A lower fragmentation mass scale in high-redshift galaxies and its implications on giant clumps: a systematic numerical study

Tamburello, Valentina; Mayer, Lucio; Shen, Sijing; Wadsley, James

doi:10.1093/mnras/stv1695

Cited by 98 publications

(164 citation statements)

References 106 publications

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“…While some simulations (Tamburello et al 2015) may imply little importance in the role clumps play in galaxy evolution, observational studies such as this work imply otherwise. Our results, although applicable to UV-selected clumps only, are significant.…”

Section: Discussionmentioning

confidence: 73%

Physical Properties of Sub-galactic Clumps at 0.5 ≤ Z ≤ 1.5 in the UVUDF

Soto

Mello

Rafelski

et al. 2017

ApJ

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We present an investigation of clumpy galaxies in the Hubble Ultra Deep Field at   z 0.5 1.5 in the rest-frame far-ultraviolet (FUV) using Hubble Space Telescope Wide Field Camera 3 broadband imaging in F225W, F275W, and F336W. An analysis of 1404 galaxies yields 209 galaxies that host 403 kpc scale clumps. These host galaxies appear to be typical star-forming galaxies, with an average of 2 clumps per galaxy and reaching a maximum of 8 clumps. We measure the photometry of the clumps and determine the mass, age, and star formation rates (SFR) using the spectral energy distribution fitting code FAST. We find that clumps make an average contribution of 19% to the total rest-frame FUV flux of their host galaxy. Individually, clumps contribute a median of 5% to the host galaxy SFR and an average of ∼4% to the host galaxy mass, with total clump contributions to the host galaxy stellar mass ranging widely from lower than 1% up to 93%. Clumps in the outskirts of galaxies are typically younger, with higher SFRs, than clumps in the inner regions. The results are consistent with clump migration theories in which clumps form through violent gravitational instabilities in gas-rich turbulent disks, eventually migrate toward the center of the galaxies, and coalesce into the bulge.

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Section: Discussionmentioning

confidence: 73%

Physical Properties of Sub-galactic Clumps at 0.5 ≤ Z ≤ 1.5 in the UVUDF

Soto

Mello

Rafelski

et al. 2017

ApJ

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“…This interpretation is further reinforced when looking at the typical stellar masses of clumps. We find that for those two-clump sys-tems with at least one bright component, the majority (∼ 77%) have stellar masses greater than log(M /M ) > 9 a limit beyond which clumps induced by VDI are not observed in simulations (see e.g., Elmegreen et al 2009;Guo et al 2012;Tamburello et al 2015;Bournaud 2016). On the other hand, ∼ 55% of clumps in multi-clump systems have stellar masses lower than log(M /M ) < 9, which might likely result from VDI as well as minor mergers.…”

Section: Clump Stellar Massesmentioning

confidence: 87%

The VIMOS Ultra-Deep Survey: A major merger origin for the high fraction of galaxies at 2 < z < 6 with two bright clumps

Ribeiro

Fèvre

Cassata

et al. 2017

A&A

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The properties of stellar clumps in star-forming galaxies and their evolution over the redshift range 2 z 6 are presented and discussed in the context of the build-up of massive galaxies at early cosmic times. We focused on galaxies with spectroscopic redshifts from the VIMOS Ultra Deep Survey (VUDS) and stellar masses log 10 (M /M ) > −0.204 × (z − 4.5) + 9.35. We analyzed HST-ACS images to identify clumps within a 20 kpc radius using a method taking into account differential surface brightness dimming and luminosity evolution with redshift. We find that the population of galaxies with more than one clump is dominated by galaxies with two clumps, representing ∼21-25% of the population, while the fraction of galaxies with three, or four and more, clumps is 8-11 and 7-9%, respectively. The fraction of clumpy galaxies is in the range ∼ 35 − 55% over 2 < z < 6, increasing at higher redshifts, indicating that the fraction of irregular galaxies remains high up to the highest redshifts. The large and bright clumps (M star ∼ 10 9 up to ∼ 10 10 M ) are found to reside predominantly in galaxies with two clumps. Smaller and lower luminosity clumps (M star < 10 9 M ) are found in galaxies with three clumps or more. We interpret these results as evidence for two different modes of clump formation working in parallel. The small low luminosity clumps are likely the result of disk fragmentation, with violent disk instabilities (VDI) forming several long-lived clumps in-situ. as suggested from simulations. A fraction of these clumps is also likely coming from minor mergers as confirmed from spectroscopy in several cases. The clumps in the dominating population of galaxies with two clumps are significantly more massive and have properties akin to those in galaxy pairs undergoing massive merging observed at similar redshifts; they appear as more massive than the most massive clumps observed in numerical simulations of disks with VDI. We infer from these properties that the bright and large clumps are most likely the result of major mergers bringing-in ex-situ matter onto a galaxy, and we derive a high major merger fraction of ∼20%. The diversity of clump properties therefore suggests that the assembly of star-forming galaxies at z∼ 2 − 6 proceeds from several different dissipative processes including an important contribution from major and minor mergers.

