1,066 research outputs found

    Multi-component parametric inversion of galaxy kinematics and stellar populations using full spectral fitting

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    The stellar line-of-sight velocity distribution (LOSVD) can be strongly asymmetric in regions where the light contributions of both disc and bulge in spiral and lenticular galaxies are comparable. Existing techniques for the stellar kinematics analysis do not take into account the difference of disc and bulge stellar populations. Here we present a novel approach to the analysis of stellar kinematics and stellar populations. We use a two-component model of spectra where different stellar population components are convolved with pure Gaussian LOSVDs. For this model we present Monte-Carlo simulations demonstrating degeneracies between the parameters.Comment: 3 pages, 2 figures; to appear in the proceedings of "The Spectral Energy Distribution of Galaxies", Preston, UK, 5-9 September 201

    NBursts+phot: parametric recovery of galaxy star formation histories from the simultaneous fitting of spectra and broad-band spectral energy distributions

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    We present NBursts+phot, a novel technique for the parametric inversion of spectrophotometric data for unresolved stellar populations where high-resolution spectra and broadband SEDs are fitted simultaneously helping to break the degeneracies between parameters of multi-component stellar population models.Comment: 3 pages, 1 figure, proceedings of the IAU Symposium 28

    Color Transformations of Photometric Measurements of Galaxies in Optical and Near-Infrared Wide-Field Imaging Surveys

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    Over the past 2 decades, wide-field photometric surveys in optical and infrared domains reached a nearly all-sky coverage thanks to numerous observational facilities operating in both hemispheres. However, subtle differences among exact realizations of Johnson and SDSS photometric systems require one to convert photometric measurements into the same system prior to analysis of composite datasets originating from multiple surveys. It turns out that the published photometric transformations lead to substantial biases when applied to integrated photometry of galaxies from the corresponding catalogs. Here we present photometric transformations based on piece-wise linear approximations of integrated photometry of galaxies in the optical surveys SDSS, DECaLS, BASS, MzLS, DES, DELVE, KiDS, VST ATLAS, and the near-infrared surveys UKIDSS, UHS, VHS, and VIKING. We validate our transformations by constructing k-corrected color-magnitude diagrams of non-active galaxies and measuring the position and tightness of the "red sequence". We also provide transformations for aperture magnitudes and show how they are affected by the image quality difference among the surveys. We present the implementation of the derived transformations in Python and IDL and also a web-based color transformation calculator for galaxies. By comparing DECaLS and DES, we identified systematic issues in DECaLS photometry for extended galaxies, which we attribute to the photometric software package used by DECaLS. As an application of our method, we compiled two multi-wavelength photometric catalogs for over 200,000 low- and intermediate-redshift galaxies originating from CfA FAST and Hectospec spectral archives.Comment: 24 pages, 21 figures, accepted for publication in PASP. The "Color transformations" web service and the Python and IDL codes are available at https://colors.voxastro.org
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