mfoylan
Arp Peculiar Object Number 023 - One-Armed Spiral Galaxy
NGC 4618 ( PGC 42575 = IC 3667 = Arp 23)
Discovered (Apr 9, 1787) by William Herschel (and later listed as NGC 4618)
Discovered (Mar 21, 1903) by Max Wolf (and later listed as IC 3667)
An 11th-magnitude spiral galaxy (type SB(rs)m) in Canes Venatici (RA 12 41 33, Dec +41 09 04)
A member of an interacting pair (with NGC 4625, which see for a discussion of the results of that interaction), hence its use as an example of a one-armed spiral galaxy in the Arp Atlas. Its 545 km/sec recessional velocity is too small, in comparison to peculiar (non-Hubble-expansion) velocities, to provide a reliable distance estimate, but is in good agreement with a redshift-independent distance estimate of 25 million light years. Given that and its apparent size of 4.2 by 3.4 arcmin, NGC 4625 is about 30 thousand light years across.
"Excerpt courtesy of Courtney Seligman" cseligman.com/text/atlas/ngc46.htm#4618
Image... Cherryvalley Observatory (I83). Telescope: 0.2-m SCT & SBIG STL-1301E CCD Camera @f7.6. Image Scale 2.17 arcsec/pixel, Field of View 46 x 37 arcmins.
Flat field and dark subtract calibration frames. Combined Stack of three images of 120 seconds each unfiltered and unbinned. CCD operating temperature: -35 degrees. Image acquisition and processing: CCD Soft v5, TheSky6 Professional and Mira Pro v7. February 18th 2016.
Dr. Halton Arp originally compiled the Atlas of peculiar galaxies with photographs he made mainly using the Palomar 200-inch telescope and the 48-inch Schmidt telescope between the years 1961 to 1966. Original image can be found here: ned.ipac.caltech.edu/level5/Arp/Figures/big_arp23.jpeg
Arp Peculiar Object Number 023 - One-Armed Spiral Galaxy
NGC 4618 ( PGC 42575 = IC 3667 = Arp 23)
Discovered (Apr 9, 1787) by William Herschel (and later listed as NGC 4618)
Discovered (Mar 21, 1903) by Max Wolf (and later listed as IC 3667)
An 11th-magnitude spiral galaxy (type SB(rs)m) in Canes Venatici (RA 12 41 33, Dec +41 09 04)
A member of an interacting pair (with NGC 4625, which see for a discussion of the results of that interaction), hence its use as an example of a one-armed spiral galaxy in the Arp Atlas. Its 545 km/sec recessional velocity is too small, in comparison to peculiar (non-Hubble-expansion) velocities, to provide a reliable distance estimate, but is in good agreement with a redshift-independent distance estimate of 25 million light years. Given that and its apparent size of 4.2 by 3.4 arcmin, NGC 4625 is about 30 thousand light years across.
"Excerpt courtesy of Courtney Seligman" cseligman.com/text/atlas/ngc46.htm#4618
Image... Cherryvalley Observatory (I83). Telescope: 0.2-m SCT & SBIG STL-1301E CCD Camera @f7.6. Image Scale 2.17 arcsec/pixel, Field of View 46 x 37 arcmins.
Flat field and dark subtract calibration frames. Combined Stack of three images of 120 seconds each unfiltered and unbinned. CCD operating temperature: -35 degrees. Image acquisition and processing: CCD Soft v5, TheSky6 Professional and Mira Pro v7. February 18th 2016.
Dr. Halton Arp originally compiled the Atlas of peculiar galaxies with photographs he made mainly using the Palomar 200-inch telescope and the 48-inch Schmidt telescope between the years 1961 to 1966. Original image can be found here: ned.ipac.caltech.edu/level5/Arp/Figures/big_arp23.jpeg