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24581. Weak Galactic radio sources spectral indices
ID:
ivo://CDS.VizieR/J/MNRAS/473/1685
Title:
Weak Galactic radio sources spectral indices
Short Name:
J/MNRAS/473/1685
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the next few years the classification of radio sources observed by the large surveys will be a challenging problem and spectral index is a powerful tool for addressing it. Here we present an algorithm to estimate the spectral index of sources from multiwavelength radio images. We have applied our algorithm to SCORPIO, a Galactic plane survey centred around 2.1GHz carried out with Australian Telescope Compact Array and found we can measure reliable spectral indices only for sources stronger than 40 times the rms noise. Above a threshold of 1mJy, the source density in SCORPIO is 20 per cent greater than in a typical extragalactic field, like Australia Telescope Large Area Survey because of the presence of Galactic sources. Among this excess population, 16 sources per square degree have a spectral index of about zero suggesting optically thin thermal emission such as HII regions and planetary nebulae, while 12 per square degree present a rising spectrum, suggesting optically thick thermal emission such as stars and UCHII regions.
24582. weak G-band stars abundances
ID:
ivo://CDS.VizieR/J/A+A/587/A42
Title:
weak G-band stars abundances
Short Name:
J/A+A/587/A42
Date:
21 Oct 2021
Publisher:
CDS
Description:
Weak G-band (wGb) stars are a very peculiar class of red giants; they are almost devoided of carbon and often present mild lithium enrichment. Despite their very puzzling abundance patterns, very few detailed spectroscopic studies existed up to a few years ago, which prevented any clear understanding of the wGb phenomenon. We recently proposed the first consistent analysis of published data for a sample of 28 wGb stars and were able to identify them as descendants of early A-type to late B-type stars, although we were not able to conclude on their evolutionary status or the origin of their peculiar abundance pattern. Using new high-resolution spectra, we present the study of a new sample of wGb stars with the aim of homogeneously deriving their fundamental parameters and surface abundances for a selected set of chemical species that we use to improve our insight on this peculiar class of objects. We obtained high-resolution and high signal-to-noise spectra for 19 wGb stars in the southern and northern hemisphere that we used to perform consistent spectral synthesis to derive their fundamental parameters and metallicities, as well as the spectroscopic abundances for Li, C, ^12^C/^13^C, N, O, Na, Sr, and Ba. We also computed dedicated stellar evolution models that we used to determine the masses and to investigate the evolutionary status and chemical history of the stars in our sample. We confirm that the wGb stars are stars with initial masses in the range 3.2 to 4.2M_{sun}_. We suggest that a large fraction could be mildly evolved stars on the subgiant branch currently undergoing the first dredge-up, while a smaller number of stars are more probably in the core He burning phase at the clump. After analysing their abundance pattern, we confirm their strong nitrogen enrichment anti-correlated with large carbon depletion, characteristic of material fully processed through the CNO cycle to an extent not known in evolved intermediate-mass stars in the field and in open clusters. However, we demonstrate here that such a pattern is very unlikely owing to self-enrichment. In the light of the current observational constraints, no solid self-consistent pollution scenario can be presented either, leaving the wGb puzzle largely unsolved.
24583. Weak lensing of SDSS galaxy clusters. III.
ID:
ivo://CDS.VizieR/J/ApJ/703/2232
Title:
Weak lensing of SDSS galaxy clusters. III.
Short Name:
J/ApJ/703/2232
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present measurements of the excess mass-to-light ratio (M/L) measured around MaxBCG galaxy clusters observed in the Sloan Digital Sky Survey. This red-sequence cluster sample includes objects from small groups with M_200_~5x10^12^/hM_{sun}_ to clusters with M_200_~10^15^/hM_{sun}_. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean {Delta}{rho}(r)={rho}(r)-{bar}{rho} for clusters in bins of richness and optical luminosity. We also measure the excess luminosity density {Delta}l(r)=l(r)-{bar}l measured in the z=0.25 i band. For both mass and light, we de-project the profiles to produce three-dimensional mass and light profiles over scales from 25h^-1^kpc to 22h^-1^Mpc. From these profiles we calculate the cumulative excess mass {Delta}M(r) and excess light {Delta}L(r) as a function of separation from the BCG.
