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AY202a Galaxies & Dynamics Lecture 3: Galaxy Characteristics

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Presentation on theme: "AY202a Galaxies & Dynamics Lecture 3: Galaxy Characteristics"— Presentation transcript:

1 AY202a Galaxies & Dynamics Lecture 3: Galaxy Characteristics

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3 Galaxy Properties vs Morphology
blue Type vs Color This is essentially star formation rate and history B-V cI Im-Sd Sc Sb Sa S0/a E/S0 U-B red

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5 JPH ‘76

6 Color vs Magnitude --- for Ellipticals
less luminous galaxies are lower metallicity and thus bluer. CM for the Virgo Cluster from Visvanathan & Sandage (1978) Use as a distance indicator?

7 SDSS (u-r) vs M Baldry et al 2004

8 SDSS

9 Color Gradients --- most galaxies get bluer with
radius. Combination of CFR + [Fe/H] Liu, C-Z. et al. 2009, Research in Astron. Astrophys. X

10 De Vaucouleurs

11 HI content Type MH/M S0 0.005 Mort Im 0.2 – 0.5 E 10-6 – 10-3
Sa Roberts Sb Sc Im – 0.5

12 Spirals HI vs T

13 Internal Motions 1970’s improvements in detectors enabled research on several questions: 1. Do E’s rotate appropriately? 2. Does σ vary with L? 3. Are E’s triaxial? 4. Are S’s stable? Illingworth 1977 Theory Data

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15 NGC 253

16 Optical Rotation Curves Radio 21-cm HI Velocity Maps
M33 NRAO Bureau & Freeman Optical Rotation Curves Radio 21-cm HI Velocity Maps

17 Luminosity vs Internal Motions For Ellipticals, L vs σ = Faber-Jackson
For Spirals, L vs v = Tully-Fisher TF 1977 FJ 1976

18 K-Band TF Masters et al. 2008

19 Comparison of FJ & TF relations
note the scatter. C. Kochanek

20 Kinematics & Luminosity
What drives the kinematics vs L relations? 1. Assume galaxies are self-similar in form <μ(r)> ~ μe 2. Assume they are made of similar stars M/L similar L ~ 4 π Re 2 μe where Re is the galaxy’s effective radius G m M / Re = ½ m V2 circular orbits, flat rotation  M ~ ½ V2 R / G and Re = L½ /(4 π μe)1/2 Thus M = ½ V2 L½ / (4 π μeG )1/2 = 1/4 V2 L½ / (π μeG )1/2 so for constant M/L , L½ = 1/4 V2 / (π μeG )1/2 or L ~ const V4 (shades of Opik) )1/2

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23 The Fundamental Plane For E Galaxies, the combination of σ vs L
+ D vs L + μ vs L , if M/L is well behaved  The Fundamental Plane (DD, 7 Sam) Re = f(σ,L) or even better f(σ,L,[Fe/H]) log Re = 0.36(<Ie> / μB) log σ0 Ditto for Sprials. TF implication is that M/L varies by most a factor of 2 over a factor of 100 in Luminosity.

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25 Galaxy Spectra & SED’s

26 Spectra

27 M77 a.k.a. NGC1068

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29 Starburst

30 The Cosmic Spectrum Glazebrook & Baldry from the 250,000 2dF Galaxy Spectra

31 Morphology Density Relation
Dressler (1980) studied the gross morphologies of galaxies in 14 clusters.

32 <L> and color, too…. SDSS

33 Remember: Reading Assignment
For this Wednesday NFW “The Structure of Cold Dark Matter Halos,” 1996, ApJ & The preface to Zwicky’s “Catalogue of Compact and Post-Eruptive Galaxies” Read, Outline, be prepared to discuss Zwicky’s comments and the NFW profile.

34 Accepting suggestions…… What should we read next week
Accepting suggestions…… What should we read next week? Topic: Galactic Structure & Internal Dynamics


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