J/A+A/704/A245 Seven candidate revived radio fossils images (Bruno+, 2025)
Resurging from the ashes: A spectral study of seven candidate revived radio
fossils in nearby low-mass galaxy clusters.
Bruno L., Botteon A., Dallacasa D., Venturi T., Balboni M., Biava N.,
Brienza M., Brueggen M., Brunetti G., de Gasperin F., De Rubeis E.,
Di Gennaro G., Gastaldello F., Ignesti A., Pasini T., Rajpurohit K.,
Shulevski A., Srikanth K.S.L., van Weeren R.J., Zhang X.
<Astron. Astrophys. 704, A245 (2025)>
=2025A&A...704A.245B 2025A&A...704A.245B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, radio
Keywords: radiation mechanisms: non-thermal -
galaxies: clusters: intracluster medium -
radio continuum: galaxies
Abstract:
Complex energy transfer processes in the intracluster medium (ICM) can
revive fossil (with spectral ages ≫100Myr) plasma initially generated
by radio galaxies. This leads to the re-ignition of faint radio
sources with irregular and filamentary morphologies, and ultra-steep
(alpha>1.5) synchrotron spectra, which can be more easily detected at
low frequencies (∼100MHz). These sources offer the opportunity to
investigate the microphysics of the ICM and its interplay with radio
galaxies, the origin of seed relativistic electrons, the merging
history of the host cluster, and the phenomenology of radio filaments.
The study of revived sources has so far been hampered by the
requirement of sensitive and high-resolution multi-frequency radio
data at low frequencies to characterise their spatial properties and
provide a proper classification. We aim to perform the analysis of a
sample of candidate revived sources identified among nearby (z≤0.35)
and low-mass (M500≤5x1014M☉) Planck clusters in the
footprint of the Second Data Release of the LOw Frequency ARray
(LOFAR) Two Metre Sky Survey (LoTSS-DR2). By inspecting LoTSS-DR2
images at 144MHz, we identified 7 targets with patchy and filamentary
morphologies, which have been followed-up with the upgraded Giant
Metrewave Radio Telescope (uGMRT) at 400MHz. By combining LOFAR and
uGMRT data, we obtained high-resolution images and spectral index
maps, which we used to interpret the nature of the sources. All
targets show regions with very steep spectra, confirming the
effectiveness of our morphology-based selection in identifying fossil
plasma. Based on their morphology, spectral properties, and optical
associations, we investigated the origin of the targets. We found a
variety of promising revived fossil sources, while also showing that
apparently intricate structures can be easily misclassified in the
absence of high-resolution and multi-band data.
Description:
We reported the spectral study at 144-400MHz of a sample of seven
candidate revived fossil radio sources.
Reduced radio images cut out around the targets (Figs. 2-7 in the
paper).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 7 Properties of the clusters hosting the candidate
revived sources analysed in this work
list.dat 117 14 List of fits images
fits/* . 14 Individual fits images
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- PSZ2 PSZ2 host cluster
15- 19 A5 --- Abell Abell host cluster name
21- 28 F8.4 deg RAdeg Right ascension (J2000)
30- 36 F7.4 deg DEdeg Declination (J2000)
38- 42 F5.3 --- z Cluster redshift
44- 47 F4.2 19+14Msun M500 Cluster mass
49- 52 F4.2 19+14Msun e_M500 Cluster mass error
54- 57 I4 kpc R500 Cluster radius
59- 60 I2 kpc e_R500 Cluster radius error
62- 66 F5.3 kpc/arcsec Scale Angular to linear scale conversion
68- 70 A3 --- Class Cluster classification as
No Diffuse Emission (NDE) or Uncertain (U)
72- 76 F5.2 10-2 C ?=- Concentration
78- 81 F4.2 10-2 e_C ? Concentration error
83- 86 F4.2 10-2 W ?=- Centroid shift morphological X-ray
parameters (1)
88- 91 F4.2 10-2 e_W ? Centroid shift morphological X-ray
parameters error
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Note (1): see Botteon et al. 2022A&A...660A..78B 2022A&A...660A..78B. Cat. J/A+A/660/A78,
Zhang et al. 2023A&A...672A..42Z 2023A&A...672A..42Z, Cat. J/A+A/672/A42, and Appendix D.
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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- 48 A21 "datime" Obs.date Observation date
50- 56 F7.3 MHz Freq Observed frequency
58- 60 I3 Kibyte size Size of FITS file
62- 77 A16 --- FileName Name of FITS file, in subdirectory fits
79-117 A39 --- Title Title of the FITS file
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Acknowledgements:
Luca Bruno, lucabruno2501(at)gmail.com
(End) Patricia Vannier [CDS] 08-Oct-2025