Polarimetry as a clue toward the nature of FeLoBAL quasars Daniel Lawther, Dark Cosmology Centre,...
-
Upload
aaliyah-daley -
Category
Documents
-
view
212 -
download
0
Transcript of Polarimetry as a clue toward the nature of FeLoBAL quasars Daniel Lawther, Dark Cosmology Centre,...
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?- What do we want to learn about them?- Can polarimetry aid our understanding?
Broad Absorption Line Quasars
Trump et al., AJ Supplement Series, 165:1-18, 2006 July
F dλ
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
Rest wavelength [Å]
C IV 1550 Å
HiBALs vs. LoBALs
Trump et al., AJ Supplement Series, 165:1-18, 2006 July
F dλ
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)Rest wavelength [Å]
Mg II 2796 Å
Hall et al. 2002, ASP Conference Series Vol. 255
Iron LoBAL Quasars
z=0.865
z=0.894
z=2.11
Mg IIFe II*Fe II*
2000 Å 2900 Å
Hall et al. 2002, ASP Conference Series Vol. 255
Iron LoBAL Quasars
z=0.865
z=0.894
z=2.11
Mg IIFe II*Fe II*
~ systemic velocity
2000 Å2900 Å
Overlapping-trough FeLoBALs
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!
1600 Å 3000 Å2500 Å 4500 ÅRest wavelength Rest wavelength
Increasingly dusty BALs...
Reichard et al., AJ, 126:2594-2607, 2003 December
Why are FeLoBALs important?
I don't know... yet. It depends on what causes them! Three possible scenarios have been suggested:
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
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.
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
BALs as an evolutionary phase
- (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?
Acc.disk
Absorbing cocoon
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.
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.
What do I want to know?
What are the characteristics of FeLoBAL host galaxies (my thesis, IR SEDs, ...)
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)
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?
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?
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 ?
FeLoBAL spectropolarimetry: existing studies, Q 0059-2735
Lemy + Hutsemekers, A&A 356 L9-L12 (2000)
FeLoBAL spectropolarimetry: existing studies, Q 0059-2735
Lemy + Hutsemekers, A&A 356 L9-L12 (2000)
High P% in BAL troughs
FeLoBAL spectropolarimetry: existing studies, Q 0059-2735
Lemy + Hutsemekers, A&A 356 L9-L12 (2000)
Similar P% across continuum, FeII
Existing studies, J 1556+3517
Flux
Polarization %
Brotherton et al. AJ 487:L113-L116, 1997 Oct
BAL troughs
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!!!)