Description of the PRIMASS-L bundle V1.0 ======================================== Bundle Generation Date: 2021-09-22 Peer Review: 2021_Asteroid_Review Discipline node: Small Bodies Node PRIMASS-Library Overview ======================== In 2010, we started the PRIMitive Asteroids Spectroscopic Survey (PRIMASS) to study the surface of primitive asteroids at different locations in the main belt, through visible and near-infrared spectroscopy. Up to 2021, PRIMASS has produced 13 papers in peer-review publications, over 20 presentations at international conferences, and has been part of three Ph. D. dissertations. The study of primitive asteroids is relevant for understanding the origin and nature of volatile and organic material in the early Solar System. Furthermore, it provides a rich source of information about the composition of the pre-biotic environment from which life formed. Spectral data from asteroids belonging to the families that could be the source of the primitive near-Earth asteroids (NEAs) are key for understanding the delivery of volatile material to Earth, and provide context and enhance the scientific outcome of the two current sample-return missions orbiting primitive NEAs (OSIRIS-REx; Lauretta et al. 2010 and Hayabusa2; Tsuda et al. 2013). Meanwhile, the existence of water ice on the surface of two asteroids in primitive families (Campins et al. 2010, Rivkin and Emery 2010, Licandro et al. 2011) in the outer belt, one of them the largest member of a collisional family, adds additional motivation to extend the study to the families and asteroid groups all across the inner Solar System. The PRIMitive Asteroid Spectroscopic Survey Library (PRIMASS-L) contains the collection of all spectra and results of the analysis published in the PRIMASS project. As of June 2021, the dataset contains 438 visible and 161 near-infrared spectra of asteroids while observations are ongoing. For PRIMASS, we use a variety of ground-based observatories. The majority of the visible spectra come from the 10.4m Gran Telescopio Canarias (GTC), located at the El Roque de Los Muchachos Observatory (ORM, La Palma, Spain). Most of the near-infrared spectra come from both, the 3.6m Telescopio Nazionale Galileo (TNG), located also at the ORM, and the 3.0m NASA Infrared Telescope Facility (IRTF) on Mauna Kea (Hawai, USA). We have also used other telescopes, like the 4.1m Southern Astrophysical Research Telescope (SOAR) at Cerro Pachon (Chile), the 3.6m New Technology Telescope (NTT) located at La Silla Observatory, and the 2.54m Issac Newton Telescope (INT) located at the El Roque de los Muchachos Observatory (ORM, La Palma, Spain). To analyze these spectra we use the Code for ANalyisis of Asteroids (CANA), a tool created by us for this purpose and introduced in De Prá et al. (2018b). This tool can be used for the analysis of spectra acquired using other telescopes and is publically available at http://github.com/cana-asteroids/cana. This package (PRIMASS-L v1.0) contains visible spectroscopy of the families in the inner- and outer-belt and of the Cybele and Hildas dynamical groups (see details below). Note that by Polana family we refer to the low albedo asteroids in the Nysa-Polana region. This includes what was later defined by Walsh et al. (2013) as the Polana and Eulalia families. To separate between Polana and Eulalia membership, refer to de Leon et al. (2016). Also note that, in the list of the Erigone family there are four targets, labeled as MP3C, referred to the database where we obtained the list of family members with physical parameters (https://mp3c.oca.eu/catalogue/index.006039_vis.xml), at the moment that we planned the observations (see Morate et al. 2016 for details). The dynamical definition of the families has changed since, and these objects are not considered family members anymore. - Inner-Belt - Erigone: 101 spectra - Sulamiti: 64 spectra - Clarissa: 33 spectra - Chaldaea: 15 spectra - Chimaera: 20 spectra - Klio: 30 spectra - Svea: 8 spectra - Polana: 67 spectra - Outer-Belt - Lixiaohua: 53 spectra - Themis: 8 spectra - Hygiea: 11 spectra - Veritas: 9 spectra - Cybele: 10 spectra - Hilda: 9 spectra Future PRIMASS-L data releases will contain the near-infrared data from these families and newly obtained visible spectroscopy of other primitive families from the main belt. Description of Files ==================== Data directories ---------------- - primassl_visible_spectral_data_collection.csv: List of acquired spectra, observing conditions, physical parameters, and corresponding PRIMASS publication in the visible spectral range. - primassl_visible_spectral_parameters.csv: Results of the analysis of each spectrum listing taxonomical classification, color in the visible, characteristics of the aqueous alteration band at 0.7 µm, and the turn-off around 0.5 µm, provided by the CANA package. - solar_analog_stars_legend.csv: Legend for the solar analogs used in the observations as described in the table primassl_visible_spectral_data_collection.csv - spectra/*: Spectral data files for each asteroid. These files are organized in folders accordingly to the respective main belt region and asteroid family or dynamical group in which the asteroid belongs. The file name is based on the asteroid number (or provisional designation, if not numbered) with a suffix indicating the wavelength range of the spectrum ("_vis" or "_nir"). If the asteroid has multiple observations