From: dwells@fits.cv.nrao.edu (Don Wells)
Subject: Re: B-O Effect (was Re: Proof of quasar non-locality?)
Organization: nrao
	<DWELLS.92Jul31224122@fits.cv.nrao.edu> <BsqH18.7Hy@well.sf.ca.us>
Date: Sat, 22 Aug 1992 05:10:37 GMT

[I have been on vacation for the past two weeks]

In article <BsqH18.7Hy@well.sf.ca.us> metares@well.sf.ca.us (Tom Van
Flandern) writes:
   dwells@fits.cv.nrao.edu (Don Wells) writes:
   > ... [the B-O Effect] .. tells us that the Universe..
   > has evolved.. [which] implies that there was a creation..

 TVF> .. Your objection is that the universe at high *galaxy* redshift
 TVF> looks different than the universe at low *galaxy* redshift,
 TVF> implying considerable evolution within a relatively short time..
 TVF> such rapid evolution would be a big surprise for the Big Bang
 TVF> theory too, where it must also be assimilated ex post facto.  So
 TVF> I do not describe your well-taken objection as support for the
 TVF> standard model. 

I agree that the B-O Effect should not be regarded as support for the
standard model, but it also is not inconsistent with it.

 TVF> ... yours is the most serious objection posed to the Meta Model
 TVF> in the discussion so far. Such a vast change of form for our
 TVF> local large scale universe would be unexpected unless all
 TVF> visible matter were undergoing some sort of change.. what I
 TVF> think is going on is that we have [an] extension of the blue
 TVF> giant branch.. into the ultraviolet, which would be not so
 TVF> easily observable through our atmosphere.. when.. galaxies are
 TVF> farther away, the ultraviolet extension shifts into the visible
 TVF> range, making the net color blue. 

You are describing the technicality which is traditionally called the
"K-Correction" in observational cosmology: it corrects broadband
magnitudes and colors back to the rest frame.  In a prior posting, I
described a spectrum of a B-O "blue" galaxy. The x-axis of that plot
was wavelength *in the rest frame*, i.e. it does not suffer from this
technical problem. A plot of any nearby object with the same type of
spectrum would look just the same. Therefore, the blue broadband color
of the distant (B-O) object cannot be due to a putative UV flux which
would be hidden in nearby objects.

This particular spectrum is similar to integrated spectra of nearby
"late" spiral and irregular galaxies; I myself have measured
integrated spectra of such objects. The term "blue" as used in the B-O
context apparently has caused you to get the impression that the B-O
galaxies in the distant clusters have unusual spectra with strong UV
emission. In fact, such galaxies have relatively little emission in
the UV (check the cited spectrum). The B-O galaxies---just like nearby
"late-type" galaxies---simply contain some hot, young B and A stars
and associated H-II regions, in addition to the usual population of
cooler, older stars. The hot stars and emission lines imply recent
star formation.

		-*-

Recently I received a relevant preprint: "High Resolution Imaging of
Distant Clusters: I. Close Pairs, Interactions and the
'Butcher-Oemler' Effect at Z=0.4", R.J.Lavery (Dept. Terrestrial
Magnetism, Carnegie Inst. Washington, 5241 Broad Branch Rd. NW,
Washington, DC 20008) and M.J. Pierce and R.D.McClure.  The
conclusions section of the paper says: "New, high-resolution images
(FWHM=0.45 arcsec) of the blue galaxies in A370 and Cl0024+1654 have
been presented. These images reveal that a significant fraction of
these galaxies are multiple systems, unresolved by previous
ground-based observations. In addition, a number of these systems show
signs of significant morphological peculiarities, suggestive of
interactions/mergers. These new data provide support for the mechanism
of galaxy-galaxy interactions/mergers as being responsible for the the
intense star formation occurring in these blue galaxies... it would
appear that the Butcher-Oemler effect is primarily produced by
interacting/merging disk galaxies undergoing starbursts. These results
imply that interactions and mergers of gas-rich systems play an
important role in the evolution of rich clusters from z~0.5 to the
present epoch."
--

Donald C. Wells             Associate Scientist        dwells@nrao.edu
National Radio Astronomy Observatory                   +1-804-296-0277
520 Edgemont Road                                 Fax= +1-804-296-0278
Charlottesville, Virginia 22903-2475 USA            78:31.1W, 38:02.2N