- ID:
- ivo://CDS.VizieR/J/A+A/282/436
- Title:
- Abundance gradients from disk PNs
- Short Name:
- J/A+A/282/436
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new determination of the radial abundance gradients of O/H, Ne/H, S/H, and Ar/H is made for disk planetary nebulae, (PN), that is, those objects of Peimbert types I, II, and III. On the basis of a sample containing 200 nebulae, it can be concluded that these gradients are generally similar, and of the same order of magnitude as the O/H gradient displayed by galactic HII regions. Some distance-independent correlations confirm the accuracy of the abundances and support the interpretation of the gradients in terms of chemical evolution models. The time evolution of the abundance gradients in the Milky Way is investigated, and their variation with the types of PN are compared with predictions of chemical evolution models.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/3664
- Title:
- Abundance gradients in low SB spirals
- Short Name:
- J/MNRAS/454/3664
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We acquired spectra of 141 HII regions in 10 late-type low surface brightness galaxies (LSBGs). The analysis of the chemical abundances obtained from the nebular emission lines shows that metallicity gradients are a common feature of LSBGs, contrary to previous claims concerning the absence of such gradients in this class of galaxies. The average slope, when expressed in units of the isophotal radius, is found to be significantly shallower in comparison to galaxies of high surface brightness. This result can be attributed to the reduced surface brightness range measured across their discs, when combined with a universal surface mass density-metallicity relation. With a similar argument we explain the common abundance gradient observed in high surface brightness galaxy (HSBG) discs and its approximate dispersion. This conclusion is reinforced by our result that LSBGs share the same common abundance gradient with HSBGs, when the slope is expressed in terms of the exponential disc scalelength.
- ID:
- ivo://CDS.VizieR/J/A+A/345/629
- Title:
- Abundance gradients in planetary nebulae
- Short Name:
- J/A+A/345/629
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial abundance gradients of the element ratios O/H, Ne/H, S/H, and Ar/H are determined on the basis of a sample of disk planetary nebulae. The behaviour of the gradients at large distances from the galactic centre, R>R_0_=7.6kpc, is emphasized. It is concluded that the derived gradients are consistent with an approximately constant slope in the inner parts of the Galaxy, and some flattening for distances larger than R_0_. A comparison is made with previous determinations using both photoionized nebulae and young stars, and some consequences on theoretical models for the chemical evolution of the galactic disk are discussed.
- ID:
- ivo://CDS.VizieR/J/ApJS/162/346
- Title:
- Abundance gradients in the Galaxy
- Short Name:
- J/ApJS/162/346
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Six HII regions at galactocentric distances of R=10-15kpc have been observed in the far-IR emission lines of [OIII] (52{mu}m, 88{mu}m), [NIII] (57{mu}m), and [SIII] (19{mu}m) using the Kuiper Airborne Observatory. These observations have been combined with Very Large Array radio continuum observations of these sources to determine the abundances of O++, N++, and S++ relative to hydrogen. In addition, eight of the most recent sets of measurements of ionic line strengths in HII regions have been reanalyzed in order to attempt to reconcile differences in optical versus far-IR abundance determinations. We have in total 168 sets of observations of 117 HII regions in our analysis.
- ID:
- ivo://CDS.VizieR/J/AJ/144/95
- Title:
- Abundance in stars of the outer galactic disk. IV.
- Short Name:
- J/AJ/144/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities and chemical abundances for nine stars in the old, distant open clusters Be18, Be21, Be22, Be32, and PWM4. For Be18 and PWM4, these are the first chemical abundance measurements. Combining our data with literature results produces a compilation of some 68 chemical abundance measurements in 49 unique clusters. For this combined sample, we study the chemical abundances of open clusters as a function of distance, age, and metallicity. We confirm that the metallicity gradient in the outer disk is flatter than the gradient in the vicinity of the solar neighborhood. We also confirm that the open clusters in the outer disk are metal-poor with enhancements in the ratios [{alpha}/Fe] and perhaps [Eu/Fe]. All elements show negligible or small trends between [X/Fe] and distance (<0.02dex/kpc), but for some elements, there is a hint that the local (R_GC_<13kpc) and distant (R_GC_>13kpc) samples may have different trends with distance. There is no evidence for significant abundance trends versus age (<0.04dex/Gyr). We measure the linear relation between [X/Fe] and metallicity, [Fe/H], and find that the scatter about the mean trend is comparable to the measurement uncertainties. Comparison with solar neighborhood field giants shows that the open clusters share similar abundance ratios [X/Fe] at a given metallicity. While the flattening of the metallicity gradient and enhanced [{alpha}/Fe] ratios in the outer disk suggest a chemical enrichment history different from that of the solar neighborhood, we echo the sentiments expressed by Friel et al. that definitive conclusions await homogeneous analyses of larger samples of stars in larger numbers of clusters. Arguably, our understanding of the evolution of the outer disk from open clusters is currently limited by systematic abundance differences between various studies.
