Eddington, Ryle and Hoyle. Jasper Wall. How a major 20th Century discovery was lost in noise and confusion. What were the great surprise discoveries of the 20th century?. Richard Ellis, arXiv:0701024:. Cosmic expansion (Slipher and Hubble 1917-1925)
Richard Ellis, arXiv:0701024:
Radar pioneer, 1939-1945
Ryle and Vonberg 1946 - first
interferometric radio astronomy
First sky surveys 38 - 159 MHz, 1950 - 55
Ryle and Hewish 1960 - Aperture synthesis
Ryle and Neville (Anne Gower) 1962 -
‘deep’ synthesis map at NCP
Gold medal of the RAS 1966
Nobel prize 1974 (with Tony Hewish - aperture synthesis / pulsars)
Ryle 1955, the Halley Lecture; Ryle and Scheuer 1955
1. The number-intensity distribution of the observed radio stars shows that they cannot be interpreted
in terms of a homogeneous distribution of sources - there is an apparent increase in the spatial density
or absolute luminosity of distant sources.
2. This increase is, within rather small statistical errors, independent of direction. It appears that the solar
system is situated at the centre of a spherical region in which the spatial density or luminosity
of the sources increases with distance, uniformly in all directions.3. It is impossible to explain the results in terms of sources situated within the galaxy, or by irregular
clustering of extra-galactic sources.
4. From limits to the integrated radiation, the minimum radius of the spherical region is comparable with that of
the optically observable universe.
5. We suggest that the observed features are due to effects on a cosmical scale; there seems every reason to
suppose that they might be explained in terms of an evolutionary theory.
6. A general explanation of the observations seems possible if it is supposed that the majority of radio stars
belong to an excessively rare class of object, having a local spatial density of about 2 × 10-26 pc-3, and an absolute
luminosity comparable with that of the intense radio source in Cygnus.
7. On this interpretation, the difficulty of identifying radio stars with optical objects finds a natural explanation;
only some tens of the main class of radio star would be within reach of the 200 in. telescope.
The slope of this integral count was ~ -2.7,
c.f. initial slope for uniformly filled universe of -1.5
1906 sources in 2C; the majority of them would prove to be false
1. Eddington bias
A little paper in 1913 MNRAS by Eddington: On a formula for correcting statistics for the effects of a known error of observation
Eddington bias rediscovered by
Submm Galaxy researchers
Left: Red points show a source count (number of sources on the `sky' per interval of 2 units in flux) from a toy Euclidean universe. The green line is the theoretical power law of slope -5/2. The blue points represent the distorted source count resulting from Eddington bias assuming a Gaussian flux measurement error of σ = 5 units. Black crosses represent the analytical calculation N’(S)=∫N(S)p(S)dS.
Right: plots of the integrand N(S)p(S) for apparent flux densities of 15, 20, 30 and 40 units (3σ, 4σ, 6σ, 8σ) given an underlying law of slope -5/2 and Gaussian errors ofσ= 5 units.
3σ is hopeless; 4σ is still seriously biased
A (double) 2.7-GHz sky integration to the confusion limit
Second integration: all features are duplicated
Yet another radar pioneer (1939-45)
(Developed the Lloyd’s mirror height
measurement technique for aircraft)
Marvellous radio presenter and publicist, wrote good SF
Brilliant theorist, physicist, cosmologist
- Tidal torques / galaxy angular momentum
- B2FH (1957) - why we exist
- Steady-State theory 1948 (with Bondi and Gold)
- Primordial He abundance in HBB (with Tayler, 1966)
- panspermia, viruses from comets drive our evolution ...
- non-cosmological redshifts, quasi-Steady State (1993)...
Gold medal of the RAS 1968
MSH: slope -1.8
P(D) and confusion again:
The Parkes 2.7-GHz survey
Wall et al. 1971, et seq => 1976
At last a decent pencil beam survey at a ‘high’ frequency!
2.7 GHz, 11cm
Twin beams 8.0 arcmin FWHM
> 30 beam areas per source
Most of southern sky up to dec +15o
Shimmins, Bolton and Wall 1968 Nature
20 July 1969
Parkes 210-ft (64m) dish
The radio ‘m - log π diagram’
following Sandage’s suggestion
Shimmins, Bolton and Wall 1968 Nature
Wall thesis 1970
No uniformly-filled relativistic universe count remotely resembles the observed count
1 chance in 1080
1 chance in 10960
Richard Ellis, arXiv:0701024: + JVW
The original arguments concerned the counts in the small boxed area, 150 MHz.
e.g. galaxy evolution via number-magnitude counts
Shanks et al. 1984
Wall, Pope & Scott 2008
Radio QSOs, X-ray QSOs, SMGs
Radio QSOs, Star-formation rate
Croton et al. 2006, Bower et al. 2006:
To effect cosmic downsizing, invoke a radio AGN phase to blast the cool gas out of the galaxy =>
Galaxy-makers have found a use for radio AGN at last!
Springel et al. 2005
themselves in such a situation. Why could they not
collaborate? e.g. Penzias & Wilson / Dicke, Peebles et al.......
altered. It took years.....