I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–1

Spi

ralG

alax

ies

SD

SS

Gal

axy

clas

sific

atio

nvi

ath

eH

ubbl

e“t

unin

gfo

rkdi

agra

m”:

“ear

lyty

pes”

:el

liptic

alga

laxi

es;“

late

type

s”:

spira

lgal

axie

s.

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–3

Spi

ralG

alax

ies

2

Spi

ralG

alax

ies

Mo

de

rate

ly

me

tal−

ric

h

Old

, m

eta

l−p

oo

r

to s

up

er

me

tal ri

ch

Ha

lo

Bu

lge

Old

, m

eta

l−p

oo

r st

ars

Da

rk H

alo

Old

−Y

ou

ng

Dis

k

up

to

>1000st

ars

pc

−3

0.1

sta

r p

c−

3

(afte

rP

rant

zos,

2008

;Pag

el,2

009)

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–4

Spi

ralG

alax

ies

3

Spi

ralG

alax

ies

Des

pite

man

ypr

oble

ms,

itis

ofte

npo

ssib

leto

roug

hly

clas

sify

star

sin

todi

ffere

nt

popu

latio

ns:

Pop

ulat

ion

Typi

cals

tars

Vel

ocity

Dis

p.S

hape

Abu

ndan

ce

(km

s−1)

wrt

.H

Hal

opo

p.II

glob

ular

clus

ters

130

sphe

rical

0.00

3

red

gian

ts

Inte

rmed

iate

high

-vst

ars

50in

term

edia

te0.

01

pop.

II

Dis

kpo

p.30

inte

rmed

iate

0.02

Inte

rmed

iate

star

sw

ith20

inte

rmed

iate

0.03

pop.

Ist

rong

lines

Ext

rem

ebl

ue10

Fla

t0.

04

pop.

Isu

perg

iant

saf

ter

Com

bes

etal

.

Opt

ical

light

:em

issi

onfr

om

Gal

axie

sis

dom

inat

edby

emis

sion

from

•st

ars

•em

issi

onne

bula

e

M90

(SD

SS

)

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–6

Dis

trib

utio

nof

Sta

rligh

t2

Sta

rligh

t

Left:

R-b

and

isop

hote

sof

NG

C73

31,M

iddl

e:R

-ban

dim

age

&C

Oem

issi

on,R

ight

:Hα

(SG

Fig

.5.3

).

The

reis

lots

ofst

ruct

ure

onga

laxy

imag

es:

Bul

ge:

circ

ular

isop

hote

s=⇒

sphe

rical

dist

ribut

ion

Dis

k:is

opho

tes

ellip

tical

=⇒

proj

ectio

nef

fect

incl

inat

ion:

∼75

◦

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–7

Dis

trib

utio

nof

Sta

rligh

t3

Dis

k

Toge

trid

ofst

ruct

ure:

aver

-

age

over

disk

=⇒

surf

ace

brig

htne

sspr

ofile

(Sei

gar

etal

.,20

02,F

ig.1

a)

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–8

Dis

trib

utio

nof

Sta

rligh

t4

Dis

k

NG

C73

31:

Sur

face

brig

htne

ssin

I-ba

nd(∼

8000

Å)

(SG

,Fig

.5.4

);N

ote:

mag

nitu

des

are

loga

rithm

ic:

5m

ag=

fact

or10

0!

Gen

eral

lysu

rface

brig

hnes

s

give

nin

mag

arcs

ec−

2,w

hich

isin

depe

nden

tofd

ista

nce.

For

hist

oric

alre

ason

sed

ge

ofdi

skde

fined

asw

here

I B=

25m

agar

csec

−2

(R25

-rad

ius)

Als

oso

met

imes

used

:H

olm

berg

-rad

ius

(IB

=26

.5m

agar

csec

−2)

For

man

ysp

irals

disk

com

pone

ntw

ellm

odel

edby

I(R

)=

I 0ex

p(−

R/h

R)

(4.1

)

whe

resc

ale

leng

th1

kpc

.h

R.

