HST Daily Report # 3325 (part 1)
HUBBLE SPACE TELESCOPE
DAILY REPORT # 3325
PERIOD COVERED: DOYs 80-82
OBSERVATIONS SCHEDULED
FLIGHT OPERATIONS SUMMARY:
ACS 9658
ACS Earth Flats
This program will obtain sequences of flat field images by observing the
bright
Earth. Several UV filters from the interim calibration program {9564}
require additional exposures to obtain the required illumination. A few UV filters from this program will be repeated to monitor for changes in the flat fields and to verify the interim results. Since no streaks are observed in the UV, the wavelength coverage is extended to longer wavelengths in order to explore the severity of streaks in the flats from clouds in the FOV. We have added exposures for the HRC in the visible filters to verify the results derived from the L-flat campaign and to explore the severity of streaks. We have also added exposures on WFC using the minimum exposure time and using filters which will not saturate the brightest WFC pixel by more than 10 times the full well.
ACS 9468
ACS Grism Parallel Survey of Emission- line Galaxies at Redshift z pl 7
We propose an ACS grism parallel survey to search for emission-line galaxies toward 50 random lines of sight over the redshift interval 0 < z pl 7. We request ACS parallel observations of duration more than one orbit at high galactic latitude to identify ~ 300 HAlpha emission-line galaxies at 0.2 pl z pl 0.5, ~ 720 O IILambda3727 emission-line galaxies at 0.3 pl z pl 1.68, and pg 1000 Ly-alpha emission-line galaxies at 3 pl z pl 7 with total emission line flux f pg 2* 10^-17 ergs s^-1 cm^-2 over 578 arcmin^2. We will obtain direct images with the F814W and F606W filters and dispersed images with the WFC/G800L grism at each position. The direct images will serve to provide a zeroth order model both for wavelength calibration of the extracted 1D spectra and for determining extraction apertures of the corresponding dispersed images. The primary scientific objectives are as follows: {1} We will establish a uniform sample of HAlpha and O II emission-line galaxies at z<1.7 in order to obtain accurate measurements of co-moving star formation rate density versus redshift over this redshift range. {2} We will study the spatial and statistical distribution of star formation rate intensity in individual galaxies using the spatially resolved emission-line morphology in the grism images. And {3} we will study high-redshift universe using Ly-alpha emitting galaxies identified at z pl 7 in the survey. The data will be available to the community immediately as they are obtained.
ACS 9463
Are OH/IR stars the youngest post-AGB stars? An ACS SNAPshot imaging survey
Essentially all well-characterized preplanetary nebulae {PPNs}– 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 propose an ACS/SNAPshot imaging survey of a large, morphologically unbiased sample of these objects, selected using their IRAS 12-to-25micron colors. Our ground-based imaging study of OH/IR stars has revealed a few compact bipolar objects, supporting our hypothesis. However since most objects remain unresolved, HST observations are needed to determine how and when the bipolar geometry asserts itself. 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 PPNs, are common or rare phenomena.
ACS 9673
CCD Daily Monitor
This program consists of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. This programme will be executed once a day for the entire lifetime of ACS
ACS 9480
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.
ACS 9476
Galaxy Evolution in the Richest Clusters at z=0.8: the EDisCS Cluster Sample
The study of distant cluster galaxies requires two key ingredients: {1} deep high-resolution imaging, to constrain galaxy structure; and {2} 8m-class spectroscopy, to measure stellar content, star-formation rates, dynamics, and cluster membership. We will reach both conditions with the addition of HST/ACS imaging to our suite of VLT {36 nights} and NTT {20 nights} observations of 10 confirmed clusters at z~0.8, drawn from the ESO Distant Cluster Survey {EDisCS}. The proposed HST/ACS data will complement our existing optical/IR imaging and spectroscopy with quantitative measures of cluster galaxy morphologies {i.e. sizes and shapes, bulge-disk decompositions, asymmetry parameters}, and with measurements of cluster masses via weak lensing. Major advantages unique to the EDisCS project include: {i} uniform selection of clusters; {ii} large enough sample sizes to characterize the substantial cluster-to-cluster variation in galaxy populations; {iii} large quantities of high quality data from 8m telescopes; {iv} uniform measurements of morphologies, spectroscopic and photometric redshifts, SEDs, star-formation/AGN activities, and internal kinematics; {v} optical selection of clusters to complement the X-ray selection of almost all high-z clusters in the ACS GTO programs; {vi} forefront numerical simulations designed specifically to allow physical interpretation of observed differences between the high-z and local clusters.
ACS 9395
Is Bulge Formation Still Going-On? An ACS Survey of Pseudo-Bulges
Pseudo-bulges, i.e., bulges with an exponential light profile, have been unveiled in the centers of many intermediate-type disks. Their structural similarity with the disks provides support to theoretical scenarios in which bulges may form due to secular evolution processes within the host disks. If at play, these processes would likely be active throughout a large fraction of cosmic history down to our days: `young’ bulges should exist. Our previous HST WFPC2 and NICMOS survey of ~100 spirals has provided V-H colors for 11 Sb-Sc pseudo-bulges, and these could be interpreted as suggestive of relatively young stellar ages. Furthermore, dense nuclei have been discovered in these pseudo-bulges, and their V-H colors may imply stellar masses sufficiently large to activate the formation of the pseudo- bulge by means of dynamical dissolution of progenitor bars. However, the V-H color, on its own, is fully degenerate towards stellar ages, metallicities and masses, as well as dust content. We therefore propose to use ACS to observe the 11 pseudo-bulges of our combined WFPC2 and NICMOS sample in the F330W, F435W, and F814W filters. Extending the wavelength baseline to the bluer passbands is essential to break the mass-age-metallicity-dust degeneracy, and will provide far more accurate estimates for the stellar population properties of the pseudo-bulges and their nuclei. Proving the existence of `young’ bulges in the local Universe would have a big impact in our understanding of the formation of the Hubble sequence.
ACS 9401
The ACS Virgo Cluster Survey
We propose the most comprehensive imaging survey to date of low-redshift, early-type galaxies. Our goal is to exploit the exceptional imaging capabilities of the ACS by acquiring deep images — in the SDSS g^ and z^ bandpasses — for 163 E, S0, dE, dE, N and dS0 galaxies in Virgo, the nearest rich cluster. This extraordinary dataset would likely constitute one of the principal legacies of HST, and would have widespread applications for many diverse areas of astrophysics. Our immediate scientific objectives are threefold: {1} measure metallicities, ages and radii for the many thousands of globular clusters {GCs} in these galaxies, and use this information to derive the protogalactic mass spectrum of each galaxy; {2} measure the central luminosity and color profile of each galaxy, and use this information to carry out a completely independent test of the merging hierarchy inferred from the GCs, with the aid of N-body codes that simulate the merger of galaxies containing massive black holes; and {3} calibrate the z^ -band SBF method, measure Virgo’s 3-D structure, and carry out the definitive study of the GC luminosity function’s precision as a standard candle. Our proposed Virgo Cluster Survey will yield a database of unprecedented depth, precision and uniformity, and will enable us to study the record of galaxy and cluster formation in a level of detail which will never be possible with more distant systems.
ACS 9440
The Composition of Io’s Pele Plume
