NASA Hubble Space Telescope Daily Report #4044

HUBBLE SPACE TELESCOPE – Continuing to collect World Class Science

DAILY REPORT #4044

PERIOD COVERED: UT February 06, 2006 (DOY 037)

OBSERVATIONS SCHEDULED

ACS/HRC 10525

Characterizing the Near-UV Environment of M Dwarfs: Implications for Extrasolar Planetary Searches and Astrobiology

We propose SNAP observations with the ACS HRC PR200L prism, designed to measure the near ultraviolet emission in a sample of 107 nearby M dwarfs. The sample spans the mass range from 0.1 – 0.6 solar masses {temperature range 2200K – 4000K} where the UV energy distributions vary widely between active and inactive stars. The strength and distribution of this UV emission can have critical consequences for the atmospheres of attendant planets. Our proposed observations will provide desperately needed constraints on models of the habitability zone and the atmospheres of possible terrestrial planets orbiting M dwarf hosts, and will be used to sharpen TPF target selection. In addition, the NUV data will be used in conjunction with existing optical, FUV and X-ray data to constrain a new generation of M dwarf atmospheric models, and to explore unanswered questions regarding the dynamo generation and magnetic heating in these low-mass stars.

ACS/HRC 10572

Resolving M32’s Main Sequence: A Critical Test for Stellar Population Studies

We propose to observe the M32 main-sequence turnoff {MSTO} with deep ACS/HRC B and V images. Only the superior resolution and blue sensitivity of ACS/HRC make this possible. M32 is the only elliptical galaxy close enough to allow direct observation of its MSTO – it is a vital laboratory for deciphering the stellar populations of all other elliptical galaxies, which can only be studied by the spectra of their integrated light, given their greater distances. Major questions about M32’s star formation history remain unanswered. Spectral studies suggest that M32 underwent a recent burst of star formation 3 to 8 billion years ago; observation of the M32 MSTO will confirm this directly. In the process, ACS will easily resolve more luminous components: hot blue stars, luminous, intermediate-age red clump and AGB stars, and any extended blue horizontal branch. These detailed CMDs will provide a direct comparison with population synthesis models for M32, providing a bridge to studies of the integrated light of more distant elliptical galaxies, a crucial ingredient for understanding their star formation histories. As M32 is projected against the edge of the M31 disk, an essential part of our proposal includes deep observation of an M31 disk field to allow the M32 photometry to be background corrected. These observations will reveal the star formation history of M31’s outer disk and are thus of interest in their own right.

ACS/HRC/WFC 10729

ACS CCDs daily monitor

This program consists of a set of basic tests to monitor, the read noise, the development of hot pixels and test for any source of noise in ACS CCD detectors. The files, biases and dark will be used to create reference files for science calibration. This programme will be for the entire lifetime of ACS. Changes from cycle 13:- The default gain for WFC is 2 e-/DN. As before bias frames will be collected for both gain 1 and gain 2. Dark frames are acquired using the default gain {2}. This program cover the period Oct, 2 2005- May, 29-2006. The second half of the program has a different proposal number: 10758.

ACS/WFC 10522

Calibrating Star Formation: The Link between Feedback and Galaxy Evolution

Stellar feedback – the return of mass and energy from star formation to the interstellar medium – is one of the primary engines of galaxy evolution. Yet, the theoretical foundation of mechanical feedback is, to date, unconstrained by observations. We propose to investigate this fundamental aspect of star formation on a sample of two local actively star-forming galaxies, NGC4449, and Holmberg II. The two galaxies have been selected to occupy an unexplored, yet crucial for quantifying mechanical feedback, niche in the two-parameter space of star formation intensity and galaxy mass. ACS/WFC and WFPC2 narrow-band observations in the light of H-beta, [OIII], H-alpha, and [NII] will be obtained for both galaxies, in order to: {1} discriminate the feedback- induced shock fronts from the photoionization regions; {2} map the shocks inside and around the starburst regions; and {3} measure the energy budget of the star-formation-produced shocks. These observations, complemented by existing data, will yield: {1} the efficiency of the feedback, i.e. the fraction of the star formation’s mechanical energy that is transported out of the starburst volume rather than confined or radiated away; {2} the dependence of this efficiency on the two fundamental parameters of star formation intensity and stellar mass. The high angular resolution of HST is crucial for separating the spatially narrow shock fronts {~5 pc, ~0.25″ at 4 Mpc} from the more extended photoionization fronts. The legacy from this project will be the most complete quantitative measurement of the energetics associated with feedback processes. We will secure the first milestone for placing feedback mechanisms on a solid physical ground, and for understanding quantitatively their role on the energetics, structure, and star formation history of galaxies at all redshifts.

