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23801. Very thin discs galaxies properties
ID:
ivo://CDS.VizieR/J/MNRAS/465/3784
Title:
Very thin discs galaxies properties
Short Name:
J/MNRAS/465/3784
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the properties of galaxies with very thin discs (VTDs) using a sample of 85 objects whose stellar disc radial-to-vertical scale ratio determined from photometric decomposition, exceeds 9. We present evidences of similarities between the VTD galaxies and low surface brightness (LSB) disc galaxies, and conclude that both small and giant LSB galaxies may reveal themselves as VTD, edge-on galaxies. Our VTD galaxies are mostly bulgeless, and those with large radial scalelength tend to have redder colours. We performed spectral observations of 22 VTD galaxies with the Dual Imaging Spectrograph on the 3.5 m telescope at the Apache Point Observatory. The spectra with good resolution (R~5000) allow us to determine the distance and the ionized gas rotation curve maximum for the galaxies. Our VTD galaxies have low dust content, in contrast to regular disc galaxies. Apparently, VTD galaxies reside in specific cosmological low-density environments and tend to have less connection with filaments. Comparing a toy model that assumes marginally low star formation in galactic discs with obtained gas kinematics data, we conclude that there is a threshold central surface density of about 88M_{sun}_/pc^2^, which we observe in the case of very thin, rotationally supported galactic discs.
23802. Very young galaxies from SDSS
ID:
ivo://CDS.VizieR/J/MNRAS/492/1791
Title:
Very young galaxies from SDSS
Short Name:
J/MNRAS/492/1791
Date:
21 Oct 2021
Publisher:
CDS
Description:
Only a handful of galaxies in the local Universe appear to be very young. We estimate the fraction of very young galaxies (VYGs), defined as those with more than half their stellar masses formed within the last Gyr. We fit non-parametric star formation histories (SFHs) to ~280000 galaxy spectra from a flux- and volume-limited subsample of the Main Galaxy Sample (MGS) of the SDSS, which is also complete in mass-to-light ratio, thus properly accounting for passive galaxies of a given mass. The VYG fractions decrease with increasing galaxy stellar mass, from ~50 per cent at m=10^8^M_{sun}_ to ~0.1 per cent at m=10^11.5^M_{sun}_, with differences of up to 1dex between the different spectral models used to estimate the SFH and on how we treat aperture effects. But old stellar populations may hide in our VYGs despite our conservative VYG sample built with galaxies that are globally bluer than within the region viewed by the SDSS fibre. The VYG fractions versus mass decrease more gradually compared to the Tweed et al. (2018MNRAS.477.1427T) predictions using analytical and semi-analytical models of galaxy formation, but agree better with the SIMBA hydrodynamical simulation. These discrepancies highlight the usefulness of VYGs in constraining the strong uncertainties in both galaxy formation models and spectral modelling of galaxy SFHs. Given the lognormal cosmic SFH, these mean VYG fractions suggest that galaxies above 10^8^M_{sun}_ undergo at most four major starbursts on average.
23803. Very young galaxies in the local Universe
ID:
ivo://CDS.VizieR/J/MNRAS/502/4815
Title:
Very young galaxies in the local Universe
Short Name:
J/MNRAS/502/4815
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the local Universe, there are a handful of dwarf compact star-forming galaxies with extremely low oxygen abundances. It has been proposed that they are young, having formed a large fraction of their stellar mass during their last few hundred Myr. However, little is known about the fraction of young stellar populations in more massive galaxies. In a previous article, we analysed 404000 Sloan Digital Sky Survey spectra to identify a surprisingly large sample of more massive very young galaxies (VYGs), defined to have formed at least 50 per cent of their stellar mass within the last 1Gyr. Here, we investigate in detail the properties of a subsample of 207 galaxies that are VYGs according to all three of our spectral models. We compare their properties with those of control sample galaxies (CSGs). We find that VYGs tend to have higher surface brightness and to be more compact, dusty, asymmetric, and clumpy than CSGs. Analysis of a subsample with H I detections reveals that VYGs are more gas rich than CSGs. VYGs tend to reside more in the inner parts of low-mass groups and are twice as likely as CSGs to be interacting with a neighbour galaxy. On the other hand, VYGs and CSGs have similar gas metallicities and large-scale environments (relative to filaments and voids). These results suggest that gas-rich interactions and mergers are the main mechanisms responsible for the recent triggering of star formation in low-redshift VYGs, except for the lowest mass VYGs, where the starbursts would arise from a mixture of mergers and gas infall.
23804. VESPA PA team server Registry
ID:
ivo://bira-iasb/__system__/services/registry
Title:
VESPA PA team server Registry
Short Name:
BIRA-IASB Reg
Date:
11 Oct 2024 00:52:43
Publisher:
The staff at the VESPA PA team server
Description:
The publishing registry for the VESPA PA team server.
23805. VESPA PA team server TAP service
ID:
ivo://bira-iasb/tap
Title:
VESPA PA team server TAP service
Short Name:
BIRA-IASB TAP
Date:
08 Oct 2024 09:26:16
Publisher:
bira-iasb
Description:
The VESPA PA team server's TAP end point. The Table Access Protocol (TAP) lets you execute queries against our database tables, inspect various metadata, and upload your own data. It is thus the VO's premier way to access public data holdings. Tables exposed through this endpoint include: epn_core from the gem_mars schema, epn_core from the nomad schema, epn_core from the soir schema, columns, groups, key_columns, keys, schemas, tables from the tap_schema schema.
