Data from the Herschel Guaranteed Time Key Program "HIFI Spectral Surveys of Star Forming Regions"

Dataset for the CHESS Herschel Guaranteed Time Key Program provided in zenodo within the framework of ACO (AstroChemical Origins): (H2020 MSCA ITN, GA:811312).

The reference article is Ceccarelli et al. 2010, Astronomy and Astrophysics, Volume 521, id.L22, 8 pp. whose doi is  10.1051/0004-6361/201015081

Herschel Guaranteed Time Key Program: "HIFI Spectral Surveys of Star Forming Regions” (also called CHESS)
(PI: Cecilia Ceccarelli, 281 hours allocated)
Summary:
Study of the molecular content of regions far beyond our Solar System has advanced enormously during the last few decades, from the first detections of diatomic molecules to the discovery of polyatomic, complex organic molecules. Nowadays, one major goal of Astrochemistry is to have the most accurate census of the molecular content (and complexity) in Star Forming Regions (SFRs). In the era of the molecular content census, unbiased spectral surveys in the radio to Infrared of SFRs have become a fundamental and necessary tool in modern astrochemistry research. In this context, the frequency range covered by HSO-HIFI, 500-2000 GHz, is of particular importance. It is in this frequency range that light molecules have their ground and low energy transitions, whereas heavier molecules have higher energy transitions. The latter are excited in the warm gas, whereas the former probe the gas at low temperatures as well. It is therefore in the HIFI frequency range that the major gas coolants (notably H2O) and some key components of the chemical composition of SFRs emit. We propose to obtain Spectral Surveys in the HSO-HIFI range of a representative sample of SFRs. To have a meaningful coverage of the different evolutionary stages and different masses requires a large amount of time, about 300 hrs. The proposed observations will provide a large dataset of uttermost interest for the entire astronomical community, and, particularly for the study of star formation processes and of the influence of chemistry on star and planet formation. These two basic aspects, a large requested observing time and an output of high archival value, make the present proposal suitable for a HSO Key Program.

SOURCE SAMPLE: 

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Source     RA(J2000)     Dec(J2000)                          Time     Dist.     Lum.               Source type                         

                                                                                     (hr)      (pc)   (L_solar)                                                      

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L1544 05h04m17.21s +25d10m42.8s                          10       120        –            Cold prestellar core                 

I16293E 16h32m28.62s –24d29m02.7s                       10       120        –            Warm prestellar core               

L1157-B1 20h39m10.20s +68d01m10.5s                     33       220        –             Outflow shock spot                 

IRAS 16293-2422 16h32m22.75s –24d28m34.2s        50       120       21           Class 0 low mass protostar      

OMC2-FIR4 05h35m26.97s –05d09m54.5s                 42       440      1e3        Intermediate mass protostar      

AFGL 2591 20h29m24.90s +40d11m21.0s                  34      1000     2e4               High mass protostar          

NGC 6334I 17h20m53.32s –35d46m58.5s                  42      1700     2e5               High mass protostar          

W51e 19h23m43.88s +14d30m28.8s                          10       7000    2e6               High mass protostar                

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OBSERVATIONS AND SPECTRAL COVERAGE:

• SPG Version: SPG14.1.0

• Processing Level: Level-2.5 data products for HIFI, Level 2 data products for PACS

• Units: Antena temperature

• Fits file, with the informations in the metadata

Almost the entire 480−1902 GHz frequency range has been covered in all sources, with the exceptions of the prestellar cores, where only the 480−636 GHz band have been observed together with a small range around 1 THz (to detect the H2D+ 111−000 line). IRAS 16293-2422 and L1157- B1 have been observed in the 57−210 μm range with the Herschel/PACS spectrometer. 

What is in zipped file

The data retrieved from the Herschel Science Archive (HSA) in March 2020 as a tar file will unpack into a directory with the request observation identifier ((<obsid>) as the name which contains the science data distributed in sub-directories called level2.5 (HIFI) or level2(PACS). Level 2 are of science quality, Level 2.5 are combinations of Level 2 products (see the Data Product Overview web page for more details).

The top context file ( h<instrument><obsid>obs_<timestamp>.fits.gz) inmediately under the <obs_id> directory contains the main keywords related to the observation and the instrument setup in the first extension header. For example: L1544/1342227398/ hhifi1342227398obs_1461431368423.fits.gz. A snapshot is also provided (example: L1544/1342227398/1342227398-herschel.ia.obs.ObservationContext-810549.jpg.jpg)

In most cases, you will be interested in the FITS files that contain the science data, which are located in the deepest levels of the <obs_id> directory. Hence, you will find the final science products resulting from the pipeline processing in the sub-directories under the level2 and level2_5 directories.

The general structure can be described as:

> directory/

           <context_file>.fits.gz

           sub_directory/

                     <context_file>.fits.gz

                     sub_subdirectory1/

                                   <science_data>.fits.gz

                    sub_subdirectory2/

                                  <science_data>.fits.gz

The sub-sub-directories are straightforward to identify: spectrum_HRS-H-LSB, spectrum_HRS-V-USB, spectrum_WBS-H-USB etc…Deconvolution is also sometimes provided. Example 16293E/1342214337/level2_5/myDecon/myDecon_WBS-H/hhifiwbshssb1342214337_25ssv20_1461340404663.fits