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Durham University

Department of Physics

Staff profile

Publication details for Dr Peter W. Draper

Martin, N.F., Schlafly, E.F., Slater, C.T., Bernard, E.J., Rix, H.-W., Bell, E.F., Ferguson, A.M.N., Finkbeiner, D.P., Laevens, B.P.M., Burgett, W.S., Chambers, K.C., Draper, P.W., Hodapp, K.W., Kaiser, N., Kudritzki, R.-P., Magnier, E.A., Metcalfe, N., Morgan, J.S., Price, P.A., Tonry, J.L., Wainscoat, R.J. & Waters, C. (2013). Perseus I: a distant satellite dwarf galaxy of Andromeda. The Astrophysical Journal Letters 779(1): L10.

Author(s) from Durham


We present the discovery of a new dwarf galaxy, Perseus I/Andromeda XXXIII, found in the vicinity of Andromeda (M31) in stacked imaging data from the Pan-STARRS1 3π survey. Located 27fdg9 away from M31, Perseus I has a heliocentric distance of 785 ± 65 kpc, compatible with it being a satellite of M31 at $374^{+14}_{-10}{\rm \,kpc}$ from its host. The properties of Perseus I are typical for a reasonably bright dwarf galaxy (MV = –10.3 ± 0.7), with an exponential half-light radius of rh = 1.7 ± 0.4 arcmin or $r_h = 400^{+105}_{-85}{\rm \,pc}$ at this distance, and a moderate ellipticity ($\epsilon = 0.43^{+0.15}_{-0.17}$). The late discovery of Perseus I is due to its fairly low surface brightness ($\mu 0=25.7^{+1.0}{-0.9}$ mag arcsec–2), and to the previous lack of deep, high quality photometric data in this region. If confirmed to be a companion of M31, the location of Perseus I, far east from its host, could place interesting constraints on the bulk motion of the satellite system of M31.