| Description |
Herschel/HIFIs unique spectroscopic capabilities will allow us to make a representative velocity-resolved inventory of important cooling lines in nearby galaxies, AGN and starburst nuclei. Such observations explore the physical conditions within regions of active star formation in low and high metallicity environments, shedding light on the physics of large scale star formation in the contemporary and, by extension, the early universe. Multi-line data combined with numerical radiative transfer and chemical network models quantitatively constrain the various phases of the interstellar medium (ISM). Key lines in Herschel/HIFIs spectral range include the bright fine-structure lines of neutral and ionized atomic carbon, nitrogen and oxygen, a unique set of water lines, and the high-excitation CO transitions.The far-infrared spectra of many galaxies reflect the gas energy balance through atomic and molecular cooling lines from photo-dissociation regions (PDRs) and forbidden fine-structure lines from HII-regions. Within the beam of an extragalactic observation, any of the ISM components (dense warm PDRs on the surfaces of UV-exposed molecular clouds, low-density warm atomic clouds will contribute to the brightness of the molecular or fine-structure lines. Our high spectral resolution studies will unravel the structure of the ISM by analysis of their main cooling lines. Velocity information provides sub-beam spatial resolution and ties HIFI observations of different species to complementary PACS line integrated intensity maps on larger scales. In addition, water is a key molecule for our understanding of the chemistry and energy balance in the denser ISM. Herschel/HIFI will measure the brightness of the ground-state transitions to determine the gas temperature of the ISM via line ratios. |
| Instrument |
HIFI_HifiPoint_load, HIFI_HifiPoint_pos, PACS_PacsRangeSpec_point, PACS_PacsLineSpec_point, SPIRE_SpireSpectrometer_, HIFI_HifiMapping_fly, PACS_PacsRangeSpec_large, HIFI_HifiPoint_dbs, HIFI_HifiMapping_load-raster, HIFI_HifiMapping_raster |
