Chandraobservation of NGC 4449: analysis of the X-ray emission from a dwarf starburst galaxy
| Autor: | Ian R. Stevens, Lesley K. Summers, David K. Strickland, Timothy M. Heckman |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
Physics
Point source business.industry Astrophysics::High Energy Astrophysical Phenomena Astrophysics (astro-ph) FOS: Physical sciences Flux Astronomy and Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Astrophysics Galaxy Spectral line Luminosity Space and Planetary Science Halo business Astrophysics::Galaxy Astrophysics Thermal energy Luminosity function (astronomy) |
| Zdroj: | Monthly Notices of the Royal Astronomical Society. 342:690-708 |
| ISSN: | 1365-2966 0035-8711 |
| Popis: | We present CHANDRA X-ray data of the nearby Magellanic Irregular dwarf starburst galaxy NGC4449. Contributions to the X-ray emission come from discrete point sources and extended diffuse emission. The extended emission has a complex morphology with an extent of 2.4x1.6kpc down to a flux density of 1.3E-13 erg/s/cm2/arcmin2. The best spectral fit to this emission is obtained with an absorbed, two temperature model giving temperatures for the two gas components of 0.28keV and 0.86keV, a total mass content of ~10^7 Msun compared with a galactic mass of several 10^{10} Msun and a total thermal energy content of ~2.5E55erg, with an average energy injection rate for the galaxy of a few 1E41 erg/s. Comparison of the morphology of the diffuse X-ray emission with that of the observed Halpha emission shows similarities in the two emissions. An expanding super-bubble is suggested by the presence of diffuse X-ray emission within what appears to be a cavity in the Halpha emission. The kinematics of this bubble suggest an expansion velocity of ~220km/s and a mass injection rate of 0.14Msun/yr, but the presence of NGC4449's huge HI halo (r~40kpc) may prevent the ejection, into the IGM, of the metal-enriched material and energy it contains. The arcsecond-resolution of CHANDRA has detected 24 X-ray point sources down to a completeness level corresponding to a flux of ~2E-14 erg/s/cm2, within the optical extent of NGC4449 and analysis of their spectra has shown them to be from at least 3 different classes of object. As well as the known SNR in this galaxy, it also harbours several X-ray binaries and super-soft sources. The point source X-ray luminosity function, for the higher luminosity sources, has a slope of ~-0.51, comparable to those of other starburst galaxies. 21 pages, 14 Figures, Accepted for publication in MNRAS |
| Databáze: | OpenAIRE |
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