J/A+A/692/A205 The putative center in NGC 1052 (Baczko+, 2024)
The putative center in NGC 1052.
Baczko A.-K., Kadler M., Ros E., Fromm M. C., Wielgus M., Perucho M.,
Krichbaum P. T., Balokovic M., Blackburn L., Chan C., Issaoun S.,
Janssen M., Ricci L., Event Horizon Telescope Collaboration
<Astron. Astrophys. 692, A205 (2024)>
=2024A&A...692A.205B 2024A&A...692A.205B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Radio continuum
Keywords: methods: observational - techniques: high angular resolution -
techniques: interferometric - galaxies: active - galaxies: jets -
galaxies: Seyfert
Abstract:
Many active galaxies harbor powerful relativistic jets. The detailed
mechanisms of their formation and acceleration remain poorly
understood.
To investigate the area of jet acceleration and collimation with the
highest available angular resolution we have studied the innermost
region of the bipolar jet in the nearby LINER galaxy NGC 1052.
We combined observations of NGC 1052 taken with the VLBA, the GMVA and
the EHT during one week in spring 2017. Our study focuses on the size
and continuum spectrum of the innermost region containing the central
engine and the footpoints of both jets. We employ a synchrotron-self
absorption model to fit the continuum radio spectrum and combine size
measurements from close to the central engine out to ∼1pc to study
jet collimation.
For the first time NGC 1052 was detected with the EHT, providing a
size of the central region in-between both jet bases of 43uas
perpendicular to the jet axes, corresponding to just around 250 RS
(Schwarzschild radii). This size estimate supports previous studies of
the jets expansion profile which suggest two breaks of the profile at
around 3x103RS and 1x104RS distances to the core. Furthermore,
we estimate the magnetic field to be 1.25 Gauss at a distance of 22uas
from the central engine by fitting a synchrotron-self absorption
spectrum to the innermost emission feature, which shows a spectral
turn-over at ∼130GHz. Assuming a purely poloidal magnetic field this
implies an upper limit on the magnetic field strength at the event
horizon of 2.6x104Gauss, which is consistent with previous
measurements.
The complex and low brightness, double-sided jet structure in NGC 1052
makes it challenging to detect the source at millimeter wavelength.
However, our first EHT observations demonstrated that detection is
possible up to at least 230GHz. This enabled us to glimpse through
the dense surrounding torus into the innermost central region where
the jets are formed, to finally resolve this region and to give
improved constraints on its expansion and magnetic field strength.
Description:
We provide here fits images and tables of model fit components from
VLBI observations of NGC 1052: Fig. 2, the clean radio image of
NGC 1052 at 86GHz observed with the GMVA. Table B contains the
model fit parameters and uncertainties of 1.6, 5.0, 8.4, 15.3,
22.2, and 43.1GHz VLBA and 86 GHz GMVA observations.
Objects:
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RA (2000) DE Designation(s)
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02 41 04.79 -08 15 20.7 NGC 1052 = MCG-01-07-034
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb.dat 84 92 Fit parameters and uncertainties of 1.6, 5.0,
8.4, 15.3, 22.2, and 43.1GHz VLBA and 86
GHz GMVA observations
list.dat 105 1 Information on fits image
fits/* . 1 fits image
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Byte-by-byte Description of file: tableb.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- ID ID of component
9- 13 F5.2 GHz Freq Observing Frequency (1.55, 4.98, 8.42, 15.26,
22.22, 43.12 and 86.25)
15- 20 F6.2 mJy SFreq Flux density at Freq
22- 27 F6.2 mas oRA Offset in right ascension (1)
29- 32 F4.2 mas e_oRA oRA error
34- 39 F6.2 mas oDE Offset in declination (1)
41- 44 F4.2 mas e_oDE oDE error
46- 50 F5.2 mas Major Major axis
52- 55 F4.2 mas e_Major Major axis error
57- 62 F6.2 --- Ratio ? Ratio major to minor axis
64- 69 F6.2 mas Dist Component angular distance
71- 76 F6.2 mas e_Dist ? Angular distance error
79 A1 --- l_logTb Limit flag on logTb
80- 84 F5.2 [K] logTb Logarithm of brightness temperature
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Note (1): Offsets from the 43 GHz map reference position
RA = 02:41:04.799, DE = -08:15:20.752
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 37 A10 "datime" Obs.date Observation date
39- 45 F7.4 GHz Freq Observed frequency
47- 50 I4 Kibyte size Size of FITS file
52- 64 A13 --- FileName Name of FITS file, in subdirectory fits
66-105 A40 --- Title Title of the FITS file
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Acknowledgements:
Anne-Kathrin Baczko, baczko(at)chalmers.se
(End) Anne-Kathrin Baczko [Chalmers, Sweden], Patricia Vannier [CDS] 02-Oct-2024