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Danielson, Dennis

doi:10.1038/35074216

Cited by 47 publications

(81 citation statements)

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“…None the less, in the subsequent analysis, following Kaufman et al (1999) and other works (e.g. Swinbank et al 2010; Danielson et al 2011), we double the observed luminosities of the optically thick lines in order to account for the fact that we see the emission only from one side of the clouds.…”

Section: Resultsmentioning

confidence: 99%

Physical conditions of the interstellar medium of high-redshift, strongly lensed submillimetre galaxies from the Herschel-ATLAS★

Valtchanov

Virdee

Ivison

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We present Herschel -SPIRE Fourier Transform Spectrometer (FTS) and radio followup observations of two Herschel -ATLAS (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 ∼ 5. 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 sub-mm 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 photo-dissociation region (PDR) models with different physical conditions, we derive the PDR cloud density n ≈ 2000 cm −3 and the far-UV ionizing radiation field G 0 ≈ 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 FIR/radio correlation, which hints that some fraction of the radio emission is coming from an AGN. The constraints on the source size from millimiter-wave observations put a very conservative upper limit of the possible AGN contribution to less than 33%. 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 an AGN.

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Section: Resultsmentioning

confidence: 99%

Physical conditions of the interstellar medium of high-redshift, strongly lensed submillimetre galaxies from the Herschel-ATLAS★

Valtchanov

Virdee

Ivison

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…As a result, it has apparent fluxes of 0.1–0.5 Jy in the FIR and submillimetre (Ivison et al 2010a). The brightness of this source enables a detailed study of its continuum and, critically for our analysis, emission‐line properties in the FIR and (sub)millimetre wavebands (Ivison et al 2010a; Danielson et al 2011).…”

Section: Observations Of Far‐infrared Lines At High Redshiftsmentioning

confidence: 99%

“…We include in our SED for SMM J2135−0102 the main emission lines observed by Ivison et al (2010a) and Danielson et al (2011): [N ii ] 122 μm, [O i ] 145 μm and [C ii ] 158 μm, as well as the full 12 CO spectral line ladder and the two [C i ] lines. To these we add several other lines at shorter, currently unobserved, wavelengths, but which are known to be bright in local LIRGs and ULIRGs.…”

Section: Observations Of Far‐infrared Lines At High Redshiftsmentioning

confidence: 99%

“…The fluxes of these lines are derived from the predictions of a PDR model constrained by the observed line properties and the existing limits on line fluxes from Ivison et al (2010a). This PDR model is described in more detail in Danielson et al (2011).…”

Section: Observations Of Far‐infrared Lines At High Redshiftsmentioning

confidence: 99%

“…The brightest lines in this source are the observed [C ii ] 158 μm line, with a L [C II] / L FIR fraction of 0.27 per cent, and the predicted strength of [O iii ] 52 μm, with L [O III] / L FIR = 0.37 per cent, while the fractions for [N iii ] 57 μm, [O i ] 63 μm, [O iii ] 88 μm, [N ii ] 122 μm and [O i ] 145 μm are 0.16, 0.16, 0.21, 0.19 and 0.13 per cent, respectively. In contrast, the integrated 12 CO ladder has a cumulative L CO / L FIR ∼ 0.01 per cent, with the two [C i ] lines contributing just 0.003 per cent (Danielson et al 2011). We note that for [O i ] 63 μm we have reduced the PDR‐predicted flux by a factor of 80 per cent to reflect the likelihood that the line may be self‐absorbed (Vasta et al 2010).…”

Section: Observations Of Far‐infrared Lines At High Redshiftsmentioning

confidence: 99%

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The potential influence of far-infrared emission lines on the selection of high-redshift galaxies

Smail

Swinbank

Ivison

et al. 2011

Monthly Notices of the Royal Astronomical Society: Letters

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We investigate whether strong molecular and atomic emission lines at far‐infrared wavelengths can influence the identification and derived properties of galaxies selected from broad‐band, far‐infrared or submillimetre observations. Several of these lines, for example, [C ii] 158 μm, have been found to be very bright in some galaxies, with fluxes of ≳0.1–1 per cent of the total far‐infrared luminosity, and may be even brighter in certain populations at high redshifts. At redshifts where these lines fall in instrument passbands, they can significantly increase the broad‐band flux measurements. We estimate that the contributions from line emission could boost the apparent broad‐band flux by ≳20–40 per cent in the Herschel and SCUBA‐2 bands. Combined with the steep source counts in the submillimetre and far‐infrared bands, line contamination has potentially significant consequences for the properties of sources detected in flux‐limited continuum surveys, biasing the derived redshift distributions and bolometric luminosities. Indeed, it is possible that some z > 4 sources found in 850‐μm surveys are being identified in part due to the line contamination from strong [C ii] emission. These biases may be even stronger for less‐luminous and lower metallicity populations at high redshifts, which are observable with the ALMA and which may have even stronger line‐to‐continuum ratios.

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