Struktura a kinematika galaxií (F7567)
Bruno Jungwiert
II. Hubbleova a de Vaucouleursova klasifikace
III. Příčky a prstence v diskových galaxiích
Hvězdná noc, 1889
1920-1924: Spiral nebulae (galaxies) and the ,,Great Debate” questions:
1) Are they made of stars or gas?
2) Are they inside or outside of our own Galaxy? If outside, how far?
3) How big is our Galaxy? 30,000 l.y.? 300,000 l.y.?
1924: Two important discoveries are made by Edwin Hubble:
1) some individual stars (Cepheids) resolved in nearby “spiral nebulae”
2) distances to these stars, and thus to their host galaxies, estimated
=> conclusions: “spiral nebulae” are made of stars; they are independent stellar
islands far beyond the outskirts of our own Galaxy
1926-1936: The Hubble Sequence (The Hubble classification of galaxies =
the first classification of galaxy morphologies)
Edwin P. Hubble, Mt. Wilson, California
from: G. de Vaucouleurs, Classification and Morphology of External Galaxies, Handbuch der Physik, 1959, Vol. 53, pp. 275-310
http://nedwww.ipac.caltech.edu/level5/Dev/frames.html
The Hubble tuning fork (1925, Mt. Wilson)
Elliptical (E), lenticular (S0), normal spiral (S), barred spiral (SB) and
irregular galaxies (I)
from: G. de Vaucouleurs, Classification and Morphology of External Galaxies, Handbuch der Physik, 1959, Vol. 53, pp. 275-310
http://nedwww.ipac.caltech.edu/level5/Dev/frames.html
E sub-types: E0 – E7, n = 10(1 – b/a)
S and SB sub-types: Sa, Sb, Sc and SBa, SBb, SBc
Edwin P. Hubble
(1889 - 1953)
Images: https://en.wikipedia.org/wiki/File:HubbleTuningFork.jpg, https://en.wikipedia.org/wiki/File:Edwin-hubble.jpg
Galaxies are classified by their morphology as:
elliptical galaxies (ellipticals) (E)
lenticular galaxies (lenticulars) (S0)
spiral galaxies (spirals)
- divided into: normal spirals (S)
barred spirals (SB)
Note: The Hubble classification does not include dwarf galaxies that dominate the galaxy counts (they are subdivided into dwarf irregular,
dwarf elliptical, dwarf spheroidal and ultra-faint dwarf galaxies).
Hooker telescope (100-inch mirror)
Mt. Wilson, California
Fundamental discoveries:
- nature of spiral nebulae: galaxies
- speeds of galaxies: expansion of the Universe
Image credit: By Antonio Ciccolella / M. De Leo - https://en.wikipedia.org/wiki/File:Hubble-Vaucouleurs.png, CC BY 3.0,
https://commons.wikimedia.org/w/index.php?curid=50260841
Revised Hubble classification (de Vaucouleurs, 1959)
elliptical galaxies,
normal spiral galaxies,
barred spiral galaxies
face-on views
edge-views
The de Vaucouleurs classification (1959, 1964)
- classes E, S0, S, Im
- families A (unbarred), AB (weakly barred), B (barred)
- varieties s (inner spiral structure), r (inner ring), rs (inner pseudo-ring)
from: G. de Vaucouleurs, Classification and Morphology of External Galaxies, Handbuch der Physik, 1959, Vol. 53, pp. 275-310
http://nedwww.ipac.caltech.edu/level5/Dev/frames.html
De Vaucouleurs (1959)
from: G. de Vaucouleurs, Classification and Morphology of External Galaxies, Handbuch der Physik, 1959, Vol. 53, pp. 275-310
http://nedwww.ipac.caltech.edu/level5/Dev/frames.html
Bulges
M 104 SA(s)a
NGC 4565 SA(s)b?
