Historical Identification: Per Dreyer, NGC 4100 (= GC 2715 = JH 1084 = WH III 717, 1860 RA 11 59 00, NPD 39 38.8) is "pretty bright, very large, very much extended 161�, very gradually a very little brighter middle". The position precesses to RA 12 06 07.8, Dec +49 34 26, a little south southwest of the center of the galaxy listed above, but well within its outline, the description fits and there is nothing else nearby, so the identification is certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 1270 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4100 is about 60 million light years away, in good agreement with redshift-independent distance estimates of about 50 to 85 million light years. Given that and its apparent size of about 5.0 by 1.6 arcmin (from the images below), the galaxy is about 85 thousand light years across. NGC 4100 is listed by the de Vaucouleurs Atlas of Galaxies as an example of type (R')SA(s)bc.

Historical Identification: Per Dreyer, NGC 4101 (= GC 2716 = JH 1083 = WH III 326, 1860 RA 11 59 00, NPD 63 39.7) is "extremely faint, very small, round, very gradually brighter middle".
Physical Information:

Historical Identification: Per Dreyer, NGC 4102 (= GC 2717 = JH 1085 = WH I 225, 1860 RA 11 59 15, NPD 36 30.6) is "bright, pretty small, round, brighter middle and bright nucleus, 12th magnitude star very near to southwest".
Physical Information:

Historical Identification: Per Dreyer, NGC 4103 (= GC 2718 = JH 3377, Dunlop #291, 1860 RA 11 59 28, NPD 150 27.9) is "a cluster, pretty large, pretty compressed, irregularly round, stars from 10th to 14th magnitude".
Note About PGC Designation: For purposes of completeness, LEDA assigns a PGC designation to almost every NGC/IC object, whether it is a galaxy or not. However, a search of the database for the designation shown above does not return a result, so it is listed in quotes.
Physical Information: Apparent size 6 arcmin? (from the LEDA entry for NGC 4103) Distance about 6000 lightyears. (Very nice image at here.)

Historical Identification: Per Dreyer, NGC 4104 (= GC 2719 = JH 1086 = WH II 370, 1860 RA 11 59 29, NPD 61 02.6) is "pretty bright, pretty small, a little extended, brighter middle".
Physical Information:

Physical Information: Vr 8920 km/sec, z 0.029757, single redshift-independent distance estimate about 460 to 465 million light years. Since the recessional velocity of NGC 4104 is 8450 km/sec, it is possible that the two galaxies are in the same region, whether they are physical companions or not.

Historical Identification: Per Dreyer, NGC 4105 (= GC 2720 = JH 3378 = WH II 865, 1860 RA 11 59 29, NPD 119 00.4) is "pretty faint, pretty small, round, pretty suddenly brighter middle, mottled but not resolved, western of 2", the other being NGC 4106.
Physical Information: The two galaxies are obviously physically interacting, so although their physical properties will be discussed in their individual entries, all images will be shown here. (Need to measure images, so get correct types, sizes, etc)

Historical Identification: Per Dreyer, NGC 4106 (= GC 2721 = JH 3379 = WH II 866, 1860 RA 11 59 34, NPD 119 00.7) is "pretty faint, pretty small, round, pretty gradually brighter middle, eastern of 2", the other being NGC 4105.
Physical Information: The two galaxies are obviously physically interacting, so although their physical properties will be discussed in their individual entries, see NGC 4105 for all images.

Historical Identification: Per Dreyer, NGC 4107 (= GC 5617, d'Arrest, 1860 RA 11 59 35, NPD 78 37.4) is "a planetary nebula, pretty bright, small, a little extended, 10th or 11th magnitude star to southeast". The first IC adds (per Burnham) "delete planetary nebula; the star is northwest". The second IC adds "Not found by Frost on plates of 4 hours exposure. Observed by Burnham in 1891".
Summary of Identification to be Added Later: Frost could not find this because d'Arrest's and Burnham's positions are incorrect, and this is actually a duplicate observation of NGC 4078.
Physical Information: Given the duplicate entry, see NGC 4078 for anything else.

