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Dwarf elliptical galaxy

From Wikipedia, the free encyclopedia

The dwarf elliptical galaxy PGC 29388

Dwarf elliptical galaxies (dEs) are elliptical galaxies that are smaller than ordinary elliptical galaxies. They are quite common in galaxy groups and clusters, and are usually companions to other galaxies.

YouTube Encyclopedic

  • 1/3
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    59 828
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  • An Open Letter to Elliptical Galaxies
  • Galaxies, part 1: Crash Course Astronomy #38
  • What is an Elliptical Galaxy?

Transcription

YouTube, Edgar here and welcome to Artifexian Here you will learn everything you ever wanted to know about world-building and then some well An open letter to elliptical galaxies dear elliptical galaxy why are you so incredibly boring I mean I've spent so long researching into you guys trying to find something interesting to say about you and to be honest you've kinda let me down for shame elliptical galaxies For shame. For starters instead having big beautiful colorful spiral arms you instead look like a featureless mono-colored blob Hanging around the cosmos. You also contain very little gas and dust so interesting things like star formation rarely occur a what stars you do contain tend to be old very old low-mass stars now I hate to be ageist but old least in the astrological sense equates to BORING!! like imagine for second our earth was suddenly transported into an elliptical galaxy what would the sky look like? Well bland. Stars would be uniformly distributed across the night sky it will be almost features save for the abnormal amount of globular clusters. Ellipticals tend to have numerous globular clusters orbiting them much more sold in spiral galaxies even still it is up for debate as to whether or not these clusters could be seen given the uniformity of the night sky call me a spiral chauvinist but I like my night sky filled with varying stellar types dust lanes and a Galactic disc arcing across the sky now to be fair there are some interesting things about you but not enough to draw the attention of the world builder but instead work noting that for one thing when it comes to size you are much more versatile then your spiral counterparts and the actual physics keeping it stable is moderately interesting I mean is nothing like Euler's identity kinda interesting book frankly I'll take whatever I can get at the moment firstly the stars inside you tend to orbit radially as opposed to in a single plane which is cool but REALLY dangerous in terms of galactic habitability also there's a tight correlation between the velocity dispersions your stars and the size of the supermassive black hole this is called M-sigma realtion its a little complicated to get into right now go check out the link in description if you're interested lastly you ellipticals tend to be found your Center galactic clusters or groups and it thought to be the result of galactic collisions....look I'm as much a fan of MASSIVE extinction level events as the next guy is especially those on a galactic level but dear ellipticals you are in every way possible the graveyards of the cosmos yours sincerely Artifexian. Guys find me on Facebook and Twitter but more importantly like subscribe right here on Youtube thank you for watching ...Edgar out

Examples

"Dwarf elliptical" galaxies should not be confused with the rare "compact elliptical" galaxy class, of which M32, a satellite of the Andromeda Galaxy, is the prototype. In 1944 Walter Baade confirmed dwarf ellipticals NGC 147 and NGC 185 as members of the Local Group by resolving them into individual stars, thanks to their relatively little distance. In the 1950s, dEs were also discovered in the nearby Fornax and Virgo clusters.[1]

Relation to other elliptical galaxy types

Dwarf elliptical galaxies have blue absolute magnitudes within the range −18 < MV < −14 : fainter than ordinary elliptical galaxies.

The surface brightness profiles of ordinary elliptical galaxies was formerly approximated using de Vaucouleur's model, while dEs were approximated with an exponentially declining surface brightness profile. However, both types fit well by a more general function, known as Sersic's model, and there is a continuity of Sersic index (which quantifies the shape of the surface brightness profile) as a function of galaxy luminosity.[2] This is interpreted as showing that dwarf elliptical and ordinary elliptical galaxies belong to a single sequence.

An even-fainter type of elliptical-like galaxies, called dwarf spheroidal galaxies, may be a genuinely distinct class.

Origins

Dwarf ellipticals may be primordial objects. Within the currently favoured cosmological Lambda-CDM model, small objects (consisting of dark matter and gas) were the first to form. Because of their mutual gravitational attraction, some of these will coalesce and merge, forming more massive objects. Further mergers lead to ever more massive objects. The process of coalescence could lead to the present-day galaxies, and has been called "hierarchical merging". If this hypothesis is correct, dwarf galaxies may be the building blocks of today's large spiral galaxies, which in turn are thought to merge to form giant ellipticals.

An alternative suggestion[3] is that dEs could be the remnants of low-mass spiral galaxies that obtained a rounder shape through the action of repeated gravitational interactions with ordinary galaxies within a cluster. This process of changing a galaxy's morphology by interactions, and the removal of much of its stellar disk, has been called "galaxy harassment". Evidence for this latter hypothesis has been claimed due to stellar disks and weak spiral arms seen in some dEs. Under this alternative hypothesis, the anaemic spiral arms and disk are a modified version of the original stellar disk of the now transformed spiral galaxy.

At the same time, the galaxy harassment scenario can not be the full picture.[4] The highly isolated dwarf elliptical galaxy CG 611 possesses the same physical attributes as dE galaxies in clusters – such as coherent rotation and faint spiral arms – attributes that were previously assumed to provide evidence that dE galaxies were once spiral galaxies prior to a transformation process requiring immersion with a cluster of galaxies. CG 611 has a gas disk which counter-rotates to its stellar disk,[5] clearly revealing that this dE galaxy's disk is growing via accretion events. If CG 611 was to fall into a galaxy cluster, ram-pressure stripping by the cluster's halo of hot X-ray gas would strip away CG 611's gas disk and leave a gas-poor dE galaxy that immediately resembles the other dEs in the cluster. That is, no removal of stars nor re-shaping of the galaxy within the dense galaxy cluster environment would be required, undermining the idea that dE galaxies were once spiral galaxies.

See also

References

  1. ^ G. Reaves (1956), Dwarf galaxies in the Virgo cluster
  2. ^ Graham, A. & Guzman, R. (June 2003). "HST photometry of dwarf elliptical galaxies in Coma, and an explanation for the alleged structural dichotomy between dwarf and bright elliptical galaxies". The Astronomical Journal. 125 (6): 2936–2958. arXiv:astro-ph/0303391. Bibcode:2003AJ....125.2936G. doi:10.1086/374992. S2CID 13284968.
  3. ^ Moore, B.; et al. (1996). "Galaxy harassment and the evolution of clusters of galaxies". Nature. 379 (6566): 613–616. arXiv:astro-ph/9510034. Bibcode:1996Natur.379..613M. doi:10.1038/379613a0. S2CID 4303659.
  4. ^ Janz, J.; et al. (2017). "Implications for the origin of early-type dwarf galaxies – the discovery of rotation in isolated, low-mass early-type galaxies". Monthly Notices of the Royal Astronomical Society. 468 (3): 2850–2864. arXiv:1703.04975. Bibcode:2017MNRAS.468.2850J. doi:10.1093/mnras/stx634.
  5. ^ Graham, A.W.; et al. (2017). "Implications for the origin of early-type dwarf galaxies: A detailed look at the isolated, rotating, early-type dwarf galaxy LEDA 2108986 (CG 611), ramifications for the fundamental plane's S2
    K
     kinematic scaling, and the spin-ellipticity diagram"
    . Astrophysical Journal. 840 (2): 68. arXiv:1705.03587. Bibcode:2017ApJ...840...68G. doi:10.3847/1538-4357/aa6e56. S2CID 54018338.
This page was last edited on 27 November 2023, at 14:37
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