ISO Beyond Point Sources: Studies of extended infrared emission

(Sep 14-17, ESAC, Madrid, Spain)


Abstracts submitted as of 9 September 1999


A. Abergel et al.

Institut d'Astrophysique Spatiale, Universite Paris-Sud, Bat. 121, 91405 Orsay Cedex, France

Abstract. The large scale ISOCAM mapping of different molecular clouds conducted in the broad-band filters LW2 (5-8.5 micron) and LW3 (12-18 micron) reveals the small scale structure (3-6'') of the emission in a wide range of physical conditions and geometry. First I will detail the origin of the emission within these two filters (aromatic features, continuum) from ISO spectroscopic measurements. Then I will discuss the extended emission within the southern part of Orion B and the main complex of rho Oph, especially the structure of illuminated interfaces, and the spectacular color variations (LW2/LW3) found from place to place.


George J. Bendo and R. D. Joseph

Institute for Astronomy, University of Hawaii

Abstract. We have observed a magnitude-limited sample of 77 galaxies chosen from the Revised Shapley-Ames Catalogue with ISOCAM at 10 micron and with ISOPHOT at 60 micron, 100 micron, and 180 micron. We have complemented these data with images at JHK and with images for four galaxies at 850 micron. We will compare the normalized intensity and distribution of mid-infrared and far-infrared emission from these galaxies to investigate the correlation of infrared activity with other global galaxy properties. Our results show that the intensity and spatial distribution of star formation in galaxies does vary with morphology. Furthermore, we will investigate the spectral energy distribution in far-infrared and submillimeter wavelengths to better understand the temperature components of dust in these galaxies. Although the mid-infrared, far-infrared, and submillimeter images show emission from similar regions in these galaxies, a close comparison shows fundamental differences between the distribution of hot and cool dust.


Simone Bianchi, Paul B. Alton, Jonathan I. Davies

Department of Physics and Astronomy, Cardiff University,
PO Box 913, Cardiff CF2 3YB, U.K.

Abstract. ISO observations at 200micron have modified our view of the dust component in spiral galaxies. For a sample of seven resolved spirals we have retrieved a mean temperature of 20K, about 10K lower than previous estimates based on IRAS data at shorter wavelengths. Because of the steep dependence of far-infrared emission on the dust temperature, the dust masses inferred from ISO fluxes are a factor of 10 higher than those derived from IRAS data only, leading to gas-to-dust ratios close to the value observed in the Galaxy. The scale-length of the 200micron emission is larger than for the IRAS 100micron emission, with colder dust at larger distances from the galactic centre, as expected if the interstellar radiation field is the main source of dust heating. The 200micron scale-length is also larger than the optical, for all the galaxies in the sample. This suggests that the dust distribution is more extended than that of the stars.
     A model of the dust heating is needed to derive the parameters of the dust distribution from the FIR emission. Therefore, we have adapted an existing radiative transfer code to deal with dust emission. Simulated maps of the temperature distribution within the dust disk and of the dust emission at any wavelength can be produced. The stellar spectral energy distribution is derived from observations in the ultraviolet, optical and near infrared. The parameters of the dust distribution (scale-lengths and optical depth) are chosen to reproduce the observed characteristics of the FIR emission, i.e. the shape of the spectrum, the flux and the spatial distribution. We describe the application of the model to one of the galaxies in the sample, NGC~6946.


M. Braun(1), G.M. Richter(1), B. Schulz(2)

(1) Astrophysical Institute Potsdam, An der Sternwarte 16, D-14482 Potsdam
(2) ISO SOC, Astrophysics Division of ESA, Villafranca, Spain

Abstract. As a close companion of the Scd-type galaxy IC~342, UGCA~86 is influenced in it's development by the considerable gravitational interaction between the two galaxies. Signs for that have been found from HI as well as from optical observations. While the distribution of neutral hydrogen shows significant distortion at large scale, the optical data reveal regions of heavy star formation most probably induced by gas infall due to the gravitational interaction.
     In order to study the physical properties of the different star-forming regions in UGCA~86, we tried to analyse FIR data just looking for dust content and temperature of the individual regions. Therefore, ISOPHOT C100 and C200 observations have been performed at wavelengths of 60, 120, 160, and 200 micron. In addition, 12, 25, 60, and 100 micron maps were derived from reprocessed IRAS data (survey and pointed observations) by applying the maximum entropy method. This deconvoluting approach was required to achieve a sufficient resolution demanded by distances between the individual regions of only 3 arcminutes.
     The recent analysis of the combined set of ISO and IRAS data revealed further significant differences -- mainly in dust temperatures -- between the star-forming regions influenced (most probably induced) and not influenced by gas infall. The warmest dust is found in the southern star-forming region. This region is the only one connected with large Halpha filaments extending for more than 1 kpc.


