Review: does the Universe have a preferred axis?

For the 13th meeting the astronomy twitter journal club discussed Detection of a Dipole in the Handedness of Spiral Galaxies with Redshifts z ~ 0.04 by Michael Longo.

There’s a brief introduction to the topic here, and the full transcript of the meeting is here.

The discussion was hosted by @DrMRFrancis and he kicked things off with a simple opening question:

Any initial thoughts on the paper? – @DrMRFrancis

weird result imho, especially in view of the Galaxy Zoo results from 2008 – @MarcelAstroph

The author does note the inconsistency between his finding and the @galaxyzoo results. – @DrMRFrancis

in fact, he says “In their analysis, they found a dipole term of about 2σ […] consistent with the axis I found” – @antisophista

Would spectroscopy help?

Has a parallel study been done with spectroscopy of edge-on galaxies? Given the final sample size, the result wd surely be clearer. If you have red-/blue-shifted spectra from same galaxy, then rotation is confirmable – @LeonBaloo

I simply assume that the number of galaxies with redshifts is too low too have enough statistics? – @antisophista

Don’t think handedness can be determined from fibre-spectroscopy, and probably not definitively from slit spectra either – @eddedmondson

I agree that spectroscopy will not easily help, and trust the the @galaxyzoo results more, I think… – @MarcelAstroph

The mirroring effect

The interesting thing that @galaxyzoo found was the whole mirroring thing @eddedmondson did – @LeonBaloo

But the mirroring effect isn’t the same thing as a chiral bias, right? Or am I misunderstanding? – @DrMRFrancis

No, that’s right – the miroring thing is picking up how well people can identify galaxy handedness – @LeonBaloo


what if his results are real? what are the implications? – @antisophista

Implications are pretty profound — universe is not isotropic if there is a preferred axis. – @DrMRFrancis

Other issues raised

Personally, I think it’s amazing that a dipole can be observed from two smallish patches of sky… – @LeonBaloo

Would like to see how the measured asymmetry excess depends on other obvious observables, eg mag, surface brightness, size, SNR… – @StephenSerjeant

It would be nice to see if the effect shows up whatever southern sample is used. – @DrMRFrancis

And finally…

OK, so “real”, “not real”, or “jury’s still out”? – @astronomyjc

Want to say ‘not real’ but don’t feel we’ve really found a strong enough argument to dismiss yet. – @eddedmondson

I’d be happier if the axis correlated in some way with WMAP’s axis of evil, or it didn’t align so well with southern sample. – @DrMRFrancis

i’d say it is unlikely but who knows… Planck data will shed some light on the “axis of evil” issue at least – @antisophista

my summary: am not fully convinced by stats/errors or sample size anisotropy issues – @LeonBaloo

I believe in these things. many people found asymmetries in the CMB. but the sample size with longo is problematic… – @heikemodest

IMO unlikely prima facie, unproven yet, dipole unconvincing, but it’d be fun to mine data to look for a systematic. – @StephenSerjeant

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