Observation by Robin Leadbeater: Abell 1314 - galaxy redshifts

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Robin Leadbeater


Robin Leadbeater


2023 Feb 12 - 21:24


2023 Feb 26 - 16:22



  • ALPY 600,200 spectrographs
  • ATIK 428 ex camera
  • Celestron C11 SCT 280mm aperture f5.5

typically 2x 1 hour per spectrum


Wigton, Cumbria, UK

Target name

Abell 1314


Abell 1314 - galaxy redshifts

About this image

For the Deep Sky Section’s Object of Interest for February 2023 (the galaxy cluster Abell 1314, specifically IC708,709,711 and 712 seen in their relative locations in this image by Richard Sargent), I decided to use low resolution spectroscopy to estimate the redshifts and verify that they are indeed members of the same cluster. An initial set of spectra was taken 20230212-13 using the ALPY 600 but the targets proved too faint so a second set was taken 20230224 using the lower resolution ALPY200 faint object spectrograph and the two sets combined to give a single set of lower resolution spectra but with reasonable signal/noise ratio.

In the absence of suitable emission lines (IC708 is catalogued as a Seyfert galaxy but no emission lines could be seen), the redshift can be estimated by cross correlating with stellar spectra, the aggregate spectrum of billions of stars in a galaxy typically approximating to that of a K type star. The foreground star HD100597 (K2iii) in the same field provided a convenient reference. The spectra of the four galaxies are very similar with many common features with no detectable offset between them, confirming that they have the same redshift. The redshift relative to HD100597 however is clear, particularly the feature marked on the plot (Fraunhofer b, the Mg triplet blend, also visible in the solar spectrum). The estimated redshift of the group is z= 0.032 which equates to a luminosity distance of ~140Mpc using 70km/s/Mpc for the Hubble constant. This is comparable with the distances in the NASA Extragalactic Database of around 150Mpc based on the Tully-Fisher technique (Although Supernova SN 2004H in IC708 was apparently a type 1a, there is no record in NED of it having being used to independently estimate the distance) 

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