NASA Hubble Space Telescope Daily Report # 3442 (part 1)

HUBBLE SPACE TELESCOPE

DAILY REPORT # 3442

PERIOD COVERED: DOYs 248-250

OBSERVATIONS SCHEDULED

NIC3 9998

NICMOS Cycle 12 Grism Calibration and Standard Stars to 2.5microns

This is the grism calibration proposal.

ACS 9984

Cosmic Shear With ACS Pure Parallels

Small distortions in the shapes of background galaxies by foreground mass provide a powerful method of directly measuring the amount and distribution of dark matter. Several groups have recently detected this weak lensing by large-scale structure, also called cosmic shear. The high resolution and sensitivity of HST/ACS provide a unique opportunity to measure cosmic shear accurately on small scales. Using 260 parallel orbits in Sloan textiti {F775W} we will measure for the first time: beginlistosetlength sep0cm setlengthemsep0cm setlength opsep0cm em the cosmic shear variance on scales <0.7 arcmin, em the skewness of the shear distribution, and em the magnification effect. endlist Our measurements will determine the amplitude of the mass power spectrum sigma_8Omega_m^0.5, with signal-to-noise {s/n} ~ 20, and the mass density Omega_m with s/n=4. They will be done at small angular scales where non-linear effects dominate the power spectrum, providing a test of the gravitational instability paradigm for structure formation. Measurements on these scales are not possible from the ground, because of the systematic effects induced by PSF smearing from seeing. Having many independent lines of sight reduces the uncertainty due to cosmic variance, making parallel observations ideal.

NIC2 9875

The Fundamental Plane of Massive Gas-Rich Mergers

We propose deep NICMOS H-band imaging of a carefully selected sample of 33 luminous, late-stage galactic mergers. This program is part of a comprehensive investigation of the most luminous mergers in the nearby universe, the ultraluminous infrared galaxies {ULIGs}. The high-resolution HST images will complement an extensive set of ground-based data that include long-slit NIR spectra from a recently approved Large VLT Programme. This unique dataset will allow us to derive with unprecedented precision structural -and- kinematic parameters for a large unbiased sample of objects spanning the entire ULIG luminosity function. These data will refine the fundamental plane of massive gas-rich mergers and enable us to answer the following questions: {1} Do ultraluminous mergers form elliptical galaxies, and in particular, giant ellipticals? {2} Do ULIGs evolve into optically bright QSOs? The results from this detailed study of massive mergers in the local universe will be relevant to understanding galaxy formation and evolution at earlier epochs, and in particular, the dusty sub-mm population that accounts for more than half of the star formation at z > 1.

ACS/HRC 9853

A Search for Young Binary Brown Dwarfs: Constraining Formation Scenarios and Masses Through Multiplicity

We propose to use the Advanced Camera for Surveys / High Resolution Camera to conduct a direct imaging multiplicity survey of 34 young brown dwarfs in the nearest regions of recent star formation, the T association Taurus-Auriga and the OB association Upper Scorpius. The determined multiplicity fraction, the separation distribution, and the mass ratio distribution will offer stringent observational constraints on proposed brown dwarf formation scenarios. Moreover, the small semi-major axes of known field and open cluster brown dwarf binaries suggest the exciting possibility of our identifying several very close binaries {< 15 AU}. Continued monitoring of these systems would yield, on a decade timescale, the first dynamical mass estimates of T Tauri brown dwarfs. With masses intermediate between those of stars and planets, brown dwarfs offer our best hope of relating the reasonably well understood processes of star formation to the less well understood processes of planet formation.

NIC1 9843

NICMOS Observations of Cool Brown Dwarf Doubles

We propose to use NICMOS to observe two brown dwarf systems discovered using HST/WFPC2 imaging. Each of the two late-L dwarf primaries has a secondary that is much fainter. Based on the limited optical photometry available, the secondaries lie at the L/T Dwarf transition, and may lie anywhere in the range from L9 {cooler than any known L dwarf} or early-T. NICMOS photometry will be used to characterize the spectral energy distribution and search for methane absorption.

ACS/WFC 9842

A Snapshot Search for Halo Very-Low-Mass Binaries

We propose a snapshot search for binary M subdwarf stars. These nearby stars have high velocities and low metallicies that identify them as members of the old Galactic halo {Population II}. ACS imaging is requested to search for secondary companions. This supplements a previous snapshot program that only obtained 10 observations. The observed binary fraction will be compared to the disk M dwarf fraction to look for differences in star formation. It is likely that a system suitable for orbital mass determinations will be found. In this case, future HST observations could determine the first masses for very-low-mass, low-metallicity stars.

