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ASTR 3520 Observations & Instrumentation II: Spectroscopy. Lecture 1 Introduction. Overview John Bally C323A Duane 492 5786 [email protected] [email protected]

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ASTR 3520

Observations & Instrumentation II:

Spectroscopy

Lecture 1

Introduction


Slide2 l.jpg

  • Overview

  • John Bally C323A Duane 492 5786

  • [email protected]

  • [email protected]

  • Office hours: Th after class (2:00 PM)

  • Wed (2:00 PM)

  • Adam Ginsburg C329 Duane 303 667 3805

  • [email protected]

  • Office Hours: Mon, Tues 11:00 AM

  • or by appointment

  • Student & Teacher Introductions:


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  • Organization

  • Review course structure, content, and Syllabus

  • Observing Projects: Stellar, nebular spectroscopy, semester projects, labs, homework.

  • Apache Point Observatory Field Trip:

  • - 5 - 6 days/ 4 - 5 nights

  • - Covered by Course Fees

  • - VLA, NSO, APO

  • - Last week of Oct. (depends on TAC)

  • Observing Proposals for Semester project due end of Sept.

  • 24” Observing Groups 5 groups / 3 to 4 each.

  • - Each group must have at last 1 experienced observer

  • Start spectrograph overview (once-over lightly)


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  • Spectroscopy: Astronomy => Astrophysics

  • Light as a wave phenomenon: = c

  • Geometrical optics => wave optics

  • Diffraction

  •  ~  / D

  • Interference:

  • n = D sin n = 1,2,3,…

  • Deep insights into the nature of atoms, molecules:

  • Discrete wavelengths => Discrete energy levels

  • Electrons stable only in certain orbits.

  • Interference of electron waves!

  •  = h / p = h / mv :de Broglie waves

  • All matter has wave-like behavior on sufficiently

  • small scale!


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Spectrograph

Focal Plane

collimator

camera

detector

Dispersing element

Slit

Telescope

Spectrograph


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  • SBO Spectrograph overview

  • Slit & Decker:

  • Restrict incoming light

  • Spatial direction vs. Spectral direction

  • Collimator & Camera:

  • Transfer image of slit onto detector.

  • Grating:

  • Disperse light: dispersion => spectral resolution

  • What determines spectral resolution & coverage?

  • - Slit-width

  • - Grating properties: Ngroves , order number

  • - Camera / collimator magnification (focal length ratio)

  • - Detector pixel size and number of pixels.


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  • Types of Spectroscopy

  • Electromagnetic Waves: Emission, absorption

  • Visual, near-IR., FIR, Radio, UV/X-ray, gamma-ray

  • - Solids, liquids, gasses, plasmas

  • - Emission, absorption

  • - Spectral line, molecular bands, continua:

  • - Thermal (~LTE, blackbody, grey-body):

  • - Non-thermal (masers, synchrotron, …)

  • - Electronic, vibrational, rotational transitions.

  • - Effects of B (Zeeman), E ( Stark), motion (Doppler),

  • pressure (collisions), natural life-time (line widths)

  • - Radiative Transfer (optical depth)

  • Other types (not covered in this course):

  • NMR

  • Raman

  • Phosprescence / Fluorecence

  • Astro-particle


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Review of Some Basics

  • c = n x l

  • Angular resolution: q = 1.22 l / D radians

  • 206,265” in a radian

  • E = h n

  • F = L / 4 p d2

  • AZ, El, RA, Dec, Ecliptic, Galactic

  • Siderial time, Hour Angle

  • G = 6.67 x 10-8 (c.g.s)

  • c = 3 x 1010 cm/sec,

  • k = 1.38 x 10-16

  • h = 6.626 x 10-27

  • mH ~ mproton = 1.67 x 10-24 grams

  • me = 0.91 x 10-27 grams

  • eV = 1.602 x 10-12 erg

  • Luminosity of Sun = 4 x 1033 erg/sec

  • Mass of the Sun= 2 x 1033 grams


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The Physics of EM Radiation

  • Light: l, n

  • - l n = c = 2.998 x 1010 cm/s (in vacuum)

  • - E = h n Photon energy (erg)

