Gas, dust, & cosmic rays in nearby clouds

(Cham, Tau, Cal, Per, Cet)

Isabelle Grenier, Quentin Remy, on behalf of the Fermi LAT Collaboration AIM, Université Paris Diderot & CEA Saclay

∲ermi

Fermi-LAT > 1 GeV

Planck + IRAS

γ rays & dust tracing of the total gas

Ferm

i 6 y

ears

> 1

GeV

Pla

nck+

.XI,

2014

, A&

A

∲ermi

Fermi-LAT > 1 GeV

Dark Neutral Medium: opt. thick HI + CO-dark H2, unknown fractions

Planck + IRAS

γ rays & dust tracing of the total gas

Ferm

i 6 y

ears

> 1

GeV

Pla

nck+

.XI,

2014

, A&

A

6 clouds 150-410 pc

2 clouds 150 + ? pc

CO

DNM

HI

21 cm

115

GH

z

353

GH

z

Cal Tau Per Cet Cha

∲ermi

30% variations locally consistent with uncertainties in the derivation of HI column densities

no trend with radial distance in the Galaxy (too short a span) no trend with altitude above/below the Galactic plane

local gas emissivities (0.4-10 GeV)

−150 −100 −50 0

5

5.5

6

6.5

7

7.5

HI

γ−

ray e

mis

sivit

y [

10

−2

7 γ

s−

1 s

r−1 H

−1]

Heigth above Galactic plane [pc]

Cet

TauS

TauN

TauM

Cal

Per

Ori

Cep−Pol

RCrA

Cha

IVA

PRELIMINARY

8.2 8.4 8.6 8.8 9

5

5.5

6

6.5

7

7.5

Galactocentric radius [kpc]

HI

γ−

ray e

mis

sivit

y [

10

−27 γ

s−

1 s

r−1 H

−1]

Cet

TauSTauN

TauM Cal

Per

Ori

Cep−Pol

RCrACha

IVA

PRELIMINARY

Rem

y et

al.,

in p

rep

Rem

y et

al.,

in p

rep

∲ermi

no spectral deviations across the HI, DNM, and H2 gas phases, down to pc scale ≈ uniform CR penetration at the current precision

uniform CR penetration inside clouds

Planck+Fermi ’15, A&A 582, 31

3 3.5 4 4.5 5

1

1.2

1.4

1.6

3 3.5 4 4.5 5

1

1.2

1.4

1.6

qH

I/qL

IS

3 3.5 4 4.5 5

1

1.5

2

2.5

3 3.5 4 4.5 5

1

1.5

2

2.5

qC

O/q

LIS

3 3.5 4 4.5 52.5

3

3.5

4

4.5

5

5.5

qff

/qL

IS

logE [Mev]3 3.5 4 4.5 5

4

5

6

7

8

q/q

LIS

logE [Mev]

Per

TauSTauM

TauNCet

Cal

DNM

COsat

free−free

log(E) [MeV]3 3.5 4 4.5 5

q

1

1.5

2

2.5

3

HICha

HIIVA

CO

DNM

HICha

HIIVA

CO

DNM

PRELIMINARY

Remy et al., in prep

∲ermi

no spectral deviations across the HI, DNM, and H2 gas phases, down to pc scale ≈ uniform CR penetration at the current precision

uniform CR penetration inside clouds

Planck+Fermi ’15, A&A 582, 31

3 3.5 4 4.5 5

1

1.2

1.4

1.6

3 3.5 4 4.5 5

1

1.2

1.4

1.6

qH

I/qL

IS

3 3.5 4 4.5 5

1

1.5

2

2.5

3 3.5 4 4.5 5

1

1.5

2

2.5

qC

O/q

LIS

3 3.5 4 4.5 52.5

3

3.5

4

4.5

5

5.5

qff

/qL

IS

logE [Mev]3 3.5 4 4.5 5

4

5

6

7

8

q/q

LIS

logE [Mev]

