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)

Motivation

All jets are not equal

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

Methods for inferring lobe particle content and energetics

X-ray inverse-Compton emission from lobesPressure comparisons

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

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

A comprehensive view of radio-galaxy environments

Ineson, JC et al. 2015 MNRAS 453 2682 & see Judith Ineson’s poster

LERGs(lowaccretionratejets) HERGs(highaccretionratejets)

Systematic pressure comparison

see Croston+ 2018 (MNRAS 476 1614)

FRIIsFRIIsFRIs FRIs

”FRII-like” energetics

see Croston+ 2018 (MNRAS 476 1614)

FRIIsFRIIsFRIs FRIs

NB. Ruled out by FRI IC limits in 7 cases

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.

Does particle content depend on morphology or accretion mode?

see Croston+ 2018 (MNRAS 476 1614)

Implications for feedback estimates

Implications for feedback estimates

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)

Predicting environments from radio properties

Croston+ 2018Croston+ 2017 MNRAS

It works if you choose your sample carefully…

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