Status Report

NASA Hubble Space Telescope Daily Report #4273

By SpaceRef Editor
January 8, 2007
Filed under , ,
NASA Hubble Space Telescope Daily Report #4273


– Continuing to collect World Class Science

PERIOD COVERED: UT January 05,06,07, 2007 (DOY 005,006,007)


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 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 images. Each observation will need its own CRMAP, as different SAA passages leave different imprints on the NICMOS detectors.

ACS/HRC 11053

Earth Flats

Sky flats will be obtained by observing the bright Earth with the HRC and WFC. These observations will be used to verify the accuracy of the latest pipeline flats and to monitor any changes. Weekly coronagraphic monitoring is required to assess the changing position of the spots.

ACS/HRC 11041

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. The files, biases and dark will be used to create reference files for science calibration. This programme will be for the entire lifetime of ACS. For cycle 15 the program will cover 18 months 12.1.06->05.31.08 and it has been divied into three different proposal each covering six months. The three proposals are 11041-11042-11043.

WFPC2 11029

WFPC2 CYCLE 15 Intflat Linearity Check and Filter Rotation Anomaly Monitor

Intflat observations will be taken to provide a linearity check: the linearity test consists of a series of intflats in F555W, in each gain and each shutter. A combination of intflats, visflats, and earthflats will be used to check the repeatability of filter wheel motions. {Intflat sequences tied to decons, visits 1-18 in prop 10363, have been moved to the cycle 15 decon proposal xxxx for easier scheduling.} Note: long-exposure WFPC2 intflats must be scheduled during ACS anneals to prevent stray light from the WFPC2 lamps from contaminating long ACS external exposures.

ACS/WFC 10918

Reducing Systematic Errors on the Hubble Constant: Metallicity Calibration of the Cepheid PL Relation

Reducing the systematic errors on the Hubble constant is still of significance and of immediate importance to modern cosmology. One of the largest remaining uncertainties in the Cepheid- based distance scale {which itself is at the foundation of the HST Key Project determination of H_o} which can now be addressed directly by HST, is the effect of metallicity on the Cepheid Period-Luminosity relation. Three chemically distinct regions in M101 will be used to directly measure and thereby calibrate the change in zero point of the Cepheid PL relation over a range of metallicities that run from SMC-like, through Solar, to metallicities as high as the most metal- enriched galaxies in the pure Hubble flow. ACS for the first time offers the opportunity to make a precise calibration of this effect which currently accounts for at least a third of the total systematic uncertainty on Ho. The calibration will be made in the V and I bandpasses so as to be immediately and directly applicable to the entire HST Cepheid-based distance scale sample, and most especially to the highest-metallicity galaxies that were hosts to the Type Ia supernovae, which were then used to extend the the distance scale calibration out to cosmologically significant distances.

FGS 10912

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.


Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies

The formative phase of the most massive galaxies may be extremely luminous, characterized by intense star- and AGN-formation. Till now, few such galaxies have been unambiguously identified at high redshift, restricting us to the study of low-redshift ultraluminous infrared galaxies as possible analogs. We have recently discovered a sample of objects which may indeed represent this early phase in galaxy formation, and are undertaking an extensive multiwavelength study of this population. These objects are bright at mid-IR wavelengths {F[24um]>0.8mJy}, but deep ground based imaging suggests extremely faint {and in some cases extended} optical counterparts {R~24-27}. Deep K-band images show barely resolved galaxies. Mid-infrared spectroscopy with Spitzer/IRS reveals that they have redshifts z ~ 2-2.5, suggesting bolometric luminosities ~10^{13-14}Lsun! We propose to obtain deep ACS F814W and NIC2 F160W images of these sources and their environs in order to determine kpc-scale morphologies and surface photometry for these galaxies. The proposed observations will help us determine whether these extreme objects are merging systems, massive obscured starbursts {with obscuration on kpc scales!} or very reddened {locally obscured} AGN hosted by intrinsically low-luminosity galaxies.

ACS/WFC 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.

ACS/WFC 10885

Deep Photometry of NGC 1569: Understanding the Closest and Strongest Starburst of the Nearby Universe

