NASA Hubble Space Telescope Daily Report #4269
HUBBLE SPACE TELESCOPE DAILY REPORT # 4269
– Continuing to collect World Class Science
PERIOD COVERED: UT December 28, 2006 (DOY 362)
OBSERVATIONS SCHEDULED
ACS/HRC 10877
A Snapshot Survey of the Sites of Recent, Nearby Supernovae
During the past few years, robotic {or nearly robotic} searches for supernovae {SNe}, most notably our Lick Observatory Supernova Search {LOSS}, have found hundreds of SNe, many of them in quite nearby galaxies {cz < 4000 km/s}. Most of the objects were discovered before maximum brightness, and have follow-up photometry and spectroscopy; they include some of the best-studied SNe to date. We propose to conduct a snapshot imaging survey of the sites of some of these nearby objects, to obtain late-time photometry that {through the shape of the light and color curves} will help reveal the origin of their lingering energy. The images will also provide high-resolution information on the local environments of SNe that are far superior to what we can procure from the ground. For example, we will obtain color-color and color-magnitude diagrams of stars in these SN sites, to determine the SN progenitor masses and constraints on the reddening. Recovery of the SNe in the new HST images will also allow us to actually pinpoint their progenitor stars in cases where pre- explosion images exist in the HST archive. This proposal is an extension of our successful Cycle 13 snapshot survey with ACS. It is complementary to our Cycle 15 archival proposal, which is a continuation of our long-standing program to use existing HST images to glean information about SN environments.
ACS/WFC 10813
MgII Absorption Line Systems: Galaxy Halos or the Metal-Enriched IGM?
MgII QSO absorption lines detected in the spectra of background QSOs were used over a decade ago to infer that all redshift z > 0.2 galaxies have gaseous halos of radius ~ 60 kpc. The actual size of the halo was believed to be proportional to the luminosity of the galaxy. However, these conclusions are now much harder to understand in light of the results from numerical simulations which show how gas evolves in the universe. These models predict that gas and galaxies merely share the same filamentary structures defined by dark matter. If these models are correct, how are MgII systems and galaxies really related? We can better understand the distribution of absorbing gas if we FIRST select galaxies close to QSO sightlines and THEN search for MgII absorption at the redshift of the intervening galaxies. This is the antithesis of the original experiments which sought to find absorbing galaxies based on known MgII systems. The frequency with which we detect MgII lines from randomly selected galaxies should enable us to better understand if absorption arises in the halos of individual galaxies, or if MgII merely arises in the same IGM that galaxies inhabit. We have used ground-based telescopes to indentify twenty z = 0.31-0.55 galaxies within 14-51 kpc of a g < 20 QSO, and to search for MgII absorption at the galaxies' redshifts. Surprisingly, we find that only 50% of our QSOs show MgII absorption. In this proposal, we seek multi-color ACS images of twelve of the fields to i} correlate the incidence of MgII with galaxy morphology; ii} determine if absorption {or lack thereof} is related to galaxy disks or halos; iii} search for signs of galaxy interactions which may explain the large cross-sections of MgII systems; and iv} look for faint interloping galaxies closer to the line of sight than the one we identified. An important component of the program is to observe each field in the SDSS g-, r- and i-bands, to permit an estimate of the photometric redshift of any objects which lie closer to the QSO sightline than the identified galaxy, and which might actually be responsible for the absorption.
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.
ACS/WFC/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.
NIC1 10797
HE0450-2958: Lonesome black hole, scantly dressed quasar or massively dust obscured host galaxy?
We propose to obtain a deep NICMOS image of the bright z=0.285 quasar HE0450-2958 that has an exceptional, undetected host galaxy, at least 6 times fainter than expected for the quasar luminosity. Several mutually exclusive explanations that were put forward in the last weeks, attempting to explain the apparently undermassive host galaxy, have important implication for their respective areas: The host could be a dust obscured ultra-luminous infrared galaxy in transition to become a quasar, HE450-2958 could have a normal host galaxy but an undermassive central black hole, or the quasar could recently have been ejected from a nearby companion galaxy in a 3-body black hole interaction or by gravitational recoil. We want to use NIC2 with the minimum-background F160W filter to obtain a >=10 times fainter limit on the host galaxy mass than is currently available with ACS, in order to set strong constraints for these very important scenarios.
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.
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.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
10581 – OBAD Failed During LOS OBAD2 scheduled at 362/10:40:16 failed. At AOS 10:58:00 ESB 1903(OBAD Failed Quaternion) was observed.
10583 – GSACQ(2,1,2) fine lock backup on FGS 2 GSACQ(2,1,2) at 362/22:34:47 acquired in fine lock backup on FGS 2 only, with QF1STOPF and QSTOP flags set on FGS 1. No other flags were seen. Vehicle was LOS at time of failure.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS GSacq 11 11
FGS REacq 02 02
OBAD with Maneuver 26 25
SIGNIFICANT EVENTS: (None)
