The Correlation between Dust Absorption and UV Spectral Slope of Galaxies from the GOODS-North
Date Issued
2012
Date
2012
Author(s)
Lei, Si-Heng
Abstract
When we study star formation rate (SFR) of high redshift galaxies, because we know well how young high mass stars emit UV radiation, we observe the rest-frame UV emission of galaxies, and convert it to UV star formation rate (UV SFR). We also need to know the dust absorption in the UV, and then correct for the absorbed part to obtain the intrinsic UV luminosity and SFR. It is widely believed now that dust absorption is correlated with the rest-frame UV spectral slope (β) of a galaxy, defined as fλ = λβ, where λ is between 1300-3500 Å in this work. This work aims to verify the above correlation; we will derive the radio SFR from the radio flux of galaxies from the radio catalog of Morrison et al. (2010). The radio emission is generated by supernova explosion from high mass stars, in which relativistic electrons are accelerated by magnetic field and produce synchrotron radiation. Therefore the radio emission can also infer high mass star formation rate. Since the radio emission is not affected by extinction, the radio-to-UV SFR ratio can indicate dust absorption. Thus we can test if there are any correlations between the UV and radio SFR ratios and β.
For the rest-frame UV fluxes and redshifts, this work uses the GOODS-N catalog from Barger et al. (2008). This catalog covers a broader range of redshift, compared to other works, and the highest redshift object in this catalog with 1.4 GHz radio flux is about z~2.6. We adopt the VLA 1.4 GHz GOODS-N catalog from Morrison et al. (2010) and use the method in Wang et al. (2012) to convert the radio flux to radio SFR. After comparing β with radio-to-UV SFR ratios, we find that there is no strong correlation between them. Then we include z – Ks colors of galaxies and use a z – Ks vs. β diagram to define two new parameters to test if they are correlated with extinction. We do not find significant correlations. Therefore, we conclude that there is not a strong correlation between dust absorption and β.
Subjects
Star Formation Rate
UV Spectral Slope
High Redshift Galaxy
Extinction
GOODS North
Type
thesis
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