J/A+A/654/A169 Radio variability to identifying changing jets (Liodakis+, 2021)
Identifying changing jets through their radio variability.
Liodakis I., Hovatta T., Aller M.F., Aller H.D., Gurwell M.A.,
Laehteenmaeki A., Tornikoski M.
<Astron. Astrophys. 654, A169 (2021)>
=2021A&A...654A.169L 2021A&A...654A.169L (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Radio sources
Keywords: relativistic processes - galaxies: active - galaxies: jets
Abstract:
Supermassive black holes can launch highly relativistic jets with
velocities reaching Lorentz factors of as high as {GAMMA}>50. How the
jets accelerate to such high velocities and where along the jet they
reach terminal velocity are open questions that are tightly linked to
their structure as well as their launching and dissipation mechanisms.
Changes in the beaming factor along the jets could potentially reveal
jet acceleration, deceleration, or bending. We aim to (1) quantify the
relativistic effects in multiple radio frequencies and (2) study
possible jet velocity-viewing angle variations at parsec scales.
We used the state-of-the-art code Magnetron to model light
curves from the University of Michigan Radio Observatory and the
Metsahovi Radio Observatory's monitoring programs in five
frequencies covering about 25 years of observations in the 4.8 to
37GHz range for 61 sources. We supplement our data set with
high-frequency radio observations in the 100-340GHz range from ALMA,
CARMA, and SMA. For each frequency we estimate the Doppler factor
which we use to quantify possible changes in the relativistic effects
along the jets.
The majority of our sources do not show any statistically significant
difference in their Doppler factor across frequencies. This is
consistent with constant velocity in a conical jet structure, as
expected at parsec scales. However, our analysis reveals 17 sources
where relativistic beaming changes as a function of frequency. In the
majority of cases, the Doppler factor increases towards lower
frequencies. Only 1253-053 shows the opposite behavior. By exploring
their jet properties we find that the jet of 0420-014 is likely bent
across the 4.8-340GHz range. For 0212+735, the jet is likely
parabolic, and still accelerating in the 4.8-37GHz range. We discuss
possible interpretations for the trends found in the remaining
sources.
Description:
We use data from the Metsahovi and University of Michigan (UMRAO)
Radio observatories for five frequencies: 4.8, 8, 14.5, 22, and 37GHz
covering a few decades of observations (Aller et al.,
1985ApJS...59..513A 1985ApJS...59..513A, 1999ApJ...512..601A 1999ApJ...512..601A, 2014ApJ...791...53A 2014ApJ...791...53A;
Salonen et al., 1987A&AS...70..409S 1987A&AS...70..409S; Terasranta et al.,
1992A&AS...94..121T 1992A&AS...94..121T; Teraesranta et al., 1998A&AS..132..305T 1998A&AS..132..305T, Cat.
J/A+AS/132/305; Terasranta et al., 2004A&A...427..769T 2004A&A...427..769T, Cat.
J/A+A/427/769, 2005A&A...440..409T 2005A&A...440..409T, Cat. J/A+A/440/409). Our sample
consists of 61 common sources, 35 of which are Flat Spectrum Radio
Quasars (FSRQs), 22 are BL Lac objects (BL Lacs), 3 are radio galaxies
and one is unidentified. Our earliest observations start in 1965 at 8
GHz and the latest end in 2018 at 14.5 and 37GHz.
table 1: Median Doppler factor estimates and their 68% confidence
intervals for all the sources in our sample.
table 2: Doppler factor versus frequency correlation results.
table 3: High-frequency variability Doppler factor estimates for the
sources in our sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 115 61 Doppler factor (deltavar) estimates
table2.dat 60 61 Correlation results
table3.dat 61 46 High frequency Doppler factor (deltavar) estimates
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See also:
J/A+AS/132/305 : Extragal. radio sources at 22, 37 and 87GHz (Terasranta+ 1998)
J/A+A/427/769 : Extragalactic sources at 22, 37 and 87GHz (Terasranta+, 2004)
J/A+A/440/409 : Extragalactic sources at 22 and 37GHz (Terasranta+, 2005)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name B1950 name, HHMM+DDd or HHMM+DDMM
11- 15 F5.3 --- z Redshift
17- 21 F5.2 --- dvar4.8 ?=- Variability Doppler factor at 4.8GHz
23- 28 F6.2 --- E_dvar4.8 ?=- Upper error on delta_{var} at 4.8GHz
30- 35 F6.2 --- e_dvar4.8 []?=- Lower error on delta_{var} at 4.8GHz
37- 41 F5.2 --- dvar8 Variability Doppler factor at 8GHz
43- 48 F6.2 --- E_dvar8 Upper error on delta_{var} at 8GHz
50- 55 F6.2 --- e_dvar8 [] Lower error on delta_{var} at 8GHz
57- 61 F5.2 --- dvar14.5 Variability Doppler factor at 14.5GHz
63- 68 F6.2 --- E_dvar14.5 Upper error on delta_{var} at 14.5GHz
70- 75 F6.2 --- e_dvar14.5 [] Lower error on delta_{var} at 14.5GHz
77- 81 F5.2 --- dvar22 Variability Doppler factor at 22GHz
83- 88 F6.2 --- E_dvar22 Upper error on delta_{var} at 22GHz
90- 95 F6.2 --- e_dvar22 [] Lower error on delta_{var} at 22GHz
97-101 F5.2 --- dvar37 ?=- Variability Doppler factor at 37GHz
103-108 F6.2 --- E_dvar37 ?=- Upper error on delta_{var} at 37GHz
110-115 F6.2 --- e_dvar37 []?=- Lower error on delta_{var} at 37GHz
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name B1950 name, HHMM+DDd
11- 15 F5.2 --- rho Median Pearson correlation coefficient
17- 22 F6.4 --- p-value Median Pearson correlation probability
24- 28 F5.2 --- Slope Median best-fit slope
30- 34 F5.2 --- E_Slope Upper error on Slope
36- 40 F5.2 --- e_Slope [] Lower error on Slope
42- 46 F5.2 --- Intercept Median best-fit intercept
48- 52 F5.2 --- E_Intercept Upper error on intercept
54- 58 F5.2 --- e_Intercept [] Lower error on intercept
60 A1 --- Sample [A/B] Sample designation (1)
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Note (1): Sample designation as follows:
A = sources that do not show a statistically significant trend
B = sources that show a statistically significant trend
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name B1950 name, HHMM+DDd
11- 15 F5.2 --- dvar100 ?=- Variability Doppler factor at 100GHz
17- 21 F5.2 --- E_dvar100 ?=- Upper error on delta_{var} at 100GHz
23- 27 F5.2 --- e_dvar100 []?=- Lower error on delta_{var} at 100GHz
29- 32 F4.2 --- dvar225 ?=- Variability Doppler factor at 225GHz
34- 38 F5.2 --- E_dvar225 ?=- Upper error on delta_{var} at 225GHz
40- 44 F5.2 --- e_dvar225 []?=- Lower error on delta_{var} at 225GHz
46- 49 F4.2 --- dvar340 ?=- Variability Doppler factor at 340GHz
51- 55 F5.2 --- E_dvar340 ?=- Upper error on delta_{var} at 340GHz
57- 61 F5.2 --- e_dvar340 []?=- Lower error on delta_{var} at 340GHz
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Acknowledgements:
Ioannis Liodakis, yannis.liodakis(at)utu.fi
FINCA, University of Turku, Finland
(End) I. Liodakis [FINCA, Univ. Turku, Finland], P. Vannier [CDS] 27-Aug-2021