NetNews Usenet Archive 1992 #18/NN_1992_18.iso/spool/sci/astro/9142

Internet Message Format | 1992-08-22 | 6.4 KB

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From: [e-mail] (Don Wells)
Newsgroups: sci.astro
Subject: Re: Supermassive stars and HD limit (was Big Bang...)
Message-ID: <[e-mail]>
Date: 22 Aug 92 14:06:30 GMT
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In-Reply-To: [e-mail]'s message of Sun, 9 Aug 1992 20: 35:15 GMT

In article <[e-mail]> [e-mail] (Tom Van
Flandern) writes:
 TVF> Earlier, I wrote:

 TVF> >> I previously had most radio jets playing the same role as those in the
 TVF> Crab pulsar, for which a plasma jet model is fine with me.

 TVF> and [e-mail] (Don Wells) replied:

 TVF> > The two phenomena (plasma jets produced by AGNs, radiation
 TVF> beams produced
 TVF> > by pulsars) have *vastly* different scales of both size and
 TVF> energy output.
 TVF> > Also, they simply are not similar morphologically.  The AGN
 TVF> jets are plasma
 TVF> > that is producing synchrotron radiation on a grand scale all along the
 TVF> > kiloparsec lengths of jets which do not rotate and which
 TVF> terminate in hot
 TVF> > spots and cocoons, while the pulsars apparently produce their rotating
 TVF> > radiation beams close to the neutron star in an AU-sized region without
 TVF> > exhibiting hot spots or cocoons..

 TVF> As I understand all of your examples, the two types of jets differ in
 TVF> scale and energy.

They also differ in *morphology*, as I point out above.

In the context of your Meta model there are two important points about
the plasma jets. First, they are very large and very energetic
phenomena!  They are as big as whole galaxies and their radiated
energies are many, many orders of magnitude greater than those of
Galactic objects like the Crab. In fact, those radiated energies are
so large as to imply that AGNs (from which the jets project) are
extraordinary phenomena, phenomena so extraordinary as to raise very
serious questions about the whole rationale behind your Meta model,
while reducing the problem with cosmological quasar luminosities to a
special case. Work the numbers!  If you do you will find that you
cannot sweep the plasma jets under the rug of the Crab so blithely.

The second point about the plasma jets is that their morphology is the
same for radio galaxies and quasars. Radio astronomers who specialize
in this field regard them all as one type of thing, differing only in
power output, orientation and galactic and intergalactic medium
effects. The continuum of morphological properties between radio
galaxies and quasars, at low and high redshifts, plus the fact that
the nearest jets occur in (otherwise) *ordinary galaxies* whose
distances are indisputable (i.e. the physical scale and power output
of the jets are indisputable), is tantamount to *proof* that quasars
are at cosmological distances.

The Meta model needs to produce a convincing explanation for the
plasma jets that tells us how they can be produced by something other
than accretion disks plus magnetic fields around big black holes. It
must tell us whether jets from radio galaxies and quasars are the same
thing or not, and if they are not it must explain why the morphology
is identical.

 TVF> But both of these conclusions assume cosmological
 TVF> distances.  Take away the standard model premises and the two
 TVF> classes of jets would start to look very similar.

Distances to the radio galaxies in nearby clusters like Virgo and
Perseus cannot be questioned if the basic velocity-distance relation
for galaxies is accepted. Objects like M87, M84 and NGC1265 are
*galaxies* that contain stars of ordinary properties, in addition to
the wonderful plasma jets which emanate from their (active) nuclei.
The plasma jet of M87 is as large as the whole galaxy! This is tens of
kiloparsecs! It is 10**4 or more larger in scale than the Crab.
Because the distance is indisputable, inverse square law tells us that
its power output is enormously larger than that of the Crab (which is
bright only because it is very nearby).  In summary, the AGN plasma
jets are not similar to the phenomena in the Crab nebula.

 TVF> The physical associations among M87, 3C273, M84, and NGC 4472
 TVF> imply that this set is at nearly the same distance from us, and
 TVF> all are related.

M87, M84 and NGC4472 are members of the Virgo Cluster, along with
hundreds of other bright and faint galaxies of various types in that
part of the sky. They are at roughly the same distance from us. 3C273
has a much larger redshift than these galaxies. M87 and M84 exhibit
plasma jets, which are morphologically analogous to the jet of 3C273.
The basic question which we are debating is the distance (and
therefore the power output) of 3C273. The fact that 3C273 is in the
same part of the sky as the Virgo Cluster does not prove anything
about its distance. The fact that its jet may align with objects in
the Virgo Cluster *may* prove something, although it is hard to say
what it proves in the absence of a detailed physical explanation which
accounts for observations made at a wide range of frequencies. The
fact that its jet resembles those of M84 and M87 does not necessarily
prove that they are the same phenomenon, but anyone who wants to claim
that they are not should bear the heavy burden of proof.

 TVF> So M84, as for other "radio galaxies", is not at its
 TVF> cosmological distance. This changes all of its deduced
 TVF> properties.

This assertion is indefensible. M84 is an ordinary elliptical galaxy
in the Virgo Cluster. As a radio source it is not particularly
prominent (unlike M87 which was one of the first sources detected and
got the name "Virgo A"); as far as I know optical observers never
suggested that there was anything exotic about it (unlike M87, whose
jet was detected 75 years ago).  Questioning its cosmological distance
is tantamount to questioning all relative distances to galaxies.
On the other hand, accepting its cosmological distance is tantamount
to saying that plasma jets in quasars might as well be at cosmological
distances.
--

Donald C. Wells             Associate Scientist        [e-mail]
National Radio Astronomy Observatory                   [phone]
520 Edgemont Road                                 Fax= [phone]
Charlottesville, Virginia 22903-2475 USA            78:31.1W, 38:02.2N