The Extended Halo of Centaurus A: Uncovering Satellites, Streams, and Substructures
Abstract
We present the widest-field resolved stellar map to date of the closest (D∼ 3.8 Mpc) massive elliptical galaxy NGC 5128 (Centaurus A; Cen A), extending out to a projected galactocentric radius of ∼150 kpc. The data set 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 (RGB) stars down to ∼1.5 mag below the tip of the RGB, reaching surface brightness limits as low as {μ }V,0∼ 32 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 {μ }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 ultradiffuse 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.
This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.- Publication:
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The Astrophysical Journal
- Pub Date:
- May 2016
- DOI:
- 10.3847/0004-637X/823/1/19
- arXiv:
- arXiv:1512.05366
- Bibcode:
- 2016ApJ...823...19C
- Keywords:
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- galaxies: dwarf;
- galaxies: groups: individual: CenA;
- galaxies: halos;
- galaxies: photometry;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 21 pages, 17 figures