Arms Of M83 Research Articles

The structure of the inner eastern spiral arm of M83

The spatial distributions of dust, Hβ, and nonthermal radio emission are studied in the inner eastern arm of M83 (NGC 5236) using VLA 20 cm continuum radio observations, a pure Hβ image, and a red continuum CCD image. Contrary to the case in, e.g., M51 and M101, the radio continuum emission in the neighborhood of the giant H II complexes is dominantly nonthermal. Nonthermal radio emission is also found to correspond well with the dust lanes, especially in the bar near the nucleus where the radio continuum is bright and the dust lanes are nearly perpendicular to the galaxy rotation. However, farther out along the eastern spiral arm, this dust-lane component of the nonthermal radio continuum fades, becoming overshadowed by a parallel ridge of strong nonthermal emission located well outside the dust lanes and following the general locus of the H II regions

A molecular gas ridge offset from the dust lane in a spiral arm of M83

A high-resolution interferometric map of the CO emission on the eastern spiral arm of M83 is presented. The detected emission originates in about five unresolved components located parallel but about 300 pc downstream from the dust lane which lies along the inner edge of the spiral arm. All the CO components in the map but one are located within 130 pc of an H II region and may represent emission from locally heated gas. The lack of CO emission on the dust lane indicates that the dense molecular gas does not pile up here in M83. Remarkable differences between the molecular gas distributions in M83 and the spiral arms or M51, where CO emission peaks on the dust lane, is attributed to the difference in the strength of their density waves. The observations of M83 are consistent with the model of Elmegreen in which diffuse gas is compressed at the shock front, producing the dust lane at the inner edge of the spiral arm while dense giant molecular clouds pass through the front and form a broad distribution on the arm.

M83. III - Age and brightness of young and old stellar populations

view Abstract Citations (68) References (98) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS M 83 III. Age and brightness of young and old stellar populations. Jensen, E. B. ; Talbot, R. J., Jr. ; Dufour, R. J. Abstract The determination of the luminosities and ages of stellar populations in an external spiral galaxy is considered, and results are presented for the spiral galaxy M83. Procedures used in the deconvolution of the light from the spheroid or bulge, old stellar disk (age greater than 100 million years) and young stellar disk (age less than 100 million years) components of the galaxy are presented, and results are indicated in the form of maps of the luminosity, age and mass distributions of the young population. It is pointed out that although star formation is seen to occur in almost all of the 27 pc resolution pixels within the inner spiral arms, most of the luminosity is confined to associations in aggregates a few hundred pc in size. The ages and positions of these associations indicate a mechanism which globally triggers the formation of massive stars in a well-defined, symmetric two-armed spiral pattern, acts locally in a largely stochastic manner, and terminates after a few tens of millions of years. Results also suggest that the initial mass function in the arms of M83 cannot be represented by a power law over the customary mass range with normal population I stars. Publication: The Astrophysical Journal Pub Date: February 1981 DOI: 10.1086/158640 Bibcode: 1981ApJ...243..716J Keywords: Early Stars; Galactic Structure; Late Stars; Spiral Galaxies; Stellar Evolution; Brightness; Chronology; Hertzsprung-Russell Diagram; Interstellar Extinction; Nuclear Fusion; Ubv Spectra; Astrophysics full text sources ADS | data products NED (8) SIMBAD (1)