Systematic variation of the stellar initial mass function with velocity dispersion in early-type galaxies

Ferreras, Ignacio; Barbera, F. La; Rosa, I. G. de la; Vazdekis, Alexandre; Carvalho, R. R. de; Falcón-Barroso, J.; Ricciardelli, E.

doi:10.1093/mnrasl/sls014

Cited by 212 publications

(221 citation statements)

References 47 publications

(53 reference statements)

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“…We set the lower and upper mass-cutoff of the IMF to 0.1 and 100 M⊙, respectively. It is worth noting that the very lowmass (< 0.6 M⊙) tapered "bimodal" IMF has been found to be consistent with the line-strengths and mass-to-light (M/L) ratios of massive ETGs (e.g., Ferreras et al 2013;La Barbera et al 2013;Spiniello et al 2014). On the contrary, the single power-law "unimodal" IMF leads to extremely high M/L values that are not supported by independent gravitational lensing and dynamical estimates (e.g., Treu et al 2000;Spiniello et al 2012).…”

Section: Imfsupporting

confidence: 57%

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Vazdekis

Coelho

Cassisi

et al. 2015

Monthly Notices of the Royal Astronomical Society

320

394

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We present models that predict spectra of old-and intermediate-aged stellar populations at 2.51Å (FWHM) with varying [α/Fe] abundance. The models are based on the MILES library and on corrections from theoretical stellar spectra. The models employ recent [Mg/Fe] determinations for the MILES stars and BaSTI scaled-solar and α-enhanced isochrones. We compute models for a suite of IMF shapes and slopes, covering a wide age/metallicity range. Using BASTI, we also compute "base models" matching The Galactic abundance pattern. We confirm that the α-enhanced models show a flux excess with respect to the scaled-solar models blue-ward ∼4500Å, which increases with age and metallicity. We also confirm that both [MgFe] and [MgFe] ′ indices are [α/Fe]-insensitive. We show that the sensitivity of the higher order Balmer lines to [α/Fe] resides in their pseudo-continua, with narrower index definitions yielding lower sensitivity. We confirm that the α-enhanced models yield bluer (redder) colours in the blue (red) spectral range. To match optical colours of massive galaxies we require both α-enhancement and a bottom-heavy IMF. The comparison of Globular Cluster line-strengths with our predictions match the [Mg/Fe] determinations from their individual stars. We obtain good fits to both full spectra and indices of galaxies with varying [α/Fe]. Using thousands of SDSS galaxy spectra we obtain a linear relation between a proxy for the abundance,

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Section: Imfsupporting

confidence: 57%

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Vazdekis

Coelho

Cassisi

et al. 2015

Monthly Notices of the Royal Astronomical Society

320

394

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“…These authors ran a 100 Mpc h −1 cosmological simulation with the N-body/SPH code gadget, with an effective resolution of 3.75 kpc h −1 . The simulations, which included physical prescriptions for momentum-driven winds and chemical enrichment, have previously shown good agreement with the galaxy mass-metallicity relation (Finlator & Davé, 2008), observed IGM enrichment (Oppenheimer & Davé, 2006, 2009, and the cosmological evolution of the UV-luminosity function. Davé et al (2010) identified SMGs as the most heavily star-forming galaxies in their simulations, and chose all SMGs above a given SFR threshold such that their abundance matched the observed number counts of SMGs.…”

Section: Cosmological Hydrodynamic Simulationsmentioning

confidence: 56%

“…For example, observations of gravity sensitive stellar absorption lines (such as FeH, the so called "Wing-Ford" band; Ca II and Na I) aimed at distinguishing K and M dwarfs from K and M giants have found the IMF to be bottom heavy in z ∼ 0 early type galaxies (van Dokkum & Conroy, 2010Conroy & van Dokkum, 2012a,b;Spiniello et al, 2012;Ferreras et al, 2013 Herschel-SPIRE Galaxy (Casey+12) Submillimeter Galaxy (Swinbank+04, Banerji+11, Chapman+prep)…”

