ASTR 1040 Recitation: Active Galactic Nucleii Ryan Orvedahl - - PowerPoint PPT Presentation

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ASTR 1040 Recitation: Active Galactic Nucleii Ryan Orvedahl Department of Astrophysical and Planetary Sciences April 14 & 16, 2014 This Week Night Observing: Monday April 14 (8:30 pm) Midterm III: Thursday April 17 (9:30 am) Review

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ASTR 1040 Recitation: Active Galactic Nucleii

Ryan Orvedahl

Department of Astrophysical and Planetary Sciences

April 14 & 16, 2014

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This Week

Night Observing: Monday April 14 (8:30 pm) Midterm III: Thursday April 17 (9:30 am) Review Session: Wednesday April 16 (5:00 pm G125) Heliostat Observing: Friday April 18 (2:30 - 4:30 pm)

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 2 / 19

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Today’s Schedule

Past/Current Homework or Lecture Questions? Redshift Quasars Active Galactic Nucleii Faster Then Light Travel?

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 3 / 19

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Cosmological Redshift

The universe is expanding, according to SNe Ia Space expands ⇒ wavelengths expand Longer λ ⇒ Redshift 1 + z = λobs/λ0

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 4 / 19

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Cosmological Redshift

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 5 / 19

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How Do We Observe Cosmological Redshift?

λobs ⇒ 1 + z = λobs/λ0 ⇒ d = v/H0 ≈ cz/H0

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 6 / 19

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Active Galactic Nucleii

1960s: observes newly discovered radio sources with visible light Typically look like normal galaxies 3C 273: looks like blue star, strong emission lines that did not seem to correspond to any known element After a few months, H emission at z ≈ 0.17 Maarten Schmidt

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 7 / 19

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AGN & Quasars

Luminosity of 3C 273: L = 1039 W ≈ 1012L⊙ ≫ LMW

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 8 / 19

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AGN & Quasars

Luminosity of 3C 273: L = 1039 W ≈ 1012L⊙ ≫ LMW Soon find many more objects with even larger redshifts

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 8 / 19

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AGN & Quasars

Luminosity of 3C 273: L = 1039 W ≈ 1012L⊙ ≫ LMW Soon find many more objects with even larger redshifts First few objects were strong radio sources and look like stars in visible light

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 8 / 19

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AGN & Quasars

Luminosity of 3C 273: L = 1039 W ≈ 1012L⊙ ≫ LMW Soon find many more objects with even larger redshifts First few objects were strong radio sources and look like stars in visible light Given name Quasars: “QUAsi-StellAr Radio Sources”

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 8 / 19

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What Powers A Quasar? Part I

How massive are they? Luminosity tells us how much mass they accrete – how?

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 9 / 19

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What Powers A Quasar? Part I

How massive are they? Luminosity tells us how much mass they accrete – how? L = ˙ Mc2

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 9 / 19

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What Powers A Quasar? Part I

How massive are they? Luminosity tells us how much mass they accrete – how? L = ˙ Mc2 Observed L gives ˙ M ≈ 1 M⊙/yr

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 9 / 19

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What Powers A Quasar? Part I

How massive are they? Luminosity tells us how much mass they accrete – how? L = ˙ Mc2 Observed L gives ˙ M ≈ 1 M⊙/yr Of all galaxies we observe, only 1% are “active”

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 9 / 19

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What Powers A Quasar? Part I

Only 1% of galaxies are “active” ⇒ 2 possibilities

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 10 / 19

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What Powers A Quasar? Part I

Only 1% of galaxies are “active” ⇒ 2 possibilities

1

All galaxies are “active” for 1% of their life

⇒ tlife ≈ 1% tuniverse ≈ 108 yrs

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 10 / 19

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What Powers A Quasar? Part I

Only 1% of galaxies are “active” ⇒ 2 possibilities

1

All galaxies are “active” for 1% of their life

⇒ tlife ≈ 1% tuniverse ≈ 108 yrs

2

Only 1% of galaxies are “active” for 100% of their life

⇒ tlife ≈ 100% tuniverse ≈ 1010 yrs

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 10 / 19

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What Powers A Quasar? Part I

How massive are they?

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 11 / 19

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What Powers A Quasar? Part I

How massive are they? We just estimated their lifetime, tlife

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 11 / 19

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What Powers A Quasar? Part I

How massive are they? We just estimated their lifetime, tlife We measure L, which gives us ˙ M ≈ 1 M⊙/ yr

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 11 / 19

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What Powers A Quasar? Part I

How massive are they? We just estimated their lifetime, tlife We measure L, which gives us ˙ M ≈ 1 M⊙/ yr Can estimate their mass: 108 − 1010M⊙

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 11 / 19

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What Powers A Quasar? Part II

What about their size?

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 12 / 19

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What Powers A Quasar? Part II

What about their size? Look at “surface blemishes” Fastest possible variation gives a time scale Turn the time scale into a distance scale through propagation speed

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 12 / 19

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What Powers A Quasar? Part II

What about their size? Pretty short timescales: ∼ seconds - hours Gives size of a few light-minutes to light-hours Distance from Sun to Earth is ∼ 8 light-minutes Distance from Sun to Saturn is ∼ 45 light-minutes Distance from Sun to Pluto is ∼ 5.5 light-hours ⇒ Black Hole!!

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 13 / 19

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Quasar Characteristics

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 14 / 19

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Quasar Characteristics

Jets Broad Line Region Narrow Line Region Obscuring Torus

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 15 / 19

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Why Does It Have Jets?

Accretion disc is very hot, mainly plasma Magnetic field becomes trapped in plasma (Frozen-In) Field becomes wrapped around rotation axis

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 16 / 19

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Frozen-In Condition

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 17 / 19

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Superluminal Jets??

Measure jet on sky (use VLBI for best resolution) Wait some time, measure it again Spatial & time difference give speeds of 6c??

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 18 / 19

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Superluminal Jets Explained

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 19 / 19

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Superluminal Jets Explained

We measure βT ≡ vT

c = β sin θ 1−β cos θ

βmax

T

= βγ > 1

  • R. Orvedahl (CU Boulder)

AGN & Quasars Apr 14 & 16 19 / 19