نتایج جستجو برای: interstellar molecular cloud
تعداد نتایج: 725777 فیلتر نتایج به سال:
We propose that galactic shocks propagating through interstellar density fluctuations provide a mechanism for the intermittent replenishment, or " pumping, " of the supersonic motions and internal density enhancements observed pervasively within cool atomic and molecular interstellar structures, without necessarily requiring the presence of self-gravity, magnetic fields, or young stars. The sho...
An absorption feature at 3.4 lm has been detected in the long-wavelength wing of the 3.1 lm H2O ice feature in three young stellar objects: IRAS 18511+0146, IRAS 21413+5442, and IRAS 04579+4703. The profile of the 3.4 lm absorption in IRAS 18511+0146 has distinct subfeatures at 3.38, 3.41, and 3.48 lm and is not similar to those found in molecular clouds but is similar to those in the diffuse i...
We observed the nearby spiral galaxy M31 with the Long-Wavelength Spectrometer on board the Infrared Space Observatory. Far-infrared line-to-continuum ratios of [C ii]/100 μm ' 6 × 10−3 were obtained for the central kiloparsec region along the major axis of the galaxy. These ratios are 2–3 times higher than those in the Galactic counterpart and are closer to those in the general Galactic plane....
An analysis of large-area CO J=3-2 maps from the James Clerk Maxwell Telescope for 12 nearby spiral galaxies reveals low velocity dispersions in the molecular component of the interstellar medium. The three lowest luminosity galaxies show a relatively flat velocity dispersion as a function of radius while the remaining nine galaxies show a central peak with a radial fall-off within 0.2 − 0.4r25...
The ionization fraction in neutral interstellar clouds is a key physical parameter controlling multiple and chemical processes, varying by orders of magnitude from the UV irradiated surface cloud to its cosmic-ray dominated central regions. Traditional observational tracers fraction, which mostly rely on deuteration ratios molecules like HCO + , suffer fact that deuterated are only detected tin...
The gas at the surfaces of molecular clouds in galaxies is heated and dissociated by photons from young stars both near and far. H i resulting from the dissociation of molecular hydrogen H2 emits hyperfine line emission at 21 cm, and warmed CO emits dipole rotational lines such as the 2.6 mm line of CO(1–0). We use previously developed models for photodissociation regions (PDRs) to compute the ...
We examine the abundance of molecular hydrogen (H2) in the spectra of gamma ray burst afterglows (GRBs). In nearby galaxies H2 traces the cold neutral medium (CNM) and dense molecular starforming interstellar gas. Though H2 is detected in at least half of all sightlines towards hot stars in the Magellanic Clouds and in ≈ 25% of damped Lyα systems toward quasars, it is not detected in any of the...
The Magellanic Mopra Assessment (MAGMA) is a high angular resolution 12CO (J = 1 → 0) mapping survey of giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud using the Mopra Telescope. Here we report on the basic physical properties of 125 GMCs in the LMC that have been surveyed to date. The observed clouds exhibit scaling relations that are similar to tho...
Systematic variations with wavelength in the position angle of interstellar linear polarization of starlight may be indicative of multiple cloud structure along the line of sight. We use polarimetric observations of two stars (HD 29647, HD 283809) in the general direction of TMC{1 in the Taurus Dark Cloud to investigate grain properties and cloud structure in this region. We show the data to be...
Absorption features from the Lyman and Werner bands of interstellar molecular hydrogen were recorded by the Interstellar Medium Absorption Profile Spectrograph (IMAPS) at λ/∆λ = 80, 000 in the spectra of δ Ori A and ǫ Ori. The objective was to find and study more examples of an unusual phenomenon found for one of the velocity components of H2 in the spectrum of ζ Ori by Jenkins & Peimbert (1997...
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