Radial measurements of IMF-sensitive absorption features in two massive ETGs

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

doi:10.1093/mnras/stx3199

Cited by 35 publications

(29 citation statements)

References 68 publications

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“…Finally, we find strong negative radial gradients in [Na/Fe] for all galaxy mass bins (see also La Barbera et al 2016;McConnell et al 2016;van Dokkum et al 2017;Vaughan et al 2018;Zieleniewski et al 2017;Alton et al 2018). The slope steepens with increasing galaxy mass, with a gradient of −0.15 ± 0.03 for the lowest mass bin in our sample, and −0.29 ± 0.02 at the higher masses.…”

Section: Element Abundancessupporting

confidence: 58%

SDSS-IV MaNGA: local and global chemical abundance patterns in early-type galaxies

Parikh

Thomas

Maraston

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Chemical enrichment signatures strongly constrain galaxy formation and evolution, and a detailed understanding of abundance patterns provides clues regarding the nucleosynthetic production pathways of elements. Using the SDSS-IV MaNGA IFU survey, we study radial gradients of chemical element abundances in detail. We use stacked spectra out to 1 R e of 366 early-type galaxies with masses 9.9−10.8 log M/M to probe the abundances of the elements C, N, Na, Mg, Ca, and Ti, relative to the abundance of Fe, by fitting stellar population models to a combination of Lick absorption indices. We find that C, Mg, and Ti trace each other both as a function of galaxy radius and galaxy mass. These similar C and Mg abundances within and across galaxies set a lower limit for star-formation timescales. Conversely, N and Ca are generally offset to lower abundances. The under-abundance of Ca compared to Mg implies delayed enrichment of Ca through Type Ia supernovae, whereas the correlated behaviour of Ti and the lighter α elements, C and Mg, suggest contributions to Ti from Type II supernovae. We obtain shallow radial gradients in [Mg/Fe], [C/Fe], and [Ti/Fe], meaning that these inferences are independent of radius. However, we measure strong negative radial gradients for [N/Fe] and [Na/Fe], of up to −0.25 ± 0.05 and −0.29 ± 0.02 dex/R e respectively. These gradients become shallower with decreasing galaxy mass. We find that N and Na abundances increase more steeply with velocity dispersion within galaxies than globally, while the other elements show the same relation locally and globally. This implies that the high Na and N abundances found in massive early type galaxies are generated by internal processes within galaxies. These are strongly correlated with the total metallicity, suggesting metallicity-dependent Na enrichment, and secondary N production in massive early-type galaxies.

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Section: Element Abundancessupporting

confidence: 58%

SDSS-IV MaNGA: local and global chemical abundance patterns in early-type galaxies

Parikh

Thomas

Maraston

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…This is consistent with previous work (e.g. Vaughan et al 2018a). However, we find that this trend depends on the models used: [α/Fe] increases towards the center when using the TMJ models (see Appendix A2).…”

Section: Age Metallicity and [α/Fe] Gradientssupporting

confidence: 94%

Galaxy properties as revealed by MaNGA – I. Constraints on IMF and M*/L gradients in ellipticals

Sánchez

Bernardi

Brownstein

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We estimate ages, metallicities, α-element abundance ratios and stellar initial mass functions of elliptical (E) and S0 galaxies from the MaNGA-DR15 survey. We stack spectra and use a variety of single stellar population synthesis models to interpret the absorption line strengths in these spectra. We quantify how these properties vary across the population, as well as with galactocentric distance. This paper is the first of a series and is based on a sample of pure elliptical galaxies at z ≤ 0.08. We confirm previous work showing that IMFs in Es with the largest luminosity (L r ) and central velocity dispersion (σ 0 ) appear to be increasingly bottom heavy towards their centres. For these galaxies the stellar mass-to-light ratio decreases at most by a factor of 2 from the central regions to R e . In contrast, for lower L r and σ 0 galaxies, the IMF is shallower and M * /L r in the central regions is similar to the outskirts, although quantitative estimates depend on assumptions about element abundance gradients.Accounting self-consistently for these gradients when estimating both M * and M dyn brings the two into good agreement: gradients reduce M dyn by ∼ 0.2 dex while only slightly increasing the M * inferred using a Kroupa IMF. This is a different resolution of the M * -M dyn discrepancy than has been followed in the recent literature where M * of massive galaxies is increased by adopting a Salpeter IMF throughout the galaxy while leaving M dyn unchanged. A companion paper discusses how stellar population differences are even more pronounced if one separates slow from fast rotators. Graves et al. 2009). We now know that the mix of stars in galaxies varies across the galaxy population, over and above the obvious variations with morphology across the Hubble sequence.In this and the following papers of this series, we focus almost exclusively on early-type galaxies (Es and S0s) since late-type galaxies (Spirals) have gas and dust which complicate the spectral analysis. In fact, in this paper, we only study Es (we study S0s in paper III -in prep.). However, even amongst Es, the stellar populations depend on other global properties such as velocity dispersion, luminosity, size, etc. (Trager et al. 1998;Thomas et al. 2005;Bernardi et al. 2005Bernardi et al. , 2006Bernardi et al. , 2011.In addition to varying across the early-type galaxy population, there are stellar population gradients even within does. These two estimates are thought to provide two distinct routes -albeit with rather different systematic biases -to the same underlying physical quantity.

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“…The introduction of a high order polynomial, as in MaNGA DAP, or splitting the wavelength range to be fitted into several segments (e.g. Vaughan et al 2018a) can relieve the problem, but significant residuals still present. We choose to mask out the entire problematic region, between 6800 and 8100 Å, and only to use the rest of the spectrum in our fitting.…”

Section: The Fitting Proceduresmentioning

confidence: 99%

“…These techniques have since been widely adopted to analyze IMF variations (e.g. Villaume et al 2017a;van Dokkum et al 2017;Vaughan et al 2018a). In addition to modeling the exact shapes of absorption features, measurements of line strengths are also used to quantify the absorption features, and to study the variations of IMF (Spiniello et al 2012(Spiniello et al , 2014(Spiniello et al , 2015Ferreras et al 2013;La Barbera et al 2013Martín-Navarro et al 2015a).…”

Section: Introductionmentioning

confidence: 99%

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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Radial measurements of IMF-sensitive absorption features in two massive ETGs

Cited by 35 publications

References 68 publications

SDSS-IV MaNGA: local and global chemical abundance patterns in early-type galaxies

SDSS-IV MaNGA: local and global chemical abundance patterns in early-type galaxies

Galaxy properties as revealed by MaNGA – I. Constraints on IMF and M*/L gradients in ellipticals

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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