NIC2 9834

Finding Planets in the Stellar Graveyard: A Faint Companion Search of White Dwarfs with NICMOS

We propose to do a deep search for substellar objects in orbit around white dwarfs with the newly refurbished NICMOS camera as part of the PI’s doctoral thesis work. Direct imaging of planets around main sequence stars is difficult due to the large contrast ratio, a problem which is much less severe for companions to white dwarfs. White dwarfs are not usually considered in planet searches but recent theoretical work and observations are motivating new searches for planetary systems and dust disks around DAZ white dwarfs. We propose to conduct the search with the NIC2 coronagraph to find resolved companions and do photometry to search for unresolved companions through Near-IR excesses. We estimate that the survey will be sensitive to brown dwarfs, high mass jovian planets, and dust disks. By probing a wide range of orbital separations and companion masses, this survey will help to answer questions about the brown dwarf desert, common envelope evolution, and planet formation. HST and NICMOS provide a unique capability to do this search, as no ground based observatory with AO can adequately search for faint companions as close and with such high contrast.

NIC1 9833

T Dwarf Companions: Searching for the Coldest Brown Dwarfs

Faint companions to known stars have historically led to the discovery of new classes of stellar and substellar objects. Because these discoveries are typically limited by the flux ratio of the components in the system, the intrinsically faintest companions are most effectively identified around the intrinsically faintest primaries. We propose to use NICMOS to image a sample of 22 of the coolest known {T-type} brown dwarfs in the Solar Neighborhood in order to search for fainter and cooler brown dwarf companions. The high spatial resolution of the NIC 1 detector enables us to distinguish binary systems with apparent separations greater than 0″08, or physical separations greater than 1.2 AU at the nominal distances of the objects in our sample. Furthermore, the substantial sensitivity of NICMOS imaging allows us to probe companion masses of 5-50 Jupiter masses and companion effective temperatures of 250-1300 K in a maximally efficient manner. Based on work to date, we expect that roughly 20% of the objects in our sample will be binary, and that one or two of these will likely harbor a significantly fainter secondary. Hence, we expect to find a companion cooler than any currently known brown dwarf, a potential prototype for the next spectral class. In addition, our investigation will add substantially to the sample of known binary brown dwarfs, allowing improved statistical analyses of the binary fraction, separation distribution, and mass ratio distribution of these systems, key quantities for probing brown dwarf formation. We will also identify optimal substellar systems for astrometric mass measurements, a critical check for theoretical models of brown dwarfs and extrasolar planets.

NIC3/ACS/HRC/WFC 9803

Deep NICMOS Images of the UDF

The ACS Ultra Deep Field {UDF} images will greatly enhance the rich suite of deep multi-wavelength images in the Chandra Deep Field South {CDF–S}. We propose to complete the image set with deep near-IR NICMOS images at 1.1 and 1.6 microns over a significant fraction of the UDF, providing a critical link between the HST ACS and SIRTF observations. The timely addition of the near-IR images ensures that investigators will have images that span the spectrum from X-ray to far IR. In recognition of the value of the near IR images this proposal is submitted as a Treasury proposal with no proprietary period. The proposal team will deliver science quality images, mosaiced images covering 4.9 sq arc min, and a photometric catalog complete to an AB mag of 28.2 in both the F110W and F160W filters. The program also delivers a parallel extremely deep ACS field, 8′ away, that reaches to within 0.6 mag of the UDF in the same filters as the UDF. The scientific program of the proposal team focuses on the star formation history of the universe, evolved galaxies at high redshift, galaxies at the epoch of reionization, and the redshift evolution of AGNs and ULIRGs. The HDF-N is currently the only field with spatially-coincident deep HST imaging in both the optical and near-IR. The small size of the HDF-N means that large scale structure is the dominant error in the results from the HDF-N. Providing observations in a field that is spatially uncorrelated is critically important. The UDF/CDF-S fulfills that goal. The depth of the UDF ACS imaging, and the wealth of Great Observatory and ground based observations in the CDF-S, make these NICMOS observations uniquely valuable. An extraordinarily rich array of science opportunities await the community from the NICMOS UDF data.