  • 1 erg sec-1 = 10-7 Watt

  • h = 6.626 x 10-27 (c.g.s)

  • 1 eV = 1.602 x 10-12 erg

  • - p = E / c = h / l Photon momentum

  • - l = h / p = h / mv deBroglie wavelength

  • Planck Function: B(T)

  • Emission, absorption, continua

  • Discrete energy levels: Hydrogen


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Refraction:

Snell’s Law: n1 sin(d1) = n2 sin(d2)

d1

n1

n1 = refractive index in region 1

n2 = refractive index in region 2

n = c / v = lvacuum / lmedium

d2

n2




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L

d

Diffraction:

Light spreads asq = l / d

In the `far field’ given byL = d2 / l


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2 slit interference

Constructive

Destructive


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2 slit interference

Anti-reflection coating




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Fermat’s Principle: d(optical path length) = 0

Diffraction grating:

order #

wavelength

diffraction angle

groove spacing

incidence angle


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CCD Imaging Review

  • Review CCD basics

  • - How CCDs work

  • - CCD properties

  • Dark, flat, and bias frames

  • Image-scales

  • - focal length, pixel-scale, FOV

  • Review photometry basics

  • - The magnitude system

  • - Calibration

  • - Atmospheric effects; Air mass, color terms


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Subaru 8m (Mauna Kea): Suprime Prime Focus CCD Mosaic

8192 x 8192 pixels using SITe chips (15 mm pixels)


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Typical

Raw image

With a CCD

Cosmic rays

Bad pixels

stars


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CCDs (Charge-Coupled Device)

  • Properties

  • - Quantum efficiency (QE):

  • => 90%

  • - Gain:

  • G = e- /ADU

  • - Dark current:

  • 1 e- / hr to 103e- /sec

  • thermal emission: => Cool to –20 to –150 C

  • - Read Noise:

  • amplifier read-out uncertainty

  • 3 e- to 100 e- per read

  • - Spatial uniformity:

  • Bad pixels, columns: ~ << 1%

  • gain & QE variations

Ee = hn - E0


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CCDs

  • Properties

  • - Cosmic Rays:

  • 5 to > 103 e- produced by each charged particle

  • usually effects 1 or few pixels.

  • non-gaussian charge distribution

  • (different from stellar image or PSF)

  • - Well depth:

  • 5 x 104 to 106 e-

  • - Pixel size:

  • 6 mm to 30 mm

  • - Array size:

  • 512 x 512 to 4096 x 4096


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Dark current:

=> cooling


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MOSAIC CCD

On KPNO 0.9m

Vacuum Dewar

LN2 (77K)

Controller

Filters & slider


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5

10

10

0

Charge Transfer

V

0

10

0

5

5






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  • CCD Corrections/Calibrations

  • Read noise: bias frames

  • - 0 second exposure

  • Dark frames:

  • - Same duration as science exposure with shutter closed

  • Flat fields:

  • - Dome flats

  • - Twilight flats

  • - Super-sky flats

  • Standard stars

  • - At several air-masses

  • A = sec (z) = 1 / cos(z)

z


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  • CCD Corrections/Calibrations

  • Types of image combinations:

  • IRAF task: imarith image1 (+,-,*,/) image2 output

  • imcombine @list_in output

  • - Average: 1/N S I(n)

  • - Mode: Most common data value

  • - Median: Value in middle of range

  • good for rejection of outliers (e.g CRs)

  • Combine (median) 3,5,7,….. An odd #

  • - bias frames

  • - flat frames


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  • CCD Corrections/Calibrations

  • Reduction:

  • I(raw) - median(bias)

  • I(reduced) =

  • norm [median(Flat – bias)]

  • Note: Bias can be a Dark if hot pixels /or dark current is large


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Flat Field Example

star

cosmic ray

Hot pixels

star

Bias or

dark level

Raw science frame

star

cosmic ray

star

Dark subtracted frame


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Flat Field Example

star

cosmic ray

star

cosmic ray

Flat frame


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Flat Field Example

cosmic ray

Flat frame

1

Normalized, dark subtracted, median of > 3 flat frames


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Flat Field Example

cosmic ray

star

Science frame

1

Normalized flat frame

star

star

Reduced science frame


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  • Photometry Basics:

