Distribution Of QSOs Research Articles

Trends among Flux, Luminosity, and Color Indices in High Redshift QSOs

The following study discusses the relationship of high redshift(z) Quasi Stellar Objects’(QSOs) flux, luminosity, and color indices. The paper analyzes observable trends among these 3 variables and uses them to understand the distribution of QSOs across space-time. While many such studies have been conducted in redshift ranges of 1<z<4, the following research or study has been done in the relatively unexplored date range of 2 <z<7. To answer this question, we used the Sloan Digital Sky Survey to obtain samples, curate the data, and analyze it using Python Data Science tools including Pandas and Matplotlib. The results suggest a general trend of increasing data density with the progression of distance and convergence of QSO Magnitude distributions about the median. This research provides insight into the evolution of QSOs over space-time and why they occurred.

The preliminary statistical analysis of LAMOST DR9 low resolution quasi-stellar objects

Based on more than 10 years of large-scale spectral sky survey, LAMOST DR9 v1.0 low resolution catalog has released 76167 data of QSOs. We adopt 48704 QSOs with redshift Z from 0.0 to 6.0, the error of redshift from 0.0 to 0.06, and the galactic latitude |b|>30° to do a research work. There are 95.36% of QSOs with the error of redshift less than or equal to 0.025. Therefore, the Z values are very reliable with small errors. Some statistical figures about Z are drawn and preliminarily analyzed. The distribution of QSOs with Z in different directions shows that universe is spatially isotropic in large-scale structure. The QSOs with high Z values and low Z values correspond to the decelerating and accelerating expansion of the universe respectively, the epoch of the matter dominance and the dark energy dominance respectively. In the epoch of matter dominance, the number density of QSOs in the statistical figures is more than that in the epoch of dark energy dominance and the gravity can slow the expansion. The large-scale spectral sky survey is helpful for us to better understand the past, present and future of the universe.

Large-scale opacity fluctuations in the Lyα forest: evidence for QSOs dominating the ionizing UV background atz∼ 5.5–6?

Lyman-alpha forest data probing the post-reionization Universe shows surprisingly large opacity fluctuations over rather large ($\ge$50 comoving Mpc/h) spatial scales. We model these fluctuations using a hybrid approach utilizing the large volume Millennium simulation to predict the spatial distribution of QSOs combined with smaller scale full hydrodynamical simulation performed with RAMSES and post-processed with the radiative transfer code ATON. We produce realictic mock absorption spectra that account for the contribution of galaxies and QSOs to the ionising UV background. This improved models confirm our earlier findings that a significant ($\ge$50%) contribution of ionising photons from QSOs can explain the large reported opacity fluctuations on large scales. The inferred QSO luminosity function is thereby consistent with recent estimates of the space density of QSOs at this redshift. Our simulations still somewhat struggle, however, to reproduce the very long (110 comoving Mpc/h) high opacity absorption through observed in ULAS J0148+0600, perhaps suggesting an even later end of reionization than assumed in our previously favoured model. Medium-deep/medium area QSO surveys as well as targeted searches for the predicted strong transverse QSO proximity effect whould illuminate the origin of the observed large scale opacity fluctuations. They would allow to substantiate whether UV fluctuations due to QSO are indeed primarily responsible, or whether significant contributions from other recently proposed mechansims such as large scale fluctuations in temperature and mean free path (even in the absence of rare bright sources) are required.

