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Modeling the Anomaly of Surface Number Densities of Galaxies on the Galactic Extinction Map due to Their FIR Emission Contamination

Abstract : The most widely used Galactic extinction map is constructed assuming that the observed far-infrared (FIR) fluxes come entirely from Galactic dust. According to the earlier suggestion by Yahata et al., we consider how FIR emission of galaxies affects the SFD map. We first compute the surface number density of Sloan Digital Sky Survey (SDSS) DR7 galaxies as a function of the r-band extinction, A r, SFD. We confirm that the surface densities of those galaxies positively correlate with A r, SFD for A r, SFD < 0.1, as first discovered by Yahata et al. for SDSS DR4 galaxies. Next we construct an analytical model to compute the surface density of galaxies, taking into account the contamination of their FIR emission. We adopt a log-normal probability distribution for the ratio of 100 μm and r-band luminosities of each galaxy, y ≡ (νL)100 μm/(νL) r . Then we search for the mean and rms values of y that fit the observed anomaly, using the analytical model. The required values to reproduce the anomaly are roughly consistent with those measured from the stacking analysis of SDSS galaxies. Due to the limitation of our statistical modeling, we are not yet able to remove the FIR contamination of galaxies from the extinction map. Nevertheless, the agreement with the model prediction suggests that the FIR emission of galaxies is mainly responsible for the observed anomaly. Whereas the corresponding systematic error in the Galactic extinction map is 0.1-1 mmag, it is directly correlated with galaxy clustering and thus needs to be carefully examined in precision cosmology.
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Submitted on : Tuesday, April 19, 2022 - 2:03:23 PM
Last modification on : Wednesday, April 20, 2022 - 3:40:04 AM

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Toshiya Kashiwagi, Yasushi Suto, Atsushi Taruya, Issha Kayo, Takahiro Nishimichi, et al.. Modeling the Anomaly of Surface Number Densities of Galaxies on the Galactic Extinction Map due to Their FIR Emission Contamination. The Astrophysical Journal, 2015, 799, ⟨10.1088/0004-637X/799/2/132⟩. ⟨insu-03644772⟩

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