Extragalactic abstracts - IRSA - California Institute of Technology
Extragalactic abstracts - IRSA - California Institute of Technology
Extragalactic abstracts - IRSA - California Institute of Technology
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Spitzer_Approved_<strong>Extragalactic</strong><br />
Mar 25, 10 16:24 Page 599/742<br />
Spitzer Space Telescope − General Observer Proposal #20626<br />
Search for Infrared Emission from the Leo <strong>Extragalactic</strong> HI Cloud<br />
Principal Investigator: George Helou<br />
Institution: Caltech<br />
Technical Contact: George Helou, Caltech<br />
Co−Investigators:<br />
Yervant Terzian, Cornell University<br />
William Latter, SSC/Caltech<br />
Stephen Schneider, University <strong>of</strong> Massachussets<br />
Science Category: galaxy clusters and groups<br />
Observing Modes: IracMap MipsScan<br />
Hours Approved: 24.2<br />
Abstract:<br />
We propose to map at 8, 24, 70 and 160um the one intergalactic HI cloud that has<br />
remained undetected at any wavelength other than the 21−cm HI line. The Leo<br />
Cloud was discovered serendipitously, and mapped subsequently in detail at both<br />
Arecibo and the VLA. The radio data reveal kinematic and spatial structure that<br />
rules out an origin as a recent tidal tail, leaving most likely the scenario<br />
that this is primordial, relatively pristine material. A detection <strong>of</strong> the dust<br />
emission from the Cloud would provide the only radiative manifestation other<br />
than HI, and would allow us to estimate the dust content <strong>of</strong> the Cloud, and<br />
therefore its metallicity. Even an upper limit would help constrain its origin<br />
and history.<br />
Spitzer_Approved_<strong>Extragalactic</strong><br />
Printed_by_SSC<br />
Mar 25, 10 16:24 Page 600/742<br />
Spitzer Space Telescope − General Observer Proposal #20740<br />
Life on the Edges: Morphological Transformation <strong>of</strong> Galaxies in Clusters <strong>of</strong><br />
Galaxies at z=1<br />
Principal Investigator: Bradford Holden<br />
Institution: University <strong>of</strong> <strong>California</strong> Observatories/Lick Observ<br />
Technical Contact: Bradford Holden, UCO/Lick<br />
Co−Investigators:<br />
Daniel Kelson, Observatories <strong>of</strong> the Carnegie Institution <strong>of</strong> Washi<br />
John Blakeslee, The Johns Hopkins University<br />
Marijn Franx, Leiden Observatory<br />
Garth Illingworth, University <strong>of</strong> <strong>California</strong>, Santa Cruz<br />
Marc Postman, Space Telescope Science <strong>Institute</strong><br />
Kim−Vy Tran, ETH<br />
Science Category: galaxy clusters and groups<br />
Observing Modes: IracMap MipsPhot<br />
Hours Approved: 29.3<br />
Abstract:<br />
Between a redshift <strong>of</strong> one and today, the mix <strong>of</strong> morphologies inside clusters <strong>of</strong><br />
galaxies has changed. Both galaxy−galaxy mergers and passive processes have been<br />
proposed to explain this evolution. However, there is ample evidence that at<br />
z=1, clusters are still being formed out <strong>of</strong> infalling groups <strong>of</strong> galaxies.<br />
Therefore, these infalling groups are a likely location for the processes that<br />
drive morphological evolution. We propose for 15 by 15 arcminute mosaics using<br />
IRAC and MIPS in the vicinity <strong>of</strong> three z=0.8−0.9 clusters <strong>of</strong> galaxies. For each<br />
cluster, we have some or all <strong>of</strong> the HST ACS imaging required to measure the<br />
distribution <strong>of</strong> galaxy types and identify merger candidates. Our ongoing program<br />
<strong>of</strong> spectra and ground based imaging will determine the rest−frame optical<br />
properties and cluster membership. Spitzer’s unique window into the rest−frame<br />
near and mid−infrared will allow us to determine accurate stellar mass estimates<br />
and star formation rates, even for red galaxies with little optical evidence <strong>of</strong><br />
any activity. With these data, we will answer the questions: (1) do the<br />
infalling galaxies have a sufficient stellar mass to become a typical z=0<br />
cluster galaxy, (2) are the mergers we observe among the infalling galaxies<br />
"dry" or are they undergoing massive amounts <strong>of</strong> star formation, and (3) are the<br />
star formation histories <strong>of</strong> these infalling galaxies consistent with them<br />
becoming the massive systems dominated by old stellar populations that we see in<br />
clusters <strong>of</strong> galaxies today?<br />
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