NASA Hubble Space Telescope Daily Report: # 4510
HUBBLE SPACE TELESCOPE DAILY REPORT # 4510
Continuing to collect World Class Science
PERIOD COVERED: UT December 18, 2007 (DOY 352)
OBSERVATIONS SCHEDULED
ACS/SBC 11199
A Hard Look at Stellar Disks at the Epoch of Planet Formation
We propose to use HST/ACS/SBC and Chandra/ACIS-S3 to observe the high energy fluxes of 4 stars surrounded by disks in the newly discovered aggregate 25 Ori, the most populous 10 Myr group known within 500 pc. Our observations will cover the 1-25A and 1250-2000A bandpasses, and will complement our optical and Spitzer data for these objects, to provide essential input to physically-consistent models of disk structure and chemistry in the age range around 10 Myr, thought to be a critical period in the planet- forming process. We will be able to determine the Ne/O ratio and determine if the anomalous metal abundances observed in X-ray spectra of young stars are an evolutionary or an environmental effect. Our proposed observations will double the number of 10 Myr old accreting stars with known high energy radiation fields, and will be the first FUV observations of low mass accreting stars in an OB association.
FGS 11211
An Astrometric Calibration of Population II Distance Indicators
In 2002 HST produced a highly precise parallax for RR Lyrae. That measurement resulted in an absolute magnitude, M{V}=3D 0.61+/-0.11, a useful result, judged by the over ten refereed citations each year since. It is, however, unsatisfactory to have the direct, parallax-based, distance scale of Population II variables based on a single star. We propose, therefore, to obtain the parallaxes of four additional RR Lyrae stars and two Population II Cepheids, or W Vir stars. The Population II Cepheids lie with the RR Lyrae stars on a common K-band Period-Luminosity relation. Using these parallaxes to inform that relationship, we anticipate a zero-point error of 0.04 magnitude. This result should greatly strengthen confidence in the Population II distance scale and increase our understanding of RR Lyrae star and Pop II Cepheid astrophysics.
NIC1/NIC2/NIC3 8795
NICMOS Post-SAA calibration – CR Persistence Part 6
A new procedure proposed to alleviate the CR-persistence problem of NICMOS. Dark frames will be obtained immediately upon exiting the SAA contour 23, and every time a NICMOS exposure is scheduled within 50 minutes of coming out of the SAA. The darks will be obtained in parallel in all three NICMOS Cameras. The POST-SAA darks will be non- standard reference files available to users with a USEAFTER date/time mark. The keyword ‘USEAFTER=3Ddate/time’ will also be added to the header of each POST-SAA DARK frame. The keyword must be populated with the time, in addition to the date, because HST crosses the SAA ~8 times per day so each POST-SAA DARK will need to have the appropriate time specified, for users to identify the ones they need. Both the raw and processed images will be archived as POST-SAA DARKSs. Generally we expect that all NICMOS science/calibration observations started within 50 minutes of leaving an SAA will need such maps to remove the CR persistence from the science i mages. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.
WFPC2 11083
The Structure, Formation and Evolution of Galactic Cores and Nuclei
A surprising result has emerged from the ACS Virgo Cluster Survey {ACSVCS}, a program to obtain ACS/WFC gz imaging for a large, unbiased sample of 100 early-type galaxies in the Virgo Cluster. On subarcsecond scales {i.e., <0.1"-1"}, the HST brightness profiles vary systematically from the brightest giants {which have nearly constant surface brightness cores} to the faintest dwarfs {which have compact stellar nuclei}. Remarkably, the fraction of galaxy mass contributed by the nuclei in the faint galaxies is identical to that contributed by supermassive black holes in the bright galaxies {0.2%}. These findings strongly suggest that a single mechanism is responsible for both types of Central Massive Object: most likely internally or externally modulated gas inflows that feed central black holes or lead to the formation of "nuclear star clusters". Understanding the history of gas accretion, star formation and chemical enrichment on subarcsecond scales has thus emerged as the single most pressing question in the study of nearby galactic nuclei, either active or quiescent. We propose an ambitious HST program {199 orbits} that constitutes the next, obvious step forward: high-resolution, ultraviolet {WFPC2/F255W} and infrared {NIC1/F160W} imaging for the complete ACSVCS sample. By capitalizing on HST's unique ability to provide high-resolution images with a sharp and stable PSF at UV and IR wavelengths, we will leverage the existing optical HST data to obtain the most complete picture currently possible for the history of star formation and chemical enrichment on these small scales. Equally important, this program will lead to a significant improvement in the measured structural parameters and density distributions for the stellar nuclei and the underlying galaxies, and provide a sensitive measure of "frosting" by young stars in the galaxy cores. By virtue of its superb image quality and stable PSF, NICMOS is the sole instrument capable of the IR observations proposed here. In the case of the WFPC2 observations, high-resolution UV imaging {< 0.1"} is a capability unique to HST, yet one that could be lost at any anytime.
