Search

We present a sensitive 870 μm survey of the Extended Chandra Deep Field South (ECDFS) combining 310 hr of observing time with the Large Apex BOlometer Camera (LABOCA) on the APEX telescope. The LABOCA ECDFS Submillimetre Survey (LESS) covers the full 30' × 30' field size of the ECDFS and has a uniform noise level of σ870 μm ≈ 1.2 mJy beam-1. LESS is thus the largest contiguous deep submillimeter survey undertaken to date. The noise properties of our map show clear evidence that we are beginning to be affected by confusion noise. We present a catalog of 126 submillimeter galaxies (SMGs) detected with a significance level above 3.7σ, at which level we expect five false detections given our map area of 1260 arcmin2. The ECDFS exhibits a deficit of bright SMGs relative to previously studied blank fields but not of normal star-forming galaxies that dominate the extragalactic background light (EBL). This is in line with the underdensities observed for optically defined high redshift source populations in the ECDFS (BzKs, DRGs, optically bright active galactic nucleus, and massive K-band-selected galaxies). The differential source counts in the full field are well described by a power law with a slope of α = -3.2, comparable to the results from other fields. We show that the shape of the source counts is not uniform across the field. Instead, it steepens in regions with low SMG density. Towards the highest overdensities we measure a source-count shape consistent with previous surveys. The integrated 870 μm flux densities of our source-count models down to S 870 μm = 0.5 mJy account for >65% of the estimated EBL from COBE measurements. We have investigated the clustering of SMGs in the ECDFS by means of a two-point correlation function and find evidence for strong clustering on angular scales

(Abridged) Studying continuum emission from interstellar dust is essential to locate and characterize the highest density regions in the interstellar medium. In particular, the early stages of massive star formation are still mysterious. Our goal is to produce a large scale, systematic database of massive pre- and proto-stellar clumps in the Galaxy, in order to better understand how and under what conditions star formation takes place. A well characterized sample of star-forming sites will deliver an evolutionary sequence and a mass function of high-mass star-forming clumps. Such a systematic survey at submm wavelengths also represents a pioneering work in preparation for Herschel and ALMA. The APEX telescope is ideally located to observe the inner Milky Way. The recently commissioned Large APEX Bolometer Camera (LABOCA) is a 295-element bolometer array observing at 870 microns, with a beam of 19". Taking advantage of its large field of view (11.4') and excellent sensitivity, we have started an unbiased survey of the Galactic Plane, with a noise level of 50-70 mJy/beam: the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). As a first step, we have covered 95 sq. deg. These data reveal 6000 compact sources brighter than 0.25 Jy, as well as extended structures, many of them filamentary. About two thirds of the compact sources have no bright infrared counterpart, and some of them are likely to correspond to the precursors of (high-mass) proto-stars or proto-clusters. Other compact sources harbor hot cores, compact HII regions or young embedded clusters. Assuming a typical distance of 5 kpc, most sources are clumps smaller than 1 pc with masses from a few 10 to a few 100 M_sun. In this introductory paper, we show preliminary results from these ongoing observations, and discuss the perspectives of the survey.

Based on millimeter-wavelength continuum observations we suggest that the recent “spectacle” of comet 17P/Holmes can be explained by a thick, air-tight dust cover and the effects of H2 O sublimation, which started when the comet arrived at the heliocentric distance ≤ 2.5 AU. The porous structure inside the nucleus provided enough surface for additional sublimation, which eventually led to the break up of the dust cover and to the observed outburst. The magnitude of the particle burst can be explained by the energy provided by insolation, stored in the dust cover and the nucleus within the months before the outburst: the subliming surface within the nucleus is more than one order of magnitude larger than the geometric surface of the nucleus – possibly an indication of the latter's porous structure. Another surprise is that the abundance ratios of several molecular species with respect to H2 O are variable. During this apparition, comet Holmes lost about 3% of its mass, corresponding to a “dirty ice” layer of 20 m.

We present observations aimed at exploring both the nature of Lya emitting nebulae (Lya blobs) at z=2.38 and the way they trace large scale structure (LSS), by exploring their proximity to maximum starbursts through submillimeter emission. Our most important objectives are to make a census of associated submillimeter galaxies (SMGs), check their properties, and look for a possible overdensity in the protocluster J2142-4426 at z=2.38. We used the newly commissioned Large APEX Bolometer Camera (LABoCa) on the Atacama Pathfinder EXperiment (APEX) telescope, in its Science Verification phase, to carry out a deep 10'x10' map at 870 micron, and we performed multiple checks of the quality of data processing and source extraction. Our map, the first published deep image, confirms the capabilities of APEX/LABoCa as the most efficient current equipment for wide and deep submm mapping. Twenty-two sources were securely extracted with 870 micron flux densities in the range 3-21 mJy, rms noise 0.8-2.4 mJy, and far-IR luminosities probably in the range ~5-20 x 10(12) Lo. Only one of the four 50 kpc-extended Lya blobs has a secure 870 micron counterpart. The 870 micron source counts in the whole area are marginally higher than in the SHADES SCUBA survey, with a possible over-density around this blob. The majority of the 3.6-24 micron SEDs of the submillimeter sources indicate they are starburst dominated, with redshifts mostly >2. However, there is evidence of a high-z AGN in ~30% of the sources., 14 pages, 9 figures, accepted for publication in A&A, fixed author list

