Normal Galaxies ASTR 2120 Sarazin
Test #2 Monday, April 8, 11-11:50 am ASTR 265 (classroom) Bring pencils, paper, calculator You may not consult the text, your notes, or any other materials or any person You may bring a 3x5 card with equations ~2/3 Quantitative Problems (like homework problems) ~1/3 Qualitative Questions Multiple Choice, Short Answer, Fill In the Blank questions No essay questions
Normal Galaxies ASTR 2120 Sarazin
Edwin Hubble (1923) Andromeda Galaxy (M31)
Galaxy Hubble Types
Galaxy Hubble Types
Morphology (shape) Elliptical Galaxies Label En n = 10 (a-b)/a E0 (round) to E7 b a
Elliptical Galaxies M87 E0 pec in Virgo cluster
Elliptical Galaxies M49 = NGC4472 E2 in Virgo cluster
Elliptical Galaxies NGC4697 E6 in Virgo cluster
Galaxy Hubble Types unbarred barred
Morphology (shape) Spiral Galaxies Label Sx or SBx B = barred, = unbarred unbarred x = a, ab, b, bc, c, cd, d barred
Galaxy Hubble Types
Unbarred Spiral Galaxies M51 Unbarred spiral
Unbarred Spiral Galaxies M74 Unbarred spiral
Galaxy Hubble Types
Barred Spiral Galaxies M83 Barred spiral
Barred Spiral Galaxies M109 Barred spiral
Barred Spiral Galaxies M91 Barred spiral
Galaxy Hubble Types early late
Morphology (shape) Spiral Galaxies Label Sx or SBx B = barred, = unbarred unbarred x = a, ab, b, bc, c, cd, d a = tightly wound, smooth spiral arms, large nuclear bulge c = open, patchy spiral arms (H II regions), small nuclear bulge barred
Early vs. Late Spiral Galaxies M81 Sab
Early vs. Late Spiral Galaxies M31 Andromeda Sb
Early vs. Late Spiral Galaxies M51 Sbc
Early vs. Late Spiral Galaxies M33 Scd
Early vs. Late Spiral Galaxies M104 Sombrero Sa edge on
Early vs. Late Spiral Galaxies Sb edge on
Early vs. Late Spiral Galaxies Sc edge on
Galaxy Hubble Types S0 = Lenticular late
S0 = Lenticular Galaxies Morphology (shape) Label S0 or SB0 B = barred, = unbarred Very large bulge Disk, but no (strong) spiral arms
S0 = Lenticular Galaxies M102 S0 edge on
S0 = Lenticular Galaxies NGC5866 S0 edge on
S0 = Lenticular Galaxies NGC2784 S0 more face on No spiral arms
Galaxy Hubble Types
Irregular Galaxies Messy, full of gas and dust, young stars Hints of disk, spiral arms Galaxies in the process of forming Today, nearly all irregular galaxies are small In past (at high redshift), large irregular galaxies
Irregular Galaxies Large Magellanic Cloud LMC Irregular
Irregular Galaxies Small Magellanic Cloud SMC Irregular
Elliptical Galaxies M87 Only old stars Nearly no cool gas or dust No star formation Ellipticals are: Red and Dead
Spiral Galaxies M51 Young and old stars Spiral arms Bluer Lots of cool gas or dust Lots of star formation
Irregular Galaxies LMC Mainly young stars Very blue Lots of cool gas or dust Lots of star formation Hints of disk, spiral arms
Elliptical, S0 vs. Spiral, Irr color E, S0: red clump Sp, Irr: blue cloud Abs. Mag
Elliptical and S0 Galaxies Found in dense environments Clusters of galaxies
Sp and Irr Galaxies Found in low density environments Isolated and groups
Hubble Tuning Fork Diagram
Hubble Tuning Fork Diagram
Hubble Tuning Fork Diagram
Hubble Classes Sequence in: round (spheroid) flat (disk) random orbits circular orbits in disk red blue old stars young stars little cool gas and dust lots of cool gas and dust dense environments sparse environments
Hubble sequence as discussed
Galaxy Properties 1) Luminosity, Mass, Diameter Ellipticals: Very large range: dwarf ellipticals, 10 5 L (globular clusters?) giant ellipticals brightest cluster galaxies (BCGs or cds), 10 13 L BCGs are the largest galaxies in Universe Spirals: Smaller range of sizes
Galaxy Properties (Cont.) 2) Light Distributions E, Sp & S0 Bulges: r I(r) = I(0) exp[ - 7.67 (r / r e ) 1/4 ] De Vaucouleurs Law r e = effective radius, 1/2 of light comes inside of r e in projection r e = 0.1-50 kpc I(0) ~ constant for normal ellipticals (Freeman s Law)
Galaxy Properties (Cont.) 2) Light Distributions (cont.) Sp & S0 Disks: I(r) = I(0) exp( - r / r o ) r o = 1-5 kpc I(0) ~ constant for spirals
Galaxy Properties (Cont.) 3) Motions Sp & S0 Disks: Nearly circular orbits in the plane of the disk, all in the same direction
Galaxy Properties (Cont.) Sp & S0 Disks: View at inclination i v r = v rot (r) sin f sin i radial velocity, Doppler shift Apparent disk = ellipse us i b a f Along major axis a v r = v rot (r) sin i cos i = b/a for very thin disk, no dust
Galaxy Properties (Cont.) Sp & S0 Disks: v rot (r) ~ constant outside of center (same as MW)
Galaxy Properties (Cont.) 3) Motions Ellipticals: Why are ellipticals elliptical? What is their 3D shape? a) Rotation? No Shape would be oblate spheroid v r would vary across galaxy, not true b) Random stellar motions
Galaxy Properties (Cont.) Elliptical motions s r2 b) Random stellar motions No rotation, but many different v r along line-of sight broaden spectral lines º <v r2 > in CM frame If spherical, s 2 = 3 s r 2
Galaxy Properties (Cont.) Elliptical motions: Why not spherical? Stars move different speeds in different directions Can be different in all 3 directions triaxial ellipsoids slower faster
Galaxy Properties (Cont.) 4) Masses Sp & S0 Disks: v rot (r) = GM (r) r M (r) = v 2 rot (r) r G v rot (r) constant M tot (r) r, most mass at large radii ρ tot (r) 1 r 2, but light and stars e r /r 0
Galaxy Properties (Cont.) 4) Masses Sp & S0 disks: Massive Dark Matter Halos Extend out to ~ 100 kpc M(Dark Matter) > 10 x M(stars and gas)
Galaxy Properties (Cont.) 4) Masses Es, Sp & S0 bulges: Random velocities σ r = radial velocity dispersion σ = 3D velocity dispersion Virial Theorem : KE = - PE/2 1 2 Mσ 2 = 1 2 M = σ 2 R G GM 2 R