A Cold Stellar Stream in Pegasus
Abstract
We report the serendipitous discovery of a stellar stream in the constellation Pegasus in the south Galactic hemisphere. The stellar stream was detected using the SDSS Data Release 14 by means of a matched filter in the color--magnitude diagram that is optimised for a stellar population that is 8 Gyr old with [Fe/H] = -0.46 dex, and located at heliocentric distance of 18 kpc. The candidate stream is faint (turnoff point at r0 19.6), sparse and barely visible in SDSS photometry. It is also detected in the (shallower) Pan-STARRs data. The residual stellar density in the (u-g)0, (g-r)0 color--color diagram gives the same estimate for the age and [Fe/H] of this stellar population. The stream is located at a Galactic coordinates (l,b) = (79.4,-24.6) and extends over 9 (2.5 kpc), with a width of 112 pc. The narrow width suggests a globular cluster progenitor.
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