| Eyes Galaxies | |
|---|---|
 NGC 4438 (top) and NGC 4435 (bottom) taken by the FORS2 instrument of theVery Large Telescope in 2011 | |
| Observation data (J2000.0epoch) | |
| Constellation | Virgo |
| Right ascension | 12h 27m 45.6s |
| Declination | +13° 00′ 31″ |
| Redshift | 0.002638/0.000237 |
| Distance | 52 millionly |
| Apparent magnitude (V) | +10 |
| Absolute magnitude (V) | 12 |
| Characteristics | |
| Type | SB0/SA(s)O/a pec |
| Apparent size (V) | 2.35 × 1.43/8.5 × 3.2 |
| Notable features | Interacting |
| Other designations | |
| NGC 4435-8,Arp 120, VV 188 VCC 1030, VCC 1043 | |
TheEyes Galaxies (NGC 4435-NGC 4438, also known asArp 120) are a pair of galaxies about52 millionlight-years away in theconstellationVirgo. The pair are members of the string of galaxies known asMarkarian's Chain.
NGC 4435 is abarredlenticular galaxy currently interacting with NGC 4438. Studies of the galaxy by theSpitzer Space Telescope revealed a relatively young (190 million years) stellar population within the galaxy's nucleus, which may have originated through the interaction with NGC 4438 compressing gas and dust in that region, triggering a starburst.[1] It also appears to have a long tidal tail possibly caused by the interaction;[2] however, other studies suggest the apparent tail is actually foregroundgalactic cirrus within theMilky Way unrelated to NGC 4435.[3]
NGC 4438 is the most curious interacting galaxy in the Virgo Cluster, due to the uncertainty surrounding the energy mechanism that heats the nuclear source; this energy mechanism may be astarburst region, or a black hole-poweredactive galactic nucleus (AGN). Both hypotheses are currently under investigation by astronomers.
This galaxy shows a highly distorteddisk, including longtidal tails due to the gravitationalinteractions with other galaxies in the cluster and its companion. The aforementioned features explain why sources differ as to its classification, defining it either as a lenticular or spiral galaxy. NGC 4438 also shows signs of a past, extended – but modest – starburst,[4] a considerable deficiency ofneutral hydrogen, as well as a displacement of the components of itsinterstellar medium – atomic hydrogen,molecular hydrogen,interstellar dust, and hot gas – in the direction of NGC 4435. This observation suggests both a tidal interaction with NGC 4435 and the effects ofram-pressure stripping[5] as NGC 4438 moves at high speed through Virgo'sintracluster medium, increased by the encounter between both galaxies.[6][7]
While there is evidence to suggest that the environmental damage to the interstellar medium of NGC 4438 may have been caused by an off-center collision with NGC 4435 millions of years ago, a recent discovery of several filaments ofionized gas links NGC 4438 with the large neighboring elliptical galaxyMessier 86,[8] in addition to a discovery of gas and dust within M86 that may have been stripped from NGC 4438 during a past encounter between the two.[9][10] Given the high density of galaxies in the center of the Virgo galaxy cluster, it is possible that the three galaxies, NGC 4435, NGC 4438, and M86, have had past interactions.[11]
{{cite journal}}: CS1 maint: multiple names: authors list (link)