Simultaneous Optical and Near‐Infrared Spectropolarimetry of Type 2 Seyfert Galaxies

Watanabe, Makoto; Nagata, T.; Sato, Shuji; Nakaya, Hidehiko; Hough, J. H.

doi:10.1086/375514

Cited by 22 publications

(36 citation statements)

References 83 publications

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“…Observational evidence suggests that this polarization is due to dichroic absorption by aligned grains. Watanabe et al (2003) also suggest the existence of an additional unpolarized component, most probably associated to electron scattering.…”

Section: Introductionmentioning

confidence: 85%

“…The warm IRAS Seyferts are believed to be viewed at an angle that is more face-on than that of cool IRAS Seyferts. Moreover, in the near-infrared, the degree of polarization of Mrk 1210 rises toward longer wavelengths, reaching ∼5% at 2.15 µm (Watanabe et al 2003). Observational evidence suggests that this polarization is due to dichroic absorption by aligned grains.…”

Section: Introductionmentioning

confidence: 96%

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Optical and NIR spectroscopy of Mrk 1210: constraints and physical conditions of the active nucleus

Mazzalay

Rodríguez-Ardila

2006

A&A

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Aims. Mrk 1210 is an outstanding Seyfert 2 galaxy because it displays signatures of recent circumnuclear star formation and a high level of X-ray activity, in addition to the classical spectral characteristics typical of an AGN. Here we investigate the extinction affecting the nuclear and extended emitting gas, the kinematics of the narrow-line region, and the physical properties and conditions of that gas. Methods. Near-infrared and optical spectra of the nuclear and extended emission region of Mrk 1210 are presented, covering the interval 0.4−2.4 µm. Emission and absorption lines were used to infer, respectively, the geometrical extension of the ionized gas and the contribution of the underlying stellar population to the observed integrated continuum. The emission line profiles were employed to study the kinematics in the NLR. The reddening and physical condition of the gas were investigated by means of flux ratios among permitted and forbidden lines. 12 CO(6−3) 1.618 µm overtone bandhead helped to estimate the contribution of the stellar population to the continuum. It was found that 83 ± 8% of the H-band continuum has a stellar origin. It improves previous estimates, which claimed that at least 50% of the observed continuum was attributed to the AGN. Analysis of the emission line profiles, both allowed and forbidden, shows a narrower (FWHM ∼ 500 km s −1 ) line on top of a broad (FWHM > 1000 km s −1 ) blue-shifted component. This seems to be associated to a nuclear outflow. This hypothesis is supported by 6 cm VLBI observations, which show a radio ejecta extending up to ∼30 pc from the nucleus. This result does not require the presence of the hidden BLR claimed to be present in previous NIR observations of this object. Internal extinction, calculated by means of several indicators including [Fe ii] flux ratios not previously used before in AGNs, reveals a dusty AGN, while the extended regions are barely affected by dust, if at all. The density and temperature are calculated for the NLR using optical and NIR lines as diagnostic ratios. The results show electronic temperatures from 10 000 K up to 40 000 K and densities between 10 3 −10 5 cm −3 . The higher temperatures show that shocks, most probably related to the radio outflow, must contribute to the line emission.

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Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 96%

Optical and NIR spectroscopy of Mrk 1210: constraints and physical conditions of the active nucleus

Mazzalay

Rodríguez-Ardila

2006

A&A

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“…5.2.1), lower and upper limits of the visual extinction towards the core of NGC 1068 must be assumed. For the upper limit we used A v = 39 mag (Packham et al 1997;Watanabe et al 2003;Lopez-Rodriguez et al 2015), interpreted as the extinction to the NIR emitting regions. For the lower limit, A v is estimated using the 9.7 µm silicate feature, τ 9.7µm ∼ 0.41, of the nuclear spectrum in a 0.4 × 0.4 arcsec (24× 24 pc) slit aperture by Mason et al (2006).…”

Section: Fitting Of the Dusty Central Structurementioning

confidence: 99%

Mid-infrared imaging- and spectro-polarimetric subarcsecond observations of NGC 1068

López-Rodríguez

Packham

Roche

et al. 2016

Mon. Not. R. Astron. Soc.

