<=== observer ===>
"EVDISHOE",\
"van Dishoeck, E.F.",\
"",\
"Leiden Observatory",\
"",\
"P.O. Box 9513",\
"2300 RA",\
"Leiden",\
"The Netherlands",\
"31 71 275874",\
"31 71 275819",\
"ewine@strwchem.leidenuniv.nl"
<=== proposal ===>
"HDGAL", 1, 2,\
{"abundances",\
"molecular clouds"},\
{"M.F. Kessler",\
"ESA/ESTEC",\
"Keplerlaan 1",\
"2200 AG Noordwijk",\
"The Netherlands",\
"J.P. Baluteau",\
"Obs. de Marseille",\
"2 Pl. Leverrier",\
"13248 Marseille",\
"Cedex 04",\
"France",\
"J.H. Black",\
"Steward Obs.",\
"Univ. of Arizona",\
"Tucson AZ85721",\
"USA",\
"P. Cox",\
"Obs. de Marseille",\
"2 Pl. Leverrier",\
"13248 Marseille",\
"Cedex 04",\
"France",\
"C. Gry",\
"Lab. d'Astronomy Spa",\
"Trav. du Siphon",\
"Les Trois Lucs",\
"13012 Marseille",\
"France",\
"H.J. Habing",\
"Leiden Observatory",\
"P.O.-Box 9513",\
"2300 RA Leiden",\
"The Netherlands"}
<=== title ===>
DEUTERIUM IN THE GALAXY:
THE HD ABUNDANCE AS A FUNCTION OF GALACTOCENTRIC DISTANCE
<=== abstract ===>
SCIENTIFIC ABSTRACT
We propose to observe the HD J=1-0 112 mu line in a dozen
interstellar clouds to determine the deuterium abundance in the solar
neighborhood, and to search for any possible gradients across the Galaxy.
In two clouds, the HD J=2-1 56 mu line will be observed as well.
The results will form important tests of cosmology and astration models.
The total amount of time including overheads is 5.5 hours.
The deuterium abundance is one of the most sensitive probes of the baryon
density in the early Universe. However, attempts to measure the [D]/[H] ratio
in stellar or interstellar sources have been plagued by a multitude of
problems. Radio searches for the 92 cm line of D I in emission in interstellar
clouds are still unsuccessful, whereas the recent possible detection of the
line in absorption against Cas A has taken several months of integration time
and is difficult to interpret. Observations of the Lyman lines of H and D
toward early type stars suffer from confusion by stellar lines and possible
stellar variability, whereas the use of deuterated molecules is hampered by
chemical fractionation effects. The best estimates from the ultraviolet
absorption line measurements give 5E-6<[D]/[H]<2E-5 in the solar neighborhood.
This deuterium abundance requires the Universe to be open. Obviously, such an
important conclusion warrants further confirmation.
In molecular clouds, virtually all deuterium is expected to be in the form of
HD. Thus, measurements of the HD abundance should provide direct limits on the
[D]/[H] ratio, provided that the H2 column density is known. The HD J=1-0 line
occurs at 112 mu, and cannot be observed from the ground or the airplane, but
should be readily detectable by ISO. In contrast with absorption line
studies, it is not limited to the Solar neighborhood, but should be observable
all over the Galaxy, thus providing information on the [D]/[H] ratio as a
function of galactocentric distance.
We propose to search for the HD 112 mu line in about 10 sources with different
distances R from the galactic Centre with the LWS Fabry Perot. Most of these
sources are giant molecular clouds which have recently been used by Langer and
Penzias (1990) to determine the 12C/13C ratio across the Galaxy from R=0 to 12
kpc. Their 13CO, C18O and 13C18O observations refer to nearly the same beam
(100'') as that of the ISO LWS, which will greatly facilitate the analysis. To
this list, we have added 4-5 molecular clouds that are located in the outer
Galaxy up to R=30 kpc and that show strong 12CO emission (Wouterloot and Brand
1989).
Because the proposal requires information with galactocentric radius, some of
the positions will fall in one of the ISO holes. If the ``hole'' falls in the
Galactic center, we will obviously loose information on the innermost part of
the Galaxy. If the ``hole'' falls in Orion, on the other hand, it should be
possible to obtain observations over the full range of galactocentric
distances.
Additional information on the HD abundance in the inner Galaxy and local
neighborhood will be obtained from observations of Sgr A, SgrB2, Orion and
other star-forming regions by Cox et al., Baluteau et al., Drapatz et al.
and van Dishoeck et al. The investigators have direct contacts with all
of these programs. These observations, however, form a less homogeneous set
and are usually of lower quality.
