Testing star formation laws in a starburst galaxy at redshift 3 resolved with ALMA

Sharda, Piyush; Federrath, Christoph; Cunha, Elisabete da; Swinbank, A. M.; Dye, S.

doi:10.1093/mnras/sty886

Cited by 44 publications

(42 citation statements)

References 155 publications

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“…High specific angular momentum galaxies with low star formation rate surface density, on average, tend to have disc-like morphologies. Assuming the galaxies in the KGES sample follow the Kennicutt-Schmidt relation (e.g Gnedin & Kravtsov 2010;Freundlich et al 2013;Orr et al 2018;Sharda et al 2018), galaxies with higher star formation rate surface densities, imply higher gas surface densities and hence likely high gas fractions. Recent hydrodynamical zoom-in simulations with the FIRE project (Hopkins et al 2014(Hopkins et al , 2018, have shown that the stellar morphology and kinematics of Milky Way mass galaxies correlate more strongly with the gaseous histories of the galaxies (Garrison-Kimmel et al 2018), in particular around the epoch the galaxy has formed half of its stars (e.g.…”

Section: Interpretation -The High-redshift Galaxy Demographicmentioning

confidence: 99%

From peculiar morphologies to Hubble-type spirals: the relation between galaxy dynamics and morphology in star-forming galaxies at z ∼ 1.5

Gillman

Tiley

Swinbank

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present an analysis of the gas dynamics of star-forming galaxies at z ∼ 1.5 using data from the KMOS Galaxy Evolution Survey (KGES). We quantify the morphology of the galaxies using HST CANDELS imaging parametrically and non-parametrically. We combine the Hα dynamics from KMOS with the high-resolution imaging to derive the relation between stellar mass (M * ) and stellar specific angular momentum (j * ). We show that high-redshift star-forming galaxies at z ∼ 1.5 follow a power-law trend in specific stellar angular momentum with stellar mass similar to that of local late-type galaxies of the form j * ∝ M 0.53 ± 0.10 * . The highest specific angular momentum galaxies are mostly disc-like, although generally, both peculiar morphologies and disc-like systems are found across the sequence of specific angular momentum at a fixed stellar mass. We explore the scatter within the j * -M * plane and its correlation with both the integrated dynamical properties of a galaxy (e.g. velocity dispersion, Toomre Q g , Hα star formation rate surface density Σ SFR ) and its parameterised restframe UV / optical morphology (e.g. Sérsic index, bulge to total ratio, Clumpiness, Asymmetry and Concentration). We establish that the position in the j * -M * plane is correlated with the star-formation surface density and the Clumpiness of the stellar light distribution. Galaxies with peculiar rest-frame UV / optical morphologies have comparable specific angular momentum to disc -dominated galaxies of the same stellar mass, but are clumpier and have higher star-formation rate surface densities. We propose that the peculiar morphologies in high-redshift systems are driven by higher star formation rate surface densities and higher gas fractions leading to a more clumpy inter-stellar medium.

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Section: Interpretation -The High-redshift Galaxy Demographicmentioning

confidence: 99%

From peculiar morphologies to Hubble-type spirals: the relation between galaxy dynamics and morphology in star-forming galaxies at z ∼ 1.5

Gillman

Tiley

Swinbank

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Following the analysis presented in Sharda et al 2018 (hereafter, S18), we study the SFR in different regions of AzTEC-1, a non-lensed starburst galaxy at z ≈ 4.3 discovered in the Cosmic Evolution Survey (COSMOS) field (Scoville et al 2007) with the AzTEC camera (Wilson et al 2008) on the James Clarke Maxwell Telescope (Scott et al 2008). A follow-up survey by the Large Millimeter Telescope found its spectroscopic redshift to be 4.3420 ± 0.0004 (Yun et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Testing star formation laws on spatially resolved regions in a z ≈ 4.3 starburst galaxy

