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- ID:
- ivo://CDS.VizieR/J/AJ/128/1254
- Title:
- VLT 3.8{mu}m Trapezium catalog
- Short Name:
- J/AJ/128/1254
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep 3.8{mu}m L' imaging observations of the Trapezium cluster in Orion obtained with the ESO VLT. We use these observations to (1) search for infrared excess emission and evidence for protoplanetary disks associated with the faint, substellar population of this young cluster and (2) investigate the nature and extent of a recently discovered population of deeply embedded sources located in dense molecular gas behind the cluster. We detected 38 L' sources with substellar luminosities. In addition, we detected 24 L' sources that were spectroscopically classified as substellar objects in previous studies. Examining the infrared colors of all these sources, we determine an infrared excess fraction of 50%{+/-}20% from the J, H, K_s_ and L' colors for both the luminosity-selected and spectroscopically selected substellar samples.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A57
- Title:
- VLT/MUSE MACS J0416.1-2403 redshift catalogue
- Short Name:
- J/A+A/646/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A census of faint and tiny star forming complexes at high redshift is key to improving our understanding of reionizing sources, galaxy growth, and the formation of globular clusters. We present the MUSE Deep Lensed Field (MDLF) program, which is aimed at unveiling the very faint population of high redshift sources that are magnified by strong gravitational lensing and to significantly increase the number of constraints for the lens model. We describe Deep MUSE observations of 17.1 hours of integration on a single pointing over the Hubble Frontier Field galaxy cluster MACS J0416, providing line flux limits down to 2x10^19^erg/s/cm^2^ within 300km/s and continuum detection down to magnitude 26, both at the three sigma level at {lambda}=7000{AA}. For point sources with a magnification ({mu}) greater than 2.5 (7.7), the MLDF depth is equivalent to integrating more than 100 (1000) hours in blank fields, as well as complementing non-lensed studies of very faint high-z sources. The source-plane effective area of the MDLF with {mu}>6.3 is <50% of the image-plane field of view. We confirm spectroscopic redshifts for all 136 multiple images of 48 source galaxies at 0.9<z<6.2. Within those galaxies, we securely identify 182 multiple images of 66 galaxy components that we use to constrain our lens model. This makes MACS J0416 the cluster with the largest number of confirmed constraints for any strong lens model to date. We identify 116 clumps belonging to background high-z galaxies; the majority of them are multiple images and span magnitude, size, and redshift intervals of [-18, -10], [~400-3] parsec and 1<z<6.6, respectively, with the faintest or most magnified ones probing possible single gravitationally bound star clusters. The multiplicity introduced by gravitational lensing allows us, in several cases, to triple the effective integration time up to 51 hours exposure per single family, leading to a detection limit for unresolved emission lines of a few 10^-20^erg/s/cm^2^, after correction for lensing magnification. Ultraviolet high-ionization metal lines (and HeII{lambda}1640) are detected with S/N>10 for individual objects down to de-lensed magnitudes between 28-30. The median stacked spectrum of 33 sources with a median M_UV_=~-17 and <z>=3.2 (1.7<z<3.9) shows high-ionization lines, suggesting that they are common in such faint sources. Deep MUSE observations, in combination with existing HST imaging, allowed us to: (1) confirm redshifts for extremely faint high-z sources; (2) peer into their internal structure to unveil clumps down to 100-200pc scale; (3) in some cases, break down such clumps into star-forming complexes matching the scales of bound star clusters (<20pc effective radius); (4) double the number of constraints for the lens model, reaching an unprecedented set of 182 bona-fide multiple images and confirming up to 213 galaxy cluster members. These results demonstrate the power of JWST and future adaptive optics facilities mounted on the Extremely Large Telescopes (e.g., European-ELT Multi-conjugate Adaptive Optics RelaY, MAORY, coupled with the Multi-AO Imaging CamerA for Deep Observations, MICADO) or Very Large Telescope (e.g., MCAO Assisted Visible Imager and Spectrograph, MAVIS) when combined in studies with gravitational telescopes.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/78
- Title:
- VLT/MUSE spectroscopic obs. of MACS J1149.5+2223
- Short Name:
- J/ApJ/822/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Multi Unit Spectroscopic Explorer (MUSE) observations in the core of the Hubble Frontier Fields (HFF) galaxy cluster MACSJ1149.5+2223, where the first magnified and spatially resolved multiple images of supernova (SN) "Refsdal" at redshift 1.489 were detected. Thanks to a Director's Discretionary Time program with the Very Large Telescope and the extraordinary efficiency of MUSE, we measure 117 secure redshifts with just 4.8hr of total integration time on a single 1arcmin^2^ target pointing. We spectroscopically confirm 68 galaxy cluster members, with redshift values ranging from 0.5272 to 0.5660, and 18 multiple images belonging to seven background, lensed sources distributed in redshifts between 1.240 and 3.703. Starting from the combination of our catalog with those obtained from extensive spectroscopic and photometric campaigns using the Hubble Space Telescope (HST), we select a sample of 300 (164 spectroscopic and 136 photometric) cluster members, within approximately 500kpc from the brightest cluster galaxy, and a set of 88 reliable multiple images associated with 10 different background source galaxies and 18 distinct knots in the spiral galaxy hosting SN "Refsdal". We exploit this valuable information to build six detailed strong-lensing models, the best of which reproduces the observed positions of the multiple images with an rms offset of only 0.26". We use these models to quantify the statistical and systematic errors on the predicted values of magnification and time delay of the next emerging image of SN "Refsdal". We find that its peak luminosity should occur between 2016 March and June and should be approximately 20% fainter than the dimmest (S4) of the previously detected images but above the detection limit of the planned HST/WFC3 follow-up. We present our two-dimensional reconstruction of the cluster mass density distribution and of the SN "Refsdal" host galaxy surface brightness distribution. We outline the road map toward even better strong-lensing models with a synergetic MUSE and HST effort.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A126
- Title:
- VLT/NaCo Large program I. Sample
- Short Name:
- J/A+A/573/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young, close stars are ideal targets for searching planets using the direct imaging technique. The determination of stellar parameters is crucial for the interpretation of imaging survey results, particularly since the luminosity of substellar objects has a strong dependence on system age. We have conducted a large program with NaCo at the VLT to search for planets and brown dwarfs in wide orbits around 86 stars. A large fraction of the targets observed with NaCo were poorly investigated in the literature. We performed a study to characterize the fundamental properties (age, distance, and mass) of the stars in our sample. To improve target age determinations, we compiled and analyzed a complete set of age diagnostics. We measured spectroscopic parameters and age diagnostics using dedicated observations acquired with FEROS and CORALIE spectrographs at La Silla Observatory. We also made extensive use of archival spectroscopic data and the results that are available in the literature. Additionally, we exploited photometric time-series, which are available in ASAS and Super-WASP archives, to derive a rotational period for a large fraction of our program stars. We provided updated characterization of all the targets observed in the VLT NaCo Large program, a survey designed to probe the occurrence of exoplanets and brown dwarfs in wide orbits. The median distance and age of our program stars are 64pc and 100Myr, respectively. Nearly all the stars have masses between 0.70 and 1.50M_{sun}_, with a median value of 1.01M_{sun}_. The typical metallicity is close to solar with a dispersion that is smaller than that of samples usually observed in radial velocity surveys. Several stars are confirmed or proposed here to be members of close young moving groups. Eight spectroscopic binaries are identified.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A3
- Title:
- VLT/NaCo Large program. IV. Statistical analysis
- Short Name:
- J/A+A/603/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Understanding the formation and evolution of giant planets (>1M_Jup_) at wide orbital separation (>5AU) is one of the goals of direct imaging. Over the past 15 years, many surveys have placed strong constraints on the occurrence rate of wide-orbit giants, mostly based on non-detections, but very few have tried to make a direct link with planet formation theories. In the present work, we combine the results of our previously published VLT/NaCo large program with the results of 12 past imaging surveys to constitute a statistical sample of 199 FGK stars within 100 pc, including three stars with sub-stellar companions. Using Monte Carlo simulations and assuming linear flat distributions for the mass and semi-major axis of planets, we estimate the sub-stellar companion frequency to be within 0.75-5.70% at the 68% confidence level (CL) within 20-300AU and 0.5-75M_Jup_, which is compatible with previously published results. We also compare our results with the predictions of state-of-the-art population synthesis models based on the gravitational instability (GI) formation scenario with and without scattering. We estimate that in both the scattered and non-scattered populations, we would be able to detect more than 30% of companions in the 1-75M_Jup_ range (95% CL). With the three sub-stellar detections in our sample, we estimate the fraction of stars that host a planetary system formed by GI to be within 1.0-8.6% (95% CL). We also conclude that even though GI is not common, it predicts a mass distribution of wide-orbit massive companions that is much closer to what is observed than what the core accretion scenario predicts. Finally, we associate the present paper with the release of the Direct Imaging Virtual Archive (DIVA), a public database that aims at gathering the results of past, present, and future direct imaging surveys.