OBSERVATION SUMMARY
We intend to search for the HD 112 mu line in 10 sources (for the
autumn launch; 9 for the spring launch) with different distances
from the Galactic Centre using the LWS Fabry Perot in the high
resolution line mode (AOT LWS04). For 2 sources in each of the launch
windows (W43 and W49 for autumn; DR21 (OH) and NGC2024 for spring),
we will also search for the HD 56 mu line, again using the AOT
LWS04. In all cases, we will take 4 res elements on either side of
the line with 4 spectral samples per resolution element in the
fast scanning mode.
The integration times have been estimated as follows. For the sources with a
strong continuum at 112 mu (>5000 Jy) (Autumn OSNs 1, 3, 4, and 5; Spring OSNs
1, 2 and 3), the line/continuum ratio is estimated to be about 0.03-0.05. Thus
a high S/N>100 on the continuum is required for adequate discrimination of the
line, resulting in an integration time of 600 seconds per source. For the
weaker sources, the estimated line/continuum ratio is 0.05-0.1. For a
S/N=30-60, this leads to integration times of 1000-2000 s. The expected
strength of the HD line in the outer galaxy sources is particularly uncertain.
For the 56 mu, a S/N on the continuum of 50-100 is needed to obtain a
detection or a meaningful upper limit. This results in integration times per
source ranging from 1200 to 4000 seconds.
<=== scientific_justification ===>
Time distribution for autumn launch targets:
TEAM: top 40% second 30% last 30%
SWS : 0. 0. 0.
LWS : 0. 0. 0.
CAM : 0. 0. 0.
PHT : 0. 0. 0.
SOT : 4360. 10300. 5140.
THE : 0. 0. 0.
JLP : 0. 0. 0.
HJH : 0. 0. 0.
AFM : 0. 0. 0.
MOH : 0. 0. 0.
Time distribution for spring launch targets:
TEAM: top 40% second 30% last 30%
SWS : 0. 0. 0.
LWS : 0. 0. 0.
CAM : 0. 0. 0.
PHT : 0. 0. 0.
SOT : 4540. 9720. 5540.
THE : 0. 0. 0.
JLP : 0. 0. 0.
HJH : 0. 0. 0.
AFM : 0. 0. 0.
MOH : 0. 0. 0.
Source List: Orion hole
========================
===============================================================================
Source RA DEC V_LSR R IRAS 100 IRAS 60
(km/s) (kpc) (Jy) (Jy)
-------------------------------------------------------------------------------
Sgr B2* 17 44 11 -28 22 30 62.0 0.1 10400 3180
W43 18 45 01 -01 59 35 90.5 5.5 8000 5600
W33 18 11 19 -17 56 46 36.0 5.7 2000 2000
W51 19 21 27 14 24 30 61.0 7.6 10000 10000
W49 19 07 54 09 01 01 7.0 9.3 18300 12000
DR21(OH) 20 37 14 42 12 -4.9 9.9 6100 2000
W3 (OH)* 02 23 17 61 39 00 -41.0 12.2 9000 6000
IRAS 02395 +6244 02 39 30.6 62 44 25 -71.6 16.2 226 255
IRAS 01045 +6505 01 04 36.0 65 05 21 -88.0 17.0 331 293
IRAS 02450 +5816 02 44 55.1 58 16 30 -103 28: 100 50
IRAS 23301 +6316 23 30 06.1 63 16 37 -95.1 16.5 200 200
IRAS 21270 +5423 21 27 13.0 54 22 30 15.0 400 200
--------------------------------------------------------------------------------
* Included in other proposals
Source List: Sagittarius Hole
=============================
===============================================================================
Source RA DEC V_LSR R IRAS 100 IRAS 60
(km/s) (kpc) (Jy) (Jy)
-------------------------------------------------------------------------------
W51 19 21 27 14 24 30 61.0 7.6 10000 10000
DR21(OH) 20 37 14 42 12 -4.9 9.9 6100 2000
NGC 2024 05 39 14 -01 55 59 9.9 10.2 8000 8000
NGC 2264 06 38 25 09 32 29 9.0 11.1 1645 980
W3 (OH)* 02 23 17 61 39 00 -41.0 12.2 9000 6000
IRAS 02395 +6244 02 39 30.6 62 44 25 -71.6 16.2 226 255
IRAS 01045 +6505 01 04 36.0 65 05 21 -88.0 17.0 331 293
IRAS 06145 +1455 06 14 32.7 14 55 52 33.8 20.3 100 50
IRAS 06158 +1517 06 15 58.1 15 18 56 31.5 19.8 100 50
IRAS 02450 +5816 02 44 55.1 58 16 30 -101 28: 100 50
--------------------------------------------------------------------------------
INTEGRATION TIMES: Orion hole
=================
=====================================================================
Source 1-0 2-1 Priority Other
112 mu 56 mu Proposals
time (s) time (s)
---------------------------------------------------------------------
Sgr B2 * * Baluteau
W43 600 2100 2
W33 2000 -- 3
W51 600 -- 2
W49 600 1500 2
DR21 (OH) 600 -- 2
W3 (OH) * -- Drapatz
IRAS 02395 +6244 2000 -- 2
IRAS 01045 +6505 2000 -- 2
IRAS 02450 +5816 2000 -- 1
IRAS 23301 +6316 2000 -- 3
IRAS 21270 +5423 2000 -- 1
---------------------------------------------------------------------
* Pro memorie only; included in proposals of Baluteau et al. and Drapatz
et al.
