NASA Hubble Space Telescope Daily Report # 4449
Notice: Due to the conversion of some ACS WFC or HRC observations into WFPC2, or NICMOS observations after the loss of ACS CCD science capability in January, there may be an occasional discrepancy between a proposal’s listed (and correct) instrument usage and the abstract that follows it.
HUBBLE SPACE TELESCOPE DAILY REPORT # 4449
– Continuing to collect World Class Science
PERIOD COVERED: UT September 17, 2007 (DOY 260)
OBSERVATIONS SCHEDULED
WFPC2 10789
The Role of Environment in the Formation of Dwarf Galaxies Clusters of galaxies contain an overdensity of dwarfs compared to the field. Within galaxy clusters there is also a correlation between the overdensity of dwarfs and local galaxy density, such that areas of lower galaxy density contain more dwarfs per giant. The origin of these ‘extra’ dwarfs is unknown, but a large fraction of them did not form through standard collapses early in the universe. Some dwarf ellipticals in clusters have metal rich and young {< 6 Gyr} stellar populations while others contain old metal poor populations, suggesting multiple formation mechanisms and time scales. We propose to test the idea that dwarfs descend from galaxies accreted into clusters during the past 8 Gyr by correlating ages and metallicities of dwarfs with their internal structures - spiral arms, bars, and disks. If dwarfs originate from more massive galaxies then these features should be common in metal rich and young dwarfs. On the other hand, if no correlation is found it would suggest that dwarfs form through in-situ collapses of gas in the intragalactic medium after the universe was reionized.
WFPC2 11027
Visible Earth Flats
This proposal monitors flatfield stability. This proposal obtains sequences of Earth streak flats to construct high quality flat fields for the WFPC2 filter set. These flat fields will allow mapping of the OTA illumination pattern and will be used in conjunction with previous internal and external flats to generate new pipeline superflats. These Earth flats will complement the Earth flat data obtained during cycles 4-14.
WFPC2 11081
RR Lyrae stars in M31 Globular Clusters: How did the M31 Spiral Galaxy Form?
The pulsation properties of the RR Lyrae stars in the globular clusters of the Andromeda galaxy {M31} have the potential to provide essential insight on the first epoch of the galaxy formation and to trace the merging episodes that led to the assembly of M31. Their mean periods along with the cluster metallicities can provide an independent estimate of the M31 cluster ages and, in turn, of the time scale of the M31 halo formation, by comparison with their Milky Way counterparts. We will observe RR Lyrae stars in 6 appropriately selected globular clusters of M31 using WFPC2 to derive periods, light curves, and physical parameters of these eyewitnesses of the first epochs of the M31 formation.
WFPC2 11084
Probing the Least Luminous Galaxies in the Local Universe
We propose to obtain deep color-magnitude data of eight new Local Group galaxies which we recently discovered: Andromeda XI, Andromeda XII, and Andromeda XIII {satellites of M31}; Canes Venatici I, Canes Venatici II, Hercules, and Leo IV {satellites of the Milky Way}; and Leo T, a new “free-floating” Local Group dwarf spheroidal with evidence for recent star formation and associated H I gas. These represent the least luminous galaxies known at *any* redshift, and are the only accessible laboratories for studying this extreme regime of galaxy formation. With deep WFPC-2 F606W and F814W pointings at their centers, we will determine whether these objects contain single or multiple age stellar populations, as well as whether these objects display a range of metallicities.
WFPC2 11178
Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries
The recent discovery of numerous transneptunian binaries {TNBs} opens a window into dynamical conditions in the protoplanetary disk where they formed as well as the history of subsequent events which sculpted the outer Solar System and emplaced them onto their present day heliocentric orbits. To date, at least 47 TNBs have been discovered, but only about a dozen have had their mutual orbits and separate colors determined, frustrating their use to investigate numerous important scientific questions. The current shortage of data especially cripples scientific investigations requiring statistical comparisons among the ensemble characteristics. We propose to obtain sufficient astrometry and photometry of 23 TNBs to compute their mutual orbits and system masses and to determine separate primary and secondary colors, roughly tripling the sample for which this information is known, as well as extending it to include systems of two near-equal size bodies. To make the most efficient possible use of HST, we will use a Monte Carlo technique to optimally schedule our observations.
WFPC2 11229
SEEDS: The Search for Evolution of Emission from Dust in Supernovae with HST and Spitzer
The role that massive stars play in the dust content of the Universe is extremely uncertain. It has long been hypothesized that dust can condense within the ejecta of supernovae {SNe}, however there is a frustrating discrepancy between the amounts of dust found in the early Universe, or predicted by nucleation theory, and inferred from SN observations. Our SEEDS collaboration has been carefully revisiting the observational case for dust formation by core-collapse SNe, in order to quantify their role as dust contributors in the early Universe. As dust condenses in expanding SN ejecta, it will increase in optical depth, producing three simultaneously observable phenomena: {1} increasing optical extinction; {2} infrared {IR} excesses; and {3} asymmetric blue-shifted emission lines. Our SEEDS collaboration recently reported all three phenomena occurring in SN2003gd, demonstrating the success of our observing strategy, and permitting us to derive a dust mass of up to 0.02 solar masses created in the SN. To advance our understanding of the origin and evolution of the interstellar dust in galaxies, we propose to use HST’s WFPC2 and NICMOS instruments plus Spitzer’s photometric instruments to monitor ten recent core- collapse SNe for dust formation and, as a bonus, detect light echoes that can affect the dust mass estimates. These space-borne observations will be supplemented by ground- based spectroscopic monitoring of their optical emission line profiles. These observations would continue our 2-year HST and Spitzer monitoring of this phenomena in order to address two key questions: Do all SNe produce dust? and How much dust do they produce? As all the SN are within 15 Mpc, each SN stands an excellent chance of detection with HST and Spitzer and of resolving potential light echoes.
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 06 06 FGS REacq 08 08 OBAD with Maneuver 30 30
SIGNIFICANT EVENTS: (None)
