Giant star-forming clumps?

Monthly Notices of the Royal Astronomical Society Letters, vol. 495, pp. L1–L6

Abstract

ABSTRACT With the spatial resolution of the Atacama Large Millimetre Array (ALMA), dusty galaxies in the distant Universe typically appear as single, compact blobs of dust emission, with a median half-light radius, ≈1 kpc. Occasionally, strong gravitational lensing by foreground galaxies or galaxy clusters has probed spatial scales 1–2 orders of magnitude smaller, often revealing late-stage mergers, sometimes with tantalizing hints of sub-structure. One lensed galaxy in particular, the Cosmic Eyelash at z = 2.3, has been cited extensively as an example of where the interstellar medium exhibits obvious, pronounced clumps, on a spatial scale of ≈100 pc. Seven orders of magnitude more luminous than giant molecular clouds in the local Universe, these features are presented as circumstantial evidence that the blue clumps observed in many z ∼ 2–3 galaxies are important sites of ongoing star formation, with significant masses of gas and stars. Here, we present data from ALMA which reveal that the dust continuum of the Cosmic Eyelash is in fact smooth and can be reproduced using two Sérsic profiles with effective radii, 1.2 and 4.4 kpc, with no evidence of significant star-forming clumps down to a spatial scale of ≈80 pc and a star formation rate of <3 M⊙ yr−1.

Authors 8

1. Rob J. Ivison corresponding

   European Southern Observatory

   Affiliation as printed

   European Southern Observatory, Karl-Schwarzschild-Strasse 2 , D-85748 Garching, Germany

2. Johan Richard

   Lyon 1 Université · Centre National de la Recherche Scientifique · Centre de Recherche Astrophysique de Lyon

   Affiliation as printed

   Univ Lyon, Univ Lyon1, Ens de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574 , F-69230 Saint-Genis-Laval, France

   Univ Lyon, Univ Lyon1, Ens de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, F-69230, Saint-Genis-Laval, France

3. Andrew D. Biggs

   European Southern Observatory

   Affiliation as printed

   European Southern Observatory, Karl-Schwarzschild-Strasse 2 , D-85748 Garching, Germany

4. Martin A. Zwaan

   European Southern Observatory

   Affiliation as printed

   European Southern Observatory, Karl-Schwarzschild-Strasse 2 , D-85748 Garching, Germany

5. Edith G. Falgarone

   Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · École Normale Supérieure - PSL · Sorbonne Université · Laboratoire de Physique de l'Ecole Normale Supérieure · Université Paris Diderot

   Affiliation as printed

   Laboratoire de Physique de l’ENS, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot , Sorbonne Paris Cité, F-75005 Paris, France

6. V. Arumugam

   European Southern Observatory · Institut de Radioastronomie Millimétrique

   Affiliation as printed

   European Southern Observatory, Karl-Schwarzschild-Strasse 2 , D-85748 Garching, Germany

   Institut de Radioastronomie Millimétrique , 300 rue de la Piscine, F-38406 Saint-Martin d’Hères, France

7. Paul P. van der Werf Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , P.O. Box 9513, NL-2300 RA Leiden, the Netherlands

8. W. Rujopakarn

   Chulalongkorn University · National Astronomical Research Institute of Thailand

   Affiliation as printed

   Department of Physics, Faculty of Science, Chulalongkorn University , 254 Phayathai Road, Pathumwan, Bangkok TH-10330, Thailand

   National Astronomical Research Institute of Thailand (Public Organisation) , Don Kaeo, Mae Rim, Chiang Mai TH-50180, Thailand