How do I determine the surface magnitude of a galaxy from a SED?

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  • Thread starter AdrianD
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  • #1
AdrianD
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Let's say I have a galaxy SED like this:

SEDgen:
from synphot import SourceSpectrum
from synphot.models import BlackBodyNorm1D
sp = SourceSpectrum(BlackBodyNorm1D, temperature=6170.4796)

wave = sp.waveset
flux = sp(wave) #Photlam
flux_flam = flux.to(u.erg / u.s / u.angstrom/u.cm**2,equivalencies=u.spectral_density(wave))

 
plt.plot(wave, flux_flam)
plt.xlim(1000, 30000) 
plt.xlabel('Wavelength (Angstrom)')
plt.ylabel('Flux [FLAM]')

How do I get surface brightness from this?
 
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  • #2
Python:
import numpy as np

# Assuming a circular aperture with a diameter in arcseconds
aperture_diameter_arcsec = 1.0  # Example: 1 arcsecond diameter aperture

# Calculate the area of the circular aperture in square arcseconds
aperture_area_arcsec2 = np.pi * (aperture_diameter_arcsec / 2)**2

# Calculate the surface brightness in FLAM per square arcsecond
surface_brightness_flam_arcsec2 = flux_flame / aperture_area_arcsec2

# Plot the surface brightness
plt.plot(wave, surface_brightness_flam_arcsec2)
plt.xlim(1000, 30000)
plt.xlabel('Wavelength (Angstrom)')
plt.ylabel('Surface Brightness [FLAM/arcsec^2]')
Replace the aperture_diameter_arcsec variable with the appropriate angular size of your source. This will give you the surface brightness inFLAM per square arcsecond.
 
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