Historical Identification: Per Dreyer, NGC 4108 (= GC 2722 = JH 1087, 1860 RA 11 59 41, NPD 22 03.5) is "bright, small, round, gradually brighter middle".
Physical Information: Apparent size 1.6 by 1.2 arcmin (from the images below).

Warning About Non-Standard Designations: Although the use of a letter attached to an NGC or IC designation is often used for galaies near an NGC object with that number, there is no system for ensuring that everyone uses the same letter for a given galaxy; so data for two or more galaxies may sometimes be conflated, resulting in misleading and often hopelessly confusing information about the objects in question. As a result, such letter designations should never be used, and this entry serves primarily as a warning against such usage.
Physical Information: Apparent size about 1.2 by 0.5 arcmin (from the images below).

Warning About Non-Standard Designations: Although the use of a letter attached to an NGC or IC designation is often used for galaies near an NGC object with that number, there is no system for ensuring that everyone uses the same letter for a given galaxy; so data for two or more galaxies may sometimes be conflated, resulting in misleading and often hopelessly confusing information about the objects in question. As a result, such letter designations should never be used, and this entry serves primarily as a warning against such usage.
Physical Information: Apparent size about 1.3 by 0.95 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4109 (= GC 5618, 3rd Lord Rosse, 1860 RA 11 59 49, NPD 46 14.5) is "very faint, I 195 is 6 arcmin to north-northeast", (WH) I 195 being NGC 4111.
Discovery Notes: Although Dreyer credits the discovery to William Parsons, 3rd Earl of Rosse, he notes that many of Rosse's nebular discoveries were actually made by one of his assistants, in this case Bindon Stoney.
Physical Information: Vr 7040 km/sec, z 0.023476, so quite possibly a physical companion of PGC 38439. Apparent size 0.6 by 0.5 arcmin (from the images below)

Physical Properties: Vr 7075 km/sec, z 0.023592, so quite possibly a physical companion of NGC 4109.

Note About Designation: NED does not recognize the PGC designation, but does recognize SDSS J120651.25+425923.4
Physical Properties: Nothing is known about the galaxy, save for its apparent magnitude and apparent size (based on the image below, about 0.15 by 0.1 arcmin); so whether it is a companion of NGC 4109 is very uncertain. In fact, since there seems to be no interaction between them, they may well be only an optical double.

Designation Note: Although NED lists one of the designations for this galaxy as PGC 2210701, a search of that database does not return a result. Instead, NED requires a search for 2MASX J12065481+4259511
Physical Properties: Based on a recessional velocity of 25825 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 2210701 is about 1200 to 1205 million light years away, in reasonable agreement with a single redshift-independent distance estimate of about 1100 to 1105 million light years. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 1180 to 1185 million light years away at the time the light by which we see it was emitted, about 1135 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of about 0.25 by 0.15 arcmin (from the image below), the galaxy is about 90 thousand light years across. Note that given its immense distance, it is certainly not a companion of NGC 4109, but merely a very distant background galaxy.

Historical Identification: Per Dreyer, NGC 4110 (= GC 2751, 3rd Lord Rosse, 1860 RA 11 59 52, NPD 70 40.9) is "faint, small".
Discovery Notes: Although Dreyer credits the discovery to William Parsons, 3rd Earl of Rosse, he notes that many of Rosse's nebular discoveries were actually made by one of his assistants, in this case William Rambaut.
Physical Information: Apparent size of about 1.2 by 0.6 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4111 (= GC 2723 = JH 1088 = WH I 195, 1860 RA 11 59 56, NPD 46 09.3) is "very bright, pretty small, much extended 151�".
Physical Information: A polar ring galaxy. Apparent size of about 4.3 by 0.65 arcmin (based on the images below). Listed by the de Vaucouleurs Atlas of Galaxies as type S0^o sp, but the image used for that classification does not show the polar ring, whence the difference in the type shown in this entry.

