scholarly journals European VLBI Network Observations of the Proposed Dual AGN SDSS J101022.95+141300.9

2021 ◽  
Vol 922 (2) ◽  
pp. 99
Author(s):  
Patrik Milán Veres ◽  
Krisztina Éva Gabányi ◽  
Sándor Frey ◽  
Zsolt Paragi ◽  
Emma Kun ◽  
...  
Keyword(s):  
Hubble Space Telescope ◽  
Galactic Nuclei ◽  
Point Sources ◽  
Optical Observations ◽  
Scale Separation ◽  
Radio Structure ◽  
Long Baseline ◽  
Optical Position ◽  
Single Feature ◽  
The Galaxy

Abstract During galaxy merger events, the supermassive black holes in the center of the galaxies may form a pair of active galactic nuclei (AGN) with kiloparsec-scale or even parsec-scale separation. Recently, optical observations revealed a promising dual-AGN candidate at the center of the galaxy SDSS J101022.95+141300.9 (hereafter J1010+1413). The presence of two distinct [O iii]-emitting point sources with a projected separation of ∼430 pc indicates a dual-AGN system. To search for AGN-dominated radio emission originating from the Hubble Space Telescope (HST) point sources, we carried out very long baseline interferometry observations. We resolved the radio structure of J1010+1413 and detected a single feature offset from the HST point sources and also from the Gaia optical position of the object. Our multiwavelength analysis of J1010+1413 inferred two possible interpretations of the observed properties challenging its proposed dual-AGN classification.

scholarly journals The radio structure of the narrow-line Seyfert 1 Mrk 783 with VLBA and e-MERLIN

2020 ◽  
Vol 499 (3) ◽  
pp. 3149-3157
Author(s):  
E Congiu ◽  
P Kharb ◽  
A Tarchi ◽  
M Berton ◽  
A Caccianiga ◽  
...  
Keyword(s):  
Position Angle ◽  
Optical Observations ◽  
Narrow Line ◽  
Radio Structure ◽  
Long Baseline ◽  
New Radio ◽  
The Galaxy ◽  
L Band ◽  
Very Long Baseline Array ◽  
Band Image

ABSTRACT In this paper, we present the analysis of new radio and optical observations of the narrow-line Seyfert 1 galaxy Mrk 783. $1.6\, \mathrm{GHz}$ observations performed with the e-MERLIN interferometer confirm the presence of the diffuse emission previously observed. The Very Long Baseline Array (VLBA) also detects the nuclear source both at $1.6\, \mathrm{GHz}$ (L band) and $5\, \mathrm{GHz}$ (C band). While the L-band image shows only an unresolved core, the C-band image shows the presence of a partially resolved structure at a position angle of 60○. The brightness temperature of the emission in both bands (${\gt}10^6\, \mathrm{K}$) suggests that it is a pc-scale jet produced by the active galactic nucleus. The relatively steep VLBA spectral index (αVLBA = 0.63 ± 0.03) is consistent with the presence of optically thin emission on milliarcsecond scales. Finally, we investigated two possible scenarios that can result in the misalignment between the kpc and pc-scale radio structure detected in the galaxy. We also analysed the optical morphology of the galaxy, which suggests that Mrk 783 underwent a merging in relatively recent times.

scholarly journals High-resolution radio imaging of two luminous quasars beyond redshift 4.5

2018 ◽  
Vol 618 ◽  
pp. A68 ◽  
Author(s):  
S. Frey ◽  
O. Titov ◽  
A. E. Melnikov ◽  
P. de Vicente ◽  
F. Shu
Keyword(s):  
High Resolution ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Brightness Distribution ◽  
Distribution Model ◽  
Radio Structure ◽  
Long Baseline ◽  
Radio Imaging ◽  
Jet Structure ◽  
East West

Context. Radio-loud active galactic nuclei in the early Universe are rare. The quasars J0906+6930 at redshift z = 5.47 and J2102+6015 at z = 4.57 stand out from the known sample with their compact emission on milliarcsecond (mas) angular scale with high (0.1 Jy level) flux densities measured at GHz radio frequencies. This makes them ideal targets for very long baseline interferometry (VLBI) observations. Aims. By means of VLBI imaging we can reveal the inner radio structure of quasars and model their brightness distribution to better understand the geometry of the jet and the physics of the sources. Methods. We present sensitive high-resolution VLBI images of J0906+6930 and J2102+6015 at two observing frequencies, 2.3 and 8.6 GHz. The data were taken in an astrometric observing programme involving a global five-element radio telescope array. We combined the data from five different epochs from 2017 February to August. Results. For one of the highest redshift blazars known, J0906+6930, we present the first-ever VLBI image obtained at a frequency below 8 GHz. Based on our images at 2.3 and 8.6 GHz, we confirm that this source has a sharply bent helical inner jet structure within ∼3 mas from the core. The quasar J2102+6015 shows an elongated radio structure in the east–west direction within the innermost ∼2 mas that can be described with a symmetric three-component brightness distribution model at 8.6 GHz. Because of their non-pointlike mas-scale structure, these sources are not ideal as astrometric reference objects. Our results demonstrate that VLBI observing programmes conducted primarily with astrometric or geodetic goals can be utilized for astrophysical purposes as well.

