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HUBBLE SPACE TELESCOPE
DAILY REPORT # 3155
PERIOD COVERED: DOYs 122-124
Part 3 of 5
ACS/WFC 9351
Determining Hubble's Constant from Observations of Cepheids in the
Host Galaxy of SN Ia 1994ae
We propose to determine the luminosity of the type Ia supernova {SN
Ia} 1994ae by observing Cepheids in the host spiral galaxy NGC 3370.
Modern CCD photometry has yielded an extremely tight Hubble diagram
for SNe Ia with a precisely determined intercept {i.e., Delta
H_0/H_0} 1 measurement of the true Hubble constant is still limited
by the calibration. The HST calibration of all but a few SNe Ia
observed to date is significantly compromised by the systematics of
photographic photometry and host galaxy extinction, as well as by the
photometric uncertainties associated with WFPC2. In contrast, SN
1994ae is one of the very best-observed SNe Ia with CCD photometry.
The exquisite B, V, R, and I light curves are well-sampled beginning
10 days before maximum brightness, and they indicate little
reddening. From our supernova photometry and the current provisional
SN Ia calibration we would find a distance of 30 +/- 2.1 Mpc, well
within the range where ACS can accurately observe Cepheid light
curves and distinguish Cepheids from nonvariable stars.
ACS/WFC/HRC 9445
Gravitational Microlensing in the NGC 3314A-B Galaxy Pair.
The Advanced Camera for Surveys (WFC and HRC) was used to determine
the composition of the dark matter that dominates the masses of
galaxies which is an important unsolved problem.
ACS/WFPC2 9481
Pure Parallel Near-UV Observations with WFPC2 within High-Latitude
ACS Survey Fields
In anticipation of the allocation of ACS high-latitude imaging
survey{s}, we request a modification of the default pure parallel
program for those WFPC2 parallels that fall within the ACS survey
field. Rather than duplicate the red bands which will be done much
better with ACS, we propose to observe in the near-ultraviolet F300W
filter. These data will enable study of the rest-frame ultraviolet
morphology of galaxies at 0 * Origin: SpaceBase(tm) Pt 1 -14.4- Van BC Canada 604-473-9358 (1:153/719.1)
SEEN-BY: 633/267 270
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