  • Vega magnitudes:

  • m(l) = -2.5 log [F(l) / FVega(l)]

  • F(l) = Counts on source

  • FVega(l) = Counts on Vega

  • A = sec (z) = 1 / cos(z)

z


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Type of Spectra

  • Continuum:

  • - Blackbody: Bn(T)

  • - free-free, free-bound

  • - Non-thermal: Synchrotron radiation

  • - Compton scattering

  • Line & Band

  • E dipole, B diplole, E quadrupole

  • fine structure, hyperfine structure

  • - electronic transitions

  • - vibrational transitions

  • - rotational transition


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Types of Spectra:

Hot,

Opaque

media

Nebulae

Stars


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The Planck Function: Black-body radiation

(erg s-1 cm-2 Hz-1 2 p sr-1)

Wien:

B(n,T) = (2 p hn3 / c2) e-hn/kT

Rayleigh-Jeans:

B(n,T) = 2kT/l2



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Spectrum of Hydrogen (& H-like ions)

Ionization (n to infinity):

E = 13.6 eV

Transitions:

E = hn = Eu – El

Ionizationat

E = 13.6 eV or less than

l = 912 Angstroms

a

b

g

Balmer

  • = R [ 1/nl2 – 1 /nu2]

    R = 3.288 x 1015 Hz

b

a

Lyman


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Bohr model:

Allowed orbits

mvr = nh /2p

Coulomb Force:

Ze2 / r2 = mv2/r

Thus,(eliminate v)

r = Ze2 / mv2 = n2h2 / 4 p2 Ze2 m

Energy E = - (1/2) Ze2 / r = - 2 p2 Z2e4m/ n2h2




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Outline & Goals: Tues, 18 Sept

  • Summary of Kitt Peak Run &Heildelberg

  • Review Spectrum of Hydrogen

  • Spectroscopic `terms’ & terminology

  • (Ch 2, 3; HW #2)

  • Review Transitions (Ch 3): Einstein

  • A, B. Collisional and radiative

  • excitation

  • Spectral line formation & Radiative

  • Transfer basics


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Bohr model:

Allowed orbits

mvr = nh /2p

Coulomb Force:

Ze2 / r2 = mv2/r

Thus,

r = Ze2 / mv2 = n2h2 / 4 p2 Ze2 m

Energy E = - (1/2) Ze2 / r = - 2 p2 Z2e4m/ n2h2


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Spectrum of Hydrogen (& H-like ions)

Ionization (n to infinity):

E = 13.6 eV

Transitions:

E = hn = Eu – El

Ionizationat

E = 13.6 eV or less than

l = 912 Angstroms

a

b

g

Balmer

  • = R [ 1/nl2 – 1 /nu2]

    R = 3.288 x 1015 Hz

b

a

Lyman


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Ionization cross-section or hydrogen

13.6 eV = 912 Angstroms

10-18

Lyman lines

Balmer lines

n-3

Cross-section (cm2)

Wavelength (1 / photon energy)


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Atomic Structure

  • Refinements to Bohr:

  • Elliptical e-orbits

  • Integral of P in r and q = lh l = 0,1,2, …,n-1

  • Relativistic effects => l makes small

  • correction to E-levels

  • Space quantization: Orientation of orbits

  • m

  • Electron spin

  • Pauli: No 2 e- in same state.


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Atomic Structure

  • Atomic quantum numbers:

  • n, l, m, s - completely specify state, E

  • n = 1, 2, 3, 4 ….

  • shell = K L M N ….

  • max ne = 2 8 ….

  • l = 0 1 2 3 4 ….

  • s p d f g ….

  • Selection rules:


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Atomic Structure

  • Refinements to Bohr: n

  • Elliptical e-orbits: k

  • Space quantization: Orientation of orbits

  • w.r.t. magnetic field: m

  • Electron spin: s

  • Pauli: Ferminons:

  • No 2 e- in same state: [n,k,m,s]

  • Shroedinger Wave function:

  • n => principle quantum number (radial)

  • l => orbital angular momentum 0, 1, … n

  • m => magnetic sublevels (degenerate if B=0)

  • s => electron spid +/- 1/2


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Atomic Structure

  • Multi-electron atoms/ions

  • Atomic quantum numbers: s = +/- 1/2

  • n, l, m, s - completely specify state, E

  • l = 0, 1, …, (n-1) m = 0, +/- 1, +/- 2, …, +/- l

  • n = 1, 2, 3, 4 ….

