Recessional velocity of 225 km/sec is too small, in comparison to peculiar (non-Hubble expansion) velocities, to be a reliable indicator of distance. And in fact, the resulting distance estimate of 10 million light years is far smaller than redshift-independent distance estimates of 30 to 65 million light years. Assuming a more reasonable distance of roughly 50 million light years, the apparent size of 2.3 by 1.6 arcmin suggests it is about 30 thousand light years across. The core of the galaxy is exceptionally bright. Recent studies have shown that the reason is that it contains large numbers of hot, bright young stars. This is very unusual in elliptical or lenticular galaxies, which contain very little gas and dust, from which new stars can be made. The explanation appears to be, as shown in the bottom photograph for this object, that it has recently (within the last billion or two years) "cannibalized" or merged with another galaxy (probably about a twentieth of its size and mass), which contained substantial amounts of gas and dust, which are the source material for the new stellar population. The "metal" (non-hydrogen and helium) content of the new stars is very low, indicating that the merged galaxy had not created many stars, or any significant amount of heavy atoms from the death of such stars, prior to its merger with NGC 4150.

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Physical Information: Based on a recessional velocity of 995 km/sec, NGC 4151 is about 45 million light years away, in reasonable agreement with widely discordant redshift-independent distance estimates of 15 to 95 million light years. Fortunately, a recent measurement (published in Nov 2014) using infrared interferometry to accurately measure the apparent size of a dusty ring surrounding the supermassive black hole in its center and compare that to the physical size determined from the interaction of the dusty ring with the black hole has provided a distance, thought to be accurate to within 10%, of 62 million light years (making this one of the best-known galaxy distances, and providing a new "yardstick" for the distance of similar galaxies.) Using that distance and the galaxy's apparent size of ? arcmin (note: this is not the size of the dusty ring used to determine the galaxy's distance, which is only about 100 light years across), NGC 4151 is about ? thousand light years across. Because of its bright central core, NGC 4151 is listed as a Seyfert galaxy (type Sy 1.5).

Below, a multispectral ? arcmin wide image of the central part of the galaxy, showing the region that led to its classification as a Seyfert Galaxy and its fanciful name. The dusty region surrounding the central core is not the "ring" used to measure the distance of the galaxy. That is in the very center of the bright core and is far too small to be imaged by any standard method, so its size could only be measured by interferometry. (Credit X-ray NASA/CXC/CfA/J.Wang et al.; Optical Isaac Newton Group Telescopes, La Palma/Jacobus Kapteyn Telescope; Radio NSF/NRAO/VLA).

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(Note: An NED search for NGC 4155 incorrectly shows NGC 4152; use the PGC listing to access the correct information.) Based on a recessional velocity of 7380 km/sec, NGC 4155 is about 340 million light years away. Given that and its apparent size of 1.1 by 1.0 arcmin, it is about 110 thousand light years across.

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Historical Identification: Per Dreyer, NGC 4157 (= GC 2761 = JH 1114 = WH I 208, 1860 RA 12 04 01, NPD 38 43.9) is "pretty faint, considerably large, very much extended 60°± (double?)". The position precesses to RA 12 11 03.7, Dec +50 29 21, barely northwest of the nucleus of the galaxy listed above, the description fits and there is nothing else nearby, so the identification is certain.
Physical Information: Based on a recessional velocity of 775 km/sec, NGC 4157 is only about 35 million light years away, in poor agreement with redshift-independent distance estimates of 50 to 75 million light years, and for objects with such small recessional velocities peculiar (non-Hubble expansion) velocities can significantly affect the measurement, so odds are that the actual distance is close to the median of the redshift-independent distances, or around 60 to 65 million light years. Given that and its apparent size of about 8.8 by 1.0 arcmin, the galaxy is probably about 160 thousand light years across.

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Per Dreyer, NGC 4165 (GC 5625, d'Arrest, 1860 RA 12 04 59, NPD 75 59.2) is "extremely faint, 10th magnitude star to northwest, h1119 (= NGC 4168) to the east". The position precesses to RA 12 12 07.6, Dec +13 14 03, a couple of arcmin southwest of the correct position, but the relative positions of the star and NGC 4168 make the identification certain. (See IC 3035 for a discussion of the duplicate listing.) Apparent size 1.2 by 0.8 arcmin. Listed as a member (VCC 47) of the Virgo Cluster.

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The second IC notes "Not found by Frost on plates of 4 hours exposure. 4168 is, however, #223 in Schwassmann's list".

NGC 4169 is listed in NED as a Seyfert galaxy (type Sy2). Based on a recessional velocity of 3785 km/sec, it is about 175 million light years away. Given that and its 1.8 by 0.9 arcmin apparent size, it is about 90 thousand light years across. NGC 4169, 4174 and 4175 may form a physical as well as an apparent triplet; but NGC 4173 is almost certainly a foreground object.

