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First results from HERSCHEL Key Programmes
The highly successful commissioning and performance verification phase of HERSCHEL led to first observations within the Science Demonstration Phase in September 2009. MPIA's guaranteed time share of 15% (corresponding to 285 hours) has been mainly invested into two Guaranteed Time Key Programmes led by the institute on The earliest phases of star formation (EPOS) (PI: O. Krause) and The Dusty Young Universe (PI: K. Meisenheimer). Our technical expertise with PACS and scientific interest led to a successful MPIA involvement in nine more HERSCHEL Key Programmes. The wide distribution of these programmes in galactic (EPOS, DIGIT, MESS, DUNES, Gould Belt, Cold Cores, HOPS) and extragalactic astronomy (Dusty Young Universe, KINGFISH, SHINING, HERCULES) - reflects the significance of HERSCHEL for the core science fields of our institute. The total observing time granted to these HERSCHEL programmes is 2600 hours, the MPIA being responsible for many key areas of data reduction and analysis.
EPOS - The Earliest Phases of Star Formation
The EPOS programme, the Earliest Phases of Star Formation, is a 112 hour Guaranteed Time Key Programme aimed at studying the initial conditions and early stages of star formation in our Galaxy. We use HERSCHEL PACS and SPIRE scan maps (Fig. 1) to construct spatially resolved spectral energy distributions of low- to high-mass star-forming cores and protostars, covering the full peak of thermal dust emission. These data allow us to determine dust temperatures, density profiles and the mass distribution with an unprecedented accuracy. Of particular interest are a number of deeply embedded protostars which appear only in the long wavelength PACS bands.
The Dusty Young Universe
The detection of a significant fraction of the highest redshift quasars (z > 5) in the (sub-)millimetre wavelength range indicates that a substantial amount of dust has been synthesised already during the first billion year since after the Big Bang. Recent 24 μm observations with SPITZER have shown that very hot dust is present close to the QSO core in most z > 5 quasars. However, both the (sub-)mm and mid infrared observations can only catch tails of the dust emission spectrum, at λrest > 200 μm, and at λrest < 5 μm, respectively. Measuring the peak of the dust emission has been beyond the capabilities of FIR satellites or ground-based sub-mm telescopes. Thus, critical properties, such as FIR luminosity, dust temperatures and mass, remain unconstrained.
The first PACS observations of two luminous sources at the edge of the universe, the most distant known quasar SDSS J1148+5251 at z = 6.42 and the mm-loud quasar BR 1202-0725 at z = 4.69, by the MPIA-led 164 hours Guaranteed Time Key Programme The Dusty Young Universe have clearly detected the sources. In both cases, the PACS photometry indicates a very continuous distribution of dust temperatures between T ~ 1000 K and T ~ 50 K.
SHINING - Survey with HERSCHEL of the ISM in Nearby Infrared Galaxies
The SHINING programme is a HERSCHEL guaranteed time key programme, whose aim is to study star formation and activity in infrared bright galaxies (starbursts, AGN, (U)LIRGs, and low metalicity galaxies) at local and intermediate redshifts. The programme consists mostly of a large and coherent spectroscopic and photometric survey with PACS, but also includes some SPIRE photometry. The MPIA has contributed observations of merging galaxies hosting very active regions of star formation due to tidal interaction.
Seen with HERSCHEL's eyes, the Antennae Galaxy (Arp 244) that consists of two merging galaxies appears like a single system with two spiral arms emerging from the northern nucleus of NGC 4038 (Fig. 2). However, the prominent optical spiral arm in the north is relatively faint, whereas the dominant emission comes from a chain of knots along an arc connecting the northern (NGC 4038) and southern (NGC 4039) nuclei and coinciding with the net of dust streamers in the optical. The PACS image shows the sites of the currently most active star formation, still hidden in the optical, reveals the metamorphosis and unveils the future appearance of this merging galaxy system, once the 100 millions of young stars being formed inside the bright FIR emission regions will destroy their surrounding dust clouds by their radiation.
KINGFISH - Key Insights on Nearby Galaxies: a Far-Infrared Survey with HERSCHEL
KINGFISH is a 536 hours Open Time Key Programme with significant participation from the MPIA, being responsible for the PACS imaging section of the survey. KINGFISH will provide for, the first time, imaging across the peak of the dust SED at a spatial resolution that matches individual SF complexes, and spectroscopic maps of key diagnostic lines to constrain the cooling and heating processes of the warm neutral medium and the obscured ionised ISM. The PACS and SPIRE imaging from 70 to 500 µm is expected to produce the first comprehensive census of dust in different galactic environments on a spatially resolved basis. Our PACS images of NGC 4559 demonstrate the capabilities of HERSCHEL in resolving individual star forming regions in the far infrared (Fig. 3).
DIGIT - Dust, Ice, and Gas in Time
The Open Time Key Programme DIGIT is aimed on observations of circumstellar disks in order to understand the processes that govern the formation of stars and planets. The MPIA team is particularly interested in full range spectroscopy using PACS which enables SED fitting and a spectral decomposition to identify the mass fraction of individual dust components. As one of the first targets of the DIGIT program, the Herbig Ae/Be star HD 100546 was observed. The PACS spectrum clearly detected the 69 μm forsterite emission feature, the shape and central position of which is currently used to measure the dust temperature and to search for hints of non-random orientation of the crystals in this system.
First results from the different programs will be submitted for publication in the dedicated A&A HERSCHEL Special Issue by March 31, 2010.