Interstellar Medium (ISM) Interstellar Extinction Star Formation
The use of PNe precursors in the study of Diffuse Interstellar Bands
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Transcript of The use of PNe precursors in the study of Diffuse Interstellar Bands
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 1
The use of PNe precursors in the The use of PNe precursors in the study of Diffuse Interstellar Bandsstudy of Diffuse Interstellar Bands
¹ ESA/ISO Data Centre. ESAC, Madrid, Spain ² E. Politécnica Superior de Alcoy, Spain
Pedro García-Lario¹, Ramon Luna² & M.A. Satorre²
In collaboration with:
H. van Winckel, M. Reyniers (K.U. Leuven);
O. Suárez (INTA/LAEFF);
B. Foing, N. Boudin (ESA/ESTEC)
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 2
– Diffuse Interstellar Bands (DIBs) are bands of variable strength and width of still unknown origin which appear overimposed on the spectra of bright but heavily reddened stars
– Discovered in the early 1900’s ! but still unknown origin (presumed interstellar because of their correlation with dust extinction)
What are DIBs ?
From P.
Jenniskens
Adapted from P. Jenniskens
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 3
– More than 300 catalogued (McCall et al. 2002) from UV to near-infrared wavelengths (3600 -10200 Å)
– The most studied ones:• 4430 Å, 5780, 5797 Å, 6284 Å
– Many carriers proposed; none convincing– A major challenge for spectroscopists, astronomers, and physicists
What do we know about DIBs ?
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 4
– Detection of substructures in the profiles of several DIBs indicates the molecular nature of some DIB carriers (e.g. 5797, 6379 and 6614 Å )
(Kerr et al. 1998)
What are their carrier(s) ?
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 5
– Existence of `families’ of DIBs suggest not a unique carrier
(Krelowski &
Walker 1987)
Families of DIBS:
1: 4430, 6180
2: 5780, 6196, 6203, 6269, 6284
3: 5797, 5850, 6376, (2200)
What are their carrier(s) ?
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 6
– Interstellar origin supported by correlation with reddening found in galactic early-type stars, measured as
E(B-V)
(Herbig 1995)
Prototypical star:
HD 183143
What are their carrier(s) ?
DB EW/E(B-V) FWHM
5780 0.44 2.2
5797 0.13 1.1
5850 0.045 1.1
6196 0.044 0.90
6284 1.1 4.5
6379 0.067 1.1
6614 0.20 1.2
6993 0.10 1.6
7224 0.20 1.3
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 7
– They are ubiquitous; detected towards a wide variety of astronomical sources
– Most promising hypothesis: large carbon-bearing molecules:• Long carbon chains? (Douglas 1977)• PAH cations? (Allamandola et al. 1998; Salama et al. 1999)• Fullerenes? (Foing & Ehrenfreund 1997)
What are their carrier(s) ?
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 8
– There are strong evidences that the relative strength of DIBs are correlated with the properties of the clouds in the line of sight
– Environmental dependence of DIBs may reflect an interplay of ionization, recombination, dehydrogenation and destruction of chemically stable, carbonaceous species (Salama et al. 1996)
– Investigations of DIBs in regions of different metallicity, chemical properties and UV radiation field may allow us to constrain the physico-chemical properties of the (different) DIB carriers.
– Difficult to probe the ISM along a given line of sight; usually this is a combination of many different clouds with inhomogeneous properties and complex morphologies
What else can we do?
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 9
– Are there also Diffuse Circumstellar Bands (DCBs) ? – First suggested by Le Bertre & Lequeux (1993)– Circumstellar shells around low- and intermediate-mass evolved
stars are a ‘natural’ environment where DB carriers may form. – They are among the most important contributors of gas and dust to
the ISM– Dense outflows of cool C-rich AGB stars are the best candidates– Observational problems because of the presence of strong
molecular bands in their optical spectra; difficult to model stellar continuum; complex photospheres
– Thus…
No attempt yet made for a systematic search for DCBs– Ways around to address the problems needed (IRC +10º216)
unsuccessful
What about circumstellar DIBs?
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 10
– Diffuse Interstellar Bands (DIBs) are
Search for DCBs in AGBs
IRC +10º 216, Kendall 2002
12.4’2’
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 11
– Diffuse Bands (DBs) may potentially be detected also towards post-AGB stars
– Post-AGB stars show a wide range of spectral types (from M to B) in their way to become PNe
– High galactic latitude helps!– For many of them we know the
chemical composition of the dust grains (ISO, mm/submm, radio)
– Some results on individual post-AGB stars look promising (Zacs et al. 1999, 2001; García-Lario et al. 1999; Klochkova et al. 2000)
A way around: post-AGB stars
post-AGB
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 12
DBs in post-AGB stars
(Zacs et al. 1999)
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 13
Not always so simple…
Not the 5850 Å DB !
