Santiago Vanegas | Searcharxiv

arXiv2019

GalRotpy: an educational tool to understand and parametrize the rotation curve and gravitational potential of disk-like galaxies

\textbf{GalRotpy} is an educational \verb+Python3+-based visual tool, which is useful to undestand how is the contribution of each mass component to the gravitational potential of disc-like galaxies by means of their rotation curve. Besides, \textbf{GalRotpy} allows the user to perform a parametric fit of a given rotation curve, which relies on a MCMC procedure implemented by using \verb+emcee+ package. Here the gravitational potential of disc-like galaxies is built from the contribution of a Miyamoto-Nagai potential model for the bulge/core and the thin/thick disc, an exponential disc, together with the NFW (Navarro-Frenk- White) potential or the Burkert (cored density profile) potential for the Dark Matter halo, where each contribution is implemented by using \verb+galpy+ package. We summarize the properties of each contribution to the rotation curve involved, and then describe how \textbf{GalRotpy} is implemented along with its capabilities. Finally we present the characterization of two galaxies, NGC6361 and M33, and show that the results for M33 provided by \textbf{GalRotpy} are consistent with those found in the literature.

astro-ph.GA↗

arXiv2015

Measuring the speed of light and the moon distance with an occultation of Mars by the Moon: a Citizen Astronomy Campaign

In July 5th 2014 an occultation of Mars by the Moon was visible in South America. Citizen scientists and professional astronomers in Colombia, Venezuela and Chile performed a set of simple observations of the phenomenon aimed to measure the speed of light and lunar distance. This initiative is part of the so called "Aristarchus Campaign", a citizen astronomy project aimed to reproduce observations and measurements made by astronomers of the past. Participants in the campaign used simple astronomical instruments (binoculars or small telescopes) and other electronic gadgets (cell-phones and digital cameras) to measure occultation times and to take high resolution videos and pictures. In this paper we describe the results of the Aristarchus Campaign. We compiled 9 sets of observations from sites separated by distances as large as 2,500 km. We achieve at measuring the speed of light in vacuum and lunar distance with uncertainties of few percent. The goal of the Aristarchus Campaigns is not to provide improved values of well-known astronomical and physical quantities, but to demonstrate how the public could be engaged in scientific endeavors using simple instrumentation and readily available technological devices. These initiatives could benefit amateur communities in developing countries increasing their awareness towards their actual capabilities for collaboratively obtaining useful astronomical data. This kind of exercises would prepare them for facing future and more advanced observational campaigns where their role could be crucial.

physics.pop-ph↗