Class FilterIdeal

Inheritance Relationships

Base Type

Class Documentation

class FilterIdeal : public phot::Filter

An idealized photometric filter whose response is a top-hat function of wavelength.

A FilterIdeal’s response is exactly 1 within [wlMin, wlMax] and exactly 0 everywhere else – useful both for idealized experiments and for computing photon fluxes above (or between) particular ionization thresholds, without needing a real instrument’s tabulated response curve.

Public Functions

inline FilterIdeal(std::string name, double wlMin, double wlMax, bool photCount = false)

Construct a FilterIdeal directly from a wavelength range.

Parameters:

  • name – Name of this filter, for output purposes

  • wlMin – Minimum wavelength of the filter’s response, in Angstrom

  • wlMax – Maximum wavelength of the filter’s response, in Angstrom

  • photCount – If true, this filter returns photon counts rather than F_lambda values; see Filter::phot() for details

Throws:

std::runtime_error – if photCount is false and wlMin <= 0 or wlMax is infinite – phot()’s energy-flux mode integrates in ln(wavelength), which breaks at either extreme (see phot()’s own comment); a photCount filter has no such restriction

explicit FilterIdeal(std::string name)

Construct a FilterIdeal by parsing its name.

Recognizes two naming conventions:

  1. ideal_<kind>_X_Y, where X and Y are wavelengths in Angstrom (Y may also be “inf”, meaning no upper bound) giving wlMin and wlMax respectively, and <kind> is either:

    • ”energy”: an energy-flux filter (photCount() is false)

    • ”phot”: a photon-counting filter (photCount() is true)

  2. Q(<spec>), where <spec> is an atomic symbol followed by a Roman numeral giving the ionization state in astronomical notation (e.g. Q(HI) = photons that ionize neutral hydrogen, Q(CII) = photons that ionize C+ to C++). Ionizing photons have energy above the ionization potential IP, i.e. wavelength below the threshold lambda = h*c/IP, so the filter is set to wlMin = 0 (no lower bound), wlMax = h*c/IP (the ionization-threshold wavelength in Angstrom, sourced from CRC data), and photCount = true.

Parameters:

name – Name of this filter; must match one of the recognized ideal-filter naming conventions (see below)

Throws:

std::runtime_error – if name does not match either recognized convention, or if the requested ionization potential is not available in the CRC data

FilterIdeal(const FilterIdeal&) = default
auto operator=(const FilterIdeal&) -> FilterIdeal& = default
FilterIdeal(FilterIdeal&&) = default
auto operator=(FilterIdeal&&) -> FilterIdeal& = default
~FilterIdeal() override = default
inline auto wlMin() const -> double

Get the minimum wavelength of this filter’s response.

Returns:

The minimum wavelength of this filter’s response, in Angstrom

inline auto wlMax() const -> double

Get the maximum wavelength of this filter’s response.

Returns:

The maximum wavelength of this filter’s response, in Angstrom

inline virtual auto wlSupport() const -> std::pair<double, double> override

Get the wavelength range over which this filter’s response is nonzero.

Returns:

{wlMin(), wlMax()}

inline virtual auto wlPivot() const -> double override

Get this filter’s pivot wavelength.

Returns:

The midpoint of [wlMin, wlMax]; wlMax if wlMin is 0 (as for a Q(*) ionization-threshold filter, whose passband has no finite lower end), or wlMin if wlMax is infinite (as for an ideal_phot_X_inf filter, whose passband has no finite upper end)

virtual auto phot(const std::vector<double> &wl, const std::vector<double> &spec) const -> double override

Compute the photometric response of this filter to a spectrum.

Parameters:

  • wl – The wavelength grid, in Angstrom

  • spec – The spectrum, in erg/s/Angstrom

Returns:

If photCount() is false: the mean value of spec over the filter’s passband [wlMin, wlMax] on a log-wavelength basis – (integral of spec d(ln λ)) / ln(wlMax / wlMin), in erg/s/Angstrom, matching Filter::phot()’s own documented units and FilterTabulated::phot()’s own dlnλ convention – over the intersection of [wlMin, wlMax] with the supplied wavelength grid; if photCount() is true: the total photon-count rate, in photons/s, computed by integrating spec × λ / (h c) dλ over the same range (a count rate, not a mean, so not normalized)