- ID:
- ivo://CDS.VizieR/J/A+A/618/A102
- Title:
- GES N/O abundance ratio in the Milky Way
- Short Name:
- J/A+A/618/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The abundance ratio N/O is a useful tool to study the interplay of galactic processes, for example star formation efficiency, timescale of infall, and outflow loading factor. We aim to trace log(N/O) versus [Fe/H] in the Milky Way and to compare this ratio with a set of chemical evolution models to understand the role of infall, outflow, and star formation efficiency in the building up of the Galactic disc. We used the abundances from idr2-3, idr4, idr5 data releases of the Gaia-ESO Survey both for Galactic field and open cluster stars. We determined membership and average composition of open clusters and we separated thin and thick disc field stars. We considered the effect of mixing in the abundance of N in giant stars. We computed a grid of chemical evolution models, suited to reproduce the main features of our Galaxy, exploring the effects of the star formation efficiency, infall timescale, and differential outflow. With our samples, we map the metallicity range -0.6<=[Fe/H]<=0.3 with a corresponding -1.2<=log(N/O)<=-0.2, where the secondary production of N dominates. Thanks to the wide range of Galactocentric distances covered by our samples, we can distinguish the behaviour of log(N/O) in different parts of the Galaxy. Our spatially resolved results allow us to distinguish differences in the evolution of N/O with Galactocentric radius. Comparing the data with our models, we can characterise the radial regions of our Galaxy. A shorter infall timescale is needed in the inner regions, while the outer regions need a longer infall timescale, coupled with a higher star formation efficiency. We compare our results with nebular abundances obtained in MaNGA galaxies, finding in our Galaxy a much wider range of log(N/O) than in integrated observations of external galaxies of similar stellar mass, but similar to the ranges found in studies of individual HII regions.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/601/A70
- Title:
- GES: pre-main-sequence clusters [Fe/H]
- Short Name:
- J/A+A/601/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The radial metallicity distribution in the Galactic thin disc represents a crucial constraint for modelling disc formation and evolution. Open clusters allow us to derive both the radial metallicity distribution and its evolution over time. In this paper we perform the first investigation of the present-day radial metallicity distribution based on [Fe/H] determinations in late type members of pre-main-sequence clusters. Because of their youth, these clusters are therefore essential for tracing the current inter-stellar medium metallicity. We used the products of the Gaia-ESO Survey analysis of 12 young regions (age<100Myr), covering Galactocentric distances from 6.67 to 8.70kpc. For the first time, we derived the metal content of star forming regions farther than 500pc from the Sun. Median metallicities were determined through samples of reliable cluster members. For ten clusters the membership analysis is discussed in the present paper, while for other two clusters (Chamaeleon I and Gamma Velorum) we adopted the members identified in our previous works. All the pre-main-sequence clusters considered in this paper have close-to-solar or slightly sub-solar metallicities. The radial metallicity distribution traced by these clusters is almost flat, with the innermost star forming regions having [Fe/H] values that are 0.10-0.15dex lower than the majority of the older clusters located at similar Galactocentric radii. This homogeneous study of the present-day radial metallicity distribution in the Galactic thin disc favours models that predict a flattening of the radial gradient over time. On the other hand, the decrease of the average [Fe/H] at young ages is not easily explained by the models. Our results reveal a complex interplay of several processes (e.g. star formation activity, initial mass function, supernova yields, gas flows) that controlled the recent evolution of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A55
- Title:
- Ge V and Ge VI oscillator strengths
- Short Name:
- J/A+A/546/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- State-of-the-art spectral analysis of hot stars by means of non-LTE model-atmosphere techniques has arrived at a high level of sophistication. The analysis of high-resolution and high-S/N spectra, however, is strongly restricted by the lack of reliable atomic data for highly ionized species from intermediate-mass metals to trans-iron elements. Especially data for the latter has only been sparsely calculated. Many of their lines are identified in spectra of extremely hot, hydrogen-deficient post-AGB stars. A reliable determination of their abundances establishes crucial constraints for AGB nucleosynthesis simulations and, thus, for stellar evolutionary theory. In a previous analysis of the UV spectrum of RE 0503-289, spectral lines of highly ionized Ga, Ge, As, Se, Kr, Mo, Sn, Te, I, and Xe were identified. Individual abundance determinations are hampered by the lack of reliable oscillator strengths. Most of these identified lines stem from Ge V. In addition, we identified Ge VI lines for the first time. We calculated Ge V and Ge VI oscillator strengths in order to reproduce the observed spectrum.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/82