another suffix is added ("_1", "_2",...) Document directory ------------------- - primassl_visible_spectral_collection_plot.pdf: A single pdf file containing the plots with the relative reflectance of all the objects grouped by family. - primassl_visible_spectral_parameters_plot.pdf: -> A single pdf file containing the plots with the parametrization of the spectra of each individual target grouped by family. These are the same representations obtained with CANA (De Prá et al. 2018b, 2020a) Spectral Parameters ==================== Spectral Gradient: This is a measure of the color of the spectrum, in a certain wavelength range, calculated following the definition of the Spectral Gradient in Luu & Jewitt (1990) with this formula: Sprim = S[lambda1,lambda2]/R_0.55 [percent/0.1 µm], where S is the linear fit to the reflectance in the wavelength range limited by 0.5 and 0.87 µm, and R_0.55 is the value of this fit at 0.55 µm. Band Center and Band Depth: These parameters are calculated for an absorption band centered around 0.7 µm that may be indicative of hydrated minerals. A wavelength range of 0.55-0.88 µm was used. The spectral continuum was estimated fitting a straight line to both the right and left edges of the absorption band, in the 0.55-0.57 and 0.84-0.88 µm intervals. Thereafter, we removed The continuum was subsequently removed from the spectrum with a fourth-order spline fit in the 0.55-0.88 µm range. The center of the band is measured at the wavelength of the minimum of the fit. The depth of the band is (1 - Rm), where Rm is the value of the spline fit at the center of the band. We identified the absorption band if the minimum reflectance of the fit contained in the 0.65-0.75 µm region is at a depth larger than 1% and above 3-sigma of the spectrum noise. If any of these criteria are not satisfied we don't consider the band identified and values are not provided the primassl_visible.spectral_parameters.csv file. Dwonturn (also referred to in the papers as turn-off): This parameter is calculated for a feature appearing around 0.50 µm and is defined in De Prá et al. (2018a). It measures the position of the point where the spectrum shows a maximum in the curvature in the 0.40-0.65µm wavelength range. We identified the downturn if the parameter surpasses a threshold established by visual inspection. The calculation of the errors in these parameters is described in De Prá et al. (2020a). The results of the analysis of this parametrization is provided in the primassl_visible.spectral_parameters_plot.pdf in the document directory. Acknowledgement ================ Support for this work was provided by NASA grants NNH17ZDA001N-PDART, Planetary Data Archiving, Restoration, and Tools, through the project "PRIMitive Asteroids Spectroscopic Survey (PRIMASS): the past as a puzzle", NNH18ZDA018C-SSERVI (CAN-1 and CAN-3) through the Center for Lunar and Asteroid Surface Science (CLASS), and by the project AYA2017-89090-P of the Spanish MINECO. This library is partially based on observations made with the Gran Telescopio Canarias (GTC), installed at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma, at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia e Inovações do Brasil (MCTI/LNA), the US National Science Foundation’s NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU), at the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica), at the Isaac Newton Telescope operated on the island of La Palma by the Isaac Newton Group of Telescopes, the latter two telescopes sited in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, and at the European Organization for Astronomical Research in the Southern Hemisphere with the New Technology Telescope (NTT). This research has made use of data and/or services provided by the International Astronomical Union's Minor Planet Center, by the JPL-HORIZONS system of the Solar System Dynamics group of the JPL, and by the Minor Planet Physical Properties Catalogue (MP3C) of the Observatoire de la Cote d’Azur. We explicitly want to express our thanks to all the support astronomers and telescope operators for their excellent assistance during the vast number of hours of observations. Caveats to the data user ======================== The spectral data files contain two columns, wavelengths and reflectance. They do not contain errors in the reflectance as the errors are commensurate with the point-to-point dispersion in the reflectance. The red and blue extremes of the spectra may have lower signal-to-noise than the rest of the spectra and/or suffer systematic effects. Therefore, these extremes have to be analyzed carefully and might have to be discarded before performing specific analyses. The results of the spectral parametrization contained in the primasl_visible.spectral_parameters.csv file are derived using an automatic pipeline contained within the Code for ANalyisis of Asteroids (CANA, De Prá et al. 2018b, 2020a) optimized for consistent analysis of PRIMASS. However, a closer inspection of these results is recommended to derive scientific conclusions. The definition of how each feature in the spectra is parameterized has evolved since and therefore the results contained in this library may (slightly) differ from those in the particular papers where each target is contained. To reproduce the results in these specific papers we refer the user to the description of the parameters in that paper referenced in the metadata.