Extended H<i>α</i> over compact far-infrared continuum in dusty submillimeter galaxies

Chen, Chian-Chou; Harrison, C. M.; Smail, Ian; Swinbank, A. M.; Turner, O. J.; Wardlow, J. L.; Brandt, W. N.; Rivera, G. Calistro; Chapman, Scott; Cooke, Elizabeth A.; Dannerbauer, H.; Dunlop, J. S.; Farrah, D.; Michałowski, M. J.; Schinnerer, E.; Simpson, J. M.; Thomson, A. P.; Werf, P. P. van der

doi:10.1051/0004-6361/201936286

Cited by 29 publications

(18 citation statements)

References 155 publications

(240 reference statements)

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“…This is in line with other studies showing that there is currently no evidence of the AGN driving the FIR continuum sizes of galaxies (e.g. Chen et al 2020).…”

Section: Potential Biases In Our Alma Size Estimatessupporting

confidence: 93%

Submillimetre compactness as a critical dimension to understand the main sequence of star-forming galaxies

Puglisi

Daddi

Valentino

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We study the interstellar medium (ISM) properties as a function of the molecular gas size for 77 infrared-selected galaxies at z ∼ 1.3, having stellar masses 109.4 ≲ M⋆ ≲ 1012.0 M⊙ and star formation rates 12 ≲ SFRFIR ≲ 1000 M⊙ yr−1. Molecular gas sizes are measured on ALMA images that combine CO(2-1), CO(5-4) and underlying continuum observations, and include CO(4-3), CO(7-6)+[CI](3P2 − 3P1), [CI](3P1 − 3P0) observations for a subset of the sample. The $\gtrsim 46 {{\ \rm per\ cent}}$ of our galaxies have a compact molecular gas reservoir, and lie below the optical disks mass-size relation. Compact galaxies on and above the main sequence have higher CO excitation and star formation efficiency than galaxies with extended molecular gas reservoirs, as traced by CO(5-4)/CO(2-1) and CO(2-1)/LIR, SF ratios. Average CO+[CI] spectral line energy distributions indicate higher excitation in compacts relative to extended sources. Using CO(2-1) and dust masses as molecular gas mass tracers, and conversion factors tailored to their ISM conditions, we measure lower gas fractions in compact main-sequence galaxies compared to extended sources. We suggest that the sub-millimetre compactness, defined as the ratio between the molecular gas and the stellar size, is an unavoidable information to be used with the main sequence offset to describe the ISM properties of galaxies, at least above M⋆ ≥ 1010.6 M⊙, where our observations fully probe the main sequence scatter. Our results are consistent with mergers driving the gas in the nuclear regions, enhancing the CO excitation and star formation efficiency. Compact main-sequence galaxies are consistent with being an early post-starburst population following a merger-driven starburst episode, stressing the important role of mergers in the evolution of massive galaxies.

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“…This is in line with other studies showing that there is currently no evidence of the AGN driving the FIR continuum sizes of galaxies (e.g. Chen et al 2020).…”

Section: Potential Biases In Our Alma Size Estimatessupporting

confidence: 93%

Submillimetre compactness as a critical dimension to understand the main sequence of star-forming galaxies

Puglisi

Daddi

Valentino

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…Moreover, while free-free emission is only affected by dust attenuation within H II regions, SFR tracers using ionized gas at shorter wavelengths, such as the Balmer lines, should be affected by dust attenuation throughout the entire galaxy. However, with the possible exception of highly dust-obscured starbursts (Chen et al 2020), the Balmer lines have been shown to agree both with panchromatic SFRs derived via SED-fitting (Shivaei et al 2016) and SFRs from radio synchrotron emission (Duncan et al 2020) at z ∼ 2. Given that free-free emission is expected to be less affected by dust than Hα, it seems unlikely that high-redshift galaxies with modest star-formation rates exhibit a systematic deficit of free-free emission.…”

