Extragalactic abstracts - IRSA - California Institute of Technology

Spitzer_Approved_Extragalactic
Mar 25, 10 16:24 Page 573/742
Spitzer Space Telescope − General Observer Proposal #20606
The evolution of early−type galaxies in nearby clusters: breaking the
age−metallicity degeneracy with Spitzer IRS Blue Peak−Up Imaging
Principal Investigator: Alessandro Bressan
Institution: INAF Padova Astronomical Observatory
Technical Contact: Alessandro Bressan, INAF Padova Astronomical Observatory
Co−Investigators:
Pasquale Panuzzo, INAF Padova
Roberto Rampazzo, INAF Padova
Lucio Buson, INAF Padova
Marcel Clemens, INAF Padova
Jose Ramon Valdes, INAOE
Gian Luigi Granato, INAF Padova
Laura Silva, INAF Trieste
Luigi Danese, SISSA
Science Category: galaxy clusters and groups
Observing Modes: IracMap IrsPeakupImage
Hours Approved: 48.9
Abstract:
We have shown with Cycle 1 observations that Spitzer has the capability of
disentangling age and metallicity in old stellar populations. By looking to the
broad emission feature left by dust enshrouded asymptotic giant branch stars
above 9.7 microns, Spitzer IRS can provide direct evidence that the colour−
magnitude relation of Virgo ellipticals is mainly driven by metallicity.
However, with the IRS spectrograph we can only probe the bright tail of the
colour−magnitude relation, and only in the nearest cluster. We propose to use
IRS Blue Peak−Up, the only Spitzer band that looks directly in the core of that
spectral feature, to reach fainter galaxies. We will perform a thorough
investigation of early type galaxies along the colour−magnitude relation in
Virgo and in Coma clusters. These observations, when coupled with already
existing IRAC and Optical−NIR observations, will allow a) an unbiased census of
the stellar populations in cluster early type galaxies; b) an estimate of the
AGB material recycled into the ISM in these systems; c) a direct check of the
universality of the colour− magnitude relation on a wide range of magnitudes;
d) a spatial study of the stellar populations within the galaxies, e.g.
investigating differences between bulge and disk populations within S0; e) the
most secure reference frame with which to compare the evolution of early type
galaxies in other environments (groups and field).
Spitzer_Approved_Extragalactic
Printed_by_SSC
Mar 25, 10 16:24 Page 574/742
Spitzer Space Telescope − Archive Research Proposal #50416
Star Formation and AGN Feedback in Brightest Cluster Galaxies
Principal Investigator: Megan Donahue
Institution: Michigan State University
Technical Contact: Megan Donahue, Michigan State University
Co−Investigators:
G. Mark Voit, Michigan State University
Kenneth Cavagnolo, Michigan State University
Robert O’Connell, University of Virginia
Science Category: galaxy clusters and groups(low−z)
Dollars Approved: 100000.0
Abstract:
Feedback from active galactic nuclei at the centers of galaxies clusters has
become crucial to our understanding of star formation in brightest cluster
galaxies (BGCs). X−ray observations have long suggested that intracluster gas
should be condensing and forming stars at the centers of galaxy clusters.
However, observed levels of star formation in these systems are only 1%−10% of
the cooling rate expected from early X−ray imaging. Now Chandra observations are
showing clear signs of AGN feedback in the form of cavities in the X−ray gas,
indicating that AGNs somehow act to limit star formation in BCGs. Yet, in many
BGCs star formation still continues at a reduced level, and there are now
abundant observations in the Spitzer archive that can help us study it. We are
therefore proposing a Spitzer archival program to compare the IR signatures of
star formation in BCGs with X−ray observations of those same systems that
provide information about the history of AGN feedback, in order to clarify the
relationship between star formation and feedback in the universe’s largest
galaxies.
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