This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.
The Near-Infrared Spectrograph (NIRSpec) is one of the four focal plane instruments on the James Webb Space Telescope. In this paper, we summarize the in-orbit performance of NIRSpec, as derived from data collected during its commissioning campaign and the first few months of nominal science operations. More specifically, we discuss the performance of some critical hardware components such as the two NIRSpec Hawaii-2RG detectors, wheel mechanisms, and the microshutter array. We also summarize the accuracy of the two target acquisition procedures used to accurately place science targets into the slit apertures, discuss the current status of the spectrophotometric and wavelength calibration of NIRSpec spectra, and provide the “as measured” sensitivity in all NIRSpec science modes. Finally, we point out a few important considerations for the preparation of NIRSpec science programs.
The Hubble Space Telescope/Cosmic Origins Spectrograph (COS) has opened a new discovery space for studying quasar absorption outflows and their contribution to AGN feedback. Specifically, COS provides high-quality far-ultraviolet (FUV) spectra covering the diagnostic-rich 500-1050Å rest frame (hereafter, EUV500) of medium redshift objects. The quality and quantity of EUV500 diagnostic troughs allow us to probe the very high-ionization phase, which carries 90% or more of the outflowing material, as well as to determine the distance of most outflows from the central source (R). The first objective is impossible to achieve with ground-based spectra, and R can be measured in only ∼1% of them. Here, we summarize the main results of the first dedicated survey of such outflows, including the following: 1) Measurements of the three most energetic outflows to date, which can be the main agents for AGN feedback processes in the environments of the host galaxies. 2) All the outflows have a very high-ionization component, similar to the one found in warm absorbers, which carries most of the outflow's kinetic luminosity. This finding suggests that all the high-ionization outflows observed from the ground also have a similar undetected very high-ionization component.3) Of the 13 studied EUV500 outflows, 9 have 100 < R < 2000 parsecs, 2 have 5 < R < 20 parsecs, 1 has 0.05 < R < 50 parsecs, and in 1 case, R cannot be determined. 4) One of the outflows has the largest velocity shift (1550 km s −1 ) and acceleration (1.5 cm s −2 ) measured to date. This outflow is physically similar to the fast X-ray outflow detected in quasar PG 1211+143.
We analyze new HST /COS spectra for two quasar absorption outflows seen in the quasi-stellar object LBQS 1206+1052. These data cover, for the first time, absorption troughs from S iv, Si ii, and P v. From the ratio of the S iv* to S iv column densities, we measure the electron number density of the higher-velocity (−1400 km s −1 , v1400) outflow to be log(n e ) = 4.23 +0.09 −0.09 cm −3 and constrain the lower-velocity (−730 km s −1 , v700) outflow to log(n e ) > 5.3 cm −3 . The n e associated with the highervelocity outflow is an order of magnitude larger than reported in prior work. We find that the previous measurement was unreliable since it was based on density-sensitive absorption troughs that were likely saturated. Using photoionization models, we determine the best χ 2 -minimization fit for the ionization parameter and hydrogen column density of the higher-velocity outflow: log(U H ) = −1.73 +0.21 −0.12 and log(N H ) = 21.03 +0.25 −0.15 cm −2 , respectively. We calculate from U H and n e a distance of 500 +100 −110 pc from the central source to the outflow. Using an SED attenuated by the v700 outflow yields a twophase photoionization solution for the v1400 outflow, separated by a ∆U 0.7. Otherwise, the resultant distance, mass flux, and kinetic luminosity are similar to the unattenuated case. However, the attenuated analysis has significant uncertainties due to a lack of constraints on the v700 outflow in 2017.
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