- Press Release
- Dec 2, 2022
NASA Hubble Space Telescope Daily Report #5027
HUBBLE SPACE TELESCOPE DAILY REPORT #5027
Continuing to Collect World Class Science
PERIOD COVERED: 5am February 4 – 5am February 5, 2010 (DOY 035/10:00z-036/10:00z)
NUV Detector Dark Monitor
The purpose of this proposal is to measure the NUV detector dark rate by taking long science exposures with no light on the detector. The detector dark rate and spatial distribution of counts will be compared to pre-launch and SMOV data in order to verify the nominal operation of the detector. Variations of count rate as a function of orbital position will be analyzed to find dependence of dark rate on proximity to the SAA. Dependence of dark rate as function of time will also be tracked.
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.
The Physical Nature and Age of Lyman Alpha Galaxies
In the simplest scenario, strong Lyman alpha emission from high redshift galaxies would indicate that stellar populations younger than 10 Myrs dominate the UV. This does not, however, constrain the stellar populations older than 100 Myrs, which do not contribute to UV light. Also, the Lyman alpha line can be boosted if the interstellar medium is both clumpy and dusty. Different studies with small samples have reached different conclusions about the presence of dust and old stellar populations in Lyman alpha emitters. We propose HST-NICMOS and Spitzer-IRAC photometry of 35 Lyman-alpha galaxies at redshift 4.5
COS-GTO: Cold ISM
With the COS, we will be able to observe interstellar spectra in a new regime, translucent clouds, for atomic, ionic, and molecular lines and bands, and extinction curves. The COS will allow us to observe stars with total visual extinctions up to 10 magnitudes, and the grain size indicator Rv up to 4.5. In translucent clouds we expect to see the transition from neutral and ionized carbon to mostly C I, and then from there, we should expect to see carbon increasingly locked up in molecular form, as CO. Other species are expected to make similar transitions, so we should find detectable abundances of molecules such as H2O, OH, CS, CH2, SiO, and others; also, lower ionization fractions of the metallic elements – and higher depletions of those elements as well. Given that we expect to find higher depletions, we should see an altered grain size distribution, which may show up in the extinction curves, probably as lower far-UV extinction than in diffuse clouds. Finally, we will search for neutral PAHs in absorption, as diffuse bands in the UV, paralleling the optical DIBs (which are thought by some scientists to be formed by singly-ionized PAHs). In translucent clouds, models show that the PAHs will be neutral, not in cationic form.
How Far Does H2 Go: Constraining FUV Variability in the Gaseous Inner Holes of Protoplanetary Disks
By studying the innermost, planet-forming regions of circumstellar disks around low-mass pre-main sequence stars we can refine theories of planet formation and develop timescales for the evolution of disks and their planets. Spitzer infrared observations of T Tauri stars have given us an unprecedented look at dust evolution in young objects, particularly the transitional disks. However, despite this ground breaking progress in studying the dust in young disks, the relationship between the dust and gas properties in the inner disk remains essentially unknown. Using STIS on HST, we propose to quantify the variability of H2 emission originating within the inner holes of transitional disks and explore its implications on dust distribution and planet formation.
Dynamical Hypermassive Black Hole Masses
We will use STIS spectra to derive the masses of 5 hypermassive black holes (HMBHs). From the observed scaling relations defined by less massive spheroids, these objects are expected to reside at the nuclei of host galaxies with stellar velocity dispersions greater than 320 km/s. These 5 targets have confirmed regular gas distributions on the scales of the black hole sphere of influence. It is essential that the sphere of influence is resolved for accurate determinations of black hole mass (0.1″). These scales cannot be effectively observed from the ground. Only two HMBHs have had their masses modeled so far; it is impossible to draw any general conclusions about the connections between HMBH mass and their massive host galaxies. With these 5 targets we will determine whether these HMBHs deviate from the scaling relations defined by less massive spheroids. A larger sample will allow us to firmly anchor the high mass end of the correlation between black hole mass and stellar velocity dispersion, and other scaling relations. Therefore we are also conducting a SNAPshot program with which we expect to detect a further 24 HMBH candidates for STIS observation in future cycles. At the completion of this project we will have populated the high mass end of the scaling relations with the sample sizes enjoyed by less massive spheroids.
