Manfred Stickel

The complete sample of 1 Jansky BL Lacertae objects. I - Summary properties

The first well-defined, homogeneous radio sample of 34 BL Lac objects selected from a large-area survey of sources brighter than 1 Jy at 5 GHz is presented. Extensive optical spectroscopy reveals weak emission lines in roughly 3/4 of the 34 BL Lac objects in the sample. Optical imaging reveals that the nearby BL Lac objects are not stellar, and that the surface brightness distribution of the surrounding fuzz is consistent with the host galaxies being bright ellipticals. The results suggest that gravitational lensing may affect three of the 17 high-redshift BL Lac objects in the sample. The observations do not support a microlensing scenario for the low-redshift objects. 92 refs.

The spiral galaxy M33 mapped in the FIR by ISOPHOT A spatially resolved study of the warm and cold dust

The Sc galaxy M 33 has been mapped with ISOPHOT in the far-infrared, at 60, 100, and 170 µm. The spatial resolution of these FIR maps allows the separation of spiral arms and interarm regions and the isolation of a large number of star-forming regions. The spectral energy distribution in the FIR indicates a superposition of two components, a warm one originating from dust at ∼45 K, and a cold one, at ∼16 K. The warm component is concentrated towards the spiral arms and the star-forming regions, and is likely heated by the UV radiation from OB stars. The cold component is more smoothly distributed over the disk, and heated by the diffuse interstellar radiation. For the about 60 star-forming regions detected the Hα/FIR flux ratio increases significantly with the distance from the galaxy center, probably due to decreasing extinction. An anti-correlation of FHa/F60 with F170 suggests the intrinsic extinction to be related to the cold dust surface brightness according to AV /S 170 ∼ 0.03 mag MJy −1 sr. For the total galaxy the star formation rate (SFR) derived from the FIR is in agreement with that derived from the de-extincted Hα emission. For individual star-forming regions, a consistency between SFRs derived from the optical and from the FIR requires only a fraction of the UV radiation to be absorbed locally. The individual star-forming regions also show a local radio-FIR correlation. This local correlation is, however, due to quite different components than to those that lead to the well-known global radio-FIR correlation for entire galaxies.

On the Far-Infrared Emission of Quasars*

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.

Broadband infrared photometry of comet Hale-Bopp with ISOPHOT

Comet Hale-Bopp was observed ve times with ISOPHOT, the photometer on board ESAs Infrared Space Observatory (ISO) between 4.6 and 2.8 AU. Each time, broadband photometry was performed using 4 dierent detectors, 5 apertures and 10 lters covering the range between 3.6 and 170 m. Background ob- servations were performed with identical instrument settings at the same positions on the sky several days after the comet observations. The observation strategy and the data reduction steps are described in some detail, including the techniques to correct for variable detector responsivity. The resulting inband power values of the Hale-Bopp observations and their uncertainties are given. The mean uncertainty is 25%. The nal fluxes were computed, taking into account the zodiacal background, possible oset of the comets position from the center of the aperture, the brightness distribution within the coma, and the spectral energy distribution of the comets emission. Strong thermal emission from a broad size distribution of dust particles was detected in all of the data sets, even at r =4 :6{4:9 AU pre-perihelion and 3.9 AU post-perihelion; the total thermal energy varied as r 3 . The 7.3{12.8 m color temperature was1.5 times the blackbody temperature, higher than that observed in any other comet. Silicate features at 10 and 25 m were prominent in all 5 data sets, the largest heliocentric distances that silicate emission has been detected in a comet. The presence of crystalline water ice grains is suggested from the 60 m excess emission at 4.6{4.9 AU, consistent with the observed QOH if the icy grains were slightly warmer than an equilibrium blackbody. The average albedo of the dust is higher than that of comet P/Halley, but lower than other albedo measurements for Hale-Bopp nearer perihelion. There is no evidence for a component of cold, bright icy grains enhancing the scattered light at 4.6 AU. Simple models for a mixture of silicate and absorbing grains were t to the ISO spectra and photometry at 2.8 AU. The observed flux at >100 mr equires a size distribution in which most of the mass is concentrated in large particles. Dust production rates of order 1:5 10 5 kg s 1 at 2.8 AU and 3 10 4 kg s 1 at 4.6 AU have been found. They correspond to dust to gas mass ratios of 6 to 10.

