- Press Release
- Dec 5, 2022
NASA Hubble Space Telescope Daily Report #4994
NASA Hubble Space Telescope Daily Report #4994
PERIOD COVERED: 5am December 16 – 5am December 17, 2009 (DOY 350/10:00z-351/10:00z)
A Timeline for Early-Type Galaxy Formation: Mapping the Evolution of Star Formation, Globular Clusters, Dust, and Black Holes
While considerable effort has been devoted to statistical studies of the origin of the red sequence of galaxies, there has been relatively little direct exploration of galaxies transforming from late to early types. Such galaxies are identified by their post-starburst spectra, bulge-dominated, tidally-disturbed morphologies, and current lack of gas. We are constructing the first detailed timeline of their evolution onto the red sequence, pinpointing when star formation ends, nuclear activity ceases, globular clusters form, and the bulk of the merging progenitors’ dust disappears. Here we propose to obtain HST and Chandra imaging of nine galaxies, whose wide range of post-starburst ages we have precisely dated with a new UV-optical technique and for which we were awarded Spitzer time. We will address 1) whether the black hole-bulge mass relation arises from nuclear feedback, 2) whether the bimodality of globular cluster colors is due to young clusters produced in galaxy mergers, and 3) what happens to the dust when late types merge to form an early type.
Beyond the Classical Paradigm of Stellar Winds: Investigating Clumping, Rotation and the Weak Wind Problem in SMC O Stars
SMC O stars provide an unrivaled opportunity to probe star formation, evolution, and the feedback of massive stars in an environment similar to the epoch of the peak in star formation history. Two recent breakthroughs in the study of hot, massive stars have important consequences for understanding the chemical enrichment and buildup of stellar mass in the Universe. The first is the realization that rotation plays a major role in influencing the evolution of massive stars and their feedback on the surrounding environment. The second is a drastic downward revision of the mass loss rates of massive stars coming from an improved description of their winds. STIS spectroscopy of SMC O stars combined with state-of-the-art NLTE analyses has shed new light on these two topics. A majority of SMC O stars reveal CNO-cycle processed material brought at their surface by rotational mixing. Secondly, the FUV wind lines of early O stars provide strong indications of the clumped nature of their wind. Moreover, we first drew attention to some late-O dwarfs showing extremely weak wind signatures. Consequently, we have derived mass loss rates from STIS spectroscopy that are significantly lower than the current theoretical predictions used in evolutionary models. Because of the limited size of the current sample (and some clear bias toward stars with sharp-lined spectra), these results must however be viewed as tentative. Thanks to the high efficiency of COS in the FUV range, we propose now to obtain high-resolution FUV spectra with COS of a larger sample of SMC O stars to study systematically rotation and wind properties of massive stars at low metallicity. The analysis of the FUV wind lines will be based on our 2D extension of CMFGEN to model axi-symmetric rotating winds.
UVIS Internal Flats
This proposal will be used to assess the stability of the flat field structure for the UVIS detector throughout the 15 months of Cycle 17. The data will be used to generate on- orbit updates for the delta-flat field reference files used in the WFC3 calibration pipeline, if significant changes in the flat structure are seen.
NUV Spectroscopic Sensitivity Monitoring
The purpose of this proposal is to monitor sensitivity of each NUV grating mode to detect any changes due to contamination or other causes.
Snapshot Survey for Planetary Nebulae in Local Group Globular Clusters
Planetary nebulae (PNe) in globular clusters (GCs) raise a number of interesting issues related to stellar and galactic evolution. The number of PNe known in Milky Way GCs, four, is surprisingly low if one assumes that all stars pass through a PN stage. However, it is likely that the remnants of stars now evolving in galactic GCs leave the AGB so slowly that any ejected nebula dissipates long before the star becomes hot enough to ionize it. Thus there should not be ANY PNe in Milky Way GCs–but there are four! It has been suggested that these Pne are the result of mergers of binary stars within GCs, i.e., that they are descendants of blue stragglers. The frequency of occurrence of PNe in external galaxies poses more questions, because it shows a range of almost an order of magnitude.
