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Andromeda's Dust: Maps of Dust and Starlight Parameters in M31

Reference: Draine, B.T., Aniano, G., Krause, O., et al. (2014): Astrophysical Journal, 780, 172.

Spitzer (IRAC, MIPS) and Herschel (PACS, SPIRE) observations of the M31 galaxy have been used to constrain models for the dust in M31. The methodology is described in Draine, Aniano, Krause et al. (2014).

Maps of the dust surface density (Sigma_Mdust), PAH abundance parameter (q_PAH), mean starlight heating rate (Ubar), and other properties of the starlight intensity distribution (U_min, gamma, alpha) are obtained. Note that (as described in the paper) the derived model parameters become unreliable at large galactocentric radii. The dust surface density can be reliably measured in individual pixels out to about 18 kpc, but beyond that it is necessary to average over many pixels. The following gzipped FITS files are available. If you use them in your research, please cite the paper describing the observations and model-fitting.

Model maps at MIPS 160 resolution (PSF FWHM = 39"; 18" x 18" pixels):

  • M31_M160_111_SSS_111_All_SurfBr_Mdust.fits.gz: Sigma_Mdust (Msol/kpc^2)
  • M31_M160_111_SSS_111_All_SurfBr_Mdust_unc.fits.gz: uncertainty in Sigma_Mdust
  • M31_M160_111_SSS_111_All_qpah.fits.gz: q_PAH
  • M31_M160_111_SSS_111_All_qpah_unc.fits.gz: uncertainty in q_PAH
  • M31_M160_111_SSS_111_All_SurfBr_Ldust.fits.gz: Sigma_Ldust (Lsol/kpc^2)
  • M31_M160_111_SSS_111_All_SurfBr_Ldust_unc.fits.gz: uncertainty in Sigma_Ldust
  • M31_M160_111_SSS_111_All_U_bar.fits.gz: Ubar
  • M31_M160_111_SSS_111_All_U_bar_unc.fits.gz: uncertainty in Ubar
  • M31_M160_111_SSS_111_All_U_min.fits.gz: U_min
  • M31_M160_111_SSS_111_All_U_min_unc.fits.gz: uncertainty in U_min
  • M31_M160_111_SSS_111_All_alpha.fits.gz: starlight heating parameter alpha
  • M31_M160_111_SSS_111_All_alpha_unc.fits.gz: uncertainty in starlight heating parameter alpha
  • M31_M160_111_SSS_111_All_gamma_unc.fits.gz: starlight heating parameter gamma
  • M31_M160_111_SSS_111_All_gamma_unc.fits.gz: uncertainty in starlight heating parameter gamma

    Model maps at SPIRE 350 resolution (PSF FWHM = 24.9"; 10" x 10" pixels):

  • M31_S350_110_SSS_110_All_SurfBr_Mdust.fits.gz: Sigma_Mdust (Msol/kpc^2)
  • M31_S350_110_SSS_110_All_SurfBr_Mdust_unc.fits.gz: uncertainty in Sigma_Mdust
  • M31_S350_110_SSS_110_All_qpah_unc.fits.gz: q_PAH
  • M31_S350_110_SSS_110_All_qpah_unc.fits.gz: uncertainty in q_PAH
  • M31_S350_110_SSS_110_All_SurfBr_Ldust.fits.gz: Sigma_Ldust (Lsol/kpc^2)
  • M31_S350_110_SSS_110_All_SurfBr_Ldust_unc.fits.gz: uncertainty in Sigma_Ldust
  • M31_S350_110_SSS_110_All_U_bar.fits.gz: Ubar
  • M31_S350_110_SSS_110_All_U_bar_unc.fits.gz: uncertainty in Ubar
  • M31_S350_110_SSS_110_All_U_min.fits.gz: U_min
  • M31_S350_110_SSS_110_All_U_min_unc.fits.gz: uncertainty in U_min
  • M31_S350_110_SSS_110_All_alpha.fits.gz: starlight heating parameter alpha
  • M31_S350_110_SSS_110_All_alpha_unc.fits.gz: uncertainty in starlight heating parameter alpha
  • M31_S350_110_SSS_110_All_gamma_unc.fits.gz: starlight heating parameter gamma
  • M31_S350_110_SSS_110_All_gamma_unc.fits.gz: uncertainty in starlight heating parameter gamma

    Gas Maps (18" x18" pixels).

    If you use these maps, please cite the original source: Braun et al. (2009) for the 21 cm data, and Nieten et al. (2006) for the CO 1-0 data.

  • M31_Original_Data_Gas_02.fits.gz: N(HI)/2.247e15 cm-2 (Braun et al 2009)
  • M31_Original_Data_Gas_02_unc.fits.gz: uncertainty in N(HI)/2.247e15 cm-2 (Braun et al 2009)
  • M31_Original_Data_Gas_03.fits.gz : I(CO 1-0)/2.475e-7 K km s-1 (Nieten et al 2006)
  • M31_Original_Data_Gas_03_unc.fits.gz: uncertainty in I(CO 1-0)/2.475e-7 K km s-1 (Nieten et al 2006)

    If you encounter difficulties downloading any of these files, please send email to draine at