Page last updated Apr 5, 2021|
Updating all entries, but especially the Arp objects
PGC 6504 (= PGC 174133)
A magnitude 16(?) irregular galaxy (type IB(s)m?) in Cetus (RA 01 46 37.9, Dec -08 40 40)
:Listed by Corwin as a possible companion of IC 159
(= PGC 6505
), but the recessional velocity of PGC 6504 is less than half that of IC 159, so they cannot have any actual connection with each other.
: Vr 1825 km/sec, 1.2 by 0.7 arcmin? LEDA 0.9 by 0.35 arcmin?
PGC 6505 (= IC 159)
A magnitude 13.2 spiral galaxy (type SB(rs)b pec) in Cetus (RA 01 46 25.0, Dec -08 38 12)
For anything else, see IC 159
PGC 6626 (= PGC 174178 = Arp 4)
A 13th-magnitude irregular galaxy (type IAB(rs)m) in Cetus (RA 01 48 25.8, Dec -12 22 53)
Based on a recessional velocity of 1615 km/sec, PGC 6626 is about 75 million light years away, in good agreement with a redshift-independent distance estimate of 65 million light years. Given that and its apparent size of 2.4 by 2.3 arcmin, it is about 55 thousand light years across. The galaxy is one of six chosen by Halton Arp for his Atlas of Peculiar Galaxies as an example of spiral galaxies of low surface brightness, hence its designation as Arp 4.
Above, a 2.4 arcmin wide view of PGC 6626
Below, a 12 arcmin wide region centered on the galaxy
A 14th-magnitude spiral galaxy (type Sc?) in Cetus (RA 01 48 32, Dec -12 23 15)
Based on recessional velocity of 14300 km/sec, about 640 million light years away. Given that and apparent size of 0.6 by 0.4 arcmin, about 100 thousand light years across.
Above, a 1 arcmin wide view of PGC 6629; for a wide-field view, see PGC 6626
PGC 6699 (= UGC 1281 = CGCG 503-026 = MCG +05-05-014)
A magnitude 12.6 spiral galaxy (type Sdm?) in Triangulum (RA 01 49 31.6, Dec +32 35 20)
Physical Information: The "recessional" velocity of PGC 6699 relative to the Cosmic Background Radiation is minus 110 km/sec, meaning that the galaxy is actually approaching us, and its "peculiar velocity" (its random motion relative to its neighbors) is greater than its Hubble Flow recessional velocity; so the only guide to its distance is various redshift-independent distance estimates, which range from about 14 to 21 million light years, with a median value of just over 17 million light years (the HST press release uses a distance of "about 18 million" light years, which is essentially the same, given the uncertainty of any such estimate). Given that and the galaxy's apparent size of about 4.35 by 0.5 arcmin (from the images below), it is about 20 to 25 thousand light years across, making it a "dwarf" spiral.
Above, a 12 arcmin wide SDSS image centered on PGC 6699, also showing PGC 6700
Below, a 5 arcmin wide SDSS image of the region
Below, a 3 by 3.6 arcmin wide HST image of part of the galaxy, also showing PGC 6700
(Image Credit ESA/Hubble & NASA, Acknowledgement Luca Limatola)
A magnitude 17.5(?) spiral galaxy (type Sc?) in Aries (RA 01 49 49.7, Dec +11 42 25)
Physical Information: Apparent size about 0.85 by 0.25 arcmin (from images below). Nothing else apparently available.
Above, a 12 arcmin wide SDSS image centered on PGC 6707, also showing NGC 683
Below a 0.9 arcmin wide SDSS image of the galaxy
PGC 6718 (= NGC 683)
A magnitude 13.6 spiral galaxy (type S(rs)cd?) in Aries (RA 01 49 46.7, Dec +11 42 05)
For anything else, see NGC 683
PGC 6830, the Phoenix Dwarf Galaxy
A magnitude 13.1 spiral galaxy (type SAm?) in Phoenix (RA 01 51 06.27, Dec -44 26 41)
Discovery Note: When first found (in 1976), it was thought to be a globular cluster. But its relatively large size (most globular clusters are only 50 to 150 light years across) has led to its reclassification as a dwarf galaxy. PGC 6830's structure is not obvious, and as a result it is variously classified as spheroidal (type E/S0), irregular (type IAm), or as shown above, loosely spiral.
Physical Information: PGC 6830's recessional velocity of 55 km/sec is too small to use the Hubble Expansion to estimate its distance. Redshift-independent distance estimates range from about 1.15 to 1.65 million light years, with about 1.4 million light years (the number in the ESO press release) being a commonly accepted value. This places it far enough away from the Milky Way that it is not considered a satellite of our galaxy (or of the Andromeda Galaxy, which is well to the north of our galaxy, while the Phoenix Dwarf is well to the south), but it is definitely a member of our Local Group of galaxies. Given its apparent size of about 8.7 by 6 arcmin (from the images below), it is about 3500 light years across. The galaxy is near a large mass of gas presumably driven out of it by relatively recent supernova activity, but the velocity of the gas is low enough that it is expected to fall back into the galaxy in the distant future, perhaps starting another wave of star formation.
Above, a 12 arcmin wide image centered on PGC 6830
(Image Credit Chart32 Team, CTIO and UNC; used by permission)
Below, a 7.5 by 12 arcmin wide image of the galaxy (Image Credit ESO)
PGC 6833 (= IC 167 = Arp 31)
A magnitude 13.1 spiral galaxy (type SAB(s)c) in Aries (RA 01 51 08.6, Dec +21 54 46)
For anything else, see IC 167