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 X-Ray Background and the AGN Luminosity Function

1999 ◽  
Vol 183 ◽  
pp. 200-209
Author(s):  
G. Hasinger
Keyword(s):  
Black Holes ◽  
Luminosity Function ◽  
Cosmic Time ◽  
Volume Density ◽  
Energy Bands ◽  
X Ray ◽  
Normal Galaxies ◽  
X Ray Background ◽  
Acid Test

ROSAT deep and shallow surveys have provided an almost complete inventory of the constituents of the soft X-ray background which led to a population synthesis model for the whole X-ray background with interesting cosmological consequences. According to this model the X-ray background is the “echo” of mass accretion onto supermassive black holes, integrated over cosmic time. A new determination of the soft X-ray luminosity function of active galactic nuclei (AGN) is consistent with pure density evolution, and the comoving volume density of AGN at redshift 2–3 approaches that of local normal galaxies. This indicates that many larger galaxies contain black holes and it is likely that the bulk of the black holes was produced before most of the stars in the universe. However, only X-ray surveys in the harder energy bands, where the maximum of the energy density of the X-ray background resides, will provide the acid test of this picture.

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 Cosmic evolution of star-forming galaxies to z ≃ 1.8 in the faint low-frequency radio source population

2019 ◽  
Vol 491 (4) ◽  
pp. 5911-5924 ◽  
Author(s):  
E F Ocran ◽  
A R Taylor ◽  
M Vaccari ◽  
C H Ishwara-Chandra ◽  
I Prandoni ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Formation Rate ◽  
Low Frequency ◽  
Source Population ◽  
Radio Luminosity ◽  
Photometric Redshifts ◽  
Space Density ◽  
Star Forming ◽  
Steep Decline ◽  
Luminosity Evolution

ABSTRACT We study the properties of star-forming galaxies selected at 610 MHz with the GMRT in a survey covering ∼1.86 deg2 down to a noise of ∼7.1 μJy beam−1. These were identified by combining multiple classification diagnostics: optical, X-ray, infrared, and radio data. Of the 1685 SFGs from the GMRT sample, 496 have spectroscopic redshifts whereas 1189 have photometric redshifts. We find that the IRRC of star-forming galaxies, quantified by the infrared-to-1.4 GHz radio luminosity ratio $\rm {\mathit{ q}_{IR}}$, decreases with increasing redshift: $\rm {\mathit{ q}_{IR}\, =\, 2.86\pm 0.04(1\, +\, \mathit{ z})^{-0.20\pm 0.02}}$ out to z ∼ 1.8. We use the $\rm {\mathit{ V}/\mathit{ V}_{max}}$ statistic to quantify the evolution of the comoving space density of the SFG sample. Averaged over luminosity our results indicate $\rm {\langle \mathit{ V}/\mathit{ V}_{max} \rangle }$ to be $\rm {0.51\, \pm \, 0.06}$, which is consistent with no evolution in overall space density. However, we find $\rm \mathit{ V}/\mathit{ V}_{max}$ to be a function of radio luminosity, indicating strong luminosity evolution with redshift. We explore the evolution of the SFGs radio luminosity function by separating the source into five redshift bins and comparing to theoretical model predictions. We find a strong redshift trend that can be fitted with a pure luminosity evolution of the form $\rm {\mathit{ L}_{610\, MHz}\, \propto \, (\, 1+\, \mathit{ z})^{(2.95\pm 0.19)-(0.50\pm 0.15)z}}$. We calculate the cosmic SFR density since $\rm {\mathit{ z} \sim 1.5}$ by integrating the parametric fits of the evolved 610 MHz luminosity function. Our sample reproduces the expected steep decline in the star formation rate density since $\rm {\mathit{ z}\, \sim \, 1}$.

The K-Band Luminosity Function of Galaxies

1998 ◽  
Vol 179 ◽  
pp. 278-280
Author(s):  
J. P. Gardner ◽  
R. M. Sharples ◽  
C. S. Frenk ◽  
B. E. Carrasco
Keyword(s):  
Luminosity Function ◽  
Near Infrared ◽  
Mass Function ◽  
Solar Mass ◽  
The Galaxy ◽  
Statistical Studies ◽  
The Absolute ◽  
Number Counts ◽  
Luminosity Evolution ◽  
K Band

The luminosity function of galaxies is central to many problems in cosmology, including the interpretation of faint number counts. The near-infrared provides several advantages over the optical for statistical studies of galaxies, including smooth and well-understood K-corrections and expected luminosity evolution. The K–band is dominated by near-solar mass stars which make up the bulk of the galaxy. The absolute K magnitude is a measure of the visible mass in a galaxy, and thus the K–band luminosity function is an observational counterpart of the mass function of galaxies.

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 Environments of Optically-Selected QSOs

1988 ◽  
Vol 130 ◽  
pp. 576-576 ◽  
Author(s):  
B. J. Boyle ◽  
T. Shanks ◽  
H. Yee
Keyword(s):  
Luminosity Function ◽  
Luminosity Evolution ◽  
Number Of Authors

In recent years much attention has been focussed on the environments of low redshift QSOs. In particular, Yee and Green (1987) have found that the average environment of radio-loud QSOs at z ≃ 0.6, as measured by the QSO-galaxy spatial covarience function, is over three times richer than that of radio-loud QSOs at z ≃ 0.4. This strongly indicates that there has been a steep evolution in the numbers of QSOs in rich clusters over a period of 109 years. This observation is therefore inconsistent with pure luminosity evolution models, which preserves QSO number with epoch, currently employed by a number of authors (see e.g. Boyle et al. 1987) to explain the observed redshift dependence of the QSO luminosity function. However, since over 90% of QSOs are radio-quiet, the main test concerning the validity of pure luminosity evolution is to look for similar evolutionary effects in the preferred environments of optically-selected QSOs.

scholarly journals Unveiling the Evolution of Type I AGNs in the IR (15μm) — As Seen by ISO in the ELAIS-S1 Region

2002 ◽  
Vol 184 ◽  
pp. 167-172
Author(s):  
Israel Matute ◽  
Fabio La Franca ◽  
Carlotta Gruppioni ◽  
Francesca Pozzi ◽  
Carlo Lari
Keyword(s):  
Power Law ◽  
Luminosity Function ◽  
Evolution Model ◽  
Cosmological Evolution ◽  
Type I ◽  
Infrared Background ◽  
Power Law Function ◽  
Cosmic Infrared Background ◽  
Luminosity Evolution

AbstractWe present the first estimate of the evolution of type 1 AGNs in the IR (15 μm) obtained from the ELAIS survey in the S1 region. We find that the luminosity function (LF) of Type 1 AGNs at 15μm is fairly well represented by a double power-law function with a bright slope of 2.9 and a faint slope of 1.1. There is evidence for significant cosmological evolution according to a pure luminosity evolution model L15(z)α(l+z)k, with in a (Ωm,ΩΛ)=(1.0,0.0) cosmology. This evolution is similar to what is observed at other wavebands. From the luminosity function and its evolution, we estimate a contribution of ~ 2% from Type 1 AGN to the total Cosmic Infrared Background (CIRB) at 15 μm.

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