The apex-sz instrument is designed for the discovery and study of galaxy clusters at mm-wavelengths using the Sunyaev Zel’dovich effect. The receiver consists of 320 superconducting transition edge sensor (TES) bolometers cooled to 250 mK with the combination of a three stage He sorption fridge and mechanical pulse tube cooler. The detectors are instrumented with a frequency domain multiplexing readout system. The receiver is mounted on the 12 m apex telescope located at 5100 m on the Atacama plateau in Chile. For the first light engineering deployment of December 2005, the receiver was configured with a 55 element wedge of the bolometers and operating in the 150 GHz atmospheric window. During the engineering run we achieved significant milestones in our instrumentation development efforts, including celestial observations with a monolithically fabricated TES bolometer array cooled with a mechanical cooler and successful implementation of a SQUID-based MHz AC-biased readout. These technology demonstrations point the way toward future large TES bolometer array instruments. Here we describe the results of this deployment and future plans for the apex-sz instrument.

In diesem Beitrag wird ein neues Verfahren zur Optimierung von Bandpassfiltern aus mehrlagigen frequenzselektiven Schirmen (FSS), die in ein Dielektrikum eingebettet sind, vorgestellt. Das Ziel ist es, die Parameter der gesamten Struktur so zu optimieren, dass ihre Transmissionseigenschaften hohe Filteranforderungen erfüllen. Als Optimierungsverfahren wird die Particle Swarm Optimization (PSO) eingesetzt. PSO ist eine neue stochastische Optimierungsmethode, die in verschieden Gebieten, besonders aber bei der Optimierung nicht linearer Probleme mit mehreren Zielfunktionen erfolgreich eingesetzt wird. In dieser Arbeit wird die PSO in die Spektralbereichsanalyse zur Berechnung komplexer FSS-Strukturen integriert. Die numerische Berechnung basiert auf einer Integralgleichungsformulierung mit Hilfe der spektralen Greenschen Funktion für geschichtete Strukturen. This paper presents a novel procedure for the optimization of band-pass filters consisting of frequency selective surfaces (FSS) embedded in a dielectric. The aim is to optimize the parameters of the complete structure so that the transmission characteristics of the filters fulfill the demanding requirements. The Particle Swarm Optimization (PSO) is used as the optimization procedure. PSO is a new stochastic optimization method that is successfully applied in different areas for the optimization of non-linear problems with several object-functions. In this work, PSO is integrated into the spectral domain analysis for the calculation of the complex FSS structures. The numerical computation is based on the formulation of an integral equation with the help of the spectral Green's function for layered media.

We present the first steps toward a 288 pixel sub-millimeter wavelength bolometer camera. We have used bolometers of the transition edge type, choosing a thermometer made of a proximity bilayer of Mo and the alloy Au/Pd with a designed transition temperature of about 500 mK. We have adapted our well-developed niobium based technology for SQUID manufacturing in order to be able to fabricate the current sensor and the bolometer on a common substrate. The function of both devices was successfully tested at the operating temperature of 300 mK.

A new polarimeter concept has been designed to be used together with the bolometer arrays developed at the Max- Planck-Institut fur Radioastronomie in Bonn. The new polarimeter has the unique characteristic of being tunable over a wide range of wavelengths and of producing negligible absorption. It has been used at the Heinrich Hertz Telescope to measure the linear polarization of several quasars and of extended sources inside our Galaxy. Some results are presented here. We detected polarization in the quasars 3C 279 and QSO B1633+382. In 3C 279 we also detected polarization variability on a time scale of a week. We also produced maps of three extended sources: the Becklin-Neugebauer/Kleinmann-Low (BNKL) complex in the Orion Molecular Cloud 1 (OMC 1), a filamentary cloud in OMC 3, and the massive star-forming region IRAS 05358+3543. The polarimeter has low spurious polarization and a high modulation efficiency, and the tests at the telescope show that it is well suited to become a permanent facility.

We have mapped the R Corona Australis molecular cloud at 1.2 mm with SIMBA on SEST and detected 25 distinct dust emission peaks. While 7 of them coincide with positions of previously known young stars, 18 are seemingly not associated with any known stellar object. We discuss the nature of individual sources and conclude that there are at least four small concentrations of young objects located along the filamentary shaped cloud. A comparison with C 1 8 O data hints at the depletion of molecules in some of the cores. Our new results yield some conflicting arguments about whether star formation proceeds from north-west to south-east in the R Cr A cloud.

We observed radio continuum emission from Comet C/1999 S4 before, during, and after break-up of its nucleus. The detections before break-up indicate a photometric diameter of 4.7 km, from which we estimate that the nuclear diameter was about 0.9 km. We derive a dust production rate of9 10 4 gs 1 , corresponding to 0.03 g s 1 per square meter of the nuclear surface area, which is comparable to the values found for comets 1P/Halley and C/1995 O1 (Hale-Bopp). The implied gas-to-dust mass production ratio was between 2 and 5. The high daily erosion rate and the continuous fragmentation over months, as derived from water production rates, could not be confirmed. The low radio emission of the fragments directly after the break-up and their low cometary activity may be explained by their low surface temperatures. The published optical and most radio data support that the main nuclear decay started July 23, 2000. Our upper limits on the flux density obtained after the nuclear disintegration put an upper bound on the particulate dust mass released during that event. A scenario in which most of the nucleus disintegrated into many big boulders and part of it into a dust cloud is consistent with our observations.