  • shell = K L M N ….

  • l = 0 0, 1 0,1,2 0,1,2,3

  • m = 0 0; -1,0,1 0;-2,-1,0,1,2 0;-3,-2,-1,0,1,2,3 max ne = 2 2+6 = 8 2+8+10 = 20 … (s = +/- 1/2)

  • max l = 0 1 2 3 4

  • s s,p s,p,d s,p,d,e

  • Selection rules: Dl = +/- 1


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n

1

2

3

4


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  • Hydrogen Ha fine structure

  • Review Transitions (Ch 3): Einstein

  • A, B. Collisional and radiative

  • excitation

  • Spectral line formation & Radiative

  • Transfer basics



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Hydrogen energy levels showing fine structure

2s+1

Fine structure const.:

 = e2/ hc = 1/137

Fine structure:

E / E ~ 4 ~ 5x10-5 eV

Spin / orbit (l * s)

3d 2D5/2

3p 2Po3/2

n=3

n=2

n=1

3d 2D3/2

3s 2S1/2

3p 2Po1/2

H

Ly

J=L+S

2p 2Po3/2

2p 2Po1/2

Hyperfine structure:

E ~ 6x10-6 eV

2s 2S1/2

Selection Rules:

l = 0, +/-1

j = 0, +/-1

even <=> odd

L = [l(l+1)]1/2 h/2

S = [s(s+1)]1/2 h/2

J = [J(J+1)]1/2 h/2

l = 0 l = 1 l = 2

S P D

1s 2S1/2


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Einstein A & B coefficients: radiative processes

u

Aul

- Spontaneous decay

Bul

- Stimulated decay (prop to Flux)

Aul

Bul

Blu

Blu

- Absrorption (prop to Flux)

l


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Ionization & Excitation

  • Radiation: Rr = s Irad

  • Collisions: Rc = n s <vthermal>

 = cross section

Vthermal ~ (3 kT / 2 m)1/2

Aul, Bul

Cul

Clu

Blu

Rate Equations:


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Spectral Line Formation &

Radiative Transfer

  • Guidelines for 24” spectroscopy

  • Simple Models for Spectrum Formation

    • emission nebulae

    • absorption line features

    • continuum processes

  • Theory of Spectrum Formation

    • optically thin and optically thick spectra

    • stellar spectra


Emission nebulae l.jpg
Emission Nebulae

  • Atoms in nebulae are excited by:

    • Incident photons

    • Collisions (high temperature or density)

  • Excited atoms decay, emitting a photon of the characteristic energy (a spectral line)

  • If the atoms are ionized, then the nebula will emit free-bound radiation (i.e. Balmer continuum) as well as spectral lines


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Ionization cross-section or hydrogen

13.6 eV = 912 Angstroms

10-18

Lyman lines

n-3

Cross-section (cm2)

Wavelength (1 / photon energy)


Slide73 l.jpg

Emission Nebula

(photo-excited or photo-ionized)

optically thin nebula:

passes most wavelengths

Star emits continuum

- light at energy equal to an atomic transition is absorbed

- that light is then reemitted in a

random direction (some of it towards the observer)

- the nebula may be optically thick at these wavelengths

The only light directed towards

the observer is that which has

energy equal to the atomic

transitions in the nebula:

an emission spectrum




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M82 – Subaru 8-m (Mauna Kea)

Emission line (Ha)

Absorption (dust, NaI, …)

continuum

emission (stars)



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M82 – 21 cm HI (VLA)

M82

M81

NGC3077


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M82 H

M82 radio (6 cm)



Absorption features l.jpg
Absorption Features

  • Continuum light is emitted from a star (or other source)

  • Intervening material absorbs light at wavelengths of atomic transitions, exciting those atoms

  • Excited atoms reemit light, but in a random direction (not towards observer)


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Absorption Feature:

the observer sees all the

wavelengths except those

at the atomic transition energy

an absorption spectrum

Star emits continuum

- light at energy equal to an atomic

transition is absorbed

- that light is then reemitted in a

random direction



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What Does an Absorption Spectrum Look Like in an Image?

