The XXL Survey

We study the space density evolution of active galactic nuclei (AGN) using the 610 MHz radio survey of the XXL-North field, performed with the Giant Metrewave Radio Telescope. The survey covers an area of 30.4 deg2, with a beamsize of 6.5 arcsec. The survey is divided into two parts, one covering an area of 11.9 deg2 with 1σ rms noise of 200 μJy beam−1 and the other spanning 18.5 deg2 with rms noise of 45 μJy beam−1. We extracted the catalog of radio components above 7σ. The catalog was cross-matched with a multi-wavelength catalog of the XXL-North field (covering about 80% of the radio XXL-North field) using a likelihood ratio method, which determines the counterparts based on their positions and their optical properties. The multi-component sources were matched visually with the aid of a computer code: Multi-Catalog Visual Cross-Matching. A flux density cut above 1 mJy selects AGN hosts with a high purity in terms of star formation contamination based on the available source counts. After cross-matching and elimination of observational biases arising from survey incompletenesses, the number of remaining sources was 1150. We constructed the rest-frame 1.4 GHz radio luminosity functions of these sources using the maximum volume method. This survey allows us to probe luminosities of 23 ≲ log(L1.4 GHz[W Hz−1]) ≲ 28 up to redshifts of z ≈ 2.1. Our results are consistent with the results from the literature in which AGN are comprised of two differently evolving populations, where the high luminosity end of the luminosity functions evolves more strongly than the low-luminosity end.

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Cosmic evolution of AGN with moderate-to-high radiative luminosity in the COSMOS field

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318000030 ◽

2017 ◽

Vol 12 (S333) ◽

pp. 195-198

Author(s):

L. Ceraj ◽

V. Smolčić ◽

I. Delvecchio ◽

J. Delhaize ◽

M. Novak

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Radio Continuum ◽

Continuum Emission ◽

Number Density ◽

X Ray ◽

Cosmic Evolution ◽

Luminosity Functions ◽

Multi Wavelength ◽

First Time

AbstractWe study the moderate-to-high radiative luminosity active galactic nuclei (HLAGN) within the VLA-COSMOS 3 GHz Large Project. The survey covers 2.6 square degrees centered on the COSMOS field with a 1σ sensitivity of 2.3 μJy/beam across the field. This provides the simultaneously largest and deepest radio continuum survey available to date with exquisite multi-wavelength coverage. The survey yields 10,830 radio sources with signal-to-noise ratios ≥5. A subsample of 1,604 HLAGN is analyzed here. These were selected via a combination of X-ray luminosity and mid-infrared colors. We derive luminosity functions for these AGN and constrain their cosmic evolution out to a redshift of z ∼ 6, for the first time decomposing the star formation and AGN contributions to the radio continuum emission in the AGN. We study the evolution of number density and luminosity density finding a peak at z ∼ 1.5 followed by a decrease out to a redshift z ∼ 6.

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First HETDEX Spectroscopic Determinations of Lyα and UV Luminosity Functions at z = 2–3: Bridging a Gap between Faint AGNs and Bright Galaxies

The Astrophysical Journal ◽

10.3847/1538-4357/ac1e97 ◽

2021 ◽

Vol 922 (2) ◽

pp. 167

Author(s):

