Found 26 talks archived in Catalogs and data

Gaia Data Release 3 (13 June 2022) contains astrophysical parameters for up to 1.5 billion sources derived from the low resolution BP and RP prism spectra, the high resolution RVS spectra, photometry and astrometry.

These include object classifications (star, galaxy, stellar spectral type,...), unresolved galaxies and quasar redshifts (~6 million), outlier objects, interstellar medium characterisation (extinction and DIBs), and spectroscopic and evolutionary parameters (~470 million) for a large variety of stellar types from ultra-cool dwarfs to hot OB stars.

In this talk, I will present an overview of the astrophysical parameter content of Gaia DR3 that was derived using the Astrophysical Parameters Inference System (Apsis) software. I will first give a brief description of the data, models and methods that were employed, and then I will focus on describing what type of parameters you can find in the archive and where to find them among the 30+ new tables. I will then describe the overall performance and present some pre-Gaia DR3 highlights.

The ExoMol project (www.exomol.com) provides comprehensive spectroscopic data (line lists) for the study of atmospheres of exoplanets and other hot bodies.  These line lists serve as input for models of radiative transport through hot atmospheres and are useful for a variety of terrestrial applications. The basic form of the database is extensive line lists; these are supplemented with partition functions, state lifetimes, cooling functions, Landé g-factors, temperature-dependent cross sections, opacities, k-coefficients and pressure broadening parameters. Currently containing 80 molecules and 190 isotopologues totaling over 700 billion transitions, the database covers infrared, visible and UV wavelengths. The field of the HR spectroscopy of exoplanets is growing extremely fast and urgently demands molecular data of high precision. Failure to detect molecules in atmospheres of exoplanets is often attributed to the lack of the underlying quality of
the line positions.  These developments have led us to begin a systematic attempt to improve the accuracy of the line positions for the line lists contained in the database. Our new ExoMolHD project aims to provide comprehensive line lists to facilitate their use in characterization of exoplanets using high resolution Doppler shift spectroscopy. Progress on this objective will be presented.

I've heard many times about the Virtual Observatory, but what really is VO? Is it just for IT people?, for data centres?, for astronomers?, for everybody? Who is behind VO? Is the Virtual Observatory sustainable in the medium-term? Was it just a nice idea or is it really having an impact on the way astronomers make science with archive data?
In this talk I'll try to answer all these questions by describing the Spanish Virtual Observatory, an initiative that began in 2004 with the aim of coordinating at national level the VO-related activities in four different fields.
Special focus will be given to usage examples of VO tools for real VO-science projects.

The IAC is the only Spanish Institution participating as a full member in SDSS-III (2009-2014). The survey finishes in June 2014, and will publicly release all data by the end of the year, including H-band high-resolution spectra for 100,000 stars in the Milky Way and optical mid-resolution spectra for 1.5 million LRGs and 160,000 quasars.

SDSS-IV will immediately follow, including spectroscopic surveys of variable sources, x-ray source follow-up observations, galaxy and quasar redshifts, Integral-field-unit spectroscopy of galaxies and high-resolution infrared spectroscopy of galactic stars, organized in the following projects: Time-Domain Spectroscopic Survey (TDSS), SPectroscopic IDentification of ERosita Sources (SPIDERS), Extended Baryon Oscillation Spectroscopic Survey (eBOSS), Mapping Nearby Galaxies at APO (MaNGA), and the APO Galaxy Evolution Experiment 2 (APOGEE-2).

The participation of the IAC in SDSS is gaining strength. As an example, in the first half of 2013, about 13% of the papers published by IAC researchers used SDSS data, and these papers contributed 33% of the citations received by the IAC in the same period. We will provide an overview of SDSS activities at the IAC, and current plans for participating in SDSS-IV (2014-2020).

This has been an exciting year for the SDSS-III collaboration. BOSS has made spectacular progress and it is running 6 months ahead of schedule. APOGEE has secured ~ 300,000 spectra for 50,000 stars, mostly red giants and nearly half of its total sample. The APOGEE Stellar Parameter and Chemical Abundance Pipeline is providing reliable atmospheric parameters, including metallicities. Data Release 10 (DR10) will take place next summer, but DR10 BOSS data are already available to the collaboration, and DR10 APOGEE data products will be internally released in the next few weeks. SDSS activity is growing at the IAC. We will report on SDSS-III news and SDSS-IV prospects, including an overview of the SDSS-IV programs APOGEE-2, eBOSS (+TDSS+SPIDERS), and MaNGA.

