Unveiling a Rich System of Faint Dwarf Galaxies in the Next Generation Fornax Survey

Abstract

We report the discovery of 158 previously undetected dwarf galaxies in the Fornax cluster central regions using a deep coadded u, g and i-band image obtained with the DECam wide-field camera mounted on the 4meter Blanco telescope at the Cerro Tololo Interamerican Observatory as part of the Next Generation Fornax Survey (NGFS). The new dwarf galaxies have quasi-exponential light profiles, effective radii 0.1 < r e < 2.8 kpc and average effective surface brightness values 22.0 < µ i < 28.0 mag arcsec −2 . We confirm the existence of ultra-diffuse galaxies (UDGs) in the Fornax core regions that resemble counterparts recently discovered in the Virgo and Coma galaxy clusters. We also find extremely low surface brightness NGFS dwarfs, which are several magnitudes fainter than the classical UDGs. The faintest dwarf candidate in our NGFS sample has an absolute magnitude of M i = −8.0 mag. The nucleation fraction of the NGFS dwarf galaxy sample appears to decrease as a function of their total luminosity, reaching from a nucleation fraction of > 75% at luminosities brighter than M i ≃ −15.0 mag to 0% at luminosities fainter than M i ≃ −10.0 mag. The two-point correlation function analysis of the NGFS dwarf sample shows an excess on length scales below ∼100 kpc, pointing to the clustering of dwarf galaxies in the Fornax cluster core.

THE FORNAX DEEP SURVEY WITH VST. I. THE EXTENDED AND DIFFUSE STELLAR HALO OF NGC 1399 OUT TO 192 kpc

“…The dashed black lines show the direction along which we extracted the radial profiles shown in Figure 9, and we observe a light excess. The black circles identify the whole sample of dwarf galaxies in the Fornax cluster observed in the DECAM images published by Muñoz et al (2015).…”

“…On this image we have identified the whole sample of the dwarf population in the Fornax cluster observed in the DECAM images published by Muñoz et al (2015). As an extra check of the detection limit of the VST data, we provide in Figure 6 the enlarged portion of the mosaic in the g band where two dwarf galaxies among the faintest and new objects discovered by Muñoz et al (2015) are located. We selected two examples, one nucleated and one nonnucleated dwarf, which appear clearly detectable also in the VST.…”

“…The absolute magnitude in the g band is Figure 6. Enlarged portion of the mosaic where two dwarf galaxies among the faintest objects detected by Muñoz et al (2015) are located. We selected two examples, one nucleated (left panel) and one nonnucleated (right panel) dwarf.…”

“…We selected two examples, one nucleated (left panel) and one nonnucleated (right panel) dwarf. The integrated magnitudes in the g and i bands were derived in a circular aperture with a radius of 2r e , where the effective radius r e is the value given by Muñoz et al (2015).…”

“…In the recent years, a big effort has been made to develop deep photometric surveys aimed at studying galaxy structures up to the faintest levels of surface brightness, which reveal lowluminosity structures and trace the stellar halos at very large distances from the galaxy center (Mihos et al 2005;Janowiecki et al 2010;Martínez-Delgado et al 2010;Roediger et al 2011;Ferrarese et al 2012;van Dokkum et al 2014;Duc et al 2015;Muñoz et al 2015;Trujillo & Fliri 2015). Recently, deep images of the Virgo cluster have revealed several faint (μ V =26-29 mag arcsec −2 ) streams of ICL among the galaxy members and made it possible to map the stellar halos of the bright cluster galaxies (BCGs) at very large distances from the center (Janowiecki et al 2010).…”