HUBBLE SPACE TELESCOPE - Continuing to collect World Class Science

DAILY REPORT       #4809

PERIOD COVERED: 5am March 11 - 5am March 12, 2009 (DOY

                           070/1000z-071/1000z)

OBSERVATIONS SCHEDULED

ACS/SBC 11980

Deep FUV Imaging of Cooling Flow Clusters

We propose to take deep ACS FUV images of a carefully selected sample of

19 bright central galaxies in nearby galaxy clusters. This program is

the last critical element of a comprehensive investigation of the impact

of stellar and AGN feedback on the local galaxy cluster environment. The

HST images will complement new, high-resolution, Halpha images obtained

with the recently commissioned Maryland-Magellan Tunable Filter (MMTF)

on the Baade 6.5m telescope, archival Chandra, VLA, and GALEX data, and

on-going H2/NIR observations. The MMTF data have revealed unsuspected

filamentary complexes in several systems. The GALEX data often show

hints of extended NUV and FUV emission on a similar scale, but their

poor spatial resolution prevents meaningful comparison with the MMTF

data. The HST data will provide this much needed gain in resolution. The

combined radio-H2-Halpha-FUV-X-ray dataset will allow us to derive with

unprecedented precision the role of the AGN, hot stars, shocks, and

relativistic particles on the excitation and thermodynamics of the

multi-phase intracluster and interstellar media in these systems. This

is an important question since the formation and evolution of most

cluster galaxies have likely been affected by these processes.

ACS/SBC 11982

Spanning the Reionization History of IGM Helium: a Large and Efficient

HST Spectral Survey of Far-UV-Bright Quasars

The reionization of IGM helium is thought to have occurred at redshifts

of z=3 to 4. Detailed studies of HeII Lyman-alpha absorption toward a

handful of QSOs at 2.7<z<3.3 demonstrated the high potential of such IGM

probes, but the small sample size and redshift range limit confidence in

cosmological inferences. The requisite unobscured sightlines to high-z

are extremely rare, but we've cross-correlated 10, 000 z>2.8 SDSS DR7

(and other) quasars with GALEX GR4 UV sources to obtain 550 new, high

confidence, sightlines potentially useful for HST HeII studies; and in

cycle 15-16 trials we demonstrated the efficacy of our SDSS/GALEX

selection approach identifying 9 new HeII quasars at unprecedented 67%

efficiency. We propose the first far-UV-bright HeII quasar survey that

is both large in scale and also efficient, via 2-orbit reconnaissance

ACS/SBC prism spectra toward a highly select subset of 40 new SDSS/GALEX

quasars at 3.1<z<5.1. These will provide a community resource list that

includes 5 far-UV-bright (restframe) HeII sightlines in each of 8

redshift bins spanning 3.1<z<3.9 (and perhaps several objects at z>4),

enabling superb post-SM4 follow-up spectra with COS or STIS. But

simultaneously and independent of any SM4 uncertainties, we will hereby

directly obtain 10-orbit UV spectral stacks from the 5 HeII quasars in

each of the 8 redshift bins to trace the reionization history of IGM

helium over at least 3.1<z<3.9. These spectral stacks will average over

cosmic variance and individual object pathology. Our new high-yield HeII

sightline sample and spectral stacks, covering a large redshift range,

will allow confident conclusions about the spectrum and evolution of the

ionizing background, the evolution of HeII opacity, the density of IGM

baryons, and the epoch of helium reionization.

WFPC2 11201

Systemic and Internal Motions of the Magellanic Clouds: Third Epoch

Images

In Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in

the Magellanic Clouds centered on background quasars. We used these data

to determine the proper motions of the LMC and SMC to better than 5% and

15% respectively. These are by far the best determinations of the proper

motions of these two galaxies. The results have a number of unexpected

implications for the Milky Way-LMC-SMC system. The implied

three-dimensional velocities are larger than previously believed, and

are not much less than the escape velocity in a standard 10^12 solar

mass Milky Way dark halo. Orbit calculations suggest the Clouds may not

be bound to the Milky Way or may just be on their first passage, both of

which would be unexpected in view of traditional interpretations of the

Magellanic Stream. Alternatively, the Milky Way dark halo may be a

factor of two more massive than previously believed, which would be

surprising in view of other observational constraints. Also, the

relative velocity between the LMC and SMC is larger than expected,

leaving open the possibility that the Clouds may not be bound to each

other. To further verify and refine our results we now request an epoch

of WFPC2/PC data for the fields centered on 40 quasars that have at

least one epoch of ACS imaging. We request execution in snapshot mode,

as in our previous programs, to ensure the most efficient use of HST

resources. A third epoch of data of these fields will provide crucial

information to verify that there are no residual systematic effects in

our previous measurements. More importantly, it will increase the time

baseline from 2 to 5 yrs and will increase the number of fields with at

least two epochs of data. This will reduce our uncertainties

correspondingly, so that we can better address whether the Clouds are

indeed bound to each other and to the Milky Way. It will also allow us

to constrain the internal motions of various populations within the

Clouds, and will allow us to determine a distance to the LMC using

rotational parallax.

WFPC2 11978

Luminous and Dark Matter in Disk Galaxies from Strong Lensing and

Stellar Kinematics

The formation of realistic disk galaxies within the LCDM paradigm is

still an unsolved problem. Theory is only now beginning to make

predictions for how dark matter halos respond to galaxy formation and

for the properties of disk galaxies. Measuring the density profiles of

dark matter halos on galaxy scales is therefore a strong test for the

standard paradigm of galaxy formation, offering great potential for

discovery. However, from an observational point of view, the degeneracy

between the stellar and dark matter contributions to galaxy rotation

curves remains a major road block. Strong gravitational lensing, when

coupled to spatially-resolved kinematics and stellar population models,

can solve this long-standing problem. Unfortunately, this joint

methodology could not be exploited so far due to the paucity of known

edge-on spiral lenses. Exploiting the full SDSS-DR7 archive we have

identified a new sample of exactly these systems. We propose multi-color

HST imaging to confirm and measure a sample of twenty spiral lenses,

covering a range of bulge to disk ratios. By combining dynamical lensing

and stellar population information for this unique sample we will

deliver the first statistical constraints on halos and disk properties,

and a new stringent test of disk galaxy formation theories.

FLIGHT OPERATIONS SUMMARY:

Significant Spacecraft Anomalies: (The following are preliminary reports

of potential non-nominal performance that will be investigated.)

HSTARS:

11716 - At 070/23:00:51, GSAcq (1,2,1) scheduled from 070/22:55:15 - 23:03:19

           failed to RGA Hold due to Search Radius Limit Exceeded error on FGS-1

           Observations affected: ACS 3, Proposal ID# 11980.

COMPLETED OPS REQUEST:

18407-1 - Restore FSW FSCMAT to 6 arc-seconds @ 070/1906Z 

COMPLETED OPS NOTES: (None)

                       SCHEDULED      SUCCESSFUL  

FGS GSAcq               06                  05    

FGS REAcq               06                  06   

OBAD with Maneuver 26                  26

SIGNIFICANT EVENTS:

FLASH REPORT - FSCMAT restoration:

Ops Request# 18407 was completed at 2009.070/19:07 to restore the FSW

Coarse Mode Angle Threshold to the usual 6 a-s.