ACS/WFC 10543

Microlensing in M87 and the Virgo Cluster

Resolving the nature of dark matter is an urgent problem. The results of the MACHO survey of the Milky Way dark halo toward the LMC indicate that a significant fraction of the halo consists of stellar mass objects. The VATT/Columbia survey of M31 finds a similar lens fraction in the M31 dark halo. We propose a series of observations with ACS that will provide the most thorough search for microlensing toward M87, the central elliptical galaxy of the Virgo cluster. This program is optimized for lenses in the mass range from 0.01 to 1.0 solar masses. By comparing with archival data, we can detect lenses as massive as 100 solar masses, such as the remnants of the first stars. These observations will have at least 15 times more sensitivity to microlensing than any previous survey, e.g. using WFPC2. This is due to the factor of 2 larger area, factor of more than 4 more sensitivity in the I-band, superior pixel scale and longer baseline of observations. Based on the halo microlensing results in the Milky Way and M31, we might expect that galaxy collisions and stripping would populate the overall cluster halo with a large number of stellar mass objects. This program would determine definitively if such objects compose the cluster dark matter at the level seen in the Milky Way. A negative result would indicate that such objects do not populate the intracluster medium, and may indicate that galaxy harassment is not as vigorous as expected. We can measure the level of events due to the M87 halo: this would be the best exploration to date of such a lens population in an elliptical galaxy. Star-star lensing should also be detectable. About 20 erupting classical novae will be seen, allowing to determine the definitive nova rate for this giant elliptical galaxy. We will determine if our recent HST detection of an M87 globular cluster nova was a fluke, or indicative of a 100x higher rate of incidence of cataclysmic variables and nova eruptions in globulars than previously believed. We will examine the populations of variable stars, and will be able to cleanly separate them from microlensing.

ACS/WFC/NIC3/WFPC2 10530

Probing Evolution And Reionization Spectroscopically {PEARS}

While imaging with HST has gone deep enough to probe the highest redshifts, e.g. the GOODS survey and the Ultra Deep Field, spectroscopic identifications have not kept up. We propose an ACS grism survey to get slitless spectra of all sources in a wide survey region {8 ACS fields} up to z =27.0 magnitude, and an ultradeep field in the HUDF reaching sources up to z =28 magnitude. The PEARS survey will: {1} Find and spectrocopically confirm all galaxies between z=4-7. {2} Probe the reionization epoch by robustly determining the luminosity function of galaxies and low luminosity AGNs at z = 4 – 6. With known redshifts, we can get a local measure of star formation and ionization rate in case reionization is inhomogeneous. {3} Study galaxy formation and evolution by finding galaxies in a contiguous redshift range between 4 < z < 7, and black hole evolution through a census of low-luminosity AGNs. {4} Get a robust census of galaxies with old stellar populations at 1 < z < 2.5, invaluable for checking consistency with heirarchical models of galaxy formation. Fitting these galaxies' spectra will yield age and metallicity estimates. {5} Study star-formation and galaxy assembly at its peak at 1< z < 2 by identifying emission lines in star-forming galaxies, old populations showing the 4000A break, and any combination of the two. {6} Constrain faint white dwarfs in the Galactic halo and thus measure their contribution to the dark matter halo. {7} Derive spectro-photometric redshifts by using the grism spectra along with broadband data. This will be the deepest unbiased spectroscopy yet, and will enhance the value of the multiwavelength data in UDF and the GOODS fields to the astronomical community. To this end we will deliver reduced spectra to the HST archives.

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.

NICMOS 8791

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.

WFPC2 10748

WFPC2 CYCLE 14 Standard Darks

This dark calibration program obtains dark frames every week in order to provide data for the ongoing calibration of the CCD dark current rate, and to monitor and characterize the evolution of hot pixels. Over an extended period these data will also provide a monitor of radiation damage to the CCDs.

WFPC2 10778

WFPC2 WF4 Supplemental Darks

An anomaly has been found in images from the WF4 CCD in WFPC2. The WF4 CCD bias level appears to have become unstable, resulting in sporadic images with either low or zero bias level. The severity and frequency of the problem is rapidly increasing, and it is possible that WF4 will soon become unusable if no work-around is found. The other three CCDs {PC1, WF2, and WF3} appear to be unaffected and continue to operate properly. These darks are to supplement those in program 10748 to ensure sufficient dark frames for routine calibration. As the WF4 anomaly grows worse, we are beginning to see episodes where too many darks are corrupted and are unusable.

FLIGHT OPERATIONS SUMMARY:

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

HSTARS: (None)

COMPLETED OPS REQUEST: (None)

COMPLETED OPS NOTES: (None)

                         SCHEDULED      SUCCESSFUL
FGS GSacq               08                     08
FGS REacq               08                     08
OBAD with Maneuver  19                     19

SIGNIFICANT EVENTS: (None)