NIC2 9801

Are OH/IR Stars the Youngest post-AGB stars? A NICMOS Imaging Survey

Essentially all well-characterized preplanetary nebulae {PPNe}– objects in transition between the AGB and planetary nebula evolutionary phases – are bipolar, whereas the mass-loss envelopes of AGB stars are strikingly spherical. In order to understand the processes leading to bipolar mass-ejection, we need to know at what stage of stellar evolution does bipolarity in the mass-loss first manifest itself. We have recently hypothesized that most OH/IR stars {evolved mass- losing stars with OH maser emission} are very young PPNe. We are conducting a multiwavelength survey program of imaging and spectroscopic observations of such objects, using a large, morphologically unbiased sample selected using IRAS 12-to-25 micron colors. Our ongoing HST/SNAP imaging survey of the optically bright half of this sample with WFPC2 and ACS is highly successful: 19/32 objects observed are extended with bipolar/multipolar shapes {remaining objects are unresolved}. Slightly more than 50% of our sample are optically too faint or undetected but have strong near-IR counterparts — we therefore propose a NICMOS SNAPshot imaging survey of these optically-faint OH/IR stars. These observations are crucial for determining how and when the bipolar geometry asserts itself. The results from our NICMOS survey {together with the WFPC2/ACS survey} will allow us to draw general conclusions about the onset of bipolar mass-ejection during late stellar evolution. Our complementary program of interferometric mapping of the OH maser emission in our sources is yielding kinematic information with spatial resolution comparable to that in the HST images. The HST/radio data will provide crucial input for theories of post-AGB stellar evolution. In addition, these data will also indicate whether the multiple concentric rings, “searchlight beams”, and truncated equatorial disks recently discovered with HST in a few PPNe, are common or rare phenomena.

ACS/HRC/WFC 9763

Calibrating the Black Hole Mass Scale for Quasars

We propose to obtain ACS/WFC imaging of all 17 low-redshift quasars that have black hole masses measured from reverberation mapping. This is a key sample since all secondary methods to estimate black hole mass in quasars depend on this local reverberation-mapped sample for their calibration. The best external check on reverberation mapping is whether it gives results that are consistent with the black hole mass- host galaxy correlations of nearby galaxies. For local Seyfert galaxies the reverberation masses appear consistent with the M-sigma correlation, but it is not known whether this also holds true for quasars because the stellar velocity dispersions of quasar hosts are virtually impossible to measure. We will use the ACS data to measure accurate bulge parameters {luminosity and effective radius} for the host galaxies of the reverberation-mapped quasars. From the fundamental plane or the Faber-Jackson relation, we can estimate the host galaxy velocity dispersion and test whether the reverberation masses follow the M-sigma relation even for objects with quasar luminosities. This is a crucial test if we are to trust the reverberation masses as the lowest rung on a “distance ladder” of black hole mass estimators for quasars, so that quasars can be used to trace the cosmological growth history of black holes. {Note added in Phase II: the TAC awarded us 8 orbits to observe 7 quasars and a PSF star.}

WFPC2/ACS/WFC 9761

A morphological study of EROs and sub-mm sources in a unique deep field

We propose a deep I-band ACS WFC survey in a unique deep field, focusing on two classes of high-redshift galaxy which are believed to be the progenitors of today’s massive ellipticals: {1} our recently-studied deep sample of 158 “extremely red objects” {EROs}; {2} a complete flux-limited sample of 14 SCUBA sub-mm sources, which may represent the formation episode of the most massive galaxies at high redshift. The basic goals are to go deep enough to obtain morphological parameters for this large sample {e.g. scale-lengths and shape parameters} to investigate whether, for example, the EROs have sizes comparable to present day elliptical galaxies. Likewise, what are the typical size scales and morphologies for the SCUBA sources? Can we visualize their formation from smaller fragments? We can achieve both goals in a single contiguous field with a mosaic of 8 deep ACS WFC fields, requiring 16 orbits.

ACS/HRC 9747

An Imaging Survey of the Statistical Frequency of Binaries Among Exceptionally-Young Dynamical Families in the Main Asteroid Belt

We propose an ambitious SNAPSHOT program to determine the frequency of binaries among two very young asteroid families in the Main Belt, with potentially profound implications. These families {of C- and S-type} have recently been discovered {Nesvorny et al. 2002, Nature 417, 720}, through dynamical modeling, to have been formed at 5.8 MY and 8.3 MY ago in catastrophic impact events. This is the first time such precise and young ages have been assigned to a family. Main-belt binaries are almost certainly produced by collisions, and we would expect a young family to have a significantly higher frequency of binaries than the background, because they may not yet have been destroyed by impact or longer-term gravitational instabilities. In fact, one of the prime observables from such an event should be the propensity for satellites. This is the best way that new numerical models for binary production by collisions {motivated largely by our ground-based discoveries of satellites among larger asteroids}, can be validated and calibrated. HST is the only facility that can be used to search for binaries among such faint objects {V>17.5}. We will also measure two control clusters, one being an “old” family, and the other a collection of background asteroids that do not have a family association, and further compare with our determined value for the frequency of large main-belt binaries {2%}. We request visits to 180 targets, using ACS/HRC.