Section: A Lack Of Free-free Emissionmentioning

confidence: 68%

COLDz: Probing Cosmic Star Formation With Radio Free-free Emission

Algera,

Hodge,

Riechers

et al. 2021

Preprint

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Radio free-free emission is considered to be one of the most reliable tracers of star formation in galaxies. However, as it constitutes the faintest part of the radio spectrum -being roughly an order of magnitude less luminous than radio synchrotron emission at the GHz frequencies typically targeted in radio surveys -the usage of free-free emission as a star formation rate tracer has mostly remained limited to the local Universe. Here we perform a multi-frequency radio stacking analysis using deep Karl G. Jansky Very Large Array observations at 1.4, 3, 5, 10 and 34 GHz in the COSMOS and GOODS-North fields to probe free-free emission in typical galaxies at the peak of cosmic star formation. We find that z ∼ 0.5 − 3 star-forming galaxies exhibit radio emission at rest-frame frequencies of ∼ 65 − 90 GHz that is ∼ 1.5 − 2× fainter than would be expected from a simple combination of freefree and synchrotron emission, as in the prototypical starburst galaxy M82. We interpret this as a deficit in high-frequency synchrotron emission, while the level of free-free emission is as expected from M82. We additionally provide the first constraints on the cosmic star formation history using free-free emission at 0.5 z 3, which are in good agreement with more established tracers at high redshift. In the future, deep multi-frequency radio surveys will be crucial in order to accurately determine the shape of the radio spectrum of faint star-forming galaxies, and to further establish radio free-free emission as a tracer of high-redshift star formation.

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“…In any cases, the optical half-light radius of late-type galaxies of similar masses and at z 3 is found to be about two times larger (∼ 3 − 8 kpc) than their star-forming extent (Sect. 4.3 van der Wel et al 2014;Fujimoto et al 2017;Elbaz et al 2018;Jiménez-Andrade et al 2019Chen et al 2020;Tadaki et al 2020). This centrally enhanced star formation is usually interpreted in the literature as a sign that the cold gas accreted by MS galaxies falls preferentially onto their central region and triggers the formation of their bulge (e.g., Fisher 2006;Goldbaum et al 2016;Tonini et al 2016).…”

Section: Compact Star Forming Extent ?mentioning

confidence: 93%

A$^{3}$COSMOS: A census on the molecular gas mass and extent of main-sequence galaxies across cosmic time

Wang,

Magnelli,

Schinnerer

et al. 2022

Preprint

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Aims. To constrain for the first time the mean mass and extent of the molecular gas of a mass-complete sample of normal > 10 10 M star-forming galaxies at 0.4 < z < 3.6. Methods. We apply an innovative uv-based stacking analysis to a large set of archival Atacama Large Millimeter/submillimeter Array (ALMA) observations using a mass-complete sample of main-sequence (MS) galaxies. This stacking analysis, performed on the Rayleigh-Jeans dust continuum emission, provides accurate measurements of the mean mass and extent of the molecular gas of galaxy populations, which are otherwise individually undetected. Results. The molecular gas mass of MS galaxies evolves with redshift and stellar mass. At all stellar masses, the molecular gas fraction decreases by a factor of ∼ 24 from z ∼ 3.2 to z ∼ 0. At a given redshift, the molecular gas fraction of MS galaxies decreases with stellar mass, at roughly the same rate as their specific star formation rate (SFR/M ) decreases. The molecular gas depletion time of MS galaxies remains roughly constant at z > 0.5 with a value of 300-500 Myr, but increases by a factor ∼ 3 from z ∼ 0.5 to z ∼ 0. This evolution of the molecular gas depletion time of MS galaxies can be predicted from the evolution of their molecular gas surface density and a seemingly universal MS-only Σ M mol − Σ SFR relation with an inferred slope of ∼ 1.13, i.e., the so-called Kennicutt-Schmidt (KS) relation. The far-infrared size of MS galaxies shows no significant evolution with redshift or stellar mass, with a mean circularized half-light radius of ∼2.2 kpc. Finally, our mean molecular gas masses are generally lower than previous estimates, likely caused by the fact that literature studies were largely biased towards individually-detected MS galaxies with massive gas reservoirs. Conclusions. To first order, the molecular gas content of MS galaxies regulates their star formation across cosmic time, while variation of their star formation efficiency plays a secondary role. Despite a large evolution of their gas content and SFRs, MS galaxies evolved along a seemingly universal MS-only KS relation.

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Extended Hα over compact far-infrared continuum in dusty submillimeter galaxies

Cited by 29 publications

References 155 publications

Submillimetre compactness as a critical dimension to understand the main sequence of star-forming galaxies

Submillimetre compactness as a critical dimension to understand the main sequence of star-forming galaxies

COLDz: Probing Cosmic Star Formation With Radio Free-free Emission

A$^{3}$COSMOS: A census on the molecular gas mass and extent of main-sequence galaxies across cosmic time

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