Showing papers by "Oliver Krause published in 2004"

Far‐infrared Source Counts at 70 and 160 Microns in Spitzer Deep Surveys

Abstract: We derive galaxy source counts at 70 and 160 μm using the Multiband Imaging Photometer for Spitzer (MIPS) to map the Chandra Deep Field-South (CDF-S) and other fields. At 70 μm, our observations extend upward about 2 orders of magnitude in flux density from a threshold of 15 mJy, and at 160 μm they extend about an order of magnitude upward from 50 mJy. The counts are consistent with previous observations on the bright end. Significant evolution is detected at the faint end of the counts in both bands, by factors of 2-3 over no-evolution models. This evolution agrees well with models that indicate that most of the faint galaxies lie at redshifts between 0.7 and 0.9. The new Spitzer data already resolve about 23% of the cosmic far-infrared background at 70 μm and about 7% at 160 μm.

The ISOPHOT-MAMBO survey of 3CR radio sources: Further evidence for the unified schemes ,

Abstract: We present the complete set of ISOPHOT observations of 3CR radio galaxies and quasars, which are contained in the ISO Data Archive, providing 75 mid- and far-infrared spectral energy distributions (SEDs) between 5 and 200µm For 28 sources they are supplemented with MAMBO 12 mm observations and for 15 sources with new submillimetre data from the SCUBA archive The sample includes flat and steep spectru m quasars, broad and narrow line radio galaxies, as well as Fanaroff-Riley FR 1 and FR 2 types The SED shapes exhibit a diversity in the infrared (IR), ranging from a smooth dominating synchrotron component in flat spectrum sources to a thermal d ust bump around 60-100 µm in steep spectrum sources The detection rate of a thermal bump in more than 50% of the cases suggests that dust emission may be a general phenomenon in these sources We check the orientation-dependent unifie d scheme, in which the powerful FR 2 narrow line galaxies are quasars viewed at high inclination, so that their nuclei are hidden behind a dust torus intercepting the optical-ultrav iolet AGN radiation and reemitting it in the infrared We find that (1) b oth the quasars and the galaxies show a high mid- to far-infrared luminosity ratio typical for powerful AGNs and (2) - when matched in 178 MHz luminosity - both show the same ratio of isotropic far-infrared to isotropic 178 MHz lobe power Therefore, from our large sample investigated here we find stron g evidence for the orientation-dependent unification of the p owerful FR 2 galaxies with the quasars The distribution of the dust- to-lobe luminosity ratio shows a dispersion which we suggest to be most likely due to the additional influence of evolutio n and environment superposed on the orientation-dependent unification We discuss our data also in the frame of the recedi ng torus model At the high 178 MHz luminosities of our sources above 10 265 W/Hz we do not find any support for this model in its original formulation and therefore we propose a refine ment: The scale height of the torus might not be independent of luminosity, rather it may increase at high luminosities due to the impact of supernovae from starbursts accompanying the AGN phenomena

The photodetector array camera and spectrometer (PACS) for the Herschel Space Observatory

Abstract: The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments for ESA's far infrared and submillimeter observatory Herschel. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 × 25 pixels, each, and two filled silicon bolometer arrays with 16 × 32 and 32 × 64 pixels, respectively, to perform imaging line spectroscopy and imaging photometry in the 60-210μm wavelength band. In photometry mode, it will simultaneously image two bands, 60-85μm or 85-130μm and 130-210μm, over a field of view of ~ 1.75' × 3.5', with full beam sampling in each band. In spectroscopy mode, it will image a field of ~50"×50", resolved into 5×5 pixels, with an instantaneous spectral coverage of ~1500 km/s and a spectral resolution of ~ 175 km/s. In both modes the performance is expected to be not far from background-noise limited, with sensitivities (5σ in 1h) of ~ 4 mJy or 3 - 20 ×10-18W/m2, respectively. We summarize the design of the instrument and its subunits, describe the observing modes in combination with the telescope pointing modes, report results from instrument level performance tests of the Qualification Model, and present our current prediction of the in-orbit performance of the instrument based on tests done at subunit level.

The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies

Abstract: The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering 15% of the far-infrared (FIR) sky at 170μm were searched for compact sources associated with optically identified galaxies. Compact Serendipity Survey sources with a high signal-to-noise ratio in at least two ISOPHOT C200 detector pixels were selected that have a positional association with a galaxy identification in the NED and/or Simbad databases and a galaxy counterpart visible on the Digitized Sky Survey plates. A catalog with 170μm fluxes for more than 1900 galaxies has been established, 200 of which were measured several times. The faintest 170μm fluxes reach values just below 0.5 Jy, while the brightest, already somewhat extended galaxies have fluxes up to 600 Jy. For the vast majority of listed galaxies, the 170μm fluxes were measured for the first time. While most of the galaxies are spirals, about 70 of the sources are classified as ellipticals or lenticulars. This is the only currently available large-scale galaxy catalog containing a sufficient number of sources with 170μm fluxes to allow further statistical studies of various FIR properties.

Prototyping of cryomechanisms for the JWST near-infrared spectrograph (NIRSpec)

Abstract: In 2011 NASA and ESA plan to launch the James Webb Space Telescope (JWST) as dignified successor of the Hubble Space Telescope. Three scientific instruments will cover the wavelength regions in the near-infrared (0.6-5μm, NIRCam and NIRSpec) and in the mid-infrared (5-28μm, MIRI), respectively. The ESA-led multi-object spectrograph NIRSpec as major European contribution is presently entering the detailed design phase in a collaboration between European space industries, scientific institutes, ESA and NASA. To allow for various operational modes in the instrument’s optical train several cryo-mechanisms are required, i.e. wheels for exchanging optical elements like filters and gratings as well as linear actuators on refocusing mirrors. We will give an overview on the detailed design, the prototyping and the testing of those mechanisms comprising highest reliability in the cryo-vacuum (~ 35K) combined with minimal power dissipation (~ 5mW on average), ultimate position accuracy (~ 0.5 - 1arcsec) combined with high launch vibration capability (ARIANE 5, ~ 60g) and a very long lifetime (~ 15 years) for ground tests and space operation under various environmental conditions. To reach this goal in a low cost and risk approach we rely on the heritage from ESA's earlier infrared missions, i.e. ISO and HERSCHEL.