Results 271 to 280 of about 20,346,263 (306)
Some of the next articles are maybe not open access.
The H II regions of NGC 6822. I - an atlas of 157 H II regions
Publications of the Astronomical Society of the Pacific, 1988A CCD survey at Hα results in a catalog of 157 H II regions in the Local Group irregular galaxy NGC 6822. Most of them are newly detected, faint surface-brightness objects. Positions and maps are given, and identifications are correlated with those of previous studies.
Paul Hodge +2 more
openaire +1 more source
Annual Review of Astronomy and Astrophysics, 1990
Article de synthese sur les regions H II extragalactiques traitant des morphologies, de la cinematique, des etoiles ionisantes et des abondances ...
openaire +1 more source
Article de synthese sur les regions H II extragalactiques traitant des morphologies, de la cinematique, des etoiles ionisantes et des abondances ...
openaire +1 more source
Publications of the Astronomical Society of the Pacific, 1994
Calibrated H-alpha and continuum CCD frames are used to measure the emission-line luminosities, sizes and morphological characteristics of 25 H II regions in the dwarf irregular galaxy Sextans A, a probable member of the Local Group. The luminosity function fits a power law with slope--1.70 and the size distribution is roughly exponential with a scale ...
Paul Hodge +2 more
openaire +1 more source
Calibrated H-alpha and continuum CCD frames are used to measure the emission-line luminosities, sizes and morphological characteristics of 25 H II regions in the dwarf irregular galaxy Sextans A, a probable member of the Local Group. The luminosity function fits a power law with slope--1.70 and the size distribution is roughly exponential with a scale ...
Paul Hodge +2 more
openaire +1 more source
1974
The luminosity of the brightest H ii regions of M31 was determined with the NRAO 3-element interferometer at 3.7 cm and 11 cm wavelength. It is unlikely that M31 has any superbright Hn regions such as W51 or W49; our Galaxy has between 10 and 20 H ii regions that are more luminous than any in M31.
J. H. Spencer, B. F. Burke
openaire +1 more source
The luminosity of the brightest H ii regions of M31 was determined with the NRAO 3-element interferometer at 3.7 cm and 11 cm wavelength. It is unlikely that M31 has any superbright Hn regions such as W51 or W49; our Galaxy has between 10 and 20 H ii regions that are more luminous than any in M31.
J. H. Spencer, B. F. Burke
openaire +1 more source
1974
The study of HII regions is very old. In the 17th century Christiaan Huygens had already observed and described the Orion nebula. Our understanding of this and similar objects increased dramatically between 1925 and 1940 when quantum theory made it possible to interprete the emission line spectra quantitatively.
openaire +1 more source
The study of HII regions is very old. In the 17th century Christiaan Huygens had already observed and described the Orion nebula. Our understanding of this and similar objects increased dramatically between 1925 and 1940 when quantum theory made it possible to interprete the emission line spectra quantitatively.
openaire +1 more source
Publications of the Astronomical Society of the Pacific, 1974
This is a review of the current status of the study of H II regions in other galaxies, especially their spatial distribution and relation to galactic structure. An extensive table compiles all available data on the H-alpha surveys of galaxies.
openaire +1 more source
This is a review of the current status of the study of H II regions in other galaxies, especially their spatial distribution and relation to galactic structure. An extensive table compiles all available data on the H-alpha surveys of galaxies.
openaire +1 more source
1987
By virtue of its spectrometers having simultaneous multichannel integration capability and relatively large input apertures, the International Ultraviolet Explorer satellite has been the first instrument capable of effective study of the ultraviolet spectra of the gas from extended H ii regions. This review will concentrate on discussing the results of
openaire +1 more source
By virtue of its spectrometers having simultaneous multichannel integration capability and relatively large input apertures, the International Ultraviolet Explorer satellite has been the first instrument capable of effective study of the ultraviolet spectra of the gas from extended H ii regions. This review will concentrate on discussing the results of
openaire +1 more source
2008
A probable evolutionary sequence of H II regions based on six distinct types of observed objects is suggested. Two examples which may deviate from this idealized sequence, are discussed. Even though a sizemean density relation for H II regions can be used as a rough indication of whether a nebula is very young or evolved, it is argued that such a ...
openaire +1 more source
A probable evolutionary sequence of H II regions based on six distinct types of observed objects is suggested. Two examples which may deviate from this idealized sequence, are discussed. Even though a sizemean density relation for H II regions can be used as a rough indication of whether a nebula is very young or evolved, it is argued that such a ...
openaire +1 more source
Publications of the Astronomical Society of the Pacific, 1986
Models of H II regions provide ionization corrections for abundance determinations and estimates of the ionizing star temperature Tasterisk and of the nebular ionization parameter U. In the absence of observed electron temperatures, models may be used to determine abundances; and a systematic procedure is described here.
openaire +1 more source
Models of H II regions provide ionization corrections for abundance determinations and estimates of the ionizing star temperature Tasterisk and of the nebular ionization parameter U. In the absence of observed electron temperatures, models may be used to determine abundances; and a systematic procedure is described here.
openaire +1 more source
Pressure and Density Gradients in H ii Regions
Astrophysics and Space Science, 2001Here we discuss the effects of large ambient pressures and decreasing density gradients on the observed properties of dusty UCH ii regions. Dust absorption can effectively reduce the size of the photoionized region, and density gradients can modify the spectral index of the emission.
José Franco +6 more
openaire +1 more source