Status Report

NASA Hubble Space Telescope Daily Report #4344

By SpaceRef Editor
April 19, 2007
Filed under , ,
NASA Hubble Space Telescope Daily Report #4344

Notice: For the foreseeable future, the daily reports may contain apparent discrepancies between some proposal descriptions and the listed instrument usage. This is due to the conversion of previously approved ACS WFC or HRC observations into WFPC2, or NICMOS observations subsequent to the loss of ACS CCD science capability in late January.


– Continuing to collect World Class Science

PERIOD COVERED: UT April 18, 2007 (DOY 108)


WFPC2 10798

Dark Halos and Substructure from Arcs & Einstein Rings The surface brightness distribution of extended gravitationally lensed arcs and Einstein rings contains super-resolved information about the lensed object, and, more excitingly, about the smooth and clumpy mass distribution of the lens galaxies. The source and lens information can non-parametrically be separated, resulting in a direct “gravitational image” of the inner mass-distribution of cosmologically-distant galaxies {Koopmans 2005; Koopmans et al. 2006 [astro-ph/0601628]}. With this goal in mind, we propose deep HST ACS-F555W/F814W and NICMOS-F160W WFC imaging of 20 new gravitational-lens systems with spatially resolved lensed sources, of the 35 new lens systems discovered by the Sloan Lens ACS Survey {Bolton et al. 2005} so far, 15 of which are being imaged in Cycle-14. Each system has been selected from the SDSS and confirmed in two time- efficient HST-ACS snapshot programs {cycle 13&14}. High-fidelity multi-color HST images are required {not delivered by the 420s snapshots} to isolate these lensed images {properly cleaned, dithered and extinction-corrected} from the lens galaxy surface brightness distribution, and apply our “gravitational maging” technique. Our sample of 35 early-type lens galaxies to date is by far the largest, still growing, and most uniformly selected. This minimizes selection biases and small-number statistics, compared to smaller, often serendipitously discovered, samples. Moreover, using the WFC provides information on the field around the lens, higher S/N and a better understood PSF, compared with the HRC, and one retains high spatial resolution through drizzling. The sample of galaxy mass distributions – determined through this method from the arcs and Einstein ring HST images – will be studied to: {i} measure the smooth mass distribution of the lens galaxies {dark and luminous mass are separated using the HST images and the stellar M/L values derived from a joint stellar-dynamical analysis of each system}; {ii} quantify statistically and individually the incidence of mass-substructure {with or without obvious luminous counter- parts such as dwarf galaxies}. Since dark-matter substructure could be more prevalent at higher redshift, both results provide a direct test of this prediction of the CDM hierarchical structure-formation model.

WFPC2 10809

The nature of “dry” mergers in the nearby Universe

Recent studies have shown that “dry” mergers of red, bulge-dominated galaxies at low redshift play an important role in shaping today’s most massive ellipticals. These mergers have been identified in extremely deep ground-based images of red sequence galaxies at z ~ 0.1. The ground-based images reach surface brightness limits of AB ~ 29, but lack the resolution to study the morphologies of the galaxies inside the effective radius. Here we propose to obtain ACS images of a representative sample of 40 of these red sequence galaxies: 15 ongoing dry mergers, 15 remnants, and 10 undisturbed objects. We will measure the isophote shapes and ellipticities of the galaxies, their dust content, morphological fine structure {shells and ripples}, AGN content, and their location on the Fundamental Plane. By comparing galaxies in different stages of the merging process we can constrain the amount of gas associated with these red mergers, the effect of active nuclei, and track structural changes. As two galaxies can be observed in a single orbit 20 orbits are requested to observe the 40 galaxies.

WFPC2 10886

The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

As a continuation of the highly successful Sloan Lens ACS {SLACS} Survey for new strong gravitational lenses, we propose one orbit of ACS-WFC F814W imaging for each of 50 high-probability strong galaxy-galaxy lens candidates. These observations will confirm new lens systems and permit immediate and accurate photometry, shape measurement, and mass modeling of the lens galaxies. The lenses delivered by the SLACS Survey all show extended source structure, furnishing more constraints on the projected lens potential than lensed-quasar image positions. In addition, SLACS lenses have lens galaxies that are much brighter than their lensed sources, facilitating detailed photometric and dynamical observation of the former. When confirmed lenses from this proposal are combined with lenses discovered by SLACS in Cycles 13 and 14, we expect the final SLACS lens sample to number 80–100: an approximate doubling of the number of known galaxy-scale strong gravitational lenses and an order-of-magnitude increase in the number of optical Einstein rings. By virtue of its homogeneous selection and sheer size, the SLACS sample will allow an unprecedented exploration of the mass structure of the early-type galaxy population as a function of all other observable quantities. This new sample will be a valuable resource to the astronomical community by enabling qualitatively new strong lensing science, and as such we will waive all but a short {3-month} proprietary period on the observations.

NIC1/NIC2/NIC3 8795

NICMOS Post-SAA calibration – CR Persistence Part 6

A new proceedure proposed to alleviate the CR-persistence problem of NICMOS. Dark frames will be obtained immediately upon exiting the SAA contour 23, and everytime 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 i mages. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.

WFPC2 10884

The Dynamical Structure of Ellipticals in the Coma and Abell 262 Clusters

We propose to obtain images of 13 relatively luminous early type galaxies in the Coma cluster and Abell 262 for which we have already collected ground based major and minor axis spectra and images. The higher resolution HST images will enable us to study the central regions of these galaxies which is crucial to our dynamical modelling. The complete data set will allow us to perform a full dynamical analysis and to derive the dark matter content and distribution, the stellar orbital structure, and the stellar population properties of these objects, probing the predictions of galaxy formation models. The dynamical analysis will be performed using an up-to-date axi-symmetric orbit superposition code.

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 any time.

WFPC2 11085

Europa in Eclipse: Tenuous Atmosphere, Electromagnetic Activity and Surface Luminescence HST Proposal 11085

We propose to image Europa during its orbital eclipse by Jupiter. This will form the basis of an investigation into the nature of the tenuous atmosphere, electromagnetic environment and surface material of Europa. We will compare the FUV oxygen line at 1356A to the optical line at 6300A and seek optical auroral hydrogen emission in Halpha. With broad continuum filters, we will search for optical emissions from other atmospheric constituents and for fluorescence of the surface material, arising from the very high level of incident energetic particle radiation. The high spatial resolution of ACS will allow us to fully resolve scales of interest and allow us to distinguish easily the different terrains on Europa’s surface. In particular we wish to compare luminesence in regions dominated by ice to those of potentially organic red material.


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

HSTARS: (None)


17597-7 – FHST Stuck-on-Bottom Macro Execution

18037-3 – MSS/CSS KF Initialization Convergence Testing

18034-0 – FSW 3.1A EEPROM Installation


                       SCHEDULED      SUCCESSFUL 
FGS GSacq               08                  08 
FGS REacq               04                  04 
OBAD with Maneuver      24                  24 


FSW 3.1A was successfully installed in HST486 EEPROM The post installation EEPROM dump completed at 108/13:55:05 and was Successfully verified by FSW. The Bit Memory Integrity Check was enabled at 14:09:01.

The Kalman Filter was restarted at 108/13:26 during orbit day and during a T2G guiding interval. The filter was activated with the default configuration of MSS and CSS sensor inputs enabled. All UKF parameters showed nominal convergence and steady-state operation. The test was an MSS/CSS Initialization Test Case with the spacecraft inertially fixed during a fast changing B-field in orbit day (M_C_INF,case #7).

SpaceRef staff editor.