E. Caux (1), C. Ceccarelli (2), C. Vastel (1) and A. Castets (2)
(1) CESR, CNRS/UPS BP 4346, F-31028 Toulouse cedex 04, France
(2) LAOG, Observatoire de Grenoble BP 53, F-38041 Grenoble cedex 09, France

Abstract. Oxygen is the most abundant element after hydrogen and helium in the Universe. It is therefore of key importance to know in which form oxygen is found in the different phases of the Interstellar Medium.
     We present low resolution (about 200) ISO-LWS observations of the [OI] (63 micron and 145 micron) lines towards the molecular cloud L1689N, which hosts the low-mass, Class 0 protostar IRAS16293-2422. From the observed ratio of the two [OI] lines, we deduce a mean gas temperature of 26 K, a molecular hydrogen density larger than about 3x10^4 cm^-3 and an [OI] column density larger than about 5x10^19 cm^-2. Combining these observations with previous CO observations, we obtain [OI]/[CO] = 50. This ratio implies that up to 98% of oxygen abundance is in atomic form in the gas phase. Furthermore, assuming all the gaseous carbon is locked into the CO, carbon has to be depleted by more than a factor 24.
     We also obtained high resolution (about 8000) observations with ISO-LWS towards the massive star formation W49N. Using a measured profile of the LWS FPs spectral response, we performed a decomposition of the detected signal, considering four distincts components: one associated with the compact HII region is seen in emission for the two [OI] lines, while the absorption part of the observed spectrum at 63 micron is due to three components associated with cold molecular clouds present in the line of sight. For the emission component, from the observed ratio of the two [OI] lines, we deduce a mean gas temperature of 42 K, a molecular hydrogen density larger than 3x10^4 cm^-3 and an [OI] column density larger than 10^20 cm^-2. For the cold molecular clouds, we compute the ``optical'' depth needed for each cloud to obtain the observed spectrum around 63 micron after convolution by the instrumental profile, assuming that OI and CO originate from the same region. From the [OI] 63 micron ``optical'' depths we derive [OI] column densities of 7x10^18 cm^-2, 7.7~10^18 cm^-2 and 2.2x10^19 cm^-2. Combining these observations with 13CO millimeter line emission observations, we obtain [OI]/[CO] about 194, 105 and 183, which also imply that in these cases a very large abundance (more than 99%) of atomic oxygen in the gas phase and a large depletion of CO.
     Therefore our observations strongly suggest that oxygen in cold molecular clouds is found mainly in the atomic form and that CO is more depleted than previously thought. This has important consequences on the thermal balance and chemical modeling of molecular clouds.


P. Cox

IAS, Bat 121, Universite Paris XI, 91405 Orsay Cedex, France

Abstract. We will discuss the results of a series of photometric and spectroscopic observations using ISOCAM, the LWS and PHOT on two nearby, fully evolved planetary nebulae, the Helix nebula (NGC 7293) and the Dumbbell nebula (NGC6853). The ISO data allow the study of the neutral envelopes of these nebulae through the pure rotational lines of molecular hydrogen and the major atomic lines, providing a quite complete view of the photo-dissociation region associated with these objects.


Herve Dole, Guilaine Lagache, Richard Gispert, Jean-Loup Puget and the FIRBACK consortium

Institut d'Astrophysique Spatiale, Orsay, France

Abstract. FIRBACK is a one of the deepest survey performed at 170 micron with ISOPHOT onboard ISO, and is aimed at the study of the cosmic far infrared background. Three low foreground contamination fields have been observed, covering four square degrees in total. About 300 extragalactic sources between 75 mJy and 1 Jy are detected. Source counts present a strong slope of 2.2 in the integral "logN-logS" plot, which cannot be due to the effect of the K-correction if no cosmological evolution is present. These sources account for less that 10% of the Cosmic Infrared Backgound at 170 micron, and their nature is still unknown, even if most of them are expected to be dust-enshrouded galaxies, and some of them above-redshift-1 sources.
     We will present a phenomenological model, based on FIRBACK and ISOCAM source counts, which constrain the galaxy luminosity function (LF) evolution with the redshift. We show that an strong evolution of a galaxy population with L_FIR = 10^11 Lsun between redshifts 0 and 1.4 (in account with the values derived from the CIB spectrum) reproduces the observed counts.
     The detection of the Cosmic Infrared Backgroud fluctuations will also be discussed. We extract point sources from the maps using a proper PHOT footprint at 170 micron, and make an analysis based on the decomposition of galactic and extragalactic components in the map's power spectrum.


