Arp catalogue: 43 imaging targets
Halton Arp published his Atlas of Peculiar Galaxies in 1966, with photographs of 338 galaxies taken at Palomar Observatory. He chose galaxies with unusual shapes, many of them pairs or groups that are colliding or pulling each other apart, with tails and bridges of stars. The planner includes 43 of them; most are small and faint, so they need a long focal length, a fine pixel scale and many hours of data.
Further reading: NED: Atlas of Peculiar Galaxies
Arp1
NGC 2857, a spiral galaxy in Ursa Major about 225 million light-years away and roughly 125,000 light-years across.
Arp10
UGC 1775, a ring galaxy in Cetus about 395 million light-years away, seen nearly face-on. Arp listed it among spiral galaxies with split arms.
Arp26
The Pinwheel Galaxy, a face-on spiral about 21 million light-years away in Ursa Major, also catalogued as M101. Halton Arp listed it among spiral galaxies with one heavy arm.
Arp78
In Aries, 106 million light-years off, this big unbarred spiral spans near 200,000 light-years, a little more than the Milky Way.
Arp81
Two interacting galaxies in Draco, about 300 million light-years away: NGC 6621 and NGC 6622.
Arp82
NGC 2535 and its neighbour NGC 2536 in Cancer, listed by Arp among spirals with a bright companion.
Arp84
NGC 5394 and NGC 5395, two interacting spirals in Canes Venatici roughly 165 million light-years away. Arp noted that the larger one has a bright companion sitting where one of its arms ends.
Arp86
NGC 7753, a large barred spiral in Pegasus, with the small companion NGC 7752 that looks attached to one of its arms. Estimates run from about 220 to 270 million light-years.
Arp87
In Leo, two galaxies swing past each other: NGC 3808A and NGC 3808B, roughly 300 to 330 million light-years away depending on the source. Arp filed it under spirals that have big, bright companions.
Arp91
Two spiral galaxies in Serpens, NGC 5953 and NGC 5954, lie about 78 million light-years away and interact; Arp filed them under spirals that have big, bright companions.
Arp94
A spiral galaxy in Leo about 77 million light-years away, with an active Seyfert nucleus.
Arp104
Keenan's System, the galaxies NGC 5216 and NGC 5218 in Ursa Major, tied together by stellar and gaseous material, a bridge roughly 22,000 light-years in extent.
Arp116
A giant elliptical galaxy in Virgo, about 57 million light-years away and ranked third in brightness among the Virgo Cluster's giant ellipticals.
Arp143
A close pair of interacting galaxies in Lynx, NGC 2444 and NGC 2445, roughly 180 to 190 million light-years away. Arp listed it among galaxies with material emanating from elliptical galaxies.
Arp147
Two ring-shaped galaxies in Cetus, catalogued as IC 298, lying roughly 430 to 440 million light-years away. Arp listed it among galaxies with associated rings.
Arp148 — Mayall's Object
Mayall's Object, two galaxies that collided about 450 million light-years away in Ursa Major. Arp listed it among galaxies with associated rings.
Arp155
NGC 3656, a peculiar galaxy in Ursa Major about 135 million light-years away, left by the merger of two disk galaxies. Arp listed it among disturbed galaxies with interior absorption.
Arp157
In Pisces, about 105 million light-years away, two spiral galaxies are merging as NGC 520. Arp listed it among disturbed galaxies with interior absorption.
Arp188 — Tadpole Galaxy
UGC 10214, a disrupted barred spiral in Draco about 470 million light-years away, trailing a long tail of stars, gas and dust drawn out in an encounter with a smaller galaxy.
Arp194
UGC 6945, three interacting galaxies in Ursa Major, about 570 million light-years away. Arp listed it among galaxies with material ejected from nuclei.
Arp199
NGC 5544 and NGC 5545, an interacting pair of spirals in Boötes, with distances of about 140 and 158 million light-years given for the two.
Arp210
Camelopardalis holds NGC 1569, an irregular dwarf galaxy about 11 million light-years away that belongs to the IC 342 group.
Arp212
NGC 7625, a peculiar spiral in Pegasus about 78 million light-years away. Arp listed it among galaxies with irregularities, absorption and resolution.
Arp214
NGC 3718, a barred spiral in Ursa Major crossed by a heavy dust lane, whose innermost gas disc orbits across the galaxy's poles; that arrangement defines a polar ring.
Arp220
Arp 220, also catalogued as IC 4553 and IC 1127, is a pair of galaxies in Serpens that are colliding and merging.
Arp222
NGC 7727, a peculiar galaxy in Aquarius about 76 million light-years away.
Arp227
NGC 474 is a lenticular galaxy of Pisces, roughly 250,000 light-years across and about 100 million light-years away.
Arp240
Two spiral galaxies in Virgo, NGC 5257 and NGC 5258, pull on each other and are linked by a tidal bridge. Wikipedia gives distances of about 342 to 345 million light-years.
Arp242 — Mice Galaxies
NGC 4676, the Mice, two spiral galaxies in Coma Berenices that have started to merge, about 345 million light-years away.
Arp244 — Antennae Galaxies
NGC 4038 and NGC 4039, the Antennae, two spiral galaxies in Corvus colliding about 60–70 million light-years away. Their long curved tails of stars and gas look like insect antennae.
Arp248 — Wild's Triplet
Wild's Triplet, in Virgo about 200–245 million light-years away.
Arp271
NGC 5426 and NGC 5427, a pair of similar spiral galaxies in Virgo about 130 million light-years away, already linked by a bridge of stars. Together they span roughly 130,000 light-years.
Arp272
NGC 6050 and IC 1179, two spirals in Hercules that touch through their arms, with a third galaxy also interacting nearby. They lie in the Hercules Cluster, around 450 million light-years away.
Arp273 — Rose Galaxies
Two galaxies in Andromeda, about 300 million light-years away, are interacting. Tidal pull from the companion UGC 1813 has bent the disc of the larger UGC 1810 into a rose-like outline.
Arp274
The NGC 5679 group in Virgo holds three galaxies, about 400 million light-years away and strung across roughly 200,000 light-years. Arp listed it among "Galaxies with connected arms".
Arp281
An edge-on barred spiral in Canes Venatici, about 30 million light-years away, seen as a wedge-shaped streak.
Arp284
Pisces holds this interacting pair, NGC 7714 with NGC 7715. NGC 7714 is a distorted spiral, about 117 million light-years away from its redshift, while other measurements give about 92 million.
Arp286
A group in Virgo around the barred spiral NGC 5566, about 66 million light-years away, with the distorted NGC 5560 and the small blue NGC 5569.
Arp293
In Draco, about 252 million light-years away, NGC 6286 and its neighbour NGC 6285 interact and show tidal distortion. Arp placed it among "Galaxies with the appearance of wind effects".
Arp295
MCG -01-60-021, a galaxy in Aquarius that SIMBAD lists with a LINER-type active nucleus.
Arp299
Two galaxies in Ursa Major, NGC 3690 and IC 694, caught mid-collision roughly 134 million light-years from us. Arp placed it among the "Unclassified double galaxies".
Arp316 — Hickson 44
Hickson 44, a compact group of four galaxies in Leo about 80 million light-years away: NGC 3185, NGC 3187, NGC 3190 and NGC 3193. Arp listed part of it as Arp 316, under "Groups of galaxies".
Arp319 — Stephan's Quintet
Stephan's Quintet, five galaxies in Pegasus, first noticed in 1877 by Édouard Stephan.