Extragalactic abstracts - IRSA - California Institute of Technology

Spitzer_Approved_Extragalactic
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Spitzer Space Telescope − General Observer Proposal #20610
Molecular Gas In The Nearby Extremely Metal−Poor Dwarf Galaxy Leo A
Principal Investigator: John Cannon
Institution: Max Planck Institute for Astronomy
Technical Contact: John Cannon, Max Planck Institute for Astronomy
Co−Investigators:
Fabian Walter, Max Planck Institute for Astronomy
Evan Skillman, University of Minnesota
Science Category: local group galaxies
Observing Modes: IrsMap
Hours Approved: 6.6
Abstract:
Knowledge of the nature of molecular gas at sub−solar metallicities is essential
for understanding the process of star formation both in the local and the
high−redshift universe. CO is usually used to trace the molecular phase, but
there have been no extragalactic detections of CO in environments more metal
poor than the SMC. With detailed studies of nearby metal−deficient systems, we
can discern trends between molecular gas properties and ambient metallicity that
may be generalized to more distant systems. In this project we propose IRS
spectral mapping observations of carefully−selected star formation regions in
the nearby extremely metal−poor (less than 5% solar abundance) dwarf galaxy Leo
A, concentrating on the S(0) H2 pure rotational line at 28 microns. The
unprecedented sensitivity of Spitzer will allow variations in molecular gas
content to be studied as a function of HI column density, stellar population, HI
line width, H Alpha luminosity, and dust content. These data will directly probe
the molecular phase, overcoming the limitations of tracer species that may be
environmentally−dependent. These observations are designed to provide the first
detections of molecular gas in extremely metal−poor environments, thus giving
new insights into the low−metallicity ISM. These observations will allow a
concise investigation of the H2 content of low−metallicity galaxies in a modest
number of telescope hours, and the results will be applicable to a wide range of
models of star formation at low metallicities.
Spitzer_Approved_Extragalactic
Printed_by_SSC
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Spitzer Space Telescope − Archive Research Proposal #30836
Star Formation in the Large Magellanic Cloud
Principal Investigator: You−Hua Chu
Institution: University of Illinois at Urbana−Champaign
Technical Contact: You−Hua Chu, University of Illinois at Urbana−Champaign
Co−Investigators:
Robert Gruendl, University of Illinois
Leslie Looney, University of Illinois
Rosie Chen, University of Illinois
Rosa Williams, University of Illinois
Mordecai Mac Low, American Museum of Natural History
Lee Hartmann, University of Michigan
Nuria Calvet, University of Michigan
Wolfgang Brandner, Max Planck Institute
Chris Smith, CTIO
Sean Points, CTIO
John Dickel, University of New Mexico
Science Category: local group galaxies
Dollars Approved: 100000.0
Abstract:
Star formation is fundamental to the evolution of galaxies. It can be simply
described on global scales, but shows remarkable variation on local scales.
Theoretical models describe numerous paths to star formation, from global
gravitational instability to local formation dynamically triggered by cloudlet
compression in superbubbles, compression by H II region expansion, and gas
accumulation in the borders of supergiant shells. For a better understanding of
star formation, one must empirically relate the initial level of gravitational
instability, and any triggering mechanisms, to the final result. The Large
Magellanic Cloud (LMC) is the optimal site for such a study, as it is close
enough to resolve protostars, yet not subject to the line−of−sight confusion of
the Galaxy. Our Cycle 1 IRAC/MIPS observations of seven LMC HII complexes
revealed a wide range of triggered star formation phenomena. The Spitzer survey
of the LMC (SAGE), carried out in Cycle 2, reveals massive protostars throughout
the entire LMC galaxy, allowing studies of global star formation. We propose to
use the archival data from the Spitzer survey, and multi− wavelength surveys of
stars and ISM in the LMC, to study star formation. We will examine both the
interstellar conditions that lead to star formation, and the mass functions and
clustering properties of protostars that are formed. For the former we will
evaluate the gravitational potential from the stellar and gas surface densities;
search for expanding shells that may be triggers; and examine the physical
conditions in star formation sites. For the latter we will create a census of
protostar candidates and their spatial distribution. Combined, these will allow
us to determine the causes of star formation and how these affect the mass
function and clustering properties of the stars formed.
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