uvex_transients.models.core.base.ComposedSpectralModel.simulate_photometry#

Simulate noisy synthetic photometry of this model at given time(s), against a real detector.

The noise-aware counterpart to mag()/flux()/as_source_spectrum(): those give the noiseless truth; this adds the detector’s own noise model (get_snr(), the same OIR CCD equation signal_to_noise_oir_ccd implements) and reports a synthetic measurement – one Gaussian realization of the true flux at each requested time and band, at that time/band’s own implied uncertainty.

Deliberately independent of any SurveySchedule or Event: t/exptime are whatever times/exposures the caller wants evaluated (e.g. a target-of-opportunity’s own chosen observing cadence), not ones a schedule was queried for. background is a required, explicit choice for the same reason – rather than an implicit default read off detector. This lets a caller decide what physics to include (dust, via ebv, is always folded into the source flux itself; the Milky Way’s diffuse UV glow via ~m4opt.synphot.background.GalacticBackground; zodiacal light via ~m4opt.synphot.background.ZodiacalBackground; …) without needing to know, let alone undo, whatever combination a particular detector happens to ship with (e.g. m4opt.missions.uvex’s own detector defaults to GalacticBackground() + ZodiacalBackground()). If background is given, it replaces detector’s own background for this call only (detector itself is never mutated); if omitted, detector’s own background is used unchanged.

observer_location/obstime matter only insofar as background actually depends on them: GalacticBackground reads only sky position (coord, by way of m4opt.synphot.observing’s target coordinate), so for a dust-and-Galactic-only call – e.g. a target of opportunity whose real observing time isn’t known yet – neither needs to be real, and both default to fixed placeholders. Pass real values (e.g. a mission’s own observer_location(obstime)) only when background includes a term that actually varies with them, such as ZodiacalBackground (sun-relative sky position, from obstime) or EarthshineBackground (spacecraft position, from observer_location).

Parameters:

t (array-like or Quantity) – Time(s) since explosion, shape (N,) (or scalar, promoted to shape (1,)) – one entry per requested observation. Unlike as_source_spectrum(), no manual trailing batch axis is needed; this method inserts and removes it internally.
exptime (Quantity) – Exposure duration(s), scalar (applied to every entry of t) or shape matching t.
detector (Detector) – Supplies bandpasses, collecting area, plate scale, and detector noise terms (dark/read noise, gain, …). Its own background is used only if background isn’t given – see above.
coord (SkyCoord) – Scalar sky position of the target.
background (SourceSpectrum, optional) – Sky background surface brightness to simulate against for this call – e.g. ~m4opt.synphot.background.GalacticBackground() alone, or combined with others via +. If None (the default), detector’s own background is used.
bands (list, optional) – Which of detector’s bandpasses to evaluate. Defaults to every bandpass detector has.
observer_location (EarthLocation, optional) – See above; defaults to a fixed placeholder location, correct whenever background doesn’t depend on it.
obstime (Time, optional) – See above; defaults to a fixed placeholder epoch, correct whenever background doesn’t depend on it.
redshift (array-like or Quantity, optional) – See as_source_spectrum().
luminosity_distance (Quantity, optional) – See as_source_spectrum().
angular_diameter_distance (Quantity, optional) – See as_source_spectrum().
proper_distance (Quantity, optional) – See as_source_spectrum().
cosmology (FLRW, optional) – See as_source_spectrum().
ebv (float, Quantity, numpy.ndarray, or str, optional) – See as_source_spectrum().
dust_law (float, Quantity, numpy.ndarray, or str, optional) – See as_source_spectrum().
n_sigma (float, optional) – Width, in multiples of flux_err, of the flux_upper/flux_lower/ mag_upper/mag_lower interval. If None (the default), uses config["simulation.detection_n_sigma"] (5 out of the box).
sys_err (float or Mapping[str, float], optional) – A per-band systematic calibration error floor, in magnitudes, combined in quadrature with the shot-noise uncertainty detector itself computes (via get_snr(), the OIR CCD equation – source and sky Poisson noise plus detector read/dark noise only, with no notion of flat-fielding, PSF-fit, or zeropoint calibration systematics). Folded into the noise realization itself, not just reported as a wider flux_err around an unchanged draw – otherwise the scatter of simulated points across repeated visits would be narrower than what their own error bars claim. A bare float applies the same floor to every band in bands; a mapping must have an entry for every band in bands. If None (the default, and the prior behavior), no systematic floor is added.
rng (numpy.random.Generator, int, or None) – Random-number source for the noise realization; see get_rng().
**parameters – This model’s parameter values. See eval_log_cgs().

Returns:

One row per (time, band), sorted by t then band, with columns t, exptime, band, snr, flux/flux_err (Jy), flux_upper/flux_lower (Jy, flux ± n_sigma*flux_err), ab_mag/mag_err, and mag_upper/mag_lower – the n_sigma interval transformed to magnitude, brighter bound first. See simulate_photometry() for the exact semantics of every column (this method implements the same math). If sys_err is given, snr/flux_err/mag_err (and everything derived from them) reflect the combined shot-noise-plus-systematic uncertainty.

Return type:

astropy.table.QTable

Raises:

ValueError – If coord is not scalar, if bands contains a name detector doesn’t have, if exptime is neither scalar nor shaped like t, or if sys_err is a mapping missing an entry for one of bands.