24584. Weak-line T Tauri in Spitzer c2d Survey. II.
ID:
ivo://CDS.VizieR/J/ApJ/667/308
Title:
Weak-line T Tauri in Spitzer c2d Survey. II.
Short Name:
J/ApJ/667/308
Date:
21 Oct 2021
Publisher:
CDS
Description:
One of the central goals of the Spitzer Legacy Project "From Cores to Disks" (c2d) is to determine the frequency of circumstellar disks around weak-line T Tauri stars (WTTSs) and to study the properties and evolutionary status of these disks. Here we present a census of disks for a sample of over 230 WTTSs located in the c2d IRAC and MIPS maps of the Ophiuchus, Lupus, and Perseus Molecular Clouds.
24585. Weak metal line absorbers sample
ID:
ivo://CDS.VizieR/J/MNRAS/476/4965
Title:
Weak metal line absorbers sample
Short Name:
J/MNRAS/476/4965
Date:
15 Dec 2021 07:14:57
Publisher:
CDS
Description:
We present a sample of 34 weak metal line absorbers at z<0.3 selected by the simultaneous >3{sigma} detections of the SiII{lambda}1260 and CII{lambda}1334 absorption lines, with W_r_(SiII)<0.2 {AA} and W_r_(CII)<0.3{AA}, in archival HST/COS spectra. Our sample increases the number of known low-z 'weak absorbers' by a factor of >5. The column densities of HI and low-ionization metal lines obtained from Voigt profile fitting are used to build simple photoionization models. The inferred densities and line-of-sight thicknesses of the absorbers are in the ranges of -3.3<logn_H_/cm^-3^<-2.4 and ~1pc-50kpc (median ~=500pc), respectively. Most importantly, 85 per cent (50 per cent) of these absorbers show a metallicity of [Si/H]>-1.0(0.0). The fraction of systems showing near-/supersolar metallicity in our sample is significantly higher than in the HI-selected sample of Wotta et al., and the galaxy-selected sample of Prochaska et al., of absorbers probing the circum-galactic medium at similar redshift. A search for galaxies has revealed a significant galaxy-overdensity around these weak absorbers compared to random positions with a median impact parameter of 166 kpc from the nearest galaxy. Moreover, we find the presence of multiple galaxies in ~=80 per cent of the cases, suggesting group environments. The observed dN/dz of 0.8+/-0.2 indicates that such metal-enriched, compact, dense structures are ubiquitous in the haloes of low-z group galaxies. We suggest that these are transient structures that are related to galactic outflows and/or stripping of metal-rich gas from galaxies.
24586. Weak MgII absorbers at 0.4<z<2.4
ID:
ivo://CDS.VizieR/J/ApJ/660/1093
Title:
Weak MgII absorbers at 0.4<z<2.4
Short Name:
J/ApJ/660/1093
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from a survey of weak MgII absorbers in the VLT/UVES spectra of 81 QSOs obtained from the ESO archive. In this survey, we identified 112 weak MgII systems within the redshift interval 0.4<z<2.4 with 86% completeness down to a rest-frame equivalent width of Wr(2796)=0.02{AA}, overing a cumulative redshift path length of {DELTA}Z~77.3.
24587. W51/e2 and G34.3+0.2 IRAM spectra
ID:
ivo://CDS.VizieR/J/A+A/582/A64
Title:
W51/e2 and G34.3+0.2 IRAM spectra
Short Name:
J/A+A/582/A64
Date:
21 Oct 2021
Publisher:
CDS
Description:
With only a few low- and high-mass star-formation regions studied in detail so far, it is unclear what role the environment plays in complex molecule formation. In this light, a comparison of relative abundances of related species between sources might be useful for explaining any observed differences. We seek to measure the relative abundance between three important complex organic molecules, ethylene glycol ((CH_2_OH)_2_), glycolaldehyde (CH_2_OHCHO) and methyl formate (HCOOCH_3_), toward high-mass protostars and thereby provide additional constraints on their formation pathways. We use IRAM30 m single-dish observations of the three species toward two high-mass star-forming regions - W51/e2 and G34.3+0.2 - and report a tentative detection of (CH_2_OH)_2_ toward both sources.