S.B. Fajardo-Acosta (1), D.E. Backman (2), R.E. Stencel (3)

(1) Jet Propulsion Laboratory
(2) Franklin and Marshall College
(3) University of Denver

Abstract. We searched for far-infrared (60 micron) extended emission, in the form of circumstellar dust disks, in the maps of seven main-sequence stars. Direct detection of circumstellar disks in these systems can advance our understanding of the Vega phenomenon and the nature of protoplanetary disk candidates.
     We obtained 60 micron maps with the PHOT C-100 3x3-pixel far-infrared camera on-board ISO, in the P32 microscanning dedicated mapping mode. The maps span 6'15''x5'45'' (RAxdecl), at a spatial resolution of about 30''. The maps presented here were obtained with integration times of 128 seconds at each spacecraft raster position. These integration times are 4 times larger than in previous similar maps of Vega-type stars obtained by Fajardo-Acosta, Stencel, and Backman (1997, ApJ, 487, L151; 1998, ApJ, 503, L193, hereafter FSB). Our goal was to increase S/N in the newer maps by a factor of 2 with respect to the previous ones.
     The stars we observed are gamma Oph (A0 V), alpha PsA (A3 V), gamma Tri (A1 Vnn), 61 Cyg A (K5 V), tau1 Eri (F5-6 V), tau Cet (G8 V), and eps Eri (K2 V). These systems are nearby, within 30 pc from us, and are suspected to harbor Vega-like circumstellar dust disks (Backman and Paresce 1993, Protostars and Planets III, ed. Levy and Lunine, 1253). We compared the maps of these systems with similar maps of the stars alpha Boo and alpha Aql, which do not possess circumstellar dust. We discuss techniques to model point-spread functions (PSFs) from the latter, and their subtraction from our Vega-type stellar maps.
     We did not spatially resolve extended emission in the maps of gamma Tri, 61 Cyg A, and tau Cet, upon comparison with our modeled PSFs. We could only marginally detect a ring of 60 micron emitting dust around eps Eri, previously reported by Fajardo-Acosta, Stencel, and Backman (1998, BAAS, 193, 69.07). This detection remains tentative.
     The maps of gamma Oph, alpha PsA, and tau1 Eri definitely show extended emission when compared with model PSFs. We confirmed the previous detection in alpha PsA by FSB, but now can detect extended emission as far as about 700 AU from the star, as opposed to about 500 AU in the previous observations. The detection in gamma Oph was only hinted at by FSB. The detection of extended emission around tau1 Eri is reported for the first time here.


C. Gabriel (1), M. Hur (2)

(1) ISO Data Centre, Satellite Tracking Station, Villafranca del Castillo, E-28080 Madrid, Spain
(2) IPAC, Pasadena, USA

Abstract. The ISOPHOT Interactive Analysis (PIA) contains several map coadding algorithms and flat-fielding techniques. They should help to optimize the results obtained with ISOPHOT raster data. They are embedded in an environment combining a large flexibility with a very high user friendliness.
     The many different ways of performing raster observations with ISOPHOT makes an assessment of the reliability of the obtained results somewhat difficult. A map simulator has been developed under the PIA framework, for addressing different questions like the validity of theoretical / experimental beam profiles; detection limits and confusion levels; optimization of the use of the mapping algorithms by the different raster configurations.


E.K. Holmes and S.F. Dermott

University of Florida

Abstract. COBE observations reveal an offset in the center of symmetry of the zodiacal cloud from the Sun. If the zodiacal cloud were symmetric about the Sun, the maximum and minimum average of the North (N) and South (S) polar brightnesses, (N + S)/2, of the cloud would occur at perihelion and aphelion, respectively. However, the minimum of the COBE curve is displaced from aphelion showing that the cloud is offset from the Sun. The variation in average polar brightness is an annual variation. COBE was only a nine month long mission, so ISO data was taken to supplement the missing three months of data. The variation of the average polar brightness was small, less than 2 MJy/sr throughout the year. In the 25 micron waveband, we show the ISO PHOT data (PHT3 and PHT5), which has some rather large errors associated with it, for the variation in (N + S)/2 with Ecliptic Longitude of Earth in comparison with the COBE data.

This research was funded in part by a NASA GSRP grant.


