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trinitree88
2011-Feb-09, 03:04 PM
A new classification technique for distant red Sne 1a's emerges. SEE:http://arxiv.org/PS_cache/arxiv/pdf/1102/1102.1692v1.pdf


pete

antoniseb
2011-Feb-09, 05:07 PM
A new classification technique for distant red Sne 1a's emerges. ...

It's pretty clear that a classification system will make discussing (and sorting out) these things easier. Hopefully there will be revealed one or more relatively common subtypes that can be used as very precise standard candles.

trinitree88
2011-Feb-09, 08:13 PM
Antoniseb. Yep. Life should be so simple. It seems every time I read the new papers, a cherished standard is called into question. Fortunately, instrumentation always improves, and a new survey answers some of the old questions while finding new wrinkles in the data. A true standard unequivocal candle would help big time. pete

Jerry
2011-Feb-09, 09:24 PM
What would truly help is establishing one set of anchor parameters and building up a good enough statistical data base to determine some empirical roots. Since 2000, I don't think we have seen three consecutive supernova studies use the same data reduction techniques. It is like trying to range-in a target while changing the scope and powder load between every shot. We won't have this sorted out for decades.

Jerry
2011-Feb-11, 07:56 PM
http://arxiv.org/abs/1102.1977


The measurements of the cosmic SNR follow the same rapid evolution in redshift as that observed in measurements of the cosmic SFR. On the other hand, the normalization of the measured cosmic SNR systematically fall a factor ∼ 2 lower than that predicted from the measured cosmic SFR...This “supernova rate problem” remains over the entire redshift range where there are direct SNR measurements (with the exception of the local rates derived from SN catalogs).

Well by gosh, by golly it sure sounds like a selection effect to me. Is something wrong with the distance modulus?

Meanwhile: http://arxiv.org/abs/1102.2005


SFRs are found to be proportional to stellar masses over three orders of magnitude in mass; this phenomenon can be explained by assuming that new stars form out of gas that co-accretes along with dark matter onto the galaxies' dark matter halos, a scenario that naturally leads to SFRs that gradually increase with time.
Well, yes and no: What Sawicki is saying is essentially that we are at a rather special time; their is just enough dust remaining in dark matter halos to increase the rate through now; but implying that the SFR will fall off rapidly in the future. There have been several papers lately making this observation. I don't think saying 'we are in a special time' cuts it when you bumb this up against the Copernican principle. A goofy distance modulus will definitely screw up your star formation rate expectations.

Jerry
2011-Mar-21, 06:24 AM
lanl.arXiv.org > astro-ph > arXiv:1103.3659
http://xxx.lanl.gov/abs/1103.3659

We show that combined X-ray output of supernova progenitors and statistics of classical novae predicted in the single degenerate scenario are inconsistent with X-ray and optical observations of nearby early type galaxies and galaxy bulges. White dwarfs accreting from a donor star in a binary system and detonating at the Chandrasekhar mass limit can account for no more than ~5% of type Ia supernovae observed in old stellar populations.