Stellar Orbital Studies in Normal Spiral Galaxies II: Restrictions to Structural and Dynamical parameters on Spiral Arms

Making use of a set of detailed potential models for normal spiral galaxies, we analyze the disk stellar orbital dynamics as the structural and dynamical parameters of the spiral arms (mass, pattern speed and pitch angle) are gradually modified. With this comprehensive study of ordered and chaotic behavior, we constructed an assemblage of orbitally supported galactic models and plausible parameters for orbitally self-consistent spiral arms models. We find that, to maintain orbital support for the spiral arms, the spiral arm mass, M$_{sp}$, must decrease with the increase of the pitch angle, $i$; if $i$ is smaller than $\sim10\deg$, M$_{sp}$ can be as large as $\sim7\%$, $\sim6\%$, $\sim5\%$ of the disk mass, for Sa, Sb, and Sc galaxies, respectively. If $i$ increases up to $\sim25\deg$, the maximum M$_{sp}$ is $\sim1\%$ of the disk mass independently in this case of morphological type. For values larger than these limits, spiral arms would likely act as transient features. Regarding the limits posed by extreme chaotic behavior, we find a strong restriction on the maximum plausible values of spiral arms parameters on disk galaxies beyond which, chaotic behavior becomes pervasive. We find that for $i$ smaller than $\sim20\deg$, $\sim25\deg$, $\sim30\deg$, for Sa, Sb, and Sc galaxies, respectively, M$_{sp}$ can go up to $\sim10\%$, of the mass of the disk. If the corresponding $i$ is around $\sim40\deg$, $\sim45\deg$, $\sim50\deg$, M$_{sp}$ is $\sim1\%$, $\sim2\%$, $\sim3\%$ of the mass of the disk. Beyond these values, chaos dominates phase space, destroying the main periodic and the neighboring quasi-periodic orbits.Comment: 51 pages in preprint format, 30 figures, Accepted for publication in Ap

The Stellar Halo in the Inner Milky Way: Predicted Shape and Kinematics

We have used N-body simulations for the Milky Way to investigate the kinematic and structural properties of the old metal-poor stellar halo in the barred inner region of the Galaxy. We find that the extrapolation of the density distribution for bulge RR Lyrae stars, $\rho\sim r^{-3}$, approximately matches the number density of RR Lyrae in the nearby stellar halo. We follow the evolution of such a tracer population through the formation and evolution of the bar and box/peanut bulge in the N-body model. We find that its density distribution changes from oblate to triaxial, and that it acquires slow rotation in agreement with recent measurements. The maximum radial velocity is $\sim15-25$ km/s at $| l|\!=10^\circ-30^\circ$, and the velocity dispersion is $\sim120$ km/s. Even though the simulated metal-poor halo in the bulge has a barred shape, just $12\%$ of the orbits follow the bar, and it does not trace the peanut/X structure. With these properties, the RR Lyrae population in the Galactic bulge is consistent with being the inward extension of the Galactic metal-poor stellar halo.Comment: 5 pages, 5 figures. Accepted for publication in MNRAS Letter

The Galactic Branches as a Possible Evidence for Transient Spiral Arms

With the use of a background Milky-Way-like potential model, we performed stellar orbital and magnetohydrodynamic (MHD) simulations. As a first experiment, we studied the gaseous response to a bisymmetric spiral arm potential: the widely employed cosine potential model and a self-gravitating tridimensional density distribution based model called PERLAS. Important differences are noticeable in these simulations, while the simplified cosine potential produces two spiral arms for all cases, the more realistic density based model produces a response of four spiral arms on the gaseous disk, except for weak arms -i.e. close to the linear regime- where a two-armed structure is formed. In order to compare the stellar and gas response to the spiral arms, we have also included a detailed periodic orbit study and explored different structural parameters within observational uncertainties. The four armed response has been explained as the result of ultra harmonic resonances, or as shocks with the massive bisymmetric spiral structure, among other. From the results of this work, and comparing the stellar and gaseous responses, we tracked down an alternative explanation to the formation of branches, based only on the orbital response to a self-gravitating spiral arms model. The presence of features such as branches, might be an indication of transiency of the arms.Comment: 17 pages, 9 figures. Accepted for publication in MNRA