10kp

can

dw

here

typi

cally

I 0,B∼

22m

agar

csec

−2.

Not

eth

atsu

rface

brig

htne

ssis

high

erby

1/co

si

whe

ndi

skis

tilte

d.

R.G

endl

er

UG

C36

97(“

Inte

gral

sign

gala

xy”,

asu

pert

hin

gala

xy;N

RA

O/A

UI)

Ver

tical

stru

ctur

e(z

-dire

ctio

n):

surfa

cebr

ight

ness

wel

ldes

crib

edby

I(R

,z)

=I(R

)ex

p

{

−|z|

hz

}

whe

reh

z∼

0.1h

R(4

.2)

Bul

ge:

wel

ldes

crib

edby

deV

auco

uleu

rs’l

aw:

log

(

I(R

)

I e

)

=−

3.33

07

[

(

R Re

)

1/4

−1]

(4.3

)

whe

reR

e:ef

fect

ive

radi

us,i

.e.,

radi

usco

ntai

ning

inha

lfof

the

tota

llum

inos

ity

Thi

sla

wis

also

valid

for

ellip

tical

s

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–12

Dis

trib

utio

nof

Sta

rligh

t8

Seq

uenc

eof

Dis

kG

alax

ies

SG

(Fig

.5.6

)

S0

gala

xies

are

lum

inou

san

dre

d,w

hile

Sc

and

late

rar

efa

inte

ran

dbl

uer

Sd:

nobu

lge

visi

ble,

Sm

:M

agel

lani

csy

stem

s

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–13

Dis

trib

utio

nof

Sta

rligh

t9

Seq

uenc

eof

Dis

kG

alax

ies

SG

(Fig

.5.2

4)

gala

xysp

ectr

a=

∑

cons

titue

nt

spec

tra

•S

0:m

ainl

yab

sorp

tion

lines

from

cool

Kst

ars,

Ca

H,K

from

G-

type

star

s

•S

c:m

ainl

ybl

uean

dU

Vem

is-

sion

,i.e

.,ho

tand

youn

gst

ars;

emis

sion

lines

from

phot

oion

ized

emis

sion

nebu

lae

•S

tarb

urst

:si

gnifi

cant

phot

oion

-

izat

ion

pres

ent(

see

late

r)

Mul

ti-C

olor

Imag

eof

NG

C73

31,I

SM

mas

s

is5×

109M

⊙.

Dis

trib

utio

nof

gas

indi

skm

ainl

ydo

neus

ing

21cm

imag

ing,

dust

usin

gIR

obse

rvat

ions

We

can

gene

rally

trac

eH

Ito

1019

Hat

oms

cm−

2,o

r∼

0.1M

⊙pc

−2.

(Reg

anet

al.,

2004

)

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–16

Dis

trib

utio

nof

Gas

and

Dus

t3

Dis

trib

utio

nof

Gas

and

Dus

t

The

dist

ribut

ion

ofdi

ffer-

entI

SM

com

pone

nts

in

Milk

yW

ayis

typi

calf

or

gala

xies

.

H16

6α:

reco

mbi

natio

nlin

e,

trac

esH

IIre

gion

s

γ:

brig

htne

ssin

γ-r

ays

Com

bes

etal

.(F

ig.2

.6)

•Le

ft:3.

6µ

m:

red

gian

tsta

rs

•M

iddl

e:0.

