7. Jałocha J., Bratek Ł., Pękala J., Sikora S., Kutschera M.
Magnetic flux density from the relative circular motion of stars and partially ionized gas in the Galaxy mid-plane vicinity
Astrophys J. , vol. 833, p. 174 (2016).
[abstract] [preprint] [journal]

Abstract:
Observations suggest a slower stellar rotation relative to gas rotation in the outer part of the Milky Way Galaxy. This difference could be attributed to an interaction with the interstellar magnetic field. In a simple model, fields of order 10 micro Gauss are then required, consistently with the observed values. This coincidence suggests a tool for estimating magnetic fields in spiral galaxies. A North-South asymmetry in the rotation of gas in the Galaxy could be of magnetic origin too.

8. Sebastian J. Szybka, Michał J. Wyrȩbowski
Backreaction for Einstein-Rosen waves coupled to a massless scalar field
Phys. Rev. D: Part. Fields , vol. 94, p. 024059 (2016).
[abstract] [preprint] [journal]

Abstract:
We present a one-parameter family of exact solutions to Einstein's equations that may be used to study the nature of the Green-Wald backreaction framework. Our explicit example is a family of Einstein-Rosen waves coupled to a massless scalar field.

9. Sebastian J. Szybka
Równania Einsteina i efekt niejednorodności w kosmologii
W ,,Ogólna teoria względności a filozofia - sto lat interakcji'', red. P. Polak, J. Mączka, CCPress, pp. 127-142 [journal]

Abstract:

10. Bratek Ł., Sikora S., Jałocha J., Kutschera M.
Velocity-density twin transforms in the thin disk model
Mon. Not. R. Astron. Soc. , vol. 451, p. 4018 (2015).
[abstract] [preprint] [journal]

Abstract:
Ring mass density and the corresponding circular velocity in thin disc model are known to be integral transforms of one another. But it may be less familiar that the transforms can be reduced to one-fold integrals with identical weight functions. It may be of practical value that the integral for the surface density does not involve the velocity derivative, unlike the equivalent and widely known Toomre's formula.

11. Jałocha J., Bratek Ł., Sikora S., Kutschera M.
Modelling vertical structure in circular velocity of spiral galaxy NGC 4244
Mon. Not. R. Astron. Soc. , vol. 451, p. 3366 (2015).
[abstract] [preprint] [journal]

Abstract:
We study the vertical gradient in azimuthal velocity of spiral galaxy NGC 4244 in a thin disc model. With surface density accounting for the rotation curve, we model the gradient properties in the approximation of quasi-circular orbits. It is worthy to note that the prediction of our model is consistent with the gradient properties inferred recently from a numerical model implementing the position-velocity diagram of this galaxy. The confirmation of our prediction by the future measurement of the gradient would provide support for the expectation that the mass distribution in this galaxy is flattened.

12. Sikora S., Bratek Ł., Jałocha J., Kutschera M.
Motion of halo tracer objects in the gravitational potential of a low-mass model of the Galaxy
Astron. Astrophys. , vol. 579, p. A134 (2015).
[abstract] [preprint] [journal]

Abstract:
Recently, we determined a lower bound for the Milky Way mass in a point mass approximation. We obtain this result for most general spherically symmetric phase-space distribution functions consistent with a measured radial velocity dispersion. As a stability test of these predictions against a perturbation of the point mass potential, in this paper we make use of a representative of these functions to set the initial conditions for a simulation in a more realistic potential of similar mass and to account for other observations. The predicted radial velocity dispersion profile evolves to forms still consistent with the measured profile, proving structural stability of the point mass approximation and the reliability of the resulting mass estimate of ~2.1 × 10^11 M⊙ within 150 kpc. As a byproduct, we derive a formula in the spherical symmetry relating the radial velocity dispersion profile to a directly measured kinematical observable.