- ID:
- ivo://CDS.VizieR/J/ApJ/705/328
- Title:
- Abundance measurements in Sculptor dSph
- Short Name:
- J/ApJ/705/328
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of Fe, Mg, Si, Ca, and Ti abundances for 388 radial velocity member stars in the Sculptor dwarf spheroidal galaxy (dSph), a satellite of the Milky Way (MW). This is the largest sample of individual {alpha} element (Mg, Si, Ca, and Ti) abundance measurements in any single dSph. The measurements are made from Keck/Deep Imaging Multi-Object Spectrometer medium-resolution spectra (6400-9000{AA}, R~6500). Based on comparisons to published high-resolution (R>~20000) spectroscopic measurements, our measurements have uncertainties of {alpha}[Fe/H]=0.14 and {alpha}[{alpha}/Fe]=0.13. We have discovered one star with [Fe/H]=-3.80+/-0.28, which is the most metal-poor star known anywhere except the MW halo, but high-resolution spectroscopy is needed to measure this star's detailed abundances.
- ID:
- ivo://CDS.VizieR/J/A+A/656/A67
- Title:
- Abundance of Ba in 47 Tuc
- Short Name:
- J/A+A/656/A67
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- While most (if not all) Type I Galactic globular clusters (GGCs) are characterised by spreads in the abundances of light chemical elements (e.g. Li, N, O, Na, Mg, Al), it is not yet well established whether similar spreads may exist in s-process elements as well. We investigated the possible difference in Ba abundance between the primordial (1P) and polluted (2P) stars in the Galactic globular cluster (GGC) 47 Tuc (NGC 104). For this purpose, we obtained homogeneous abundances of Fe, Na, and Ba in a sample of 261 red giant branch (RGB) stars. Abundances of Na and Ba were determined using archival GIRAFFE/VLT spectra and 1D non-local thermodynamic equilibrium (NLTE) abundance analysis methodology. Contrary to the finding of Gratton et al. (2013A&A...549A..41G), we did not detect any significant Ba-Na correlation or 2P-1P Ba abundance difference in the sample of 261 RGB stars in 47 Tuc. This corroborates the result of D'Orazi et al. (2010ApJ...719L.213D), who found no statistically significant Ba-Na correlation in 110 RGB stars in this GGC. The average barium-to-iron ratio obtained in the sample of 261 RGB stars, <[Ba/Fe]_1DNLTE_>=-0.01+/-0.06, agrees well with those determined in Galactic field stars at this metallicity and may therefore represent the abundance of primordial proto-cluster gas that has not been altered during the subsequent chemical evolution of the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/142/63
- Title:
- Abundance of five stars in NGC 6397
- Short Name:
- J/AJ/142/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundances in three red giants and two turnoff (TO) stars in the metal-poor Galactic globular cluster (GC) NGC 6397 based on spectroscopy obtained with the Magellan Inamori Kyocera Echelle high-resolution spectrograph on the Magellan 6.5m Clay telescope. Our results are based on a line-by-line differential abundance analysis relative to the well-studied red giant Arcturus and the Galactic halo field star HIP 66815.
- ID:
- ivo://CDS.VizieR/J/A+A/457/651
- Title:
- Abundance of nine beta Cephei stars
- Short Name:
- J/A+A/457/651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Seismic modelling of the beta Cephei stars promises major advances in our understanding of the physics of early B-type stars on (or close to) the main sequence. However, a precise knowledge of their physical parameters and metallicity is a prerequisite for correct mode identification and inferences regarding their internal structure. Here we present the results of a detailed NLTE abundance study of nine prime targets for theoretical modelling: gamma Peg, delta Cet, nu Eri, beta CMa, xi1 CMa, V836 Cen, V2052 Oph, beta Cep and DD (12) Lac. The following chemical elements are considered: He, C, N, O, Mg, Al, Si, S and Fe. Our abundance analysis is based on a large number of time-resolved, high-resolution optical spectra covering in most cases the entire oscillation cycle of the stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/220/7
- Title:
- Abundance of X-shaped radio sources. I. VLA survey
- Short Name:
- J/ApJS/220/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cheung (2007, J/AJ/133/2097) identified a sample of 100 candidate X-shaped radio galaxies using the NRAO FIRST survey; these are small-axial-ratio extended radio sources with off-axis emission. Here, we present radio images of 52 of these sources that have been made from archival Very Large Array data with resolution of about 1". Fifty-one of the 52 were observed at 1.4GHz, 7 were observed at 1.4 and 5GHz, and 1 was observed only at 5GHz. We also present overlays of the Sloan Digital Sky Survey red images for 48 of the sources, and DSS-II overlays for the remainder. Optical counterparts have been identified for most sources, but there remain a few empty fields. Our higher resolution VLA images along with FIRST survey images of the sources in the sample reveal that extended extragalactic radio sources with small axial ratios are largely (60%) cases of double radio sources with twin lobes that have off-axis extensions, usually with inversion-symmetric structure. The available radio images indicate that at most 20% of sources might be genuine X-shaped radio sources that could have formed by a restarting of beams in a new direction following an interruption and axis flip. The remaining 20% are in neither of these categories.
