The SLUGGS Survey: Trails of SLUGGS galaxies in a modified spin-ellipticity diagram

Abstract

We present radial tracks for four early-type galaxies with embedded intermediate-scale discs in a modified spin-ellipticity diagram. Here, each galaxy's spin and ellipticity profiles are shown as a radial track, as opposed to a single, flux-weighted aperture-dependent value as is common in the literature. The use of a single ellipticity and spin parameter is inadequate to capture the basic nature of these galaxies, which transition from fast to slow rotation as one moves to larger radii where the disc ceases to dominate. After peaking, the four galaxy's radial tracks feature a downturn in both ellipticity and spin with increasing radius, differentiating them from elliptical galaxies, and from lenticular galaxies whose discs dominate at large radii. These galaxies are examples of so-called discy elliptical galaxies, which are a morphological hybrid between elliptical (E) and lenticular (S0) galaxies, and have been designated ES galaxies. The use of spin-ellipticity tracks provides extra structural information about individual galaxies over a single aperture measure. Such tracks provide a key diagnostic for classifying early-type galaxies, particularly in the era of 2D kinematic (and photometric) data beyond one effective radius.

9 pages, 3 figures, 21 tables, accepted for publication in MNRAS

References in corpus (11)

• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• The SAURON project -- IX. A kinematic classification for early-type galaxies
• The SAMI Galaxy Survey: instrument specification and target selection
• The SAGES Legacy Unifying Globulars and GalaxieS Survey (SLUGGS): Sample definition, methods, and initial results
• The SLUGGS survey: Exploring the metallicity gradients of nearby early-type galaxies to large radii
• Hiding in plain sight: An abundance of compact massive spheroids in the local Universe
• The SLUGGS Survey: stellar masses and effective radii of early-type galaxies from Spitzer Space Telescope 3.6$\mu$m imaging
• The Stellar Haloes of Massive Elliptical Galaxies III: Kinematics at Large Radius
• Implications for the origin of dwarf early-type galaxies: a detailed look at the isolated rotating dwarf early-type galaxy CG 611, with ramifications for the Fundamental Plane's (S_K)^2 kinematic scaling and the spin-ellipticity diagram
• The SLUGGS survey: Using extended stellar kinematics to disentangle the formation histories of low mass S0 galaxies
• Disky elliptical galaxies and the allegedly over-massive black hole in the compact massive `ES' galaxy NGC 1271

Cited by in corpus (8)

• The SAMI Galaxy Survey: a statistical approach to an optimal classification of stellar kinematics in galaxy surveys
• A galaxy classification grid that better recognises early-type galaxy morphology
• Reading the tea leaves in the $M_{\mathrm{bh}}$-$M_{\ast ,\mathrm{sph}}$ and $M_{\mathrm{bh}}$-$R_{\mathrm{e},\mathrm{sph}}$ diagrams: dry and gaseous mergers with remnant angular momentum
• Resequencing the Hubble sequence and the quadratic (black hole mass)-(spheroid stellar mass) relation for elliptical galaxies
• Disc cloaking: Establishing a lower limit to the number density of local compact massive spheroids/bulges and the potential fate of some high-z red nuggets
• The SAMI Galaxy Survey: rules of behaviour for spin-ellipticity radial tracks in galaxies
• Elliptical (E) and ellicular (ES) galaxies in the M_bh-M_*,sph diagram, and a merger-driven explanation for the origin of ES galaxies, anti-truncated stellar discs in lenticular galaxies, and the Sersicification of E galaxy light profiles
• On the scaling relations of bulges and early-type galaxies