Parallax vs Redshift distance comparisons

Wasn't it Abdul Ahad who wrote:
Mike Williams wrote in message news:ZHkVeAAuYgAAFw4
...
Wasn't it Abdul Ahad who wrote:

That's the method that Hubble used to measure the distances to enough
galaxies to be able to determine that those outside the local cluster
were moving away from us. He observed Cepheids in galaxies up to about
32 Megaparsecs away (over 40 times the distance to M31).


Hubble's law and the validity of redshift for distance assumptions
seems to break down completely when it comes to Quasars.

I think you're wrong there. If you're thinking about the evidence that
the expansion of the universe is accelerating, then you're considerably
overstating the situation. There's a slight deviation from Hubble's law.

So why do we
put so much faith in redshift-based distances overall? Is it merely
because its the *only* best-fit model we have at present? Have any
Cepheids been directly observed in galaxies that are far away enough
for 'fly-away' redshifts to become viable for effective distance
measurements

If you read the page that I previously referred to
http://www.astronomynotes.com/galaxy/s16.htm
You'll see that observations of Cepheid variables is just one of several
methods commonly used for measuring astronomical distances. The methods
are useful over different distance ranges, and the results obtained by
one method allow us to calibrate the next method. Cepheid Variable
observation is only valid out to about 40 MegaParsecs.

One method that's useful at very large distances is the fact that the
intrinsic brightness of a type 1a supernova correlates with how quickly
it dims. This allows us to use observations of this type of supernova in
a similar way to Cepheid Variable stars, but we can see supernovae out
to immense distances. Such supernovae are fairly rare. Fairly recent
techniques have made it possible for automated systems to watch large
numbers of galaxies and automatically detect supernova events. In this
way, it has been possible to detect small changes in the relationship
between the distance (measured by supernovae) and the speed of recession
(measured by redshift) which indicate that the expansion of the universe
is accelerating.

--
Mike Williams
Gentleman of Leisure

Greg Crinklaw wrote in message ...
Abdul Ahad wrote:
Hubble's law and the validity of redshift for distance assumptions
seems to break down completely when it comes to Quasars.

That's not a true statement. Arp's work has been largely discredited
based on statistical bias and other huge flaws in the methodology.


The chart at the bottom of this page:
http://www.geocities.com/newastronomy/quasars.htm

shows that quasars fall way outside the line of best-fit. The way I
understand it, Hubble's law stipulates that if you plot the redshift
of galaxies (or their recession velocity) against their distances
(visual brightness) then one should get a broadly straight-line
relationship.

It appears that this does not hold true for quasars, causing some
astronomers to suspect that quasars may be nearer than we think?
There are also independent cases I have read in a book called "Seven
wonders of the universe" where it *appears* that quasars seemingly
*gravitationally associated* with a galaxy have much larger redshifts
than the galaxy itself!

AA

That's not a true statement. Arp's work has been largely discredited
based on statistical bias and other huge flaws in the methodology.


The chart at the bottom of this page:
http://www.geocities.com/newastronomy/quasars.htm

shows that quasars fall way outside the line of best-fit. The way I
understand it, Hubble's law stipulates that if you plot the redshift
of galaxies (or their recession velocity) against their distances
(visual brightness) then one should get a broadly straight-line
relationship.

Yes,

but if you look at the rest of the web-site, do you really trust a web-site
that claims galaxies are optical illusions produced by gravitational
lensing?

DaveL

There is nothing reliable on that page. It includes many misleading
statement and several downright falshoods. Find a more reputable source.

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html

To reply remove spleen

Wasn't it Abdul Ahad who wrote:
Greg Crinklaw wrote in message news:101da283j7eg7
...
Abdul Ahad wrote:
Hubble's law and the validity of redshift for distance assumptions
seems to break down completely when it comes to Quasars.

That's not a true statement. Arp's work has been largely discredited
based on statistical bias and other huge flaws in the methodology.


The chart at the bottom of this page:
http://www.geocities.com/newastronomy/quasars.htm

shows that quasars fall way outside the line of best-fit. The way I
understand it, Hubble's law stipulates that if you plot the redshift
of galaxies (or their recession velocity) against their distances
(visual brightness) then one should get a broadly straight-line
relationship.

It appears that this does not hold true for quasars, causing some
astronomers to suspect that quasars may be nearer than we think?
There are also independent cases I have read in a book called "Seven
wonders of the universe" where it *appears* that quasars seemingly
*gravitationally associated* with a galaxy have much larger redshifts
than the galaxy itself!

