Transcript Bolometer Arrays for ballon experiments

Dust polarization at long wavelengths
J.-Ph. Bernard
CESR Toulouse
• Dust polarization expectations
• The PILOT experiment
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
Dust Polarization
° Measured in absorption in the visible
Matthewson & Ford 1970
° Measured in emission in the FIR/mm
(ground, Archeops, Boomerang)
850 mm OMC-3 in Orion A
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
Lessons from extinction
UV extinction
UV rise (PAH) is not polarized
Bump (VSG) is not polarized
- Visible extinction (BG) is
polarized
- 10 mm absorption feature is
polarized
- 3.4 mm ice feature is polarized
IR extinction
So, small (Carbonaceous)
grain emission is not expected
to be polarized while large
(Silicate) grains is.
Desert et al 1990
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
Complications ...
Model by Finkbeiner, Davis, Schlegel (FDS)
warm dust (graphite ?)
cold dust (silicate ?)
mm excess:
- FIRAS data show b=1.7
near the Galactic plane
- WMAP data show that
this extends down to l>2-3 mm
T1=9.6 K, b1=1.5
T2=16.4 K, b2=2.6
100 mm
1 mm
10 mm
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
Complications ...
Model by Finkbeiner, Davis, Schlegel (FDS)
warm dust (graphite ?)
cold dust (silicate ?)
mm excess:
- FIRAS data show b=1.7
near the Galactic plane
- WMAP data show that
this extends down to l>2-3 mm
T1=9.6 K, b1=1.5
T2=16.4 K, b2=2.6
X-foreground = magnetic dipole
emission from vibrating dust
Would imply a polarization
degree highly variable
with wavelength
X-foreground =
spinning small dust
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
Alternative Models
Meny et al. in prep.
Two-Level Systems
In principle, such models
predict no large change of
polarization with
wavelength
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
Alternative Models
DCD+TLS Model
DCD
TLS: resonant
TLS: hoping
FDS
Best fit: T  17.9  0.22 K
lc  2.6  0.17 nm
Ahop  63.8  1.3
Ares  1.06  0.4
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
FIR/submm Observations ?
Dust polarization certainly varies with l
in some (dense to very dense) objects ...
From Vaillancourt et al.
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
FIR/submm Observations ?
From Vaillancourt et al.
... but the observed variations match none of the models.
Indeed, they could be entirely due to confusion on line-ofsight, so ..
We have no clue if it varies in the diffuse ISM
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
FIR/submm Planck
Predictions of TLS model
with dust Temperature
TLS Res.
DCD
TLS Hoping
Planck will be very
sensitive to the shape of
the dust emissivity and
therefore, should allow
to select a dust model
Dust Temperature is an
important parameter.
For B-pol, we may
consider measuring
it (with B-pol itself, or
otherwise) in order to
understand dust
foreground.
Planck: polarized
Planck: unpolarized
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
Planck sensitivity to dust polar
For a resolution of 15'
0.5 mag
From Pelkonen et al.
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
FIR/submm Planck
Planck should allow to
detect l-variations of the
dust polarization
(at 3-s every 1° below
Av=0.5 mag).
Detecting more precisely
smaller variations
toward more diffuse
clouds may require using
a polarized instrument
at higher frequency like
PILOT
Planck: polarized
Planck: unpolarized
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
PILOT vs Planck l-coverage
Planck: polarized
Planck: unpolarized
PILOT
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006
Conclusion (Dust polarization)
- Today, we don't really know if dust polarization will vary with
l in the sub-mm, and if yes, how ...
- So, it is difficult to devise how well we will be able to subtract
it from CMB channels for B-pol (and even Planck, actually ...).
- WMAP has only one dust-dominated channel (90GHz). We
could compare it to Archeops polarization at 353 GHz to start
constraining variations.
- Planck (and PILOT) should answer the question ... but actual
life could be significantly more complicated than described
here.
° Other open questions:
+ Is there l-variations appart from dust distribution ?
+ Is there a contribution from spinning dust ?
+ Is there a contribution from HVCs ?
+ Is there a contribution from ZL ? J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26
th
2006
The END
• PILOT will attempt at measuring the linear
polarization from dust emission in our Galaxy to very
high accuracy levels at high frequencies
• The goal is to understand the physics of dust
polarization, to ultimately help with component
separation for B-pol
• PILOT is a test-bed for the use of compact multiplexed
bolometer arrays for polarization measurements
• PILOT is funded by CNES. Detailed definition is
ending and realization of the instrument is starting.
• First flight expected in end-2008 (Kiruna)
PILOT
PILOT is the pilot fish
Future CMB-pol mission ?
http://pilot.cesr.fr
J.-Ph. Bernard, Orsay, Bpol meeting 2006, Oct26th 2006