M. Juvela, K. Mattila

Helsinki University Observatory, P.O.Box 14, SF-00014 University of Helsinki, Finland

Abstract. We have studied the spectrum of the galactic cirrus in low surface brightness regions using ISOPHOT raster maps made at wavelengths 90, 150, and 180 micron.
     We will first discuss the calibration of the observations. The ISOPHOT surface brightness values have been compared with DIRBE data and the methods used in this comparison are described. A good correspondence is found at 90 micron while at longer wavelengths the DIRBE surface brightness values tend to be higher.
     Surface brightness variations caused by cirrus fluctuations make it possible to determine the spectrum of the emission. Cirrus spectra have been derived for several regions with average surface brightness values between 2 and 8 MJy/sr. Some results from this study will be shown.


P. Lamy

Laboratoire d'Astronomie Spatiale, Marseille

Abstract. Thermal infra-red images of comets Hale-Bopp, 126P/IRAS, 103P/Hartley 2, 22P/Kopff, 133P/Elst-Pizarro, 55P/Tempel-Tuttle and 46P/Wirtanen have been acquired in 1996 and 1998 with ISOCAM using its highest spatial resolution of 1.5 arcsec/pixel and several filters centered at 7-15 micron. After correction from the instrumental response (dark current, flat-field, glitches and transient), the images are fitted by the sum of the coma and nucleus contribution, convolved by the PSF to photometrically discriminate the signal of the nucleus from that of the coma. This technique is also used to interpret HST images of comets (Lamy et al., A&A 337, 945, 1998). The thermal emission from the nucleus of comet Hale-Bopp and of four short-period comets is successfully detected. The thermal spectrum of Hale-Bopp exhibits the silicate feature at 10 micron, the first time that it is detected on a cometary nucleus, and helps to constain its thermal model and finally its size. In three cases, Hale-Bopp, 22P/Kopff and 55P/Tempel-Tuttle, independent optical observations with the HST allow to determine the albedo and therefore the size with limited assumptions. For the other comets, and in the absence of optical data, the Standard Thermal Model is applied to estimate the size of their nucleus. Preliminary results on the thermal properties of the dust coma of Hale-Bopp will also be shown, the maps of the temperature distribution and the strength of the silicate feature.
     Upper limits are derived for the other comets P/Kopff and P/IRAS. We will propose a preliminary interpretation of these fluxes in terms of the nuclei properties.


R.J. Laureijs (1), U. Herbstmeier (2), P. Abraham (2,3), U. Klaas (2), D. Lemke (2)

(1) ISO Data Centre, Satellite Tracking Station, Villafranca del Castillo, E-28080 Madrid, Spain
(2) Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg, Germany
(3) Konkoly Observatory of the Hungarian Academy of Sciences, P.O. Box 67, H-1525 Budapest, Hungary

Abstract. We have measured the spectral energy distribution of infrared cirrus using 9 filterbands in the 60--200 micron wavelength range with ISO. The spectrum is obtained by correlating the same spatial structures at different wavelengths. We have accurately determined the peak in the spectral energy distribution from which we can derive the temperature of the large dust particles assuming a fixed value for the power beta in the emissivity: 17.0 K for beta =2 and 20.5 K for beta =1. The observations were centred on an IRAS point source which was classified as a ``cirrus'' source only detected by IRAS at 100 micron. With ISO we have been able to resolve the source and we confirm that the far-infrared colours of the source for lambda > 100 micron are indeed indistinguishable from the cirrus background. At 60 micron the emission is relatively higher than the background suggesting a higher abundance of very small grains. Because of the small size of the source (of order 3'), we derive a moderately high density of n(H)>10^3 cm^-2 which suggests that the IRAS source must be a significant density enhancement. The mass of the source is not sufficient to make the cloudlet gravitationally bound but is only a few times below the critical mass. Our results suggest that a fraction of the 100 micron ``cirrus'' point source detections by IRAS could contain cloudlets that are diffuse/translucent but also gravitationally bound.


T. Le Bertre (1), N. Mauron (2), G. Lagache (3), F. Boulanger (3), F.X. Desert (4), N. Epchtein (5) and P. Le Sidaner (1)

(1) Observatory of Paris, Paris, France
(2) ISTEEM, Montpellier, France
(3) IAS, Orsay, France
(4) Observatory of Grenoble, Grenoble, France
(5) Observatory of Nice, Nice, France

Abstract. With ISOPHOT we have obtained maps in 2 bands, 60 and 90 micron, of 18 fields at proximity of red giants (however one of the maps, at 60 micron, is incomplete). The data were acquired with C100 and the fields were covered with 3x3 rasters (AOT: PHT22).
     The data show gradients of emission towards the positions of the red giants. (In all cases the red giant has been kept out of the observed field.) In general, emission from an extended circumstellar shell is seen, but we have no evidence for detached shells. In half of the cases we detect isolated sources of emission, probably due to blobs of interstellar matter heated to about 25-40 K by the nearby (<= 2 pc) red giant. We will detail a few examples and characterize these blobs.
     We have encountered difficulties mainly with flat-fielding, especially when the gradient of emission covers the whole field, and with the absolute photometric calibration. Preliminary results of our study have been presented in [1], [2] and [3].

