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 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 Luminosity Functions for Extra Galactic Radio Sources

1977 ◽  
Vol 74 ◽  
pp. 171-182
Author(s):  
R. Fanti ◽  
G. C. Perola
Keyword(s):  
Luminosity Function ◽  
Unit Volume ◽  
Radio Observation ◽  
Log P ◽  
Radio Sources ◽  
Type I ◽  
Complete Sample ◽  
Space Density ◽  
Luminosity Functions ◽  
Galactic Radio

The monochromatic luminosity function of radio sources (RLF) is the number of sources per unit volume as a function of the luminosity P at a frequency v and of the cosmic epoch (z). Symbol : n(P(v),z). It is often given per interval of log P, or Mr, the absolute radio magnitude. This function is determined only for sources associated with optical objects (galaxies and QSO's). It can be given for all kinds of associations, or for sources associated with a specific type of object. In this case the normalized, or fractional, RLF is sometimes used, Fi (P,z) = ni (P,z)/ρi (z), where ρi is the space density of type i objects. The word “bivariate” is used for the RLF defined per interval of the optical luminosity (or magnitude M). A RLF can be determined using either a radio–optically complete sample of identified sources, or the radio observation of an optically selected sample. The merits of methods used to estimate a RLF from a complete sample are discussed by Felten (1976). Translation of a RLF from one frequency to another must be done with care if, at the two frequencies, different radio components (like the extended and the compact) would be preferentially sampled. We shall review the estimates of local (z = 0) RLF's using Ho = 100 Kms−1 Mpc−1 and the unit WHz−1 for P.

scholarly journals THE SPACE DENSITY OF COMPTON-THICK ACTIVE GALACTIC NUCLEUS AND THE X-RAY BACKGROUND

2009 ◽  
Vol 696 (1) ◽  
pp. 110-120 ◽  
Author(s):  
E. Treister ◽  
C. Megan Urry ◽  
Shanil Virani
Keyword(s):  
Active Galactic Nucleus ◽  
Space Density ◽  
X Ray ◽  
X Ray Background

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 Evolution of the AGN UV luminosity function from redshift 7.5

2019 ◽  
Vol 488 (1) ◽  
pp. 1035-1065 ◽  
Author(s):  
Girish Kulkarni ◽  
Gábor Worseck ◽  
Joseph F Hennawi
Keyword(s):  
Active Galactic Nuclei ◽  
Luminosity Function ◽  
Galactic Nuclei ◽  
Systematic Errors ◽  
Selection Function ◽  
Data Sets ◽  
Multiple Data ◽  
Luminosity Functions ◽  
Multiple Data Sets ◽  
Photoionization Rate

ABSTRACTDeterminations of the ultraviolet (UV) luminosity function of active galactic nuclei (AGN) at high redshifts are important for constraining the AGN contribution to reionization and understanding the growth of supermassive black holes. Recent inferences of the luminosity function suffer from inconsistencies arising from inhomogeneous selection and analysis of data. We address this problem by constructing a sample of more than 80 000 colour-selected AGN from redshift $z$ = 0 to 7.5 using multiple data sets homogenized to identical cosmologies, intrinsic AGN spectra, and magnitude systems. Using this sample, we derive the AGN UV luminosity function from redshift $z$ = 0 to 7.5. The luminosity function has a double power-law form at all redshifts. The break magnitude M* shows a steep brightening from M* ∼ −24 at $z$ = 0.7 to M* ∼ −29 at $z$ = 6. The faint-end slope β significantly steepens from −1.9 at $z$ < 2.2 to −2.4 at $z$ ≃ 6. In spite of this steepening, the contribution of AGN to the hydrogen photoionization rate at $z$ ∼ 6 is subdominant (<3 per cent), although it can be non-negligible (∼10 per cent) if these luminosity functions hold down to M1450 = −18. Under reasonable assumptions, AGN can reionize He ii by redshift $z$ = 2.9. At low redshifts ($z$ < 0.5), AGN can produce about half of the hydrogen photoionization rate inferred from the statistics of H i absorption lines in the intergalactic medium. Our analysis also reveals important systematic errors in the data, which need to be addressed and incorporated in the AGN selection function in future in order to improve our results. We make various fitting functions, codes, and data publicly available.

scholarly journals An ALMA survey of the brightest sub-millimetre sources in the SCUBA-2–COSMOS field

