Stellar populations dominated by massive stars in dusty starburst galaxies across cosmic time

Zhang, Zhi-Yu; Romano, D.; Ivison, R. J.; Papadopoulos, Panagiotis; Matteuccí, F.

doi:10.1038/s41586-018-0196-x

Cited by 226 publications

(263 citation statements)

References 75 publications

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“…Therefore large clumps cannot further fragment into small ones (Omukai et al 2005). High gas temperature may also cause top-heavy stellar initial mass functions as seen both in the metal-poor LMC and high-z starburst galaxies (Zhang et al 2018;Schneider et al 2018). The difficulty in gas fragmentation at extremely low metallicity suggests a small number of dense clumps in which stars can form.…”

Section: Resultsmentioning

confidence: 99%

Oversized Gas Clumps in an Extremely Metal-poor Molecular Cloud Revealed by ALMA’s Parsec-scale Maps

Shi

Wang

Zhang

et al. 2020

ApJ

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Metals are thought to have profound effects on the internal structures of molecular clouds in which stars are born. The absence of metals is expected to prevent gas from efficient cooling and fragmentation in theory. However, this effect has not yet been observed at low metallicity environments, such as in the early Universe and local dwarf galaxies, because of the lack of high spatial resolution maps of gas. We carried out ALMA observations of the carbon monoxide (CO) J=2-1 emission line at 1.4-parsec resolutions of a molecular cloud in DDO 70 at 7% solar metallicity, the most metal-poor galaxy currently known with a CO detection. In total, five clumps have been identified and they are found to follow more or less the Larson's law. Since the CO emission exists in regions with visual extinction A V around 1.0, we converted this A V to the gas mass surface density using a gas-to-dust ratio of 4,594±2,848 for DDO 70. We found that the CO clumps in DDO 70 exhibit significantly larger (on average four times) sizes than those at the same gas mass surface densities in massive star-formation regions of the Milky Way. The existence of such large clumps appears to be consistent with theoretical expectations that gas fragmentation in low metallicity clouds is suppressed. While our observation is only for one cloud in the galaxy, if it is representative, the above result implies suppressed gas fragmentation during the cloud collapse and star formation in the early Universe.

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Section: Resultsmentioning

confidence: 99%

Oversized Gas Clumps in an Extremely Metal-poor Molecular Cloud Revealed by ALMA’s Parsec-scale Maps

Shi

Wang

Zhang

et al. 2020

ApJ

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“…into a greater abundance of bright galaxies than expected under the assumption of a universal initial mass function (IMF). Observational evidence of a top-heavy IMF has been reported by Zhang et al (2018) in four gravitational lensed sub-mm galaxies at z ∼ 2-3. How do the counts of high-z galaxies implied by the IMF advocated by Zhang et al (2018) compare with observations?…”

Section: Introductionmentioning

confidence: 83%

“…Figure 3. Comparison of the most recent determinations of the high-z IR luminosity functions of galaxies with the model by Cai et al (2013) for different choices for the IMF of high-z proto-spheroidal galaxies: a universal "Chabrier" IMF (baseline model; k ⋆,IR = 3.1); the "top-heavy" (k ⋆,IR = 3.1 × 1.4) and the "Ballero" IMFs (k ⋆,IR = 3.1 × 1.9) IMFs advocated by Zhang et al (2018); the extreme, flat, IMF (k ⋆,IR = 3.1 × 4) used by Baugh et al (2005). Galaxy SEDs, with total IR luminosity normalized to unit, associated to the "Chabrier", "top-heavy", "Ballero", and "Baugh" IMFs of proto-spheroidal galaxies.…”

Section: A Top-heavier Imf?mentioning

confidence: 99%

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

Cai

Zotti

Bonato

2020

ApJ

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Recent estimates point to abundances of z > 4 sub-mm galaxies far above model predictions. The matter is still debated. According to some analyses the excess may be substantially lower than initially thought and perhaps accounted for by flux boosting and source blending. However, there is no general agreement on this conclusion. An excess of z > 6 dusty galaxies has also been reported albeit with poor statistics. On the other hand, Zhang et al. (2018) reported evidence of a top-heavy initial mass function (IMF) in high-z galaxies. This would translate into higher a sub-mm luminosity of dusty galaxies at fixed star-formation rate (SFR), i.e., into a higher abundance of high-z galaxies than expected for an universal IMF. Exploiting the physical model by Cai et al. (2013) we argue that some excess can be understood in terms of a somewhat top-heavier IMF for proto-spheroidal galaxies compared to late-type galaxies. Such IMF is consistent with that advocated by Zhang et al. (2018) to account for the low 13 C/ 18 O abundance ratio measured by them in four z = 2-3 dusty galaxies. However, the IMF impact on the star formation history of galaxies is far less dramatic than suggested by these authors and extreme top-heavy IMFs are inconsistent with the data.

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“…since in more massive spheroids an overabundance of massive stars at early times is necessary to explain many of their features, such as the colour-luminosity relation (Gibson & Matteucci 1997) and the observed [α/F e] (e.g. De Masi et al 2018) in local galaxies and the isotopic ratios (Zhang et al 2018) in high redshift ones. For spirals and irregulars instead, in addition to the Salpeter (1955) IMF, we use also a Scalo (1986) IMF, derived for the solar vicinity:…”

Section: The Birthrate Functionmentioning

confidence: 99%

Galactic Archaeology at High Redshift: Inferring the Nature of GRB Host Galaxies from Abundances

Palla

Matteuccí

Calura

et al. 2020

ApJ

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We identify the nature of high redshift long Gamma-Ray Bursts (LGRBs) host galaxies by comparing the observed abundance ratios in the interstellar medium with detailed chemical evolution models accounting for the presence of dust. We compare abundance data from long Gamma-Ray Bursts afterglow spectra to abundance patterns as predicted by our models for different galaxy types. We analyse [X/F e] abundance ratios (where X is C, N , O, M g, Si, S, N i, Zn) as functions of [F e/H]. Different galaxies (irregulars, spirals, spheroids) are, in fact, characterised by different star formation histories, which produce different [X/F e] vs. [F e/H] relations ("time-delay model"). This allows us to identify the star formation history of the host galaxies and to infer their age (i.e. the time elapsed from the beginning of star formation) at the time of the GRB events. Unlike previous works, we use newer models in which we adopt updated stellar yields and prescriptions for dust production, accretion and destruction. We consider a sample of seven LGRB host galaxies. Our results suggest that two of them (GRB 050820, GRB 120815A) are star forming spheroids, two (GRB 081008, GRB 161023A) are spirals and three (GRB 090926A, GRB 050730, GRB 120327A) are irregulars. The inferred ages of the considered host galaxies span from 10 M yr to slightly more than 1 Gyr.

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Stellar populations dominated by massive stars in dusty starburst galaxies across cosmic time

Cited by 226 publications

References 75 publications

Oversized Gas Clumps in an Extremely Metal-poor Molecular Cloud Revealed by ALMA’s Parsec-scale Maps

Oversized Gas Clumps in an Extremely Metal-poor Molecular Cloud Revealed by ALMA’s Parsec-scale Maps

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

Galactic Archaeology at High Redshift: Inferring the Nature of GRB Host Galaxies from Abundances

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