Dr Katherine InskipMontse Villar-Martín (IAA Granada)
Clive Tadhunter, Joanna Holt, Dan Dicken (Sheffield)
Raffaella Morganti (ASTRON)
Friday 20th October 2006
Extended Emission Line Regions:
Nature, origins & implications
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The data PKS1932-46
VIMOS data: ~210 minutes over 3 nights Includes useful emission lines:
H – [SII]6731 PKS2250-41
VIMOS data: ~200 minutes over 4 nights
(and several months…!) Includes useful emission lines:
[OII]3727 – [SII]6731 Long-slit optical FORS1 spectrum at PA~70° (offset ° (offset
from radio axis)from radio axis) Also have Spitzer photometry of both sources, and
optical/IR imaging
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So, what can we learn?
Distribution of line-emitting material Ionization state of the gas Density and temperature diagnostics Gas kinematics – relative velocities and line widths
Pros: all the usual tools/results of narrow-band imaging and long-slit spectra, plus the ability to tune into regions of interest.
Cons: Targeted observations give better depth, and a less restrictive FOV.
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FRII radio galaxy at z=0.231FRII radio galaxy at z=0.231RA: 19RA: 19hh3535mm56.656.6ss : -46: -46°°202041.841.8 (J2000) (J2000)
PKS1932–464
PA -9PA -9° spectra ° spectra (63° offset from radio (63° offset from radio axis) show 150kpc axis) show 150kpc knotty, knotty, star-forming EELR.star-forming EELR.
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IFU fly-through: PKS1932-46
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IFU fly-through: PKS1932-46
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Host galaxy at z=0.23; extension to E, +further emission
just beyond radio lobe More blobs in surrounding IGM,
including star-forming blobs to south
Possible companion galaxy to NE
PKS1932-46:– fitting the [OIII] emission
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PKS1932-46: – fitting the [OIII] emission
Line width Line shift
Northern blob bright in [OII]3727 shocks?… but from what? Relative velocities vary by ~600kms-1… but generally line widths suggest
quiescent material. O and S line ratios consistent with ne~100cm-3 and T ~ few 104K.
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The companion galaxy… z=0.229 (cf. 0.231 for PKS1932-46) [OIII]/H ~1 star formation! Also, v. bright in Spitzer data. Narrow blueshifted emission around PKS1932-46 host galaxy
– same redshift as companion Obvious question: Is this an interacting system?
Did interaction trigger AGN activity? Clearly a very messy system!
24m 70m
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IFU fly-through: PKS2250-41
[OIII]5007 (left) and [OII]3727 (right)
FRII radio galaxy at z=0.308 RA: 22h53m03.1s : -40°5746 (J2000)
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IFU fly-through: PKS2250-41
[OIII]5007 (left) and [OII]3727 (right)
FRII radio galaxy at z=0.308 RA: 22h53m03.1s : -40°5746 (J2000)
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IFU fly-through: PKS2250-41
[OIII]5007 (left) and [OII]3727 (right)
FRII radio galaxy at z=0.308 RA: 22h53m03.1s : -40°5746 (J2000)
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PKS2250-41: – EELR Ionization State
As expected, we can clearly pinpoint shocked region near hotspot. Elsewhere, gas appears photoionized.
[OIII]5007Å
[OII]/[OIII] [OII]3727Å
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PKS2250-41:– EELR [OIII] kinematics
Most extreme line widths observed near AGN and along jet axis, not near hotspot.
Distant regions – narrow line widths. Apparent rotating structure. Similar kinematics observed in FORS1
spectrum
Narrow line regions (~150-220kms-1) with broad-ish (400-500kms-1) blue wings:
Observed near hotspots and towards centre of EELRIonization state suggests shocks/post-shock gas
Also see broadening on south side of EELR, seemingly unconnected with radio source kinematics/shock ionization
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Ionized gas pointing towards
the nearby galaxy
[OIII] image Cont. image
~ 12’’ or 54 kpc
FORS1 spectrum of PKS2250-41: – the very extended emission line region
[OIII] image, not continuum subtracted
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The faint emission in the western lobe:
Balmer absorption detected in companion galaxy
suggests similar redshifts
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Concluding thoughts…
Radio source/EELR interactions fairly well understood, but… Origin of EELR gas is not! Links with questions of AGN triggering and galaxy growth. Many similarities between PKS2250-41 and PKS1932-46:
Radio source strongly interacting with EELR Can we disentangle cause/effect when it comes to clumpy
IGM/halo material?
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Concluding thoughts… similarities cont.:
Strong potential for merger/interactions in local environment Both sources have close companions, and emission from
blobs lying well off the radio axis Gas kinematics – narrow FWHM at a variety of velocity
offsets Other activity:
Evidence for star formation in blobs Overall:
radio galaxy halos are interesting, unsettled environments, with a lot of physics going on – and it’s not just shocks!
Potential to greatly improve our understanding of the triggering process and links to interactions, and ongoing AGN-related feedback
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