Quasars as a Tracer of Large-Scale Structures in the Distant Universe

Song, Hyun Hoon; Park, Changbom; Lietzen, H.; Einasto, M.

doi:10.3847/0004-637x/827/2/104

Cited by 16 publications

(12 citation statements)

References 92 publications

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“…We found that X-ray AGN trace the distribution of X-ray clusters at a <25-45 Mpc scale: the fraction of agglomerates located in the vicinity of X-ray clusters is ∼1.5-2 times higher than for randomly distributed agglomerates in both considered redshift ranges. This is in agreement with Arnold et al (2009) and also with optical AGN studies by Hwang et al (2012) and Song et al (2016), where the authors show that the AGN fractions in the field environment are higher than in clusters. Kocevski et al (2009) found that Seyfert-2 galaxies avoid the densest regions of superclusters and are instead located in intermediate density environments.…”

Section: Large-scale Structure Of the Xxl-ssupporting

confidence: 91%

“…This is in agreement with previous works for AGN selected in the optical, X-ray, and radio (cf. Gilmour et al 2009;Constantin et al 2008;Silverman et al 2009;Lietzen et al 2009Lietzen et al , 2011Tasse et al 2008Tasse et al , 2011Melnyk et al 2013;Hwang et al 2012;Gendre et al 2013;Manzer & De Robertis 2014;Karouzos et al 2014a,b;Song et al 2016). On the other hand, according to the small-scale analysis, the Kolmogorov-Smirnov probability that the AGN overdensity distribution is consistent with the mock distribution is less than 10 −3 in the first redshift range and for both the bright and faint environments.…”

Section: Small-and Large-scale Environments Of X-ray Agnmentioning

confidence: 99%

“…It also agrees with some studies for optical AGN, although there are many studies of optical AGN that do not agree. For example, Hwang et al (2012) and Song et al (2016) found that the fraction of AGN in the field is higher than in clusters (see also the references in those papers), contrary to Manzer & De Robertis (2014) for whom the AGN fraction increases with decreasing distance to the group centroid. However, Melnyk et al (2015) and Argudo-Fernández et al (2016) independently found no difference in the prevalence of optical AGN (mainly type 2) in isolated and paired galaxies.…”

Section: Small-and Large-scale Environments Of X-ray Agnmentioning

confidence: 99%

“…We again note that our assumption here was that the X-ray sources closely trace the distribution of optical galaxies. According to Song et al (2016), the optical quasar density changes somewhat more slowly than the galaxy density. Nevertheless, taking into account the field galaxies, those authors showed a weak positive correlation between the black hole mass and the large-scale environmental density, and a negative correlation between the optical luminosity and the density.…”

Section: Small-and Large-scale Environments Of X-ray Agnmentioning

confidence: 99%

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The XXL Survey

Мelnyk

Elyiv

Smolčić

et al. 2018

A&A

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Context. This work is part of a series of studies focusing on the environment and the properties of the X-ray selected active galactic nuclei (AGN) population from the XXL survey. The present survey, given its large area, continuity, extensive multiwavelength coverage, and large-scale structure information, is ideal for this kind of study. Here, we focus on the XXL-South (XXL-S) field. Aims. Our main aim is to study the environment of the various types of X-ray selected AGN and investigate its possible role in AGN triggering and evolution. Methods. We studied the large-scale (>1 Mpc) environment up to redshift z = 1 using the nearest neighbour distance method to compare various pairs of AGN types. We also investigated the small-scale environment (<0.4 Mpc) by calculating the local overdensities of optical galaxies. In addition, we built a catalogue of AGN concentrations with two or more members using the hierarchical clustering method and we correlated them with the X-ray galaxy clusters detected in the XXL survey. Results. It is found that radio detected X-ray sources are more obscured than non-radio ones, though not all radio sources are obscured AGN. We did not find any significant differences in the large-scale clustering between luminous and faint X-ray AGN, or between obscured and unobscured ones, or between radio and non-radio sources. At local scales (<0.4 Mpc), AGN typically reside in overdense regions, compared to non-AGN; however, no differences were found between the various types of AGN. A majority of AGN concentrations with two or more members are found in the neighbourhood of X-ray galaxy clusters within <25–45 Mpc. Our results suggest that X-ray AGN are typically located in supercluster filaments, but they are also found in over- and underdense regions.

