ABSTRACT
Supernova remnants (SNRs) are well-recognized dust producers, but their net dust production rate remains elusive due to uncertainties in grain properties that propagate into observed dust ...mass uncertainties, and determine how efficiently these grains are processed by reverse shocks. In this paper, we present a detection of polarized dust emission in the Crab pulsar wind nebula, the second SNR with confirmed polarized dust emission after Cassiopeia A. We constrain the bulk composition of the dust with new SOFIA/HAWC+ polarimetric data in band C 89 μm and band D 154 μm. After correcting for synchrotron polarization, we report dust polarization fractions ranging between 3.7–9.6 per cent and 2.7–7.6 per cent in three individual dusty filaments at 89 and 154 μm, respectively. The detected polarized signal suggests the presence of large (≳0.05–0.1 μm) grains in the Crab Nebula. With the observed polarization, and polarized and total fluxes, we constrain the temperatures and masses of carbonaceous and silicate grains. We find that the carbon-rich grain mass fraction varies between 12 and 70 per cent, demonstrating that carbonaceous and silicate grains co-exist in this SNR. Temperatures range from ∼40 to ∼70 K and from ∼30 to ∼50 K for carbonaceous and silicate grains, respectively. Dust masses range from ∼10−4 to ∼10−2 M⊙ for carbonaceous grains and to ∼10−1 M⊙ for silicate grains, in three individual regions.
Within the framework of the HerM33es Key Project for Herschel and in combination with multi-wavelength data, we study the Spectral Energy Distribution (SED) of a set of H ii regions in the Local ...Group Galaxy M33. Using the Hα emission, we perform a classification of a selected H ii region sample in terms of morphology, separating the objects in filled, mixed, shell and clear shell objects. We obtain the SED for each H ii region as well as a representative SED for each class of objects. We also study the emission distribution of each band within the regions. We find different trends in the SEDs for each morphological type that are related to properties of the dust and their associated stellar cluster. The emission distribution of each band within the region is different for each morphological type of object.
Dust properties and distribution in dwarf galaxies Lisenfeld, Ute; Relaño, Monica; Vílchez, José ...
Proceedings of the International Astronomical Union,
06/2008, Letnik:
4, Številka:
S255
Journal Article
Recenzirano
Odprti dostop
We present a study of the extinction, traced by the Balmer decrement, in HII regions in the dwarf galaxies NGC 1569 and NGC 4214. We find that the large-scale extinction around the most prominent HII ...regions in both galaxies forms a shell in which locally the intrinsic extinction can adopt relatively high values (AV = 0.8 − 0.9 mag) despite the low metallicity and thus the low overall dust content. The small-scale extinction (spatial resolution ~0.3″) shows fluctuations that are most likely due to variations in the dust distribution. We compare the distribution of the extinction to that of the dust emission, traced by Spitzer emission at 8 and 24μm, and to the emission of cold dust at 850μm. We find in general a good agreement between all tracers, except for the 850μm emission in NGC 4214 which is more extended than the extinction and the other emissions. Whereas in NGC 1569 the dust emission at all wavelengths is very similar, NGC 4214 shows spatial variations in the 24-to-850μm ratio. We furthermore compared the 24μm and the extinction-corrected Hα emission from HII regions in a sample of galaxies with a wide range of metallicities and found a good correlation, independent of metallicity. We suggest that this lack of dependence on metallicity might be due to the formation of dust shells with a relatively constant opacity, like the ones observed here, around ionizing stars.
Abstract We present new observations of the central 1 kpc of the M82 starburst obtained with the James Webb Space Telescope near-infrared camera instrument at a resolution θ ∼ 0.″05–0.″1 (∼1–2 pc). ...The data comprises images in three mostly continuum filters (F140M, F250M, and F360M), and filters that contain Fe ii (F164N), H 2 v = 1 → 0 (F212N), and the 3.3 μ m polycyclic aromatic hydrocarbon (PAH) feature (F335M). We find prominent plumes of PAH emission extending outward from the central starburst region, together with a network of complex filamentary substructures and edge-brightened bubble-like features. The structure of the PAH emission closely resembles that of the ionized gas, as revealed in Paschen α and free–free radio emission. We discuss the origin of the structure, and suggest the PAHs are embedded in a combination of neutral, molecular, and photoionized gas.
We have measured the emission line profiles in Hα from populations of HII regions in nearby spiral galaxies, and extracted their non-thermal line widths. These are supersonic for the more luminous ...regions. We infer from plots of line width, σ, against Hα luminosity, a set of regions in virial equilibrium, and derive their masses summing all known components. The virial masses are considerably larger. If this discrepancy, and the supersonic line widths, are due to the presence of magnetic fields, we can estimate their strengths at a few microgauss. Observational confirmation is clearly required.
We present observations of the nearby barred starburst galaxy M83 (NGC 5236), with the new Fabry-Perot interferometer GHaFaS mounted on the 4.2 m William Herschel Telescope on La Palma. The ...unprecedented high-resolution observations, of 16 pc FWHM super(-1), of the Ha-emitting gas cover the central 2 kpc of the galaxy. The velocity field displays the dominant disk rotation with signatures of gas inflow from kpc scales down to the nuclear regions. At the inner inner Lindblad resonance radius of the main bar and centered at the dynamical center of the main galaxy disk, a nuclear (5.5 plus or minus 0.9) x 10 super(8) M unk rapidly rotating disk with scale length of 60 plus or minus 20 pc has formed. The nuclear starburst is found in the vicinity as well as inside this nuclear disk, and our observations confirm that gas spirals in from the outer parts to feed the nuclear starburst, giving rise to several star formation events at different epochs, within the central 100 pc radius of M83.
We present high-resolution Hα velocity fields and rotation curves of the circum nuclear star-forming regions of five barred galaxies. Two of the five objects show substantially smaller initial rises ...than the three others; these two objects also have spiral structure inside the circum nuclear star-forming ring.PUBLICATION ABSTRACT
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