INTEGRATION TIMES: Sagittarius hole
=================
=====================================================================
Source 1-0 2-1 Priority Other
112 mu 56 mu Proposals
time (s) time (s)
---------------------------------------------------------------------
W51 600 -- 2
DR21 (OH) 600 4000 2
NGC 2024 600 1200 2
NGC 2264 1000 -- 3
W3 (OH) * -- Drapatz
IRAS 02395 +6244 2000 -- 2
IRAS 01045 +6505 2000 -- 2
IRAS 06145 +1455 2000 -- 3
IRAS 06158 +1517 2000 -- 1
IRAS 02450 +5816 2180 -- 1
---------------------------------------------------------------------
* Pro memorie only; included in proposal of Drapatz et al.
<=== autumn_launch_targets ===>
1, "LWS04", 2., "N", "W43 ", 18.75028, -1.99306, 1950, 0., 0., 2880, 0
2, "LWS04", 3., "N", "W33 ", 18.18861, -17.94611, 1950, 0., 0., 2180, 0
3, "LWS04", 2., "N", "W51 ", 19.35750, 14.40833, 1950, 0., 0., 780, 0
4, "LWS04", 2., "N", "W49 ", 19.13167, 9.01694, 1950, 0., 0., 2280, 0
5, "LWS04", 3., "N", "DR21(OH) ", 20.62056, 42.20000, 1950, 0., 0., 780, 0
6, "LWS04", 2., "N", "IRAS 02395 +6244", 2.65850, 62.74028, 1950, 0., 0., 2180, 0
7, "LWS04", 2., "N", "IRAS 01045 +6505", 1.07667, 65.08917, 1950, 0., 0., 2180, 0
8, "LWS04", 1., "N", "IRAS 02450 +5816", 2.74864, 58.27500, 1950, 0., 0., 2180, 0
9, "LWS04", 3., "N", "IRAS 23301 +6316", 23.50169, 63.27694, 1950, 0., 0., 2180, 0
10, "LWS04", 1., "N", "IRAS 21270 +5423", 21.45361, 54.37500, 1950, 0., 0., 2180, 0
<=== spring_launch_targets ===>
1, "LWS04", 2., "N", "W51 ", 19.35750, 14.40833, 1950, 0., 0., 780, 0
2, "LWS04", 2., "N", "DR21(OH) ", 20.62056, 42.20000, 1950, 0., 0., 4780, 0
3, "LWS04", 2., "N", "NGC 2024 ", 5.65389, -1.93306, 1950, 0., 0., 1980, 0
4, "LWS04", 3., "N", "NGC 2264 ", 6.64028, 9.54139, 1950, 0., 0., 1180, 0
5, "LWS04", 2., "N", "IRAS 02395 +6244", 2.65850, 62.74028, 1950, 0., 0., 2180, 0
6, "LWS04", 3., "N", "IRAS 01045 +6505", 1.07667, 65.08917, 1950, 0., 0., 2180, 0
7, "LWS04", 1., "N", "IRAS 06145 +1455", 6.24242, 14.93111, 1950, 0., 0., 2180, 0
8, "LWS04", 3., "N", "IRAS 06158 +1517", 6.26614, 15.31556, 1950, 0., 0., 2180, 0
9, "LWS04", 1., "N", "IRAS 02450 +5816", 2.74864, 58.27500, 1950, 0., 0., 2360, 0