23806. Vespa Vrije Universiteit Amsterdam
ID:
ivo://vovu.vu
Title:
Vespa Vrije Universiteit Amsterdam
Short Name:
VOVU
Date:
09 Feb 2018 11:44:20
Publisher:
vovu.vu
Description:
The Vrije University Amsterdam IT team is providing support for the Geology-Geochemistry group of Earth Science that are responsible for providing Trans National Access to multiple labs within the Europlanet2020 RI. Data obtained within TA visits will be stored and made open access with a format designed to be readily retrievable. Data storage system is designed in line with protocols used within the Virtual Observatory, VESPA hosted by the Paris Astronomical Data Centre who offer a central support to the various projects through central storage and web servers computing facilities.
23807. vespa-vu Registry
ID:
ivo://vovu.vu/__system__/services/registry
Title:
vespa-vu Registry
Short Name:
VOVU Reg
Date:
09 Feb 2018 11:44:20
Publisher:
The staff at the vespa-vu
Description:
The publishing registry for the vespa-vu.
23808. (4) Vesta adopted polarimetric light curves
ID:
ivo://CDS.VizieR/J/MNRAS/456/248
Title:
(4) Vesta adopted polarimetric light curves
Short Name:
J/MNRAS/456/248
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of the in situ exploration of the asteroid (4) Vesta by the Dawn spacecraft open new perspectives in the field of interpretation of remote-sensing polarimetric measurements of asteroids. (4) Vesta has long been known to be the only asteroid exhibiting a cyclic variation of the degree of linear polarization of the sunlight scattered by its surface, with a period which is synchronous with the object's rotation. This variation must be the consequence of some heterogeneity of the asteroid's surface, including regions characterized by different albedo, or composition, or regolith properties, or a combination of the above features. For a long time, this kind of conclusion has remained essentially qualitative. Now, after the extensive exploration of Vesta's surface by Dawn, it is possible to interpret the data set of polarimetric measurements of Vesta, including some unpublished data presented here for the first time, in terms of a correspondence between the degree of linear polarization and the variation of local properties of the surface visible to ground-based observers during Vesta's rotation, as seen at different epochs and under different illumination conditions. This makes it possible to refine our knowledge of the empirical relation between polarization properties and albedo, which is commonly used to derive the albedo from remote-sensing measurements of linear polarization of atmosphereless Solar system bodies.
23809. VEXAS DR2 catalogs
ID:
ivo://CDS.VizieR/II/369
Title:
VEXAS DR2 catalogs
Short Name:
II/369
Date:
22 Feb 2022
Publisher:
CDS
Description:
We present the second public data release of the VISTA EXtension to Auxiliary Surveys (VEXAS DR2), where we classify objects into stars, galaxies and quasars based on an ensemble of machine learning algorithms. The aim of VEXAS is to build the widest multi-wavelength catalogue, providing reference magnitudes, colours and morphological information for a large number of scientific uses. We apply an ensemble of thirty-two different machine learning models, based on three different algorithms and on different magnitude sets, training samples and classification problems (two or three classes) on the three VEXAS Data Release 1 (DR1) optical+infrared (IR) tables. The tables were created in DR1 cross-matching VISTA near-infrared data with Wide-field Infrared Survey Explorer far-infrared data and with optical magnitudes from the Dark Energy Survey (VEXAS-DESW), the Sky Mapper Survey (VEXAS-SMW), and the Panoramic Survey Telescope and Rapid Response System Survey (VEXAS-PSW). We assemble a large table of spectroscopically confirmed objects (VEXAS-SPEC-GOOD, 415 628 unique objects), based on the combination of six different spectroscopic surveys that we use for training. We develop feature imputation to classify also objects for which magnitudes in one or more bands are missing. We classify in total 90106 objects in the Southern Hemisphere. Among these, ~62.9x10^6^ (~52.6x10^6^) are classified as 'high confidence' ('secure') stars, ~920000 (~750000) as 'high confidence' ('secure') quasars and ~34.8 (~34.1) millions as 'high confidence' ('secure') galaxies, with pclass>=0.7 (pclass>=0.9). The DR2 tables update the DR1 with the addition of imputed magnitudes and membership probabilities to each of the three classes. The density of high-confidence extragalactic objects varies strongly with the survey depth: at pclass>0.7; there are 111/deg^2^ quasars in the VEXAS-DESW footprint and 103/deg^2^ in the VEXAS-PSW footprint, while only 10.7/deg^2^ in the VEXASSM footprint. Improved depth in the midIR and coverage in the optical and nearIR are needed for the SM footprint that is not already covered by DESW and PSW.
23810. VEx ASPERA-4 ELS Background Derived Data Collection
ID:
ivo://pds-ppi/vex_aspera4_els_derived/ppi/epn_core
Title:
VEx ASPERA-4 ELS Background Derived Data Collection
Short Name:
VEX-ASPERA4-DER
Date:
15 Dec 2022 19:25:01
Publisher:
Planetary Data System
Description:
This collection contains the derived data products for the Venus Express Electron Spectrometer Background Data Bundle.

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