Ground-based astronomical continuum observations at (sub)millimeter wavelengths are especially difficult, because the emission of the atmospheric water vapor is usually much stronger than any astronomical signal. We present here the principles of the data reduction and first results of a new observing method that accounts for the atmospheric emission by measuring its total power with an array of detectors. We call the method fastscanning. We outline the data reduction for (sub)millimeter bolometer arrays and demonstrate the effectiveness by presenting results of astronomical observations done with the new method.

Cryogenic bolometers are adequate sensing devices for sub-millimeter observations. They are used for instrumentation in radio telescopes like the Atacama Pathfinder Experiment (APEX), which is a 12-m radio telescope in Chile's Atacama desert. Through its thin and dry atmosphere, star formation in the red-shifted early universe can be observed. A suitable bolometer has a high sensitivity and consists of several tens to hundreds of pixels that are combined to an array. To meet these requirements, we use transition edge sensors. They detect radiation by measuring a temperature increase in an appropriate absorber. For highest sensitivity, the absorber is only in weak thermal contact to its surroundings. This is achieved by placing it on a SiN membrane that is structured to further decrease the thermal coupling. A superconductor that is biased at its transition temperature serves as thermometer for the transition edge sensor. We present the fabrication of such devices and discuss encountered difficulties. Further, we briefly describe the incorporation of a sensor chip with an array of 39 pixels into an instrument that currently operates at APEX. For the fall of 2010 the installation of a 300 pixel array is scheduled.

Imaging polarimetry is an important tool for the study of cosmic magnetic fields. In our Galaxy, polarization levels of a few up to $\sim$10\% are measured in the submillimeter dust emission from molecular clouds and in the synchrotron emission from supernova remnants. Only few techniques exist to image the distribution of polarization angles, as a means of tracing the plane-of-sky projection of the magnetic field orientation. At submillimeter wavelengths, polarization is either measured as the differential total power of polarization-sensitive bolometer elements, or by modulating the polarization of the signal. Bolometer arrays such as LABOCA at the APEX telescope are used to observe the continuum emission from fields as large as $\sim0\fdg2$ in diameter. %Here we present the results from the commissioning of PolKa, a polarimeter for Here we present PolKa, a polarimeter for LABOCA with a reflection-type waveplate of at least 90\% efficiency. The modulation efficiency depends mainly on the sampling and on the angular velocity of the waveplate. For the data analysis the concept of generalized synchronous demodulation is introduced. The instrumental polarization towards a point source is at the level of $\sim0.1$\%, increasing to a few percent at the $-10$db contour of the main beam. A method to correct for its effect in observations of extended sources is presented. Our map of the polarized synchrotron emission from the Crab nebula is in agreement with structures observed at radio and optical wavelengths. The linear polarization measured in OMC1 agrees with results from previous studies, while the high sensitivity of LABOCA enables us to also map the polarized emission of the Orion Bar, a prototypical photon-dominated region.

Fastscanning is a new observing technique for millimeter and submillimeter astronomy from ground based telescopes. The atmosphere is eliminated by taking advantage of detector arrays. Instead of wobbling the secondary mirror with a fixed frequency of a few Hz to filter the atmospheric contribution, we sample the detector outputs at a much higher rate without a modulation by the secondary mirror. The atmospheric contribution is then removed later in the off line data reduction by correlation analysis between the detector pixels. In order to satisfy the AC requirement of the amplifiers in the absence of modulation, the telescope scans fast to convert the spatial frequencies of the sky into the detector frequency band. The acquired AC signals are then deconvolved with the corresponding filter function in order to reconstruct quasi-DC signals. This article describes the technique of this new method and shows simulations and preliminary test results.

We present a study on the origin of the vibrational noise originating from pumped helium chambers (1 K pots) that are continuously replenished from a main bath at 4.2 K. The vibrations can be eliminated by thermalizing the helium, coming from the main bath, to the pot temperature. Vibrations in 1 K pots are a source of excess noise in cryogenic detectors and therefore have detrimental consequences on their performance.

We present observations at 250 GHz (1.2 mm), 43 GHz, and 1.4 GHz of a sample of 41 QSOs at z > 3.7 found in the Sloan Digital Sky Survey. We detect 16 sources with a 250 GHz flux density greater than 1.4 mJy. The combination of centimeter and millimeter wavelength observations indicates that the 250 GHz emission is most likely thermal dust emission. Assuming a dust temperature of 50 K, the implied dust masses for the 16 detected sources are in the range 1.5e8 to 5.9e8 Msun, and the dust emitting regions are likely to be larger than 1 kpc in extent. The radio-through-optical spectral energy distributions for these sources are within the broad range defined by lower redshift, lower optical luminosity QSOs. We consider possible dust heating mechanisms, including UV emission from the active nucleus (AGN) and a starburst concurrent with the AGN, with implied star formation rates between 500 and 2000 Msun/year., 4 figures, aasms4.sty. to appear in the Astrophysical Journal

This paper deals with transmission anomalies of freestanding two-dimensional bandgap structures, which have found a large application range as filter and guiding structures in communication systems and radioastronomical applications in the far infrared region. The effect appears as a sharp breakdown of the transmission factor in the passband of quadratic patch and slot structures, first revealed by measurements. This paper outlines the numerical confirmation of these effects by computer simulations based on the method of moments combined with the Floquet theorem. The transmission and reflection behavior is examined for different structure geometries, frequency ranges, angle, and polarization of the incident wave also revealing alternative structures suppressing these effects. The modeling with electric and magnetic currents allows the characterization of both patch and slot arrays. Finally, cross shaped structures are examined allowing the complete suppression of this kind of anomalies.

