The far-infrared region is currently one of the last wavelength regions where lack of spatial resolution and lack of sensitivity hinders progress in science. While the upcoming Herschel and SPICA missions will provide major steps forward in sensitivity, these two observatories lack the high spatial resolution necessary for detailed studies of individual objects. In the coming decade ALMA and JWST, which have high spatial resolution as well as high sensitivity, will be major facilities to be used by the astronomical community. However, the wavelength region in between is not covered by any comparable instrument yet, so in fact there exists a “Far-Infrared Gap”.
The existence of this gap was identified by the astrophysical community as well as by the European Space Agency’s Astronomy Working Group. In the ESLAB 2005 symposium, as part of the Cosmic Vision process, a high spatial resolution (0.1-0.02 arcsec at 100 micrometer) far-infrared observatory was listed as one of the major priorities of the astronomy program. Since the Cosmic Vision process ends early next year, it is timely to make an inventory of the science to be done with a FIRM.
In this workshop we want to define the key requirements for such a future observatory. Especially the following topics will be discussed:Star- and planet-formation Evolution of (the ISM in) galaxies The nature of the far-IR background, star-formation throughout the history of the Universe Three concepts for a FIRM
Star- and planet-formation: The star-formation process is poorly understood because of the large quantities of dust obscuring the sites where stars and planets are born. A high spatial resolution far-infrared observatory could really probe scales smaller than 1 AU in nearby star-forming regions and give, for the first time a detailed in-sight in the physics and dynamics of the process, especially in those regions warmer than ALMA can observe and too highly obscured for JWST to examine.
Evolution of (the ISM in) galaxies: While Hubble has shown fantastic pictures of merging galaxies, submm and near-IR observations have shown that the real action is completely obscured by large quantities of dust. Only in the far-IR the dust becomes transparant, while spectral lines can be used to determine the conditions that lead to star-formation on massive scales. In fact only a high spatial resolution far-IR observatory is capable to bring ISM studies for other galaxies, like the famous Antennae, to the same level as for our own Milky Way.
While half of all the radiation in the Universe is coming out in the far-infrared wavelength region its nature is almost completely unknown. Only with high spatial resolution and spectral capabilities will it be possible to break the confusion limit and determine the properties of the individual objects. Since it is expected that many of the galaxies will be at large redshifts, we may even probe the rotational lines of molecular hydrogen, shifted into the far-IR. These would be unique probes of the formation of the earliest stars in the Universe.
Also the enigmatic starburst –AGN symbiosis in distant galaxies can only be studied using FIRM resolution.
It is clear that these three science topics have in common that they will make extensive use of both the continuum radiation coming from these sources as well as spectroscopy of molecular, atomic and ionic lines.