Historical Identification: Per Dreyer, NGC 4112 (= GC 2724 = JH 3380, 1860 RA 11 59 56, NPD 129 25.3) is "faint, small, very little extended, gradually a little brighter middle, 3 bright stars near".
Physical Information: Vr 2715 km/sec. Apparent size of about 2.0 by 1.0 arcmin (from the images below, counting the fainter outer regions).

Physical Properties: Vr 2605 km/sec, so quite possibly a physical conpanion of NGC 4112. Apparent size (based on the image below) of about 0.9 by 0.4 arcmin.

Historical Identification: Per Dreyer, NGC 4113 (= GC 2725 = JH 1089, 1860 RA 12 00 01, NPD 55 13.8) is "extremely faint". The second IC notes (per Wolf, list VIII (March 27, 1906) "Nothing in this place".
Summary of Identification: Although later shown to be NGC 4122, as is usual in such cases the galaxy is almost always designated by the lower NGC number, even though its observation was completely incorrect.
Physical Information: Vr 7970 km/sec, z 0.026578, apparent size of about 1.15 by 0.95 arcmin (from the images below, including the fainter outer regions)

Designation Notes: Although LEDA assigns a PGC designation to this object, a search of the database for that designation returns no result, hence its inclusion in quotes. Both LEDA and NED yield results when using the SDSS designation.
Physical Information: Vr 8140 km/sec, z 0.027155, so certainly in the same region as NGC 4113, and therefore probably a physical companion. Apparent size about 0.2 by 0.1 arcmin (from the image below).

Historical Identification: Per Dreyer, NGC 4114 (= GC 2726 = JH 3381 = WH III 533, 1860 RA 12 00 01, NPD 103 24.4) is "cnsiderably faint, small, irregularly round, gradually brighter middle".
Physical Information: Apparent size of about 2.0 by 0.95 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4115 (= GC 2727 = JH 1090, 1860 RA 12 00 02, NPD 74 49.2) is "extremely faint, suspected". The position preceses to RA 12 07 11.5, Dec +14 24 02, but there is nothing there. However, as noted by Corwin, the sweep was correctly reduced, and the description would perfectly fit a faint star under less than ideal conditions, so the star just over half an arcmin to the northwest of the NGC position is probably what Herschel observed, and as a result it is generally accepted that as listed above, it is the correct identification of NGC 4115.

Historical Identification: Per Dreyer, NGC 4116 (= GC 2728, 3rd Lord Rosse, Peters, 1860 RA 12 00 28, NPD 86 32.2) is "very faint, extended (hook shape), southwestern of 2", the other presumably being NGC 4123.
Discovery Notes: Although Dreyer credits the discovery to William Parsons, 3rd Earl of Rosse, he notes that many of Rosse's nebular discoveries were actually made by one of his assistants, in this case Bindon Stoney.
Physical Information: Apparent size about 3.9 by 2.45 arcmin (from the images below). Probably a polar ring galaxy. Note: The galaxy to the southwest of NGC 4116 (PGC 3121899) is not associated with the galaxy, but is much more distant background object.

Historical Identification: Per Dreyer, NGC 4117 (= GC 2729 = JH 1091 = WH III 708, d'Arrest, 1860 RA 12 00 40, NPD 46 05.7) is "very faint, very small".
Physical Information: Apparent size of about 1.5 by 0.5 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4118 (= GC 5619, 4th Lord Rosse, 1860 RA 12 00 41, NPD 46 06.8) is "extremely faint, very small, 1 arcmin south of III 708", (WH) III 708 being NGC 4117.
Discovery Notes: Although Dreyer credits the discovery to Lawrence Parsons, 4th Earl of Rosse, the date of discovery suggests that is actually a typographical error for William Parsons, 3rd Earl of Rosse, for whom Dreyer notes that many of the 3rd Earl's nebular discoveries were actually made by one of his assistants, in this case R. J. Mitchell.
Physical Information: Apparent size of about 0.5 by 0.3 arcmin (from the image below).