Yechi Zhang ◽

Masami Ouchi ◽

Karl Gebhardt ◽

Erin Mentuch Cooper ◽

Chenxu Liu ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Rest Frame ◽

High Redshift ◽

Galactic Nuclei ◽

Emission Lines ◽

Bright Galaxy ◽

Number Density ◽

Luminosity Functions ◽

Best Fit

Abstract We present Lyα and ultraviolet (UV)-continuum luminosity functions (LFs) of galaxies and active galactic nuclei (AGNs) at z = 2.0–3.5 determined by the untargeted optical spectroscopic survey of the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). We combine deep Subaru imaging with HETDEX spectra resulting in 11.4 deg2 of fiber spectra sky coverage, obtaining 18,320 galaxies spectroscopically identified with Lyα emission, 2126 of which host type 1 AGNs showing broad (FWHM > 1000 km s−1) Lyα emission lines. We derive the Lyα (UV) LF over 2 orders of magnitude covering bright galaxies and AGNs in log L Ly α / [ erg s − 1 ] = 43.3 – 45.5 (−27 < M UV < −20) by the 1/V max estimator. Our results reveal that the bright-end hump of the Lyα LF is composed of type 1 AGNs. In conjunction with previous spectroscopic results at the faint end, we measure a slope of the best-fit Schechter function to be α Sch = − 1.70 − 0.14 + 0.13 , which indicates that α Sch steepens from z = 2–3 toward high redshift. Our UV LF agrees well with previous AGN UV LFs and extends to faint-AGN and bright-galaxy regimes. The number fraction of Lyα-emitting objects (X LAE) increases from M UV * ∼ − 21 to bright magnitude due to the contribution of type 1 AGNs, while previous studies claim that X Lyα decreases from faint magnitudes to M UV * , suggesting a valley in the X Lyα –magnitude relation at M UV * . Comparing our UV LF of type 1 AGNs at z = 2–3 with those at z = 0, we find that the number density of faint (M UV > −21) type 1 AGNs increases from z ∼ 2 to 0, as opposed to the evolution of bright (M UV < −21) type 1 AGNs, suggesting AGN downsizing in the rest-frame UV luminosity.

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Polarimetric Properties of Blazars Caught by the WEBT

Galaxies ◽

10.3390/galaxies9020042 ◽

2021 ◽

Vol 9 (2) ◽

pp. 42

Author(s):

Claudia M. Raiteri ◽

Massimo Villata

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Plasma Jets ◽

Line Of Sight ◽

Optical Behaviour ◽

Relativistic Jets ◽

Comprehensive Picture ◽

Multi Wavelength ◽

Extreme Variability ◽

Continuous Range

Active galactic nuclei come in many varieties. A minority of them are radio-loud, and exhibit two opposite prominent plasma jets extending from the proximity of the supermassive black hole up to megaparsec distances. When one of the relativistic jets is oriented closely to the line of sight, its emission is Doppler beamed and these objects show extreme variability properties at all wavelengths. These are called “blazars”. The unpredictable blazar variability, occurring on a continuous range of time-scales, from minutes to years, is most effectively investigated in a multi-wavelength context. Ground-based and space observations together contribute to give us a comprehensive picture of the blazar emission properties from the radio to the γ-ray band. Moreover, in recent years, a lot of effort has been devoted to the observation and analysis of the blazar polarimetric radio and optical behaviour, showing strong variability of both the polarisation degree and angle. The Whole Earth Blazar Telescope (WEBT) Collaboration, involving many tens of astronomers all around the globe, has been monitoring several blazars since 1997. The results of the corresponding data analysis have contributed to the understanding of the blazar phenomenon, particularly stressing the viability of a geometrical interpretation of the blazar variability. We review here the most significant polarimetric results achieved in the WEBT studies.

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Proper motion in lensed radio jets at redshift 3: A possible dual super-massive black hole system in the early Universe

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935427 ◽

2019 ◽

Vol 630 ◽

pp. A108 ◽

Cited By ~ 4

Author(s):

C. Spingola ◽

J. P. McKean ◽

D. Massari ◽

L. V. E. Koopmans

Keyword(s):