15527. VLTS. B stars multiplicity
- ID:
- ivo://CDS.VizieR/J/A+A/580/A93
- Title:
- VLTS. B stars multiplicity
- Short Name:
- J/A+A/580/A93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the multiplicity properties of 408 B-type stars observed in the 30 Doradus region of the Large Magellanic Cloud with multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS). We use a cross-correlation method to estimate relative radial velocities from the helium and metal absorption lines for each of our targets. Objects with significant radial-velocity variations (and with an amplitude larger than 16km/s) are classified as spectroscopic binaries. We find an observed spectroscopic binary fraction (defined by periods of <10^3.5^d and mass ratios >0.1) for the B-type stars, f_B_(obs)=0.25+/-0.02, which appears constant across the field of view, except for the two older clusters (Hodge 301 and SL 639). These two clusters have significantly lower binary fractions of 0.08+/-0.08 and 0.10+/-0.09, respectively. Using synthetic populations and a model of our observed epochs and their potential biases, we constrain the intrinsic multiplicity properties of the dwarf and giant (i.e. relatively unevolved) B-type stars in 30 Dor. We obtain a present-day binary fraction f_B_(true)=0.58+/-0.11, with a flat period distribution. Within the uncertainties, the multiplicity properties of the B-type stars agree with those for the O stars in 30 Dor from the VFTS.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A91
- Title:
- VLTS. B-type main-sequence binary systems
- Short Name:
- J/A+A/603/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A spectroscopic analysis has been undertaken for the B-type multiple systems (excluding those with supergiant primaries) in the VLT-FLAMES Tarantula Survey (VFTS). Projected rotational velocities, vsini, for the primaries have been estimated using a Fourier Transform technique and confirmed by fitting rotationally broadened profiles. A subset of 33 systems with vsini<=80km/s have been analysed using a TLUSTY grid of model atmospheres to estimate stellar parameters and surface abundances for the primaries. The effects of a potential flux contribution from an unseen secondary have also been considered. For 20 targets it was possible to reliably estimate their effective temperatures (Teff) but for the other 13 objects it was only possible to provide a constraint of 20000<=Teff<=26000K - the other parameters estimated for these targets will be consequently less reliable. The estimated stellar properties are compared with evolutionary models and are generally consistent with their membership of 30 Doradus, while the nature of the secondaries of 3 SB2 system is discussed. A comparison with a sample of single stars with vsini<=80km/s obtained from the VFTS and analysed with the same techniques implies that the atmospheric parameters and nitrogen abundances of the two samples are similar. However, the binary sample may have a lack of primaries with significant nitrogen enhancements, which would be consistent with them having low rotational velocities and having effectively evolved as single stars without significant rotational mixing. This result, which may be actually a consequence of the limitations of the pathfinder investigation presented in this paper, should be considered as a motivation for spectroscopic abundance analysis of large samples of binary stars, with high quality observational data.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A81
- Title:
- VLTS. 30Dor O giants and supergiants
- Short Name:
- J/A+A/600/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Tarantula region in the Large Magellanic Cloud contains the richest population of spatially resolved massive O-type stars known so far. This unmatched sample offers an opportunity to test models describing their main-sequence evolution and mass-loss properties. Using ground-based optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to determine stellar, photospheric and wind properties of 72 presumably single O-type giants, bright giants and supergiants and to confront them with predictions of stellar evolution and of line-driven mass-loss theories. We apply an automated method for quantitative spectroscopic analysis of O stars combining the non-LTE stellar atmosphere model FASTWIND with the genetic fitting algorithm PIKAIA to determine the following stellar properties: effective temperature, surface