Elliptical galaxy#Sizes and shapes

• 3C 244.1
• M49 (NGC 4472)
• M59 (NGC 4621)
• M60 (NGC 4649)
• M87 (NGC 4486), whose supermassive black hole was the first black hole to be imaged by the Event Horizon Telescope.{{cite journal |author=The Event Horizon Telescope Collaboration |year=2019 |title=First M87 Event Horizon Telescope results. IV. Imaging the central supermassive black hole |journal=The Astrophysical Journal |volume=875 |issue=1 |page=L4 |issn=2041-8213 |doi=10.3847/2041-8213/ab0e85 |arxiv=1906.11241 |bibcode=2019ApJ...875L...4E |s2cid=146068771 |url=https://repository.ubn.ru.nl/bitstream/2066/202543/1/202543.pdf |doi-access=free }}{{cite magazine |author=Jeffrey, K. |date=10 April 2019 |title=These are the first pictures of a black hole — And that's a big, even supermassive, deal |magazine=Time |url=https://time.com/5566225/first-black-hole-picture-photo/ |access-date=10 April 2019}}
• M89 (NGC 4552)
• M105 (NGC 3379)
• NGC 4697, part of the NGC 4697 Group
• ESO 383-76, one of the largest galaxies known.
• IC 1101, the central galaxy of Abell 2029
• Hercules A, supergiant elliptical galaxy
• Maffei 1, the closest giant elliptical galaxy
• CGCG 049-033, known for having the longest galactic jet discovered
• Centaurus A (NGC 5128), an elliptical/lenticular radio galaxy with peculiar morphology and unusual dust lanes
• NeVe 1, the source of the Ophiuchus Supercluster eruption, the most powerful astronomical event known
• M86 (4406) an elliptical or lenticular galaxy in the constellation Virgo

File:Elliptical galaxy IC 2006.jpg{{cite web|title=Elliptical galaxy IC 2006|url=http://www.spacetelescope.org/images/heic1508a/|website=www.spacetelescope.org|publisher=ESA/Hubble|access-date=21 April 2015}}]]

Elliptical galaxies are characterized by several properties that make them distinct from other classes of galaxy. They are spherical or ovoid masses of stars, starved of star-making gases. Furthermore, there is very little interstellar matter (neither gas nor dust), which results in low rates of star formation, few open star clusters, and few young stars; rather elliptical galaxies are dominated by old stellar populations, giving them red colors. Large elliptical galaxies typically have an extensive system of globular clusters. They generally have two distinct populations of globular clusters: one that is redder and metal-rich, and another that is bluer and metal-poor.{{cite journal|doi=10.3847/1538-3881/ac680d|title=The Ancient Globular Clusters of NGC 1291 |year=2022 |last1=Hixenbaugh |first1=Kyle |last2=Chandar |first2=Rupali |last3=Mok |first3=Angus |journal=The Astronomical Journal |volume=163 |issue=6 |page=271 |s2cid=248853311 |arxiv=2205.14047 | bibcode=2022AJ....163..271H |doi-access=free }}

File:Galactic fireflies.jpg, a giant elliptical galaxy.{{Cite web |last=information@eso.org |title=Galactic fireflies |url=https://esahubble.org/images/potw1246a/ |access-date=2024-09-12 |website=www.esahubble.org |language=en}}]]

The dynamical properties of elliptical galaxies and the bulges of disk galaxies are similar, suggesting that they may be formed by the same physical processes, although this remains controversial. The luminosity profiles of both elliptical galaxies and bulges are well fit by Sersic's law, and a range of scaling relations between the elliptical galaxies' structural parameters unify the population.Graham, A.W. (2013), [http://adsabs.harvard.edu/abs/2013pss6.book...91G Elliptical and Disk Galaxy Structure and Modern Scaling Laws]

