PDA

View Full Version : type II standard candles



trinitree88
2009-Oct-12, 04:44 PM
Stan Woosley is usually out there somewhere calculating supernovae phenomena, and is amongst the world's foremost authorities on the matter. In his recent paper, he suggests there's a pretty tight relationship between intrinsic luminosity and expansion velocity in these babies. He makes his case for ~ an order of magnitude variance but thinks that that may inprove by color balancing the results, yielding ~ a 20% error bar in distances from them as standard candles. SEE:http://arxiv.org/PS_cache/arxiv/pdf/0910/0910.1590v1.pdf

George
2009-Oct-13, 03:03 AM
Since you're good with the weak force, my poor understanding of math seems to show Type 1a error bars (for comparison to your Type II) are around 7%. [From Riess et. al. (2007) (http://www.astro.ucla.edu/~wright/sne_cosmology.html) ] But I notice thaat at z < 0.2, the error bars (sigma) just gets worse, so I must be doing this all wrong, right?

Kwalish Kid
2009-Oct-13, 03:10 AM
Since you're good with the weak force, my poor understanding of math seems to show Type 1a error bars (for comparison to your Type II) are around 7%. [From Riess et. al. (2007) (http://www.astro.ucla.edu/~wright/sne_cosmology.html) ] But I notice thaat at z < 0.2, the error bars (sigma) just gets worse, so I must be doing this all wrong, right?
The error bars are worse for many of the very low redshift supernovae because these are the oldest ones recorded that are still in the sample. They used older equipment and the supernovae were not recorded to the same extent that contemporary ones are.

George
2009-Oct-14, 03:32 AM
The error bars are worse for many of the very low redshift supernovae because these are the oldest ones recorded that are still in the sample. They used older equipment and the supernovae were not recorded to the same extent that contemporary ones are.I would have bet money against me, and wouldn't have guessed the closer ones were the poorer data. :) The Hi-Z team used greater filtering techniques to improve their sigma, which gave them a better fit though they had fewer sn to work with. That impressed me much.