(zdroj: Binney & Merrifield,
Galactic Astronomy, kapitola IV)
B/D – bulge-to-disk ratio
B/T = B/(B+D) – bulge-tototal
luminosity ratio
SA(s)a
SA(s)b
Bars (příčky)
> 2/3 diskových galaxií mají příčku viditelnou v optickém oboru
typ SA: galaxie bez příčky ~1/3
typ SAB: galaxie se ,,slabou” příčkou ~1/3
typ SB: galaxie se ,,silnou” příčkou ~1/3
v blízké infračervené oblasti je frekvence příček > 80%
SAB(s)c SAB(rs)cd
SB(r'l)b
Dvojpříčky (double bars, bars-in-bars)
Nukleární příčky (nuclear bars, baby bars)
Double bar in NGC 1433 (R'1
SB(rs)ab)
(B band, Buta & Combes 1996) (H band, JCA, 1997)
Prstence (rings) a
pseudo-prstence (pseudo-rings)
v diskových galaxiích
označení:
prstence pseudo-prstence
- vnější (outer): R, R1
, R2
R', R'1
, R'2
- vnitřní (inner): r rs (nebo r')
- nukleární: nr nr'
Příklady vnějších a vnitřních prstenců
NGC 7020 (Buta & Combes 1996)
(R)SA(r)0+
(R'(R'11)SB(r)ab)SB(r)ab (Sy)(Sy)
(R'(R'22)SAB(r)b)SAB(r)b
Nukleární prstenec v NGC 1097
SB(r'l,nr)b
Nukleární spirály
NGC 1365, SB(s)bNGC 1365, SB(s)b
optical imageoptical image near-IR image (H-band)near-IR image (H-band)
(different scale; from JCA, 1997)
Normal (unbarred) spiral galaxies (Hubble type SA)
M81 (Bode’s galaxy) (SAab)
M94 (SAab)
M64 (Black eye) (SAab)
M104 (Sombrero) (SAa)
NGC 891 (SAb)
Normal (unbarred) spiral galaxies (Hubble type SA)
M74 (Phantom) (SAc)M51 (Whirlpool galaxy) (SAbc)
M88 (SAb)
M33 (Triangulum) (SAcd)NGC 4565 (Needle
galaxy) (SAb?) M63 (Sunflower galaxy) (SAbc)
Normal (unbarred) spiral galaxies (Hubble type SA)
M81 (Bode’s galaxy) (SAab)
M94 (SAab)
M64 (Black eye) (SAab)
M104 (Sombrero) (SAa)
NGC 891 (SAb)
Weakly barred spiral galaxies (Hubble type SAB)
M90 (SABab)
M96 (SABab)
M61 (SABbc)
M101 (Pinwheel) (SABcd) M83 (Southern pinwheel) (SABc)
NGC 4625 (SABm)
Strongly barred spiral galaxies (Hubble type SB)
M91 (SBb)
NGC 1365 (SBb)
NGC 1097 (SBb)
NGC 1300 (SBbc) NGC 2903 (SBd)
NGC 1672: Barred Spiral Galaxy from Hubble
Image Credit: Hubble Legacy Archive, NASA, ESA; Processing & Copyright: Steve Cooper
Explanation: Many spiral galaxies have bars across their centers. Even our own Milky Way Galaxy is thought to have a modest central bar. Prominently barred
spiral galaxy NGC 1672, featured here, was captured in spectacular detail in an image taken by the orbiting Hubble Space Telescope. Visible are dark
filamentary dust lanes, young clusters of bright blue stars, red emission nebulas of glowing hydrogen gas, a long bright bar of stars across the center, and a
bright active nucleus that likely houses a supermassive black hole. Light takes about 60 million years to reach us from NGC 1672, which spans about 75,000
light years across. NGC 1672, which appears toward the constellation of the Dolphinfish (Dorado), is being studied to find out how a spiral bar contributes to
star formation in a galaxy's central regions.
http://apod.nasa.gov/apod/ap160913.html
Elliptical galaxies (Hubble type E)
Lenticular galaxies (Hubble type S0)
The largest known galaxy: IC 1101
a supergiant lenticular galaxy
(Hubble type S0)
size: 5 million light years across
(25 times the Milky Way disk)
distance: 1.2 billion l.y. (redshift: 0.08)
number of stars: 100 trillion (1014
)
(500 x more than the Milky Way Galaxy)
For the first time observed in 1790 by
William Herschel
The smallest known galaxy:
Segue 2
a dwarf spheroidal galaxy (dSph),
member of the Local Group
size: 200 light years
distance: 110,000 light years
number of stars: 3,000
Discovered in 2009