10 research outputs found
The orientation and kinematics of inner tidal tails around dwarf galaxies orbiting the Milky Way
Using high-resolution collisionless N-body simulations we study the
properties of tidal tails formed in the immediate vicinity of a two-component
dwarf galaxy evolving in a static potential of the Milky Way (MW). The stellar
component of the dwarf is initially in the form of a disk and the galaxy is
placed on an eccentric orbit motivated by CDM-based cosmological simulations.
We measure the orientation, density and velocity distribution of the stars in
the tails. Due to the geometry of the orbit, in the vicinity of the dwarf,
where the tails are densest and therefore most likely to be detectable, they
are typically oriented towards the MW and not along the orbit. We report on an
interesting phenomenon of `tidal tail flipping': on the way from the pericentre
to the apocentre the old tails following the orbit are dissolved and new ones
pointing towards the MW are formed over a short timescale. We also find a tight
linear relation between the velocity of stars in the tidal tails and their
distance from the dwarf. Using mock data sets we demonstrate that if dwarf
spheroidal (dSph) galaxies in the vicinity of the MW are tidally affected their
kinematic samples are very likely contaminated by tidally stripped stars which
tend to artificially inflate the measured velocity dispersion. The effect is
stronger for dwarfs on their way from the peri- to the apocentre due to the
formation of new tidal tails after pericentre. Realistic mass estimates of dSph
galaxies thus require removal of these stars from kinematic samples.Comment: 8 pages, 7 figures, accepted for publication in MNRA
NOVICE AND EXPERIENCED TEACHERS’ VIEWS ON PROFESSIONALISM
This article discusses teachers’ practical knowledge and beliefs of their profession based on reflective writings of twenty Estonian teachers.Ten novice and ten experienced teachers participated in the study. They put together their professional portfolios, which among other documents included reflective writings regarding professionalism. The teachers’ writings enabled us to qualitatively analyse how they described and interpreted their teaching activities and what being a professional teacher means to them. The results showed that when speaking about the image of a professional teacher, novice teachers stressed technological teaching aspects, for instance – skills in using IT equipment. The essays by the experienced teachers included more keywords related to the development of students and stressed the teacher’s role as an educator. Both novice and experienced teachers valued the pedagogical education of teachers