  • [1] Le Bertre T., Lagache G., Mauron N., Boulanger F., Desert F.X., Epchtein N., Le Sidaner P., 1998, A&A 335, 287
  • [2] Le Bertre T., Mauron N., Lagache G., Boulanger F., Desert F.X., Epchtein N., Le Sidaner P., 1999, Proc. ``The Universe as seen by ISO'', P. Cox & M. Kessler (eds.), in press
  • [3] Le Bertre T., Mauron N., Lagache G., Boulanger F., Desert F.X., Epchtein N., Le Sidaner P., 1999, ``Atmospheres of M, S and C Giants'', J. Hron and S. Hoefner (eds.), pp. 101-102


    K. Lehtinen (1), K. Mattila (1), D. Lemke (2)

    (1) Helsinki University Observatory, P.O.Box 14, SF-00014 University of Helsinki, Finland
    (2) Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg, Germany

    Far-infrared mapping of globules
    We have mapped two globules at 100 and 200 micron wavelength by using the ISOPHOT instrument. The other globule, Thumbprint Nebula (TPN) has no star formation, while the other globule (DC303.8-14.2) has an embedded IRAS source at its center.
         The properties of the TPN has been discussed by Lehtinen et al. (A&A 1998, 333, 702). One of the main results is that the diffuse interstellar radiation field is enough to be the only heating source of dust in this dark cloud. The dust temperature at the cloud center is about 14-16 K.
         At the center of the globule DC303.8-14.2 there is an IRAS point source with a steeply rising spectral energy distribution (SED), typical for a deeply embedded young stellar object. We have combined our 100 and 200 micron flux densities with 1300 micron flux density (Henning et al. 1993 A&A, 276, 129), and fitted the data with a modified blackbody. The derived temperature of circumstellar dust is about 23 K.
         We have used the 1.3 mm continuum emission, together with the derived dust temperature, to estimate the circumstellar mass. We obtain Mcs = 0.2 Msun. The derived bolometric temperature of the IRAS source is about 59 K, which places it on the border line between Class 0 and Class I objects.

    ISO, IRAS and COBE/DIRBE surface brightness calibration
    In order to check the calibration of the surface brightness values in the ISOPHOT maps at 100 micron, we have compared the brightness values given by ISOPHOT to the IRAS and COBE/DIRBE values. We use COBE/DIRBE 'zodiacal subtracted mission average' and IRAS ISSA maps. The values of COBE/DIRBE are treated as 'absolute' values, while the IRAS data serves only as an intermediate step in order to have better angular resolution than given by COBE/DIRBE data. The surface brightness in our ISO maps is relatively bright, i.e. about 10-60 MJy/sr.
         ISO data has been processed with PIA V7.2.2 and V7.3. The calibration of ISO 100 micron data is based on default responsivities, while the 200 micron calibration is based on actual responsivities. All three datasets have been colour corrected for a spectrum of a modified blackbody nuB(nu, T=18 K).
         The procedure is the following: 1) the ISSA map is convolved with the DIRBE beam, 2) the relation I(DIRBE)=k I(IRAS) is derived, 3) the ISO data is convolved with a gaussian to IRAS resolution, 4) zodiacal light is subtracted from ISO data (about 2 MJy/sr), 5) the ISO data is compared, pixel by pixel, with the DIRBE-corrected IRAS data.
         In different areas we get the following results. Chamaeleon~I region (size 41'x41'): I(ISO) = 1.8xI(DIRBE). R~Corona Australis region (26'x26'): I(ISO) = 2.2xI(DIRBE). Dark cloud L183 (32'x32'): I(ISO) = 2.4xI(DIRBE). Dark cloud DC~303.8-14.2 (23'x23'): I(ISO) = 1.7xI(DIRBE). That is, the 100 micron surface brightness values given by ISO are about two times the COBE/DIRBE values.
         Due to the presence of bright point sources, a direct DIRBE-ISO comparison at 200 micron is easy only for L183, which has no bright point sources. Simply taking the DIRBE pixel closest to the ISO map center, fitting the DIRBE values at 100, 140 and 240 micron with a modified blackbody, gives I(DIRBE)=43 MJy/sr. An average over the whole ISO map gives I(ISO)=47 MJy/sr., i.e. I(ISO)=1.1xI(DIRBE).