We present detections of emission at 250 GHz (1.2 mm) from two high redshift QSOs from the Sloan Digital Sky Survey sample using the bolometer array at the IRAM 30m telescope. The sources are SDSSp 015048.83+004126.2 at z = 3.7, and SDSSp J033829.31+002156.3 at z = 5.0, which is the third highest redshift QSO known, and the highest redshift mm emitting source yet identified. We also present deep radio continuum imaging of these two sources at 1.4 GHz using the Very Large Array. The combination of cm and mm observations indicate that the 250 GHz emission is most likely thermal dust emission, with implied dust masses of 1e8 M_solar. We consider possible dust heating mechanisms, including UV emission from the active nucleus (AGN), and a massive starburst concurrent with the AGN, with implied star formation rates > 1e3 M_solar/year.

We are developing bolometer arrays for continuum detection in millimeter and submillimeter astronomy [1]. For the 2 mm atmospheric window, where the transmission is comparatively high, a bolometer temperature of about 100 mK is necessary in order to avoid being limited by the system noise. Our new 2 mm array is cooled by a 3 He / 4 He -dilution refrigerator with a base temperature of 30 mK. The substrate for the 19 channel bolometer array consists of a single-crystal silicon wafer with silicon-nitride membranes. Radiation is collected by a single-mode horn array in front of the wafer and coupled into efficient absorbers in the center of the membranes. Resulting temperature changes of the absorbers are measured with NTD-germanium thermistors. In the first stage of the read out electronics, we use JFETs working at 150 K. Cold RF-filters prevent RF interference from entering the bolometer array cavity. The combination of several mesh filters and a short piece of cylindrical waveguide at the end of each horn defines the bandpass for the incoming radiation, which is matched to the 2 mm atmospheric window.

At the Max-Planck-Institut fur Radioastronomie we built a 19-channel bolometer array for 150 GHz operating at 100 mK. We give an overview of how our new bolometer array is installed at mm/submm telescopes. With results obtained during observing runs at the 10 m HHT and the IRAM 30 m-telescope we illustrate the performance of the instrument. Measurements of the Sunyaev–Zel'dovich effect (SZE) at mm-wavelength towards distant clusters of galaxies allow us to determine the Hubble constant and the radial cluster velocities. In the diffraction limit of a 10 m telescope our instrument's beamwidth matches the size of many clusters of galaxies making it an ideal tool for observations of the SZE. As first measurements we observed the clusters CL0016+16 and A2218 and the blank sky as a control and we present preliminary results of the detection of the SZE.

Continuum radiometers based on bolometers have a long tradition at the Max-Planck-Institut fur Radioastronomie (MPIfR) in Bonn, Germany. Arrays of bolometers have been under development since the early 1990s. A small seven-element system, operating at 300 mK, saw first light in 1992 at the IRAM 30-m telescope and has been used successfully by numerous observers at that facility since then. While this array had a conventional `composite' design, it was obvious that larger arrays, especially for higher frequencies, could take advantage of microfabrication technology. The recent MPIfR bolometer arrays employ a hybrid approach. They combine a single-mode horn array with a planar bolometer array on a single crystal Silicon wafer with Silicon–Nitride membranes. With efficient absorbing structures, the bolometers couple to the single mode of the radiation field collected by the horns, without needing integrating cavities. Readout is provided by NTD-Germanium thermistors that are attached to the absorbers. This paper covers the history of this development, the design aspects of the bolometer arrays, including the coupling to the telescope, and the status of work in progress.

Infrared spectral energy distributions between 4.8 and 200 μm are presented for a subsample of 10 quasars and radio galaxies from the European Central Quasar Programme observed with the Infrared Space Observatory. For three of the sources, this represents the first far-infrared detection. The spectral energy distributions (SEDs) reveal signatures of thermal dust as well as synchrotron emission. In most cases, one of the two components is so dominant that the other remains hidden. The SEDs of the radio-quiet and steep-spectrum quasars show a bump around 60 μm and a decline longward of 100 μm—strong evidence for thermal emission. It can be described as a superposition of several modified blackbodies, showing the broad variety of temperatures from hot (≈ 600 K) to cool (≈ 30 K) dust present in these objects. The infrared emission of the flat-spectrum radio quasars is in smooth continuation of the radio spectrum, supporting the interpretation as synchrotron emission. For one of these sources (3C 279), a bump is prying above the synchrotron spectrum, and we interpret it as thermal emission. For comparison within the framework of unified schemes, the radio galaxies Cyg A (3C 405) and 3C 20 are observed. While 3C 20 has not been detected, Cyg A reveals an infrared spectrum surprisingly similar to that of 3C 48 and the radio-quiet quasars, which strongly supports the interpretation of the radio galaxy Cyg A as a hidden quasar.

An enhanced version of the ”Polarimeter fur bolometer Kameras” (PolKa) has been installed on the APEX telescope (Atacama Pathfinder EXperiment) in October 2009, to work in combination with LABOCA (the Large APEX Bolometer Camera). This polarimeter was included in the design of LABOCA’s optics from the beginning and it is now going through a commissioning and science verification phase. The combination of PolKa, LABOCA and APEX provides superior capabilities in mapping the polarization of the continuum at submillimeter wavelengths. We present here some preliminary results of the last commissioning run.

