Definitive ISM Abundances through Low-mass X-ray Binaries as Lighthouses
We propose observations of the UV spectra of two low-mass X-ray binaries (Sco X-1 and Cyg X-2) with existing Chandra X-Ray Observatory (CXO) data. From the X-ray data we will measure total (phase-independent) column densities of O, Ne, and Fe. From the UV data we will determine gas-phase column densities of H and O. The data in conjunction will allow us to make unique measurements of the total interstellar abundances of oxygen, neon, and iron, and direct measurements of the dust-phase abundances of O and Fe.
NUV Internal/External Wavelength Scale Monitor
This program monitors the offsets between the wavelength scale set by the internal wavecal versus that defined by absorption lines in external targets. This is accomplished by observing two external radial velocity standard targets: HD187691 with G225M and G285M and HD6655 with G285M and G230L. The two standard targets have little flux in the wavelength range covered by G185M and so Feige 48 (sdO) is observed with this grating. Both Feige 48 and HD6655 are also observed in SMOV. The cenwaves observed in this program are a subset of the ones used during Cycle 17. Observing all cenwaves would require a considerably larger number of orbits. Constraints on scheduling of each target are placed so that each target is observed once every ~2-3 months. Observing the three targets every month would also require a considerably larger number of orbits.
How Galaxies Acquire their Gas: A Map of Multiphase Accretion and Feedback in Gaseous Galaxy Halos
We propose to address two of the biggest open questions in galaxy formation - how galaxies acquire their gas and how they return it to the IGM - with a concentrated COS survey of diffuse multiphase gas in the halos of SDSS galaxies at z = 0.15 - 0.35. Our chief science goal is to establish a basic set of observational facts about the physical state, metallicity, and kinematics of halo gas, including the sky covering fraction of hot and cold material, the metallicity of infall and outflow, and correlations with galaxy stellar mass, type, and color - all as a function of impact parameter from 10 - 150 kpc. Theory suggests that the bimodality of galaxy colors, the shape of the luminosity function, and the mass-metallicity relation are all influenced at a fundamental level by accretion and feedback, yet these gas processes are poorly understood and cannot be predicted robustly from first principles. We lack even a basic observational assessment of the multiphase gaseous content of galaxy halos on 100 kpc scales, and we do not know how these processes vary with galaxy properties. This ignorance is presently one of the key impediments to understanding galaxy formation in general. We propose to use the high-resolution gratings G130M and G160M on the Cosmic Origins Spectrograph to obtain sensitive column density measurements of a comprehensive suite of multiphase ions in the spectra of 43 z < 1 QSOs lying behind 43 galaxies selected from the Sloan Digital Sky Survey. In aggregate, these sightlines will constitute a statistically sound map of the physical state and metallicity of gaseous halos, and subsets of the data with cuts on galaxy mass, color, and SFR will seek out predicted variations of gas properties with galaxy properties. Our interpretation of these data will be aided by state-of-the-art hydrodynamic simulations of accretion and feedback, in turn providing information to refine and test such models. We will also use Keck, MMT, and Magellan (as needed) to obtain optical spectra of the QSOs to measure cold gas with Mg II, and optical spectra of the galaxies to measure SFRs and to look for outflows. In addition to our other science goals, these observations will help place the Milky Way's population of multiphase, accreting High Velocity Clouds (HVCs) into a global context by identifying analogous structures around other galaxies. Our program is designed to make optimal use of the unique capabilities of COS to address our science goals and also generate a rich dataset of other absorption-line systems.
COS FUV DCE Memory Dump
Whenever the FUV detector high voltage is on, count rate and current draw information is collected, monitored, and saved to DCE memory. Every 10 msec the detector samples the currents from the HV power supplies (HVIA, HVIB) and the AUX power supply (AUXI). The last 1000 samples are saved in memory, along with a histogram of the number of occurrences of each current value.
In the case of a HV transient (known as a "crackle" on FUSE), where one of these currents exceeds a preset threshold for a persistence time, the HV will shut down, and the DCE memory will be dumped and examined as part of the recovery procedure. However, if the current exceeds the threshold for less than the persistence time (a "mini-crackle" in FUSE parlance), there is no way to know without dumping DCE memory. By dumping and examining the histograms regularly, we will be able to monitor any changes in the rate of "mini-crackles" and thus learn something about the state of the detector.
CCD Dark Monitor Part 2
Monitor the darks for the STIS CCD.
CCD Bias Monitor-Part 2
Monitor the bias in the 1x1, 1x2, 2x1, and 2x2 bin settings at gain=1, and 1x1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.
Star Formation, Extinction, and Metallicity at 0.7
The global star formation rate (SFR) is ~10x higher at z=1 than today. This could be due to drastically elevated SFR in some fraction of galaxies, such as mergers with central bursts, or a higher SFR across the board. Either means that the conditions in z=1 star forming galaxies could be quite different from local objects. The next step beyond measuring the global SFR is to determine the dependence of SFR, obscuration, metallicity, and size of the star-forming region on galaxy mass and redshift. However, SFR indicators at z=1 typically apply local calibrations for UV, [O II] and far-IR, and do not agree with each other on a galaxy-by-galaxy basis. Extinction, metallicity, and dust properties cause uncontrolled offsets in SFR calibrations. The great missing link is Balmer H-alpha, the most sensitive probe of SFR. We propose a slitless WFC3/G141 IR grism survey of GOODS-N, at 2 orbits/pointing. It will detect Ha+[N II] emission from 0.7 600 galaxies, and a small number of higher-redshift emitters. This will produce: an emission-line redshift survey unbiased by magnitude and color selection; star formation rates as a function of galaxy properties, e.g. stellar mass and morphology/mergers measured by ACS; comparisons of SFRs from H-alpha to UV and far-IR indicators; calibrations of line ratios of H-alpha to important nebular lines such as [O II] and H-beta, measuring variations in metallicity and extinction and their effect on SFR estimates; and the first measurement of scale lengths of the H-alpha emitting, star-forming region in a large sample of z~1 sources.
Infrared Survey of Star Formation Across Cosmic Time
We propose to use the unique power of WFC3 slitless spectroscopy to measure the evolution of cosmic star formation from the end of the reionization epoch at z>6 to the close of the galaxy-building era at z~0.3.Pure parallel observations with the grisms have proven to be efficient for identifying line emission from galaxies across a broad range of redshifts. The G102 grism on WFC3 was designed to extend this capability to search for Ly-alpha emission from the first galaxies. Using up to 250 orbits of pure parallel WFC3 spectroscopy, we will observe about 40 deep (4-5 orbit) fields with the combination of G102 and G141, and about 20 shallow (2-3 orbit) fields with G141 alone.
Our primary science goals at the highest redshifts are: (1) Detect Lya in ~100 galaxies with z>5.6 and measure the evolution of the Lya luminosity function, independent of of cosmic variance; 2) Determine the connection between emission line selected and continuum-break selected galaxies at these high redshifts, and 3) Search for the proposed signature of neutral hydrogen absorption at re-ionization. At intermediate redshifts we will (4) Detect more than 1000 galaxies in Halpha at 0.5
To identify single-line Lya emitters, we will exploit the wide 0.8--1.9um wavelength coverage of the combined G102+G141 spectra. All [OII] and [OIII] interlopers detected in G102 will be reliably separated from true LAEs by the detection of at least one strong line in the G141 spectrum, without the need for any ancillary data. We waive all proprietary rights to our data and will make high-level data products available through the ST/ECF.
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).
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).