Historical Identification: Per Dreyer, NGC 4119 (= GC 2730 = WH II 14, 1860 RA 12 00 42, NPD 79 41.0) is "a little extended". The second IC adds "Not found by Frost on plates of 4 hours exposure", suggesting a problem in the NGC position, which precesses to RA 12 07 51.7, Dec +09 32 14, and as might be expected there is nothing there nor anywhere near there. In his 1912 notes for Sir William Herschel's Scientific Papers Dreyer lists several corrections attempted by Herschel himself, repeats Frost's failure to find anything even at the "corrected" position, and uses a comparison of the original measurement of II 14 to one done in the following sweep (which was done later that same night, after a period of poor seeing ended the first sweep), namely II 15. That object had a good position, and based on a comparison of the two measurements, Dreyer suggests that II 14 was probably the same as WH I 33 (= WH II 60), 50 arcmin north of the position given for II 14, and about 29 1/2 minutes of time to the west of II 15. That would make NGC 4119 a duplicate observation of NGC 4124, as shown in the title for this entry, but rather oddly, in Dreyer's 1912 summary of corrections to the NGC based on his analysis of Herschel's papers, he fails to mention the duplicate entry. Still, the description given for II 14, though brief, agrees with that for NGC 4124, and per Corwin the latter galaxy is the only thing in the region that is bright enough for Herschel to have seen, so Dreyer's identification of the duplicate entry is considered essentially certain. (For a discussion of the duplicate entry involving IC 3011, see that entry.)
Discovery Note: Herschel's early observations were not as accurate as his later ones, and a poor position for his initial observation of this galaxy led to its being assigned two NGC numbers and (much later on) an IC number, as well (as shown in the title for this entry). As quoted by Dreyer in a note at the end of the NGC, John Herschel wrote "II 14. Owing to an erratum in P.T., Auwers gives quite an erroneous place for this nebula," P.T. meaning the Philosophical Transactions paper listing William Herschel's first catalogue of 1000 nebulae and clusters. However, since even the "correct" position for II 14 was wrong, Auwers' inevitable "error" was irrelevant.
Physical Information: (Rewrite using the 3K CMB as the reference) Based on its recessional velocity of 1680 km/sec, NGC 4119 is about 80 million light years away, in only fair agreement with a redshift-independent distance estimate of 55 million light years. Using the larger distance, its apparent size of 4.5 by 1.0 arcmin corresponds to about 100 thousand light years across.

Historical Identification: Per Dreyer, NGC 4120 (= GC 2731 = WH III 904, 1860 RA 12 00 56, NPD 19 38.0) is "extremely faint, very small, extended".
Physical Information: Apparent size of about 1.6by 0.45 arcmin (from the images below)

Historical Identification: Per Dreyer, NGC 4121 (= GC 5620, d'Arrest, 1860 RA 12 00 56, NPD 24 06.4) is "faint, very small, a little extended, mottled but not resolved".
Physical Information: Apparent size of about 0.5 by 0.45 arcmin (from the images below)

Historical Identification: Per Dreyer, NGC 4122 (= GC 2732 = JH 1093, 1860 RA 12 00 59, NPD 56 13.1) is "extremely faint, very small, round, much brighter middle".
Physical Information: Given the duplicate entry, see NGC 4113 for anything else.

