Does the fine structure constant vary?:

A detailed investigation into systematic errors

With:

Chris Churchill (PSU)

Victor Flambaum (UNSW)

Jason Prochaska (UCSC)

Wallace Sargent (Caltech)

Rob Simcoe (Caltech)

John Webb (UNSW)

Arthur Wolfe (UCSD)

Outline: Systematic errors for the MM method

Detailed analyses:• Atmospheric dispersion effects• Isotopic ratio evolution

Consistency checks• Line removal• Other tests for simple, unknown systematics

Candidate systematic errors:? Wavelength calibration errors – JOHN’S TALK ? Instrumental profile variations

? Laboratory wavelength errors (z=0+qx)

? Line blending? Temperature changes during observations? Heliocentric velocity variation? Atmospheric dispersion effects? Isotopic ratio evolution? Differential isotopic saturation? Hyperfine structure effects

See Murphy et al., 2001, MNRAS, 327, 1223 for details

? ?? ?

Atmospheric dispersion effects:

Atmospheric dispersion results:

Pre-rotator Post-rotator

Rotator

Isotopic ratio evolution:

Isotopic ratio evolution:

Isotopic ratio evolution results:

Isotope

Line removal checks:

Removing MgII2796: Post-removal Pre-removal

Line Removal

Removing MgII2796: Post-removal Pre-removal

Line Removal

Number of systems where transition(s) can be removed

Transition(s) removed

Pre-removalPost-removal

Other line-removal tests:High-z (1.8 – 3.5) Low-z (0.5 – 1.8)

FeII

MgI, MgII

ZnII

CrII

FeIIPositiveMediocre

Anchor

MediocreNegative

SiIV

Correcting for both systematics:

Rotator + Isotope

Conclusions: Main systematics:

• Atmospheric dispersion• Isotopic ratio evolution

Known systematic errors cannot explain results Nor can simple, unknown systematics

Iodine cell measurements planned for Keck Independent optical check required: VLT & Subaru Sleep loss?

Future: