Piercing the Milky Way: an all-sky view of the Orphan Stream. (arXiv:1812.08172v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Koposov_S/0/1/0/all/0/1">S. E. Koposov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Belokurov_V/0/1/0/all/0/1">V. Belokurov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_T/0/1/0/all/0/1">T. S. Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mateu_C/0/1/0/all/0/1">C. Mateu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Erkal_D/0/1/0/all/0/1">D. Erkal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Grillmair_C/0/1/0/all/0/1">C. J. Grillmair</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hendel_D/0/1/0/all/0/1">D. Hendel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Price_Whelan_A/0/1/0/all/0/1">A. M. Price-Whelan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Laporte_C/0/1/0/all/0/1">C. F. P. Laporte</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hawkins_K/0/1/0/all/0/1">K. Hawkins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sohn_S/0/1/0/all/0/1">S. T. Sohn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pino_A/0/1/0/all/0/1">A. del Pino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Evans_N/0/1/0/all/0/1">N. W. Evans</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Slater_C/0/1/0/all/0/1">C. T. Slater</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kallivayalil_N/0/1/0/all/0/1">N. Kallivayalil</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Navarro_J/0/1/0/all/0/1">J. F. Navarro</a>
We use astrometry, broad-band photometry and variability information from the
Data Release 2 of ESA’s Gaia mission (GDR2) to identify members of the Orphan
Stream (OS) across the whole sky. The stream is traced above and below the
celestial equator and in both Galactic hemispheres, thus increasing its visible
length to ~ 210 degrees equivalent to ~150 kpc in physical extent. Taking
advantage of the large number of RR Lyrae stars in the OS, we extract accurate
distances and proper motions across the entire stretch of the tidal debris
studied. As delineated by the GDR2 RR Lyrae, the stream exhibits two prominent
twists in its shape on the sky which are accompanied by changes in the
tangential motion. We complement the RR Lyrae maps with those created using
GDR2 Red Giants and the DECam Legacy Survey Main Sequence Turn-Off stars. The
behavior of the OS track on the sky is consistent across all three tracers
employed. We detect a strong non-zero motion in the across-stream direction for
a substantial portion of the stream. Such a misalignment between the debris
track and the streaming velocity cannot be reproduced in a static gravitational
potential and signals an interaction with a massive perturber.
We use astrometry, broad-band photometry and variability information from the
Data Release 2 of ESA’s Gaia mission (GDR2) to identify members of the Orphan
Stream (OS) across the whole sky. The stream is traced above and below the
celestial equator and in both Galactic hemispheres, thus increasing its visible
length to ~ 210 degrees equivalent to ~150 kpc in physical extent. Taking
advantage of the large number of RR Lyrae stars in the OS, we extract accurate
distances and proper motions across the entire stretch of the tidal debris
studied. As delineated by the GDR2 RR Lyrae, the stream exhibits two prominent
twists in its shape on the sky which are accompanied by changes in the
tangential motion. We complement the RR Lyrae maps with those created using
GDR2 Red Giants and the DECam Legacy Survey Main Sequence Turn-Off stars. The
behavior of the OS track on the sky is consistent across all three tracers
employed. We detect a strong non-zero motion in the across-stream direction for
a substantial portion of the stream. Such a misalignment between the debris
track and the streaming velocity cannot be reproduced in a static gravitational
potential and signals an interaction with a massive perturber.
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