    C. Lloyd

    RAL, UK

    Abstract. Pointed observations of Mars are used to map the apparent beam profile of the LWS detectors with the aim of extending the point source calibration to extended sources. The LWS profile is found to be narrower than expected and also shows some asymmetry. For point sources observed off axis and generally for extended sources the LWS spectra show varying degrees of fringing. The Mars observations are used to explore the fringe amplitude and phase behaviour within the LWS beam.


    C. Meny, G. Serra, J.M. Lamarre, I. Ristorcelli, J.P. Bernard, M. Giard, F. Pajot, B. Stepnik, J.P. Torre

    CESR, CNRS/UPS BP 4346, F-31028 Toulouse cedex 04, France

    Abstract. PRONAOS observations show strong variations in color ratio in the wavelength range extending from 200 to 600 micron, within all the surveyed areas (star forming interstellar complexes, quiet molecular clouds, and galactic cirrus). These variations, observed at angular scales of a few arcmin, are not always correlated with the 60 over 100 micron ratio.
         The PRONAOS submillimeter observations coupled with IRAS and ISO data reveal the presence of very cold condensations (T = 10 to 13 K) with emissivity index values higher than n = 1.8, embedded in warm halos (T > 17 K) with lower index values. The unique PRONAOS brightness sensitivity gives access to the very extended emissions, leading to the assessment of the mass bulk, complementary with the millimeter ground-based high angular resolution observations.
         The PRONAOS results show that the IRAS survey is not sufficient to extrapolate sky brightness in the submillimeter range for angular scales around a few arcmin, even at high galactic latitude. The understanding of the changes of dust properties and the knowledge of galactic dust emission at these angular scales requires additional sensitive measurements in the wavelength range 200 to 600 micron.


    Thomas G. Muller

    ISO Data Centre, ESA Astrophysics Division, Villafranca del Castillo, Spain

    Abstract. Multi-aperture photometry between lambda=3.2 micron and 120 micron with PHT04 has been used to determine extended emission around point sources (circumstellar disks, envelopes), extended structures (galaxies, diffuse interstellar medium, comets), companions, brightness distributions (galaxies, comet coma, comet tails) and nucleus/disk separation in galaxies.
         The PHT04 observing mode has not been scientifically validated so far, due to uncertainties in the beam and aperture profiles and due to detector non-linearities which affect the aperture sequences strongly. By going from the 5'' aperture to the 180'' aperture the signals can change up to 3 orders of magnitude while internal FCS calibration is only done in the largest aperture.
         Here the results from the PHT04 calibration observations on point sources and on the background are presented. In cases where the aperture area does not scale with the signal (due to non-flat aperture profiles) empirical correction factors have been derived. In parallel to the measurements a Point Spread Function (PSF) model has been developed to simulate aperture sequences on point and different types of extended sources. The following results have been obtained:

  • Aperture sequences on well-centered point sources follow the prediction from the PSF model within the derived signal uncertainties
  • Aperture sequences on the background show deviations from the PSF modelling due to non-flat aperture profiles, but correction factors relative to the ``standard'' and to the 180'' aperture have been determined.
  • Absolute calibration of ``non-standard'' apertures using the internal calibration source (FCS) are still problematic
  • With the derived correction factors a relative calibration between a set of apertures is possible
  • Extended structures and brightness profiles can be determined from PHT04 sequences (if an aperture sequence with sufficiently small apertures has been choosen) The combination of model parameters with the calibration data allows now to analyse the scientific programmes. First results with structures around point sources are presented. A comparison of a PHT04 aperture sequence with ISOCAM observations on HD 97300 (Siebenmorgen et al., A&A 339, 1998) confirms the reliability of this mode under certain circumstances. Software to analyse the scientific PHT04 programmes is available.


    M. Perault and P. Hennebelle

    Groupe de Radioastronomie, Laboratoire de Physique de l'ENS, 24 Rue Lhomond, F75005 Paris

    Abstract. The Isogal survey (P.I. A. Omont) has provided 7 and 15 um images of about 10 square degrees in the inner galactic disk, as a collection of small fields of 0.01 to 0.1 square degree each, distributed along the galactic equator, mostly between longitudes +/- 45 degrees. In addition to the tens of thousands stars detected, which were the primary goal of the survey, for galactic structure studies, much structure is seen in the diffuse emission, both in emission and absorption. The study of the absorption features will be emphasized:

  • technical considerations on the extraction of the objects seen in absorption, using the multi-resolution analysis software of Bijaoui's group in Nice on clipped inverse images.
  • analysis of the extracted objects
  • preliminary results of a follow-up study conducted with the Iram 30m-telescope, and physical characterization of these highly condensed objects.