I propose a SNAPshot survey aimed at discovering PNe in the GC systems of Local Group galaxies outside the Milky Way. These clusters, some of which may be much younger than their counterparts in our galaxy, might contain many more PNe than those of our own galaxy. I will use the standard technique of emission-line and continuum imaging, which easily discloses PNe. This proposal continues a WFPC2 program started in Cycle 16, but with the more powerful WFC3. As a by-product, the survey will also produce color-magnitude diagrams for numerous clusters for the first time, reaching down to the horizontal branch.
Calibration of Surface Brightness Fluctuations for WFC3/IR
We aim to characterize galaxy surface brightness fluctuations (SBF), and calibrate the SBF distance method, in the F110W and F160W filters of the Wide Field Camera 3 IR channel. Because of the very high throughput of F110W and the good match of F160W to the standard H band, we anticipate that both of these filters will be popular choices for galaxy observations with WFC3/IR. The SBF signal is typically an order of magnitude brighter in the near-IR than in the optical, and the characteristics (sensitivity, FOV, cosmetics) of the WFC3/IR channel will be enormously more efficient for SBF measurements than previously available near-IR cameras. As a result, our proposed SBF calibration will allow accurate distance derivation whenever an early-type or bulge- dominated galaxy is observed out to a distance of 150 Mpc or more (i.e., out to the Hubble flow) in the calibrated passbands. For individual galaxy observations, an accurate distance is useful for establishing absolute luminosities, black hole masses, linear sizes, etc. Eventually, once a large number of galaxies have been observed across the sky with WFC3/IR, this SBF calibration will enable accurate mapping of the total mass density distribution in the local universe using the data available in the HST archive. The proposed observations will have additional important scientific value; in particular, we highlight their usefulness for understanding the nature of multimodal globular cluster color distributions in giant elliptical galaxies.
CCD Daily Monitor (Part 1)
This program comprises basic tests for measuring the read noise and dark current of the ACS WFC and for tracking the growth of hot pixels. The recorded frames are used to create bias and dark reference images for science data reduction and calibration. This program will be executed four days per week (Mon, Wed, Fri, Sun) for the duration of Cycle 17. To facilitate scheduling, this program is split into three proposals. This proposal covers 352 orbits (22 weeks) from 31 August 2009 to 31 January 2010.
Optical and Ultraviolet Photometry of Isolated Neutron Stars
We propose ultraviolet and B-band observations of 5 nearby, thermally emitting neutron stars. These data will measure the Rayleigh-Jeans tails of their spectra, providing a vital complement to X-ray spectroscopy and helping to constrain atmospheric models, working toward the ultimate goal of unraveling the physics of neutron stars. With these data we will have good-quality optical and UV data for the full sample of these objects, allowing detailed comparisons between them. Finally, the data should allow us to measure proper motions for one or two objects, and will serve as the reference data for the remaining objects; such proper motions allow ages to be determined for these objects by tracing them back to likely birth locations.
COS-GTO: Studies of the He II Reionization Epoch
Intergalactic Ly-alpha opacity suggests that H I was reionized at z ~ 6, while He II reionization was delayed to z ~ 3. Both epochs are slightly in disagreement with recent (WMAP-3) inferences from the CMB optical depth, which suggest that IGM reionization occurred at z = 10.7 (+2.7, -2.3) (Spergel et al. 2007). However, these two methods are sensitive to different ranges of ionization (neutral fractions), which allows a partially ionized IGM between z = 6-10 produced by early stars and black holes. One of the major contributions of FUSE to cosmological studies was the detection of He II Ly-alpha (Gunn-Peterson) absorption in the spectra of two AGN at redshifts z = 2.72-2.89. The He II absorption is quite patchy between redshifts z = 2.6 and 3.2 probably because the IGM is clumpy and the reionization process is affected by source fluctuations, spectra, and radiative transfer through the IGM. Observations of the He II absorption can therefore be used as diagnostics of the ionizing sources and radiative transport over large (30-50 Mpc) distances through the IGM. The ionizing radiation field appears to be softer (higher He II/H I) in the galaxy voids. These void regions may be ionized by local soft sources (dwarf starburst galaxies), or the QSO radiation may softened by escape from AGN cores and transport through denser regions in the cosmic web. With COS, we will observe the brightest He II target, HE2347-4342, a QSO with z_em = 2.885. Our goal is to obtain a G130M moderate-resolution (R = 20, 000) spectrum from 1145-1450A. Because COS has far greater throughput than either STIS or FUSE, we will be able to resolve and characterize the He II absorption lines. The region shortward of the redshifted He II (Ly-alpha) corresponds to z = 2.77-2.92, where He II exhibits patchy transmission and absorption. The ratio of He II/H I (Ly-alpha line) opacities will provide information on the ionizing radiation field (and ionizing sources) at 1 and 4 ryd. We will perform similar He II studies on three other targets, HS1700+6416, PKS1935-692, and Q0302-003.