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 Disks, Accretion, and Outflows (DAO) of T Tau Stars
Classical T Tauri stars undergo magnetospheric accretion, power outflows, and possess the physical and chemical conditions in their disks to give rise to planet formation. Existing high resolution FUV spectra verify that this spectral region offers unique diagnostics of these processes, which have the potential to significantly advance our understanding of the interaction of a star and its accretion disk. To date the limited results are intriguing, with dramatic differences in kinematic structure in lines ranging from C IV to H2 among the few stars that have been observed. We propose to use HST/COS to survey the disks, outflows, and accretion (the DAO) of 26 CTTS and 6 WTTS in the FUV at high spectral resolution. A survey of this size is essential to establish how properties of accretion shocks, winds and disk irradiation depend on disk accretion rate. Specifically, our goals are to (1) measure the radiation from and understand the physical properties of the gas very near the accretion shock as a function of accretion rate using emission line profiles of hot lines (C IV, Si IV, N V, and He II); (2) measure the opacity, velocity, and temperature at the base of the outflow to constrain outflow models using wind absorption features; and (3) characterize the radiation incident on disks and protoplanetary atmospheres using H2 line and continuum emission and reconstructed bright Ly-alpha line emission.
A SNAPSHOT Survey of the Local Interstellar Medium: New NUV Observations of Stars with Archived FUV Observations
We propose to obtain high-resolution STIS E230H SNAP observations of MgII and FeII interstellar absorption lines toward stars within 100 parsecs that already have moderate or high-resolution far-UV (FUV), 900-1700 A, observations available in the MAST Archive. Fundamental properties, such as temperature, turbulence, ionization, abundances, and depletions of gas in the local interstellar medium (LISM) can be measured by coupling such observations. Due to the wide spectral range of STIS, observations to study nearby stars also contain important data about the LISM embedded within their spectra. However, unlocking this information from the intrinsically broad and often saturated FUV absorption lines of low-mass ions, (DI, CII, NI, OI), requires first understanding the kinematic structure of the gas along the line of sight. This can be achieved with high resolution spectra of high-mass ions, (FeII, MgII), which have narrow absorption lines, and can resolve each individual velocity component (interstellar cloud). By obtaining short (~10 minute) E230H observations of FeII and MgII, for stars that already have moderate or high- resolution FUV spectra, we can increase the sample of LISM measurements, and thereby expand our knowledge of the physical properties of the gas in our galactic neighborhood. STIS is the only instrument capable of obtaining the required high resolution data now or in the foreseeable future.
STIS Cycle 17 MAMA Dark Monitor
This proposal monitors the behavior of the dark current in each of the MAMA detectors.
The basic monitor takes two 1380s ACCUM darks each week with each detector. However, starting Oct 5, pairs are only included for weeks that the LRP has external MAMA observations planned. The weekly pairs of exposures for each detector are linked so that they are taken at opposite ends of the same SAA free interval. This pairing of exposures will make it easier to separate long and short term temporal variability from temperature dependent changes.
For both detectors, additional blocks of exposures are taken once every six months. These are groups of five 1314s FUV-MAMA Time-Tag darks or five 3x315s NUV ACCUM darks distributed over a single SAA-free interval. This will give more information on the brightness of the FUV MAMA dark current as a function of the amount of time that the HV has been on, and for the NUV MAMA will give a better measure of the short term temperature dependence.
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).
UVIS Hot Pixel Anneal
The on-orbit radiation environment of WFC3 will continually generate new hot pixels. This proposal performs the procedure required for repairing those hot pixels in the UVIS CCDs. During an anneal, the two-stage thermo-electric cooler (TEC) is turned off and the four-stage TEC is used as a heater to bring the UVIS CCDs up to ~20 deg. C. As a result of the CCD warmup, a majority of the hot pixels will be fixed; previous instruments such as WFPC2 and ACS have seen repair rates of about 80%. Internal UVIS exposures are taken before and after each anneal, to allow an assessment of the procedure’s effectiveness in WFC3, provide a check of bias, global dark current, and hot pixel levels, as well as support hysteresis (bowtie) monitoring and CDBS reference file generation. One IR dark is taken after each anneal, to provide a check of the IR detector.
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
FGS GSAcq 08 08
FGS REAcq 06 06
OBAD with Maneuver 05 05
SIGNIFICANT EVENTS: (None)