The first IC notes "= Bigourdan 169, RA 12 05 11, NPD 60 01".

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Because of its nearly edge-on presentation, it is difficult to determine the galaxy type for NGC 4173. It is clearly less dense and more irregular in appearance than "typical" spirals, but is listed as type SBd and Sdm in NED (the d and dm suffixes meaning that it is some kind of low-density spiral, and the S and SB prefixes meaning that the presence or absence of a bar is a matter of opinion). Based on a recessional velocity of 1125 km/sec, NGC 4173 is about 55 million light years away; however, that is very uncertain, as the sole redshift-independent distance estimate is just over 30 million light years. Presuming a distance of around 45 million light years, NGC 4173's apparent size of 5.0 by 0.7 arcmin suggests that it is around 65 thousand light years across. NGC 4169, 4174 and 4175 may form a physical as well as an apparent triplet; but NGC 4173 is almost certainly a foreground object, so an NED reference to its being a member of a triplet is equally certainly wrong.

Based on a recessional velocity of 4045 km/sec, NGC 4174 is about 190 million light years away. Given that and its 0.8 by 0.5 arcmin apparent size, it is about 45 thousand light years across. NGC 4169, 4174 and 4175 may form a physical as well as an apparent triplet; but NGC 4173 is almost certainly a foreground object.

Based on a recessional velocity of 4010 km/sec, NGC 4185 is about 185 million light years away. Given that and its 1.8 by 0.4 arcmin apparent size, it is about 100 thousand light years across. NGC 4169, 4174 and 4175 may form a physical as well as an apparent triplet; but NGC 4173 is almost certainly a foreground object.

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Apparent size 5.0 by 1.7 arcmin. Listed as a member (VCC 66) of the Virgo Cluster. (See IC 3042 for a discussion of the double listing.)

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The second IC lists a corrected RA (per Howe) of 12 06 57.

Based on recessional velocity of 2115 km/sec, about 95 million light years away, in good agreement with redshift-independent distance estimates of 55 to 105 million light years. Given that and apparent size of 2.4 by 1.7 arcmin, about 65 thousand light years in diameter.

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Historical Identification: Per Dreyer, NGC 4192 (= GC 2786 = JH 1132, Méchain, M98, 1860 RA 12 06 40, NPD 74 19.3) is "bright, very large, very much extended 152°, very suddenly very much brighter middle". The position precesses to RA 12 13 48.0, Dec +14 53 59, essentially dead center on the galaxy listed above and the description fits, so the identification is certain.
Physical Information: The "recessional" velocity of -140 km/sec (which would mean it is actually approaching our galaxy) is useless as a distance indicator (even a conflicting value of +785 km/sec is too small in comparison with peculiar (non-Hubble expansion) velocities to be a reliable indicator of its distance), but redshift-independent distance estimates fix its distance as about 55 million light years, give or take 10 million light years. Given that and its apparent size of 9.8 by 2.8 arcmin, it is about 150 thousand light years across. The galaxy is also a Seyfert galaxy (type Sy 3).

Based on recessional velocity of 2480 km/sec, about 110 million light years away, in good agreement with redshift-independent distance estimates of 95 to 135 million light years. Given that and apparent size of 2.65 by 0.95 arcmin, about 85 thousand light years in diameter.

Historical Identification: Per Dreyer, NGC 4194 (= GC 2788 = JH 1135 = WH II 867, 1860 RA 12 07 07, NPD 34 40.8) is "pretty bright, very small, very suddenly much brighter middle equal to 12th magnitude star". The position precesses to RA 12 14 05.0, Dec +54 32 29, just over an arcminute northwest of the galaxy listed above, the description fits and there is nothing else nearby, so the identification is certain.
Physical Information: NGC 4194 is a merging pair of galaxies, with a brilliantly lit starburst core and broadly extended scatterings of stars south of the core and fainter scatterings of stars and star-forming regions streaming away from the core in the opposite direction, all enclosed in an even larger fainter envelope. Because of the 'hairlike' nature of the extended streams just to the north of the core, it is sometimes referred to as the Medusa merger. Based on a recessional velocity of 2500 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4194 is about 115 to 120 million light years away, in reasonable agreement with widely varying redshift-independent distance measurements of about 30 to 130 million light years (the HST press release uses a value of about 130 million light years, while the Chandra press release uses a value of about 110 million light years). Given that and its apparent size of about 0.75 by 0.55 arcmin (from the images below), the central region is about 25 thousand light years across, and from the apparent size of about 2.75 by 1.5 arcmin for the outermost envelope (also from the images below), it spans about 90 to 95 thousand light years. The galaxy is used by the Arp Atlas as an example of a disturbed galaxy with interior absorption.

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