The first detection of thermal water emission from a Herbig-Haro object is presented. The observations were performed with theLws (Long Wavelength Spectrograph) aboard Iso (InfraredSpace Observatory).Besides H 2O, rotational lines of CO are present in the spectrum of HH 54. These highJ CO lines are used to derive the physical model parameters of the Fir (far-infrared) molecular line emitting regions. This model fits simultaneously the observed OH and H 2O spectra for an OH abundanceX(OH) = 10 6 and a water vapour abundance X(H2O) = 10 5. At a distance of 250 pc, the total CO, OH and H 2O rotational line cooling rate is estimated to be 1.3 10 2 L , which is comparable to the mechanical luminosity generated by the 10 km s 1 shocks, suggesting that practically all of the cooling of theweak-shock regions is done by these three molecular species alone.

A high signal-to-noise 52–90 μm spectrum is presented for the central part of the Sagittarius B2 complex. The data were obtained with the Long Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The [O I] 63 μm line is detected in absorption even at the grating spectral resolution of 0.29 μm. A lower limit for the column density of atomic oxygen of the order of 10 cm is derived. This implies that more than 40% of the interstellar oxygen must be in atomic form along the line of sight toward the Sgr B2 molecular cloud.

A high signal-to-noise 52–90 μm spectrum is presented for the central part of the Sagittarius B2 complex. The data were obtained with the Long Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The [O I] 63 μm line is detected in absorption even at the grating spectral resolution of 0.29 μm. A lower limit for the column density of atomic oxygen of the order of 10 cm is derived. This implies that more than 40% of the interstellar oxygen must be in atomic form along the line of sight toward the Sgr B2 molecular cloud.

A total of 86 galaxies have been detected at 60 μm in the high galactic latitude portion of the IRAS minisurvey. The surface density of detected galaxies with flux densities greater than 0.5 Jy is 0.25 deg2• Virtually all the galaxies detected are spiral galaxies and have an infrared to blue luminosity ratio ranging from 50 to 0.5. For the infrared-selected sample, no obvious correlation exists between infrared excess and color temperature. The infrared flux from 10 to 100 μm contributes approximately 5% of the blue luminosity for galaxies in the magnitude range 14 < mpg< 18 mag. The fraction of interacting galaxies is between one-eighth and one-fourth of the sample. Subject headings: galaxies: photometryinfrared: general infrared: sources

We review the "strong source correction", which is used to remove the effects of de-biasing in LWS data and present a new investigation of corrections needed for the change of spectral and detector response with bias.

We present the first full FIR spectrum of Centaurus A (NGC 5128) from 43 - 196.7 um. The data was obtained with the ISO Long Wavelength Spectrometer (LWS). We conclude that the FIR emission in a 70 arcsec beam centred on the nucleus is dominated by star formation rather than AGN activity. The flux in the far-infrared lines is ~ 1 % of the total FIR: the [CII] line flux is ~ 0.4 % FIR and the [OI] line is ~ 0.2 %, with the remainder arising from [OIII], [NII] and [NIII] lines. These are typical values for starburst galaxies. The ratio of the [NIII]/[NII] line intensities from the HII regions in the dust lane can be modelled as a ~ 6 million year old starburst. This suggests that the galaxy underwent either a recent merger or a merger which triggered a series of bursts. We estimate that < 5 % of the observed [CII] arises in the cold neutral medium (CNM) and that ~ 10 % arises in the warm ionized medium (WIM). The main contributors to the [CII] emission are the PDRs, which are located throughout the dust lane and in regions beyond where the bulk of the molecular material lies. On scales of ~ 1 kpc the average physical properties of the PDRs are modelled with a gas density, n ~ 1000 cm^-3, an incident far-UV field, G ~ 100 times the local Galactic field, and a gas temperature of ~ 250 K.

We present the results of Infrared Space Observatory (ISO) spectroscopic observations of seven Seyfert galaxies collected for the ISO Core Programme. For the galaxies 3C 120, MKN 573, MKN 3, MKN 6 and I ZW 92 we have observed low and high ionization lines with the LWS and SWS spectrometers in partial scan grating mode. MKN 463 and IC 4329A have been observed only with the LWS. Line ratio diagrams are used to separate the nonthermal activity produced in the Narrow Line Regions of the nuclei from the emission originating in starbursts and photodissociation regions.Using standard photoionization models, we fit the observed infrared high ionization fine-structure lines of the NLR of MKN 3, MKN 573 and 3C 120 and estimate the main photoionization model parameters. The lower ionization and neutral fine-structure lines are stronger than predicted by these photoionization models, suggesting that an additional contribution from photodissociation regions (PDR) and HII regions is present. However with the exception of NGC 1068 and Cen A, whose low excitation line ratios resemble those of starburst galaxies, the AGN are characterized by lower [CII]/[OI] ratios, suggesting unusual PDR or XDR conditions.

