A multi-band study and exploration of the radio wave–<i>γ</i>-ray connection in 3C 84

Paraschos, Georgios Filippos; Mpisketzis, Vasilis; Kim, J.-Y.; Witzel, G.; Krichbaum, T. P.; Zensus, J. A.; Gurwell, Mark A.; Lähteenmäki, A.; Tornikoski, M.; Kiehlmann, S.; Readhead, A. C. S.

doi:10.1051/0004-6361/202244814

Cited by 11 publications

(6 citation statements)

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“…We computed a core brightness temperature of T B = (3.6 ± 1.5) × 10 11 K from ν m , assuming that the angular size of the components at ν m is the same as at 228 GHz (as the system is optically thin at both frequencies). Within the error budget, the system seems to be in equipartition (Singal 1986) between kinetic and magnetic energies (also reported by Paraschos et al 2023, based on light-curve variability analysis).…”

Section: Insights From the Synchrotron Spectrumsupporting

confidence: 55%

“…We also disregarded the core shift effects (see e.g. Paraschos et al 2021;Oh et al 2022;Paraschos et al 2023) between the images at different frequencies, because their effect is negligible for our analysis (of the order of a few tens of µas). Our results are summarised in Table A.1.…”

Section: Appendix C: Multi-frequency Template Matchingmentioning

confidence: 99%

“…Here, k u is a ratio that provides an estimate of the energy in relativistic protons compared to electrons and f is a factor denoting the fraction of the total volume of the emitting region occupied by the plasma and magnetic field in equipartition. Under the assumption of an electron-positron pair plasma (see Paraschos et al 2023, for a discussion about electron-positron pair plasma in the vicinity of the SMBH in 3C 84), which is volume filling, k u = 0 and f = 1.…”

Section: Appendix D: Magnetic Field Estimatementioning

confidence: 99%

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Pinpointing the jet apex of 3C 84

Paraschos

Kim

Krichbaum

et al. 2021

A&A

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Nearby radio galaxies that contain jets are extensively studied with very long baseline interferometry (VLBI), addressing jet launching and the physical mechanisms at play around massive black holes. 3C 84 is unique in this regard because the combination of its proximity and large super massive black hole mass provides a high spatial resolution to resolve the complex structure at the jet base. For 3C 84, an angular scale of 50 μas corresponds to 200−250 Schwarzschild radii (Rs). Recent RadioAstron VLBI imaging at 22 GHz has revealed an east-west elongated feature at the northern end of the VLBI jet, which challenges past interpretations. Here we propose instead that the jet apex is not located within the 22 GHz VLBI core region but more upstream in the jet. We base our arguments on a 2D cross-correlation analysis of quasi-simultaneously obtained VLBI images at 15, 43, and 86 GHz, which measures the opacity shift of the VLBI core in 3C 84. With the assumption of the power-law index (kr) of the core shift being set to 1, we find the jet apex to be located 83 ± 7 μas north (upstream) of the 86 GHz VLBI core. Depending on the assumptions for kr and the particle number density power-law index, n, we find a mixed toroidal-poloidal magnetic field configuration, consistent with a region that is offset from the central engine by about 400–1500 Rs. The measured core shift is then used to estimate the magnetic field strength, which amounts to B = 1.80−4.0 G near the 86 GHz VLBI core. We discuss some physical implications of these findings.

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Section: Insights From the Synchrotron Spectrumsupporting

confidence: 55%

Section: Appendix C: Multi-frequency Template Matchingmentioning

confidence: 99%

Section: Appendix D: Magnetic Field Estimatementioning

confidence: 99%

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Pinpointing the jet apex of 3C 84

Paraschos

Kim

Krichbaum

et al. 2021

A&A

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“…In future studies, we will analyze the variability of TeVblazars and perform correlation studies with multi-wavelength light curves, similar to previous studies of GeV-emitting AGN (e.g., Paraschos et al 2023;Rösch et al 2022;Fuhrmann et al 2014). For several individual sources we already demonstrated the multi-wavelength capabilities of our program (e.g., Gokus et al 2022;de Menezes et al 2021), especially in combination with our complementary Southern Hemisphere monitoring program at the Australia Telescope Compact Array (e.g., Eppel et al 2023;Satalecka et al 2021).…”

Section: Discussionmentioning

confidence: 98%

TELAMON: Effelsberg monitoring of AGN jets with very-high-energy astroparticle emission