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 14
– 9 of the strongest Diffuse Interstellar Bands (DIBs) were investigated in a sample of 33 post-AGB stars
– Spectral types: B – G– A mixture of C-rich and O-rich stars (chemistry derived from ISO
data in most cases; also from submm and/or radio observations)– Wide range of galactic latitudes and overall extinction – high-radial velocity stars were favoured (to help discrimination of
ISM vs. CSE features)– Several runs using 5 telescopes at three different observatories
• ESO/La Silla (ESO 1.52m/FEROS + ESO NTT/EMM)
• ESO/Paranal (VLT/UVES)
• Roque de los Muchachos, La Palma (TNG/SARG + WHT/UES)
– Spectral resolution 50,000; most of the observations so far analyzed were initially taken for other purposes
A systematic search for DBs
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 15
A systematic search for DBs
Recalculation of EW / E(B-
V) dependence using a
sample of
53 reddened stars of early
spectral type
(Thorburn et al. 2003)
At 5780, 5797, 6196,
6284, 6379 and 6614 Å
Original spectroscopic data
R 38000
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 16
A systematic search for DBs
Recalculation of EW/E(B-V) dependence
using 4 reddened early type stars
(Jenniskens et al. 2003)
At 5850, 6196 and 7224 Å
Original spectroscopic data: R 20000
EW = α· E(B-V)
DB r EW/E(B-V)
5780 0.65 0.46
5797 0.70 0.19
5850 0.96 0.050
6196 0.79 0.053
6284 0.74 1.05
6379 0.59 0.093
6614 0.78 0.21
6993 0.95 0.12
7224 0.99 0.25
EW/E(B-V)
0.44
0.13
0.045
0.044
1.1
0.067
0.20
0.10
0.20
HD 183143
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 17
ISM vs. CS extinction
Overall extinction = ISM contribution + CS contribution
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 18
A systematic search for DBs
Old Observations available
IRAS 04296+3429 IRAS 12175-5338 IRAS 17436+5003 IRAS 20462+3416
IRAS 05113+1347 IRAS 16594-4656 IRAS 18025-3906 IRAS 22023+5249
IRAS 05341+0852 IRAS 17086-2403 IRAS 18062+2410 IRAS 22223+4327
IRAS 06530-0213 IRAS 17097-3210 HD 172324 IRAS 22272+5435
IRAS 07134+1005 IRAS 17150-3224 IRAS 19114+0002 IRAS 23304+6147
IRAS 08005-2356 IRAS 17245-3951 IRAS 19386+0155
IRAS 08143-4406 IRAS 17395-0841 IRAS 19500-1709
IRAS 08544-4431 IRAS 17423-1755 IRAS 20000+3239
September 2003 observations
IRAS 01005+7910 IRAS Z02229+6208 IRAS F05251-1244 IRAS 19200+3457
June 2004 observations (under analysis)
IRAS 17023-1534 IRAS 17364-1238 IRAS 18379-1707 IRAS 21153-6842
IRAS 17074-1845 IRAS 17381-1616 IRAS 18442-1144 IRAS 21190+5140
IRAS 17195-2710 IRAS 17542-0603 IRAS 20572+4919 IRAS 21546+4721
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 19
A systematic search for DBs
t
t t
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 20
The DB at 6284 Å
IRAS 19500-1709
E(B-V) = 0.37
IRAS 22023+5249
E(B-V) = 0.52
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 21
No clear correlation between
EW and E(B-V) in P-AGB stars
Many stars show values well below
the expectations
Some DBs are not even detected in
strongly reddened P-AGB stars
DB strength vs. E(B-V)
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 22
In general, DCS PAGB stars show
always the lower values
Non-detections at high E(B-V) are
only found in DCS PAGB stars
Non-DCS PAGB stars show values
which are in many cases
consistent with the values
expected for ISM DIBs
DB strength vs. E(B-V)
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 23
The DB at 6284 Å
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 24
The DB at 5780 Å
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 25
The DB at 5797 Å
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 26
The DB at 6614 Å
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 27
The DB at 7224 Å
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 28
Analysis of radial velocities
Na D2 5896 Å
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 29
Analysis of radial velocities
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Pedro GARCIA-LARIOPlanetary Nebulae as Astronomical Tools / Gdańsk, June 28/July 2 2005, Page 30
– The strength of 9 of the strongest DBs has been systematically searched and analysed in a sample of 33 PAGB stars.
– They are found to be extremely weak as compared to the results obtained in other samples of reddened stars
– The effect is more clearly observed in P-AGB stars dominated by circumstellar extinction
– Our results suggest that DIBs are not formed (yet) in the circumstellar shells around PAGB stars
– If connected with PAHs, as suggested in the literature, their carriers must form at a later stage as the result of their processing by the hard UV field in the ISM
– Their identification as strongly ionized PAHs and/or radicals liberated from carbonaceous species as a consequence of photoevaporation of dust grains in the ISM would be consistent with our observations
– Interesting to observe CSPNe with various dominant chemistries and a lot of internal extinction!
Conclusions