NASA Hubble Space Telescope Daily Report #3971
HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science
DAILY REPORT # 3971
PERIOD COVERED: UT October 20, 2005 (DOY 293)
OBSERVATIONS SCHEDULED
ACS/WFC 10576
An ACS Imaging Survey of the Galaxies Hosting Strong Mg II Absorption
Strong MgII absorbers {with rest-frame absorption equivalent width W_MgII > 0.3 A} at redshift z < 1 are known to arise in extended gaseous halos around luminous galaxies. Detailed absorption line studies based on high-solution spectra of background quasars yield tight constraints on the metallicity, ionization state, and kinematics of the gaseous clouds. But whether they originate in gas accreted from surrounding satellite galaxies or outflows associated with active starburst in the host galaxies remains unclear. We have recently completed a search of the Sloan Digital Sky Survey data archive for strong MgII absorbers and identified over 1000 new systems that are previously unknown. A subset of these MgII absorbers with W_MgII > 1.8 A exhibit extreme kinematics with velocity widths {exceeding 200 km/s} in our follow-up echelle spectra. Their dynamics are consistent with various scenarios that include gas accretion {with speeds exceeding the virial velocity} and starburst outflows {possibly driven by recent merger events}. Independent of their exact nature, it is clear that strong MgII systems serve as signposts to galactic halos with extreme gas dynamics. Here we propose to conduct a snapshot survey of galaxies in the fields toward high-redshift quasars with known, strong MgII absorbers at 0.5 < z < 2. We plan to obtain high spatial-resolution ACS/WFC images of 60 fields to uncover galaxies fainter than L* at the redshifts of these absorbers and study their morphology. We will complement the HST observations with follow-up spectroscopic observations and IR images acquired at the Keck and Magellan Observatories to for redshift identifications and for measuring broad-band colors. We will investigate the correlation between absorption line kinematics and galaxy morphology. In particular, we will address whether on-going mergers is responsible for the extreme dynamics observed in MgII absorption based on their rest-frame ultraviolet morphology.
ACS/WFC 10586
The Rosetta Stone without a Distance: Hunting for Cepheids in the Primordial Galaxy I Zw 18
The Blue Compact Dwarf galaxy I Zw 18 is one of the most intriguing objects in the Local Universe. It has the lowest nebular metallicity of all known galaxies {Z=1/32 solar}. It has long been regarded as a possible example of a galaxy undergoing its first burst of star formation. However, its real evolutionary state continues to be controversial. The WFPC2 and NICMOS detection of AGB stars by our group and others suggested the presence of an underlying older population. However, deeper ACS observations by Izotov & Thuan {2004} recently failed to detect the signature of RGB stars. This was interpreted as confirmation that I Zw 18 is in fact a galaxy “in formation”, a local analog of primordial galaxies in the distant Universe. This result was widely reported in the international news media. However, an alternative possibility is that I Zw 18 is somewhat further away than previously believed, so that Red Giant Branch stars were too faint to detect. Quoted distances in the literature have ranged from 10 to 20 Mpc. We intend to resolve this controversy by direct determination of the distance to 1 Mpc accuracy using Cepheids. For this we request 12 visits of two orbits each, to execute at carefully planned intervals. We will obtain V and I band ACS/WFC photometry in each visit. The new data will be combined with archival data, but we show that the archival data by themselves are insufficient to achieve our science goals. The distance will allow us to place I Zw 18 into its proper place in the evolutionary sequence of galaxy formation.
ACS/WFC 10587
Measuring the Mass Dependence of Early-Type Galaxy Structure
We propose two-color ACS-WFC Snapshot observations of a sample of 118 candidate early- type gravitational lens galaxies. Our lens-candidate sample is selected to yield {in combination with earlier results} an approximately uniform final distribution of 40 early-type strong lenses across a wide range of masses, with velocity dispersions {a dynamical proxy for mass} ranging from 125 to 300 km/s. The proposed program will deliver the first significant sample of low-mass gravitational lenses. All of our candidates have known lens and source redshifts from Sloan Digital Sky Survey data, and all are bright enough to permit detailed photometric and stellar- dynamical observation. We will constrain the luminous and dark-matter mass profiles of confirmed lenses using lensed-image geometry and lens-galaxy structural/photometric measurements from HST imaging in combination with dynamical measurements from spatially resolved ground-based follow-up spectroscopy. Hence we will determine, in unprecedented detail, the dependence of early-type galaxy mass structure and mass-to-light ratio upon galaxy mass. These results will allow us to directly test theoretical predictions for halo concentration and star-formation efficiency as a function of mass and for the existence of a cuspy inner dark- matter component, and will illuminate the structural explanation behind the fundamental plane of early-type galaxies. The lens-candidate selection and confirmation strategy that we propose has been proven successful for high-mass galaxies by our Cycle 13 Snapshot program {10174}. The program that we propose here will produce a complementary and unprecedented lens sample spanning a wide range of lens-galaxy masses.
ACS/WFC 10626
A Snapshot Survey of Brightest Cluster Galaxies and Strong Lensing to z = 0.9
We propose an ACS/WFC snapshot survey of the cores of 150 rich galaxy clusters at 0.3 < z < 0.9 from the Red Sequence Cluster Survey {RCS}. An examination of the galaxian light in the brightest cluster galaxies, coupled with a statistical analysis of the strong-lensing properties of the sample, will allow us to contrain the evolution of both the baryonic and dark mass in cluster cores, over an unprecedented redshift range and sample size. In detail, we will use the high- resolution ACS images to measure the metric {10 kpc/h} luminosity and morphological disturbances around the brightest clusters galaxies, in order to calibrate their accretion history in comparison to recent detailed simulations of structure formation in cluster cores. These images will also yield a well-defined sample of arcs formed by strong lensing by these clusters; the frequency and detailed distribution {size, multiplicity, redshifts} of these strong lens systems sets strong constraints on the total mass content {and its structure} in the centers of the clusters. These data will also be invaluable in the study of the morphological evolution and properties of cluster galaxies over a significant redshift range. These analyses will be supported by extensive ongoing optical and near-infrared imaging, and optical spectroscopy at Magellan, VLT and Gemini telescopes, as well as host of smaller facilities.
