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To convert from DN to absolute flux units (e.g., see Eq. In the FITS headers of L1b products, and allows one This information is stored as the MAGZP keyword Photometry relative to a standard star network (see section A calibrationįactor (or equivalent photometric zero-point offset) isĬomputed downstream in the WSDS pipeline using The pixel values in a calibrated intensity frame Sample-Up-the-Ramp (SUR) values generated by the Focal-plane Electronics Box Is the fitted slope (or rate) to non-destructively read General form: a + b*slopefit, where slopefit The DEB (Data Number or DN) output is given by For details on frame QA,Īre expected to be those as generated by the on-board Digital Electronics Box Metrics and plots are also generated for each frame. Pixel and are used in generating the Atlas Image Image contains a 1-sigma error estimate in the intensity signal for every The ICal pipeline generates three (level-1b or L1b) FITS imageĪccompanying uncertainty frame, and mask image.įrameID-w BAND- msk-1b.fits respectively. This could be due to the different environmentĪnd/or electronics used in ground testing. It's important to note that the pre-flight (ground) calibrations The payload and detectors is given in section III.2.Ĭharacterization and specific detector properties The HgCdTe arrays (serving W1, W2 at 3.4, 4.6μm respectively)Īnd Si:As arrays (serving W3, W4 at 12.1, 22.2μm respectively). The calibrations are band dependent and differ considerably between The intent here is to summarize processing algorithms, how calibrations were made, and their overall performance. This stores the status of processing on each pixel as well as prior knowledge of bad hardware pixels. These uncertainties are propagated and updating downstream as calibrations are applied.Ī bit-mask image is also initiated per frame and updated. ICal also initiates pixel uncertainties for a frame using a noise model. These are covered in detail under the ARTID processing system. Optical artifacts and signatures induced by telescope optics, e.g., ghosts, glints, global FOV distortion, PSF non-isoplanicity, including image persistence (latents) are not discussed here. The purpose of instrumental calibration (ICal) is to read in a raw (Level-0 or L0) single exposure frame and correct it for instrumental signatures, e.g., dark current, non-uniform responsivity, non-linearity, and other detector-induced electronic signatures. Analysis of Spatial-Responsivity Residuals
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Band 1 and 2 Channel-noise and Bias CorrectionsĢ. Relative Responsivity (Flat-field) Calibration
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Frame-mask Initialization and Bad-pixel Masking Electronic Gain and Read-Noise Calibration Single Frame Exposure Instrumental Calibration (ICal)ġ.
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While the AGN continuum luminosity at 5100 Å is usually used to predict the Hβ reverberation lag, we show that the luminosity of the Hβ broad component can be used instead without any loss of precision, thus eliminating the difficulty of accurately accounting for the host-galaxy contribution to the observed luminosity.WISE All-Sky Release Explanatory Supplement: Data Processing We present simplified empirical formulae for estimating black hole masses from the Hβ λ4861 and C IV λ1549 emission lines. We confirm the recent findings that, in addition to luminosity and line width, a third parameter is required to obtain accurate masses, and that parameter seems to be Eddington ratio. Here we investigate estimation of black hole masses in AGNs based on individual or "single-epoch" observations, with a particular emphasis in comparing mass estimates based on line dispersion and FWHM. We argue here that use of FWHM introduces a bias, stretching the mass scale such that high masses are overestimated and low masses are underestimated. An unresolved key issue is the choice of parameter used to characterize the line width, either FWHM or line dispersion $$ (the square root of the second moment of the line profile). It is well known that reverberation mapping of active galactic nuclei (AGNs) reveals a relationship between AGN luminosity and the size of the broad-line region, and that use of this relationship, combined with the Doppler width of the broad emission line, enables an estimate of the mass of the black hole at the center of the active nucleus based on a single spectrum.