We can't observe Cepheid Variables or Type 1a Supernovae in quasars. We
don't have any way to estimate the intrinsic brightness of a quasar. We
can't use parallax or main sequence fitting or any distance measure
except using their redshift and Hubble's Law.

The page you quote seems to attempt to estimate the distance to a quasar
by looking at the brightness of galaxies that are nearly in the same
line of sight. If that leads to results that disagree with Hubble's Law,
then it's probably Hubble that is correct.

Recent theories about quasars suggest that they might be the cores of
active galaxies that just happen to have their jets oriented towards us.
Active galaxies at that distance that have jets oriented in other
directions are not visible to us. If that is the case, then it's
possible that the redshifts we observe are blue shifted by the real
motion of material in the jet. This would suggest that the quasars could
be much further away than the observed redshifts suggest rather than
closer as suggested on that web page.

--
Mike Williams
Gentleman of Leisure

(Abdul Ahad) wrote in message . com...

The chart at the bottom of this page:
http://www.geocities.com/newastronomy/quasars.htm

shows that quasars fall way outside the line of best-fit. The way I
understand it, Hubble's law stipulates that if you plot the redshift
of galaxies (or their recession velocity) against their distances
(visual brightness) then one should get a broadly straight-line
relationship.

The chart shows that Quasars are brighter than galaxies, nothing
else! This falls into the "well DUH" catagory. Notice that the
axes are labled aparent magnitude and redshift, while the conventional
use of the Hubble law indicates a relationship between distance and
redshift. We can "see" quasars because they are bright, in reality,
though, we can see then a generation earlier than we get large
enough telescopes that can image their surroundings, nothing more.

(Mitch Alsup) wrote in message . com...
(Abdul Ahad) wrote in message . com...

The chart at the bottom of this page:
http://www.geocities.com/newastronomy/quasars.htm

shows that quasars fall way outside the line of best-fit. The way I
understand it, Hubble's law stipulates that if you plot the redshift
of galaxies (or their recession velocity) against their distances
(visual brightness) then one should get a broadly straight-line
relationship.

The chart shows that Quasars are brighter than galaxies, nothing
else! This falls into the "well DUH" catagory. Notice that the
axes are labled aparent magnitude and redshift, while the conventional
use of the Hubble law indicates a relationship between distance and
redshift.

I think the intention in this chart is to say that apparent
*brightness* (magnitude) is supposed to correspond to actual
*luminosity* (light output). Example: if a galaxy is of 15th magnitude
in appearence, then by Hubble's law we expect it to have a redshift of
X. If a quasar is of 15th magnitude and it has a greater redshift of
say X times 3 ...the implication is either the quasar is immensely
super-luminous compared to the galaxy and it lies at the further
redshift-predicted distance of three times that of the galaxy - or it
is in fact much closer to us than inferred by its redshift, hence it
looks visually brighter and therefore defies Hubble's law!

I don't put too much confidence in these charts as the source is not
credible. However in a book called "Seven wonders of the Cosmos" by
some professor named Jayant V. Narlikar, published by Cambridge
University Press 1999, on pages 307 through 311 reference is made to
H. C. Arp's peculiar findings.

In the first case, three quasars were found within small angular
distances of 73, 59, 73 seconds of arc from the galaxy NGC 3842. We
know quasars are relatively rare objects, sparsely scattered across
the sky. The odds of three quasars aligning around the galaxy by pure
chance is the same as getting 20 consecutive heads when tossing a coin
at random! Statistically speaking one would therefore be compelled to
say the three quasars *must* be associated with the galaxy! But how
can this be, when the galaxy has a redshift z=0.02, the 3 quasars have
z=0.34, 0.95 and 2.20!

In the second case, Narlikar quotes two triplets of 6 quasars - all 6
found on *one* of H. C. Arp's photographic plates. Each of the two
triplets of quasars were *perfectly* lined up on a straight line! The
odds of this happening by random chance are quoted as 4000 to 1 or
getting 12 heads straight after one another in a row, when randomly
tossing a coin!

The third case does not involve quasars but where two galaxies of
different redshifts seem to be connected by a thick filament! Quote
from the book: "The large galaxy [NGC 7603] has z=0.029 while the
small one...has z=0.057. If we assume the connection is real, then the
smaller galaxy has a relative radial velocity of about 8,300 km/s.
This is too high high to be explained as a random relative motion. So,
in order to keep Hubble's law alive...we have to assume that the two
galaxies *are not connected*, that the smaller galaxy happens to be
projected just at the end of the filament issuing from the big
galaxy!" /quote.

