Polarized Hα Wings in the Symbiotic Stars AG Draconis and Z Andromedae

Ikeda, Yuji; Akitaya, Hiroshi; Matsuda, Kaho; Homma, K.; Seki, M.; Kawabata, Koji S.; Hirata, Ryuko; Okazaki, Akira

doi:10.1086/381877

Cited by 9 publications

(9 citation statements)

References 20 publications

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“…Lee & Yun 1998; Yoo, Bak & Lee 2002). This mechanism requires the presence of large H i column densities N H i ≳ 10 20 cm −2 , and has been observed to operate around symbiotic stars (Ikeda et al 2004), and potentially in close proximity to quasars (Lee & Yun 1998). In distant galaxies, however, these emission regions would be completely unresolved, and the polarization averages out to zero.…”

Section: Discussionmentioning

confidence: 99%

The polarization of scattered LyÎ± radiation around high-redshift galaxies

Dijkstra

Loeb

2008

Monthly Notices of the Royal Astronomical Society

131

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The high‐redshift Universe contains luminous Lyα emitting sources such as galaxies and quasars. The emitted Lyα radiation is often scattered by surrounding neutral hydrogen atoms. We show that the scattered Lyα radiation obtains a high level of polarization for a wide range of likely environments of high‐redshift galaxies. For example, the backscattered Lyα flux observed from galaxies surrounded by a superwind‐driven outflow may reach a fractional polarization as high as ∼40 per cent. Equal levels of polarization may be observed from neutral collapsing protogalaxies. Resonant scattering in the diffuse intergalactic medium typically results in a lower polarization amplitude (≲7 per cent), which depends on the flux of the ionizing background. Spectral polarimetry can differentiate between Lyα scattering off infalling gas and outflowing gas; for an outflow, the polarization should increase towards longer wavelengths while for infall the opposite is true. Our numerical results suggest that Lyα polarimetry is feasible with existing instruments, and may provide a new diagnostic of the distribution and kinematics of neutral hydrogen around high‐redshift galaxies. Moreover, polarimetry may help suppress infrared lines originating in the Earth's atmosphere, and thus improve the sensitivity of ground‐based observations to high‐redshift Lyα emitting galaxies outside the currently available redshift windows.

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Section: Discussionmentioning

confidence: 99%

The polarization of scattered LyÎ± radiation around high-redshift galaxies

Dijkstra

Loeb

2008

Monthly Notices of the Royal Astronomical Society

131

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“…As a result we have to investigate other possibilities to identify the main source of radiation contributing to the broad Hα wings. For example, Ikeda et al (2004) found that the polarization profile of Hα does not agree with that of the Raman λ6830 line for Z And on 25/10/02 (i.e. during the 2002/03 brightening).…”

Section: Raman λ6825 and [Fe Vii] λ6087 Profilesmentioning

confidence: 99%

Structure of the hot object in the symbiotic prototype Z Andromedae during its 2000–03 active phase

Skopal

Vittone

Errico

et al. 2006

A&A

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Aims. To investigate structure of the hot object in the symbiotic prototype Z And during its major 2000−03 active phase. Methods. Analysis of the far ultraviolet, optical low-and high-resolution spectroscopy and UBVR photometry. Reconstruction of the spectral energy distribution (SED) during the outburst. The Raman scattering process. Results. At the initial stages of the outburst the hot object was characterized by the two-temperature spectrum (a warm stellar radiation and a strong nebular emission) with signatures of a mass-outflow at moderate (∼100−200 km s −1 ) and very high (≈1000−2000 km s −1 ) velocities. The corresponding structure of the hot object consists of an optically thick, slowly-expanding disk-like material encompassing the accretor at the orbital plane and a fast optically thin wind over the remainder of the star. The disk-like shell persisted around the central star until 2002 August as was indicated by the eclipse effect. Then, a significant dilution of the optically thick material and evolution of a fast wind from the hot star, concentrated more at the orbital plane, were detected. A striking similarity of [Fe vii] λ6087 and Raman λ6825 profiles at/after the dilution of the disk suggests their origin within the interaction zone where the winds from the binary components collide.

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“…Ikeda et al (2004) performed linear spectropolarimetry around Hα of the two symbiotic stars Z And and AG Dra. No Raman‐scattered He ii features have been reported in these objects, and their analyses were confined to Hα wings and Raman‐scattered O vi 6825 and 7088.…”

Section: Discussion and Summarymentioning

confidence: 99%

On the linear spectropolarimetry of Raman-scattered Heâii 6545 in young planetary nebulae

Lee

2009

Monthly Notices of the Royal Astronomical Society

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Using a Monte Carlo technique, we compute the profiles and linear polarization of Ramanscattered He II λ6545 in young planetary nebulae. We assume that the He II emission region is a rotating ring surrounded by a cylindrical neutral shell. We also assume that the He II emission line is characterized by the rotation speed of the emission ring convolved with the turbulent speed, whereas the scattering region is allowed to expand or rotate with respect to the central star. We provide fitting formulae for the total and Raman scattering cross-sections around Lyβ up to the first order of λ − λ 0 with λ 0 being the wavelength of He II λ1025. For small velocity scales associated with the emission region, the linear degree of polarization as a function of wavelength bends convex upwards for a rotating scattering region, whereas an opposite behaviour is obtained for an expanding scattering region. For large turbulent and bulk velocity scales of the emission region, the linear degree of polarization decreases almost linearly for both models. The redwards decrease of the linear degree of polarization is a result of the increase of the Raman scattering optical depth towards the resonance of atomic hydrogen. The slope of the linear degree of polarization can be a useful diagnostic to find the H I column density near N H I = 10 20 cm −2 . We propose that linear spectropolarimetry of Raman-scattered He II may put strong constraints on N H I to lift the degeneracy problem in the line profile involving the covering factor and N H I .

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Polarized Hα Wings in the Symbiotic Stars AG Draconis and Z Andromedae

Cited by 9 publications

References 20 publications

The polarization of scattered LyÎ± radiation around high-redshift galaxies

The polarization of scattered LyÎ± radiation around high-redshift galaxies

Structure of the hot object in the symbiotic prototype Z Andromedae during its 2000–03 active phase

On the linear spectropolarimetry of Raman-scattered Heâii 6545 in young planetary nebulae

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Polarized Hα Wings in the Symbiotic Stars AG Draconis and Z Andromedae

Cited by 9 publications

References 20 publications

The polarization of scattered LyÎ± radiation around high-redshift galaxies

The polarization of scattered LyÎ± radiation around high-redshift galaxies

Structure of the hot object in the symbiotic prototype Z Andromedae during its 2000–03 active phase

On the linear spectropolarimetry of Raman-scattered Heâii 6545 in young planetary nebulae

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On the linear spectropolarimetry of Raman-scattered Heâii 6545 in young planetary nebulae