1. Jet/environment interactions in FRI radio galaxies
Judith Croston University of Hertfordshire With thanks to: Martin Hardcastle, Mark Birkinshaw, Diana Worrall, Ralph Kraft, Dan Evans, Robert Laing
Extragalactic Jets – Girdwood, Alaska
23/05/07

2. Questions
What is the relationship between large-scale environment and radio-source properties?
What are FRIs made of?
What is their impact on their environment?

3. A representative sample of FRI environments with XMM-Newton
NGC 1044
3C 296
NGC 315
3C 31
3C 76.1
3C 66B
NGC 4261
NGC 6251
3C 449

4. What is the relationship between large-scale environment and radio-source properties?

5. Cavities

6. Asymmetries Croston et al. 2003, MNRAS, 346, 1041
Surface brightness profiles for NGC315?
Croston et al. 2003, MNRAS, 346, 1041

7. What are FRIs made of?

8. Internal vs. external pressures
FRI equipartition lobe pressures are typically lower than thermal pressure of environment (e.g. Morganti et al. 1988, Worrall & Birkinshaw 2000, Croston et al. 2003).
Lack of IC emission rules out dominant electron population as source of missing pressure.
“Average” pressure ratios for this sample range from 0.7 and 45.
Not all FRIs require pressure from non-radiating particles…
Is there anything special about the ones that don’t?

9. Pressure ratios and particle content
If entrainment is the origin of the non-radiating pressure component, then the apparent imbalance should depend on its efficiency.
Sources with jets inside lobes: 3C 76.1, 3C 296, NGC 4261, 3C 66B(?)
Sources with jets propagating through the IGM: 3C31, NGC1044, NGC315, 3C449, NGC6251
No surrounding
lobes
Jets within lobes

10. The first direct evidence that entrainment is responsible for the apparent pressure imbalance?
NGC1044 – no lobes
Lobe sources
No lobe sources
3C296 – lobes

11. What is their impact on the environment?

12. (groups sample from Croston et al. 2005, MNRAS, 357, 279)RL RQ
XMM RGs
(groups sample from Croston et al. 2005, MNRAS, 357, 279)

13. Can PdV work by current radio source explain this effect?

14. Cen A
NGC 3801
Croston et al. 2007, ApJ, 660, 191
Kraft et al. 2003, 2006
+ see Hardcastle poster
NGC 1052

15. Summary
FRIs of all morphological types live in group environments (1041 erg s-1 < LX < 1043 erg s-1)
Radio source morphology is related to gas distribution.
Non-radiating particles are required in most, but not all, FRIs to achieve pressure balance with the environment.
Pressure imbalance is linked to source morphology: direct evidence that entrainment provides the non-radiating particle population.
Radio-source environments are hotter than comparable radio-quiet groups, but PdV work by the current radio galaxy may not be able to achieve this heating.
Small (young?) FRIs can shock-heat galaxy atmospheres, injecting large amounts of energy – potentially an important galaxy feedback process.

16. Thanks

17. Pressure ratio vs. distance where jet becomes 2-sided