Sharda

Cunha

Federrath

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We probe the star formation properties of the gas in AzTEC-1 in the COSMOS field, one of the best resolved and brightest starburst galaxies at z ≈ 4.3, forming stars at a rate > 1000 M yr −1 . Using recent ALMA observations, we study star formation in the galaxy nucleus and an off-center star-forming clump and measure a median star formation rate (SFR) surface density of Σ nucleus SFR = 270 ± 54 and Σ sfclump SFR = 170 ± 38 M yr −1 kpc −2 , respectively. Following the analysis by Sharda et al.(2018), we estimate the molecular gas mass, freefall time and turbulent Mach number in these regions to predict Σ SFR from three star formation relations in the literature. The Kennicutt-Schmidt (Kennicutt 1998, KS) relation, which is based on the gas surface density, underestimates the Σ SFR in these regions by a factor 2-3. The Σ SFR we calculate from the single-freefall model of Krumholz et al. 2012 (KDM) is consistent with the measured Σ SFR in the nucleus and the star-forming clump within the uncertainties. The turbulence-regulated star formation relation by Salim et al. 2015 (SFK) agrees slightly better with the observations than the KDM relation. Our analysis reveals that an interplay between turbulence and gravity can help sustain high SFRs in high-redshift starbursts. It can also be extended to other high-and low-redshift galaxies thanks to the high angular resolution and sensitivity of ALMA observations.

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“…Star formation is known to occur in filamentary structures (Goldsmith et al 2008;André et al 2014) in molecular clouds (Wong & Blitz 2002;Kennicutt et al 2007;Blanc et al 2009;Krumholz 2014) and it can be characterized by a quantity known as the star formation efficiency per free-fall time ff (Krumholz & McKee 2005), which measures the fraction of the gas that is converted to stars per free-fall time. On molecular cloud scales, the average value of ff is E-mail: shivankhullar@gmail.com (SK) known to be small, ≈ 0.01 1 (e.g., Krumholz & Tan 2007;Krumholz et al 2012;Federrath 2013a;Evans et al 2014;Salim et al 2015;Vutisalchavakul et al 2016;Heyer et al 2016;Leroy et al 2017;Sharda et al 2018; see Krumholz et al 2019 for a recent review) This means that on giant molecular cloud (GMC) or molecular cloud length scales (∼ 100 pc down to 1 pc), star formation is very inefficient. However, as we move towards smaller length scales (∼ 0.1 pc down to AU scales) tracing gas at densities exceeding ∼ 10 7 cm −3 , eventually there must be some density or size scale beyond which most of the mass in gas would wind up in a star ∼ 1 dynamical time later.…”

Section: Introductionmentioning

confidence: 99%

Determining Star Formation Thresholds from Observations

Khullar

Krumholz

Federrath

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Most gas in giant molecular clouds is relatively low-density and forms star inefficiently, converting only a small fraction of its mass to stars per dynamical time. However, star formation models generally predict the existence of a threshold density above which the process is efficient and most mass collapses to stars on a dynamical timescale. A number of authors have proposed observational techniques to search for a threshold density above which star formation is efficient, but it is unclear which of these techniques, if any, are reliable. In this paper we use detailed simulations of turbulent, magnetised star-forming clouds, including stellar radiation and outflow feedback, to investigate whether it is possible to recover star formation thresholds using current observational techniques. Using mock observations of the simulations at realistic resolutions, we show that plots of projected star formation efficiency per free-fall time ff can detect the presence of a threshold, but that the resolutions typical of current dust emission or absorption surveys are insufficient to determine its value. In contrast, proposed alternative diagnostics based on a change in the slope of the gas surface density versus star formation rate surface density (Kennicutt-Schmidt relation) or on the correlation between young stellar object counts and gas mass as a function of density are ineffective at detecting thresholds even when they are present. The signatures in these diagnostics sometimes taken as indicative of a threshold in observations, which we generally reproduce in our mock observations, do not prove to correspond to real physical features in the 3D gas distribution. 1 As discussed in the Krumholz et al. (2019) review, the amount of spread about this average is a subject of current debate; Krumholz et al. argue that the weight of evidence favours a relatively small spread of ≈ 0.3 dex, but some authors argue for larger spreads of 1 dex.

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Testing star formation laws in a starburst galaxy at redshift 3 resolved with ALMA

Cited by 44 publications

References 155 publications

From peculiar morphologies to Hubble-type spirals: the relation between galaxy dynamics and morphology in star-forming galaxies at z ∼ 1.5

From peculiar morphologies to Hubble-type spirals: the relation between galaxy dynamics and morphology in star-forming galaxies at z ∼ 1.5

Testing star formation laws on spatially resolved regions in a z ≈ 4.3 starburst galaxy

Determining Star Formation Thresholds from Observations

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