The Environment of Local Ultraluminous Infrared Galaxies

The spatial cluster-galaxy correlation amplitude, Bgc, is computed for a set of 76 (z < 0.3) ultraluminous infrared galaxies (ULIRGs) from the 1-Jy sample. The Bgc parameter is used to quantify the richness of the environment within 0.5 Mpc of each ULIRG. We find that the environment of local ULIRGs is similar to that of the field with the possible exceptions of a few objects with environmental densities typical of clusters with Abell richness classes 0 and 1. No obvious trends are seen with redshift, optical spectral type, infrared luminosity, or infrared color. We compare these results with those of local AGNs and QSOs at various redshifts. The 1-Jy ULIRGs show a broader range of environments than local Seyferts, which are exclusively found in the field. The distribution of ULIRG Bgc-values overlaps considerably with that of local QSOs, consistent with the scenario where some QSOs go through a ultraluminous infrared phase. However, a rigorous statistical analysis of the data indicates that these two samples are not drawn from the same parent population. The Bgc distribution of QSOs shows a distinct tail at high Bgc-values which is not apparent among the ULIRGs. This difference is consistent with the fact that some of the QSOs used for this comparison have bigger and more luminous hosts than the 1-Jy ULIRGs.

Survey for Galaxies Associated withz∼ 3 Damped Lyα Systems. II. Galaxy‐Absorber Correlation Functions

We use 211 galaxy spectra from our survey for Lyman break galaxies (LBGs) associated with 11 damped Lyman alpha systems (DLAs) to measure the three-dimensional LBG auto-correlation and DLA-LBG cross-correlation functions with the primary goal of inferring the mass of DLAs at z~3. Conventional binning of the data while varying both r_0 and gamma parameters of the fiducial model of the correlation function xi(r)=(r/r_0)^{-gamma} resulted in the best fit values and 1 sigma uncertainties of r_0=2.65+/-0.48, gamma=1.55+/-0.40 for the LBG auto-correlation and r_0=3.32+/-1.25, gamma=1.74+/-0.36 for DLA-LBG cross-correlation function. To circumvent shortcomings found in binning small datasets, we perform a maximum likelihood analysis based on Poisson statistics. The best fit values and 1 sigma confidence levels from this analysis were found to be r_0=2.91(+1.0,-1.0), gamma=1.21(+0.6,-0.3) for the LBG auto-correlation and r_0=2.81(+1.4,-2.0), gamma=2.11(+1.3,-1.4) for the DLA-LBG cross-correlation function. We report a redshift spike of five LBGs with Delta z = 0.015 of the z=2.936 DLA in the PSS0808+5215 field and find that the DLA-LBG clustering signal survives when omitting this field from the analysis. Using the correlation functions measurements and uncertainties, we compute the z~3 LBG galaxy bias b_LBG to be 1.5<b_LBG<3 corresponding to an average halo mass of 10^(9.7)<M_LBG<10^(11.6) M_odot and the z~3 DLA galaxy bias b_DLA to be 1.3<b_DLA<4 corresponding to an average halo mass of 10^(9)<M_LBG<10^(12) M_odot. Lastly, two of the six QSOs discovered in this survey were found to lie within Delta z = 0.0125 of two of the survey DLAs. We estimate the probability of this occurring by chance is 1 in 940 and may indicate a possible relationship between the distribution of QSOs and DLAs at z~3.

First tentative detection of anisotropy in the QSO distribution around nearby edge-on spiral galaxies

Aims.To check whether the polar angle distribution of QSOs around nearby spiral galaxies is isotropic or not.

Patchy He II reionization and the physical state of the intergalactic medium

We present a Monte Carlo model of He II reionization by quasi-stellar objects (QSOs, quasars) and its effect on the thermal state of the clumpy intergalactic medium (IGM). The model assumes that patchy reionization develops as a result of the discrete distribution of QSOs. It includes various recipes for the propagation of the ionizing photons, and treats photoheating self-consistently. The model predicts the fraction of He III, the mean temperature in the IGM, and the He II mean optical depth - all as a function of redshift. It also predicts the evolution of the local temperature versus density relation during reionization. Our findings are as follows. The fraction of Hem increases gradually until it becomes close to unity at z ∼ 2.8-3.0. The He II mean optical depth decreases from τ ∼ 10 at z ≥ 3.5 to τ ≤ 0.5 at z ≤ 2.5. The mean temperature rises gradually between z ∼ 4 and z ∼ 3 and declines slowly at lower redshifts. The model predicts a flattening of the temperature-density relation, with significant increase in the scatter during reionization at z ∼ 3. Towards the end of reionization, the scatter is reduced and a tight relation is re-established. This scatter should be incorporated in the analysis of the Lya forest at z ≤ 3. Comparison with observational results of the optical depth and the mean temperature at moderate redshifts constrains several key physical parameters.

