- ID:
- ivo://CDS.VizieR/J/A+A/603/A81
- Title:
- Trumpler 14 and 16 in the Carina nebula
- Short Name:
- J/A+A/603/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first extensive spectroscopic study of the global population in star clusters Trumpler 16, Trumpler 14, and Collinder 232 in the Carina nebula, using data from the Gaia-ESO Survey, down to solar-mass stars. In addition to the standard homogeneous survey data reduction, a special processing was applied here because of the bright nebulosity surrounding Carina stars. We find about 400 good candidate members ranging from OB types down to slightly subsolar masses. About 100 heavily reddened early-type Carina members found here were previously unrecognized or poorly classified, including two candidate O stars and several candidate Herbig Ae/Be stars. Their large brightness makes them useful tracers of the obscured Carina population. The spectroscopically derived temperatures for nearly 300 low-mass members enables the inference of individual extinction values and the study of the relative placement of stars along the line of sight. We find a complex spatial structure with definite clustering of low-mass members around the most massive stars and spatially variable extinction. By combining the new data with existing X-ray data, we obtain a more complete picture of the three-dimensional spatial structure of the Carina clusters and of their connection to bright and dark nebulosity and UV sources. The identification of tens of background giants also enables us to determine the total optical depth of the Carina nebula along many sightlines. We are also able to put constraints on the star formation history of the region with Trumpler 14 stars found to be systematically younger than stars in other subclusters. We find a large percentage of fast-rotating stars among Carina solar-mass members, which provide new constraints on the rotational evolution of pre-main-sequence stars in this mass range.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/1783
- Title:
- 33 T Tauri stars in Taurus Halpha measurements
- Short Name:
- J/MNRAS/469/1783
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a 12-month monitoring campaign of 33 T Tauri stars (TTS) in Taurus. Our goal was to monitor objects that possess a disc but have a weak H{alpha} line, a common accretion tracer for young stars, in order to determine whether they host a passive circumstellar disc. We used medium-resolution optical spectroscopy to assess the accretion status of the objects and to measure the H{alpha} line. We found no convincing examples of passive discs: only transition disc and debris disc systems in our sample are non-accreting. Among accretors, we found no example of flickering accretion, leading to an upper limit of 2.2 per cent on the duty cycle of accretion gaps, assuming that all accreting TTS experience such events. When combining literature results with our observations, we found that the reliability of traditional H{alpha}-based criteria to test for accretion is high but imperfect, particularly for low-mass TTS. We found a significant correlation between stellar mass and the full width at 10 per cent of the peak (W_10_) of the H{alpha} line that does not seem to be related to variations in free-fall velocity. Finally, our data revealed a positive correlation between the H{alpha} equivalent width and its W_10_, indicative of a systematic modulation in the line profile whereby the high-velocity wings of the line are proportionally more enhanced than its core when the line luminosity increases. We argue that this supports the hypothesis that the mass accretion rate on the central star is correlated with the H{alpha} W_10_ through a common physical mechanism.