ACS/WFC 9744

HST Imaging of Gravitational Lenses

Gravitational lenses offer unique opportunities to study cosmology, dark matter, galactic structure, galaxy evolution and quasar host galaxies. They are also the only sample of galaxies selected based on their mass rather than their luminosity or surface brightness. While gravitational lenses can be discovered with ground-based optical and radio observations, converting them into astrophysical tools requires HST. HST has demonstrated that it is the only telescope that can in each case precisely locate the lens galaxy, measure its luminosity, color and structure, and search for lensed images of the source host galaxy given the typical image separations of ~1”. We will obtain ACS/WFC V and I images and NICMOS H images of 21 new lenses never observed by HST and NICMOS H images of 16 lenses never observed by HST in the IR. As in previous cycles, we request that the data be made public immediately.

NIC1/NIC2/STIS/CCD/WFPC2 9738

Spectroscopy and Polarimetry of Mars at Closest Approach

We plan a coordinated program of spectroscopy, imaging, and spectropolarimetry of Mars during the August 2003 opposition to study the composition and physical state of surface materials and airborne aerosols. The observations include {a} Moderate spectral resolution 290 to 570 nm STIS long-slit push-broom imaging spectroscopy of Mars, to constrain the properties of airborne aerosol particles and to search for and globally map iron-bearing minerals that are diagnostic of specific past climatic conditions; {b} WFPC2 UV-VIS images designed primarily to quantify the effects of ice and dust aerosols on our STIS spectra; {c} NICMOS near-IR images to search for and globally map the presence of hydrated surface minerals; and {d} ACS multispectral polarizer images to provide critical phase function measurements needed to constrain the physical properties of the Martian surface layer. The observations are timed to take advantage of the closest approach of Mars to Earth for the next several hundred years. Images and spectra will be acquired at a spatial scale comparable to existing spacecraft orbital spectroscopy data {~10 km/pixel} and in wavelength regions not sampled by past or current Mars spacecraft instrumentation. These observations also provide complementary scientific and calibration measurements in support of current and future NASA and ESA Mars exploration missions.

STIS/CCD/MA1 9724

Towards a global understanding of accretion physics – Clues from an UV spectroscopic survey of cataclysmic variables

Accretion inflows and outflows are fundamental phenomena in a wide variety of astrophysical environments, such as Young Stellar Objects, galactic binaries, and AGN. Observationally, cataclysmic variables {CVs} are particularly well suited for the study of accretion processes. We are currently carrying out a Cycle 11 STIS UV spectroscopic snapshot survey of CVs to fully exploit the diagnostic potential of these objects for our understanding of accretion physics. While the data obtained so far are of excellent quality, the number of targets that will be observed in Cycle 11 is too small for a statistically significant analysis {only 19 objects out of our 149 accepted Cycle 11 snapshot targets have been observed at the time of writing}. We propose here to extend this survey into Cycle 12, building a homogenous database of accretion disc and wind outflow spectra covering a wide range of mass transfer rates and binary inclinations. We will analyze these spectra with state-of-the-art accretion disc model spectra {SYNDISK}, testing our current knowledge of the accretion disc structure, and, thereby, providing new insight into the so far not well understood process of viscous dissipation. We will use our parameterised wind model PYTHON for the analysis of the radiation driven accretion disc wind spectra, assessing the fundamental question whether the mass loss rate correlates with the disc luminosity. In addition, our survey data will identify a number of systems in which the white dwarf significantly contributes to the UV flux, permitting an analysis of the impact of mass accretion on the evolution of these compact stars. This survey will triple the number of currently available high-quality accretion disc / wind outflow / accreting white dwarf spectra, and we waive our proprietary rights to permit a timely use of this database.

WFPC2 9712

Pure Parallel Near-UV Observations with WFPC2 within High-Latitude ACS Survey Fields

In anticipation of the allocation of ACS high-latitude imaging survey{s}, we request a modification of the default pure parallel program for those WFPC2 parallels that fall within the ACS survey field. Rather than duplicate the red bands which will be done much better with ACS, we propose to observe in the near-ultraviolet F300W filter. These data will enable study of the rest-frame ultraviolet morphology of galaxies at 0