Per

TauSTauM

TauNCet

Cal

DNM

COsat

free−free

log(E) [MeV]3 3.5 4 4.5 5

q

1

1.5

2

2.5

3

HICha

HIIVA

CO

DNM

HICha

HIIVA

CO

DNM

total

gas t

racin

g in γ

rays

PRELIMINARY

Remy et al., in prep

∲ermi

DNM traced by CR & dust correlation DNM mass if same CR flux in the HI & DNM phases

DNM spatial extent between the diffuse HI and compact CO

gas phases in the Chameleon

Planck+Fermi ’15, A&A 582, 31

HIIVA

Lat

itu

de

[deg

]

-35

-30

-25

-20

-15

-10

HICha

DNM

Longitude [deg]280290300310320

Lat

itu

de

[deg

]

-35

-30

-25

-20

-15

-10

CO

log(NH

)

Longitude [deg]280290300310320

19.7

20.2

20.8

21.3

CODN

M

HI

21 cm115 GHz

353 GHz

∲ermi

DNM traced by CR & dust correlation DNM mass if same CR flux in the HI & DNM phases

DNM spatial extent between the diffuse HI and compact CO

gas phases in the Chameleon

Planck+Fermi ’15, A&A 582, 31

HIIVA

Lat

itu

de

[deg

]

-35

-30

-25

-20

-15

-10

HICha

DNM

Longitude [deg]280290300310320

Lat

itu

de

[deg

]

-35

-30

-25

-20

-15

-10

CO

log(NH

)

Longitude [deg]280290300310320

19.7

20.2

20.8

21.3

CODN

M

HI

21 cm115 GHz

353 GHz

∼76%

∼15% ∼8%

∲ermi

MDNM only assumption: qHI = qDNM DNM spatial extent between the diffuse HI and compact CO

gas phases in Taurus-Perseus-California

76% ± 1%

15% ± 1% 8% ± 1%

Lat

itude

[deg

]

HI

−50

−40

−30

−20

−10

Longitude [deg]

CO

140150160170180190

DNM

Longitude [deg]

Lat

itude

[deg

]

HII

140150160170180190

−50

−40

−30

−20

−10

lo

g(N

H)

[cm

−2]

19.5

20

20.5

21

21.5

22

Remy et al., in prep

PREL

IMIN

ARY

∲ermi

MDNM only assumption: qHI = qDNM DNM spatial extent between the diffuse HI and compact CO

gas phases in Taurus-Perseus-California

76% ± 1%

15% ± 1% 8% ± 1%

Lat

itude

[deg

]

HI

−50

−40

−30

−20

−10

Longitude [deg]

CO

140150160170180190

DNM

Longitude [deg]

Lat

itude

[deg

]

HII

140150160170180190

−50

−40

−30

−20

−10

lo

g(N

H)

[cm

−2]

19.5

20

20.5

21

21.5

22

Remy et al., in prep

≈ 60% ≈ 21%

≈ 19%PR

ELIM

INA

RY

∲ermi

MDNM only assumption: qHI = qDNM DNM spatial extent between the diffuse HI and compact CO

gas phases in Taurus-Perseus-California

76% ± 1%

15% ± 1% 8% ± 1%

Lat

itude

[deg

]

HI

−50

−40

−30

−20

−10

Longitude [deg]

CO

140150160170180190

DNM

Longitude [deg]

Lat

itude

[deg

]

HII

140150160170180190

−50

−40

−30

−20

−10

lo

g(N

H)

[cm

−2]

19.5

20

20.5

21

21.5

22

Remy et al., in prep

≈ 60% ≈ 21%

≈ 19%PR

ELIM

INA

RY

large

DNM co

ntrib

ution

to th

e tot

al clo

ud m

ass

∲ermi

significant increase in grain emission cross section grain evolution across all phases, more pronounced in CO

gas tracing with dust emission

15 Tdust [K] 20

τ 353

/ N

Hmλ

[10-2

6 cm

2 ]

2

4

6

~ AV

Q[m

ag]

0

1

2

3

4

5

NH. [1020 cm!2]10 20 30 40 50

~ AV

Q=N

H.

