NASA Hubble Space Telescope Daily Status Report #4434

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.

HUBBLE SPACE TELESCOPE DAILY REPORT #4434

– Continuing to collect World Class Science

PERIOD COVERED: UT August 24,25,26, 2007 (DOY 236,237,238)

OBSERVATIONS SCHEDULED

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 11329

The Final SHOE; Completing a Rich Cepheid Field in NGC 1309

The Cycle 15 SHOES program {GO 10802} is a large HST program allocated 186 orbits to rebuild the distance ladder using NGC 4258 as a new anchor, a set of 6 recent, ideal type Ia supernovae and Cepheids in their hosts, and NICMOS as a single, homogeneous photometer of long period Cepheids. These tools provide the means to achieve a 4% measurement of the Hubble constant, an invaluable constraint for cosmic concordance fits to dark energy models. Unfortunately, the SHOES NICMOS integrations of long period Cepheids in the last and most recent nearby type Ia supernova host, NGC 1309, are too short because the preliminary estimate of its distance, 30 Mpc, was too low. Our refined estimate now based on the full reduction of both our Cycle 14 and 15 ACS data is 36 Mpc, or 0.4 mag farther. Fortunately, Nature was extremely kind providing a single rich NIC2 field in which we can fully make up for the shortfall due to its abundance of Cepheids. We are expensing our final 4 orbits on this field of a dozen P>30 day Cepheids and seek an additional 5 orbits to reach the depth for measuring the mean F160W magnitudes of the long-period Cepheids with the necessary signal-to-noise ratios of better than 10.

FGS 11295

Trigonometric Calibration of the Distance Scale for Classical Novae

The distance scale for classical novae is important for understanding the stellar physics of their thermonuclear runaways, their contribution to Galactic nucleosynthesis, and their use as extragalactic standard candles. Although it is known that there is a relationship between their absolute magnitudes at maximum light and their subsequent rates of decline–the well-known maximum-magnitude rate-of-decline {MMRD} relation–it is difficult to set the zero-point for the MMRD because of the very uncertain distances of Galactic novae. We propose to measure precise trigonometric parallaxes for the quiescent remnants of the four nearest classical novae. We will use the Fine Guidance Sensors, which are proven to be capable of measuring parallaxes with errors of ~0.2 mas, well below what is possible from the ground.

WFPC2 11292

The Ring Plane Crossings of Uranus in 2007

The rings of Uranus turn edge-on to Earth in May and August 2007. In between, we will have a rare opportunity to see the unlit face of the rings. With the nine optically thick rings essentially invisible, we will observe features and phenomena that are normally lost in their glare. We will use this opportunity to search thoroughly for the embedded “shepherd” moons long believed to confine the edges of the rings, setting a mass limit roughly 10 times smaller than that of the smallest shepherd currently known, Cordelia. We will measure the vertical thicknesses of the rings and study the faint dust belts only known to exist from a single Voyager image. We will also study the colors of the newly-discovered faint, outer rings; recent evidence suggests that one ring is red and the other blue, implying that each ring is dominated by a different set of physical processes. We will employ near- edge-on photometry from 2006 and 2007 to derive the particle filling factor within the rings, to observe how ring epsilon responds to the “traffic jam” as particles pass through its narrowest point, and to test the latest models for preserving eccentricities and apse alignment within the rings. Moreover, this data set will allow us to continue monitoring the motions of the inner moons, which have been found to show possibly chaotic orbital variations; by nearly doubling the time span of the existing Hubble astrometry, the details of the variations will become much clearer.