Historical Identification: Per Dreyer, NGC 4123 (= GC 2733 = JH 1092 = WH V 4, 1860 RA 12 00 59, NPD 86 20.7) is "considerably faint, very large, extended 90��, brighter middle and nucleus".
Physical Information: Apparent size of about 4.8 by 4.65 arcmin (from the images below, counting the faint outer arms)

Historical Identification: Per Dreyer, NGC 4124 (= GC 2734 = JH 1094 = WH I 33 = WH II 60, 1860 RA 12 01 01, NPD 78 50.5) is "pretty bright, pretty large, much extended 118�, brighter middle, mottled but not resolved".
Physical Information: Given the duplicate entry, see NGC 4119 for anything else.

Historical Identification: Per Dreyer, NGC 4125 (= GC 2735, Hind, 1860 RA 12 01 04, NPD 24 02.7) is "pretty bright, pretty large, considerably extended, much brighter middle (Auwers 28)".
Discovery Notes: Auwers' notes show that he observed the object himself, but do not appear to indicate the date of his observation.
Physical Information: Apparent size of about 5.5 by 4.4 arcmin (from the images below, including the widely extended outer regions). The galaxy is peculiar in two ways: (1) It has huge areas surrounding it with scattered stars, and (2) there are many small patches of dark dusty material scattered across the otherwise apparently normal part of the galaxy (as shown in the HST image).

Historical Identification: Per Dreyer, NGC 4126 (= GC 2736 = JH 1095 = WH III 68, 1860 RA 12 01 28, NPD 73 05.2) is "very faint, small, round, pretty suddenly a little brighter middle, between 2 very small (faint) stars".
Physical Information: Apparent size of about 0.85 by 0.65 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4127 (= GC 2737 = JH 1096 = WH I 279, 1860 RA 12 01 35, NPD 12 25.0) is "faint, pretty large, very little extended, gradually a little brighter middle".
Physical Information: Apparent size of about 1.7 by 0.85 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4128 (= GC 2738 = WH I 263, 1860 RA 12 01 36, NPD 20 27.0) is "considerably bright, a little extended, brighter middle".
Physical Information:

Warning About Non-Standard Designations: Although the use of a letter attached to an NGC or IC designation is often used for galaies near an NGC object with that number, there is no system for ensuring that everyone uses the same letter for a given galaxy; so data for two or more galaxies may sometimes be conflated, resulting in misleading and often hopelessly confusing information about the objects in question. As a result, such letter designations should never be used, and this entry serves primarily as a warning against such usage.
Physical Information: Apparent size of about 0.7 by 0.6 arcmin (from the images below)

Historical Identification: Per Dreyer, NGC 4129 (= GC 2739 = JH 1097 = JH 3382 = WH II 548, 1860 RA 12 01 42, NPD 98 15.3) is "faint, pretty large, pretty much extended 95��, very gradually a little brighter middle".
Physical Information: Apparent size of about 2.25 by 0.4 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4130 (= GC 5621, d'Arrest, 1860 RA 12 01 45, NPD 93 14.6) is "pretty extended, a little brighter middle, 13th magnitude star 5 arcmin to west".
Physical Information: Given the duplicate entry, see NGC 4129 for anything else.

Historical Identification: Per Dreyer, NGC 4131 (= GC 2740 = JH 1098 = WH III 356, 1860 RA 12 01 47, NPD 59 55.5) is "considerably faint, small, round, 1st of 3", the others being NGC 4132 and 4134.
Physical Information: Apparent size of about 1.35 by 0.45 arcmin (from the images below)

Historical Identification: Per Dreyer, NGC 4132 (= GC 2741 = JH 1099 = WH III 357, 1860 RA 12 01 53, NPD 59 59.0) is "considerably faint, small, irregularly round, 2nd of 3", the others being NGC 4131 and 4134.
Physical Information: Apparent size of about 0.95 by 0.35 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4133 (= GC 2742 = JH 1100 = WH I 278, 1860 RA 12 01 59, NPD 14 19.3) is "pretty bright, considerably large, round, gradually much brighter middle".
Physical Information: Apparent size of about 1.6 by 1.05 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4134 (= GC 2743 = JH 1101 = WH II 371, 1860 RA 12 02 01, NPD 60 03.1) is "pretty faint, pretty large, a little extended, 3rd of 3", the others being NGC 4131 and 4132.
Physical Information: Apparent size of about 1.8 by 0.75 (from the images below).