[10!

22m

agcm

2]

5

6

7

8

9

10

~= 353

[#105]

0

5

10

NH. [1020 cm!2]10 20 30 40 50

~= 353

=N

H.

[10!

27cm

2]

10

15

20

25

~ R[1

0!

7W

m!

2sr!

1]

0

5

10

1 10 100 1000

NH. [1020 cm!2]10 20 30 40 50

4:~ R=N

H.

[10!

31W

]

3

4

5

61 2 3 4 5 NHγ [1021 cm-2]

0 0.2 0.4 0.6 0.8 1

1

2

3

4

5

τ3

53/N

Hm

λ [

10

−2

6 c

m2 H

−1]

0 0.2 0.4 0.6 0.8 1

0.5

1

1.5

2

NH2

/NHmλ

AV

Q/N

Hm

λ [

10

−2

2 m

ag. cm

2 H

−1]

20.5 21 21.5 22

1

2

3

4

5

20.5 21 21.5 22

0.5

1

1.5

2

log(NHmλ

) [cm−2

]

15 20 25

1

2

3

4

5

15 20 25

0.5

1

1.5

2

Tdust

[K]

Tdust [K]

τ 353

/ N

Hmλ

[10-2

6 cm

2 ]

x 4.6

x 3Ta

urus

-Per

seus

-Cal

iforn

ia

C

ham

aele

on

PRELIMINARY

PRELIMINARY

Plan

ck+

Ferm

i ’15

, A&

A 5

82, 3

1

Rem

y et

al.,

in p

rep

PRELIMINARY

Rem

y et

al.,

in p

rep

Plan

ck+

Ferm

i ’15

, A&

A 5

82, 3

1

∲ermi

significant increase in grain emission cross section grain evolution across all phases, more pronounced in CO

gas tracing with dust emission

15 Tdust [K] 20

τ 353

/ N

Hmλ

[10-2

6 cm

2 ]

2

4

6

~ AV

Q[m

ag]

0

1

2

3

4

5

NH. [1020 cm!2]10 20 30 40 50

~ AV

Q=N

H.

[10!

22m

agcm

2]

5

6

7

8

9

10

~= 353

[#105]

0

5

10

NH. [1020 cm!2]10 20 30 40 50

~= 353

=N

H.

[10!

27cm

2]

10

15

20

25

~ R[1

0!

7W

m!

2sr!

1]

0

5

10

1 10 100 1000

NH. [1020 cm!2]10 20 30 40 50

4:~ R=N

H.

[10!

31W

]

3

4

5

61 2 3 4 5 NHγ [1021 cm-2]

0 0.2 0.4 0.6 0.8 1

1

2

3

4

5

τ3

53/N

Hm

λ [

10

−2

6 c

m2 H

−1]

0 0.2 0.4 0.6 0.8 1

0.5

1

1.5

2

NH2

/NHmλ

AV

Q/N

Hm

λ [

10

−2

2 m

ag. cm

2 H

−1]

20.5 21 21.5 22

1

2

3

4

5

20.5 21 21.5 22

0.5

1

1.5

2

log(NHmλ

) [cm−2

]

15 20 25

1

2

3

4

5

15 20 25

0.5

1

1.5

2

Tdust

[K]

Tdust [K]

τ 353

/ N

Hmλ

[10-2

6 cm

2 ]

x 4.6

x 3Ta

urus

-Per

seus

-Cal

iforn

ia

C

ham

aele

on

PRELIMINARY

PRELIMINARY

Plan

ck+

Ferm

i ’15

, A&

A 5

82, 3

1

Rem

y et

al.,

in p

rep

gas t

racin

g with

dust

emiss

ion if

NH < fe

w 1021 cm

-2

PRELIMINARY

Rem

y et

al.,

in p

rep

Plan

ck+

Ferm

i ’15

, A&

A 5

82, 3

1

∲ermi

hints that Xco increases from dense cores to diffuse envelopes of the clouds

Xco(dust) systematically larger then Xco(γ) because of grain evolution in CO

CO-to-H2 conversion

0 2 4 6 8 10 120.4

0.6

0.8

1

1.2

WCO [K km s−1]

