Anomalous behaviour of the galactocentric distance of the stream according to Ibata polinomials.

[martinmestre]

@Charly-Arguelles @danielcarpintero: One image is worth a thousand words, please see the plot at the bottom of galactocentric distance vs. the phi_1 angle. The red lines, fitted are the original solutions (not varying barions in the optimization). At the end there is a further comment.

It is bad that the uncertainties in the heliocentric distances measured by Ibata propagate into such unphysical values of the galactocentric distances. This is something to mention in the paper.
Any comments?
PS: The objective of this computations was to know exactly within what gal-distance range does the stream observations move. I was surprised that it is only 1.5 kpc (between 14 and 15.5 kpc). In the literature they say that the stream satisfies perigalacticon of 14.4 kpc and apogalacticon of 28.7 kpc. I have not verified this yet in our simulations. Then GD-1 is just passing its pericentre. It would be nice to make an N-body simulation to know if with only one pericentric passage is enough to form its tidal tails.
Another question to think about: Having fitted the Ibata data, do we have information of only that small galactocentric range (1.5kpc) or we have information of all the orbit somehow?

[danielcarpintero]

Martín: Suppose our model is correct. If the uncertainties of the measured distances are large, then it is expected to have large discrepancies between model and observations, attributable to the 'poor' observations. I mean, if the observations are not good enough, the discrepancies can be attached to the observations and not to the model. Daniel El vie, 8 abr 2022 a las 18:19, martinmestre ***@***.***>) escribió:

…

@Charly-Arguelles <https://github.com/Charly-Arguelles> @danielcarpintero <https://github.com/danielcarpintero>: One image is worth a thousand words, please see the plot at the bottom of galactocentric distance vs. the phi_1 angle. The red lines, fitted are the original solutions (not varying barions in the optimization). At the end there is a further comment. [image: sky_pot-slice_from_IbataPolysGaiaDR2-data] <https://user-images.githubusercontent.com/58749264/162532830-75db09e9-46a5-498f-bc00-63bbea9eda8e.png> It is bad that the uncertainties in the heliocentric distances measured by Ibata propagate into such unphysical values of the galactocentric distances. This is something to mention in the paper. Any comments? — Reply to this email directly, view it on GitHub <#8>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ATTASC5WOZ4MABIZFIM2U53VECPELANCNFSM5S5VINDQ> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[martinmestre]

Gracias @danielcarpintero! Para mayor claridad hablo en español, la curva de distancia galactocentrica observada (en realidad fiteada por Ibata) tiene per se una caracteristica no fisica, ya que cambia la convexidad. Yo creo que si en vez de usar esos datos, se usara la integral de los datos de velocidad radial, se podria obtener algo mas razonable. Lo voy a probar.