R. Meijerink, P. van der Werf, F. Israel and the HEXGAL team HERSCHEL OBSERVATIONS OF Edo Loenen,...
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Transcript of R. Meijerink, P. van der Werf, F. Israel and the HEXGAL team HERSCHEL OBSERVATIONS OF Edo Loenen,...
R. Meijerink, P. van der Werf, F. Israel
and the HEXGAL team
HERSCHEL OBSERVATIONS OF
Edo Loenen, Leiden Observatory
EXTRA GALACTIC STAR FORMATIONMESSIER 82
HEXGAL
Herschel EXtraGALactic Key Program 13 sub-programs using HIFI & PACS
Molecular spectroscopy of dense gas in galactic nuclei
Cooling lines in 10 starbursts with HIFI:CO & 13CO[CI] , [CII] & [NII]
why CO?
It’s high abundance CO ladder reflects the physical condition of
the ISM
Only low-J lines (<6) observable from groundLow(er) density gas
Herschel HIFI: J=5-4 up to J=13-12Dense gas = sites of star formation!Determine conditions of those sites
Observations
M82:archetypical starburstSFR ~150 Mʘ yr
-1
Very nearby: 3.9 Mpc
Herschel HIFI (total time ~1.5 hrs) :CO J=5-4 ... 10-9 + J=13-12 13CO J=5-4 ... 10-92 x [CI], [CII] & [NII]
Focussed on nucleus
Spectra
A third component?
2 main components: NE & SW lobes 3rd component @ high-J CO and 13CO?
A third component
CO(3-2) JCMT
t?
2 main components: NE & SW lobes 3rd component @ high-J CO and 13CO?
A third component
CO(6-5) JCMT
O?
t?
2 main components: NE & SW lobes 3rd component @ high-J CO and 13CO
CO excitation
Use integrated line fluxesCorrected for beam size using 450 µm map
Combine with other data:Low-J (<5) lines from ground (Ward+ 2003)
High-J (>4) lines from SPIRE (Panuzzo+ 2010)
Excellent agreement HIFI & SPIRE (<10%)
PDR models of Meijerink & Spaans (2005):Chemical & thermal balance in 1D cloudRadiative transfer line fluxes
CO excitiation
ground based (Ward+ 2003)Herschel SPIRE (Panuzzo+ 2010)
CO excitiation
n=105, G0=102.75
n=103.5, G0=102
40% : 60%
CO excitiation
n=106, G0=103.25
n=105, G0=102.75
n=103.5, G0=102
70% : 29% : 1%
Conclusions
Need 3 components to fit CO ladder
Most gas has “normal” properties:70% shielded diffuse gas29% dense irradiated gas (SF regions)
3rd component:1%, but dominates J>7 CO and 13CO J>3100 km/s feature...
Super Orion Bar?