High-z Dusty Star-forming Galaxies: A Top-heavy Initial Mass Function?

Cai, Zhen-Yi; Zotti, G. de; Bonato, M.

doi:10.3847/1538-4357/ab7231

Cited by 12 publications

(14 citation statements)

References 77 publications

(94 reference statements)

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“…The possible need for a top-heavy IMF in high-z dusty star-forming galaxies has been suggested in some observations and models (e.g., Zhang et al 2018;Cai et al 2020). For example, Zhang et al (2018) inferred a topheavy IMF based on observations of isotopologue ratios of CO in sub-millimeter galaxies at z ∼ 2-3.…”

Section: Discussionmentioning

confidence: 99%

Resolved Multi-element Stellar Chemical Abundances in the Brightest Quiescent Galaxy at z ∼ 2

Jafariyazani

Newman

Mobasher

et al. 2020

ApJL

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Measuring the chemical composition of galaxies is crucial to our understanding of galaxy formation and evolution models. However, such measurements are extremely challenging for quiescent galaxies at high redshifts, which have faint stellar continua and compact sizes, making it difficult to detect absorption lines and nearly impossible to spatially resolve them. Gravitational lensing offers the opportunity to study these galaxies with detailed spectroscopy that can be spatially resolved. In this work, we analyze deep spectra of MRG-M0138, a lensed quiescent galaxy at z = 1.98 which is the brightest of its kind, with an H-band magnitude of 17.1. Taking advantage of full spectral fitting, we measure [Mg/Fe] = 0.51 ± 0.05, [Fe/H] = 0.26 ± 0.04, and, for the first time, the stellar abundances of 6 other elements in this galaxy. We further constrained, also for the first time in a z ∼ 2 galaxy, radial gradients in stellar age, [Fe/H], and [Mg/Fe]. We detect no gradient in age or [Mg/Fe] and a slightly negative gradient in [Fe/H], which has a slope comparable to that seen in local early-type galaxies. Our measurements show that not only is MRG-M0138 very Mg-enhanced compared to the centers of local massive early-type galaxies, it is also very iron rich. These dissimilar abundances suggest that even the inner regions of massive galaxies have experienced significant mixing of stars in mergers, in contrast to a purely inside-out growth model. The abundance pattern observed in MRG-M0138 challenges simple galactic chemical evolution models that vary only the star formation timescale and shows the need for more elaborate models.

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Section: Discussionmentioning

confidence: 99%

Resolved Multi-element Stellar Chemical Abundances in the Brightest Quiescent Galaxy at z ∼ 2

Jafariyazani

Newman

Mobasher

et al. 2020

ApJL

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“…Different works have been devoted to the study of the dust con-Full Table 3 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc. u-strasbg.fr/viz-bin/cat/J/A+A/641/A168 tent in galaxies in the Local Universe (Lisenfeld & Ferrara 1998;Dwek 1998;Hirashita 1999;da Cunha et al 2010;Zhukovska 2014;Schneider et al 2016;Rémy-Ruyer et al 2015;Popping et al 2017;Gioannini et al 2017;De Vis et al 2017McKinnon et al 2018;Ginolfi et al 2018) as well as in a variety of high-redshift galaxies (Graziani et al 2020;Burgarella et al 2020), including quasars at z > 6 ( Valiante et al 2014;Calura et al 2014;Mancini et al 2015;Aoyama et al 2017;Wang et al 2017) and sub-millimetre galaxies (Rowlands et al 2014;Cai et al 2020).…”

Section: Introductionmentioning

confidence: 99%

The gas, metal, and dust evolution in low-metallicity local and high-redshift galaxies

Nanni

Burgarella

Theulé

et al. 2020

A&A

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Context. The chemical enrichment in the interstellar medium (ISM) of galaxies is regulated by several physical processes: star birth and death, grain formation and destruction, and galactic inflows and outflows. Understanding such processes and their relative importance is essential to following galaxy evolution and the chemical enrichment through the cosmic epochs, and to interpreting current and future observations. Despite the importance of such topics, the contribution of different stellar sources to the chemical enrichment of galaxies, for example massive stars exploding as Type II supernovae (SNe) and low-mass stars, as well as the mechanisms driving the evolution of dust grains, such as for example grain growth in the ISM and destruction by SN shocks, remain controversial from both observational and theoretical viewpoints. Aims. In this work, we revise the current description of metal and dust evolution in the ISM of local low-metallicity dwarf galaxies and develop a new description of Lyman-break galaxies (LBGs) which are considered to be their high-redshift counterparts in terms of star formation, stellar mass, and metallicity. Our goal is to reproduce the observed properties of such galaxies, in particular (i) the peak in dust mass over total stellar mass (sMdust) observed within a few hundred million years; and (ii) the decrease in sMdust at a later time. Methods. We fitted spectral energy distribution of dwarf galaxies and LBGs with the “Code Investigating GALaxies Emission”, through which the total stellar mass, dust mass, and star formation rate are estimated. For some of the dwarf galaxies considered, the metal and gas content are available from the literature. We computed different prescriptions for metal and dust evolution in these systems (e.g. different initial mass functions for stars, dust condensation fractions, SN destruction, dust accretion in the ISM, and inflow and outflow efficiency), and we fitted the properties of the observed galaxies through the predictions of the models. Results. Only some combinations of models are able to reproduce the observed trend and simultaneously fit the observed properties of the galaxies considered. In particular, we show that (i) a top-heavy initial mass function that favours the formation of massive stars and a dust condensation fraction for Type II SNe of around 50% or more help to reproduce the peak of sMdust observed after ≈100 Myr from the beginning of the baryon cycle for both dwarf galaxies and LBGs; (ii) galactic outflows play a crucial role in reproducing the observed decline in sMdust with age and are more efficient than grain destruction from Type II SNe both in local galaxies and at high-redshift; (iii) a star formation efficiency (mass of gas converted into stars) of a few percent is required to explain the observed metallicity of local dwarf galaxies; and (iv) dust growth in the ISM is not necessary in order to reproduce the values of sMdust derived for the galaxies under study, and, if present, the effect of this process would be erased by galactic outflows.

