The stellar population and initial mass function of NGC 1399 with MUSE

Vaughan, Sam P.; Davies, Roger L.; Zieleniewski, Simon; Houghton, R. C. W.

doi:10.1093/mnras/sty1434

Cited by 51 publications

(70 citation statements)

References 108 publications

(145 reference statements)

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“…LoM-50, however, shows steeper positive radial gradients due to a deficit of α-elements in the inner regions. These results are in broad agreement with [Mg/Fe] gradients in observed galaxies which seem to vary on a case-by-case basis from either being flat (Mehlert et al 2003;Parikh et al 2018), to weakly positive (Spolaor et al 2008;Brough et al 2007), or strongly positive (as is the case for NGC 1399; Vaughan et al 2018b). The offsets between our simulations relative to Ref-50 are consistent with those for the (galaxy-wide) [Mg/Fe]−σe relation seen in Paper I, and are due to the decreased (increased) number of type II SNe resulting from a steeper (shallower) IMF slope in LoM-50 (HiM-50).…”

Section: Radial Gradients In Stellar Population Propertiessupporting

confidence: 87%

Calibrated, cosmological hydrodynamical simulations with variable IMFs III: spatially resolved properties and evolution

Barber

Schaye

Crain

2018

Monthly Notices of the Royal Astronomical Society

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Recent spatially-resolved observations of massive early-type galaxies (ETGs) have uncovered evidence for radial gradients of the stellar initial mass function (IMF), ranging from super-Salpeter IMFs in the centre to Milky Way-like beyond the halflight radius, r e . We compare these findings with our new cosmological, hydrodynamical simulations based on the EAGLE model that self-consistently vary the IMF on a perparticle basis such that it becomes either bottom-heavy (LoM-50) or top-heavy (HiM-50) in high-pressure environments. These simulations were calibrated to reproduce inferred IMF variations such that the IMF becomes "heavier" due to either excess dwarf stars or stellar remnants, respectively, in galaxies with increasing stellar velocity dispersion. In agreement with observations, both simulations produce negative radial IMF gradients, transitioning from high to low excess mass-to-light ratio (MLE) at around r e . We find negative metallicity radial gradients for both simulations, but positive and flat [Mg/Fe] gradients in LoM-50 and HiM-50, respectively. Measured in radial bins, the MLE increases strongly with local metallicity for both simulations, in agreement with observations. However, the local MLE increases and decreases with local [Mg/Fe] in LoM-50 and HiM-50, respectively. These qualitative differences can be used to break degeneracies in the manner with which the IMF varies in these highmass ETGs. At z = 2, we find that the MLE has a higher and lower normalization for bottom-and top-heavy IMF variations, respectively. We speculate that a hybrid of our LoM and HiM models may be able to reconcile observed IMF diagnostics in star-forming galaxies and ETGs.

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Section: Radial Gradients In Stellar Population Propertiessupporting

confidence: 87%

Calibrated, cosmological hydrodynamical simulations with variable IMFs III: spatially resolved properties and evolution

Barber

Schaye

Crain

2018

Monthly Notices of the Royal Astronomical Society

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“…IMF variations within a single galaxy make sense under the 'two-phase' formation scenario, where the initial physical conditions at the beginning of each phase were completely different (which has recently been reproduced by simulations; e.g Barber et al 2019). Vaughan et al (2018) suggested that this change in the IMF (in that case for the giant elliptical NGC 1399) also coincided with the light profile transitioning from an 'inner' Sérsic component to a component suggested to be attributed to the 'accreted' stars (Spavone et al 2017).…”

Section: Discussionmentioning

confidence: 99%

Spatially Resolved Stellar Populations and Kinematics with KCWI: Probing the Assembly History of the Massive Early-type Galaxy NGC 1407

Ferré-Mateu

Forbes

McDermid³

et al. 2019

ApJ

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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 ∼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.

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“…A number of earlier investigations have reported the presence of IMF gradients indicating dwarf-richer stellar populations towards the centers of massive ETGs (e.g. Martín-Navarro et al 2015a;La Barbera et al 2017;van Dokkum et al 2017;Vaughan et al 2018b;Sarzi et al 2018;Parikh et al 2018), with the exceptions in some other investigations (Vaughan et al 2018a;Zieleniewski et al 2015Zieleniewski et al , 2017McConnell et al 2016;Alton et al 2017).…”

Section: Radial Dependencementioning

confidence: 98%

SDSS-IV MaNGA: stellar initial mass function variation inferred from Bayesian analysis of the integral field spectroscopy of early-type galaxies

Zhou

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We analyze the stellar initial mass functions (IMF) of a large sample of early type galaxies (ETGs) provided by MaNGA. The large number of IFU spectra of individual galaxies provide high signal-to-noise composite spectra that are essential for constraining IMF and to investigate possible radial gradients of the IMF within individual galaxies. The large sample of ETGs also make it possible to study how the IMF shape depends on various properties of galaxies. We adopt a novel approach to study IMF variations in ETGs, use Bayesian inferences based on full spectrum fitting. The Bayesian method provides a statistically rigorous way to explore potential degeneracy in spectrum fitting, and to distinguish different IMF models with Bayesian evidence. We find that the IMF slope depends systematically on galaxy velocity dispersion, in that galaxies of higher velocity dispersion prefer a more bottom-heavy IMF, but the dependence is almost entirely due to the change of metallicity, Z, with velocity dispersion. The IMF shape also depends on stellar age, A, but the dependence is completely degenerate with that on metallicity through a combination AZ −1.42 . Using independent age and metallicity estimates we find that the IMF variation is produced by metallicity instead of age. The IMF near the centers of massive ETGs appears more bottom-heavy than that in the outer parts, while a weak opposite trend is seen for low-mass ETGs. Uncertainties produced by star formation history, dust extinction, α-element abundance enhancement and noise in the spectra are tested.

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The stellar population and initial mass function of NGC 1399 with MUSE

Cited by 51 publications

References 108 publications

Calibrated, cosmological hydrodynamical simulations with variable IMFs III: spatially resolved properties and evolution

Calibrated, cosmological hydrodynamical simulations with variable IMFs III: spatially resolved properties and evolution

Spatially Resolved Stellar Populations and Kinematics with KCWI: Probing the Assembly History of the Massive Early-type Galaxy NGC 1407

SDSS-IV MaNGA: stellar initial mass function variation inferred from Bayesian analysis of the integral field spectroscopy of early-type galaxies

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