Cryogenic bolometers are among the most sensitive devices for the detection of electromagnetic radiation in the submillimeter wavelength range. Such radiation is of interest for astronomical observations as well as for security checks. We describe how we fabricate an array of these bolometers. Standard contact lithography is sufficient for these relatively coarse features. To increase the sensitivity, it is imperative to weaken the thermal link between the thermistors (the sensing devices) and the temperature bath. This is achieved by placing them on a silicon nitride membrane that is structured so that the thermistors are placed on a platform which is held only by a few beams. The fabrication process does not require sophisticated lithographic techniques, but special care to achieve the desired yield of 100 % intact bolometers in one array. We discuss bolometer basics and requirements for our applications, critical fabrication issues, and show results of complete systems built for a radio telescope and for security cameras.

An enhanced version of the "Polarimeter f¨ur bolometer Kameras" (PolKa) has been installed on the APEX telescope (Atacama Pathfinder EXperiment) in October 2009, to work in combination with LABOCA (the Large APEX Bolometer Camera). This polarimeter was included in the design of LABOCA's optics from the beginning and it is now going through a commissioning phase. Preliminary tests on sky have confirmed that the combination of PolKa, LABOCA and APEX provides unprecedented capabilities in mapping the polarization of the continuum emission at submillimeter wavelengths.

Cosmic Microwave Background observations became the tool to probe the the first events of cosmic history. After WMAP data releases, galactic and extragalactic foregrounds are perceived as the main limiting uncertainity for the near-future search for the B-mode polarization inprints from the inflationary era, either through satellites or ground-based experiments like Brain at Dome-C. A combination of technology, scanning strategy and above all, accurate knowledge of polarized foregrounds will be necessary for an optimal mapping of B-mode CMB Polarization. In addition, the search for a better understanding of the galactic foregrounds will provide unprecedented knowledge on the Milky Way structure and star formation. © 2010 EAS, EDP Sciences.

We summarize the results of the Cosmic Microwave Background (CMB) working group of the ARENA project. The focus has been on precision measurements of CMB polarization (looking for the echoes of cosmological inflation) and high angular resolution CMB measurements (looking for Sunyaev Zeldovich effect in distant clusters of Galaxies, to probe the evolution of the Universe, Dark Matter and Dark Energy). For both projects the Dome C site represents the best choice worldwide. © 2010 EAS, EDP Sciences.

We present the experimental results and a bolometer model of the voltage-biased superconducting bolometer on the low stress silicon nitride (Si3N4) membrane, developed in collaboration between the Max-Planck-Institut fur Radioastronomie (MPIfR), Bonn and the Institute for Photonic Technology (IPHT), Jena, Germany. The superconducting thermistor, de- posited on the low stress silicon nitride membrane, is a bilayer of gold-palladium and molybdenum and is designed for a transition temperature of 450 mK. Bolometers for the 1.2 mm atmospheric window were designed, built and tested. The thermal conductance of the bolometer is tuned by structuring the silicon nitride membrane into spider-like geometries. The incident radiation is absorbed by crossed dipoles made from gold-palladium alloy with a surface resistance of 10 Ω/square. Using the COSMOS finite element analysis package, the thermal conductance is obtained for the bolometers of different geometries. FEA simulations showed that the deposition of a gold ring around the absorbing area could increase the sensitivity of the bolometer. Therefore, a gold ring is deposited around the center absorbing patch of the silicon nitride membrane. For the bolometer with a gold ring, the measured NEP is 1.7 × 10 −16 W/ √ Hz and the time constant is in the range between 1.4 and 2 ms.

Terahertz (THz) cameras are expected to be a powerful tool for future security applications. If such a technology shall be useful for typical security scenarios (e.g. airport check-in) it has to meet some minimum standards. A THz camera should record images with video rate from a safe distance (stand-off). Although active cameras are conceivable, a passive system has the benefit of concealed operation. Additionally, from an ethic perspective, the lack of exposure to a radiation source is a considerable advantage in public acceptance. Taking all these requirements into account, only cooled detectors are able to achieve the needed sensitivity. A big leap forward in the detector performance and scalability was driven by the astrophysics community. Superconducting bolometers and midsized arrays of them have been developed and are in routine use. Although devices with many pixels are foreseeable nowadays a device with an additional scanning optic is the straightest way to an imaging system with a useful resolution. We demonstrate the capabilities of a concept for a passive Terahertz video camera based on superconducting technology. The actual prototype utilizes a small Cassegrain telescope with a gyrating secondary mirror to record 2 kilopixel THz images with 1 second frame rate.

We present large scale 870 micron maps of the nearby starburst galaxies NGC253, NGC4945 and the nearest giant elliptical radio galaxy Centaurus A (NGC 5128) obtained with the newly commissioned Large Apex Bolometer Camera (LABOCA) operated at the APEX telescope. Our continuum images reveal for the first time the distribution of cold dust at a angular resolution of 20" across the entire optical disks of NGC253 and NGC4945 out to a radial distance of 10' (7.5 kpc). In NGC5128 our LABOCA image also shows, for the first time at submillimeter wavelengths, the synchrotron emission associated with the radio jet and the inner radio lobes. From an analysis of the 870 micron emission in conjunction with ISO-LWS, IRAS and long wavelengths radio data we find temperatures for the cold dust in the disks of all three galaxies of 17-20 K, comparable to the dust temperatures in the disk of the Milky Way. The total gas mass in the three galaxies is determined to be 2.1, 4.2 and 2.8 x 10^9 solar masses for NGC253, NGC4945 and NGC5128, respectively. A detailed comparison between the gas masses derived from the dust continuum and the integrated CO(1-0) intensity in NGC253 suggests that changes of the CO luminosity to molecular mass conversion factor are mainly driven by a metallicity gradient and only to a lesser degree by variations of the CO excitation. An analysis of the synchrotron spectrum in the northern radio lobe of NGC5128 shows that the synchrotron emission from radio to the ultraviolet wavelengths is well described by a broken power law and that the break frequency is a function of the distance from the radio core as expected for aging electrons. We derive an outflow speed of ~0.5c at a distance of 2.6kpc from the center, consistent with the speed derived in the vicinity of the nucleus., Comment: 12 pages, 11 figures. Accepted for publication in A&A

