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Polarimetry as a clue toward the nature of FeLoBAL quasars

Polarimetry as a clue toward the nature of FeLoBAL quasars. Daniel Lawther, Dark Cosmology Centre, Uni. of Copenhagen. Polarimetry as a clue toward the nature of FeLoBAL quasars. Structure of this talk: - What are FeLoBAL quasars? - Why are they important?

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Polarimetry as a clue toward the nature of FeLoBAL quasars

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  1. Polarimetry as a clue toward the nature of FeLoBAL quasars Daniel Lawther, Dark Cosmology Centre, Uni. of Copenhagen

  2. Polarimetry as a clue toward the nature of FeLoBAL quasars Structure of this talk: - What are FeLoBAL quasars? - Why are they important? - What do we want to learn about them? - Can polarimetry aid our understanding?

  3. Broad Absorption Line Quasars C IV 1550 Å Absorption troughs can reach line widths of a few thousand km/s, can be detached from the BEL, and are blueshifted. 10-40% of quasars have C IV BAL - selection issues! Emission line properties seem identical to non-BALs F dλ Rest wavelength [Å] Trump et al., AJ Supplement Series, 165:1-18, 2006 July

  4. HiBALs vs. LoBALs Mg II 2796 Å HiBAL: broad absorption in high-ionization lines (e.g., C IV 1550Å) only. LoBAL: also in low ionization lines (e.g., Mg II 2796 Å). LoBALs: ~1% of optically-selected, ~10% of IR-selected quasars. (Boroson and Meyers 92) F dλ Rest wavelength [Å] Trump et al., AJ Supplement Series, 165:1-18, 2006 July

  5. Iron LoBAL Quasars Fe II* Mg II Fe II* z=0.865 z=0.894 z=2.11 2000 Å 2900 Å Hall et al. 2002, ASP Conference Series Vol. 255

  6. Iron LoBAL Quasars Fe II* Mg II Fe II* z=0.865 ~ systemic velocity z=0.894 z=2.11 2000 Å 2900 Å Hall et al. 2002, ASP Conference Series Vol. 255

  7. Overlapping-trough FeLoBALs 1600 Å 2500 Å Rest wavelength 4500 Å Rest wavelength 3000 Å Hall et al. 2002, ASP Conference Series Vol. 255 These objects are (obviously) heavily reddened. Combined with a weak X-ray output, this makes them easy to miss in surveys!

  8. Increasingly dusty BALs... Reichard et al., AJ, 126:2594-2607, 2003 December

  9. Why are FeLoBALs important? • I don't know... yet. It depends on what causes them! Three possible scenarios have been suggested:

  10. Why are FeLoBALs important? • I don't know... yet. It depends on what causes them! Three possible scenarios have been suggested: • 1) (FeLo)BALs are an orientation effect - the underlying mechanism is present in all quasars

  11. BAL quasars: an orientation effect? Predictions: BALs will always be seen at a specific range of radio-axis PAs; a suitable mirror will reveal unabsorbed LOS.

  12. Why are FeLoBALs important? • I don't know... yet. It depends on what causes them! Three possible scenarios have been suggested: • 1) (FeLo)BALs are an orientation effect - the underlying mechanism is present in all quasars • 2) (FeLo)BALs are an early stage of quasar evolution

  13. BALs as an evolutionary phase Absorbing cocoon Acc. disk - (FeLo)BALs as an intermediate step between ULIRG and ordinary quasar? - Predictions: BALs will have a wide range of radio-axis PAs; spectropolarimetric signature of a shell geometry?

  14. Why are FeLoBALs important? • I don't know... yet. It depends on what causes them! Three possible scenarios have been suggested: • 1) (FeLo)BALs are an orientation effect - the underlying mechanism is present in all quasars • 2) (FeLo)BALs are an early stage of quasar evolution • 3) FeLoBALs are just weird - intrinsically different from normal quasars, irrespective of viewing angle and active lifetime.

  15. Why are FeLoBALs important? ...because they can constrain the unification model OR because they are a key piece of the quasar turn-on puzzle OR because they must somehow form in a different manner to ordinary quasars.

  16. What do I want to know? • What are the characteristics of FeLoBAL host galaxies (my thesis, IR SEDs, ...)

  17. What do I want to know? • What are the characteristics of FeLoBAL host galaxies (my thesis, IR SEDs, ...) • FeLoBAL inclination range (from radio axis, from polarimetry, from radio spectral index)

  18. What do I want to know? • What are the characteristics of FeLoBAL host galaxies (my thesis, IR SEDs, ...) • FeLoBAL inclination range (from radio axis, from polarimetry, from radio spectral index) • How reliable are the inclination indicators if FeLoBALs are wierd?

  19. What do I want to know? • What are the characteristics of FeLoBAL host galaxies (my thesis, IR SEDs, ...) • FeLoBAL inclination range (from radio axis, from polarimetry, from radio spectral index) • How reliable are the inclination indicators if FeLoBALs are wierd? • Where are the LoBAL outflows?

  20. What do I want to know? • What are the characteristics of FeLoBAL host galaxies (my thesis, IR SEDs, ...) • FeLoBAL inclination range (from radio axis, from polarimetry, from radio spectral index) • How reliable are the inclination indicators if FeLoBALs are wierd? • Where are the LoBAL outflows? • Where is the absorbing Fe* II ?

  21. FeLoBAL spectropolarimetry: existing studies, Q 0059-2735 Lemy + Hutsemekers, A&A 356 L9-L12 (2000)

  22. FeLoBAL spectropolarimetry: existing studies, Q 0059-2735 High P% in BAL troughs Lemy + Hutsemekers, A&A 356 L9-L12 (2000)

  23. FeLoBAL spectropolarimetry: existing studies, Q 0059-2735 Similar P% across continuum, FeII Lemy + Hutsemekers, A&A 356 L9-L12 (2000)

  24. Existing studies, J 1556+3517 Flux Polarization % BAL troughs Brotherton et al. AJ 487:L113-L116, 1997 Oct

  25. FeLoBAL spectropolarimetry: a few suggestions What is the sp.polarimetric signature of an absorbing shell? - look at more FeLoBALs in spectropolarimetry: do we generally see polarized BELs? Polarized light in BAL troughs? What do overlapping-trough objects look like in spectropolarimetry? Is there a lot of scattered nuclear light in BAL troughs? (May be problematic for my thesis!!!)

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