The Influence of Environment on the Chemical Evolution in Low-Mass Galaxies

Yi-qing, Liu; Ho, Luis C.; Peng, Eric W.

doi:10.3847/2041-8205/829/2/l26

Cited by 12 publications

(27 citation statements)

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“…There are many αelement sensitive and iron-sensitive indices within the MaNGA wavelength coverage. Within these indices, Hβ, Mgb, Fe5270, and Fe5335 (see below for definitions) have been proven to be the strongest and best set of spectral indices for studying α abundances (e.g., Thomas et al 2011;Liu et al 2016a). Hβ is sensitive to stellar age and has a negative correlation with age; Mgb is most sensitive to magnesium, which is an important αelement; Fe5270 and Fe5335 are most sensitive to iron abundance (Thomas et al 2003(Thomas et al , 2011.…”

Section: Spectral Index Measurementsmentioning

confidence: 99%

“…As shown in the Introduction, stellar velocity dispersion is well correlated with the α-to-iron ratio. Stellar velocity dispersion values from the literature (e.g., Liu et al 2016a) are mostly measured using single fibers with fixed angular sizes or long slits with arbitrary apertures and thus may introduce biases for very small or large galaxies. Here we use an effective stellar velocity dispersion σ * (Cappellari et al 2013;Li et al 2018) estimated in a R 0.3 e aperture calculated for each galaxy.…”

Section: Effective Stellar Velocity Dispersionmentioning

confidence: 99%

“…It has been claimed that Mgb/á ñ Fe (or [α/Fe]) is best correlated with stellar velocity dispersion (e.g., Kuntschner et al 2010;Thomas et al 2010;Liu et al 2016a). We hence plot Mgb/á ñ Fe versus the effective stellar velocity dispersion σ * for the central regions (within 0.3R e ) of all our sample galaxies in Figure 5.…”

Section: Mgb/〈fe〉-σ * Relationmentioning

confidence: 99%

“…There have been many studies on the [α/Fe] ratios of nearby galaxies and a major finding is that the [α/Fe] ratios of earlytype galaxies are best correlated with stellar velocity dispersion σ 14 (e.g., Worthey et al 1992;Trager et al 2000;Thomas et al 2005Thomas et al , 2010Sánchez-Blázquez et al 2006a;Sansom & Northeast 2008;Kuntschner et al 2010;Johansson et al 2012;Liu et al 2016a). Studies that do not have morphological cuts (e.g., Proctor & Sansom 2002;Smith et al 2007;Scott et al 2017) find similar trends for late-type galaxies, albeit using smaller sample sizes.…”

Section: Introductionmentioning

confidence: 97%

“…Recently, Liu et al (2016a) compiled measurements from the literature of [α/Fe] and the Lick index ratios Mgb/á ñ Fe of thousands of early-type galaxies in different environments and found that the low-σ end of the [α/Fe]-σ relation has larger intrinsic scatters and is dependent on environment: low-σ earlytype galaxies in high-density clusters are enhanced in Mgb/ á ñ Fe and [α/Fe]. However, these measurements are from different telescopes and instruments and have different systematic offsets and different apertures.…”

Section: Introductionmentioning

confidence: 99%

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SDSS-IV MaNGA: Environmental Dependence of the Mgb/ – Relation for Nearby Galaxies

Zhang

Mao

et al. 2019

ApJ

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We use a sample of ∼3000 galaxies from the MaNGA MPL-7 internal data release to study the α abundance distribution within low-redshift galaxies. We use the Lick index ratio Mgb/á ñ Fe as an α abundance indicator to study relationships between the α abundance distribution and galaxy properties such as effective stellar velocity dispersion within 0.3 effective radii (σ *), galaxy environment, and dark matter halo formation time (z f). We find that (1) all galaxies show a tight correlation between Mgb/á ñ Fe and * s ; (2) "old" (Hβ < 3) low-σ * galaxies in high local density environment and inner regions within galaxy groups are enhanced in Mgb/á ñ Fe , while "young" (Hβ > 3) galaxies and high-mass galaxies show no or less environmental dependence; (3) "old" galaxies with high-z f show enhanced Mgb/á ñ Fe over low-and medium-z f ; and (4) Mgb/á ñ Fe gradients are close to zero and show dependence on σ * but no obvious dependence on the environment or z f. Our study indicates that stellar velocity dispersion or galaxy mass is the main parameter driving the Mgb/á ñ Fe enhancement, although environments appear to have modest effects, particularly for low-and medium-mass galaxies.