scholarly journals A multiwavelength study of the dual nuclei in Mrk 212

2020 ◽  
Vol 500 (3) ◽  
pp. 3908-3919
Author(s):  
K Rubinur ◽  
P Kharb ◽  
M Das ◽  
P T Rahna ◽  
M Honey ◽  
...  
Keyword(s):  
Radio Source ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Radio Observations ◽  
Radio Structure ◽  
Very Large Array ◽  
Extended Radio ◽  
The Galaxy ◽  
Double Radio Source ◽  
Tidal Tails

ABSTRACT We present radio observations of the galaxy merger remnant Mrk 212 with the Karl G. Jansky Very Large Array (VLA) and the upgraded Giant Meter Radio Telescope (uGMRT). Mrk 212 has two previously known radio sources associated with the two optical nuclei, S1 and S2, with a projected separation of ∼6 kpc, making it a dual active galactic nuclei (AGN) candidate. Our new 15-GHz VLA observations reveal that S1 is a double radio source centred around the optical nucleus; its total extent is ∼750 pc its average 1.4−8.5 GHz spectral index is −0.81 ± 0.06. S1 therefore resembles a compact symmetric object. The 15-GHz VLA image identifies the radio source at S2 to be a compact core. Our radio observations therefore strongly support the presence of a dual AGN in Mrk 212. The optical emission line flux ratios obtained from the Himalayan Chandra Telescope (HCT) observations however, show that S1 and S2 both fall in the AGN + star formation (SF) region of the Baldwin, Philips and Terlevich (BPT) diagram. Weak AGN lying in the SF or AGN + SF intermediate regions in the BPT diagram have indeed been reported in the literature; our sources clearly fall in the same category. We find an extended radio structure in our newly reduced 8.5-GHz-VLA data, that is offset by ∼1 arcsec from the optical nucleus S2. New deep FUV and NUV observations with the Ultraviolet Imaging Telescope aboard AstroSat reveal SF knots around S2 as well as kpc-scale tidal tails; the SF knots around S2 coincide with the extended radio structure detected at 8.5 GHz. The radio spectral indices are consistent with SF. Any possible association with the AGN in S2 is unclear at this stage.

A deep Chandra survey for faint X-ray sources in the Galactic globular cluster M30, and searches for optical and radio counterparts

2020 ◽  
Vol 499 (3) ◽  
pp. 3338-3355
Author(s):  
Yue Zhao ◽  
Craig O Heinke ◽  
Haldan N Cohn ◽  
Phyllis M Lugger ◽  
Sebastien Guillot ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Cataclysmic Variables ◽  
Galactic Nuclei ◽  
Point Sources ◽  
Very Large Array ◽  
X Ray ◽  
Radial Profiles

ABSTRACT We present a deep (∼330 ks) Chandra survey of the Galactic globular cluster M30 (NGC 7099). Combining the new Cycle 18 with the previous Cycle 3 observations we report a total of 10 new X-ray point sources within the 1${_{.}^{\prime}}$03 half-light radius, compiling an extended X-ray catalogue of a total of 23 sources. We incorporate imaging observations by the Hubble Space Telescope and the Karl G. Jansky Very Large Array from the MAVERIC survey to search for optical and radio counterparts to the new and old sources. Two X-ray sources are found to have a radio counterpart, including the known millisecond pulsar PSR J2140−2310A, the radio position of which also matches a previously reported faint optical counterpart which is slightly redder than the main sequence. We found optical counterparts to 18 of the 23 X-ray sources, identifying two new cataclysmic variables (CVs), five new CV candidates, two new candidates of RS CVn type of active binary (AB), and two new candidates of BY Dra type of AB. The remaining unclassified X-ray sources are likely background active galactic nuclei (AGNs), as their number is consistent with the expected number of AGN at our X-ray sensitivity. Finally, our analysis of radial profiles of different source classes suggests that bright CVs are more centrally distributed than faint CVs in M30, consistent with other core-collapsed globular clusters.

