Typhon: a polar stream from the outer halo raining through the Solar neighborhood. (arXiv:2206.10405v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Tenachi_W/0/1/0/all/0/1">Wassim Tenachi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Oria_P/0/1/0/all/0/1">Pierre-Antoine Oria</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ibata_R/0/1/0/all/0/1">Rodrigo Ibata</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Famaey_B/0/1/0/all/0/1">Benoit Famaey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yuan_Z/0/1/0/all/0/1">Zhen Yuan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arentsen_A/0/1/0/all/0/1">Anke Arentsen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martin_N/0/1/0/all/0/1">Nicolas Martin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Viswanathan_A/0/1/0/all/0/1">Akshara Viswanathan</a>
We report on the discovery in the Gaia DR3 astrometric and spectroscopic
catalog of a new polar stream that is found as an over-density in action space.
This structure is unique as it has an extremely large apocenter distance,
reaching beyond 100 kpc, and yet is detected as a coherent moving structure in
the Solar neighborhood with a width of $sim 4$ kpc. A sub-sample of these
stars that was fortuitously observed by LAMOST has a mean spectroscopic
metallicity of $langle {rm [Fe/H]}rangle = -1.60^{+0.15}_{-0.16}$ dex and
possesses a resolved metallicity dispersion of $sigma({rm [Fe/H]}) =
0.32^{+0.17}_{-0.06}$ dex. The physical width of the stream, the metallicity
dispersion and the vertical action spread indicate that the progenitor was a
dwarf galaxy. The existence of such a coherent and highly radial structure at
their pericenters in the vicinity of the Sun suggests that many other dwarf
galaxy fragments may be lurking in the outer halo.
We report on the discovery in the Gaia DR3 astrometric and spectroscopic
catalog of a new polar stream that is found as an over-density in action space.
This structure is unique as it has an extremely large apocenter distance,
reaching beyond 100 kpc, and yet is detected as a coherent moving structure in
the Solar neighborhood with a width of $sim 4$ kpc. A sub-sample of these
stars that was fortuitously observed by LAMOST has a mean spectroscopic
metallicity of $langle {rm [Fe/H]}rangle = -1.60^{+0.15}_{-0.16}$ dex and
possesses a resolved metallicity dispersion of $sigma({rm [Fe/H]}) =
0.32^{+0.17}_{-0.06}$ dex. The physical width of the stream, the metallicity
dispersion and the vertical action spread indicate that the progenitor was a
dwarf galaxy. The existence of such a coherent and highly radial structure at
their pericenters in the vicinity of the Sun suggests that many other dwarf
galaxy fragments may be lurking in the outer halo.
http://arxiv.org/icons/sfx.gif
