16.11.2012 Views

Extragalactic abstracts - IRSA - California Institute of Technology

Extragalactic abstracts - IRSA - California Institute of Technology

Extragalactic abstracts - IRSA - California Institute of Technology

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Spitzer_Approved_<strong>Extragalactic</strong><br />

Mar 25, 10 16:24 Page 609/742<br />

Spitzer Space Telescope − General Observer Proposal #30507<br />

Far−infrared Emission from the Coma Cluster <strong>of</strong> Galaxies<br />

Principal Investigator: Tetsu Kitayama<br />

Institution: Toho University<br />

Technical Contact: Tetsu Kitayama, Toho University<br />

Co−Investigators:<br />

Hidehiro Kaneda, <strong>Institute</strong> <strong>of</strong> Space and Astronautical Science<br />

Hidenori Takahashi, The University <strong>of</strong> Tokyo<br />

Yuka Yoshikawa Tajiri, The University <strong>of</strong> Tokyo<br />

Takashi Onaka, The University <strong>of</strong> Tokyo<br />

Itsuki Sakon, The University <strong>of</strong> Tokyo<br />

Naomi Ota, RIKEN<br />

Hirohisa Nagata, National Astronomical Observatory <strong>of</strong> Japan<br />

Kenkichi Yamada, Toho University<br />

Science Category: galaxy clusters and groups<br />

Observing Modes: MipsScan<br />

Hours Approved: 11.4<br />

Abstract:<br />

We propose MIPS observations <strong>of</strong> the Coma cluster <strong>of</strong> galaxies (A1656), aiming at<br />

the first firm detection <strong>of</strong> intergalactic dust grains. Clusters <strong>of</strong> galaxies<br />

provide a unique environment <strong>of</strong> dust−gas interactions; the X−ray emitting plasma<br />

can heat the dust to 10−20 K via collisions, as well as destroy small grains via<br />

sputtering. Recent claim <strong>of</strong> detecting collisionally heated dust grains in Coma<br />

by ISOPHOT (Stickel et al. 2002), however, has been much debated owing to<br />

insufficient quality <strong>of</strong> the data. With MIPS, we can test their result<br />

unambiguously for the first time. In addition, multi−wavelength detections<br />

enable us to determine both the amount and the mean temperature <strong>of</strong> the grains.<br />

Combined with X−ray and optical data, they further provide powerful clues to<br />

understanding the dust−gas interaction and the ejection history <strong>of</strong> dust from<br />

galaxies. In case <strong>of</strong> no detection, we are still able to place severe constraints<br />

on its amount, which is a meaningful step forward in the long−standing argument<br />

regarding the intergalactic dust. Our observation will therefore provide a<br />

unique opportunity <strong>of</strong> probing the nature <strong>of</strong> dust grains in relation to the<br />

ambient hot gas and host galaxies.<br />

Spitzer_Approved_<strong>Extragalactic</strong><br />

Printed_by_SSC<br />

Mar 25, 10 16:24 Page 610/742<br />

Spitzer Space Telescope − General Observer Proposal #40652<br />

Galaxy Evolution in the Cluster/Filament Environment<br />

Principal Investigator: Dale Kocevski<br />

Institution: University <strong>of</strong> <strong>California</strong>, Davis<br />

Technical Contact: Dale Kocevski, University <strong>of</strong> <strong>California</strong>, Davis<br />

Co−Investigators:<br />

Harald Ebeling, University <strong>of</strong> Hawaii<br />

Cheng−Jiun Ma, University <strong>of</strong> Hawaii<br />

Science Category: galaxy clusters and groups(high−z)<br />

Observing Modes: IracMap MipsScan<br />

Hours Approved: 16.0<br />

Abstract:<br />

Recent studies have found that the outskirts <strong>of</strong> galaxy clusters, such as the<br />

filament networks which feed them, play a pivotal role in driving galaxy<br />

evolution well before galaxies reach the cluster environment. Several processes<br />

have been proposed that would transform galaxies in the low−density regime, some<br />

<strong>of</strong> which directly suppress star formation activity and others that would instead<br />

trigger a burst <strong>of</strong> star formation that consumes most <strong>of</strong> the galaxy’s gas supply.<br />

We can directly test for this latter class <strong>of</strong> mechanisms by searching for a<br />

starbursting population <strong>of</strong> galaxies in and around clusters. Furthermore since<br />

many <strong>of</strong> the proposed processes are most effective at different galaxy and gas<br />

densities, the properties <strong>of</strong> the local environment in which starburst galaxies<br />

are found can help constrain the mechanisms which trigger them. We propose 3.6−8<br />

micron IRAC and 24 micron MIPS observations <strong>of</strong> a well defined and highly studied<br />

large−scale filament feeding the massive cluster MACS J0717.5+3745 at z=0.55.<br />

The filament is a highly coherent, spectroscopically confirmed structure<br />

detected in our galaxy surface density maps, weak lensing analysis and X−ray<br />

observations. We have compiled an extensive multi−wavelength dataset to aid in<br />

this study, including an 18−pointing, high−resolution HST ACS mosaic <strong>of</strong> the<br />

field. The environment around MACS J0717.5+3745 is well suited to investigate<br />

the mechanisms which trigger starburst activity and drive galaxy evolution in<br />

clusters as it provides a full range <strong>of</strong> environments to probe, from the cluster<br />

core to the filament−cluster interface and out to the low density regime <strong>of</strong> the<br />

filament proper. By examining the properties <strong>of</strong> the local environment in which<br />

starburst galaxies are activated, along with their morphological and<br />

spectroscopic attributes we can place strong constraints on the physical<br />

processes which trigger such activity and ultimately transform field galaxies<br />

into the passively evolving population <strong>of</strong> galaxies predominately found in<br />

clusters.<br />

Thursday March 25, 2010 xgal_covers.txt<br />

305/371

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!