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Section: Large-scale Structure Of the Xxl-ssupporting

confidence: 91%

Section: Small-and Large-scale Environments Of X-ray Agnmentioning

confidence: 99%

Section: Small-and Large-scale Environments Of X-ray Agnmentioning

confidence: 99%

Section: Small-and Large-scale Environments Of X-ray Agnmentioning

confidence: 99%

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The XXL Survey

Мelnyk

Elyiv

Smolčić

et al. 2018

A&A

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“…On the other hand, previous studies show that quasar pairs at low redshift (z < 1) do not always reside in dense environments. A recent study by Song et al (2016) shows that z ∼ 1 single quasar environments have a slight tendency toward high density regions, while the enhancement of the quasar density is weaker than expected from a proportional relation of the galaxy density. From this section, we extend the redshift range down to z ∼ 1 to compare with the high-redshift pairs and also with single quasars at the same redshift.…”

Section: Quasar Pairs At Z ∼mentioning

confidence: 88%

Enhancement of galaxy overdensity around quasar pairs at z < 3.6 based on the Hyper Suprime-Cam Subaru Strategic Program Survey

Onoue

Kashikawa

Uchiyama

et al. 2017

Publications of the Astronomical Society of Japan

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We investigate the galaxy overdensity around proto-cluster scale quasar pairs at high (z > 3) and low (z ∼ 1) redshift based on the unprecedentedly wide and deep optical survey of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). Using the first-year survey data covering effectively ∼ 121 deg 2 with the 5σ depth of i ∼ 26.4 and the SDSS DR12Q catalog, we find two luminous pairs at z ∼ 3.3 and 3.6 which reside in > 5σ overdense regions of gdropout galaxies at i < 25. The projected separations of the two pairs are R ⊥ = 1.75 and 1.04 proper Mpc, and their velocity offsets are ∆V = 692 and 1448 km s −1 , respectively. This result is in clear contrast to the average z ∼ 4 quasar environments as discussed in Uchiyama et al. (2017) and implies that the quasar activities of the pair members are triggered via major mergers in proto-clusters, unlike the vast majority of isolated quasars in general fields that may turn on via non-merger events such as bar and disk instabilities. At z ∼ 1, we find 37 pairs with R ⊥ < 2 pMpc and ∆V < 2300 km s −1 in the current HSC-Wide coverage, including four from Hennawi et al. (2006). The distribution of the peak overdensity significance within two arcminutes around the pairs has a long tail toward high density (> 4σ) regions. Thanks to the large sample size, we find a statistical evidence that this excess is unique to the pair environments when compared to single quasar and randomly selected galaxy environments at the same redshift range. Moreover, there are nine small-scale (R ⊥ < 1 pMpc) pairs, two of which are found to reside in cluster fields. Our results demonstrate that < 2 pMpc-scale quasar pairs at both redshift range tend to occur in massive haloes, although perhaps not the most massive ones, and that they are useful to search for rare density peaks.

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VarIabiLity seLection of AstrophysIcal sources iN PTF (VILLAIN)

Bruun¹,

Agnello²,

Hjorth³

2023

A&A

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Context. Light-curve variability is well-suited to characterising objects in surveys with high cadence and a long baseline. This is especially relevant in view of the large datasets to be produced by the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). Aims. We aim to determine variability parameters for objects in the Palomar Transient Factory (PTF) and explore differences between quasars (QSOs), stars, and galaxies. We relate variability and colour information in preparation for future surveys. Methods. We fit joint likelihoods to structure functions (SFs) of 71 million PTF light curves with a Markov chain Monte Carlo method. For each object, we assume a power-law SF and extract two parameters: the amplitude on timescales of one year, A, and a power-law index, γ. With these parameters and colours in the optical (Pan-STARRS1) and mid-infrared (WISE), we identify regions of parameter space dominated by different types of spectroscopically confirmed objects from SDSS. Candidate QSOs, stars, and galaxies are selected to show their parameter distributions. Results. QSOs show high-amplitude variations in the R band, and the highest γ values. Galaxies have a broader range of amplitudes and their variability shows relatively little dependency on timescale. With variability and colours, we achieve a photometric selection purity of 99.3% for QSOs. Even though hard cuts in monochromatic variability alone are not as effective as seven-band magnitude cuts, variability is useful in characterising object subclasses. Through variability, we also find QSOs that were erroneously classified as stars in the SDSS. We discuss perspectives and computational solutions in view of the upcoming LSST.

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Quasars as a Tracer of Large-Scale Structures in the Distant Universe

Cited by 16 publications

References 92 publications

The XXL Survey

The XXL Survey

Enhancement of galaxy overdensity around quasar pairs at z < 3.6 based on the Hyper Suprime-Cam Subaru Strategic Program Survey

VarIabiLity seLection of AstrophysIcal sources iN PTF (VILLAIN)

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Quasars as a Tracer of Large-Scale Structures in the Distant Universe

Cited by 16 publications

References 92 publications

The XXL Survey

The XXL Survey

Enhancement of galaxy overdensity around quasar pairs at z &lt; 3.6 based on the Hyper Suprime-Cam Subaru Strategic Program Survey

VarIabiLity seLection of AstrophysIcal sources iN PTF (VILLAIN)

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Product

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Enhancement of galaxy overdensity around quasar pairs at z < 3.6 based on the Hyper Suprime-Cam Subaru Strategic Program Survey