COS-GTO: Activity of Solar Mass Stars from Cradle to Grave
COS spectra will be very useful for answering the question of how chromospheric and coronal activity of stars decline as stars lose angular momentum and magnetic fields with age. This question is important for modeling the atmospheres of young planets that are blasted by strong ultraviolet radiation and winds from young stars. COS will obtain spectra of solar mass stars with a range of ages from 10 Myr to 7 Gyr.
The LMC as a QSO Absorption Line System
We propose to obtain high resolution, high signal-to-noise observations of QSOs behind the Large Magellanic Clouds. These QSOs are situated beyond the star forming disk of the galaxy, giving us the opportunity to study the distribution of metals and energy in regions lacking significant star formation. In particular, we will derive the metallicities and study the ionization characteristics of LMC gas at impact parameters 3-17 kpc. We will compare our results with high-z QSO absorption line systems.
CCD Dark Monitor Part 1
The purpose of this proposal is to monitor the darks for the STIS CCD.
CCD Bias Monitor-Part 1
The purpose of this proposal is to monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.
The Co-Evolution of Spheroids and Black Holes in the Last Six Billion Years
The masses of giant black holes are correlated with the luminosities, masses, and velocity dispersions of the bulges of their host galaxies. This empirical correlation of phenomena on widely different scales (from pcs to kpcs) suggests that the formation and evolution of galaxies and central black holes are closely linked. In Cycle 13, we have started a campaign to map directly the co-evolution of spheroids and black-holes by measuring in observationally favorable redshift windows the empirical correlations connecting their properties. By focusing on Seyfert 1s, where the nucleus and the stars contribute comparable fractions of total light, black hole mass and bulge dispersion are obtained from Keck spectroscopy. HST is required for accurate measurement of the non- stellar AGN continuum, the morphology of the galaxy, and the structural parameters of the bulge. The results at z=0.36 indicate a surprisingly fast evolution of bulges in the past 4 Gyrs (significant at the 95%CL), in the sense that bulges were significantly smaller for a given black hole mass. Also, the large fraction of mergers and disturbed galaxies (4+2 out of 20) identifies gas-rich mergers as the mechanisms responsible for bulge- growth. Going to higher redshift – where evolutionary trends should be stronger – is needed to confirm these tantalizing results. We propose therefore to push our investigation to the next suitable redshift window z=0.57 (lookback-time 6 Gyrs). Fifteen objects are the minimum number required to map the evolution of the empirical correlations between bulge properties and black-hole mass, and to achieve a conclusive detection of evolution (>99%CL).
