Abstract
We present 0.″4 resolution imaging polarimetry at 8.7, 10.3, and 12.5
μ
m, obtained with CanariCam at the Gran Telescopio Canarias, of the central 0.11 pc × 0.28 pc (4.″2 × 10.″8) region of ...W51 IRS2. The polarization, as high as ∼14%, arises from silicate particles aligned by the interstellar magnetic field (
B
-field). We separate, or unfold, the polarization of each sightline into emission and absorption components, from which we infer the morphologies of the corresponding projected
B
-fields that thread the emitting- and foreground-absorbing regions. We conclude that the projected
B
-field in the foreground material is part of the larger-scale ambient field. The morphology of the projected
B
-field in the mid-infrared (mid-IR) emitting region spanning the cometary H
ii
region W51 IRS2W is similar to that in the absorbing region. Elsewhere, the two
B
-fields differ significantly with no clear relationship between them. The
B
-field across the W51 IRS2W cometary core appears to be an integral part of a champagne outflow of gas originating in the core and dominating the energetics there. The bipolar outflow, W51north jet, that appears to originate at or near SMA1/N1 coincides almost exactly with a clearly demarcated north–south swath of lower polarization. While speculative, comparison of mid-IR and submillimeter polarimetry on two different scales may support a picture in which SMA1/N1 plays a major role in the
B
-field structure across W51 IRS2.
Abstract
We present the first mid-IR detection of the linear polarization toward the star CygOB2-12, a luminous blue hypergiant that, with
A
V
≈ 10 mag of foreground extinction, is a benchmark in the ...study of the properties of dust in the diffuse interstellar medium. The 8–13
μ
m spectropolarimetry, obtained with the CanariCam multimode camera at the Gran Telescopio CANARIAS shows clear trends with wavelength characteristic of silicate grains aligned in the interstellar magnetic field. The maximum polarization, detected with 7.8
σ
statistical significance near 10.2
μ
m, is (1.24 ± 0.28)% with position angle 126° ± 8°. We comment on these measurements in the context of recent models for the dust composition in the diffuse interstellar medium.
Observations of oscillations of temperature and wind in planetary atmospheres provide a means of generalizing models for atmospheric dynamics in a diverse set of planets in the Solar System and ...elsewhere. An equatorial oscillation similar to one in the Earth's atmosphere has been discovered in Jupiter. Here we report the existence of similar oscillations in Saturn's atmosphere, from an analysis of over two decades of spatially resolved observations of its 7.8- m methane and 12.2- m ethane stratospheric emissions, where we compare zonal-mean stratospheric brightness temperatures at planetographic latitudes of 3.6° and 15.5° in both the northern and the southern hemispheres. These results support the interpretation of vertical and meridional variability of temperatures in Saturn's stratosphere as a manifestation of a wave phenomenon similar to that on the Earth and in Jupiter. The period of this oscillation is 14.8 ± 1.2 terrestrial years, roughly half of Saturn's year, suggesting the influence of seasonal forcing, as is the case with the Earth's semi-annual oscillation.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We have modeled two mid-infrared imaging photometry data sets to determine the spatial distribution of physical conditions in the BN/KL infrared complex. We observed the BN/KL region using the 10-m ...Keck I telescope and the LWS in the direct imaging mode, over a 13” × 19” field (Figure 1, left). We also modeled images obtained with COMICS (Kataza et al. 2000) at the 8.2-m SUBARU telescope, over a total field of view is 31” × 41” (Figure 1, right), in a total of nine bands: 7.8, 8.8, 9.7, 10.5, 11.7, 12.4, 18.5, 20.8 and 24.8 μm with ~1 μm bandwidth interference filters.
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