The Fornax Deep Survey with the VST

Abstract

Context. We present the study of a magnitude limited sample (mB ≤ 16.6 mag) of 13 late type galaxies (LTGs), observed inside the virial radius, Rvir ∼ 0.7 Mpc, of the Fornax cluster within the Fornax Deep Survey (FDS). Aims. The main objective is to use surface brightness profiles and g − i colour maps to obtain information on the internal structure of these galaxies and find signatures of the mechanisms that drive their evolution in high-density environments inside the virial radius of the cluster. Methods. By modelling galaxy isophotes, we extract the azimuthally averaged surface brightness profiles in four optical bands. We also derive g − i colour profiles, and relevant structural parameters like total magnitude and effective radius. For ten of the galaxies in this sample, we observe a clear discontinuity in their typical exponential surface brightness profiles, derive their “break radius”, and classify their disc-breaks into Type II (down-bending) or Type III (up-bending). Results. We find that Type II galaxies have bluer average (g − i) colour in their outer discs while Type III galaxies are redder. The break radius increases with stellar mass and molecular gas mass while it decreases with molecular gas-fractions. The inner and outer scale-lengths increase monotonically with absolute magnitude, as found in other works. For galaxies with CO(1-0) measurements, there is no detected cold gas beyond the break radius (within the uncertainties). In the context of morphological segregation of LTGs in clusters, we also find that, in Fornax, galaxies with morphological type 5 < T ≤ 9 (∼60% of the sample) are located beyond the high-density, ETG-dominated regions, however there is no correlation between T and the disc-break type. We do not find any correlation between the average (g − i) colours and cluster-centric distance, but the colour-magnitude relation holds true. Conclusions. The main results of this work suggest that the disc-breaks of LTGs inside the virial radius of the Fornax cluster seem to have arisen through a variety of mechanisms (e.g. ram-pressure stripping, tidal disruption), which is evident in their outer-disc colours and the absence of molecular gas beyond their break radius in some cases. This can result in a variety of stellar populations inside and outside the break radii.

Power-law Sérsic profiles in hydrostatic stellar galaxy discs

“…Whether this profile form is the result of physical processes or a fortuitous approximation has not always been clear, since early observations did not extend to very faint surface brightness levels. However, in recent years the observations have gone much deeper, confirming the exponential fit over 10 scale lengths in an increasing number of cases (e.g., Bland-Hawthorn, et al 2005Gadotti 2009, Erwin, et al 2005, Pohlen & Trujillo 2006, Herrmann, et al 2013, and Zheng, et al 2015, Hillis, et al 2016, Trujillo & Fliri 2016, Watkins, et al 2016Raj, et al 2019, Staudaher, et al 2019. The accuracy of the fit over such a large dynamic range suggests there is a physical cause.…”

AlFoCS + Fornax3D: resolved star formation in the Fornax cluster with ALMA and MUSE

“…These were calculated through the conversion SFR (Calzetti et al 2012). Stellar mass surface densities, defined here as half the stellar mass divided by the effective radius R e (from Venhola et al 2018, or Raj et al 2019, see Table caption) are listed in column 11.…”

“…9: Total star formation rate in the MUSE FoV from Iodice et al (2019, except FCC207, which is from this work); 10: Stellar mass surface density: half the stellar mass divided by the area within the effective radius R e . Effective radii from (Iodice et al 2019, no uncertainties given), effective radii from Venhola et al (2018), remaining effective radii are from Raj et al (2019).…”

“…A galaxy's SMSD is a crude measure of its radial mass profile, and can therefore be interpreted as a proxy for its morphology. Effective radii are taken from Venhola et al (2018) for dwarf galaxies, and from Raj et al (2019) and Iodice et al (2019) for more massive galaxies. Markers and lines are the same as in Figure 4.…”

The Fornax Deep Survey with VST

“…In the last decade, also thanks to the advent of efficient large-format imaging cameras, a number of observational programs have carried out intensive surveys dedicated to covering large sections of nearby galaxy systems, superseding, in terms of both limiting magnitude and spatial resolution, any previous optical or near-IR study (e.g., Ferrarese et al 2012;Iodice et al 2016), thus providing a rich variety of data ideal for investigating compact stellar systems and faint stellar structures in different galaxy environments (de Jong et al 2013;Muñoz et al 2014;Durrell et al 2014;Iodice et al 2019;Venhola et al 2019;Wittmann et al 2019) Within this framework, the Fornax Deep Survey (FDS) has carried out observations of the Fornax galaxy cluster centered on NGC 1399 out to one virial radius and further extended observations in the direction of the Fornax A sub-cluster in the South-West with its brightest member, NGC 1316, with a list of scientific topics: diffuse light and intracluster medium (Iodice et al 2016), galaxy scaling relations (Iodice et al 2019;Venhola et al 2017Venhola et al , 2019Raj et al 2019), extragalactic star clusters and, more generally, compact stellar systems (D'Abrusco et al 2016;Cantiello et al 2018a), etc. In addition, the survey also contributes to research programs dealing with the study of the background galaxy population (e.g., identification of lensed systems and of their physical properties) and spectroscopic programs -for globular clusters (Pota et al 2018), planetary nebulae (Spiniello et al 2018), IFU study of galaxies in the cluster (Mentz et al 2016).…”