DD Observations of the Coldest Brown Dwarf
We request DD observations of the SDWFS J1433+35, which is a strong candidate for the coldest brown dwarf yet discovered and the first example of the elusive “Y-dwarf” spectral class. This source was discovered from a deep, wide-field survey of 10 square degrees with the IRAC instrument on Spitzer, and is redder in both [3.6]-[4.5] and H-[4.5] than any published brown dwarfs. The spectrum falls beyond 5 microns, strongly implying that the red mid-infrared colors are due to methane absorption in the IRAC 3.6 micron channel rather than dust obscuration. The source is undetected in deep, ground- based near-IR images, with a H>24.2 (Vega) limit derived from Keck AO imaging. The proposed WFC3 imaging should provide detections in two near-infrared bands. By showing the target is morphologically unresolved and that it has the non-uniform spectral energy distribution of an ultracool brown dwarf, the proposed observations will definitely show that (i) SDWFS J1433+35 is the coldest brown dwarf known, (ii) test models of ultracool, planet-like, brown dwarf atmospheres, and (iii) refine predictions and strategies for the Wide-Field Infrared Survey Explorer (WISE; planned to launch this December).
IR Dark Current Monitor
Analyses of ground test data showed that dark current signals are more reliably removed from science data using darks taken with the same exposure sequences as the science data, than with a single dark current image scaled by desired exposure time. Therefore, dark current images must be collected using all sample sequences that will be used in science observations. These observations will be used to monitor changes in the dark current of the WFC3-IR channel on a day-to-day basis, and to build calibration dark current ramps for each of the sample sequences to be used by Gos in Cycle 17. For each sample sequence/array size combination, a median ramp will be created and delivered to the calibration database system (CDBS).
Galaxy-Scale Strong Lenses from the CFHTLS Survey
We aim to investigate the origin and evolution of early-type galaxies using gravitational lensing, modeling the mass profiles of objects over a wide range of redshifts. The low redshift (z = 0.2) sample is already in place following the successful HST SLACS survey; we now propose to build up and analyze a sample of comparable size (~50 systems) at high redshift (0.4 < z < 0.9) using HST WFC3 Snapshot observations of lens systems identified by the SL2S collaboration in the CFHT legacy survey. WFC3/UVIS 11905 WFC3 UVIS CCD Daily Monitor The behavior of the WFC3 UVIS CCD will be monitored daily with a set of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K subarray biases are acquired at less frequent intervals throughout the cycle to support subarray science observations. The internals from this proposal, along with those from the anneal procedure (Proposal 11909), will be used to generate the necessary superbias and superdark reference files for the calibration pipeline (CDBS). WFC3/UVIS/IR 11644 A Dynamical-Compositional Survey of the Kuiper Belt: A New Window Into the Formation of the Outer Solar System The eight planets overwhelmingly dominate the solar system by mass, but their small numbers, coupled with their stochastic pasts, make it impossible to construct a unique formation history from the dynamical or compositional characteristics of them alone. In contrast, the huge numbers of small bodies scattered throughout and even beyond the planets, while insignificant by mass, provide an almost unlimited number of probes of the statistical conditions, history, and interactions in the solar system. To date, attempts to understand the formation and evolution of the Kuiper Belt have largely been dynamical simulations where a hypothesized starting condition is evolved under the gravitational influence of the early giant planets and an attempt is made to reproduce the current observed populations. With little compositional information known for the real Kuiper Belt, the test particles in the simulation are free to have any formation location and history as long as they end at the correct point. Allowing compositional information to guide and constrain the formation, thermal, and collisional histories of these objects would add an entire new dimension to our understanding of the evolution of the outer solar system. While ground based compositional studies have hit their flux limits already with only a few objects sampled, we propose to exploit the new capabilities of WFC3 to perform the first ever large-scale dynamical-compositional study of Kuiper Belt Objects (KBOs) and their progeny to study the chemical, dynamical, and collisional history of the region of the giant planets. The sensitivity of the WFC3 observations will allow us to go up to two magnitudes deeper than