Status Report

NASA Hubble Space Telescope Daily Report # 4640

By SpaceRef Editor
June 26, 2008
Filed under , ,
NASA Hubble Space Telescope Daily Report # 4640


Continuing to collect World Class Science

PERIOD COVERED: 5am June 25 – 5am June 26, 2008 (DOY 177/0900z-178/0900z)


NIC1/NIC2/NIC3 8795

NICMOS Post-SAA Calibration – CR Persistence Part 6

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.

NIC2 11237

The Origin of the Break in the AGN Luminosity Function

We propose to use NICMOS imaging to measure rest-frame optical luminosities and morphological properties of a complete sample of faint AGN host galaxies at redshifts z ~ 1.4. The targets are drawn from the VLT-VIMOS Deep Survey, and they constitute a sample of the lowest luminosity type 1 AGN known at z > 1. The spectroscopically estimated black hole masses are up to an order of magnitude higher than expected given their nuclear luminosities, implying highly sub-Eddington accretion rates. This exactly matches the prediction made by recent theoretical models of AGN evolution, according to which the faint end of the AGN luminosity function is populated mainly by big black holes that have already exhausted a good part of their fuel. In this proposal we want to test further predictions of that hypothesis, by focussing on the host galaxy properties of our low-luminosity, low- accretion AGN. If the local ratio between black hole and bulge masses holds at least approximately at these redshifts, one expects most of these low-luminosity AGN to reside in fairly big ellipticals with stellar masses around and above 10^11 solar masses (in contrast to the Seyfert phenomenon in the local universe). With NICMOS imaging we will find out whether that is true, implying also a sensitive test for the validity of the M_BH/M_bulge relation at z ~ 1.4.

NIC2 11341

Lower Luminosity AGNs at Cosmologically Interesting Redshifts: SEDs and Accretion Rates of z~0.36 Seyferts

We propose a multiwavelength campaign to constrain the SEDs of Seyferts at z~0.36. This epoch, corresponding to a look back time of 4 Gyrs, is cosmologically interesting for studies of the coeval development of black holes and their host galaxy bulges. Our sample, comprising 24 Seyferts, has unprecedented high quality Keck spectroscopy and HST imaging already invested to extract host galaxy bulge properties, estimate black hole masses, and separate nuclear and host optical luminosities. To supplement and extend this successful program, we request 93 ks of Chandra time (to measure the shape and power of the AGN-only X-ray continuum), 11 hrs each of Spitzer and Gemini (to constrain the dust temperature), and 7 orbits of HST (to determine the nuclear luminosity for the final 7 objects).

NIC3/WFPC2 11192

NICMOS Confirmation of Candidates of the Most Luminous Galaxies at z

> 7

While the deepest pencil-beam near-IR survey suggested that the Universe was too young to build up many luminous galaxies by z ~ 7–8 (Bouwens & Illingworth 2006), there is also evidence indicating the contrary. It is now known that some galaxies with stellar masses of M>1e10 Msun were already in place by z ~ 6–7, which strongly suggests that their progenitors should be significantly more luminous, and hence detectable in deep, wide-field near-IR surveys (Yan et al. 2006). As galaxies at such a high redshift should manifest themselves as “dropouts” from the optical, we have carried out a very wide-field, deep near-IR survey in the GOODS fields to search for z-band dropouts as candidates of galaxies at z > 7. In total, six promising candidates have been found in ~ 300 sq. arcmin to J_AB ~ 24.5 mag (corresponding to restframe M(UV) < -22.5 mag at z ~ 7). By contrast, the galaxy luminosity function (LF) suggested in BI06 would predict at most 3--5 galaxies over the entire 2-pi sky at this brightness level. Here we propose to observe these candidates with NIC3 in F110W and F160W to further investigate their nature. If any of these candidates are indeed at z > 7, the result will lead to a completely new picture of star formation in the early universe. If none of our candidates are consistent with being at z > 7, then the depth and area of our near-IR survey (from which the candidates are drawn) will let us set a very stringent upper limit on the bright end of the galaxy LF at those redshift. As a result, our program will still be able to provide new clues about the processes of early galaxy formation, such as their dust contents and their merging time scale (Yan et al. 2006).