Physical state of the intergalactic medium at redshiftsz= 2-4

We use two large surveys of quasars (QSOs), namely, 2QZ–6QZ and SDSS DR1, to estimate mean properties of the background ultraviolet (UV) radiation and the temperature of intergalactic gas at redshifts z≈ 2–4. We show that the intensity of the UV background radiation as estimated by Haardt & Madau (1996) should be increased by ∼20–30 per cent. We also briefly discuss spatial variations of both the intensity of background UV radiation and the gas temperature. These variations can be studied in more detail with high-resolution observations of the proximity effects, Lyman α absorbers and metal systems. Using the minimal spanning tree technique, we analyse the spatial distribution of QSOs and show that it is quite similar to random (Poissonian).

The Transverse Proximity Effect: A Probe to the Environment, Anisotropy, and Megayear Variability of QSOs

The transverse proximity effect is the expected decrease in the strength of the Lya forest absorption in a QSO spectrum when another QSO lying close to the line of sight enhances the photoionization rate above that due to the average cosmic ionizing background. We select three QSOs from the Early Data Release of the Sloan Digital Sky Survey that have nearby foreground QSOs, with proper line of sight tangential separations of 0.50, 0.82, and 1.10 h^{-1} Mpc. We estimate that the ionizing flux from the foreground QSO should increase the photoionization rate by a factor (94, 13, 13) in these three cases, which would be clearly detectable in the first QSO and marginally so in the other two. We do not detect the transverse proximity effect. Three possible explanations are provided: an increase of the gas density in the vicinity of QSOs, time variability, and anisotropy of the QSO emission. We find that the increase of gas density near QSOs can be important if they are located in the most massive halos present at high redshift, but is not enough to fully explain the absence of the transverse proximity effect. Anisotropy requires an unrealistically small opening angle of the QSO emission. Variability demands that the luminosity of the QSO with the largest predicted effect was much lower 10^6 years ago, whereas the transverse proximity effect observed in the HeII Lya absorption in QSO 0302-003 by Jakobsen et al. (2003) implies a lifetime longer than 10^7 years. A combination of all three effects may better explain the lack of Lya absorption reduction. A larger sample of QSO pairs may be used to diagnose the environment, anisotropy and lifetime distribution of QSOs.

QSOs from the variability and proper motion survey in the M 3 field

We present results of the spectroscopical follow-up observations of QSO candidates from a combined variability and proper motion (VPM) survey in a � 10 square degrees region centered on the globular cluster M3. The search is based on a large number of digitised Schmidt plates with a time-baseline of three decades. This paper reviews the candidate selection, the follow-up spectroscopy, and general properties of the resulting QSO sample. In total, 175 QSOs and Sey1s were identified among the objects from the VPM survey, with 114 QSOs and 10 Sey1s up to the pre-estimated 90% completeness limit of the survey at Blim � 19.7. The redshift range of the QSOs is 0.4 < z < 3. Among the 80 QSO candidates of highest priority we confirm 75 QSOs/Sey1s and 2 NELGs. We present magnitudes, colours, redshifts, and variability indices for all 181 identified QSOs/Sey1s/NELGs and spectra for the 77 QSOs/Sey1s/NELGs from our spectroscopic follow-up observations. The VPM survey uses selection criteria that are not directly relying on the spectral energy distribution of QSOs. It is therefore remarkable that the properties of the VPM QSOs do not significantly differ from those of samples from colour selection or slitless spectroscopy. In particular, we do not detect a substantial number of unusually red QSOs. The total surface density of the brighter QSOs (17 � B � 18.5) in our search field is found to be by a factor of � 1.8 larger than that derived from previous optical surveys.