Massive starbursts drive the evolution of galaxies at high redshift, but they can only be studied in detail in the nearby Universe where they are much rarer. The dwarf irregular galaxy NGC 1569 at 2.2 Mpc is the closest example of a true starburst. It has sustained exceptionally high star formation {SF} activity over the last Gyr, 2-3 orders of magnitude higher than in normal dwarf irregulars and spirals. This SF has been probed extensively by previous HST observations that have reached just below the tip of the red giant branch {RGB}. But the data have not been able to constrain the more ancient SF history {SFH}, so that our understanding remains very incomplete. It is an open question whether NGC 1569 just started to form stars around 1 Gyr ago, or whether significant SF was already active before that. We do not know what triggered the recent SF, how long the current intense SF activity has been going on, and whether such SF activity has been a more common occurrence in the past history of this galaxy. More importantly, most of these questions remain unanswered for other starburst galaxies in the nearby and distant universe as well. HST is the only telescope that can do the necessary crowded-field photometry to resolve these issues. We propose to use ACS/WFC to build a deep I vs. V-I color-magnitude diagram {CMD} that goes some 4 magnitudes deeper than the RGB tip. This will detect and characterize the red clump {RC} and horizontal branch {HB} features. The CMD will be interpreted by fitting synthetic CMDs constructed from evolutionary tracks to infer the SFH. The joint constraints from the presence, apparent magnitude, and width of the RC, HB and RGB features will independently constrain both the age and metallicity of the old and evolved stellar population of NGC 1569, the presence of multiple bursts if any, and their duration and metallicity spread. This will reveal the evolutionary status over cosmic time, and more generally will constrain the processes at play in the origin and evolution of galaxies. This project is only possible because of the high sensitivity of ACS, and it can be done very efficiently because of the location of NGC 1569 in the CVZ. Since NGC 1569 is so close, it may be the only nearby starburst for which these issues can be addressed in the foreseeable future.

ACS/HRC 10878

An ACS Prism Snapshot Survey for z~2 Lyman Limit Systems

We propose to conduct a spectroscopic survey of Lyman limit absorbers at redshifts 1.7 < z < 2.2, using ACS/HRC and the PR200L prism. We have selected 100 quasars at 2.3 < z < 2.6 from the Sloan Digital Sky Survey Spectroscopic Quasar sample, for which no BAL signature is found at the QSO redshift and no strong metal absorption lines are present at z > 2.3 along the lines of sight. The survey has three main observational goals. First, we will determine the redshift frequency dN/dz of the LLS over the column density range 16.3 < log N_HI < 20.3 cm^-2. Second, we will measure the column density frequency distribution f{N} for the partial Lyman limit systems {PLLS} over the column density range 16.3 < log N_HI < 17.5 cm^-2. Third, we will identify new sightlines for measurements of the primordial D/H ratio. With this survey, we will also constrain two key quantities of cosmological relevance: First, the measurements of dN/dz for optically thick LLS and f{N} for the PLLS are critical to estimating the attenuation of extragalactic ionizing sources {e.g. QSOs}. Currently, uncertainties in dN/dz and f{N} are the greatest sources of uncertainty for inferring the shape and intensity of the UV background radiation field. Second, we will estimate the amount of metals in the LLS using the f{N} and ground based observations of metal line transitions. It is possible that a significant fraction of the "missing metals" at z~2 are associated with these highly ionized absorbers. Third, analysis of the LLS lends to investigations of the interface between galaxies {i.e. the damped Lyman alpha systems} and the intergalactic medium {i.e. the Lyman alpha forest}. This survey is ideal for a snapshot observing program, because the on-object integration times are less than 10 minutes, and the targets cover the majority of the northern sky.

ACS/WFC 10835

Probing The Globular Cluster / Low Mass X-ray Binary Connection in Early-type Galaxies At Low X-ray

Combined high-resolution imaging from Hubble and Chandra {CXO} has revolutionized our understanding of extragalactic low-mass X-ray binaries {LMXBs} and globular clusters {GCs}, yet their connection in early-type galaxies has remained unstudied at the luminosities of the Galactic LMXBs in GCs. NGC 4278 and 3379 will be the first two prototypical elliptical galaxies with deep CXO observations enabling the study of LMXBs at lower luminosities. We propose mosaic ACS observations of both galaxies {5 fields per galaxy} that will provide the most comprehensive view into the connection between GCs and LMXBs in early-type galaxies. We will detect ~860 and ~270 GCs in all of NGC 4278 and NGC 3379, respectively. These two galaxies will have among the greatest number of detected GC-LMXBs to date {~130 & 50} and will include the faintest GC-LMXBs in a normal early-type galaxy. We will measure the fraction of GCs which contain LMXBs, as a function of X-ray luminosity, galactocentric distance, color, and GC half-light radius. Using the radial profiles of optical light, GCs, and LMXBs, we will determine the percentage of field LMXBs which may have originated in GCs. We will use the measured GC properties over the entire extent of both galaxies to constrain theories of GC formation and evolution.

