Second Announcement

Workshop on Submillimeter and Far-Infrared Laboratory Spectroscopy in Support of Herschel, SOFIA, and ALMA

Three new facilities for astronomy-Herschel, SOFIA and ALMA-will all become operational in the next few years exploiting the previously little explored far-infrared spectral region. They will offer unprecedented sensitivity, spectral coverage and instantaneous data bandwidth. The first instrument to operate will be Herschel, which drives the near-term needs for line identification at high resolution (R=10⁷). It will open up the spectrum to 2 THz with 4 GHz of double sideband IF bandwidth. Many important lines and species not easily available from the ground will be accessible (e.g., H₂O, HF, CH⁺, etc.) The expected launch date for Herschel is 2008.

SOFIA will extend the frequency coverage of Herschel to at least 5.2 THz with similar IF bandwidths. ALMA with its small beam will not suffer from beam dilution as the other instruments do and will generate 8 or 16 GHz of spectrum per local oscillator setting with stunning sensitivity. Collectively, these instruments will offer complete access to the physical and chemical processes that govern the interstellar medium and an unprecedented potential to discover and classify the physical and chemical conditions most likely to be favorable for the formation of stars and planets, and ultimately for life itself.

Existing studies have revealed that the underlying spectrum of many astrophysical sources is highly complex at millimeter and shorter wavelengths. Unfortunately, the transition frequencies of molecules well-studied at lower frequencies cannot be extrapolated with required accuracy into the far-infrared frequency regime. In spite of the tremendous advances in the molecular theory, infrared and optical spectroscopy of molecules, the required accuracy to identify lines in the far-infrared cannot be achieved without resorting to far-infrared/submillimeter techniques in the laboratory. A symptom of the lack of necessary information is that the number of unidentified lines found in the existing ground-based spectral scans increases dramatically with frequency and sensitivity. The great capabilities of SOFIA and ALMA will only exacerbate the problem facing Herschel, making it essential that every effort be made in laboratory spectroscopy throughout the world to determine transition frequencies in an expanded range of frequencies so that proper planning and full exploitation of observations can take place. Without accurate and complete knowledge of expected features, it will be difficult or impossible to separate with confidence exciting, new species from a forest of imprecisely determined lines from known molecules.

Currently some 141 different molecular species and many of their isotopologues have been identified in the interstellar medium, leading to millions of potential spectral features. Software models and databases are being developed by Herschel, ALMA and SOFIA for identification of molecular species based on global, multi-line analysis of spectra, but the fundamental input for these models and databases-a listing of accurate transition frequencies, energy levels and transition strengths-can only be obtained by far-infrared laboratory spectroscopy. All of these new facilities and many of the models and databases are international projects, making it is clear that solving the spectral line identification problem will also require international cooperation. The purpose of this workshop then is to devise a plan that identifies the most urgent needs and takes into account the existing capabilities in the United States and other countries.

1) Identify the relevant existing spectroscopic capabilities in the US and other countries.

2) Categorize molecules in terms of difficulty in predicting sufficiently accurate transition frequencies in the wavelength and energy ranges required.

3) Prioritize the molecules most in need of further study according to their astrophysical importance.

5) Determine the necessary facilities and any other enabling technologies for implementation of the program.

6) Determine the funding level and profile necessary for US laboratories to make their contribution of essential laboratory data.

We would welcome your participation in this workshop and assistance in developing a plan for far-infrared laboratory spectroscopy in support of Herschel, SOFIA, and ALMA. We do anticipate having limited funds available to support participants from most US institutions, and expect to be able to provide up to $1000 toward travel and most expenses per participant. We request that interested parties register by September 11 by email to Rena Becerra-Rasti. There is no registration fee. If you intend to request travel reimbursement, please so indicate. A list of Pasadena hotels is included following the Workshop Agenda (rates listed are for 2005) along with a local area Pasadena map showing the distance from the hotels/motels to Campus (some are in walking distance). Information about the Pasadena area bus service, including maps, schedules, and bus stop lists can be found at http://www.ci.pasadena.ca.us/trans/transit/trans_arts.asp. Also included is the Campus Map showing locations of the workshop (Keith Spalding Building) and the closest parking structure. Visitor parking permits may be purchased at an automated pay station inside the parking structure at the rate of $1 per hour, or $5 per day. Additional parking information is available at http://parking.caltech.edu/permits.html#visitor.