Quasar 3C273

Deneb

It looks almost identical to the background object!

All the absorption is in a few lines, the continuum

is relatively unchanged.


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Dark or Reflection Nebula:

optically thick nebula:

-observer can’t see background

object (i.e. star) because light

has been scattered away

- dark nebula

Star emits continuum

dust scatters light

optically thick nebula:

-observer sees cloud shining in

scattered light (a continuum)

-reflection nebula


Continuum phenomena reflection and dark nebulae l.jpg
Continuum Phenomena:Reflection and Dark Nebulae

reflection

  • Dust scatters incident light

  • Not a line process, scatters continuum

dark

dark


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Basic Radiative Transfer Terms

lMFP = mean free path (cm)

au = opacity (cm-1) – cross section per unit volume (aka absorptivity)

lMFP = 1/au

tu = optical depth (unitless)


Optical depth l.jpg
Optical Depth

  • Optical depth measures the attenuation of light

  • The light we see from an optically thick source was emitted at t approximately 1

tu = 1 at s = lMFP


Radiative transfer l.jpg
Radiative Transfer

What does the observer see?

-assume that the background

cloud is opaque (t1 >> 1)

-assume both clouds are uniform

T1

t1>> 1

T2

t2

This equation has two simple limits …


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Optically Thick (tu >> 1)

many scatterings through the cloud

  • Optically Thin (tu << 1)

    • one or fewer scatterings through the cloud on average

contribution from

background cloud

contribution from

foreground cloud

since the foreground cloud is optically thick, all the contribution is from that cloud


Stellar spectra l.jpg
Stellar Spectra:

  • The spectrum of a star forms in its atmosphere

  • The temperature in the atmosphere is stratified

  • The emission at any temperature is a blackbody (for an optically thick source)

  • The opacity is a function of wavelength


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  • At each wavelength, t=1 corresponds to a different depth in the atmosphere and thus a different temperature

  • The opacity in a line is much higher than in a continuum

  • In a line, we see to a very shallow depth in the atmosphere



Slide95 l.jpg

Based upon the previous image, does temperature in the Sun increase or

decrease with height in the atmosphere?

Temperature decreases with height because the lines (which are formed higher up) are darker than the continuum and thus are emitted from a cooler region.

This allows us to probe the temperature of the sun as a function of depth.


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Solar Spectrum Trace: increase or

notice the different linewidths in different lines

and the strong Calcium H & K lines

Ca K

Ca H


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Sun is brighter in center increase or

than at edges. Why?

Solar Limb Darkening


Solar limb darkening98 l.jpg
Solar Limb Darkening increase or

At edge you only see down to a shallower depth (lower temperature) at t~1

At center you see down to a certain depth at t~1


Terminology l.jpg
Terminology increase or

  • Surface brightness is synonymous with temperature

The continuum has a TB of 5,000K

The line has a TB of 10,000K


Terminology radio astronomy l.jpg
Terminology: Radio Astronomy increase or

  • Radio astronomers often plot spectra as TB vs l

    • TB is a physical measurement

    • but only for thermal processes (that are optically thick)

  • Why is this terminology most appropriate for radio astronomy?

    • radio astronomy is well into the R-J tail


Terminology radio astronomy101 l.jpg

0.1 increase or mm

10mm

1mm

Terminology: Radio Astronomy


The cmb spectrum l.jpg
The CMB Spectrum increase or


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Summary & Goals: Oct 4 increase or

  • Discuss observing proposals

  • What we covered:

  • Review EM basics, atomic structure basics

  • Intro to gratings & spectrographs: Grating equation

  • Black-bodies. Fluxes, exposure time estimation

  • The H atom & its spectrum

  • Einstein A & B coefficients; radiative & collision rates

  • Radiative transfer & spectral line formation

  • To be covered by Field Trip:

  • Saha equation: ionization of atoms into successive stages of

  • ionization

  • Stellar classification basics

  • Nebula ionization & excitation: the roles of UV

  • Spectrograph design: optics, matching R, pixels, and seeing

  • Radio astronomy


Slide104 l.jpg

Ionization Balance: (Saha formula) increase or

Each element has an ionization potential for each

every electron: Roman numeral is number

of electrons lost + 1

Netural H = HI

Ionized H = HII

Molecular H = H2

HI – 13.6 eV

HeI – 24.58 eV, HeII – 54.416 eV

CI - 11.26 eV, CII – 25.14 eV, CIII – 47.89 eV, CIV – 64.49 eV,

CV – 392 eV, CVI – 490 eV

OI – 13.6 eV, OII – 35.11 eV, OIII – 54.9 eV

Ca XXI – 5,469 eV


Slide105 l.jpg

Ionization stage increase or

I

II

III

IV

V

Relative abundance

Temperature


Slide106 l.jpg

Saha Formula increase or

Partition function (# of states)

Ionization potential

Electron density

Next ionization stage density

Previous ionization stage density


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Stellar Spectra: increase or Temperature,

Ionization state



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Ionization Balance: Ionized nebulae increase or

HII regions, planetary nebulae: UV

Supernova remnants: shocks

Ionization produced by:

- UV to X-ray radiation fields:

stars, white dwarves, neutron stars, accreting WDs, NS,

and black holes

- Collisions: Shock heated gas

Recombinations: Electrons re-combine with ions

Stromgren (photo-ionization equilibrium):HII regions

Q = (4 p/3) r3 ne2aB

Q = Lyman continuum luminosity (~1049 photons/sec for O7 star)

aB = 2.6 x 10-13 cm3 /sec (Recombination coeff. for H at 10,000 K)


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Thor’s helmet: increase or

NGC 2359

HD 56925


Slide118 l.jpg

S106 star forming region in Cygnus increase or

(Subaru telescope)



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HH 131 increase or

Orion A:

- Outflows up to

30 pc long !

M42

HH34

HH 1/2


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YSOs near massive stars: UV photo-ablation of disks increase or

irradiated jets

d253-535 in M43


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HH 46/47 increase or


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HH 46/47 increase or

HST 1997 - 1994


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HH 46/47 increase or

HST 1997 - 1994


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Stromgren radius of an HII region: increase or

Lyman continuum luminosity of O, B stars:

O3: L(LyC) = 1.0 x 1050 photons s-1 T = 60,000 K

O5: L(LyC) = 4.7 x 1049 photons s-1 T = 48,000 K

O7: L(LyC) = 6.7 x 1048 photons s-1 T = 35,000 K

O9: L(LyC) = 1.7 x 1048 photons s-1 T = 32,000 K

B0: L(LyC) = 4.7 x 1047 photons s-1 T = 30,000 K

B3: L(LyC) = 4.7 x 1045 photons s-1 T = 20,000 K

n = 1000, O5 star:

L(Lyc) ~ n2 r3 aB => r ~ [L(LyC) / n2 aB]1/3

5.6 x 1018 (cm)

1.8 pc


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Photo-ionization equilibrium increase or

(in-class exercise)

Consider an O7 star that emits 1049 Lyman continuum

photons per second which is embedded in a uniform

density cloud with n(H) = 1 cm-3.

- What is the Stromgren radius?

- What is the mass that is ionized?

- How would these answers change if n(H) = 104 cm-3


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  • HII (ionized nebulae) cooled and traced increase or

  • by trace elements & ions

  • Many forbidden transitions have DE ~ 2 eV (visible)

  • long life-times, low decay rates (Einstein A coefficients)

  • Collision rate: Rcoll = n<sv>

  • n ~ 102 cm-3

  • s ~ 10-15cm-2 (for atoms. Depends on v for ions)

  • v ~ (kT / mm)1/2 (sound speed ~ 10 km/s for H

  • at 10,000 K)

  • R ~ 10-7 sec-1 (1 collision every 107 sec)

  • Collision rate ~ decay rate => each ion can radiate

  • Thousands of times before recombining => bright line


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Some common transitions in ionized nebulae: increase or