scholarly journals VLBI observations of the H2O gigamaser in TXS 2226-184

2020 ◽  
Vol 637 ◽  
pp. A57
Author(s):  
G. Surcis ◽  
A. Tarchi ◽  
P. Castangia
Keyword(s):  
Galactic Nuclei ◽  
Radio Continuum ◽  
Integration Time ◽  
Absolute Position ◽  
Maser Emission ◽  
Long Baseline ◽  
Systemic Velocity ◽  
The Galaxy ◽  
Very Long Baseline Array ◽  
First Time

Context. Outside the Milky Way the most luminous H2O masers at 22 GHz, called megamasers because of their extreme luminosity with respect to the Galactic and extragalactic H2O masers associated with star formation, are mainly detected in active galactic nuclei. In the case of the H2O maser detected in the nuclear region of the galaxy TXS 2226-184, the term gigamaser was used for the first time. However, the origin of this very luminous H2O maser emission has never been investigated in detail. Aims. We study the nature of the 22 GHz H2O gigamaser in TXS 2226-184 by measuring its absolute position for the first time at milliarcsecond resolution, by comparing the morphology and characteristics of the maser emission on very long baseline interferometry (VLBI) scales after about 20 years, and by trying to detect its polarized emission. Methods. We observed the 22 GHz H2O maser emission toward TXS 2226-184 three times: the very first time with the NRAO Very Long Baseline Array (VLBA, epoch 2017.45) and the next two times with the European VLBI Network (EVN, epochs 2017.83 and 2018.44). The first two epochs (2017.45 and 2017.83) were observed in phase-reference mode, while the last epoch (2018.44) was observed in full-polarization mode, but not in phase-reference mode to increase the on-source integration time. We also retrieved and analyzed the VLBA archival data at 22 GHz of TXS 2226-184 observed in epoch 1998.40. Results. We detected six H2O maser features in epoch 2017.45 (VLBA), one in epoch 2017.83 (EVN), and two in epoch 2018.44 (EVN). All but one are red-shifted with respect to the systemic velocity of TXS 2226-184; we detected only one blue-shifted maser feature and it is the weakest one. All the H2O maser features but the blue-shifted one are composed of two components with very different linewidths. For the first time we were able to measure the absolute position of the H2O maser features with errors below 1 milliarcsec. No linear and circular polarization was detected. Conclusions. We were able to associate the H2O maser features in TXS 2226-184 with the most luminous radio continuum clump reported in the literature. The comparison between epochs 1998.40 and 2017.45 reveals a difference in the morphology and velocity of the maser features that can be justified accounting for maser variability.

scholarly journals Milliarcsecond Radio Structure of AGN as a Cosmological Probe

1996 ◽  
Vol 168 ◽  
pp. 477-480
Author(s):  
L.I. Gurvits
Keyword(s):  
Active Galactic Nuclei ◽  
Basic Concept ◽  
Very Long Baseline Interferometry ◽  
Galactic Nuclei ◽  
Radio Structure ◽  
Long Baseline ◽  
Standard Object

Recent achievements in Very Long Baseline Interferometry (VLBI) allow the reconsideration of milliarcsecond radio structure of Active Galactic Nuclei (AGN) as a “standard object”. The basic concept of this approach is described and illustrated.

scholarly journals J1110+4817 – a compact symmetric object candidate revisited

2020 ◽  
Vol 496 (2) ◽  
pp. 1811-1818 ◽  
Author(s):  
Máté Krezinger ◽  
Sándor Frey ◽  
Tao An ◽  
Sumit Jaiswal ◽  
Yingkang Zhang
Keyword(s):  
Large Scale ◽  
Galactic Nuclei ◽  
Host Galaxy ◽  
Nuclear Activity ◽  
Radio Structure ◽  
Long Baseline ◽  
Extended Radio ◽  
Evolutionary Phase ◽  
Resolution Imaging ◽  
Jet Structure

ABSTRACT Compact symmetric objects (CSOs) are radio-emitting active galactic nuclei (AGNs) typically with a double-lobed radio structure confined to within 1 kpc. CSOs represent the earliest evolutionary phase of jetted AGNs. Some of them may eventually evolve into large-scale extended double sources, while others stall within the host galaxy and die out, depending on the longevity of nuclear activity, the jet power, and parameters of the surrounding galactic environment. Studying CSOs is a useful tool for understanding the evolution of the galaxies and the interactions between the jets and the medium of the host galaxy. Based on milliarcsec-resolution imaging observations using very long baseline interferometry (VLBI), it is not always straightforward to distinguish between a compact double-lobed or a core–jet structure. The quasar J1110+4817 was considered a CSO candidate in the literature earlier, but because of the lack of clear evidence, it could not be securely classified as a CSO. Here we present a comprehensive analysis of archival multifrequency VLBI observations combined with accurate Gaia optical astrometric information. Lower frequency VLBI images reveal an extended radio feature nearly perpendicular to the main structural axis of the source, apparently emanating from the brighter northern feature, which is rare among the known CSOs. While the presence of a binary AGN system cannot be fully excluded, the most plausible explanation is that J1110+4817 is a CSO.

