Young stellar population gradients in central cluster galaxies from NUV and optical spectroscopy

Salvador-Rusiñol, Núria; Beasley, Michael A.; Vazdekis, Alexandre

doi:10.1093/mnras/staa3419

Cited by 15 publications

(1 citation statement)

References 113 publications

(129 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The gwIMF of low-mass stars is also variable. It becomes bottom-light (containing fewer low-mass stars) in metal-poor environments (Gennaro et al 2018;Yan et al 2020) and bottom-heavy for the super-solar-metallicity E galaxies (e.g., Salvador-Rusiñol et al 2021). This means the gwIMF would change over time depending on the SFH and metal enrichment history, which helps to build up the highmetallicity and [Mg/Fe] ratio for the massive E galaxies.…”

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

View full text Add to dashboard Cite

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.

show abstract

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

View full text Add to dashboard Cite

show abstract

INSPIRE: INvestigating Stellar Population In RElics

Spiniello

Tortora

D’Ago

et al. 2021

A&A

View full text Add to dashboard Cite

Context. The INvestigating Stellar Population In RElics (INSPIRE) is an ongoing project targeting 52 ultra-compact massive galaxies at 0.1 < z < 0.5 with the X-shooter at VLT spectrograph (XSH). These objects are the ideal candidates to be ‘relics’, massive red nuggets that have formed at high redshift (z > 2) through a short and intense star formation burst, and then have evolved passively and undisturbed until the present day. Relics provide a unique opportunity to study the mechanisms of star formation at high-z. Aims.INSPIRE is designed to spectroscopically confirm and fully characterise a large sample of relics, computing their number density in the redshift window 0.1 < z < 0.5 for the first time, thus providing a benchmark for cosmological galaxy formation simulations. In this paper, we present the INSPIRE Data Release (DR1), comprising 19 systems with observations completed in 2020. Methods. We use the methods already presented in the INSPIRE Pilot, but revisiting the 1D spectral extraction. For the 19 systems studied here, we obtain an estimate of the stellar velocity dispersion, fitting the two XSH arms (UVB and VIS) separately at their original spectral resolution to two spectra extracted in different ways. We estimate [Mg/Fe] abundances via line-index strength and mass-weighted integrated stellar ages and metallicities with full spectral fitting on the combined (UVB+VIS) spectrum. Results. For each system, different estimates of the velocity dispersion always agree within the errors. Spectroscopic ages are very old for 13/19 galaxies, in agreement with the photometric ones, and metallicities are almost always (18/19) super-solar, confirming the mass–metallicity relation. The [Mg/Fe] ratio is also larger than solar for the great majority of the galaxies, as expected. We find that ten objects formed more than 75% of their stellar mass (M⋆) within 3 Gyr from the big bang and classify them as relics. Among these, we identify four galaxies that had already fully assembled their M⋆ by that time and are therefore ‘extreme relics’ of the ancient Universe. Interestingly, relics, overall, have a larger [Mg/Fe] and a more metal-rich stellar population. They also have larger integrated velocity dispersion values compared to non-relics (both ultra-compact and normal-size) of similar stellar mass. Conclusions. The INSPIRE DR1 catalogue of ten known relics is the largest publicly available collection, augmenting the total number of confirmed relics by a factor of 3.3, and also enlarging the redshift window. The resulting lower limit for the number density of relics at 0.17 < z < 0.39 is ρ ∼ 9.1 × 10−8 Mpc−3.

show abstract

Chemical composition of the young massive cluster NGC 1569-B

Gvozdenko

Larsen

Beasley

et al. 2022

A&A

View full text Add to dashboard Cite

Context. The chemical composition of young massive clusters (YMCs) provides stellar population information on their host galaxy. As potential precursors of globular clusters (GCs), their properties can help us understand the origins of GCs and their evolution. Aims. We present a detailed chemical abundance analysis of the YMC NGC 1569-B. The host galaxy, NGC 1569, is a dwarf irregular starburst galaxy at a distance of 3.36±0.20 Mpc. We derive the abundances of the α, Fe-peak, and heavy elements. Methods. We determined the abundance ratios from the analysis of an optical integrated-light (IL) spectrum of NGC 1569-B, obtained with the HIRES echelle spectrograph on the Keck I telescope. We considered different red-to-blue supergiant ratios (N RS G /N BS G ), namely: the ratio obtained from a theoretical isochrone (N RS G /N BS G =1.24), the ratio obtained from a resolved colour-magnitude diagram of the YMC (N RS G /N BS G =1.53), and the ratio that minimises the χ 2 when comparing our model spectra with the observations (N RS G /N BS G =1.90). We adopted the latter ratio for our resulting chemical abundances. Results. The derived iron abundance is sub-solar with [Fe/H] = −0.74 ± 0.05. In relation to the scaled solar composition, we find enhanced α-element abundances, [/Fe] = +0.25±0.11, with a particularly high Ti abundance of +0.49±0.05. Other super-solar elements include [Cr/Fe] = +0.50±0.11, [Sc/Fe] = +0.78±0.20, and [Ba/Fe] = +1.28±0.14, while other Fe-peak elements are close to scaled solar abundances: ([Mn/Fe] = −0.22±0.12 and [Ni/Fe] = +0.13±0.11).Conclusions. The composition of NGC 1569-B resembles the stellar populations of the YMC NGC 1705-1, located in a blue compact dwarf galaxy. The two YMCs agree with regard to α-elements and the majority of the Fe-peak elements, except for Sc and Ba, which are extremely super-solar in NGC 1569-B -and higher than in any YMC studied so far. The blue part of the optical spectrum of a young population is still a very challenging wavelength region to analyse using IL spectroscopic studies. This is due to the uncertain contribution to the light from blue supergiant stars, which can be difficult to disentangle from turn-off stars, even when resolved photometry is available. We suggest that the comparison of model fits at different wavelengths offers a route to determining the red-to-blue supergiant ratio from IL spectroscopy.

show abstract

Young stellar population gradients in central cluster galaxies from NUV and optical spectroscopy

Cited by 15 publications

References 113 publications

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

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

INSPIRE: INvestigating Stellar Population In RElics

Chemical composition of the young massive cluster NGC 1569-B

Contact Info

Product

Resources

About