Two long-slit spectra of the diffuse ionized gas in NGC 891 are presented. The first reveals variations parallel to the major axis in emission line ratios in the halo gas at z = 700 pc. It is found that filaments of Hα emission show lower values of [N II]/Hα, [S II]/Hα and [O I]/Hα. Although this result is expected if the filaments represent the walls of evacuated chimneys, it merely reflects a...

A large portion of the Galaxy (ℓ = 123 • to 164 • , b = −6 • to −35 •), which samples regions of the Local (Orion) spiral arm and the more distant Perseus arm, has been mapped with the Wisconsin H-Alpha Mapper (WHAM) in the [S II] λ6716 and [N II] λ6583 lines. By comparing these data with the maps from the WHAM Hα Sky Survey, we begin an investigation of the global physical properties of the Wa...

2MASSI J1315309−264951 is an L3 dwarf with strong Hα emission discovered in the course of a colorselected survey for active galactic nuclei using the Two-Micron All-Sky Survey (2MASS). The strength of its Hα emission decreased by about a factor of two between two epochs separated by 137 days. This is the first time that variable Hα emission has been reported in an L dwarf, and is probably the f...

We have measured the Hα+[N II] fluxes of the I-selected Canada−France Redshift Survey (CFRS) galaxies lying at a redshift z below 0.3, and hence derived the Hα luminosity function. The magnitude limits of the CFRS mean that only the galaxies withMB ∼> −21 mag were observed at these redshifts. We obtained a total Hα luminosity density of at least 10 erg s Mpc at a mean z = 0.2 for galaxies with ...

We compare simultaneous sequences of Hα and He ii 304Å images near the solar limb. We propose to distinguish polar surges and giant spicules (macrospicules), among the He ii structures observed beyond the solar limb. Polar surges have a complex structure when observed in Hα and an erup-tive nature, reminiscent of normal surges in small scale. Giant spicules are simple spikes, very narrow compar...

We present results of an Hα survey in the rich cluster A 1689 at z = 0.18, using the LDSS++ spectrograph on the AAT. We obtained spectra covering redshifted Hα at z = 0.16–0.22, for 522 galaxies brighter than I = 22.5, covering a field of 8.7×8.7(∼ 1.1×1.1h Mpc at z = 0.18). We securely detect Hα emission in 46 of these galaxies; accounting for selection effects due to sampling and cluster memb...

We study the star formation rate and dust extinction properties of a sample of nearby star forming galaxies as derived from Hα and UV (∼ 2000 Å) observations and we compare them to those of a sample of starburst galaxies. The dust extinction in Hα is estimated from the Balmer decrement and the extinction in UV using the FIR to UV flux ratio or the attenuation law for starburst galaxies of Calze...

We present the relation of the spatial distribution of Hα kernels with the distribution of hard X-ray (HXR) sources seen during the 2001 April 10 solar flare. This flare was observed in Hα with the Sartorius telescope at Kwasan Observatory, Kyoto University, and in hard X-rays (HXRs) with the Hard X-ray Telescope (HXT) onboard Yohkoh. We compared the spatial distribution of the HXR sources with...

Abstract The ratio of Hα intensity to 1.4 GHz radio continuum in the North Polar Spur (NPS) is measured be ≲ 50, two orders magnitude smaller than values ∼104 observed typical shell-type old supernova remnants, Cygnus Loop and S147. extremely low Hα-to-radio favours Galactic-Centre explosion model for NPS, which postulates a giant shock wave at distance several kilo parsecs hot low-density Gala...

We have used archival ultraviolet (UV) imaging of 50 nearby star-forming galaxies obtained with the Ultraviolet Imaging Telescope (UIT) to derive integrated near-UV and far-UV magnitudes, and have combined these data with Hα, far-infrared, and thermal radio continuum measurements to explore the consistency of UV and Hα star formation rates (SFRs). In agreement with previous studies, we find tha...