Historical Identification: Per Dreyer, NGC 4135 (Stephan list XI (XIa #16), 1860 RA 12 02 04, NPD 45 13.0) is "very faint, pretty small, round, 2 faint stars involved".
Physical Information: Apparent size of about 0.8 by 0.5 arcmin (from the images below). A Seyfert galaxy (type Sy 2).

Historical Identification: Per Dreyer, NGC 4136 (= GC 2744 = JH 1108 = WH II 321, 1860 RA 12 02 07, NPD 59 18.1) is "faint, very large, very gradually much brighter middle".
Physical Information: Apparent size of about 3.9 by 3.7 arcmin (from the images below). Listed by the de Vaucouleurs Atlas of Galaxies as type SA(r)c.

Historical Identification: Per Dreyer, NGC 4137 (Stephan list XI (XIa #17), 1860 RA 12 02 13, NPD 45 07.8) is "very faint, pretty small, round, a little fainter than the southwestern one", the other one being NGC 4135.
Physical Information: Based on a recessional velocity of 11190 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4137 is about 520 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 500 million light years away at the time the light by which we see it was emitted, about 510 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of about 1.1 by 0.7 arcmin (from the images below), the galaxy is about 160 thousand light years across. It is almost certainly physically interacting with PGC 200283, which lies at the end of its most extended arm, and PGC 38629 is also a possible physical companion. Listed by the de Vaucouleurs Atlas of Galaxies as type SA(r)a.

Physical Information: Based on a recessional velocity of 11170 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 200283 is about 520 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 500 million light years away at the time the light by which we see it was emitted, about 510 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of about 0.2 by 0.1 arcmin (from the image below), the galaxy is about 30 thousand light years across. PGC 200283 is listed as a starburst galaxy. Given its apparent position at the end of an extended arm of NGC 4137, and their essentially identical distances, PGC 200283 is probably a physically interacting companion of the NGC object.

Physical Information: Based on a recessional velocity of 11315 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 38629 is about 525 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 505 million light years away at the time the light by which we see it was emitted, about 510 to 515 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of about 0.4 by 0.35 arcmin (from the image below), the galaxy is about 55 to 60 thousand light years across. PGC 38629 is listed as a Seyfert galaxy (type Sy 2). Given its recessional velocity and the uncertainty lent to such values by unknown peculiar (non-Hubble-expansion) velocities, PGC 38629 is probably relatively close to NGC 4137, and although they may merely be in the same region of space, there is a reasonable chance that they are gravitationally bound companions.

Historical Identification: Per Dreyer, NGC 4138 (= GC 2745 = WH I 196, 1860 RA 12 02 23, NPD 45 32.5) is "bright, pretty large, a little extended, very gradually brighter middle, star to northwest".
Physical Information: Apparent size of about 3.0 by 1.8 arcmin (from the images below). Listed by the de Vaucouleurs Atlas of Galaxies as type SA(r)a.

