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

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!!!)