Observational setup
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Planned observations
We propose to perform FIR spectroscopy of molecular clouds heated by UV radiation from massive stars, and by the dynamic impact from violent outflows from these stars. Using the high resolution of HIFI we can for the first time simultaneously determine the gas composition and its kinematics in a large set of sources.
Herschel observations will aim at the following tracers:
- main cooling species regulating the energy balance
- key species in the chemical network
Transitions
We will map the spatial variation of the line intensities across the PDR interfaces. In general, at least two transitions per species are to be observed to disentangle temperature and abundance variations. We use a common set of frequencies for most sources to guarantee a uniform data set and a long-term value of the key project data.
| molecule | transition | frequency [GHz] (HIFI) | wavelength [μm] (PACS) | lower level energy [K] | bonus line | strategy |
|---|---|---|---|---|---|---|
| CII | 2P3/2 - 2P1/2 | 1900.545 | 0 | all PDRs and SNRs | ||
| 13CII | 2P3/2 - 2P1/2 | 1900.950 | 0 | few PDRs | ||
| OI | 3P1 - 3P2 | 63.17 | 0 | all PDRs and SNRs | ||
| 3P0 - 3P1 | 145.53 | 228 | all PDRs and SNRs | |||
| NII | 3P2 - 3P1 | 121.91 | 70 | all PDRs and SNRs | ||
| 3P1 - 3P0 | 1462.131 | 205.18 | 0 | all PDRs and SNRs | ||
| NIII | 2P3/2-2P1/2 | 57.32 | 300 | all PDRs | ||
| OIII | 3P2-3P1 | 88.36 | 0 | all PDRs | ||
| HD | 1-0,R(0) | 112.07 | 0 | all PDRs and SNRs | ||
| CH | 2Π3/2 1,2- -2Π1/2 1,1+ | 536.761 | 0 | all PDRs | ||
| 2Π5/2 2,3- - 2Π3/2 1,2+ | 1656.961 | 180.93 | 26 | √ | all PDRs | |
| CH+ | 1-0 | 835.07 | 0 | all PDRs | ||
| CO | 9-8 | 1036.912 | 199 | all PDRS | ||
| 10-9 | 1151.985 | 249 | all SNRs | |||
| > 14-13 | 186.13 | 504 | all PDRs and SNRs | |||
| 13CO | 10-9 | 1101.350 | 238 | all PDRs and SNRs | ||
| NH | 3Σ- 1, 1/2 -0, 1/2 | 974.479 | 0 | all PDRs | ||
| NH+ | 2Π1/2 3/2-1/2 | 1012.561 | 0 | bright PDRs | ||
| NH2 | 11,0-00,0 | 952.578 | 54 | few PDRs | ||
| NH3 | 10-00 | 572.498 | 0.5 | all PDRs | ||
| OH | 2Π3/2 5/2-3/2 | 119.44 | 0 | all PDRs and SNRs | ||
| 2Π1/2 3/2-1/2 | 163.40 | 181 | all PDRs and SNRs | |||
| 2Π1/2-2Π3/2 1/2-3/2 | 79.18 | 0 | all PDRs and SNRs | |||
| OH+ | 3Σ- 1,2,5/2 - 0,1,3/2 | 971.804 | 0 | √ | bright PDRs | |
| H3O+ | 11,1-11,0 | 1655.814 | 181.05 | 0 | all PDRs | |
| 00,1-10,0 | 984.697 | 7 | √ | all PDRs and SNRs | ||
| p-H2O | 11,1-00,0 | 1113.343 | 0 | √ | all PDRs and SNRs | |
| 20,2-11,1 | 987.927 | 53 | √ | all PDRs and SNRs | ||
| 21,1-20,2 | 752.033 | 101 | bright PDRs, all SNRs | |||
| 22,0-11,1 | 100.98 | 53 | all PDRs and SNRs | |||
| 31,3-20,2 | 138.53 | 101 | all PDRs and SNRs | |||
| 40,4-31,3 | 125.35 | 205 | all PDRs and SNRs | |||
| 51,5-40,4 | 95.63 | 319 | all PDRs and SNRs | |||
| 60,6-51,5 | 83.28 | 470 | all PDRs and SNRs | |||
| o-H2O | 11,0-10,1 | 556.936 | 0 | √ | all PDRs and SNRs | |