our ground based studies, allowing us the capability of optimally selecting a target list for a large survey rather than simply taking the few objects that can be measured, as we have had to do to date. We have carefully constructed a sample of 120 objects which provides both overall breadth, for a general understanding of these objects, plus a large enough number of objects in the individual dynamical subclass to allow detailed comparison between and within these groups. These objects will likely define the core Kuiper Belt compositional sample for years to come. While we have many specific results anticipated to come from this survey, as with any project where the field is rich, our current knowledge level is low, and a new instrument suddenly appears which can exploit vastly larger segments of the population, the potential for discovery — both anticipated and not — is extraordinary. WFC3/UVIS/IR 11700 Bright Galaxies at z>7.5 with a WFC3 Pure Parallel Survey
The epoch of reionization represents a special moment in the history of the Universe as it is during this era that the first galaxies and star clusters are formed. Reionization also profoundly affects the environment where subsequent generations of galaxies evolve. Our overarching goal is to test the hypothesis that galaxies are responsible for reionizing neutral hydrogen. To do so we propose to carry out a pure parallel WFC3 survey to constrain the bright end of the redshift z>7.5 galaxy luminosity function on a total area of 176 arcmin^2 of sky. Extrapolating the evolution of the luminosity function from z~6, we expect to detect about 20 Lyman Break Galaxies brighter than M_* at z~8 significantly improving the current sample of only a few galaxies known at these redshifts. Finding significantly fewer objects than predicted on the basis of extrapolation from z=6 would set strong limits to the brightness of M_*, highlighting a fast evolution of the luminosity function with the possible implication that galaxies alone cannot reionize the Universe. Our observations will find the best candidates for spectroscopic confirmation, that is bright z>7.5 objects, which would be missed by small area deeper surveys. The random pointing nature of the program is ideal to beat cosmic variance, especially severe for luminous massive galaxies, which are strongly clustered. In fact our survey geometry of 38 independent fields will constrain the luminosity function like a contiguous single field survey with two times more area at the same depth. Lyman Break Galaxies at z>7.5 down to m_AB=26.85 (5 sigma) in F125W will be selected as F098M dropouts, using three to five orbits visits that include a total of four filters (F606W, F098M, F125W, F160W) optimized to remove low-redshift interlopers and cool stars. Our data will be highly complementary to a deep field search for high-z galaxies aimed at probing the faint end of the luminosity function, allowing us to disentangle the degeneracy between faint end slope and M_* in a Schechter function fit of the luminosity function. We waive proprietary rights for the data. In addition, we commit to release the coordinates and properties of our z>7.5 candidates within one month from the acquisition of each field.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
#12126 COS Status Buffer message #913 (External shutter open move was blocked because the TDF was down) received during LOS @350/10:47z due to 350/10:42:33z REAcq(1,2,1) FGS 1 searching for ~25 arcseconds before acquiring the star and SCI INIT achieved @350/10:46:59z.
Observations possibly affected: COS #59-63 Proposal #11532
#12127 REAcq(1,0,1) takes two attempts to achieve FL @350/16:01z
Observations possibly affected: WFC3 #57-59 Proposal #12044
#12129 GSAcq(1,2,1) @350/21:26z failed to gyro control with search radius limit exceeded on FGS-2 @ 350/21:29z
Observations affected: COS #64-70 Proposal #11528; WFC3 #70-76 Proposal #11905; STIS #19-22 Proposal #11846
#12130 GSAcq(1,2,1) @351/02:57:49z Search Radius Limit exceeded on FGS 1 and 2
Observations affected: COS #71-78 Proposal #11692; WFC3 #77-83 Proposal #11912
#12132 GSAcq(1,2,1) @351/06:06:09z and REAcq(1,2,1) @351/06:52:29z Failed with Search Radius Limit exceeded on FGS 1
Observations affected: COS #79-88 Proposal #11625
#12133 GSAcq(1,2,1) @351/07:51z failed with Search Radius Limit exceeded on FGS 1
Observations affected: WFC3 #84 Proposal #11714
#12134 During LOS, both GSAcq(1,2,1) @351/08:49:50z cycled through Loss of Lock until 351/09:16z and REAcq(1,2,1) @351/10:25z failed to gyro control
Observations affected: WFC3 #85-95 Proposal #11643
#12124 SE PTAS processing found that REAcq(1,2,1) @338/00:19:10z took 2 attempts to achieve FL
Observations possibly affected: COS #38-41 Proposal #11896; ACS #69-70 Proposal #11879; WFC3 #87-88 Proposal #11905; STIS #56-57 Proposal #11844.
