Fornax 3D project: assessing the diversity of IMF and stellar population maps within the Fornax Cluster

Abstract

The stellar initial mass function (IMF) is central to our interpretation of astronomical observables and to our understanding of most baryonic processes within galaxies. The universality of the IMF, suggested by observations in our own Milky Way, has been thoroughly revisited due to the apparent excess of low-mass stars in the central regions of massive quiescent galaxies. As part of the efforts within the Fornax 3D project, we aim to characterize the two-dimensional IMF variations in a sample of 23 quiescent galaxies within the Fornax cluster. For each galaxy in the sample, we measured the mean age, metallicity, [Mg/Fe], and IMF slope maps from spatially resolved integrated spectra. The IMF maps show a variety of behaviors and internal substructures, roughly following metallicity variations. However, metallicity alone is not able to fully explain the complexity exhibited by the IMF maps. In particular, for relatively metal-poor stellar populations, the slope of the IMF seems to depend on the (specific) star formation rate at which stars were formed. Moreover, metallicity maps have systematically higher ellipticities than IMF slope ones. At the same time, both metallicity and IMF slope maps have at the same time higher ellipticities than the stellar light distribution in our sample of galaxies. In addition we find that, regardless of the stellar mass, every galaxy in our sample shows a positive radial [Mg/Fe] gradient. This results in a strong [Fe/H]-[Mg/Fe] relation, similar to what is observed in nearby, resolved galaxies. Since the formation history and chemical enrichment of galaxies are causally driven by changes in the IMF, our findings call for a physically motivated interpretation of stellar population measurements based on integrated spectra that take into account any possible time evolution of the stellar populations.

14 pages and 10 figures (plus Appendix including all the stellar population maps). Accepted for publication in Astronomy and Astrophysics

References in corpus (55)

• Array Programming with NumPy
• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• The SAURON project -- IX. A kinematic classification for early-type galaxies
• The GALAH+ Survey: Third Data Release
• A systematic variation of the stellar initial mass function in early-type galaxies
• The Atlas3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies
• Evolutionary stellar population synthesis with MILES - II. Scaled-solar and α-enhanced models
• Population Synthesis in the Blue IV: Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations
• A new library of theoretical stellar spectra with scaled-solar and alpha-enhanced mixtures
• The SAURON project - VI. Line strength maps of 48 elliptical and lenticular galaxies
• Radial variations in the stellar initial mass function of early-type galaxies
• Firefly (Fitting IteRativEly For Likelihood analYsis): a full spectral fitting code
• Spatially resolved spectroscopy of early-type galaxies over a range in mass
• The evolution of CNO isotopes: a new window on cosmic star-formation history and the stellar IMF in the age of ALMA
• On the interpretation of age and chemical composition of composite stellar populations determined with line-strength indices
• The SL2S Galaxy-scale Lens Sample. V. Dark Matter Halos and Stellar IMF of Massive Early-type Galaxies out to Redshift 0.8
• Transition of the initial mass function in the metal-poor environments
• The Extended IRTF Spectral Library: Expanded coverage in metallicity, temperature, and surface gravity
• The Fornax 3D project: unveiling the thick disk origin in FCC 170: signs of accretion?
• The stellar initial mass function of early type galaxies from low to high stellar velocity dispersion: homogeneous analysis of ATLAS${}^{3D}$ and Sloan Lens ACS galaxies
• Timing the formation and assembly of early-type galaxies via spatially resolved stellar populations analysis
• IMF shape constraints from stellar populations and dynamics from CALIFA
• IMF and [Na/Fe] abundance ratios from optical and NIR Spectral Features in Early-type Galaxies
• Testing the Accuracy of Synthetic Stellar Libraries
• The Fornax3D project: Tracing the assembly history of the cluster from the kinematic and line-strength maps
• The Fornax 3D project: a two-dimensional view of the stellar initial mass function in the massive lenticular galaxy FCC 167
• Systematic variations of central mass density slopes in early-type galaxies
• SDSS-IV MaNGA: Radial Gradients in Stellar Population Properties of Early-Type and Late-Type Galaxies
• The CALIFA view on stellar angular momentum across the Hubble sequence
• Spatially resolved variations of the IMF mass normalisation in early-type galaxies as probed by molecular gas kinematics
• Further evidence for a time-dependent initial mass function in massive early-type galaxies
• The Fornax 3D project: Thick disks in a cluster environment
• Galaxy structure from multiple tracers: III. Radial variations in M87's IMF
• Connection between dynamically derived IMF normalisation and stellar population parameters
• Characterization of ICM Temperature Distributions of 62 Galaxy Clusters with XMM-Newton
• Metallicity and the Universality of the IMF
• Disentangling the formation history of galaxies via population-orbit superposition: method validation
• Stellar populations across galaxy bars in the MUSE TIMER project
• The Fornax3D project: Assembly histories of lenticular galaxies from a combined dynamical and population orbital analysis
• The kinematics of massive quiescent galaxies at $1.4<z<2.1$: dark matter fractions, IMF variation, and the relation to local early-type galaxies
• SDSS-IV MaNGA: global and local stellar population properties of elliptical galaxies
• Radial gradients in initial mass function sensitive absorption features in the Coma brightest cluster galaxies
• Extreme CO Isotopologue Line Ratios in ULIRGS: Evidence for a top-heavy IMF
• AlFoCS + Fornax3D: resolved star formation in the Fornax cluster with ALMA and MUSE
• The last 6 Gyr of dark matter assembly in massive galaxies from the Kilo Degree Survey
• Is it possible to reconcile extragalactic IMF variations with a universal Milky Way IMF?
• A preserved high-z compact progenitor in the heart of NGC3311 revealed with MUSE 2D stellar population analysis
• Initial Mass Function Variability (or not) Among \\ Low-Velocity Dispersion, Compact Stellar Systems
• What does (not) drive the variation of the low-mass end of the stellar initial mass function of early-type galaxies
• Fornax 3D project: automated detection of planetary nebulae in the centres of early-type galaxies and first results
• The density of dark matter haloes of early-type galaxies in low-density environments
• The Fornax 3D project: dust mix and gas properties in the center of early-type galaxy FCC 167
• Evidence of a Bottom-heavy Initial Mass Function in Massive Early-type Galaxies from Near-infrared Metal Lines