Multifrequency study of three giant radio galaxies with recurrent jet-formation activity: J1021+1216, J1528+0544, and J2345−0449 - I. Radio observations

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Volume 704 (December 2025)

A&A, 704 (2025) A284

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Table 4.

Results of the preliminary spectral age estimation for the inner and outer doubles of J1021+1216, J1528+0544, and J2345–0449.

Component	Minimum	Maximum	Break	Spectral
	spectral	spectral	frequency	age
	index	index	[MHz]	[Myr]
(1)	(2)	(3)	(4)	(5)
J1021+1216
Outer eastern	0.56	1.10±0.14	8.5 × 10²	64±11
Outer western	0.48	1.16±0.17	6.3 × 10²	74±10
Inner ^(a)	0.46	0.60±0.10	3.5 × 10⁴	10 $_{- 10}^{+ 18}$ $^{+18}_{-10}$
J1528+0544
Outer eastern	0.37	0.93±0.41	9.8 × 10²	79±36
Outer western	0.43	0.70±0.13	3.8 × 10³	40±25
Inner eastern	0.57	0.86±0.21	2.4 × 10⁴	16±14
Inner western	0.63	0.79±0.22	1.7 × 10⁵	6 $_{- 6}^{+ 19}$ $^{+19}_{-6}$
J2345–0449
Outer northern	0.43	0.93±0.11	4.3 × 10²	107±16
Outer southern	0.61	1.35±0.14	2.7 × 10²	134±12
Inner northern	0.67	0.78±0.09	1.4 × 10⁵	6 $_{- 6}^{+ 16}$ $^{+16}_{-6}$
Inner southern	0.73	0.83±0.11	3.0 × 10⁵	5 $_{- 5}^{+ 18}$ $^{+18}_{-5}$

Notes. For the outer doubles, the maximum values of α observed in a given lobe were assumed. For the inner doubles, the average spectral index was assumed.

^(a)

In case of the inner double of J1021+1216, the α_h and α measurements are the same in both lobes. We therefore combined the result.

Column designation: (1) Name of the component, (2) minimum spectral index measured at the head of the radio lobe, assumed to be equivalent to the injection index, (3) maximum spectral index recovered from the spectral age profiles (Fig. 7), (4) break frequency estimated using the method described in Sect. 3.5, and (5) upper limit of spectral age derived using Equation (6).

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