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Identifier

000446365

Title

Measurement of the magnetic field in the polaris flare region using data from the RoboPol instrument

Alternative Title

Μέτρηση μαγνητικού πεδίου στη περιοχή του Polaris Flare χρησιμοποιώντας δεδομένα από το όργανο

Author

Γκιμήση, Κάτια Α.

Thesis advisor

Τάσσης, Κωνσταντίνος

Reviewer

Χαρμανδάρης, Βασίλης
Ζέζας, Ανδρέας

Abstract

The Galactic magnetic field influences various astrophysical processes but its role in stellar formation is still being investigated. In order to gain insight into the early stages of this process, we examine the magnetic field of clouds with no apparent star formation activity. The Polaris Flare is a translucent diffuse molecular cloud that is in the quiescent stage. Panopoulou et. al (2015, 2016) explored the magnetic field properties of this cloud using optical polarization data observed with the RoboPol instrument at Skinakas Observatory. They removed artifacts from the sample by setting statistical limits. Then, they made an estimation for the magnetic field strength applying the DCF method. Because of some issues in their analysis, we revisit their approach in this work. We used the same polarization data from the Polaris Flare region but we removed the artefacts using a convolutional neural network together with the limit on the ratio between polarization (P) and reddening (E) of each star, P/E(B-V)≤13%. This procedure resulted to 624 stars in our final poralization data sample. To estimate the magnetic field strength, we used the method proposed by Skalidis and Tassis (2021), by applying information for the kinematics of the gas, together with information from the polarization data and the gas mass density of the region to the formula they derived. With the use of CO observation data, we were able to explore the gas kinematics of a region in the Polaris Flare and found that the gas moves in two distinct directions, so we decided to split that region into two (A and B) and continue our analysis separately. The gas mass desnity in the regions was estimated using an H2 column density map together with the RADEX online tool for radiative transfer computations, and the ratio of number densities N_CO/N_H2≃9.3•10^-6. The parameters needed for the computations of RADEX were extracted from the CO data as well. By combining all of our tools, we were able to estimate the magnetic field strength in the two regions as B_o,A=18μG(+5, -2) and B_o,B=44μG(+13,-6) accordingly. The errorbars are the result of choosing three characteristic temperatures for our estimations, which were 20 ^oK, 35 ^oK and 50 ^oK.

Language

English

Subject

Astrophysics

ISM

Interstellar dust

Magnetic field strength

Polarization

St method

Αστρική πόλωση

Αστροφυσική

Διαστρική σκόνη