2020 ◽  
Vol 495 (3) ◽  
pp. 3409-3430 ◽  
Author(s):  
J M Simpson ◽  
Ian Smail ◽  
U Dudzevičiūtė ◽  
Y Matsuda ◽  
B-C Hsieh ◽  
...  
Keyword(s):  
Pilot Study ◽  
Flux Density ◽  
Luminosity Function ◽  
Spectral Energy Distribution ◽  
Line Emission ◽  
Spectral Energy ◽  
Complete Sample ◽  
Photometric Redshifts ◽  
Photometric Redshift ◽  
Number Counts

ABSTRACT We present an ALMA study of the ∼180 brightest sources in the SCUBA-2 850-μm map of the COSMOS field from the S2COSMOS survey, as a pilot study for AS2COSMOS – a full survey of the ∼1000 sources in this field. In this pilot study, we have obtained 870-μm continuum maps of an essentially complete sample of the brightest 182 sub-millimetre sources ($S_{850\, \mu \rm m}\gt $ 6.2 mJy) in COSMOS. Our ALMA maps detect 260 sub-millimetre galaxies (SMGs) spanning a range in flux density of $S_{870\, \mu \rm m}$ = 0.7–19.2 mJy. We detect more than one SMG counterpart in 34 ± 2 per cent of sub-millimetre sources, increasing to 53 ± 8 per cent for SCUBA-2 sources brighter than $S_{850\, \mu \rm m}\gt $ 12 mJy. We estimate that approximately one-third of these SMG–SMG pairs are physically associated (with a higher rate for the brighter secondary SMGs, $S_{870\, \mu \rm m}\gtrsim$ 3 mJy), and illustrate this with the serendipitous detection of bright [C ii] 157.74-μm line emission in two SMGs, AS2COS 0001.1 and 0001.2 at z = 4.63, associated with the highest significance single-dish source. Using our source catalogue, we construct the interferometric 870-μm number counts at $S_{870\, \mu \rm m}\gt $ 6.2 mJy. We use the extensive archival data of this field to construct the multiwavelength spectral energy distribution of each AS2COSMOS SMG, and subsequently model this emission with magphys to estimate their photometric redshifts. We find a median photometric redshift for the $S_{870\, \mu \rm m}\gt $ 6.2 mJy AS2COSMOS sample of z = 2.87 ± 0.08, and clear evidence for an increase in the median redshift with 870-μm flux density suggesting strong evolution in the bright end of the 870-μm luminosity function.

scholarly journals ANTI-HIERARCHICAL EVOLUTION OF THE ACTIVE GALACTIC NUCLEUS SPACE DENSITY IN A HIERARCHICAL UNIVERSE

2014 ◽  
Vol 794 (1) ◽  
pp. 69 ◽  
Author(s):  
Motohiro Enoki ◽  
Tomoaki Ishiyama ◽  
Masakazu A. R. Kobayashi ◽  
Masahiro Nagashima
Keyword(s):  
Active Galactic Nucleus ◽  
Space Density

scholarly journals Significant new planetary nebula discoveries as powerful probes of the LMC

2008 ◽  
Vol 4 (S256) ◽  
pp. 36-42
Author(s):  
Warren A. Reid ◽  
Quentin A. Parker
Keyword(s):  
Luminosity Function ◽  
Narrow Band ◽  
Large Magellanic Cloud ◽  
Emission Sources ◽  
Wide Field ◽  
Complete Sample ◽  
Co Addition ◽  
Fresh Insight ◽  
Insight Into ◽  
Flux Calibration

AbstractOur discovery and analysis of 452 new planetary nebulae (PNe) in the Large Magellanic Cloud (LMC) has tripled the number of known LMC PNe, providing a powerful new resource for probing the kinematics of the LMC as well as contributing fresh insight into the PN luminosity function (PNLF) which we now extend to over 10 magnitudes in [O iii] and Hα. These discoveries have resulted from a new, deep (R ≡ 22), high resolution Hα map of the central 25 deg2 of the LMC, achieved by a process of multi-exposure median co-addition of a dozen 2-hour exposures. The resulting map is at least 1 magnitude deeper than the best wide-field narrow-band LMC images currently available and has proven a major resource for the discovery of emission objects of all kinds. As a result, the near complete sample of the PN population in the central 25 deg2 of the LMC has permitted truly meaningful quantitative determinations of the PNLF, distribution, abundances and kinematics. We briefly describe the importance of these PN discoveries, the additional spectroscopic confirmation of >2,000 compact emission sources, flux calibration, the newly derived electron temperatures and electron densities.

Sign in / Sign up

Export Citation Format

Share Document