Status Report

NASA Hubble Space Telescope Daily Report # 3873

By SpaceRef Editor
June 3, 2005
Filed under , ,

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT        # 3873



ACS/HRC 10431

A Search for Faint Companions of Altair

We propose to use the innovative new technique of spectral
deconvolution {Sparks & Ford 2002} to search for very faint
companions, possibly extrasolar planets shining by reflected light,
around Altair, the nearest bright, single star to the Sun. The
technique offers a Poisson-limited detection capability that brings
Jovian-class planets into the realm of feasibility for a select few
stars. We turn the wavelength dependence of the coronagraphic PSF to
advantage and use it to eliminate stray light from the host star. As
part of the detection process, we obtain a spectrum over the
wavelength range, 750 nm to 1 micron, with 9% resolution. The search
will be orders of magnitude more sensitive than all previous efforts
and should take us to within about an order of magnitude of the Jovian
luminosity flux limit.


Accurate and Robust Calibration of the Extragalactic Distance Scale
with the Maser Galaxy NGC4258 II

The extragalactic distance scale {EDS} is defined by a comparison of
Cepheid Period-Luminosity {PL} relations for nearby galaxies and the
LMC, whose uncertain distance is thereby the SOLE anchor. Studies of
masers orbiting the central black hole in NGC4258 have provided the
most accurate extragalactic distance ever {7.2+/-0.5 Mpc}, and new
radio data and analysis techniques will reduce the uncertainty to < 3.5% {0.07 mag} by 2005. Since this distance is well determined and based on geometric arguments, NGC4258 can provide a much needed new anchor for the EDS. Ultimately, the combination of an independent measurement of H0 and measurements of CMB fluctuations {e.g., WMAP} can be used to directly constrain cosmological parameters including the equation of state of dark energy. In our Cycle 12 proposal, we defined a program spanning two cycles. The Cycle 12 portion was accepted. We have acquired WFC images and are constructing well sampled PL relations in 3 colors {BVI}. The purpose of the Cycle 13 observations is to address systematic sources of error and is crucial for the success of the entire program. To disentangle the effects of reddening and metallicity, and to characterize the effects of blending, we require 50 orbits to obtain H-band photometry {NICMOS/NIC2} and high resolution images {ACS/HRC}.

ACS/WFC 10258

Tracing the Emergence of the Hubble Sequence Among the Most Luminous
and Massive Galaxies

There is mounting evidence that the redshift range 1 < z < 2 was an important era when massive galaxies assembled their stellar content and assumed their present-- day morphologies. Despite extensive HST imaging surveys, however, there is very little data in the optical rest frame {i.e., observed near--infrared} on the morphologies of the most luminous galaxies at these redshifts. We propose to image a carefully selected set of 20 of the most luminous, K--band selected GOODS galaxies at 1.3 < z < 2, using NICMOS camera 2. This offers diffraction-- limited, critically sampled imaging at 1.6 microns to ensure the best angular resolution for comparison to ACS. The galaxies are chosen to span a simple 4--fold parameter space of morphological and spectral type, in order to provide the most information about the variety of massive galaxy properties in this redshift range. We will investigate the emergence of large scale--length disks, stable spiral structure, mature bulges with red stellar populations, central bar structures, the incidence of disturbed morphology, the existence {or lack thereof} of blue ellipticals, and other questions that concern the evolution and maturation of the brightest, largest, and most massive ordinary galaxies in this critical redshift range.


Determining the Origin of Virgo’s Intracluster Stars

Intracluster stars constitute about 20% of the total stellar
population of a typical galaxy cluster, and their existence provides a
vital clue for our understanding of cluster formation and evolution.
However, to exploit their probative value, we need to know their
origins: are they the remnants of dwarf galaxies, long since destroyed
by the cluster potential, or have the stars been harassed from their
parent galaxies at recent epochs? To answer this question, we propose
to use the Wide-Field Channel of ACS to make an I, {V-I}
color-magnitude diagram of Virgo’s intracluster stars. From the
position and morphology of the population’s red giant branch, we will
be able to determine the metallicity distribution function of the
stars, and thereby determine their likely origin and ejection
mechanisms. Only HST with the ACS has the sensitivity and resolution
to perform this fundamental measurement. This program has two options.
Option one uses conventional methods of cluster photometry and
requires 37 orbits of exposure time. Option two involves a novel
analysis technique, which promises to achieve most of the same science
in two- thirds the time {23 orbits}. We describe this alternative
method of analysis and demonstrate its use via simulations.


NICMOS Post-SAA calibration – CR Persistence Part 2

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.


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

HSTARS: (None)



                                 SCHEDULED     SUCCESSFUL    FAILURE TIMES 
 FGS Gsacq                     05                        05 
 FGS Reacq                     09                        09 
 FHST Update                  08                        08 


SpaceRef staff editor.