scholarly journals The oxygen abundance gradient in M81 and the robustness of abundance determinations in H ii regions

2015 ◽  
Vol 455 (3) ◽  
pp. 2627-2643 ◽  
Author(s):  
K. Z. Arellano-Córdova ◽  
M. Rodríguez ◽  
Y. D. Mayya ◽  
D. Rosa-González
Keyword(s):  
H Ii Regions ◽  
Oxygen Abundance ◽  
Abundance Gradient

scholarly journals Differential Abundances of B-type Supergiants in M33

1999 ◽  
Vol 192 ◽  
pp. 272-276
Author(s):  
M. I. Monteverde ◽  
A. Herrero
Keyword(s):  
H Ii Regions ◽  
Line Formation ◽  
Atmospheric Parameters ◽  
Oxygen Abundance ◽  
Abundance Gradient ◽  
Preliminary Results ◽  
Metal Abundances ◽  
Effective Temperatures ◽  
Abundance Determination

In previous papers we have published preliminary results on the stellar oxygen-abundance gradient in M33 by using B-type supergiants. In the following study, we include one new B-supergiant and derive effective temperatures and gravities for these stars. Determination of atmospheric parameters is based on analyses of silicon ionisation balance.Detailed non-LTE model atmospheres and non-LTE line formation calculations were used for the abundance determination of Si and O. Careful differential analyses are used to quantify the differences in metal abundances between M33 stars and MK spectral standards in our Galaxy.We compare our results with the abundances expected from studies of H II regions.

scholarly journals Evidence for azimuthal variations of the oxygen-abundance gradient tracing the spiral structure of the galaxy HCG 91c

2017 ◽  
Vol 601 ◽  
pp. A61 ◽  
Author(s):  
F. P. A. Vogt ◽  
E. Pérez ◽  
M. A. Dopita ◽  
L. Verdes-Montenegro ◽  
S. Borthakur
Keyword(s):  
Spiral Structure ◽  
Oxygen Abundance ◽  
Abundance Gradient ◽  
The Galaxy

scholarly journals The time evolution of the Milky Way’s oxygen abundance gradient

2018 ◽  
Author(s):  
M Mollá ◽  
Á I Díaz ◽  
O Cavichia ◽  
B K Gibson ◽  
W J Maciel ◽  
...  
Keyword(s):  
Time Evolution ◽  
Oxygen Abundance ◽  
Abundance Gradient

scholarly journals Planetary Nebulae in Local Group Galaxies

1983 ◽  
Vol 103 ◽  
pp. 443-460
Author(s):  
Holland C. Ford
Keyword(s):  
Local Group ◽  
Planetary Nebulae ◽  
Stellar Populations ◽  
Chemical Compositions ◽  
H Ii Regions ◽  
Helium Abundance ◽  
Abundance Gradient ◽  
Star Forming ◽  
Ic 10 ◽  
Ngc 6822

Recent surveys for planetary nebulae have given the first identifications in Fornax, NGC 6822, M33, IC 10, Leo A, Sextans A, Pegasus, WLM, NGC 404, and M81, and extended the identifications in the SMC, the LMC, and M31. Observations of planetaries have established chemical compositions in old or intermediate age populations in 8 Local Group galaxies. The chemical compositions show that i) the helium abundance is higher in planetary nebulae than in H II regions in the same galaxy, and ii) nitrogen is overabundant relative to H II regions by factors of 4 to 100. Planetary nebulae are not a major source of helium in star-forming galaxies, and are a major source of nitrogen. The planetary in Fornax has a relatively high O abundance, and, together with Fornax's carbon stars, establishes the presence of at least 2 stellar populations. The abundance gradient derived from 3 planetaries in M31 is very shallow, and gives high abundances at ~ 20 kpc. By using planetary nebulae as standard candles, upper and lower distance limits have been set for 10 Local Group candidates, and a new distance estimated for M81.

scholarly journals Oxygen abundance distributions in six late-type galaxies based on SALT spectra of H II regions

2015 ◽  
Vol 582 ◽  
pp. A35 ◽  
Author(s):  
I. A. Zinchenko ◽  
A. Y. Kniazev ◽  
E. K. Grebel ◽  
L. S. Pilyugin
Keyword(s):  
H Ii Regions ◽  
Late Type ◽  
Oxygen Abundance