24588. WEB Catalog of Radial Velocities
ID:
ivo://CDS.VizieR/III/190B
Title:
WEB Catalog of Radial Velocities
Short Name:
III/190B
Date:
21 Oct 2021
Publisher:
CDS
Description:
We give a common version of the two catalogues of Mean Radial Velocities by Wilson (1953; catalogue <III/21>) and Evans (1978; catalogue <III/47>) to which we have added the catalogue of spectroscopic binary systems (Batten et al. 1989; catalogue <V/64>). For each star, when possible, we give: 1) an acronym to enter SIMBAD (Set of Identifications Measurements and Bibliography for Astronomical Data; see <http://cdsweb.u-strasbg.fr/Simbad.html>) of the CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the number HIC of the HIPPARCOS catalogue (Turon 1992; catalogue <I/196>). 3) the CCDM number (Catalogue des Composantes des etoiles Doubles et Multiples) by Dommanget & Nys (1994; catalogue <I/211>). For the cluster stars, a precise study has been done, on the identification numbers. Numerous remarks point out the problems we have had to deal with.
24589. WeCAPP Survey. M31 variables
ID:
ivo://CDS.VizieR/J/A+A/445/423
Title:
WeCAPP Survey. M31 variables
Short Name:
J/A+A/445/423
Date:
21 Oct 2021
Publisher:
CDS
Description:
The observations in the WeCAPP microlensing survey towards the Andromeda galaxy (M31) for a period of three years (2000-2003) resulted in a database with unprecedented time coverage for an extragalactic variable star study. We have monitored a 16.1' x 16.6' field centered on the nucleus of M31 in two optical bands (R and I) using the 0.8-m telescope at Wendelstein, Germany and the 1.2-m telescope at Calar Alto, Spain. Using the difference imaging method we detected 23781 variable sources for which we calculated the periods and variation amplitudes. We classified the variables according to their position in the R-band period-amplitude plane. Three groups can be distinguished; while the first two groups can be mainly associated with Cepheid-like variables (population I Cepheids in group I; type II Cepheids and RV Tauri stars in group II), the third one consists of Long Period Variables (LPVs). We detected 37 RV Tauri stars and 11 RV Tauri candidates, which makes this catalogue one of the largest collections of this class of stars to date. The classification scheme is supported by Fourier decomposition of the light curves. The catalogue of variable stars contains the positions, the periods in R and I, the significance of the assigned periods, and the variation amplitudes in the R and I bands.
24590. Well sampled stars FEROS+HARPS radial velocities
ID:
ivo://CDS.VizieR/J/A+A/632/A37
Title:
Well sampled stars FEROS+HARPS radial velocities
Short Name:
J/A+A/632/A37
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stars show various amounts of Radial Velocity (RV) jitter due to varying stellar activity levels. The typical amount of RV jitter as a function of stellar age and observational timescale has not been systematically quantified so far, although it is often larger than the instrumental precision of modern high-resolution spectrographs used for Doppler planet detection and characterization. We aim to empirically determine the intrinsic stellar RV variation for mostly G and K dwarf stars on different timescales and for different stellar ages independently of stellar models. We also focus on young stars (~<30Myr), where the RV variation is known to be large. We use archival FEROS and HARPS RV data of stars which were observed at least 30 times spread over at least two years. We then apply the Pooled Variance (PV) technique to these data sets to identify the periods and amplitudes of underlying, quasiperiodic signals. We show that the PV is a powerful tool to identify quasiperiodic signals in highly irregularly sampled data sets. We derive activity-lag functions for 20 assumingly single stars stars, where lag is the timescale on which the stellar jitter is measured. Since the ages of all stars are known, we also use this to formulate an activity-age-lag relation which can be used to predict the expected RV jitter of a star given its age and the timescale to be probed. The maximum RV jitter on timescales of decades decreases from over 500m/s for 5Myr old stars to 2.3m/s for stars with ages around 5Gyr. The decrease in RV jitter when considering a time scale of only 1d instead of 1yr is smaller by roughly a factor of 4 for stars with an age of about 5Myr, and a factor of 1.5 for stars with an age of 5Gyr. How fast the RV jitter increases with lag strongly depends on stellar age and reaches 99% of the maximum RV jitter between a few days for a few Myr old stars up to presumably decades or longer for stars with an age of a few Gyr.

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