Status Report

NASA Hubble Space Telescope Daily Report # 4480

By SpaceRef Editor
November 1, 2007
Filed under , ,
NASA Hubble Space Telescope Daily Report # 4480

Notice: Due to the conversion of some ACS WFC or HRC observations into WFPC2, or NICMOS observations after the loss of ACS CCD science capability in January, there may be an occasional discrepancy between a proposal’s listed (and correct) instrument usage and the abstract that follows it.


– Continuing to collect World Class Science

PERIOD COVERED: UT October 31, 2007 (DOY 304)


ACS/SBC 10840

The FUV fluxes of Tauri stars in the Taurus molecular cloud

Present and forthcoming ground-based and space surveys of the T Tauri stars in the Taurus molecular cloud will provide information from high energy stellar and accretion radiation to low energy solid state and molecular emission from the disk, making those stars perfect laboratories to carry out self-consistent studies of disk physics and evolution. We propose to complete this wealth of information by obtaining ACS/FUV spectra for a significant sample of Taurus T Tauri stars, covering a range of accretion properties and dust evolutionary stages. FUV fluxes carry ~ 10 – 100 more energy than X-rays into these disks and are thus crucial gas heating agents and key to disk dispersal by photoevaporation. These observations are a pre-requisite to interpret observations with Spitzer, SOFIA, Herschel, and ALMA, and will become one of the important legacies of HST to the star formation community.

WFPC2 10905

The Dynamic State of the Dwarf Galaxy Rich Canes Venatici I Region

With accurate distances, the nearest groups of galaxies can be resolved in 3 dimensions and the radial component of the motions of galaxies due to local density perturbations can be distinguished from cosmological expansion components. Currently, with the ACS, galaxy distances within 8 Mpc can be measured effectively and efficiently by detecting the tip of the red giant branch {TRGB}. Of four principal groups at high galactic latitude in this domain, the Canes Venatici I Group {a} is the least studied, {b} is the most populated, though overwhelmingly by dwarf galaxies, and {c} is likely the least dynamically evolved. It is speculated that galaxies in low mass groups may fail to retain baryons as effectively as those in high mass groups, resulting in significantly higher mass-to-light ratios. The CVn I Group is suspected to lie in the mass regime where the speculated astrophysical processes that affect baryon retention are becoming important.

NIC1/NIC2/NIC3 11330

NICMOS Cycle 16 Extended Dark

This takes a series of Darks in parallel to other instruments.

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 DARKs. 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 11197

Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble Diagram

We propose building a high-z Hubble Diagram using type Ia supernovae observed in the infrared rest-frame J-band. The infrared has a number of exceptional properties. The effect of dust extinction is minimal, reducing a major systematic that may be biasing dark energy measurements. Also, recent work indicates that type Ia supernovae are true standard candles in the infrared meaning that our Hubble diagram will be resistant to possible evolution in the Phillip’s relation over cosmic time. High signal-to-noise measurements of 16 type Ia events at z~0.4 will be compared with an independent optical Hubble diagram from the ESSENCE project to test for a shift in the derived dark energy equation of state due to a systematic bias. In Cycle 15 we obtained NICMOS photometry of 8 ESSENCE supernovae and are awaiting template observations to place them on the IR Hubble diagram. Here we request another 8 supernovae be studied in the final season of the ESSENCE search. Because of the bright sky background, H-band photometry of z~0.4 supernovae is not feasible from the ground. Only the superb image quality and dark infrared sky seen by HST makes this test possible. This experiment may also lead to a better, more reliable way of mapping the expansion history of the universe with the Joint Dark Energy Mission.

S/C 11163

Accreting Pulsating White Dwarfs in Cataclysmic Variables

Recent ground-based observations have increased the number of known pulsating white dwarfs in close binaries with active mass transfer {cataclysmic variables} from 5 to 11 systems. Our past Cycles 8 and 11 STIS observations of the first 2 known, followed by our Cycle 13 SBC observations of the next 3 discovered, revealed the clear presence of the white dwarf and increased amplitude of the pulsations in the UV compared to the optical. The temperatures derived from the UV spectra show 4 systems are much hotter than non- interacting pulsating white dwarfs. A larger sample is needed to sort out the nature of the instability strip in accreting pulsators i.e. whether effects of composition and rotation due to accretion result in a well-defined instability strip as a function of Teff.