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We present sub-arcsecond 7.5−13 µm imaging-and spectro-polarimetric observations of NGC 1068 using CanariCam on the 10.4-m Gran Telescopio CANARIAS. At all wavelengths, we find: (1) A 90 × 60 pc extended polarized feature in the northern ionization cone, with a uniform ∼44 • polarization angle. Its polarization arises from dust and gas emission in the ionization cone, heated by the active nucleus and jet, and further extinguished by aligned dust grains in the host galaxy. The polarization spectrum of the jet-molecular cloud interaction at ∼24 pc from the core is highly polarized, and does not show a silicate feature, suggesting that the dust grains are different from those in the interstellar medium. (2) A southern polarized feature at ∼9.6 pc from the core. Its polarization arises from a dust emission component extinguished by a large concentration of dust in the galaxy disc. We cannot distinguish between dust emission from magnetically aligned dust grains directly heated by the jet close to the core, and aligned dust grains in the dusty obscuring material surrounding the central engine. Silicate-like grains reproduce the polarized dust emission in this feature, suggesting different dust compositions in both ionization cones. (3) An upper limit of polarization degree of 0.3 per cent in the core. Based on our polarization model, the expected polarization of the obscuring dusty material is 0.1 per cent in the 8−13 µm wavelength range. This low polarization may be arising from the passage of radiation through aligned dust grains in the shielded edges of the clumps.

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“…Polarization position angle behavior has proved to be useful in the past for elucidating the structure of AGNs. The prototype hidden broadline region ( BLR) Seyfert 2 galaxy NGC 1068 shows at least two rotations in in the optical/near-IR: a gradual change of $30 between 1 and 2 m (Watanabe et al 2003), and a more abrupt flip of $70 near 5 m (Bailey et al 1988). Both features indicate changes in the dominant polarizing mechanism, and have been used to constrain the geometry and properties of material surrounding the central emission regions (Watanabe et al 2003).…”

Section: Comparison With Existing Modelsmentioning

confidence: 99%

“…The prototype hidden broadline region ( BLR) Seyfert 2 galaxy NGC 1068 shows at least two rotations in in the optical/near-IR: a gradual change of $30 between 1 and 2 m (Watanabe et al 2003), and a more abrupt flip of $70 near 5 m (Bailey et al 1988). Both features indicate changes in the dominant polarizing mechanism, and have been used to constrain the geometry and properties of material surrounding the central emission regions (Watanabe et al 2003). When considering the $1% optical polarization often seen in the integrated light of type 1 (broad line) Seyfert galaxies, Goodrich & Miller (1994;see also Berriman et al 1990;Brindle et al 1990;Smith et al 2004) reiterated a trait first noted by Antonucci (1983).…”

Section: Comparison With Existing Modelsmentioning

confidence: 99%

Multiple Scattered Sight Lines to the Red QSO 2MASX J10494334+5837501

Schmidt

Smith

Hines

et al. 2007

ApJ

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The reddened, highly polarized QSO 2MASX J1049334+5837501 (2M 1049+5837) shows a strong IR dust signature with a spectral energy distribution peaked at $20 m and a luminosity of $10 11 L , but the active nucleus is outshone at optical wavelengths by the host galaxy. Remarkable variations with wavelength in the degree and position angle of polarization require two primary sources of scattered flux from the active nucleus. These are: (1) a reddened component with P ! 8% that we identify with material near the axis of a presumed obscuring dust torus in the context of orientation-dependent unification schemes for active galactic nuclei (AGNs); and (2) a faint, very blue source that is only important at k P 4500 8. The latter component is only revealed because of its extremely high polarization (P ¼ 20%Y30%) and the fact that flux from the nucleus and the scattering lobes is nearly completely extinguished in this spectral region. High-resolution images show extensions approximately orthogonal to the two position angles of polarization. Consideration of these characteristics suggests refinements to the standard, first-order picture offered by the unified scheme for AGNs. Namely, that there can be multiple scattered sight lines within some AGNs, and that it is possible that the ''polar scattering lobes'' can provide sufficient scattering optical depth that the emergent nuclear spectrum is highly reddened. These deviations are useful in explaining the existence of highly polarized, red, type 1 AGNs that form a significant fraction of the QSOs found in near-IR surveys. Importantly, the utility of the type 1/type 2 spectral signature as an indicator of orientation becomes less effective as the dust covering factor increases and nuclear radiation is more effectively scattered into all sight lines.

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Simultaneous Optical and Near‐Infrared Spectropolarimetry of Type 2 Seyfert Galaxies

Cited by 22 publications

References 83 publications

Optical and NIR spectroscopy of Mrk 1210: constraints and physical conditions of the active nucleus

Optical and NIR spectroscopy of Mrk 1210: constraints and physical conditions of the active nucleus

Mid-infrared imaging- and spectro-polarimetric subarcsecond observations of NGC 1068

Multiple Scattered Sight Lines to the Red QSO 2MASX J10494334+5837501

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