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.

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 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.

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 Luminosity Function of Long Gamma-Ray Burst and their rate at z ≥ 6

2008 ◽  
Vol 4 (S255) ◽  
pp. 212-216
Author(s):  
R. Salvaterra ◽  
S. Campana ◽  
G. Chincarini ◽  
T. R. Choudhury ◽  
S. Covino ◽  
...  
Keyword(s):  
Star Formation ◽  
Luminosity Function ◽  
Gamma Ray ◽  
Formation Rate ◽  
Gamma Ray Bursts ◽  
Test Model ◽  
The Past ◽  
Model Predictions ◽  
Low Metallicity ◽  
Luminosity Evolution

AbstractWe compute the luminosity function (LF) and the formation rate of long gamma ray bursts (GRBs) in three different scenarios: i) GRBs follow the cosmic star formation and their LF is constant in time; ii) GRBs follow the cosmic star formation but the LF varies with redshift; iii) GRBs form preferentially in low–metallicity environments. We then test model predictions against the Swift 3-year data, showing that scenario i) is robustly ruled out. Moreover, we show that the number of bright GRBs detected by Swift suggests that GRBs should have experienced some sort of luminosity evolution with redshift, being more luminous in the past. Finally we propose to use the observations of the afterglow spectrum of GRBs at z ≥ 5.5 to constrain the reionization history, and then applied our method to the case of GRB 050904.

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 $\rm {\mathit{ z}\, \sim \, 1}$.

scholarly journals Cosmic Distribution of Optically Selected Quasars

1987 ◽  
Vol 124 ◽  
pp. 619-625
Author(s):  
Maarten Schmidt
Keyword(s):  
Luminosity Function ◽  
Birth Rate ◽  
Emission Lines ◽  
Short Life ◽  
Large Redshift ◽  
X Ray ◽  
Wide Range ◽  
X Ray Background ◽  
Spectral Survey ◽  
Luminosity Evolution

Counts of optically selected quasars as a function of magnitude and redshift show the effects of strong evolution. If quasars have relatively short life times, then the observed numbers at a given redshift are mostly determined by their birth rate and mean luminosity over their lifetime. In this case the evolution of the luminosity function can be described by density evolution, where the rate of evolution may depend on luminosity and other properties. On the other hand, if all quasars were formed at large redshift and have been decaying in luminosity since that time, then the evolution of the luminosity function is best described in terms of luminosity evolution. We discuss some of the consequences of luminosity evolution for the mass of quasars and for the X-ray background.We explore the observational aspects of the redshift cutoff of quasars. The situation is complicated by the unavoidable bias in slitless surveys against weak-line objects. Since quasar emission lines show a wide range of equivalent widths, a spectral survey will be characterized by a distribution of limiting continuum magnitudes rather than by a single value. The decline in the space density of quasars at large redshift may depend on luminosity, and may also have structure, such as a steep drop, but not a total cutoff, in density at a redshift near 3.

scholarly journals The Evolution and Luminosity Function of Quasars

1999 ◽  
Vol 194 ◽  
pp. 105-112
Author(s):  
Vahé Petrosian
Keyword(s):  
Selection Criteria ◽  
Luminosity Function ◽  
Star Formation Rate ◽  
Gradual Increase ◽  
High Redshift ◽  
Formation Rate ◽  
Bivariate Distribution ◽  
Density Peaks ◽  
Redshift Surveys ◽  
Luminosity Evolution

I report results from analysis of data from several quasar samples (Durham/AAT, LBQS, HBQS and EQS) on the density and the luminosity evolution of quasars. We have used new statistical methods whereby we combine these different samples with varying selection criteria and multiple truncations. With these methods the luminosity evolution can be found through an investigation of the correlation of the bivariate distribution of luminosities and redshifts. Of the two most commonly used models for luminosity evolution, L = ekt(z) and L = (1 + z)k', we find that the second form, with k' = 2.58 (one σ range [2.14,2.91]), gives a better description of the data at all luminosities. Using this form of luminosity evolution we determine a global luminosity function and the evolution of the co-moving density for the two classes of cosmological models. We find a gradual increase of the co-moving density up to z ˜ 2, at which point the density peaks and begins to decrease rapidly. This is in agreement with results from high redshift surveys and in disagreement with the pure luminosity evolution (i.e. constant co-moving density) model. We find that the local luminosity function exhibits the usual double power law behavior. The luminosity density is found to increase rapidly at low redshift and to reach a peak at around z ≍ 2. This result is compared with those from high redshift surveys and with the evolution of the star formation rate.

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