Normal Galaxies ASTR 2120 Sarazin

Transcription

1 Normal Galaxies ASTR 2120 Sarazin

2 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

3 Normal Galaxies ASTR 2120 Sarazin

4 Edwin Hubble (1923) Andromeda Galaxy (M31)

5 Galaxy Hubble Types

6 Galaxy Hubble Types

7 Morphology (shape) Elliptical Galaxies Label En n = 10 (a-b)/a E0 (round) to E7 b a

8 Elliptical Galaxies M87 E0 pec in Virgo cluster

9 Elliptical Galaxies M49 = NGC4472 E2 in Virgo cluster

10 Elliptical Galaxies NGC4697 E6 in Virgo cluster

11 Galaxy Hubble Types unbarred barred

12 Morphology (shape) Spiral Galaxies Label Sx or SBx B = barred, = unbarred unbarred x = a, ab, b, bc, c, cd, d barred

13 Galaxy Hubble Types

14 Unbarred Spiral Galaxies M51 Unbarred spiral

15 Unbarred Spiral Galaxies M74 Unbarred spiral

16 Galaxy Hubble Types

17 Barred Spiral Galaxies M83 Barred spiral

18 Barred Spiral Galaxies M109 Barred spiral

19 Barred Spiral Galaxies M91 Barred spiral

20 Galaxy Hubble Types early late

21 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

22 Early vs. Late Spiral Galaxies M81 Sab

23 Early vs. Late Spiral Galaxies M31 Andromeda Sb

24 Early vs. Late Spiral Galaxies M51 Sbc

25 Early vs. Late Spiral Galaxies M33 Scd

26 Early vs. Late Spiral Galaxies M104 Sombrero Sa edge on

27 Early vs. Late Spiral Galaxies Sb edge on

28 Early vs. Late Spiral Galaxies Sc edge on

29 Galaxy Hubble Types S0 = Lenticular late

30 S0 = Lenticular Galaxies Morphology (shape) Label S0 or SB0 B = barred, = unbarred Very large bulge Disk, but no (strong) spiral arms

31 S0 = Lenticular Galaxies M102 S0 edge on

32 S0 = Lenticular Galaxies NGC5866 S0 edge on

33 S0 = Lenticular Galaxies NGC2784 S0 more face on No spiral arms

34 Galaxy Hubble Types

35 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

36 Irregular Galaxies Large Magellanic Cloud LMC Irregular

37 Irregular Galaxies Small Magellanic Cloud SMC Irregular

38 Elliptical Galaxies M87 Only old stars Nearly no cool gas or dust No star formation Ellipticals are: Red and Dead

39 Spiral Galaxies M51 Young and old stars Spiral arms Bluer Lots of cool gas or dust Lots of star formation

40 Irregular Galaxies LMC Mainly young stars Very blue Lots of cool gas or dust Lots of star formation Hints of disk, spiral arms

41 Elliptical, S0 vs. Spiral, Irr color E, S0: red clump Sp, Irr: blue cloud Abs. Mag

42 Elliptical and S0 Galaxies Found in dense environments Clusters of galaxies

43 Sp and Irr Galaxies Found in low density environments Isolated and groups

44 Hubble Tuning Fork Diagram

45 Hubble Tuning Fork Diagram

46 Hubble Tuning Fork Diagram

47 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

48

49 Hubble sequence as discussed

50

51 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), L BCGs are the largest galaxies in Universe Spirals: Smaller range of sizes

52 Galaxy Properties (Cont.) 2) Light Distributions E, Sp & S0 Bulges: r I(r) = I(0) exp[ (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 = kpc I(0) ~ constant for normal ellipticals (Freeman s Law)

53 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

54 Galaxy Properties (Cont.) 3) Motions Sp & S0 Disks: Nearly circular orbits in the plane of the disk, all in the same direction

55 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

56 Galaxy Properties (Cont.) Sp & S0 Disks: v rot (r) ~ constant outside of center (same as MW)

57 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

58 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

59 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

60 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

61 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)

62 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