Publication Date:
2016-09-18
Description:
We report the discovery of a very diverse set of five low-surface brightness (LSB) dwarf galaxy candidates in Hickson Compact Group 90 (HCG 90) detected in deep U - and I -band images obtained with Very Large Telescope/Visible Multi-Object Spectrograph. These are the first LSB dwarf galaxy candidates found in a compact group of galaxies. We measure spheroid half-light radii in the range 0.7 r eff /kpc 1.5 with luminosities of –11.65 M U –9.42 and –12.79 M I –10.58 mag, corresponding to a colour range of ( U – I ) 0 ~= 1.1–2.2 mag and surface brightness levels of μ U ~= 28.1 mag arcsec –2 and μ I ~= 27.4 mag arcsec –2 . Their colours and luminosities are consistent with a diverse set of stellar population properties. Assuming solar and 0.02 Z metallicities we obtain stellar masses in the range M * | Z ~= 10 5.7 – 6.3 M and $M_{\ast }|_{0.02\,\mathrm{Z}_{\odot }} \simeq 10^{6.3-8}\,\mathrm{M}_{{\odot }}$ . Three dwarfs are older than 1 Gyr, while the other two significantly bluer dwarfs are younger than ~2 Gyr at any mass/metallicity combination. Altogether, the new LSB dwarf galaxy candidates share properties with dwarf galaxies found throughout the Local Volume and in nearby galaxy clusters such as Fornax. We find a pair of candidates with ~2 kpc projected separation, which may represent one of the closest dwarf galaxy pairs found. We also find a nucleated dwarf candidate, with a nucleus size of r eff ~= 46–63 pc and magnitude M U , 0 = –7.42 mag and ( U – I ) 0 = 1.51 mag, which is consistent with a nuclear stellar disc with a stellar mass in the range 10 4.9 – 6.5 M .
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
