Status Report

NASA Hubble Space Telescope Daily Report #4789

By SpaceRef Editor
February 16, 2009
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Continuing to collect World Class Science

PERIOD COVERED: 5am February 10 – 5am February 11, 2009 (DOY 041/1000z-042/1000z)


WFPC2 11612

Eta Carinae’s Continuing Instability and Recovery – the 2009 Event

Eta Carinae is the only really observable example of structural recovery from a massive giant eruption, a “supernova imposter’ event. Moreover it is the only well-observed star above 100 Msun, and its 5.5-year-recurrent spectroscopic events provide extraordinary clues to its surface instability. This truly unique combination of attributes makes it valuable for understanding the most massive stars. A fresh development arose a few years ago: The star has brightened much faster than before, and appears to have entered a rapid stage in its post-eruption recovery.

A spectroscopic event will occur at 2009.0, soon after the planned HST servicing mission. Because of the recent secular trend, this event is expected to differ from its well-observed 2003.5 predecessor. The differences will be very important, because they offer clues to very-massive-star structural instabilities that can’t be observed in any other known way.

Some of the needed observations require HST’s high spatial resolution and UV coverage. We propose an efficient, well-chosen set of STIS and ACS observations around the critical time. If the servicing mission is too late for the event, then a subset of the observations will still be merited.

WFPC2 11966

The Recent Star Formation History of SINGS Galaxies

The Spitzer Legacy project SINGS provided a unique view of the current state of star formation and dust in a sample of galaxies of all Hubble types. This multi-wavelength view allowed the team to create current star formation diagnostics that are independent of the dust content and increased our understanding of the dust in galaxies. Even so, using the SINGS data alone we can only make rough estimates of the recent star formation history of these galaxies. The lack of high resolution observations (especially U-band and H-alpha) means that it is impossible to estimate the ages of young clusters. In addition, the low resolution of the Spitzer and ground-based observations means that what appear to be individual Spitzer sources can actually be composed of many individual clusters with varying ages. We need to know the ages, star formation histories, and extinction of these individual clusters to understand how these clusters form and age and thus influence the evolution of the galaxy. In this proposal we address this missing area of SINGS by obtaining high-resolution WFPC2 UBVI & H-alpha observations to not only accurately locate and determine the ages of the young stellar clusters in the actively star forming SINGS galaxies but to also address a variety of other scientific issues. Over 500 HST orbits and 500 hours of Spitzer observing time have been dedicated to observations of the SINGS sample. But the HST observations have not been systematic. By adding a relatively small fraction of this time for these requested observations, we will greatly enhance the legacy value of the SINGS observations by creating a uniform high resolution multi-wavelength HST archive that matches the quality of the lower resolution SINGS archive.

WFPC2 11967

WFPC2 Imaging of the Lockman Hole

In order to understand galaxy evolution and constrain theoretical models, we require both multiwavelength photometry (to robustly determine physical parameters such as star formation rates and stellar masses) and detailed morphological information. Galaxy morphology encodes crucial information about galaxy formation history and the physical processes that trigger star formation and AGN activity, and high-resolution imaging for large samples of galaxies is currently only obtainable with HST. The Lockman Hole has been the target of extensive multi-wavelength observations from the X-ray to the radio, and will be the target of the deepest wide-area blankfield thermal IR observations with Herschel, but currently lacks comprehensive HST imaging. We propose to obtain WFPC2 imaging of ~500 arcmin2 of the central region of the Lockman Hole in F606W and F814W, to a depth of V606~26.8 and I814~26. This imaging is crucial in order to characterize the sources detected at other wavelengths.


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

HSTARS: (None)



                `        SCHEDULED      SUCCESSFUL

FGS GSacq                 05                 05
FGS REacq                 09                 09
OBAD with Maneuver        28                 28


SpaceRef staff editor.