Showing papers on "Infrared dark cloud published in 2003"

The G11.11–0.12 Infrared-dark Cloud: Anomalous Dust and a Nonmagnetic Isothermal Model

Abstract: The G11.11-0.12 infrared-dark cloud has a filamentary appearance, both in absorption against the diffuse 8 μm Galactic background and in emission from cold dust at 850 μm. A detailed comparison of the dust properties at these two wavelengths reveals that standard models for the diffuse interstellar dust in the Galaxy are not consistent with the observations. The ratio of absorption coefficients within the cloud is κ8/κ850 ≤ 1010, which is well below that expected for the diffuse interstellar medium where κ8/κ850 ~ 1700. This may be due to the formation of ice mantles on the dust and grain coagulation, both of which are expected within dense regions of molecular clouds. The 850 μm emission probes the underlying radial structure of the filament. The profile is well represented by a marginally resolved central region and a steeply falling envelope, with Σ(r) ∝ r-α, where α ≥ 3, indicating that G11.11-0.12 is the first observed filament with a profile similar to that of a nonmagnetic isothermal cylinder.

The G11.11-0.12 Infrared-Dark Cloud: Anomalous Dust and a Non-Magnetic Isothermal Model

Abstract: The G11.11-0.12 Infrared-Dark Cloud has a filamentary appearance, both in absorption against the diffuse 8micron Galactic background, and in emission from cold dust at 850micron. Detailed comparison of the dust properties at these two wavelengths reveals that standard models for the diffuse interstellar dust in the Galaxy are not consistent with the observations. The ratio of absorption coefficients within the cloud is kappa_8/kappa_850 <= 1010, which is well below that expected for the diffuse ISM where kappa_8/kappa_850 ~ 1700. This may be due to the formation of ice mantles on the dust and grain coagulation, both of which are expected within dense regions of molecular clouds. The 850micron emission probes the underlying radial structure of the filament. The profile is well represented by a marginally resolved central region and a steeply falling envelope, with Sigma(r) proportional to r^(-a), where a <= 3, indicating that G11.11-0.12 is the first observed filament with a profile similar to that of a non-magnetic isothermal cylinder.

Interactions between a bright young stellar object and the midcourse space experiment infrared-dark cloud g79.3+0.3: an early stage of triggered star formation?

Abstract: Millimeter and mid-infrared observations have been made of the dense clumps of dust and gas and of young stellar objects (YSOs) associated with the bright, compact submillimeter source G79.3+0.3 P1 in the relatively nearby MSX infrared-dark cloud G79.3+0.3. The Gemini mid-infrared observations reported here indicate the presence of three YSOs within the cloud. BIMA 3 mm continuum observations show that the brightest of the YSOs is likely to be a Herbig Ae/Be star. High angular resolution molecular line observations suggest that a wind from this star may be triggering collapse in the adjacent molecular cloud. The submillimeter source G79.3+0.3 P1 itself does not contain infrared sources and may represent an earlier stage of star formation.