cosmological framework is that of the flat cosmology, for which we provided the luminosity distance, the inverse relation for the luminosity distance, and the distance modulus.
topic quasars
active or peculiar galaxies
objects
systems cosmology
url http://www.mdpi.com/2075-4434/5/2/25
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