Cosmic rays in the local interstellar medium - GALPROP: Home · PDF fileIgor V. Moskalenko 5 GALPROP Workshop, Dec. 5-6, 2011 Stanford Why is the local interstellar medium? • Can

Igor V. Moskalenko/NASA-GSFC 1 Nuclear Data-2004/09/28, Santa Fe

Cosmic rays in the local interstellar medium

Igor V. MoskalenkoStanford

LMC (Magellanic Cloud Emission Line Survey: Smith, Points)

R - HG - [S II]

B - [O III]

Igor V. Moskalenko 2 GALPROP Workshop, Dec. 5-6, 2011 Stanford

R - HG - [S II]

B - [O III]500 pc

Supergiant shells

~ 1000 pc

~ 107 yr

(multi generations)

Superbubbles ~ 100 pc ~ 106 yr (OB associations)

Bubbles, SNRs ~ 10 - 50 pc ~ 103 – 105 yr (single star)

MCELS: Smith, Points


Red: H Green: [O III]

Blue: X-ray

LMC Superbubble: N11

LMC Superbubble: N57 LMC Superbubble: N70


Motivation

• SNRs are the conventional sources of the majority of CRs

• Multiple SN explosions within a single OB association may have a profound effect on CR spectra and CR distribution in a galaxy

• May leave signatures in isotopic source abundances (e.g. 22Ne)

• The evolution of a SNR shell in a superbubble (rarefied ionized gas) may be quite different from that of a SNR in the typical cold ISM (e.g. may accelerate to higher energies)


Why is the local interstellar medium?

• Can be probed fairly well assuming the spectra of CR species do not change much within ~100 pc (see yesterday’s talk by Seth Digel)

• May have measurable signatures due to the proximity of the sources and propagation effects (e.g. PAMELA positron fraction, breaks in p & He spectra at 230 GV)

• May produce visible effects on the gamma-ray skymaps (e.g features and residuals)


Fermi-LAT residual skymaps (submitted to ApJ)

Model 44: LorimerZ6R20T∞C5 (see Gulli’s talk)

PRELIMINARY


Local Bubble

X-Y plane

X-Z plane


The origin of the Local Bubble

• The LB - low-density region around the Sun, filled with hot/warm H I gas• The size of the region is about 200 pc • It is likely that the LB was produced in a series of SN explosions• Most probably its progenitor was OB star associations• The age ~10 Myr, the last SN explosion was ~1–2 Myr ago, or three SNs

during the last 5 Myr• A detailed study (Abt 2011) shows three different regions with different

ages:– The region towards the Galactic center ~4 Myr (with a pulsar ~4 Myr old)– The central lobe <160 Myr– Pleiades lobe ~50 Myr


450 pc in the solar neighborhood

High density molecular clouds around starforming regions

OB associations

Hot ionized gas

Credit: Frisch


The location of interstellar clouds in the Galactic Plane


Four closest warm clouds

Shapes of the four closest to the heliosphere interstellar clouds (edges within 1-5 pc) in Galactic coordinates Linsky&Redfield’2009


The morphologies of 15 clouds (within 15 pc)

Frisch+’2011


Mean extinction for stars within 500 pc

Frisch’2007

Magenta contours – interaction of Loop I with the LB

Rings – OB associations

Black contours –

the integrated stellar radiation at 1565 Å (TD-1 satellite)


44: LorimerZ6R20T∞C5


Effects on Cosmic Rays


Propagation of CRs

• Effect of the local underdensity on “radioactive clock” isotopes 10Be, 26Al, 36Cl (Donato+’2002)

– Reduces the abundance of radioactive isotopes at the position of the Sun

– 36Cl/Cl is the most sensitive (shortest half-life)

– Affects propagation parameters

• However, the diffusion coefficient in the LB is unknown


Propagation of CRs

• Effect on propagation parameters due to the local component of CRs at low energies (Moskalenko+’2003). Only primary local elements were considered

– Increased abundances of primary elements (C, O, Fe…) at LE

– Secondary elements are produced by Galactic CRs and are not produced by the local CRs

– Affects propagation parameters: more secondaries to be produced Galaxy-wide (e.g., larger B/C)

Galactic

Local


Total inelastic nuclear cross sections

Ekin, MeV/nucleon

² The inelastic cross section gives a probability of interaction

² Rises with the atomic number as ~A2/3

² As the result of interaction the original nucleus is destroyed

Wellisch & Axen 1996


Effective propagation distance: LE nuclei

² The interaction time scale at ~1 GeV – 1 TeV:

τ ~ L/c ~ [σnc]-1 ~ 3×1013/[0.25 (A/12)2/3] s ~ 3×106 yr (A/12)−2/3

σCarbon(A=12) ≈ 250 mb;n ~ 1 cm−3 (in the plane)

² The diffusion coefficient (4 kpc halo):

D ~ 3×1028 R1/2 cm2/s, R – rigidity in GV

² Effective propagation distance (in the plane):

<X> ~ √6Dτ ~ 4.5×1021 R1/4 (A/12)−1/3 cm ~ 1.5 kpc R1/4 (A/12) −1/3

Helium: ~ 2.1 kpc R1/4

Carbon: ~ 1.5 kpc R1/4 0.36% of the surface area (25 kpc radius)

Iron: ~ 0.9 kpc R1/4 0.16%

(anti-) protons:~ 6 kpc R1/4 5.76%

² γ-rays: probe CR p (pbar) and e± spectra in the whole Galaxy ~50 kpc across


Direct probes of CR propagation

² Direct measurements probe a very small volume of the Galaxy

² The propagation distances are shown for rigidity ~1 GV

50 kpc

pC

Fe


Energy losses of electrons

² The ionization and Coulomb losses are calculated for the gas number density 0.01 cm-3

² Energy density of the radiation and magnetic fields 1 eV cm-3 (Thomson regime)


Effective propagation distance: HE electrons

² The energy loss time scale (IC) at ~1 GeV – 1 TeV:

τ~ 300 E12−1 kyr ~ 1013 E12−1 s; E12 – energy in TeV

² The diffusion coefficient:

D ~ (0.5-1)×1030 E121/2 cm2/s

² Effective propagation distance:

<X> ~ √6Dτ ~ 5×1021 E12−1/4 cm ~ 1 kpc E12−1/4

~ a few kpc at 10 GeV

² The cutoff energy of the electron spectrum ~1 TeV can be used to estimate the distance to the local HE electron sources: ≥ a few 100 pc.


Direct probes of CR propagation

² Direct measurements probe a very small volume of the Galaxy

² The propagation distances are shown for nuclei for rigidity ~1 GV, and for electrons ~1 TeV

50 kpc

p, 10 GeV eC

Fe, TeV e

Igor V. Moskalenko 24 GALPROP Workshop, Dec. 5-6, 2011 StanfordWR-124 in Sagittarius—Hubble Image

The origin of cosmic rays


Detailed comparison

Good

Xsections

Well-known

15N33S

55Mn

41Ca*

53Mn*40Ca

22Ne

20Ne

32S

F

P

ScTiV

IM+’2007



A-dependence of the source abundance ratio

Meyer+’1997


0.25

0.3

0.4

0.5

0.60.70.80.9

1

2

3

4

5

66

76G

e/74

Ge

72G

e/74

Ge

70G

e/74

Ge

71G

a/69

Ga

68Z

n/64

Zn

66Z

n/64

Zn

65C

u/63

Cu

WR Model CRIS data (Binns et al. 2005)Combined data corr for volatility New CRIS UH-Isotopes

Rat

io R

elat

ive

to S

ola

r S

yste

m A

bun

danc

es

64N

i/58N

i

62N

i/58N

i

61N

i/58N

i

60N

i/58N

i

58F

e/56

Fe

12C

/16O

13C

/12C

14N

/16O

22N

e/20

Ne

23N

a/24

Mg

25M

g/24

Mg

26M

g/24

Mg

29S

i/28S

i30

Si/28

Si

34S

/32S

54F

e/56

Fe

57F

e/56

Fe

N/N

e

Model source abundance:

80% solar + 20% Wolf-Rayet

Relative isotopic source abundance

Binns+’2011

• Why Wolf-Rayet material is so important?


Schematic OB association timeline

Binns+’2008


Elemental Abundances relative to 80/20 mix of SS and massive

star outflow (MSO)

10 20 30 40 50 60 70 80 90100

0.1

1

GC

RS

/Lod

ders

-SS

Atomic Mass

Mg

Al

Si

P

CaFe

Co

Ni

Sr

N

Ne S

Ar

Cu

Zn

Ga

Ge

Se

Refractories

Volatiles

TIGER-LDB/Meetings/COSPAR-2010/100-0 mix_TIGER_Bobs_fits

TIGER+HEAO-C2 data

TIGER+HEAO-3 data

Elemental Abundances relative to SS only

Rauch+’2009


Same dependence at TeV energies

ACE/CRIS CREAM

Rauch+’2009 Ahn+’2010


Backup slides


THANKS TO EVERYBODY AND ESPECIALLY TO GUESTSWHO MADE IT TO STANFORD !


