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Zahl
2008-Feb-10, 01:40 PM
I am surprised that nobody has posted anything about this important release. The preprint is here (http://arxiv.org/abs/0801.1491) and the numerical data is here (http://cosmology.berkeley.edu/group/swlh/acbar/data_2008/index.html)

As you may know, the Arcminute Cosmology Bolometer Array Receiver (ACBAR) is one of the high resolution limited sky coverage CMB experiments that complement the lower resolution (but full sky coverage) WMAP. They have a new superb measurement of the first five peaks of the TT power spectrum and it matches the LCDM prediction extremely well, giving yet another resounding win for the standard model of cosmology. The third peak is tall, contrary to the MONDian predictions.

As ACBAR is only observing a few fields in the "Southern hole", a region of exceptionally low foregrounds, but still sees the same peak pattern that WMAP has measured over the full sky, we have a solid refutation of the idea that the WMAP data is substantially contaminated by foregrounds.

The ACBAR team also says that they have 3 sigma evidence of weak gravitational lensing in the CMB. If confirmed, this would give yet another line of evidence that the CMB and the anisotropy pattern are truly cosmic.

antoniseb
2008-Feb-10, 02:46 PM
Thanks Zahl, this is the first I've seen this, but it seems pretty important.

folkhemmet
2008-Feb-12, 04:58 AM
Zahl, thanks for informing us of this important result and the step forward in cosmology it has helped to bring about. Yes, I had actually started a thread labeled "ACBAR data" over a year ago which basically asked if anyone knew the status of the new data.

Just as you wonder why nobody posted anything about the ACBAR results I am surprised that nobody has posted anything about the impending publication of the next batch of microlensing planet discoveries. Apparently, 4 new microlensed planets are going to be announced this year including one that is less than 5 earth masses! You know the term Fp, fraction of stars with planets, in the Drake equation, well, this next batch of microlensed planets will give us a very good lower limit (better than the RV technique) for the value of Fp.

Jerry
2008-Feb-14, 01:25 AM
There are parts of the spectrum where Bomberango3 and ACBAR error bars do not overlap - primarily near the second peak. Weren't both data sets taken from overlapping regions?

Nereid
2008-Feb-19, 10:08 AM
There are parts of the spectrum where Bomberango3 and ACBAR error bars do not overlap - primarily near the second peak. Weren't both data sets taken from overlapping regions?
I think you mean "BOOMERANG", and the third acoustic peak (at l ~ 800).

A quick look at Figure 1 in each paper shows that there is some overlap of fields, but that the ACBAR coverage is considerably greater than that of B03. Further, the ACBAR paper includes a detailed comparison of "the deep region of B03" (the CMB8 field), shown in Figure A13 ... it's pretty clear the two datasets are essentially the same, though part of the motivation for observing CMB8 was calibration. It would be interesting to compare Montroy (2002) and Masi et al. (2005) with these ACBAR results (and B03), as they involve analysis of the 245 and 345 GHz data (B03 is at 145 GHz; ACBAR 150 GHz).

Zahl
2008-Feb-22, 11:14 PM
There are parts of the spectrum where Bomberango3 and ACBAR error bars do not overlap - primarily near the second peak. Weren't both data sets taken from overlapping regions?

Boomerang and ACBAR data are in excellent agreement with each other. The band power errors are 1 sigma only, meaning that if the red curve in figure 6 of the ACBAR preprint is correct, 68% of the ACBAR and Boomerang data points should capture it. As it turns out, about as many do capture it.