The Next Generation Fornax Survey (NGFS). II. The Central Dwarf Galaxy Population

Abstract

We present a photometric study of the dwarf galaxy population in the core region (≲ r vir 4) of the Fornax galaxy cluster based on deep u ′ g ′ i ′ photometry from the Next Generation Fornax Cluster Survey. All imaging data were obtained with the Dark Energy Camera mounted on the 4-meter Blanco telescope at the Cerro-Tololo Interamerican Observatory. We identify 258 dwarf galaxy candidates with luminosities −17 ≲ M g ′ ≲ −8 mag, corresponding to typical stellar masses of 9.5 ≳ log M ⋆ M ⊙ ≳ 5.5, reaching ∼ 3 mag deeper in point-source luminosity and ∼4 mag deeper in surface-brightness sensitivity compared to the classic Fornax Cluster Catalog. Morphological analysis shows that the dwarf galaxy surface-brightness profiles are well represented by singlecomponent Sérsic models with average Sérsic indices of ⟨n⟩ u ′ ,g ′ ,i ′ = (0.78 − 0.83) ± 0.02, and average effective radii of ⟨r e ⟩ u ′ ,g ′ ,i ′ = (0.67 − 0.70) ± 0.02 kpc. Color-magnitude relations indicate a flattening of the galaxy red sequence at faint galaxy luminosities, similar to the one recently discovered in the Virgo cluster. A comparison with population synthesis models and the galaxy mass-metallicity relation reveals that the average faint dwarf galaxy is likely older than ∼5 Gyr. We study galaxy scaling relations between stellar mass, effective radius, and stellar mass surface density over a stellar mass range covering six orders of magnitude. We find that over the sampled stellar mass range several distinct mechanisms of galaxy mass assembly can be identified: i) dwarf galaxies assemble mass inside the half-mass radius up to log M ⋆ ≈ 8.0, ii) isometric mass assembly in the range 8.0 ≲ log M ⋆ M ⊙ ≲ 10.5, and iii) massive galaxies assemble stellar mass predominantly in their halos at log M ⋆ ≈10.5 and above.

Metal-poor nuclear star clusters in two dwarf galaxies near Centaurus A suggesting formation from the in-spiraling of globular clusters

“…Although NSCs are very common in all types of galaxies (e.g. Georgiev et al 2009a;Eigenthaler et al 2018), their formation is still under debate and two main pathways are usually discussed. In the GC accretion or GC in-spiral scenario, the NSC builds out of the (dry) mergers of GCs that migrate into the galaxy's centre due to dynamical friction (e.g.…”

A spectroscopic census of the Fornax cluster and beyond: preparing for next generation surveys

“…The Fornax cluster has recently been at the centre of several major observing programmes over a wide range of wavelengths. This includes deep optical imaging (Iodice et al 2016;Venhola et al 2018;Eigenthaler et al 2018), optical integral field unit (IFU) observations of selected targets (Scott et al 2014;Mentz et al 2016;Sarzi et al 2018), ALMA observations (Zabel et al 2019;Morokuma-Matsui et al 2019), far-infrared Herschel imaging (Davies et al 2013) and, at radio wavelengths, a survey carried out with the Australia Telescope Compact Array (ATCA; Lee-Waddell et al 2018).…”

The Next Generation Fornax Survey (NGFS). VI. The Alignment of Dwarf Galaxies in the Fornax Cluster

“…In our previous NGFS papers (Muñoz et al 2015;Eigenthaler et al 2018;Ordenes-Briceño et al 2018a), we reported the detection of the extended sources in the Fornax cluster from the RGB full-color image; in total, there are 643 dwarf galaxies which are very likely to be the members of the Fornax cluster (according to their locations in the color-magnitude diagrams, morphologies, and sizes; see Eigenthaler et al 2018 for details), including the known 299 ones from previous works (Ferguson 1989;Mieske et al 2007). Among the 643 dwarfs, seven galaxies are ultradiffuse galaxies (UDGs; van Dokkum et al 2015;Rong et al 2017a).…”

“…The deep multiwavelength Next Generation Fornax Survey (NGFS; Muñoz et al 2015), covering the entire Fornax galaxy cluster out to its virial radius (R vir 1.4 Mpc, Drinkwater et al 2001), provides the u , g , and i -band photometries (reaching pointsource detections with S/N∼ 5 at 26.5, 26.1, and 25.3 mag, respectively) obtained with the Dark Energy Camera (DE-Cam;Flaugher et al 2015) mounted on the 4m Blanco telescope at Cerro Tololo Interamerican Observatory (CTIO) and J and K s -band photometry from VIRCam mounted on the 3.7 m VISTA at ESO's Paranal Observatory (Sutherland et al 2015). NGFS encompasses the unprecedented accuracy to study the properties of the extremely-faint and low-mass objects (∼ 10 6 M ) in the nearby cluster, including the stellar masses and ages of the nuclear star clusters (NSCs) in the nucleated dwarf galaxies (Ordenes-Briceño et al 2018b), color distributions of NSCs and dwarf spheroids (Eigenthaler et al 2018), dwarf clustering (Ordenes-Briceño et al 2018a), and in particular, morphologies of dwarfs. Further, since the morphologies of dwarfs are relevant to their properties and environments, e.g., the presence of NSCs, galactic luminosities/stellar masses, and their locations in galaxy clusters/groups (e.g., Sánchez-Janssen et al 2019Roychowdhury et al 2013), it is reasonable to compare the alignment signals of the NGFS dwarfs with the different properties.…”