The lives of FR I radio galaxies

H.R. de Ruiter; M. Murgia; P. Parma; R. Fanti

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The lives of FR I radio galaxies

P. Parma, M. Murgia, H.R. de Ruiter, R. Fanti

Astrophysics · Submitted 14 Oct 1999

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim The derived ages are of the order 10^7-10^8 years, 2-4 times larger than the ages inferred from dynamical arguments and a factor 5-10 larger than the ages of FRII sources.

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Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 4,945 input tokens, $0.0002 reported.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.80 · human participants 0.01 · controlled comparison 0.26 · randomized assignment 0.01 · states quantitative result 0.98 · compares with prior results 0.95 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; show every role.

After a brief introduction to the morphological properties of FRI radio sources, we discuss the possibility that FRI jets are relativistic at their bases and decelerate quickly to non-relativistic velocities. From two-frequency data we determine spectral index distributions and consequently the ages of FRI sources. We show that in the large majority of cases synchrotron theory provides unambiguous and plausible answers; in a few objects re-acceleration of electrons may be needed. The derived ages are of the order 10^7-10^8 years, 2-4 times larger than the ages inferred from dynamical arguments and a factor 5-10 larger than the ages of FRII sources. The linear sizes of FRI and FRII sources make it unlikely that many FRII's evolve into FRI's. A brief discussion is given of the possibility that radio sources go through different cycles of activity.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	After a brief introduction to the morphological properties of FRI radio sources, we discuss the possibility that FRI jets are relativistic at their bases and decelerate quickly to non-relativistic velocities.	background 0.82	0.21	0.10	hedged possibility 0.94
s1	From two-frequency data we determine spectral index distributions and consequently the ages of FRI sources.	method 0.96	0.95	0.04	asserted 1.00
s2	We show that in the large majority of cases synchrotron theory provides unambiguous and plausible answers; in a few objects re-acceleration of electrons may be needed.	result 0.84	0.89	0.12	asserted 0.87
s3	The derived ages are of the order 10^7-10^8 years, 2-4 times larger than the ages inferred from dynamical arguments and a factor 5-10 larger than the ages of FRII sources.	result 1.00	0.94	0.35	asserted 1.00
s4	The linear sizes of FRI and FRII sources make it unlikely that many FRII's evolve into FRI's.	interpretation 0.81	0.54	0.20	hedged possibility 0.82
s5	A brief discussion is given of the possibility that radio sources go through different cycles of activity.	interpretation 0.41	0.34	0.03	hedged possibility 0.61

What kind of paper the classifier reports this is: empirical study 0.98 · evidence from analysis of existing data 0.73.

What was examined, and what was not

sources read

arXiv listing abstract v1

not examined

full text
figures and tables
references and citing sentences
relations to other papers

levels run

P abstract

not run

S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

The paper

Original abstract

After a brief introduction to the morphological properties of FRI radio sources, we discuss the possibility that FRI jets are relativistic at their bases and decelerate quickly to non-relativistic velocities. From two-frequency data we determine spectral index distributions and consequently the ages of FRI sources. We show that in the large majority of cases synchrotron theory provides unambiguous and plausible answers; in a few objects re-acceleration of electrons may be needed. The derived ages are of the order 10^7-10^8 years, 2-4 times larger than the ages inferred from dynamical arguments and a factor 5-10 larger than the ages of FRII sources. The linear sizes of FRI and FRII sources make it unlikely that many FRII's evolve into FRI's. A brief discussion is given of the possibility that radio sources go through different cycles of activity.

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How the literature uses it

4 arXiv papers cite this in 4 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 3 sentences without a confident label

Uses its data or values 1 paper

The all-sky spectra from such cascade components are shown as solid lines in Fig. [ref] for $B_IMGF = 10^-15$ G and $B_IGMF = 10^-14$ G, assuming that the blazar 1ES 0229+200 has been emitting for $10^7$ years.[This value is used as an estimate of the maximum AGN activity timescale [ref] .

Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation · Gamma-ray observables of the IGMF at high field strengths · 0.83

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