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Section: Spectral Index Measurementsmentioning

confidence: 99%

Section: Effective Stellar Velocity Dispersionmentioning

confidence: 99%

Section: Mgb/〈fe〉-σ * Relationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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SDSS-IV MaNGA: Environmental Dependence of the Mgb/ – Relation for Nearby Galaxies

Zhang

Mao

et al. 2019

ApJ

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The star formation timescale of elliptical galaxies

Yan

Jeřabková

Kroupa

2019

A&A

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The alpha element to iron peak element ratio, for example [Mg/Fe], is a commonly applied indicator of the galaxy star formation timescale (SFT) since the two groups of elements are mainly produced by different types of supernovae that explode over different timescales. However, it is insufficient to consider only [Mg/Fe] when estimating the SFT. The [Mg/Fe] yield of a stellar population depends on its metallicity. Therefore, it is possible for galaxies with different SFTs and at the same time different total metallicity to have the same [Mg/Fe]. This effect has not been properly taken into consideration in previous studies. In this study, we assume the galaxy-wide stellar initial mass function (gwIMF) to be canonical and invariant. We demonstrate that our computation code reproduces the SFT estimations of previous studies, where only the [Mg/Fe] observational constraint is applied. We then demonstrate that once both metallicity and [Mg/Fe] observations are considered, a more severe “downsizing relation” is required. This means that either low-mass ellipticals have longer SFTs (> 4 Gyr for galaxies with mass below 1010 M⊙) or massive ellipticals have shorter SFTs (≈200 Myr for galaxies more massive than 1011 M⊙) than previously thought. This modification increases the difficulty in reconciling such SFTs with other observational constraints. We show that applying different stellar yield modifications does not relieve this formation timescale problem. The quite unrealistically short SFT required by [Mg/Fe] and total metallicity would be prolonged if a variable stellar gwIMF were assumed. Since a systematically varying gwIMF has been suggested by various observations this could present a natural solution to this problem.

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Downsizing revised: Star formation timescales for elliptical galaxies with an environment-dependent IMF and a number of SNIa

Yan

Jeřabková

Kroupa

2021

A&A

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Previous studies of the stellar mean metallicity and [Mg/Fe] values of massive elliptical (E) galaxies suggest that their stars were formed over a very short timescale that cannot be reconciled with estimates from stellar population synthesis (SPS) studies and with hierarchical assembly. Applying the previously developed chemical evolution code, GalIMF, which allows an environment-dependent stellar initial mass function (IMF) to be applied to the integrated galaxy initial mass function theory instead of an invariant canonical IMF, the star formation timescales (SFT) of E galaxies are re-evaluated. The code’s uniqueness lies in it allowing the galaxy-wide IMF and associated chemical enrichment to evolve as the physical conditions in the galaxy change. The calculated SFTs become consistent with the independent SPS results if the number of type Ia supernovae (SNIa) per unit stellar mass increases for more massive E galaxies. This is a natural outcome of galaxies with higher star formation rates producing more massive star clusters, spawning a larger number of SNIa progenitors per star. The calculations show E galaxies with a stellar mass ≈109.5 M⊙ to have had the longest mean SFTs of ≈2 Gyr. The bulk of more massive E galaxies were formed faster (SFT ≈ 1 Gyr) leading to domination by M dwarf stars and larger dynamical mass-to-light ratios as observed, while lower mass galaxies tend to lose their gas supply more easily due to their shallower potential and therefore also have similarly-short mean SFTs. This work achieves, for the first time, consistency of the SFTs for early-type galaxies between chemical-enrichment and SPS modelling. Equally, it leads to an improved understanding of how the star formation environment may affect the total number of SNIa per unit stellar mass formed.

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The Influence of Environment on the Chemical Evolution in Low-Mass Galaxies

Cited by 12 publications

References 50 publications

SDSS-IV MaNGA: Environmental Dependence of the Mgb/ – Relation for Nearby Galaxies

SDSS-IV MaNGA: Environmental Dependence of the Mgb/ – Relation for Nearby Galaxies

The star formation timescale of elliptical galaxies

Downsizing revised: Star formation timescales for elliptical galaxies with an environment-dependent IMF and a number of SNIa

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