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authorAaron LI <aaronly.me@outlook.com>2016-10-11 22:26:01 +0800
committerAaron LI <aaronly.me@outlook.com>2016-10-11 22:26:01 +0800
commit0ce54992d3f4f3c64083337f71418cfec5326409 (patch)
tree6a07f3e1fd8f9e6aeab88f86d05d06fd986005fb /fg21sim
parent34191e3525f258b850dc41616eb08da9a5520a23 (diff)
downloadfg21sim-0ce54992d3f4f3c64083337f71418cfec5326409.tar.bz2
galactic/freefree: Mask regions where absorption is uncertain
* Mask the regions where the dust absorption is too high to well determine the true Halpha absorption. There are regions (e.g., Galactic plane) have too large dust absorption which cause float overflow when applying absorption correction to the Halpha map. * Fix a bug on the wrong parameter passed to "_calc_ratio_a()" method in "_simulate_frequency()" * Move "_correct_dust_absorption()" invokation from "simulate()" to "_simulate_frequency()" Already tested and OK!
Diffstat (limited to 'fg21sim')
-rw-r--r--fg21sim/galactic/freefree.py29
1 files changed, 25 insertions, 4 deletions
diff --git a/fg21sim/galactic/freefree.py b/fg21sim/galactic/freefree.py
index 28a92d6..0dd131d 100644
--- a/fg21sim/galactic/freefree.py
+++ b/fg21sim/galactic/freefree.py
@@ -129,16 +129,37 @@ class FreeFree:
"""Correct the H{\alpha} map for dust absorption using the
100-{\mu}m dust map.
- References: [Dickinson2003], Eq.(3)
+ References: [Dickinson2003]: Eq.(1, 3); Sec.(2.5)
"""
if hasattr(self, "dust_corrected") and self.dust_corrected:
return
#
+ logger.info("Correct H[alpha] map for dust absorption")
# Effective dust fraction in the LoS actually absorbing Halpha
f_dust = 0.33
+ logger.info("Effective dust fraction: {0}".format(f_dust))
+ # NOTE:
+ # Mask the regions where the true Halpha absorption is uncertain.
+ # When the dust absorption goes rather large, the true Halpha
+ # absorption can not well determined.
+ # Therefore, the regions where the calculated Halpha absorption
+ # greater than 1.0 mag are masked out.
+ halpha_abs_th = 1.0 # Halpha absorption threshold, unit: [ mag ]
+ # Corresponding dust absorption threshold, unit: [ MJy / sr ]
+ dust_abs_th = halpha_abs_th / 0.0462 / f_dust
+ logger.info("Dust absorption mask threshold: " +
+ "{0:.1f} MJy/sr ".format(dust_abs_th) +
+ "<-> H[alpha] absorption threshold: " +
+ "{0:.1f} mag".format(halpha_abs_th))
+ mask = (self.dustmap > dust_abs_th)
+ self.dustmap[mask] = np.nan
+ fp_mask = 100 * mask.sum() / self.dustmap.size
+ logger.warning("Dust map masked fraction: {0:.1f}%".format(fp_mask))
+ #
halphamap_corr = self.halphamap * 10**(self.dustmap * 0.0185 * f_dust)
self.halphamap = halphamap_corr
self.dust_corrected = True
+ logger.info("Done dust absorption correction")
def _calc_ratio_a(self, Te, nu_GHz):
"""Calculate the ratio factor a(T, nu), which will be used to
@@ -159,11 +180,13 @@ class FreeFree:
NOTE: [Dickinson2003], Eq.(11) may wrongly have the "10^3" term.
"""
+ # Correct for dust absorption first
+ self._correct_dust_absorption()
# Assumed electron temperature [ K ]
Te = 7000.0
T4 = Te / 1e4
nu = frequency * self.freq_unit.to(au.GHz) # frequency [ GHz ]
- ratio_a = self._calc_ratio_a(T4, nu)
+ ratio_a = self._calc_ratio_a(Te, nu)
# NOTE: ignored the "10^3" term in the referred equation
ratio_mK_R = (8.396 * ratio_a * nu**(-2.1) *
T4**0.667 * 10**(0.029/T4) * (1+0.08))
@@ -218,8 +241,6 @@ class FreeFree:
def simulate(self, frequencies):
"""Simulate the free-free map at the specified frequencies."""
- self._correct_dust_absorption()
- #
hpmaps = []
for f in np.array(frequencies, ndmin=1):
logger.info("Simulating free-free map at {0} ({1}) ...".format(