ASTR 1040 Recitation: Cosmic Distance Ryan Orvedahl Department of - - PowerPoint PPT Presentation

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ASTR 1040 Recitation: Cosmic Distance Ryan Orvedahl Department of - - PowerPoint PPT Presentation

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ASTR 1040 Recitation: Cosmic Distance Ryan Orvedahl Department of Astrophysical and Planetary Sciences April 7 & 9, 2014 This Week Night Observing: Wednesday April 9 (8:30 pm) Fiske Planetarium: Thursday April 10 (9:30 am) Heliostat

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SLIDE 1

ASTR 1040 Recitation: Cosmic Distance

Ryan Orvedahl

Department of Astrophysical and Planetary Sciences

April 7 & 9, 2014

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SLIDE 2

This Week

Night Observing: Wednesday April 9 (8:30 pm) Fiske Planetarium: Thursday April 10 (9:30 am) Heliostat Observing: Thursday April 10 (2:00 - 4:00 pm)

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 2 / 24

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SLIDE 3

Today’s Schedule

Past/Current Homework or Lecture Questions? Density Wave Theory Standard Candles Magnitudes Cosmic Distances

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 3 / 24

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SLIDE 4

Why Spiral Structure? – Density Waves

Gas/Stars move in/out of dense regions Gas/stars are pulled toward high density Clumping gives rise to spiral structure Spiral structure has high star formation

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 4 / 24

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SLIDE 5

Density Waves in Action

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 5 / 24

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SLIDE 6

Density Waves in Action

M51 – Whirlpool Galaxy

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 6 / 24

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SLIDE 7

Cosmic Distances

The universe is big How do we know? We measured it

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 7 / 24

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SLIDE 8

Cosmic Distance Ladder

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 8 / 24

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SLIDE 9

Standard Candles

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 9 / 24

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SLIDE 10

Standard Candles

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 10 / 24

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SLIDE 11

Parallax, α ≥ 10 microarcseconds

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 11 / 24

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SLIDE 12

The Local Neighborhood ∼ 40 pc

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 12 / 24

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SLIDE 13

The Local Bubble ∼ 100 pc

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 13 / 24

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SLIDE 14

Apparent vs Absolute Magnitudes

Apparent Magnitude: m ≡ how bright does it appear

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 14 / 24

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SLIDE 15

Apparent vs Absolute Magnitudes

Apparent Magnitude: m ≡ how bright does it appear Absolute Magnitude: M ≡ how bright if d = 10 pc

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 14 / 24

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SLIDE 16

Apparent vs Absolute Magnitudes

Apparent Magnitude: m ≡ how bright does it appear Absolute Magnitude: M ≡ how bright if d = 10 pc m2 − m1 = 2.5 log10

  • f1

f2

  • = 2.5 log10
  • L1

4πd2

1

4πd2

2

L2

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 14 / 24

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SLIDE 17

Apparent vs Absolute Magnitudes

Apparent Magnitude: m ≡ how bright does it appear Absolute Magnitude: M ≡ how bright if d = 10 pc m2 − m1 = 2.5 log10

  • f1

f2

  • = 2.5 log10
  • L1

4πd2

1

4πd2

2

L2

  • M2 −M1 = 2.5 log10
  • L1

L2

  • ⇒ M⋆ −M⊙ = −2.5 log10
  • L⋆

L⊙

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 14 / 24

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SLIDE 18

Apparent vs Absolute Magnitudes

Apparent Magnitude: m ≡ how bright does it appear Absolute Magnitude: M ≡ how bright if d = 10 pc m2 − m1 = 2.5 log10

  • f1

f2

  • = 2.5 log10
  • L1

4πd2

1

4πd2

2

L2

  • M2 −M1 = 2.5 log10
  • L1

L2

  • ⇒ M⋆ −M⊙ = −2.5 log10
  • L⋆

L⊙

  • Distance modulus: m⋆ − M⋆ = 5 log10
  • d⋆

10 pc

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 14 / 24

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SLIDE 19

Main Sequence Fitting

90% of stars are on the Main Sequence Look for parallel tracks on the HR diagram

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 15 / 24

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SLIDE 20

Main Sequence Fitting

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 16 / 24

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SLIDE 21

Local Galactic Group ∼ 2 Mpc

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 17 / 24

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SLIDE 22

Cepheid Variables

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 18 / 24

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SLIDE 23

Cepheid Variables

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 19 / 24

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SLIDE 24

Cepheid Variables ∼ 50 Mpc

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 20 / 24

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SLIDE 25

Tully-Fisher Relation

Empirical relationship between luminosity and line widths Measure width of emission lines (e.g. 21 cm), infer luminosity Measure apparent magnitude, calculate distance

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 21 / 24

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SLIDE 26

Tully-Fisher Relation ∼ 500 Mpc

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 22 / 24

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SLIDE 27

Type Ia Supernovae

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 23 / 24

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Type Ia Supernovae

Phillips relationship (1993): Mmax(B) = −21.726 + 2.698∆m15(B)

  • R. Orvedahl (CU Boulder)

Cosmic Distance Apr 7 & 9 24 / 24