scholarly journals Kiloparsec Scale Radio Structure in Active Galaxies

1983 ◽  
Vol 6 ◽  
pp. 467-480 ◽  
Author(s):  
A. S. Wilson
Keyword(s):  
Interstellar Medium ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Active Galaxies ◽  
Radial Acceleration ◽  
Radio Structure ◽  
Interstellar Clouds ◽  
Ram Pressure ◽  
The Galaxy

AbstractA substantial fraction of active galaxies contain linear radio sources with sizes of a few hundreds or thousands of parsecs. Such sources are found in essentially all classes of active galactic nuclei, including Seyfert galaxies of both types, X-ray selected active nuclei, radio galaxies and quasars. The radio emission is clearly energised by the active nucleus, probably in the form of a jet. A number of observable consequences of the interaction of the jet with the interstellar medium of the galaxy are discussed. These processes include jet disruption by instabilities, acceleration of cosmic rays by shocks or turbulence, ionization and radial acceleration of interstellar clouds, creation of a hot thermal component through the agency of shock waves and bending of the jet by the ram pressure of a rotating interstellar medium.

scholarly journals Active Galactic Nuclei in polarized light

2019 ◽  
Vol 28 (1) ◽  
pp. 213-219
Author(s):  
Elena Shablovinskaya ◽  
Viktor Afanasiev
Keyword(s):  
Active Galactic Nuclei ◽  
Galaxy Evolution ◽  
Electromagnetic Waves ◽  
Polarized Light ◽  
Galactic Nuclei ◽  
Optical Observations ◽  
Special Astrophysical Observatory ◽  
Physical Processes ◽  
The Galaxy ◽  
Central Regions

Abstract Due to the compactness active galactic nuclei (AGN) are still unresolved with optical observations. However, structure and physical conditions of the matter in their central parts are especially important to study the processes of the matter accretion to supermassive black holes and eventually these investigations are essential to understand the galaxy evolution. Polarization contains information about the interaction of electromagnetic waves with the environment and provides information about the physical processes in the central regions of the AGNs that could not be found with the help of other optical observations. In this paper the importance of applying polarimetry methods to the study of geometry, kinematics, and physical processes in AGN in polarized light is discussed. An overview of the mechanisms of polarization formation, their connection with different structures and scales are provided. Also, we overview the polarimetric investigations based on different assumptions that are done using the observations conducted in Special Astrophysical Observatory of Russian Academy of Sciences.

scholarly journals Testing the evolution of correlations between supermassive black holes and their host galaxies using eight strongly lensed quasars

2020 ◽  
Vol 501 (1) ◽  
pp. 269-280
Author(s):  
Xuheng Ding ◽  
Tommaso Treu ◽  
Simon Birrer ◽  
Adriano Agnello ◽  
Dominique Sluse ◽  
...  
Keyword(s):  
Black Holes ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Host Galaxy ◽  
Wide Field ◽  
Host Galaxies ◽  
Field Surveys ◽  
Instrumental Resolution ◽  
The Moment

ABSTRACT One of the main challenges in using high-redshift active galactic nuclei (AGNs) to study the correlations between the mass of a supermassive black hole ($\mathcal {M}_{\rm BH}$) and the properties of its active host galaxy is instrumental resolution. Strong lensing magnification effectively increases instrumental resolution and thus helps to address this challenge. In this work, we study eight strongly lensed AGNs with deep Hubble Space Telescope imaging, using the lens modelling code lenstronomy to reconstruct the image of the source. Using the reconstructed brightness of the host galaxy, we infer the host galaxy stellar mass based on stellar population models. $\mathcal {M}_{\rm BH}$ are estimated from broad emission lines using standard methods. Our results are in good agreement with recent work based on non-lensed AGNs, demonstrating the potential of using strongly lensed AGNs to extend the study of the correlations to higher redshifts. At the moment, the sample size of lensed AGNs is small and thus they provide mostly a consistency check on systematic errors related to resolution for non-lensed AGNs. However, the number of known lensed AGNs is expected to increase dramatically in the next few years, through dedicated searches in ground- and space-based wide-field surveys, and they may become a key diagnostic of black holes and galaxy co-evolution.

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