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As part of our survey of galactic stellar halos, we investigate the structure and stellar populations of the northern outer part of the stellar halo in NGC55, a member galaxy of the Sculptor Group, using deep and wide-field V- and I-band images taken with Subaru/Suprime-Cam. Based on the analysis of the color-magnitude diagrams (CMDs) for red-giant-branch (RGB) stars, we derive a tip of RGB (TRGB)-based distance modulus to the galaxy of (m-M)_0 = 26.58 +/- 0.11 (d = 2.1 +/- 0.1 Mpc). From the stellar density maps, we detect the asymmetrically disturbed, thick disk structure and two metal-poor overdense substructures in the north region of NGC55, which may correspond to merger remnants associated with hierarchical formation of NGC55s halo. In addition, we identify a diffuse metal-poor halo extended out to at least z ~ 16 kpc from the galactic plane. The surface-brightness profiles toward the z-direction perpendicular to the galactic plane suggest that the stellar density distribution in the northern outer part of NGC55 is described by a locally isothermal disk at z <~ 6 kpc and a likely diffuse metal-poor halo with V-band surface brightness of mu_V >~ 32 mag arcsec^{-2}, where old RGB stars dominate. We derive the metallicity distributions (MDs) of these structures on the basis of the photometric comparison of RGB stars with the theoretical stellar evolutionary models. The MDs of the thick disk structures show the peak and mean metallicity of [Fe/H]peak ~ -1.4 and [Fe/H]mean ~ -1.7, respectively, while the outer substructures show more metal-poor features than the thick disk structure. Combined with the current results with our previous study for M31s halo, we discuss the possible difference in the formation process of stellar halos among different Hubble types.
We present a photometric survey of the stellar halo of the Andromeda galaxy, using Suprime-Cam on the Subaru Telescope. A detailed analysis of VI color-magnitude diagrams of the resolved stellar population is used to measure properties such as line-o
We present the first results of the Subaru/Hyper Suprime-Cam (HSC) survey of the interacting galaxy system, NGC4631 and NGC4656. From the maps of resolved stellar populations, we identify 11 dwarf galaxies (including already-known dwarfs) in the oute
We report the discovery of a new ultra-faint dwarf satellite companion of the Milky Way based on the early survey data from the Hyper Suprime-Cam Subaru Strategic Program. This new satellite, Virgo I, which is located in the constellation of Virgo, h
We report on the global structure of the Milky Way (MW) stellar halo up to its outer boundary based on the analysis of blue-horizontal branch stars (BHBs). These halo tracers are extracted from the $(g,r,i,z)$ band multi-photometry in the internal da
We present the clustering analysis of photometric luminous red galaxies (LRGs) at a redshift range of $0.1leq z leq 1.05$ using $615,317$ photometric LRGs selected from the Hyper Suprime-Cam Subaru Strategic Program covering $sim124$ deg$^{2}$. Our s