***************************************************
SECOND ANNOUNCEMENT
"Up: Have Observations Revealed a Variable Upper
End of the Initial Mass Function?"
to be held June 20-25, 2010,
in Sedona, Arizona, USA
http://up2010.obs.carnegiescience.edu
DEADLINE FOR ABSTRACT SUBMISSION IS
MONDAY, FEBRUARY 15, 2010
***************************************************
MEETING ABSTRACT
The stellar initial mass function (IMF) is a
fundamental parameter that not only encodes the
complex gas phase astrophysics of star formation,
but is also crucial for interpreting the vast
majority of observations made in extragalactic
astronomy today. Therefore, it is imperative to
constrain its functional form, and the manner in
which it may vary between different environments.
Since the idea of the "original" mass function
was introduced by Salpeter in 1955, considerable
effort has been made to verify its form, and
previous observations have led many to assume that
it is invariant. In recent years, however, work
challenging this assumption has been accumulating.
In particular, some observations and models suggest
a deficiency of high mass stars in low-density
regions, such as those found in star-forming dwarf
galaxies and the outer disks of spiral galaxies.
Other observations suggest an excess of high mass
stars in some regions, including starbursts and high
redshift galaxies. High mass stars dominate the
luminous and chemical output of galaxies, and
are the basis of most star formation indicators. If
such variations are proven real, they would have
broad consequences for studies of the star
formation histories and chemical evolution
of galaxies, and theoretical work on star
formation.
A general commonality of recent work providing
possible evidence for IMF variations is that they
are based on the light integrated over galaxies
or regions of galaxies. Such observations only provide
indirect constraints, since IMF variations will be
degenerate with population age and star formation
history. A range of other confounding parameters
must also be considered given that stars are not
being measured individually. On the other hand,
there is some evidence for consistency between
observations and semi-analytic models which assume
systematic deficiencies or excesses in high mass stars.
The presence of observations both for and against
the universality of the IMF suggest that this is an
appropriate time for a critical re-evaluation of the
ensemble of accumulated observational evidence
constraining the upper end of the IMF, and for
garnering new insights into the physical parameters
controlling high mass star and cluster formation.
The goal of this meeting will be to synthesize a
coherent picture of the IMF slope and characteristic
mass within individual galaxies and across the galaxy
population. Further implications and observational
tests of potential IMF variations must also
be formulated, particularly in the context of the
new capabilities enabled by the recent refurbishment
of HST, the next generation of extremely large
telescopes, or capabilities not yet planned that
must be developed to finally provide unambiguous
constraints on this fundamental astrophysical issue.
SOC: Daniela Calzetti, Edvige Corbelli, Julianne Dalcanton,
Bruce Elmegreen, Janice Lee (chair), Mark Krumholz,
Pavel Kroupa, Barry Madore, Francesca Matteucci,
Chris Martin, Naveen Reddy, David Schiminovich,
Mark Seibert, David Thilker
