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Herschel Guaranteed Time Key Programmes (Galaxies/AGNs)

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Herschel Guaranteed Time Key Programmes (Galaxies/AGNs)

Posted by 曹晨 at August 24. 2007

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SCIENCE CATEGORY: Galaxies/AGNs (5)
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Proposal ID: KPGT_cwilso01_1
Title: "Physical Processes in the Interstellar Medium of Very Nearby Galaxies"
Principal Investigator: Christine Wilson (McMaster University)
Category: KPGT
Summary
We propose to use the SPIRE and PACS instruments on Herschel to measure the emission spectrum from dust as well as important cooling lines from the gaseous interstellar medium in sample of 13 very nearby galaxies (M51, M81, NGC2403, NGC891, M83, M82, Arp220, NGC4038/39, NGC1068, NGC4151, CenA, NGC4125, and NGC205). These galaxies have been chosen to probe as wide a
region in galaxy parameter space as possible while maximizing the achievable spatial resolution and are already well-studied from X-ray and optical through to radio wavelengths. The far-infrared and submillimeter wavelengths probed by Herschel are absolutely crucial for understanding the physical processes and properties of the interstellar medium,the interplay between star formation and the interstellar medium in galaxies, and how they may depend on the wider galaxian environment.



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Proposal ID: KPGT_smadde01_1
Title: "The ISM in Low Metallicity Environments: Bridging the Gap Between Local Universe and Primordial Galaxies"
Principal Investigator: Suzanne Madden (CEA Saclay)
Category: KPGT
Summary
While much of what we have gleaned of the details of dust and gas properties and the processes of dust recycling and heating and cooling in galaxies has been limited to Galactic studies, with Herschel we will be able to explore these issues in low metallicity dwarf galaxies which are known by now to exhibit dust and gas properties different from more metal-rich galaxies. Because these objects are relatively nearby, it is possible to relate the observed variations in the SEDs to the actual physical phenomena occuring within the ISM of the galaxy, allowing the construction of a rich interpretative framework for unresolved, more distant galaxies in the early universe. Using the SPIRE and PACS instruments on Herschel, we propose to map the dust and gas in a 51 dwarf galaxies, sampling a broad metallicity range of 1/50 to 1/3 solar. These data, in conjunction with other ancillary data, will be used to construct the emission spectrum of the dust plus that of the gas in the most important cooling lines. The combination of these instruments onboard Herschel will provide the first opportunity to study the dust and gas in extremely low metallicity environments that have not yet experienced repeated recycling through the ISM. The interpretation of this data will open the door to comprehending primordial ISM conditions and star formation in the young universe.



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Proposal ID: KPGT_rguesten_1
Title: "The HEXGAL (Herschel EXtraGALactic) Key Project: Physical and Chemical Conditions of the ISM in Galactic Nuclei"
Principal Investigator: Rolf Güsten (Max Planck Institut fuer Radioastronomie)
Category: KPGT
Summary:
Herschel/HIFI?s 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/HIFI?s 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.



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Proposal ID: KPGT_esturm_1
Title: "Star formation and activity in infrared bright galaxies at 0<z<1"
Principal Investigator: Eckhard Sturm (Max Planck Institut fuer E. Physik)
Category: KPGT
Summary:
We will perform a comprehensive far-infrared spectroscopic and photometric survey of infrared bright galaxies at local and intermediate redshifts. Our goal is to use the superior sensitivity, spatial and spectral resolution of Herschel to study these galaxies with minimal extinction effects. We aim to obtain a comprehensive view of the physical processes at work in the interstellar medium of local galaxies ranging from objects with moderately enhanced star formation to the most dense, energetic, and obscured environments in ultra-luminous infrared galaxies (ULIRGs) and around AGN. The objects cover a wide parameter range in luminosity, activity level, and metal enrichment, and will be complemented by a few objects at intermediate redshifts, i.e. at a more active epoch of star formation. In particular we plan to - study the obscuration and physical conditions of the central regions of infrared galaxies by obtaining full PACS and SPIRE spectra of five template starbursts, AGN and ULIRGs. - characterise for a larger local sample the state of the ionised medium and of photo-dissociation and X-ray dominated regions through PACS observations of key diagnostic fine-structure and molecular lines. The densest and warmest region near AGN will also be probed for highly excited CO emission, - determine the role of metallicity in star formation processes of low metallicity galaxies from the nearby LMC/SMC to more distant galaxies, - search for evolution from the intermediate redshift population close to the peak of cosmic star formation till the present time, - study the triggering mechanisms and temporal evolution of infrared activity by photometric mapping of a large sample of interacting galaxies, - determine the structure of a few local templates by spectroscopic mapping along characteristic axes. These PACS line maps will establish the physical conditions of nuclear region, spiral arms/disk, and wind regions.



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Proposal ID: KPGT_seales01_1
Title: "The Herschel Reference Survey"
Principal Investigator: Stephen Eales (Cardiff University)
Category: KPGT
Summary:
Despite IRAS, ISO and Spitzer, there is still much we do know about dust in galaxies, partly because of sensitivity limitations and partly because previous telescopes were insensitive to dust colder than about 15 K. Our knowledge is especially poor for ellipticals which have barely been detected by previous telescopes. As part of the SPIRE GT programme, we propose to obtain images at 250, 350 and 520 microns of a sample of 323 galaxies selected to be useful both for studying the dust in individual galaxies and for drawing statistical conclusions about the role of dust in galaxies in general. The Herschel Reference Survey will be the first survey sensitive to all the dust in galaxies and which will detect dust in galaxies of all Hubble types. Apart from its legacy value, we intend to use the survey for the following projects:


1) We will make a comprehensive study of dust along the Hubble sequence, investigating how the dust mass varies with Hubble type: mass of stars, current star formation rate, past star formation rate, and the masses of molecular and atomic gas. 


2) We will investigate within individual galaxies the connections between the star formation rate and the different phases of the ISM, from the nucleus to the HI outside the optical disk.


3) We will investigate how the mass and distribution of dust depend on a galaxy's environment.


4) We will investigate whether there is an intergalactic dust cycle by looking for dusty halos, dusty superwinds and tidally-stripped dust around galaxies.


5) We will investigate the origin of dust in ellipticals, and the evolution of the galaxies themselves, by looking for dust disks and dust shells and by looking for correlations between the mass and distribution of the dust and the other properties of the galaxy.


6) We will measure the local luminosity and dust-mass functions, which will be necessary to interpret the results of the deep surveys, another part of the proposed GT programme. The total time required for the survey is 112.6 hours.
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