Active Galactic Nuclei ◽

Early Universe ◽

Gravitational Lensing ◽

Proper Motion ◽

Galactic Nuclei ◽

Massive Black Hole ◽

Radio Jets ◽

Long Baseline ◽

Multi Wavelength ◽

Low Probability

In this paper, we exploit the gravitational lensing effect to detect proper motion in the highly magnified gravitationally lensed source MG B2016+112. We find positional shifts up to 6 mas in the lensed images by comparing two Very Long Baseline Interferometric (VLBI) radio observations at 1.7 GHz that are separated by 14.359 years, and provide an astrometric accuracy of the order of tens of μas. From lens modelling, we exclude a shift in the lensing galaxy as the cause of the positional change of the lensed images, and we assign it to the background source. The source consists of four sub-components separated by ∼175 pc, with proper motion of the order of tens μas yr−1 for the two components at highest magnification (μ ∼ 350) and of the order of a few mas yr−1 for the two components at lower magnification (μ ∼ 2). We propose single active galactic nuclei (AGN) and dual AGN scenarios to explain the source plane. Although, the latter interpretation is supported by the archival multi-wavelength properties of the object. In this case, MG B2016+112 would represent the highest redshift dual radio-loud AGN system discovered thus far, and would support the merger interpretation for such systems. Also, given the low probability (∼10−5) of detecting a dual AGN system that is also gravitationally lensed, if confirmed, this would suggest that such dual AGN systems must be more abundant in the early Universe than currently thought.

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Evolution of the AGN UV luminosity function from redshift 7.5

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1493 ◽

2019 ◽

Vol 488 (1) ◽

pp. 1035-1065 ◽

Cited By ~ 42

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.

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Quasi-stellar object redshift estimates from optical, near-infrared, and ultraviolet colours

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936179 ◽

2019 ◽

Vol 629 ◽

pp. A56 ◽

Cited By ~ 1

Author(s):

S. J. Curran ◽

J. P. Moss

Keyword(s):

Active Galactic Nuclei ◽

Rest Frame ◽

Near Infrared ◽

Galactic Nuclei ◽

Additional Contribution ◽

Stellar Objects ◽

Simple Estimate ◽

Photometric Redshift ◽

Wide Range ◽

Quasi Stellar Objects

A simple estimate of the photometric redshift would prove invaluable to forthcoming continuum surveys on the next generation of large radio telescopes, as well as mitigating the existing bias towards the most optically bright sources. While there is a well-known correlation between the near-infrared K-band magnitude and redshift for galaxies, we find the K − z relation to break down for samples dominated by quasi-stellar objects. We hypothesise that this is due to the additional contribution to the near-infrared flux by the active galactic nucleus, and, as such, the K-band magnitude can only provide a lower limit to the redshift in the case of active galactic nuclei, which will dominate the radio surveys. From a large optical dataset, we find a tight relationship between the rest-frame (U − K)/(W2 − FUV) colour ratio and spectroscopic redshift over a sample of 17 000 sources, spanning z ≈ 0.1−5. Using the observed-frame ratios of (U − K)/(W2 − FUV) for redshifts of z ≲ 1, (I − W2)/(W3 − U) for 1 ≲ z ≲ 3, and (I − W2.5)/(W4 − R) for z ≳ 3, where W2.5 is the λ = 8.0 μm magnitude and the appropriate redshift ranges are estimated from the W2 (4.5 μm) magnitude, we find this to be a robust photometric redshift estimator for quasars. We suggest that the rest-frame U − K colour traces the excess flux from the AGN over this wide range of redshifts, although the W2 − FUV colour is required to break the degeneracy.

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Monitoring the Extragalactic High Energy Sky

Galaxies ◽

10.3390/galaxies7010009 ◽

2019 ◽

Vol 7 (1) ◽

pp. 9 ◽

Cited By ~ 2

Author(s):

Jean-Philippe Lenain

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

High Energy ◽

Line Of Sight ◽

Data Sets ◽

High Energies ◽

Multi Wavelength ◽

Rich Data ◽

Very High

Blazars are jetted active galactic nuclei with a jet pointing close to the line of sight, hence enhancing their intrinsic luminosity and variability. Monitoring these sources is essential in order to catch them flaring and promptly organize follow-up multi-wavelength observations, which are key to providing rich data sets used to derive e.g., the emission mechanisms at work, and the size and location of the flaring zone. In this context, the Fermi-LAT has proven to be an invaluable instrument, whose data are used to trigger many follow-up observations at high and very high energies. A few examples are illustrated here, as well as a description of different data products and pipelines, with a focus given on FLaapLUC, a tool in use within the H.E.S.S. collaboration.

