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

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 Observing: Thursday April 10 (2:00 - 4:00 pm) R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 2 / 24

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

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

Density Waves in Action R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 5 / 24

Density Waves in Action M51 – Whirlpool Galaxy R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 6 / 24

Cosmic Distances The universe is big How do we know? We measured it R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 7 / 24

Cosmic Distance Ladder R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 8 / 24

Standard Candles R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 9 / 24

Standard Candles R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 10 / 24

Parallax, α ≥ 10 microarcseconds R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 11 / 24

The Local Neighborhood ∼ 40 pc R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 12 / 24

The Local Bubble ∼ 100 pc R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 13 / 24

Apparent vs Absolute Magnitudes Apparent Magnitude: m ≡ how bright does it appear R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 14 / 24

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

Apparent vs Absolute Magnitudes Apparent Magnitude: m ≡ how bright does it appear Absolute Magnitude: M ≡ how bright if d = 10 pc � � � 4 π d 2 � f 1 L 1 m 2 − m 1 = 2 . 5 log 10 = 2 . 5 log 10 2 4 π d 2 f 2 L 2 1 R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 14 / 24

Apparent vs Absolute Magnitudes Apparent Magnitude: m ≡ how bright does it appear Absolute Magnitude: M ≡ how bright if d = 10 pc � � � 4 π d 2 � f 1 L 1 m 2 − m 1 = 2 . 5 log 10 = 2 . 5 log 10 2 4 π d 2 f 2 L 2 1 � � � � L 1 L ⋆ M 2 − M 1 = 2 . 5 log 10 ⇒ M ⋆ − M ⊙ = − 2 . 5 log 10 L 2 L ⊙ R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 14 / 24

Apparent vs Absolute Magnitudes Apparent Magnitude: m ≡ how bright does it appear Absolute Magnitude: M ≡ how bright if d = 10 pc � � � 4 π d 2 � f 1 L 1 m 2 − m 1 = 2 . 5 log 10 = 2 . 5 log 10 2 4 π d 2 f 2 L 2 1 � � � � L 1 L ⋆ M 2 − M 1 = 2 . 5 log 10 ⇒ M ⋆ − M ⊙ = − 2 . 5 log 10 L 2 L ⊙ � � d ⋆ Distance modulus: m ⋆ − M ⋆ = 5 log 10 10 pc R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 14 / 24

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

Main Sequence Fitting R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 16 / 24

Local Galactic Group ∼ 2 Mpc R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 17 / 24

Cepheid Variables R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 18 / 24

Cepheid Variables R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 19 / 24

Cepheid Variables ∼ 50 Mpc R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 20 / 24

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

Tully-Fisher Relation ∼ 500 Mpc R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 22 / 24

Type Ia Supernovae R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 23 / 24

Type Ia Supernovae Phillips relationship (1993): M max ( B ) = − 21 . 726 + 2 . 698∆ m 15 ( B ) R. Orvedahl (CU Boulder) Cosmic Distance Apr 7 & 9 24 / 24