The outer regions of galaxies
نویسندگان
چکیده
منابع مشابه
The Extreme Outer Regions of Disk Galaxies: I. Chemical Abundances of Hii Regions
We present the first results of an ongoing project to investigate the present-day chemical abundances of the extreme outer parts of galactic disks, as probed by the emission line spectra of a new sample of HII regions. The galaxies studied here, NGC 628, NGC 1058 and NGC 6946, are all late-type spiral galaxies, characterized by larger than average HI-to-optical sizes. Our deep Hα images have re...
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We present an analysis of four off-axis ROSAT PSPC observations of the Perseus cluster of galaxies (Abell 426). We detect the surface brightness profile to a radius of 80 arcmin (∼ 2.4h 50 Mpc) from the X-ray peak. The profile is measured in various sectors and in three different energy bands. Firstly, a colour analysis highlights a slight variation of NH over the region, and cool components in...
متن کاملDiscovery of Recent Star Formation in the Extreme Outer Regions of Disk Galaxies
We present deep Hα images of three nearby late-type spiral galaxies (NGC 628, NGC 1058 and NGC 6946), which reveal the presence of HII regions out to, and beyond, two optical radii (defined by the 25th B-band isophote). The outermost HII regions appear small, faint and isolated, compared to their inner disk counterparts, and are distributed in organized spiral arm structures, likely associated ...
متن کاملThe Extreme Outer Regions of Disk Galaxies: Star Formation and Metal Abundances
The extreme outer regions of disk galaxies, lying at or beyond the classical optical radius defined by R25, present an opportunity to study star formation and chemical evolution under unique physical conditions, possibly reminscent of those which existed during the early stages of disk evolution. We present here some of the first results from a large study to measure star formation rates and me...
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We present deep optical imaging of three face-on disk galaxies together with a detailed description of the reduction and calibration methods used, in order to measure the intrinsic shape of their outer stellar edges. Whereas it is now well accepted that disks of spiral galaxies are not infinite exponential beyond galactocentric distances of about 3-5 radial scalelengths, the genuine structure o...
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ژورنال
عنوان ژورنال: Nature
سال: 1982
ISSN: 0028-0836,1476-4687
DOI: 10.1038/298421a0