[SII] 6717/6731 A (density tracer)

[NII] 6748/6784 A

Ha 6563 A

[OI] 6300/6363 A

[OIII] 5007 A

[OII] 3729/3726 A


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Long-slit: increase or

Spectrum

of a planetary

nebula



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Planetary nebula increase or

M57 (Ring nebula)

Objective prism (slitless) spectra:





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n increase or -3

~2 eV

Why `forbidden’ emission lines are bright

13.6 eV

Ha

9.2 eV

Photo-ionization =>

recombination

Collisional

Excitation

<E >~3/2 kT = 1.3 eV @104 K


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Measuring nebular density using [SII] lines increase or

1.4

1.0

[S II] I(6717/6731)

0.6

101 102 103 104

Density (cm-3)


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O star embedded in semi-infinite wall near edge: increase or

n(H)

Q = L(LC) = 1050g s-1

d


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O star next to an infinite wall of hydrogen: increase or

Q = L(LC) = 1050g s-1

d


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Three problems: increase or

Star with a wind spherical cloud star in a pipe


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Ionization Balance: (Saha formula) increase or

Each element has an ionization potential for each

every electron: Roman numeral is number

of electrons lost + 1

Netural H = HI

Ionized H = HII

Molecular H = H2

HI – 13.6 eV

HeI – 24.58 eV, HeII – 54.416 eV

CI - 11.26 eV, CII – 25.14 eV, CIII – 47.89 eV, CIV – 64.49 eV,

CV – 392 eV, CVI – 490 eV

OI – 13.6 eV, OII – 35.11 eV, OIII – 54.9 eV

Ca XXI – 5,469 eV


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Ionization stage increase or

I

II

III

IV

V

Relative abundance

Temperature


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Saha Formula increase or

Partition function (# of states)

Ionization potential

Electron density

Next ionization stage density

Previous ionization stage density


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Stellar Spectra: increase or Temperature,

Ionization state



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Wolf-Rayet stars: increase or

> 60 Solar mass, post-main sequence

WR 124


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2006 APO Field Trip increase or

  • What to Bring:

  • - Pack light (like carry-on on an airplane)

  • - Jacket, hat, gloves (prepare for cold near freezing)

  • - Flashlight

  • - Cash for food (supermarket + stops during drive)

  • - Personal items

  • Where:

  • - Meet at Circle at NW corner of Benson @ 9:00 AM Monday

  • 30 Oct (be early!)

  • Need two volunteers with sleeping bags for Mon night

  • (Socorro)

  • - Return Friday (3 Nov) in the evening.


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2006 APO Field Trip increase or

Itinerary:

- Monday: Drive from Boulder to Socorro, NM (9 - 10 hrs)

- Tuesday: Meet Debra Shepherd at NRAO ~ 8:30 AM

Drive to VLA site (1 hr)

Tour VLA

Return to Socorro - have lunch

Drive to APO (4 hrs) & shop for food

Settle in to dorm rooms / houses

Observe till 1:00 AM (If we are late, remote

observers will operate remotely from Boulder)

- Wed: PM tour of NSO (?) + cook dinner

Observe all night

- Thurs: Sleep during day / observe first half

- Friday: Rise at 8:00 AM, drive back (10 - 11 hrs)


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Project / Observing Summary increase or

Itinerary:

Tues (first half) M17 LBV, Ceph A DIS new high red

Hyades WDs (Audrey, Ward, Nate)

Wed (whole night) Comet Swan (Corey, Julia, Tedd)

Eyepiece on Moon etc.

Metallicity

QSO outflow (Max)

HL/XZ Tau (Alexi, Courtney, Carlee, Beau)

DIS new high red / eyepiece / DIS / SpiCam / eyepiece (dawn):

Orion, NGC1068, Saturn

thurs (first half) APOLLO laser

finish projects as needed.


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Atacama Large Millimeter Array: Sajnantor Chile, ~ 64 12 meter dishes Baselines: 150 meter to 10 km


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ALMA site: Sajnantor Chile, meter dishes Baselines: 150 meter to 10 km

Elevation ~ 5,000 meters!


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