If the world's most prominent astronomers have dismissed Arp's
contra-Hubble findings on misrepresented facts or statistical errors,
then who am I to argue? Personally, I don't give that much credence to
these redshift anomalies but I thought I should share them anyway!

Abdul Ahad
http://uk.geocities.com/aa_spaceagen...eprojects.html
"We have lingered long enough on the shores of the cosmic ocean. We
are at last ready to set sail for the stars" - Carl Sagan.

One of these guys wrote:

In article ,
(Abdul Ahad) wrote:

(Mitch Alsup) wrote in message
. com...

(Abdul Ahad) wrote in message
. com...


[snip]

I don't put too much confidence in these charts as the source is not
credible. However in a book called "Seven wonders of the Cosmos" by
some professor named Jayant V. Narlikar, published by Cambridge
University Press 1999, on pages 307 through 311 reference is made to
H. C. Arp's peculiar findings.

Narlikar is a prominent anti-big-banger, in fact he and Padmanabhan
wrote "STANDARD COSMOLOGY and ALTERNATIVES: A Critcal Appraisal" for
the 2001 Annual Review of Astronomy and Astrophysics.

The basic question is whether apparent proximity on the sky means
proximity in space. The anti-BBs claim it must and advance various
statistical and visual ( tendrils, bridges, etc ) arguments to conclude
that, in this case, it does.

These arguments have failed to convince most cosmologists. The basic
counter-agument is that there are lots and lots of quasars and a few
close alignments are not unlikely. We have been burned too many times
to give "look-like" arguments much weight ( the canals on Mars are
just one example ).

A second counter argument is: If not due to do Hubble expansion
what is causing the red-shift? It can not be due to peculiar
velocity as all the Arp objects have higher red-shifts than the host.
( Nobody, not even Narlikar, beleives that they are preferentialy
moving away from Earth. ) It can not be gravitational red-shift as
the masses required would strongly distort the hosts.

The key is to find an independent measure of the distance. This
distance would use neither red-shift nor proximity. Two methods
are Type 1a SNe and Tully-Fisher, in a few cases where one of the
Arp objects is a spiral galaxy one or another of these methods have
been used to show that the galaxy is spatialy remote from the host.

Unfortunately quasars display neither SNe ( too far away ;-) )
nor rotating spiral arms. Figure out a method to measure the
distance and you will start getting invited to all the big-time
conferences.

Dark skies,

tom

PS Each of the two triplets of quasars were *perfectly* lined up
on a straight line! The odds of this happening by random chance
are quoted as 4000 to 1 ...

Since there are around a hundred thousand quasars your job
is to explain why there are so FEW of these alignments, at
4000-to-1 the expectation is about 25 per 100,000. I suspect
that if we look carefully many more alignments will be found
but that is a guess.

The third case does not involve quasars but where two galaxies of
different redshifts *seem* to be connected by a thick filament!

This is a look-like argument, see the canals of Mars for further
references. ( I added the stars around *seem*. )

--
We have discovered a therapy ( NOT a cure )
for the common cold. Play tuba for an hour.

Let's not forget that we have imaged "fuzz" around quasars. This fuzz
is the parent galaxy; something that was predicted by the current
interpretation of what a quasar is. Not only that, but there are a
range of qauasar-like objects going from classic point sources to
obvious galaxies that have bright active nuclei. Finally, we have a
theory that explains the energy source for the entire range of objects.
This argument was pretty much put to bed over a decade ago.

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html

To reply remove spleen

Tom Kirke wrote:
The basic question is whether apparent proximity on the sky means
proximity in space. The anti-BBs claim it must and advance various
statistical and visual ( tendrils, bridges, etc ) arguments to conclude
that, in this case, it does.

These arguments have failed to convince most cosmologists. The basic
counter-agument is that there are lots and lots of quasars and a few
close alignments are not unlikely. We have been burned too many times
to give "look-like" arguments much weight ( the canals on Mars are
just one example ).

They have failed to convince most statistics people, too. With 100,000
quasars scattered about 40,000 odd square degrees (closer to 41,253, but
what's a few square degrees among friends?), the average concentration
is about 2.5 quasars per square degree. If we assume that the quasars
are Poisson, the probability that a second unrelated quasar will be
found within, say, 1 arcminute of a first one is merely 1 in 500. If
they aren't Poisson, that means that there is a bias to the distribution
and the probability of a chance alignment that close increases. (Are
the quasars far enough away that clustering can largely be ignored and
the Poisson distribution assumed? I don't know.)

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt