NASA Hubble Space Telescope Daily Report #3986
HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science
DAILY REPORT # 3986
PERIOD COVERED: UT November 10, 2005 (DOY 314)
OBSERVATIONS SCHEDULED
ACS/HRC 10556
Neutral Gas at Redshift z=0.5
Damped Lyman-alpha systems {DLAs} are used to track the bulk of the neutral hydrogen gas in the Universe. Prior to HST UV spectroscopy, they could only be studied from the ground at redshifts z>1.65. However, HST has now permitted us to discover 41 DLAs at z<1.65 in our previous surveys. Followup studies of these systems are providing a wealth of information about the evolution of the neutral gas phase component of the Universe. But one problem is that these 41 low-redshift systems are spread over a wide range of redshifts spanning nearly 70% of the age of the Universe. Consequently, past surveys for low-redshift DLAs have not been able to offer very good precision in any small redshift regime. Here we propose an ACS-HRC- PR200L spectroscopic survey in the redshift interval z=[0.37, 0.7] which we estimate will permit us to discover another 41 DLAs. This will not only allow us to double the number of low-redshift DLAs, but it will also provide a relatively high-precision regime in the low-redshift Universe that can be used to anchor evolutionary studies. Fortunately DLAs have high absorption equivalent width, so ACS-HRC-PR200L has high-enough resoultion to perform this proposed MgII-selected DLA survey.
ACS/WFC 10523
The Halo Shape and Metallicity of Massive Spiral Galaxies
We propose to resolve the stellar populations of the halos of seven nearby, massive disk galaxies using a SNAP survey with WFC/ACS. These observations will provide star counts and color-magnitude diagrams 2-3 magnitudes below the tip of the Red Giant Branch along the two principal axes and one intermediate axis of each galaxy. We will measure the metallicity distribution functions and stellar density profiles from star counts down to very low average surface brightnesses, equivalent to ~31 V-mag per square arcsec. This proposal will create a unique sampling of galaxy halo properties, as our targets cover a range in galaxy mass, luminosity, inclination, and morphology. As function of these galaxy properties this survey will provide:- the first systematic measurement of radial light profiles and axial ratios of the diffuse stellar halos and outer disks of spiral galaxies- a comprehensive analysis of halo metallicity distributions as function of galaxy type and position within the galaxy- an unprecedented study of the stellar metallicity and age distribution in the outer disk regions where the disk truncations occur- the first comparative study of globular clusters and their field stellar populations We will use these fossil records of the galaxy assembly process to test halo formation models within the hierarchical galaxy formation scheme.
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 10596
AGNs with Intermediate-mass Black Holes: A Test of the Black Hole-Bulge Paradigm
The recent progress in the study of central black holes in galactic nuclei has led to a general consensus that supermassive {10^6-10^9 solar mass} black holes are closely connected with the formation and evolutionary history of large galaxies, especially their bulge component. Two outstanding issues, however, remain unresolved. Can central black holes form in the absence of a bulge? And does the mass function of central black holes extend below 10^6 solar masses? Intermediate-mass black holes {10^4-10^6 solar masses}, if they exist, may offer important clues to the nature of the seeds of supermassive black holes. In a first systematic search using the Sloan Digital Sky Survey, we have recently discovered 19 Type 1 AGNs with candidate intermediate-mass black holes that reside in low-luminosity, presumably late-type host galaxies. Follow-up observations with Keck indicate that these objects obey the low-mass extension of the well-known correlation between black hole mass and bulge stellar velocity dispersion. However, very little is known about the host galaxies themselves, including the crucial question of whether they have bulges or not. We propose to obtain ACS/WFC images of this unique sample of AGNs in order to investigate the detailed structural properties of the host galaxies. We are particularly keen to determine whether the hosts contain bulges, and if so, where they lie on the fundamental plane of spheroids compared to the bulges of supermassive black holes. We will also be able to measure an accurate optical luminosity for the AGN, which is an essential ingredient to improve the current mass estimates.
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 telescope, as well as host of smaller facilities.