- ID:
- ivo://CDS.VizieR/VI/107
- Title:
- Tubingen Ultraviolet Echelle Spectrometer
- Short Name:
- VI/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Tubingen Echelle Spectrograph (TUES), designed and managed at the University of Tubingen, flew on the Orbiting and Retrievable Far and Extreme Ultraviolet Spectrograph (ORFEUS)-SPAS II space shuttle mission in 1996, returning spectra in the 900 Angstrom to 1400 Angstrom wavelength range. The instrument was designed to achieve a spectral resolution of 10000 when used with an entrance aperture of 10" diameter. During the 17.7 day flight, TUES returned 239 spectra of 62 targets.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A49
- Title:
- TW Hya CO (2-1), CN (2-1) and CS (5-4) data cubes
- Short Name:
- J/A+A/592/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to obtain a spatially resolved measurement of velocity dispersions in the disk of TW Hya. We obtained images with high spatial and spectral resolution of the CO J=2-1, CN N=2-1 and CS J=5-4 emission with ALMA in Cycle 2. The radial distribution of the turbulent broadening was derived with two direct methods and one modelling approach. The first method requires a single transition and derives T_ex_ directly from the line profile, yielding a v_turb_. The second method assumes that two different molecules are co-spatial, which allows using their relative line widths for calculating T_kin_ and v_turb_. Finally we fitted a parametric disk model in which the physical properties of the disk are described by power laws, to compare our direct methods with previous values.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A46
- Title:
- TW Hydrae association with X-shooter
- Short Name:
- J/A+A/632/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Measurements of the protoplanetary disk frequency in young star clusters of different ages indicate disk lifetimes <10Myr. However, our current knowledge of how mass accretion in young stars evolves over the lifespans of disks is subject to many uncertainties, especially at the lower stellar masses. In this study, we investigate ongoing accretion activity in the TW Hydrae association (TWA), the closest association of pre-main sequence stars with active disks. The age (8-10Myr) and the proximity of the TWA render it an ideal target to probe the final stages of disk accretion down to brown dwarf masses. The study is based on homogeneous spectroscopic data from 300nm to 2500nm, obtained synoptically with X-shooter, which allows simultaneous derivation of individual extinction, stellar parameters, and accretion parameters for each star. The continuum excess emission diagnostics is used to estimate the accretion luminosities and mass accretion rates of our disk-bearing targets, and the shape and intensity of permitted and forbidden emission lines are analyzed to probe the physics of the star-disk interaction environment.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/836
- Title:
- Type 1 AGN at low z. III.
- Short Name:
- J/MNRAS/431/836
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the optical narrow-line ratios in a Sloan Digital Sky Survey (SDSS) based sample of 3175 broad H{alpha} selected type 1 active galactic nuclei (AGN), and explore their positions in the BPT diagrams as a function of the AGN and the host properties. We find the following: (1) the luminosities of all measured narrow lines (H{alpha}, H{beta}, [OIII], [NII], [SII], [OI]) show a Baldwin relation relative to the broad H{alpha} luminosity LbH{alpha}, with slopes in the range of 0.53-0.72. (2) About 20 percent of the type 1 AGN reside within the "Composite" and "star-forming" (SF) regions of the Baldwin, Phillips & Terlevich (BPT) diagrams. These objects also show excess narrow H{alpha} and ultraviolet (UV) luminosities, for their LbH{alpha}, consistent with contribution from star formation which dominates the narrow-lines emission, as expected from their positions in the BPT diagrams. (3) The type 1 which reside within the AGN region in the BPT diagrams, are offset to lower [SII]/H{alpha} and [NII]/H{alpha} luminosity ratios, compared to type 2 AGN. This offset is a selection effect, related to the lower AGN/host luminosity selection of the type 2 AGN selected from the SDSS galaxy sample. (4) The [NII]/H{alpha} and [NII]/[SII] ratios in type 1 AGN increase with the host mass, as expected if the mass-metallicity relation of quiescent galaxies holds for the AGN narrow-line region (NLR). (5) The broad lines optical Fe ii is higher for a higher [NII]/H{alpha}, at a fixed Lbol and Eddington ratio L/LEdd. This suggests that the broad line region metallicity is also related to the host mass. (6) The fraction of AGN which are low-ionization nuclear emission-line regions (LINERs) increases sharply with decreasing L/LEdd. This fraction is the same for type 1 and type 2 AGN. (7) The BPT position is unaffected by the amount of dust extinction of the optical-UV continuum, which suggests that the extincting dust resides on scales larger than the narrow-line region (NLR).
- ID:
- ivo://CDS.VizieR/J/ApJ/708/427
- Title:
- Type 2 AGNs with double-peaked [OIII] lines
- Short Name:
- J/ApJ/708/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 167 type 2 active galactic nuclei (AGNs) with double-peaked [OIII]4959,5007 narrow emission lines, selected from the Seventh Data Release of the Sloan Digital Sky Survey. The double-peaked profiles can be well modeled by two velocity components, blueshifted and redshifted from the systemic velocity. Half of these objects have a more prominent redshifted component. In cases where the H{beta} emission line is strong, it also shows two velocity components whose line-of-sight (LOS) velocity offsets are consistent with those of [OIII]. The relative LOS velocity offset between the two components is typically a few hundred km/s, larger by a factor of ~1.5 than the line full width at half maximum of each component. The offset correlates with the host stellar velocity dispersion {sigma}_*_. The host galaxies of this sample show systematically larger {sigma}_*_, stellar masses, and concentrations, and older luminosity-weighted mean stellar ages than a regular type 2 AGN sample matched in redshift, [OIII]5007 equivalent width, and luminosity; they show no significant difference in radio properties. These double-peaked features could be due to narrow-line region kinematics, or binary black holes.