The Small Magellanic Cloud in the far infrared. II. Global properties

We present global IR properties of the Small Magellanic Cloud using an ISOPHOT 170 µm map and re-visited IRAS data. The integrated 170 µm flux is 14 950 ± 2300 Jy, and the integrated IR flux is F1−1000 = 7.48 × 10 −10 Wm −2 . Discrete sources contribute 28%, 29%, and 36% to the integrated flux at 60 µm, 100 µm, and 170 µm, respectively. Most of the total emission arises from diffuse emission regions surrounding the HII regions. The SED can be modelled by the composition of a 45 K, a 20.5 K and a 10 K blackbody component with emissivity index n = 2. A color temperature map is constructed from the ISOPHOT 170 µm and the IRAS 100 µm HiRes maps. The average dust temperature is TD = 20.3 K. The total dust mass is found to be MD = 7.8 × 10 5 M� , yielding a gas-to-dust mass ratio Mgas/Mdust ≈ 540, a value 25 times lower than found by former studies. The global star formation rate is estimated to SFRtotal ≈ 0.05 Myr −1 . The comparison with other irregular

Far infra-red emission from NGC 7078: First detection of intra-cluster dust in a globular cluster

Improved data analysis of far infrared imaging data of the globular cluster NGC 7078 obtained with the ISO instru- ment ISOPHOT at 60 µm, 70 µm and 90 µm has detected the thermal emission from dust in its core, the first secure detection of intra-cluster dust in a globular cluster. The amount of dust is broadly consistent with mass-loss from evolved, metal-deficient stars in NGC 7078 in the time since it last crossed the Galactic plane.

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

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.

3D continuum radiative transfer in complex dust configurations: II. 3D structure of the dense molecular cloud core ρ Oph D

Constraints on the density and thermal 3D structure of the dense molecular cloud core Rho Oph D are derived from a detailed 3D radiative transfer modeling. Two ISOCAM images at 7 and 15 micron are fitted simultaneously by representing the dust distribution in the core with a series of 3D Gaussian density profiles. Size, total density, and position of the Gaussians are optimized by simulated annealing to obtain a 2D column density map. The projected core density has a complex elongated pattern with two peaks. We propose a new method to calculate an approximate temperature in an externally illuminated complex 3D structure from a mean optical depth. This T(tau)-method is applied to a 1.3 mm map obtained with the IRAM 30m telescope to find the approximate 3D density and temperature distribution of the core Rho Oph D. The spatial 3D distribution deviates strongly from spherical symmetry. The elongated structure is in general agreement with recent gravo-turbulent collapse calculations for molecular clouds. We discuss possible ambiguities of the background determination procedure, errors of the maps, the accuracy of the T(tau)-method, and the influence of the assumed dust particle sizes and properties.

The Small Magellanic Cloud in the far infrared - I. ISO's 170 μm map and revisit of the IRAS 12–100 μm data

The ISOPHOT experiment onboard the ISO satellite generated a complete view of the Small Magellanic Cloud (SMC) at 170 µm with 1.5 arcmin resolution. The map is analysed using an automated photometry program enabling accurate photometric characterization of the far infrared (FIR) emitting regions. An integrated FIR luminosity of 8 .5×10 7 Lis obtained, leading to a star formation rate of SFRFIR = 0.015 M� /yr. With an average dust temperature of , the total dust mass follows to MD = 3.7 × 10 5 M� . In this paper, the sources detected at 170 µm are compared with those obtainable from the IRAS satellite data. For this purpose, the 12 µm, 25 µm, 60 µm, and 100 µm IRAS high resolution (HiRes) maps of the SMC are re-examined using the same method. In contrast to former studies, this provides an all-band ISO/IRAS source catalog which is no longer based on eyeball classification, but relies on an algorithm which is capable of automated, repeatable photometry, even for irregular sources. In the mid infrared IRAS bands numerous bright FIR emitting regions in the SMC are detected and classified: 73 sources are found at 12 µm, 135 at 25 µm (most of them with Fν 30 K) for the first time. A comparison with earlier IRAS results suggests that many source flux densities in those studies have been under- or overestimated because of non-standardized fitting methods. Many sources with flux densities up to 40 Jy listed in former catalogs cannot be identified in our data.

The European Large Area ISO Survey – IX. The 90-μm luminosity function from the Final Analysis sample

We present the 90-mum luminosity function of the Final Analysis of the European Large Area ISO Survey (ELAIS), extending the sample size of our previous analysis (Paper IV) by about a factor of 4. Our sample extends to z = 1.1, similar to50 times the comoving volume of Paper IV, and 10(7.7) 70 mJy), we obtained redshifts for 61 per cent of the sample (151 redshifts) to B <21 identified at 7 mum, 15 mum, 20 cm or with bright (B <18.5) optical identifications. The selection function is well-defined, permitting the construction of the 90-mum luminosity function of the Final Analysis catalogue in the ELAIS northern fields, which is in excellent agreement with our Preliminary Analysis luminosity function in the ELAIS S 1 field from Paper IV. The luminosity function is also in good agreement with the recent IRAS-based prediction of Serjeant and Harrison - which, if correct, requires luminosity evolution of (1 + z)(3.4 +/- 1.0) for consistency with the source counts. This implies an evolution in comoving-volume-averaged star formation rate at z less than or similar to 1 consistent with that derived from rest-frame optical and ultraviolet surveys.