ACS/WFC/WFPC2 10585
NGC 4449: a Testbed for Starbursts in the Low- and High-Redshift Universe
We will obtain deep ACS/WFC broad-band imaging in F435W, F555W, and F814W of the Magellanic irregular galaxy NGC 4449 in order to infer the properties of the resolved {young and old} stellar population, compare the current strong star-formation activity to that at earlier epochs, trace the major episodes of star formation over cosmic time, and relate them to the past history of interaction/merging of this galaxy. NGC 4449 is one of the closest {< 5 Mpc} global starbursts with a widespread star-formation activity that could have been triggered by interaction or accretion. It is, therefore, the perfect laboratory where to address issues related to star formation in extreme environments and investigate processes connected to the formation and evolution of galaxies in the early universe. At a distance of 4.2 Mpc, the stellar content in NGC 4449 can easily be resolved with HST. Yet, up to date no comprehensive dataset has been collected that is suited to infer a global star-formation history of the galaxy and to better understand its evolution. ACS/WFC provides the angular resolution and sensitivity to easily reach magnitude limits necessary for the detection of individual stars at the tip of the red giant branch {i.e., with ages from 1 Gyr up to 12 Gyr} with the required accuracy. A mosaic of 2 pointings along the major axis will give a good coverage of the galaxy and will allow us to infer a star- formation history unbiased by local properties of peculiar regions. Narrow-band imaging in F658N {Halpha} will provide a map of the ionized gas. Finally, WFPC2 parallel observations in F555W and F814W will allow to search deep in the HI halo of NGC 4449 for evidence of stars belonging to tidal streams. Our investigation of NGC 4449 will benefit from the wealth of observations already available over almost the whole electromagnetic spectrum and will be crucial in better understanding how starbursts can be influenced by merging phenonema in both the low- and high-redshift universe.
FGS 10432
Precise Distances to Nearby Planetary Nebulae
We propose to carry out astrometry with the FGS to obtain accurate and precise distances to four nearby planetary nebulae. In 1992, Cahn et al. noted that “The distances to Galactic planetary nebulae remain a serious, if not THE most serious, problem in the field, despite decades of study.” Twelve years later, the same statement still applies. Because the distances to planetary nebulae are so uncertain, our understanding of their masses, luminosities, scale height, birth rate, and evolutionary state is severely limited. To help remedy this problem, HST astrometry can guarantee parallaxes with half the error of any other available approach. These data, when combined with parallax measurements from the USNO, will improve distance measurements by more than a factor of two, producing more accurate distances with uncertainties that are of the order of ~6%. Lastly, most planetary nebula distance scales in the literature are statistical. They require several anchor points of known distance in order to calibrate their zero point. Our program will provide “gold standard” anchor points by the end of 2006, a decade before any anticipated results from future space astrometry missions.
FGS 10480
Parallaxes of Extreme Halo Subgiants: Calibrating Globular Cluster Distances and the Ages of the Oldest
The ages of the oldest stars are a key constraint on the evolution of our Galaxy, the history of star formation, and cosmological models. These ages are usually determined from globular clusters. However, it is alternatively possible to determine ages of extreme Population II subgiants in the solar neighborhood based on trigonometric parallaxes, without any recourse to clusters. This approach completely avoids the vexing issues of cluster distances, reddenings, and chemical compositions. There are 3 known nearby, extremely metal-deficient Pop II subgiants with Hipparcos parallax errors of 6-11% which are available for such age determinations. At present, based on the latest isochrones, the derived ages of these stars {HD 84937, HD 132475, and HD 140283} are all close to 14 Gyr, uncomfortably close to or higher than current estimates of the age of the universe. However, the errors in the Hipparcos parallaxes imply uncertainties of at least 2 Gyr in the ages of the 3 stars. We propose to measure parallaxes of these three Pop II subgiants using HST’s Fine Guidance Sensor 1R. We expect to reduce the Hipparcos parallax error bars by factors of 5-6, providing the most stringent test yet of current theoretical