Historical Identification: Per Dreyer, NGC 4139 (= GC 5622, d'Arrest, 1860 RA 12 02 24, NPD 87 25.5) is "faint, small, difficult, western of double nebula", the other one being NGC 4140. The position precesses to RA 12 09 34.1, Dec +01 47 45, but there is nothing there. However, Corwin notes that there is a double nebula (IC 2989 and NGC 4077) five minutes of time to the west of d'Arrest's position, and the descriptions of those objects match the descriptions of NGC 4139 and NGC 4140, so there is no doubt that d'Arrest simply made a single digit error in the positions, and the identification of the galaxy above as NGC 4139 is certain.
Discovery Notes: Todd's observation was made during his unsuccessful search for a trans-Neptunian planet (reference S348? With NGC 4140, = #14a/b and #16a/b). It was not used by Dreyer, but is in Steinicke's database (and also noted by Corwin), whence its inclusion above.
Designation Note: Although the position of NGC 4139 was incorrect, while that of IC 2989 was correct, tradition gives the lower or earlier designation (in this case, NGC 4139) precedence, so despite Bigourdan's observation being the better one, the galaxy is always referred to as NGC 4139.
Physical Information: Vr = 5600 km/sec, redshift-independent distances 82.2 to 96.4 Mpc. Apparent size of about 1.0 by 0.45 arcmin (from the images below). Although apparently paired with NGC 4077, the latter is 70 million light years further away, so they are merely an optical double.

Historical Identification: Per Dreyer, NGC 4140 (= GC 5623, d'Arrest, 1860 RA 12 02 29, NPD 87 25.9) is "faint, small, difficult, eastern of double nebula", the other one being NGC 4139. The position precesses to RA 12 09 39.1, Dec +01 47 21, but there is nothing there, nor anywhere near there. However, Corwin notes that there is a double nebula (IC 2989 and NGC 4077) five minutes of time to the west of d'Arrest's position, and the descriptions of those objects match the descriptions of NGC 4139 and NGC 4140, so there is no doubt that d'Arrest simply made a single digit error in the positions, and the identification of the galaxy above as NGC 4140 is certain.
Discovery Notes: Todd's observation was made during his unsuccessful search for a trans-Neptunian planet (reference S348? With NGC 4140, = #14a/b and #16a/b). It was not used by Dreyer, but is noted by Corwin in his discussion of the error in d'Arrest's position, whence its inclusion above.
Physical Information: Given the duplicate entry, see NGC 4077 for anything else.

Historical Identification: Per Dreyer, NGC 4141 (= GC 2746 = JH 1102 = WH III 795, 1860 RA 12 02 30, NPD 30 22.0) is "very faint, pretty small, a little extended, gradually brighter middle, mottled but not resolved".
Physical Information: Apparent size of about 1.2 by 0.7 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4142 (= GC 2747 = JH 1103 = WH III 814, 1860 RA 12 02 31, NPD 36 06.1) is "very faint, small, irregular figure, very gradually a little brighter middle, extremely mottled but not resolved".
Discovery Note: In the notes at the end of the NGC Dreyer writes "(J)h 1103 = (W)H III 814. Auwers' NPD is 1° too great, owing to an erratum in Pfaff's translation of (W)H's paper; 0° 32' north of 5 Canum (Venaticorum) should be 1° 32'. P.T. has the correct figure", P.T. meaning the Philosophical Transactions paper containing William Herschel's third catalogue of "500" nebulae and clusters.
Physical Information: Apparent size of about 2.0 by 1.05 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4143 (= GC 2748 = JH 1104 = WH IV 54, d'Arrest, 1860 RA 12 02 32, NPD 46 41.2) is "considerably bright, round, very gradually then very suddenly brighter middle and nucleus".
Physical Information: Apparent size 2.3 by 1.4 arcmin. Listed by the de Vaucouleurs Atlas of Galaxies as type SAB0^-.

Historical Identification: Per Dreyer, NGC 4144 (= GC 2749 = JH 1107 = WH II 747, 1860 RA 12 02 54, NPD 42 46.3) is "pretty faint, considerably large, very much extended 109�, very gradually brighter middle". The position precesses to RA 12 09 58.7, Dec +46 26 57, only half an arcmin south of the center of the galaxy listed above, the description fits and there is nothing else nearby, so the identification is certain.
Physical Information: The recessional velocity of 265 km/sec is too small to give any reliable distance indication, and redshift-independent distance estimates vary from 12 to 32 million light years, so the median of about 22 million light years is the best (albeit uncertain) estimate of the distance of NGC 4144 (most published estimates of the distance are essentially the same as the median given here). Given that and its apparent size of about 6.3 by 1.3 arcmin (from the images below), the galaxy is about 40 thousand light years across.

