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Classification parameters for the emission-line spectra of extragalactic objects
An investigation is made of the merits of various emission-line intensity ratios for classifying the spectra of extragalactic objects. It is shown empirically that several combinations of
The Primordial helium abundance from observations of extragalactic H-II regions
The pre-galactic (assumed primordial) helium mass fraction Y p is determined to be 0.228 ± 0.005 (s.e.) or Y p < 0.242 with 95 per cent confidence, taking reasonably likely systematic errors into
New Light on the Search for Low-Metallicity Galaxies
We present a simple metallicity estimator based on the logarithmic [N ii] λ6584/Hα ratio, hereafter N2, which we envisage will become very useful for ranking galaxies in a metallicity sequence from
The stellar populations and evolution of H II galaxies - I. High signal-to-noise optical spectroscopy.
On presente les donnees spectroscopiques concernant 32 galaxies HII. Certaines comportent des sursauts de formation stellaire (36 ont ete observes au total) pour lesquels on a obtenu les temperatures
The evolution of C/O in dwarf galaxies from Hubble Space Telescope FOS observations
We present UV observations of seven H II regions in low-luminosity dwarf irregular galaxies and the Magellanic Clouds obtained with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope
Abundances in southern Local Group dwarf irregular galaxies
La spectrophotometrie des regions H II des galaxies naines irregulieres NGC 6822, WLM et Sag DIG, du Groupe Local sud, est presentee. La composition chimique de ces trois galaxies est determinee.
Violent star formation in NGC 2363
This is an electronic version of an article published in The Astrophysical Journal. Gonzalez-Delgado, R.M. et al. Violent star formation in NGC 2363. The Astrophysical Journal 437 (1994): 239-261
Carbon in spiral galaxies from Hubble Space Telescope spectroscopy
We present measurements of the gas-phase abundance ratio C/O in six H II regions in the spiral galaxies M101 and NGC 2403, based on ultraviolet spectroscopy using the Faint Object Spectrograph on the
A Supernova at z = 0.458 and Implications for Measuring theCosmological Deceleration
We have begun a program to discover high-redshift supernovae ($z \approx$ 0.25--0.5), and study them with follow-up photometry and spectroscopy. We report here our first discovery, a supernova at $z
Group, field and isolated early‐type galaxies – I. Observations and nuclear data
This is the first paper of a series on the investigation of stellar population properties and galaxy evolution of an observationally homogeneous sample of early-type galaxies in groups, field and