We present the first complete far-infrared spectrum (43-197 μm) of M82, the brightest infrared galaxy in the sky, taken with the Long Wavelength Spectrometer of the Infrared Space Observatory (ISO). We detected seven fine structure emission lines, [O I] 63 and 145 μm, [O III] 52 and 88 μm , [N II] 122 μm, [N III] 57 μm, and [C II] 158 μm, and fitted their ratios to a combination starburst and photodissociation region (PDR) model. The best fit is obtained with H II regions with n=250 cm-3, an ionization parameter of 10-3.5, and PDRs with n=103.3 cm-3 and a far-ultraviolet flux of G0=102.8. We applied both continuous and instantaneous starburst models, with our best fit being a 3-5 Myr old instantaneous burst model with a 100 M☉ cutoff. We also detected the ground-state rotational line of OH in absorption at 119.4 μm. No excited level OH transitions are apparent, indicating that the OH is almost entirely in its ground state with a column density ~4×1014 cm-2. The spectral energy distribution over the long-wavelength spectrometer wavelength range is well fitted with a 48 K dust temperature and an optical depth, τDust ∝ λ-1.

We present the results of the first spectrophotometric survey of a sample of eleven Herbig Ae/Be stars (HAEBE) obtained with the Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory (ISO). The [OI] 63 mu m and the [CII] 158 mu m lines an obsereved in all the investigated sources, while the [OI] 145 mu m transition, due to its relative faintness, sometimes remains undetected. By comparing line intensity ratios with model predictions, photodissociation, due to the UV photons from the central star, results the dominating excitation mechanism although contributions of C-shocks to the [OI] emission cannot be ruled out. A clear example for the presence of a photodissociation region (PDR) illuminated by an HAEBE is shown by LWS spectroscopic mapping of NGC 7129. Some diagnostic probes of the radiation held and density are provided for the objects in our sample: these substantially agree with the known characteristics of both the star and its circumstellar environment, although the observed ratio [OI]63/[OI] 145 tends to be smaller than predicted by PDR models. The most likely explanation for this behaviour is self-absorption at 63 mu m bq cold atomic oxygen. Fine structure lines of the ionised species [OIII], [NII] were detected whenever the star had a spectral type of B0 or earlier: in particular, around the star CoD-42 degrees 11721, besides a compact HII region, evidence is given for an extended low electron density ionised region. Finally, molecular line emission is associated with stars powering a CO outflow, and clumpy PDR models, better than C-shock models, predict for them relative cooling (CO vs OI and CO vs OH) similar to the observed ones.

We present an outline of various stages of the Long Wavelength Spectrometer (LWS) data pipeline processing, from the conversion of the output from the detectors through to a calibrated spectrum. Normal calibration is based on a linear relationship between the Uranus data from the LWS and a theoretical model of the planet. For strong sources, however, some of the detectors behave non-linearly We show that, using a strong source for which we have a good model as a calibrator, these data can be corrected. Examples of the resulting spectra are shown.

We present the first ISO-LWS observations of the molecular FIR lines in 3 out of a sample of 11 Herbig Ae/Be stars (HAEBE), namely IRAS12496-7650, RCrA and LkH alpha 234. High-J rotational CO lines (from J(up),, = 14 to J(up),, = 19) have been observed in all the spectra, while two (at 79 mu m and 84 mu m) and three OH lines (at 71 mu m, 79 mu m and 84 mu m) were detected in LkH alpha 234 and RCrA respectively.For all sources the molecular emission has been consistently fitted with a Large Velocity Gradient (LVG) model and it results originated in a warm (T greater than or similar to 200 K) and dense (n(H2), greater than or similar to 10(5) cm(-3)) gas located in very compact regions having diameters of few hundreds of AU.These three sources are those with the highest density among the stars of the sample; this suggests that the molecular emission arises in regions showing density peaks.By comparing the observed cooling ratios with model predictions, we find that the FUV radiation from the central source (or from a more embedded companion) is the most likely responsible for the line excitation. At least for the sources where OH has been observed, the contribution of shocks to the line emission can be reasonably ruled out because of the absence in the spectra of any water vapour lints, in contrast with the predictions for molecular emission coming from warm shocked environments.

Based on far-infrared spectroscopy of a small sample of nearbyinfrared-bright and ultraluminous infrared galaxies (ULIRGs) with theISO Long Wavelength Spectrometer we find adramatic progression in ionic/atomic fine-structure emission line andmolecular/atomic absorption line characteristics in these galaxiesextending from strong [O III]52,88 μm and [N III]57 μm lineemission to detection of only faint [C II]158 μm line emissionfrom gas in photodissociation regions in the ULIRGs. The molecularabsorption spectra show varying excitation as well, extending fromgalaxies in which the molecular population mainly occupies the groundstate to galaxies in which there is significant population in higherlevels. In the case of the prototypical ULIRG, the merger galaxy Arp220, the spectrum is dominated by absorption lines of OH, H 2 O, CH,and [O I]. Low [O III]88 μm line flux relative to the integratedfar-infrared flux correlates with low excitation and does not appear tobe due to far-infrared extinction or to density effects. A progressiontoward soft radiation fields or very dusty H II regions may explainthese effects.

