henize 2-10

Henize 2-10

IC 342M 83

NGC 253

NGC 6946

COMPARISON OF GAS AND DUST COOLINGRATES IN NEARBY GALAXIES

E.Bayet: LRA-LERMA-ENS (Paris)

IC 10

Antennae

Moriond – March, 6th-12th 2005E. Bayet

INTRODUCTION :

OBJECTS : warm and dense molecular clouds in the nuclei of 20 nearby galaxies with different morphological types (D < 10 Mpc)

GOALS : 1) describe the physical properties of these objects localize the GMCs in these nuclei correlations morphological types - cooling rates ? prediction of emission lines for more distant objects 2) understand the links existing between dust and gas cooling rates

HOW : Observations of C and CO lines in mm-submm windows (υ=200-850 GHz) with CSO (Hawaii, USA) and IRAM-PdB (FRANCE) for the first time

C(3P2-3P1) (υ=809 GHz) high-J CO lines observed : 12CO(6-5), (7-6) (υ=691 GHz, 806 GHz)

LVG (radiative transfer calculations) and PDR (photodissociation regions- thermal balance) models to derive the physical properties

targets for ALMA and Herschel


GALAXIES SAMPLE :

Properties : - accessibles from the northern hemisphere - bright in the low-J CO lines, e.g., 12CO(1-0) and 12CO(2-1) - ~20 nearby galaxies with different morphological types:

normal spiral galaxies: IC 342, M 51, NGC 6946

irregular star forming galaxies: Henize 2-10 , IC 10

starburst galaxies: M 82, M 83, NGC 253

interacting galaxies: NGC 6090, IRAS 10565+2448, the Antennae

ULIRGs: Markarian 231, Arp 220

LINER: NGC 4736, NGC 3079 …

IC 342, NGC 6946

Henize 2-10

M 83, NGC 253

the Antennae


OBSERVED LINES :

CO = good tracer of H2 molecular masses C linked with PDRs (mostly in the first layers)

Study of the variation of C over CO density ratio N(C)/ N(CO) in the molecular cloud

Clouds are ruled by: heating - photoelectric effects on grains- collisionnal deexcitation of H2

cooling (condensation of clouds = star formation)

- neutral layer (Av < 5): CII, OI- molecular layer (Av > 5) : CO & C

CO lines refer to transitions between two rotationnal levels C lines refer to transitions between two electronical levelsFrom Hollenbach & Tielens (1999)


MODELS :

LVG ( Large Velocity Gradient ) : radiative transfer calculations with one standard spherical component + Tk and gas density considered as constant

4 input parameters : N(CO)/FWHM , n(H2), Tk andabundance ratio 12CO/13CO (13CO used for discriminating solutions)

PDR or «photodissociation regions» : 2 input parameters :

radiation field and n(H) + gaseous phase abundances, etc…

Intensities of each CO lines are computed up to 12CO(15-14) and we computed intensities of C lines C(3P1-3P0) & C(3P2-3P1)

Physical properties of the ISM derived !!From Hollenbach & Tielens (1999)

Comparison with observations

N(CO)/FWHM, n(H2), Tk12CO/13CO

radiation field


RESULTS : example (IC 342) of CO cooling curve

Observations of the 13CO(6-5), 12CO(8-7) and up will be veryuseful to discriminatemodels solutions

ALMA & Herschel !!

2 LVG models needed to reproduce cold and warm molecular gas


CO cooling curves :

He 2-10, M 83 & Cloverleaf QSO : peak position 12CO(7-6) and up

IC 10, NGC 253, NGC 4038, NGC 6946 & Overlap :

peak position 12CO(6-5) IC 342 and Center of Milky Way : peak position 12CO(5-4) and below

CO(5-4) to CO(7-6) = majorcoolants C(3P2-3P1) = major coolant

CO cooling rate > C coolingrateSimilarities in the CO cooling curves mean similarities in the physical properties, morphological types

Grey full points are derived from PDR models


Comparison between differents tracers : 1) Morphologic(neutral and molecular gas + dust)

Dust cooling Dust cooling

Heating efficiency

R

adia

tion

fie

ld (

CII

/ C

)

D

ensi

ty (

CII

/ O

I)

Larger dispersion in dust cooling thanin radiation fieldand density

CO cooling rate more efficient than C cooling rate

Contribution of the CII from PDR more important in NGC 6946

IC 10 clearly differs from others

C

ooli

ng

effi

cien

cy (

CO

/ F

IR &

C/ F

IR)

Dust cooling

PD

R /

TO

TA

L (

CII

)


Comparison between differents tracers : 1) Morphologic (bis)(neutral and molecular gas + dust)

Dust cooling

* CO(1-0) known as tracer of star formation

* Total CO cooling ratescomputed from 1-0 to 15-14 lines (PDR) also good tracer


Comparison between differents tracers : 2) Coolants (neutral and molecular gas + dust)

Correlations betweenCII, C and COcooling rates

CII cooling rate > OI coolingrate

Starburst galaxies(NGC 253, M 83) have the highest CII, OI, C & COcooling rates and highest FIR flux

Merger and irregular galaxieshave the lowest rates


PERSPECTIVES :

Finish the analysis of these figures and quantify precisely the links existing between o morphological type of nuclei & lines which contribute the most to the CO and C cooling rateso different coolant species (relation between neutral, molecular gas and dust)o cooling and heating processes in the GMCs

Complete these results with the other galaxies from our sample: LVG and PDR modelsshould be applied (already published paper in A&A: The submillimeter C and CO lines in Henize 2-10 and NGC 253 and paper in preparation for the other sources) Other works in progress: - Localize the GMCs in IC 10 nucleus from high resolutionIRAM-Plateau De Bure observations and compare CO with ISO data (LW2 et LW3 at 7 and 15 µm)

- Collaboration at the Leiden Observatory (F. Israel) concerning models: plan to use a combined XDR-PDR models in development

My PhD work shall be included in the future large programs performed by ALMA, the Herschel satellite with the HIFI, PACS and SPIRE instruments and the Spitzer Space Satellite with the IRAC camera and the IRS spectrometer.

MERCI !


CO & C : several lines which emit: 12CO(1-0), 12CO(2-1), 12CO(3-2), 12CO(4-3)… 13CO(1-0), 13CO(2-1)... C(3P1-3P0), C(3P2-3P1)

CO lines : transitions between two rotationnal levels ex: CO(3-2) transition from

level J = 3 to J = 2 C lines : transitions between two electronical

levels ex: C(3P1-3P0) transitions from level 3P1 to 3P0

CII & OI emission lines from literature (ISO, KAO…)

Observations and study of high-J CO lines (12CO(6-5) et (7-6)) = signature of warm and dense molecular gas (n(H2) ~104 cm-3, Tk ~50-100 K)

OBSERVED LINES :

1-0

Hollenbach & Tielens (1999)

henize 2-10

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