Cet TauS

TauN

TauM

Cal

Per

Cha

Cet TauS

TauN

TauM

Cal

Per

Cha

Cet TauS

TauN

TauM

Cal

Per

Cha

Cet TauS

TauN

TauM

Cal

Per

Cha

Cet TauS

TauN

TauM

Cal

Per

Cha

Cet TauS

TauN

TauM

Cal

Per

Cha

Cet TauS

TauN

TauM

Cal

Per

Cha

0 0.1 0.2 0.3 0.4 0.5 0.60.4

0.6

0.8

1

1.2

SRdense

XC

O [

10

20 c

m−

2K

−1km

−1s]

Cet

TauS

TauN

TauM

Cal

Per

Cha

Cet

TauS

TauN

TauM

Cal

Per

Cha

Cet

TauS

TauN

TauM

Cal

Per

Cha

Cet

TauS

TauN

TauM

Cal

Per

Cha

Cet

TauS

TauN

TauM

Cal

Per

Cha

Cet

TauS

TauN

TauM

Cal

Per

Cha

Cet

TauS

TauN

TauM

Cal

Per

Cha

0 10 20 30 400.4

0.6

0.8

1

1.2

MCO [103 M⊙]

Cet

TauSTauN

TauM

Cal

Per

Cha

Cet

TauSTauN

TauM

Cal

Per

Cha

Cet

TauSTauN

TauM

Cal

Per

Cha

Cet

TauSTauN

TauM

Cal

Per

Cha

Cet

TauSTauN

TauM

Cal

Per

Cha

Cet

TauSTauN

TauM

Cal

Per

Cha

Cet

TauSTauN

TauM

Cal

Per

Cha

PRELIMINARY

PRELIMINARY

SRdense =SWCO>7Kkm/s

SWCO>1Kkm/s

1 2 3 4 5 6 71

1.5

2

2.5

τ353[105]

XC

O

dust /X

CO

γ

Cet

Cha

TauS

TauN

TauM

Cal

Per

Xdust

CO

/X� CO

⌧353 [⇥105]1

Rem

y et

al.,

in p

rep

Rem

y et

al.,

in p

rep

PRELIMINARY

in-depth study of other clouds

underway

∲ermithe Chameleon complex

Lat

itu

de

[deg

]

-35

-30

-25

-20

-15

-10

0

0.2

0.4

0.6

0.8

1

log(Nγ)

0

0.5

1

log(NγISM

)

Lat

itu

de

[deg

]

-35

-30

-25

-20

-15

-10

-1

-0.5

0

0.5

log(AVQ

)

-1

-0.5

0

0.5

log(AV Q)

Lat

itu

de

[deg

]

-35

-30

-25

-20

-15

-10

-6

-5.5

-5

-4.5

-4

log(τ353

)

-6

-5.5

-5

-4.5

-4log(τ353)

Longitude [deg]280290300310320

Lat

itu

de

[deg

]

-35

-30

-25

-20

-15

-10

-7

-6.5

-6

log(R)

Longitude [deg] 280290300310320

-7

-6.5

-6

log(R)

LAT 0.4-100 GeV

dust opt. depth

dust radiance

modified dust opt. depth

γ(ISM) 0.4-100 GeV

Fermi-Plaanck+ XXVIII, 2015

∲ermithe Taurus complex

Fermi LAT & Planck collaborations: gas & dust in the Chamaeleon

log(τ353

)

−6

−5.5

−5

−4.5

−4

−3.5

Longitude [deg]

140160180 β

1.3

1.4

1.5

1.6

1.7

1.8

1.9

Lat

itude

[deg

]