    S. B. Peschke (1), M. Stickel (2), I. Heinrichsen (3), C. M. Lisse (4), E. Gruen (5)

    (1) ISO Data Centre (VILSPA)
    (2) MPI fuer Astronomie
    (3) IPAC
    (4) STScI
    (5) MPI fuer Kernphysik

    Abstract. First maps of a comet at 60 and 175 micron were obtained using ISOPHOT, the photometer of the Infrared Space Observatory(ISO). The observations were carried out on December 30, 1997 , mapping an area of 9'x9' centered on comet Hale-Bopp at both filters. Each measurement consisted of 3 individual submaps offset by a third of a pixel in both directions to increase the final resolution of the maps. The final maps were composed of the submaps with the use of a drizzle algorithm. Within the same orbit 3-175 micron filter photometry on comet Hale-Bopp was performed as well as multi-aperture photometry near the peak wavelength of thermal emission. The same photometric sequence was repeated as 'shadow observation' at the same position as that tracked in the initial sequence for precise background subtraction. From the 60 and 175 micron, radial intensity profiles have been derived which are compared to optical/near-IR data and to the results of multi-aperture photometry. Since dust grains have the highest thermal emitting efficiency closest to their own size, the emission in the maps observed with the two filters are dominated by the the thermal emission of different size grains. >From the comparison of the different wavelength maps, indications on perferred concentration of different grain sizes can be derived. Grain size distribution modeling has been carried out for the spectral energy distribution derived with multi-filter photometry to get an indication of the coma composition with will in turn be used as input for dynamical modeling. Latest results will be presented.


    Goeran L. Pilbratt

    ESA Astrophysics Division, Space Science Department, ESTEC/SCI-SA, Keplerlaan 1, NL-2201 AZ Noordwijk, The Netherlands; email:

    Abstract. The `Far InfraRed and Submillimetre Telescope', (FIRST), is the fourth cornerstone mission in the European Space Agency (ESA) science programme. FIRST will perform photometry and spectroscopy in approximately the 80-670 micron range in the far infrared and submillimetre part of the spectrum. The FIRST wavelength range bridges the gap between what can be well observed from current and future groundbased facilities and that of other space missions. The key scientific topics to be addressed by FIRST will be diverse and include:

  • Deep extragalactic broadband photometric surveys in the 100-600 micron FIRST `prime' wavelength band and related research.
  • Follow-up spectroscopy of especially interesting objects discovered in the survey.
  • Detailed studies of the physics and chemistry of the interstellar medium in galaxies, both locally in our own Galaxy as well as in external galaxies.
  • Observational astrochemistry (of gas and dust) as a quantitative tool.
  • Detailed high resolution spectroscopy of a number of comets, high resolution molecular spectroscopy of atmospheres of the cool outer planets and their satellites.
         Given the science objectives of the FIRST mission it is clear that projects in the form of large spatial and spectral surveys will constitute very important elements of the observing programme. It is also clear that FIRST will be observing sources of extended emission; both as sources in their own right, and as unwanted foreground or background sources.
         FIRST will have a passively cooled 3.5 m diameter, low emissivity, Cassegrain/Ritchey-Chretien telescope, to be provided by JPL as part of NASA's involvement in the FIRST mission. The science payload complement will consist of three instruments, two `cameras' with medium resolution spectrometers called PACS (PI: A. Poglitsch, MPE) and SPIRE (PI: M. Griffin, QMW), and a very high resolution heterodyne spectrometer (PI: Th. de Graauw, SRON). They will be housed inside a superfluid helium cryostat based on the successful ISO design.
         I will describe the present state of all aspects of the FIRST mission, and provide the current implementation schedule.


    J.M. Rodriguez Espinosa and Ana M. Perez Garcia

    Instituto de Astrofisica de Canarias La Laguna Tenerife, Spain

    Abstract. Far IR (90 micron) ISO Maps of four Seyfert galaxies will be presented. We find that the far-infrared emission is extended in all cases out to radii comparable to optical radii. To reach this conclusion an ISO PSF has been modeled that compares satisfactorily with an actual IRAS point source observed by ISO under the same instrumental conditions. Several tests of the PIA mapping algorithm will be presented to explain the algorithm selected by us.


    A. Salama

    ISO Data Centre, Astrophysics Division, Space Science Department of ESA, Villafranca del Castillo, P.O. Box 50727, 28080 Madrid, Spain.

