- 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.
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Search Results
- 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/A+A/421/539
- Title:
- VLT spectroscopy of Tol 1214-277 & Tol 65
- Short Name:
- J/A+A/421/539
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present VLT spectroscopic observations with different spectral resolutions and different slit orientations of the two metal-deficient blue compact dwarf (BCD) galaxies Tol 1214-277 and Tol 65. The oxygen abundances in the brightest HII regions of Tol 1214-277 and Tol 65 are found to be 12+logO/H=7.55+/-0.01 and 7.54+/-0.01, or Z_{sun}_/24. The nitrogen-to-oxygen abundance ratios in the two galaxies are logN/O=-1.64+/-0.03 and -1.60+/-0.02 and lie in the narrow range found for other most metal-deficient BCDs. The helium mass fraction derived in several HII regions in both galaxies is consistent with a high primordial helium mass fraction, Yp~0.244. We confirm the detection of the high-ionization forbidden emission line [FeV]4227 in the spectrum of Tol 1214-277. Additionally, weak [NeIV]4725, [FeVI]5146,5177, and [FeVII]5721,6087 emission lines are detected in the high-resolution spectrum of Tol 1214-277. The detection of these lines implies the presence of hard radiation with photon energy in the range ~4-8Ryd. Emission lines are detected in the spectra of eight galaxies in the fields of Tol 1214-277 and Tol 65. Seven of these galaxies are background objects, while one galaxy has a redshift close to that of Tol 1214-277. Situated at a projected distance of ~14.5kpc from Tol 1214-277, this galaxy is probably a companion of the BCD.
- 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/A+A/532/A138
- Title:
- V838 Mon spectrum in 2009
- Short Name:
- J/A+A/532/A138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- V838 Mon erupted at the beginning of 2002. In the course of the outburst the object evolved to low effective temperatures and declined as a very late M-type supergiant. Among various scenarios proposed to explain the nature of the outburst, the most promising is a stellar merger event. We aim at studying the structure and evolution of the object in the decline from the 2002 eruption. We obtained spectroscopic observations of V838 Mon in January-March 2009 with UVES/VLT. The results are analysed and compared with similar observations obtained in October 2005 with HIRES/Keck. The most striking difference between 2009 and 2005 is a complete absence of the B3 V component and of the [FeII] emission lines in 2009. The present spectrum displays only the spectrum of the 2002 eruption remnant. It resembles that of an ~M6 giant, although the molecular bands in V838 Mon are deeper than those in standard stellar spectra of a similar spectral class. Several atomic lines, which displayed P-Cyg profiles in 2005, are now dominated by pure absorptions. Some of these lines, however, show a narrow emission component, which, as we argue, measures the radial velocity of V838 Mon. The resulting heliocentric velocity is 71km/s, which very well agrees with the velocity obtained from SiO maser observations. The atomic lines and the molecular bands show very complex kinematics. In some atomic lines and high-excitation molecular bands we observe matter infalling in the object atmosphere. The infall components were already observed in 2005, but were less pronounced and present in fewer lines than in 2009. We argue that the most negative radial velocity components seen in the resonance atomic lines and in the low-excitation molecular bands were formed in the ejecta of the 2002 eruption. The B3V companion most probably became engulfed in an opaque dusty matter of the 2002 V838 Mon ejecta.
- ID:
- ivo://CDS.VizieR/J/ApJ/889/148
- Title:
- V346 Nor IJHKs photometry & IR spectra
- Short Name:
- J/ApJ/889/148
- Date:
- 17 Jan 2022 11:51:03
- Publisher:
- CDS
- Description:
- FU Orionis-type objects (FUors) are young low-mass stars undergoing powerful accretion outbursts. The increased accretion is often accompanied by collimated jets and energetic, large-scale molecular outflows. The extra heating during the outburst may also induce detectable geometrical, chemical, and mineralogical changes in the circumstellar material, affecting possible planet formation around these objects. V346 Nor is a southern FUor with peculiar spectral characteristics. Decades after the beginning of its outburst, it unexpectedly underwent a fading event around 2010 due to a decrease in the mass accretion rate onto the star by at least two orders of magnitude. Here we present optical and near-infrared photometry and spectroscopy obtained after the minimum. Our light curves show a gradual re-brightening of V346 Nor, with its Ks-band brightness only 1.5mag below the outburst brightness level. Our Very Large Telescope (VLT)/XSHOOTER spectroscopic observations display several strong forbidden emission lines toward the source from various metals and molecular hydrogen, suggesting the launch of a new jet. Our N-band spectrum obtained with VLT/VISIR outlines a deeper silicate absorption feature than before, indicating that the geometry of the circumstellar medium has changed in the post-outburst period compared to peak brightness.
- ID:
- ivo://CDS.VizieR/J/A+AS/136/95
- Title:
- V380 Ori emission line spectrum
- Short Name:
- J/A+AS/136/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 3 presents the emission line spectrum of V380 Ori in the optical region observed at OHP in January 1995 with a mean resolution of 10000. For the line blends the wavelength and flux (not reddening corrected) of each contributor are given. For the P-Cygni profiles the equivalent widths of the absorption component are also reported. We estimate an error of less than 10% for the strongest lines, 10% to 40% for the weakest lines.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A135
- Title:
- V646 Pup TESS and ground photometry and spectrum
- Short Name:
- J/A+A/644/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate small-scale light variations in V646 Pup occurring in the timescales of days, weeks and years. To check if this variability is similar to that observed in FU Ori. We observed V646 Pup on six occasions at the SAAO and CTIO during 2013-2018 in Johnson and Sloan filters, typically with 1 d cadence maintained for 2-4 weeks. We also utilise the public-domain 1512 day long ASAS-SN light curve and TESS photometry obtained in 2019 during 24.1 days with 30 min cadence. New SAAO low-resolution spectra help to update major disc parameters, while the archival high-resolution Keck spectra are used to search for temporal changes in the disc rotational profiles. The ground-based observations confirm the constantly decreasing brightness of V646 Pup at the rate of 0.018mag per year. Precise i-band sensitive TESS data show that the little 0.005-0.01mag light variations imposed on this general trend do consist of a few independent wave trains of apparently time-coherent nature. Assuming that this is typical situation, from analysis of colour-magnitude diagrams obtained on earlier epochs we preliminarily inferred that the bulk of observed light changes could be owing to rotation of disc photosphere inhomogeneities, arising between 10-12 solar radii from the star. It is not excluded that these inhomogeneities could also manifest themselves in rotational profiles of the disc, as obtained from the high-resolution spectra. Assuming Keplerian rotation of these inhomogeneities, we preliminarily determine the stellar mass at 0.7-0.9 solar masses. At least during certain weeks V646 Pup shows time-coherent light variability pattern(s) that could be explained by rotation of an inhomogeneous disc photosphere. These preliminary results are similar to those better established for FU Ori, what suggests a common driving mechanism(s).