The inner 20×20 arcmin2 of the COSMOS field was imaged at 250 GHz (1.2 mm) to an rms noise level of ~1 mJy per 11" beam using the Max-Planck Millimeter Bolometer Array (MAMBO-2) at the IRAM 30 m telescope. We detect 15 sources at significance between 4 and 7 σ, 11 of which are also detected at 1.4 GHz with the VLA with a flux density >24 μJy (3 σ). We identify 12 more lower significance mm sources based on their association with faint radio sources. We present the multifrequency identifications of the MAMBO sources, including VLA radio flux densities, optical and near-infrared identifications, as well as the XMM-Newton X-ray detection for two of the mm sources. We compare radio and optical photometric redshifts and briefly describe the host galaxy morphologies. The colors of the identified optical counterparts suggest most of them to be high-redshift (z~2-3) star-forming galaxies. At least three sources appear lensed by a foreground galaxy. We highlight some MAMBO sources that do not show obvious radio counterparts. These sources could be dusty starburst galaxies at redshifts >3.5. The 250 GHz source areal density in the COSMOS field is comparable to that seen in other deep mm fields. Based on observations with the 30 m telescope of the Institute for Radioastronomy at Millimeter Wavelengths (IRAM), which is funded by the German Max-Planck-Society, the French CNRS, and the Spanish National Geographical Institute. Also based on observations with the Very Large Arrray of the National Radio Astronomy Observatory, which is a facility of the National Science Foundation, operated under cooperative agreement by Associated University Inc. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under NASA contract NAS 5-26555 also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under cooperative agreement with the National Science Foundation; and the Canada-France-Hawaii Telescope operated by the National Research Council of Canada, Centre National de la Recherche Scientifique de France and the University of Hawaii.

This paper presents a novel procedure for the optimization of band-pass filters consisting of frequency selective surfaces (FSS) embedded in a dielectric. The approach is based on an innovative stochastic algorithm, namely, the particle swarm optimization (PSO), which is integrated into a spectrum domain analysis code.

We present the experimental results of voltage-biased superconducting bolometers (VSB) on silicon nitride (Si 3 N 4 ) membranes with niobium wiring developed in collaboration between the Institut fur Physikalische Hochtechnologie (IPHT), Jena, Germany and the Max-Planck-Institut fur Radioastronomie (MPIfR), Bonn, Germany. The bolometer current is measured with the superconducting quantum interference device (SQUID), and as expected, the current responsivity is proportional to the inverse of the bias voltage. The experiments were performed with bilayer gold-palladium molybdenum thermistor at 300 mK 3 He cooled cryostat and the desired transition temperature of T c = 450 mK is achieved. The strong negative electro-thermal feedback of the VSB maintains the constant bolometer temperature and reduces the response time from 4 ms to 100 μs. We have tested thermistors of various size and shape on a continuous membrane and achieved a noise equivalent power (NEP) of 3.5 × 10 -16 W/√Hz. The measured NEP is relatively high due to the comparatively high background and high thermal conductance of the unstructured silicon nitride (Si 3 N 4 ) membrane. We have fabricated 8-leg spider structured membranes in three different geometries and the relation between the geometry and the thermal conductance ( G ) is studied. Using the COSMOS finite element analysis tool, we have modeled the TES bolometers to determine the thermal conductance for different geometries and calculated the various parameters. Due to the demands of large number pixel bolometer camera we plan to implement multiplex readout with integrated SQUIDs in our design.

Ever since the first proposal of the voltage-biased transition-edge bolometer the astrophysics community desired bolometer arrays with as many pixels as possible. With respect to the technical problem due to the need of lots of readout SQUID sensors only with multiplexing it is possible to go beyond a few hundred pixel. A technology which allows the manufacture of detector and readout on one chip would simplify this task substantially. Here we demonstrate the fabrication of a transition edge sensor based on a thermistor out of a molybdenum / gold-palladium bilayer. The alloy of gold-palladium (Au-Pd), which allows the tuning of molybdenum's critical temperature by one order of magnitude, is taken from our foundry process for SQUID manufacturing. Au-Pd can further be used for shunt resistances, absorber patterns and bond pads, and, therefore, it is a good choice for a combined technology. The thermistor is placed on a moderately patterned silicon nitride membrane in the shape of an 8-legged spider. The radiation band of interest is coupled via a conical feed horn to a simple grid of dipole-like antenna patterns. This removes the need for the poorly reproducible high-resistance absorption films for the matching of the free space impedance. The simple detector technology is compatible with the SQUID manufacturing. Hence, some of the SQUID layers can be merged with the corresponding detector layer, i.e. the thermistor wiring and the SQUID washer are made in a single niobium layer. The concept of feed horn coupling eases the design requirements, consequently the SQUID can be placed close to the detector, thereby allowing a simpler wiring to be used and in theory a better performance to be obtained.

