Spatially-resolved stellar populations and kinematics with KCWI: probing the assembly history of the massive early-type galaxy NGC 1407

Abstract

Using the newly commissioned KCWI instrument on the Keck-II telescope, we analyse the stellar kinematics and stellar populations of the well-studied massive early-type galaxy (ETG) NGC 1407. We obtained high signal-to-noise integral-field-spectra for a central and an outer (around one effective radius towards the south-east direction) pointing with integration times of just 600s and 2400s, respectively. We confirm the presence of a kinematically distinct core also revealed by VLT/MUSE data of the central regions. While NGC 1407 was previously found to have stellar populations characteristic of massive ETGs (with radially constant old ages and high alpha-enhancements), it was claimed to show peculiar super-solar metallicity peaks at large radius that deviated from an otherwise strong negative metallicity gradient, which is hard to reconcile within a `two-phase' formation scenario. Our outer pointing confirms the near-uniform old ages and the presence of a steep metallicity gradient, but with no evidence for anomalously high metallicity values at large galactocentric radii. We find a rising outer velocity dispersion profile and high values of the 4th-order kinematic moment -- an indicator of possible anisotropy. This coincides with the reported transition from a bottom-heavy to a Salpeter initial mass function, which may indicate that we are probing the transition region from the `in-situ' to the accreted phase. With short exposures, we have been able to derive robust stellar kinematics and stellar populations in NGC 1407 to about 1 effective radius. This experiment shows that future work with KCWI will enable 2D kinematics and stellar populations to be probed within the low surface brightness regions of galaxy halos in an effective way.

Accepted for publication ApJ, 11 pages, 6 figures

References in corpus (24)

• 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 MUSE second-generation VLT instrument
• UV-extended E-MILES stellar population models: young components in massive early-type galaxies
• The Atlas3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies
• Size evolution of the most massive galaxies at 1.7<z<3 from GOODS NICMOS survey imaging
• Triaxial orbit based galaxy models with an application to the (apparent) decoupled core galaxy NGC 4365
• The MASSIVE Survey - I. A Volume-Limited Integral-Field Spectroscopic Study of the Most Massive Early-Type Galaxies within 108 Mpc
• The SAURON project - VIII. OASIS/CFHT integral-field spectroscopy of elliptical and lenticular galaxy centres
• Radial variations in the stellar initial mass function of early-type galaxies
• Dynamical modelling of luminous and dark matter in 17 Coma early-type galaxies
• The SAGES Legacy Unifying Globulars and GalaxieS Survey (SLUGGS): Sample definition, methods, and initial results
• 2-Dimensional Kinematics of Simulated Disc Merger Remnants
• The Carnegie-Irvine Galaxy Survey. III. The Three-Component Structure of Nearby Elliptical Galaxies
• Two new confirmed massive relic galaxies: red nuggets in the present-day Universe
• The SLUGGS survey: Exploring the metallicity gradients of nearby early-type galaxies to large radii
• The MASSIVE Survey - VIII. Stellar Velocity Dispersion Profiles and Environmental Dependence of Early-Type Galaxies
• The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. IV. A Super-Salpeter IMF in the center of NGC 1407 from Non-Parametric Models
• The SLUGGS Survey: stellar masses and effective radii of early-type galaxies from Spitzer Space Telescope 3.6$\mu$m imaging
• The early-type galaxies NGC 1407 and NGC 1400 - II: star formation and chemical evolutionary history
• The early-type galaxies NGC 1407 and NGC 1400 - I: spatially resolved radial kinematics and surface photometry
• The MASSIVE Survey - XII Connecting Stellar Populations of Early-Type Galaxies to Kinematics and Environment
• The SLUGGS Survey: Multi-population dynamical modelling of the elliptical galaxy NGC 1407 from stars and globular clusters
• A tale of a rich cluster at z$\sim$0.8 as seen by the Star Formation Histories of its ETGs

Cited by in corpus (9)

• The massive relic galaxy NGC 1277 is dark matter deficient. From dynamical models of integral-field stellar kinematics out to five effective radii
• INSPIRE: INvestigating Stellar Population In RElics -- I. Survey presentation and pilot program
• INSPIRE: INvestigating Stellar Population In RElics II. First Data Release (DR1)
• Low-mass compact elliptical galaxies: spatially-resolved stellar populations and kinematics with the Keck Cosmic Web Imager
• INSPIRE: INvestigating Stellar Population In RElics III. Second data release (DR2): testing the systematics on the stellar velocity dispersion
• The assembly history of the nearest S0 galaxy NGC 3115 from its kinematics out to six half-light radii
• Keck Cosmic Web Imager (KCWI) Spectra of Globular Clusters and Ultra Compact Dwarfs in the Halo of M87
• Galaxy archaeology for wet mergers: Globular cluster age distributions in the Milky Way and nearby galaxies
• Stellar populations of a sample of far-IR AGN and non-AGN green valley galaxies