Towards a library of synthetic galaxy spectra and preliminary results of classification and parametrization of unresolved galaxies for Gaia

Tsalmantza, P; Kontizas, M; Bailer-Jones, CAL; Rocca-Volmerange, B; Korakitis, R; Kontizas, E; Livanou, E; Dapergolas, A; Bellas-Velidis, I; Vallenari, A; Fioc, M

dc.contributor.author	Tsalmantza, P	en
dc.contributor.author	Kontizas, M	en
dc.contributor.author	Bailer-Jones, CAL	en
dc.contributor.author	Rocca-Volmerange, B	en
dc.contributor.author	Korakitis, R	en
dc.contributor.author	Kontizas, E	en
dc.contributor.author	Livanou, E	en
dc.contributor.author	Dapergolas, A	en
dc.contributor.author	Bellas-Velidis, I	en
dc.contributor.author	Vallenari, A	en
dc.contributor.author	Fioc, M	en
dc.date.accessioned	2014-03-01T01:27:29Z
dc.date.available	2014-03-01T01:27:29Z
dc.date.issued	2007	en
dc.identifier.issn	0004-6361	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/18472
dc.subject	Galaxies: fundamental parameters	en
dc.subject	Techniques: photometric	en
dc.subject	Techniques: spectroscopic	en
dc.subject.classification	Astronomy & Astrophysics	en
dc.subject.other	Emission spectroscopy	en
dc.subject.other	Light extinction	en
dc.subject.other	Spectrophotometry	en
dc.subject.other	Spectrum analysis	en
dc.subject.other	Support vector machines	en
dc.subject.other	Astrometric survey	en
dc.subject.other	Galaxies: fundamental parameters	en
dc.subject.other	Metallicity evolution	en
dc.subject.other	Techniques: photometric	en
dc.subject.other	Techniques: spectroscopic	en
dc.subject.other	Galaxies	en
dc.title	Towards a library of synthetic galaxy spectra and preliminary results of classification and parametrization of unresolved galaxies for Gaia	en
heal.type	journalArticle	en
heal.identifier.primary	10.1051/0004-6361:20077300	en
heal.identifier.secondary	http://dx.doi.org/10.1051/0004-6361:20077300	en
heal.language	English	en
heal.publicationDate	2007	en
heal.abstract	Aims. The Gaia astrometric survey mission will, as a consequence of its scanning law, obtain low resolution optical (330-1000 nm) spectrophotometry of several million unresolved galaxies brighter than V = 22. We present the first steps in a project to design and implement a classification system for these data. The goal is both to determine morphological classes and to estimate intrinsic astrophysical parameters via synthetic templates. Here we describe (1) a new library of synthetic galaxy spectra, and (2) first results of classification and parametrization experiments using simulated Gaia spectrophotometry of this library. Methods. We have created a large grid of synthetic galaxy spectra using the PÉGASE.2 code, which is based on galaxy evolution models that take into account metallicity evolution, extinction correction, emission lines (with stellar spectra based on the BaSeL library). Our classification and regression models are Support Vector Machines (SVMs), which are kernel-based nonlinear estimators. Results. We produce a basic library of about 3600 zero redshift galaxy spectra covering the main Hubble types over wavelength range 250 to 1050 nm at a sampling of 1 nm or less. It is computed on a regular grid of four key astrophysical parameters for each type and for intermediate random values of the same parameters. An extended library reproduces this at a series of redshifts. Initial results from the SVM classifiers and parametrizers are promising, indicating that Hubble types can be reliably predicted and several parameters estimated with low bias and variance. Comparing the colours of our synthetic library with Sloan Digital Sky Survey (SDSS) spectra we find good agreement over the full range of Hubble types and parameters. © ESO 2007.	en
heal.publisher	EDP SCIENCES S A	en
heal.journalName	Astronomy and Astrophysics	en
dc.identifier.doi	10.1051/0004-6361:20077300	en
dc.identifier.isi	ISI:000247981000039	en
dc.identifier.volume	470	en
dc.identifier.issue	2	en
dc.identifier.spage	761	en
dc.identifier.epage	770	en