Abstract
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 3{\pi} survey. Located 27.9{\deg} 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 kpc from its host. The properties of Perseus I are typical for a reasonably bright dwarf galaxy (M_V = -10.3 +/- 0.7), with an exponential half-light radius of r_h = 1.7 +/- 0.4 arcminutes or r_h = 400 +105/-85 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.
Highlights
Aside from the individual importance of dwarf galaxies to constrain low-mass galaxy formation in a cosmological context, these faint systems are powerful probes of their environment. Can they be used to study the intricacies of star formation processes in their comparatively shallow potentials (e.g., Brown et al 2012) or constrain the dark matter content of their host (e.g., Watkins et al 2010), but they can provide information on the transverse bulk motion of external satellite systems with an accuracy that is difficult, or even impossible to reach through direct proper motion measurements
We reproduce the analysis of Martin et al (2013b, Section 3.3) to determine the total magnitude of Perseus I (Per I): we start by summing up the flux contribution of all stars within the half-light radius of the dwarf galaxy that satisfy 20.7 < iP1,0 < 21.5 and a colorcut to weed out obvious non-red giant branch (RGB) stars
In this Letter, we present the discovery of a new Local Group galaxy, Perseus I, in the stellar catalog generated from stacked rP1- and iP1-Pan-STARRS1 Surveys (PS1) imaging
Summary
Aside from the individual importance of dwarf galaxies to constrain low-mass galaxy formation in a cosmological context, these faint systems are powerful probes of their environment Can they be used to study the intricacies of star formation processes in their comparatively shallow potentials (e.g., Brown et al 2012) or constrain the dark matter content of their host (e.g., Watkins et al 2010), but they can provide information on the transverse bulk motion of external satellite systems with an accuracy that is difficult, or even impossible to reach through direct proper motion measurements (van der Marel & Guhathakurta 2008). The latest releases of the Sloan Digital Sky Survey (SDSS, DR8 and beyond; Aihara et al 2011) include the coverage of large regions south of M31, which led to the discovery of its two distant satellite dwarf galaxies, And XXVIII and And XXIX, located at 27◦.7 and 15◦.1, respectively (Bell et al 2011; Slater et al 2011).
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