Pattern speed of main spiral arms in NGC 2997: Estimate based on very young stellar complexes - Astrophysics > Astrophysics of GalaxiesReportar como inadecuado




Pattern speed of main spiral arms in NGC 2997: Estimate based on very young stellar complexes - Astrophysics > Astrophysics of Galaxies - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: Deep JHK-Brg photometry of the southern arm of the grand-design spiral galaxyNGC 2997 was obtained by ISAAC-VLT. All sources in the field brighter than K=19mag were located. Color-color diagrams were used to identify young stellarcomplexes among the extended sources. Ages can be estimated for the youngestcomplexes and correlated with azimuthal distances from the spiral arms definedby the K-band intensity variation. The extended sources with Mk <-12 magdisplay a diffuse appearance and are more concentrated inside the arm regionthan fainter ones, which are compact and uniformly distributed in the disk. TheNIR colors of the bright diffuse objects are consistent with them being youngstarforming complexes with ages <10 Myr and reddened by up to 8 mag of visualextinction. They show a color gradient as a function of their azimuthaldistance from the spiral arms. Interpreting this gradient as an age variation,the pattern speed Op = 16 km-s-kpc of the main spiral was derived assumingcircular motion. The alignment and color gradient of the bright, diffusecomplexes strongly support a density wave scenario for NGC 2997. Only thebrightest complexes with Mk <-12 mag show a well aligned structure along thearm, suggesting that a strong compression in the gas due to the spiralpotential is required to form these most massive aggregates, while smallerstarforming regions are formed more randomly in the disk. The sharp transitionbetween the two groups at Mk = -12 mag may be associated with expulsion of gaswhen the first supernovae explode in the complex.



Autor: P. Grosbol H. Dottori

Fuente: https://arxiv.org/







Documentos relacionados