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“…This limitation raises the question whether an observed clump is actually a single object or blending of a few nearby smaller clumps. For example, Tamburello et al (2015) argued that many of the giant clumps (with M M 10 8 * >  ) identified in observations are not due to in situ formation but are the result of the blending of smaller structures due to the low resolution of the observations. Similarly, Dessauges-Zavadsky et al (2017a) claimed that the clump masses observed in non-lensed galaxies with a limited spatial resolution of ∼1 kpc are artificially increased due to the clustering of clumps of smaller mass.…”

Section: A Challenge Of Clump Studies and The Motivation Of This Papermentioning

confidence: 99%

Clumpy Galaxies in CANDELS. II. Physical Properties of UV-bright Clumps at 0.5 ≤ z < 3

Guo

Rafelski

Bell

et al. 2018

ApJ

108

150

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Studying giant star-forming clumps in distant galaxies is important to understand galaxy formation and evolution. At present, however, observers and theorists have not reached a consensus on whether the observed "clumps" in distant galaxies are the same phenomenon that is seen in simulations. In this paper, as a step to establish a benchmark of direct comparisons between observations and theories, we publish a sample of clumps constructed to represent the commonly observed "clumps" in the literature. This sample contains 3193 clumps detected from 1270 galaxies at z 0.5 3.0  < . The clumps are detected from rest-frame UV images, as described in our previous paper. Their physical properties (e.g., rest-frame color, stellar mass (M * ), star formation rate (SFR), age, and dust extinction) are measured by fitting the spectral energy distribution (SED) to synthetic stellar population models. We carefully test the procedures of measuring clump properties, especially the method of subtracting background fluxes from the diffuse component of galaxies. With our fiducial background subtraction, we find a radial clump U−V color variation, where clumps close to galactic centers are redder than those in outskirts. The slope of the color gradient (clump color as a function of their galactocentric distance scaled by the semimajor axis of galaxies) changes with redshift and M * of the host galaxies: at a fixed M * , the slope becomes steeper toward low redshift, and at a fixed redshift, it becomes slightly steeper with M * . Based on our SED fitting, this observed color gradient can be explained by a combination of a negative age gradient, a negative E(B−V ) gradient, and a positive specific SFR gradient of the clumps. We also find that the color gradients of clumps are steeper than those of intra-clump regions. Correspondingly, the radial gradients of the derived physical properties of clumps are different from those of the diffuse component or intra-clump regions.

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A lower fragmentation mass scale in high-redshift galaxies and its implications on giant clumps: a systematic numerical study

Cited by 98 publications

References 106 publications

Physical Properties of Sub-galactic Clumps at 0.5 ≤ Z ≤ 1.5 in the UVUDF

Physical Properties of Sub-galactic Clumps at 0.5 ≤ Z ≤ 1.5 in the UVUDF

The VIMOS Ultra-Deep Survey: A major merger origin for the high fraction of galaxies at 2 < z < 6 with two bright clumps

Clumpy Galaxies in CANDELS. II. Physical Properties of UV-bright Clumps at 0.5 ≤ z < 3

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