Every massive elliptical galaxy contains a supermassive black hole at its center. Observations of 46 elliptical galaxies, 20 classical bulges, and 22 pseudobulges show that each contain a black hole at the center.{{Cite journal|last1=Kormendy|first1=John|last2=Ho|first2=Luis C.|date=18 August 2013|title=Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies|journal=Annual Review of Astronomy and Astrophysics|volume=51|issue=1|pages=511–653|doi=10.1146/annurev-astro-082708-101811|issn=0066-4146|arxiv = 1304.7762 |bibcode = 2013ARA&A..51..511K |s2cid=118172025}} The mass of the black hole is tightly correlated with the mass of the galaxy,Graham, A.W. (2016), [http://adsabs.harvard.edu/abs/2016ASSL..418..263G Galaxy Bulges and Their Massive Black Holes: A Review] evidenced through correlations such as the M–sigma relation which relates the velocity dispersion of the surrounding stars to the mass of the black hole at the center.

Elliptical galaxies are preferentially found in galaxy clusters and in compact groups of galaxies.

Unlike flat spiral galaxies with organization and structure, elliptical galaxies are more three-dimensional, without much structure, and their stars are in somewhat random orbits around the center.

File:A Multi-Wavelength View of Radio Galaxy Hercules A.jpg, a supergiant elliptical galaxy and also a radio galaxy. The radio lobes shown here in pink are over a million light-years across.]]

The largest galaxies are supergiant ellipticals, or type-cD galaxies. Elliptical galaxies vary greatly in both size and mass with diameters ranging from 3,000 light years to more than 700,000 light years, and masses from 10⁵ to nearly 10¹³ solar masses.{{cite book|last1=Fraknoi|first1=Andrew|last2=Morrison|first2=David|last3=Wolf|first3=Sidney C.|title=Open Stax Astronomy|date=13 January 2017|url=https://cnx.org/contents/LnN76Opl@10.13:1G3DS4T6@3/Properties-of-Galaxies|access-date=2 February 2017}} This range is much broader for this galaxy type than for any other. The smallest, the dwarf elliptical galaxies, may be no larger than a typical globular cluster, but contain a considerable amount of dark matter not present in clusters. Most of these small galaxies may not be related to other ellipticals.File:MACSJ1423.8+2404.jpg MACS J1423.8+2404. It has a diameter of 380,000 light-years.{{Cite web|url=https://ned.ipac.caltech.edu/cgi-bin/objsearch?objname=SDSS+J142347.87+240442.4&extend=no&hconst=67.74&omegam=0.3089&omegav=0.6911&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES|title=Your NED Search Results|website=ned.ipac.caltech.edu|accessdate=8 May 2023}} Note the gravitational lensing.]]

The Hubble classification of elliptical galaxies contains an integer that describes how elongated the galaxy image is.

The classification is determined by the ratio of the major (a) to the minor (b) axes of the galaxy's isophotes:

:$10\; \backslash times\; \backslash left(1\; -\; \backslash frac\{b\}\{a\}\backslash right)$

Thus for a spherical galaxy with a equal to b, the number

is 0, and the Hubble type is E0. While the limit in the literature is about E7, it has been known since 1966 that the E4 to E7 galaxies are misclassified lenticular galaxies with disks inclined at different angles to our line of sight. This has been confirmed through spectral observations revealing the rotation of their stellar disks.Graham, A.W. et al. (1998), [http://adsabs.harvard.edu/abs/1998A%26AS..133..325G Extended stellar kinematics of elliptical galaxies in the Fornax cluster]Emsellem, E. (2011), [http://adsabs.harvard.edu/abs/2011MNRAS.414..888E The ATLAS^3D project – III. A census of the stellar angular momentum within the effective radius of early-type galaxies: unveiling the distribution of fast and slow rotators] Hubble recognized that his shape classification depends both on the intrinsic shape of the galaxy, as well as the angle with which the galaxy is observed. Hence, some galaxies with Hubble type E0 are actually elongated.

