Spectropolarimetry of the 3 Micron Ice Feature toward the Becklin-Neugebauer Object

Hough, J. H.; Chrysostomou, A.; Messinger, David W.; Whittet, D. C. B.; Aitken, D. K.; Roche, P. F.

doi:10.1086/177111

Cited by 32 publications

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“…Also ice-features show polarisation (3.1 μm O−H stretching mode of water ice; Hough et al 1996, or ice features near 4.6−4.7 μm show polarization due to CO and CN-bearing species; Chrysostomou et al 1996). These detections have been taken as evidence for alignment of core/mantle grains in molecular clouds.…”

Section: Introductionmentioning

confidence: 99%

Linear and circular spectropolarimetry of diffuse interstellar bands

Cox

Ehrenfreund

Foing

et al. 2011

A&A

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Context. The identification of the carriers of diffuse interstellar bands (DIBs) remains one of the long-standing mysteries in astronomy. The detection of a polarisation signal in a DIB profile can be used to distinguish between a dust or gas-phase carrier. The polarisation profile can give additional information on the grain or molecular properties of the absorber. Aims. To measure the polarisation efficiency of the carriers of the diffuse interstellar bands. Methods. In order to detect and measure the linear and circular polarisation of the DIBs we observed reddened lines of sight showing continuum polarisation. For this study we selected two stars HD 197770 and HD 194279. We used high-resolution (R ∼ 64 000) spectropolarimetry in the wavelength range from 3700 to 10 480 Å with the ESPaDOnS échelle spectrograph mounted at the CFHT. Results. High S/N and high resolution Stokes V (circular), Q and U (linear) spectra were obtained. We constrained upper limits by a factor of 10 for previously observed DIBs. Furthermore, we analysed ∼30 additional DIBs for which no spectropolarimetry data has been obtained before. This included the 9577 Å DIB and the 8621 Å DIB. The former is attributed to the C + 60 fullerene, which could become aligned in a magnetic field. The latter shows a tight correlation with the amount of dust in the line-of-sight and therefore most likely may show a polarisation signal related the aligned grains. Conclusions. The lack of polarisation in 45 DIB profiles suggests that none of the absorption lines is induced by a grain-type carrier. The strict upper limits, less than ∼0.01%, derived for the observed lines-of-sight imply that if DIBs are due to gas-phase molecules these carriers have polarisation efficiencies which are at least 6 times, and up to 300 times, smaller than those predicted for grainrelated carriers.

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Section: Introductionmentioning

confidence: 99%

Linear and circular spectropolarimetry of diffuse interstellar bands

Cox

Ehrenfreund

Foing

et al. 2011

A&A

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“…The high degree of polarization of BN, which is proportional to the extinction with the far infrared (FIR)-inferred magnetic field directions, has been used to deduce that BN is polarized by dichroic absorption at all NIR and mid-infrared (MIR) wavelengths where it has been measured (e.g., Lee & Draine 1985;Hough et al 1996;Aitken et al 1997;Smith et al 2000). However, Jiang et al (2005) used NIR-adaptive optics-aided, very high resolution imaging polarimetry to successfully reveal an outflow/disk system around BN.…”

Section: Introductionmentioning

confidence: 99%

Near-Infrared Imaging Polarimetry of M42: Aperture Polarimetry of Point-Like Sources

Kusakabe

Tamura

Kandori

et al. 2008

The Astronomical Journal

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We have conducted aperture polarimetry of ∼500 stars of the Orion Nebula Cluster in M42 based on our widefield (∼8 ×8 ) JHKs-band polarimetry. Most of the near-infrared (NIR) polarizations are dichroic, with position angles of polarization agreeing, both globally and locally, with previous far-infrared (FIR) and submillimeter observations, having taken into account the 90• difference in angles between dichroic absorption and emission. This is consistent with the idea that both NIR dichroic polarizations and FIR/submillimeter thermal polarizations trace the magnetic fields in the OMC-1 region. The magnetic fields inferred from these observations show a pinch at scales less than 0.5 pc with a centroid near IRc2. The hourglass-shaped magnetic field pattern is explained by the models in which the magnetic field lines are dragged along with the contracting gas and then wound up by rotation in a disk. The highly polarized region to the northwest of IRc2 and the low-polarized region near the bright bar are also common among NIR and FIR/submillimeter data, although a few regions of discrepancy exist. We have also discerned ∼50 possible highly polarized sources whose polarizations are more likely to be intrinsic rather than dichroic. Their polarization efficiencies (P (H )/A(H )) are too large to be explained by the interstellar polarization. These include ten young brown dwarfs that suggest a higher polarization efficiency, which may present geometrical evidence for (unresolved) circumstellar structures around young brown dwarfs.