First Ionization Potential (FIP) vs. Volatility

• Low-FIP ~ Refractories• Rb, Cs – break the rule• Other important elements: Na,

Cu, Zn, Ga, Ge, Pb

Rb

CsK

Pb

GeGa

Na

Zn

Se

Cu

~104 K

Meyer, Drury, Ellison’1997


Rauch+’2009

36

Measured isotopic abundance ratios compared to Solar System Abundances (Lodders, 2003)

36

0.0

0.2

0.4

0.6

0.8

1.0

1.2

70/64

Ratio SS(Lodders)

Rat

io

65/63

Cu Zn Ga Ge

66/64 68/64 71/69 70/74 72/74 76/74

7_29_11_ICRC-Isotope_corrections/Isotope_ratio_figure.opj

• Abundances corrected for

– nuclear interactions in instrument

– Energy intervals• Abundances include

first order leaky box propagation back to the source

37

Comparison with 80%/20% mix of Solar System and WR material

37

• For these isotope ratios, the 80/20 mix is very similar to pure SS, within the accuracy of our measurement

• Measured ratios are consistent with either pure Solar System or an 80/20 mix of SS and massive star ejecta

0.0

0.2

0.4

0.6

0.8

1.0

1.2

70/64

Ratio SS(Lodders) 80%/20% SS/WR mix

Rat

io

65/63

Cu Zn Ga Ge

66/64 68/64 71/69 70/74 72/74 76/74

7_29_11_ICRC-Isotope_corrections/Isotope_ratio_figure.opj

38

30 32 34 36 38 40

1E-6

1E-5

1E-4

1E-3

ACE HEAO-C2 TIGERSolar System (LPK 2009)

Rel

ativ

e A

bund

ance

(F

e=1)

Charge (Z)

Abundances at thetop of the atmosphere

8_2_11-Element ICRC paper/Abund_rel_Fe_ACE_TIG_HEAO

Elemental Abundances Relative to Fe

Correction factors for saturated pulse heights at high-Z:

Z Corr

34 1.03

36 1.2

38 1.57

40 2.39

39

In Context of Previous Data at Lower Charge

39

0.25

0.3

0.4

0.5

0.60.70.80.9

1

2

3

4

5

66

76 G

e/7

4 Ge

72 G

e/7

4 Ge

70 G

e/7

4 Ge

71 G

a/6

9 Ga

68 Z

n/6

4 Zn

66 Z

n/6

4 Zn

65 C

u/6

3 Cu

WR Model CRIS data (Binns et al. 2005)Combined data corr for volatility New CRIS UH-Isotopes

R

atio

Rel

ativ

e to

Sol

ar S

yste

m A

bun

danc

es

64 N

i/58 N

i

62 N

i/58 N

i

61 N

i/58 N

i

60 N

i/58 N

i

58 F

e/5

6 Fe

12 C

/16 O

13 C

/12 C

14 N

/16 O

22 N

e/2

0 Ne

23 N

a/2

4 Mg

25 M

g/2

4 Mg

26 M

g/2

4 Mg

29 S

i/28 S

i3

0 Si/2

8 Si

34 S

/32 S

54 F

e/5

6 Fe

57 F

e/5

6 Fe

N/N

e

Binns+’2011

40

10 20 30 40 50 60 70 80 90100

0.1

1

TIGER Vol (gas) TIGER Ref (grains) HEAO-C2 VolHEAO C2 Ref HEAO C2-Mixed Vol & Ref ACE-Volatiles ACE-Refractories

GC

R S

ourc

e/(8

0% S

S +

20%

MS

O) (

Fe=1

)

Atomic Mass (A)8_2_11-Element ICRC paper/Spirce_GCRs_vs_Mass_80-20.opj

TIGER

ACE

Refractory

VolatileN

O

Ne

MgAl

Si

P

S

Ar

Ca Fe

Ni

Sr

Cu

Zn

Ga

Ge

Se

Elemental Abundances relative to 80/20 mix of SS and MSO

10 20 30 40 50 60 70 80 90100

0.1

1

GC

RS

/Lod

ders

-SS

Atomic Mass

Mg

Al

Si

P

CaFe

Co

Ni

Sr

N

Ne S

Ar

Cu

Zn

Ga

Ge

Se

Refractories

Volatiles

TIGER-LDB/Meetings/COSPAR-2010/100-0 mix_TIGER_Bobs_fits

TIGER+HEAO-C2 data

TIGER+HEAO-3 data

Elemental Abundances relative to SS only

Documents

Cosmic rays in the local interstellar medium - GALPROP: Home · PDF fileIgor V. Moskalenko 5 GALPROP Workshop, Dec. 5-6, 2011 Stanford Why is the local interstellar medium? • Can