College of Letters & Science

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The College of Letters and Science, the largest center for learning, teaching and research at Montana State University, offers students an excellent liberal arts and sciences education in nearly 50 majors, 25 minors and over 25 graduate degrees within the four areas of the humanities, natural sciences, mathematics and social sciences.

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Author: search.filters.author.Nidever, David L.Subject: search.filters.subject.galaxy: halo-galaxy

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    Discovery of a split stellar stream in the periphery of the Small Magellanic Cloud
    (Oxford University Press, 2024-07) Nidever, David L.
    I report the discovery of a stellar stream (Sutlej) using Gaia DR3 (third data release) proper motions and XP metallicities located ∼15◦ north of the Small Magellanic Cloud (SMC). The stream is composed of two parallel linear components (‘branches’) approximately ∼8◦ × 0.6◦ in size and separated by 2.5◦. The stars have a mean proper motion of (μRA , μDec. ) = (+0.08 mas yr−1 , −1.41 mas yr−1 ), which is quite similar to the proper motion of stars on the western side of the SMC. The colour–magnitude diagram of the stream stars has a clear red giant branch, horizontal branch, and main-sequence turn-off that are well matched by a PARSEC isochrone of 10 Gyr, [Fe/H] = −1.8 at 32 kpc, and a total stellar mass of ∼33 000 M . The stream is spread out over an area of 9.6 deg2 and has a surface brightness of 32.5 mag arcsec−2 . The metallicity of the stream stars from Gaia XP spectra extends over −2.5≤ [M/H] ≤−1.0 with a median of [M/H] = −1.8. The tangential velocity of the stream stars is 214 km s−1 compared to the values of 448 km s−1 for the Large Magellanic Cloud and 428 km s−1 for the SMC. While the radial velocity of the stream is not yet known, a comparison of the space velocities using a range of assumed radial velocities shows that the stream is unlikely to be associated with the Magellanic Clouds. The tangential velocity vector is misaligned with the stream by nearly 90◦, which might indicate an important gravitational influence from the nearby Magellanic Clouds.
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