Status Report

NASA Hubble Space Telescope Daily Report #4475

By SpaceRef Editor
October 25, 2007
Filed under , ,
NASA Hubble Space Telescope Daily Report #4475

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.


– Continuing to collect World Class Science

PERIOD COVERED: UT October 24, 2007 (DOY 297)


WFPC2 10795

The Largest Galaxies in the Local Universe: New Light on Disk Galaxy Formation?

In the standard scenario of disk galaxy formation in a hierarchical Universe, large disks form late via the accretion of either hot or cold gas. Direct observational evidence for such late accretion-driven disk formation has not been forthcoming. In this proposal, we describe the discovery of a rare new type of galaxy that may be examples of massive disks in the process of assembly. We have identified a sample of three such galaxies selected from the SDSS DR4. They are extremely large {diameters over 100 kpc} and highly luminous systems with amorphous structures {no obvious spiral arms or bulges}. They are larger than the largest normal spirals in the survey, and have significantly bluer colors, lower metallicities, lower dust extinctions, higher UV luminosities and higher total star formation rates than the most massive ordinary spirals. We request HST images in the rest-frame near-UV and red to provide detailed maps of the underlying structure of these galaxies as well as the distribution of the young stars. The interstellar medium of these galaxies is evidently quite different from that of normal large spirals and starburst galaxies and they may be experiencing a different mode of star formation. We believe they are worthy of further investigation with the high-resolution imaging capabilities of HST.

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=3Ddate/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 DARKs. 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 Reionization, and the High Redshift Obscured Universe

(uses ACS/SBC and WFPC2)

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 11194

Beyond the Bullet: Direct Detection of Dark Matter in Merging Galaxy Clusters

Our comparison of the distribution of baryons {stars and gas} and mass {from weak lensing} in the “Bullet” Cluster has recently yielded concrete evidence for dark matter independent of basic assumptions regarding the nature of the gravitational force. The one incomplete aspect of the argument relates to potential, although highly unlikely, coincidences {special alignments along the line of sight, and/or fortuitous canceling in non-standard gravitational models} that can always be invoked against results derived from the study of one object. Therefore, we propose to complete this line of investigations by increasing the size of our sample with observations of an additional cluster. Here we propose to obtain HST WFPC2 imaging mosaics around the cores of the cluster to detect at high significance if the weak gravitational lensing mass peaks are routinely displaced from the X-ray plasma clouds and aligned with the galaxy concentrations in interacting clusters. With a relatively modest allocation of time, we seek to complete a significant step toward the eventual resolution of the dark matter question.

WFPC2 11203

A Search for Circumstellar Disks and Planetary-Mass Companions around Brown Dwarfs in Taurus

During a 1-orbit program in Cycle 14, we used WFPC2 to obtain the first direct image of a circumstellar disk around a brown dwarf. These data have provided fundamental new constraints on the formation process of brown dwarfs and the properties of their disks. To search for additional direct detections of disks around brown dwarfs and to search for planetary-mass companions to these objects, we propose a WFPC2 survey of 32 brown dwarfs in the Taurus star-forming region.


Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)

                       SCHEDULED      SUCCESSFUL

FGS GSacq                07                 07
FGS REacq                07                 07
OBAD with Maneuver       28                 28


SpaceRef staff editor.