−50

−40

−30

−20

−10

log(AvQ) [Av]

−1

−0.5

0

0.5

1

Longitude [deg]

Lat

itude

[deg

]

140160180

−50

−40

−30

−20

−10

Tdust

[K]15

20

25

Fig. 4: Optical depthat 353 GHz (top left)and AvQ extinction (topright) in logarithmicscale, � index (lower left)and temperature (lowerright). The black marksout the analysis region.

lo

g(N

γ)

0

0.5

1

Lat

itude

[deg

]

−50

−40

−30

−20

−10

lo

g(N

γIS

M)

0

0.5

1

Longitude [deg]

140160180

log(τ

con

v)

−6

−5.5

−5

−4.5

−4

Longitude [deg]

Lat

itude

[deg

]

140160180

−50

−40

−30

−20

−10

lo

g(A

v con

v)

−1

−0.5

0

0.5

Fig. 5: Top row : �-rayscount in the 102.6 - 105

MeV energy band for allphotons (left) and forthe photons of interstel-lar origin (right). Lowerrow : dust optical depth(left) and AvQ (right)processed through theLAT IRFs. The ISMphoton map was con-structed by subtractingthe non-gaseous com-ponent derived in the�-rays fit. Regions ex-cluded from the anal-ysis have been maskedout.

required, in addition to CO and HI, an other gas com-ponent to reproduce the total gas column density. Indeedsimilar structures appear in both models residuals withnon-negligible densities (up to half of the CO density).These structured residuals surround the CO clouds at in-termediate HI column densities so they can be used todefine a DNM template. The main feature of our analysisis a cyclic algorithm between dust and �-rays models. The

DNM template extracted from dust fit the positive residu-als is injected into the �-rays fit, producing a new residualmap that we used to build a new DNM template for thenext dust fit. The procedure is repeated iteratively untilreaching a maximum in the �-rays fit log-likelihood (4 it-erations in the Taurus analysis). This method improve theestimates of the DNM templates on each iteration by re-ducing the excessive contribution of the other components

Article number, page 5 of 20

LAT 0.4-100 GeV

dust opt. depth

modified dust opt. depth

γ(ISM) 0.4-100 GeV

PRELIMINARY

∲ermi

CRays in HI: N(HI)

CRays in H2:

CRays in dark neutral gas:

Galactic inverse Compton

γ-ray source

dust in HI

dust in H2

• dust in dark neutral gas

CIB + CMB

IR sources

γ-ray and dust modelling

!"#$%&'()&*+'' ,-&.$/0%12)&3$44567&80990&#0:&79$66$2;&2/67#<71&/:&=>7&!"#$%&,!. **?@*

6/)8-%"%?'34&':,"/9":8&

#"+=,#(%&.+9

" &%*(!,+$%,-0$*!(="%*(+=""$)'.($)&7(#'"0!+(

" 3*7*$%&$*(#'"0!+(07,E"%='.($"($)*,%(#"%*+

1&==&D%&.(,7$*7+,$.(a

',7*&%(#"=-,7&$,"7("E(1&+(#"'0=7(!*7+,$,*+'d(BBB

`VZ(5W

bFR(%(`VZAW

!0+$(%*+,!0&'+(%(`VZW!&%H

+

+

+

+

+

+ constant ?

XCO =N(H2)

W(CO) XCO =N(H2)

W(CO)

⌧dustNH

dNCR

dV

I� � aN(HI)� bW(CO) ⌧dust � a0 N(HI)� b0 W(CO)

∲ermi

CRays in HI: N(HI)

CRays in H2:

CRays in dark neutral gas:

Galactic inverse Compton

γ-ray source

dust in HI

dust in H2

• dust in dark neutral gas

CIB + CMB

IR sources

γ-ray and dust modelling

!"#$%&'()&*+'' ,-&.$/0%12)&3$44567&80990&#0:&79$66$2;&2/67#<71&/:&=>7&!"#$%&,!. **?@*

