I like the starting point: “collapse [at] z<10+”
The “+” makes it. Collapse could happen any time. Redshift less than 10. Or redshift greater than 10. Whenever.
I really empathize with Simon here. This is a problem I’ve often faced as an observer. How do I express the predictions of a theory that makes no [agreed] prediction?
I really empathize with Simon here. This is a problem I’ve often faced as an observer. How do I express the predictions of a theory that makes no [agreed] prediction?
It induces a flashback. At the Maryland conference in 1998, a some of us were discussing the epoch of galaxy formation over lunch. Amid suggestions that galaxies might be present at [then] surprisingly high redshift, Carlos Frenk declared “There are no galaxies before redshift 7”
There simply isn’t time for structure to form that early, he explained. In the great astronomical tradition of taking theorists at their word, the rest of us immediately pulled out our wallets and endowed the “7 up” prize for the first confirmed detection of a galaxy at z > 7.
The committee to decide if an object met the criteria was Carlos, Vera Rubin, and Bruce Partridge (all present). They made it clear that the standard was high: at least two convincingly identifies lines, not just a dropout implying a Lyman alpha edge. At stake, ~ $100 & prestige.
The money was held by Marv Leventhal, who I guess pocketed it. Everyone else seems to have forgot about it. At any rate, it was many years before a suitable detection was made, and no one [to my knowledge] has been awarded the 7 up prize.
At this juncture, it is clear it *should* have been awarded. I’m not sure to whom. Nial Tanvir certainly has a good claim, but there might be others I’m not familiar with. At any rate, we know there are galaxies at high redshift, so act and talk like we expected this all along.
We did not.
This has been my career-long frustration with [L]CDM. There is no prediction so obvious, so clear, that it can’t be fudged. Even in structure formation, it’s alleged strong point.
In the early ‘00s, on the eve of WMAP’s first report of the redshift of reionization, the prediction was “certainly not before z=6” (Peacock). Then it was measured to be 10. Sure, no problem. Never missed a beat. Meant that all along. High mass Pop III stars mumble mumble.
In the mid-00s, Jim Schombert identified some galaxy clusters around z=1.7, where the optical band conveniently shift into near-IR JHK, enabling us to study galaxy evolution with a minimum of K-corrections. (It was a Great Concenience if you don’t know what a K-correction is).
When I described this project to my colleagues, if routinely get the response “galaxy clusters don’t exist at the redshift”. Yes they do: look at the data. “Those are chance superpositons. Gravitationally bound clusters haven’t formed yet.” The bright galaxies all had the same z.
Flash forward, and clusters up to z~2 are taken for granted. At one point that was the hard cut above which they simply could not exist in LCDM (Frenk). I haven’t heard that repeated for a decade. High z clusters abound, though their dynamical state remains an open question.
Recent PhD Jay Franck identified a lot of these in his thesis, for which he constructed the CCPC - Candidate Cluster and Prorocluster Catalog. Don’t know which are real, but do know we see more in the data than in the Millennium simulation using the same selection techniques.
The individual galaxies are bigger, brighter, and more evolved (older red sequence) than they should be at these redshifts (many above 2, some up to 6!) and yet, what do you bet he heard from many referees? “These objects you’re seeing can’t exist.”
Yes, we know that. They *shouldn’t* exist. But they do. That’s why they’re important.
But give it a decade & it will become the new normal. Just like the RAR. A decade ago, most theorists refused to engage with that. Can’t be true. Now everyone and their brother explains it.
But give it a decade & it will become the new normal. Just like the RAR. A decade ago, most theorists refused to engage with that. Can’t be true. Now everyone and their brother explains it.
That’s enough tea for today.
