- ID:
- ivo://CDS.VizieR/J/A+A/601/A79
- Title:
- VLTS. Properties of O dwarf in 30 Dor
- Short Name:
- J/A+A/601/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VLT-FLAMES Tarantula Survey has observed hundreds of O-type stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). We study the properties of 105 apparently single O-type dwarfs. To determine stellar and wind parameters, we used the IACOB-GBAT package, an automatic procedure based on a large grid of atmospheric models calculated with the FASTWIND code. In addition to classical techniques, we applied the Bayesian BONNSAI tool to estimate evolutionary masses. We provide a new calibration of effective temperature vs. spectral type for O-type dwarfs in the LMC, based on our homogeneous analysis of the largest sample of such objects to date and including all spectral subtypes. Good agreement with previous results is found, although the sampling at the earliest subtypes could be improved. Rotation rates and helium abundances are studied in an evolutionary context. We find that most of the rapid rotators (vsini higher than 300km/s) in our sample have masses below 25 MSun and intermediate rotation-corrected gravities (logg_c_ between 3.9 and 4.1). Such rapid rotators are scarce at higher gravities (i.e. younger ages) and absent at lower gravities (larger ages). This is not expected from theoretical evolutionary models, and does not appear to be due to a selection bias in our sample. We compare the estimated evolutionary and spectroscopic masses, finding a trend that the former is higher for masses below 20M_{sun}_. This can be explained as a consequence of limiting our sample to the O-type stars, and we see no compelling evidence for a systematic mass discrepancy. For most of the stars in the sample we were unable to estimate the wind-strength parameter (hence mass-loss rates) reliably, particularly for objects with luminosity lower than logL/L_{sun}_ about 5.1. Ultraviolet spectroscopy is needed to undertake a detailed investigation of the wind properties of these dwarfs.
Number of results to display per page
Search Results
24242. VLT Survey Telescope ATLAS
- ID:
- ivo://CDS.VizieR/II/350
- Title:
- VLT Survey Telescope ATLAS
- Short Name:
- II/350
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VLT Survey Telescope ATLAS survey is an optical ugriz survey aiming to cover ~4700deg^2^ of the southern sky to similar depths as the Sloan Digital Sky Survey (SDSS). From reduced images and object catalogues provided by the Cambridge Astronomical Surveys Unit, we first find that the median seeing ranges from 0.8-arcsec FWHM (full width at half-maximum) in i to 1.0-arcsec in u, significantly better than the 1.2-1.5arcsec seeing for SDSS. The 5{sigma} mag limit for stellar sources is r_AB_=22.7 and in all bands these limits are at least as faint as SDSS. SDSS and ATLAS are more equivalent for galaxy photometry except in the z band where ATLAS has significantly higher throughput. We have improved the original ESO magnitude zero-points by comparing m<16 star magnitudes with the AAVSO Photometric All-Sky Survey in gri, also extrapolating into u and z, resulting in zero-points accurate to ~+/-0.02mag. We finally compare star and galaxy number counts in a 250deg^2^ area with SDSS and other count data and find good agreement. ATLAS data products can be retrieved from the ESO Science Archive, while support for survey science analyses is provided by the OmegaCAM Science Archive, operated by the Wide-Field Astronomy Unit in Edinburgh.
- ID:
- ivo://CDS.VizieR/J/A+A/512/A12
- Title:
- VLT/VIMOS spectroscopy in GOODS-South field
- Short Name:
- J/A+A/512/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the full data set of the VIsible Multi-Object Spectrograph (VIMOS) spectroscopic campaign of the ESO/GOODS program in the Chandra Deep Field South (CDFS), which complements the FORS2 ESO/GOODS spectroscopic campaign. The ESO/GOODS spectroscopic programs are aimed at reaching signal-to-noise ratios adequate to measure redshifts for galaxies with AB magnitudes in the range ~24-25 in the B and R band using VIMOS, and in the z band using FORS2.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A25
- Title:
- VLT/X-shooter observations of PHL293B
- Short Name:
- J/A+A/533/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present VLT/X-shooter spectroscopic observations in the wavelength range {lambda}{lambda}3000-23000{AA} of the extremely metal-deficient blue compact dwarf (BCD) galaxy PHL 293B containing a luminous blue variable (LBV) star and compare them with previous data. This BCD is one of the two lowest-metallicity galaxies where LBV stars were detected, allowing us to study the LBV phenomenon in the extremely low metallicity regime. We determine abundances of nitrogen, oxygen, neon, sulfur, argon, and iron by analyzing the fluxes of narrow components of the emission lines using empirical methods and study the properties of the LBV from the fluxes and widths of broad emission lines.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A136
- Title:
- VLT/X-SHOOTER spectrum of COLA1
- Short Name:
- J/A+A/619/A136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Distant luminous Lyman-{alpha} emitters (LAEs) are excellent targets for spectroscopic observations of galaxies in the epoch of reionisation (EoR). We present deep high-resolution (R=5000) VLT/X-shooter observations, along with an extensive collection of photometric data of COLA1, a proposed double peaked LAE at z=6.6. We rule out the possibility that COLA1's emission line is an [OII] doublet at z=1.475 on the basis of i) the asymmetric red line-profile and flux ratio of the peaks (blue/red=0.31+/-0.03) and ii) an unphysical [OII]/H{alpha} ratio ([OII]/H{alpha}>22). We show that COLA1's observed B-band flux is explained by a faint extended foreground LAE, for which we detect Ly{alpha} and [OIII] at z=2.142. We thus conclude that COLA1 is a real double-peaked LAE at z=6.593, the first discovered at z>6. COLA1 is UV luminous (M1500=-21.6+/-0.3), has a high equivalent width (EW0,Ly{alpha}=120_-40_^+50^{AA}) and very compact Ly{alpha} emission (r50,Ly{alpha}=0.33_-0.04_^+0.07^kpc). Relatively weak inferred H{beta}+[OIII] line-emission from Spitzer/IRAC indicates an extremely low metallicity of Z<1/20Z_{sun}_ or reduced strength of nebular lines due to high escape of ionising photons. The small Ly{alpha} peak separation of 220+/-20km/s implies a low HI column density and an ionising photon escape fraction of ~15-30%, providing the first direct evidence that such galaxies contribute actively to the reionisation of the Universe at z>6. Based on simple estimates, we find that COLA1 could have provided just enough photons to reionise its own ~0.3pMpc (2.3cMpc) bubble, allowing the blue Ly{alpha} line to be observed. However, we also discuss alternative scenarios explaining the detected double peaked nature of COLA1. Our results show that future high-resolution observations of statistical samples of double peaked LAEs at z>5 are a promising probe of the occurrence of ionised regions around galaxies in the EoR.
