"g" == greywolf42 <mingstb@marssim-ss.com> writes:

g> So, argue with Ned's "latest" references (who refuse to mention
g> French), not with me. I'm not a bit surprised that sooner or later
g> some study of I Zw 18 will find an "adjustment" sufficient to bring
g> it back into the theoretical fold. And I fully expect the Priests
g> to immediately consign all other studies to the same memory hole to
g> which the consigned French.

My recollection is that French (or some other author from about the
same time) had a long discussion on the difficulty of extracting
reliable abundance ratios from I Zw 18.

A VERY long section lists various authors have studied the problem with
care, observation and theory. Yet I Zw 18 refuses to respond to all
efforts. So Izotov concludes: "But these assumptions** are very
uncertain, and as long as they are not well understood, I Zw 18 CANNOT
BE USED FOR THE DETERMINATION OF THE PRIMORDIAL HELIUM
ABUNDANCE." (emphasis in original)

While I see you often
claiming that this is an example of data suppression, I don't recall
any sensible rebuttal of the actual issue,

Can reliable abundances be
extracted from the spectrum of I Zw 18?

The other possibility of course is that our technology has improved in
the past 20 years and that it is now possible to obtain higher quality
spectra toward I Zw 18. In this case, it seems a bit weird to be
arguing about what results people should have obtained in 1980.

"g" == greywolf42 <mingstb@marssim-ss.com> writes:

g> So, argue with Ned's "latest" references (who refuse to mention
g> French), not with me. I'm not a bit surprised that sooner or later
g> some study of I Zw 18 will find an "adjustment" sufficient to bring
g> it back into the theoretical fold. And I fully expect the Priests
g> to immediately consign all other studies to the same memory hole to
g> which the consigned French.

My recollection is that French (or some other author from about the
same time) had a long discussion on the difficulty of extracting
reliable abundance ratios from I Zw 18.

While I see you often
claiming that this is an example of data suppression, I don't recall
any sensible rebuttal of the actual issue, Can reliable abundances be
extracted from the spectrum of I Zw 18?

The other possibility of course is that our technology has improved in
the past 20 years and that it is now possible to obtain higher quality
spectra toward I Zw 18.

In this case, it seems a bit weird to be
arguing about what results people should have obtained in 1980.

"g" == greywolf42 <mingstb@marssim-ss.com> writes:

g> I mean just what I say. I have no need to twist words.
g> Calculation by drawing a theoretical straight line through a series
g> of shotgun data points, and then picking the zero intercept is not
g> "direct observation" in anyone's dictionary.

Then what you say is a gross mischaracterization of French's work.

I presume you are referring to Figure 6 of his paper.

A simple visual
analysis should be enough to convince one that this is not a scatter
plot or a "series of shotgun data point."

He did not "draw" a line nor "pick the zero intercept," he fit a line.

Indeed, his methodology is exactly what one would expect.

You (or
anybody else) are of course free to use his data, assume a different
model (which must make quantitative predictions of course), and fit to
see what parameters of that model that you find.

greywolf42 wrote:

"Bjoern Feuerbacher" <feuerbac@thphys.uni-heidelberg.de> wrote in
message news:d4nias$bh4$1@news.urz.uni-heidelberg.de...

Now, could you please explicitly state whether you agree
or disagree with Ned Wright's claim (and the methodology of all of these
BB papers) that stellar generation of He always produces the same
ratios of "metals?"

Since the heavy elements are mainly produced by the populations I and
II, the contribution of the population III is fairly negligible, and
hence that claim should be essentially right.

[snip]

Where did you get this number from, specifically? Could you please
help me out?

This value came from section III.d of the paper, on page 52. And I see
upon rereading the paper, that it was not French who observed the 11%
value, but Searle and Sargent (1972) who obtained "approximately" that
value for I Zw 40 and I Zw 18 (0.7 average and 0.5 average,
respectively).

You seem to misunderstand quite a bit here. French says that *this*
study, i.e. *his own*, found about 0.5 and 0.7 of the "normal" value
(which is approx. 0.11), respectively. In contrast, Searle and Sargent
found *normal* abundances.

Additionally, the value 0.11 is *not* Y, but He/H (numbers of atoms).
This gives an Y value of about 30.6%!

Then it could hardly be considered between 0.5 and 0.7 of the "normal"
value (of 22 to 25%), now could it?

Err, French did not say that the 0.11 are between 0.5 and 0.7 of the
normal value. He said that 0.11 is the normal value, and that "this study"

found values between 0.5 and 0.7 of this "normal value".

Feel free to post the entire section here, so all can see whether this
0.11 value below Yp, or not.

