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Exploring Extended Emission Line Regions: Origins and Implications of Active Galactic Nuclei

This study investigates the extended emission line regions (EELRs) of two FRII radio galaxies, PKS1932-46 and PKS2250-41. Utilizing VIMOS and FORS1 data, we analyze the distribution, ionization state, density, and gas kinematics of the line-emitting material surrounding these active galactic nuclei (AGN). Our findings reveal complex interactions between the gas and radio jets, highlighting the potential for ongoing star formation and implications for AGN activity. This research enhances our understanding of EELR origins and their connections to galaxy growth.

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Exploring Extended Emission Line Regions: Origins and Implications of Active Galactic Nuclei

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  1. Extended Emission Line Regions: Nature, origins & implications Dr Katherine Inskip Montse Villar-Martín (IAA Granada)Clive Tadhunter, Joanna Holt, Dan Dicken (Sheffield) Raffaella Morganti (ASTRON) Friday 20th October 2006

  2. 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 from radio axis) • Also have Spitzer photometry of both sources, and optical/IR imaging The Central Engine of Active Galactic Nuclei

  3. 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. The Central Engine of Active Galactic Nuclei

  4. PKS1932–464 • PA -9° spectra (63° offset from radio axis) show 150kpc knotty, star-forming EELR. • FRII radio galaxy at z=0.231RA: 19h35m56.6s: -46°2041.8 (J2000) The Central Engine of Active Galactic Nuclei

  5. IFU fly-through: PKS1932-46 The Central Engine of Active Galactic Nuclei

  6. IFU fly-through: PKS1932-46 The Central Engine of Active Galactic Nuclei

  7. PKS1932-46: – fitting the [OIII] emission • 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 The Central Engine of Active Galactic Nuclei

  8. PKS1932-46: – fitting the [OIII] emission • 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. Line width Line shift The Central Engine of Active Galactic Nuclei

  9. 24m 70m 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! The Central Engine of Active Galactic Nuclei

  10. IFU fly-through: PKS2250-41 • FRII radio galaxy at z=0.308 RA: 22h53m03.1s : -40°5746 (J2000) [OIII]5007 (left) and [OII]3727 (right) The Central Engine of Active Galactic Nuclei

  11. IFU fly-through: PKS2250-41 • FRII radio galaxy at z=0.308 RA: 22h53m03.1s : -40°5746 (J2000) [OIII]5007 (left) and [OII]3727 (right) The Central Engine of Active Galactic Nuclei

  12. IFU fly-through: PKS2250-41 • FRII radio galaxy at z=0.308 RA: 22h53m03.1s : -40°5746 (J2000) [OIII]5007 (left) and [OII]3727 (right) The Central Engine of Active Galactic Nuclei

  13. As expected, we can clearly pinpoint shocked region near hotspot. Elsewhere, gas appears photoionized. [OII]3727Å • [OII]/[OIII] PKS2250-41: – EELR Ionization State • [OIII]5007Å The Central Engine of Active Galactic Nuclei

  14. PKS2250-41: – EELR [OIII] kinematics 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 • 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 The Central Engine of Active Galactic Nuclei

  15. [OIII] image, not continuum subtracted FORS1 spectrum of PKS2250-41: – the very extended emission line region [OIII] image Cont. image Ionized gas pointing towards the nearby galaxy ~ 12’’ or 54 kpc The Central Engine of Active Galactic Nuclei

  16. The faint emission in the western lobe: Balmer absorption detected in companion galaxy suggests similar redshifts The Central Engine of Active Galactic Nuclei

  17. 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? The Central Engine of Active Galactic Nuclei

  18. 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 The Central Engine of Active Galactic Nuclei

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