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Previous Next Up Topic Cosmology / Alternative Cosmology / Juarez et al: The metallicity of the most distant quasars (3014 hits)
By Ari Jokimäki Date 2009-01-09 07:24
New paper in arXiv. Chapter 4.3. The carbon problem, ;) .
By Jade Annand Date 2009-01-09 22:07
Nifty. They go over a few other troubles at the beginning of the paper, but those are troubles for which there are possible excuses, e.g.

Juarez et al said:

No evolution was found in the ratio FeII/MgII; however, since the FeII bump is a strong BLR coolant, its strength depends on several other parameters and may not depend primarily on the iron abundance.


In the 4.1 section they have their discussion on the evolutionary vs. selection effects and attempt to explain some of the non-evolution away on the basis that before significant metallicity, quasars might be low luminosity or obscured.

Juarez et al said:

Indeed, according to many models, during the early phases, when the host galaxy is still metal poor, the accreting black hole is embedded within the dusty ISM, and therefore difficult to detect in optical surveys. Only during the late evolutionary phases, when the galaxy is already metal rich, the quasar develops winds powerful enough to expel large quantities of gas and dust, so that the quasar becomes visible to optical observations.


The carbon problem is interesting... (how many elements do we have a problem name for besides carbon and lithium now?). Now, the time scale difference isn't humungous, but it is problematic - the universe would be an estimated 0.95 Gyr old at z=6, although they do go to z=6.4, which would yield about 0.875 Gyr, and the carbon effect should take place at a minimum of 1 Gyr or top of the presumed 0.05 Gyr startup time after star formation, but it seems well within the realm of fudgeability.

The paper almost made it sound like no evolutionary effects have been found. I remember, from watching some presentations on the SDSS at the time when they were finding high metallicity quasars at z<5.5 that they thought they might have found tentative signs of evolutionary effects above that redshift.

I would have thought that we might get apparent evolutionary effects because of selection effects, but... this is not the case?

Also, sometimes I wish research papers were threaded like a giant forum so I could see which papers are rebuttals or confirmations of which other papers. I'd like to know how people end up addressing the "carbon problem" :)
By Ari Jokimäki Date 2009-01-10 16:33
Ritchie said:

Also, sometimes I wish research papers were threaded like a giant forum so I could see which papers are rebuttals or confirmations of which other papers. I'd like to know how people end up addressing the "carbon problem" :)

There is the citation system that sort of does that, but you have to do some work in order to get what you want. In ADS you can take the paper that you're interested in, this Holmberg (1969) paper for example which is the paper where the Holmberg effect first was introduced. Click the "citations to the article" link, and you get a list of papers citing the Holmberg paper. Problem is that not all of these are relevant to the subject (they might be studying something complete different and mention Holmberg work in passing for some reason, maybe as an example of something). Another problem is that not all relevant papers are on the list. For example you can look up the Yang et al. (2006) paper from the list, and click citations for that paper. Only then you find Jokimäki, Orr & Russell (2008) who also discussed Holmberg effect but didn't cite the original paper. Also, the Holmberg paper deals with lot of other stuff as well, so you get lot of papers in that citation list who are citing Holmberg for other reason than the effect.

It certainly would be nice to have the kind of system that you asked, even if one can find the relevant papers relatively easily. It would make things easy. But hey, isn't there a nice and useful subject for a website...
By Jade Annand Date 2009-01-16 04:56
Ari said:

It certainly would be nice to have the kind of system that you asked, even if one can find the relevant papers relatively easily. It would make things easy. But hey, isn't there a nice and useful subject for a website...


*laugh* I probably have the abilities to design and code something like that, but I fear I will never have the spare mental energy ever again :)
Previous Next Up Topic Cosmology / Alternative Cosmology / Juarez et al: The metallicity of the most distant quasars (3014 hits)

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