- Title:
- GeV gamma-ray bursts with the ARGO-YBJ detector
- Short Name:
- J/ApJ/794/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The search for gamma-ray burst (GRB) emission in the energy range of 1-100 GeV in coincidence with the satellite detection has been carried out using the Astrophysical Radiation with Ground-based Observatory at YangBaJing (ARGO-YBJ) experiment. The high-altitude location (4300 m a.s.l.), the large active surface (~6700 m^2^ of Resistive Plate Chambers), the wide field of view (~2 sr, limited only by the atmospheric absorption), and the high duty cycle (>86%) make the ARGO-YBJ experiment particularly suitable to detect short and unexpected events like GRBs. With the scaler mode technique, i.e., counting all the particles hitting the detector with no measurement of the primary energy and arrival direction, the minimum threshold of ~1 GeV can be reached, overlapping the direct measurements carried out by satellites. During the experiment lifetime from 2004 December 17 to 2013 February 7, a total of 206 GRBs occurring within the ARGO-YBJ field of view (zenith angle {theta}<=45{deg}) have been analyzed. This is the largest sample of GRBs investigated with a ground-based detector. Two light curve models have been assumed and since in both cases no significant excess has been found, the corresponding fluence upper limits in the 1-100 GeV energy region have been derived, with values as low as 10^-5^ erg/cm2. The analysis of a subset of 24 GRBs with known redshift has been used to constrain the fluence extrapolation to the GeV region together with possible cutoffs under different assumptions on the spectrum.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A140
- Title:
- g'G'Ag-CH3CH2CHOHCH2OH transition frequencies
- Short Name:
- J/A+A/619/A140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The continuously enhanced sensitivity of radioastronomical observations allows the detection of increasingly complex organic molecules. These systems often exist in a large number of isomers leading to very congested spectra. We explore the conformational space of 1,2-butanediol and provide sets of spectroscopic parameters to facilitate searches for this molecule at millimeter wavelengths. We recorded the rotational spectrum of 1,2-butanediol in the 59.6-103.6GHz frequency region (5.03-2.89mm) using a free-jet millimeter-wave absorption spectrometer, and we analyzed the properties of 24 isomers with quantum chemical calculations. Selected measured transition lines were then searched on publicly available ALMA Band 3 data on IRAS 16293-2422 B. We assigned the spectra of six conformers, namely aG'Ag, gG'Aa, g'G'Ag, aG'G'g, aG'Gg, and g'GAa, to yield the rotational constants and centrifugal distortion constants up to the fourth or sixth order. The most intense signal belong to the aG'Ag species, that is the global minimum. Search for the corresponding 30_x,30_-29_x,29_ transition lines toward IRAS 16293-2422 B was unsuccessful. Our present data will be helpful for identifying 1,2-butanediol at millimeter wavelengths with radio telescope arrays. Among all possible conformers, first searches should be focused on the aG'Ag conformers in the 400-800GHz frequency spectral range.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/5191
- Title:
- Ggalactic young stellar cluster lifetimes
- Short Name:
- J/MNRAS/477/5191
- Date:
- 17 Jan 2022 00:27:47
- Publisher:
- CDS
- Description:
- Photometric detections of dust circumstellar discs around pre-main sequence (PMS) stars, coupled with estimates of stellar ages, provide constraints on the time available for planet formation. Most previous studies on disc longevity, starting with Haisch, Lada & Lada, use star samples from PMS clusters but do not consider data sets with homogeneous photometric sensitivities and/or ages placed on a uniform time-scale. Here we conduct the largest study to date of the longevity of inner dust discs using X-ray and 1-8um infrared photometry from the MYStIX and SFiNCs projects for 69 young clusters in 32 nearby star-forming regions with ages t<=5Myr. Cluster ages are derived by combining the empirical Age_JX_ method with PMS evolutionary models, which treat dynamo-generated magnetic fields in different ways. Leveraging X-ray data to identify disc-free objects, we impose similar stellar mass sensitivity limits for disc-bearing and disc-free young stellar objects while extending the analysis to stellar masses as low as M~0.1M_{sun}_. We find that the disc longevity estimates are strongly affected by the choice of PMS evolutionary model. Assuming a disc fraction of 100 per cent at zero age, the inferred disc half-life changes significantly, from t_1/2_~1.3-2Myr to t_1/2_~3.5Myr when switching from non-magnetic to magnetic PMS models. In addition, we find no statistically significant evidence that disc fraction varies with stellar mass within the first few Myr of life for stars with masses <2M_{sun}_, but our samples may not be complete for more massive stars. The effects of initial disc fraction and star-forming environment are also explored.
