Extragalactic abstracts - IRSA - California Institute of Technology

Spitzer_Approved_Extragalactic
Mar 25, 10 16:24 Page 275/742
Spitzer Space Telescope − Guaranteed Time Observer Proposal #198
Tidal Dwarf Galaxies
Principal Investigator: James R. Houck
Institution: Cornell University
Technical Contact: Sarah Higdon, Cornell University
Science Category: high−z galaxies (z>0.5)
Observing Modes: IracMap IrsStare
Hours Approved: 10.9
Abstract:
Tidal Dwarf Galaxies (TDG’s) are formed from material stripped from the disks of
spiral galaxies, which are undergoing tidal interactions with a nearby
companion. These galaxies provide important clues to our understanding of galaxy
formation, evolution and cosmic recycling. Using the IRS we will measure the
star formation activity in 6 TDG candidates. We will measure the ionization
state ( [NeII] 12.8 um, [NeIII] 15.6 um and [NeV] 14.3um and [OIV] 25.9 um), the
density in the ionized gas ([SIII] 18.7um/33.5um), the PAH fractions at 5.5−9um
and 11−12.2um and possibly (optimistic here!) molecular hydrogen emission form
PDRs at H2 (S0) 28um and H2 (S1) at 17um. In addition to the IRS observations we
will map both the Guitar and Stephan’s Quintet with IRAC. This will enable us to
compare the PAH fraction in the dwarf galaxy to that of its parent. Similarly we
will compare our observation of the proposed TDG at the southern tip of NGC 4038
with the GT observations of the central region of the Antennae. This program
compliments two existing GT programmes: 1) the high−Z program − these
observations enable us to observe in fine detail the nearby/present day analogs
of galaxy formation in the early universe. 2) Blue Compact Dwarf programme − On
first inpsection BCD’s and TDG’s appear the same: BCDs are similar in size to
TDG’s, but TDG’s may not have a large dark matter halo component (affecting the
long term stability of an object) and BCD’s typically have a much lower
metallicity. We will be able to compare the star formation activity in terms of
the ionization state and PAH fraction in the two galaxy types.
Spitzer_Approved_Extragalactic
Printed_by_SSC
Mar 25, 10 16:24 Page 276/742
Spitzer Space Telescope − Guaranteed Time Observer Proposal #30184
Spitzer Observations Of A Z=2.3 Galaxy Cluster
Principal Investigator: James R. Houck
Institution: Cornell University
Technical Contact: James R. Houck, Cornell University
Co−Investigators:
James Higdon, Cornell University
Sarah Higdon, Cornell University
Terry Herter, Cornell University
Science Category: high−z galaxies (z>0.5)
Observing Modes: IracMap MipsPhot
Hours Approved: 3.0
Abstract:
Understanding the development of large scale structure and the evolution of
galaxies in high−redshift clusters are key goals of observational astrophysics.
We have identified a cluster of 14 luminous H−alpha emission line sources within
a ~2 Mpc diameter region at z=2.3 towards the quasar FBQS J1416+2649. The J1416
cluster represents one of the richest known high−z galaxy clusters. We will use
3−hours of Spitzer Space Telescope time to otbain deep IRAC 3.6−8.0 um and MIPS
24 um images of the J1416 cluster in order to measure the rest−frame near− and
mid−infrared emission from the 14 robustly star forming (or AGN dominated)
galaxies. The final rest−frame optical to mid−infrared spectral energy
distribution will be used to (1) constrain the evolved stellar populations in
the cluster galaxies, allowing us to (2) model their star formation histories
(i.e., recent starburst or exponentially decaying SFR, etc.) with Starburst99
and Pegase. Moreover, we will (3) identify highly obscured cluster galaxies and
AGN and (4) estimate photometric redshifts for objects dominated by evolved
stars throughout the young galaxy cluster. Selecting cluster galaxies based on
both massive star formation and evolved stellar content will yield a more
complete census of star and galaxy formation in an important epoch.
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