stellar models of Pop II stars and pushing the age uncertainties to below 0.5 Gyr. These data will also provide a major new constraint on the distance scale of globular clusters, with wide implications for stellar evolution and the calibration of Pop II standard candles. The ages of the oldest stars are a key constraint on the evolution of our Galaxy, the history of star formation, and cosmological models. These ages are usually determined from globular clusters. However, it is alternatively possible to determine ages of extreme Population II subgiants in the solar neighborhood based on trigonometric parallaxes, without any recourse to clusters. This approach completely avoids the vexing issues of cluster distances, reddenings, and chemical compositions. There are 3 known nearby, extremely metal- deficient Pop II subgiants with Hipparcos parallax errors of 6-11% which are available for such age determinations. At present, based on the latest isochrones, the derived ages of these stars {HD 84937, HD 132475, and HD 140283} are all close to 14 Gyr, uncomfortably close to or higher than current estimates of the age of the universe. However, the errors in the Hipparcos parallaxes imply uncertainties of at least 2 Gyr in the ages of the 3 stars. We propose to measure parallaxes of these three Pop II subgiants using HST’s Fine Guidance Sensor 1R. We expect to reduce the Hipparcos parallax error bars by factors of 5-6, providing the most stringent test yet of current theoretical stellar models of Pop II stars and pushing the age uncertainties to below 0.5 Gyr. These data will also provide a major new constraint on the distance scale of globular clusters, with wide implications for stellar evolution and the calibration of Pop II standard candles.
FGS 10610
Astrometric Masses of Extrasolar Planets and Brown Dwarfs
We propose observations with HST/FGS to estimate the astrometric elements {perturbation orbit semi-major axis and inclination} of extra-solar planets orbiting six stars. These companions were originally detected by radial velocity techniques. We have demonstrated that FGS astrometry of even a short segment of reflex motion, when combined with extensive radial velocity information, can yield useful inclination information {McArthur et al. 2004}, allowing us to determine companion masses. Extrasolar planet masses assist in two ongoing research frontiers. First, they provide useful boundary conditions for models of planetary formation and evolution of planetary systems. Second, knowing that a star in fact has a plantary mass companion, increases the value of that system to future extrasolar planet observation missions such as SIM PlanetQuest, TPF, and GAIA.
NIC1/NIC2/NIC3 10380
Cycle 13 NICMOS dark current, shading profile, and read noise monitoring program
The purpose of this proposal is to monitor the dark current, read noise, and shading profile for all three NICMOS detectors throughout the duration of Cycle 13. This proposal is an essentially unchanged continuation of PID 9993 which cover the duration of Cycle 12.
NIC2 10717
Quasar Bolometri Luminosity and Spectral Energy Distributions from Radio to X-ray
We propose to build the best SED data set spanning from radio to X-ray wavelengths for 35 quasars. We will use new and archival mid-to-far IR data from Spitzer as well as other existing multi-wavelength data. We have unique quasi-simultaneous FUV/UV-optical spectra for our sample, greatly reducing the uncertainty due to quasar intrinsic time variability in the UV bump. We will derive accurate bolometric luminosities for the sample and seek to establish a more reliable and accurate way to obtain the bolometric luminosity of quasars from their partial SEDs and/or spectral properties. We will also apply multivariate analysis to the SEDs, study the quasar multi-wavelength spectral properties and their dependence on the overall SEDs, and thus better understand the physical processes quasars employ emitting across the entire electromagnetic spectrum. HST NICMOS observations will be used to remove host galaxy contamination from the quasar SEDs. This is a joint Spitzer-HST project.
NICMOS 8790
NICMOS Post-SAA calibration – CR Persistence Part 1.
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.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
HSTARS:
10012 – GSAcq(2,1,1) requires multiple attempts to achieve CT-DV @ 307/05:01:59z
GSAcq(2,1,1) required six attempts to achieve CT-DV on FGS2. The acquisition was ultimately successful.
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
SCHEDULED SUCCESSFUL
FGS GSacq 10 10
FGS REacq 05 05
OBAD with Maneuver 26 26
SIGNIFICANT EVENTS: (None)
