J/MNRAS/532/3069 Extreme radio variability in early-stage AGN (Jarvela+, 2024)
Unprecedented extreme high-frequency radio variability in early-stage active
galactic nuclei.
Jarvela E., Savolainen T., Berton M., Lahteenmaki A., Kiehlmann S.,
Hovatta T., Varglund I., Readhead A.C.S., Tornikoski M., Max-moerbeck W.,
Reeves R.A., Suutarinen S.
<Mon. Not. R. Astron. Soc., 532, 3069-3101 (2024)>
=2024MNRAS.532.3069J 2024MNRAS.532.3069J (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Galaxies, radio ; Galaxies, Seyfert
Keywords: galaxies: active - galaxies: jets - galaxies: Seyfert -
radio continuum: general
Abstract:
We report on the discovery of one of the most extreme cases of
high-frequency radio variability ever measured in active galactic
nuclei (AGNs), observed on time-scales of days and exhibiting
variability amplitudes of 3-4 orders of magnitude. These sources, all
radio-weak narrow-line Seyfert 1 (NLS1) galaxies, were discovered some
years ago at Aalto University Metsahovi Radio Observatory (MRO) based
on recurring flaring at 37 GHz, strongly indicating the presence of
relativistic jets. In subsequent observations with the Karl G. Jansky
Very Large Array (JVLA) at 1.6, 5.2, and 9.0GHz no signs of jets were
seen. To determine the cause of their extraordinary behaviour, we
observed them with the JVLA at 10, 15, 22, 33, and 45GHz, and with
the Very Long Baseline Array (VLBA) at 15GHz. These observations were
complemented with single-dish monitoring at 37 GHz at MRO, and at
15GHz at Owens Valley Radio Observatory (OVRO). Intriguingly, all but
one source either have a steep radio spectrum up to 45GHz, or were
not detected at all. Based on the 37GHz data, the time-scales of the
radio flares are a few days, and the derived variability brightness
temperatures and variability Doppler factors are comparable to those
seen in blazars. We discuss alternative explanations for their extreme
behaviour, but so far no definite conclusions can be made. These
sources exhibit radio variability at a level rarely, if ever, seen in
AGN. They might represent a new type of jetted AGN, or a new
variability phenomenon, and thus deserve our continued attention.
Description:
JVLA and VLBA data of a sample of extremely radio variable early-stage
AGN. Non-simultaneous single-dish monitoring data for all of these
sources from MRO and OVRO.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sample.dat 114 7 Basic properties of the sample (table 1)
table3.dat 84 42 Interferometric data (JVLA, VLBA)
table4.dat 51 1822 Single dish data (MRO and OVRO)
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Byte-by-byte Description of file: sample.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS Source SDSS name
21- 22 A2 --- Note Band the coordinates are from (1)
24- 33 A10 --- SName Short alias
35- 36 I2 h RAh Right ascension (J2000)
38- 39 I2 min RAm Right ascension (J2000)
41- 45 F5.2 s RAs Right ascension (J2000)
47 A1 --- DE- Declination sign (J2000)
48- 49 I2 deg DEd Declination (J2000)
51- 52 I2 arcmin DEm Declination (J2000)
54- 58 F5.2 arcsec DEs Declination (J2000)
60- 64 F5.3 --- z redshift
66- 70 F5.3 kpc/arcmin Scale Scale at the redshift of the source
72- 75 F4.2 [Msun] logMBH logarithmic black hole mass (2)
77- 88 A12 --- LSenv large-scale environment (3)
90-114 A25 --- Host Host galaxy morphology (4)
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Note (1): Band the coordinates are from as follows:
G = Gaia
Ka = Ka band (33 GHz)
X = X band (10 GHz)
Note (2): taken from Lahteenmaki et al. (2018A&A...614L...1L 2018A&A...614L...1L, Cat. J/A+A/614/L1)
Note (3): taken from Jarvela et al. (2017A&A...606A...9J 2017A&A...606A...9J)
Note (4): Notes as follows:
PB = pseudo-bulge
(a) = taken from Jarvela, Lahteenmaki & Berton (2018A&A...619A..69J 2018A&A...619A..69J)
(b) = Olguin-Iglesias et al. (2020MNRAS.492.1450O 2020MNRAS.492.1450O)
(c) = Varglund et al. (2022A&A...668A..91V 2022A&A...668A..91V)
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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- 19 A19 --- SDSS Source SDSS name
21- 22 I2 GHz Freq Frequency (10,15,22,33,43,45)
24- 32 F9.4 yr Time Time of the observation
34 A1 --- l_Fpeak Upper limit flag for peak flux density
36- 40 F5.3 mJy/beam Fpeak Peak flux density
42- 46 F5.3 mJy/beam e_Fpeak ? Peak flux density error
48- 52 F5.3 mJy Fint ? Integrated flux density
54- 58 F5.3 mJy e_Fint ? Integrated flux density error
60- 61 I2 uJy/beam rms rms
63- 69 F7.5 arcsec BeamMaj Beam major axis
71- 77 F7.5 arcsec BeamMin Beam minor axis
80- 84 F5.1 deg BeamPA [] Beam position angle
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS Source SDSS name
21- 22 I2 GHz Freq [15 37] Frequency (15 for OVRO, 37 for MRO)
24- 34 F11.6 yr Time Time of the observation
36 A1 --- l_Flux Upper limit flag for flux density
37- 44 F8.3 mJy Flux Flux density
46- 51 F6.2 mJy e_Flux ? Flux density error
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Acknowledgements:
Emilia Jarvela, ejarvela(at)ttu.edu
Texas Tech University
(End) Ethan Gfrorer, Emilia Jarvela [TTU], Patricia Vannier [CDS] 15-Oct-2024