- ID:
- ivo://CDS.VizieR/J/A+A/656/A101
- Title:
- G305 Giant Molecular Cloud II. Clump properties
- Short Name:
- J/A+A/656/A101
- Date:
- 21 Mar 2022 07:03:46
- Publisher:
- CDS
- Description:
- G305 star-forming complex was observed in the 3-2 lines of 12 & 13CO to investigate the effect of feedback from the central OB stars on the complex. The region was decomposed into clumps using dendrogram analysis. A catalog of clump properties was created. The surface mass densities of the clumps were plotted as a function of the incident 8um flux. A mask of the region with 8um flux >100MJy/sr was created and clumps were categorized based on the extent of overlap with the mask into "mostly inside", "partly inside" & "outside". The surface mass density distribution of each of these populations were plotted. This was followed by comparing G305 clumps with the Galactic average taken from the ATLASGAL and CHIMPS clumps. Finally, the cumulative distribution functions (CDF) of the clump masses in G305 & their L/M ratios were compared to that of the Galactic sample. The surface mass densities of clumps showed a positive correlation with incident 8um flux. The data did not have sufficient velocity resolution to discern the effects of feedback on the linewidths of the clumps. The sub-sample of clumps named "mostly inside" had the highest surface mass densities followed by "partly -inside" and "outside" sub-samples. These differences between the three sub-samples were shown to be statistically significant using the KS test. The "mostly inside" sample also showed the highest level of fragmentation compared to the other two. These prove that clumps inside the G305 region are triggered. The G305 clump population is also statistically different from the Galactic average population rejecting redistribution as a likely consequence of feedback. The CDFs of clump masses and their L/M ratios are both flatter than the Galactic average, indicating that feedback in G305 has triggered star formation. The collect & collapse method is the dominant mechanism at play in G305.
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/2251
- Title:
- G0-G3 main-sequence stars with V<15
- Short Name:
- J/MNRAS/444/2251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The basic stellar atmospheric parameters (effective temperature, surface gravity and global metallicity) were determined simultaneously for a sample of 233 stars, limited in magnitude (V<15), with spectral types between G0 and G3 and luminosity class V (main sequence). The analysis was based on spectroscopic observations collected at the Observatorio Astrofisico Guillermo Haro and using a set of Lick-like indices defined in the spectral range 3800-4800{AA}. An extensive set of indices computed in a grid of theoretical spectra was used as a comparison tool in order to determine the photospheric parameters. The method was validated by matching the results from spectra of the asteroids Vesta and Ceres with the Sun parameters. The main results were as follows: (i) the photospheric parameters were determined for the first time for 213 objects in our sample and (ii) a sample of 20 new super-metal-rich star candidates was found.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A12
- Title:
- GG Tau A ALMA ^13^CO and C^18^O(3-2) maps
- Short Name:
- J/A+A/635/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- GG Tau A is the prototype of a young triple T Tauri star that is surrounded by a massive and extended Keplerian outer disk. The central cavity is not devoid of gas and dust and at least GG Tau Aa exhibits its own disk of gas and dust emitting at millimeter wavelengths. Its observed properties make this source an ideal laboratory for investigating planet formation in young multiple solartype stars. We used new ALMA ^13^CO and C^18^O(3-2) observations obtained at high angular resolution (~0.2") together with previous CO(3-2) and (6-5) ALMA data and continuum maps at 1.3 and 0.8mm in order to determine the gas properties (temperature, density, and kinematics) in the cavity and to a lesser extent in the outer disk. By deprojecting, we studied the radial and azimuthal gas distribution and its kinematics. We also applied a new method to improve the deconvolution of the CO data and in particular better quantify the emission from gas inside the cavity. We perform local nonlocal thermodynamic equilibrium studies in order to determine the excitation conditions and relevant physical parameters inside the ring and in the central cavity. Residual emission after removing a smooth-disk model indicates unresolved structures at our angular resolution, probably in the form of irregular rings or spirals. The outer disk is cold, with a temperature <20K beyond 250au that drops quickly ({prop.to}r^-1^). The kinematics of the gas inside the cavity reveals infall motions at about 10% of the Keplerian speed. We derive the amount of gas in the cavity, and find that the brightest clumps, which contain about 10% of this mass, have kinetic temperatures 40-80K, CO column densities of a few 10^17^cm^-2^, and H_2_ densities around 10^7^cm^-3^. Although the gas in the cavity is only a small fraction of the disk mass, the mass accretion rate throughout the cavity is comparable to or higher than the stellar accretion rate. It is accordingly sufficient to sustain the circumstellar disks on a long timescale.
- ID:
- ivo://CDS.VizieR/J/MNRAS/388/500
- Title:
- GHASP: H{alpha} data cubes for 108 galaxies
- Short Name:
- J/MNRAS/388/500
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Fabry-Perot observations obtained for a new set of 108 galaxies in the frame of the Gassendi H{alpha} survey of SPirals (GHASP). The GHASP survey consists of 3D H{alpha} data cubes for 203 spiral and irregular galaxies, covering a large range in morphological types and absolute magnitudes, for kinematics analysis. The new set of data presented here completes the survey. The GHASP sample is by now the largest sample of Fabry-Perot data ever published. The analysis of the whole GHASP sample will be done in forthcoming papers. Using adaptive binning techniques based on Voronoi tessellations, we have derived H{alpha} data cubes from which are computed H{alpha} maps, radial velocity fields as well as residual velocity fields, position-velocity diagrams, rotation curves and the kinematical parameters for almost all galaxies.