6/)8-%"%?'34&':,"/9":8&

#"+=,#(%&.+9

" &%*(!,+$%,-0$*!(="%*(+=""$)'.($)&7(#'"0!+(

" 3*7*$%&$*(#'"0!+(07,E"%='.($"($)*,%(#"%*+

1&==&D%&.(,7$*7+,$.(a

',7*&%(#"=-,7&$,"7("E(1&+(#"'0=7(!*7+,$,*+'d(BBB

`VZ(5W

bFR(%(`VZAW

!0+$(%*+,!0&'+(%(`VZW!&%H

+

+

+

+

+

+ constant ?

XCO =N(H2)

W(CO) XCO =N(H2)

W(CO)

⌧dustNH

dNCR

dV

I� � aN(HI)� bW(CO) ⌧dust � a0 N(HI)� b0 W(CO)

compo

nent

sepa

ration

if litt

le cro

ss-tal

k

⇒ good

angu

lar re

solut

ion !

γ-ray

/dus

t ana

lysis

iterat

ions ⇒

DNM

& redu

ce bi

ases

in aHI a

nd bCO

∲ermi

average τ353/NH ≈ (2-3) times the all-sky average, twice the HI cirrus value 2 to 4.6-fold rise in τ353/NH and 1.5 to 2.9-fold rise in AVQ/NH over a single decade in NH

albeit 2-fold decline in radiated power opacity rise related to increase in density and H2 fraction peaks in CO because of opt. thick 12CO

dust evolution in the Chameleon complexA

VQ

/NH

mλ

10

15

20

τ3

53/N

Hmλ

10

20

30

40

50

60

70

NH2

/NHmλ

0 0.5 1

4π

R/N

Hmλ

2

3

4

5

6

log(NHmλ

) [cm-2

]

20.8 21.2 21.6Temperature [K]

14 16 18 20 22

-35

-30

-25

-20

-15

-10

AVQ/N

Hγ

ratio

0.5

1

1.6

3.2

AV

Q/N

Hmλ

rat

io

0.5

1

1.6

3.2

-35

-30

-25

-20

-15

-10

τ 353/N

Hγ

ratio

0.5

1

1.6

3.2

τ 353/N

Hmλ

rat

io

0.5

1

1.6

3.2

Longitude [deg]280290300310320

-35

-30

-25

-20

-15

-10

4πR/N

Hγ

ratio

0.5

1

1.6

3.2

Longitude [deg] 280290300310320

4π

R/N

Hmλ

rat

io

0.5

1

1.6

3.2

NHmλ = NHI + 2*Xcoγ * WCO + NHDNMγ

∲ermi

average τ353/NH ≈ (2-3) times the all-sky average, twice the HI cirrus value 2 to 4.6-fold rise in τ353/NH and 1.5 to 2.9-fold rise in AVQ/NH over a single decade in NH

albeit 2-fold decline in radiated power opacity rise related to increase in density and H2 fraction peaks in CO because of opt. thick 12CO

dust evolution in the Chameleon complexA

VQ

/NH

mλ

10

15

20

τ3

53/N

Hmλ

10

20

30

40

50

60

70

NH2

/NHmλ

0 0.5 1

4π

R/N

Hmλ

2

3

4

5

6

log(NHmλ

) [cm-2

]

20.8 21.2 21.6Temperature [K]

14 16 18 20 22

-35

-30

-25

-20

-15

-10

AVQ/N

Hγ

ratio

0.5

1

1.6

3.2

AV

Q/N

Hmλ

rat

io

0.5

1

1.6

3.2

-35

-30

-25

-20

-15

-10

τ 353/N

Hγ

ratio

0.5

1

1.6

3.2

τ 353/N

Hmλ

rat

io

0.5

1

1.6

3.2

Longitude [deg]280290300310320

-35

-30

-25

-20

-15

-10

4πR/N

Hγ

ratio

0.5

1

1.6

3.2

Longitude [deg] 280290300310320

4π

R/N

Hmλ

rat

io

0.5

1

1.6

3.2

NHmλ = NHI + 2*Xcoγ * WCO + NHDNMγ

gas tracing by dust if NH < 2 1021 cm-2

∲ermi

NHmλ = NHI + 2*Xcoγ * WCO + NHDNMγ

dust evolution in the Taurus complex

rela

tive

tau 3

53/N

Hγ

0.5

1

1.5

Longitude [deg]