- ID:
- ivo://CDS.VizieR/J/other/NewA/8.645
- Title:
- Vmag/plx relation for Hyades stars
- Short Name:
- J/other/NewA/8.6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, relation was established for Hyades stars between their apparent magnitudes and parallaxes. The precision criteria of this relation are very satisfactory. The importance of this relation was illustrated through its usages as: (1) A criterion for membership of the cluster, (2) a generating function for evaluating some parameters of the cluster.
- ID:
- ivo://wfau.roe.ac.uk/vmcDR4-dsa
- Title:
- VMC DR4 - VISTA Magellanic System survey
- Date:
- 04 Dec 2019 13:42:27
- Publisher:
- WFAU, Institute for Astronomy, University of Edinburgh
- Description:
- The VMC survey aims to obtain YJKs band photometry across the system down to Ks=20.3 at S/N=10. This sensitivity corresponds to the bottom of the red giant branch field stellar population and allows us to determine the global spatially resolved star formation history with unprecedented quality and to construct a three-dimensional map of the system. A wide-area encompassing the D25 as well as major features delineated by the distribution of stars and HI gas, will both trace the structure of the galaxies and signatures of past and present interactions. Contemporary optical and kinematic observations of comparable sensitivity will provide the community with a superior database for future studies of the system and will give us an excellent insight as to what has happened elsewhere in the Universe.
- ID:
- ivo://wfau.roe.ac.uk/vmcDR3-dsa
- Title:
- VMC DR3 - VISTA Magellanic System survey
- Short Name:
- VMC DR3
- Date:
- 04 Dec 2019 13:42:19
- Publisher:
- WFAU, Institute for Astronomy, University of Edinburgh
- Description:
- The VMC survey aims to obtain YJKs band photometry across the system down to Ks=20.3 at S/N=10. This sensitivity corresponds to the bottom of the red giant branch field stellar population and allows us to determine the global spatially resolved star formation history with unprecedented quality and to construct a three-dimensional map of the system. A wide-area encompassing the D25 as well as major features delineated by the distribution of stars and HI gas, will both trace the structure of the galaxies and signatures of past and present interactions. Contemporary optical and kinematic observations of comparable sensitivity will provide the community with a superior database for future studies of the system and will give us an excellent insight as to what has happened elsewhere in the Universe.
- ID:
- ivo://wfau.roe.ac.uk/vmcDR2-dsa
- Title:
- VMC DR2 - VISTA Magellanic System survey
- Short Name:
- VMC DR2
- Date:
- 04 Dec 2019 13:42:10
- Publisher:
- WFAU, Institute for Astronomy, University of Edinburgh
- Description:
- The VMC survey aims to obtain YJKs band photometry across the system down to Ks=20.3 at S/N=10. This sensitivity corresponds to the bottom of the red giant branch field stellar population and allows us to determine the global spatially resolved star formation history with unprecedented quality and to construct a three-dimensional map of the system. A wide-area encompassing the D25 as well as major features delineated by the distribution of stars and HI gas, will both trace the structure of the galaxies and signatures of past and present interactions. Contemporary optical and kinematic observations of comparable sensitivity will provide the community with a superior database for future studies of the system and will give us an excellent insight as to what has happened elsewhere in the Universe.
- ID:
- ivo://wfau.roe.ac.uk/vmcDR1-dsa
- Title:
- VMC DR1 - VISTA Magellanic System survey
- Short Name:
- VMC DR1
- Date:
- 04 Dec 2019 13:41:53
- Publisher:
- WFAU, Institute for Astronomy, University of Edinburgh
- Description:
- The VMC survey aims to obtain YJKs band photometry across the system down to Ks=20.3 at S/N=10. This sensitivity corresponds to the bottom of the red giant branch field stellar population and allows us to determine the global spatially resolved star formation history with unprecedented quality and to construct a three-dimensional map of the system. A wide-area encompassing the D25 as well as major features delineated by the distribution of stars and HI gas, will both trace the structure of the galaxies and signatures of past and present interactions. Contemporary optical and kinematic observations of comparable sensitivity will provide the community with a superior database for future studies of the system and will give us an excellent insight as to what has happened elsewhere in the Universe.
