Max Planck Institute for Radio Astronomy

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Main collaborators: L. C. Debbrecht, J. A. Hodgson, M. Janßen, J.-Y. Kim, J.-A. Kramer, T. P. Krichbaum,

I. Liodakis, N. R. MacDonald, D. Nair, J. Röder, E. Ros, T. Savolainen, E. Traianou, M. Wielgus, J. A. Zensus

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The M2FINDERS project (PI: J. A. Zensus) has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 101018682).

Investigating launching of black hole jets with the combined power of the EVN and the EHT

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Georgios Filippos Paraschos

October 17 2024

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• Very long baseline interferometry
• Why is 3C84 interesting?
• SMBH, core,& accretion
• Magnetic field & Downstream Jet
• Conclusions

Outline

GMVA/H. Rottmann

Jet launching, acceleration and collimation

are still unanswered fundamental questions

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RGs provide a prime testbed to explore:

• Jet base?
• BH location?
• Jet kinematics?
• Jet launching speed
• Acceleration
• Non-ballistic motion?

Jet launching models can be distinguished at the jet base

Very-long-baseline interferometry (VLBI)

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Increase D

Space VLBI

Decrease λ

mm-VLBI

RadioAstron

Global mm-VLBI Array (GMVA), Credit: H. Rottmann

D = 350,000 km

λ = 3 mm

Radio source

Fringes

Synchrotron radiation

mm-VLBI offers a number of advantages

• With mm-VLBI we can:
• peer through self-absorbed regions
• explore the physics of the central engine
• study the origin of jets
• zoom into the hearts of RGs, typical spatial scales are <0.1pc / ~ 1000-10000R_s

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• At 3mm-VLBI with the GMVA: excellent uv-coverage & high dynamic range

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• Synergy:
• Spectral studies (e.g. 7mm, 3mm, 1mm)
• Broadband MWL campaigns (e.g. IXPE, Chandra, Fermi)

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Hɑ emission (HST), Fabian+2008

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3C84 (NGC1275) at higher energies

optical

X-ray + radio (1.4 GHz)

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Zooming into the nucleus reveals a jet

Walker+2000

22 GHz ground-based

• NGC1275, central galaxy of Perseus cluster
• Elliptical, Seyfert 1.5 / FR I, peculiar
• M_BH≤2×10⁹M_o

22 GHz from space

Giovannini+2018

1.8 pc

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86 GHz GMVA image (Kim+2019)

Limb brightening in polarisation

continues into sub-mas region

May 2015

The core elongation is also visible in fractional polarisation

The Event Horizon Telescope is famous for observing

black hole shadows with remarkable consistency …

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… but it can also observe AGN jets!

For a good enough (u, v) coverage,

it can look like this:

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3C279

Kim+2020

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While we are used to gaps in the uv-coverage when doing VLBI, the 2017 3C84 EHT data used in our analysis are on another level

Therefore, at 1.3mm only geometrical model fitting was possible

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The core region of 3C84, as revealed with the

EHT is comprised of 3 components: E, C, & W

Paraschos+2024a

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2 versus 3

component models

• Fitting both 2 and 3 Gaussian componentes produces equally acceptable χ² in total intensity

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• Examining the fit to the closure phase non-trivial triangle clearly reveals that a 3 component model is necessary to reproduce the data

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We can squeeze out even more information

from the polarised light

• Component C, identified as the core, appears unpolarised

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• The two components E and W framing it, exhibit high amounts of fractional polarisation (20-80%)

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• E and W could correspond to the footpoints of the emerging jet

mtot=17%

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The turnover frequency gives clues to estimate

the SMBHs magnetic field, accretion flow state, and spin

→B~3-6G, a_*=1 (rapid rotation, ADAF), φ~40-90 (MAD)

→ preference for BZ type of jet launching (consistent with GP+23)

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To study the entire pc-scale jet we need to decrease the observing frequency and take advantage of the increase in the uv-coverage

Paraschos+2024b

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Our Global-EVN observations reveal that the limb brightening is reaching deep into the compact region

• At 22GHz the downstream

jet is resolved

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• The double rail structure

is recovered (cf. RadioAstron)

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• Jet stratification?

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The two limbs are also visible in linear polarisation

• Polarised emission in

the core traces the double rails

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• An inner spine is also detected at 4σ in linear polarisation

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• EVPAs are ∥ (⟂) at the spine (rails)

to the bulk jet flow

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• Jet shear or shock?

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Comparison with RMHD simulations reveals a

helical/toroidal magnetic field configuration

• RMHD simulations show that the EVPAS follow the bulk jet flow at the spine and are orthogonal to it at the limbs when the magnetic field is helical or toroidal

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• A poloidal field on the other hand does not reproduce the observed geometry

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• Consistent with spine-sheath geometry

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Other parameter

combinations do not

reproduce the observations

The bulk Lorentz factor Γ &

the underlying magnetic field configuration were varied

A rotating, helical filament located within the broader jet may explain:

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• Elongated core

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• Jet stratification

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• Jet bends

see also Steffen+1995

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This helicity is also detected

in our Global-EVN data

• The blue line traces the jet ridge

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• Precession/Nutation and/or KH instability?

We have demonstrated the capability of mm-VLBI

to resolve jets of nearby radio galaxies transversely

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• Highly coherent, strong magnetic field around central, SMBH of 3C84
• Advection-dominated accretion flow (ADAF) in a magnetically arrested (MAD) state around a rapidly rotating (a_*~1) SMBH
• Polarised emission in the core region traces the brightened limbs
• The EVPA orientation suggests a toroidal magnetic field configuration consistent with a spine/sheath geometry