ner_tags: O O O O O O O O O O O O O O O O O O O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O B-Organization O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O B-Instrument O O O B-Organization O O O O O O O O O O O O O O O O O O O B-Wavelength O B-Wavelength O O B-Archive O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O B-Wavelength O O O O B-CelestialObject I-CelestialObject O O B-Wavelength O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O B-Instrument O O O O O O O O O O O O O O O O O O O O O O B-Wavelength B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O B-Model I-Model I-Model O B-Model I-Model I-Model I-Model O O B-Model I-Model I-Model I-Model O O O O O O O B-Model I-Model O O B-Software O O B-Software O O B-Citation I-Citation I-Citation B-Software I-Software I-Software I-Software I-Software I-Software O B-Software O O B-URL O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Instrument O O O O O O O O O O O B-Wavelength O O O B-Wavelength O O O O O O O O O O O O O O O B-Formula O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
tokens: length of just 0.5 kpc, the gas will have cooled and recombined before escaping. These baryons will therefore become visible to Lyman series absorption studies and the oxygen will be visible to O i absorption (e.g., at 1302 Å). APPENDIX MATCHING THE POINT-SPREAD FUNCTION The diffuse halo of O vi emission could be mimicked if the F125LP PSF is broader than that of F140LP. We used custom software to match images to a common PSF. Point sources (stars) that are bright in the FUV are rare, making empirical studies of the SBC PSFs challenging, and the models available from STScI severely underestimate the power in the extended wings of the PSF (at radii larger than 1 arcsec). We instead build empirical PSF models by examining multi-epoch calibration data of the globular cluster NGC 6681. These were obtained under many programs by the ACS instrument team at STScI, stretching back to 2002 when the instrument was first mounted. We have obtained all the calibration images taken in F125LP and F140LP from the MAST, drizzled and stacked them using the same methods as for our science data. The total exposure time in F125LP is 13,530 and 7350 s in F140LP. The brightest star in NGC 6681 has a FUV AB magnitude of 18.0, giving a countrate of 22 counts per second in the brightest pixel in F125LP. This is just below the nonlinear regime of the SBC detector, indicating that calibration data are as good as possible for deriving the PSF. We then selected 45 (48) stars in the F125LP (F140LP) images, extracted stamps, and stacked them to produce a very deep point-source image. A model PSF consisting of a combination of three 2D functions (an elliptical Moffat function, a radially symmetric Gaussian function, and a symmetric fourth-order polynomial function) was fitted to the stacked image using least-squares fitting with the LMFIT package for Python. 6 6 Newville et al., LMFIT: Non-Linear Least-Square Minimization and Curve-Fitting for Python, 2014, doi: 10.5281/zenodo.11813 . The stacking was then redone iteratively with the contribution from nearby stars removed by subtracting the model PSF. The final stacked images in the two filters were normalized to have a total sum of 1 and are presented in Figure 12 , while the final best fitting models were used to compute the matching convolution kernel. Figure 12. Point-spread function of the SBC filters. The top left panels show the empirical PSF of the F125LP (left-hand side) and F140LP (right-hand side) filters in log scale. The bottom left panels show the relative difference map, (F125LP–F140LP)/F140LP, without any PSF matching on the left and with PSF matching on the right. Note that the 2D PSF models are only trustworthy (at a level) out to a radius of about 1.3 arcsec. The top right panel shows the surface brightness profiles of the two empirical PSFs with the shaded regions showing the errors per annulus, and the inset showing the inner 0.5 arcsec of the profile. The lower right panel shows the signal-to-noise