Horizon-AGN virtual observatory – 2: Template-free estimates of galaxy properties from colours. (arXiv:1905.13233v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Davidzon_I/0/1/0/all/0/1">Iary Davidzon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Laigle_C/0/1/0/all/0/1">Clotilde Laigle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Capak_P/0/1/0/all/0/1">Peter L. Capak</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ilbert_O/0/1/0/all/0/1">Olivier Ilbert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Masters_D/0/1/0/all/0/1">Daniel C. Masters</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hemmati_S/0/1/0/all/0/1">Shoubaneh Hemmati</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Apostolakos_N/0/1/0/all/0/1">Nikolaos Apostolakos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Coupon_J/0/1/0/all/0/1">Jean Coupon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Torre_S/0/1/0/all/0/1">Sylvain de la Torre</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Devriendt_J/0/1/0/all/0/1">Julien Devriendt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dubois_Y/0/1/0/all/0/1">Yohan Dubois</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kashino_D/0/1/0/all/0/1">Daichi Kashino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paltani_S/0/1/0/all/0/1">Stephane Paltani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pichon_C/0/1/0/all/0/1">Christophe Pichon</a>
Using the textsc{Horizon-AGN} hydrodynamical simulation and self-organising
maps (SOMs), we show how to compress the complex data structure of a
cosmological simulation into a 2-d grid which is much easier to analyse. We
first verify the tight correlation between the observed 0.3$!-!5mu$m
broad-band colours of textsc{Horizon-AGN} galaxies and their high-resolution
spectra. The correlation is found to extend to physical properties such as
redshift, stellar mass, and star formation rate (SFR). This direct mapping from
colour to physical parameter space is shown to work also after including
photometric uncertainties that mimic the COSMOS survey. We then label the SOM
grid with a simulated calibration sample and estimate redshift and SFR for
COSMOS-like galaxies up to $zsim3$. In comparison to state-of-the-art
techniques based on synthetic templates, our method is comparable in
performance but less biased at estimating redshifts, and significantly better
at predicting SFRs. In particular our “data-driven” approach, in contrast to
model libraries, intrinsically allows for the complexity of galaxy formation
and can handle sample biases. We advocate that obtaining the calibration for
this method should be one of the goals of next-generation galaxy surveys.
Using the textsc{Horizon-AGN} hydrodynamical simulation and self-organising
maps (SOMs), we show how to compress the complex data structure of a
cosmological simulation into a 2-d grid which is much easier to analyse. We
first verify the tight correlation between the observed 0.3$!-!5mu$m
broad-band colours of textsc{Horizon-AGN} galaxies and their high-resolution
spectra. The correlation is found to extend to physical properties such as
redshift, stellar mass, and star formation rate (SFR). This direct mapping from
colour to physical parameter space is shown to work also after including
photometric uncertainties that mimic the COSMOS survey. We then label the SOM
grid with a simulated calibration sample and estimate redshift and SFR for
COSMOS-like galaxies up to $zsim3$. In comparison to state-of-the-art
techniques based on synthetic templates, our method is comparable in
performance but less biased at estimating redshifts, and significantly better
at predicting SFRs. In particular our “data-driven” approach, in contrast to
model libraries, intrinsically allows for the complexity of galaxy formation
and can handle sample biases. We advocate that obtaining the calibration for
this method should be one of the goals of next-generation galaxy surveys.
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