Status Report

NASA Hubble Space Telescope Daily Report #4249

By SpaceRef Editor
November 30, 2006
Filed under , ,
NASA Hubble Space Telescope Daily Report #4249


– Continuing to collect World Class Science

PERIOD COVERED: UT November 29, 2006 (DOY 333)



ACS CCDs daily monitor

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 programme will be for the entire lifetime of ACS. Changes from cycle 13:- The default gain for WFC is 2 e-/DN. As before bias frames will be collected for both gain 1 and gain 2. Dark frames are acquired using the default gain {2}. This program cover the period May, 31 2006- Oct, 1-2006. The first half of the program has a different proposal number: 10729.

ACS/SBC 10578

Eclipsing Binaries in the Local Group: Calibration of the Zero-point of the Cosmic Distance Scale and

The Andromeda Galaxy {M31} is potentially a crucial calibrator for the Cosmic Distance Scale, and thus for determining the age and evolution of the Universe. Yet currently the M31 distance modulus {~750 kpc} is is still uncertain to within 0.1-0.15 mag. We have demonstrated in our work on the LMC distance that double-lined eclipsing binaries can serve as excellent “standard candles”. Distances derived from eclipsing binaries are basically geometric and essentially free from many assumptions and uncertainties that plague other less direct methods, such as metallicity differences and calibration zeropoints. The absolute radii of the component stars of eclipsing binaries can be determined to better than a few percent from the time-tested analyses of their light and radial velocity curves. With accurate radii and temperatures, it is possible to determine reliable distances. We are extending our program of using eclipsing binaries as standard candles to determine an accurate distance to M31. As a first step, we are proposing to carry out HST spectroscopy of two carefully selected 19th mag early-B eclipsing binaries in M31. HST/ACS prism/grism low-resolution spectrophotometry {115-900 nm} is only missing key element of this program and is used to determine reliable values for T_eff, [Fe/H], and ISM extinction. These quantities, when combined with the results from our existing light and radial velocity curves for the two targets, will yield the stellar masses, radii, luminosities, and, importantly, the distances. The resulting fundamental stellar properties will be the first determined for stars in M31. Based on our previous experience, we expect to reduce the uncertainty of the M31 distance to better than 5%, thereby leading to a firmer calibration of the Cosmic Distance Scale and the zeropoint of H_0.

ACS/WFC 10521

ACS Imaging of a Unique Spitzer Field: Morphology of mid-IR Variable Sources

We propose to observe the IRAC Dark Field, an extragalactic field 15 arcminutes in diameter near the north ecliptic pole, using 50 orbits of ACS imaging at I-band. This field is extraordinarily deep and is uniquely suited to detecting variable objects in the mid-infrared. The high spatial resolution ACS imaging will be used to derive morphological information about the galaxies in the field, which will then be correlated with mid-infrared variable objects {specifically AGN and supernovae} we have discovered. This field is the dark current calibration target for the Spitzer Space Telescope, the infrared counterpart to HST. Because the field is observed frequently as part of routine operations, it is now similar in size and depth to the infrared component of the GOODS program, and is confusion-limited in the mid-infrared. More importantly, due to the periodicity of the observations, the Spitzer observations are sensitive to variability on week timescales, ultimately spanning a baseline of five years, and are the only mid-infrared dataset that will ever have this capability at this depth. By complementing our wide range of lower resolution imaging at optical and infrared wavelengths, we hope to exploit one of HST’s most unique capabilities – unparalleled spatial resolution in the optical. While our specific interest lies in analysis of variable sources, we will request no proprietary period on the ACS data so that it may be used by the community to complement the publicly available Spitzer data.

NIC1/NIC2/NIC3 8794

NICMOS Post-SAA calibration – CR Persistence Part 5

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=date/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 images. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.

NIC2, ACS/WFC 10802

SHOES-Supernovae, HO, for the Equation of State of Dark energy

The present uncertainty in the value of the Hubble constant {resulting in an uncertainty in Omega_M} and the paucity of Type Ia supernovae at redshifts exceeding 1 are now the leading obstacles to determining the nature of dark energy. We propose a single, integrated set of observations for Cycle 15 that will provide a 40% improvement in constraints on dark energy. This program will observe known Cepheids in six reliable hosts of Type Ia supernovae with NICMOS, reducing the uncertainty in H_0 by a factor of two because of the smaller dispersion along the instability strip, the diminished extinction, and the weaker metallicity dependence in the infrared. In parallel with ACS, at the same time the NICMOS observations are underway, we will discover and follow a sample of Type Ia supernovae at z > 1. Together, these measurements, along with prior constraints from WMAP, will provide a great improvement in HST’s ability to distinguish between a static, cosmological constant and dynamical dark energy. The Hubble Space Telescope is the only instrument in the world that can make these IR measurements of Cepheids beyond the Local Group, and it is the only telescope in the world that can be used to find and follow supernovae at z > 1. Our program exploits both of these unique capabilities of HST to learn more about one of the greatest mysteries in science.

NIC3/ACS/WFC 10404

The Nature of Protocluster Galaxies at z=2.16: Morphology-Density and Color-Magnitude Relations To establish the epoch when galaxy environment manifests itself as a large-scale evolutionary process, we propose to extend the study of galaxy colors and morphologies to a protocluster at z=2.16. Here the universe is only 3 Gyrs old and significant differences are expected between scenarios favoring a morphology-radius relation over a morphology-density relation. In addition, because the fractional age differences among cluster galaxies are larger, study of the color- magnitude relation provides considerable leverage for determining the epoch of early-type galaxy formation. To facilitate direct comparison to studies at lower redshift, one must probe the same rest-frame wavelengths with high photometric accuracy and at similar physical scales. Its near-infrared photometric stability {low, constant background} and ability to image large areas of sky at high angular-resolution {compared to adaptive optics} makes HST/NICMOS ideal for this program. Six pointings of NICMOS camera 3 will result in rest-frame optical, high resolution images of 16 confirmed protocluster members, and an additional 60 candidate protocluster members including 29 EROs. These galaxies were selected with a variety of techniques and span a range of projected radii within the protocluster. The proposed observations constitute a unique opportunity to extend the study of galaxies in overdense regions to an early time in cosmic history.

NIC3/ACS/WFC 10921

Tangential Velocities of Objects in the Orion Nebula and Locating the Embedded Outflow Sources.

The Orion Nebula is arguably the Rosetta Stone for studying a very young star cluster and how the radiation and outflowing plasma from its stars interact with ambient material. It has been the subject of numerous HST imaging studies, which means that there is good opportunity for determining tangential velocities by obtaining second epoch images during Cycle 15, which may be the last cycle for which the WFPC2 is available. These velocities in the plane-of-the-sky will allow us to determine the patterns of outflow from micro-jets smaller than the Solar System to jet driven shocks more than a parsec from their sources. Combined with radial velocities, we’ll obtain spatial velocities, which are critical to determining where the embedded sources are located that produce the numerous HH objects coming from the Orion-S and BN-KL regions. We’ll also be able to determine the physics that is operating in the LL Ori type of outflows {where a bipolar jet is being distorted by a slow wind coming from the nebula}. We will also be able to search for runaway stars caused by the disintegration of young multiple-star systems. All of this is possible because the long-time base of the WFPC2 and ACS observations allow a new level of astrometric precision to be obtained and to be done efficiently by making coordinated parallel observations with all images.


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

HSTARS: (None)



                          SCHEDULED      SUCCESSFUL
FGS GSacq               08                     08
FGS REacq                07                     07
OBAD with Maneuver  30                     30


SpaceRef staff editor.