NASA Hubble Space Telescope Daily Report #4016
HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science
DAILY REPORT #4016
PERIOD COVERED: UT December 27, 2005 (DOY 361)
OBSERVATIONS SCHEDULED
ACS/WFC 10181
ACS/NICMOS Imaging of Bright Lyman Break Galaxy Candidates from SDSS
The recent surprising discovery of six unusually bright {r~20 mag} Lyman break galaxy {LBG} candidates with z=2.45-2.80 in the Sloan Digital Sky Survey {SDSS} raises a number of questions that only HST can address. Specifically, what is the true nature of these objects, and what role if any is played by gravitational lensing? We propose to use the superior resolution and sensitivity of ACS and NICMOS to obtain deep images of these objects and their environments. Compared to SDSS images, HST will allow us to determine their morphologies {extended, point-source, or lensed}, the appearance of their environments {rich or poor}, and to detect any faint foreground groups or clusters that might be responsible for lensing these objects. All outcomes would be intriguing. If the objects are lensed, it increases from 1 {MS1512- cB58} to 7 the number of normal LBGs bright enough to study individually. If they are instead unlensed point sources, they will represent a new class of previously unidentified absorption- line quasars. Finally, if they are unlensed and extended star-forming galaxies, they are at least 4mag brighter than L_* LBGs, thus making them the most luminous star-forming objects yet seen, representing a heretofore unknown extreme population of objects.
ACS/WFC 10496
Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters
We propose a novel HST approach to obtain a dramatically more useful “dust free” Type Ia supernovae {SNe Ia} dataset than available with the previous GOODS searches. Moreover, this approach provides a strikingly more efficient search-and-follow-up that is primarily pre- scheduled. The resulting dark energy measurements do not share the major systematic uncertainty at these redshifts, that of the extinction correction with a prior. By targeting massive galaxy clusters at z > 1 we obtain a five-times higher efficiency in detection of Type Ia supernovae in ellipticals, providing a well-understood host galaxy environment. These same deep cluster images then also yield fundamental calibrations required for future weak lensing and Sunyaev-Zel’dovich measurements of dark energy, as well as an entire program of cluster studies. The data will make possible a factor of two improvement on supernova constraints on dark energy time variation, and much larger improvement in systematic uncertainty. They will provide both a cluster dataset and a SN Ia dataset that will be a longstanding scientific resource.
ACS/WFC 10574
Witnessing Galaxy Transformation in Galaxy Groups at z > 1
The recent discover of five galaxy groups in the Lynx supercluster region offers us the exciting opportunity to observe for the first time groups in the process of collapsing into a merging pair of clusters at z > 1. Our current picture of structure formation suggests that substantial evolution of galaxy properties can occur in groups and filaments well before they enter the environs of massive clusters. However, neither current theoretical models nor observations give us a complete understanding of the relative importance of the different physical processes that control the structural and spectral transformations that occur prior to, during, and after infall into a dense environment. We propose direct observation of these newly discovered dynamically young structures in the Lynx region, in order to provide a critical benchmark in testing not only whether galaxy evolution occurs mostly prior to entry into the densest regions but will also constrain the relative importance of initial conditions in determining the fate of galaxy systems. Our analysis of these proposed ACS measurements will be complemented with an unique dataset we have already in the optical, infrared, mid-infrared, and X-ray.
ACS/WFC 10765
The Discrete X-ray Source Population in NGC~5253, our nearest post-starburst
We propose a 140ksec ACIS-S and HST-ACS observations of NGC5253, our nearest post- starburst galaxy. This observation, together with archival data, will yield a sensitivity limit of 5×10^35 ergs allowing us to detect for the first time in an evolved star-burst galaxy, the vast majority of active HMXBs. Our major goal is to compare the various X-ray source populations {distinguished from their X-ray and optical properties} and associate them with the evolutionary stage of the starburst. By combining these data with observations of other nearby star-forming galaxies which with NGC~5253 form a starburst age sequence, we will investigate the variations of the XRB populations {and their XLF} as a function of the starburst age. This way we will test XRB population synthesis models.
WFPC2 10608
Probing the star formation law in the extreme outer limits of M83, a prototypical XUV-disk galaxy
The Galaxy Evolution Explorer {GALEX} has discovered a new sub-class of spiral galaxy, which we refer to as extended UV-disk {XUV-disk} galaxies. They are distinguished by conspicuous UV-bright star clusters located at galactocentric radii extending to many times the optical {R25} extent, and appear to represent a population of spiral galaxies still actively building, or augmenting, their stellar disk. However, XUV-disks pose a mystery in the form of a relative lack of HII regions {traced by H-alpha emission} associated with outer disk, UV-bright stellar clusters. M83 is an XUV-disk prototype and the focus of this proposal. It has an H-alpha surface brightness profile characterized by a steep decline at the radius beyond which the gaseous disk is thought to become dynamically stable {against collapse and ensuing star formation}, but GALEX UV profiles show no “edge” at this location. Our HST study of M83 aims to resolve this puzzling discrepancy, confirmed in several XUV-disks, by searching for Lyman-continuum producing O stars that are either absent or present without nebulosity. HST provides the only means of resolving individual massive stars in the FUV band at M83’s distance. Without HST, we lose the critical ability to photometrically classify O and B stars. Our multiwavelength observations will also constrain the history of star formation in the outer disk over Gyr timescales by characterizing the evolved stellar population, both using resolved giants and color analysis of the diffuse background.
WFPC2 10745
WFPC2 CYCLE 14 INTERNAL MONITOR
This calibration proposal is the Cycle 14 routine internal monitor for WFPC2, to be run weekly to monitor the health of the cameras. A variety of internal exposures are obtained in order to provide a monitor of the integrity of the CCD camera electronics in both bays {both gain 7 and gain 15 — to test stability of gains and bias levels}, a test for quantum efficiency in the CCDs, and a monitor for possible buildup of contaminants on the CCD windows. These also provide raw data for generating annual super-bias reference files for the calibration pipeline.
WFPC2 10751
WFPC2 CYCLE 14 Intflat Linearity Check and Filter Rotation Anomaly Monitor
Intflat observations will be taken to provide a linearity check: the linearity test consists of a series of intflats in F555W, in each gain and each shutter. A combination of intflats, visflats, and earthflats will be used to check the repeatability of filter wheel motions. {Intflat sequences tied to decons, visits 1-18 in prop 10363, have been moved to the cycle 14 decon proposal 10744 for easier scheduling.} Note: long-exposure WFPC2 intflats must be scheduled during ACS anneals to prevent stray light from the WFPC2 lamps from contaminating long ACS external exposures.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS: (None)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS GSacq 05 05
FGS REacq 10 10
OBAD with Maneuver 30 30
SIGNIFICANT EVENTS: (None)
