NASA Hubble Space Telescope Daily Report #4301
HUBBLE SPACE TELESCOPE DAILY REPORT # 4301
– Continuing to collect World Class Science
PERIOD COVERED: UT February 15, 2007 (DOY 046)
OBSERVATIONS SCHEDULED
WFPC2 10520
Resolving the Complex Star Formation History of the Leo I Dwarf Spheroidal Galaxy
Determining the star formation histories {SFHs} and chemical evolution of nearby galaxies gives us powerful constrains on the physical processes that regulate galaxy evolution. The SFHs can be measured most accurately by comparing the observed densities of stars in color-magnitude diagrams {CMDs} to predictions from stellar evolutionary models. WFPC2 imaging of the Leo I dSph shows it is unique because its stellar population is relatively young. Approximately 68% of its stars formed between 1 and 7 Gyr ago and only 12% of its stars formed >~ 10 Gyr ago. We propose to vastly improve the derived SFH of Leo I by exploiting ACS/WFC’s higher quantum efficiency at bluer wavelengths, higher spatial resolution, and larger field-of-view. The figure of merit for our proposed observations, defined as the age resolution times the number of stars detected, will be a factor of 12 higher than existing WFPC2 observations. To surmount the degeneracy of age and metallicity in the CMD, we have independently measured the metallicity distribution of its stars using spectroscopy. Simultaneously modeling the metallicity distribution and CMD, we will firmly constrain the evolution of the Leo I dSph, a unique example of an isolated dwarf galaxy that has not been influenced by interactions with the Milky Way or M31.
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.
NIC3 11082
NICMOS Imaging of GOODS: Probing the Evolution of the Earliest Massive Galaxies, Galaxies Beyond
Deep near-infrared imaging provides the only avenue towards understanding a host of astrophysical problems, including: finding galaxies and AGN at z > 7, the evolution of the most massive galaxies, the triggering of star formation in dusty galaxies, and revealing properties of obscured AGN. As such, we propose to observe 60 selected areas of the GOODS North and South fields with NICMOS Camera 3 in the F160W band pointed at known massive M > 10^11 M_0 galaxies at z > 2 discovered through deep Spitzer imaging. The depth we will reach {26.5 AB at 5 sigma} in H_160 allows us to study the internal properties of these galaxies, including their sizes and morphologies, and to understand how scaling relations such as the Kormendy relationship evolved. Although NIC3 is out of focus and undersampled, it is currently our best opportunity to study these galaxies, while also sampling enough area to perform a general NIR survey 1/3 the size of an ACS GOODS field. These data will be a significant resource, invaluable for many other science goals, including discovering high redshift galaxies at z > 7, the evolution of galaxies onto the Hubble sequence, as well as examining obscured AGN and dusty star formation at z > 1.5. The GOODS fields are the natural location for HST to perform a deep NICMOS imaging program, as extensive data from space and ground based observatories such as Chandra, GALEX, Spitzer, NOAO, Keck, Subaru, VLT, JCMT, and the VLA are currently available for these regions. Deep high-resolution near-infrared observations are the one missing ingredient to this survey, filling in an important gap to create the deepest, largest, and most uniform data set for studying the faint and distant universe. The importance of these images will increase with time as new facilities come on line, most notably WFC3 and ALMA, and for the planning of future JWST observations.
WFPC2 10871
Observations of the Galilean Satellites in Support of the New Horizons Flyby
On February 28 2007 the New Horizons {NH} spacecraft will fly by Jupiter on its way to Pluto, and will conduct an extensive series of observations of the Jupiter system, including the Galilean satellites. We propose HST observations to support and complement the New Horizons observations in four ways: 1} Determine the distribution and variability of Io’s plumes in the two weeks before NH closest approach, to look for correlations with Io- derived dust streams that may be detected by New Horizons, to understand the origin of the dust streams; 2} Imaging of SO2 and S2 gas absorption in Io’s plumes in Jupiter transit, which cannot be done by NH; 3} Color imaging of Io’s surface to determine the effects of the plumes and volcanos seen by New Horizons on the surface- New Horizons cannot image the sunlit surface in color due to saturation; 4} Imaging of far-UV auroral emissions from the atmospheres of Io, Europa, and Ganymede in Jupiter eclipse, near- simultaneously with disk-integrated NH UV spectra, to locate the source of the UV emissions seen by NH and use the response of the satellite atmospheres to the eclipse to constrain production mechanisms.
WFPC2 10890
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.
WFPC2 11089
WFPC2 UV Throughput Check after 27-Jan-2007 Safemode
Check UV throughput of standard star GRW+70D5824 in all four chips following safemode caused by ACS Side 2 failure.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS: (None)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL FGS GSacq 10 10 FGS REacq 05 05 OBAD with Maneuver 30 30
SIGNIFICANT EVENTS:
Flash Report: ACS Side-1 Switch and SBC-Only Operations The Flight Readiness Review for the switch to ACS Side-1 and subsequent SBC-Only Operations was held on 15 February 2007 (DOY 046). Authority was given to proceed with the first two steps of switching to Side-1, which consist of establishing ACS in its Side-1 Safing configuration and updating the SMAC20. Ops Requests #18018 and #18017 will be executed between 047/15:54 and 047/16:39.
Further ACS Side-1 reconfigurations will stand down until the ST ScI reports their analysis of WFPC2 UV Images. A telephone tag-up is planned for noon, February 16, for the ST ScI to report their findings. The remaining ACS transitions are planned to be executed between 047/18:00 and 048/02:25, pending HST Project approval at the tag-up telecon.