| 31,2-22,1 | 1153.127 | 160 | √ | all SNRs | ||
| 21,2-10,1 | 179.53 | 0 | all PDRs and SNRs | |||
| 22,1-11,0 | 108.07 | 27 | all PDRs and SNRs | |||
| 30,3-21,2 | 174.63 | 80 | all PDRs and SNRs | |||
| 41,4-30,3 | 113.54 | 162 | all PDRs and SNRs | |||
| 50,5-41,4 | 99.49 | 289 | all PDRs and SNRs | |||
| 61,6-50,5 | 82.03 | 434 | all PDRs and SNRs | |||
| p-H218O | 11,1-00,0 | 1101.698 | 0 | √ | all PDRs and SNRs | |
| o-H218O | 11,0-10,1 | 547.676 | 0 | all PDRs | ||
| HDO | 11,1-00,0 | 893.639 | 0 | bright PDRs |
Sources
The sources are selected to:
- cover a wide range of cloud properties, i.e. density (103 to 107 cm-3), radiation field (1 to 105 average Galactic radiation fields), dust properties, and properties of the ionization front.
- be located nearby in order to probe small linear scales; unfortunately closer PDRs tend to have lower UV fields.
- have a well defined orientation with respect to the observer and a simple geometry with respect to the configuration between illuminating stars and molecular cloud so that it is possible to analyze the stratified structure of the interface region.
- the spectral type of the illuminating sources should be well known
- complementary chemical information. All sources have been studied in many other tracers by ground-based observations
As a reference, we will perform complementary observations of one dense cloud which is exposed to the standard interstellar radiation field only and not influenced by shocks (B68).
| Source | surface UV [χ] | FUV source | Distance [pc] | Geometry | HIFI [h] | PACS [h] |
|---|---|---|---|---|---|---|
| NGC 3603 | 106 | rich cluster, 6 O3 stars | 7700 | 2 irrad. clumps | 5.1 | 3.0 |
| Mon R2 | 105 | Mon R2 IRS1 | 850 | arc | 9.1 | 2.0 |
| Carina | 2000 | Tr14, Tr16, 6 O3 stars | 2500 | edge-on, clumpy | 7.9 | 4.0 |
| NGC 7023 | 1300 | B5 HD200775 | 430 | edge-on shell, 3 PDRs | 7.0 | 2.6 |
| IC 63/59 | 650 | B0 IV | 200 | edge-on shell | 7.9 | 3.1 |
| Ced 201 | 200 | cool, high proper motion | 420 | face-on, circular | 2.5 | 0.2 |
| S140 | 150 | B0V star, X-ray rich | 900 | edge-on, clumpy | 9.3 | 1.2 |
| Rosette | 140 | cluster O4-B3 | 1600 | edge-on, clumpy | 5.2 | 4.1 |
| Horsehead nebula | 60 | O9.5V σ Ori | 400 | edge-on, flat | 4.6 | 5.2 |
| B 68 | 1 | standard IRF | 125 | low-UV reference | 6.2 | 5.9 |
AOR files
We have performed detailed time estimates for all observations. Here, you find the AOR file combining all 347 observing requests contained in the proposal.
Complementary observations
Currently we perform an extended program to obtain complementary observational data to trace the physical and chemical processes in these sources: H2 ro-vibrational lines, the dust emission from the cloud interior, atomic carbon, rotational lines of CO, and observations of many other ``heavy´´ molecules. The observation of additional molecular species is required to derive the comprehensive inventory of the chemical network.
