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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 606636.0, MPI für Astronomie / Publikationen_mpia
Physical conditions of the interstellar medium of high-redshift, strongly lensed submillimetre galaxies from the Herschel-ATLAS
Authors:Valtchanov, I.; Virdee, J.; Ivison, R. J.; Swinyard, B.; van der Werf, P.; Rigopoulou, D.; da Cunha, E.; Lupu, R.; Benford, D. J.; Riechers, D.; Smail, I.; Jarvis, M.; Pearson, C.; Gomez, H.; Hopwood, R.; Altieri, B.; Birkinshaw, M.; Coia, D.; Conversi, L.; Cooray, A.; de Zotti, G.; Dunne, L.; Frayer, D.; Leeuw, L.; Marston, A.; Negrello, M.; Portal, M. S.; Scott, D.; Thompson, M. A.; Vaccari, M.; Baes, M.; Clements, D.; Michałowski, M. J.; Dannerbauer, H.; Serjeant, S.; Auld, R.; Buttiglione, S.; Cava, A.; Dariush, A.; Dye, S.; Eales, S.; Fritz, J.; Ibar, E.; Maddox, S.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Smith, D. J. B.; Temi, P.; Carpenter, J.; Bolatto, A.; Gurwell, M.; Vieira, J. D.
Date of Publication (YYYY-MM-DD):2011
Journal Abbrev.:Monthly Notices of the Royal Astronomical Society
Issue / Number:4
Start Page:3473
End Page:3484
Audience:Not Specified
Abstract / Description:We present Herschel-Spectral and Photometric Imaging Receiver (SPIRE) Fourier transform spectrometer (FTS) and radio follow-up observations of two Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS)-detected strongly lensed distant galaxies. In one of the targeted galaxies H-ATLAS J090311.6+003906 (SDP.81), we detect [O III] 88 μm and [C II] 158 μm lines at a signal-to-noise ratio of Ëœ5. We do not have any positive line identification in the other fainter target H-ATLAS J091305.0-005343 (SDP.130). Currently, SDP.81 is the faintest submillimetre galaxy with positive line detections with the FTS, with continuum flux just below 200 mJy in the 200-600 μm wavelength range. The derived redshift of SDP.81 from the two detections is z = 3.043 ± 0.012, in agreement with ground-based CO measurements. This is the first detection by Herschel of the [O III] 88 μm line in a galaxy at redshift higher than 0.05. Comparing the observed lines and line ratios with a grid of photodissociation region (PDR) models with different physical conditions, we derive the PDR cloud density n ≈ 2000 cm-3 and the far-ultraviolet ionizing radiation field G0≈ 200 (in units of the Habing field - the local Galactic interstellar radiation field of 1.6 × 10-6 W m-2). Using the CO-derived molecular mass and the PDR properties, we estimate the effective radius of the emitting region to be 500-700 pc. These characteristics are typical for star-forming, high-redshift galaxies. The radio observations indicate that SDP.81 deviates significantly from the local far-infrared/radio (FIR/radio) correlation, which hints that some fraction of the radio emission is coming from an active galactic nucleus (AGN). The constraints on the source size from millimetre-wave observations put a very conservative upper limit of the possible AGN contribution to less than 33 per cent. These indications, together with the high [O III]/FIR ratio and the upper limit of [O I] 63 μm/[C II] 158 μm, suggest that some fraction of the ionizing radiation is likely to originate from the AGN. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Correction added after online publication 2011 July 12: author added.
Free Keywords:galaxies: evolution; galaxies: individual: SDP.81: H-ATLAS J090311.6+003906; galaxies: individual: SDP.130: H-ATLAS J091305.0-005343; infrared: galaxies; radio continuum: galaxies; submillimetre: ISM
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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