140160180

rel

ativ

e A

vQ

/NH

γ

0.5

1

1.5

Lat

itude

[deg

]

−50

−40

−30

−20

−10

rel

ativ

e A

vQ

/NH

mλ

0

0.5

1

1.5

2

2.5

Longitude [deg]

Lat

itude

[deg

]

140160180

−50

−40

−30

−20

−10

rel

ativ

e A

vQ

/NH

mλ

0

0.5

1

1.5

2

2.5

rela

tive τ 3

53/N

Hmλ

0 0.2 0.4 0.6 0.8 10.5

1

1.5

2

2.5

3

3.5

rela

tiv

e τ 3

53/N

Hm

λ

0 0.2 0.4 0.6 0.8 10.5

1

1.5

2

2.5

3

fH2

γ

Av

Q/N

Hm

λ

20.5 21 21.5 220.5

1

1.5

2

2.5

3

3.5

4

20.5 21 21.5 220.5

1

1.5

2

2.5

3

3.5

log(NHmλ

) [cm−2

]

14 16 18 20 22 24 260.5

1

1.5

2

2.5

3

3.5

4

4.5

14 16 18 20 22 24 260.5

1

1.5

2

2.5

3

3.5

4

T (K)

PRELIMINARY

∲ermi

NHmλ = NHI + 2*Xcoγ * WCO + NHDNMγ

dust evolution in the Taurus complex

rela

tive

tau 3

53/N

Hγ

0.5

1

1.5

Longitude [deg]

140160180

rel

ativ

e A

vQ

/NH

γ

0.5

1

1.5

Lat

itude

[deg

]

−50

−40

−30

−20

−10

rel

ativ

e A

vQ

/NH

mλ

0

0.5

1

1.5

2

2.5

Longitude [deg]

Lat

itude

[deg

]

140160180

−50

−40

−30

−20

−10

rel

ativ

e A

vQ

/NH

mλ

0

0.5

1

1.5

2

2.5

rela

tive τ 3

53/N

Hmλ

0 0.2 0.4 0.6 0.8 10.5

1

1.5

2

2.5

3

3.5

rela

tiv

e τ 3

53/N

Hm

λ

0 0.2 0.4 0.6 0.8 10.5

1

1.5

2

2.5

3

fH2

γ

Av

Q/N

Hm

λ

20.5 21 21.5 220.5

1

1.5

2

2.5

3

3.5

4

20.5 21 21.5 220.5

1

1.5

2

2.5

3

3.5

log(NHmλ

) [cm−2

]

14 16 18 20 22 24 260.5

1

1.5

2

2.5

3

3.5

4

4.5

14 16 18 20 22 24 260.5

1

1.5

2

2.5

3

3.5

4

T (K)

PRELIMINARY

gas tracing by dust if NH < 5 1021 cm-2

∲ermi

HI decline around 8 1020 cm-2 CO onset around 1.5 1021 cm-2

HI-DNM transition varies between clouds retains 30% toward CO because of envelopes

phases transitions in the Chameleon complex

N

H/N

Hmλ

0

0.2

0.4

0.6

0.8

1

NHmλ

[cm-2

]

20 20.2 20.4 20.6 20.8 21 21.2 21.4 21.6N

H2

DN

M/N

H2

0

0.2

0.4

0.6

0.8

1

HI DNM CO

∲ermiphase transitions in the Taurus complex

Longitude [deg]

Lat

itude

[deg

]