ACS/WFC 10703
Life in the fast lane: The dark-matter distribution in the most massive galaxy clusters in the Universe at z>0.5
We propose two-filter ACS observations of a complete sample of 12 very X-ray luminous galaxy clusters at 0.5< z <0.7 as a cornerstone of a comprehensive multi-wavelength study of the properties of the most massive clusters in the universe. Our sample includes the famous systems Cl0016+16 and MS0451-03; all other clusters are new discoveries from the MACS survey. Being the counterparts of the best-studied systems at lower and higher redshift and comprising ALL massive clusters at 0.5< z <0.7 observable from Mauna Kea this sample will become the ultimate reference for cluster studies at z>0.5. HST’s unique capabilities will allow us to: 1} measure accurately the clusters’ dark matter distribution on scales from tens to more than 500/h_50 kpc from observations of strong and weak gravitational lensing, 2} use galaxy-galaxy lensing to measure the shape, extent, and mass content of the dark-matter halos of both cluster and field galaxies, and 3} study the color morphology of mergers and the star formation history of galaxies in a high-density environment. The proposed observations are complemented by Chandra observations of all our targets {all 12 awarded, 11 executed to date} which provide independent constraints on the dark matter and gas distribution in the cluster cores, as well a by extensive groundbased observations of weak lensing on yet larger scales, galaxy dynamics, and the SZ effect.
ACS/WFC/NIC3 10632
Searching for galaxies at z>6.5 in the Hubble Ultra Deep Field
We propose to obtain deep ACS {F606W, F775W, F850LP} imaging in the area of the original Hubble Ultra Deep Field NICMOS parallel fields and – through simultaneous parallel observations – deep NICMOS {F110W, F160W} imaging of the ACS UDF area. Matching the extreme imaging depth in the optical and near-IR bands will result in seven fields with sufficiently sensitive multiband data to detect the expected typical galaxies at z=7 and 8. Presently no such a field exist. Our combined optical and near-IR ultradeep fields will be in three areas separated by about 20 comoving Mpc at z=7. This will allow us to give a first assessment of the degree of cosmic variance. If reionization is a process extending over a large redshift interval and the luminosity function doesn’t evolve strongly beyond z=6, these data will allow us to identify of the order of a dozen galaxies at 6.5< z <8.5 - using the Lyman break technique - and to place a first constrain on the luminosity function at z>6.5. Conversely, finding fewer objects would be an indication that the bulk of reionization is done by galaxies at z=6. By spending 204 orbits of prime HST time we will capitalize on the investment of 544 prime orbits already made on the Hubble Ultra Deep Field {UDF}. We have verified that the program as proposed is schedulable and that it will remain so even if forced to execute in the 2-gyro mode. The data will be non-proprietary and the reduced images will be made public within 2 months from the completion of the observations.
NIC1/NIC2/NIC3 8793
NICMOS Post-SAA calibration – CR Persistence Part 4
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.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
9983 – GSacq(1,3,3) was not attempted @ 293/20:18:52z GSacq(1,3,3) scheduled at 293/20:18:52 was not attempted due to open loop timer. At 293/20:09:00 ESB 1806 (open look timer expired) was received. This caused a transition from T2G to M2G. observation affected: ACS 10703
The Reacqs at 21:52:48 and 23:28:44 also were not attempted. Two OBADs were excecuted at 294/00:32:00 to attempt recovery of the remaining Reacqs.
9984 – GSacq(1,3,3) Reacq failed @ 294/01:08:57z Target Reacq GSAcq(1,3,3) scheduled at 294/01:04:40 failed. Also:
GSACQ(1,3,3) Reacq at 02:40:34 failed at 02:44:32 with “A0E” atatus buffer message.
GSACQ(1,3,3) Reacq at 04:16:29 failed at 04:20:17 with “A0E” status buffer message.
GSACQ(1,3,3) Reacq at 05:52:24 and at 07:28:20 did not make any attempt to acquire lock.
COMPLETED OPS REQUEST:
- 17575-0 – ACS MIE Recovery – 2/2 (CANCELLED)
- 17576-0 – ACS MIE Reset and MIE RAM Dump @ 293/1654z
- 17577-0 – Reset ACS and Recover to Operate Mode @ 293/2315z
- 17578-0 – OBAD Execution @ 294/0033z, 294/0040z
- 17579-1 – OBAD Execution @ 294/0212z
- 17580-1 – Execute OBAD @ 294/0355z
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL HSTAR REFERENCE
FGS Gsacq 06 05 (HSTAR
# 9983)
FGS Reacq 08 01 (HSTAR
# 9983 & #9984)
OBAD with Maneuver 16 16
SIGNIFICANT EVENTS:
1. Flash Report “ACS Image Dump and Boot-Operate Transition” Commanding for Ops Request 17577-0 was completed at 293/23:15. The ACS was transitioned down to Boot and back up to Operate, with the MIE successfully returning to its OperStby mode. Upon reaching Operate, the Cal Door and Filter Wheel were then repositioned to correctly intercept the ACS science timeline. Lastly, NSSC-1 event flag 2 was cleared to allow stored commanding to the SBC. ACS has now been restored to its nominal observing configuration.
