View Single Post
  #14 (permalink)  
Old 12-March-2008, 05:22 PM
Nereid Nereid is online now
Order of Kilopi
 
Join Date: Mar 2004
Posts: 10,941
Default

Quote:
Originally Posted by parejkoj View Post
Also, to just make a couple of quick comments about Bell 2007:

Dear FSM, how lazy was the reviewer? Seriously, how the heck (when mentioning this paper to a colleague, I used rather stronger language) did this make it into ApJ? It's terrible.

I've said elsewhere that Bell doesn't understand selection, and this absolutely proves it. He doesn't even understand what samples went into the catalog he used!



Hmm... If I go to SIMBAD and look at the names of the objects included in Véron-Cetty & Véron, 2006, I see several at the top of the list with "SDSS" in the name. Seems pretty clear to me. And I didn't even have to read their paper to determine that!

Strike one! Though, in truth, that's enough to completely chuck it, I'd say.



Huh... Really? This is news to me. Guess there were a whole slew of posters at the latest AAS meeting that were completely irrelevant...

That statement is true for certain classes of AGN, given certain types of observations. And it is certainly true for luminous (optically selected, broad line) quasars. But for AGN in general? Not for any commonly used definitions of the term. I'm not familiar enough with VC-V to know whether this is a safe assumption for their catalog, but considering Bell didn't even know whether the catalog included SDSS quasars (and it took me literally 2 minutes to check, most of which was waiting for SIMBAD to load), I'm definitely not trusting his word on it.

Strike two!

Really, those two should be enough to toss this one out on the curb. But, since I started counting strikes, here's a good choice for number 3: his use of Stickel et al. 1994 to define the "radio galaxy" sample. Certainly FIRST is a better choice for looking at radio sources: it is uniform (as opposed to a literature search) it goes down to 1 mJy (compared to 1 Jy), has 5" resolution and includes about a million sources (compared to ~600). And it overlaps completely with SDSS, so there are optical identifications with spectra for many of the sources (a very trivial and stupid check gives ~40,000 SDSS spectra of FIRST sources). I have no idea why someone would use a much older survey to define a sample cut.

Unless Bell isn't aware of FIRST.

Which is odd, because it's one of the best large area radio surveys in currently existence.

I sense a trend here...

That makes three. Can we burn it now?
I'm not sure if you used the link in rtomes' post to access the Bell paper, or read the actual published one.

ArXiv has two versions; rtomes' link is to v1.

Your three strikes apply to v2 (apparently), though I think strike 1 is a little more subtle than as you have written it .... in any case, the three strikes provide a nice, concrete example of one class of difficulties a concrete attempt to examine rtomes' proposal would encounter, and also shows just how difficult (if not impossible) it would be to reach "a very clear result" (rtomes' explicitly stated goal) if no discussion of definitions were permitted.