    Abstract. The ISO instruments beam profiles and their usage in the determination of extended source brightness will be reviewed. A summary will be given of how the beam profiles have been derived, the main problems encountered and their availability.


    A.K. Speck (1), M. Meixner (2), and G.R. Knapp (2)

    (1) Astronomy Department, University of Illinois at Urbana/Champaign 1002 W. Green St., Urbana, IL 61801, USA
    (2) Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA

    Abstract. We present preliminary results from linear scans with ISOPHOT of nine post-AGB objects; NGC 246, CRL 618, HD16179, NGC 6543, IRAS 18184, NGC 6720, NGC 6853, CRL 2688 and NGC 7293. The goals of these observations are: (1) to determine the history of mass-loss as imprinted on the circumstellar dust envelopes in these protoplanetary nebulae (PPNe) and planetary nebulae PNe, and (2) to measure the total mass of the circumstellar dust from which we can infer a lower limit to the initial mass of the progenitor main sequence stars. In particular, the radial profiles of dust density derived from these observations will provide a record of mass-loss and test current theories of episodic and accelerated mass-loss. Understanding the mass-loss process is a key problem within astrophysics because most of the returned interstellar dust and gas originates from these stellar sources.
         We used the PHT32 AOT in both the C100 and C200 arrays in order to obtain diffraction limited spatial resolution for our linear maps, which have angular resolutions of 76'' at 90~micron and at 134'' at 160 micron. These linear maps have the maximum possible length (about 30' for the 90 micron filter and about 46' for the 160 micron) in order to cover background sky and to allow the observation of any large scale structure. The use of the two filters allows the derivation of colour temperature distributions and provides independent verification that the structures we are observing are not artifacts due to scattering or detector memory. We have used both forward and reverse scans on these sources in order to evaluate the reliability of observed structure with radial distance. A preliminary look at this data shows that five sources are certainly extended and two others are probably also extended.
         In addition we discuss some of the difficulties and unresolved issues in the processing of this data.


    J-L. Starck

    DSM/DAPNIA/SEI-SAP, CEA/Saclay, 91191 Gif-sur-Yvette, France

    Abstract. The Multiscale Vision Model is a recent object detection method, based on the wavelet transform. It allows us to extract all objects contained in an image, whatever their size or their shape. On each extracted object, information concerning its flux or its shape can easely be determined. We show that such an approach can be combined with a deconvolution, leading to the reconstruction of deconvolved objects. The advantages to do this are:

  • morphological parameters (gallaxy ellipticity, ...) are more accurate;
  • as each object is deconvolved separately, a variant point spread function can easely be taken into account;
  • very large images can be deconvolved.


    J. Tauber

    Astrophysics Division, Space Science Department of ESA, ESTEC, P.O. Box 299, 2200AG Noordwijk, The Netherlands

    Abstract. Planck is the third Medium-Sized Mission (M3) of ESA's Horizon 2000 Scientific Programme. It is designed to image the anisotropies of the Cosmic Microwave Background (CMB) over the whole sky, with unprecedented sensitivity (Delta T/T = 2x10^(-6)) and angular resolution (better than 10 arcminutes). Planck will provide a major source of information relevant to several cosmological and astrophysical issues, such as testing theories of the early universe and the origin of cosmic structure.
         The ability to measure to high accuracy the angular power spectrum of the CMB fluctuations will allow the determination of fundamental cosmological parameters such as the density parameter (Omega_0), the Hubble constant H_0, and the cosmological parameter (Lambda), with an uncertainty of order a few percent. In addition to the main cosmological goals of the mission, the Planck sky survey will be used to study in detail the very sources of emission which ``contaminate'' the signal due to the CMB, and will result in a wealth of information on the properties of extragalactic sources, and on the dust and gas in our own galaxy. One specific notable result will be the measurement of the Sunyaev-Zeldovich effect in many thousands of galaxy clusters.
         In order to meet its ambitious objectives the design of Planck calls for:

  • a telescope with a physical aperture of size of about 1.5 metre to achieve the angular resolution;
  • state-of-the-art broadband cryogenic detectors covering the range 30 to 900 GHz, to achieve the required sensitivity and the ability to remove foreground sources of emission;
  • a survey with near-all-sky coverage carried out from a far-Earth orbit;
  • extreme attention to rejection of unwanted systematic effects.
         The same design features required to map the CMB make Planck an instrument ideally suited to map extended foreground emission at far-IR and submm wavelengths. We shall present an overview of the Planck mission, its scientific objectives and the key elements of its technical design, in particular those related to the topic of the workshop.