I am working on a map for a science fiction story and using what information is available I have a good idea of locations of nearby galaxy groups and clusters and where the known supermassive black holes are.

As the Norma cluster is a big area of debate and due to that and other areas being obscured by our own galaxies, observing what is in those areas is difficult. Going off Wikipedia this cluster has a binding mass of 1E15 solar masses, which is the same as the Virgo cluster and only one galaxy is mentioned which is ESO 137-001.

Is this mass based of our galaxies motion in that direction so mass behind the cluster (some believe the Shapley supercluster) is giving the value we have or is that a known mass of galaxies in that cluster? If so can we predict if it has a similar number of large galaxies and supermassive black holes as the Virgo cluster or is there other predictions for the Norma cluster?

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    $\begingroup$ @planetmaker the OP has now addressed it $\endgroup$
    – uhoh
    Commented Aug 25, 2020 at 23:51

1 Answer 1


VizieR lists two catalogues of Norma cluster members:

  • J/MNRAS/383/445 Woudt, P.A. et al. (2008) "Radial velocities in the Norma cluster (A3627)"
  • J/MNRAS/396/2367 Skelton, R.E. et al. (2009) "NIR Ks photometry of Norma cluster (A3627)" (this one contains angular diameter information)

The paper associated with the first of these, "The Norma Cluster (ACO 3627): I. A Dynamical Analysis of the Most Massive Cluster in the Great Attractor" describes the methodology used for estimating the cluster mass from their measurements of the radial velocities (in particular their dispersion) of the galaxies. From the paper:

For the determination of the dynamical mass of the Norma cluster, we have used both the virial theorem ($M_{\rm VT}$) and the projected mass estimator ($M_{\rm PME}$), see equations (21) and (22) of Pinkney et al. (1996). The use of the biweight velocity centroid and scale (Beers et al. 1990) in the virial theorem (instead of the velocity mean and standard deviation) leads to a more robust mass estimate ($M_{\rm RVT}$). The latter is more robust against the effects of contamination by the inclusion of possible non-members in the analysis. The projected mass estimator (Bird 1995), on the other hand, is sensitive to the presence of (spatially separated) subclusters due to its proportionality to the projected distance between galaxy $i$ and the cluster centroid ($R_{\rm \perp,i}$) (see equation 22 in Pinkney et al. 1996).

They also note that the masses they derive are consistent with masses estimated from the X-ray emission by Böhringer et al. (1996) and Tamura et al. (1998).

As regards what types of galaxy these are, unfortunately neither of the catalogues provide morphological types directly. On the other hand, they do include for many of the objects a reference to the WKK98 catalogue (Woudt, P.A. & Kraan-Korteweg, R.C. 1998).

WKK98 is also available on VizieR as J/A+A/380/441 and does include the morphological type.

You can use the VizieR query interface to join the tables (or you can download the tables in their entirety via the FTP page on VizieR and do the joining on your local machine, e.g. via the various lookup functions in your spreadsheet software of choice), which will give you a list of the morphological types of the objects.


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