Change of Plans

Well obviously I have not been sticking to my original goal of posting 5 days a week.  I thought I would state why.  Blogging my research each day was very time consuming, ~30 minutes each day.  That would be fine if I used the blog as a research tool for myself but I feel that there are better research tools I could spend that time on.  In particular I have been using that time to better document my research in my electronic notebook.  I use Microsoft OneNote (see image below), which is by far the best electronic notebook program I have found and highly recommend it  (even on a mac, it is worth getting VMware Fusion for).

The one disadvantage of not blogging and focusing on my notebook is the lack of public outreach and openness.  To try to compensate I have spent more time documenting my research on my website.  My plan is that after each paper I will summarize the results in a manor more accessible to the public.  I have already done this with our first paper on the Musket Ball Cluster, see my research page. Perhaps I will also copy these summaries to this blog as well.

Unrest at UC Davis

I have to admit that I barely got any work done today.  Most of my time was spent thinking about the recent actions at UC Davis (horrible on the part of police and administrators and amazing on the part of faculty and students).  The day began with an open meeting in our the Physics Department chair's office (attended by faculty and students)  followed by a campus wide rally that involved thousands of students, faculty and community members. I am impressed by the outstanding behavior of my fellow students and comforted by how much the faculty care for the students and are willing to stand side-by-side with them.

Peak Error Estimate

Today I was finalizing making update figures for the DLSCL J0916.2+2953 letter and one of the details had to do with adding peak error bars to the weak lensing mass maps.  First I estimate the peak using an analysis that takes advantage of all the observed galaxies. Then to estimate the variance I use weak lensing maps that are the product of a bootstrap sample of the observed galaxies.  Taking extraction regions around each subcluster I then measure the distribution of peaks in the bootstrap sample. See the screen capture from my research note book (side note: I highly recommend Microsoft OneNote).

Weak Lensing Peak Variance Estimate Notes

This gives me a distribution in each peaks RA and Dec. For example the y-pixel coordinate of the Subaru weak lensing southern peak is shown below.  The dashed lines represent the 1 sigma deviations and the blue and red lines are just different statistics.

Finally this information is plotted on the weak lensing mass map as blue cross-hairs.

More Referee Comments Addressed

Spent most of the day addressing the referee's comments and updating the DLSCL J0916.2+2953 paper.  I am about 75% of the way through them and should have them all addressed by the end of the week. 

There was also an interesting talk by the John Felde at the UC Davis Physics Grad Colloquium about measuring the theta_13 mixing angle at Double Chooz experiment. I am particularly interested by the possibility of detecting additional mixing angles due to more than the 3 expected neutrinos when their near detector comes on line to complement their far detector.  This is possible by examining the near and far signals and studying the ratio. This is still a few years off and might even be a few experiments off but there seems to be potential.

Improved Peak Measurements

Part of the day was spent helping Dave put the finishing touches on his NSF proposal.  I think it turned out pretty good.  The main focus of the proposal was on weak lensing shear peaks, clusters and filaments. Here's hoping that it gets accepted.

A large part of the day was improving my measurement of the shear peak centers' errors for DLSCL J0916.2+2951.

Another interesting note is that Sophie Maurogordato, whom I mentioned in a arXiv to the Rescue, is interested in applying the method that I developed to constrain the dynamics of cluster mergers to her merging cluster A2163.  It is a great feeling to have something you developed be useful to someone else.  This is actually the second time I will have applied my method to another cluster (the first was to a high redshift cluster pair that Brian Lemaux has been working on.

When Noise Looks Like Signal

I was pretty excited when I first measured number distribution of galaxies for my filament candidate stack. In the figure titled Signal to the right white/red represent more galaxies continuing to purple/black representing fewer galaxies. Right where it is expected there were more galaxies (along the filaments).  Now compare this this with the figure below titled Null.  These two figures look very similar.  This is a problem because in the bottom figure I have stacked clusters pairs that are so far separated in redshift space that they should definitely not have a filament between them.

First things first; understand why even in the null case there is what appears to be a filament signal.  I have two primary suspects:

1. Some of the postage stamp regions extend beyond the survey area. Thus when adding all the postage stamps  together there will be fewer galaxies at the larger radii from the filament axis simply because not all postage stamps had  observed galaxies at these larger radii.
2. This is just due to the expected signal from two over lapping clusters. 

Second things second. Correct for this systematic noise. Theoretically I know how to correct either of the above effects.  Now practically may be another story. 

Line of Sight

I have been working on addressing the referee's comments for our DLSCL J0916.2+2951 paper.  One item that was crossed off the to do list was making a redshift histogram to show if there are any line-of-sight structures that may confuse our results.

The black histogram is our sample of spectroscopic redshifts (0.1<z<1.0) in the area of our cluster.  The over-plotted red histogram is the subsample of galaxies that satisfy the photo-z cut 0.43<z<0.63, which we use to select likely cluster members.  We want the red histogram to completely cover the black histogram at the cluster redshift of z=0.53 but not cover the black histogram at any other redshifts.  Unfortunately this is not the case, otherwise photometric redshifts would be just as good as spectroscopic redshifts.

The good news is that there is not much structure along the line-of-sight.  There is a small peak at z~0.6, and worse we include a lot of these galaxies in our photo-z cut.  While it is a much smaller concentration than our cluster galaxies it is worth investigating. Looking at the projected distribution of these galaxies they are very evenly distributed across the area of the cluster and there is no apparent structure to these galaxies.  Thus it should not affect our results in any significant way.  It is curious though, I wonder if it is a wall?