The Stellar Oxygen Abundance Gradient in M33

1997 ◽  
Vol 474 (2) ◽  
pp. L107-L110 ◽  
Author(s):  
M. I. Monteverde ◽  
A. Herrero ◽  
D. J. Lennon ◽  
R.-P. Kudritzki
Keyword(s):  
Oxygen Abundance ◽  
Abundance Gradient

scholarly journals Helium abundances and its radial gradient from the spectra of H ii regions and ring nebulae of the Milky Way

2020 ◽  
Vol 496 (3) ◽  
pp. 2726-2742 ◽  
Author(s):  
J E Méndez-Delgado ◽  
C Esteban ◽  
J García-Rojas ◽  
K Z Arellano-Córdova ◽  
M Valerdi
Keyword(s):  
Milky Way ◽  
H Ii Regions ◽  
Abundance Gradient ◽  
Radial Gradient ◽  
Physical Conditions ◽  
The Galaxy ◽  
Ring Nebulae ◽  
Gaia Dr2 ◽  
Disc Galaxies ◽  
Weakly Dependent

ABSTRACT We determine the radial abundance gradient of helium in the disc of the Galaxy from published spectra of 19 H ii regions and ring nebulae surrounding massive O-type stars. We revise the Galactocentric distances of the objects considering Gaia DR2 parallaxes (Gaia Collaboration 2018) and determine the physical conditions and the ionic abundance of He+ in a homogeneous way, using between 3 and 10 He i recombination lines in each object. We estimate the total He abundance of the nebulae and its radial abundance gradient using four different ionization correction factor (ICF; He) schemes. The slope of the gradient is always negative and weakly dependent on the ICF(He) scheme, especially when only the objects with log(η) < 0.9 are considered. The slope values go from −0.0078 to −0.0044 dex kpc−1, consistent with the predictions of chemical evolution models of the Milky Way and chemodynamical simulations of disc galaxies. Finally, we estimate the abundance deviations of He, O, and N in a sample of ring nebulae around Galactic Wolf–Rayet stars, finding a quite similar He overabundance of about +0.24 ± 0.11 dex in three stellar ejecta ring nebulae.

scholarly journals Relations between abundance characteristics and rotation velocity for star-forming MaNGA galaxies

2019 ◽  
Vol 623 ◽  
pp. A122 ◽  
Author(s):  
L. S. Pilyugin ◽  
E. K. Grebel ◽  
I. A. Zinchenko ◽  
Y. A. Nefedyev ◽  
J. M. Vílchez
Keyword(s):  
Rotation Velocity ◽  
Effective Radius ◽  
Oxygen Abundance ◽  
Abundance Gradient ◽  
Star Forming ◽  
The Galaxy ◽  
Basic Parameters ◽  
Central Oxygen ◽  
The Mean ◽  
Optical Radius

We derive rotation curves, surface brightness profiles, and oxygen abundance distributions for 147 late-type galaxies using the publicly available spectroscopy obtained by the MaNGA survey. Changes of the central oxygen abundance (O/H)0, the abundance at the optical radius (O/H)R25, and the abundance gradient with rotation velocity Vrot were examined for galaxies with rotation velocities from 90 km s−1 to 350 km s−1. We find that each relation shows a break at Vrot∗ ∼ 200 km s−1. The central (O/H)0 abundance increases with rising Vrot and the slope of the (O/H)0–Vrot relation is steeper for galaxies with Vrot ≲ Vrot∗. The mean scatter of the central abundances around this relation is 0.053 dex. The relation between the abundance at the optical radius of a galaxy and its rotation velocity is similar; the mean scatter in abundances around this relation is 0.081 dex. The radial abundance gradient expressed in dex/kpc flattens with the increase of the rotation velocity. The slope of the relation is very low for galaxies with Vrot ≳ Vrot∗. The abundance gradient expressed in dex/R25 is roughly constant for galaxies with Vrot ≲ Vrot∗, flattens towards Vrot∗, and then again is roughly constant for galaxies with Vrot ≳ Vrot∗. The change of the gradient expressed in terms of dex/hd (where hd is the disc scale length), in terms of dex/Re, d (where Re, d is the disc effective radius), and in terms of dex/Re, g (where Re, g is the galaxy effective radius) with rotation velocity is similar to that for gradient in dex/R25. The relations between abundance characteristics and other basic parameters (stellar mass, luminosity, and radius) are also considered.

Sign in / Sign up

Export Citation Format

Share Document