It is sometimes said that there are two physical types of ellipticals: the giant ellipticals with slightly "boxy"-shaped isophotes, whose shapes result from random motion which is greater in some directions than in others (anisotropic random motion); and the "disky" normal and dwarf ellipticals, which contain disks.Pedraz, S. et al. (2002), [http://adsabs.harvard.edu/abs/2002MNRAS.332L..59P Evidence of fast rotation in dwarf elliptical galaxies]Toloba, E. et al. (2015), [http://adsabs.harvard.edu/abs/2015ApJ...799..172T Stellar Kinematics and Structural Properties of Virgo Cluster Dwarf Early-type Galaxies from the SMAKCED Project. III. Angular Momentum and Constraints on Formation Scenarios] This is, however, an abuse of the nomenclature, as there are two types of early-type galaxy, those with disks and those without. Given the existence of ES galaxies with intermediate-scale disks, it is reasonable to expect that there is a continuity from E to ES, and onto the S0 galaxies with their large-scale stellar disks that dominate the light at large radii.

Dwarf spheroidal galaxies appear to be a distinct class: their properties are more similar to those of irregulars and late spiral-type galaxies.

At the large end of the elliptical spectrum, there is further division, beyond Hubble's classification. Beyond gE giant ellipticals, lies D-galaxies and cD-galaxies. These are similar to their smaller brethren, but more diffuse, with large haloes that may as much belong to the galaxy cluster within which they reside than the centrally-located giant galaxy.

File:A galactic mega-merger.jpg is the product of a collision between two galaxies. It is evolving into a giant elliptical galaxy.]]

In recent years, evidence has shown that a reasonable proportion (~25%) of early-type (E, ES and S0) galaxies have residual gas reservoirs{{cite journal|author=Young, L. M.|display-authors=etal|date=June 2011|title=The Atlas3D project – IV: the molecular gas content of early-type galaxies|journal=Monthly Notices of the Royal Astronomical Society|volume=414|issue=2|pages=940–967|arxiv=1102.4633|bibcode=2011MNRAS.414..940Y|doi=10.1111/j.1365-2966.2011.18561.x|doi-access=free |s2cid=119267988}}

and low-level star formation.{{cite journal|last=Crocker|first=A. F.|display-authors=etal|date=January 2011|title=Molecular gas and star formation in early-type galaxies|journal=Monthly Notices of the Royal Astronomical Society|volume=410|issue=2|pages=1197–1222|arxiv=1007.4147|bibcode=2011MNRAS.410.1197C|doi=10.1111/j.1365-2966.2010.17537.x|doi-access=free |s2cid=54764264}}

Herschel Space Observatory researchers have speculated that the central black holes in elliptical galaxies keep the gas from cooling enough for star formation.{{Cite web|url=http://www.hngn.com/articles/25442/20140227/red-and-dead-galaxies-have-beating-black-hole-hearts-preventing-star-formation.htm|title=Red And Dead Galaxies Have Beating Black Hole 'Hearts', Preventing Star Formation | HNGN - Headlines & Global News|date=27 February 2014 |accessdate=8 May 2023}}

• Firehose instability
• Fundamental plane (elliptical galaxies)
• Galaxy color–magnitude diagram
• Galaxy morphological classification
• Hubble sequence
• Lenticular galaxy
• Osipkov–Merritt model
• Sersic profile

{{reflist|30em}}

• {{Citation |last1=Mo |first1= Houjun|last2=van den Bosch|first2=Frank|last3=White|first3=Simon|title=Galaxy Formation and Evolution |publisher= Cambridge University Press |date=June 2010 |edition=1 |isbn= 978-0521857932 }}

{{Commons category|Elliptical galaxies}}

• [http://messier.seds.org/elli.html Elliptical Galaxies], SEDS Messier pages
• [http://csep10.phys.utk.edu/astr162/lect/galaxies/elliptical.html Elliptical Galaxies] ([https://web.archive.org/web/20130412000638/http://csep10.phys.utk.edu/astr162/lect/galaxies/elliptical.html Archived])

{{Galaxy}}

Category:Galaxy morphological types