WFPC2 11128
Time Scales Of Bulge Formation In Nearby Galaxies
Traditionally, bulges are thought to fit well into galaxy formation models of hierarchical merging. However, it is now becoming well established that many bulges formed through internal, secular evolution of the disk rather than through mergers. We call these objects pseudobulges. Much is still unknown about pseudobulges, the most pressing questions being: How, exactly, do they build up their mass? How long does it take? And, how many exist? We are after an answer to these questions. If pseudobulges form and evolve over longer periods than the time between mergers, then a significant population of pseudobulges is hard to explain within current galaxy formation theories. A pseudobulge indicates that a galaxy has most likely not undergone a major merger since the formation of the disk. The ages of pseudobulges give us an estimate for the time scale of this quiescent evolution. We propose to use 24 orbits of HST time to complete UBVIH imaging on a sample of 33 nearby galaxies that we have observed with Spitzer in the mid-IR. These data will be used to measure spatially resolved stellar population parameters {mean stellar age, metallicity, and star formation history}; comparing ages to star formation rates allows us to accurately constrain the time scale of pseudobulge formation. Our sample of bulges includes both pseudo- and classical bulges, and evenly samples barred and unbarred galaxies. Most of our sample is imaged, 13 have complete UBVIH coverage; we merely ask to complete missing observations so that we may construct a uniform sample for studying bulge formation. We also wish to compare the stellar population parameters to a variety of bulge and global galaxy properties including star formation rates, dynamics, internal bulge morphology, structure from bulge-disk decompositions, and gas content. Much of this data set is already or is being assembled. This will allow us to derive methods of pseudobulge identification that can be used to accurately count pseudobulges in large surveys. Aside from our own science goals, we will present this broad set of data to the community. Thus, we waive proprietary periods for all observations.
WFPC2 11222
Direct Detection and Mapping of Star Forming Regions in Nearby, Luminous Quasars
We propose to carry out narrow-band emission line imaging observations of 8 quasars at z=3D0.05-0.15 with the WFPC2 ramp filters and with the NICMOS narrow-band filters. We will obtain images in the [O II], [O III], H-beta, and Pa-alpha emission line bands to carry out a series of diagnostic tests aimed at detecting and mapping out star-forming regions in the quasar host galaxies. This direct detection of star-forming regions will confirm indirect indications for star formation in quasar host galaxies. It will provide a crucial test for models of quasar and galaxy evolution, that predict the co-existence of starbursts and “monsters” and will solve the puzzle of why different indicators of star formation give contradictory results. A secondary science goal is to assess suggested correlations between quasar luminosity and the size of the narrow-line region.
WFPC2 11344
Velocity Gradients in the Jets of BL Lac Objects
We propose to observe the arcsec-scale jets of 2 BL Lac objects with highly relativistic jets (bulk Lorentz factor of 16) on parsec scales in order to determine whether a velocity gradient exists between the axis and edge of the jet and along the length of the jet. Models both for the morphology of jets in BL Lac objects and for the launching of the jet predict such gradients. If radio-selected BL Lac objects are end-on FR 1 sources, there should be strong X-ray emission from inverse Compton scattering of CMB photons along the highly beamed fast spine of the jet. The imaging observations with Chandra, HST, SST, and the VLA will therefore verify whether such a spine exists and on what length scale it decelerates to nonrelativistic speeds.
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: 17597-9 – FHST Stuck-on-Bottom Macro Execution
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS GSacq 05 05
FGS REacq 11 11
OBAD with Maneuver 32 32
SIGNIFICANT EVENTS: (None)