8µ

m,s

tar

subt

ract

ed:

PAH

s

•R

ight

:C

O(1

-0)

mos

aic

(circ

le:

oute

rra

nge

ofde

tect

ion)

(Reg

anet

al.,

2006

,Fig

.1)

Rad

iali

nten

sity

profi

les:

•re

d:PA

H

•bl

ue:

CO

•m

agen

ta:

ratio

(Reg

anet

al.,

2006

,Fig

.3)

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–19

Dis

trib

utio

nof

Gas

and

Dus

t6

Dis

trib

utio

nof

Gas

and

Dus

t

SG

(Fig

.5.1

5)

•op

enci

rcle

s:M

ass

ofH

Iga

sas

func

tion

ofR

25(n

ote:

∝R

2 25;s

lope

:10

M⊙

pc−

2)

•fil

led

circ

les:

diam

eter

whe

resu

rface

dens

itydr

ops

to1

M⊙

pc−

2(s

lope

:3.

6M

⊙pc

−2

with

in

diam

eter

)

=⇒

HIdi

skex

tend

sge

nera

llyto∼

2R25

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–20

Dis

trib

utio

nof

Gas

and

Dus

t7

Dis

trib

utio

nof

Gas

and

Dus

t

The

IRlu

min

osity

and

the

CO

lum

inos

-

ity(=

H2-c

onte

nt)

ofsp

irals

are

gene

rally

corr

elat

ed.

Line

:m

ilky

way

LIR/M

H2:

good

indi

cato

rfo

rst

arfo

rma-

tion,

for

norm

alsp

irals

ratio

is1.

..3,

for

star

burs

ts20

–30,

for

“IR

AS

-gal

axie

s”

can

reac

h20

0.

Com

bes

etal

.(F

ig.2

.11)

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–21

Mag

netic

Fie

lds

1

Syn

chro

tron

radi

atio

n

Mag

netic

field

s:tr

ace

thro

ugh

sync

hrot

ron

radi

atio

nfr

omel

ectr

ons

mov

ing

arou

ndB

-fiel

dlin

es.

Lore

ntz-

forc

e(G

auss

ian

units

!):

dp dt

=e cv

×B

whe

rep

=m

ev

√

1−

β2

=γm

ev

with

γ=

1√

1−

β2

and

β=

v c(4

.4)

The

refo

reth

eac

cele

ratio

nis

dv dt

=e

cγm

ev×

B(4

.5)

Sin

cev×

Bis

alw

ays

perp

endi

cula

rto

van

dB

,the

com

pone

ntof

val

ong

the

B-fi

eld

does

not

chan

ge.

Thi

sco

nsta

ntpe

rpen

dicu

lar

forc

ere

sults

toa

helic

alm

otio

nar

ound

the

B-fi

eld

line

with

the

freq

uenc

y

ωB

=eB γm

ec

=ω

L γw

ithth

eLa

rmor

freq

uenc

yω

L=

2πν L

=eB m

ec

(4.6

)

For

typi

calI

SM

valu

es,t

heLa

rmor

freq

uenc

yan

dLa

rmor

radi

usar

e

ν L=

2.8×

106B

10−

6G

MH

zan

dR

L=

γv ⊥ ω

L∼

2A

U·

E

1G

eV·

(

B

10−

6G

)

−1

(4.7

)

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–22

Mag

netic

Fie

lds

2

Syn

chro

tron

radi

atio

n

12

∆θ

a

1/γ

Obs

erve

r

(afte

rF

ig.6

.2of

Ryb

icki

&Li

ghtm

an,1

979)

Ele

ctro

nsar

eac

cele

rate

d,an

dth

eref

ore

radi

ate.

For

rela

tivis

ticel

ectr

ons:

radi

atio

nis

forw

ard

beam

edin

toco

new

ithop

enin

gan

gle

∆θ∼

1/γ

.In

the

Ele

ctro

nfr

ame

ofre

st:

beam

pass

esob

-

serv

erdu

ring

time

∆t

=∆

θ

ωB

=m

ecγ

eB

2 γ=

2 ωL

(4.8

)

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–22

Mag

netic

Fie

lds

3

Syn

chro

tron

radi

atio

n

12

∆θ

a

1/γ

Obs

erve

r

(afte

rF

ig.6

.2of

Ryb

icki

&Li

ghtm

an,1

979)

Obs

erve

rfr

ame:

Dop

pler

effe

ct!

