|Proposal Number||Subject Category||PI Name||Target Name||Total Chandra Time||Title|
|08701038||Active Galaxies and Quasars||John Biretta||M87 (NGC4486)||35ks||HST / Chandra Monitoring of a Dramatic Flare in the M87 Jet|
|08801039||Clusters of Galaxies||Mike Gladders||RCS2-2327.4-0204||25ks||The Halo Structure of RCS2-2327.4-0204|
Subject Category: Active Galaxies and Quasars
Proposal Number: 08701038
Title:HST / Chandra Monitoring of a Dramatic Flare in the M87 Jet
PI Name: John Biretta
As the nearest galaxy with an optical jet, M87 affords an unparalleled opportunity to study extragalactic jet phenomena at the highest resolution. During 2002, HST and Chandra monitoring of the M87 jet detected a dramatic flare in knot HST-1 located ~1" from the nucleus. Its optical brightness eventually increased seventy-fold and peaked in 2005; the X-rays show a similarly dramatic outburst. In both bands HST-1 is still extremely bright and greatly outshines the galaxy nucleus. To our knowledge this is the first incidence of an optical or X-ray outburst from a jet region which is spatially distinct from the core source -- this presents an unprecedented opportunity to study the processes responsible for non-thermal variability and the X-ray emission. We propose five epochs of HST/ACS flux monitoring during Cycle 15, as well as seven epochs of Chandra/ACIS observation (5ksec each, five Chandra epochs contemporary with HST). At two of the HST/ACS epochs we also gather spectral information and map the magnetic field structure. The results of this investigation are of key importance not only for understanding the nature of the X-ray emission of the M87 jet, but also for understanding flares in blazar jets, which are highly variable, but where we have never before been able to resolve the flaring region in the optical or X-rays. These observations will allow us to test synchrotron emission models for the X- ray outburst, constrain particle acceleration and loss timescales, and study the jet dynamics associated with this flaring component.
Subject Category: Clusters of Galaxies
Proposal Number: 08801039
Title: The Halo Structure of RCS2-2327.4-0204
PI Name: Mike Gladders
We propose ACS, NICMOS, and Chandra observations of the central region of the extraordinary and newly discovered galaxy cluster: RCS2-2327.4-0204 at z=0.700. This cluster shows 3 or more arcs in ground-based imaging, with an Einstein radius of 49". Such a large Einstein radius (3-4 times larger than seen in most clusters) has been seen in precisely one other cluster in the universe - namely Abell 1689 at z=0.18. From our proposed data we expect to see ~70 lensed source images, from ~20 image families. We will use both strong and weak lensing constraints from these data to construct the central mass profile of the cluster, which, when combined with ground based data extending to a half degree FOV, will allow us to measure critically important dark matter halo parameters (such as concentration). The target cluster is selected from a large ongoing survey with a well- defined search volume, which allows us to compare our results to expectations from simulations. We will also compare the lensing derived mass profiles to the x-ray equivalent measures; this will illuminate whether the dominant baryonic component is in equilibrium with the potential. The area of high magnification behind this cluster is an order of magnitude larger than typical lensing clusters observed previously by HST; this order of magnitude increase in area directly translates into a 10 times better chance for finding very high redshift galaxies. Many of the highest redshift galaxies found to date have been found behind massive lensing clusters observed by HST, and we expect to add to that sample dramatically.