He/H = 0.11 implies Y=30.6%, which is above Yp. 0.5 times 0.11 gives
0.055, which is very close to the value 0.052 which French gives for I Zw

That galaxy indeed seems to have an Y below Yp in this study; I
commented on that elsewhere.

French also notes that Lequeux (1972) also arrives at
"low" numbers (though French does not give the number).

From the context, I take it that Lequeux' values are consistent with
French's values (they both get low values).

And low values disprove the BB -- which cannot tolerate a single case
less than Yp.

Non sequitur. "low" is not the same as "less than Yp".

There is some
discussion on the relative weighting to specific helium lines (more in
Peimbert & Torres-Peimbert, 1974).

As noted in the followup thread, the "mainstream" has abandoned the
inclusion of I Zw 18 in such studies (even with higher values) --
explicitly because no theoretical explanation has been found that saves
the BB theory, if it is included.

We can discuss this point further, if you like. But first I would like
to settle the point above, about the 11%.

Feel free to respond after you've completely read all the references
that you desire. You do seem to have a tendency to make claims
based on a quick skim, or simply abstracts.

Feel free to admit now that you misunderstood French's remark about
the 0.11 completely.

[snip]

IIRC, Ned didn't use the assumption that O/Z is constant
anywhere in his approach.

Then how do you explain the following statement, theoretically? (from
above)

"for every 3.2 grams of helium produced, stars produce 1 gram of heavier
elements (French, 1980, ApJ, 240, 41)."

The absolute ratio of Y/Z is constant. And how are you going to do this
(theoretically) with a changing internal ratio of Z? [Oxygen is one
contributor of Z.]

Where exaxtly do you see the problem with that???

[snip]

That did refer to another article, not to French's paper, IIRC.

Nope. That was French's article, too.

Right. I misremembered, sorry.

All of these papers that calculate
Yp perform precisely the same process. They just use different sources
and different "filters" to adjust the observations.

But the data points are not like a shotgun scatter.

I calculated the
correlation coefficient for the data shown in Fig. 6 of French; it's
0.548. That's a quite clear positive correlation.

Could
we please try to stay on topic until the questions I originally asked
you are settled?

The *topic* under discussion is Ned Wright's claim:
"for every 3.2 grams of helium produced, stars produce 1 gram of heavier
elements "

No. The topic of this thread were my questions. Don't try to obfuscate
them by bringing up additional issues.

And you are responding to *my* posts.

I asked some questions about some details in them. I never said that I
wanted to open that whole discussion again. *You* brought all that
stuff up.

Wherein, I show that Ned's own
*linear* approach (based on French's *data*) contradict the BB. So far,
you've avoided identifying an error in my calculation.

Err, just above, with your comment 'That would count as a "someplace
else."', you admitted yourself that I indeed identified an error in
your calculation.

But you apparently
fear to publicly contradict Ned's linear approach. So you are
attempting to divert from the issue.

So far, the only one who tries to divert (from my argument that your
assumption that O/Z is constant is wrong) is *you*.

I have neither the desire -- nor time -- to get into endless, tangential
quibbles.

Then why did you bring all this irrelevant stuff up?

You see, it is the BB theory that requires 0/Z to be constant

Why do you think so?

Because Ned's linear approach requires this.

No. Why on earth do you think so?

If you disagree, then please state so explicitly ... and demonstrate how
this is possible.

A hypothetical example: two sources, both with H, He, O and N.
1) He/H = 0.1, O/H = 10^(-4), N/H = 10^(-6)
2) He/H = 0.1, O/H = 0.95 * 10^(-4), N/H = 5*10^(-6)

Both have the same Y/Z (and therefore also the same delta Y/delta Z),
but different values of O/Z.

Otherwise the premise fails. The only relatively constant ratio that I
could find in them, was that Oxygen to the-rest-of-the-metals (O/Z) was
roughly constant -- regardless of source or observer.

"in them". To which papers does that refer, specifically?

To the ones that I explicitly referenced in the post, of course.

So these papers show that in the Orion nebula and the LMC, O/Z is
roughly constant. So what? That does not in the least justify using
that value as the cosmic abundance of oxygen.

Now, in Lerner's Plasma Cosmology, the "first generation" of stars in a
galaxy are much larger (on average) than later generations. These
stars release larger He/metal ratios when they die than the current
mix. But the BB cosmology assumes that the mix of stars is roughly
constant in the early-to-mid life of galaxies (or other star-bearing
regions).

But in the BB theory, the first stars are *also* much large (on
average) than later generations. Never heard of population III?

Of course I have.

Then why did you feel thee need to mention above that in Plasma
Cosmology, the first stars are much larger, and pretend that in the
BBT, that is not the case?

[snip]