To derive a new Hα luminosity function and to understand the clustering properties of star-forming galaxies at z ≈ 0.24, we have made a narrow-band imaging survey for Hα emitting galaxies in the HST COSMOS 2 square degree field. We used the narrow-band filter NB816 (λc = 8150 Å, ∆λ = 120 Å) and sampled Hα emitters with EWobs(Hα + [Nii]) > 12 Å in a redshift range between z = 0.233 and z = 0.251...

We present optical integral field spectroscopy of the Hα-luminous (> 10 42 erg s −1) central cluster galaxies in the cores of the cooling flow clusters A1664, A1835, A2204 and Zw8193. From the [NII]+Hα complex in these moderate resolution (70–150 km s −1) spectra we derive two-dimensional views of the distribution and kinematics of the emission line gas, and further diagnostics from the [SII] a...

We present Monte Carlo simulations of the Diffuse Hα Galactic Background. Our models comprise direct and multiply scattered Hα radiation from the kpc scaleheight Warm Ionized Medium and midplane H II regions. The scattering is off dust that is assumed to be well mixed with the gas, with an axisymmetric density distribution taken from the literature. The results of our simulations are all-sky Hα...

Optical emission lines provide an important new window on the HVCs. Recent studies of the Hα line reveal that ionized hydrogen is pervasively associated with the neutral hydrogen in HVCs. The Wis-consin Hα Mapper (WHAM) instrument has so far detected Hα from high-velocity clouds in the M, A, and C complexes. We find a close spatial correspondence between the neutral and ionized portions of the ...

Observations of the chromosphere with Deslandres’s spectroheliograph started at Paris Observatory in 1893 and were followed by systematic observations Meudon since 1908. The solar collection Hα CaII K images is probably longest available worldwide, associated products such as synoptic maps tables. Since 2018, only instrument producing data-cubes full line profiles H, Hα, for each pixel disk. Sl...

ABSTRACT We describe ISAAC/ESO-VLT observations of the Hα λ6563 Balmer line of 33 field galaxies from the Canada-France Redshift Survey (CFRS) with redshifts selected between 0.5 and 1.1. We detect Hα in emission in 30 galaxies and compare the properties of this sample with the low-redshift sample of CFRS galaxies at z ∼ 0.2 (Tresse & Maddox 1998). We find that the Hα luminosity, L(Hα), is tigh...

Context The morphology of massive star formation in the central regions of galaxies is an important tracer of the dynamical processes that govern the evolution of disk, bulge, and nuclear activity. Aims We present optical imaging of the central regions of a sample of 73 spiral galaxies in the Hα line and in optical broad bands, and derive information on the morphology of massive star formation....

We investigate the Hα and infrared star formation rate (SFR) diagnostics for galaxies in the Nearby Field Galaxy Survey (NFGS). For the 81 galaxies in our sample, we derive Hα fluxes (included here) from integrated spectra. There is a strong correlation between the ratio of far-infrared to optical luminosities L(FIR)/L(Hα) and the extinction E(B − V ) measured with the Balmer decrement. Before ...