Comments on the HUBBLE Diagram, the Luminosity Function and the Space Density Evolution of Radio Quiet Quasars

1979 ◽  
Vol 300 (4) ◽  
pp. 197-201 ◽  
Author(s):  
Peter Notni
Keyword(s):  
Luminosity Function ◽  
Hubble Diagram ◽  
Density Evolution ◽  
Space Density

scholarly journals Evolution of the Luminosity Function

1986 ◽  
Vol 119 ◽  
pp. 429-438
Author(s):  
Richard F. Green
Keyword(s):  
Luminosity Function ◽  
Cosmic Time ◽  
Volume Density ◽  
Density Evolution ◽  
Space Density ◽  
Mathematical Representations ◽  
Long Lifetime ◽  
Luminosity Evolution ◽  
Fixed Population ◽  
Intrinsic Luminosity

In this review, the currently published, complete, spectroscopically identified samples of quasars are assembled to produce a composite luminosity function, independent of evolutionary assumptions. Two interpretations of the change with cosmic time provide reasonable fits to the data. Luminosity evolution implies a fixed population of host objects, with nuclear luminosity that fades with advancing cosmic time; some dependence of the timescale on intrinsic luminosity is required. Density evolution traces objects of comparable luminosity to find the change in space density, without a requirement of long lifetime. The change in co-moving volume density depends on luminosity; newer data suggest that somewhat stronger evolution is required at the low luminosity end than the models of Schmidt and Green allowed. Caution is advised in drawing direct physical conclusions about the evolution of individual quasars from mathematical representations of ensemble properties.

scholarly journals The Space Density of Ultra-luminous QSOs at the End of Reionization Epoch by the QUBRICS Survey and the AGN Contribution to the Hydrogen Ionizing Background

2022 ◽  
Vol 924 (2) ◽  
pp. 62
Author(s):  
Andrea Grazian ◽  
Emanuele Giallongo ◽  
Konstantina Boutsia ◽  
Giorgio Calderone ◽  
Stefano Cristiani ◽  
...  
Keyword(s):  
Active Galactic Nucleus ◽  
Luminosity Function ◽  
Density Evolution ◽  
Complete Sample ◽  
Space Density ◽  
Photoionization Rate

Abstract Motivated by evidences favoring a rapid and late hydrogen reionization process completing at z ∼ 5.2–5.5 and mainly driven by rare and luminous sources, we have reassessed the estimate of the space density of ultra-luminous QSOs at z ∼ 5 in the framework of the QUBRICS survey. A ∼ 90% complete sample of 14 spectroscopically confirmed QSOs at M 1450 ≤ −28.3 and 4.5 ≤ z ≤ 5.0 has been derived in an area of 12,400 deg2, thanks to multiwavelength selection and Gaia astrometry. The space density of z ∼ 5 QSOs within −29.3 ≤ M 1450 ≤ −28.3 is three times higher than previous determinations. Our results suggest a steep bright-end slope for the QSO luminosity function at z ∼ 5 and a mild redshift evolution of the space density of ultrabright QSOs (M 1450 ∼ −28.5) at 3 < z < 5.5, in agreement with the redshift evolution of the much fainter active galactic nucleus (AGN) population at M 1450 ∼ −23. These findings are consistent with a pure density evolution for the AGN population at z > 3. Adopting our z ∼ 4 QSO luminosity function and applying a mild density evolution in redshift, a photoionization rate of Γ HI = 0.46 − 0.09 + 0.17 × 10 − 12 s − 1 has been obtained at z = 4.75, assuming an escape fraction of ∼70% and a steep faint-end slope of the AGN luminosity function. The derived photoionization rate is ∼50–100% of the ionizing background measured at the end of the reionization epoch, suggesting that AGNs could play an important role in the cosmological reionization process.

scholarly journals The Surface Density of Quasars

1978 ◽  
Vol 79 ◽  
pp. 295-303 ◽  
Author(s):  
J.G. Bolton ◽  
Ann Savage
Keyword(s):  
Surface Density ◽  
Luminosity Function ◽  
Statistical Significance ◽  
Comprehensive Investigation ◽  
Space Density ◽  
Close Pairs

A knowledge of the surface density of quasars as a function of magnitude is important for two reasons. Firstly it is necessary in order to assess the possible statistical significance of close pairs of quasars or the association between quasars and bright galaxies. Secondly it is a necessary step in the determination of the space density or luminosity function of QSOs. We have carried out what we believe to be currently the most comprehensive investigation into the surface density of quasars. Three techniques have been used in this investigation. These are

scholarly journals The luminosity function and space density of the most luminous galaxies in the IRAS survey

1986 ◽  
Vol 303 ◽  
pp. L41 ◽  
Author(s):  
B. T. Soifer ◽  
D. B. Sanders ◽  
G. Neugebauer ◽  
G. E. Danielson ◽  
Carol J. Lonsdale ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Space Density ◽  
Luminous Galaxies

scholarly journals The Space Density of Spiral Galaxies as function of their Luminosity, Surface Brightness and Scalesize

1999 ◽  
Vol 171 ◽  
pp. 52-59 ◽  
Author(s):  
Roelof S. de Jong ◽  
Cedric Lacey
Keyword(s):  
Surface Brightness ◽  
Luminosity Function ◽  
Spiral Galaxies ◽  
Structural Parameters ◽  
Space Density ◽  
Cosmological Redshift ◽  
Density Distributions ◽  
Low Surface Brightness ◽  
Local Space ◽  
Log Normal

AbstractThe local space density of galaxies as a function of their basic structural parameters -like luminosity, surface brightness and scalesize-is still poorly known. Our poor knowledge is mainly the result of strong selection biases against low surface brightness and small scalesize galaxies in any optically selected sample. We show that in order to correct for selection biases one has to obtain accurate surface photometry and distance estimates for a large (≳ 1000) sample of galaxies. We derive bivariate space density distributions in the (scalesize, surface brightness)-plane and the (luminosity, scalesize)-plane for a sample of ~1000 local Sb-Sdm spiral galaxies. We present a parameterization of these bivariate distributions, based on a Schechter type luminosity function and a log-normal scalesize distribution at a given luminosity. We show how surface brightness limits and (1+z)4 cosmological redshift dimming can influence interpretation of luminosity function determinations and deep galaxy counts.

The Stromlo-APM Redshift Survey. I - The luminosity function and space density of galaxies

1992 ◽  
Vol 390 ◽  
pp. 338 ◽  
Author(s):  
J. Loveday ◽  
B. A. Peterson ◽  
G. Efstathiou ◽  
S. J. Maddox
Keyword(s):  
Luminosity Function ◽  
Space Density ◽  
Redshift Survey

scholarly journals Radio Source Evolution Derived from Low Frequency Surveys

2002 ◽  
Vol 199 ◽  
pp. 50-53
Author(s):  
C.A. Jackson ◽  
J.V. Wall
Keyword(s):  
Radio Source ◽  
Luminosity Function ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Parametric Models ◽  
Radio Luminosity ◽  
Space Density ◽  
Radio Data ◽  
Radio Luminosity Function

We find simple parametric models to describe the space density evolution of radio-loud AGN, treating FRI and FRII radio galaxies separately as the two parent populations in our dual-population unified scheme. In this we use low frequency radio data (v < 500 MHz), where radio samples are unbiased by Doppler beaming. Incorporated into this latest analysis is a new determination of the local radio luminosity function at 1.4 GHz from galaxies common to both the 2dFGRS and NVSS surveys.

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