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 11167

A Unique High Resolution Window to Two Strongly Lensed Lyman Break Galaxies

On rare occasions, the otherwise very faint Lyman Break Galaxies {LBGs} are magnified by gravitational lensing to provide exceptional targets for detailed spectroscopic and imaging studies. We propose HST WFPC2 and NICMOS imaging of two strongly lensed Lyman Break Galaxies {LBGs} that were recently discovered by members of our team. These two LBGs — the “8 O’Clock Arc” and the “SDSS J1206+5142 Arc” — are currently the brightest known LBGs, roughly 3 times brighter than the former record-holder, MS1512-cB58 {a.k.a. “cB58”}. The z=2.73 “8 O’Clock Arc” extends ~10 arcsec in length and is magnified by a factor of 12. The z=2.00 “SDSS J1206+5142 Arc” also extends ~10 arcsec in length and is magnified by a factor of 30. Due to their brightness and magnification, these two strongly lensed LBGs offer an unprecedented opportunity for the very detailed investigation of two individual galaxies at high redshift. We are currently pursuing a vigorous ground-based campaign to obtain multi-wavelength {UV, optical, NIR, radio} observations of these two LBGs, but our campaign currently lacks a means of obtaining high-resolution optical/NIR imaging — a lack that currently only HST can address. Our prime objective for this proposal is to obtain high resolution HST images of these two systems with two-orbit WFPC2 images in the BVI bands and two-orbit NICMOS/NIC2 images in the J and H bands. These data will allow us to construct detailed lensing models, probe the mass and light profiles of the lenses and their environments, and constrain the star formation histories and rest-frame UV/optical spectral energy distributions of the LBGs.

WFPC2 11169

Collisions in the Kuiper belt

For most of the 15 year history of observations of Kuiper belt objects, it has been speculated that impacts must have played a major role in shaping the physical and chemical characteristics of these objects, yet little direct evidence of the effects of such impacts has been seen. The past 18 months, however, have seen an explosion of major new discoveries giving some of the first insights into the influence of this critical process. From a diversity of observations we have been led to the hypotheses that: {1} satellite- forming impacts must have been common in the Kuiper belt; {2} such impacts led to significant chemical modification; and {3} the outcomes of these impacts are sufficiently predictable that we can now find and study these impact-derived systems by the chemical and physical attributes of both the satellites and the primaries. If our picture is correct, we now have in hand for the first time a set of incredibly powerful tools to study the frequency and outcome of collisions in the outer solar system. Here we propose three linked projects that would answer questions critical to the multiple prongs of our hypothesis. In these projects we will study the chemical effects of collisions through spectrophotometric observations of collisionally formed satellites and through the search for additional satellites around primaries with potential impact signatures, and we will study the physical effects of impacts through the examination of tidal evolution in proposed impact systems. The intensive HST program that we propose here will allow us to fully test our new hypotheses and will provide the ability to obtain the first extensive insights into outer solar system impact processes.

WFPC2 11229

SEEDS: The Search for Evolution of Emission from Dust in Supernovae with HST and Spitzer

The role that massive stars play in the dust content of the Universe is extremely uncertain. It has long been hypothesized that dust can condense within the ejecta of supernovae {SNe}, however there is a frustrating discrepancy between the amounts of dust found in the early Universe, or predicted by nucleation theory, and inferred from SN observations. Our SEEDS collaboration has been carefully revisiting the observational case for dust formation by core-collapse SNe, in order to quantify their role as dust contributors in the early Universe. As dust condenses in expanding SN ejecta, it will increase in optical depth, producing three simultaneously observable phenomena: {1} increasing optical extinction; {2} infrared {IR} excesses; and {3} asymmetric blue-shifted emission lines. Our SEEDS collaboration recently reported all three phenomena occurring in SN2003gd, demonstrating the success of our observing strategy, and permitting us to derive a dust mass of up to 0.02 solar masses created in the SN.  To advance our understanding of the origin and evolution of the interstellar dust in galaxies, we propose to use HST’s WFPC2 and NICMOS instruments plus Spitzer’s photometric instruments to monitor ten recent core- collapse SNe for dust formation and, as a bonus, detect light echoes that can affect the dust mass estimates. These space-borne observations will be supplemented by ground- based spectroscopic monitoring of their optical emission line profiles. These observations would continue our 2-year HST and Spitzer monitoring of this phenomena in order to address two key questions: Do all SNe produce dust? and How much dust do they produce? As all the SN are within 15 Mpc, each SN stands an excellent chance of detection with HST and Spitzer and of resolving potential light echoes.

WFPC2 11418

Investigating the Spectacular Outburst of Comet 17P/Holmes

Comet 17P/Holmes is currently undergoing a spectacular eruption in activity, with its brightness increasing by ~14 mag over a 24 hour period. The comet is shedding huge amounts of dust, presumably associated with a major splitting event at the nucleus. The high spatial resolution and high sensitivity of Hubble has proven to be invaluable during previous observations of several fragmenting comets, and the 2007 apparition of 17P/Holmes represents another excellent opportunity to investigate this important cometary phenomenon. We request 3 orbits of WFPC2 observations to measure the size and V-R color of the principal nucleus, perform a deep search for large fragments released during the outburst, monitor the temporal development of the event, and search for a satellite whose collision with the principal nucleus may have triggered the current outburst, as was suggested for the similar outburst observed in 1892.


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

HSTARS: (None)


18151-0 – Clear ACS SBC Event Flag #2 for OBS #11163

18152-1 – Modify CSS 3/4 Scale Factors for UKF

18054-0 – Preview KF Sun Vector Data via Telemetry Diags


                        SCHEDULED      SUCCESSFUL 
FGS GSacq               06                 06 
FGS REacq               09                 09 
OBAD with Maneuver      30                30 


The execution of Ops Request 18152-1, Modify CSS 3/4 Scale Factors for UKF, completed successfully at 2007/304 18:57.

SpaceRef staff editor.