Estudio de los valores de la PIO en una región de Cataluña

Objectiu: Estudiar els valors de la pressió intraocular (PIO), segons els següents factors: ull (dret i esquerre), franja horària en què es realitza la mesura de la PIO, sexe, edat, estat refractiu, pressió arterial, presència de diabetis, presència de glaucoma i origen. Aquest estudi s'ha realitzat a Catalunya (Terrassa), escollint una mostra obtinguda en el centre universitari de la visió (CUV). Mètode: Es trien com a mostra a un total de 150 individus en un rang d'edats entre 8-85 anys i dels quals 81 són dones i 69 homes. A cadascuna d'aquestes persones se li realitza una anamnesi amb més èmfasi en les preguntes relatives als factors rellevants per al treball. D'altra banda, es realitza un examen refractiu subjectiu de cada ull, els individus que presentaven un astigmatisme> 0,5 D van ser exclosos de l'estudi i seguidament es mesura la PIO amb el tonòmetre de no contacte i anotem l'hora del dia a la qual hem realitzat la mesura. Les dades obtingudes s'analitzen amb el programa d'estadística Minitab 2016. Conclusions: La PIO augmenta significativament amb l'edat. Els individus amb refracció neutra presenten valors de PIO significativament menors que la resta. Pacients que presenten glaucoma tenen valors de PIO significativament més elevats que els pacients que no ho padeixen. La pressió intraocular augmenta significativament amb la pressió arterial. Hi ha altres factors com el sexe, origen, presència de diabetis i la franja horària que no són determinants en la influència sobre els valors de PIO

Revisiting the Tale of Hercules: how stars orbiting the Lagrange points visit the Sun

We propose a novel explanation for the Hercules stream consistent with recent measurements of the extent and pattern speed of the Galactic bar. We have adapted a made-to-measure dynamical model tailored for the Milky Way to investigate the kinematics of the solar neighborhood (SNd). The model matches the 3D density of the red clump giant stars (RCGs) in the bulge and bar as well as stellar kinematics in the inner Galaxy, with a pattern speed of 39 km s$^{-1}$ kpc$^{-1}$. Cross-matching this model with the $Gaia$ DR1 TGAS data combined with RAVE and LAMOST radial velocities, we find that the model naturally predicts a bimodality in the $U\!-\!V$-velocity distribution for nearby stars which is in good agreement with the Hercules stream. In the model, the Hercules stream is made of stars orbiting the Lagrange points of the bar which move outward from the bar's corotation radius to visit the SNd. While the model is not yet a quantitative fit of the velocity distribution, the new picture naturally predicts that the Hercules stream is more prominent inward from the Sun and nearly absent only a few $100$ pc outward of the Sun, and plausibly explains that Hercules is prominent in old and metal-rich stars.Comment: 7 pages, 5 figures. ApJ Letters, in pres

Smart token for the university using blockchain

The National Taiwan University of Science and Technology is established as a world-class university of multifaceted excellence through international outreach and applied research. In order to make the university more efficient, concerned, adapt it to the use of new technologies incoming and make it more innovative Professor Shuo-Yan Chou among other professors came to the idea of creating a Smart Campus. This project involves interdepartmental efforts, ideas and new technologies to reach the main goal. Some of the projects concerning this Smart Campus are faced in developing apps to report maintenance problems; others want to use new technologies such as machine learning to facilitate the study of human flow; and other projects want to improve energy consumption by monitoring the usage of water dispensers. This particular project sought the objective of creating a rewarding system and a micro-economy sharing society to be implemented in the smart campus. According to that, applying the newest technologies is the key point. For the past few years, the technology of blockchain has been in upswing. This technology breaks with the centralized systems of nowadays to reach a decentralized network with peer-to-peer communication. Furthermore, blockchain enables users to create and use smart contracts that, among all of their characteristics, highlight the possibility of the creation of a token/cryptocurrency to be exchanged. After a deep research in blockchain, a first brief introduction to the main characteristics of it is given to the reader. When the basic concepts of this revolutionary technology have been achieved, it is time to apply blockchain to the rewarding system project. To do so, a private network based on the Ethereum Platform has been created. This network is sustained by a certain number of computers, working as nodes, that verify transactions happening across the network. Once the blockchain is created, the project goes through the creation of a token (named NTUSToken) that is given as a reward for making some good practices and is interchangeable by the students, giving them the sense of a micro-economy society based on the token. On this private blockchain, users can create accounts, transfer tokens and check their balances. Finally, the last key point of the project is to make this system handy and attractive to users. As blockchain is not a trivial technology to understand, users have to be able to register, log in to their accounts and share tokens without the necessity of knowing the technology behind it. For this purpose, a browser application connected to the private network has been created. With this application, users have an easy platform to join the micro-economy. By now, the implementation of a micro-economy and a rewarding system in the NTUST has been achieved and can be implemented by following this thesis. Some of the codes and files used are shown and detailed in the Annex