Galaxy Group Hickson 76 (part of Abell 2085)


Galaxy Cluster Hickson 76


This picture was made from fifteen 1 minute exposures with an ST-6 CCD camera thru Kopernik's 20-inch F/8.1 Ritchey Chretien Cassegrain telescope. The field of view is about 5x7 arc minutes with North at the top.

Hickson 76 is a relatively loose group of seven galaxies, all with similar red shifts, meaning that all are probably close together in space. Dr. Paul Hickson's Atlas of Compact Groups of Galaxies contains 100 galaxy groups that may be in the process of colliding or even combining into a single galaxy. This group lies at the core of the large and rich Galaxy Cluster Abell 2085.

This is one of the parts of the sky where various catalogs disagree on the identifications of objects. Hickson 76 includes NGC 5944, NGC 5942, and NGC 5941. Unfortunately, there is much confusion over exactly which is which. These are three of a group of four nebulae discovered by Lewis Swift on April 19th 1887. Bigourdan observed these galaxies two years later, but disagreed with Swift's positions versus his descriptions. The MCG and CGCG also differ on the identification, and the RNGC reversed Swift's designations and used Bigourdan's. There have been several recent attempts at determining exactly which of these galaxies Swift observed. The Kopernik image and the table below use the identifications suggested by Dr. HG Corwin and currently used in the NASA Extra-Galactic Database.

Based on the red shift study, a distance estimate (using a Hubble Constant of 62 Km/sec per Mpc) for this cluster is 536 Million light years. At that distance the picture above covers 0.8 by 1 million light years.

Galaxy Group Hickson 76 ( part of Abell 2085)

Hickson-76 ID

Object Name

Equatorial J2000.0

Mag-
nitude

Type

Velocity/Redshift

RA RA

RA

DEC

   

km/s

z

A

NGC 5944

15h31m48s

+07d18m29s

15.87

spiral

10,088

0.03365

B

NGC 5941

15h31m40.2s

+07d20m20

14.91

elliptical

10,002

0.033363

C

NGC 5942

15h31m36.8s

+07d18m44s

15.31

lenticular

10,663

0.035568

D

MCG +01-40-002

15h31m42.2s

+07d17m14s

15.83

elliptical

10,150

0.033857

E

PGC 055325

15h31m50.3s

+07d18m39s

17.35

lenticular

10,328

0.034450

F

CGCG 050-011

15h31m38.8s

+07d20m51s

17.27

lenticular

10,109

0.033720

G

PGC 055307

15h31m35.8s

+07d20m57s

17.65

spiral

9,843

0.032833

 


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George Normandin, KAS

May 8th, 2001