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- ID:
- ivo://CDS.VizieR/J/A+A/462/123
- Title:
- VLT/Flames spectroscopic data of NGC 6530
- Short Name:
- J/A+A/462/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mechanisms regulating the evolution of pre-main sequence stars can be understood by studying stellar properties such as rotation, disk accretion, internal mixing and binarity. To investigate such properties, we studied a sample of 332 candidate members of the massive and populous star forming region NGC 6530. We want to select cluster members by using different membership criteria, to study the properties of pre-main sequence stars with or without circumstellar disks. We use intermediate resolution spectra including the LiI6707.8{AA} line to derive radial and rotational velocities, binarity and to measure the Equivalent Width of the lithium line; these results are combined with X-ray data to study the cluster membership. Optical-IR data and H{alpha} spectra, these latter available for a subsample of our targets, are used to classify CTTS and WTTS and to compare the properties of stars with and without disks. We find a total of 237 certain members including 53 binaries. The rotational velocity distributions of stars with IR excesses are statistically different from that of stars without IR excesses, while the fraction of binaries with disks is significantly smaller than that of single stars. Stars with evidence for accretion show circumstellar disks; youth of cluster members is confirmed by the lithium abundance consistent with the initial content. As indicated by the disk-locking picture, stars with disks have in general rotational velocities lower than stars without disks. Binaries in NGC 6530 seem have undergone a significant disk evolution.
- 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/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/568/L8
- Title:
- VUDS extreme emission line 0.2<~z<~0.9 galaxies
- Short Name:
- J/A+A/568/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 31 low-luminosity (-14.5>~M_AB_(B)>~-18.8), extreme emission line galaxies (EELGs) at 0.2<~z<~0.9 identified by their unusually high rest-frame equivalent widths (100<=EW[OIII]<=1700{AA}) as part of the VIMOS Ultra Deep Survey (VUDS). VIMOS optical spectra of unprecedented sensitivity (I_AB_~25mag) along with multiwavelength photometry and HST imaging are used to investigate spectrophotometric properties of this unique sample and to explore, for the first time, the very low stellar mass end (M_*_<~10^8^M_{sun}_) of the luminosity-metallicity (LZR) and mass-metallicity (MZR) relations at z<1. Characterized by their extreme compactness (R_50_<1kpc), low stellar mass and enhanced specific star formation rates (sSFR=SFR/M_*_~10^-9^-10^-7^yr^-1^), the VUDS EELGs are blue dwarf galaxies likely experiencing the first stages of a vigorous galaxy-wide starburst. Using Te-sensitive direct and strong-line methods, we find that VUDS EELGs are low-metallicity (7.5<~12+log(O/H)<~8.3) galaxies with high ionization conditions (log(q_ion_)>~8cm/s), including at least three EELGs showing HeII{lambda}4686{AA} emission and four extremely metal-poor (<~10% solar) galaxies. The LZR and MZR followed by VUDS EELGs show relatively large scatter, being broadly consistent with the extrapolation toward low luminosity and mass from previous studies at similar redshift. However, we find evidence that galaxies with younger and more vigorous star formation --as characterized by their larger EWs, ionization and sSFR-- tend to be more metal poor at a given stellar mass.
1998. Warm IRAS sources. II.
- ID:
- ivo://CDS.VizieR/J/A+AS/96/389
- Title:
- Warm IRAS sources. II.
- Short Name:
- J/A+AS/96/389
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical spectra for a sample of 563 high-latitude IRAS sources selected from the Point Source Catalog to have relatively warm 25 to 60 micron colours. We have shown this selection criterion to be an efficient indicator for finding Seyfert galaxies. Plots of the optical spectra are shown and the fluxes of the strongest emission lines in these spectra are tabulated. After excluding 128 sources which are clearly galactic foreground objects, we obtained spectroscopic information for 358 extragalactic objects. Emission-line ratios have been used to classify these objects, resulting in 80 Seyfert 1, 141 Seyfert 2 and 133 HII-type objects. In comparison with samples of active nuclei selected in other ways, about 50% of known Seyfert nuclei are included by our colour criteria. This fraction is larger for high luminosities, reaching 80% for quasar luminosities. For lower-luminosity objects, contamination by the host galaxies becomes important and the sample becomes seriously incomplete. It should be moderately complete and representative for core luminosities greater than 10^23.5^W/Hz at 12m. Finally, the infrared luminosity function for each type of object is derived; the shapes for Seyfert 1 and 2 nuclei are identical, with a type 2/type 1 space-density ratio of 3.0. Our census is consistent with an obscuration scheme for producing both types of object from a single parent population, though the origin of excess cool IR radiation Irom many Seyferts is still unclear. We note the appearance of an apparent type II supernova in IRAS 0225-103 observed in 1985 September. Its spectrum suggests that it was observed between 1 and 2 months after maximum, perhaps in a "plateau" phase.
- ID:
- ivo://CDS.VizieR/J/AJ/156/295
- Title:
- Warm molecular hydrogen in nearby LIRGs
- Short Name:
- J/AJ/156/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mid-infrared molecular hydrogen (H_2_) emission is a powerful cooling agent in galaxy mergers and in radio galaxies; it is a potential key tracer of gas evolution and energy dissipation associated with mergers, star formation, and accretion onto supermassive black holes. We detect mid-IR H_2_ line emission in at least one rotational transition in 91% of the 214 Luminous Infrared Galaxies (LIRGs) observed with Spitzer as part of the Great Observatories All-sky LIRG Survey. We use H_2_ excitation diagrams to estimate the range of masses and temperatures of warm molecular gas in these galaxies. We find that LIRGs in which the IR emission originates mostly from the Active Galactic Nuclei (AGN) have about 100 K higher H_2_ mass-averaged excitation temperatures than LIRGs in which the IR emission originates mostly from star formation. Between 10% and 15% of LIRGs have H_2_ emission lines that are sufficiently broad to be resolved or partially resolved by the high-resolution modules of Spitzer's Infrared Spectrograph (IRS). Those sources tend to be mergers and contain AGN. This suggests that a significant fraction of the H_2_ line emission is powered by AGN activity through X-rays, cosmic rays, and turbulence. We find a statistically significant correlation between the kinetic energy in the H_2_ gas and the H_2_ to IR luminosity ratio. The sources with the largest warm gas kinetic energies are mergers. We speculate that mergers increase the production of bulk inflows leading to observable broad H_2_ profiles and possibly denser gas.
- ID:
- ivo://CDS.VizieR/J/ApJ/669/959
- Title:
- Warm molecular hydrogen in SINGS galaxy sample
- Short Name:
- J/ApJ/669/959
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results on the properties of warm molecular hydrogen in 57 normal galaxies are derived from measurements of H_2_ rotational transitions, obtained as part of SINGS. This study extends previous extragalactic surveys of emission lines of H_2_ to fainter and more common systems (LFIR = 10^7^-6x10^10^L_{sun}_). The 17um S(1) transition is securely detected in the nuclear regions of 86% of galaxies with stellar masses above 10^9.5^M_{sun}_.
