STAR Atlas:PRO frequently asked questions - FAQs

Can I list the individual galaxies that make up each Hickson Compact Galaxy Group ?

Yes, with STAR Atlas:PRO you can do exactly that. Follow the procedure below to see how simple this information can be found.

1. Start STAR Atlas:PRO
2. click [Locate] or L on keyboard
3. click the menu option [10] - Hickson Compact Groups of Galaxies
4. Hickson Group Number 1 is the first Hickson Compact Group to be displayed. The bottom half of this information panel displays the Member Galaxies ( the individual Galaxies that make up each Hickson Compact Group).
Upon further study, you will see there is much astrophysical data displayed about each of the Member Galaxies.
The grid in which this information is displayed may be scrolled left to right before all the data can be seen (there is too much to fit on one screen).
5. if you wish to locate the information for another Hickson Compact Group then choose the [Find] button (bottom of information panel) and then enter the number of the Hickson Compact Group of Galaxies ( i.e. try Group number 52 )

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Additional Information - (advanced users):
Following is a description of the information displayed about each Hickson Compact Group of Galaxies ( from the STAR Atlas:PRO Manual)

This is the information listed for each Hickson Compact Group of Galaxies.

Group Type A two-character code (a letter followed by a number) classifies the group according to its 2 brightest members:

S    The brightest galaxy is a spiral galaxy.
E    The brightest galaxy is not a spiral galaxy.
1    m(b) - m(a) >= 1.0
2    0.5 <= m(b) - m(a) < 1.0
3    m(b) - m(a) < 0.5

where m(a) and m(b) are the estimated red magnitudes of the brightest and second brightest members, respectively, of the cluster.
Member Count Number of galaxies in the group. Only those galaxies within three  magnitudes of the brightest galaxy are counted as members.
Angular Size Angular diameter, in arc minutes, of the smallest circle containing the geometric centers of all galaxies in the group.
Total Magnitude of Group Total estimated red magnitude of those galaxies counted as group members
Magnitude of Brightest member Estimated red magnitude of the brightest galaxy.
Redshift Corrected redshift of the brightest galaxy
Other Catalogues Other designations of the galaxy group.

Common Positional Data

Common information to all Catalogues.

This is the information listed for each member galaxy of a Hickson Compact Group of Galaxies.

Component Galaxy in HCG group (a-i)
Semi-major Semi-major axis at 25.0mag/arcsec^2^ isophote
Semi-minor Semi-minor axis at 25.0mag/arcsec^2^ isophote
Hubble Morphological Hubble Morphological type
Numerical Numeric morphological type
Heliocentric Heliocentric velocity
Est. rms Estimated rms in Rvhel
Bmag B magnitude within 24.5mag/arcsec^2^ isophote
Dia 24.5mag Diameter of B=24.5mag/arcsec^2^ isophote
R mag 24.5 R magnitude within 24.0mag/arcsec^2^ isophote
Dia of r=24.5 Diameter of R=24.0mag/arcsec^2^ isophote
Colour 24.5 Colour within the 24.5mag/arcsec^2^ isophote
BT asymptotic B_T_ asymptotic magnitude
BT asymptotic mag ext B_T_ asymptotic magnitude corrected for internal and external extinction
Abs Mag Absolute magnitude of individual galaxies, h=H0/100, H0=Hubble constant
Names Other names

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