- ID:
- ivo://CDS.VizieR/J/ApJ/773/53
- Title:
- Type Ia SNe spectroscopy by the CSP
- Short Name:
- J/ApJ/773/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first release of optical spectroscopic data of low-redshift Type Ia supernovae (SNe Ia) by the Carnegie Supernova Project including 604 previously unpublished spectra of 93 SNe Ia. The observations cover a range of phases from 12 days before to over 150 days after the time of B-band maximum light. With the addition of 228 near-maximum spectra from the literature, we study the diversity among SNe Ia in a quantitative manner. For that purpose, spectroscopic parameters are employed such as expansion velocities from spectral line blueshifts and pseudo-equivalent widths (pW). The values of those parameters at maximum light are obtained for 78 objects, thus providing a characterization of SNe Ia that may help to improve our understanding of the properties of the exploding systems and the thermonuclear flame propagation. Two objects, namely, SNe 2005M and 2006is, stand out from the sample by showing peculiar Si II and S II velocities but otherwise standard velocities for the rest of the ions. We further study the correlations between spectroscopic and photometric parameters such as light-curve decline rate and color. In agreement with previous studies, we find that the pW of Si II absorption features are very good indicators of light-curve decline rate. Furthermore, we demonstrate that parameters such as pW2 (Si II 4130) and pW6 (Si II 5972) provide precise calibrations of the peak B-band luminosity with dispersions of {approx}0.15mag. In the search for a secondary parameter in the calibration of peak luminosity for SNe Ia, we find a {approx}2{sigma}-3{sigma} correlation between B-band Hubble residuals and the velocity at maximum light of S II and Si II lines.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1648
- Title:
- Type Ia supernovae at high and low redshifts
- Short Name:
- J/AJ/131/1648
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using archival data of low-redshift (z<0.01; Center for Astrophysics and SUSPECT databases) Type Ia supernovae (SNe Ia) and recent observations of high-redshift (0.16<z<0.64) SNe Ia, we study the "uniformity" of the spectroscopic properties of nearby and distant SNe Ia. We find no difference in the measurements we describe here. In this paper we base our analysis solely on line-profile morphology, focusing on measurements of the velocity location of maximum absorption (v_abs_) and peak emission (v_peak_).
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/1973
- Title:
- Type Ia supernovae igh-velocity features
- Short Name:
- J/MNRAS/451/1973
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 'High-velocity features' (HVFs) are spectral features in Type Ia supernovae (SNe Ia) that have minima indicating significantly higher (by greater than about 6000km/s) velocities than typical 'photospheric-velocity features' (PVFs). The PVFs are absorption features with minima indicating typical photospheric (i.e. bulk ejecta) velocities (usually~9000-15000km/s near B-band maximum brightness). In this work, we undertake the most in-depth study of HVFs ever performed. The data set used herein consists of 445 low-resolution optical and near-infrared (NIR) spectra (at epochs up to 5d past maximum brightness) of 210 low-redshift SNe Ia that follow the 'Phillips relation'. A series of Gaussian functions is fit to the data in order to characterize possible HVFs of CaII H&K, SiII {lambda}6355, and the CaII NIR triplet. The temporal evolution of the velocities and strengths of the PVFs and HVFs of these three spectral features is investigated, as are possible correlations with other SN Ia observables. We find that while HVFs of CaII are regularly observed (except in underluminous SNe Ia, where they are never found), HVFs of Siii {lambda}6355 are significantly rarer, and they tend to exist at the earliest epochs and mostly in objects with large photospheric velocities. It is also shown that stronger HVFs of SiII {lambda}6355 are found in objects that lack CII absorption at early times and that have red ultraviolet/optical colours near maximum brightness. These results lead to a self-consistent connection between the presence and strength of HVFs of SiII {lambda}6355 and many other mutually correlated SN Ia observables, including photospheric velocity.