We review the results of the observations in the 45-190 μm wavelength range with the ISO Long Wavelength Spectrometer of a sample of Class 0, Class I, Class II pre-Main Sequence objects. We briefly discuss the role of [OI] and of molecular lines in the cooling of these sources.

A far-infrared (43 - 197 mu m) spectroscopic survey of a small sample of relatively nearby infrared-bright galaxies using the Infrared Space Observatory (ISO) Long Wavelength Spectrometer (LWS) reveals a dramatic progression in emission and absorption line characteristics in these galaxies extending from strong [O III]52,88 mu m and [N III]57 mu m fine-structure line emission to detection of only faint [C II]158 mu m line emission from gas in photodissociation regions. The several ultraluminous galaxies (ULIGs) included in the full spectral sample have the weakest emission line characteristics and show absorption due to OH, H2O, CH, and [O I]. We compare the full spectra of six galaxies and examine the importance of parameters such as far-infrared extinction, density, and starburst evolution in producing the observed sequence.

We present the results obtained with the ISO Long Wavelength Spectrometer on a sample of Pre-MS sources, where several molecular lines of CO, H 2 O and OH have been detected. The analysis of the CO lines indicates that gas temperatures as low as 200 K are consistent with the data. This would be in agreement with the relatively low abundance of water in the gas phase measured in most of the objects.

The prototypical Seyfert type 2 galaxy NGC 1068 has been observed with the LWS (Long Wavelength Spectrometer) on board the ISO (Infrared Space Observatory, ESA) satellite from 43 to 197 mu m. All the expected ionic fine structure lines have been detected. Also present are OH rotational lines in emission, at 79, 119 and 163 mu m.The ionic line intensities and ratios in NGC 1068 are discussed in the context of photoionization models of nonthermal (AGN) and thermal (starburst) origin and photodissociation regions models of the host-galaxy interstellar medium.Emission in the low-lying rotational lines of OH seems to be due to rotational or ro-vibrational radiative pumping in an optically thick layer illuminated by a warm continuum source.

We present the first ISO-LWS observations of the molecular FIR lines in 3 out of a sample of 11 Herbig Ae/Be stars (HAEBE), namely IRAS12496-7650, RCrA and LkHα234. High-J pure rotational CO lines (from J up = 14 to J up = 19) have been observed in all the spectra, while two (at 79 μm and 84 μm) and three OH lines (at 71, 79 and 84 μm) have been detected in LkHα234 and RCrA, respectively. For all the sources the molecular emission has been consistently fitted with a Large Velocity Gradient (LVG) model and results as originated in a warm (T ≥ 200 K) and dense (n H 2 ≥ 10 5 cm -3 ) gas. By comparing the observed cooling ratios with models predictions, we find that the FUV radiation is the most probable responsible for line excitation. Shock mechanism contributions can be reasonably ruled out, especially because of the absence in the spectra of any water vapour line, in contrast with the predictions on the molecular emission coming from warm shocked environments.

We present far infrared spectra of the B335 dark cloud region, obtained with the Long Wavelength Spectrometer (LWS) on-board the ISO satellite. Deep spectra were obtained towards the far infrared outflow exciting source, located in the B335 core, and on the three associated Herbig Haro (HH) objects HH119 A, B and C. In addition, a region of about 9 0 in RA and 4 0 in Dec. was mapped which covers the whole molecular outflow. (CII)158 m emission was found to be uniformly distributed across the observed region, with the intensity expected for a pho- todissociation region excited by the average interstellar field. The (OI)63m emission was detected only towards two out of the three HH objects and from the B335 FIR source; excitation from the high-velocity shocks responsible for the HH119 knots can account for the observed line intensity. CO line emission from the rotational levels J =15 to J =18 was detected only to- wards B335 FIR and can be modelled as arising in warm gas whose excitation temperature is in the range 150-800 K, located in a compact ( 10 3 pc) and dense (nH2 10 6 cm 3 ) region. If we assume that the CO J =6 !5 line observed from the ground is also emitted from the same gas component, we derive for this component a temperature of 350 K and a density of 510 5 cm 3 . Current collapse models for the B335 core fail to predict the presence of such warm gas in the infalling source envelope, at the spatial scales implied by our model fit. It is likely that the molecular emission is excited in a low-velocity (v 10 km s 1 ) non-dissociative shock, originating at the base of the flow.