ACS/WFC 10826

Galaxy Evolution During Half the Age of the Universe: ACS imaging of rich galaxy clusters

Detailed studies of nearby galaxies {z<0.05} show that galaxies have very complex histories of formation and evolution involving mergers, bursts of star formation, and morphological changes. Even so, the global properties of the galaxies {radii, luminosities, rotation velocities, velocity dispersions, and absorption line strengths} follow a number of very tight {empirical} scaling relations, e.g. the Tully-Fisher relation and the Fundamental Plane {FP}. We use the scaling relations plus quantative morphological measures for galaxy clusters up to z=1 to constrain models for galaxy evolution. Here we request 24 orbits to obtain ACS imaging of the remaining three clusters in our sample at z~0.7-1.0. High resolution imaging of the clusters is critical for our study of star formation histories and structural evolution in dense environments since z<1. We have previously obtained deep spectroscopic observations of the clusters with Gemini. The data will provide samples large enough to establish the slope of the FP for each cluster. With multiple clusters at similar redshifts, we can probe evolutionary differences within a single epoch in order to decouple changes due to different environments. Our two other high-z clusters exhibit different chemical enrichment histories, which we argue are due to the different merging histories of these clusters.

ACS/WFC 10816

The Formation History of Andromeda’s Extended Metal-Poor Halo

We propose deep ACS imaging in the outer spheroid of the Andromeda galaxy, in order to measure the star formation history of its true halo. For the past 20 years, nearly all studies of the Andromeda “halo” were focused on the spheroid within 30 kpc of the galaxy’s center, a region now known to host significant substructure and populations with high metallicity and intermediate ages. However, two groups have recently discovered an extended metal-poor halo beyond 30 kpc; this population is distinct in its surface-brightness profile, abundance distribution, and kinematics. In earlier cycles, we obtained deep images of the inner spheroid {11 kpc on the minor axis}, outer disk {25 kpc on the major axis}, and giant tidal stream, yielding the complete star formation history in each field. We now propose deep ACS imaging of 4 fields bracketing this 30 kpc transition point in the spheroid, so that the inner spheroid and the extended halo populations can be disentangled, enabling a reconstruction of the star formation history in the halo. A wide age distribution in the halo, as found in the inner spheroid, would imply the halo was assembled through ongoing accretion of satellite galaxies, while a uniformly old population would be a strong indication that the halo was formed during the early rapid collapse of the Andromeda proto-galaxy.

NIC2, ACS/WFC 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.

ACS/WFC 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.

ACS/WFC 10794

Direct Age Determination of the dE Galaxies NGC 147 and NGC 185

Dwarf elliptical {dE} galaxies form some of the most numerous galaxies in the universe, yet their origins remain a mystery. The most popular formation scenarios are that dEs are either ancient, primordial objects, or the recent remnants of disrupted progenitor galaxies. These scenarios predict significantly different ratios of old and intermediate age stars. Stellar population characteristics can therefore discriminate between these scenarios. Previous spectroscopic work based on line strengths has had too many uncertainties to uniquely infer the stellar populations. Resolved color magnitude diagrams are needed instead. Since dE galaxies generally do not have stars younger than 1 Gyr, resolving the main sequence turnoff is required to directly quantify the star formation histories. Only ACS on HST can reach this depth, and it can only do so for the nearest two dE galaxies in the Local Group: the M31 dE satellites NGC 147 and NGC 185. Their main sequence turnoffs are expected to be at an apparent magnitude of V=29; we request F606W/F814W imaging one half magnitude fainter than this limit {and more than four magnitudes fainter than the deepest previous dE observations}. This will quantify the ratio of old to intermediate-age stars and will allow us to discriminate between the competing models of dE formation. On-going Keck/DEIMOS spectroscopy of several hundred red giant stars in each of these two dE galaxies, coupled with dynamical modeling and spectral synthesis, will complement the ACS measurement by providing information on chemical abundance patterns, dark matter content and internal dynamics. The proposed ACS data will be the first to directly quantify the onset and duration of star formation episodes in any dE galaxy. This measurement can only be done with HST/ACS, and it can only be done for these two galaxies in the dE class. This project will therefore be unique, and will be the most comprehensive study to date of any dE galaxy.

ACS/WFC 10633

GRB afterglows and host galaxies at very high redshifts

Cosmology is beginning to constrain the nature of the earliest stars and galaxies to form in the universe, but direct observation of galaxies at z>6 remains highly challenging due to their scarcity, intrinsically small size, and high luminosity distance. GRB afterglows, thanks to their extreme luminosities, offer the possibility of circumventing these normal constraints by providing redshifts and spectral information which couldn’t be obtained by direct observation of the hosts themselves. In addition, the association of GRBs with massive stars means that they are a tracer of star formation, and that their hosts are likely responsible for a large proportion of the ionizing radiation during that era. Our collaboration is mounting a campaign to rapidly identify and study candidate very high redshift bursts, bringing to bear a network of 2, 4 and 8m telescopes with nIR instrumentation. The capabilities of Swift to detect faint, distant GRBs, and to report accurate positions for many bursts in near real-time makes our program now feasible. HST is crucial to this endeavour, allowing us {a} to monitor the late time afterglows and hence compare them to lower-z bursts and test the use of GRBs as standard candles; and {b} characterise the basic properties, luminosities, and in some cases morphologies, of the hosts, which is essential to understanding these primordial galaxies and their relationship to other populations.

