The central region of NGC 3311 is obscured by a dust cloud[14] with an estimated diameter of 1,700 ly (0.53 kpc).[15] It has an amorphous and complex structure and its small size and disturbed morphology suggests that the cloud originated from amerger event with another galaxy that occurred within the past 10 million years. Oddly though, there are no shells or isophote distortions in the outer regions of NGC 3311 that would have been the result of such a recent merger. Other scenarios for the origin of the dust cloud are by acooling flow or by galactic wind failure.
The total estimated mass of the dust cloud is 4,600 solar masses (4.6×104M☉).[14]
In NGC 3311, it has been detected that there is an excess blue population in the central region of the galaxy. The spectrum of the galaxy appears to resemble that of anH II region. This suggests that the excess blue population represents an ongoing formation of young bright stars.[16]
The outer halo of NGC 3311 appears to have formed from the accretion[17] and mergers of massivesatellite galaxies in vicinity of the galaxy.[18] The halo is made up ofintra-cluster stars with a dominant part of these stars coming from the outskirts of bright early-type galaxies and the rest originating from dwarf galaxies.[19] However, the build-up of its extended halo is still ongoing due to the infall of a group of 14dwarf galaxies including the galaxies HCC 026 and HCC 007 that are currently being tidally disputed and adding their stars to the outer halo.[18][17][20][9] In contrast, the inner galaxy formed from the mergers of gas-rich lumps reminiscent of the first phase ofgalaxy formation.[18]
The stars in the central region of NGC 3311 and in the halo are very old, with ages of over 10Gyrs. However the stars in the central galaxy have a highermetallicity than the halo suggesting the stars in the stars in the central galaxy formed in a rapid but short period of star formation that occurred early on though a gas-rich dissipative collapse while the stars in halo formed in smaller accreted satellite galaxies with more extended star formation.[21]
NGC 3311 contains an off centered-envelope that was first detected by Arnaboldi et al. The off centered-envelope has a highermetallicity than the outer halo[20] and is located close to the infalling group of dwarf galaxies.[18][20]
The envelope appears to have been offset from the center of NGC 3311 by a tidal interaction with thedark matter halos of the infalling group of dwarf galaxies or halo associated with NGC 3309. This tidal interaction would have also stripped gas and dust from the outer halo of NGC 3311.[18]
NGC 3311 has one of the largest globular cluster systems known in the local universe. With an estimated population of about16,500 ± 2,000 globular clusters, NGC 3311's globular cluster system rivals that ofMessier 87's, which has about 13,000 globular clusters.[4] NGC 3309, another nearby giantelliptical has an unusually low number of globular clusters. This suggests that NGC 3311 stripped part of NGC 3309's globular clusters, with some of its globular clusters becoming members of NGC 3311's system.[24]
NGC 3311's globular cluster system was initially detected in 1976[26] and was found by Harris et al. in 1983 to contain a massive globular cluster system similar toMessier 87.[27]
An analysis by Secker et al. in 1995 using Washington photometry from theCerro Tololo Inter-American Observatory concluded that NGC 3311 had the most metal-rich globular cluster system known, with a complete absence of populations of metal-poor and intermediate-metallicity globular clusters.[28] However, Brodie et al. and Wehner et al. determined that the globular cluster system shows a bimodal color distribution with equal numbers of metal-rich and metal-poor clusters.[29][4]
A large population of about 50ultra-compact dwarf galaxies (UDCs)[30] have been detected in theHydra Cluster,[31][30] with most of them being dynamically associated to NGC 3311. It appears that theultra-compact dwarf galaxies, especially the brighter and more massive ones such as HUCD1 with amass of 5×107 and ahalf-light radius of 83 ly (25.4 pc) are the remnant nuclei ofdwarf galaxies whose stellar envelopes were stripped off during an interaction with another galaxy or the cluster itself.[30]
^Richter, O.-G. (February 1989). "The Hydra I cluster of galaxies. V - A catalogue of galaxies in the cluster area".Astronomy and Astrophysics Supplement Series.77:237–256.Bibcode:1989A&AS...77..237R.
^Kotanyi, C. (November 1990). "NGC 3309: an S-shaped radio galaxy in a nearby cluster".Revista Mexicana de Astronomía y Astrofísica.21:173–176.Bibcode:1990RMxAA..21..173K.
^abLindblad, P. O.; Jorsater, S., S.; Sandqvist, Aa. (March 1985). "The nuclear radio sources in the elliptical galaxies NGC 3309 and NGC 3311 in the cluster Abell 1060".Astronomy and Astrophysics.144:496–501.Bibcode:1985A&A...144..496L.
^abGrillmair, Carl J.; Faber, S. M.; Lauer, Tod R.; Baum, William A.; Lynds, Roger C.; O'Neil, Earl J. Jr.; Shaya, Edward J. (July 1994). "The nuclear regions of NGC 3311 and NGC 7768 imaged with the Hubble Space Telescope Planetary Camera".The Astronomical Journal.108: 102.Bibcode:1994AJ....108..102G.doi:10.1086/117049.ISSN0004-6256.
^abVasterberg, A. R.; Jorsater, S.; Lindblad, P. O. (July 1991). "An optical study of the cD galaxy NGC 3311 and the giant elliptical galaxy NGC 3309 in the cluster Hydra I".Astronomy and Astrophysics.247:335–347.Bibcode:1991A&A...247..335V.
^McMahon, P. M.; van Gorkom, J. H.; Richter, O.-G.; Ferguson, H. C. (February 1992). "H I imaging of NGC 3312 and NGC 3314a - A foreground group to the Hydra cluster?".The Astronomical Journal.103: 399.Bibcode:1992AJ....103..399M.doi:10.1086/116068.ISSN0004-6256.
