Science
The scientific programme for SPIRE will consist of two primary themes:
- The Extragalactic Survey. Galaxies emit a large fraction of their energy in the far infrared due to reprocessing of stellar ultraviolet radiation by interstellar dust. The far-infrared peak is shifted into the SPIRE wavelength domain for galaxies with red shift larger than ~1. A deep, unbiased photometric survey will be carried out to identify and count distant galaxies and to measure their bolometric luminosities as a function of red shift.
- The Galactic Survey. Stars form through the fragmentation and collapse of dense cloud cores in the interstellar medium. An unbiased photometric survey of our own galaxy will be will be carried out to identify and count young protostars and pre-stellar clumps. By measuring the photometric flux in several channels which span the peak in the thermal emission spectrum, the bolometric luminosities and temperatures can be determined.
Both surveys will be followed by low-resolution spectroscopic observations of selected objects for more detailed measurement of the spectral energy distributions.
The goal of the SPIRE extragalactic deep survey is to cover a large area of sky to a depth that is at the confusion limit for galaxies. The confusion limit is defined by the diffraction-limited angular resolution of the telescope. A substantial amount of HERSCHEL observing time will be devoted to the extragalactic survey. Currently, the SPIRE proposal specifies a confusion-limited survey of 60 sq. degrees of the sky over an observing period of 6 months.
The goal of the SPIRE extragalactic deep survey is to cover a large area of sky to a depth that is at the confusion limit for galaxies. The confusion limit is defined by the diffraction-limited angular resolution of the telescope. A substantial amount of HERSCHEL observing time will be devoted to the extragalactic survey. Currently, the SPIRE proposal specifies a confusion-limited survey of 60 sq. degrees of the sky over an observing period of 6 months.
SPIRE will survey nearby molecular clouds to detect complete samples of prestellar, protostellar, and young-stellar objects. SPIRE is to be sensitive enough to detect faint objects, covering a large area in a reasonable time, while having sufficient dynamic range to simultaneously measure bright sources.
Also important are follow-up spectroscopic observations of the sources identified in the surveys outlined above. This will allow determination of redshifts, spectrophotometric mapping, and investigation of the physical conditions of the gases in these sources.
SPIRE will also be used to address many other astrophysical problems:
- the formation and evolution of the giant planets
- chemical evolution of cometary material
- the galactic interstellar medium and nearby galaxies
- the energetics of ultraluminous infrared galaxies and AGNs
These other scientific objectives will benefit from the high sensitivity, high angular resolution, and stable performance required for the deep surveys.