Historical Identification: Per Dreyer, NGC 4145 (= GC 2750 = JH 1105 = WH I 169, 1860 RA 12 02 54, NPD 49 20.0) is "bright, very large, very gradually a little brighter middle".
Physical Information: Apparent size of about 6.0 by 3.2 arcmin (fromthe images below). Listed by the de Vaucouleurs Atlas of Galaxies as type SAB(rs)d.

Warning About Non-Standard Designations: Although the use of a letter attached to an NGC or IC designation is often used for galaies near an NGC object with that number, there is no system for ensuring that everyone uses the same letter for a given galaxy; so data for two or more galaxies may sometimes be conflated, resulting in misleading and often hopelessly confusing information about the objects in question. As a result, such letter designations should never be used, and this entry serves primarily as a warning against such usage.
Additional Designation Note: Although LEDA recognizes PGC 38778, it does not list it or any other galaxy as NGC 4145A. NED does list the galaxy as NGC 4145A, but does not list it as PGC 38778; instead, VV 814 or UGC07175 are the "standard" designations recognized by NED and LEDA.
Physical Information: Vr = 1170 km/sec, redshift-independent distance estimates 9.08 to 22.9 Mpc. Apparent size of about 1.55 by 0.4 arcmin (from the images below). An optical double with PGC 213942, but not in any way connected to the much more distant apparent companion.

Physical Information: Although PGC 213942 looks like it could be a physical companion of PGC 38778 in wide-field images, closer views show that it is probably merely an optical double, and its recessional velocity proves that it is a very distant background galaxy. Based on its recessional velocity of 29380 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 213942 is about 1365 to 1370 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 1220 to 1225 million light years away at the time the light by which we see it was emitted, about 1280 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of about 0.3 by 0.25 arcmin (from the image below), the galaxy is about 105 thousand light years across.

Historical Identification: Per Dreyer, NGC 4146 (= GC 2753 = WH III 327, 1860 RA 12 02 57, NPD 62 48.0) is "very faint, pretty small".
Physical Information: Apparent size of about 1.45 by 1.45 arcmin (from the images below), including the outer ring.

Historical Identification: Per Dreyer, NGC 4147 (= GC 2752 = JH 1106 = WH I 19, 1860 RA 12 02 58, NPD 70 40.7) is "a globular cluster, very bright, pretty large, round, gradually brighter middle, well resolved, clearly consisting of stars". The position precesses to RA 12 10 06.5, Dec +18 32 33, dead center on the cluster listed above, the description fits and there is nothing else nearby, so the identification is certain.
Physical Information: NGC 4147 is thought to be one of the oldest globular clusters in our galaxy, due to its stars having an exceptionally low percentage of elements other than hydrogen and helium. Its age is estimated at about 14 billion years, whereas most of the globular clusters in our galaxy are between 12 and 13 billion years in age. It is one of the intrinsically faintest globular clusters in our galaxy, with a mass estimated at less than 40 thousand solar masses (though with an uncertainty of a factor of two). Its distance is thought to be about 60 thousand light years. Given that and its apparent size of about 4.35 arcmin (from LEDA, and in apparent agreement with the images below), it is about 75 light years across.

Historical Identification: Per Dreyer, NGC 4148 (= GC 5624, d'Arrest, 1860 RA 12 03 01, NPD 53 20.9) is "faint, small, 12th magnitude star to southeast".
Physical Information: Apparent size of about 1.4 by 1.0 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 4149 (= GC 2754 = JH 1109 = WH II 802, 1860 RA 12 03 23, NPD 30 56.2) is "faint, small, extended".
Physical Information: Apparent size of about 1.45 by 0.25 arcmin (from the images below).