APEX, the Atacama Pathfinder Experiment, has been successfully commissioned and is in operation now. This novel submillimeter telescope is located at 5107 m altitude on Llano de Chajnantor in the Chilean High Andes, on what is considered one of the world's outstanding sites for submillimeter astronomy. The primary reflector with 12 m diameter has been carefully adjusted by means of holography. Its surface smoothness of 17-18 mu m makes APEX suitable for observations up to 200 mu m, through all atmospheric submm windows accessible from the ground.

With ESO and Onsala Space Observatory as partners, the Max-Planck-Institut fur Radioastronomie (MPIfR) is building a submillimeter telescope of 12 m diameter (APEX), to be placed on the ALMA site (Chajnantor) in Chile. The telescope will be a modified copy of that ALMA prototype antenna, which has been designed by Vertex. First light is foreseen for 2003. As a result of the excellent atmospheric conditions of the site, APEX will offer unique opportunities for submm astronomy in the southern hemisphere. Many kinds of astronomical reseach projects benefit from large format bolometer arrays, especially the search for early galaxies and QSOs at very high redshifts. Designed for this purpose, LABOCA, the large bolometer camera, will operate at a wavelength of 870 m and is planned to be operational soon after first light of APEX. Keywords: APEX, bolometer, submillimeter astronomy, micromachining, pulse tube INTRODUCTION Some of the most interesting objects in the universe are only accessible through astronomical observations in the atmospheric windows at submillimeter wavelengths. The submillimeter emission from molecular spectral lines and from warm dust allows an almost unhindered, unique view of star-forming regions and galactic nuclei, from our own Milky Way to the most distant galaxies and quasars in the early Universe. Furthermore, the southern celestial hemisphere is almost unexplored at submillimeter wavelengths. An international collaboration led by the Millimeter and Submillimeter Astronomy Group at the Max-Planck-Institut fur Radioastronomie (MPIfR) will therefore place a 12-meter radio telescope at the best accessible site for submillimeter observations, Llano de Chajnantor in Chile's Atacama desert. The new telescope is called "Atacama Pathfinder Experiment" (APEX). The Astronomisches Institut Ruhr-Universitat Bochum (AIRUB), the European Southern Observatory (ESO) and the Onsala Space Observatory (OSO) have agreed with the MPIfR to share APEX funding and observing time, with 10% of the observing time being set aside for Chilean astronomers. Construction of the antenna by Vertex Antennentechnik

Temperatures between 4 K and 1 K are obtained by pumping on a 4He bath. In order to reduce the consumption of liquid helium, it is common to pump only on a small volume of He inside a small chamber (1 K pot), continuously replenished from the main bath through an impedance. 1 K pots are a necessary cooling stage in dilution refrigerators, which are used to cool many different kind of sensitive detectors to temperatures in the mK range, e.g. gravitational antennas, bolometers for far-infrared radiation or high resolution particle detection. It is known that continuously filled 1 K pots are affected by vibrations that are a source of excess noise, and thus can decrease the performance of the detectors. We present our study on the origin of these vibrations and a solution we have found to eliminate this excess noise from the detectors.

Arrays consisting of large numbers of sensitive bolometers have become powerful tools for Mm/Submm Astronomy. On large ground-based telescopes for example they were essential in the discovery of a population of faint, highly redshifted point sources which provide important clues to the star-formation history of the universe. The Bolometer group at the Max-Planck-Institut fur Radioastronomie has been developing bolometer arrays since 1980. This paper is meant to give an overview of the state and future of this effort.

We have measured the Sunyaev-Zeldovich effect towards the Coma cluster (A1656) with the MITO experiment, a 2.6-m telescope equipped with a 4-channel 17 arcminute (FWHM) photometer. Measurements at frequency bands 143+/-15, 214+/-15, 272+/-16 and 353+/-13 GHz, were made during 120 drift scans of Coma. We describe the observations and data analysis that involved extraction of the S-Z signal by employing a spatial and spectral de-correlation scheme to remove a dominant atmospheric component. The deduced values of the thermal S-Z effect in the first three bands are DT_{0} = -179+/-38,-33+/-81,170+/-35 microKelvin in the cluster center. The corresponding optical depth, tau=(4.1+/-0.9) 10^{-3}, is consistent (within errors) with both the value from a previous low frequency S-Z measurement, and the value predicted from the X-ray deduced gas parameters., Ap.J.Letters accepted, 4 pages, 2 figures

We report the strategy for observing the Sunyaev-Zeldovich effect towards the Coma cluster of galaxies with the MITO telescope. The instrument has a 17 arcminutes FWHM field of view and uses a 3-field square wave mechanical modulation with a beamthrow of 41 arcminutes. The channels centered at 2.1, 1.4, 1.1 and 0.85 mm allow for matching the Sunyaev-Zeldovich effect spectral range and monitoring atmospheric fluctuations for spectral decorrelation. In this paper we describe both the analysis procedure and the preliminary results of our observations. We also make a first comparison with the available X-ray data.