The IAC started in June 2010 its participation as an institutional member in the current phase of the Sloan Digital Sky Survey (SDSS-III). In the last year there has been plenty of news in all four projects of the survey: BOSS, MARVELS, SEGUE-2 and APOGEE. In this talk we will summarize the main results, give a progress report, describe the next public data release (DR9), and highlight the contributions and involvement at the IAC. SDSS-III will end in 2014, and we will provide a glimpse of what is coming up afterward.

We compare the Hubble type and the spectroscopic class of the galaxies with spectra in SDSS/DR7. As it is long known, elliptical galaxies tend to be red whereas spiral galaxies tend to be blue, however, this relationship presents a large scatter, which we measure and quantify in detail. We compare the Automatic Spectroscopic K-means based classification (ASK) with most of the commonly used morphological classifications. All of them provide consistent results. Given a spectral class, the morphological type wavers with a standard deviation between 2 and 3 T types, and the same large dispersion characterizes the variability of spectral classes fixed the morphological type. The distributions of Hubble types given an ASK class are very skewed -- they present long tails that go to the late morphological types for the red galaxies, and to the early morphological types for the blue spectroscopic classes. The scatter is not produced by problems in the classification, and it remains when particular subsets are considered. A considerable fraction of the red galaxies are spirals (40--60 %), but they never present very late Hubble types (Sd or later). Even though red spectra are not associated with ellipticals, most ellipticals do have red spectra: 97 % of the ellipticals in the morphological catalog by Nair & Abraham, used here for reference, belong to ASK 0, 2 or 3. It contains only a 3 % of blue ellipticals. The galaxies in the green valley class (ASK~5) are mostly spirals, and the AGN class (ASK 6) presents a large scatter of Hubble types from E to Sd. We investigate variations with redshift using a volume limited subsample. From redshift 0.25 to now the galaxies redden from ASK 2 to ASK 0, as expected from the passive evolution of their stellar populations. Two of the ASK classes (1 and 4) gather edge-on spirals, and they may be useful in studies requiring knowing the intrinsic shape of a galaxy (e.g., weak lensing calibration).

Since June last year, the IAC is an institutional member in the third phase of the Sloan Digital Sky Survey (SDSS-III). Many of us have already got an account in the wiki, a bunch are following closely the evolution of one or more of the four surveys, BOSS, MARVELS, SEGUE-2 and APOGEE, through the mailing lists and the teleconferences, and there are even some who are already working actively on them. All this in a period of one year since the IAC´s participation was first proposed. In this seminar, we'll make a quick summary of the activities related to SDSS at the IAC, we'll present the latest news, and will make a live demonstration on how to access DR8 data.

Using the k-means cluster analysis algorithm, we carry out an unsupervised classification of all galaxy spectra in the seventh and final Sloan Digital Sky Survey data release (SDSS/DR7). Except for the shift to rest-frame wavelengths and the normalization to the g-band flux, no manipulation is applied to the original spectra. The algorithm guarantees that galaxies with similar spectra belong to the same class. We find that 99% of the galaxies can be assigned to only 17 major classes, with 11 additional minor classes including the remaining 1%. The classification is not unique since many galaxies appear in between classes; however, our rendering of the algorithm overcomes this weakness with a tool to identify borderline galaxies. Each class is characterized by a template spectrum, which is the average of all the spectra of the galaxies in the class. These low-noise template spectra vary smoothly and continuously along a sequence labeled from 0 to 27, from the reddest class to the bluest class. Our Automatic Spectroscopic K-means-based (ASK) classification separates galaxies in colors, with classes characteristic of the red sequence, the blue cloud, as well as the green valley. When red sequence galaxies and green valley galaxies present emission lines, they are characteristic of active galactic nucleus activity. Blue galaxy classes have emission lines corresponding to star formation regions. We find the expected correlation between spectroscopic class and Hubble type, but this relationship exhibits a high intrinsic scatter. Several potential uses of the ASK classification are identified and sketched, including fast determination of physical properties by interpolation, classes as templates in redshift determinations, and target selection in follow-up works (we find classes of Seyfert galaxies, green valley galaxies, as well as a significant number of outliers). The ASK classification is publicly accessible through various Web sites.