The physics and life-cycle of local radio AGN

40 Pages·2017·54.15 MB·English

Netherlands Institute for Radio Astronomy
The physics and life-cycle of local
radio AGN
Raffaella Morganti
ASTRON and Kapteyn Institute (Groningen)
ASTRON is part of the Netherlands Organisation for Scientific Research (NWO) R. Morganti - Low Frequency Conference | Bologna June 2017
Low frequencies for the study of nearby
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AGN: physics and impact of these AGN a
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Low frequencies: energetics and the life-cycle 

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➔ occurrence of remnants and comparison with mock catalogues 

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R. Morganti - Low Frequency Conference | Bologna June 2017
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~ Life of a radio
galaxy
Younger radio
galaxies
“Adult”
radio galaxies
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~ Life of a radio
galaxy
Younger radio
galaxies
“Adult”
radio galaxies
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p
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~ Life of a radio
galaxy
Younger radio
galaxies
old (remnant)
radio galaxies
“Adult”
radio galaxies
c older lobe
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galaxy
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Younger radio
restarted, young
galaxies
radio source
Restarted radio old (remnant)
galaxies radio galaxies
“Adult”
radio galaxies
older lobe
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Younger radio
restarted, young
galaxies radio source
Restarted radio old (remnant)
galaxies radio galaxies
“Adult”
radio galaxies
older lobe
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p
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Affected by a number of uncertainties 


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0 (e.g. magnetic field and its structure, injection index, 

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a energy losses….)

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k we need to know more about the physics 

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u and dependence on type of radio sources
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Younger radio
restarted, young
galaxies radio source
Restarted radio old (remnant)
galaxies radio galaxies
High power radio sources
Energetics and magnetic field: internal conditions (via X-ray inverse
Compton) and environmental information (specifically external pressure) 

➔ linked to low frequencies ➔ electron dominated, relatively small
deviation from equipartition, overpressure compared to external
pressure
‣
we can now use radio properties alone to estimate internal
energy of FRII ➔ to use for survey data!
Ineson et al. 2017, Croston et al. 2017
R. Morganti - Low Frequency Conference | Bologna June 2017
Need for resolved studies to trace injection index…
Better constrained spectrum at low frequencies. 

Injection index (as derived from the lobe emission) remains steeper than
classically assumed values even when considered on well resolved scales at low
frequencies ➔ greater amount of energy is contained in the low-energy electron
population than previously thought.
Harwood et al. 2015, 2016
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3 absorption of hotspot emission and/or non-homogeneous and
additional acceleration mechanisms
See talk of Harwood
R. Morganti - Low Frequency Conference | Bologna June 2017