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Particle content, morphology and jet power: all jets are not equal
Judith Croston
Thanks to Judith Ineson (Southampton) and Martin Hardcastle (Herts)
see Croston+ 2018 (MNRAS 476 1614)
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Motivation
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All jets are not equal
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Samejets!
Radiative mode = High Excitation RG (HERG)
Jet mode = Low Excitation RG (LERG)
(figure from Heckman & Best 2014 ARA&A 52 589)
All jets are not equal
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Methods for inferring lobe particle content and energetics
X-ray inverse-Compton emission from lobesPressure comparisons
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FRI energetics from pressure balance
See also Morganti+ 1988, Birkinshaw & Worrall 2000, Croston+ 2003, 2008, Dunn & Fabian 2004, Bîrzan+ 2008, Heesen et al. 2018
Croston & Hardcastle 2014
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FRII energetics from inverse-Compton emission
HERG
LERG
Median
No
. so
urc
es
0
2
4
6
8
10
12
14
16
Observed/equipartition magnetic field
10.2 0.5
FRII LERG
FRII HERG
Pext=Pobs
Ex
tern
al
mid
-lo
be
pre
ssu
re (
Pa
)
10−15
10−14
10−13
10−12
10−11
10−10
Observed (IC) lobe pressure (Pa)
10−15
10−14
10−13
10−12
10−11
10−10
10−9
Ineson, JC et al. 2017 MNRAS 467 1586 & see Judith Ineson’s poster
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A comprehensive view of radio-galaxy environments
Ineson, JC et al. 2015 MNRAS 453 2682 & see Judith Ineson’s poster
LERGs(lowaccretionratejets) HERGs(highaccretionratejets)
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Systematic pressure comparison
see Croston+ 2018 (MNRAS 476 1614)
FRIIsFRIIsFRIs FRIs
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”FRII-like” energetics
see Croston+ 2018 (MNRAS 476 1614)
FRIIsFRIIsFRIs FRIs
NB. Ruled out by FRI IC limits in 7 cases
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Why can’t FRIs and FRIIs have the same energy balance?
see Croston+ 2018 (MNRAS 476 1614)
• FRIs with FRII-like sub-equipartition fields ruled out by IC limits in 7 cases
• Substantial proton content in FRIIs would overpressurise lobes at midpoints and “pinch” points.
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Does particle content depend on morphology or accretion mode?
see Croston+ 2018 (MNRAS 476 1614)
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Implications for feedback estimates
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Implications for feedback estimates
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Jet power and morphology
1024 1025 1026 1027 1028 1029 1030
L150 (W Hz�1)
1036
1037
1038
1039
1040
Q(W
)
Willott+ (99)Simulation rangeActiveRemnant
0.5 1.0 1.5 2.0 2.5 3.0 3.5z
1024 1025 1026 1027 1028 1029 1030
L150 (W Hz�1)
1036
1037
1038
1039
1040
Q(W
)
Willott+ ( f = 5)Ineson+ 17Best linear fitActiveRemnant
13.25 13.50 13.75 14.00 14.25 14.50 14.75M500
Hardcastle 2018 (MNRAS 475 2768)
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Predicting environments from radio properties
Croston+ 2018Croston+ 2017 MNRAS
It works if you choose your sample carefully…
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SummarySystematic X-ray study of radio-galaxy environments and energetics has taught us:
• FRI and FRII radio galaxies have different particle content and energy balance
• FRIs best explained by significant proton contribution from entrainment/mixing, not present in more “pristine” FRIIs
• This affects relationship between jet power and radio observables (but so do many other factors)
Vital to understand the make-up of your population (including life stages!) before trying to infer jet power or feedback effects
see Croston+ 2018 MNRAS 476 1614 & 2017 MNRAS 470 1943