gravity, mass-loss rate, helium abundance, and projected rotational velocity. The latter has been constrained without taking into account the contribution from macro-turbulent motions to the line broadening. We present empirical effective temperature versus spectral subtype calibrations at LMC-metallicity for giants and supergiants. The calibration for giants shows a +1kK offset compared to similar Galactic calibrations; a shift of the same magnitude has been reported for dwarfs. The supergiant calibrations, though only based on a handful of stars, do not seem to indicate such an offset. The presence of a strong upturn at spectral type O3 and earlier can also not be confirmed by our data. In the spectroscopic and classical Hertzsprung-Russell diagrams, our sample O stars are found to occupy the region predicted to be the core hydrogen-burning phase by state-of-the-art models. For stars initially more massive than approximately 60M_{sun}_ the giant phase already appears relatively early on in the evolution; the supergiant phase develops later. Bright giants, however, are not systematically positioned between giants and supergiants at M_init_>25M_{sun}. At masses below 60M_{sun} the dwarf phase clearly precedes the giant and supergiant phases; however this behavior seems to break down at $M_init_<18M_{sun}_. Here, stars classified as late O III and II stars occupy the region where O9.5-9.7V stars are expected, but where few such late O V stars are actually seen. Though we can not exclude that these stars represent a physically distinct group, this behaviour may reflect an intricacy in the luminosity classification at late O spectral subtype. Indeed, on the basis of a secondary classification criterion, the relative strength of SiIV to HeI absorption lines, these stars would have been assigned a luminosity class IV or V. Except for five stars, the helium abundance of our sample stars is in agreement with the initial LMC composition. This outcome is independent of their projected spin rates. The aforementioned five stars present moderate projected rotational velocities (i.e., vrot<200km/s) and hence do not agree with current predictions of rotational mixing in main-sequence stars. They may potentially reveal other physics not included in the models such as binary-interaction effects. Adopting theoretical results for the wind velocity law, we find modified wind momenta for LMC stars that are ~0.3dex higher than earlier results. For stars brighter than 10^5^L_[sun}_, that is, in the regime of strong stellar winds, the measured (unclumped) mass-loss rates could be considered to be in agreement with line-driven wind predictions if the clump volume filling factors were f_V_~1/8 to 1/6.
- ID:
- ivo://CDS.VizieR/J/AJ/153/115
- Title:
- VLT/SINFONI observations of MIPSGAL "bubbles"
- Short Name:
- J/AJ/153/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Very Large Telescope/Spectrograph for INtegral Field Observations in the Near Infrared H- and K-band spectra of potential central stars within the inner 8"-by-8" regions of 55 MIPSGAL "bubbles" (MBs), sub-arcminute circumstellar shells discovered in the mid-IR survey of the Galactic plane with Spitzer/MIPS. At magnitudes brighter than 15, we detect a total of 230 stars in the K band and 179 stars in the H band. We spectrally identify 145 stars in all but three MBs, with average magnitudes of 13.8 and 12.7 respectively, using spectral libraries and previous studies of near-IR stellar spectra. We also use tabulated intrinsic stellar magnitudes and colors to derive distances and extinction values, and to better constrain the classifications of the stars. We reliably identify the central sources for 21 of the 55 MBs, which we classify as follows: one Wolf-Rayet, three luminous blue variable candidates, four early-type (O to F), and 15 late-type (G to M) stars. The 21 central sources are, on average, one magnitude fainter than these in the most recent study of MBs, and we notice a significant drop in the fraction of massive star candidates. For the 34 remaining MBs in our sample, we are unable to identify the central sources due to confusion, low spectroscopic signal-to-noise ratio, and/or lack of detections in the images near the centers of the bubbles. We discuss how our findings compare with previous studies and support the trend, for the most part, between the shells' morphologies in the mid-IR and central sources spectral types.