140145150155160165170175180185190

−55

−50

−45

−40

−35

−30

−25

−20

−15

−10

−5

WC

O [

K k

m s

−1]

0

1

4

9

16

25

36

49

64

CetusDNM region IDNM region IIBubbleNorth armPerseusL1521−HCL2L1536+B18+L1498+L1506L1495+B213

20.6 20.8 21 21.2 21.4 21.6 21.8 220

0.2

0.4

0.6

0.8

1

NH

/NH

tot

20.6 20.8 21 21.2 21.4 21.6 21.8 220

0.2

0.4

0.6

0.8

NHtot

[cm−2

]

NH

/NH

tot

HI

DNM

CO

DNMco

HI

CO

COth

DNM

PRELIMINARY

∲ermi

DNM dominates H2 densities up to AV ≈ 0.9 mag in Cham

DNM mass fractions: wide range in local clouds often exceeds the 30% theoretical expectation unexplained rise with <AVCO>

DNM-to-CO transition

ACOV [mag]

0.3 0.4 0.5 0.6 0.7 0.8 0.9

MD

NM

/Mto

t

0.1

0.15

0.2

0.25

CO-dark H2 mass fraction0 0.2 0.4 0.6 0.8 1

num

ber o

f clo

uds

1

2

3

4 50% H2 100% H2 DNM

Ferm

i+Pl

anck

+ 20

14, a

rXiv

:140

9.32

68

Gre

nier

, Bla

ck, S

trong

AR

AA, 2

015

AV [mag]

0 0.5 1 1.5 2 2.5 3 3.5 4

NH

2 d

ark/N

H2 t

ot

0

0.2

0.4

0.6

0.8

1

1.2

Chamaeleon

∲ermi

DNM dominates H2 densities up to AV ≈ 0.9 mag in Cham

DNM mass fractions: wide range in local clouds often exceeds the 30% theoretical expectation unexplained rise with <AVCO>

DNM-to-CO transition

ACOV [mag]

0.3 0.4 0.5 0.6 0.7 0.8 0.9

MD

NM

/Mto

t

0.1

0.15

0.2

0.25

CO-dark H2 mass fraction0 0.2 0.4 0.6 0.8 1

num

ber o

f clo

uds

1

2

3

4 50% H2 100% H2 DNM

Ferm

i+Pl

anck

+ 20

14, a

rXiv

:140

9.32

68

Gre

nier

, Bla

ck, S

trong

AR

AA, 2

015

AV [mag]

0 0.5 1 1.5 2 2.5 3 3.5 4

NH

2 d

ark/N

H2 t

ot

0

0.2

0.4

0.6

0.8

1

1.2

Chamaeleon

theoretical trend

30%Wolfire+ 2010

∲ermi

XCOγ(kpc-scale) ≈ 2 XCOγ(pc-scale) value XCO(pc) ≈ 0.9 1020 cm-2 (K km/s)-1 XCO(kpc) ≈ 1.9 1020 cm-2 (K km/s)-1 possible causes: phase confusions ? pile-up along sightline? XCOγ increase with radius: TBC ! X12CO-13CO increase due to assumed [Z]/[Z⊙] gradient !

often XCOdust >> XCOγ due to dust evolution rather than cosmic-ray exclusion

AV/NH ratios in the DNM γ-ray estimates consistent with Bohlin+ 1978

XCO = CO-to-H2 conversion ratio

XC

O [

10

20 c

m-2

K-1

km

-1 s

]

0

1

2

3

4

5Cep-PolRCrAOriChaCygnus2Q local arm3Q local arminter arm1Q Per arm2Q Per arm3Q Per arm

Galactocentric radius [kpc]2 4 6 8 10 12 14 16

AV

/NHD

NM

[1

0-2

2 m

ag

cm

-2]

2

3

4

5

6

7

8

9Cep-Pol

RCrA

Cha

Cygnus

3Q local arm

Pineda+ 2013

Bohlin

Gre

nier

, Stro

ng, B

lack

201

5

Fermi LAT

dust