WFPC2 11289

SL2S: The Strong Lensing Legacy Survey

Recent systematic surveys of strong galaxy-galaxy lenses {CLASS, SLACS, GOODS, etc.} are producing spectacular results for galaxy masses roughly below a transition mass M~10^13 Mo. The observed lens properties and their evolution up to z~0.2, consistent with numerical simulations, can be described by isothermal elliptical potentials. In contrast, modeling of giant arcs in X-ray luminous clusters {halo masses M >~10^13 Mo} favors NFW mass profiles, suggesting that dark matter halos are not significantly affected by baryon cooling. Until recently, lensing surveys were neither deep nor extended enough to probe the intermediate mass density regime, which is fundamental for understanding the assembly of structures. The CFHT Legacy Survey now covers 125 square degrees, and thus offers a large reservoir of strong lenses probing a large range of mass densities up to z~1. We have extracted a list of 150 strong lenses using the most recent CFHTLS data release via automated procedures. Following our first SNAPSHOT proposal in cycle 15, we propose to continue the Hubble follow-up targeting a larger list of 130 lensing candidates. These are intermediate mass range candidates {between galaxies and clusters} that are selected in the redshift range of 0.2-1 with no a priori X-ray selection. The HST resolution is necessary for confirming the lensing candidates, accurate modeling of the lenses, and probing the total mass concentration in galaxy groups up to z~1 with the largest unbiased sample available to date.

FGS 11212

Filling the Period Gap for Massive Binaries

The current census of binaries among the massive O-type stars is seriously incomplete for systems in the period range from years to millennia because the radial velocity variations are too small and the angular separations too close for easy detection. Here we propose to discover binaries in this observational gap through a Faint Guidance Sensor SNAP survey of relatively bright targets listed in the Galactic O Star Catalog. Our primary goal is to determine the binary frequency among those in the cluster/association, field, and runaway groups. The results will help us assess the role of binaries in massive star formation and in the processes that lead to the ejection of massive stars from their natal clusters. The program will also lead to the identification of new, close binaries that will be targets of long term spectroscopic and high angular resolution observations to determine their masses and distances. The results will also be important for the interpretation of the spectra of suspected and newly identified binary and multiple systems.

WFPC2 11203

A Search for Circumstellar Disks and Planetary-Mass Companions around Brown Dwarfs in Taurus

During a 1-orbit program in Cycle 14, we used WFPC2 to obtain the first direct image of a circumstellar disk around a brown dwarf. These data have provided fundamental new constraints on the formation process of brown dwarfs and the properties of their disks. To search for additional direct detections of disks around brown dwarfs and to search for planetary-mass companions to these objects, we propose a WFPC2 survey of 32 brown dwarfs in the Taurus star-forming region.

WFPC2 11178

Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries

The recent discovery of numerous transneptunian binaries {TNBs} opens a window into dynamical conditions in the protoplanetary disk where they formed as well as the history of subsequent events which sculpted the outer Solar System and emplaced them onto their present day heliocentric orbits. To date, at least 47 TNBs have been discovered, but only about a dozen have had their mutual orbits and separate colors determined, frustrating their use to investigate numerous important scientific questions. The current shortage of data especially cripples scientific investigations requiring statistical comparisons among the ensemble characteristics. We propose to obtain sufficient astrometry and photometry of 23 TNBs to compute their mutual orbits and system masses and to determine separate primary and secondary colors, roughly tripling the sample for which this information is known, as well as extending it to include systems of two near-equal size bodies. To make the most efficient possible use of HST, we will use a Monte Carlo technique to optimally schedule our observations.

NIC3 11080

Exploring the Scaling Laws of Star Formation

As a variety of surveys of the local and distant Universe are approaching a full census of galaxy populations, our attention needs to turn towards understanding and quantifying the physical mechanisms that trigger and regulate the large-scale star formation rates {SFRs} in galaxies.

NIC3/NIC1/NIC2 11059

Flats Stability

This calibration proposal is the Cycle 15 NICMOS flat field monitor program. A series of camera 1, 2, & 3 flat fields will be obtained to monitor the health of the cameras.

WFPC2 11039

Polarizers Closeout

Observations of standard stars and a highly polarized reflection nebula are made as a final calibration for the WFPC2 polarizers. VISFLATS are also obtained.

