Measuring the surface brightness changes in HST images in Hα and [O III]5007 Å taken with a time interval of 6.84 yr, we show how to detect separately the changes due to density variations and those due to temperature variations. Following O'Dell et al., we used the brightness changes to show and measure proper motions in streams and fronts at up

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We present the kinematics of a sample of bipolar planetary nebulae (PNs) which cover a wide range of observed morphologies and collimation degrees, from bipolar PNs (BPNs) with a marked equatorial ring and wide lobes to highly collimated objects. We use an empirical model in order to derive the expansion velocity, collimation degree, and

We present a kinematic analysis of the double-barred early-type galaxy NGC 357. The radial velocity and velocity dispersion profiles along both the nuclear bar axis and the semi-major axis clearly reveal the presence of the two bars. The results indicate that the bulge is pressure supported whereas the |vr|/σ ratio shows a plateau along the nuclear

We report on the discovery of over 50 strong Hα emitting objects towards the large OB association Cyg OB2 and the HII region DR 15 on its southern periphery. This was achieved using the INT Photometric Hα Survey of the Northern Galactic Plane (IPHAS), combined with follow-up spectroscopy using the MMT multi-object spectrometer HectoSpec. We present

We present results derived from Hα images of 327 local galaxies from the HaGS (Hα Galaxy Survey), where we have correlated the star formation rates with the interaction characteristics of the galaxies. We see a significant increase in the star formation rate in galaxies with close neighbors, an increase which has probably been triggered by galaxy