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Register a new userISO LWS Spectroscopy of M82: A Unified Evolutionary Model
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We present the first complete far-infrared spectrum (43 to 197 um) 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, [OI] 63 and 145 um, [OIII] 52 and 88 um, [NII] 122 um, [NIII] 57 um and [CII] 158 um, and fit their ratios to a combination starburst and photo-dissociation region (PDR) model. The best fit is obtained with HII regions with n = 250 cm^{-3} and an ionization parameter of 10^{-3.5} and PDRs with n = 10^{3.3} cm^{-3} and a far-ultraviolet flux of G_o = 10^{2.8}. 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_o cut-off. We also detected the ground state rotational line of OH in absorption at 119.4 um. No excited level OH transitions are apparent, indicating that the OH is almost entirely in its ground state with a column density ~ 4x10^{14} cm^{-2}. The spectral energy distribution over the LWS wavelength range is well fit with a 48 K dust temperature and an optical depth, tau_{Dust} proportional to lambda^{-1}.
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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.
(Abridged) The Long Wavelength Spectrometer (LWS) onboard the Infrared Space Observatory (ISO) observed the four large main-belt asteroids (1) Ceres, (2) Pallas, (4) Vesta, and (10) Hygiea multiple times. The photometric and spectroscopic data cover the wavelength range between 43 and 197 um, and are a unique dataset for future investigations and detailed characterisations of these bodies. The standard ISO archive products, produced through the last post-mission LWS pipeline, were still affected by instrument artefacts. Our goal was to provide the best possible data products to exploit the full scientific potential of these observations. We performed a refined reduction of all measurements, corrected for various instrumental effects, and re-calibrated the data. We outline the data reduction process and give an overview of the available data and the quality of the observations. We apply a thermophysical model to the flux measurements to derive far-IR based diameter and albedo values of the asteroids. The measured thermal rotational lightcurve of (4) Vesta is compared to model predictions. The absolute photometric accuracy of the data products was foubd to be better than 10%. The calibrated spectra will serve as source for future mineralogical studies of dwarf planets and dwarf planet candidates.
Inspired by biological evolution, we explain the rationality of Vision Transformer by analogy with the proven practical Evolutionary Algorithm (EA) and derive that both of them have consistent mathematical representation. Analogous to the dynamic local population in EA, we improve the existing transformer structure and propose a more efficient EAT model, and design task-related heads to deal with different tasks more flexibly. Moreover, we introduce the spatial-filling curve into the current vision transformer to sequence image data into a uniform sequential format. Thus we can design a unified EAT framework to address multi-modal tasks, separating the network architecture from the data format adaptation. Our approach achieves state-of-the-art results on the ImageNet classification task compared with recent vision transformer works while having smaller parameters and greater throughput. We further conduct multi-model tasks to demonstrate the superiority of the unified EAT, e.g., Text-Based Image Retrieval, and our approach improves the rank-1 by +3.7 points over the baseline on the CSS dataset.
A full spectral survey was carried out towards the Giant Molecular Cloud complex, Sagittarius B2 (Sgr B2), using the ISO Long Wavelength Spectrometer Fabry-Perot mode. This provided complete wavelength coverage in the range 47-196 um (6.38-1.53 THz) with a spectral resolution of 30-40 km/s. This is an unique dataset covering wavelengths inaccessible from the ground. It is an extremely important region of the spectrum as it contains both the peak of the thermal emission from dust, and crucial spectral lines of key atomic (OI, CII, OIII, NII and NIII) and molecular species (NH3, NH2, NH, H2O, OH, H3O+, CH, CH2, C3, HF and H2D+). In total, 95 spectral lines have been identified and 11 features with absorption depth greater than 3 sigma remain unassigned. Most of the molecular lines are seen in absorption against the strong continuum, whereas the atomic and ionic lines appear in emission (except for absorption in the OI 63 um and CII 158 um lines). Sgr B2 is located close to the Galactic Centre and so many of the features also show a broad absorption profile due to material located along the line of sight. A full description of the survey dataset is given with an overview of each detected species and final line lists for both assigned and unassigned features.
We present spectrophotometric ISO imaging with the LWS and the CAM-CVF of the Serpens molecular cloud core. The LWS map is centred on the far infrared and submillimetre source SMM1 and its size is 8 x 8. The fine structure line emission in [OI] and [CII] is extended and can be successfully modelled to originate in a PDR with G_0 = 15 and n(H2) about 10^4 - 10^5 cm^-3. Extended emission is also observed in the rotational line emission of H2O and high-J CO. However, lack of sufficient angular resolution prevents us from excluding the possibility that the emssion regions of these lines are point like, which could be linked to the embedded objects SMM9 and SMM4. Toward the Class0 source SMM1, the LWS observations reveal, in addition to fine structure line emission, a rich spectrum of molecular lines. The sub-thermally excited and optically thick CO, H2O and OH lines are tracing an about 10^3 AU source with temperatures higher than 300 K and densities above 10^6 cm^-3. We show that geometry is of concern for the correct interpretation of the data and based on 2D-radiative transfer modelling of the disk/torus around SMM1, which successfully reproduces the entire observed SED and the observed line profiles of CO isotopomers, we can exclude the disk to be the source of the LWS-molecular line emission. The CAM-CVF permits us to see a region of rotational H2 emission. This H2 gas has a temperature of 10^3 K, which suggests that the heating of the gas is achieved through relatively slow shocks. Although we are not able to establish any firm conclusion regarding the detailed nature of the shock waves, our observations of the molecular line emission from SMM1 can be explainable in terms of an admixture of J-shocks and of C-shocks.
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