Section: Stellar Imfmentioning

confidence: 99%

Dusty star-forming galaxies at high redshift

2014

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Far-infrared and submillimeter wavelength surveys have now established the important role of dusty, star-forming galaxies (DSFGs) in the assembly of stellar mass and the evolution of massive galaxies in the Universe. The brightest of these galaxies have infrared luminosities in excess of 10 13 L with implied star-formation rates of thousands of solar masses per year. They represent the most intense starbursts in the Universe, yet many are completely optically obscured. Their easy detection at submm wavelengths is due to dust heated by ultraviolet radiation of newly forming stars. When summed up, all of the dusty, star-forming galaxies in the Universe produce an infrared radiation field that has an equal energy density as the direct starlight emission from all galaxies visible at ultraviolet and optical wavelengths. The bulk of this infrared extragalactic background light emanates from galaxies as diverse as gas-rich disks to mergers of intense starbursting galaxies. Major advances in far-infrared instrumentation in recent years, both spacebased and ground-based, has led to the detection of nearly a million DSFGs, yet our understanding of the underlying astrophysics that govern the start and end of the dusty starburst phase is still in nascent stage. This review is aimed at summarizing the current status of DSFG studies, focusing especially on the detailed characterization of the bestunderstood subset (submillimeter galaxies, who were summarized in the last review of this field over a decade ago, Blain et al. 2002), but also the selection and characterization of more recently discovered DSFG populations. We review DSFG population statistics, their physical properties including dust, gas and stellar contents, their environments, and current theoretical models related to the formation and evolution of these galaxies.

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“…There are indications that the light of stars in massive early type galaxies is consistent with populations formed with a bottom-heavy IMF, as given by the analysis of their spectral features (van Dokkum & Conroy 2010Ferreras et al 2013;La Barbera et al 2013;; in other works, the mass-to-light ratio of massive early type galaxies is constrained by using dynamical tools (Cappellari et al 2012;Dutton et al 2012;Tortora et al 2013) or strong gravitational lensing Treu et al 2010). However, these methods present a degeneracy in the sense that a higher ratio of less massive stars implies either a bottom heavy IMF or a top heavy IMF, since massive stars end their lives in short time-scales and contribute to the total emitted light only during star formation events and shortly after.…”

Section: Discussionmentioning

confidence: 96%

Chemoarchaeological downsizing in a hierarchical universe: impact of a top-heavy IGIMF

Gargiulo¹,

Cora²,

Padilla³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We make use of a semi-analytical model of galaxy formation to investigate the origin of the observed correlation between [α/Fe] abundance ratios and stellar mass in elliptical galaxies. We implement a new galaxy-wide stellar initial mass function (Top Heavy Integrated Galaxy Initial Mass Function, TH-IGIMF) in the semi-analytic model SAG and evaluate its impact on the chemical evolution of galaxies. The SFR-dependence of the slope of the TH-IGIMF is found to be key to reproducing the correct [α/Fe]-stellar mass relation. Massive galaxies reach higher [α/Fe] abundance ratios because they are characterized by more top-heavy IMFs as a result of their higher SFR. As a consequence of our analysis, the value of the minimum embedded star cluster mass and of the slope of the embedded cluster mass function, which are free parameters involved in the TH-IGIMF theory, are found to be as low as 5 M ⊙ and 2, respectively. A mild downsizing trend is present for galaxies generated assuming either a universal IMF or a variable TH-IGIMF. We find that, regardless of galaxy mass, older galaxies (with formation redshifts 2) are formed in shorter time-scales ( 2 Gyr), thus achieving larger [α/Fe] values. Hence, the time-scale of galaxy formation alone cannot explain the slope of the [α/Fe]-galaxy mass relation, but is responsible for the big dispersion of [α/Fe] abundance ratios at fixed stellar mass. We further test the hyphothesis of a TH-IGIMF in elliptical galaxies by looking into mass-to-light ratios, and luminosity functions. Models with a TH-IGIMF are also favoured by these constraints. In particular, mass-to-light ratios agree with observed values for massive galaxies while being overpredicted for less massive ones; this overprediction is present regardless of the IMF considered.

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Systematic variation of the stellar initial mass function with velocity dispersion in early-type galaxies

Cited by 212 publications

References 47 publications

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Dusty star-forming galaxies at high redshift

Chemoarchaeological downsizing in a hierarchical universe: impact of a top-heavy IGIMF

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