#12125 SE PTAS processing found that GSAcq(2,1,1) @339/01:49:53z failed to FLBU (2,0,2)
Observation possibly affected: WFC3 #123 Proposal #11714
#12128 SE PTAS processing found that REAcq(2,1,1) @344/01:11:27z took 2 attempts to achieve FL
Observations possibly affected: WFC3 #117-120 Proposal #11712; STIS #26-28 Proposal #11846; WFC3 #121-122 Proposal #11905
COMPLETED OPS REQUEST:
#18781-4 Configure Gyro 3 Heater to Backup Controller @ 350/2147z
#18568-1 LBBIAS Updates for Extended Gyro Guiding Intervals (Generic) @ 351/00:06z, 351/01:43z, 351/03:31z, 351/04:56z, 351/05:04z, 351/06:34z, 351/09:45z
#18562-1 CONTINGENCY: Continuous FGS Loss of Lock looping (Generic) @ 351/03:14z, 351/09:16z
#18784-0 LBBIAS Gyro Bias Update @ 351/06:34z
COMPLETED OPS NOTES: (None)
FGS GSAcq 8 3
FGS REAcq 5 4
OBAD with Maneuver 4 4
Flash Report: Gyro 3 Reconfiguration to Backup Heater
Approval to switch the Gyro 3 heater controller to the backup heater at 352/00:30 was given at the FRR on Wednesday, December 16. Subsequently, HSTAR 12126 was generated on the GS re-acquisition at 350/10:44 which required a 25 arcsecond spiral search and appeared to be related to a high uncompensated observer bias. Additionally, HSTAR 12127 was generated on the GS re-acquisition at 16:01 which required two attempts to converge on the vehicle bias and acquire the guide stars prior to the Loss of Lock check, also indicating a high uncompensated observer bias.
In reviewing these events with the STScI planning group, it was suggested that the heater switch be performed at 350/21:45 in order to avoid failures of critical science observations on day 351 while risking minor transient responses from the gyro 3 heater controller switch. This plan was proposed to project management and approved. However, the GS acquisition at 350/21:27 failed to RGA hold due to a search radius limit exceed. An initial review of the failure indicates that the problem was due to star issues and not a bias problem. This FGS guiding interval was a CVZ observation scheduled to last approximately 3 orbits. Since interference with science observations was no longer an issue, approval was given to proceed with the heater controller switch via Ops Request 18781-4.
The heater controller switch was executed at 350/21:47:30. As expected the heater caused transients in the motor current, heater duty cycle and temperature. The heater duty cycle initially jumped to 66%, quickly dropped to 13% and then gradually rose back to its previous operational level of 23% all over a period of 3 minutes. The motor current had two samples to 120.4 milliamps, one count above the pre-switch range of 114.8 to 117.6 (a one count toggle range) and subsequently 3 samples to 112.0 milliamps, one count below the pre-switch range, before returning to the pre-switch range. The temperature rose by one count (56.9 to 57.2 degC) and remained there for approximately 2 minutes before returning to 56.9 degC. All of this telemetry has been trending nominally since the initial transient.
With the failure of the GS acquisition at 21:27, the FOT was directed to execute the generic Ops Request 18568-1, LBBIAS Updates for Extended Gyro Guiding Intervals, in order to correct residual gyro bias and to correct any vehicle attitude error prior to the GS acquisition at 351/02:58. Initial biases measurements up to 351/01:50 were nominal and the LBBIAS was successfully uplinked at 351/01:46. However the GS acquisition at 351/02:57 failed to Loss of Lock (LOL) looping which is indicative of a bias issue. Subsequent biases appeared to increase in the V2 and V3 axes and acquisitions between 06:07 and 10:27 failed due to search radius limit exceeds (SRLEX) or LOL looping while efforts were made to correct the bias. The GS acquisition at 12:01 was successful and performed an onboard bias update. The GS acquisition at 13:05 failed due to a dim star and another full acquisition will not occur until 19:01. Another LBBIAS update is in work to correct the bias.