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“…For example, at z = 2 the [C i i] 157.7 µm line will allow the detection of SFRs down to about 60 M yr −1 by the "all-sky" survey and down to 30 M yr −1 for the "deep" survey. Our conservative estimates, that do not allow for the possibility of a top-heavier IMF at high z indicated by theoretical arguments and by some observational results (see Cai et al, 2020, for a discussion), yield the detection of thousands of galaxies at z 6 and of several tens at z 8.…”

Section: Discussionmentioning

confidence: 82%

“…A more top-heavy IMF would yield higher surface densities of ultra-luminous high-z galaxies. An excess of z ∼ > 4 dusty galaxies over model expectations has been reported, but the issue is controversial (see Cai et al, 2020, for a recent discussion and references).…”

Section: Sfr Functions and Redshift Distributionsmentioning

confidence: 99%

Understanding galaxy formation and evolution through an all-sky submillimetre spectroscopic survey

Negrello

Bonato

Cai

et al. 2020

Publ. Astron. Soc. Aust.

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We illustrate the extraordinary discovery potential for extragalactic astrophysics of a far-infrared/submillimetre (far-IR/submm) all-sky spectroscopic survey with a 3-m-class space telescope. Spectroscopy provides a three-dimensional view of the Universe and allows us to take full advantage of the sensitivity of present-day instrumentation, close to fundamental limits, overcoming the spatial confusion that affects broadband far-IR/submm surveys. A space telescope of the 3-m class (which has already been described in recent papers) will detect emission lines powered by star formation in galaxies out to $z\,{\simeq}\,8$ . It will specifically provide measurements of spectroscopic redshifts, star-formation rates (SFRs), dust masses, and metal content for millions of galaxies at the peak epoch of cosmic star formation and of hundreds of them at the epoch of reionisation. Many of these star-forming galaxies will be strongly lensed; the brightness amplification and stretching of their sizes will make it possible to investigate (by means of follow-up observations with high-resolution instruments like ALMA, JWST, and SKA) their internal structure and dynamics on the scales of giant molecular clouds (40–100 pc). This will provide direct information on the physics driving the evolution of star-forming galaxies. Furthermore, the arcmin resolution of the telescope at submm wavelengths is ideal for detecting the cores of galaxy proto-clusters, out to the epoch of reionisation. Due to the integrated emission of member galaxies, such objects (as well as strongly lensed sources) will dominate at the highest apparent far-IR luminosities. Tens of millions of these galaxy-clusters-in-formation will be detected at $z \simeq 2 - 3$ –3, with a tail extending out to $z\,{\simeq}\,7$ , and thousands of detections at $6\,{<}\,z\,{<}\,7$ . Their study will allow us to track the growth of the most massive halos well beyond what is possible with classical cluster surveys (mostly limited to $z\,\lesssim\, 1.5 - 2$ –2), tracing the history of star formation in dense environments and teaching us how star formation and galaxy-cluster formation are related across all epochs. The obscured cosmic SFR density of the Universe will thereby be constrained. Such a survey will overcome the current lack of spectroscopic redshifts of dusty star-forming galaxies and galaxy proto-clusters, representing a quantum leap in far-IR/submm extragalactic astrophysics.

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High-z Dusty Star-forming Galaxies: A Top-heavy Initial Mass Function?

Cited by 12 publications

References 77 publications

Resolved Multi-element Stellar Chemical Abundances in the Brightest Quiescent Galaxy at z ∼ 2

Resolved Multi-element Stellar Chemical Abundances in the Brightest Quiescent Galaxy at z ∼ 2

The gas, metal, and dust evolution in low-metallicity local and high-redshift galaxies

Understanding galaxy formation and evolution through an all-sky submillimetre spectroscopic survey

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