Unbarred spiral galaxy

An unbarred spiral galaxy[1][2] is a type of spiral galaxy without a central bar, or one that is not a barred spiral galaxy. It is designated with an SA in the galaxy morphological classification scheme.

The Whirlpool Galaxy and its companion satellite. The Whirlpool is an unbarred spiral galaxy

Barless spiral galaxies are one of three general types of spiral galaxies under the de Vaucouleurs system classification system, the other two being intermediate spiral galaxy and barred spiral galaxy. Under the Hubble tuning fork, it is one of two general types of spiral galaxy, the other being barred spirals.

Grades
Under the de Vaucouleurs classification system, SA-galaxies are one of three types of spiral galaxy
Example Type Image Information Notes
SA0- SA0- is a type of lenticular galaxy
SA0 SA0 is a type of lenticular galaxy
SA0+ SA0+ is a type of lenticular galaxy
NGC 3593 SA0/a SA0/a can also be considered a type of unbarred lenticular galaxy NGC 3593 is an "SA(s)0/a"
NGC 3169 SAa NGC 3169 is an "SA(s)a pec"
Messier 81 SAab M81 is an "SA(s)ab"
Messier 88 SAb M88 is an "SA(rs)b"
NGC 3949 SAbc NGC 3949 is an "SA(s)bc"
NGC 4414 SAc NGC 4414 is an "SA(rs)c"
Triangulum Galaxy SAcd Triangulum is an "SA(s)cd"
NGC 300 SAd NGC 300 is an "SA(s)d"
NGC 45 SAdm SAdm can also be considered a type of unbarred Magellanic spiral NGC 45 is an "SA(s)dm"
NGC 4395 SAm SAm is a type of Magellanic spiral (Sm) NGC 4395 is an "SA(s)m"
An example of this type, imaged by the Hubble Space Telescope

Unbarred lenticular galaxy

An unbarred lenticular galaxy is a lenticular version of an unbarred spiral galaxy. They have the Hubble type of SA0.

An example of this is the galaxy, AM 0644-741. For other examples see Category:Unbarred lenticular galaxies.

References
  1. Astronomical Journal, "Near-infrared surface photometry and morphology in virgo cluster spiral galaxy nuclear regions", Bernard J. Rauscher, April 1995, Bibcode:1995AJ....109.1608R, doi:10.1086/117389
  2. Astronomy Pictures, "M99" (accessed 18 April 2010)


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