Constraints on the star formation histories of galaxies in the Local Cosmological Volume

Kroupa, Pavel; Haslbauer, Moritz; Banik, Indranil; Togere, Nagesh, Srikanth; Pflamm-Altenburg, Jan

doi:10.1093/mnras/staa1851

Cited by 18 publications

(34 citation statements)

References 66 publications

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“…The average specific star-formation rate of galaxies from our sample is equal to −10.1 ± 0.1 (yr −1 ) which practically coincides with the parameter log H0 = −10.14 (yr −1 ). This agreement, also noticed by Kroupa et al (2020), again indicates the smouldering character of star formation in late-type dwarf galaxies at the cosmic time-scale. The distribution of temporarily excited and temporarily quiescent galaxies on their ratio log[SF R(Hα)/SF R(F U V )] and the tidal index is shown in the bottom panel of Fig.…”

Section: Sfr In Different Environment Conditionssupporting

confidence: 80%

Local Volume Late-Type Galaxies with an Extreme Ratio of $Hα$-to-$FUV$ Star-Formation Rates

Karachentsev,

Kaisina,

Kaisin

2021

Preprint

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Using a currently most representative sample of 477 late-type galaxies within 11 Mpc of the Milky Way with measured star-formation rates (SF Rs) from the far ultraviolet (F U V ) and Hα emission line fluxes, we select galaxies with the extreme ratios: SF R(Hα)/SF R(F U V ) > 2 and SF R(Hα)/SF R(F U V ) < 1/20. Each subsample amounts to ∼ 5% of the total number and consists of dwarf galaxies with the stellar masses M * /M ⊙ = (5.5 − 9.5) dex. In spite of a huge difference in their SF R(Hα) activity on a scale of ∼ 10 Myr, the temporarily "excited" and temporarily "quiescent" galaxies follow one and the same relation between SF R(F U V ) and M * on a scale of ∼ 100 Myr. Their average specific star-formation rate log[SF R(F U V )/M * ] = −10.1 ± 0.1 (yr −1 ) coinsides with the Hubble parameter log(H 0 ) = −10.14 (yr −1 ). On a scale of t ∼ 10 Myr, variations of SF R have a moderate flash amplitude of less than 1 order above the main-sequence and a fading amplitude to 2 orders below the average level. In general, both temporarily excited and temporarily quiescent galaxies have almost similar gas fractions as normal main-sequence galaxies, being able to maintain the current rate of star-formation on another Hubble time scale. Ranging the galaxies according to the density contrast produced by the nearest massive neighbor exhibits only a low average excess of SF R caused by tidal interactions.

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Section: Sfr In Different Environment Conditionssupporting

confidence: 80%

Local Volume Late-Type Galaxies with an Extreme Ratio of $Hα$-to-$FUV$ Star-Formation Rates

Karachentsev,

Kaisina,

Kaisin

2021

Preprint

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“…At low 𝑀 𝑆 , our results show a deviation from the extrapolated observed curve derived by Speagle et al (2014). This can be interpreted as evidence for deviation of low-mass galaxies from the observed main sequence defined by more massive galaxies (Kroupa et al 2020). Alternatively, if the SFE of galaxies is a function of stellar mass such that a lower mass galaxy would have a lower value of the SFE, then the low mass galaxies would reach a lower SFR compared to that calculated here for a constant SFE in all galaxies.…”

Section: Comparison Of the Sfr In Newtonian And Mond Gravitycontrasting

confidence: 40%

The Kennicutt-Schmidt law and the main sequence of galaxies in Newtonian and Milgromian dynamics

Zonoozi,

Lieberz,

Banik

et al. 2021

Preprint

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The Kennicutt-Schmidt law is an empirical relation between the star formation rate surface density (Σ SFR ) and the gas surface density (Σ gas ) in disc galaxies. The relation has a power-law form Σ SFR ∝ Σ 𝑛 gas . Assuming that star formation results from gravitational collapse of the interstellar medium, Σ SFR can be determined by dividing Σ gas by the local free-fall time 𝑡 ff . The formulation of 𝑡 ff yields the relation between Σ SFR and Σ gas , assuming that a constant fraction (𝜀 SFE ) of gas is converted into stars every 𝑡 ff . This is done here for the first time using Milgromian dynamics (MOND). Using linear stability analysis of a uniformly rotating thin disc, it is possible to determine the size of a collapsing perturbation within it. This lets us evaluate the sizes and masses of clouds (and their 𝑡 ff ) as a function of Σ gas and the rotation curve. We analytically derive the relation Σ SFR ∝ Σ 𝑛 gas both in Newtonian and Milgromian dynamics, finding that 𝑛 = 1.4. The difference between the two cases is a change only to the constant pre-factor, resulting in increased Σ SFR of up to 25% using MOND in the central regions of dwarf galaxies. Due to the enhanced role of disk self-gravity, star formation extends out to larger galactocentric radii than in Newtonian gravity, with the clouds being larger. In MOND, a nearly exact representation of the present-day main sequence of galaxies is obtained if 𝜖 SFE = constant ≈ 1.1%. We also show that empirically found correction terms to the Kennicutt-Schmidt law are included in the here presented relations. Furthermore, we determine that if star formation is possible, then the temperature only affects Σ SFR by at most a factor of √ 2.

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“…The vast number of galaxies are rotationally-supported disk galaxies with quite constant star-formation histories (Schombert et al 2019;Kroupa et al 2020a;Hoffmann et al 2020), and they comprise the standard outcome of galaxy formation. Elliptical (E) galaxies are rare pressure-supported stellar systems, comprising only a few per cent of the galaxy population (Delgado-Serrano et al 2010), but they include the most massive galaxies with a dynamical mass (stars and stellar remnants) larger than M dyn ≈ 10 10 M .…”

Section: Introductionmentioning

confidence: 99%

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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Constraints on the star formation histories of galaxies in the Local Cosmological Volume

Cited by 18 publications

References 66 publications

Local Volume Late-Type Galaxies with an Extreme Ratio of $Hα$-to-$FUV$ Star-Formation Rates

Local Volume Late-Type Galaxies with an Extreme Ratio of $Hα$-to-$FUV$ Star-Formation Rates

The Kennicutt-Schmidt law and the main sequence of galaxies in Newtonian and Milgromian dynamics

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

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