[Paper Review] The Fornax Deep Survey (FDS) with the VST: IV. A size and magnitude limited catalog of dwarf galaxies in the area of the Fornax cluster

A. Venhola, R. F. Peletier+21 more|arXiv (Cornell University)|Oct 1, 2018

Video Surveillance and Tracking Methods1 references42 citations

TL;DR

The paper presents a size- and magnitude-limited catalog of Fornax cluster dwarfs from the FDS with the VST, detailing data reduction, membership selection, and first morphology classifications, yielding 14,095 galaxies with 590 likely cluster members.

ABSTRACT

The Fornax Deep Survey (FDS), an imaging survey in the u', g', r', and i'-bands, has a supreme resolution and image depth compared to the previous spatially complete Fornax Cluster Catalog (FCC). Our new data allows us to study the galaxies down to r'-band magnitude m$_{r'}\approx$21 mag (M$_{r'}\approx$-10.5 mag). These data provide an important legacy dataset to study the Fornax cluster. We aim to present the Fornax Deep Survey (FDS) dwarf galaxy catalog, focusing on explaining the data reduction and calibrations, assessing the quality of the data, and describing the methods used for defining the cluster memberships for the catalog objects. As a first step we used the SExtractor fine-tuned for dwarf galaxy detection, to find galaxies from the FDS data, covering a 26 deg$^2$ area of the main cluster, and the area around the Fornax A substructure. We made 2D-decompositions of the identified galaxies using GALFIT. We used color-magnitude, luminosity-radius and luminosity-concentration relations to separate the cluster galaxies from the background galaxies. We then divided the cluster galaxies into early- and late-type galaxies according to their morphology and gave first order morphological classifications. Our final catalog includes 14,095 galaxies. We classify 590 galaxies as being likely Fornax cluster galaxies, of which 564 are dwarfs (M$_{r'}$ > -18.5 mag) consisting our Fornax dwarf catalog. Of the cluster dwarfs we classify 470 as early-types, and 94 as late-type galaxies. Our final catalog reaches its 50% completeness limit at magnitude M$_{r'}$ = -10.5 mag and surface brightness $\barμ_{e,r'}$ = 26 mag arcsec-2, which is approximately three magnitudes deeper than the FCC. Based on previous works and comparison with a spectroscopically confirmed subsample, we estimate that our final Fornax dwarf galaxy catalog has < 10% contamination from the background objects.

Motivation & Objective

• Present the Fornax Deep Survey (FDS) dwarf galaxy catalog covering the Fornax cluster area.
• Explain data reduction, calibration, and quality assessments of the FDS data.
• Describe methods to define cluster membership and first-order morphological classifications.
• Outline the main scientific questions the catalog enables for future studies.
• Provide a resource for follow-up studies of Fornax cluster dwarf galaxies.

Proposed method

• Detect galaxies using a SExtractor configuration tuned for dwarfs.
• Perform 2D decompositions with GALFIT to obtain structural parameters.
• Measure aperture colors and basic morphologies (concentration and residual flux fraction).
• Use color-magnitude, luminosity-radius, and luminosity-concentration relations to separate cluster members from background galaxies.
• Divide cluster dwarfs into early- and late-type categories using visual and parametric classifications.

Experimental results

Research questions

• RQ1 How can Fornax cluster membership be robustly inferred for faint, low-surface-brightness galaxies using photometric properties?
• RQ2 What are the completeness and contamination levels of the FDS dwarf galaxy catalog?
• RQ3 What are the morphological distributions (early vs. late) among Fornax cluster dwarfs and their photometric properties?
• RQ4 What is the depth and limiting surface brightness achieved for the Fornax dwarfs compared to previous surveys?

Key findings

• Final catalog contains 14,095 galaxies.
• 590 galaxies are classified as likely Fornax cluster members, of which 564 are dwarfs (M_r' < -10.5 mag).
• Among the cluster dwarfs, 470 are early-types and 94 are late-types.
• The catalog reaches 50% completeness at M_r' = -10.5 mag and 50% completeness surface brightness μ̄_e,r' = 26 mag arcsec^-2.
• Estimated contamination from background objects is ≲10% based on comparison with previous work and spectroscopic subsamples.
• Significantly deeper (≈3 mag) than the FCC.