Simultaneous analysis of SDSS spectra and GALEX photometry with STARLIGHT: Method and early results. (arXiv:1811.11255v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Werle_A/0/1/0/all/0/1">Ariel Werle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fernandes_R/0/1/0/all/0/1">Roberto Cid Fernandes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Asari_N/0/1/0/all/0/1">Natalia Vale Asari</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bruzual_G/0/1/0/all/0/1">Gustavo Bruzual</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charlot_S/0/1/0/all/0/1">Stéphane Charlot</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Delgado_R/0/1/0/all/0/1">Rosa Gonzalez Delgado</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Herpich_F/0/1/0/all/0/1">Fabio Herpich</a>
We combine data from the Sloan Digital Sky Survey and the Galaxy Evolution
Explorer to simultaneously analyze optical spectra and ultraviolet photometry
of 231643 galaxies with the STARLIGHT spectral synthesis code using
state-of-the-art stellar population models. We present a new method to estimate
GALEX photometry in the SDSS spectroscopic aperture, which proves quite
reliable if applied to large samples. In agreement with previous experiments
with CALIFA, we find that adding UV constraints leads to a moderate increase on
the fraction of $sim 10^7$ – $10^8$ yr populations and a concomitant decrease
of younger and older components, yielding slightly older luminosity weighted
mean stellar ages. These changes are most relevant in the low-mass end of the
blue cloud. An increase in dust attenuation is observed for galaxies dominated
by young stars. We investigate the contribution of different stellar
populations to the fraction of light in GALEX and SDSS bands across the
UV-optical color-magnitude diagram. As an example application, we use this
$lambda$ dependence to highlight differences between retired galaxies with and
without emission lines. In agreement with an independent study by Herpich et
al., we find that the former show an excess of intermediate age populations
when compared to the later. Finally, we test the suitability of two different
prescription for dust, finding that our dataset is best fitted using the
attenuation law of starburst galaxies. However, results for the Milky Way
extinction curve improve with decreasing $tau_V$, especially for edge-on
galaxies.
We combine data from the Sloan Digital Sky Survey and the Galaxy Evolution
Explorer to simultaneously analyze optical spectra and ultraviolet photometry
of 231643 galaxies with the STARLIGHT spectral synthesis code using
state-of-the-art stellar population models. We present a new method to estimate
GALEX photometry in the SDSS spectroscopic aperture, which proves quite
reliable if applied to large samples. In agreement with previous experiments
with CALIFA, we find that adding UV constraints leads to a moderate increase on
the fraction of $sim 10^7$ – $10^8$ yr populations and a concomitant decrease
of younger and older components, yielding slightly older luminosity weighted
mean stellar ages. These changes are most relevant in the low-mass end of the
blue cloud. An increase in dust attenuation is observed for galaxies dominated
by young stars. We investigate the contribution of different stellar
populations to the fraction of light in GALEX and SDSS bands across the
UV-optical color-magnitude diagram. As an example application, we use this
$lambda$ dependence to highlight differences between retired galaxies with and
without emission lines. In agreement with an independent study by Herpich et
al., we find that the former show an excess of intermediate age populations
when compared to the later. Finally, we test the suitability of two different
prescription for dust, finding that our dataset is best fitted using the
attenuation law of starburst galaxies. However, results for the Milky Way
extinction curve improve with decreasing $tau_V$, especially for edge-on
galaxies.
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