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6.8. A multi wavelength study of the circumnuclear region of NGC 1365

Symposium - International Astronomical Union ◽

10.1017/s0074180900084916 ◽

1998 ◽

Vol 184 ◽

pp. 277-278

Author(s):

H. Kristen ◽

Aa. Sandqvist ◽

P.O. Lindblad

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Radio Continuum ◽

Nuclear Region ◽

High Excitation ◽

Multi Wavelength ◽

Optical Wavelengths ◽

Barred Spiral Galaxy ◽

Seyfert Nucleus ◽

Ngc 1365

The nuclear region of the supergiant barred spiral galaxy NGC 1365 contains bright “hot spots”, as seen at optical wavelengths, as well as a number of non-thermal radio continuum sources, some of which remain unresolved at 0.25” × 0.10” resolution (Sandqvist et al. 1995, A&A 295, 585).The distribution of [OIII] λ5007 emission from the nuclear region supports the scenario of an [OIII] cone emanating from the Seyfert nucleus. The velocity field of the high excitation gas in the cone has been modeled by Hjelm & Lindblad (1996, A&A 305, 727) in terms of an accelerated bipolar conical outflow. Such conical or biconical high-excitation emission-line structures extending from the position of the nucleus are found in several active galactic nuclei.

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A Multi-Wavelength Study of X-ray Selected AGN

Symposium - International Astronomical Union ◽

10.1017/s0074180900140823 ◽

1989 ◽

Vol 134 ◽

pp. 199-200

Author(s):

R. J. V. Brissenden ◽

I. R. Tuohy ◽

G. V. Bicknell ◽

R. A. Remillard ◽

D. A. Schwartz

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

High Energy ◽

Astronomy Observatory ◽

X Ray ◽

Preliminary Results ◽

Multi Wavelength ◽

Uv Excess ◽

Modulation Collimator

A sample of Active Galactic Nuclei (AGN) have been discovered during a program to identify the optical counterparts of X-ray sources detected by the Modulation Collimator experiment of the High Energy Astronomy Observatory-1 (HEAO-1). UV-excess techniques were used to identify the X-ray sources (Remillard et al. 1986) and the details of the identifications are given elsewhere (Remillard et al. 1988, Brissenden et al. 1988). We report here the preliminary results of a multi-wavelength study of these new AGN.

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The Extremes of AGN Variability

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317001648 ◽

2016 ◽

Vol 12 (S324) ◽

pp. 168-171 ◽

Cited By ~ 3

Author(s):

S. Komossa ◽

D. Grupe ◽

N. Schartel ◽

L. Gallo ◽

J. L. Gomez ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

X Ray ◽

Accretion Flow ◽

Multi Wavelength ◽

Long Term Monitoring ◽

Term Monitoring ◽

Spectral States ◽

Ongoing Monitoring

AbstractWe present results from our ongoing monitoring programs aimed at identifying and understanding Active Galactic Nuclei (AGN) in extreme flux and spectral states. Observations of AGN in extreme states can reveal the nature of the inner accretion flow, the physics of matter under strong gravity, and they provide insight on the properties of ionized absorbers and outflows launched near supermassive black holes (SMBHs). We present new results from our long-term monitoring of IC 3599, WPVS007, and Mrk 335, multi-wavelength follow-ups of the newly identified changing-look AGN HE 1136–2304, and UV–X-ray follow-ups of the binary SMBH candidate OJ 287 after its 2015 optical maximum, now in a new optical-X-ray–high-state.

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