Compton scattering of the cosmic microwave background radiation by electrons in the hot gas in clusters of galaxies - the Sunyaev-Zeldovich effect - has long been recognized as a uniquely important feature, rich in cosmological and astrophysical information. We briefly describe the effect, and emphasize the need for detailed S-Z and X-ray measurements of nearby clusters in order to use the effect as a precise cosmological probe. This is the goal of the MITO project, whose first stage consisted of observations of the S-Z effect in the Coma cluster. We report the results of these observations., To appear in Proceedings of `Understanding our Universe at the close of XXth century', School held Apr 25 - May 6 2000, Cargese, 16 pages LaTeX, 2 figures ps (using elsart.sty & elsart.cls), text minor revision

This paper reviews transmission anomalies of freestanding frequency surfaces (FSS), which are commonly used as filter and guiding structures in the far IR region. The effect is characterized by a sharp breakdown of the transmission factor in the passband and was first revealed by measurements. The paper demonstrates the numerical confirmation of these effects by computer aided calculations based on the method of moments combined with the Floquet theorem. The scattering characteristics are examined for different sets of parameters like the geometry of the structure, frequency, angle and polarization of the incident wave. The modeling with electric and magnetic currents allows the characterization of both patch and slot arrays.

We summarize the current status of the ISOPHOT Guaranteed Time Proposal on quasars and radio-galaxies. The ISO data from 4.8 to 200 μm, complemented by additional ground-based measurements at 1300 μm, yield spectral energy distributions that show two components of different strength: i) synchrotron emission that dominates the radio range and — depending on the spectral slope — may extend into the near infrared regime. ii) Thermal dust emission that dominates the infrared regime but may be masked — in extreme cases of flat spectrum radio quasars — by the synchrotron component. The spectralenergy distributions exhibit different shapes that reflect the various contributions of the AGN and the star formation to the heating of the dust in the nucleus and the outer parts of the host galaxy. The relative contributions of synchrotron and dust emission and the broad range of dust temperatures support a picture where the observational appearance of quasars and radio-galaxies is determined by the dust morphology (circum-nuclear torus/individual dust clouds) and by different viewing angles (beamed radio emission/ scattered blue emission) towards the source.

We summarize results from sensitive, wide-field imaging at 250 GHz using the Max-Planck Bolometer Array at the IRAM 30m telescope, including source counts, clustering, and redshift distribution., Comment: 5 pages. 'Deep Millimeter Surveys: Implications for Galaxy Formation and Evolution,' eds. Lowenthal and Hughes, World Scientific. For higher quality figures see: http://www.aoc.nrao.edu/~ccarilli/ccarilli.shtml

We discuss results from sensitive, wide-field imaging of the millimeter extragalactic background using the Max-Planck Millimeter Bolometer array (MAMBO) at the IRAM 30m telescope., Comment: 4 pages, 3 figures, uses newpasp.sty. To appear in Proc. JD9, IAU Manchester 2000, `Cold Gas and Dust at High Redshift' ed. D.J. Wilner, Highlights of Astronomy Vol. 12. PASP

Continuum radiometers based on bolometers have a long tradition at the Max-Planck-Institut fur Radioastronomie (MPIfR) in Bonn, Germany. Arrays of bolometers have been under development since the early 90s. A small 7-element system, operating at 300 mK, saw first light in 1992 at the IRAM 30 m- telescope and has been used successfully by numerous observers at that facility since then. While this array had a conventional 'composite' design, it was obvious that larger arrays, especially for higher frequencies, could take advantage of microfabrication technology. The recent MPIfR bolometer arrays employ a hybrid approach. They combine a single-mode horn array with a planar bolometer array on a single crystal Silicon wafer with Silicon-Nitride membranes. With efficient absorbing structures, the bolometers couple to the single mode of the radiation field collected by the horns, without needing integrating cavities. Readout is provided by NTD-Germanium thermistors that are attached to the absorbers. This paper covers the history of this development, the general aspects of the bolometer arrays, including the coupling to the telescope, and the status of work in progress.

We report on the electrical conductivity $\ensuremath{\sigma}$ of a series of nominally uncompensated neutron-transmutation-doped isotopically enriched ${}^{70}$Ge:Ga samples with the Ga concentration [Ga] near ${N}_{c}$ for the metal-insulator transition. $\ensuremath{\sigma}$ of all insulating samples obeys $\mathrm{ln}\ensuremath{\sigma}\ensuremath{\propto}\ensuremath{-}({T}_{0}/T{)}^{1/2}$ with ${T}_{0}\ensuremath{\propto}({N}_{c}\ensuremath{-}[\mathrm{Ga}]){/N}_{c}$ while the zero temperature conductivity $\ensuremath{\sigma}(0)$ of the metallic samples is $\ensuremath{\sigma}(0)\ensuremath{\propto}{([\mathrm{Ga}]\ensuremath{-}{N}_{c}){/N}_{c}{}}^{\ensuremath{\nu}}$ with the critical exponent $\ensuremath{\nu}\ensuremath{\approx}0.5$. The values of ${N}_{c}$ obtained from the two independent scalings of ${T}_{0}$ and $\ensuremath{\sigma}(0)$ are identical, i.e., $\ensuremath{\nu}\ensuremath{\approx}0.5$ is established unambiguously for uncompensated Ge:Ga.

We have performed a systematic study of the 1.25mm continuum emission of radio-quiet QSOs with z > 4, with the IRAM 30 m telescope. In addition to the case of BR 1202-0725 previously reported, five new sources with z > 4 have been detected, as well as one with z = 2.7. Their fluxes range from 2.5 to 10mJy. In addition 18 other sources with z ~ 4 were searched for but not detected with fluxes probably smaller than 3–4 mJy.