Periodicity versus selection effects in the redshift distribution of QSOs

Periodicities and selection effects in the redshift (z) distribution of QSOs have been debated for a long time in the literature. Here we show that peaks and troughs in the redshift distribution of three new samples, claimed to demonstrate the existence of a periodicity, can be interpreted in terms of known selection effects. This analysis confirms earlier findings that the presence of such selection effects seriously weakens any suggestion for periodicity of the form Δl n (1 + z) = constant.

Periodicity versus selection effects in the redshift distribution of QSOs

Periodicity versus selection effects in the redshift distribution of QSOs

On the periodicity in the redshift distribution of QSOs: Wang Jia-qing Department of Physics, Anhui Normal University, Wuhu, 241001

On the periodicity in the redshift distribution of QSOs: Wang Jia-qing Department of Physics, Anhui Normal University, Wuhu, 241001

Redshift distribution of QSOs as a probe of initial spectrum on small scales

Abstract The dependence of the quasar abundance at different redshifts (n QSO (z)) on initial power spectrum is studied. It is shown that the preferable model for explaining the observable number density of QSOs over redshift (Schmidt et al., 1991) is the tilted CDM model with ω b = 0.1 and n = 0.7. The possibility of the reconstruction of initial power spectrum on small scale from the observable data on the quasar abundance over redshift is analysed too. It is shown that such spectrum in comparison with standart CDM has steep reducing of power at 1 ≤ k ≤ 10hMpc−1 and bump at k > 10hMpc−1.

Peaks and Periodicities in the Redshift Distribution of Quasi-Stellar Object

There have been claims from time to time that there are periodicities in the redshift distribution of QSOs. These claims are examined from various statistical angles for a sample of 2164 QSO redshifts, with redshifts lying in the range 0.025 – 4.43 taken from the latest compilation (1993) by Hewitt &amp;amp; Burbidge. We have not included QSOs whose redshifts were obtained by ‘grism’ technique, because of a possible selection effect (Scott 1991). For our analysis we use several staistical techniques, including the Burbidge - O'Dell type Power spectrum analysis (1972), the Rayleigh test, the Kolmogorov-Smirnov test, and the so called ‘Comb-tooth’ template test. the tests are not inter related and have the advantage of checking the claim for nonuniformity of the distribution from various independent angles. We have also carried out Monte Carlo simulations of the redshift distribution of QSOs to check for any systematic effect that can give rise to a spurious periodic effect.

Typical scales in the spatial distribution of QSOs

view Abstract Citations (15) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Typical Scales in the Spatial Distribution of QSOs Deng, Zugan ; Xia, Xiaoyang ; Fang, Li-Zhi Abstract We present results of searching for possible typical scales in the spatial distribution of QSOs. Our method is based on the second derivative of the two-point correlation function. This statistic is sensitive to the scale of the maximum in the spectrum P(k) of the density perturbation in the universe. This maximum or bend scale can be detected as the wavelengths of the periodic component in the second derivative of the integral correlation function. For various QSO samples compiled from surveys of pencil beam and bright QSOs, a typical scale of about 93 +/- 10h^-1^ Mpc for q_0_ = 0.5 has been detected. This typical scale is in good agreement with that found in the spatial distributions of galaxies, clusters of galaxies, and C IV absorption systems of QSOs if q_0_ is taken to be ~0.2. Therefore, it is likely a common or universal scale in the large-scale structure traced by these objects. This result is consistent with the assumption that the typical scale comes from a characteristic scale in the spectrum of the density perturbation in the universe. Publication: The Astrophysical Journal Pub Date: August 1994 DOI: 10.1086/174503 arXiv: arXiv:astro-ph/9402052 Bibcode: 1994ApJ...431..506D Keywords: Galactic Clusters; Galactic Evolution; Perturbation Theory; Quasars; Red Shift; Spatial Distribution; Absorption Spectra; Cosmology; Data Correlation; Pencil Beams; Power Spectra; Astrophysics; COSMOLOGY: THEORY; GALAXIES: CLUSTERING; COSMOLOGY: LARGE-SCALE STRUCTURE OF UNIVERSE; GALAXIES: QUASARS: GENERAL; Astrophysics E-Print: 16 pages, 13 figures (available upon request), Latex, AZPH-TH/94-02, to appear in Ap. J full text sources arXiv | ADS |

