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arXiv · 1512.05366

The extended halo of Centaurus A: uncovering satellites, streams, and substructures

D. Crnojević·D. J. Sand·K. Spekkens·N. Caldwell·P. Guhathakurta·B. McLeod·A. Seth·J. Simon·J. Strader·E. Toloba
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Abstract

We present the widest-field resolved stellar map to date of the closest ($D\sim3.8$ Mpc) massive elliptical galaxy NGC 5128 (Centaurus A; Cen A), extending out to a projected galactocentric radius of $\sim150$ kpc. The dataset is part of our ongoing Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) utilizing the Magellan/Megacam imager. We resolve a population of old red giant branch stars down to $\sim1.5$ mag below the tip of the red giant branch, reaching surface brightness limits as low as $\mu_{V,0}\sim32$ mag arcsec$^{-2}$. The resulting spatial stellar density map highlights a plethora of previously unknown streams, shells, and satellites, including the first tidally disrupting dwarf around Cen A (CenA-MM-Dw3), which underline its active accretion history. We report 13 previously unknown dwarf satellite candidates, of which 9 are confirmed to be at the distance of Cen A (the remaining 4 are not resolved into stars), with magnitudes in the range $M_V=-7.2$ to $-13.0$, central surface brightness values of $\mu_{V,0}=25.4-26.9$ mag arcsec$^{-2}$, and half-light radii of $r_h=0.22-2.92$ kpc. These values are in line with Local Group dwarfs but also lie at the faint/diffuse end of their distribution; interestingly, CenA-MM-Dw3 has similar properties to the recently discovered ultra-diffuse galaxies in Virgo and Coma. Most of the new dwarfs are fainter than the previously known Cen A satellites. The newly discovered dwarfs and halo substructures are discussed in light of their stellar populations, and they are compared to those discovered by the PAndAS survey of M31.

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D. Crnojević, D. J. Sand, K. Spekkens, N. Caldwell, P. Guhathakurta, B. McLeod, A. Seth, J. Simon, J. Strader, E. Toloba. 2015-12-16. The extended halo of Centaurus A: uncovering satellites, streams, and substructures. https://doi.org/10.3847/0004-637x/823/1/19

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