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Dear all,<br>
this week our weekly seminar will take place on <b>Thursday</b> at
10:30 instead of Friday.<br>
<br>
Title: A revised picture of properties of clumps observed in distant
star-forming galaxies.<br>
Speaker: Miroslava Dessauges-Zavadsky (Geneva Observatory).<br>
<br>
<b>Thursday</b> 2nd of November from 10:30 to 11:30 at <b>FB54</b>.<br>
<br>
Abstract:<br>
Clumpy rest-frame UV morphologies have been revealed among z=1-3
star-forming galaxies, with the majority of galaxies shown to be
dominated by ordered disk rotation. It has been suggested that the
observed clumps are formed during the disk fragmentation resulting
from gravitational instabilities maintained by the gas inflow onto
galaxies. The physical properties (masses and radii) of these clumps
and their possible role in the galactic bulge formation are,
however, largely debated both on the observational point of view and
in numerical simulations. Comparing clumps selected in different
ways, and in lensed or blank field galaxies, we examine the effects
of spatial resolution and sensitivity on the inferred stellar masses
and radii. Large differences are found, with median stellar masses
ranging from ~109 M☉ for clumps in the often-referenced field
galaxies to ~107 M☉ for fainter clumps selected in deep-field or
lensed galaxies. We argue 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. Furthermore, we show that the sensitivity threshold used for
the clump selection affects the inferred masses even more strongly
than resolution, biasing clumps at the low-mass end. Both improved
spatial resolution and sensitivity appear to shift the clump stellar
mass distribution to lower masses by almost two orders of magnitude,
in agreement with clump masses found in recent high-resolution
simulations of disk fragmentation. We discuss: (1) the nature of the
most massive clumps and the connection with the mass of their host
galaxies; and (2) the existence of a characteristic clump mass scale
against the hierarchical structure of clumps. Finally, we provide a
direct proof of the resolution and sensitivity effects on clump
properties thanks to a unique case-study supplied by an exceptional
lensing configuration in the field of the galaxy cluster MACSJ1206,
allowing to reach in one counter-image 30 pc physical scales in a
z=1 galaxy. A coherent view of the formation and evolution of clumps
in distant galaxies emerges fully in agreement with state-of-the art
numerical and mock simulations.<br>
<br>
<br>
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