Orientation effects in QSO spectra

view Abstract Citations (22) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Orientation Effects in QSO Spectra Francis, Paul J. Abstract The consequences of anisotropic continuum emission for the equivalent- width distribution of QSOs are investigated and compared with observations from a large QSO survey. Isotropic line emission is assumed, and a variety of continuum anisotropy models are investigated. Far fewer high equivalent width QSOs are observed than most models predict. Both thick and thin accretion disks are ruled out, unless their radiation is reprocessed into a more isotropic angular distribution, or an obscuring torus conceals the broad-line region of nearly edge-on QSOs. Publication: The Astrophysical Journal Pub Date: March 1993 DOI: 10.1086/172344 Bibcode: 1993ApJ...405..119F Keywords: Accretion Disks; Line Spectra; Luminosity; Quasars; Anisotropic Media; Astronomical Models; Astrophysics; ACCRETION; ACCRETION DISKS; GALAXIES: QUASARS: GENERAL full text sources ADS |

Statistical and physical evolution of quasi-stellar objects

view Abstract Citations (16) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Statistical and Physical Evolution of Quasi-stellar Objects Caditz, David ; Petrosian, Vahe Abstract We discuss the relationship between the physical evolution of discrete extragalactic sources, the statistical evolution of the observed population of sources, and the cosmological model. Three simple forms of statistical evolution-pure luminosity evolution (PLE), pure density evolution (PDE), and generalized luminosity evolution (GLE)--are considered in detail together with what these forms imply about the physical evolution of individual sources. Two methods are used to analyze the statistical evolution of the observed distribution of QSOs from combined flux-limited samples. It is shown that both PLE and PDE are inconsistent with the data over the redshift range 0.2 < z < 2.2 and that a more complicated form of evolution such as GLE is required, independent of the cosmological model. This result is important for physical models of AGN, and in particular, for the accretion disk model which recent results show may be inconsistent with PLE. Publication: The Astrophysical Journal Pub Date: July 1990 DOI: 10.1086/168923 Bibcode: 1990ApJ...357..326C Keywords: Accretion Disks; Galactic Evolution; Galactic Nuclei; Quasars; Red Shift; Statistical Analysis; Astronomical Models; Cosmology; Energy Sources; Stellar Mass Accretion; Astrophysics; GALAXIES: EVOLUTION; GALAXIES: NUCLEI; QUASARS full text sources ADS |

Quasar Pairs

This paper summarizes various uses which have been made of QSO pairs. Statistical studies using pairs show that the sky distribution of QSOs of arbitrary redshifts is random, and that QSOs of similar redshifts are clustered on a linear scale similar to that of galaxies today. Close pairs are used to set limits on the masses of QSOs. And absorption line studies of QSO pairs support the extrinsic hypothesis for the origin of the narrow absorption lines and the cosmological interpretation of the redshift, they demonstrate the presence of absorbing matter around QSOs, and they set limits on the sizes of the absorbers.

The close QSO pair Q1548+114A, B

IPCS spectroscopic and CCD imaging observations have been made of the QSOs Q1548+114A and B, which are separated by 4.8 arcsec and have redshifts of 0.44 and 1.90. There is no evidence either for line-locking in the absorption spectrum of B or for associated absorption in B at the redshift of A, both of which had previously been reported. Galactic H and K absorption is present in both spectra. This remains the closest pair of distinct QSOs, although the number of QSOs has increased tenfold since its discovery, and its existence is consistent with a random distribution of QSOs on the sky.