Status Report

NASA Hubble Space Telescope Daily Report #3943

By SpaceRef Editor
September 13, 2005
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HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT         # 3943

PERIOD COVERED: UT September 12, 2005 (DOY 255)


ACS/HRC 10559

Astrometric monitoring of binary L and T dwarfs

We propose to obtain high angular resolution ACS images of five binary L and T dwarfs in order to determine their orbital parameters and dynamical masses, and directly constrain the evolutionary models of ultracool and substellar objects. The binaries have estimated periods ranging between 5 and 14 years. All of them have already been resolved at least twice {sometimes more} using HST, providing first and second epochs measurements. We propose to obtain two more ACS imaging observations separated by 9 to 12 months during cycle 14. The expected period coverage should therefore range between 35% and 117%, allowing us to compute precise orbital parameters and masses. Our sample is large enough and covers a sufficiently wide range of spectral types {from L3 to T5.5} to allow us to obtain strong constraints the evolutionnary models.

ACS/HRC 10606

Ultraviolet Snapshots of 3CR Radio Galaxies

Radio galaxies are an important class of extragalactic objects: they are one of the most energetic astrophysical phenomena and they provide an exceptional probe of the evolving Universe, lying typically in high density regions but well-represented across a wide redshift range. In earlier Cycles we carried out extensive HST observations of the 3CR sources in order to acquire a complete and quantitative inventory of the structure, contents and evolution of these important objects. Amongst the results, we discovered new optical jets, dust lanes, face-on disks with optical jets, and revealed point-like nuclei whose properties support FR-I/BL Lac unified schemes. Here, we propose to obtain ACS NUV images of 3CR sources with z<0.3 as a major enhancement to an already superb dataset. We aim to reveal dust in galaxies, regions of star and star cluster formation frequently associated with dust and establish the physical characteristics of the dust itself. We will measure frequency and spectral energy distributions of point-like nuclei, seek spectral turnovers in known synchrotron jets and find new jets. We will strongly test unified AGN schemes and merge these data with existing X-ray to radio observations for significant numbers of both FR-I and FR-II sources. The resulting database will be an incredibly valuable resource to the astronomical community for years to come.


ACS CCDs daily monitor – Cycle 13 – Part 2

This program consists of a set of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. The files, biases and dark will be used to create reference files for science calibration. This program will be for the entire lifetime of ACS.

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 10505

The Onset of Star Formation in the Universe: Constraints from Nearby Isolated Dwarf Galaxies.

The details of the early star formation histories of tiny dwarf galaxies can shed light on the role in galaxy formation of the reionization which occured at high redshift. Isolated dwarfs are ideal probes since their evolution is not complicated by environmental effects owing to the vicinity of the Milky Way and M31. In addition, dwarf galaxies are the most common type of galaxies, and potentially the building blocks of larger galaxies. Since we can date the oldest stars in them, their study represents a complementary approach to the study of the formation and evolution of galaxies through high-z observations. We propose to use the ACS to obtain a homogeneus dataset of high-quality photometry, down to the old {13 Gyr} main-sequence turnoffs, for a representative sample of 4 isolated Local Group dwarf galaxies. These data are essential to unambiguously determine their early star formation histories, through comparison with synthetic color-magnitude diagrams, and using the constraints provided by their variable stars. Parallel WFPC2 observations of their halos will allow us to reveal the actual nature of their stellar population gradients, providing important aditional constraints on their evolution. The proposed observations are being complemented with ground-based spectroscopy, to obtain metallicity and kinematic information. The observations requested here, which must reach M_I=+3.5 {I=27.5- 28.2} with S/N=10 in crowded systems, can only be achieved with HST using ACS, and won’t be possible with planned ground- or space-based facilities such as JWST. Based on deep WFPC2 observations and ACS image simulations, our team has designed an observational strategy which carefully considers the optimal filter combination, the necessary photometry depth and the effects of stellar crowding.

ACS/WFC 10604

The Formation History of the M81 Spheroid

Spheroidal stellar populations {elliptical galaxies, bulges, and halos} contain a significant fraction of all stars and metals in the local universe. The mechanisms responsible for their formation are ultimately the ones which governed galaxy formation during early epochs. To begin understanding the M81 spheroid, we are currently studying the globular cluster population using HST/WFPC2 multiband imaging and ground based optical spectroscopy. To complete this effort, we propose to use ACS/WFC to obtain deep {I, V-I} color magnitude diagrams {to the horizontal branch} of two fields in M81 – one dominated by thick disk stars and the other halo stars. These observations will provide tight constraints on the formation timescales and chemical enrichment history of the field star population. Combined with results on the globular clusters, we will reconstruct the early formation history of M81, and compare with those found for other nearby, massive galaxies. Because M81 is the earliest type spiral galaxy {Sab} available for such a detailed study, it provides a unique opportunity to probe the connection between elliptical halos and lower mass spiral spheroids.

WFPC2 10359

WFPC2 CYCLE 13 Standard Darks

This dark calibration program obtains dark frames every week in order to provide data for the ongoing calibration of the CCD dark current rate, and to monitor and characterize the evolution of hot pixels. Over an extended period these data will also provide a monitor of radiation damage to the CCDs.


Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)


9947 – OBAD Failed Identification @255/2001z At 255/20:25:02 Received 486 ESB messages 1902 (OBAD Failed Identification) and two (2) 1805 (T2G Moving Target Detected). Current OBAD error values: V1 -92.26, V2 -8.75, V3 -13.28, RSS 93.62.



                              SCHEDULED     SUCCESSFUL 
 Gsacq                   09                    09 

FGS Reacq                   05                    05 
 OBAD with Maneuver     18                    18 


SpaceRef staff editor.