NIC2 10847

Coronagraphic Polarimetry of HST-Resolved Debris Disks

We propose to take full advantage of the recently commissioned coronagraphic polarimetry modes of ACS and NICMOS to obtain imaging polarimetry of circumstellar debris disks that were imaged previously by the HST coronagraphs, but without the polarizers. It is well established that stars form in gas-rich protostellar disks, and that the planets of our solar system formed from a circum-solar disk. However, the connection between the circumstellar disks that we observe around other stars and the processes of planet formation is still very uncertain. Mid-IR spectral studies have suggested that disk grains are growing in the environments of young stellar objects during the putative planet-formation epoch. Furthermore, structures revealed in well resolved images of circumstellar disks suggest gravitational influences on the disks from co-orbital bodies of planetary mass. Unfortunately, existing imaging data provides only rudimentary information about the disk grains and their environments. Our proposed observations, which can be obtained only with HST, will enable us to quantitatively determine the sizes of the grains and optical depths as functions of their location within the disks {i.e., detailed tomography}. Armed with these well-determine physical and geometrical systemic parameters, we will develop a set of self- consistent models of disk structures to investigate possible interactions between unseen planets and the disks from which they formed. Our results will also calibrate models of the thermal emission from these disks, that will in turn enable us to infer the properties of other debris disks that cannot be spatially resolved with current or planned instruments and telescopes.

NIC2 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.

WFPC2 10789

The Role of Environment in the Formation of Dwarf Galaxies

Clusters of galaxies contain an overdensity of dwarfs compared to the field. Within galaxy clusters there is also a correlation between the overdensity of dwarfs and local galaxy density, such that areas of lower galaxy density contain more dwarfs per giant. The origin of these ‘extra’ dwarfs is unknown, but a large fraction of them did not form through standard collapses early in the universe. Some dwarf ellipticals in clusters have metal rich and young {< 6 Gyr} stellar populations while others contain old metal poor populations, suggesting multiple formation mechanisms and time scales. We propose to test the idea that dwarfs descend from galaxies accreted into clusters during the past 8 Gyr by correlating ages and metallicities of dwarfs with their internal structures - spiral arms, bars, and disks. If dwarfs originate from more massive galaxies then these features should be common in metal rich and young dwarfs. On the other hand, if no correlation is found it would suggest that dwarfs form through in-situ collapses of gas in the intragalactic medium after the universe was reionized.

WFPC2 10599

Multi-color imaging of two 1 Gyr old debris disks within 20 pc of the Sun: Astrophysical mirrors of our Kuiper Belt

We report the first scattered light detections of two debris disk around an F star and a K star using optical coronagraphy and the Hubble Space Telescope. With ages ~1 Gyr, these are the oldest debris disks thus far seen in the optical. We propose deep, multi-roll angle coronagraphic imaging with HST ACS and NICMOS to confirm and characterize the disks in terms of structure and composition. The disks appear to have belt-like morphology that is consistent with the existence of planetary companions or other perturbing bodies. Since these disks are close to our Kuiper Belt in an evolutionary context, detailed understanding of their mass, structure and composition will provide a fresh perspective for inferring the history and properties of our own trans-Neptunian region.

NIC2 10487

A Search for Debris Disks in the Coeval Beta Pictoris Moving Group

Resolved observations of debris disks present us with the opportunity of studying planetary evolution in other solar systems. We propose to search for debris disks in the Beta Pictoris moving group {8-20 Myrs, 10-50 pc away} , which provides a coeval sample of multiple spectral types, and it has already produced two magnificent resolved debris disks: AU Mic and Beta Pic. Such coeval sample will provide us with a snapshop of the crucial time in disk evolution in which the disk makes the transition from optically thick to optically thin, and it will be useful to study the stellar mass dependence of the disk evolution.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS:

10954 – REACQ(2,1,1) failed

REACQ(2,1,1) at 236/11:36:07 failed to RGA control. FGS 1 acquired fine lock at 11:40:05 but lost it at 11:42:00. No flags or ESB messages were seen. GSACQ(2,1,1) at 08:25:54 was successful as was a previous REACQ at 10:00:14.

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL 

FGS GSacq               31                 31 
FGS REacq               10                 09 
OBAD with Maneuver      82                 82 

SIGNIFICANT EVENTS: (None)