Probing isotopic ratios at z=0.89
Molecular line absorptions
in front of the quasar PKS 1830-211
Sébastien Muller
(ASIAA, Taiwan)
M. Guélin (IRAM)
M. Dumke (ESO)
R. Lucas (IRAM)
IAU Colloquium 199 Probing galaxies through quasar absorption lines, ShangHai, China, 2005 March 14-19
Absorption systems
- Lyman  forest
1012 - 1019 cm-2
 gas filaments in extragalactic medium
- Damped Lyman  & HI 21 cm absorption
1019 - 1021 cm-2
 outer parts of spiral galaxies
- Molecular absorption
1020 - 1024 cm-2
 central parts of galaxies
Background quasars & molecular absorption
Need a background continuum source …
 mm flux of quasars weaker than in the radio cm
(SNR depending on the background continuum source)
And an absorption system !
 Dense gas, closer to the center
of the intervening galaxy
(small impact parameter)
 Highly probable association with gravitational lensing
Molecular absorption systems in the mm
Zabs
N H2 (cm-2)
Cen A
0.002
2. 10
3C293
0.04
> 6. 10
PKS 1413+135
0.25
5. 10
B3 1504+377
0.67
1.2 10
B 0218+357
0.68
4. 10
23
Background QSR
PKS 1830-211
0.89
4. 10
22
Background QSR
20
20
Host galaxy
Host galaxy
20
Host galaxy
21
Host galaxy
PKS 1830-211
Intervening galaxy :
MERLIN 6cmz=0.89
Typical spiral
HST WFPC2
I band image
Photometry from HST
NE
1’’
(Winn et al 2002)
I = 22
V > 24.7
SW position
I > 24.9
V > 26.3
1st case of QSR lensed
SWby a face-on spiral
Mass within 3 kpc:
(Wiklind & Combes 1998)
Patnaik et al 1994
6 – 9 1010 M
2–4 kpc
Plateau de Bure Interferometer observations
HCO+
(1-2)
94.6 GHz
H13CO
(1-2)
92.0 GHz
+
HC18O
+
HC17O
+
 Summer time
between 1999 – 2002
 Compact configuration
 Self calibration
14
(1-2)
92.3 GHz
N/15N
16O/18O
(1-2)
94.0 GHz
(1-2)
91.3 GHz
HNC
(1-2)
96.2 GHz
HN13C
(1-2)
92.4 GHz
H15NC
(1-2)
94.2 GHz
HCN
Observations :
(1-2)
90.3 GHz
12C/13C
H13CN
HC15N
18
(1-2)
O/17O91.6 GHz
32S/34S
Main isotopomers
 2 components
NE and SW
 SW : complete
absorption for HCO+
 non symetric profiles
 = sum of velocity
components with widths
similar to MW clouds
(~10 km/s)
Iabs = IO (1-exp-)
Let’s compare the isotopic ratios in:
 One beam pencil in a
galaxy at z = 0.89
6.4 Gyr ago
 Solar System
4.5 Gyr ago
 Local ISM
now !
(Lucas & Liszt 1998)
 Galactic Center
 IRC +10216
 LMC
(Cernicharo et al 2000)
(Chin 1999)
 NGC 4945
(Wanf et al 2004)
archetype of AGB star
low metallicity galaxy
nucleus of a nearby SB galaxy
Is there a clear chemical evolution ???
12C
: produced directly from He in massive stars (primary)
13C : produced from 12C and 16O in H burning (secondary)
Problems : selected photodissociation, chemical fractionation,
optically thin lines for 12C
14N
: secondary, enhanced in CNO cycle at equilibrium
15N : secondary, destroyed in CNO,
produced in explosive H or He burning
14N / 15N : increases with metallicity (gradient in the MW)
16O
: primary, produced in massive stars
18O : secondary, produced in He burning from
14N
18O
/ 17O : constant value through the disk of the MW
17O : secondary, produced in low mass stars
Sulfur : product of explosive O burning in MASSIVE stars
Ratio 32S / 34S ???
Summary
Isotopic ratios in the z=0.89 galaxy are :
 Different from SS, local ISM, GC
 Very different from IRC+10216 !
 Closer to SBs
no time for the low and intermediate mass stars
to release the processed materials
Nearby SB : because of time scale,
outputs from massive stars dominate
 Different from LMC (O) (metallicity ?)
Conclusion
Isotopic ratios = signature of the chemical evolution
and nuclear processing (???)
Molecular absorption measurements
Galaxy at z = 0.89 : look back time of 6.4 Gyr
But only one beam pencil
STATISTICS and chemical evolution : MORE SOURCES !!!
Need to observe more absorption systems at different z !
ALMA
Background
source
Absorption
And even 2
lensed
images !
Solar
System
Local
ISM
IRC
+10216
Nuclei of
nearby SB
NGC 4945
LMC
10
89
40 - 70
45
50
62
-50+130
270
240
> 4400
100
114
490
600
1300
200
> 2000
PKS 1830
12C
/ 13C
32
14N
/ 15N 140
16O
/ 18O
18O
/ 17O
13 3
5.5
3.5
0.7
6
2
32S
/ 34S
10 1
20
19
22
13.5
18
67
24
Lucas &
Liszt
1998
Cernicharo
et al
2000
Wang et al
2004
Chin 1999