Found 10 talks width keyword catalogs
We present a sample of 734 ultracool dwarfs using LAMOST DR7 spectra, i.e., those having a spectral type of or later than M6, including an L0. All of these red or brown dwarfs are within 360 pc, with a Gaia G magnitude brighter than 19.2 mag, a BP-RP color redder than 2.5 mag and an absolute G magnitude fainter than 9 mag. Their stellar parameters (Teff, log g, and [M/H]) are consistent with being the Galactic thin-disk population, which is further supported by their kinematics using LAMOST radial velocity plus Gaia proper motion and parallax. A total of 77 are detected with the lithium absorption line at 6708 A, signifying youth and substellar nature. We report on their kinematic ages estimated by the velocity dispersion. Thirty five close pairs are identified, of which the binarity of six is discovered for the first time.
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.
Galaxy morphologies are one of the key diagnostics of galaxy evolutionary tracks, but visual classifications are extremely time-consuming. The sheer size of Big Data surveys, containing millions of galaxies, make this approach completely impractical. Deep Learning (DL) algorithms, where no image pre-processing is required, have already come to the rescue for image analysis of large data surveys. In this seminar, I will present the largest multi-band catalog of automated galaxy morphologies to date containing morphological classifications of ∼27 million galaxies from the Dark Energy Survey. The classification separates: (a) early-type galaxies (ETGs) from late-types (LTGs); and (b) face-on galaxies from edge-on. These classifications have been obtained using a supervised DL algorithm. Our Convolutional Neural Networks (CNNs) are trained on a small subset of DES objects with previously known classifications, but hese typically have mr < 17.7 mag. We overcome the lack ofa training sample by modeling fainter objects up to mr < 21.5 mag, i.e., by simulating what thebrighter objects with well-determined classifications would look like if they were at higher redshifts.The CNNs reach a 97% accuracy to mr < 21.5 on their training sets, suggesting that they are ableto recover features more accurately than the human eye. We obtain secure classifications for 87%and 73% of the catalog for the ETG vs. LTG and edge-on vs. face-on models, respectively.
Time-domain space missions have revolutionized our understanding of stellar physics and stellar populations. Virtually all evolved stars can be detected as oscillators in missions such as Kepler, K2, TESS and PLATO. Asteroseismology, or the study of stellar oscillations, can be combined with spectroscopy to infer masses, radii and ages for very large samples of stars. This asteroseismic data can also be used to train machine learning tools to infer ages for even larger stellar population studies, sampling a large fraction of the volume of the Milky Way galaxy. In this talk I demonstrate that asteroseismic radii are in excellent agreement with those inferred using Gaia and spectroscopic data; this demonstrates that the current asteroseismic data is precise and accurate at the 1-2% level. Major new catalogs for Kepler and K2 data are nearing completion, and I present initial results from both. We find unexpected age patterns in stars though to be chemically old, illustrating the power of age information for Galactic archeology. Prospects for future progress in the TESS era will also be discussed.
The Sloan Digital Sky Survey (SDSS) is one of the most successful and prolific projects in the history of Astronomy.
In its fifth iteration SDSS-V (2020-2025) will provide a more comprehensive, global picture of the local universe by
studying the interplay between galactic genesis, stellar and black hole processes, and the physics of the ISM. I will
review the main science goals of the project, the exciting new hardware being implemented (robot fibre positioner,
large IFU systems), and the operational challenges. As in its previous incarnations, SDSS-V remains committed to
providing high-quality data products for the astronomical and educational communities. I will discuss some of the
new ideas being developed for SDSS-V with regards to data reduction, release, archival, and visualisation.
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.
I will present an extensive analysis of the 850 microns (353 GHz) polarization maps of the SCUBA Polarimeter Legacy (SCUPOL) Catalogue produced by Matthews et al., focusing on the molecular clouds and star-forming regions. The first half of the presentation will concern the several methods used in order to analyze and characterize the observed polarization maps and a statistical analysis of the results will be presented. The second half of the talk will focus on a method used for describing the turbulent regimes of the four well sampled regions, S106, OMC-2/3, W49, and DR21, based on comparisons with three-dimensional magnetohydrodynamics (MHD) numerical simulations scaled to the observed polarization maps. It will be shown how this method can be used for constraining the values of the inclination angle of the mean magnetic field with respect to the line of sight. Consistency of the results obtained from the comparison of the information extracted from the analysis of the observed and simulated maps with results obtained from independent observation data analysis by other authors will be discussed. Conclusions regarding how simple, ideal, isothermal, and non-self-gravitating MHD simulations may be sufficient in order to describe the large-scale observed physical properties of some molecular cloud envelopes will be given.
Golden Age of Astronomy” does not only influence professional but also amateur astronomy. Today, amateurs basically use the same technologies as the professionals. This includes the most important tool – spectroscopy. There is an important gap in professional astronomical spectroscopy which can be filled by amateurs and their smaller telescopes. Some stellar phenomena need longer time coverage, of order, e.g., some weeks. This is especially valid for binary stars. One such interesting target is Wolf-Rayet 140, a WR+O binary with a highly eccentric orbit and a period of about 8 years. The observation of its periastron passage in the visible wavelength range is valuable for measurements in other wavelength domains to understand the wind-wind shock interaction of both components and the global geometry and physics of the system. For this and some other massive star targets, a group of amateur and professional astronomers performed a successful campaign for 116 nights at the 50 cm Mons telescope at Teide observatory, supported by the IAC and embedded in a joint worldwide X-ray, visual and IR campaign. The group of observers was a mix of enthusiastic astronomers from various professions (e.g., physicists, a physics student, a chemist, a physician, a schoolboy, a pilot) but they all have been experienced and enthusiastic observers. The talk will highlight the most important results of this campaign
AbstractThe main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 21. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovae (including SNIa), search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System, and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes.
« Newer Older »
- Temperature inhomogeneities cause the abundance discrepancy in H II regionsDr. J. Eduardo Méndez-DelgadoTuesday June 13, 2023 - 12:30 GMT+1 (Aula)
- TBDDr. Doug RennehanThursday June 15, 2023 - 10:30 GMT+1 (Aula)