(ele

ctro

nis

clos

erto

usat

end

oftim

ein

terv

al)

=⇒

obse

rved

puls

edu

ratio

n:

τ=

(

1−

v c

)

∆t

=(1

−β

)∆t

(4.9

)

I

EF

CO

DRI

L

AI

N

R

DN

XAEA

ESII

C

M LMV

A

AI

AD

R

E

LGE

4–23

Mag

netic

Fie

lds

4

Syn

chro

tron

radi

atio

n

ν5/

2

ν−

(p−

1)/2

log

freq

uenc

y

log flux

afte

rS

hu(1

991,

Fig

.18.

6)A

tlow

ν:

sync

hrot

ron

emitt

ing

elec

tron

sca

nab

sorb

sync

hrot

ron

phot

ons:

sync

hrot

ron

self-

abso

rptio

n.

For

apo

wer

law

elec

tron

dist

ribut

ion∝

E−

p,t

otal

spec

tral

shap

eca

nbe

show

nto

be:

For

low

freq

uenc

ies:

Pν∝

B−

1/2ν

5/2

(inde

pend

ento

fp!)

For

larg

efr

eque

ncie

s:P

ν∝

ν−

(p−

1)/2

One

ofte

nus

esth

ete

rms

optic

ally

thic

k/th

into

desc

ribe

the

abso

rbed

/una

bsor

bed

part

ofa

sync

hrot

ron

spec

trum

.T

hetu

rnov

erde

scrib

esth

eτ

=1

surfa

ce,e

.g.,

ofa

jet.

Inge

nera

l:τ∝

R(R

:si

zeof

the

emit-

ting

regi

on).

Mor

eco

mpa

ctre

gion

sar

eop

tical

lyth

ick,

mor

eex

tend

edre

gion

sar

eop

tical

lyth

in.

Inad

ditio

nto

spec

tral

shap

e,sy

nchr

otro

n

radi

atio

nis

stro

ngly

pola

rized

.

Pol

ariz

atio

nca

nbe

used

tofin

dB

-fiel

d

vect

ors!

B-fi

eld

vect

ors

infe

rred

from

the

degr

eeof

pola

rizat

ion

in

spira

lgal

axy

M51

by

rota

tion

ofth

eob

serv

ed

E-fi

eld-

vect

ors

by90

◦

(Nei

ning

er19

92,A

&A

263,

30)

4–24

Pag

elB

.E.J

.,20

09,

Nuc

leos

ynth

esis

and

Che

mic

alE

volu

tion

ofG

alax

ies,

CU

P,C

ambr

idge

,2n

ded

ition

Pra

ntzo

sN

.,20

08,

In:

C.C

harb

onne

l&J.

-P.Z

ahn

(ed.

)S

tella

rN

ucle

osyn

thes

is:

50ye

ars

afte

rB

2FH

,Vol

.32.

EA

SP

ubl.

Ser

.,p.

311

Reg

anM

.W.,

Tho

rnle

yM

.D.,

Ben

doG

.J.,

etal

.,20

04,A

pJS

154,

204

Reg

anM

.W.,

Tho

rnle

yM

.D.,

Vog

elS

.N.,

etal

.,20

06,A

pJ65

2,11

12

Ryb

icki

G.B

.,Li

ghtm

anA

.P.,

1979

,R

adia

tive

Pro

cess

esin

Ast

roph

ysic

s,W

iley,

New

York

Sei

gar

M.,

Car

ollo

C.M

.,S

tiave

lliM

.,et

al.,

2002

,AJ

123,

184

Shu

F.H

.,19

91,

The

Phy

sics

ofA

stro

phys

ics,

Vol

.I.R

adia

tion,

Uni

vers

ityS

cien

ceB

ooks

,Mill

Val

ley,

CA