Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/jwst/overview/history/drm/drm8.pdf Дата изменения: Unknown Дата индексирования: Tue Feb 5 14:10:20 2013 Кодировка: Поисковые слова: galaxy cluster

Next Generation Space Telescope

Ad-Hoc Science Working Group Design Reference Mission Proposal

The formation and evolution of galaxies III: Cluster galaxies
Program contacts: Simon Lilly, MikeFall, Massimo Stiavelli, Piero Madau, Avi Loeb, Jon Gardner, Marcia Rieke Scienti c category: DISTANT GALAXIES Instruments: OPT CAM, NIR CAM, NIR SPEC Days of observation: 21

Abstract
Rich clusters of galaxies are interesting as the most massive gravitationally bound objects in the Universe. Although containing only about 1 of all galaxies, they provide an environment for the formation and evolution of galaxies that is unique, and in many regards, the population of galaxies seen today in rich clusters di ers from that found in the eld. We therefore propose to complement the DRM programs that are targeted at eld galaxies with similar observations of 20 rich clusters or their progenitors at 1 z 5.


ASWG DRM Proposal The formation and evolution of galaxies III: Cluster galaxies

Observing Summary:
Target IMAGINGX7 IMAGINGX20 DIAGNOSTICX7 KINEMATICX20 KINEMATICX7

Con guration mode OPT CAM R3 NIR CAM R3 NIR SPEC R1000 NIR SPEC R5000 NIR SPEC R5000 Grand total days NOTE: This grand total 31 does not equal the number 21 given on page 1

RA TBD TBD TBD TBD TBD

Dec TBD TBD TBD TBD TBD

mAB 33 at I 32.5 at L 27 at L 27 at L 22 at N

Days 3 7 7 7 7 31

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ASWG DRM Proposal The formation and evolution of galaxies III: Cluster galaxies

Scienti c Ob jectives
Scienti c Ob jectives
Understanding the formation and evolution of galaxies at high redshifts is a central topic of the Origins program and a ma jor theme of the NGST DRM. Previous DRM proposals are aimed at carrying out deep imaging and spectroscopic surveys that are designed to yield a de nitive understanding of the eld galaxy population in the 1 z 5 redshift range and proto-galactic units at even higher redshifts in principle to z 20 , 40. Field galaxies are selected randomly without regard to their cluster environments and are thus typical" galaxies and the high redshift galaxies studied in these programs will evolve into galaxies similar to the Milky Way and other galaxies seen around us. However, about 1 of galaxies at the present epoch are found in rich clusters of galaxies. Rich clusters are of intrinsic interest in that they represent the most massive gravitationally bound structures in the Universe, with masses of order 1015 Msolar . The number densityof such structures in the Universe is thus a sensitive measure of the amplitude and gravitational growth of the density spectrum on large scales. Rich clusters of galaxies represent a unique environment for galaxies in manyways: a the average number density of galaxies is much higher than in the eld; b there is a hot high pressure intergalactic medium; c in many cases there is evidence for the deposition of large amounts of baryonic material out of the hot intergalactic medium in the form of cooling ows"; d the interactions between galaxies are at much higher velocities in clusters. Finally, even before the cluster forms, the collapsing density uctuation has an average densitymuch higher than surrounding regions, mimicing the dynamical environment of a super-critical Universe with 1. There are many indications that the formation evolution of galaxies in these unusual environments has indeed proceeded di erently from more typical eld" galaxies but it is not clear whether these primarily re ect di erences in the initial formation of the galaxies in regions of slightly higher average density or in the subsequent evolution in a di erent environment. Examples of these pronounced di erences include a the mix of di erent morphological types is di erentinrich clusters than in the eld, with a much higher fraction of early type galaxies that do not show evidence for ongoing star-formation; b the elliptical galaxies at 0 z 1 display a tight colour magnitude relation, suggesting an early and homogeneous formation of their constituent stellar populations; c clusters also display a large population of dwarf elliptical galaxies not present in the eld, and d the central cD galaxies the most massive and luminous galaxies in the Universe displaya number of unique properties. Because it is gravitationally bound to the cluster, the intergalactic medium is also more easily studied in rich clusters of galaxies than in the eld. A ma jor unanswered question concerns the origin of the metals in the intergalactic medium with a metallicity of approximately 1 3 solar, the intergalactic medium contains more metals than the galaxies in the cluster. Understanding the evolution of galaxies in clusters thus represents an important aspect 3


ASWG DRM Proposal The formation and evolution of galaxies III: Cluster galaxies of the general problem, and the proposed program is directed at addressing the following questions by contrasting the appearance and detailed properties of galaxies in young clusters at the highest possible redshifts with those in the eld. Key questions are as follows: Why did star formation stop at an early epoch in the giant ellipticals? What is the origin of the heavy elements seen in the intergalactic medium? What is the origin of the dwarf elliptical population? When did the cores of the great clusters form? Our proposed strategy is to observe galaxies in rich clusters of galaxies at high redshifts z 2 in the same way as eld galaxies will be observed with imaging and spectroscopic observations so as to allow comparisons to be made in the detailed properties of the galaxies. While the eld" surveys of random parts of the sky will sample galaxies in groups suchas the Local Group, they will not cover su cientvolume to yield large numbers of rich clusters and such environments must be studied with pointed observations at previously identi ed clusters. Almost no clusters are presently known at z 1 the number density of such clusters would set strong constraints on cosmogonic models but several indications suggest that the ellipticals in the cores of such clusters formed at higher redshifts and therefore that these proto-cluster cores should be detectable at z 2. Several search strategies show promise for nding such cluster cores in the future including the detections of clusters through the Sunyaev-Zeldovich e ect the S-Z signal is independent of distance producing secondary anisotropies on the CMB. The next generation of X-ray satellites will likely also nd clusters at high redhsifts, while deep wide- eld imaging surveys on ground-based telescopes should also yield samples of clusters at z 1. We propose to observe a future sample of such clusters at the highest possible redshifts with observations that are as similar as possible to those of the eld surveys. In fact, the nature of the clusters and the prior knowledge of their redshifts should lead to an increased e ciency of the observations. For instance, fewer lters need be used probably three instead of eight and the multiplexing gain of the slit masks should be increased. If possible, seven such clusters will be studied as follows: A, Aand a Imaging: In three lters placed at rest wavelengths of approximately 2000 4000 8000 to the depth of wide eld imaging survey total exposure time 1.3 days. A b Diagnostic spectroscopy One mask at R=1000 to observe of order 100 cluster galaxies in the rest-frame 3500A 7000A region, to a depth comparable to the eld survey exposure time 1 day. c Kinematic spectroscopy One mask at R=10000 to observe of order 100 cluster galaxies in H , to a depth comparable to the eld survey exposure time 1 day. Please see associated imaging and spectroscopic survey DRM proposals. 4

NGST Uniqueness Relationship to Other Facilities


ASWG DRM Proposal The formation and evolution of galaxies III: Cluster galaxies

Observing Strategy Special Requirements
Explained in detail in context of science above. 0.1 mas at 2 m 10000 at 1-5 m 2? arcmin2 at 1-5 m 15 mas 15 mas Minimum Spatial Resolution: Minimum Spectral Resolution: Minimum FOV: RMS o set accuracy: RMS repointing accuracy:

Precursor Supporting Observations

The target clusters must be found! CMB anisotropy measurements should yield S-Z candidates, and deep imaginging from the ground should also work. X-rays also a possiblility.

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