24th Nov 2005


Red Shift of Seyfert Galaxy UGC 545 (IZW1, QSO B0050+124)

UGC 545 is a mag 14.1 galaxy with an Active Galactic Nucleus. The high luminosity of the core makes it visible despite being at a significant distance from us.

The almost stellar appearance allows the Star Analyser diffraction grating to be used in a slitless configuration.

SC3 "PIPCAM" +VC200L @ f6.4

This is the faintest object recorded to date. Dispersion was 31.4 A/pixel.

Two repeat spectra were recorded with the Star Analyser rotated between exposures to check if any features were due to background stars.

A spectrum of Vega was also recorded to enable a wavelength calibration to be made based on the H Balmer lines.

The H alpha emission line is clear in the Galaxy spectrum. It is displaced 5.5 +-1% to the red compared with the reference H alpha absorption line in Vega.

This compares well with the published figure of 6.1% redshift for UGC545 (An error of 0.5% is equivalent to 1 pixel)

A cosmological redshift of 0.061c corresponds to a distance of about 250Mpc so the mag 14 galactic core has an abolute magnitude of roughly -23. excluding any absorption this is around 150 billion times more luminous than the Sun.


See also a spectrum of QSO 3C273