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We present ~2'x2' spectral-maps of Orion BN/KL outflows taken with Herschel at ~12'' resolution. For the first time in the far-IR domain, we spatially resolve the emission associated with the bright H2 shocked regions "Peak 1" and "Peak 2" from that of the Hot Core and ambient cloud. We analyze the ~54-310um spectra taken with the PACS and SPIRE spectrometers. More than 100 lines are detected, most of them rotationally excited lines of 12CO (up to J=48-47), H2O, OH, 13CO, and HCN. Peaks 1/2 are characterized by a very high L(CO)/L(FIR)~5x10^{-3} ratio and a plethora of far-IR H2O emission lines. The high-J CO and OH lines are a factor ~2 brighter toward Peak 1 whereas several excited H2O lines are ~50% brighter toward Peak 2. A simplified non-LTE model allowed us to constrain the dominant gas temperature components. Most of the CO column density arises from Tk~200-500 K gas that we associate with low-velocity shocks that fail to sputter grain ice mantles and show a maximum gas-phase H2O/CO~10^{-2} abundance ratio. In addition, the very excited CO (J>35) and H2O lines reveal a hotter gas component (Tk~2500 K) from faster (v_S>25 km/s) shocks that are able to sputter the frozen-out H2O and lead to high H2O/CO>~1 abundance ratios. The H2O and OH luminosities cannot be reproduced by shock models that assume high (undepleted) abundances of atomic oxygen in the preshock gas and/or neglect the presence of UV radiation in the postshock gas. Although massive outflows are a common feature in other massive star-forming cores, Orion BN/KL seems more peculiar because of its higher molecular luminosities and strong outflows caused by a recent explosive event., Comment: 21 pages, 11 figures. Accepted for publication in ApJ (english not edited)

We present a method to derive the relative pointing offsets for SPIRE Fourier-Transform Spectrometer (FTS) solar system object (SSO) calibration targets, which were observed regularly throughout the Herschel mission. We construct ratios of the spectra for all observations of a given source with respect to a reference. The reference observation is selected iteratively to be the one with the highest observed continuum. Assuming that any pointing offset leads to an overall shift of the continuum level, then these ratios represent the relative flux loss due to mispointing. The mispointing effects are more pronounced for a smaller beam, so we consider only the FTS short wavelength array (SSW, 958-1546 GHz) to derive a pointing correction. We obtain the relative pointing offset by comparing the ratio to a grid of expected losses for a model source at different distances from the centre of the beam, under the assumption that the SSW FTS beam can be well approximated by a Gaussian. In order to avoid dependency on the point source flux conversion, which uses a particular observation of Uranus, we use extended source flux calibrated spectra to construct the ratios for the SSOs. In order to account for continuum variability, due to the changing distance from the Herschel telescope, the SSO ratios are normalised by the expected model ratios for the corresponding observing epoch. We confirm the accuracy of the derived pointing offset by comparing the results with a number of control observations, where the actual pointing of Herschel is known with good precision. Using the method we derived pointing offsets for repeated observations of Uranus (including observations centred on off-axis detectors), Neptune, Ceres and NGC7027. The results are used to validate and improve the point-source flux calibration of the FTS., Comment: 17 pages, 19 figures, accepted for publication in Experimental Astronomy

Herschel/SPIRE Fourier transform spectrometer (FTS) observations contain emission from both the Herschel Telescope and the SPIRE Instrument itself, both of which are typically orders of magnitude greater than the emission from the astronomical source, and must be removed in order to recover the source spectrum. The effects of the Herschel Telescope and the SPIRE Instrument are removed during data reduction using relative spectral response calibration curves and emission models. We present the evolution of the methods used to derive the relative spectral response calibration curves for the SPIRE FTS. The relationship between the calibration curves and the ultimate sensitivity of calibrated SPIRE FTS data is discussed and the results from the derivation methods are compared. These comparisons show that the latest derivation methods result in calibration curves that impart a factor of between 2 and 100 less noise to the overall error budget, which results in calibrated spectra for individual observations whose noise is reduced by a factor of 2-3, with a gain in the overall spectral sensitivity of 23% and 21% for the two detector bands, respectively., Comment: 15 pages, 13 figures, accepted for publication in Experimental Astronomy

Emission from the Herschel telescope is the dominant source of radiation for the majority of SPIRE Fourier transform spectrometer (FTS) observations, despite the exceptionally low emissivity of the primary and secondary mirrors. Accurate modelling and removal of the telescope contribution is, therefore, an important and challenging aspect of FTS calibration and data reduction pipeline. A dust-contaminated telescope model with time invariant mirror emissivity was adopted before the Herschel launch. However, measured FTS spectra show a clear evolution of the telescope contribution over the mission and strong need for a correction to the standard telescope model in order to reduce residual background (of up to 7 Jy) in the final data products. Systematic changes in observations of dark sky, taken over the course of the mission, provide a measure of the evolution between observed telescope emission and the telescope model. These dark sky observations have been used to derive a time dependent correction to the telescope emissivity that reduces the systematic error in the continuum of the final FTS spectra to ~0.35 Jy., Comment: 12 pages, 14 figures, accepted for publication in Experimental Astronomy

The Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) on board the ESA Herschel Space Observatory has two detector setting modes: (a) a nominal mode, which is optimized for observing moderately bright to faint astronomical targets, and (b) a bright-source mode recommended for sources significantly brighter than 500 Jy, within the SPIRE FTS bandwidth of 446.7-1544 GHz (or 194-671 microns in wavelength), which employs a reduced detector responsivity and out-of-phase analog signal amplifier/demodulator. We address in detail the calibration issues unique to the bright-source mode, describe the integration of the bright-mode data processing into the existing pipeline for the nominal mode, and show that the flux calibration accuracy of the bright-source mode is generally within 2% of that of the nominal mode, and that the bright-source mode is 3 to 4 times less sensitive than the nominal mode., Comment: 15 pages, 16 figures, accepted for publication in Experimental Astronomy

The Herschel SPIRE Fourier transform spectrometer (FTS) performs spectral imaging in the 447-1546 GHz band. It can observe in three spatial sampling modes: sparse mode, with a single pointing on sky, or intermediate or full modes with 1 and 1/2 beam spacing, respectively. In this paper, we investigate the uncertainty and repeatability for fully sampled FTS mapping observations. The repeatability is characterised using nine observations of the Orion Bar. Metrics are derived based on the ratio of the measured intensity in each observation compared to that in the combined spectral cube from all observations. The mean relative deviation is determined to be within 2%, and the pixel-by-pixel scatter is ~7%. The scatter increases towards the edges of the maps. The uncertainty in the frequency scale is also studied, and the spread in the line centre velocity across the maps is found to be ~15 km/s. Other causes of uncertainty are also discussed including the effect of pointing and the additive uncertainty in the continuum., Comment: 12 pages, 9 figures, accepted for publication in Experimental Astronomy

The Spectral and Photometric Imaging Receiver (SPIRE) on the European Space Agency's Herschel Space Observatory utilizes a pioneering design for its imaging spectrometer in the form of a Fourier Transform Spectrometer (FTS). The standard FTS data reduction and calibration schemes are aimed at objects with either a spatial extent much larger than the beam size or a source that can be approximated as a point source within the beam. However, when sources are of intermediate spatial extent, neither of these calibrations schemes is appropriate and both the spatial response of the instrument and the source's light profile must be taken into account and the coupling between them explicitly derived. To that end, we derive the necessary corrections using an observed spectrum of a fully extended source with the beam profile and the source's light profile taken into account. We apply the derived correction to several observations of planets and compare the corrected spectra with their spectral models to study the beam coupling efficiency of the instrument in the case of partially extended sources. We find that we can apply these correction factors for sources with angular sizes up to \theta_{D} ~ 17". We demonstrate how the angular size of an extended source can be estimated using the difference between the sub-spectra observed at the overlap bandwidth of the two frequency channels in the spectrometer, at 959<\nu<989 GHz. Using this technique on an observation of Saturn, we estimate a size of 17.2", which is 3% larger than its true size on the day of observation. Finally, we show the results of the correction applied on observations of a nearby galaxy, M82, and the compact core of a Galactic molecular cloud, Sgr B2., Comment: Accepted for publication by A&A

High spectral resolution ISO-LWS observations of the [OI] 63.2 and 145.5 microns and [CII] 157.7 microns fine structure lines are presented for the center of the Sagittarius B2 complex (SgrB2). Both the [OI] 63.2 microns and the [CII] 157.7 microns lines are detected in absorption. Using observations of the CO isotopes and of the HI lines, absorption components can be associated with many clouds along the Sgr B2 line of sight. From these data, we were able to disentangle three different layers, as predicted by PDR models, which contain atomic oxygen. We derive lower limits for the column densities of C and O. The fact that the [CII] 157.7 microns line is detected in absorption implies that the main cooling line of the interstellar medium can be optically thick especially in the direction of large star-forming complexes or in the nuclei of galaxies. This could partially account for the deficiency in the [CII] 157.7 microns line which has been recently found toward infrared bright galaxies in ISO data., Comment: 33 pages, 9 figures. Accepted in Astrophysical Journal

Here we present new optical data from the Hubble Space Telescope of the NGC 253 central region, which reveal numerous discrete sources in a ring--like structure. This is combined with data at infrared, millimeter, radio and X-ray wavelengths to examine the nature of these discrete sources and the nucleus itself. We find that the majority of optical/IR/mm sources are young star clusters which trace out a ~50 pc ring, that defines the inner edge of a cold gas torus. This reservoir of cold gas has probably been created by gas inflow from a larger scale bar and deposited at the inner Lindblad resonance. The family of compact radio sources lie interior to the starburst ring, and in general do not have optical or IR counterparts. They are mostly SNRs. The radio nucleus, which is probably an AGN, lies near the centre of the ring. The X-ray emission from the nuclear source is extended in the ROSAT HRI detector indicating that not all of the X-ray emission can be associated with the AGN. The lack of X-ray variability and the flat radio spectrum of the nucleus, argues against an ultraluminous SN as the dominant energetic source at the galaxy core. The diffuse emission associated with the outflowing superwind is present in the central region on a size scale consistent with the idea of collimation by the gas torus., Comment: 26 pages, Latex, 6 figures, 4 tables, submitted to MNRAS