arXiv subjects

L. Spinoglio

Publications and source records attributed to L. Spinoglio.

150 records · Page 9Linked to original sources

arXiv2000

The ISO-LWS map of the Serpens cloud core: I. The SEDs of the IR/SMM sources

ISO-LWS mapping observations of the Serpens molecular cloud core are presented. The spectral range is 50 - 200 micron and the map size is 8' X 8'. These observations suffer from severe source confusion at FIR wavelengths and we employ a Maximum Likelihood Method for the spectro-spatial deconvolution. The strong and fairly isolated source SMM1 FIRS1 presented a test case, whose modelled spectral energy distribution (SED), within observational errors, is identical to the observed one. The model results for the other infrared and submillimetre sources are therefore likely to represent their correct SEDs. Simulations demonstrating the reliability and potential of the developed method support this view. For the majority of sources the peak of the SEDs is found within the spectral range of the LWS and derived temperatures are generally higher (>30K) than have been found by earlier deconvolution attempts using IRAS data. SMM sizes are found to be only a few arcsec in diameter. In addition, the SMMs are generally optically thick even at LWS wavelengths. Self-consistent radiative transfer calculations indicates that the SMMs are optically thick out to even longer wavelengths. Models were calculated for five sources, for which sufficient data were available, viz. SMM 1, 2, 3, 4 and 9. These models are optically thick out to millimetre wavelengths (wavelength of unit optical depth 900 to 1400 micron). Envelope masses for these SMMs are in the range 2-6 Msun, which is of course considerably more massive than estimates based on the optically thin assumption. The luminosities are in the range 10-70 Lsun, suggesting the formation of low-mass to intermediate mass stars, so that the existence of such massive envelopes argues for extreme youth of the SMMs in the Serpens cloud core.

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arXiv2000

ISO-LWS spectroscopy of Centaurus A: extended star formation

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.

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arXiv1999

ISO Far-IR Spectroscopy of IR-Bright Galaxies and ULIRGs

Based on far-infrared spectroscopy of a small sample of nearby infrared-bright and ultraluminous infrared galaxies (ULIRGs) with the ISO Long Wavelength Spectrometer, we find a dramatic progression in ionic/atomic fine-structure emission line and molecular/atomic absorption line characteristics in these galaxies extending from strong [O III]52,88 and [N III]57 micron line emission to detection of only faint [C II]158 micron line emission from gas in photodissociation regions in the ULIRGs. The molecular absorption spectra show varying excitation as well, extending from galaxies in which the molecular population mainly occupies the ground state to galaxies in which there is significant population in higher levels. In the case of the prototypical ULIRG, the merger galaxy Arp 220, the spectrum is dominated by absorption lines of OH, H2O, CH, and [O I]. Low [O III]88 micron line flux relative to the integrated far-infrared flux correlates with low excitation and does not appear to be due to far-infrared extinction or to density effects. A progression toward soft radiation fields or very dusty HII regions may explain these effects.

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arXiv1999

Shock excited far-infrared molecular emission around T Tau

The first complete far-infrared spectrum of T Tau has been obtained with the LWS spectrometer on-board the Infrared Space Observatory, which detected strong emission from high-J (J=14-25) CO, para- and ortho-H2O and OH transitions over the wavelength range from 40 to 190 micron. Most of the observed molecular emission can be explained by a single emission region at T~300-900 K and n(H_2)~10^(5-6) cm^(-3),with a diameter of about 2-3 arcsec. This corresponds to a very compact region of 300-400 AU at the distance of 140 pc. An higher temperature component seems to be needed to explain the highest excitation CO and water lines. We derive a water abundance of 1-7x10^(-5) and an OH abundance of ~3x10^(-5) with respect to molecular hydrogen, implying water and OH enhancements by more than a factor of 10 with respect to the expected ambient gas abundance. The observed cooling in the various species amounts to 0.04 L(sun),comparable to the mechanical luminosity of the outflow, indicating that the stellar winds could be responsible of the line excitation through shocks. In order to explain the observed molecular cooling in T Tau in terms of C-type shock models, we hypothesise that the strong far-ultraviolet radiation field photodissociates water in favour of OH. This would explain the large overabundance of OH observed. The estimated relatively high density and compactness of the observed emission suggest that it originates from the shocks taking place at the base of the molecular outflow emission, in the region where the action of the stellar winds from the two stars of the binary system is important.

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arXiv1998

ISO LWS Spectroscopy of M82: A Unified Evolutionary Model

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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arXiv1993

The Extended 12 Micron Galaxy Sample

We have selected an all--sky sample of 893 galaxies from the IRAS FSC--2, defined by a total (ADDSCAN) 12um flux limit of 0.22~Jy. Completeness is verified to 0.30~Jy, below which we have quantified the incompleteness down to 0.22~Jy for our statistical analysis. ¶The Seyfert subsample is the largest unbiased sample of (118) Seyfert galaxies ever assembled and is complete not only to 0.30~Jy at 12um, but also with respect to a bolometric flux limit of $\sim2.0\times10^{-10}$~(cgs). The average $V/V_{max}$ for the full sample, corrected for incompleteness at low fluxes, is $0.51\pm0.04$, while that for Seyferts is $0.46\pm0.10$, suggesting that several Seyferts are yet to be identified in our sample. The AGN luminosity functions (LFs) are more complete than those of the optically selected CfA Seyfert galaxies for all luminosities and AGN types. ¶The 60um LF for a complete 60um--flux--limited (at 8.3~Jy) subsample of 235 galaxies is in satisfactory agreement with those derived from the bright galaxy sample (BGS) and the deep high--galactic latitude sample, both selected at 60um. Over the high lum. range where our sample and the BGS overlap, however, our space densities are systematically lower by a factor of $\sim 1.5$, whereas at low lum. our space densities are higher by about the same amount. Comparable results are obtained when comparing the far--IR LF of our entire sample with the one derived from the BGS. This is not unexpected, because of the bias towards high-luminosity spirals caused by selection at 60um.

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