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<p>Hello</p>
<p>On Friday the 17h we have the third astronomy seminar of the year
with our own Nushkia Chamba (Stockholm University) speaking via
Zoom at 10:30.</p>
<p><b>Unveiling the outskirts of galaxies using deep imaging </b>
</p>
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<p class=""><span style="font-size: 11pt;" class="">The
traditional measurement of the size of galaxies, the
effective radius, is a relic of the epoch when shallow
imaging was unable to capture the full extension of
astronomical sources. However, current deep imaging
surveys have revolutionised our view of galaxies and the
characteristics of their faint outskirts, allowing us to
regard critically our own conventions. From this
perspective, it is time to move from a size definition
based on the light concentration of galaxies, the
effective radius, to a definition that intuitively
captures the concept of the size of galaxies, such as its
edge or boundary. In this talk, a physically motivated
definition for the size of a galaxy based on the gas
density threshold value for star formation in galaxies is
studied. Remarkably, the new size definition not only
captures what the human visual system identifies as the
edge of a galaxy, but also dramatically decreases the
scatter in the stellar mass–size relation by more than a
factor of two. Compared to other size measures, the new
parameter is unique in that it also unifies galaxies
spanning five orders of magnitude in stellar mass on a
single mass–size relationship. To place this discovery in
the context of galaxy formation and evolution, its
application is discussed on the understanding of the
origin of discs and the nature of ultra-diffuse galaxies.</span></p>
<p>We are trying something new this year with leaving the Zoom
call open after the formal hour of the seminar is up to
allow the speaker, if they wish, to chat informally with
anyone who is interested.</p>
Thanks<br>
<p> Chris and Tine</p>
<p>Christopher Usher is inviting you to a scheduled Zoom
meeting.
<br>
<br>
Topic: Astronomy Department Seminar - Nushkia Chamba
<br>
Time: Sep 17, 2021 10:30 AM Stockholm
<br>
<br>
Join Zoom Meeting
<br>
<a class="moz-txt-link-freetext" href="https://stockholmuniversity.zoom.us/j/68003268702?pwd=Q085dHZrT0Y0djZHelZNL3RVb2x0Zz09">https://stockholmuniversity.zoom.us/j/68003268702?pwd=Q085dHZrT0Y0djZHelZNL3RVb2x0Zz09</a>
<br>
<br>
Meeting ID: 680 0326 8702
<br>
Passcode: eRmiTeXA
<br>
One tap mobile
<br>
46844682488,,68003268702</p>
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