ACS/HRC 10627

A Snapshot Survey of Post-AGB Objects and Proto-Planetary Nebulae

We propose an ACS/HRC snapshot survey of 50 post-AGB sources, objects which have evolved from the AGB but may or may not become planetary nebulae {PNe}. This survey will complement existing HST images of proto-planetary nebulae {PPNe} and PNe in addressing circumstellar envelope morphology as a function of: 1} the progenitor star mass; 2} the chemical composition; and 3} evolutionary stage. We will connect the observed diversity of nebualar shapes with the main physical and chemical conditions characterizing post-AGB objects, to identify the mechanism that breaks the symmetry of AGB mass loss. To our knowledge, no previous HST projects have been specifically designed to address this issue. From our database of 360 post-AGB candidates, we have selected approximately 50 targets, none of which have been or are being observed with HST, to sample different central star masses, chemical compositions, and evolutionary stages, uniformly across the sky. These new data will also provide important constraints to a quantitative analysis of Spitzer Space Telescope {SST} observations planned for a similar sample of objects. We will model the HST images and SST spectra using our axisymmetric dust code 2-Dust, to derive dust density distributions, pole to equator density ratios, dust shell masses, inclination angles as well as dust composition.


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


10597 – GSacq((2,1,1) failed due to Seaarch Radius Limit exceeded on FGS 1 GSacq(2,1,1) failed at 17:48:29 due to search radius limit exceeded for FGS 1. Received 486 ESB a05 “Exceeded SRL”. OBAD 1 RSS unavailable until engineering dump OBAD 2 RSS 5.66 a/s MAP RSS 7.17 a/s

10599 – REAcq (2,1,1) failed due to Search Radius Limit Exceeded on FGS 1 At AOS (005/19:24:15) REAcq (2,1,1) scheduled at 005/19:20:13-19:27:26 failed due to Search Radius Limit Exceeded on FGS 1. Received 486 ESB message a05 “Exceeded_SRL”. OBAD #1 unavailable due to LOS OBAD #2: V1 -1.17, V2 -4.23, V3 1.15, RSS 4.54 OBAD MAP: V1 2.22, V2 10.99, V3 2.32, RSS 11.46

10600 – GSAcq(2,1,2) results in fine lock (2,0,2) Upon acquisition of signal at 005/23:27:35, the GSAcq(2,1,2) scheduled at 005/22:48:15 – 22:56:20 had resulted in fine lock backup (2,0,2) using FGS-2 due to (QF1STOPF) stop flag indication on FGS-1. Pre-acquisition OBADs showed (RSS) attitude correction values of 5173.60 and 6.80 arcseconds. Post-acquisition OBAD/MAP not scheduled. Subsequent REacq(2,1,2) scheduled at 006/00:03:38 also resulted in fine lock backup (2,0,2) using FGS-2 due to stop flag on FGS-1.

10601 – GSacq(2,1,1) failed due to search radius limit exceeded. During LOS GSacq(2,1,1) scheduled at 006/22:31:10 failed due to search radius limit exceeded on FGS 1. Subsequent REacq(2,1,1) at 007/00:05:26 also failed to RGA Hold (Gyro Control) due to (QF1SRLEX) search radius limit exceeded on FGS-1. One 486 ESB “a05” (FGS Coarse Track failed – Search Radius Limit Exceeded) was received at 007/00:09:38. Pre-acquisition OBADs showed (RSS) values of 2986.84 and 12.76 arcseconds. Post-acq OBAD/MAP showed (RSS) value of 16.81 arcseconds.

10602 – REacq(1,3,3) failed to RGA Hold (Gyro Control) Upon acquisition of signal at 008/06:33:31, the REacq(1,3,3)scheduled at 008/05:10:57 – 05:19:02 was observed to have failed to RGA Hold due to (QF1STOPF) stop flag indication on FGS-1. Pre-acquisition OBADs (RSS) attitude correction values not available due to LOS.


17987-0 – Disable Aero Torque Compensation


                         SCHEDULED      SUCCESSFUL
FGS GSacq               25                      23
FGS REacq               12                       09
OBAD with Maneuver  76                      76


Flash Report: Aero compensation disabled.

At approximately 2007/005 14:35, aerodynamic torque compensation was disabled per Ops Request 17987. The aero compensation has been performing as expected, but several recent guide star acquisition failures and the currently low values of aero torque disturbances motivated temporarily disabling it. The computed aero torques continue to be monitored via TMDIAGs.

SpaceRef staff editor.