We analyse the optical properties of ∼300 galaxies within and around three prominent voids of the Center for Astrophysics Redshift Survey (Geller & Huchra 1989). We determine CCD morphologies and Hα equivalent widths from our imaging and spectroscopic survey (Grogin & Geller 1999). We also describe a redshift survey of 250 neighboring galaxies in the imaging survey fields. We assess the morphol...

Previously published Hα data and UBV photometry of blue stars in the inner kpc of M33 are used to study the distribution of OB stars and HII regions in the galaxy and to determine whether individual regions of the galaxy are separately and/or collectively in a state of ionization balance. Based on the surface brightness of the Hα emission, we identify three distinct ionized gas environments (br...

Reig, Fabregat & Coe (1997) plotted the equivalent width of Hα emission against the orbital period for several Be star/X-ray binary systems, and find a correlation. If instead of the equivalent width, which is a relative quantity, the luminosity of Hα emission, which is an absolute quantity, is used the correlation is not found.

ABSTRACT We use a sample of 706 galaxies, selected as [O ii]λ3727 ([O ii]) emitters in the Survey for High-z Absorption Red and Dead Sources (SHARDS) on CANDELS/GOODS-N field, to study differential attenuation nebular emission with respect stellar continuum. The includes only galaxies counterpart infrared log10(M*/M⊙) > 9, over redshift interval 0.3 ≲ z 1.5. Our methodology consists comp...

ASTRONOMY AND ASTROPHYSICS The origin of the ionization of the diffuse ionized gas in spirals. Abstract. In this paper we make a quantitative study of the hypothesis that the diffuse Hα emitted from the discs of spiral galaxies owes its origin to the ionizing photons escaping from H ii regions. The basis of the models is the assumption that a fraction of the Lyc luminosity from the OB stars wit...

Long-slit observations of the blue compact galaxy Haro 2 have been performed around Hα and Hβ. The main aim of these observations was to detect the Hα emission originating in the partially ionized wind outflow-ing at 200 km/s, that had been previously detected with the Hubble Space Telescope (HST). A shallow broadening of the Hα line wings has been observed, consistent with the existence of an ...

We investigate the systematic variation of the [OII]λ3727/Hα flux line ratio as a function of various galaxy properties, i.e., luminosity, metallicity, reddening, and excitation state, for a sample of 1 124 emission-line galaxies, with a mean redshift z ∼ 0.06, drawn from the Two Degree Field Galaxy Redshift Survey. The mean observed and extinction-corrected emission-line flux ratios agree well...

We study the variability of Hα emission in midto late-M dwarfs on timescales of ∼ 0.1 − 1 hr as a proxy for magnetic activity. We spectroscopically observed 43 active dwarfs with spectral types M3.5–M8.5 for ∼ 1 hr each, and with an exposure cadence of 5–10 minutes. About 80% of the objects exhibit statistically significant variability on the full range of timescales probed by the observations,...

We present the results of a search for strong Hα emission line galaxies (rest frame equivalent widths greater than 50Å) in the z ≈ 0.23 cluster Abell 2390. The survey contains 1189 galaxies over 270 ⊓⊔′, and is 50% complete at Mr ≈ −17.5 + 5 log h. The fraction of galaxies in which Hα is detected at the 2σ level rises from 0.0 in the central regions (excluding the cD galaxy) to 12.5±8% at R200....

in this paper, a chaotic particle swarm optimization with mutation-based classifier particle swarm optimization is proposed to classifypatterns of different classes in the feature space. the introduced mutation operators and chaotic sequences allows us to overcomethe problem of early convergence into a local minima associated with particle swarm optimization algorithms. that is, the mutationope...