WFPC2/NIC3 11188

First Resolved Imaging of Escaping Lyman Continuum

The emission from star-forming galaxies appears to be responsible for reionization of the universe at z>6. However, the models that attempt to describe the detailed impact of high- redshift galaxies on the surrounding inter-galactic medium {IGM} are strongly dependent upon several uncertain parameters. Perhaps the most uncertain is the fraction of HI-ionizing photons produced by young stars which escape into the IGM. Most attempts to measure this “escape fraction” {f_esc} have produced null results. Recently, a small subset of z~3 Lyman Break Galaxies {LBGs} has been found exhibiting large escape fractions. It remains unclear however, what differentiates them from other LBGs. Several models attempt to explain how such a large fraction of ionizing continuum can escape through the HI and dust in the ISM {eg. “chimneys” created by SNe winds, globular cluster formation, etc.}, each producing unique signatures which can be observed with resolved imaging of the escaping Lyman continuum. We propose a deep, high resolution WFPC2 image of the ionizing continuum {F336W} and the rest-frame 1500 Angstrom continuum {F606W} of five of the six known LBGs with large escape fractions. These LBGs all fit within a single WFPC2 pointing, yielding high observing efficiency. Additionally, they all have z~3.1 or higher, the optimal redshift range for probing the Lyman Continuum region with available WFPC2 filters. These factors make our proposed sample especially suitable for follow- up. With these data we will discern the mechanisms responsible for producing large escape fractions, and therefore gain insight into the process of reionization.


Building on the Significant NICMOS Investment in GOODS: A Bright, Wide-Area Search for z>=7 Galaxies

One of the most exciting frontiers in observational cosmology has been to trace the buildup and evolution of galaxies from very early times. While hierarchical theory teaches us that the star formation rate in galaxies likely starts out small and builds up gradually, only recently has it been possible to see evidence for this observationally through the evolution of the LF from z~6 to z~3. Establishing that this build up occurs from even earlier times {z~7-8} has been difficult, however, due to the small size of current high-redshift z~7-8 samples — now numbering in the range of ~4-10 sources. Expanding the size of these samples is absolutely essential, if we are to push current studies of galaxy buildup back to even earlier times. Fortunately, we should soon be able to do so, thanks to ~50 arcmin**2 of deep {26.9 AB mag at 5 sigma} NICMOS 1.6 micron data that will be available over the two ACS GOODS fields as a result of one recent 180- orbit ACS backup program and a smaller program. These data will nearly triple the deep near-IR imaging currently available and represent a significant resource for finding and characterizing the brightest high-redshift sources — since high-redshift candidates can be easily identified in these data from their red z-H colours. Unfortunately, the red z-H colours of these candidates are not sufficient to determine that these sources are at z>=7, and it is important also to have deep photometry at 1.1 microns. To obtain this crucial information, we propose to follow up each of these z-H dropouts with NICMOS at 1.1 microns to determine which are at high redshift and thus significantly expand our sample of luminous, z>=7 galaxies. Since preliminary studies indicate that these candidates occur in only 30% of the NIC3 fields, our follow-up strategy is ~3 times as efficient as without this preselection and 9 times as efficient as a search in a field with no pre-existing data. In total, we expect to identify ~8 luminous z-dropouts and possibly ~2 z~10 J-dropouts as a result of this program, more than tripling the number currently known. The increased sample sizes are important if we are to solidify current conclusions about galaxy buildup and the evolution of the LF from z~8. In addition to the high redshift science, these deep 1.1 micron data would have significant value for many diverse endeavors, including {1} improving our constraints on the stellar mass density at z~7-10 and {2} doubling the number of galaxies at z~6 for which we can estimate dust obscuration.


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


11353 – GSacq(2,1,1) failed to RGA control @ 177/11:05:04:13z

GSacq(2,1,1) at 177/11:05:04 failed to RGA control with QF2STOPF and QSTOP flags set. #44 commands did not change since previous acquisition. OBAD prior to acquisition had RSS error of 8.07 arcseconds.

Observation affected: NICMOS 154 proposal #11237.



                        SCHEDULED      SUCCESSFUL

FGS GSacq               05                  04
FGS REacq               10                  10
OBAD with Maneuver      30                  30


SpaceRef staff editor.