Eppel,

Kadler,

Heßdörfer

et al. 2024

A&A

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We introduce the TELAMON program which is using the Effelsberg 100-m telescope to monitor the radio spectra of active galactic nuclei (AGN) under scrutiny in astroparticle physics, specifically TeV blazars and candidate neutrino-associated AGN. Here, we present and characterize our main sample of TeV-detected blazars. We analyzed the data sample from the first sim 2.5 years of observations between August 2020 and February 2023 in the range from 14\,GHz to 45\,GHz. During this pilot phase, we observed all 59 TeV-detected blazars in the Northern Hemisphere (i.e., Dec. $>0^ known at the time of observation. We discuss the basic data reduction and calibration procedures used for all TELAMON data and introduce a sub-band averaging method used to calculate average light curves for the sources in our sample. T he TeV-selected sources in our sample exhibit a median flux density of 0.12\,Jy at 20\,mm, 0.20\,Jy at 14\,mm, and 0.60\,Jy at 7\,mm. The spectrum for most of the sources is consistent with a flat radio spectrum and we found a median spectral index ($S( of $ Our results on flux density and spectral index are consistent with previous studies of TeV-selected blazars. Compared to the GeV-selected F-GAMMA sample, TELAMON sources are significantly fainter in the radio band. This is consistent with the double-humped spectrum of blazars being shifted towards higher frequencies for TeV-emitters (in particular for high-synchrotron peaked BL Lac type objects ), which results in a lower radio flux density. The spectral index distribution of our TeV-selected blazar sample is not significantly different from the GeV-selected F-GAMMA sample. Moreover, we present a strategy to track the light curve evolution of sources in our sample for future variability and correlation analysis.

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“…We also disregarded the core shift effects (see e.g. Oh et al 2022;Paraschos et al 2023) between the images at different frequencies, because their effect is negligible for our analysis (of the order of a few tens of µas). Our results are summarised in Table A.1.…”

Section: Appendix A: Additional Methodology Commentsmentioning

confidence: 99%

Ordered magnetic fields around the 3C 84 central black hole

Paraschos,

Kim,

Wielgus

et al. 2024

A&A

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Context. 3C 84 is a nearby radio source with a complex total intensity structure, showing linear polarisation and spectral patterns. A detailed investigation of the central engine region necessitates the use of very-long-baseline interferometry (VLBI) above the hitherto available maximum frequency of 86 GHz. Aims. Using ultrahigh resolution VLBI observations at the currently highest available frequency of 228 GHz, we aim to perform a direct detection of compact structures and understand the physical conditions in the compact region of 3C 84. Methods. We used Event Horizon Telescope (EHT) 228 GHz observations and, given the limited (u, v)-coverage, applied geometric model fitting to the data. Furthermore, we employed quasi-simultaneously observed, ancillary multi-frequency VLBI data for the source in order to carry out a comprehensive analysis of the core structure. Results. We report the detection of a highly ordered, strong magnetic field around the central, supermassive black hole of 3C 84. The brightness temperature analysis suggests that the system is in equipartition. We also determined a turnover frequency of νm = (113 ± 4) GHz, a corresponding synchrotron self-absorbed magnetic field of BSSA = (2.9 ± 1.6) G, and an equipartition magnetic field of Beq = (5.2 ± 0.6) G. Three components are resolved with the highest fractional polarisation detected for this object (mnet = (17.0 ± 3.9)%). The positions of the components are compatible with those seen in low-frequency VLBI observations since 2017–2018. We report a steeply negative slope of the spectrum at 228 GHz. We used these findings to test existing models of jet formation, propagation, and Faraday rotation in 3C 84. Conclusions. The findings of our investigation into different flow geometries and black hole spins support an advection-dominated accretion flow in a magnetically arrested state around a rapidly rotating supermassive black hole as a model of the jet-launching system in the core of 3C 84. However, systematic uncertainties due to the limited (u, v)-coverage, however, cannot be ignored. Our upcoming work using new EHT data, which offer full imaging capabilities, will shed more light on the compact region of 3C 84.

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A multi-band study and exploration of the radio wave–γ-ray connection in 3C 84

Cited by 11 publications

References 82 publications

Pinpointing the jet apex of 3C 84

Pinpointing the jet apex of 3C 84

TELAMON: Effelsberg monitoring of AGN jets with very-high-energy astroparticle emission

Ordered magnetic fields around the 3C 84 central black hole

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