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“…The brightest nearinfrared (NIR) and mid-infrared (MIR) source in the region, the Becklin-Neugebauer object BN (Becklin & Neugebauer 1967), is possibly a runaway B star from the Trapezium cluster (Plambeck et al 1995;Tan 2004). It is still surrounded by an optically thick envelope containing silicate dust and ices, which are identified via their infrared spectral features (e.g., Lee & Draine 1985;Hough et al 1996). Genzel & Stutzki (1989) list the indicators of star formation in their review of the literature to 1989: At MIR and far-infrared (FIR) wavelengths, BN is outshone by the extended nebulosity $10 00 to the south called the Kleinmann-Low Nebula (KL; Kleinmann & Low 1967), which has a total luminosity of 6 ; 10 4 -1:2 ; 10 5 L (Genzel & Stutzki 1989).…”

Section: Introductionmentioning

confidence: 99%

“…Polarization due to dichroic absorption has long been used to map out the orientation of the magnetic field in the Milky Way and other galaxies at optical and NIR wavelengths (see the review of Milky Way polarization by Heiles & Crutcher 2005). The high degree of polarization of BN, proportional to the extinction (Aitken et al 1985(Aitken et al , 1989Capps et al 1978;Minchin et al 1991) and in angular agreement with the FIR-inferred magnetic field directions, has been used to deduce that BN is polarized by dichroic absorption at all NIR and MIR wavelengths where it has been measured (e.g., Lee & Draine 1985;Hough et al 1996;Aitken et al 1997;Smith et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Hubble Space TelescopeNICMOS Polarization Measurements of OMC‐1

Simpson

Colgan

Erickson

et al. 2006

ApJ

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We present 2 m polarization measurements of positions in the IRc2 and BN regions of the Orion Molecular Cloud (OMC-1) made with NICMOS Camera 2 (0B2 resolution) on the Hubble Space Telescope. Our results are as follows: BN is $29% polarized by dichroic absorption and appears to be the illuminating source for most of the nebulosity to its north and for up to $5 00 to its south. Although the stars are probably all polarized by dichroic absorption, there are a number of compact but non-point-source objects that could be polarized by a combination of both dichroic absorption and local scattering of starlight. We identify several candidate YSOs, including an approximately edge-on bipolar YSO 8B7 east of BN, and a deeply embedded variable star. Additional strongly polarized sources are IRc2-B, IRc2-D, and IRc7, all of which are obviously self-luminous at mid-infrared wavelengths and may be YSOs. None of these is a reflection nebula illuminated by a star located near radio source I, as was previously suggested. Other IRc sources are clearly reflection nebulae: IRc3 appears to be illuminated by IRc2-B or a combination of the IRc2 sources, and IRc4 and IRc5 appear to be illuminated by an unseen star in the vicinity of radio source I, or by star n or IRc2-A. Trends in the magnetic field direction are inferred from the polarization of the 26 stars that are bright enough to be seen as NICMOS point sources. The most polarized star has a polarization position angle different from its neighbors by $40, but in agreement with the grain alignment inferred from millimeter polarization measurements of the cold dust cloud in the southern part of OMC-1.

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Spectropolarimetry of the 3 Micron Ice Feature toward the Becklin-Neugebauer Object

Cited by 32 publications

References 0 publications

Linear and circular spectropolarimetry of diffuse interstellar bands

Linear and circular spectropolarimetry of diffuse interstellar bands

Near-Infrared Imaging Polarimetry of M42: Aperture Polarimetry of Point-Like Sources

Hubble Space TelescopeNICMOS Polarization Measurements of OMC‐1

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